Polyvinyl alcohol-based water-soluble film, polyvinyl alcohol-based resin solution, and method for producing polyvinyl alcohol-based water-soluble film

Abstract

To provide a polyvinyl alcohol-based resin solution capable of suppressing growth of microorganisms without using a large amount of microbicide or preservative, and a polyvinyl alcohol-based water-soluble film with suppressed growth of microorganisms, as well as a method for producing the polyvinyl alcohol-based water-soluble film.SOLUTION: A polyvinyl alcohol-based water-soluble film comprises a polyvinyl alcohol-based resin and benzalkonium chloride, wherein the polyvinyl alcohol-based water-soluble film comprises the benzalkonium chloride in an amount of 0.025 pt.mass to 0.1 pt.mass relative to 100 pts.mass of the polyvinyl alcohol-based resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyvinyl alcohol-based water-soluble film, a polyvinyl alcohol-based resin solution, and a method for producing a polyvinyl alcohol-based water-soluble film, and more particularly to a polyvinyl alcohol-based resin solution in which the growth of microorganisms such as mold is inhibited, a polyvinyl alcohol-based water-soluble film obtained from the polyvinyl alcohol-based resin solution, and a method for producing a polyvinyl alcohol-based water-soluble film. [Background technology]

[0002] In recent years, polyvinyl alcohol-based water-soluble films have been widely used as packaging materials to facilitate the measurement and dropping of enclosed agents (see, for example, Patent Document 1). Such a water-soluble polyvinyl alcohol-based film is generally obtained by first mixing and dissolving various raw materials as film-forming raw materials to prepare a polyvinyl alcohol-based resin solution, forming the polyvinyl alcohol-based resin solution into pellets as needed, and then forming the film-forming raw materials into a film by a melt extrusion method, a casting method, or the like using a film-forming device.

[0003] On the other hand, polyvinyl alcohol-based water-soluble films are increasingly being used for cosmetic packaging and food and beverage packaging. When used for cosmetic packaging and food and beverage packaging, the polyvinyl alcohol-based water-soluble film, i.e., the polyvinyl alcohol-based resin solution used as a raw material, is required to have few impurities from a safety standpoint. However, reducing the impurities in the polyvinyl alcohol-based resin solution may facilitate the growth of microorganisms such as mold.

[0004] If microorganisms are present in the polyvinyl alcohol resin solution, which is a film-forming raw material, the polyvinyl alcohol resin solution may be discolored or foreign matter may be generated. If the polyvinyl alcohol-based resin solution discolors or contains foreign matter, it may cause malfunctions in the film production line, defects in the produced water-soluble film, or problems when processing the water-soluble film. Therefore, it is necessary to suppress the growth of microorganisms in polyvinyl alcohol resin solutions. Furthermore, the water-soluble film thus produced may absorb moisture and increase its moisture content when used in various environments with different humidity, temperature, etc. Therefore, it is necessary that the water-soluble film be capable of suppressing the growth of microorganisms even when the water content is high.

[0005] To suppress the growth of microorganisms, it is conceivable to add a disinfectant or preservative to the polyvinyl alcohol resin solution, which is the raw material for film formation. However, from the viewpoint of the safety of the resulting water-soluble polyvinyl alcohol film, it is not preferable to use a large amount of such a disinfectant or preservative. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2011 / 094472 Summary of the Invention [Problem to be solved by the invention]

[0007] Under these circumstances, the present invention aims to provide a polyvinyl alcohol-based resin solution, a polyvinyl alcohol-based water-soluble film, and a method for producing a polyvinyl alcohol-based film, which are capable of inhibiting the growth of microorganisms without using large amounts of disinfectants or preservatives. [Means for solving the problem]

[0008] However, in view of these circumstances, the present inventors have conducted extensive research and found that the growth of microorganisms in polyvinyl alcohol-based resin solutions and polyvinyl alcohol-based water-soluble films can be inhibited by adding 0.025 to 0.1 parts by mass of benzalkonium chloride to 100 parts by mass of polyvinyl alcohol-based resin, thereby completing the present invention.

[0009] That is, the present invention has the following aspects. [1] A composition comprising a polyvinyl alcohol resin and benzalkonium chloride, A polyvinyl alcohol-based water-soluble film containing 0.025 to 0.1 parts by mass of the benzalkonium chloride relative to 100 parts by mass of the polyvinyl alcohol-based resin. [2] It also contains methylparaben, The water-soluble polyvinyl alcohol film according to [1], which contains 0.3 to 1.5 parts by mass of methylparaben per 100 parts by mass of the polyvinyl alcohol resin. [3] A polyvinyl alcohol-based resin solution, Contains a polyvinyl alcohol resin and benzalkonium chloride, A polyvinyl alcohol-based resin solution containing 0.025 to 0.1 parts by mass of the benzalkonium chloride relative to 100 parts by mass of the polyvinyl alcohol-based resin. [4] It also contains methylparaben, The polyvinyl alcohol-based resin solution according to [3], containing 0.3 to 1.5 parts by mass of methylparaben per 100 parts by mass of the polyvinyl alcohol-based resin. [5] A method for producing a polyvinyl alcohol-based water-soluble film, comprising: a dissolving and mixing step of dissolving a polyvinyl alcohol-based resin in water to prepare a polyvinyl alcohol-based resin solution; a film-forming step of forming a film using the polyvinyl alcohol-based resin solution obtained in the dissolving and mixing step, the polyvinyl alcohol-based resin solution prepared in the dissolving and mixing step has a solids concentration of 10 to 65 mass %; the polyvinyl alcohol-based resin solution contains a polyvinyl alcohol-based resin and benzalkonium chloride, The method for producing a polyvinyl alcohol-based water-soluble film comprises containing 0.025 to 0.1 parts by mass of the benzalkonium chloride relative to 100 parts by mass of the polyvinyl alcohol-based resin. [6] The polyvinyl alcohol-based resin solution further contains methylparaben, The method for producing a water-soluble polyvinyl alcohol-based film according to [5], wherein the methylparaben is contained in an amount of 0.3 to 1.5 parts by mass per 100 parts by mass of the polyvinyl alcohol-based resin. [7] The method for producing a water-soluble polyvinyl alcohol-based film according to [5] or [6], wherein the film-forming step is a casting film-forming step of the polyvinyl alcohol-based resin solution. [Effects of the Invention]

[0010] The present invention relates to a water-soluble polyvinyl alcohol film comprising a polyvinyl alcohol resin and benzalkonium chloride, in which the benzalkonium chloride is contained in an amount of 0.025 to 0.1 part by mass per 100 parts by mass of the polyvinyl alcohol resin. Therefore, the growth of microorganisms in a polyvinyl alcohol resin solution prepared by mixing and dissolving various materials prior to the film-forming process can be inhibited, and sufficient consideration has been given to safety. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0012] In the present embodiment, when expressed as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it means "greater than or equal to X and less than or equal to Y", and also means "preferably greater than X" or "preferably smaller than Y". Furthermore, when it is expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y." Furthermore, in this embodiment, the term "film" also includes the meaning of "sheet."

[0013] This embodiment will be specifically described below. The polyvinyl alcohol-based water-soluble film of the present embodiment contains a polyvinyl alcohol-based resin and benzalkonium chloride, and contains 0.025 to 0.1 parts by mass of the benzalkonium chloride per 100 parts by mass of the polyvinyl alcohol-based resin. In addition, the polyvinyl alcohol-based resin solution of the present embodiment is a solution (film-forming raw material) before the formation of the polyvinyl alcohol-based water-soluble film, and the component composition does not change before and after the film formation. Therefore, the following explanation of the components will mainly be given for the polyvinyl alcohol-based film, but the same applies to the polyvinyl alcohol-based resin solution and has the same composition and effect as the polyvinyl alcohol-based film. In the description of this embodiment, polyvinyl alcohol may be abbreviated as "PVA," and a water-soluble film containing a polyvinyl alcohol-based resin as a main component may be abbreviated as "PVA-based film." Hereinafter, each component contained in this embodiment will be explained, followed by an explanation of its shape.

[0014] [Polyvinyl alcohol (PVA) resin] The PVA film of the present embodiment is a film containing a PVA resin as a main component. Here, "mainly composed of a PVA resin" means that the PVA resin is contained in an amount of typically 50% by mass or more, preferably 55% by mass or more, and particularly preferably 60% by mass or more, based on the entire PVA film. If the content is too low, the solubility in water and the mechanical properties of the film tend to decrease. The upper limit of the content is typically 99% by mass or less, preferably 95% by mass or less, and particularly preferably 90% by mass or less, from the viewpoint of shape stability over time when the PVA film is used as a packaging material.

[0015] The PVA resin used in this embodiment may be an unmodified PVA resin or a modified PVA resin.

[0016] The unmodified PVA resin and the modified PVA resin can be produced by a production method known in the art, for example, as follows.

[0017] The unmodified PVA resin can be produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester compound.

[0018] Examples of such vinyl ester compounds include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, and vinyl stearate, with vinyl acetate being preferred. The vinyl ester compounds may be used alone or in combination of two or more.

[0019] The modified PVA resin can be produced by copolymerizing the vinyl ester compound with an unsaturated monomer copolymerizable with the vinyl ester compound, followed by saponification.

[0020] Examples of unsaturated monomers copolymerizable with the vinyl ester compound include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, and 5-hexen-1-ol, and derivatives thereof such as acylated products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid, their salts, monoesters, and dialkyl esters; amides such as diacetone acrylamide, acrylamide, and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or their salts; and N-vinyl pyrrolidone. These can be used alone or in combination of two or more.

[0021] In addition to the above, modified PVA resins also include those having primary hydroxyl groups in the side chains. For example, the number of primary hydroxyl groups in the side chains is typically 1 to 5, preferably 1 to 2, and particularly preferably 1. Furthermore, it is preferable that the modified PVA resins have secondary hydroxyl groups in addition to the primary hydroxyl groups. Examples of such modified PVA resins include PVA resins having hydroxyalkyl groups in the side chains and PVA resins having 1,2-diol structural units in the side chains. PVA resins having 1,2-diol structural units in the side chains can be produced, for example, by saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, saponifying and decarboxylating a copolymer of vinyl acetate and vinyl ethylene carbonate, saponifying and deketalizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane, or saponifying a copolymer of vinyl acetate and glycerin monoallyl ether.

[0022] In terms of solubility, the modified PVA resin used in this embodiment is preferably one modified with at least one hydrophilic group selected from a carboxy group, a sulfonic acid group, a phosphate group, a pyrrolidone ring group, etc. Note that these modified groups also include salts of these functional groups, such as sodium and potassium. Of these, it is preferable to use an anionic group-modified PVA resin, and examples of the anionic group include a carboxy group, a sulfonic acid group, and a phosphate group. In terms of solubility stability over time, a carboxy group and a sulfonic acid group are particularly preferred, and a carboxy group is even more preferred.

[0023] The carboxyl group-modified PVA resin can be produced by any method, and examples of the production method include (I) a method of copolymerizing an unsaturated monomer having a carboxyl group with a vinyl ester compound and then saponifying the copolymer; and (II) a method of polymerizing a vinyl ester compound in the presence of an alcohol, aldehyde, or thiol having a carboxyl group as a chain transfer agent, and then saponifying the copolymer.

[0024] The unsaturated monomer having a carboxy group in the method (I) may be an ethylenically unsaturated dicarboxylic acid (maleic acid, fumaric acid, itaconic acid, etc.), an ethylenically unsaturated dicarboxylic acid monoester (maleic acid monoalkyl ester, fumaric acid monoalkyl ester, itaconic acid monoalkyl ester, etc.), an ethylenically unsaturated dicarboxylic acid diester (maleic acid dialkyl ester, fumaric acid dialkyl ester, itaconic acid dialkyl ester, etc.) (however, it is necessary that these diesters are converted to a carboxy group by hydrolysis during saponification of the copolymer), or an ethylenically unsaturated carboxylic acid anhydride (maleic anhydride, Examples of suitable monomers include monomers such as maleic acid, maleic acid monoalkyl esters, maleic acid dialkyl esters, maleic acid salts, maleic anhydride, itaconic acid, itaconic acid monoalkyl esters, itaconic acid dialkyl esters, (meth)acrylic acid, and the like. Of these, it is preferable to use maleic acid, maleic acid monoalkyl esters, maleic acid dialkyl esters, maleic acid salts, and maleic anhydride, and it is particularly preferable to use maleic acid, maleic acid monoalkyl esters, maleic acid dialkyl esters, maleic acid salts, and maleic anhydride, with maleic acid monoalkyl esters being even more preferable. These may be used alone or in combination of two or more.

[0025] In the method (II) above, compounds derived from thiols, which have a particularly large chain transfer effect, are effective, and examples thereof include compounds represented by the following general formulas (1) to (3).

[0026] [ka]

[0027] [ka]

[0028] [ka]

[0029] Further, salts of the compounds represented by the general formulas (1) to (3) above may also be used. Specific examples include mercaptoacetate, 2-mercaptopropionate, 3-mercaptopropionate, 2-mercaptostearate, etc. These compounds may be used alone or in combination of two or more.

[0030] In addition to the unsaturated monomer having a carboxy group and the vinyl ester compound, other general monomers may be added to the polymerization to the extent that water solubility is not impaired, and examples of such monomers include alkyl esters of ethylenically unsaturated carboxylic acids, allyl esters of saturated carboxylic acids, α-olefins, alkyl vinyl ethers, alkyl allyl ethers, as well as (meth)acrylamide, (meth)acrylonitrile, styrene, vinyl chloride, etc. These may be used alone or in combination of two or more.

[0031] The method for producing the carboxyl group-modified PVA-based resin is not limited to the above-mentioned method, and other methods may also be employed, such as a method in which a PVA-based resin (partially saponified or completely saponified) is post-reacted with a carboxyl group-containing compound having a functional group reactive with a hydroxyl group, such as a dicarboxylic acid, an aldehydecarboxylic acid, or a hydroxycarboxylic acid.

[0032] When a sulfonic acid-modified PVA-based resin modified with a sulfonic acid group is used, the resin can be produced by, for example, a method of copolymerizing a copolymerization component such as vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, or 2-acrylamido-2-methylpropanesulfonic acid with a vinyl ester-based compound and then saponifying the copolymer, or a method of subjecting vinyl sulfonic acid or a salt thereof, 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof, or the like, to Michael addition to a PVA-based resin.

[0033] On the other hand, methods for post-modifying the unmodified PVA resin include methods of acetoacetic esterification, acetalization, urethanization, etherification, grafting, phosphate esterification, and oxyalkylenation of the unmodified PVA resin.

[0034] When a modified PVA resin is used, maleic acid-modified PVA resin and itaconic acid-modified PVA resin are preferred because they are easy to handle, highly polymerizable with vinyl ester monomers, and have excellent productivity. In particular, maleic acid-modified PVA resin is preferred because it maintains stability over time in the solubility of the film when a drug is packaged and is less susceptible to the pH of the drug.

[0035] The average saponification degree of the PVA resin (A) is preferably 80 mol% or more, particularly preferably 82 to 99.9 mol%, further preferably 85 to 98.5 mol%, and particularly preferably 85 to 90 mol%. If the average saponification degree is too low, the solubility of the film in water tends to decrease. However, if the average saponification degree is too high, the water solubility tends to decrease. The average degree of saponification is measured in accordance with JIS K 6726 3.5.

[0036] The degree of polymerization of the PVA resin (A) can generally be indicated by the viscosity of its aqueous solution, and the viscosity of a 4 mass% aqueous solution at 20°C is preferably 1 to 60 mPa·s, particularly 2 to 55 mPa·s, and further preferably 3 to 50 mPa·s. The viscosity of a 4% by mass aqueous solution of the PVA resin at 20°C means that the viscosity of a 4% by mass aqueous solution of the entire PVA resin contained in the PVA film at 20°C falls within these ranges. In the present embodiment, when a plurality of PVA-based resins are contained, the viscosity of a 4% by mass aqueous solution of the entire PVA-based resin at 20°C is calculated from the following formula using the proportion of each PVA-based resin contained in the entire PVA-based resin and the viscosity of a 4% by mass aqueous solution at 20°C. (Formula) Viscosity of 4% by mass aqueous solution of all PVA-based resins at 20°C = Content of PVA-based resin (i) × Viscosity of 4% by mass aqueous solution of PVA-based resin (i) at 20°C + Content of PVA-based resin (ii) × Viscosity of 4% by mass aqueous solution of PVA-based resin (ii) at 20°C + (the rest is omitted)

[0037] From the viewpoint of solubility as the PVA resin (A), the viscosity of a 4 mass% aqueous solution at 20°C is preferably 0.5 to 55 mPa·s, more preferably 1 to 45 mPa·s, particularly preferably 2 to 30 mPa·s, further preferably 3 to 15 mPa·s, and particularly preferably 3 to 12 mPa·s. In terms of mechanical properties, the PVA resin (A) preferably has a viscosity of a 4% by mass aqueous solution at 20°C of 5 to 60 mPa·s, particularly preferably 15 to 55 mPa·s, further preferably 17 to 53 mPa·s, even more preferably 21 to 50 mPa·s, and even more preferably 21.5 to 48 mPa·s. If the viscosity is too low, the mechanical strength of the water-soluble film used as a packaging material tends to decrease, whereas if the viscosity is too high, productivity and solubility tend to decrease. The viscosity of the 4 mass % aqueous solution is measured in accordance with JIS K 6726 3.11.2.

[0038] When an unmodified PVA resin is used, the average saponification degree of the unmodified PVA resin is preferably 80 mol% or more, particularly preferably 82 to 98.5 mol%, and further preferably 85 to 90 mol%. If the average saponification degree is too low, the solubility of the water-soluble film in water tends to decrease. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0039] When an unmodified PVA resin is used, the viscosity of a 4% by mass aqueous solution of the unmodified PVA resin at 20° C. is preferably 1 to 60 mPa·s, particularly preferably 2 to 55 mPa·s, and even more preferably 3 to 50 mPa·s. If the viscosity is too low, the mechanical strength of the water-soluble film used as a packaging material tends to decrease, whereas if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to be high, reducing productivity and decreasing solubility.

[0040] The modification amount of the modified PVA resin is preferably 15 mol% or less, particularly preferably 10 mol% or less, further preferably 5 mol% or less, and particularly preferably 2 mol% or less. The lower limit is usually 0 mol%. If the modification amount is too high, the productivity of the PVA resin tends to decrease, biodegradability tends to decrease, and blocking tends to occur.

[0041] In the PVA-based film of the present embodiment, the PVA-based resin (A) can be used alone, or two or more unmodified PVA-based resins or PVA-based resins that differ in at least one of the degree of saponification, viscosity, modified species, modification amount, etc. can be used in combination. From the viewpoint of safety and stability, it is preferable to use an unmodified PVA resin, and furthermore, it is preferable to use two or more unmodified PVA resins in combination in order to easily adjust the balance between solubility and mechanical properties.

[0042] The PVA resin used in the present embodiment is preferably a PVA resin with a low impurity content in view of preferred applications, and in particular, the sodium acetate content (mass %) is preferably 0.1 or less, more preferably 0.08 or less, and particularly preferably 0.05 or less.

[0043] [Benzalkonium chloride] In this embodiment, the benzalkonium chloride content is 0.025 to 0.1 parts by mass, preferably 0.03 to 0.07 parts by mass, and more preferably 0.04 to 0.05 parts by mass, relative to 100 parts by mass of the PVA resin. If the benzalkonium chloride content is too high, it becomes difficult to use the PVA film for packaging cosmetics or food and drink products from a safety standpoint, and if the content is too low, the growth of microorganisms cannot be suppressed.

[0044] [Methylparaben] In this embodiment, it is preferable to use methylparaben (methyl parahydroxybenzoate) as an optional component. Use of methylparaben tends to be able to inhibit the growth of a wider variety of microorganisms. When methylparaben is used, the content of methylparaben is preferably 0.3 to 1.5 parts by mass, more preferably 0.5 to 1.0 part by mass, and even more preferably 0.8 to 1.0 part by mass, per 100 parts by mass of the PVA resin. If the methylparaben content is too high, it tends to be difficult to use the PVA-based film for packaging cosmetics or food and beverages from a safety standpoint, while if the content is too low, it tends to be difficult to obtain the effect of inhibiting the growth of microorganisms, and in particular, it tends to be difficult to obtain the effect of inhibiting filamentous fungi such as Aspergillus niger.

[0045] When methylparaben is used as an optional component, the mass ratio of methylparaben to benzalkonium chloride (methylparaben / benzalkonium chloride) is preferably in the range of 5-30, and more preferably in the range of 15-30. When the mass ratio of methylparaben to benzalkonium chloride is within the above range, the growth of a wider variety of microorganisms tends to be inhibited more efficiently.

[0046] [Plasticizer] In the present embodiment, it is preferable to contain a plasticizer as an optional component, since this can impart appropriate flexibility to the film. The plasticizers can be used alone or in combination of two or more.

[0047] Examples of the plasticizer typically include glycerins such as glycerin, diglycerin, and triglycerin, alkylene glycols such as triethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, and propylene glycol, and sugar alcohols such as trimethylolpropane, sorbitol, xylitol, maltitol, mannitol, and erythritol. These may be used alone or in combination of two or more.

[0048] In this embodiment, it is preferable to use a polyhydric alcohol (a) (hereinafter sometimes abbreviated as "plasticizer (a)") having a melting point of 50°C or less in terms of mechanical properties. Examples of the plasticizer (a) include aliphatic alcohols, such as, preferably, dihydric alcohols such as ethylene glycol (-13°C), diethylene glycol (-11°C), triethylene glycol (-7°C), propylene glycol (-59°C), tetraethylene glycol (-5.6°C), 1,3-propanediol (-27°C), 1,4-butanediol (20°C), 1,6-hexanediol (40°C), tripropylene glycol, and polyethylene glycols with a molecular weight of 2000 or less, and trihydric or higher alcohols such as glycerin (18°C), diglycerin, and triethanolamine (21°C). These may be used alone or in combination of two or more. The values ​​in parentheses indicate melting points. Among these, those having a melting point of 30° C. or less are particularly preferred, and those having a melting point of 20° C. or less are even more preferred, in view of the excellent flexibility of the PVA-based film. The lower limit of the melting point is usually −80° C., preferably −10° C., and particularly preferably 0° C.

[0049] Furthermore, among the plasticizers (a), those having four or less hydroxyl groups in one molecule are preferred, and those having three or less hydroxyl groups in particular are preferred because this makes it easier to control flexibility at around room temperature (25°C). Specifically, for example, glycerin is suitable.

[0050] Furthermore, the plasticizer (a) preferably has a molecular weight of 100 or less, particularly preferably 50 to 100, and even more preferably 60 to 95, in order to make it easier to control flexibility. Specifically, for example, glycerin is suitable.

[0051] In the present embodiment, when two or more plasticizers are used in combination, it is preferable to use the plasticizer (a) in combination with a polyhydric alcohol (b) having a melting point of 80°C or higher (hereinafter sometimes abbreviated as "plasticizer (b)") in view of the toughness, mechanical properties, processability, etc. of the film.

[0052] As the plasticizer (b), for example, many sugar alcohols such as monosaccharides and polysaccharides can be used. Among them, for example, dihydric alcohols such as salicylic alcohol (83°C), catechol (105°C), resorcinol (110°C), hydroquinone (172°C), bisphenol A (158°C), bisphenol F (162°C), neopentyl glycol (127°C), trihydric alcohols such as phloroglucinol (218°C), erythritol (121°C), threitol (88°C), pentaerythritol (121°C), threitol (121°C), pentyl glycol (127°C), etc. Examples of suitable alcohols include tetrahydric alcohols such as taerythritol (260°C), pentahydric alcohols such as xylitol (92°C), arabitol (103°C), fucitol (153°C), glucose (146°C), and fructose (104°C), hexahydric alcohols such as mannitol (166°C), sorbitol (95°C), and inositol (225°C), octahydric alcohols such as lactitol (146°C), sucrose (186°C), and trehalose (97°C), and nonahydric or higher alcohols such as maltitol (145°C). These may be used alone or in combination of two or more. The numbers in parentheses indicate melting points. Among these, from the viewpoint of the tensile strength of the PVA-based film, those having a melting point of 85° C. or higher are preferred, and those having a melting point of 90° C. or higher are particularly preferred. The upper limit of the melting point is preferably 300° C., and particularly preferably 200° C.

[0053] Furthermore, among the plasticizers (b), those having 4 or more hydroxyl groups in one molecule are preferred in terms of compatibility with the PVA-based resin, with 5 to 10 being particularly preferred, and 6 to 8 being even more preferred. Specific examples of suitable plasticizers include sorbitol, sucrose, and trehalose.

[0054] Furthermore, from the viewpoint of the toughness of the PVA-based film, the plasticizer (b) preferably has a molecular weight of 150 or more, particularly preferably 160 to 500, and even more preferably 180 to 400. Specific examples of suitable plasticizers include sorbitol, xylitol, and sucrose.

[0055] When the plasticizer is used, the content thereof is preferably 1 to 25 parts by mass, more preferably 5 to 20 parts by mass, and particularly preferably 6 to 18 parts by mass, relative to 100 parts by mass of the PVA resin. If the content of the plasticizer is too low, the mechanical properties tend to be insufficient and the processability of the film tends to be reduced, whereas if the content is too high, blocking tends to occur and the balance between the mechanical properties and the solubility tends to be poor.

[0056] When the plasticizer (a) is used, the content thereof is preferably 1 to 20 parts by mass, particularly preferably 1.5 to 18 parts by mass, further preferably 2 to 15 parts by mass, and particularly preferably 2.5 to 10 parts by mass, relative to 100 parts by mass of the PVA resin. If the content of the polyhydric alcohol (a) is too low, the mechanical properties tend to decrease, whereas if it is too high, the mechanical properties and formability of the film tend to decrease.

[0057] On the other hand, when the plasticizer (b) is used, the content thereof is preferably 1 to 25 parts by mass, particularly preferably 3 to 20 parts by mass, and further preferably 5 to 18 parts by mass, relative to 100 parts by mass of the PVA resin. If the content of the plasticizer (b) is too low, the mechanical properties and moldability of the film tend to decrease.

[0058] When plasticizer (a) and plasticizer (b) are used in combination as optional components, the mass ratio of plasticizer (b) to plasticizer (a) (plasticizer (b) / plasticizer (a)) is preferably 0.5 to 10, particularly preferably 0.8 to 8, even more preferably 1 to 7, and especially preferably 1.5 to 6. When the mass ratio of the plasticizer (a) to the plasticizer (b) is within the above range, the film tends to have a better balance of mechanical properties, solubility, and moldability.

[0059] [Filler] In the present embodiment, it is preferable to contain a filler as an optional component, since it can impart blocking resistance to the film. The filler can be used alone or in combination of two or more types.

[0060] When the filler is used, the content thereof is preferably 0.1 to 30 parts by mass, particularly preferably 0.5 to 20 parts by mass, and further preferably 0.7 to 10 parts by mass, relative to 100 parts by mass of the PVA-based resin. If the content is too low, blocking tends to increase, while if it is too high, the flexibility and toughness of the film tend to decrease.

[0061] The average particle size of the filler is preferably 0.1 to 50 μm, and particularly preferably 1 to 35 μm. The average particle size of the filler is a value measured with a laser diffraction particle size distribution analyzer, and is calculated from the D50 value (particle size at 50% of the cumulative volume) of the obtained cumulative volume distribution.

[0062] Examples of the filler include organic fillers and inorganic fillers, and among these, organic fillers are preferably used.

[0063] In this embodiment, the organic filler refers to particulate matter (primary particles) made of an organic compound and having any shape, such as needle-like, rod-like, layer-like, scale-like, or spherical, or an aggregate of such particulate matter (secondary particles). The organic filler is mainly selected from polymer compounds, and examples thereof include melamine-based resins, polymethyl (meth)acrylate-based resins, polystyrene-based resins, as well as biodegradable resins such as starch and polylactic acid, etc. These can be used alone or in combination of two or more. Among these, biodegradable resins such as polymethyl (meth)acrylate resins, polystyrene resins, and starch are preferred, and starch is particularly preferred from the viewpoint of dispersibility in PVA resins.

[0064] Examples of the starch include raw starches (cornstarch (maize starch), potato starch, sweet potato starch, wheat starch, cassava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, kudzu starch, bracken starch, lotus starch, and water chestnut starch), physically modified starches (α-starch, fractionated amylose, and heat-moisture treated starch), enzyme-modified starches (hydrolyzed dextrin, enzymatically decomposed dextrin, and amylose), chemically decomposed and modified starches (acid-treated starch, hypochlorite-oxidized starch, and dialdehyde starch), and chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, and cross-linked starch). These may be used alone or in combination of two or more. Of these, raw starch, particularly corn starch and rice starch, is preferably used from the standpoint of availability and economy.

[0065] The average particle size of the organic filler is preferably from 2 to 50 μm, particularly preferably from 4 to 45 μm, further preferably from 10 to 40 μm, and particularly preferably from 15 to 35 μm. If the average particle size is too small, the blocking tendency of the film tends to increase, whereas if it is too large, the fillers tend to aggregate with each other, resulting in reduced dispersibility, and pinholes tend to form when the film is stretched during molding processing.

[0066] In this embodiment, inorganic filler refers to particulate matter (primary particles) composed of an inorganic compound and having any shape, such as needle-like, rod-like, layer-like, scale-like, or spherical, or an aggregate of such particulate matter (secondary particles). Examples of the inorganic filler include oxide-based inorganic compounds such as silica (silicon dioxide), diatomaceous earth, titanium oxide, calcium oxide, magnesium oxide, aluminum oxide, barium oxide, germanium oxide, tin oxide, and zinc oxide, as well as talc, clay, kaolin, mica, asbestos, gypsum, graphite, glass balloons, glass beads, calcium sulfate, barium sulfate, ammonium sulfate, calcium sulfite, calcium carbonate, whisker-like calcium carbonate, magnesium carbonate, dawsonite, dolomite, potassium titanate, carbon black, glass fibers, alumina fibers, boron fibers, processed mineral fibers, carbon fibers, hollow carbon spheres, bentonite, montmorillonite, copper powder, sodium sulfate, potassium sulfate, zinc sulfate, copper sulfate, iron sulfate, magnesium sulfate, aluminum sulfate, potassium aluminum sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, aluminum nitrate, ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium phosphate, and potassium chromate. These may be used alone or in combination of two or more.

[0067] Of these, it is preferable to use an oxide-based inorganic compound or talc, more preferably titanium oxide, talc or silica, and particularly preferably silica.

[0068] The inorganic filler preferably has an average particle size of 1 to 20 μm, particularly preferably 2 to 15 μm, and further preferably 3 to 10 μm. If the average particle size is too small, the film tends to have high blocking properties and reduced flexibility and toughness, while if the average particle size is too large, the film tends to have reduced mechanical properties.

[0069] [Surfactants] In this embodiment, it is preferable to contain a surfactant as an optional component in order to improve the film peelability from the casting surface during film formation of the PVA-based film. The surfactant may be used alone or in combination of two or more.

[0070] Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, etc. Examples of such surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylnonyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyalkylene alkyl ether phosphate ester monoethanolamine salts, polyoxyethylene lauryl amino ether, polyoxyethylene stearyl amino ether, and other polyoxyethylene alkyl amino ethers, and these surfactants may be used alone or in combination of two or more. Among these, polyoxyalkylene alkyl ether phosphate monoethanolamine salt and polyoxyethylene lauryl amino ether are preferred in terms of production stability.

[0071] When the surfactant is used, its content is preferably 0.1 to 5 parts by mass, particularly preferably 0.2 to 4.5 parts by mass, and even more preferably 0.3 to 4 parts by mass, relative to 100 parts by mass of the PVA-based resin. If the content is too low, the peelability between the casting surface of the film-forming device and the formed PVA-based film tends to decrease, resulting in lower productivity, while if the content is too high, the adhesive strength during sealing tends to decrease.

[0072] [Disinfectants and preservatives] In this embodiment, a disinfectant or preservative other than the benzalkonium chloride and methylparaben may be used, as it can further suppress the growth of microorganisms in the PVA film or the PVA resin solution used to form the film. Examples of such disinfectants and preservatives include 1,2-benzisothiazolin-3-one (BIT), ethyl parahydroxybenzoate, propyl parahydroxybenzoate, butyl parahydroxybenzoate, isothiazolinone, sodium salicylate, sodium benzoate, phenoxyethanol, potassium sorbate, sodium dehydroacetate, isopropylmethylphenol, glyceryl caprylate, glyceryl caprate, glycerin fatty acid esters, chlorphenesin, salicylic acid, bisabolol, methylisothiazolinone, methylchloroisothiazolinone, etc. Among these, 1,2-benzisothiazolin-3-one (BIT), ethyl parahydroxybenzoate, propyl parahydroxybenzoate, butyl parahydroxybenzoate, phenoxyethanol, isopropylmethylphenol, etc. However, when a disinfectant or preservative other than the benzalkonium chloride or methylparaben is used, the content thereof is preferably 2 parts by mass or less, more preferably 1.5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the PVA-based resin. If the content of the bactericide and preservative other than benzalkonium chloride and methylparaben is too high, the object of the present invention cannot be achieved.

[0073] [Antioxidants] In this embodiment, an antioxidant may be added to suppress yellowing of the PVA film. Examples of the antioxidant include sulfites such as sodium sulfite, potassium sulfite, calcium sulfite, and ammonium sulfite, as well as tartaric acid, ascorbic acid, sodium thiosulfate, catechol, and Rongalite. These can be used alone or in combination of two or more. Among these, sulfites, particularly sodium sulfite, are preferred. When an antioxidant is used, the amount thereof is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, and particularly preferably 0.3 to 3 parts by mass, per 100 parts by mass of the PVA resin.

[0074] [Other optional ingredients] In this embodiment, in addition to the essential components of PVA resin and benzalkonium chloride and the various optional components described above, it is also possible to further contain, within the scope of the invention, fragrances, rust inhibitors, colorants, bulking agents, antifoaming agents, ultraviolet absorbers, fluorescent brighteners, liquid paraffins, bitter components (e.g., denatonium benzoate, etc.), etc. These can be used alone or in combination of two or more.

[0075] [PVA film] In the present embodiment, the water-soluble film means a film that is soluble in water at room temperature (20° C.). The solubility of the PVA-based film can be evaluated as follows. That is, the PVA film was cut into a size of 3 cm x 5 cm, placed in a 1-liter beaker containing 1 liter of water, and fixed with a jig. The water temperature was kept at 20°C and stirred with a stirrer (rotor length 3 cm, rotation speed 750 rpm). The PVA film was deemed dissolved when no insoluble fine particles with a diameter of 1 mm or more were visible to the naked eye.

[0076] The moisture content of the PVA film is preferably 3 to 15% by mass, particularly preferably 5 to 12% by mass, and even more preferably 6 to 10% by mass, from the viewpoint of mechanical strength and sealing property. If the moisture content is too low, the film becomes too hard, which tends to reduce the formability when made into a package during secondary processing, reduce the impact resistance of the package, and cause poor sealing. If the moisture content is too high, blocking and wrinkles from winding tend to occur. The water content can be adjusted by appropriately setting the film-forming conditions, drying conditions, and humidity control conditions. The moisture content is measured in accordance with JIS K 6726 3.4, and the value of the volatile content obtained is taken as the moisture content.

[0077] The thickness of the PVA film is appropriately selected depending on the application, etc., but is preferably 10 to 130 μm, particularly preferably 20 to 110 μm, further preferably 30 to 100 μm, and particularly preferably 45 to 90 μm. If the thickness is too thin, the mechanical strength of the film tends to decrease, while if the thickness is too thick, the dissolution rate in water tends to decrease and the film-forming efficiency also tends to decrease.

[0078] The width of the PVA film is appropriately selected depending on the application, etc., but is preferably 300 to 5000 mm, particularly preferably 500 to 4000 mm, and further preferably 600 to 3000 mm. If the width is too narrow, production efficiency tends to decrease, while if the width is too wide, it tends to become difficult to control slack and film thickness.

[0079] The length of the PVA film is appropriately selected depending on the application, etc., but is preferably 100 to 20,000 m, particularly preferably 800 to 15,000 m, and further preferably 1,000 to 10,000 m. If the length is too short, switching between films tends to be time-consuming, while if it is too long, tight winding tends to result in poor appearance and excessive weight.

[0080] The PVA film is transported and is usually wound around a core tube to form a film roll. The obtained film roll can be supplied as a product as it is, but preferably can also be supplied as a film roll slit into a film width of a desired size.

[0081] The PVA-based film is useful for various packaging applications, such as cosmetic packaging, food and beverage packaging, unit packaging for pharmaceuticals such as pesticides and detergents, (hydraulic) transfer film, sanitary products such as napkins and disposable diapers, waste disposal products such as ostomy bags, medical products such as blood-absorbing sheets, and temporary base materials such as seedling raising sheets, seed tape, and embroidery base fabric, and is particularly suitable for use in cosmetic packaging and food and beverage packaging.

[0082] The PVA-based film of this embodiment can be manufactured, for example, as follows. <Manufacture of PVA-based film> The PVA-based film of this embodiment is manufactured by passing through a dissolution and mixing step of preparing a PVA-based resin solution containing the PVA-based resin and a predetermined amount of benzalkonium chloride, and a film forming step of forming the PVA-based resin solution into a film (shaping it into a film shape) and, if necessary, performing a drying treatment to obtain a film. Hereinafter, the steps for manufacturing this PVA-based film will be described.

[0083] [Dissolution and mixing step] In the dissolution and mixing step, in order to prepare a film forming raw material to be used in the film forming step described later, the PVA-based resin, preferably a plasticizer, and if necessary, a filler, a surfactant, etc. are dissolved or dispersed using water, and benzalkonium chloride, and if necessary, a bactericide such as methyl paraben, a preservative are added to prepare a PVA-based resin solution, and shaped if necessary. These bactericides and preservatives may be blended simultaneously when dissolving or dispersing the PVA-based resin and each component in water to prepare the film forming raw material. As the dissolution method when dissolving in the water, usually, normal temperature dissolution, high temperature dissolution, pressure dissolution, etc. are adopted. Among them, high temperature dissolution is preferable because there are few undissolved substances and productivity is excellent. Also, a PVA-based resin solution, which is a film forming raw material, can be prepared by mixing the PVA-based resin, benzalkonium chloride, and each main raw material with water using an extruder and dissolving or dispersing them. In this embodiment, the PVA-based resin solution includes a PVA-based resin aqueous solution prepared by dissolving or dispersing in water and a PVA-based resin composition obtained by melt kneading with water by aqueous extrusion. The PVA-based resin solution of this embodiment is mainly used for the film forming step of the film.

[0084] The solids concentration of the PVA resin solution is preferably 10 to 65% by mass, particularly preferably 12 to 60% by mass, and further preferably 15 to 55% by mass. If the concentration is too low, film productivity tends to decrease, while if the concentration is too high, the viscosity becomes too high, which tends to require a long time to degas the PVA resin solution and to cause die lines during film formation.

[0085] The content of benzalkonium chloride in the PVA resin solution is preferably 0.003 to 0.03% by mass, particularly preferably 0.0075 to 0.02% by mass, and further preferably 0.01 to 0.015% by mass. If the concentration is too low, the growth of microorganisms in the PVA resin solution and the PVA film obtained using the same tends to be insufficient to be inhibited, whereas if the concentration is too high, safety tends to be a concern depending on the application.

[0086] Furthermore, when methylparaben is used, the content of methylparaben in the PVA resin solution is preferably 0.03 to 0.4% by mass, particularly preferably 0.06 to 0.3% by mass, and even more preferably 0.1 to 0.3% by mass. If the concentration is too low, the growth of microorganisms in the PVA resin solution and the PVA film obtained using the same tends to be insufficient to be inhibited, whereas if the concentration is too high, safety tends to be a concern depending on the application.

[0087] [Film forming process] In the film-forming process, the PVA resin solution, which is the film-forming raw material prepared in the dissolving and mixing process, is formed into a film, and a drying process is carried out as necessary to form the film. The PVA-based resin solution can be formed into a film by, for example, casting film formation or melt extrusion film formation using a film formation device, but casting film formation is preferred in terms of film thickness accuracy. In forming a film, for example, the PVA-based resin solution is extruded from a slit such as a T-slit die, cast onto a casting surface such as the metal surface of an endless belt or a drum roll, a polyethylene terephthalate film, or a plastic substrate such as polypropylene, and dried to produce a PVA-based film.

[0088] The PVA-based film of the present embodiment obtained in this manner can suppress the growth of microorganisms in the film-forming raw material (PVA-based resin solution) without using large amounts of disinfectants or preservatives, so the entire film-forming equipment line is not contaminated, and even in areas not exposed to high heat, microorganisms do not continue to grow within the film-forming equipment, ensuring safety. In this embodiment, "large amounts of disinfectant and preservative" means that each of them is 2.5% by mass or more, or the total of these is 5% by mass or more, based on the solid content of the PVA-based film.

[0089] Furthermore, since the PVA-based film of the present embodiment does not contain a large amount of disinfectants or preservatives, it can also be suitably used for packaging cosmetics and food and drink products, which are subject to strict safety standards.

[0090] In this embodiment, the microorganisms include bacteria (gram-negative bacteria, gram-positive bacteria) and fungi (yeasts and molds). Examples of the Gram-negative bacteria include Escherichia coli, Salmonella, and Pseudomonas aeruginosa. Examples of the Gram-positive bacteria include Staphylococcus aureus, lactic acid bacteria, bifidobacteria, etc. The present embodiment is particularly excellent in inhibiting the growth of Gram-negative bacteria. On the other hand, examples of the yeast include fungi of the genus Candida, Saccharomyces cerevisiae, etc. Furthermore, examples of the mold (filamentous fungi) include fungi of the genus Aspergillus, as well as fungi of the genus Aspergillus, etc. [Example]

[0091] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by mass.

[0092] First, the following materials were prepared for the PVA film: ·PVA resin: Unmodified PVA resin: 4% aqueous solution viscosity at 20°C: 4.3 to 6.3 mPa·s, average degree of saponification: 88 mol% Plasticizer: glycerin Xylitol Sorbitol Filler: cornstarch Disinfectants and preservatives: Phenoxyethanol Methylparaben Ethylhexylglycerin Benzalkonium chloride

[0093] Next, the following microorganisms were prepared as target microorganisms, and each was suspended in physiological saline to prepare a microbial solution having a predetermined concentration per 1 mL as shown below. Staphylococcus aureus (ATCC 6538) ·Escherichia coil ATCC 8739 Candida yeast (Candida albicans ATCC 10231) Aspergillus brasiliensis ATCC 16404

[0094] Example 1 First, 100 parts of PVA resin, 3 parts of glycerin as a plasticizer, 8 parts of xylitol, 6 parts of sorbitol, 0.8 parts of filler, and water were mixed and dissolved to prepare an aqueous dispersion of the resin composition with a solids concentration of 30%. Next, 1 part of methylparaben and 0.1 parts of a 50% aqueous solution of benzalkonium chloride (amount of benzalkonium chloride: 0.05 parts) were added to the aqueous dispersion liquid so that the amount was 100 parts of PVA, to prepare a PVA-based resin solution. Note that in this embodiment, all disinfectants and preservatives are expressed as active ingredients.

[0095] <Examples 2 to 5, Comparative Examples 1 to 4, Reference Examples 1 and 2> As shown in Table 1 below, a PVA-based resin solution was prepared in the same manner as in Example 1, except that the composition of the materials was changed.

[0096] The PVA resin solution thus obtained was subjected to a microbial growth inhibition test as described below, and the growth inhibition ability against each microorganism was evaluated according to the indices shown below. The evaluation results are shown in Table 1 below.

[0097] [Microbial growth inhibition test] 0.01 mL of the microbial solution was added to 1 g of each of the obtained PVA-based resin solutions, and the mixture was mixed so that the microorganisms were distributed throughout the PVA-based resin solution to prepare a test formulation. This test formulation was left to stand at room temperature (around 23°C) to culture the contained microorganisms, and after 24 hours, 9 mL of neutralizing solution was added, mixed well, and left to stand for 30 minutes to neutralize the disinfectant and preservative contained in the test formulation.

[0098] 20 μL of the neutralized test formulation was added to each well of a microplate containing 180 μL of liquid medium, and the turbidity in each well was measured over a period of 24 to 48 hours using a microplate reader to determine the growth rate (growth curve) of the microorganisms.

[0099] The growth curves of each test formulation were then compared with the acceptance standard, and growth inhibition was evaluated based on the following criteria: The acceptance standard correlates with ISO 11930 for all microorganisms and is set at a level higher than the ISO 11930 acceptance level to prevent false positives. ◎ (Excellent): The growth curve of the test formulation does not rise (no growth). ◯ (Pass): The growth curve of the test formulation rises, but is at the same level as or to the right of the pass standard (growth rate is slow). × (Fail): The growth curve of the test formulation rises and is to the left of the passing standard (fast growth rate).

[0100] [Table 1]

[0101] The results in Table 1 above show that Example 1, which contains specific amounts of methylparaben and benzalkonium chloride, inhibits the growth of both bacteria (Staphylococcus aureus, Escherichia coli) and fungi (Candida yeast, Aspergillus niger). Furthermore, it can be seen that Examples 2 to 5, which contain a specific amount of benzalkonium chloride, do not inhibit the growth of Aspergillus niger, a filamentous fungus, but do reliably inhibit the growth of other bacteria (Staphylococcus aureus, Escherichia coli) and Candida yeast, a fungus. In contrast, in Comparative Examples 1 to 4, which do not contain benzalkonium chloride as a disinfectant or preservative, it is clear that the growth of Escherichia coli cannot be inhibited even when other disinfectants or preservatives are contained in the same amount as or slightly more than benzalkonium chloride. In particular, it can be seen that Comparative Examples 1 and 2, which contain small amounts of other disinfectants and preservatives, do not inhibit the growth of any microorganisms. As shown in Reference Examples 1 and 2, other disinfectants and preservatives can also inhibit the growth of microorganisms if they are added in large amounts, but such substances do not meet the objectives of the present invention and are therefore not suitable for use in packaging cosmetics or food and beverage packaging. [Industrial Applicability]

[0102] The polyvinyl alcohol-based water-soluble film of the present invention can be used for packaging cosmetics and food and drink products, which require high safety.

Claims

1. Contains a polyvinyl alcohol resin and benzalkonium chloride, The polyvinyl alcohol-based water-soluble film contains 0.025 to 0.1 parts by mass of the benzalkonium chloride relative to 100 parts by mass of the polyvinyl alcohol-based resin.

2. Furthermore, it contains methylparaben, 2. The polyvinyl alcohol-based water-soluble film according to claim 1, wherein the polyvinyl alcohol-based resin contains 0.3 to 1.5 parts by mass of methylparaben relative to 100 parts by mass of the polyvinyl alcohol-based resin.

3. A polyvinyl alcohol-based resin solution, Contains a polyvinyl alcohol resin and benzalkonium chloride, The polyvinyl alcohol-based resin solution contains 0.025 to 0.1 parts by mass of the benzalkonium chloride per 100 parts by mass of the polyvinyl alcohol-based resin.

4. Furthermore, it contains methylparaben, The polyvinyl alcohol-based resin solution according to claim 3, wherein the methylparaben is contained in an amount of 0.3 to 1.5 parts by mass per 100 parts by mass of the polyvinyl alcohol-based resin.

5. A method for producing a water-soluble polyvinyl alcohol film, comprising: a dissolving and mixing step of dissolving a polyvinyl alcohol-based resin in water to prepare a polyvinyl alcohol-based resin solution; a film-forming step of forming a film using the polyvinyl alcohol-based resin solution obtained in the dissolving and mixing step, The polyvinyl alcohol-based resin solution prepared in the dissolving and mixing step has a solids concentration of 10 to 65% by mass, the polyvinyl alcohol-based resin solution contains a polyvinyl alcohol-based resin and benzalkonium chloride, The method for producing a polyvinyl alcohol-based water-soluble film comprises containing 0.025 to 0.1 parts by mass of the benzalkonium chloride per 100 parts by mass of the polyvinyl alcohol-based resin.

6. The polyvinyl alcohol-based resin solution further contains methylparaben, The method for producing a water-soluble polyvinyl alcohol film according to claim 5, wherein the polyvinyl alcohol resin contains 0.3 to 1.5 parts by mass of methylparaben relative to 100 parts by mass of the polyvinyl alcohol resin.

7. The method for producing a water-soluble polyvinyl alcohol-based film according to claim 5 or 6, wherein the film-forming step comprises casting the polyvinyl alcohol-based resin solution to form a film.

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