Water-soluble film and package

Abstract

The water-soluble film contains polyvinyl alcohol, an anionic surfactant, and a nonionic surfactant. The anionic surfactant satisfies the following condition 1. The nonionic surfactant has an HLB of 8-11. The content of the anionic surfactant is 0.5-1.5 mass parts per 100 mass parts of the polyvinyl alcohol. The content of the nonionic surfactant is 0.3-1.2 mass parts per 100 mass parts of the polyvinyl alcohol. Condition 1: The cloud point of an aqueous solution containing 0.15 mass% of the anionic surfactant and 0.15 mass% of a polyoxyethylene alkyl ether having three oxyethylene groups and an HLB of 8.1 is 60-130°C.

Description

Water-soluble films and packaging

[0001] The present invention relates to a water-soluble film and a package using the same.

[0002] Taking advantage of their excellent solubility in water, water-soluble films are used in a wide range of applications, such as packaging for liquid detergents, pesticides, and other chemicals, and seed tapes for containing seeds, etc. Polyvinyl alcohol (hereinafter sometimes referred to as "PVA") is mainly used for the water-soluble films used in such applications.

[0003] When producing a water-soluble film containing PVA, problems such as winding around the metal drum due to poor peeling from the metal drum surface can occur because PVA has an affinity for metal. To address this problem, it is known that adding a surfactant can improve the peelability of the film from the metal drum surface during film production. Patent Document 1 describes that adding a surfactant having a specific structure suppresses changes in film appearance during long-term storage and enables the production of a film that is easily peeled from a heat-sealing plate during heat sealing.

[0004] International Publication No. 2016 / 167135

[0005] It is thought that increasing the amount of surfactant added would improve the releasability from the metal drum surface. However, the transparency of the water-soluble film tends to decrease depending on the amount of surfactant added. Therefore, it is not easy to achieve both releasability from the metal drum surface and transparency in a water-soluble film containing PVA.

[0006] In view of the above circumstances, an object of the present invention is to provide a water-soluble film that has excellent releasability from the surface of a metal drum or the like and high transparency, and a package using such a water-soluble film.

[0007] The present invention relates to [1] to

[13] . [1] A water-soluble film comprising polyvinyl alcohol, an anionic surfactant, and a nonionic surfactant, wherein the anionic surfactant satisfies the following condition 1: the HLB of the nonionic surfactant is 8 to 11, the content of the anionic surfactant is 0.5 to 1.5 parts by mass per 100 parts by mass of the polyvinyl alcohol, and the content of the nonionic surfactant is 0.3 to 1.2 parts by mass per 100 parts by mass of the polyvinyl alcohol. Condition 1: The cloud point of an aqueous solution containing 0.15% by mass of the anionic surfactant and 0.15% by mass of a polyoxyethylene alkyl ether having 3 oxyethylene groups and an HLB of 8.1 is 60 to 130°C. [2] The water-soluble film of [1], wherein the degree of saponification of the polyvinyl alcohol is 80.0 to 95.5 mol%. [3] The water-soluble film of [1] or [2], wherein the degree of polymerization of the polyvinyl alcohol is 500 to 2,000. [4] The water-soluble film of any of [1] to [3], further comprising a plasticizer, wherein the plasticizer is a polyhydric alcohol. [5] The water-soluble film of any of [1] to [4], wherein the total content of the anionic surfactant and the nonionic surfactant is 1.3 to 2.4 parts by mass per 100 parts by mass of the polyvinyl alcohol. [6] The water-soluble film of any of [1] to [5], wherein the mass ratio of the anionic surfactant to the nonionic surfactant is 1.0:0.3 to 1.0:1.2. [7] The water-soluble film of any of [1] to [6], wherein the anionic surfactant satisfies the following condition 2: Condition 2: The surface tension of an aqueous solution containing 0.13 mass % of the anionic surfactant and 0.13 mass % of a polyoxyethylene alkyl ether having 3 oxyethylene groups and an HLB of 8.1 after a lifetime of 100 ms is 27 to 31 mN / m. [8] The water-soluble film of any of [1] to [7], wherein the nonionic surfactant is at least one selected from the group consisting of alkyl ether type, ester type, ester ether type, amino ether type, and alkanolamide type. [9] The water-soluble film of any of [1] to [8], wherein the anionic surfactant is at least one selected from the group consisting of sulfate ester type, sulfonic acid type, and sarcosinic acid type.

[10] The water-soluble film of any one of [1] to [9], which takes 150 seconds or less to completely dissolve when immersed in deionized water at 10°C.

[11] A package comprising the water-soluble film of any one of [1] to

[10] and a chemical contained in the water-soluble film.

[12] The package of

[11] , wherein the chemical is a pesticide, detergent, or disinfectant.

[13] The package of

[11] or

[12] , wherein the chemical is in liquid form.

[0008] According to the present invention, it is possible to provide a water-soluble film that has excellent releasability from the surface of a metal drum or the like and is highly transparent, and a package using such a water-soluble film.

[0009] In this specification, a numerical range described using "to" means that the numerical values ​​before and after "to" are included as the lower and upper limits. Furthermore, in this specification, the upper and lower limits of numerical ranges (contents, physical properties, etc.) can be combined as appropriate.

[0010] <Water-Soluble Film> A water-soluble film according to one embodiment of the present invention comprises polyvinyl alcohol (PVA), an anionic surfactant, and a nonionic surfactant, wherein the anionic surfactant satisfies the following condition 1, in which the HLB of the nonionic surfactant is 8 to 11, the content of the anionic surfactant is 0.5 to 1.5 parts by mass per 100 parts by mass of the PVA, and the content of the nonionic surfactant is 0.3 to 1.2 parts by mass per 100 parts by mass of the PVA. Condition 1: The cloud point of an aqueous solution containing 0.15% by mass of the anionic surfactant and 0.15% by mass of a polyoxyethylene alkyl ether having 3 oxyethylene groups and an HLB of 8.1 is 60 to 130°C.

[0011] The water-soluble film exhibits excellent releasability from metal drum surfaces and high transparency. The reason for this effect is believed to be as follows. The inventors' investigations revealed that the nonionic surfactant present on the film surface, in particular, contributes to releasability from metal drum surfaces. Therefore, it is believed that if the water-soluble film contains a large amount of nonionic surfactant, the amount of nonionic surfactant present on the film surface increases, facilitating releasability from hydrophilic metal drum surfaces. However, since nonionic surfactants tend to form droplets due to aggregation in hydrophilic PVA, containing large amounts of nonionic surfactant increases the haze of the water-soluble film and tends to impair transparency. In contrast, by combining an anionic surfactant with a predetermined physical property and a nonionic surfactant with a predetermined physical property in predetermined amounts, the nonionic surfactant is incorporated into the micelle structure formed by the anionic surfactant, thereby suppressing aggregation of the nonionic surfactant. Furthermore, because the nonionic surfactant interacts with PVA, when the nonionic surfactant is used alone, it is dispersed throughout the PVA film. In contrast, by using an anionic surfactant having predetermined physical properties in combination with a nonionic surfactant having predetermined physical properties, the nonionic surfactant is incorporated into the micelle structure formed by the anionic surfactant. In such a case, it is thought that the nonionic surfactant is less likely to interact with the PVA, and as a result, the nonionic surfactant is more likely to be unevenly distributed on the film surface. Thus, in the water-soluble film, the predetermined anionic surfactant and the predetermined nonionic surfactant are each contained in predetermined amounts, so that the nonionic surfactant can be unevenly distributed on the film surface while suppressing aggregation of the nonionic surfactant inside the film, and as a result, it is thought that the effects of excellent releasability from metal drum surfaces and high transparency can be achieved.

[0012] (PVA) PVA is a polymer consisting of vinyl alcohol units (-CH ２It is a polymer having a vinyl alcohol unit (—CHOH—). The PVA may have a monomer unit other than the vinyl alcohol unit. As the PVA, one produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer can be used. The polymerization and saponification can be carried out by conventionally known methods.

[0013] Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate, with vinyl acetate being preferred.

[0014] The vinyl ester polymer is preferably one obtained by using only one or more vinyl ester monomers as the monomer, more preferably one obtained by using only one vinyl ester monomer as the monomer, but may also be a copolymer of one or more vinyl ester monomers with other monomers copolymerizable therewith.

[0015] Examples of other monomers copolymerizable with vinyl ester monomers include ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene, and isobutene; acrylic acid or a salt thereof; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid or a salt thereof; methyl methacrylate, ethyl methacrylate, methacrylic acid, and the like. Methacrylic acid esters such as n-propyl acrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or a salt thereof, and N-methylolacrylamide or a derivative thereof. acrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or a salt thereof, N-methylolmethacrylamide or a derivative thereof; N-vinylamides such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether vinyl ethers such as butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or a salt, ester, or acid anhydride thereof; itaconic acid or a salt, ester, or acid anhydride thereof; vinylsilyl compounds such as vinyltrimethoxysilane; and isopropenyl acetate.The vinyl ester polymer and PVA may have monomer units derived from one or more of these other monomers.

[0016] Among other monomers copolymerizable with these vinyl ester monomers, from the viewpoint of water solubility, preferred are olefins having a small number of carbon atoms (for example, 2 to 3 carbon atoms), such as ethylene and propylene, carboxylic acid monomers, such as acrylic acid and methacrylic acid, and sulfonic acid monomers.

[0017] The PVA may be either a modified PVA such as a carboxylic acid-modified PVA or a sulfonic acid-modified PVA, or an unmodified PVA (a PVA having no modifying group), as long as the effects of the present invention are not impaired. Note that the unmodified PVA refers to a PVA consisting only of monomer units (vinyl alcohol units and vinyl ester units) derived from vinyl ester monomers.

[0018] The PVA may be a carboxylic acid-modified PVA obtained by saponifying a carboxylic acid-modified vinyl ester polymer obtained by copolymerizing a vinyl ester monomer and a carboxylic acid-based monomer. The upper limit of the modification degree of the carboxylic acid-modified PVA is preferably 10 mol%, more preferably 8 mol%, and even more preferably 6 mol%. On the other hand, the lower limit of the modification degree of the carboxylic acid-modified PVA is preferably 0.5 mol%, more preferably 1 mol%, and even more preferably 2 mol%. The modification degree refers to the content (mol%) of monomer units derived from other monomers (e.g., carboxylic acid-based monomers) copolymerizable with the vinyl ester monomer relative to the total monomer units.

[0019] The PVA may be a sulfonic acid-modified PVA obtained by saponifying a sulfonic acid-modified vinyl ester polymer obtained by copolymerizing a vinyl ester monomer and a sulfonic acid-based monomer. The upper limit of the modification degree of the sulfonic acid-modified PVA is preferably 8 mol%, more preferably 6 mol%, and even more preferably 4 mol%. On the other hand, the lower limit of the modification degree of the sulfonic acid-modified PVA is preferably 0.3 mol%, more preferably 0.7 mol%, and even more preferably 1 mol%.

[0020] The upper limit of the content (modification degree) of monomer units derived from monomers other than vinyl ester monomers relative to the total monomer units of PVA is preferably 15 mol %, more preferably 10 mol %, and may be 5 mol %, 2 mol %, 1 mol %, 0.5 mol %, or 0.1 mol %, from the viewpoints of water solubility of the water-soluble film, suppression of hole formation, etc.

[0021] The degree of polymerization of PVA is not particularly limited and may be, for example, 100 to 3,000, but is preferably 500 to 2,000. When the degree of polymerization of PVA is equal to or greater than the lower limit, the strength of the water-soluble film can be increased. The lower limit of the degree of polymerization of PVA is more preferably 800, even more preferably 1,000, and even more preferably 1,200. On the other hand, when the degree of polymerization of PVA is equal to or less than the upper limit, the productivity of PVA and the water-soluble film, the water solubility of the water-soluble film, etc. can be increased. The upper limit of the degree of polymerization of PVA is more preferably 1,800. Here, the degree of polymerization of PVA means the viscosity-average degree of polymerization (Po) measured in accordance with the description of JIS K6726-1994, and is calculated by the following formula from the intrinsic viscosity [η] (dl / g) measured in water at 30°C after resaponifying and purifying the PVA: Po=([η]×10 ４ / 8.29) （１／０．６２）

[0022] The saponification degree of the PVA is not particularly limited and may be, for example, 70 to 100 mol%, but from the viewpoint of water solubility, 80.0 to 95.5 mol% is preferable. The upper limit of the saponification degree of the PVA is more preferably 94.0 mol%, even more preferably 93.0 mol%, and even more preferably 92.0 mol%. By setting the saponification degree at or below the upper limit, it is possible to increase the water solubility of the water-soluble film. The lower limit of the saponification degree of the PVA is more preferably 83.0 mol%, even more preferably 85.0 mol%, and even more preferably 87.0 mol%. By setting the saponification degree at or above the lower limit, it is more likely that the water solubility and strength of the water-soluble film will be compatible. Here, the saponification degree of the PVA refers to the ratio (mol %) of the number of moles of vinyl alcohol units to the total number of moles of vinyl alcohol units and monomer units (typically vinyl ester units) that can be converted to vinyl alcohol units by saponification contained in the PVA. The degree of saponification of PVA can be measured in accordance with the description of JIS K6726-1994.

[0023] The PVA may be one type of PVA used alone, or two or more types of PVAs having different degrees of polymerization, saponification, etc. may be mixed and used.

[0024] The content of PVA in the water-soluble film is not particularly limited, but the lower limit is preferably 50% by mass, more preferably 80% by mass, even more preferably 85% by mass, and may be 90% by mass. The upper limit of the PVA content in the water-soluble film may be, for example, 99% by mass, 95% by mass, 90% by mass, or 85% by mass.

[0025] (Anionic Surfactant) The anionic surfactant contained in the water-soluble film is not particularly limited as long as it satisfies condition 1, but it is preferably at least one type selected from the group consisting of sulfate ester type, sulfonic acid type, and sarcosinic acid type.

[0026] Examples of sulfate ester type anionic surfactants include R ａ -O-SO ３ － (R ａan alkyl sulfate salt having an anion represented by the formula (R is an alkyl group) (sodium lauryl sulfate, sodium dodecyl sulfate, etc.); ａ -O-(R ｂ O) ｎ -SO ３ － (R ａ is an alkyl group, R ｂ is an alkylene group) (e.g., polyoxyethylene isotridecyl ether sodium sulfate, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene polyoxypropylene lauryl ether sodium sulfate); and the like.

[0027] Of these, the sulfate type anionic surfactants are preferably polyoxyalkylene alkyl ether sulfates, and more preferably polyoxyethylene alkyl ether sulfates.

[0028] Examples of sulfonic acid type anionic surfactants include: dialkyl sulfosuccinates such as dialkyl sulfosuccinates and sodium di-2-ethylhexyl sulfosuccinate; alkyl sulfonates (linear or branched alkyl sulfonates) such as octyl sulfate, lauryl sulfate, sodium lauryl sulfonate and sodium lauryl sulfoacetate; alpha olefin sulfonates such as alpha olefin sulfonate and sodium tetradecene sulfonate; linear or branched alkyl benzene sulfonates such as alkyl benzene sulfonates and sodium dodecyl benzene sulfonate; condensates of naphthalene sulfonates and formaldehyde such as sodium naphthalene sulfonate-formaldehyde condensate; and the like.

[0029] Of these, alkyl sulfonates are preferred as sulfonic acid type anionic surfactants.

[0030] Examples of sarcosinate-type anionic surfactants include acyl sarcosinates such as N-lauroyl sarcosinate.

[0031] The cation of the anionic surfactant is not particularly limited, and examples thereof include metal cations such as sodium cation, potassium cation, and calcium cation, and ammonium. Among these, metal cations are preferred, alkali metal cations such as sodium cation and potassium cation are more preferred, and sodium cation is even more preferred.

[0032] As the anionic surfactant, sulfonic acid type and / or sarcosinic acid type are preferred from the viewpoint of dispersibility of nonionic surfactants, etc. Furthermore, from the viewpoint of further improving the releasability and transparency of the water-soluble film from the surface of a metal drum, etc., sulfate ester type and / or sarcosinic acid type are preferred.

[0033] The anionic surfactant satisfies the following condition 1: Condition 1: The cloud point of an aqueous solution containing 0.15% by mass of an anionic surfactant and 0.15% by mass of a polyoxyethylene alkyl ether having 3 oxyethylene groups and an HLB of 8.1 is 60 to 130°C.

[0034] The aqueous solution under Condition 1 is composed only of the anionic surfactant, the polyoxyethylene alkyl ether, and water. Furthermore, if the polyoxyethylene alkyl ether has 3 oxyalkylene groups and an average alkyl group carbon number of 12 to 13, the HLB can be adjusted to 8.1. To achieve an average carbon number of 12 to 13, polyoxyethylene alkyl ethers with 12 or 13 carbon atoms can be used, or polyoxyethylene alkyl ethers with less than 12 carbon atoms and more than 13 carbon atoms can be mixed. Methods for adjusting the HLB include changing the number of carbon atoms in the alkyl group of the polyoxyethylene alkyl ether used, making the alkyl group linear / branched, and appropriately mixing polyoxyethylene alkyl ethers with alkyl groups having 12 to 13 carbon atoms. For example, the nonionic surfactant used in Example 1 described below has an HLB of 8.1, and this nonionic surfactant may also be used. As a polyoxyethylene alkyl ether with 3 oxyalkylene groups and an HLB of 8.1, a polyoxyethylene alkyl ether with 3 oxyethylene groups and a linear alkyl group having 12 carbon atoms may be used.

[0035] In this specification, HLB is a value calculated by the Griffin method. Specifically, it is a value determined by the following formula: HLB = 20 × formula weight of hydrophilic group / total molecular weight

[0036] In the case of an anionic surfactant whose aqueous solution has a cloud point of 60°C or higher as measured under condition 1, the anionic surfactant is likely to form micelles, and these micelles are likely to incorporate the nonionic surfactant. As a result, the interaction between the nonionic surfactant and PVA is reduced, and the nonionic surfactant is likely to be unevenly distributed on the film surface. On the other hand, in the case of an anionic surfactant whose cloud point is 130°C or lower, micelles of the anionic surfactant are prevented from becoming too large, and the transparency of the water-soluble film can be improved. From the viewpoint of further improving the transparency of the water-soluble film, anionic surfactants whose cloud point is 125°C or lower or 120°C or lower are preferred.

[0037] It is also preferable that the anionic surfactant satisfies the following condition 2: Condition 2: The surface tension of an aqueous solution containing 0.13% by mass of an anionic surfactant and 0.13% by mass of a polyoxyethylene alkyl ether having 3 oxyethylene groups and an HLB of 8.1 is 27 to 31 mN / m after a lifetime of 100 ms.

[0038] The aqueous solution under condition 2 is composed only of the anionic surfactant, the polyoxyethylene alkyl ether, and water. The surface tension measured under condition 2 is dynamic surface tension measured in an environment of 75°C.

[0039] In the case of an anionic surfactant whose aqueous solution has a surface tension of 27 mN / m or more as measured under condition 2, micelles of the anionic surfactant are prevented from becoming too large, thereby further improving the transparency of the water-soluble film. From the viewpoint of further improving the transparency of the water-soluble film, an anionic surfactant whose surface tension is 28.0 mN / m or more is more preferred. On the other hand, in the case of an anionic surfactant whose surface tension is 31 mN / m or less, the anionic surfactant is likely to form micelles, and these micelles are likely to incorporate the nonionic surfactant. As a result, the interaction between the nonionic surfactant and PVA is further reduced, and the nonionic surfactant is more likely to be unevenly distributed on the film surface.

[0040] The content of the anionic surfactant in the water-soluble film is 0.5 to 1.5 parts by mass relative to 100 parts by mass of PVA. From the viewpoint of more fully exerting the effects of the anionic surfactant, the lower limit of the content is preferably 0.6 parts by mass, more preferably 0.8 parts by mass. Furthermore, from the viewpoint of improving transparency, the upper limit of the content is preferably 1.4 parts by mass, more preferably 1.2 parts by mass.

[0041] (Nonionic Surfactant) The HLB of the nonionic surfactant contained in the water-soluble film is 8 to 11. By using a nonionic surfactant having an HLB in the above range in combination with a predetermined anionic surfactant, it is possible to achieve both transparency of the water-soluble film and releasability from the surface of a metal drum or the like. The HLB of the nonionic surfactant is preferably 8.0 to 11.0, and more preferably 8.1 to 10.8. HLB (Hydrophile-Lipophile Balance) refers to the hydrophilic-lipophilic ratio of a surfactant, and is used as a value representing the degree of affinity of a surfactant for water and oil (organic compounds insoluble in water).

[0042] The nonionic surfactant is not particularly limited as long as its HLB is within a predetermined range, and examples thereof include alkyl ether types (straight-chain or branched alkyl ether types) such as polyoxyethylene alkyl ethers (polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, etc.) and polyoxypropylene alkyl ethers; ester types such as polyoxyethylene sorbitan fatty acid esters; ester ether types such as polyoxyethylene sorbitan monolaurate; amino ether types such as polyoxyethylene lauryl amino ether; alkyl phenyl ether types such as polyoxyethylene octyl phenyl ether; alkyl ester types such as polyoxyethylene laurate; alkyl amine types such as polyoxyethylene lauryl amino ether; alkyl amide types such as polyoxyethylene lauric acid amide; polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether; alkanolamide types such as lauric acid diethanolamide and oleic acid diethanolamide; and allyl phenyl ether types such as polyoxyalkylene allyl phenyl ether.

[0043] From the viewpoint of releasability from the surface of a metal drum or the like, the nonionic surfactant is preferably at least one selected from the group consisting of alkyl ether type, ester type, ester ether type, amino ether type, and alkanolamide type, more preferably at least one selected from the group consisting of alkyl ether type and amino ether type, even more preferably alkyl ether type, and even more preferably polyoxyethylene alkyl ether. Polyoxyethylene alkyl ethers include polyoxyethylene primary alkyl ethers and polyoxyethylene secondary alkyl ethers. The number of oxyethylene groups (average number per molecule) in the polyoxyethylene alkyl ether is preferably 2 to 6, more preferably 3 to 5.

[0044] The content of the nonionic surfactant in the water-soluble film is 0.3 to 1.2 parts by mass per 100 parts by mass of PVA. From the viewpoint of improving releasability from the surface of a metal drum or the like, the lower limit of the content is preferably 0.4 parts by mass. Furthermore, from the viewpoint of improving the transparency of the water-soluble film, the upper limit of the content is preferably 1.1 parts by mass.

[0045] The anionic surfactant and the nonionic surfactant may be used alone or in combination of two or more thereof.

[0046] The lower limit of the total content of the anionic surfactant and the nonionic surfactant in the water-soluble film is preferably 1.3 parts by mass, more preferably 1.5 parts by mass, per 100 parts by mass of PVA. By setting the total content at or above this lower limit, the releasability of the water-soluble film from the surface of a metal drum or the like can be further improved. On the other hand, the upper limit of the total content is preferably 2.4 parts by mass, more preferably 2.0 parts by mass. By setting the total content at or below this upper limit, the transparency of the water-soluble film can be further improved.

[0047] The mass ratio of the anionic surfactant to the nonionic surfactant in the water-soluble film is preferably 1.0:0.3 to 1.0:1.2, and more preferably 1.0:0.4 to 1.0:1.1. By setting the mass ratio of the anionic surfactant to the nonionic surfactant within this range, the releasability and transparency of the water-soluble film from the surface of a metal drum or the like can be further improved.

[0048] (Plasticizer) The water-soluble film preferably contains a plasticizer. By including a plasticizer, it is possible to impart good flexibility to the water-soluble film. In this case, the water-soluble film has good mechanical strength such as impact strength, good processability during secondary processing, and the like.

[0049] As the plasticizer, polyhydric alcohols such as ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, trimethylolpropane, and sorbitol are preferred from the viewpoint of being less likely to bleed out onto the surface of the water-soluble film, and at least one selected from the group consisting of ethylene glycol, glycerin, diglycerin, propylene glycol, and diethylene glycol is more preferred.

[0050] When the water-soluble film contains a plasticizer, from the viewpoint of achieving both mechanical strength and handleability of the water-soluble film, the lower limit of the content of the plasticizer in the water-soluble film is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 5 parts by mass, relative to 100 parts by mass of PVA, while the upper limit of the content of the plasticizer is preferably 50 parts by mass, more preferably 40 parts by mass, relative to 100 parts by mass of PVA.

[0051] (Starch / Water-Soluble Polymer) The water-soluble film may contain a water-soluble polymer other than starch and / or PVA for the purposes of imparting mechanical strength to the water-soluble film or improving the handleability of the water-soluble film.

[0052] Examples of starch include natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and sago starch; and processed starches that have been subjected to etherification, esterification, oxidation, or the like, with processed starches being preferred.

[0053] The lower limit of the starch content in the water-soluble film is preferably 1 part by mass, more preferably 2 parts by mass, per 100 parts by mass of PVA. When the starch content is equal to or greater than this lower limit, it is possible to increase the mechanical strength of the water-soluble film. The upper limit of the starch content in the water-soluble film is preferably 15 parts by mass, more preferably 10 parts by mass, per 100 parts by mass of PVA. When the starch content is equal to or less than this upper limit, processability is improved during production of the water-soluble film.

[0054] Examples of water-soluble polymers other than PVA include dextrin, gelatin, glue, casein, shellac, gum arabic, polyacrylic acid amide, sodium polyacrylate, polyvinyl methyl ether, a copolymer of methyl vinyl ether and maleic anhydride, a copolymer of vinyl acetate and itaconic acid, polyvinylpyrrolidone, cellulose, acetyl cellulose, acetyl butyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and sodium alginate.

[0055] The upper limit of the content of the water-soluble polymer other than PVA in the water-soluble film is preferably 15 parts by mass, more preferably 10 parts by mass, relative to 100 parts by mass of PVA, and the lower limit of the content of the water-soluble polymer other than PVA in the water-soluble film may be 0 parts by mass, 0.1 parts by mass, 0.5 parts by mass, or 1 part by mass, relative to 100 parts by mass of PVA.

[0056] (Filler) The water-soluble film may contain a filler, which can improve the mechanical strength and handling properties of the water-soluble film.

[0057] Examples of fillers include carbon black, metal powder, silica, alumina, calcium carbonate, titanium dioxide, talc, mica, clay minerals such as bentonite, etc. Among these, talc, mica, and clay minerals are preferred.

[0058] The upper limit of the filler content in the water-soluble film is preferably 40 parts by mass, more preferably 20 parts by mass, and even more preferably 10 parts by mass, relative to 100 parts by mass of PVA. The lower limit of the filler content in the water-soluble film may be 0 parts by mass, 0.1 parts by mass, 0.5 parts by mass, or 1 part by mass, relative to 100 parts by mass of PVA.

[0059] (Other Components) The water-soluble film may further contain other components in addition to PVA, anionic surfactant, nonionic surfactant, plasticizer, starch, water-soluble polymer other than PVA, and filler, as long as the effects of the present invention are not impaired. Examples of other components include water, antioxidants, UV absorbers, lubricants, crosslinking agents, colorants, preservatives, antifungal agents, and other polymer compounds. However, the total content of PVA, anionic surfactant, nonionic surfactant, plasticizer, starch, water-soluble polymer other than PVA, and filler in the water-soluble film is preferably within the range of 60 to 100% by mass, more preferably within the range of 80 to 100% by mass, and even more preferably within the range of 90 to 100% by mass. The lower limit of the total content may be 95%, 97%, or 99% by mass. The total content of the PVA, anionic surfactant, nonionic surfactant, plasticizer, and starch in the water-soluble film is preferably in the range of 60 to 100% by mass, more preferably in the range of 80 to 100% by mass, and even more preferably in the range of 90 to 100% by mass. The lower limit of the total content may be 95%, 97%, or 99% by mass.

[0060] (Physical Properties, etc.) The complete dissolution time of the water-soluble film when immersed in deionized water at 10°C is not particularly limited, but is preferably within the following range. That is, the complete dissolution time is preferably within 150 seconds, more preferably within 90 seconds, even more preferably within 60 seconds, and particularly preferably within 45 seconds. A water-soluble film having a complete dissolution time within the above range completes dissolution relatively quickly, and can therefore be suitably used as a packaging (packaging) film for pharmaceuticals and the like. On the other hand, the lower limit of the complete dissolution time is not particularly limited, but is preferably 5 seconds, more preferably 10 seconds, even more preferably 15 seconds, and particularly preferably 20 seconds. A water-soluble film having such a complete dissolution time that is not too short is less likely to suffer from blocking (sticking) between water-soluble film layers due to absorption of moisture in the atmosphere, or from a decrease in the mechanical strength of the water-soluble film itself.

[0061] The complete dissolution time of a water-soluble film when immersed in deionized water at 10°C is measured specifically by the following procedure. (1) A rectangular sample measuring 40 mm long and 35 mm wide is cut from the water-soluble film. The sample is sandwiched and fixed between two 50 mm x 50 mm plastic plates with rectangular windows (holes) measuring 35 mm long and 25 mm wide, with the length of the sample parallel to the length of the windows and positioned approximately in the center of the width of the windows. (2) 500 mL of deionized water is placed in a 500 mL beaker, and the water temperature is adjusted to 10±1.0°C while stirring with a magnetic stirrer equipped with a 5 cm long bar so that the vortex created by stirring is approximately one-fifth of the water volume. (3) The sample fixed to the plastic plate in (1) above is immersed in the deionized water in the beaker, taking care not to let it come into contact with the magnetic stirrer bar. (4) The time from immersion to complete dissolution of the sample in the deionized water is measured. The phrase "the sample completely disappears" means that no visible dissolved residue of the water-soluble film is visible.

[0062] The average thickness or central thickness of the water-soluble film is not particularly limited, but the upper limit is preferably 120 μm, more preferably 100 μm, even more preferably 80 μm, and may be 70 μm, 60 μm, or 50 μm. When the average thickness or central thickness of the water-soluble film is equal to or less than the upper limit, the water solubility of the water-soluble film is easily ensured. On the other hand, the lower limit of the average thickness or central thickness of the water-soluble film is preferably 5 μm, more preferably 10 μm, even more preferably 15 μm, and particularly preferably 20 μm. When the average thickness or central thickness of the water-soluble film is equal to or greater than the lower limit, it is possible to suppress the occurrence of holes when the water-soluble film is used as a package. The average thickness of the water-soluble film can be determined by measuring the thickness at any 10 locations (for example, any 10 locations on a line drawn in the longitudinal direction of the water-soluble film) and averaging the measured values.

[0063] The water-soluble film may be, for example, a long film. The length of the water-soluble film is not particularly limited, and may be, for example, 100 m or more, 1,000 m or more, or 3,000 m or more. The length of the water-soluble film may be, for example, 50,000 m or less, or 10,000 m or less. The water-soluble film may be formed, cut, welded, or the like into a predetermined shape.

[0064] (Method for Producing Water-Soluble Film) The method for producing a water-soluble film according to one embodiment of the present invention is not particularly limited. For example, a film-forming solution obtained by adding a solvent, an anionic surfactant, a nonionic surfactant, or the like to PVA and homogenizing it may be produced by a casting film-forming method, a wet film-forming method (discharge into a poor solvent), a dry-wet film-forming method, a gel film-forming method (a method in which the film-forming solution is cooled to gel, and then the solvent is extracted and removed to obtain a water-soluble film), or a combination of these. Other known methods for film production include a melt-extrusion film-forming method in which a film-forming solution is obtained using an extruder or the like and then extruded through a T-die or the like to form a film, and an inflation molding method. Among these, the casting film-forming method and the melt-extrusion film-forming method are preferred because they can produce a homogeneous water-soluble film with good productivity. The casting film-forming method and the melt-extrusion film-forming method will be described below.

[0065] When a water-soluble film is produced by a casting method or a melt extrusion method, a film-forming solution on a support such as a metal drum is heated to remove the solvent, thereby solidifying the film into a film. The solidified film is peeled off from the support such as the metal drum. This film is dried, if necessary, using a drying roll or a drying oven, and further heat-treated if necessary, and then wound up to obtain a long roll of water-soluble film.

[0066] The upper limit of the volatile content of the membrane-forming solution (the content of volatile components such as solvents removed by evaporation during membrane formation, etc.) is preferably 90% by mass, more preferably 80% by mass. When the volatile content of the membrane-forming solution is equal to or less than the upper limit, the viscosity of the membrane-forming solution becomes sufficiently high, improving productivity and the uniformity of the thickness of the obtained water-soluble film. On the other hand, the lower limit of the volatile content of the membrane-forming solution is preferably 50% by mass, more preferably 55% by mass. When the volatile content of the membrane-forming solution is equal to or more than the lower limit, the viscosity of the membrane-forming solution becomes sufficiently low, improving productivity and the uniformity of the thickness of the obtained water-soluble film.

[0067] The "volatile content of the membrane-forming solution" refers to the volatile content calculated by the following formula: Volatile content of the membrane-forming solution (mass%) = {(Wa - Wb) / Wa} x 100 (where Wa represents the mass (g) of the membrane-forming solution, and Wb represents the mass (g) of the membrane-forming solution Wa (g) after drying it in an electric dryer at 105°C for 16 hours.)

[0068] The method for preparing the film-forming solution is not particularly limited. Preferred methods include, for example, a method in which PVA, an anionic surfactant, a nonionic surfactant, and the like are dissolved in a dissolution tank or the like, and a method in which, when water-containing PVA is melt-kneaded using a single-screw or twin-screw extruder, the PVA is melt-kneaded together with an anionic surfactant and a nonionic surfactant.

[0069] The prepared film-forming solution is sent to a T-die or the like through a pipe or the like, and is extruded in the form of a film onto a support through a die lip.

[0070] In a method for producing a water-soluble film in which a film-forming solution containing PVA is cast from a die through a die lip onto a support in the form of a film and dried, the draft ratio, calculated by dividing the linear velocity of the support onto which the film-forming solution is cast by the linear velocity of the film-forming solution at the die lip, is usually 2 to 60. A draft ratio within this range tends to improve the thickness uniformity, water solubility, etc. of the water-soluble film. The linear velocity of the film-forming solution at the die lip can be calculated by dividing the volumetric flow rate of the film-forming solution by the area of ​​the die lip opening (die lip width x lip opening).

[0071] While the coating film is heated and dried on the support, hot air may be blown uniformly over the entire area of ​​the non-contact side of the coating film to adjust the drying speed. The temperature of the hot air is usually 75 to 105°C. The speed of the hot air is usually 3 to 10 m / sec.

[0072] The coating film formed by casting the film-forming solution onto a support is dried on the support preferably to a volatile content of 5 to 50% by mass, then peeled off, and further dried as necessary. The drying method is not particularly limited, and examples include contacting the coating film with a drying oven or drying rolls. When drying is performed with multiple drying rolls, it is preferable to alternately contact one side of the coating film with the drying rolls in order to uniformize the physical properties of both sides of the resulting water-soluble film. The temperature of the drying oven or drying rolls can be selected as appropriate and is usually 40 to 110°C.

[0073] The method for producing a water-soluble film may include a step of heat-treating the film at a temperature of 80 to 300° C. When the heat-treatment temperature is within this range, the occurrence of wrinkles in the package over time can be suppressed.

[0074] The water-soluble film thus produced may be further subjected to humidity conditioning, embossing, cutting of both edges (edges) of the film, etc., as required, and then wound into a roll on a cylindrical core.

[0075] The upper limit of the volatile content of the water-soluble film finally obtained by the series of treatments is preferably 5% by mass, more preferably 4% by mass, and the lower limit of the volatile content of the water-soluble film may be 0% by mass, 1% by mass, or 2% by mass.

[0076] <Uses of Water-Soluble Film and Package> The water-soluble film according to one embodiment of the present invention can be suitably used for various water-soluble film applications. Examples of such water-soluble films include films for packaging medicines, base films for hydraulic transfer printing, substrate films for embroidery, release films for molding artificial marble, films for packaging seeds, and films for waste collection bags. Among these, the water-soluble film of the present invention is preferably used as a film for containing medicines (medicinal packaging film) because the effects of the present invention are more pronounced.

[0077] When the water-soluble film is used as a pharmaceutical packaging film, examples of the pharmaceutical include pesticides, detergents (including bleach), disinfectants, etc. The physical properties of the pharmaceutical are not particularly limited, and the pharmaceutical may be acidic, neutral, or alkaline. Therefore, the water-soluble film can be suitably used as a package for pesticides, detergents (including bleach), disinfectants, etc. The pharmaceutical may be in any form, such as powder, block, gel, or liquid. The packaging form is not particularly limited, but a unit packaging form in which the pharmaceutical is packaged (preferably sealed) in unit amounts is preferred. In particular, a package in which a liquid pharmaceutical is packaged using the water-soluble film can be used without the pharmaceutical coming into contact with the skin.

[0078] Thus, a package comprising a water-soluble film according to one embodiment of the present invention and a drug contained in the water-soluble film is a preferred embodiment of the present invention. Examples of drugs packaged in the package include those described above, and are preferably pesticides, detergents, or disinfectants. The form of the drug packaged in the package can also be those described above, but a preferred embodiment is that the drug is in liquid form.

[0079] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples in any way.

[0080] <Cloud Point> 10 mL of an aqueous solution containing 0.15% by mass of the anionic surfactant used in each Example or Comparative Example and 0.15% by mass of polyoxyethylene alkyl ether (oxyethylene group number: 3, HLB: 8.1) was prepared and placed in a pressure-resistant vial and sealed. The pressure-resistant vial was left standing in a hot air dryer at 40°C for 30 minutes, then removed, and the state of the aqueous solution immediately after removal was confirmed. If the aqueous solution was not cloudy, the vial was left standing in a hot air dryer with the set temperature increased by 10°C for 30 minutes, and the state of the aqueous solution immediately after removal was confirmed. This process was repeated until the aqueous solution became cloudy, and the temperature at which the aqueous solution became cloudy was measured as the cloud point.

[0081] <Surface Tension> 100 mL of an aqueous solution was prepared by dissolving 0.13% by mass of the anionic surfactant used in each Example or Comparative Example and 0.13% by mass of polyoxyethylene alkyl ether (number of oxyethylene groups: 3, HLB: 8.1), and the solution was allowed to stand for 2 hours in a dryer set at 85° C. The dynamic surface tension of each solution was measured three times in an environment of 75° C. using an automatic dynamic surface tensiometer (manufactured by Kyowa Interface Science Co., Ltd., "BP-D5"), and the average value of the surface tension over a lifetime of 100 ms was calculated.

[0082] <Average Thickness> The water-soluble films obtained in each Example or Comparative Example were measured for thickness at any 10 points on a line drawn in the longitudinal direction of the central part of the film in the width direction using a film thickness meter (manufactured by Ono Sokki Co., Ltd., "DG-5100"), and the average value of the thicknesses was calculated.

[0083] <Peel tension from metal drum surface> In each example or comparative example, when peeling the dried film from the metal drum surface, a tension meter ("ZTS-DPU-50N" manufactured by Imada Co., Ltd.) was attached to the center of the film in the width direction at the peel start position, and the film was peeled while being pulled together with the tension meter, and the force applied to the film during peeling was measured as the peel tension. A peel tension of 0.70 N or less was evaluated as having excellent releasability from the metal drum surface, etc.

[0084] <Haze> The water-soluble films obtained in each Example or Comparative Example were heat-treated in a hot air dryer at 120°C for 10 minutes, and five 4 cm square film samples were cut out. The haze values ​​of the cut film samples were measured in accordance with JIS K7136 using a haze meter ("HZ-2" manufactured by Suga Test Instruments Co., Ltd.), and the average value of the results for the five samples was calculated. A haze of 12.0 or less was determined to have high transparency.

[0085] Example 1 An aqueous solution containing 100 parts by mass of PVA (degree of polymerization 1,700, degree of saponification 89.0 mol%), 15 parts by mass of glycerin as a plasticizer, 1.0 part by mass of sodium alkylsulfonate as an anionic surfactant, 0.5 parts by mass of polyoxyethylene alkyl ether (oxyethylene (OE) group number 3, HLB 8.1) as a nonionic surfactant, and 2.8 parts by mass of starch, with a PVA content of 13.3 mass% was prepared as a film-forming solution. The cloud point and surface tension of the anionic surfactant used, measured by the method described above, were 130°C and 27.6 mN / m, respectively. The film-forming solution was cast onto a metal drum at 60°C and dried for 30 minutes. The dried film was then peeled from the metal drum surface to produce a water-soluble film with an average thickness of 76 μm. The peel tension from the metal drum surface was 0.60 N. The haze of the resulting water-soluble film, measured by the method described above, was 11.3. The results are shown in Table 1. The mass ratio of polyvinyl alcohol to each surfactant contained in the obtained water-soluble film is the same as the mass ratio of polyvinyl alcohol to each surfactant in the film-forming solution.

[0086] [Example 2] A water-soluble film was produced in the same manner as in Example 1, except that the anionic surfactant in the film-forming solution was changed to sodium acyl sarcosinate. The cloud point of the anionic surfactant used, measured by the method described above, was 110°C, and the surface tension was 30.3 mN / m. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0087] [Example 3] A water-soluble film was produced in the same manner as in Example 1, except that the anionic surfactant in the film-forming solution was changed to sodium acyl sarcosinate and the nonionic surfactant was changed to polyoxyethylene alkyl ether (oxyethylene group number 3, HLB 8.2). The cloud point and surface tension of the anionic surfactant used, measured by the method described above, were 110°C and 30.3 mN / m, respectively. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0088] [Example 4] A water-soluble film was produced in the same manner as in Example 1, except that in the film-forming solution, the anionic surfactant was changed to sodium polyoxyethylene alkyl ether sulfate, the nonionic surfactant was changed to polyoxyethylene alkyl ether (5 oxyethylene groups, HLB 10.7), and the amount of nonionic surfactant added was changed to 1.0 part by mass. The cloud point of the anionic surfactant used, measured by the method described above, was 120°C, and the surface tension was 28.5 mN / m. The peel tension and haze of the obtained water-soluble film were measured by the method described above. The results are shown in Table 1.

[0089] [Example 5] A water-soluble film was produced in the same manner as in Example 1, except that the anionic surfactant in the film-forming solution was changed to sodium polyoxyethylene alkyl ether sulfate. The cloud point of the anionic surfactant used, measured by the method described above, was 120°C, and the surface tension was 28.5 mN / m. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0090] Example 6 A water-soluble film was produced in the same manner as in Example 1, except that in the film-forming solution, 100 parts by mass of PVA (degree of polymerization 1,700, degree of saponification 89.0 mol%) was replaced with a mixture of 50 parts by mass of PVA (degree of polymerization 1,700, degree of saponification 89.0 mol%) and 50 parts by mass of PVA (degree of polymerization 500, degree of saponification 89.0 mol%), and the anionic surfactant was changed to sodium acyl sarcosinate. The cloud point and surface tension of the anionic surfactant used, measured by the method described above, were 110°C and 30.3 mN / m, respectively. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0091] Comparative Example 1 A water-soluble film was produced in the same manner as in Example 1, except that no anionic surfactant was added to the film-forming solution, the nonionic surfactant was changed to polyoxyethylene alkyl ether (7 oxyethylene groups, HLB 12.1), and the amount of nonionic surfactant added was changed to 1.0 part by mass. The peel tension and haze of the obtained water-soluble film were measured by the methods described above. The results are shown in Table 1.

[0092] Comparative Example 2 A water-soluble film was produced in the same manner as in Example 1, except that the anionic surfactant in the film-forming solution was changed to sodium polyoxyethylene alkyl ether sulfate and no nonionic surfactant was added. The cloud point of the anionic surfactant used, measured by the method described above, was 120°C, and the surface tension was 28.5 mN / m. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0093] Comparative Example 3 A water-soluble film was produced in the same manner as in Example 1, except that the anionic surfactant in the film-forming solution was changed to a sodium naphthalenesulfonate-formaldehyde condensate. The cloud point and surface tension of the anionic surfactant used, measured by the methods described above, were 40°C and 40.3 mN / m, respectively. The peel tension and haze of the resulting water-soluble film were measured by the methods described above. The results are shown in Table 1.

[0094] Comparative Example 4 A water-soluble film was produced in the same manner as in Example 1, except that the amount of anionic surfactant added to the film-forming solution was changed to 2.0 parts by mass. The cloud point of the anionic surfactant used, measured by the method described above, was 130°C, and the surface tension was 27.6 mN / m. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0095] Comparative Example 5 A water-soluble film was produced in the same manner as in Example 1, except that the anionic surfactant in the film-forming solution was changed to sodium polyoxyethylene alkyl ether sulfate, the nonionic surfactant was changed to polyoxyethylene alkyl ether (5 oxyethylene groups, HLB 10.7), and the amount of nonionic surfactant added was changed to 0.1 parts by mass. The cloud point and surface tension of the anionic surfactant used, measured by the method described above, were 120°C and 28.5 mN / m, respectively. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0096] Comparative Example 6 A water-soluble film was produced in the same manner as in Example 1, except that the anionic surfactant in the film-forming solution was changed to sodium polyoxyethylene alkyl ether sulfate and the nonionic surfactant was changed to polyoxyethylene alkyl ether (15 oxyethylene groups, HLB 15.3). The cloud point and surface tension of the anionic surfactant used, measured by the method described above, were 120°C and 28.5 mN / m, respectively. The peel tension and haze of the resulting water-soluble film were measured by the method described above. The results are shown in Table 1.

[0097] In addition, all of the water-soluble films obtained in the Examples and Comparative Examples were completely dissolved within 150 seconds when immersed in deionized water at 10° C. by the above-mentioned method.

[0098]

[0099] As shown in Table 1, each of the water-soluble films of Examples 1 to 6 had a peel tension from the metal drum surface of 0.70 N or less and a haze value of 12.0 or less, and thus had excellent peelability from the metal drum surface and high transparency.

[0100] The water-soluble film of the present invention can be suitably used as a packaging material for various chemicals such as liquid detergents and agricultural chemicals.

Claims

1. A water-soluble film comprising polyvinyl alcohol, an anionic surfactant and a nonionic surfactant, the anionic surfactant satisfying the following condition 1, the HLB of the nonionic surfactant being 8 to 11, the content of the anionic surfactant being 0.5 to 1.5 parts by mass relative to 100 parts by mass of the polyvinyl alcohol, and the content of the nonionic surfactant being 0.3 to 1.2 parts by mass relative to 100 parts by mass of the polyvinyl alcohol. Condition 1: The cloud point of an aqueous solution containing 0.15% by mass of the anionic surfactant and 0.15% by mass of a polyoxyethylene alkyl ether having 3 oxyethylene groups and an HLB of 8.1 is 60 to 130°C.

2. The water-soluble film according to claim 1, wherein the degree of saponification of the polyvinyl alcohol is 80.0 to 95.5 mol %.

3. The water-soluble film according to claim 1 or 2, wherein the degree of polymerization of the polyvinyl alcohol is 500 to 2,000.

4. The water-soluble film according to claim 1 or 2, further comprising a plasticizer, said plasticizer being a polyhydric alcohol.

5. The water-soluble film according to claim 1 or 2, wherein the total content of the anionic surfactant and the nonionic surfactant is 1.3 to 2.4 parts by mass per 100 parts by mass of the polyvinyl alcohol.

6. The water-soluble film according to claim 1 or 2, wherein the mass ratio of said anionic surfactant to said nonionic surfactant is 1.0:0.3 to 1.0:1.

2.

7. The water-soluble film according to claim 1 or 2, wherein the anionic surfactant satisfies the following condition 2. Condition 2: the surface tension of an aqueous solution containing 0.13% by mass of the anionic surfactant and 0.13% by mass of a polyoxyethylene alkyl ether having 3 oxyethylene groups and an HLB of 8.1 is 27 to 31 mN / m for a life time of 100 ms.

8. The water-soluble film according to claim 1 or 2, wherein the nonionic surfactant is at least one selected from the group consisting of alkyl ether type, ester type, ester ether type, amino ether type and alkanol amide type.

9. The water-soluble film according to claim 1 or 2, wherein the anionic surfactant is at least one selected from the group consisting of sulfate ester type, sulfonic acid type and sarcosinic acid type.

10. The water-soluble film according to claim 1 or 2, which is completely dissolved in 150 seconds or less when immersed in deionized water at 10°C.

11. A package comprising the water-soluble film according to claim 1 or 2 and a drug contained in the water-soluble film.

12. The package of claim 12, wherein the agent is a pesticide, a detergent or a disinfectant.

13. The package of claim 12, wherein the medication is in liquid form.

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