JP2024027621A - wet tissue - Google Patents

Abstract

To provide a wet tissue which has good feeling and excellent wiping property, and is hard to be ruptured even when paper having excellent biodegradability and economical efficiency is used as a sheet to be impregnated with a chemical solution.SOLUTION: A wet tissue comprises a paper-made sheet containing at least pulp fibers and impregnated with a chemical solution, wherein the tensile strength of the sheet in both its longitudinal direction and transverse direction is 2.2 N/25 mm or over when wet, and the sheet thickness Tm when applying a load of 50 gf/cm2 to the sheet with a KES compression testing machine is 160 μm or over and 440 μm or under.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wet tissue made of a paper sheet impregnated with a chemical solution.

Wet tissue products are generally manufactured by impregnating a sheet of nonwoven fabric with a chemical solution.

Spunlace nonwoven fabrics that are widely used as sheets contain many petroleum-derived chemical fibers such as polyester and polyolefin in addition to wood-derived fibers such as rayon, so most of them are not biodegradable.

However, recently, in order to be more environmentally friendly, wet tissues that use paper as a base material and water-disintegrable paper that develops strength through the interaction between chemicals added to the paper and components in the chemical solution, such as toilet cleaner sheets, are being developed. Wet tissues are also available on the market.

As a document on wet tissues using paper as a base material, for example, Patent Document 1 states that 5 to 40 parts by weight of polyols are added to 100 parts by weight of a laminate obtained by laminating a plurality of wet pulp sheets with a basis weight of 10 to 30 g/ ^m2 . A wiping sheet comprising an embossed laminated sheet containing parts by weight is disclosed.
Further, as a document on wet tissues made of water-disintegratable paper, Patent Document 2 discloses that a base sheet containing 80% by mass or more of cellulose fibers and having a basis weight of 20 to 120 g/m ² is impregnated with a liquid detersive composition. The liquid cleaning composition contains 0.01 to 0.50% by mass of an organic acid, 0.1 to 1.0% by mass of a surfactant, and 0.5 to 5.0% by mass of a divalent or higher metal ion compound. Disclosed is a disinfecting cleaning article containing:

Japanese Patent Application Publication No. 11-332777 JP 2017-110323 Publication

Nonwoven fabrics used for the above-mentioned wet tissues include spunlace nonwoven fabrics made only of wood materials such as cotton and cellulose, and nonwoven fabrics made by combining chemical fibers with rayon and polylactic acid to give them biodegradability. However, these are inferior in economic efficiency and are expensive as nonwoven fabrics for general-purpose wet tissues. As described above, it has been difficult to achieve both environmental friendliness and economic efficiency in conventional products.

Paper is made from pulp, which is a woody material, and is an economical and biodegradable material. However, as in Patent Document 1, when paper is used as a base material for wet tissues, there are problems such as the volume decreases when impregnated with a chemical solution, resulting in poor texture, and the strength decreases, causing the sheet to tear. Decreasing the amount of chemical solution impregnated can suppress a decrease in bulk, but there are problems in that sufficient wettability cannot be imparted, making it impossible to wipe thoroughly or drying out during storage.
Another method of obtaining bulkiness is to add embossing to the sheet, but this method requires specialized equipment and increases the number of manufacturing steps, making it less economical.

Furthermore, in the case of a wet tissue made of water-disintegrable paper that develops strength through the interaction between a chemical applied to the paper and a component in the chemical liquid, as in Patent Document 2, the chemical liquid to be used is limited, and the applications are limited. Furthermore, in order to obtain sufficient strength, it is necessary to increase the basis weight of the water-disintegratable paper, making it less economical.

As described above, when paper with excellent economic efficiency and low environmental impact is used for wet tissue sheets, it has been difficult to achieve both texture and strength without limiting the chemical formulation or manufacturing equipment.

The present invention was made in view of these circumstances, and even if paper, which is excellent in biodegradability and economical efficiency, is used as a sheet impregnated with a chemical solution, it has a good texture, is easy to wipe, and is difficult to tear. The purpose is to provide wet tissues.

The inventor conducted extensive research and determined the tensile strength in the longitudinal and lateral directions when the sheet is wet, and the tensile strength of the sheet under a predetermined load. By setting the respective numerical ranges of the thickness of the sheet within the predetermined range, even if paper, which is highly biodegradable and economical, is used as the sheet to be impregnated with the chemical solution, it will have a good texture and be easy to wipe off. We were able to create a wet tissue that is both excellent and hard to tear, and the present invention has been completed. That is, the present invention provides the following.

(1) A first aspect of the present invention is a wet tissue in which a paper sheet containing at least pulp fibers is impregnated with a chemical solution, wherein the sheet has a tensile strength in the longitudinal and transverse directions when wet. , both are 2.2N/25mm or more, and the thickness T _m of the sheet when a load of 50 gf/cm ² is applied to the sheet by a KES compression tester is 160 μm or more and 440 μm or less. , wet tissue.

(2) A second aspect of the present invention is the wet tissue according to (1), in which the sheet has a 0.5 gf/cm ² load when applied with the KES compression tester. It is characterized in that (T ₀ -T _m )/T ₀ is 0.40 or more, where T 0 is the _thickness .

(3) A third aspect of the present invention is the wet tissue according to (1), characterized in that the sheet has a basis weight in an absolutely dry state of 20 g/m ² or more and 50 g/m ² or less. It is something to do.

(4) A fourth aspect of the present invention is the wet tissue according to (1), in which the sheet has a 0.5 gf/cm ² load when applied with the KES compression tester. It is characterized in that the thickness T ₀ is 400 μm or more and 800 μm or less.

(5) A fifth aspect of the present invention is the wet tissue according to (1), characterized in that the impregnation ratio of the chemical solution into the sheet is 2 times or more and 4 times or less. be.

According to the present invention, even if a sheet impregnated with a chemical solution is made of paper that is excellent in biodegradability and economical efficiency, it is possible to provide a wet tissue that has a good texture, excellent wipeability, and is hard to tear.

This is an XY plane image of the height profile (mapping) of the sheet taken with a microscope. It is an image of the profile of the height of the unevenness (measured cross-sectional curve S) on the line segment S1-S2 in FIG. 1(b). It is an image of a roughness curve W obtained by processing the (measured) cross-sectional curve S of FIG. 2. FIG. 4 is a diagram showing how to determine the height of unevenness caused by a paper machine in the sheet from FIG. 3; FIG. 2 is a schematic diagram of a portion where irregularities derived from a paper machine are imparted in the paper making process of a sheet.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail. The present embodiment below is an illustration for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be implemented with appropriate modifications within the scope of its gist.

<Wet tissue>
The wet tissue according to this embodiment is a wet tissue in which a paper sheet containing at least pulp fibers is impregnated with a chemical solution.
Since the sheet is made of paper and does not contain synthetic fibers, it has excellent biodegradability and can be made into an economical wet tissue. Note that it is preferable that the sheet is one ply and that multiple sheets are not laminated.

As the pulp fiber used for the sheet, general pulp fibers (wood pulp) such as softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP) can be used. Among these, it is preferable to include softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP). Further, the content ratio of NBKP and LBKP in the pulp fiber is preferably 50:50 or more and 100:0 or less, more preferably 70:30 or more and 100:0 or less, even more preferably 90:10 or more and 100:0 or less, and 100:0. is most preferred.
As NBKP, fibers made of, for example, radiata pine, slash pine, southern pine, lodgepole pine, spruce, and Douglas fir are preferred. Note that NUKP can be used instead of NBKP, and LUKP can be used instead of LBKP.

Further, the chemical liquid with which the sheet is impregnated may contain alcohol, a humectant, a preservative, an antibacterial agent, a stabilizer, etc., which are usually used in wet tissues.
At this time, the impregnation ratio of the chemical solution into the sheet is preferably 2 times or more and 4 times or less, more preferably 2.3 times or more and 3.5 times or less, and 2.5 times or more and 3.2 times. It is more preferable that it is the following. When the impregnation ratio is less than 2 times, the chemical solution is not sufficient and the wipeability of the wet tissue is poor, and when it exceeds 4 times, the wet tissue becomes sticky and has a poor texture. The method for measuring the impregnation ratio is to first measure the area and weight of the wet tissue, then wash the wet tissue with an alcohol solution and dry it completely. After completely drying, the humidity is controlled in an environment of 23° C. and 50% RH, and the weight of the sheet is measured. The weight of the chemical solution impregnated with respect to 1 g of paper is defined as the impregnation ratio.

In addition, in order to facilitate optimization of the wet tensile strength of the sheet, which will be described later, it is preferable that the sheet is not water-decomposable. In addition, the sheet is not limited to equipment such as embossing rolls during manufacturing, there is no reduction in sheet strength due to embossing, and it is easy to optimize the tensile strength of the sheet when wet. It is preferable not to have any.

(Physical properties of sheet)
The basis weight of the sheet in an absolutely dry state is preferably 20 g/m ² or more and 50 g/m ² or less, more preferably 25 g/m ² or more and 45 g/m ² or less, and 30 g/m 2 or more and 40 g/m ² or less. More preferably, it is ² or less. When the basis weight is less than 20 g/m ² , the sheet tends to tear, and when it exceeds 50 g/m ² , the sheet becomes stiff and difficult to wipe off. Basis weight is measured in accordance with JIS P 8124.

In addition, the wet tissue (sheet) according to the present embodiment has a tensile strength in both the vertical and horizontal directions when wet, of 2.2 N/25 mm or more, preferably 2.4 N/25 mm or more, and 2.2 N/25 mm or more, preferably 2.4 N/25 mm or more. More preferably, it is .6N/25mm or more.

More specifically, the wet tissue according to the present embodiment preferably has a longitudinal tensile strength of 2.9 N/25 mm or more and 6.9 N/25 mm or less when wet. Further, the tensile strength in the lateral direction of the wet tissue when wet is preferably 2.2 N/25 mm or more and 3.7 N/25 mm or less. If the longitudinal tensile strength is less than 2.9 N/25 mm or the transverse tensile strength is less than 2.2 N/25 mm, the wet tissue (sheet) is likely to tear. If the longitudinal tensile strength exceeds 6.9 N/25 mm or the transverse tensile strength exceeds 3.7 N/25 mm, the wet tissue (sheet) will have poor texture.
The longitudinal tensile strength of the wet tissue when wet is more preferably 3.4 N/25 mm or more and 6.4 N/25 mm or less, and preferably 3.9 N/25 mm or more and 5.9 N/25 mm or less. More preferred. Further, the tensile strength in the lateral direction of the wet tissue when wet is more preferably 2.4 N/25 mm or more and 3.5 N/25 mm or less, and preferably 2.6 N/25 mm or more and 3.2 N/25 mm or less. More preferred.

The tensile strength in each direction when wet was determined by taking out one wet tissue, cutting it into a width of 25 mm, and measuring it using a tensile tester with a grip width of 100 mm and a stretching speed of 300 ± 5 mm/min, and the average of 10 times. value.
Note that the tensile strength of the sheet in each direction when wet can be adjusted by a general method such as adding a wet paper strength agent during the papermaking process. Further, the longitudinal and lateral directions of the sheet can be similarly adjusted by the fiber orientation.

Further, the thickness T _m of the sheet when a load of 50 gf/cm ² is applied to the sheet using a KES compression tester is 160 μm or more and 440 μm or less, preferably 200 μm or more and 400 μm or less, and 250 μm or more and 350 μm or less. It is more preferable. If T _m is less than 160 μm, the sheet feels poor when held in the hand, and if T m exceeds 440 μm, the sheet becomes stiff and difficult to wipe off.

Furthermore, when T ₀ is the thickness of the sheet when a load of 0.5 gf/cm ² is applied using a KES compression tester, (T ₀ - T _m )/T ₀ is 0.40 or more. It is preferably 0.45 or more, more preferably 0.50 or more. If the value is less than 0.40, the feel of the sheet when held in the hand is poor.

Note that the above T ₀ is preferably 400 μm or more and 800 μm or less, more preferably 500 μm or more and 780 μm or less, and even more preferably 600 μm or more and 750 μm or less. If T ₀ is less than 400 μm, the sheet feels poor when held in the hand, and if T 0 exceeds 800 μm, the sheet becomes stiff and difficult to wipe off.

In relation to the above thickness, it is preferable that the WC (compression work) of the KES compression tester is 0.15 gf·cm/cm ² or more and 0.65 gf·cm/cm ² or less. If the WC is less than 0.15 gf·cm/cm ² , the sheet will have poor texture, and if it exceeds 0.65 gf·cm/cm ² , it will be difficult to transmit force to the object through the sheet during wiping, making it difficult to wipe it.
In addition, WC (compression work) is more preferably 0.25 gf·cm/cm ² or more and 0.55 gf·cm/cm ² or less, and 0.35 gf·cm/cm ² or more and 0.50 gf·cm/ It is more preferable that it is below cm ² .

Thickness and WC are measured using a KES-G5 automated compression tester (manufactured by Kato Tech Co., Ltd.).
A sample obtained by cutting a sheet (wet tissue) impregnated with a chemical solution into a size of 140 mm x 200 mm was placed between a 2 cm ² pressure plate and a pressure receiving plate, and the pressure plate was lowered at a speed of 0.020 cm/sec. The pressure that changes at that time and the thickness of the sample at that time are measured.
T ₀ is the thickness (μm) of the sample at a pressure of 0.5 gf/cm ² , and T _m is the thickness (μm) of the sample at a pressure of 50 gf/cm ² . The values of T ₀ and T _m are values calculated as average values of 10 measurements. Further, WC is the compression work, and the average value of 10 times is similarly calculated.

Note that it is preferable that the surface of the sheet has an uneven pattern derived from a paper machine, which is different from embossing, and that the combined height of the protrusions and recesses is 100 μm or more and 300 μm or less.
When the height of the uneven pattern is within the above numerical range, it is easy to optimize the thickness and WC such as T _m and T ₀ described above. The height of the uneven pattern is more preferably 130 μm or more and 270 μm or less, and even more preferably 150 μm or more and 250 μm or less. Further, the unevenness caused by the paper machine can be adjusted by a general method such as crepe ratio or wet crepe.

The height of the unevenness of the sheet due to the paper machine is measured using a microscope. As the microscope, the product name "One-shot 3D measurement macroscope VR-3100" manufactured by KEYENCE can be used. The product name "VR-H1A" can be used as microscope image observation/measurement/image analysis software. Further, the measurement conditions are a measurement magnification of 12 times and a visual field area of 24 mm x 18 mm. The measurement magnification and visual field area may be changed as appropriate depending on the desired size of unevenness. Note that three-dimensional measuring machines and contour shape measuring machines measure points and lines, but in the case of one-shot 3D measurement, the entire surface is measured, so the overall shape and undulations are easy to understand.

A specific method for measuring the height of unevenness caused by a paper machine will be described with reference to FIGS. 1 to 4. Note that the measurement is performed on a sheet (wet tissue) impregnated with a chemical solution.
FIG. 1(a) is an XY plane image of a height profile (mapping) taken using a microscope. The vertical direction in FIG. 1 is the horizontal direction of the sheet, and the horizontal direction is the vertical direction of the sheet. Then, as shown in Fig. 1(b), if a line segment S1-S2 parallel to the vertical direction is drawn at an arbitrary position in the vertical direction of the XY plane image of the height profile (mapping), Fig. 2 is obtained. The height (measured cross-sectional curve) profile of the irregularities shown is obtained. Note that each unevenness extends along the vertical direction, and the line segment S1-S2 crosses these multiple unevennesses, so at what position in the vertical direction of the XY plane image should the line segment S1-S2 be drawn? However, the height profile of the unevenness remains almost unchanged.

Here, the height profile is a (measured) cross-sectional curve S that represents the unevenness of the actual sheet surface, but noise (fiber lumps on the sheet surface, fibers extending like whiskers, areas with no fibers, etc.) It is necessary to remove such noise peaks when calculating the height of the unevenness.
Therefore, the (measured) cross-sectional curve S in FIG. 2 is smoothed by setting the filter size of the weighted average radio button to ±12 to obtain the cross-sectional curve W in FIG. 3. Note that smoothing using the weighted average radio button filter can be automatically obtained using the above analysis software.

Regarding the obtained roughness curve W, as shown in FIG. 4, the difference in the vertical axis between the convex portion and the adjacent concave portion is measured at 10 points (H1 to H10), and the average is taken as the height of the concavo-convex portion (Rc). Furthermore, three line segments S1-S2 are set for one height profile image, and three roughness curves W shown in FIG. 3 are obtained. Then, Rc is determined for each of these three roughness curves W. Three images of the sample are prepared, and the height of the unevenness is determined by averaging a total of nine pieces of data (Rc).

(Method for manufacturing wet tissue)
The wet tissue (sheet) according to this embodiment can be manufactured using the same steps as those for ordinary wet tissue products. Specifically, a laminate of wet tissues (sheets) can be obtained through the following steps: (1) paper making and creping, (2) cutting, (3) folding, lamination, and impregnation with a chemical solution. Note that if the product is not a laminate but a roll to be packed in a bottle, the product goes through the winding process without being cut. Moreover, the timing of impregnation with the chemical solution may be either before or after lamination, or the lamination and impregnation may be performed simultaneously.

In the papermaking process, it is preferable that the sheet be provided with an uneven pattern derived from the papermaking process, as described above. By having this uneven pattern, it is easy to optimize the thickness and WC such as T _m and T ₀ of the sheet. Note that "derived from the paper making process" means that it is applied between the head box of the paper machine and the entrance of the Yankee dryer 12 in the paper making process of the sheet. Specifically, in a part of the papermaking process shown in FIG. 5, the belt press section 10 disposed between the dewatering roll 11 and the Yankee dryer 12 can provide the unevenness. The belt press section 10 presses the wet paper 14 and the uneven belt 13 (the uneven belt 13 loops around the belt press section 10 and the Yankee dryer 12) together, thereby imparting an uneven pattern to the wet paper 14. can do.

(Processing method, packaging form)
Thereafter, the laminate (or rolled-up product) of wet tissues (sheets) is packaged as a wet tissue. Note that the lamination and packaging forms that are normally used for wet tissue, such as four-fold, six-fold, pop-up format, and bottle format, can be applied without particular limitation.
The size of one side of the sheet manufactured by the above manufacturing method is preferably 80 mm or more and 300 mm or less, and more preferably 120 mm or more and 220 mm or less. In addition, in the above-mentioned papermaking process, paper may be made in a wide width (for example, 1000 mm), and then cut into 10 sheets (for example, 100 mm in width) using a processing machine.

As explained above, according to the present embodiment, a wet tissue with good texture, excellent wiping properties, and resistance to tearing can be provided even if paper, which is excellent in biodegradability and economic efficiency, is used as a sheet impregnated with a chemical solution. be able to.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples in any way.

Wet tissues of Examples 1 to 17 and Comparative Examples 1 to 10 were prepared under the conditions shown in Tables 1 to 3, and the following evaluations were performed. Note that the wet tissue of Comparative Example 9 in Table 3 was made not from paper (pulp) but from a nonwoven fabric (rayon/PET), and the wet tissue of Comparative Example 10 was made from a nonwoven fabric (100% rayon). In addition, each parameter other than the evaluation below was performed according to the standards or measurement methods described above.
In addition, "wet strength" in Tables 1 to 3 is determined by measuring the wet tensile strength in the longitudinal and transverse directions of the sheets of each example and each comparative example, and the lower value (depending on the fiber orientation, the This is the horizontal value).

1. Texture The texture of the wet tissue (sheet) was evaluated in four stages by 30 monitors. The evaluation was rated ◎ if the texture was excellent, ○ if the texture was to some extent, △ if the texture was slightly poor, and × if the texture was poor.

2. Wipability Thirty monitors evaluated the wipeability of the wet tissue (sheet) on a four-level scale when wiping off dirt with a wet tissue (sheet). The evaluation was rated ◎ if dirt could be wiped off well, ○ if it could be wiped off to some extent, △ if it could not be wiped off very much, and × if it could hardly be wiped off.

3. Tear Resistance Thirty monitors evaluated the strength of the wet tissue (sheet) during use on a four-level scale. The evaluation was rated ◎ if there was no problem in strength (resistance to tearing) during use, ○ if there was no problem in practical use, △ if there was some tearing, and × if not practical.

4. Biodegradability The biodegradability of wet tissue sheets was evaluated in two stages. In the evaluation, wet tissue sheets (original fabrics) using only wood fibers such as pulp were rated ◎, and those containing non-biodegradable synthetic fibers were rated ×.

5. Economical Efficiency The economical efficiency (cost performance) of the wet tissue was evaluated relative to four levels using general paper (basis weight 38 g/m ² ) as a standard. The evaluation was given as ◎ if it was very economical compared to paper for wiping, etc., ○ if it was economical, △ if it was a little uneconomical, and × if it was very uneconomical.

Tables 1 and 2 show the conditions and evaluation results of each Example, and Table 3 shows the conditions and evaluation results of each Comparative Example.

From the above, it was confirmed that according to this example, wet tissues with good texture, excellent wipeability, and resistance to tearing can be obtained even if paper, which is excellent in biodegradability and economic efficiency, is used as the sheet impregnated with the chemical solution. It was done.

10 Belt press section 11 Dewatering roll 12 Yankee dryer 13 Uneven belt 14 Wet paper

Claims (5)

A wet tissue comprising a paper sheet containing at least pulp fibers impregnated with a chemical solution,
The tensile strength of the sheet in the longitudinal and transverse directions when wet is both 2.2 N/25 mm or more,
A wet tissue characterized in that the sheet has a thickness T _m of 160 μm or more and 440 μm or less when a load of 50 gf/cm ² is applied to the sheet using a KES compression tester. When T ₀ is the thickness of the sheet when a load of 0.5 gf/cm ² is applied to the sheet by the KES compression tester, (T ₀ −T _m )/T ₀ is 0.40 or more. Wet tissue according to claim 1, characterized in that: The wet tissue according to claim 1, wherein the sheet has a basis weight in an absolutely dry state of 20 g/m ² or more and 50 g/m ² or less. The wet sheet according to claim 1, wherein the sheet has a thickness T ₀ of 400 μm or more and 800 μm or less when a load of 0.5 gf/cm ² is applied to the sheet by the KES compression tester. Tissue. The wet tissue according to claim 1, wherein the impregnating ratio of the chemical solution into the sheet is 2 times or more and 4 times or less.