Water-soluble film and package

Abstract

A water-soluble film which contains a polyvinyl alcohol, an anionic surfactant, and a nonionic surfactant, wherein in a first surface that is one of two surfaces which are orthogonal to the thickness direction of the water-soluble film, the component ratio of the anionic surfactant is 3% or more, and the component ratio of the nonionic surfactant is 30% or more as determined by X-ray photoelectron spectroscopy.

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

[12] . [1] A water-soluble film containing polyvinyl alcohol, an anionic surfactant, and a nonionic surfactant, wherein, on a first surface, which is one of two surfaces perpendicular to the thickness direction of the water-soluble film, the component ratio of the anionic surfactant is 3% or more and the component ratio of the nonionic surfactant is 30% or more, as measured by X-ray photoelectron spectroscopy. [2] The water-soluble film of [1], wherein, on the first surface, the sum of the component ratios of the anionic surfactant and the nonionic surfactant is 40% or more. [3] The water-soluble film of [1] or [2], wherein, on the first surface, the ratio of the component ratio of the nonionic surfactant to the component ratio of the anionic surfactant is 1 to 12. [4] The water-soluble film of any one of [1] to [3], wherein 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. [5] The water-soluble film of any one of [1] to [4], wherein the anionic surfactant is at least one selected from the group consisting of sulfate ester type, sulfonic acid type, and sarcosinic acid type. [6] The water-soluble film of any one of [1] to [5], wherein the anionic surfactant comprises at least one selected from the group consisting of sodium alkylsulfonate, sodium acylsarcosinate, and sodium polyoxyethylene alkyl ether sulfate. [7] The water-soluble film of any one of [1] to [6], 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. [8] The water-soluble film of any one of [1] to [7], wherein the nonionic surfactant comprises a polyoxyethylene alkyl ether. [9] The water-soluble film of any one of [1] to [8], which takes 150 seconds or less to completely dissolve when immersed in deionized water at 10°C.

[10] A package comprising the water-soluble film of any one of [1] to [9] and a chemical contained in the water-soluble film.

[11] The package of

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

[12] The package of

[10] or

[11] , wherein the drug 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. In addition, 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 is a water-soluble film containing polyvinyl alcohol (PVA (A)), an anionic surfactant (B), and a nonionic surfactant (C), and on a first surface, which is one of two surfaces orthogonal to the thickness direction of the water-soluble film, the component ratio (BX1) of the anionic surfactant (B) is 3% or more, and the component ratio (CX1) of the nonionic surfactant (C) is 30% or more, as determined by X-ray photoelectron spectroscopy.

[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, if the water-soluble film contains a large amount of nonionic surfactant, the amount of nonionic surfactant present on the film surface increases, which is thought to facilitate releasability from hydrophilic metal drum surfaces. However, since nonionic surfactants tend to form droplets through aggregation in hydrophilic PVA, simply containing a large amount of nonionic surfactant increases the haze of the water-soluble film and tends to impair transparency. In contrast, the use of an anionic surfactant in combination with a nonionic surfactant is thought to incorporate the nonionic surfactant 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 a nonionic surfactant is used alone, it is dispersed throughout the PVA film. In contrast, when an anionic surfactant is used in combination with a nonionic surfactant, the nonionic surfactant is incorporated into the micelle structure formed by the anionic surfactant. In such cases, it is believed that the nonionic surfactant is less likely to interact with PVA, resulting in the nonionic surfactant being more likely to be unevenly distributed on the film surface. However, simply using a nonionic surfactant in combination with an anionic surfactant does not produce the above-mentioned effect of unevenly distributing the nonionic surfactant on the film surface while suppressing aggregation of the nonionic surfactant inside the film. The above-mentioned effect may not be achieved depending on the amount and type of each surfactant added. In other words, if a sufficient amount of nonionic surfactant and anionic surfactant is present on the film surface, aggregation of the nonionic surfactant inside the film is suppressed, and the nonionic surfactant is unevenly distributed on the film surface, resulting in the above-mentioned effect.In this water-soluble film, the component ratios of anionic surfactant and nonionic surfactant on the film surface (first surface) are equal to or greater than a predetermined value, and aggregation of the nonionic surfactant inside the film is suppressed while the nonionic surfactant is unevenly distributed on the film surface. As a result, it is presumed that the film has excellent releasability from the surface of a metal drum, etc., and high transparency.

[0012] (Component ratio in the first surface) The first surface of the water-soluble film is one of two surfaces perpendicular to the thickness direction of the water-soluble film. The first surface is usually the surface that was in contact with the metal drum surface or the like (the surface of a metal drum or other support) when the film-forming solution is cast onto a support such as a metal drum to produce a water-soluble film. Whether or not the surface was in contact with the metal drum surface or the like can be determined by the surface properties, etc. For example, the surface that was in contact with the metal drum surface may have a shape that is a transfer of the surface shape, such as smoothness, specific to the metal drum surface.

[0013] The lower limit of the component ratio (BX1) of the anionic surfactant (B) on the first surface, as determined by X-ray photoelectron spectroscopy, is 3%, preferably 3.2%, and more preferably 3.5%. By ensuring that the component ratio (BX1) of the anionic surfactant (B) is equal to or greater than the lower limit, the nonionic surfactant (C) can be sufficiently distributed unevenly on the film surface. That is, even if the component ratio (CX1) of the nonionic surfactant (C) is high, if the component ratio (BX1) of the anionic surfactant (B) is low, the amount of nonionic surfactant (C) added may be simply too high, resulting in a state where the nonionic surfactant (C) is not distributed unevenly on the surface, and the effects of excellent releasability from a metal drum surface and high transparency may not be achieved. The lower limit of the component ratio (BX1) may be 4%, 6%, 8%, 10%, 15%, or 20%. The upper limit of the component ratio (BX1) is not particularly limited, but is preferably 50%, and may be 40%, 35%, 30%, 25%, 20%, 15%, 10%, or 5%. By setting the component ratio (BX1) of the anionic surfactant (B) to the above upper limit or less, it is possible to further increase transparency, etc.

[0014] In the first surface, the lower limit of the component ratio (CX1) of the nonionic surfactant (C) obtained by X-ray photoelectron spectroscopy is 30%, preferably 32%, and more preferably 35%. When the component ratio (CX1) of the nonionic surfactant (C) is equal to or greater than the lower limit, excellent releasability from the surface of a metal drum or the like is achieved. The upper limit of the component ratio (CX1) of the nonionic surfactant (C) is not particularly limited, but is preferably 60%, and more preferably 55%. When the component ratio (CX1) of the nonionic surfactant (C) is equal to or less than the upper limit, transparency can be further improved.

[0015] On the first surface, the lower limit of the sum (BX1 + CX1) of the component ratio (BX1) of the anionic surfactant (B) and the component ratio (CX1) of the nonionic surfactant (C) is preferably 40%, more preferably 42%. The sufficient presence of the anionic surfactant (B) and the nonionic surfactant (C) on the surface can further improve releasability from the surface of a metal drum, etc. The lower limit of the sum (BX1 + CX1) may be 45%, 50%, 55%, or 60%. The upper limit of the sum (BX1 + CX1) is preferably 80%, more preferably 70%. By setting the sum (BX1 + CX1) to the above upper limit or less, transparency can be further improved. The upper limit of the sum (BX1 + CX1) may be 60% or 50%.

[0016] On the first surface, the ratio (CX1 / BX1) of the component ratio (CX1) of the nonionic surfactant (C) to the component ratio (BX1) of the anionic surfactant (B) is preferably 1 to 12, more preferably 1.2 to 11.5. When the ratio (CX1 / BX1) is within the above range, the balance between the anionic surfactant (B) and the nonionic surfactant (C) is optimized, and releasability from the surface of a metal drum or the like and transparency can be further improved.

[0017] The component ratio (BX1) of the anionic surfactant (B) and the component ratio (CX1) of the nonionic surfactant (C) on the first surface can be obtained by X-ray photoelectron spectroscopy, specifically by the method described in the Examples below. The component ratio (BX1) of the anionic surfactant (B) and the component ratio (CX1) of the nonionic surfactant (C) are both mass-based ratios, and the respective units (%) may be expressed as mass%. The component ratio (BX2) of the anionic surfactant (B) and the component ratio (CX2) of the nonionic surfactant (C) on the second surface, which is the other of the two surfaces perpendicular to the thickness direction of the water-soluble film, obtained by X-ray photoelectron spectroscopy are not particularly limited.

[0018] Hereinafter, each of the constituent components of the water-soluble film according to one embodiment of the present invention will be described in detail.

[0019] (PVA(A)) PVA(A) is a vinyl alcohol unit (-CH ２ The PVA (A) is a polymer having a vinyl alcohol unit (—CHOH—). The PVA (A) may have a monomer unit other than the vinyl alcohol unit. As the PVA (A), a PVA 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.

[0020] 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.

[0021] 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.

[0022] 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 (A) may have monomer units derived from one or more of these other monomers.

[0023] 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.

[0024] The PVA (A) 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. The unmodified PVA means a PVA consisting only of monomer units (vinyl alcohol units and vinyl ester units) derived from vinyl ester monomers.

[0025] The PVA (A) 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.

[0026] The PVA (A) 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%.

[0027] 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 (A) is preferably 15 mol %, more preferably 10 mol %, from the viewpoints of water solubility of the water-soluble film, suppression of hole formation, etc., and may be 5 mol %, 2 mol %, 1 mol %, 0.5 mol %, or 0.1 mol %.

[0028] The degree of polymerization of PVA (A) is not particularly limited and may be, for example, 100 to 3,000, but preferably 500 to 2,000. When the degree of polymerization of PVA (A) 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 (A) 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 (A) is equal to or less than the upper limit, the productivity of PVA (A) and the water-soluble film, the water solubility of the water-soluble film, and the like can be increased. The upper limit of the degree of polymerization of PVA (A) is more preferably 1,800. Here, the degree of polymerization of PVA (A) refers to the viscosity-average degree of polymerization (Po) measured in accordance with JIS K6726-1994, and is calculated from the intrinsic viscosity [η] (dL / g) measured in water at 30°C after resaponification and purification of PVA (A) using the following formula: Po = ([η] x 10 ４ / 8.29) （１／０．６２）

[0029] The degree of saponification of PVA (A) is not particularly limited and may be, for example, 70 to 100 mol%, but from the viewpoint of water solubility, etc., 80.0 to 95.5 mol% is preferable. The upper limit of the degree of saponification of PVA (A) is more preferably 94.0 mol%, even more preferably 93.0 mol%, and even more preferably 92.0 mol%. By setting the degree of saponification at or below the upper limit, it is possible to increase the water solubility of the water-soluble film. The lower limit of the degree of saponification of PVA (A) is more preferably 83.0 mol%, even more preferably 85.0 mol%, and even more preferably 87.0 mol%. By setting the degree of saponification at or above the lower limit, it is likely that the water solubility and strength of the water-soluble film will be compatible. Here, the degree of saponification of PVA (A) 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 PVA (A). The degree of saponification of the PVA (A) can be measured in accordance with the description of JIS K6726-1994.

[0030] The PVA (A) may be one type of PVA used alone, or two or more types of PVAs different from each other in degree of polymerization, degree of saponification, etc. may be mixed and used.

[0031] The content of PVA (A) 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 content of PVA (A) in the water-soluble film may be, for example, 99% by mass, 95% by mass, 90% by mass, or 85% by mass.

[0032] (Anionic Surfactant (B)) The anionic surfactant (B) contained in the water-soluble film is not particularly limited, but is preferably at least one selected from the group consisting of sulfate ester type, sulfonic acid type, and sarcosinic acid type.

[0033] Examples of the sulfate ester type anionic surfactant (B) include: 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.

[0034] Among these, the sulfate type anionic surfactant (B) is preferably a polyoxyalkylene alkyl ether sulfate, more preferably a polyoxyethylene alkyl ether sulfate.

[0035] Examples of the sulfonic acid type anionic surfactant (B) 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.

[0036] Of these, alkyl sulfonates are preferred as the sulfonic acid type anionic surfactant (B).

[0037] Examples of the sarcosinate type anionic surfactant (B) include acyl sarcosinates such as N-lauroyl sarcosinate.

[0038] The cation of the anionic surfactant (B) 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.

[0039] The anionic surfactant (B) preferably contains at least one selected from the group consisting of sodium alkylsulfonate, sodium acyl sarcosinate, and sodium polyoxyethylene alkyl ether sulfate, from the viewpoint of further improving the releasability and transparency of the water-soluble film from the surface of a metal drum, 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., the anionic surfactant (B) is also preferably a sulfate ester type or a sarcosinate type.

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

[0041] (Nonionic Surfactant (C)) The nonionic surfactant (C) contained in the water-soluble film is not particularly limited, 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; allyl phenyl ether types such as polyoxyalkylene allyl phenyl ether; and the like.

[0042] As the nonionic surfactant (C), from the viewpoint of releasability from the surface of a metal drum or the like, at least one selected from the group consisting of alkyl ether type, ester type, ester ether type, amino ether type, and alkanolamide type is preferred, at least one selected from the group consisting of alkyl ether type and amino ether type is more preferred, alkyl ether type is even more preferred, and polyoxyethylene alkyl ether is even more preferred. The nonionic surfactant (C) also preferably contains a polyoxyethylene alkyl ether. Polyoxyethylene alkyl ethers include polyoxyethylene primary alkyl ethers, polyoxyethylene secondary alkyl ethers, and the like. The number of oxyethylene groups (average number per molecule) in the polyoxyethylene alkyl ether is preferably 2 to 6, more preferably 3 to 5.

[0043] The HLB of the nonionic surfactant (C) is preferably 8 to 11, and more preferably 8.0 to 11.0. By using a nonionic surfactant (C) having an HLB in the above range, the transparency of the water-soluble film and its releasability from the surface of a metal drum or the like can be further improved. HLB (Hydrophile-Lipophile Balance) refers to the hydrophilic-lipophilic ratio and is used as a value representing the degree of affinity of a surfactant for water and oil (organic compounds insoluble in water). 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

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

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

[0046] The lower limit of the total content of the anionic surfactant (B) and the nonionic surfactant (C) in the water-soluble film is preferably 1.0 part by mass, more preferably 1.3 parts by mass, and even more preferably 1.5 parts by mass, per 100 parts by mass of the PVA (A). 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 3.0 parts by mass, more preferably 2.4 parts by mass, and even 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 (B) to the nonionic surfactant (C) in the water-soluble film is preferably 1.0:0.2 to 1.0:1.5, more preferably 1.0:0.3 to 1.0:1.2, and even more preferably 1.0:0.4 to 1.0:1.1. By setting the mass ratio of the anionic surfactant (B) to the nonionic surfactant (C) 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, per 100 parts by mass of PVA (A), while the upper limit of the content of the plasticizer is preferably 50 parts by mass, more preferably 40 parts by mass, per 100 parts by mass of PVA (A).

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

[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 (A). 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 (A). When the starch content is equal to or less than this upper limit, processability is improved during the production of the water-soluble film.

[0054] Examples of water-soluble polymers other than PVA (A) 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 (A) in the water-soluble film is preferably 15 parts by mass, more preferably 10 parts by mass, per 100 parts by mass of PVA (A). The lower limit of the content of the water-soluble polymer other than PVA (A) 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, per 100 parts by mass of PVA (A).

[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 (A). 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 (A).

[0059] (Other Components) The water-soluble film may further contain other components in addition to the PVA (A), anionic surfactant (B), nonionic surfactant (C), plasticizer, starch, water-soluble polymer other than the PVA (A), 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 the PVA (A), anionic surfactant (B), nonionic surfactant (C), plasticizer, starch, water-soluble polymer other than the PVA (A), 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 (A), the anionic surfactant (B), the nonionic surfactant (C), the plasticizer, and the 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 (B), a nonionic surfactant (C), or the like to PVA (A) 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 methods. 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, but examples of preferred methods include a method in which PVA (A), an anionic surfactant (B), a nonionic surfactant (C), and the like are dissolved in a dissolution tank or the like, and a method in which, when PVA (A) in a water-containing state is melt-kneaded using a single-screw or twin-screw extruder, the anionic surfactant (B), the nonionic surfactant (C), and the like are melt-kneaded together.

[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 (A) 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 determined 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] <XPS> (Component Ratio of Anionic Surfactant (B) and Nonionic Surfactant (C)) For the PVA films obtained in each Example or Comparative Example, the surface that contacts the metal drum surface during film formation was designated as the first surface of the two surfaces perpendicular to the thickness direction of the PVA film. The first surface was analyzed by X-ray photoelectron spectroscopy (XPS) to determine the mass-based component ratio (BX1) of the anionic surfactant (B) and the mass-based component ratio (CX1) of the nonionic surfactant (C). The other surface (opposite the first surface) of the two surfaces perpendicular to the thickness direction of the PVA film was designated as the second surface. XPS analysis was performed under the same conditions to determine the mass-based component ratio (BX2) of the anionic surfactant (B) and the mass-based component ratio (CX2) of the nonionic surfactant (C). The second surface was designated as the surface that does not contact the metal drum surface during film formation. Specific measurement methods for XPS measurement are described below.

[0081] XPS measurement involves irradiating a sample surface with X-rays to excite the atomic core electrons and then detecting the kinetic energy of the emitted photoelectrons, thereby identifying and quantifying the elements present on the sample surface and analyzing their chemical bonding states. Furthermore, the spectrum obtained by photoelectrons from carbon atoms present on the sample surface (C1s spectrum) is the sum of various peaks that depend on the bonding state of the carbon atoms. The positions of these various peaks are determined by the bonding state of the carbon atoms. For example, carbon-carbon single bonds (C-C) or carbon-hydrogen bonds (C-H) are believed to exhibit peaks at 284.8 eV, carbon-oxygen single bonds (C-O) at 286.4 eV, carbonyl (C=O) at 287.6 eV, and COO bonds (C(=O)-O) at 288.6 eV. These peaks can be identified by detailed analysis (narrow scan) of the C1s spectrum and separating them into individual peaks. Peak separation can be performed, for example, using automatic waveform separation fitting in the analysis software installed in the XPS measurement instrument.

[0082] [Measurement Method] The elemental ratios of carbon (1s orbital electrons: C1s), nitrogen (1s orbital electrons: N1s), oxygen (1s orbital electrons: O1s), sodium (1s orbital electrons: Na1s), and sulfur (2p inertial electrons: S2p) were quantified using wide-scan XPS measurements. Furthermore, a narrow scan was performed in the range of 280 to 300 eV to obtain a C1s spectrum. Using the analysis software of the XPS measurement instrument, peaks were separated for the carbon bonding states, C—C bonds, C—H bonds, C—O bonds, C═O bonds, and COO bonds, by automatic waveform separation fitting of the analysis software installed in the XPS measurement instrument, and the peaks of each bond were identified. Thereafter, the proportion of each bond to the sum of all peak intensities was calculated from the peaks derived from C-C bonds and C-H bonds (peak position: 284.8 eV), C-O bonds (peak position: 286.4 eV), C=O bonds (peak position: 287.6 eV), and COO bonds (peak position: 288.6 eV). Here, the "surface" of the water-soluble film in the XPS measurement is determined by the "X-ray beam diameter" and "signal acceptance angle" of the XPS measurement conditions described below, and refers to the position where the XPS measurement was performed under the following conditions for "X-ray beam diameter" and "signal acceptance angle."

[0083] [Measurement conditions] Measurement device: PHI (registered trademark) Quantera SXM (ULVAC-PHI. INC.) Analysis software: PHI MultiPak version 9.0 (ULVAC-PHI. INC.) X-ray source: monochromated AlKα (1486.6 eV) X-ray beam diameter: 100 μmφ (25 W, 15 kV) Measurement range: 1,000 μm × 300 μm Signal acceptance angle: 45° Charge neutralization conditions: neutralization electron gun, Ar ＋ Ion gun Vacuum level: 1 x 10 ―６ Pa

[0084] [Method for Quantifying Surfactant] The elemental ratios of carbon, oxygen, sulfur, sodium, and nitrogen, and the ratio of carbon bonding modes were quantified from the XPS measurement. Using these values, the amount of surfactant present on the surface was calculated by the following method.

[0085] [Calculation Examples] (1) Calculation of Anionic Surfactant (B) The ratio (BX) of the anionic surfactants (B1) to (B3) described below present on the surface of the water-soluble film was calculated using the following formula (I): BX (%) = [(X Ｃ＿ＢＸ ・M Ｃ ) + (X Ｏ＿ＢＸ ・M Ｏ ) + (X Ｓ＿ＢＸ ・M Ｓ ) + (X Ｎａ＿ＢＸ ・M Ｎａ ) + (X Ｎ＿ＢＸ ・M Ｎ ) ] / [(X Ｃ＿Ｔｏｔａｌ ・M Ｃ ) + (X Ｏ＿Ｔｏｔａｌ ・M Ｏ ) + (X Ｓ＿Ｔｏｔａｌ ・M Ｓ ) + (X Ｎａ＿Ｔｏｔａｌ ・M Ｎａ ) + (X Ｎ＿Ｔｏｔａｌ ・M Ｎ ) )]×100(%) (I) The values ​​calculated in the following (a) to (c) were substituted for the variables in the above formula (I).

[0086] (a) In a film containing an anionic surfactant, the abundance ratio of each element (carbon, oxygen, sulfur, sodium, and nitrogen) determined by wide scanning of XPS is expressed as X Ｃ＿Ｔｏｔａｌ , X Ｏ＿Ｔｏｔａｌ , X Ｓ＿Ｔｏｔａｌ , X Ｎａ＿Ｔｏｔａｌ and X Ｎ＿Ｔｏｔａｌ X ｉ＿Ｔｏｔａｌ is the measurement result, and the subscript i is the element type. For example, X Ｃ＿ｔｏｔａｌ represents the abundance ratio of total carbon.

[0087] (b) X Ｃ＿ＢＸ , X Ｏ＿ＢＸ , X Ｓ＿ＢＸ , X Ｎａ＿ＢＸ and X Ｎ＿ＢＸ is the abundance ratio of each element derived from the anionic surfactant, and the subscript i is the element type. For example, X Ｃ＿ＢＸ represents the abundance ratio of carbon derived from the anionic surfactant. In the case of the anionic surfactants (B1) and (B3), since they have an elemental composition containing one sulfur element and no nitrogen element in one molecule, X Ｃ＿ＢＸ =X Ｓ＿Ｔｏｔａｌ ・NＣ (Formula 1) Ｏ＿ＢＸ =X Ｓ＿Ｔｏｔａｌ ・N Ｏ (Formula 2) Ｓ＿ＢＸ =X Ｓ＿Ｔｏｔａｌ (Formula 3), X Ｎａ＿ＢＸ =X Ｎａ＿Ｔｏｔａｌ (Equation 4), and X Ｎ＿ＢＸ = 0 (Equation 5). In addition, in the case of the anionic surfactant (B2), since it has an elemental composition containing one nitrogen element and no sodium element in one molecule, X Ｃ＿ＢＸ =X Ｎ＿Ｔｏｔａｌ ・N Ｃ (Formula 6) Ｏ＿ＢＸ =X Ｎ＿Ｔｏｔａｌ ・N Ｏ (Formula 7) Ｓ＿ＢＸ =0 (Formula 8), X Ｎａ＿ＢＸ = 0 (Equation 9), and X Ｎ＿ＢＸ =X Ｎ＿Ｔｏｔａｌ (Equation 10). N ｉ is the number of atoms in a molecule, and the subscript i is the element type. For example, N Ｃ is the number of carbon atoms present in one molecule of anionic surfactant. The structure of anionic surfactants is identified using NMR measurement, etc. For example, in the case of sodium lauryl sulfate, C １２ H ２５ O ４ Since it can be expressed by the composition formula SNa, Nc = 12, No = 4, N Ｎ = 0, Ns = 1, N Ｎａ = 1. In some cases, each constituent component may have a distribution. For example, when a C12 component and a C13 component coexist as an anionic surfactant, the abundance ratio thereof is calculated by liquid chromatography or the like, and the calculation formula takes this abundance ratio into account.

[0088] (c) M ｉ is the atomic mass, and the subscript i is the elemental species. For example, M Ｃ is the atomic weight of carbon, and its value is 12.00 g / mol.

[0089] (2) Calculation of Nonionic Surfactant (C) The ratio (CX) of the nonionic surfactants (C1) to (C5) described below present on the surface of the water-soluble film was calculated by the following formula (II): CX (%) = [(X Ｃ＿ＣＸ ・M Ｃ ) + (X Ｏ＿ＣＸ ・M Ｏ ) + (X Ｓ＿ＣＸ ・M Ｓ ) + (X Ｎａ＿ＣＸ ・M Ｎａ ) + (X Ｎ＿ＣＸ ・M Ｎ ) ] / [(X Ｃ＿Ｔｏｔａｌ ・M Ｃ ) + (X Ｏ＿Ｔｏｔａｌ ・M Ｏ ) + (X Ｓ＿Ｔｏｔａｌ ・M Ｓ ) + (X Ｎａ＿Ｔｏｔａｌ ・M Ｎａ ) + (X Ｎ＿Ｔｏｔａｌ ・M Ｎ ) )] × 100(%) (II) The values ​​calculated in the following (a) to (c) were substituted for each variable in the formula (II): (a) In the film containing the nonionic surfactant, the abundance ratio of each element (carbon, oxygen, sulfur, sodium, and nitrogen) determined by the wide scan of XPS was calculated as X Ｃ＿Ｔｏｔａｌ , X Ｏ＿Ｔｏｔａｌ , X Ｓ＿Ｔｏｔａｌ , X Ｎａ＿Ｔｏｔａｌ and X Ｎ＿Ｔｏｔａｌ X ｉ＿Ｔｏｔａｌ is the measurement result, and the subscript i is the element type. For example, X Ｃ＿ｔｏｔａｌ represents the abundance ratio of total carbon.

[0090] (b) X Ｃ＿ＣＸ , X Ｏ＿ＣＸ , X Ｓ＿ＣＸ , X Ｎａ＿ＣＸ and X Ｎ＿ＣＸ is the abundance ratio of each element derived from the nonionic surfactant, and the subscript i therein is the element type. For example, X Ｃ＿ＣＸ represents the abundance ratio of carbon derived from the nonionic surfactant. In the nonionic surfactants (C1) to (C5), from these elemental compositions, X Ｓ＿ＣＸ =0 (Formula 11), X Ｎａ＿ＣＸ = 0 (Equation 12), and X Ｎ＿ＣＸ = 0 (Equation 13).Ｃ＿ＣＸ and X Ｏ＿ＣＸ was calculated as follows: X Ｃ＿ＣＸ =X Ｃ＿Ｔｏｔａｌ -X Ｃ＿ＢＸ -X Ｃ＿ＰＶＯＨ (Formula 14) Ｏ＿ＣＸ =X Ｏ＿Ｔｏｔａｌ -X Ｏ＿ＢＸ -X Ｏ＿ＰＶＯＨ (Formula 15) X in the formulas 14 and 15 Ｃ＿ＢＸ and X Ｏ＿ＢＸ was calculated from the above formulas 1, 2, 6, and 7. Ｃ＿ＰＶＯＨ and X Ｏ＿ＰＶＯＨ was calculated from the following formulas 16 and 17. Ｃ＿ＰＶＯＨ = (X Ｃ＿Ｒｅｆ -IX Ｃ＿ＢＸ ) / I (Formula 16) Ｏ＿ＰＶＯＨ = (X Ｏ＿Ｒｅｆ -IX Ｏ＿ＢＸ ) / I (Equation 17) I = [X Ｃ＿Ｒｅｆ ・△COO Ｒｅｆ ] / [X Ｃ＿Ｔｏｔａｌ ・△COO Ｔｏｔａｌ ]. X Ｃ＿Ｒｅｆ , X Ｏ＿Ｒｅｆ and △COO Ｒｅｆ is the total carbon abundance ratio (X ) determined from the wide scan of XPS in a water-soluble film to which neither anionic surfactant nor nonionic surfactant is added. Ｃ＿Ｒｅｆ ) and the total oxygen abundance ratio (X Ｏ＿Ｒｅｆ ), and the abundance ratio of ester bonds (COO bonds) determined from the narrow scan derived from the carbon bonds described above (ΔCOO Ｒｅｆ ) represents X Ｃ＿Ｔｏｔａｌ and △COO Ｔｏｔａｌ is the total carbon abundance ratio (X Ｃ＿Ｔｏｔａｌ ), and the abundance ratio of ester bonds (COO bonds) determined from the narrow scan derived from the carbon bonds described above (ΔCOO Ｔｏｔａｌ In the case where the anionic surfactants (B1) and (B3) are used, X in Formulas 7 and 8 Ｃ＿ＢＸ and X Ｏ＿ＢＸ was set to 0 because there was no COO bond derived from carboxylic acid.

[0091] (C) M ｉ is the atomic mass, and the subscript i is the elemental species. For example, M Ｃ is the atomic weight of carbon, and its value is 12.00 g / mol.

[0092] <Average Thickness> The thickness of each water-soluble film obtained in each Example or Comparative Example was measured at 10 arbitrary points on a line drawn in the longitudinal direction of the central part of the width direction of the film using a film thickness meter (manufactured by Ono Sokki Co., Ltd., "DG-5100"), and the average value of the thicknesses was calculated.

[0093] <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.

[0094] <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.

[0095] <Surfactants> The anionic surfactants (B) and nonionic surfactants (C) used in the examples and comparative examples are as follows: (Anionic surfactants (B)) B1: Sodium alkylsulfonate B2: Sodium acylsarcosinate B3: Sodium polyoxyethylene alkyl ether sulfate (Nonionic surfactants (C)) C1: Polyoxyethylene alkyl ether (number of oxyethylene (OE) groups: 3, HLB: 8.1) C2: Polyoxyethylene alkyl ether (number of OE groups: 3, HLB: 8.2) C3: Polyoxyethylene alkyl ether (number of OE groups: 5, HLB: 10.7) C4: Polyoxyethylene alkyl ether (number of OE groups: 7, HLB: 12.1) C5: Polyoxyalkylenesiloxane copolymer (number of OE groups: unknown, HLB: less than 8)

[0096] Example 1 An aqueous solution containing 100 parts by mass of PVA (degree of polymerization 1,700, degree of saponification 89.0 mol%), 1.0 part by mass of anionic surfactant (B1) (sodium alkylsulfonate), 0.5 part by mass of nonionic surfactant (C1) (polyoxyethylene alkyl ether (oxyethylene (OE) group number 3, HLB 8.1)), 15 parts by mass of glycerin as a plasticizer, and 2.8 parts by mass of starch was prepared as a film-forming solution. The film-forming solution was cast onto a metal drum at 60°C and dried for 30 minutes. The dried film was peeled from the metal drum surface to produce a water-soluble film with an average thickness of 76 μm. The obtained water-soluble film was subjected to XPS, haze, and peel tension measurements using the methods described above. The results are shown in Table 1. The mass ratio of polyvinyl alcohol to each surfactant contained in the obtained water-soluble film was the same as the mass ratio of polyvinyl alcohol to each surfactant in the film-forming solution.

[0097] [Examples 2 to 5, Comparative Example 3] Water-soluble films were produced and measurements were carried out in the same manner as in Example 1, except that the type of anionic surfactant (B) and the type and content of nonionic surfactant (C) were changed as shown in Table 1. The results are shown in Table 1.

[0098] Comparative Example 1 A water-soluble film was produced and each measurement was carried out in the same manner as in Example 1, except that the anionic surfactant (B) was not added. The results are shown in Table 1.

[0099] Comparative Example 2 A water-soluble film was produced and each measurement was carried out in the same manner as in Example 1, except that the nonionic surfactant (C) was not added. The results are shown in Table 1.

[0100] 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.

[0101]

[0102] As shown in Table 1, each of the water-soluble films of Examples 1 to 5 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.

[0103] 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, wherein on a first surface, which is one of two surfaces perpendicular to the thickness direction of the water-soluble film, the component ratio of the anionic surfactant is 3% or more and the component ratio of the nonionic surfactant is 30% or more, as measured by X-ray photoelectron spectroscopy.

2. The water-soluble film according to claim 1, wherein the sum of the component ratio of said anionic surfactant and the component ratio of said nonionic surfactant on said first surface is 40% or more.

3. A water-soluble film according to claim 1 or 2, wherein the ratio of the component ratio of the nonionic surfactant to the component ratio of the anionic surfactant on the first surface is 1 to 12.

4. The water-soluble film according to claim 1 or 2, wherein 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.

5. 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.

6. The water-soluble film according to claim 1 or 2, wherein the anionic surfactant comprises at least one selected from the group consisting of sodium alkylsulfonate, sodium acylsarcosinate, and sodium polyoxyethylene alkyl ether sulfate.

7. 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.

8. The water-soluble film according to claim 1 or 2, wherein the nonionic surfactant comprises a polyoxyethylene alkyl ether.

9. 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.

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

11. The package of claim 10, wherein the agent is a pesticide, a detergent or a disinfectant.

12. The package of claim 10, wherein the medication is in liquid form.

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