JP7837658B2 - Cleansing wipes - Google Patents

Description

This invention relates to a cleaning sheet in which a base sheet is impregnated with an aqueous composition containing a preservative enhancer and a solubilizer.

Traditionally, wet-type cleansing wipes have been used to facilitate the wiping away of dirt during diaper changes for infants and those receiving care, or to wipe away dirt from hands and bodies. Wet-type cleansing wipes are typically manufactured by impregnating a base sheet with an aqueous composition containing antibacterial agents in purified water.

The aforementioned aqueous composition should ideally contain a low amount of antibacterial agents and other substances in the purified water to reduce skin irritation. In particular, for cleansing wipes used by infants and elderly people with sensitive skin, it is desirable that the aqueous composition impregnates the wipes with the lowest possible amount of irritating ingredients and a high concentration of purified water. On the other hand, cleansing wipes impregnated with an aqueous composition with a high concentration of purified water may experience a decrease in storage stability due to the growth of bacteria and mold over extended storage periods.

Patent documents 1 to 3 below disclose aqueous solutions containing antibacterial agents and the like.
Patent Document 1, described below, states that parabens (parahydroxybenzoic acid esters), which have been widely used as antibacterial and preservative agents in cosmetics and the like, require the addition of solubilizers such as surfactants, but that the antibacterial and preservative power of parabens is significantly reduced when solubilizers are added. Therefore, Patent Document 1 discloses a topical skin preparation that does not contain parabens, in which component (A) is 0.2% by mass or more of 2,2-bis(hydroxymethyl)propionic acid n-hexyl, and component (B) is at least twice the amount of C6-C8 alkyl glyceryl ether and/or C8-C12 fatty acid glyceryl ester. Caprylic acid glyceryl is given as an example of the fatty acid glyceryl ester.

Patent Document 2 discloses a foaming antimicrobial skin detergent as a personal care composition, which does not contain triclosan, a substance of environmental sustainability and health concern, and includes a cationic active ingredient, a cationic compatible surfactant, a foam promoter, a foam structure strengthening agent, and a skin modifier that reduces irritation to mammalian skin tissue. Glyceryl caprate is cited as the foam promoter. Patent Document 3 discloses a preservative for hand towels or wet tissues containing a glycerin fatty acid ester and a quaternary ammonium salt.

Patent documents 4 to 6 below disclose cleaning sheets and the like impregnated with aqueous solution compositions.
Patent Document 4 discloses a baby wipe sheet for wiping the bottom of infants, in which a nonwoven fabric sheet is impregnated with a cleaning agent. The purified water concentration in the cleaning agent is in the range of 99.80 to 99.90% by weight, and the cleaning agent contains benzalkonium chloride, iodide propynyl butylcarbamate, and propylene glycol or 1,3-butylene glycol as antiseptics and preservatives. It is also stated that such a wipe sheet can suppress skin irritation.

Patent Document 5 discloses a water-soluble composition for impregnating fiber sheets, comprising a mixture of polyaminopropyl biguanide and a quaternary ammonium salt, sodium benzoate, citric acid, disodium ethylenediaminetetraacetate, and a nonionic surfactant, with a pH of 3.5 to 4.5, and a fiber sheet impregnated with this water-soluble composition. Patent Document 6 discloses a wet sheet impregnated with a base sheet containing a liquid formulation comprising lactic acid, citric acid or salts thereof, a quaternary ammonium salt-type surfactant, and water, but without ethanol, and with a pH of 3.0 or higher and less than 6.0 at 25°C.

Patent No. 4927986 Patent No. 6431180 Japanese Patent Publication No. 2021-003399 Patent No. 5876981 Patent No. 5845098 Japanese Patent Publication No. 2020-199090

The topical skin preparations disclosed in Patent Document 1 are formulated to exert antibacterial and preservative effects in solutions with high concentrations of additive components, such as creams, lotions, and emulsions. Therefore, it is necessary to include a relatively large amount of antibacterial and preservative agents in the topical skin preparations. In the foaming antibacterial skin detergent disclosed in Patent Document 2, glyceryl caprate is included as a foam enhancer, along with foam structure strengthening agents such as polyethylene glycol (PEG) 8000, to provide sufficient foam volume and a high-density, stable foam structure during washing. Furthermore, in the formulation examples of this skin detergent, additive components other than pure water are included in large quantities, approximately 15-20% by weight.

The examples in Patent Document 3 suggest that the antibacterial activity is insufficient when the preservative component is only glyceryl caprate. Therefore, it is assumed that the antibacterial agent in the disclosed preservative is mainly a quaternary ammonium salt such as benzalkonium chloride. However, if the antibacterial agent is only benzalkonium chloride, the antibacterial activity decreases in the weakly acidic pH range, and if the antibacterial agent is substantially a single component, there is a risk that it will not exhibit sufficient antibacterial effect due to the presence of bacterial species resistant to that antibacterial agent. In the cleaning sheet disclosed in Patent Document 4, propynyl iodide butylcarbamate is contained as a bactericidal preservative in the impregnated cleaning agent, but a cleaning sheet that does not contain this component is desired. Furthermore, improved mold resistance is also desired in such a cleaning sheet.

The water-soluble composition for impregnating fiber sheets disclosed in Patent Document 5 contains sodium benzoate as a bactericidal and preservative agent. Since sodium benzoate effectively exhibits antibacterial properties in a weakly acidic range, multiple pH adjusters are added to adjust the pH of the water-soluble composition. Furthermore, nonionic surfactants are added to reduce skin irritation, resulting in a large number of additive components. Patent Document 6 discloses a liquid formulation for impregnating wet wipes, describing a blend of lactic acid, citric acid, etc., in amounts of 3 to 10 times the weight of a quaternary ammonium salt type surfactant. Therefore, the concentration of purified water in the liquid formulation becomes relatively low, and the document states that a purified water concentration of 97.0 to 99.7% by mass is preferable. While the liquid formulation describes the blending of lactic acid, quaternary ammonium salt type surfactant, etc., as disinfectants and evaluates their antibacterial properties, the evaluation of their antifungal properties is not described.

When multiple preservatives are added to improve both the antibacterial and antifungal properties of the aqueous composition impregnated into the cleaning sheets, it generally becomes difficult to maintain a high concentration of purified water. Furthermore, to reduce the skin irritation of the cleaning sheets, it is desirable to maintain a high concentration of purified water and adjust the pH to a weakly acidic range. However, in this case, the addition of a pH adjuster is generally necessary, and there is a problem that the antibacterial properties decrease depending on the type of antibacterial agent at a weakly acidic pH.
The present invention has been made in view of these circumstances, and aims to provide a cleansing sheet that can be suitably used on infants with delicate skin and elderly people with sensitive skin by selectively incorporating a specific preservative enhancer into an aqueous composition impregnated into a base sheet, thereby improving antibacterial and antifungal properties, and by maintaining a high concentration of purified water and maintaining a slightly acidic pH.

In view of the above-mentioned prior art, the present inventors have, in order to improve the shelf life of an aqueous composition for impregnation of a cleaning sheet, used a combination of benzalkonium chloride, which may be affected by pH, and polyaminopropyl biguanide hydrochloride, which is less affected by pH, as antibacterial agents, and also included glyceryl caprate as an antifungal agent, and a solubilizer based on the formulation of glyceryl caprate, and further, in order to suppress skin irritation, the concentration of purified water in the aqueous composition is maintained at a high concentration, and predetermined amounts of benzalkonium chloride and polyaminopropyl biguanide hydrochloride are included, respectively, to enable the pH of the aqueous composition to be kept in the weakly acidic range,
We discovered that it is possible to obtain a cleansing sheet that has excellent storage stability and further reduces skin irritation, which led to the completion of the present invention.
In other words, the gist of the present invention is the invention described in (1) to (8) below.

(1) A cleaning sheet comprising a base sheet made of woven or nonwoven fabric impregnated with an aqueous composition containing a preservative enhancer and a solubilizer,
The aforementioned aqueous composition contains, in purified water, benzalkonium chloride and polyaminopropyl biguanide hydrochloride as preservatives, which are antimicrobial components, and glyceryl caprate as an antifungal component, and a solvent that solubilizes glyceryl caprate as a solubilizer.
In the aqueous composition, the content of benzalkonium chloride (b1) is 0.030% by mass or more and 0.050% by mass or less, the content of polyaminopropyl biguanide hydrochloride (b2) is 0.025% by mass or more and 0.070% by mass or less, and the content of glyceryl caprate (c1) is 0.003% by mass or more and 0.050% by mass or less.
The pH of the aqueous phase in the aforementioned cleaning sheet is weakly acidic.
Furthermore, the cleaning sheet is characterized in that the concentration of purified water in the aqueous composition is 99.85% by mass or more and 99.92% by mass or less.

(2) The cleaning sheet according to (1), wherein the total amount (b1 + b2) of the content of benzalkonium chloride (b1) and the content of polyaminopropyl biguanide hydrochloride (b2) in the aqueous composition is 0.060% by mass or more and 0.105% by mass or less, and the mass ratio (b2/b1) of the content of polyaminopropyl biguanide hydrochloride (b2) to the content of benzalkonium chloride (b1) is 0.625 or more and 2.00 or less.
(3) The cleaning sheet according to (1) or (2) above, wherein the mass ratio (c1/(b1+b2)) of the content of glyceryl caprate, which is an antifungal agent component, in the aqueous composition to the total amount (b1+b2) of the content of benzalkonium chloride, which is an antibacterial agent component, and the content of polyaminopropyl biguanide hydrochloride, which is an antibacterial agent component, is 0.035 or more and 0.833 or less.

(4) The cleaning sheet according to any one of (1) to (3), wherein the mass ratio (d1/c1) of the content of the solvent for solubilizing glyceryl caprate (d1) to the content of the antifungal agent component glyceryl caprate (c1) in the aqueous composition is 0.60 or more and 2.14 or less.
(5) The solvent in the aqueous composition that solubilizes glyceryl caprate is a polyether that is liquid at room temperature of 15 to 25°C and has OH-terminated groups.
A cleaning sheet as described in any of (1) to (4) above.

(6) The cleaning sheet according to any one of (1) to (5), wherein the solvent for solubilizing glyceryl caprate in the aqueous composition is polyethylene glycol having a number average molecular weight of 100 or more and 600 or less.
(7) The cleaning sheet according to any one of (1) to (6), wherein the pH of the aqueous phase portion of the cleaning sheet at 25°C is 6.1 or more and 6.6 or less.
(8) The cleansing sheet according to any one of (1) to (7) above, wherein the cleansing sheet is for wiping the bottom of an infant or for wiping the body of a sick person, an elderly person, or an infant.

The cleaning sheet of the present invention comprises a base sheet made of woven or nonwoven fabric impregnated with an aqueous composition, the aqueous composition containing specific amounts of benzalkonium chloride and polyaminopropyl biguanide hydrochloride, which are antibacterial agents, and glyceryl caprate, which is an antifungal agent, as preservatives. Therefore, the cleaning sheet of the present invention has improved storage stability by enhancing both antibacterial and antifungal properties.
Furthermore, in the present invention, the content of preservatives and solubilizers in the impregnated aqueous composition is kept to a minimum, thereby increasing the concentration of purified water. In addition, predetermined amounts of benzalkonium chloride and polyaminopropyl biguanide hydrochloride are contained, and the pH is maintained in the weakly acidic range, thereby reducing skin irritation caused by the cleansing sheet.

The cleaning sheet of the present invention will be described below.
The present invention provides a cleaning sheet comprising a base sheet made of woven or nonwoven fabric impregnated with an aqueous composition containing a preservative enhancer and a solubilizer,
The aforementioned aqueous composition contains, in purified water, benzalkonium chloride and polyaminopropyl biguanide hydrochloride as preservatives, and glyceryl caprate as an antifungal agent.
Furthermore, it contains a solvent that solubilizes glyceryl caprate as a solubilizing agent.
The aqueous composition is characterized in that the content of benzalkonium chloride (b1) is 0.030% by mass or more and 0.050% by mass or less, the content of polyaminopropyl biguanide hydrochloride (b2) is 0.025% by mass or more and 0.070% by mass or less, and the content of glyceryl caprate (c1) is 0.003% by mass or more and 0.050% by mass or less, the pH of the aqueous phase of the cleaning sheet is weakly acidic, and furthermore, the concentration of purified water in the aqueous composition is 99.85% by mass or more and 99.92% by mass or less.
The cleaning sheet of the present invention will be described in detail below, divided into (1) an aqueous composition, (2) a base sheet, and (3) a cleaning sheet.

(1) Aqueous Composition (1-1) Purified Water The purified water used in the aqueous composition is preferably purified by using ordinary water such as tap water, and after pretreatment as necessary, by one or more methods selected from ion exchange, distillation, filtration, etc., and more preferably by sterilization treatment using an ultraviolet sterilization device. Examples of water sterilization treatments include ultraviolet sterilization, thermal sterilization, ozone water sterilization, and chlorine-based sterilization, but ultraviolet sterilization is preferred as it does not require large equipment or a large amount of heat and does not affect water quality. The purified water obtained by the above means preferably has an electrical conductivity of 1 μS/cm or less at 25°C after purification, or after purification and sterilization treatment. Electrical conductivity indicates how easily electricity is conducted in an aqueous solution, and is the reciprocal of the electrical resistance of the solution. Electrical conductivity increases as the amount of ionic impurities increases.

(1-2) Preservatives When using cleansing sheets for wiping the bottoms of infants or for wiping the bodies of sick people, the elderly, or infants, it is preferable to have a higher concentration of purified water in the aqueous composition impregnated into the cleansing sheets in order to reduce skin irritation. On the other hand, aqueous compositions with a higher concentration of purified water are more prone to bacterial and mold growth during storage, which can lead to storage problems. Therefore, in order to minimize skin irritation by keeping the concentration of preservatives in the aqueous composition as low as possible and to enable long-term storage, the selection of preservatives and the determination of their content are extremely important.

Various antibacterial agents are known as preservatives, but there is a tendency to avoid the use of parabens, which have been widely used until now. Therefore, in the present invention, benzalkonium chloride and polyaminopropyl biguanide hydrochloride, which are antibacterial components, and glyceryl caprate, which is an antifungal component, are used as preservatives, all of which are used in cosmetics.
In the present invention, "antibacterial agent component" means a component that primarily exhibits antibacterial properties, and "fungal agent component" means a component that primarily exhibits fungicidal properties.

While benzalkonium chloride is listed as an antibacterial agent in the list of preservatives permissible in cosmetics (positive list), it is desirable to reduce its content. In formulations consisting solely of benzalkonium chloride, the antibacterial activity may decrease in the weakly acidic pH range, and the antibacterial effect may not be fully realized due to the presence of bacterial species resistant to the agent. Therefore, since the use of at least two antibacterial agents is preferable, this invention uses benzalkonium chloride in combination with polyaminopropyl biguanide hydrochloride, which exhibits less reduction in antibacterial activity with pH changes. This combination improves antibacterial activity, and by adjusting the ratio of benzalkonium chloride and polyaminopropyl biguanide hydrochloride, the pH of the aqueous composition can be adjusted to a weakly acidic pH with low skin irritation.

When selecting only benzalkonium chloride and polyaminopropyl biguanide hydrochloride, which are antibacterial agents, as preservatives, sufficient antifungal properties cannot be expected. Therefore, by combining them with glyceryl caprate, an antifungal agent, it is possible to improve both antibacterial and antifungal properties. Furthermore, when including glyceryl caprate in an aqueous composition, since this component has low solubility in aqueous solutions, it is necessary to include a solvent that solubilizes glyceryl caprate as a solubilizing agent.

By using benzalkonium chloride and polyaminopropyl biguanide hydrochloride in combination as antibacterial agents, it is possible to reduce the amount of benzalkonium chloride. Thus, by incorporating small amounts of benzalkonium chloride and polyaminopropyl biguanide hydrochloride into the aqueous composition to improve its antibacterial properties, and further incorporating small amounts of glyceryl caprate to improve its antifungal properties, the present invention provides an aqueous composition with improved storage stability and a slightly acidic pH, resulting in a composition with low irritation to human skin.

The preservatives and solubilizers contained in the aqueous composition are described below.
(1-3) Components in preservatives (i) Benzalkonium chloride Benzalkonium chloride, which is widely used as an antibacterial agent in the cosmetics field, has the chemical name alkyldimethylbenzylammonium chloride and is represented by the following chemical formula (1).
[RC ₆ H ₅ CH ₂ N ⁺ (CH ₃ ) ₂ ]Cl ^-・・・・・・・・・・・・(1)
The benzalkonium chloride represented by the above chemical formula (1) is a mixture _{in which} some or all of the alkyl groups (R) consist of alkyl groups having 8 to 18 carbon atoms ( _C8H17 to _C18H37 ).

Benzalkonium chloride, in its diluted aqueous solution, is weakly alkaline and exhibits excellent bactericidal properties in a weakly alkaline environment. However, it is known that its bactericidal properties decrease when the pH is adjusted to a neutral or weakly acidic aqueous solution. For example, using the carbolic coefficient (a numerical value indicating how many times more bactericidal a substance is compared to carbolic acid) for commercially available benzalkonium chloride, the relationship between pH and bactericidal properties is known to decrease at around room temperature: at pH 7, the bactericidal properties at pH 9 and 11 are approximately 0.86 and 0.54 times lower than at pH 9 and 11, respectively; and at pH 5, the bactericidal properties are approximately 0.78 and 0.49 times lower than at pH 9 and 11, respectively.

(ii) Polyaminopropyl biguanide hydrochloride Polyaminopropyl biguanide is a cationic polymer with numerous positive charges in its molecule, represented by the following chemical formula (2).
[-NH-C(=NH)-NH-C(=NH) -NH-(CH ₂ ) ₃ -] _n ...(2)
Polyaminopropyl biguanide is known to exist in the form of inorganic salts such as hydrochloride and organic salts such as fumarate. When used as an antibacterial agent, it can be used as polyaminopropyl biguanide or its inorganic salt, but in the present invention, polyaminopropyl biguanide hydrochloride is preferred.

Polyaminopropyl biguanide hydrochloride has high solubility in water and maintains stable antibacterial activity over a wide temperature and pH range. Furthermore, while polyaminopropyl biguanide hydrochloride exhibits antibacterial activity against bacteria such as E. coli, Staphylococcus aureus, and Pseudomonas aeruginosa, thus possessing a broad antibacterial spectrum against bacteria, it is known to have relatively low antifungal activity against fungi such as Candida and Aspergillus niger.
In the above chemical formula (2), the degree of polymerization n of polyaminopropyl biguanide is preferably 5 to 50, and more preferably 10 to 20. Furthermore, the weight-average molecular weight of polyaminopropyl biguanide is preferably 800 to 8000, and more preferably 2000 to 3000. The weight-average molecular weight (Mw) can be determined by known measurement methods.

(iii) Glyceryl Caprate Glyceryl caprate is a monoester of capric acid, a saturated fatty acid with 10 carbon atoms, and glycerol, and has two isomers, represented by the following chemical formulas (3) and (4).
_CH2OH -CHOH- _CH2 -O-CO-( _CH2 ) _8CH3 ...( ₃ )
_CH2OH -CH-O-(CO-( _CH2 ) _{8CH3 ) -CH2OH} ...(4)
Monoesters of fatty acids with 8, 10, and 12 carbon atoms and glycerin are known. Among these, considering the synergistic effect of antibacterial and antifungal properties when used in combination with other antibacterial components, solubility in aqueous solutions using solubilizers, antifungal effect at low concentrations, and ease of availability, glyceryl caprate, which is a monoester of capric acid with 10 carbon atoms and glycerin, is preferred as the antifungal component.

Glyceryl caprate is a nonionic surfactant generally synthesized by esterifying naturally derived vegetable oil fatty acids, such as soybean oil, with glycerin. Glyceryl caprate is solid at room temperature and is lipophilic, so its solubility in aqueous solutions is 126 mg/liter at 25°C. While glyceryl caprate has primarily been used in oily and emulsified cosmetics, it can also be incorporated into water-based products when used in combination with a solubilizer.

(1-4) Content of each component of the preservative enhancer In order to improve the storage stability of the cleaning sheet of the present invention and reduce skin irritation, the blending range of each component of the preservative enhancer in the aqueous composition impregnated into the cleaning sheet must be as follows.

The content of benzalkonium chloride, an antibacterial agent component (b1), is 0.030% by mass or more and 0.050% by mass or less, preferably 0.035% by mass or more and 0.050% by mass or less. The content of polyaminopropyl biguanide hydrochloride, an antibacterial agent component (b2), is 0.025% by mass or more and 0.070% by mass or less, preferably 0.035% by mass or more and 0.070% by mass or less. The content of glyceryl caprate, an antifungal agent component (c1), is 0.003% by mass or more and 0.050% by mass or less, preferably 0.0035% by mass or more and 0.050% by mass or less.
In the aqueous composition, benzalkonium chloride, polyaminopropyl biguanide hydrochloride, and glyceryl caprate can effectively exhibit antibacterial and antifungal properties, respectively, at the aforementioned concentrations.

(1-5) Content ratio of each component of the preservative improving agent In order to further consider the storage stability and reduction of skin irritation of the cleaning sheet of the present invention, it is preferable that the content ratio of each component of the preservative improving agent in the aqueous composition impregnated into the cleaning sheet be as follows.
Considering antibacterial properties, the total amount of benzalkonium chloride (b1) and polyaminopropyl biguanide hydrochloride (b2) (b1 + b2) is preferably 0.06% by mass or more and 0.105% by mass or less. Considering the pH of the aqueous composition to reduce skin irritation, the mass ratio of polyaminopropyl biguanide hydrochloride (b2) to benzalkonium chloride (b1) (b2/b1) is preferably 0.625 or more and 2.00 or less.

Furthermore, considering the improvement of both the antibacterial and antifungal properties of the aqueous composition, the mass ratio (c1/(b1+b2)) of the content of the antifungal agent component, glyceryl caprate (c1), to the total amount (b1+b2) of the antibacterial agents, benzalkonium chloride (b1) and polyaminopropyl biguanide hydrochloride (b2), is preferably 0.035 or more and 0.833 or less.

(1-6) Solubilizers As described above, glyceryl caprate has extremely low solubility in aqueous solutions. Therefore, in order to uniformly dissolve glyceryl caprate in the aqueous composition, it is necessary to include a solvent that solubilizes glyceryl caprate. The solvent is not particularly limited as long as it can uniformly dissolve glyceryl caprate in the aqueous composition. However, considering solubility with glyceryl caprate, water solubility, content, and safety, a polyether that is liquid at room temperature (15-25°C) and has OH-terminated groups is preferred. Examples of such polyethers include polyethylene glycol obtained by the addition reaction of ethylene oxide, as well as polyethers obtained by the addition reaction of ethylene oxide with propylene oxide or 1,3-butylene oxide. Since these polyethers all have ether bonds and OH bonds at their ends, they are excellent solvents, heat stable, and relatively inert to many chemicals.

Among the polyethers mentioned above, polyethylene glycol with a number average molecular weight of 100 to 600 is more preferred, and polyethylene glycol with a number average molecular weight of 200 to 300 is even more preferred, considering its liquid state at room temperature, reduced irritation, and the solubilization of glyceryl caprate. Polyethylene glycol with a number average molecular weight of 100 to 600 has a low vapor pressure and can suppress stickiness when dissolved in an aqueous solution at low concentrations. Furthermore, in order to reduce skin irritation, it is preferable that the polyether does not contain lower alcohols such as methanol or ethanol.
To maintain solubilization in aqueous compositions, prevent stickiness, and maintain a high concentration of purified water, the mass ratio (d1/c1) of the solvent content (d1) to the capric acid content (c1) in the aqueous composition is preferably 0.60 or more and 2.14 or less.

(1-7) Purified water concentration and pH value in aqueous composition The concentration of purified water in the aqueous composition is 99.85% by mass or more and 99.92% by mass or less. The aqueous composition contains a preservative and a solubilizer in the purified water, but as described above, by keeping the amount of each small, it is possible to maintain a high concentration of purified water and reduce skin irritation.

Furthermore, considering the need to reduce skin irritation to infants, the elderly, and people with sensitive skin, and the fact that the pH of the skin surface is weakly acidic (as will be discussed later), the pH of the aqueous composition at 25°C is preferably 3.47 to 3.83. The pH value of the aqueous composition is measured using a HORIBA pH METER F-21 manufactured by HORIBA, Ltd. When an aqueous composition within this pH range is impregnated into a nonwoven fabric sheet obtained from, for example, a composite fiber consisting of polyethylene terephthalate fibers and rayon fibers, it becomes possible to maintain the pH of the aqueous phase in the resulting cleansing sheet at a weakly acidic level of approximately 6.1 to 6.6, thereby reducing skin irritation when wiping the body with the cleansing sheet.

(1-8) Other Additives It is also possible to include small amounts of other additives in the aqueous composition, as long as they do not impair the effect of the preservatives. Examples of such additives include hyaluronic acid and collagen, which have moisturizing properties.

(2) Base Sheet The base sheet used in the cleaning sheet of the present invention can be either a woven fabric or a nonwoven fabric, but the use of a nonwoven fabric is preferred. A nonwoven fabric is a sheet in which fibers are intertwined without weaving, and specifically, fibers are bonded or intertwined together by heat, physical or chemical action to form a sheet. Examples of materials for woven or nonwoven fabrics include polypropylene fibers, polyethylene terephthalate fibers, polyamide fibers, rayon fibers, acrylic fibers, polyurethane fibers, pulp fibers (including paper), and composite fibers made of two or more of these, but the use of composite fibers is preferred in order to impart desirable functions to the base sheet.

When using composite fibers, it is preferable that they contain rayon fibers, which have high hygroscopicity and a pleasant feel against the skin. A preferred composite fiber is one composed of polyethylene terephthalate fibers and rayon fibers, in which case it is more preferable that the composite fiber contains 40 to 60% by mass of rayon fibers. Another preferred composite fiber is one composed of pulp fibers and rayon fibers, in which case it is more preferable that the composite fiber contains 10 to 30% by mass of rayon fibers.
The basis weight of the base sheet is preferably 20 to 80 g/ ^m² , and more preferably 30 to 60 g/ ^m² . Furthermore, it is desirable that the base sheet be sterilized by ultraviolet irradiation or the like before or after impregnation with the aqueous composition.

(3) Cleansing Sheet The cleansing sheet to which the present invention is applied is a sheet in which a water-based composition is impregnated into a base sheet made of the woven or nonwoven fabric, and is not limited to being used for wiping the bottom of infants, or for wiping the bodies of sick people, the elderly, or infants, but can be widely used as a makeup remover sheet, a hand towel sheet, a kitchen wipe sheet, a cleaner for office automation products, etc.

(3-1) Impregnation of the base sheet with an aqueous composition Examples of methods for impregnating the base sheet with an aqueous composition include, but are not limited to, spraying the aqueous composition onto a dry base sheet, applying it using a roll containing the aqueous composition, and immersing the sheet in the aqueous composition.

In the present invention's cleaning sheet, the amount of aqueous composition impregnated into the base sheet is preferably 100 to 300 parts by mass, and more preferably 150 to 270 parts by mass, based on the dry mass of the base sheet, from the viewpoint of exhibiting the cleaning function. If the impregnation amount is less than 100 parts by mass, the aqueous composition cannot be impregnated into the entire base sheet, which may hinder wiping. If the impregnation amount exceeds 300 parts by mass, the aqueous composition cannot be fully impregnated into the base sheet, which may cause the skin to become wet and uncomfortable after wiping.

(3-2) pH of the aqueous phase of the cleaning sheet
The pH of the aqueous phase in the cleaning sheet of the present invention, that is, the pH of the aqueous phase in a nearly equilibrium state after impregnating the base sheet with the aqueous composition, is preferably 6.1 or higher and 6.6 or lower at 25°C. The pH of the aqueous phase is the pH value measured using a LAQUA twin pH meter manufactured by Horiba, Ltd.
On the skin surface, beneficial bacteria such as Staphylococcus epidermidis, which are part of the skin's normal flora, secrete fatty acids to maintain a slightly acidic pH, preventing the invasion of harmful bacteria and viruses. On the other hand, if the skin surface becomes alkaline, harmful bacteria such as Staphylococcus aureus become more active, which can increase the likelihood of skin problems.

The pH of the skin surface is maintained at a slightly acidic level of approximately 4.5 to 6.5, although this varies from person to person, creating an environment where beneficial skin flora can easily thrive. Furthermore, since the pH of an infant's skin surface rises to approximately 6.0 to 7.0 after 5 to 6 weeks of age, it is preferable to maintain the pH of the aqueous phase in the cleansing sheet within this range. One of the features of this invention is that the pH of the aqueous phase in the cleansing sheet can be adjusted to a slightly acidic level by adjusting the ratio of the antibacterial components, benzalkonium chloride and polyaminopropyl biguanide hydrochloride, without the addition of a pH adjusting agent.

The present invention's cleaning sheet will be specifically described with reference to the following examples and comparative examples, but the present invention is not limited to these examples. In these examples and comparative examples, the aqueous composition for impregnating the cleaning sheet and the cleaning sheet impregnated with the aqueous composition will be described separately.

First, the raw materials and samples used in this example and comparative example are listed below.
(1) Purified water: Ordinary water was purified using an ion exchange resin to prepare purified water with an electrical conductivity of 1 μS/cm or less.
(2) Preservatives and Solubilizers The preservatives and solubilizers described below were used as components added to the aqueous composition. pH was measured using a HORIBA pH METER F-21 manufactured by HORIBA, Ltd.
(i) Benzalkonium chloride was a commercially available product, and the pH of its 1% by mass aqueous solution was 7.91, and the pH of its 10% by mass aqueous solution was 8.93.
(ii) Polyaminopropyl biguanide hydrochloride was a commercially available product, with a pH of 3.26 for a 1% by mass aqueous solution and a pH of 3.45 for a 10% by mass aqueous solution, and a weight-average molecular weight of 2000 to 3000.
(iii) Glyceryl caprate was a commercially available product, and its properties were those of a waxy mass. Since this component is poorly soluble in water, pH measurement was not performed.
(iv) Propynyl iodide butylcarbamate was a commercially available product.
(v) Polyethylene glycol was a commercially available product with a number-average molecular weight of 200.
(vi) A commercially available polypropylene glycol was used.

(3) Base sheet The nonwoven fabric used for the base sheet was a spunlace composite fiber made of rayon and polyethylene terephthalate with a basis weight of 32 g/ ^m² , and the rayon fiber content in the composite fiber was 40 to 60% by mass.

[Examples 1-9, Comparative Examples 1-8]
1. Evaluation Tests of Aqueous Compositions Evaluation tests were conducted on aqueous compositions for impregnation of cleaning sheets.
1-1. Preparation of aqueous compositions In Examples 1 to 9 and Comparative Examples 1 to 8, aqueous compositions for impregnation of cleaning sheets were prepared.
Specifically, the aqueous compositions shown in Tables 1 to 3 were prepared by dissolving predetermined amounts of the preservative and solubilizer in the purified water according to each example and comparative example. Glyceryl caprate was pre-dissolved in polyethylene glycol, a solubilizer, before being added to the aqueous composition. Since the aqueous composition evaluated in Comparative Example 5 did not contain a solubilizer, a waxy solid was ground and added directly to the aqueous composition. Furthermore, in Comparative Example 8, since the aqueous composition was a blank example, the purified water was used as is instead of the aqueous composition.
The aqueous compositions prepared above were evaluated as follows.

1-2. Evaluation of Aqueous Compositions In Examples 1-9 and Comparative Examples 1-8, the aqueous compositions were subjected to the following tests before being impregnated into the substrate sheets: (1) pH measurement, (2) observation for the presence or absence of turbidity or precipitate formation, and (3) preservative efficacy test.
(1) pH measurement In Examples 1 to 9 and Comparative Examples 1 to 4 and 8, the pH of the prepared aqueous compositions was measured at room temperature (25°C). The pH measuring device used was a HORIBA pH METER F-21 manufactured by HORIBA, Ltd.
The pH measurement results are shown in Table 1-3. In the aqueous compositions of Examples 1-9, the pH at room temperature (25°C) was in the range of 3.47-3.83. From Tables 1-3, it was confirmed that the pH value of the aqueous composition decreased as the mass ratio (b2/b1) of the polyaminopropyl biguanide hydrochloride content (b2) to the benzalkonium chloride content (b1) increased.

(2) Observation of the presence or absence of turbidity or precipitate In Examples 1 to 9 and Comparative Examples 1 to 7, aqueous compositions prepared with the preservative and solubilizer at the concentrations shown in Tables 1 to 3 were thoroughly stirred and then allowed to stand, and the presence or absence of turbidity or precipitate was visually observed. The results of the observation of the presence or absence of turbidity or precipitate are shown in Tables 1 to 3. In Comparative Example 5, which did not contain a solubilizer, turbidity or precipitate was observed in the aqueous composition.

(3) Preservative efficacy test In Examples 1 to 9, the preservative efficacy test of the aqueous compositions was performed in accordance with the test method described in the "Preservative Efficacy Test Method" of the 17th edition of the Japanese Pharmacopoeia.

(i) Test method The preservative efficacy test is a test in which a certain number of bacteria and fungi are mixed into an aqueous composition, and the number is measured over time to confirm the preservative effect.
The following three types of bacteria and two types of fungi, designated as test strains, were inoculated, and the number of viable cells was measured after 7, 14, and 28 days.
Test bacterial strains (bacteria) for antimicrobial testing
(a) Escherichia coli (NBRC 3972)
(b) Staphylococcus aureus (NBRC 12732)
(c) Pseudomonas aeruginosa (12689)
Test strains (fungi) for antifungal testing
(d) Candida (NBRC 1385)
(e) Aspergillus oryzae (NBRC 105649)

(ii) Evaluation method and evaluation results The evaluation was performed based on the rate of reduction in the number of inoculum. The method for calculating the rate of reduction is shown below.
Reduction rate (%) = [((Initial bacterial count) - (Viable bacterial count after 7, 14, and 28 days)) / Initial bacterial count] × 100
The evaluation results for the aqueous compositions prepared in Examples 1 to 9 are shown in Tables 1 and 2.
In Tables 1 and 2, the blank column in the preservation efficacy test indicates the number of viable bacteria after 7 days, following the inoculation of a predetermined number of the above-mentioned bacteria and fungi into purified water instead of the aqueous composition.
In Examples 1-5, the number of viable bacteria and fungi was measured after inoculation, at 7, 14, and 28 days, respectively. In Examples 6-9, the number of bacteria was measured after 7 days.
In all of the preservation efficacy tests using the above-mentioned test bacterial strains, the rate of viable cell reduction after 7 days and beyond was 100%, confirming that the aqueous compositions prepared in Examples 1 to 9 possess excellent antibacterial and antifungal properties.

2. Evaluation tests and results for the cleansing sheets Cleansing sheet test pieces were prepared by impregnating a base sheet with the aqueous compositions prepared in Examples 1 to 9 and Comparative Examples 1 to 4, 6, and 7. The obtained cleansing sheet test pieces were subjected to the following storage stability tests and evaluations regarding skin irritation.
(i) Storage stability test As part of the storage stability test, an antimicrobial test (in accordance with JIS L 1902), an antifungal test (in accordance with JIS L 1921), and a mold resistance test (in accordance with JIS Z 2911) were conducted.
Regarding the evaluation of the antifungal properties of the cleaning sheet test pieces, in Examples 1 to 4, a quantitative evaluation of antifungal properties, the "Antifungal Properties Test (in accordance with JIS L 1921)," was performed to clarify the superiority over the comparative examples. In Examples 5 to 9, since superiority over the comparative examples was anticipated, a qualitative evaluation of antifungal properties, the "Mold Resistance Test (in accordance with JIS Z 2911)," was performed.
(ii) Evaluation of skin irritation As part of the evaluation of skin irritation tests, the pH of the aqueous phase of the cleansing sheet test piece was measured, and a primary skin irritation test was performed.

2-1. Preparation of Cleaning Sheet Test Specimens Cleaning sheet test specimens were prepared by uniformly spraying the aqueous composition prepared above onto the nonwoven fabric sheets cut to a predetermined size, using a hand sprayer, so that the impregnation amount was 80 g/ ^m² . These specimens were to be evaluated in Examples 1-9 and Comparative Examples 1-4 and 6-8, respectively. After impregnating the nonwoven fabric sheets with the aqueous composition, they were sterilized using ultraviolet light.

2-2. Evaluation Test of Cleaning Sheet Test Pieces (1) pH Measurement of the Aqueous Phase of Cleaning Sheet Test Pieces Cleaning sheet test pieces were prepared by impregnating the base sheets with the aqueous compositions prepared in Examples 1 to 9 and Comparative Examples 1 to 4 and 8, and then left to stand for approximately 60 minutes. After that, the extract obtained by squeezing the cleaning sheet test pieces with a padding machine (mangle) was maintained at room temperature (25°C), and the pH was measured using a pH measuring device (LAQUA twin pH meter, manufactured by Horiba, Ltd.). The measurement results are shown in Tables 4 to 6.
The pH of the aqueous phase of the cleaning sheet test pieces impregnated with the aqueous compositions prepared in Examples 1 to 9 was in the range of 6.1 to 6.6 in all cases.

(2) Antimicrobial Test The cleaning sheet test pieces obtained by impregnating the base sheets with the aqueous compositions prepared for evaluation in Examples 1 to 9 and Comparative Examples 1 to 4 and 6 to 8 were subjected to antimicrobial tests in accordance with JIS L 1902 (2015). JIS L 1902 is a qualitative test for evaluating the antimicrobial properties of antimicrobial fibers and specifies the method for evaluating the antimicrobial activity of all antimicrobial fiber products, including nonwoven fabrics.
(i) Test method The following two types of bacteria were used as test subjects.
Escherichia coli (NBRC 3301)
Staphylococcus aureus (NBRC 12732)
E. coli and Staphylococcus aureus were added to agar plates, and these plates were placed in petri dishes and allowed to solidify. A cleansing sheet test piece was placed in the center of the petri dish. The petri dish was left at 37°C for 48 hours, and once the bacteria had grown on the medium, the width (mm) of the inhibition zone (halo) formed around the test piece where bacteria did not grow was measured on all four sides, and the average value was calculated. Note that in Table 6, only for Comparative Examples 6 and 7, the presence or absence of a halo is indicated as an evaluation result.

(ii) Evaluation Results The halo widths measured for the test bacteria, Escherichia coli and Staphylococcus aureus, are shown in Tables 4 to 6. The criteria for determining the presence or absence of a halo, based on JIS L 1902, are as follows.
When the average width of the halo > 0: Halo present When the average width of the halo = 0: Halo absent In Examples 1 to 9, the antibacterial test evaluation was "Halo present" in all cases.

(3) Antifungal Test The cleaning sheet test pieces obtained by impregnating the base sheet with the aqueous compositions prepared for evaluation in Examples 1 to 4 and Comparative Example 4 were subjected to an antifungal test in accordance with JIS L 1921 (2015). The antifungal test is a quantitative test method that investigates the antifungal power to kill a certain amount of mold in a relatively short time.

(i) Overview of the test Spores are collected from pre-cultured test molds to prepare a test spore suspension. Next, the test spore suspension is inoculated onto a cleansing sheet test piece and a control sample (cotton standard cloth), respectively, and the amount of ATP is measured after incubation at 25°C for 18 and 24 hours to determine the amount of mold surviving on the sample. By comparing the amount of mold on the cleansing sheet test piece and the control sample, the "antifungal activity value" is calculated, which indicates how well mold growth was suppressed. Note that the measurement of ATP amount refers to making ATP (adenosine triphosphate) present in the cells of living organisms emit light using enzymes, etc., and measuring the amount of light emitted. The amount of light emitted increases as the amount of ATP in the cell increases.

The "antifungal activity value" can be calculated using the following formula.
Antifungal activity value (Aa): (Fb - Fa) - (Fc - Fo)
Fb: Common logarithm of the arithmetic mean of ATP levels after 42 hours of incubation of untreated cotton fibers Fa: Common logarithm of the arithmetic mean of ATP levels immediately after inoculation of untreated cotton fibers Fc: Common logarithm of the arithmetic mean of ATP levels after 42 hours of incubation of cleansing sheet test pieces Fo: Common logarithm of the arithmetic mean of ATP levels immediately after inoculation of cleansing sheet test pieces

(ii) Test mold species The following molds were selected as test mold species.
Aspergillus oryzae (NBRC 105649)
(iii) Evaluation criteria and results The antifungal activity value (Aa) indicates that the higher the value, the higher the antifungal performance. According to the evaluation criteria, a value of 2.0 or higher indicates antifungal properties.
Table 4 shows the antifungal activity values (Aa) calculated for Examples 1-4 and Comparative Example 4. From Table 4, it can be seen that the cleaning sheet test pieces of Examples 1-4 all had an antifungal activity value (Aa) of 2.0 or higher, and were found to be superior in antifungal properties compared to the cleaning sheet test piece of Comparative Example 4.

(4) Mold Resistance Test The cleaning sheet test pieces obtained by impregnating each of the aqueous compositions onto a base sheet were evaluated according to the mold resistance test (JIS Z 2911 (2018)). The mold resistance test is a qualitative test that evaluates the resistance of the test piece to mold, and it is possible to evaluate the mold resistance of the test piece over a relatively long incubation period.

(i) Overview of the test Mold resistance tests were performed on cleaning sheet test pieces obtained by impregnating a base sheet with the aqueous compositions prepared for evaluation in Examples 5-9 and Comparative Examples 1-3 and 8.
In addition, since the antifungal properties were already evaluated in the antifungal properties test described above for Examples 1 to 4 and Comparative Example 4, the mold resistance test was omitted.
The test specimens were placed on an inorganic salt medium in a petri dish, and the spore suspension of the following mold was evenly sprayed onto the surface of the specimens. After incubation at 28±4°C for 4 weeks, the growth of mycelium on the specimens was observed with the naked eye and under a microscope.

(ii) Test molds The following (a) single type of mold and (b) a mixture of three types of mold were used.
(a) Aspergillus niger NBRC 105649
(b) Mixed of three species: Penicillium citrinum (NBRC 6352)
Chaetomium globosum (NBRC 6347)
Myrothecium verrucaria (NBRC 6113)

(iii) Criteria for evaluation, evaluation results
Based on JIS Z 2911 (2018), the criteria for determining the state of mold growth are shown in the following three stages, with a rating of "0 or 1" indicating mold resistance.
0: No mycelial growth was observed in the inoculated area of the test specimen.
1. The area of mycelium observed in the inoculated portion of the test specimen does not exceed 1/3 of the total area.
2. The area of mycelium observed in the inoculated portion of the test specimen exceeds 1/3 of the total area.
The evaluation results based on the above criteria are shown in Tables 5 and 6. From Tables 5 and 6, it can be seen that the mold growth status of the cleaning sheet test pieces prepared in Examples 5 to 9 was all judged as 1, and it was confirmed that they had superior mold resistance compared to the cleaning sheet test pieces prepared in Comparative Examples 1 to 3 and 8.

(5) Primary skin irritation test A primary skin irritation test was conducted in accordance with the "Guidelines for Safety Evaluation of Cosmetics" issued by the Japan Cosmetic Industry Association.
A primary skin irritation test was performed on a cleansing sheet test piece prepared by impregnating it with the aqueous composition prepared for evaluation in Example 6, and on a cleansing sheet test piece prepared by impregnating it with the same aqueous composition as prepared in Example 6 (Example 11), except that the aqueous composition prepared in Example 6 contained 0.0500% by mass of benzalkonium chloride, 0.0500% by mass of polyaminopropyl biguanide hydrochloride, 0.0300% by mass of glyceryl caprate, and 0.0100% by mass of polyethylene glycol.

(i) Test Method Twenty healthy male and female subjects had skin test tapes (evaluation cleansing sheets) applied to the normal skin on their backs. After 24 hours, the skin test tapes were removed and the skin condition was visually inspected and evaluated according to the following evaluation criteria.
No reaction: 0.0 points Slight erythema: 0.5 points Obvious erythema: 1.0 points Erythema and edema or papules: 2.0 points Erythema and edema/papules and vesicles: 3.0 points Large vesicles: 4.0 points

(ii) Skin irritation index and determination The evaluation score for each subject was determined, and the skin irritation index was calculated using the following formula.
Skin irritation index = (Sum of scores / Number of subjects) × 100
Next, the safety of the cosmetic product was determined based on the skin irritation index measured by the meter, according to the classification of skin irritation indices (safe product: 5.0 or less, acceptable product: 5.0 to 15.0, product requiring improvement: 15.0 to 30.0, dangerous product: 30.0 or more).
The evaluation results showed that the skin irritation index of the cleansing sheet test pieces prepared in Examples 6 and 11 was 2.5 or less in all cases, and they were classified as "safe products."

Claims (8)

A cleaning sheet comprising a base sheet made of woven or nonwoven fabric impregnated with an aqueous composition containing a preservative enhancer and a solubilizer,
The aforementioned aqueous composition contains, in purified water, benzalkonium chloride and polyaminopropyl biguanide hydrochloride as preservatives, and glyceryl caprate as an antifungal agent.
Furthermore, it contains a solvent that solubilizes glyceryl caprate as a solubilizing agent.
In the aqueous composition, the content of benzalkonium chloride (b1) is 0.030% by mass or more and 0.050% by mass or less, the content of polyaminopropyl biguanide hydrochloride (b2) is 0.025% by mass or more and 0.070% by mass or less, and the content of glyceryl caprate (c1) is 0.003% by mass or more and 0.050% by mass or less.
The pH of the aqueous phase in the aforementioned cleaning sheet is weakly acidic.
Furthermore, the cleaning sheet is characterized in that the concentration of purified water in the aqueous composition is 99.85% by mass or more and 99.92% by mass or less. In the aqueous composition,
The total amount of benzalkonium chloride (b1) and polyaminopropyl biguanide hydrochloride (b2) (b1 + b2) is 0.060% by mass or more and 0.105% by mass or less.
Furthermore, the mass ratio (b2/b1) of the polyaminopropyl biguanide hydrochloride content (b2) to the benzalkonium chloride content (b1) is 0.625 or more and 2.00 or less.
The cleaning sheet according to claim 1. In the aqueous composition,
The mass ratio (c1/(b1+b2)) of the amount of glyceryl caprate (c1), an antifungal agent component, and the total amount of benzalkonium chloride (b1) and polyaminopropyl biguanide hydrochloride (b2), both antibacterial agents (b1+b2), is between 0.035 and 0.833.
A cleaning sheet according to claim 1 or 2. In the aqueous composition, the mass ratio (d1/c1) of the content of the solvent that solubilizes glyceryl caprate (d1) to the content of glyceryl caprate, which is an antifungal agent component (c1), is 0.60 or more and 2.14 or less.
A cleaning sheet according to any one of claims 1 to 3. In the aqueous composition, the solvent for solubilizing glyceryl caprate is a polyether that is liquid at room temperature (15-25°C) and has OH-terminated groups.
A cleaning sheet according to any one of claims 1 to 4. In the aqueous composition, the solvent for solubilizing glyceryl caprate is polyethylene glycol having a number average molecular weight of 100 to 600.
A cleaning sheet according to any one of claims 1 to 5. The pH of the aqueous phase portion of the cleaning sheet at 25°C is 6.1 or higher and 6.6 or lower.
A cleaning sheet according to any one of claims 1 to 6. The aforementioned cleansing sheet is for wiping the bottom of an infant, or for wiping the body of a sick person, the elderly, or an infant.
A cleaning sheet according to any one of claims 1 to 7.