JP7629751B2 - Wiping Sheet - Google Patents

Description

The present invention relates to a wiping sheet.

Wet cleaning sheets impregnated with liquids are sometimes used to clean hard surfaces in buildings, such as floors, toilets, kitchens, etc.

Patent Document 1 discloses a water-disintegrable cleaning cloth that includes a water-soluble base sheet and a coating layer formed on at least one surface of the base sheet, with the aim of improving the release and retention of liquid ingredients. The same document also discloses that the coating layer of this cleaning cloth is formed from an aqueous dispersion containing an activator, a thickener, and an organic solvent.

Japanese Patent Application Publication No. 10-251952

In general, when wet sheets are used for cleaning, the liquid agent released from the wet sheets makes it easy to capture particulate dirt such as dust, but the liquid agent can cause fibrous dirt such as hair to stick to the surface being cleaned, making it difficult to capture. On the other hand, if the liquid agent is made highly viscous in order to improve the ability to capture fibrous dirt, the ability to capture fibrous dirt can be improved, but the sheet may feel unpleasant to the touch when it is removed or used. In this way, the technology of Patent Document 1 does not consider at all how to achieve the two opposing properties of improving the ability to capture fibrous dirt such as hair and improving the feel when touching the sheet.

Therefore, the present invention relates to a wiping sheet that combines excellent fiber dirt collection with a pleasant feel.

The present invention relates to a wiping sheet.
The wiping sheet is preferably a fibrous sheet containing pulp and a binder impregnated with an aqueous chemical.
The aqueous agent preferably has a viscosity of 2000 mPa·s or more at 25° C. when measured with a Brookfield viscometer at a rotation speed of 0.3 rpm, and preferably has a viscosity of 1000 mPa·s or less at 25° C. when measured with a Brookfield viscometer at a rotation speed of 60 rpm.
The wiping sheet is preferably water-dispersible.

The present invention provides a wiping sheet that is excellent in both fiber dirt collection and sheet feel.

The wiping sheet of the present invention will be described below based on a preferred embodiment. The wiping sheet of the present invention is a fiber sheet containing pulp and a binder impregnated with an aqueous chemical. In other words, the wiping sheet is a wet sheet in which the aqueous chemical is carried throughout the fiber sheet and is in a wet state at 25°C and 1 atmosphere.

In this specification, wiping includes both cleaning and wiping. Surfaces to be cleaned include hard surfaces such as floors, walls, ceilings, and pillars in buildings, shelves, windowpanes, mirrors, doors, doorknobs, and other fixtures, and other items such as desks, dining tables, kitchens, and toilets, and can also be used to wipe the body, such as hands, feet, fingers, nose, mouth, and the skin surfaces around these surfaces. Typically, wiping is performed by bringing one side of the wiping sheet into surface contact with the surface to be cleaned or wiped. In the following description, unless otherwise specified, wiping of hard surfaces and wiping of the body are collectively referred to simply as "cleaning," and surfaces to be cleaned or wiped are collectively referred to as "surface to be cleaned."

The aqueous chemical impregnated in the wiping sheet is an aqueous liquid containing water. One of the characteristics of this aqueous chemical is that its viscosity is different when measured at a high rotation speed of a rotor in a B-type viscometer, which is a type of viscosity measuring device, and when measured at a low rotation speed.
The inventors conducted extensive research into wet sheets impregnated with aqueous chemicals in order to improve both the fibrous soil collection performance and the feel of the sheet, and found that there is a correlation between the behavior of the wiping sheet during its cleaning operation or at the end of the cleaning operation and the change in viscosity according to the rotation speed of a viscometer. As a result, they found that it is possible to improve both the fibrous soil collection performance and the feel of the sheet.

In detail, during the cleaning operation of the wiping sheet, the sheet is used while applying an external force to move the sheet against the surface to be cleaned; therefore, by configuring the viscosity of the aqueous chemical to be low at this time, the feel of the sheet when it touches the fingers is improved, while also improving the slipperiness of the sheet when in use, thereby improving operability when in use.
On the other hand, when the wiping sheet finishes its cleaning operation, the sheet is either stationary or moving at a slower speed than during the cleaning operation. Therefore, by configuring the viscosity of the aqueous chemical to be high at this time, when the sheet is separated from the surface to be cleaned, fibrous dirt such as hair that is present between the sheet and the surface to be cleaned can be adsorbed onto the sheet by utilizing the viscosity of the aqueous chemical, thereby making it possible to efficiently collect the dirt.
That is, the aqueous agent has a property that the viscosity decreases when an external force is applied and increases when the external force is removed, and one of its characteristics is that it has a higher thixotropy than those conventionally known in the art. The above-mentioned change in viscosity may be either nonlinear or linear.

The viscosity at 25°C at a rotation speed of 60 rpm measured with a B-type viscometer, which is an index of the viscosity of the aqueous chemical during the cleaning operation of the wiping sheet, is preferably 1000 mPa·s or less, more preferably 500 mPa·s or less, and even more preferably 300 mPa·s or less, and 2 mPa·s or more is realistic, and preferably 100 mPa·s or more. With such a viscosity, it is possible to reduce the sliminess and stickiness of the sheet when it touches the fingers, improving the feel of the sheet. In addition, it is possible to improve the slipperiness of the sheet during use, thereby improving the operability during use. The reason for focusing on the rotation speed of 60 rpm mentioned above is that it corresponds to the shear speed during the cleaning operation of the wiping sheet.

In addition, the viscosity at 25°C at a rotation speed of 0.3 rpm measured with a B-type viscometer, which is an index of the viscosity of the aqueous agent at the end of the cleaning operation of the wiping sheet, is preferably 2000 mPa·s or more, more preferably 3000 mPa·s or more, and even more preferably 5000 mPa·s or more. With such a viscosity, when the cleaning operation of the wiping sheet is ended and the wiping sheet is separated from the surface to be cleaned, various types of dirt present between the sheet and the surface to be cleaned can be adsorbed to the sheet side by utilizing the viscosity of the aqueous agent, and not only fine particle dirt but also fibrous dirt such as hair, which was difficult to collect with conventional technology, can be efficiently collected. Generally, fiber sheets containing pulp tend to have a high density of constituent fibers, and tend to have difficulty in collecting fibrous dirt in the gaps between the fibers. Therefore, by expressing such a viscosity characteristic in the aqueous agent, even when a sheet containing pulp and an aqueous agent is used for cleaning or wiping, the aqueous agent can effectively collect fibrous dirt. The reason we focused on the rotation speed of 0.3 rpm mentioned above is because it corresponds to the shear speed of the wiping sheet at the end of the cleaning operation.

From the viewpoint of reducing uneven impregnation of the aqueous chemical during the manufacture of the wiping sheet while maintaining an appropriate moist state of the entire wiping sheet, the viscosity at 25°C at a rotation speed of 0.3 rpm measured with a B-type viscometer is preferably 50,000 mPa·s or less, more preferably 40,000 mPa·s or less, and even more preferably 38,000 mPa·s or less.

The above-mentioned viscosity range can be achieved, for example, by including a specified amount of a water-soluble polymer such as xanthan gum in the aqueous drug. Details of the water-soluble polymer and its content will be described later.

The method for measuring the above-mentioned viscosity is as follows.
Using a B-type viscometer (e.g., TVB-10 type viscometer, manufactured by Toki Sangyo Co., Ltd.), rotor No. M2, M3, M4, rotor rotation speed 0.3 rpm or 60 rpm, measurement is started, and the value 90 seconds after the start of measurement is obtained. This measurement is performed five times under each condition using the same sample, and the arithmetic mean value of the obtained values is the viscosity under each condition of the present invention. In all measurements of the viscosity of the aqueous agent, the liquid temperature is 25°C, and the measurement environment is 24°C, 40% RH. The sample of the aqueous agent subjected to the viscosity measurement is, for example, an extract extracted from the wiping sheet by squeezing, pressing, or solid-liquid separation of the wiping sheet.
In order to set the viscosity of the aqueous chemical within the above-mentioned range, it can be appropriately adjusted, for example, by changing the content of water in the aqueous chemical, or by changing the presence or absence, type and content of additives described below.

The fiber sheet contains pulp. Examples of pulp include bleached wood pulp such as softwood bleached kraft pulp (NBKP), softwood bleached sulfite pulp (NBSP), and hardwood bleached kraft pulp (LBKP); natural pulp such as cotton and hemp; mercerized pulp that has been chemically treated and alkali-swollen, chemically crosslinked pulp with a spiral structure, and microfibrous cellulose. These can be used alone or in combination. Of these, from the viewpoint of achieving both flexibility and strength of the sheet, it is preferable to use at least one of NBKP and NBSP, and it is even more preferable to use both NBKP and NBSP.

The content of pulp in the fiber sheet is preferably 60% by mass or more, more preferably 70% by mass or more, and is preferably 100% by mass or less, more preferably 97% by mass or less, based on the total mass of the fiber sheet in a dry state. In other words, the fiber sheet may be composed only of pulp.

The fiber sheet contains a binder. The binder binds the pulp fibers together, so that when the fiber sheet is impregnated with an aqueous chemical, it exhibits sufficient wet strength and shape retention to withstand use. The binder content is preferably 1% by mass or more, more preferably 3% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total mass of the fiber sheet in a dry state.

Examples of binders include anionic binders, polyvinyl alcohol, starch or its derivatives, etc. Anionic binders are those that easily generate carboxylates in water, and examples of such binders include carboxymethyl cellulose (CMC) or its salts, carboxyethyl cellulose or its salts, and carboxymethylated starch or its salts. These binders can be used alone or in combination.

From the viewpoint of making the wiping sheet water-dispersible and facilitating disposal of the sheet after use, the binder is preferably a water-soluble binder, and more preferably at least one of carboxymethyl cellulose (CMC) or a salt thereof, and polyvinyl alcohol.

From the viewpoint of allowing the wiping sheet to be easily disposed of after use and maintaining the cleanliness of the surrounding environment, it is preferable that the wiping sheet is water-dispersible. In addition, it is preferable that the fiber sheet constituting the wiping sheet is also water-dispersible. Water-dispersible refers to a sheet in which, when the sheet is placed in a large amount of water, the shape of the sheet is distorted and the constituent fibers of the sheet are dispersed in the water, but the shape of the sheet does not collapse when impregnated with an aqueous chemical. In this way, because the sheet has the property of being water-dispersible, when the wiping sheet is disposed of after use in the presence of a large amount of water, such as in a flush toilet, the shape of the sheet easily disintegrates and it becomes possible to flush it down the sewer.

The degree of water dispersibility can be evaluated as the ease of disintegration measured according to JIS P4501. A fiber sheet is water dispersible if the time for disintegration (water disintegration time) measured according to JIS P4501:2006 is less than 100 seconds, and preferably 80 seconds or less. The shorter the water disintegration time, the better the water dispersibility of the sheet. The water disintegration time of the wiping sheet can be the same as that of the above-mentioned fiber sheet. The water disintegration time can be adjusted as appropriate, for example, by using a water-soluble binder or by changing the presence or absence, type and content of additives in the aqueous agent.

The aqueous agent may further contain additives in addition to water depending on the object and use to which the wiping sheet is applied. The additives may include at least one of the following: viscosity adjusters, surfactants, disinfectants, crosslinking agents for binders, water-soluble organic solvents such as monohydric or polyhydric alcohols, chelating agents, electrolytes, dyes, fragrances, antioxidants, and pH adjusters. From the viewpoint of uniform dispersion in the aqueous agent, such additives are preferably water-soluble.

From the viewpoint of easily and efficiently expressing the above-mentioned viscosity characteristics in the aqueous agent, it is preferable that the aqueous agent contains a viscosity modifier. Examples of such viscosity modifiers include water-soluble polymers, and more specifically, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl butyral, dextrin, polyethylene oxide, water-soluble nylon, natural polysaccharides, etc. Natural polysaccharides include sodium alginate, trant gum, guar gum, xanthan gum, gum arabic, carrageenan, galactomannan, gelatin, casein, albumin, and purpuran, as well as salts thereof. These viscosity modifiers can be used alone or in combination as long as they can express the above-mentioned viscosity characteristics.

Of these, it is preferable to use natural polysaccharides as viscosity modifiers, and it is even more preferable to use xanthan gum or a salt thereof, from the viewpoint of improving both operability during use and the feel of the surface to be cleaned after cleaning by adjusting the volatility of the aqueous agent so that the aqueous agent released on the surface to be cleaned remains on the surface to an appropriate extent. Natural polysaccharides such as xanthan gum have the advantage that they can cause the aqueous agent to exhibit the above-mentioned viscosity characteristics while also having a high affinity with pulp, making it difficult to feel the viscosity on the floor surface or palms during wiping, further improving the feel of use.
As shown in the examples described later, from the viewpoint of fully exhibiting the water-disintegrability of the sheet, it is also preferable that the aqueous agent does not contain polyethylene glycol.

When a viscosity modifier is included, from the viewpoint of efficiently expressing the above-mentioned viscosity characteristics and thereby improving operability during use and improving the feel of the surface to be cleaned after cleaning, the content of the viscosity modifier in the aqueous agent is preferably 0.20% by mass or more, more preferably 0.25% by mass or more, even more preferably 0.30% by mass or more, and preferably 0.50% by mass or less, more preferably 0.45% by mass or less, even more preferably 0.40% by mass or less. When two or more types of viscosity modifiers are included, the total amount of the viscosity modifiers is the above-mentioned content.

When xanthan gum or a salt thereof is included as a viscosity modifier, from the same viewpoint, the content of xanthan gum or a salt thereof in the aqueous formulation is preferably 0.20% by mass or more, more preferably 0.25% by mass or more, and preferably 0.50% by mass or less, more preferably 0.40% by mass or less, and even more preferably 0.35% by mass or less.

It is also preferable that the aqueous chemical contains a surfactant as an additive. By including a surfactant, in addition to capturing particulate dirt and fibrous dirt, the ability to remove oily dirt such as sebum, animal fat, and vegetable oil adhering to the surface to be cleaned can be improved.

Examples of the surfactant include ionic surfactants, nonionic surfactants, and amphoteric surfactants. These may be used alone or in combination as long as the effects of the present invention are achieved.
Examples of the ionic surfactant include cationic surfactants such as quaternary ammonium salts, such as cetyl benzalkonium phosphate, benzethonium chloride, benzalkonium chloride, and cetylpyridinium chloride, and anionic surfactants, such as alkylbenzenesulfonic acid.
Examples of nonionic surfactants include polyoxyethylene alkyl ethers, alkyl glucosides, etc. Examples of amphoteric surfactants include alkyl dimethylaminoacetate betaines, alkyl dimethylamine oxides, alkyl carboxybetaines, alkyl sulfobetaines, etc.

When a surfactant is contained in the aqueous agent, the content of the surfactant is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and preferably 3% by mass or less, more preferably 1% by mass, based on the total mass of the aqueous agent, from the viewpoint of achieving both improved dirt capture and removal performance and improved usability. When two or more types of surfactants are contained, the total amount of the surfactants is the above-mentioned content.

It is also preferable that the aqueous agent contains a disinfectant as an additive. By including a disinfectant, it is possible to develop disinfecting performance on the surface to be cleaned after cleaning and to increase the storage stability of the product. Examples of such disinfectants include benzoic acid and its salts, paraoxybenzoic acid esters such as alkyl paraoxybenzoate and benzyl paraoxybenzoate, and phenoxyethanol. These may be used alone or in combination.

The content of the disinfectant is preferably 0.10% by mass or more, more preferably 0.20% by mass or more, and preferably 1.00% by mass or less, more preferably 0.50% by mass or less, based on the total mass of the aqueous drug. When two or more types of disinfectants are contained, the total amount of the disinfectants is the above-mentioned content.

From the viewpoint of achieving both wet strength of the fiber sheet during cleaning and water-disintegratability at the time of disposal, the aqueous agent preferably contains, as an additive, a crosslinking agent for the binder described above.
When an anionic binder such as CMC is used as the binder, the crosslinking agent is preferably a water-soluble salt of a polyvalent metal, more preferably a water-soluble salt of a divalent metal. As the polyvalent metal, one or more metals selected from the group consisting of alkaline earth metals such as calcium, strontium, barium, manganese, zinc, cobalt, and nickel can be used, and preferably the water-soluble salts of calcium and zinc. As these metal salts, the hydroxides, chlorides, sulfates, nitrates, carbonates, formates, acetates, etc. of the above-mentioned metals can be used.

From the viewpoint of achieving a balance between wet strength and water disintegratability, the content of the crosslinking agent in the aqueous agent is preferably 1 mass % or more, more preferably 2 mass % or more, and is preferably 5 mass % or less, more preferably 4 mass % or less, relative to the total mass of the aqueous agent.
The above-mentioned crosslinking agent is added so that the amount of metal ions derived from the crosslinking agent is preferably 0.25 mol or more, more preferably 0.5 mol or more, per 1 mol of carboxyl groups in the anionic binder.

From the viewpoint of simultaneously improving the dirt collection ability and the wet strength of the fiber sheet, the water content of the aqueous agent is preferably 50% by mass or more, more preferably 60% by mass or more, and is preferably 100% by mass or less, more preferably 90% by mass, based on the total mass of the aqueous agent.

From the viewpoint of enhancing dirt collection, the content of the water-soluble organic solvent is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 30% by mass or less, and more preferably 25% by mass or less, based on the total mass of the aqueous agent. When two or more water-soluble organic solvents are used in combination, the content is based on the total mass of these. By having the content of the water-soluble organic solvent in this range, stickiness of the sheet is reduced, and the feeling of use after cleaning is improved.

The aqueous agent preferably has a pH of 3.0 or more, more preferably 3.5 or more, and preferably less than 6.0, more preferably 5.0 or less, at 25°C. This pH level allows the disinfecting performance to be effectively exerted on the surface to be cleaned after cleaning, and also reduces irritation to the skin of the user of the sheet when the aqueous agent comes into contact with the skin.

From the viewpoint of achieving both wet strength and dirt collection performance of the fiber sheet, the impregnation amount of the aqueous chemical is preferably 100% by mass or more, more preferably 180% by mass or more, and is preferably 500% by mass or less, more preferably 250% by mass or less, based on the dry mass of the fiber sheet.

The fiber sheet may be a single-layered sheet or a multi-layered sheet. In addition, one or both sides of the fiber sheet may have a large number of projections and recesses, and a large number of openings penetrating the fiber sheet in the thickness direction may be formed. A multi-layered sheet can be produced, for example, by stacking single-layered sheets and bonding them with a binder or water-soluble adhesive, or by performing a bonding process such as embossing.

As long as the effects of the present invention are achieved, the fiber sheet may contain other fibers other than pulp. Examples of other fibers include polyvinyl alcohol fibers, polyolefin resin fibers such as polyethylene, polyester resin fibers, and synthetic resin fibers using biodegradable resins such as polylactic acid; and regenerated fibers such as rayon, lyocell, and cupra. From the viewpoint of effectively expressing the water dispersibility of the sheet described below, the content of these other fibers is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 0% by mass, based on the total mass of the fiber sheet. In other words, it is even more preferable that the fiber sheet does not contain other fibers.

From the viewpoint of achieving both sheet strength and impregnation with an aqueous chemical, the basis weight of the fiber sheet is preferably ²⁰ g/m2 or more, more preferably 30 g/ ^m2 or more, and is preferably 100 g/m2 or ^less , more preferably 80 g/m2 or ^less .

The wiping sheet may be in the form of, for example, a single sheet having a predetermined dimension. In this case, the single sheets may be manufactured or distributed as a package in which a plurality of stacked sheets are housed in a packaging bag or packaging container. Such a wiping sheet may be held by hand alone or attached to a cleaning tool such as a wiper and is preferably used for wiping hard surfaces such as floors, walls, ceilings, pillars, and other buildings, shelves, window panes, mirrors, doors, doorknobs, and other fixtures, desks, dining tables, kitchens, toilets, and other items. Even when the wiping sheet is held by hand, the sheet can be made to feel good by reducing the sliminess and stickiness of the sheet when it touches the fingers.

The wiping sheet having the above-mentioned configuration can efficiently collect fine particle dirt such as dust and lint by means of the pulp fibers.
In addition, by adjusting the aqueous agent to exhibit the above-mentioned viscosity characteristics, it becomes possible to efficiently capture hair and other fibrous dirt, which was difficult to capture with conventional wet sheets, by adsorbing it to the sheet side. As a result, the sheet has excellent capture capabilities for fine dirt such as dust and lint, and for fibrous dirt such as hair.
In addition, by adjusting the viscosity characteristics of the aqueous chemical to be expressed, the sheet feels good to the touch when it touches the fingers during use by reducing sliminess and stickiness, while also improving the sliding of the sheet against the surface to be cleaned, further improving operability.
Furthermore, by making the wiping sheet water-dispersible, the wiping sheet after use can be easily disposed of by simply flushing it down the drain, improving the cleanliness of the surrounding environment.

When using an aqueous agent to which additives such as a surfactant or disinfectant have been added for the purpose of exerting disinfecting performance on the surface to be cleaned after cleaning, the aqueous agent that does not have the above-mentioned viscosity characteristics may volatilize water and additives early after being released from the wiping sheet and adhering to the surface to be cleaned, and the liquid may not be retained on the surface to an extent that disinfecting performance can be exerted. In this regard, the aqueous agent of the present invention increases in viscosity when the application of external force is released after adhering to the surface to be cleaned, so that the evaporation of water and additives can be appropriately delayed and the amount of liquid and time to exert disinfecting performance can be secured. Therefore, the wiping sheet contains a viscosity adjuster so that the aqueous agent impregnated in the sheet can exert the above-mentioned viscosity characteristics, and also contains a surfactant and a disinfectant in combination, thereby improving the collection ability of various types of dirt such as fine particles and hair, while improving the removal performance and disinfecting performance of oily dirt, while reducing the sliminess and stickiness of the surface to be cleaned when touching the sheet during use and after cleaning, thereby improving the feeling of use.

The wiping sheet can be produced, for example, by the following method.
First, a sheet-shaped pulp aggregate is wet-formed from a dispersion containing pulp, and the pulp aggregate is press-dehydrated or semi-dried. Next, a binder is applied and dried, or the binder is applied and dried to obtain a fiber sheet containing pulp and binder. If necessary, the fiber sheet may be embossed to form an uneven shape. Then, the fiber sheet can be impregnated with an aqueous agent adjusted to exhibit a predetermined viscosity characteristic to produce the fiber sheet. It is preferable to adjust the types and amounts of various additives such as viscosity modifiers and surfactants in the aqueous agent.
Examples of wet paper machines used in wet papermaking include short wire paper machines, fourdrinier paper machines, twin-wire paper machines, on-top paper machines, hybrid paper machines, and cylinder paper machines.
Examples of drying devices used for drying the sheet include a through air dryer and a Yankee dryer.
The fiber sheet can be impregnated with the aqueous agent by, for example, coating with a gravure coater, a die coater, or a spray, or by immersion in a liquid.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above-mentioned embodiments. For example, as is clear from the above description, a method of using a wiping sheet of the above-mentioned embodiment to remove dirt from a surface to be cleaned is also provided. In detail, this method removes dirt such as fibrous dirt present on the surface to be cleaned by contacting one side of the wiping sheet with the surface to be cleaned, while releasing a release liquid from the wiping sheet onto the surface to be cleaned. If necessary, the sheet may be pressed against the surface to be cleaned, or slid or rubbed on the surface to be cleaned while maintaining the contact state of the two surfaces.

The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. In the following table, columns marked with "-" indicate non-containment or non-implementation.

[Examples 1 to 4]
NBKP was used as the pulp. This pulp was dispersed in water to obtain a slurry with a fiber concentration of 2% by mass. This slurry was introduced into a short wire paper machine and wet-laid to obtain a wet paper. A 5% by mass aqueous solution of CMC sodium salt (manufactured by Nippon Paper Industries Co., Ltd., Sunrose (registered trademark), degree of etherification: 0.9) was sprayed and applied as a binder to one side of the wet paper. This wet paper was dried with a dryer to obtain a single-layered paper with the binder applied to one side. The basis weight of the obtained single-layered paper was 40 g/m ^2. The obtained single-layered papers were stacked so that the binder-coated surfaces of the papers faced each other, and embossed in that state to obtain a water-dispersible fiber sheet with a basis weight of 80 g/m ^2. The obtained fiber sheet had dimensions of 250 mm long x 250 mm wide. The binder content was 5% by mass with respect to the total mass of the fiber sheet. This fiber sheet was water-dispersible.

Next, the obtained fiber sheet was impregnated by spray application with an aqueous agent containing xanthan gum (manufactured by CP Kelco A Huber Company (USA), product name: KELTROL CG LAX-T) as a viscosity modifier, which is a type of additive, in the amount shown in Table 1 below, to obtain the desired wiping sheet. The impregnated amount of the aqueous agent was 210% by mass based on the dry mass of the fiber sheet.
The aqueous chemical contains, in addition to the viscosity adjuster described above, 0.2% by mass of a nonionic surfactant (alkyl glucoside) and 3% by mass of a cross-linking agent (a water-soluble divalent metal salt containing Ca, Zn, etc.), and is an aqueous solution adjusted so that these components are released onto the surface to be cleaned.

Comparative Example 1
The intended wiping sheet was obtained in the same manner as in Example 1, except that the fiber sheet was impregnated with an aqueous agent not containing a viscosity modifier.

Comparative Examples 2 to 4
The intended wiping sheets were obtained in the same manner as in Example 1, except that the fiber sheet was impregnated with an aqueous agent adjusted so as to release the amount of xanthan gum used in Example 1 shown in Table 1 below. The viscosity at 25°C of the aqueous agent in each comparative example was as shown in Table 1 below.

Comparative Example 5
A wiping sheet was obtained in the same manner as in Example 1, except that polyethylene glycol (Meisei Chemical Industry Co., Ltd., Alkox E-45 (trade name), polymerization degree 600,000) was used instead of xanthan gum, and an aqueous drug adjusted to release the amount shown in Table 1 below was impregnated into the fiber sheet.

[Evaluation of Viscosity of Aqueous Drugs]
The wiping sheets of the Examples and Comparative Examples were squeezed by hand to obtain extracts, and the viscosities were measured at 25° C. under the above-mentioned conditions when the rotor rotation speed was set to 0.3 rpm (low speed condition) or 60 rpm (high speed condition). The results are shown in Table 1 below.

[Evaluation of fiber soil collection ability]
Ten hairs of 10 cm were scattered as fiber dirt on a floor surface of a flooring (manufactured by Kitakei Co., Ltd., product name: DAG Floor, dimensions: length 900 mm x width 900 mm). Next, one wiping sheet of the Example and Comparative Example was placed so as to cover the entire area of the hair scattering, and the sheet was subjected to a load of 60 g/cm ² and cleaned once along the length direction in an area of 400 mm long x 150 mm wide, including the entire area of the hair scattering. After that, the sheet was lifted vertically from the floor surface, and the number of hairs collected by the sheet was counted, and the percentage of the number of hairs collected to the number of scattered hairs was taken as the collection rate (%). This operation was performed independently eight times to calculate the arithmetic average value of the collection rate obtained, and the arithmetic average value was used to evaluate the collection rate according to the following criteria. The results are shown in Table 1 below.

<Evaluation criteria for fiber dirt collection ability>
A: The arithmetic mean value of the collection rate is 50% or more, and the collection performance of fiber dirt is good.
B: The arithmetic mean value of the collection rate is less than 50%, and the collection performance of fiber dirt is poor.

[Evaluation of seat feel]
The feel of the wiping sheets of the Examples and Comparative Examples when touched by hand was evaluated according to the following criteria. The results are shown in Table 1 below.

<Evaluation criteria for seat feel>
A: No sliminess, stickiness, stringiness or other stickiness is perceived, and the sheet has an excellent feel.
B: At least one of the following is perceived: sliminess, stickiness, stringiness, etc., and the feel of the sheet is poor.

[Evaluation of usability during cleaning]
The wiping sheets of the Examples and Comparative Examples were used to clean a surface to be cleaned (a hardwood floor), and the slipperiness of the sheet during cleaning and the feel of the surface to be cleaned after cleaning were manually evaluated according to the following criteria. The results are shown in Table 1 below.

<Evaluation criteria for usability when cleaning>
A: The sheet slides smoothly during cleaning, and the surface to be cleaned feels smooth after cleaning, providing an excellent feel when used.
B: The sheet did not slide well during cleaning, or the surface to be cleaned felt slimy or sticky after cleaning, and the feeling of use was poor.

[Evaluation of Water Dispersibility]
The wiping sheets of the examples and comparative examples were evaluated for water dispersibility (water disintegrability) according to JIS P4501. A 300 mL beaker containing 300 mL of water (water temperature 20±5° C.) was placed on a magnetic stirrer, and the rotation speed of the rotor (disk-shaped with a diameter of 35 mm and a thickness of 12 mm) was adjusted to 600±10 rotations/min. A fiber sheet having a planar dimension of 70 mm×60 mm was placed therein, and measurement with a stopwatch was started. The stopwatch was stopped when the rotation speed of the rotor recovered to 540 rotations, and the time was measured in 1 second units. This measurement was performed five times, and the arithmetic average value was taken as the water disintegration time (seconds).

<Evaluation Criteria for Water Dispersibility>
If the water dissolution time was less than 100 seconds, the water dispersibility was judged to be good (indicated by "A" in the table), and if the water dissolution time was 100 seconds or more, the water dispersibility was judged to be poor (indicated by "B" in the table). The results are shown in Table 1 below.

[Evaluation of Wet Strength of Sheet]
The wet strength of the wiping sheets of the examples and comparative examples was measured according to the following method in accordance with JIS P8113. First, the wiping sheet to be measured was cut into a length of 70 mm x width of 25 mm with a dumbbell cutter in a wet state to obtain a test piece. Next, the test piece was attached to a chuck of a tensile tester (Shimadzu Autograph AG-1kN) with a chuck distance of 50 mm so that the longitudinal direction of the test piece coincides with the tensile direction without tension. Then, the test piece attached to the chuck was pulled at a tensile speed of 300 mm/min, and the maximum strength (unit: cN/25 mm) until the test piece broke was measured. This measurement was performed 10 times for one measurement object, and the arithmetic average of the measured values was taken as the wet tensile strength of the measurement object. Based on the value of this wet tensile strength, the wet strength was evaluated according to the following criteria. The results are shown in Table 1 below.

<Wet strength evaluation criteria>
A: Wet tensile strength is 400 cN/25 mm or more, and has high wet strength sufficient for practical use.
B: The wet tensile strength is less than 400 cN/25 mm, and the wet strength is unreliable for practical use.

[Evaluation of impregnation of aqueous chemicals during sheet production]
About 12 mL of the aqueous chemicals used in the Examples and Comparative Examples were dropped onto the dry fiber sheet (basis weight 80 g/ ^m2 ) produced by the above-mentioned method using a dropper, and the sheet was left to stand for one day. The impregnation of the sheet was evaluated visually and by touch according to the following criteria. The results are shown in Table 1 below.

<Evaluation Criteria for Impregnation>
A: The sheet is entirely impregnated with the aqueous chemical, and the impregnation is good.
B: The aqueous chemical does not spread over the entire sheet and the impregnation state is uneven, or droplets of the aqueous chemical are present on the sheet, and the impregnation is poor.

As shown in Table 1, the wiping sheets of the examples impregnated with an aqueous agent adjusted to have predetermined viscosity characteristics under low and high speed conditions are superior to those of the comparative examples in terms of both the ability to collect fiber dirt such as hair and the feel of the sheet. In addition, the impregnation of the aqueous agent during sheet production is good, resulting in excellent production efficiency and a sheet that combines high levels of usability, water dispersibility, and wet strength.

On the other hand, the wiping sheet of Comparative Example 5, which was impregnated with an aqueous agent containing polyethylene glycol, was water-dispersible as a fiber sheet itself, but was not water-dispersible as a wiping sheet. This is thought to be because the polyethylene glycol unintentionally crosslinked the pulp fibers, making them non-water-dispersible.

Claims (5)

A wet-processed fiber sheet containing pulp and a binder is impregnated with an aqueous chemical;
The aqueous chemical is impregnated in an amount of 100% by mass or more and 500% by mass or less based on the dry mass of the fiber sheet,
The aqueous drug is
The viscosity at 25°C measured with a B-type viscometer at a rotation speed of 0.3 rpm is 2000 mPa s or more,
The viscosity at 25° C. measured with a B-type viscometer at a rotation speed of 60 rpm is 1000 mPa s or less,
Contains xanthan gum or a salt of xanthan gum in an amount of 0.20% by mass or more and 0.50% by mass or less as a viscosity modifier ;
Contains a surfactant in an amount of 0.05% by mass or more and 3% by mass or less,
The surfactant comprises a nonionic surfactant,
Contains a crosslinking agent in an amount of 1% by mass or more and 5% by mass or less;
A wiping sheet having a time required for easy disentanglement measured in accordance with JIS P4501:2006 of less than 100 seconds. The wiping sheet according to claim 1 , wherein the binder comprises one or more selected from the group consisting of carboxymethyl cellulose or a salt of carboxymethyl cellulose , and polyvinyl alcohol. The wiping sheet according to claim 1 or 2, which is used for wiping the body. The wiping sheet according to claim 1 or 2, which is used for cleaning hard surfaces. The wiping sheet according to any one of claims 1 to 4, which is used by being held by hand.