Water-soluble film, method for producing same, package, medicine package, and method for producing same

Abstract

The present invention provides a water-soluble film which is excellent in terms of mechanical properties such as strength and stretchability in cases where a polyvinyl alcohol-based resin is used in combination with a naturally derived starting material in a relatively high content, and which is excellent in terms of water sealability that is useful for packaging applications.　The present invention discloses a water-soluble film which contains a polyvinyl alcohol-based resin and at least one naturally derived starting material that is selected from the group consisting of saccharides, sugar alcohols, lipids, proteins, and salts thereof. The content of the naturally derived starting material is 40 mass% or more with respect to 100 mass% of the water-soluble film (the solid content), and the viscosity at 20°C of the 1 mass% aqueous solution of the water-soluble film is 2.00-2.60 mPa∙s.

Description

Water-soluble film and method for producing the same, packaging, drug packaging and method for producing the same

[0001] The present invention relates to a water-soluble film containing naturally-derived raw materials. More specifically, the present invention relates to a water-soluble film containing a specific amount or more of naturally-derived raw materials, a package and a pharmaceutical package using the same, and methods for producing them.

[0002] In recent years, from the viewpoint of protecting the global environment, there has been a growing expectation for the development of more biodegradable films made from naturally derived materials, instead of conventional plastic films made from petroleum-derived materials.

[0003] Meanwhile, water-soluble films using pullulan, a water-soluble polysaccharide, as a naturally-derived raw material are known, as shown in Patent Documents 1 and 2. For example, Patent Document 1 describes a water-soluble film containing pullulan and polyvinyl alcohol, and describes that the film has excellent printability and adhesiveness. Patent Document 2 also describes a film containing pullulan as a naturally-derived raw material and a water-soluble polymer, and describes that the film can be used for edible purposes.

[0004] Japanese Unexamined Patent Publication No. 5-001198 Special Publication No. 2005-528328

[0005] However, when a polyvinyl alcohol-based resin is used together with a naturally-derived raw material such as pullulan, as in the water-soluble films of Patent Documents 1 and 2, the physical properties and sealing properties of the resulting film are poor. In particular, for individual packaging of foods, medicines, etc., sealing properties are required in addition to mechanical properties such as strength and extensibility, and further improvements have been required to produce films that are stronger and have excellent sealing properties.

[0006] Therefore, under such circumstances, the present invention provides a water-soluble film and a method for producing the same, a package, and a pharmaceutical package and a method for producing the same, which, when a polyvinyl alcohol-based resin is used in combination with a relatively high content of naturally-derived raw materials, have excellent mechanical properties such as strength and stretchability, and excellent water-sealing properties useful for packaging applications.

[0007] However, in light of these circumstances, the present inventors have conducted extensive research and found that, in a water-soluble film that combines a polyvinyl alcohol-based resin with a relatively high content of naturally derived raw materials, a water-soluble film that has excellent mechanical properties and excellent sealing properties useful for packaging applications can be obtained by adjusting the viscosity of a 1% by mass aqueous solution of the water-soluble film to 2.00 to 2.60 mPa·s at 20° C. Furthermore, because polyvinyl alcohol-based resins are biodegradable resins, the above problems can be solved without significantly reducing the biodegradability of the water-soluble film as a whole.

[0008] That is, the present invention has the following aspects. [1] A water-soluble film comprising a polyvinyl alcohol-based resin and at least one naturally-derived raw material selected from the group consisting of sugars, sugar alcohols, lipids, proteins, and salts thereof, wherein the content of the naturally-derived raw material is 40% by mass or more relative to 100% by mass (solid content) of the water-soluble film, and a 1% by mass aqueous solution of the water-soluble film has a viscosity of 2.00 to 2.60 mPa·s at 20°C. [2] The water-soluble film according to [1], wherein the naturally-derived raw material comprises a naturally-derived raw material having a weight-average molecular weight of 10,000 or more. [3] A method for producing the water-soluble film according to [1] or [2], comprising the steps of: preparing a film-forming raw material containing the polyvinyl alcohol-based resin and the naturally-derived raw material; casting the film-forming raw material onto a casting surface; and drying the film-forming raw material cast on the casting surface. [4] A package containing the water-soluble film according to any one of [1] to [3]. [5] A drug package containing a package containing the water-soluble film according to any one of [1] to [4] and a drug encapsulated in the package. [6] The drug package according to [5], wherein the drug is a liquid detergent. [7] A method for producing the drug package according to [5] or [6], comprising the steps of: preparing a first water-soluble film, a second water-soluble film, and the drug; arranging the drug between the first water-soluble film and the second water-soluble film; and bringing the first water-soluble film and the second water-soluble film into contact with each other and pressing them together.

[0009] The water-soluble film of the present invention has excellent mechanical properties and water-sealing properties, making it suitable for individual packaging applications, particularly for individual packaging of medicines and foods.

[0010] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0011] As used herein, "x and / or y (x and y are any configuration)" refers to at least one of x and y, and can mean three things: x only, y only, or x and y. In this specification, when "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it also means "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." In this specification, when "X or more" (X is any number) or "Y or less" (Y is any number) is used, it also means "preferably greater than X" or "preferably less than Y." For numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described herein, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples.

[0012] The present invention will be specifically described below.

[0013] In the present invention, the term "water-soluble film" refers to a film that dissolves in water at about room temperature (20°C). In the present invention, the solubility of a film is determined as follows: a film is cut into a size of 3 cm x 5 cm, placed in a 1-liter beaker containing water (1 liter) and secured with a jig, and stirred with a stirrer (rotor length 3 cm, rotation speed 750 rpm) while maintaining the water temperature at 20°C. The film is deemed "dissolved" when no insoluble fine particles of the film with a diameter of 1 mm or more are observed.

[0014] A water-soluble film according to one embodiment of the present invention (hereinafter referred to as "the water-soluble film") contains a polyvinyl alcohol-based resin and at least one naturally occurring raw material selected from the group consisting of sugars, sugar alcohols, lipids, proteins, and salts thereof.

[0015] In this specification, "naturally derived raw materials" refers to raw materials of plant, animal, or microbial origin that are obtained by physical treatment such as drying or grinding without chemical synthesis (natural raw materials), or raw materials that are natural raw materials that have been processed by chemical synthesis without introducing carbon atoms derived from non-natural raw materials.

[0016] From the viewpoint of protecting the global environment, the present water-soluble film contains a relatively high amount of naturally-derived raw materials compared to conventional films, and the content of naturally-derived raw materials is 40% by mass or more, preferably 43% by mass or more, more preferably 45% by mass or more, even more preferably 47% by mass or more, and particularly preferably 50% by mass or more, relative to 100% by mass of the solid content of the water-soluble film. The upper limit is usually 90% by mass, and from the viewpoint of maintaining the film shape, it is preferably 80% by mass or less, and may be 75% by mass or less. The numerical range of such content is, for example, 40 to 90% by mass.

[0017] Generally, the higher the content of naturally-derived raw materials in a water-soluble film, the more the film's physical properties deteriorate, making it difficult to commercialize it for various applications. However, the present water-soluble film has a higher content of naturally-derived raw materials than conventional films, and yet a 1% by mass aqueous solution of the water-soluble film has a viscosity of 2.00 to 2.60 mPa·s at 20°C, which prevents deterioration in water-sealing properties and mechanical strength.

[0018] In this specification, polyvinyl alcohol may be abbreviated as "PVA." Furthermore, the term "film" includes "tape" and "sheet."

[0019] <<Water-Soluble Film>> The water-soluble film is a water-soluble film whose main component is the sum of the PVA-based resin (A) and the above-mentioned naturally-derived raw material (excluding plasticizers and fillers). Here, the term "main component" refers to the component that is the most abundant in the target material, and the content of the component is usually 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may even be 100% by mass.

[0020] <PVA Resin (A)> Examples of the PVA resin (A) used in the present water-soluble film include unmodified PVA and modified PVA resins.

[0021] The unmodified PVA and modified PVA-based resins can be produced by a production method known in the art, for example, as follows.

[0022] The unmodified PVA can be produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester compound.

[0023] Examples of such vinyl ester compounds include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, etc., with vinyl acetate being preferred. The above vinyl ester compounds may be used alone or in combination of two or more.

[0024] The modified PVA resin can be produced by copolymerizing the vinyl ester compound with an unsaturated monomer copolymerizable with the vinyl ester compound, followed by saponification.

[0025] Examples of unsaturated monomers copolymerizable with the vinyl ester compounds include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, and 5-hexen-1-ol, and derivatives thereof such as acylated products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid, as well as their salts, monoesters, and dialkyl esters; amides such as diacetone acrylamide, acrylamide, and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, as well as their salts; and N-vinyl pyrrolidone. These may be used alone or in combination of two or more.

[0026] The modified PVA-based resin may have, for example, primary hydroxyl groups in the side chain, typically 1 to 5, preferably 1 to 2, and particularly preferably 1 primary hydroxyl group in the side chain, and preferably has a secondary hydroxyl group in addition to the primary hydroxyl group. Examples of such modified PVA-based resins include PVA-based resins having hydroxyalkyl groups in the side chain and PVA-based resins having 1,2-diol structural units in the side chain. PVA-based resins having 1,2-diol structural units in their side chains can be produced by, for example, (1) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (2) a method of saponifying and decarboxylating a copolymer of vinyl acetate and vinyl ethylene carbonate, (3) a method of saponifying and deketalizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane, or (4) a method of saponifying a copolymer of vinyl acetate and glycerin monoallyl ether.

[0027] In terms of solubility, the modified PVA-based resin used in the present water-soluble film is preferably one modified with at least one hydrophilic group selected from anionic groups such as carboxyl groups, sulfonic acid groups, and phosphate groups, pyrrolidone ring groups, and amino groups. Anionic group-modified PVA-based resins are particularly preferred. These modifying groups include salts of the above-mentioned functional groups, such as sodium and potassium salts. Hereinafter, modified PVA-based resins modified with hydrophilic groups may be simply referred to as "hydrophilic group-modified PVA-based resins."

[0028] Examples of hydrophilic group-modified PVA-based resins include anionic group-modified PVA-based resins such as carboxy group-modified PVA-based resins, sulfonic acid group-modified PVA-based resins, and phosphate group-modified PVA-based resins, pyrrolidone ring-modified PVA-based resins, and amino group-modified PVA-based resins.

[0029] [Anionic Group-Modified PVA-Based Resin] The anionic group-modified PVA-based resin has an anionic group, and examples of the anionic group include a carboxy group, a sulfonic acid group, a phosphate group, etc. Among these, the carboxy group and the sulfonic acid group are preferred, and the carboxy group is more preferred, in terms of excellent solubility in water and chemical resistance.

[0030] Anionic group-modified PVA-based resins can be produced, for example, by saponifying a copolymer of a vinyl ester-based monomer and an anionic unsaturated monomer, or by post-modifying a PVA-based resin.

[0031] Examples of the unsaturated monomer having an anionic group include a carboxy group-containing unsaturated monomer, a sulfonic acid group- or sulfonate salt group-containing unsaturated monomer, and a phosphate group-containing unsaturated monomer.

[0032] Examples of carboxyl-containing unsaturated monomers include carboxyl-containing unsaturated compounds such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid, as well as compounds in which the carboxyl groups have been fully or partially neutralized with a base such as an alkali compound (e.g., sodium hydroxide or potassium hydroxide), as well as monoalkyl esters of the above carboxyl-containing unsaturated compounds such as methyl acrylate, ethyl acrylate, methyl methacrylate, monomethyl fumarate, and monomethyl maleate, and dialkyl esters of the above carboxyl-containing unsaturated compounds such as diethyl fumarate and diethyl maleate. From the standpoints of economy and practicality, the carbon number of these esters is typically 1 to 20, preferably 1 to 10, and particularly preferably 1 to 4. Among these, maleic acid compounds are preferred, with monomethyl maleate being more preferred.

[0033] Examples of the sulfonic acid group- or sulfonate salt-containing unsaturated monomer include olefin sulfonic acids or salts thereof, such as vinyl sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid; sulfoalkyl maleates, such as sodium sulfopropyl-2-ethylhexyl maleate, sodium sulfopropyl-2-ethylhexyl maleate, sodium sulfopropyl tridecyl maleate, and sodium sulfopropyl eicosyl maleate; sulfoalkyl(meth)acrylamides, such as sodium sulfomethylacrylamide, sodium sulfo-t-butylacrylamide, sodium sulfo-s-butylacrylamide, and sodium sulfo-t-butylmethacrylamide; and sulfoalkyl(meth)acrylates, such as sodium sulfomethylacrylamide, sodium sulfo-t-butylacrylamide, sodium sulfo-s-butylacrylamide, and sodium sulfo-t-butylmethacrylamide. One or more unsaturated monomers selected from these unsaturated monomers may be used. In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0034] Examples of the phosphoric acid group-containing unsaturated monomer include phosphonocarboxylic acid compounds and alkali metal salts thereof.

[0035] Examples of vinyl ester monomers to be copolymerized with the above unsaturated monomers include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, etc. These may be used alone or in combination of two or more, but vinyl acetate is preferred in practice.

[0036] As the polymerization method, any known polymerization method can be used, such as solution polymerization, emulsion polymerization, suspension polymerization, etc., but the polymerization is usually carried out by solution polymerization using an alcohol such as methanol, ethanol, or isopropyl alcohol as a solvent.

[0037] The polymerization catalyst can be appropriately selected from known polymerization catalysts such as azo catalysts (e.g., azobisisobutyronitrile) and peroxide catalysts (e.g., acetyl peroxide, benzoyl peroxide, lauroyl peroxide), depending on the polymerization method, and can be used alone or in combination of two or more. The reaction temperature is selected from the range of 35°C to the boiling point of the solvent.

[0038] Saponification can also be carried out by known methods, and is usually carried out by dissolving the obtained polymer in alcohol in the presence of a saponification catalyst. Examples of alcohol include methanol, ethanol, and butanol. These can be used alone or in combination of two or more. The concentration of the copolymer in the alcohol is selected from the range of 20 to 50% by mass in terms of solubility.

[0039] As the saponification catalyst, for example, an alkali catalyst such as an alkali metal hydroxide or alcoholate, such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, or potassium methylate, can be used, or an acid catalyst can also be used. These can be used alone or in combination of two or more. The amount of the saponification catalyst used is preferably 1 to 100 millimole equivalents relative to the vinyl ester compound.

[0040] The modification amount of the anionic group-modified PVA-based resin is preferably 1 to 15 mol%, more preferably 2 to 10 mol%, further preferably 2 to 8 mol%, and particularly preferably 3 to 7 mol%. If the modification amount is too small, the solubility in water tends to decrease, while if the modification amount is too large, the productivity of the PVA-based resin tends to decrease, biodegradability tends to decrease, and blocking tends to occur easily, which tends to reduce practical use.

[0041] The viscosity of a 4% by mass aqueous solution of the anionic group-modified PVA-based resin at 20° C. is preferably 5 to 50 mPa s, more preferably 13 to 40 mPa s, and even more preferably 17 to 30 mPa s. If the viscosity is too low, the mechanical strength of the water-soluble film tends to decrease, while if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to increase, resulting in decreased productivity.

[0042] The average saponification degree of the anionic group-modified PVA resin is preferably 80 mol% or more, more preferably 85 to 99.9 mol%, even more preferably 88 to 99 mol%, and particularly preferably 90 to 98 mol%. If the saponification degree is too high, the solubility in water tends to decrease, whereas if it is too low, the solubility of the water-soluble film in water tends to decrease over time depending on the packaging material.

[0043] In the present embodiment, the PVA-based resin (A) may be used alone or in combination of two or more types differing in saponification degree, viscosity, modified species, modification amount, etc.

[0044] In this embodiment, in view of compatibility with the naturally-occurring raw materials, it is preferable to use an anionic group-modified PVA-based resin as the PVA-based resin (A). In particular, in view of the balance between compatibility and water solubility and ease of handling, a carboxy group-modified PVA-based resin or a sulfonic acid group-modified PVA-based resin is preferably used, and a carboxy group-modified PVA is particularly preferably used.

[0045] The average saponification degree of the PVA-based resin (A) is preferably 80 mol% or more, more preferably 82 to 99.9 mol%, even more preferably 85 to 99 mol%, and particularly preferably 90 to 98 mol%. If the average saponification degree is too low, the solubility of the film in water tends to decrease, or the solubility of the film tends to decrease over time depending on the packaging material. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0046] The viscosity of a 4% by mass aqueous solution of the PVA-based resin (A) at 20° C. is preferably 5 to 60 mPa s, more preferably 10 to 45 mPa s, and even more preferably 15 to 40 mPa s. If the viscosity is too low, the mechanical strength of the water-soluble film tends to decrease, whereas if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to increase, resulting in decreased productivity.

[0047] The content of the PVA-based resin (A) is preferably 10 to 90% by mass of the water-soluble film, more preferably 20 to 80% by mass, and even more preferably 30 to 70% by mass, but in the present water-soluble film, it is preferably 60% by mass or less, more preferably 57% by mass or less, still more preferably 55% by mass or less, and particularly preferably 52% by mass or less. When the content of the PVA-based resin (A) is within the above range, the mechanical properties of the film, particularly the elongation of the film, tend to be excellent.

[0048] The present water-soluble film can use the above-mentioned hydrophilic group-modified PVA-based resin in combination with other PVA-based resins. For example, unmodified PVA can be used in combination to adjust the film properties such as sealability and viscoelasticity.

[0049] When a hydrophilic-group-modified PVA-based resin and an unmodified PVA are used in combination, the ratio (mass ratio) of the hydrophilic-group-modified PVA-based resin to the unmodified PVA is preferably 97 / 3 to 50 / 50, more preferably 95 / 5 to 70 / 30, and even more preferably 93 / 7 to 85 / 15. If the ratio is too large, the compatibility of the PVA-based resin (A) with the naturally-derived raw material tends to decrease.

[0050] <Naturally Originated Raw Materials> The naturally originated raw materials used in the present water-soluble film are at least one naturally originated raw material selected from the group consisting of sugars, sugar alcohols, lipids, proteins, and salts thereof.

[0051] The content of naturally derived raw materials is 40% by mass or more, preferably 43% by mass or more, more preferably 45% by mass or more, even more preferably 47% by mass or more, and particularly preferably 50% by mass of the water-soluble film (solid content, the same applies hereinafter). The upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, particularly preferably 70% by mass or less, and especially preferably 65% ​​by mass or less. The numerical range of such content is, for example, 40 to 90% by mass.

[0052] The mass ratio of the naturally-derived raw materials to the PVA-based resin (A) (naturally-derived raw materials / PVA-based resin) is usually 1 / 99 to 99 / 1, preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, even more preferably 30 / 70 to 70 / 30, and particularly preferably 40 / 60 to 60 / 40. If the content of the naturally-derived raw materials is too high, the compatibility with the PVA-based resin (A) tends to be poor, and the solubility of the film in water tends to be reduced. Furthermore, mechanical properties such as film strength tend to be reduced.

[0053] In terms of achieving a specific viscosity, it is preferable that the naturally derived raw material contains a polymeric naturally derived raw material, and the weight average molecular weight (Mw) of such a polymer is preferably 10,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, particularly preferably 150,000 or more, and especially preferably 1,000,000 or more. The upper limit is not particularly limited, but is usually 1×10 ９ The weight average molecular weight is in the range of 10,000 to 1×10 ９ The weight average molecular weight is usually measured by GPC, but for high molecular weight substances such as starch, the weight average molecular weight is measured by high performance liquid chromatography (HPLC) or high performance anion exchange chromatography (HPAE).

[0054] The content of polymers having a weight-average molecular weight of 10,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, particularly preferably 150,000 or more, and especially preferably 1,000,000 or more in naturally derived raw materials is preferably the main component of the naturally derived raw materials, excluding the plasticizers described below, and is more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and especially preferably 90% by mass or more. The upper limit is 100% by mass. The numerical range of such content is, for example, 60 to 100% by mass.

[0055] The sugars, sugar alcohols, lipids, and proteins will be explained in detail below.

[0056] [Sugars] The sugars are not particularly limited, but include, excluding sugar alcohols, monosaccharides such as glucose, fructose, galactose, etc.; disaccharides such as sucrose, lactose, maltose, etc.; trisaccharides such as maltotriose, etc.; oligosaccharides such as fructooligosaccharides, galactooligosaccharides, isomaltooligosaccharides, etc.; and polysaccharides such as pullulan, starch (amylose, amylopectin), cellulose, glycogen, dextrin, chitosan, chitin, etc. These can be used alone or in combination of two or more kinds. Among these, pullulan and starch are preferred.

[0057] Normally, when polysaccharides are contained, it is expected that the physical properties of the water-soluble film will deteriorate. However, in this embodiment, even when polysaccharides are contained, deterioration in the physical properties of the film can be effectively suppressed.

[0058] The content of polysaccharides is preferably 10% by mass or more of the water-soluble film, more preferably 15% by mass or more, and even more preferably 20% by mass or more. The upper limit is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less. The numerical range of such a content is, for example, 10 to 60% by mass. By containing a certain amount or more of such polysaccharides, the water-soluble film can be used as a sustainable resource with less environmental impact.

[0059] Pullulan is a type of polysaccharide consisting only of glucose, and has a structure in which three glucose molecules are linked by an α1-4 bond to form maltotriose, which is linked by an α1-6 bond. It is usually obtained by cultivating a microorganism (a type of filamentous fungus) in a medium containing starch syrup, and is highly soluble in water and has properties such as lubricity, adhesiveness, caking, adhesion, stickiness, film formation, and formability.

[0060] (Starch) The starch is not particularly limited, and examples thereof include corn starch, potato starch, wheat starch, rice starch, tapioca starch, sweet potato starch, sago palm starch, soybean starch, arrowroot starch, bracken starch, lotus starch, cassava starch, waxy corn starch, high-amylose corn starch, and commercially available amylose powders. These may be used alone or in combination of two or more. Among these, waxy corn starch, which has a high amylopectin content, is preferred.

[0061] In this specification, "starch" refers to unmodified starch, excluding starch derivatives in which functional groups have been introduced into the hydroxyl groups of starch and chemically modified starch derivatives such as oxidized starch, and means starch that has not been subjected to chemical treatment.

[0062] Examples of starch include raw starch, as well as physically processed starches that have been physically treated, such as pregelatinized starch and moist heat-treated starch (e.g., pregelatinized starch, fractionated amylose, moist heat-treated starch, etc.), decomposed starches obtained by decomposing starch with acid (e.g., acid-treated starch, etc.), and enzyme-treated starches obtained by decomposing starch with an enzyme (e.g., hydrolyzed dextrin, enzymatically decomposed dextrin, amylose, etc.). From the viewpoints of solubility in water and compatibility with PVA-based resins, physically processed starches are preferred, and pregelatinized starch is more preferred.

[0063] The amylopectin content of the starch is 85% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, from the viewpoints of mechanical properties, moldability, and sealability. The upper limit is not particularly limited, but is usually 100% by mass, and the range of the content is, for example, 85 to 100% by mass. When the starch is a mixture of two or more starches, the amylopectin content of the mixture should be 85% by mass or more.

[0064] The starch described in this specification also includes starch used as a filler (i.e., starch particles of 0.1 μm or more present in a water-soluble film that are not dissolved but disperse in water at room temperature (20° C.)) as described below, so long as it is a naturally occurring raw material.

[0065] The amylopectin content refers to the mass ratio of amylopectin when the total amount of amylose and amylopectin contained in starch is taken as 100% by mass. The amylopectin content can be measured by a colorimetric measurement method using an iodine reactant or a quantitative method using concanavalin A as described in, for example, Carbohydrate Research, Vol. 180, 301-313 or Starch / Starke, Vol. 42, 302-305.

[0066] When the starch is a mixture of two or more types of starch, the amylopectin content of the starch (mixture) may be the weighted average of the amylopectin contents of each starch, or the amylopectin content of the mixture of two or more types of starch may be measured by the above-mentioned method and the value measured may be used as the amylopectin content of the starch. When the amylopectin content is calculated as a weighted average, it can be determined from the amylopectin ratio of each starch using the following formula: Amylopectin content of starch (% by mass) = Σ(n ａ i×M ａ i) / 100 n ａ i: Amylopectin content (mass%) of each starch M ａ i: Proportion of each starch in starch (mass%)

[0067] [Sugar alcohol] The sugar alcohol is not particularly limited, but examples thereof include monosaccharide sugar alcohols such as glycerin, erythritol, xylitol, sorbitol, mannitol, etc.; disaccharide sugar alcohols such as maltitol, lactitol, etc.; and hydrogenated starch hydrolysates, which can be used alone or in combination of two or more. Among these, glycerin, sorbitol, xylitol, and sorbitol are preferred. The monosaccharide sugar alcohols and disaccharide sugar alcohols mentioned above tend to be more effective as plasticizers, and sugar alcohols made from naturally occurring raw materials also include the sugar alcohols used as plasticizers described below, so long as they are made from naturally occurring raw materials.

[0068] [Lipids] Examples of lipids include glycerides (monoglycerides, diglycerides, triglycerides); and phospholipids such as lecithin and cephalin.

[0069] [Protein] Examples of proteins include casein, gelatin, collagen, etc., and among these, casein and gelatin are preferred.

[0070] (Casein) Casein is the major protein that accounts for the majority of the proteins contained in milk and is primarily composed of a mixture of α-casein, β-casein, and κ-casein. There are several methods for separating casein from milk. For example, casein obtained by adding an acid is called acid casein and is produced industrially. However, since acid casein is poorly water-soluble, salts of casein, which are highly water-soluble and easy to handle, are generally used. Examples of casein salts include potassium caseinate, sodium caseinate, calcium caseinate, and magnesium caseinate. These salts can be used alone or in combination of two or more. Among these, sodium caseinate is preferred in terms of its solubility in water and compatibility with PVA-based resins.

[0071] (Gelatin) Gelatin is extracted from collagen, the main component of the bones and skin of animals such as cows and pigs, and is chemically composed primarily of a linear polymer of amino acids (protein). It is generally used as a food additive as a gelling agent or thickener.

[0072] Typically, an aqueous gelatin solution gels at temperatures below 25°C and dissolves at temperatures above 30°C. Gelatin is classified into two types, acid-treated and alkali-treated, depending on the manufacturing method, and each has a different isoelectric point. While the isoelectric point of acid-treated gelatin is a wide range from 6 to 9, the isoelectric point of alkali-treated gelatin is a narrow range around 5. Normally, using gelatin at a pH near its isoelectric point leads to a decrease in gel strength and turbidity of the gel.

[0073] In the present water-soluble film, it is preferable to use alkali-treated gelatin because it has excellent physical properties.

[0074] In the present water-soluble film, it is preferable to use polysaccharides as naturally occurring raw materials, in that they can easily improve mechanical properties such as strength and the water-sealing properties of the film, and among them, it is preferable to use pullulan or starch.

[0075] <Plasticizer> The present water-soluble film preferably contains a plasticizer in order to impart appropriate flexibility to the film. One type of plasticizer may be used alone, or two or more types may be used in combination, but it is also preferable to use two or more types in combination in terms of the mechanical properties and moldability of the film.

[0076] Examples of such plasticizers include glycerins such as glycerin, diglycerin, and triglycerin; alkylene glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and dipropylene glycol; sugar alcohols such as sorbitol, xylitol, and maltitol; and trimethylolpropane. These may be used alone or in combination of two or more. Among these, glycerin, diglycerin, and polyethylene glycol are preferred because they are easily available and can achieve a plasticizing effect with a small amount, and sorbitol is preferred in terms of the stability of the package over time. Such plasticizers may be naturally derived materials, and among the specific examples mentioned above, glycerin, sorbitol, xylitol, and maltitol are sugar alcohols and are included in the sugar alcohols of naturally derived materials mentioned above.

[0077] The content of the plasticizer is preferably 5 to 80 parts by mass, more preferably 10 to 70 parts by mass, still more preferably 15 to 60 parts by mass, particularly preferably 18 to 50 parts by mass, and especially preferably 20 to 45 parts by mass, based on 100 parts by mass of the total of the PVA-based resin (A) and the naturally derived raw material (excluding the plasticizer and the filler). If the content of the plasticizer is too low, the plasticizing effect is low, resulting in a decrease in processability, and when used as a package, the toughness of the water-soluble film tends to be impaired over time. If the content of the plasticizer is too high, the strength of the film tends to be reduced and blocking tends to occur easily.

[0078] <Filler> The present water-soluble film may further contain a filler, if necessary.

[0079] The filler is contained for the purpose of enhancing blocking resistance. Such a filler is not particularly limited, and either an organic filler or an inorganic filler may be used, with organic fillers being particularly preferred. These may be used alone or in combination of two or more. The average particle size of the filler is preferably 0.1 to 50 μm, and more preferably 1 to 35 μm. The average particle size of the filler is a value measured using a laser diffraction particle size distribution analyzer, and is calculated from the D50 value (particle size at 50% of the cumulative total) of the obtained cumulative volume distribution.

[0080] The organic filler refers to particulate matter (primary particles) composed of an organic compound and having any shape, such as needle-like, rod-like, layer-like, scale-like, or spherical, or an aggregate of such particulate matter (secondary particles). Such organic fillers are mainly selected from polymer compounds, and examples thereof include melamine-based resins, polymethyl (meth)acrylate-based resins, polystyrene-based resins, as well as biodegradable resins such as starch and polylactic acid. Among these, biodegradable resins such as polymethyl (meth)acrylate-based resins, polystyrene-based resins, and starch are preferred, and starch is particularly preferred in terms of dispersibility in the PVA-based resin (A).

[0081] Examples of the starch include raw starches (corn starch, potato starch, sweet potato starch, wheat starch, cassava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, kudzu starch, bracken starch, lotus starch, water chestnut starch, etc.), physically modified starches (gelatinized starch, fractionated amylose, moist heat-treated starch, etc.), enzyme-modified starches (hydrolyzed dextrin, enzymatically decomposed dextrin, amylose, etc.), chemically decomposed modified starches (acid-treated starch, hypochlorite-oxidized starch, dialdehyde starch, etc.), and chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, cross-linked starch, etc.). Of these, raw starches, particularly corn starch and rice starch, are preferably used from the standpoints of availability and economy.

[0082] When starch is used as a filler, the content of starch as a filler is preferably 0.5 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 2 to 30 parts by mass, based on 100 parts by mass of the total of the PVA-based resin (A) excluding the starch as a filler and the naturally-derived raw material. If the content is too low, blocking tends to occur, whereas if the content is too high, the sealing property of the film tends to decrease and the moldability during production of a package tends to decrease.

[0083] The average particle size of the organic filler is preferably 2 to 50 μm, more preferably 4 to 45 μm, even more preferably 10 to 40 μm, and particularly preferably 15 to 35 μm. If the average particle size is too small, the blocking tendency of the film tends to increase, while if it is too large, the fillers tend to aggregate with each other, reducing dispersibility and causing pinholes when the film is stretched during molding.

[0084] The inorganic filler refers to particulate matter (primary particles) composed of an inorganic compound and having any shape, such as needle-like, rod-like, layer-like, scale-like, or spherical, or an aggregate of such particulate matter (secondary particles). Examples of inorganic fillers include oxide-based inorganic compounds such as silica (silicon dioxide), diatomaceous earth, titanium oxide, calcium oxide, magnesium oxide, aluminum oxide, barium oxide, germanium oxide, tin oxide, and zinc oxide, as well as talc, clay, kaolin, mica, asbestos, gypsum, graphite, glass balloons, glass beads, calcium sulfate, barium sulfate, ammonium sulfate, calcium sulfite, calcium carbonate, whisker-like calcium carbonate, magnesium carbonate, dawsonite, dolomite, potassium titanate, carbon black, glass fibers, alumina fibers, boron fibers, processed mineral fibers, carbon fibers, hollow carbon spheres, bentonite, montmorillonite, copper powder, sodium sulfate, potassium sulfate, zinc sulfate, copper sulfate, iron sulfate, magnesium sulfate, aluminum sulfate, potassium aluminum sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, aluminum nitrate, ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium phosphate, and potassium chromate. These may be used alone or in combination of two or more.

[0085] Among these, it is preferable to use an oxide-based inorganic compound or talc, more preferably to use titanium oxide, talc or silica, and even more preferably to use silica.

[0086] The average particle size of the inorganic filler is preferably 1 to 20 μm, more preferably 2 to 15 μm, and even more preferably 3 to 10 μm. If the average particle size is too small, the flexibility and toughness of the film tend to decrease and blocking tends to increase, while if the average particle size is too large, pinholes tend to form when the film is stretched during molding.

[0087] When a filler is used, the content of the filler is preferably 1 to 30 parts by mass, more preferably 1.5 to 25 parts by mass, and even more preferably 2 to 20 parts by mass, per 100 parts by mass of the total of the PVA-based resin (A) and the naturally-derived raw material (excluding the plasticizer and the filler). If the content is too low, the blocking property of the film tends to increase, whereas if the content is too high, the flexibility and toughness of the film tend to decrease.

[0088] <Surfactant> The water-soluble film may further contain a surfactant, etc., if necessary. The surfactant used in the water-soluble film is added for the purpose of improving releasability from the casting surface during film production, and typically includes nonionic surfactants, cationic surfactants, and anionic surfactants. Examples of such surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylnonyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene alkylamino ethers such as polyoxyalkylene alkyl ether phosphate monoethanolamine salts, polyoxyethylene lauryl amino ether and polyoxyethylene stearyl amino ether, sorbitan monopalmitate, sorbitan monostearate, glycerol stearate, and sucrose fatty acid esters. Among these, polyoxyalkylene alkyl ether phosphate monoethanolamine salts and polyoxyethylene lauryl amino ether are preferred in terms of production stability. These may be used alone or in combination of two or more.

[0089] The content of the surfactant is preferably 0.01 to 3 mass % of the water-soluble film, more preferably 0.05 to 2.5 mass %, and even more preferably 0.1 to 2 mass %. If the content is too low, the peelability of the formed film from the casting surface of the film-forming device tends to decrease, resulting in a decrease in productivity. If the content is too high, blocking tends to occur easily, and when the film is used to form a package, the adhesive strength at the time of sealing tends to decrease.

[0090] <Other Components> It is also possible to include other components, such as water-soluble polymers other than the PVA-based resin (A) and the naturally-derived raw materials (e.g., sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, methyl cellulose, hydroxyethyl cellulose, etc.), fragrances, rust inhibitors, colorants, bulking agents, antifoaming agents, ultraviolet absorbers, liquid paraffins, fluorescent brighteners, bitter components (e.g., denatonium benzoate, etc.), etc., within the scope of not impairing the object of the invention. These can be used alone or in combination of two or more.

[0091] The content of the other components is preferably 5 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less, based on 100 parts by mass of the total of the PVA-based resin (A) and the naturally-derived raw materials (excluding the plasticizer and the filler). The lower limit is usually 0 part by mass, and the range of the content is, for example, 0 to 5 parts by mass. If the content is too high, the compatibility with the naturally-derived raw materials decreases, and durability tends to decrease.

[0092] In this embodiment, an antioxidant may be blended. Examples of such antioxidants include sulfites such as sodium sulfite, potassium sulfite, calcium sulfite, and ammonium sulfite, as well as tartaric acid, ascorbic acid, sodium thiosulfate, techol, and Rongalit. Of these, sulfites, particularly sodium sulfite, are preferred. The blending amount is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and even more preferably 0.3 to 3% by mass of the water-soluble film.

[0093] <<Production of the Present Water-Soluble Film>> In this embodiment, as described above, the PVA-based resin (A) and a naturally-derived raw material, preferably further a plasticizer, and optionally other components such as a filler and a surfactant are blended together, and the blended materials are dissolved or dispersed in water to prepare a film-forming raw material, which is then formed into a film.

[0094] <Dissolving Step> In the dissolving step, the above-mentioned blended components are dissolved or dispersed in water to prepare an aqueous solution or aqueous dispersion serving as a film-forming raw material. The method for mixing the PVA-based resin (A), the naturally-derived raw materials, and other additives in preparing the film-forming raw material is not particularly limited, and examples thereof include a method of mixing the naturally-derived raw materials, the PVA-based resin (A), and other additives to prepare a mixture and then mixing the mixture with water to dissolve the mixture; a method of separately dissolving the PVA-based resin (A), the naturally-derived raw materials, and other additives in water and then mixing the mixture; and a method of separately dissolving the PVA-based resin (A) and the naturally-derived raw materials in water and then mixing the mixture with the other additives to dissolve the mixture.

[0095] As the dissolution method for dissolving in water, room temperature dissolution, high temperature dissolution, pressurized dissolution, etc. are usually adopted, and among them, high temperature dissolution and pressurized dissolution are preferred because they leave little undissolved material and are excellent in productivity. The dissolution temperature is usually 80 to 100°C, preferably 90 to 100°C, in the case of high temperature dissolution, and usually 80 to 130°C, preferably 90 to 120°C, in the case of pressurized dissolution. The dissolution time is usually 1 to 20 hours, preferably 2 to 15 hours, and more preferably 3 to 10 hours. If the dissolution time is too short, undissolved material tends to remain, and if it is too long, productivity tends to decrease.

[0096] Furthermore, after dissolution, the obtained film-forming raw material is subjected to a degassing treatment. Examples of such degassing methods include static degassing, vacuum degassing, and twin-screw extrusion degassing, with static degassing and twin-screw extrusion degassing being preferred. The degassing temperature is usually 50 to 100°C, preferably 60 to 95°C, and more preferably 65 to 80°C. If the degassing temperature is too high, the molecular chains of the naturally derived raw material tend to be cleaved, reducing the viscosity of the film-forming raw material. If the degassing temperature is too low, the viscosity increases, requiring longer degassing times and reducing productivity. The degassing time is usually 2 to 30 hours, preferably 5 to 25 hours.

[0097] The solids concentration of the film-forming raw material is preferably 10 to 60% by mass, more preferably 12 to 50% by mass, and even more preferably 15 to 40% by mass. If the concentration is too low, film productivity tends to decrease, while if the concentration is too high, the viscosity becomes too high, which tends to require a long time to degas the film-forming raw material and to cause die lines during film formation. The pH of the film-forming raw material is usually 4 to 8, and preferably 4.8 to 7.5.

[0098] <Film-forming process> In the film-forming process, the film-forming raw material prepared in the dissolving process is formed into a film, and if necessary, dried to prepare a water-soluble film with a water content of less than 15% by mass. As the film-forming method, for example, a melt extrusion method or a casting method can be adopted, and the casting method is preferred in terms of the accuracy of the film thickness. When performing the casting method, for example, the film-forming raw material is extruded from a slit such as a T-slit die, cast onto a casting surface such as the metal surface of an endless belt or a drum roll, or the surface of a plastic substrate such as a polyethylene terephthalate film, dried, and if necessary, further heat-treated to produce a water-soluble film.

[0099] The water-soluble film peeled from the casting surface, such as the surface of a plastic substrate, during the film-forming process is transported and wound up around a core tube to obtain a film roll. The obtained film roll can be supplied as a product as is, but preferably, the water-soluble film can also be supplied as a film roll obtained by slitting the water-soluble film to a film width of a desired size.

[0100] Thus, the present water-soluble film is obtained.

[0101] The viscosity of a 1% by mass aqueous solution of the water-soluble film at 20°C is 2.00 to 2.60 mPa s, with the lower limit being preferably 2.03 mPa s or more, more preferably 2.05 mPa s or more, even more preferably 2.10 mPa s or more, and particularly preferably 2.15 mPa s or more. The upper limit is 2.60 mPa s or less, preferably 2.55 mPa s or less, more preferably 2.50 mPa s or less, and even more preferably 2.45 mPa s or less. If the viscosity is too lower or too higher than the range specified in the present invention, the water-sealing property of the water-soluble film tends to decrease.

[0102] The viscosity of a 1% by mass aqueous solution of the water-soluble film at 20°C is a value measured by the viscosity measurement method using a falling ball viscometer described in "JIS Z 8803:2011 Methods for measuring viscosity of liquids," and can be measured by the method described in the examples below.

[0103] In this embodiment, the viscosity at a low concentration of 1% by mass aqueous solution is specified, and this is an index of the viscosity when the polymer chains are spread out and there is little influence of interactions between the polymers. The more the polymer chains spread when the polymer contained in the film is dissolved in water, the more entanglement occurs during sealing, and the better the sealing performance. In this embodiment, the viscosity of the water-soluble film in a so-called dilute solution is important.

[0104] The surface of the water-soluble film may be plain, but from the viewpoints of blocking resistance, slipperiness during processing, reduced adhesion between products, and appearance, it is also preferable to provide one or both sides of the film with a textured finish such as an embossed pattern, a fine textured pattern, or a specially engraved design.

[0105] The thickness of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 10 to 120 μm, more preferably 15 to 110 μm, and even more preferably 20 to 100 μm. If the thickness is too thin, the mechanical strength of the film tends to decrease, while if the thickness is too thick, the dissolution rate in water tends to decrease and the film-forming efficiency also tends to decrease.

[0106] The width of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 300 to 5000 mm, more preferably 500 to 4000 mm, and even more preferably 600 to 3000 mm. If the width is too narrow, productivity tends to decrease, while if the width is too wide, it tends to become difficult to control slack and film thickness.

[0107] The length of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 100 to 20,000 m, more preferably 800 to 15,000 m, and even more preferably 1,000 to 10,000 m. If the length is too short, film switching is time-consuming and the productivity tends to decrease, while if the length is too long, poor appearance tends to occur due to tight winding.

[0108] The water content of the water-soluble film is preferably 3 to 15% by mass, more preferably 5 to 9% by mass, and even more preferably 6 to 8% by mass, from the viewpoints of mechanical strength and heat sealability. If the water content is too low, the film becomes too hard, which tends to reduce the formability when made into a package and the impact resistance of the package. If the water content is too high, blocking tends to occur. The water content can be adjusted by appropriately setting the drying conditions and humidity control conditions. The water content is measured in accordance with JIS K 6726 3.4, and the value of the volatile content obtained is taken as the water content.

[0109] The tensile strength of the present water-soluble film is preferably 5 MPa or more, more preferably 10 MPa or more, and even more preferably 13 MPa or more. The upper limit is not particularly limited, but is usually 100 MPa or less, preferably 60 MPa or less, and the numerical range of such tensile strength is, for example, 5 to 100 MPa. Within this range, the film exhibits excellent mechanical properties such as strength and stretchability during packaging. The tensile strength of the present water-soluble film can be measured by the method described in the Examples below.

[0110] The tensile elongation of the present water-soluble film is preferably 200% or more, more preferably more than 300%, and even more preferably 330% or more. The upper limit is not particularly limited, but is usually 800% or less, preferably 600% or less, and the numerical range of such tensile elongation is, for example, 200 to 800%. Within this range, the film exhibits excellent mechanical properties such as strength and stretchability during packaging. The tensile elongation of the present water-soluble film can be measured by the method described in the Examples below.

[0111] The water-soluble film may be used as a single layer, or may be used as a multilayer structure in which other films or resin layers are laminated.

[0112] The water-soluble film thus obtained is particularly useful for packaging (unit packaging) chemicals such as pesticides and detergents, and for edible food packaging. The food to be packaged in the film may be in the form of granules, tablets, powder, etc., and is preferably dried food such as ingredients and toppings for instant foods.

[0113] <<Medicine Package>> A medicine package according to one embodiment of the present invention (hereinafter referred to as the "medicine package") comprises a package made of the water-soluble film and a medicine contained in the package. These are described below.

[0114] This drug package is formed by coating a drug with a package made of the obtained water-soluble film. Because this drug package contains a drug packaged in a package made of a water-soluble film, when the drug package is placed in water, the surface package (water-soluble film) dissolves, exposing the drug, which then dissolves or disperses in the water, thereby exerting its effects. Therefore, this drug package is suitable as a drug package containing a relatively small amount of drug, such as a single dose.

[0115] The shape of the drug package may be selected appropriately and is not particularly limited, but may be, for example, a substantially cubic shape, a substantially spherical shape, a substantially flattened spherical shape, a substantially teardrop shape, etc. The drug package may be composed of a single compartment or may have multiple compartments.

[0116] The number of compartments in the drug package is not particularly limited and is selected appropriately depending on the type of contents, etc., but is, for example, 2 to 10 compartments, preferably 3 to 8 compartments, and more preferably 4 to 6 compartments. It is also preferable that different types of contents are packed in each of the compartments.

[0117] The surface of the pharmaceutical packaging body is usually smooth, but from the standpoint of blocking resistance, slipperiness during processing, reduced adhesion between products (individually packaged bodies), and appearance, the outer surface of the packaging body (water-soluble film) may be textured with an embossed pattern, a finely textured pattern, a specially engraved pattern, or the like.

[0118] Examples of the above-mentioned chemicals include agricultural chemicals such as insecticides, fungicides, and herbicides, fertilizers, detergents, etc., and detergents such as laundry detergents and dishwashing detergents are particularly preferred. Such chemicals may be liquid or solid, and if solid, may be in the form of granules, tablets, powder, etc. The chemicals are preferably those that are dissolved or dispersed in water, and are particularly preferably those that contain liquid detergents. The pH of such chemicals may be alkaline, neutral, or acidic.

[0119] The liquid detergent preferably has a pH value of 6 to 12, more preferably 7 to 11, when dissolved or dispersed in water to a concentration of 1% by mass. The liquid detergent also preferably has a water content of 15% by mass or less, more preferably 0.1 to 10% by mass, and even more preferably 0.1 to 7% by mass. When the water content of the liquid detergent is within the above range, the water-soluble film tends to be free from gelation or insolubilization, and the water solubility tends to be excellent. The pH value is measured in accordance with JIS K 3362 8.3. The water content is measured in accordance with JIS K 3362 7.21.3.

[0120] <<Manufacturing of Drug Packages>> Drug packages can be manufactured by using the water-soluble film to package drugs such as liquid detergents. For example, drug packages can be manufactured by placing the drug between two opposing water-soluble films (a first water-soluble film and a second water-soluble film) and then crimping and bonding the overlapping portions (contact portions) of the water-soluble films around the drug. Specifically, a lower mold of a molding device is prepared, which has a recess shaped to accommodate the drug. A first water-soluble film (bottom film) is fixed to the lower mold, and the bottom film is molded to a shape that conforms to the lower mold. Meanwhile, a second water-soluble film (top film) is also fixed to the upper mold of the molding device. A separately prepared drug such as liquid detergent is then placed (introduced) into the molded bottom film. The upper and lower molds are then clamped together, bringing the top and bottom films around the drug into contact, and the contact portions are then crimped under vacuum. After crimping, the vacuum is released to obtain a drug package in which the drug is encapsulated in the water-soluble film.

[0121] Examples of methods for bonding the film include heat sealing, water sealing, and glue sealing. Of these, water sealing is preferred because it is easy to control the bonding conditions.

[0122] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" refers to parts by mass.

[0123] The following materials were prepared as the water-soluble film components:

[0124] [PVA Resin (A)] PVA1 (carboxy group-modified PVA-based resin): 4% by mass aqueous solution viscosity at 20°C 22 mPa s, average degree of saponification 94 mol%, modification amount with maleic acid monomethyl ester 2.0 mol%. PVA2 (unmodified PVA): 4% by mass aqueous solution viscosity at 20°C 43 mPa s, average degree of saponification 88 mol%. PVA3 (unmodified PVA): 4% by mass aqueous solution viscosity at 20°C 5 mPa s, average degree of saponification 88 mol%.

[0125] [Naturally derived ingredients] (Naturally derived ingredients other than plasticizers) Gelatin: "#200" manufactured by Nitta Gelatin Co., Ltd., alkali-treated (weight-average molecular weight: 100,000) Pullulan: Pullulan manufactured by Hayashibara Co., Ltd. (weight-average molecular weight: 200,000) Collagen: "Collagen peptide" manufactured by Fujifilm Corporation, enzymatically hydrolyzed (weight-average molecular weight: 2,000) Starch 1: Pregelatinized starch (amylopectin content 100%, "Waxy Alpha Y" manufactured by Sanwa Starch Co., Ltd.) (weight-average molecular weight: 1,000,000 or more) Casein: "Casein sodium 180" manufactured by Fonterra (weight-average molecular weight: 23,000) (filler) Starch 2: Corn starch, average particle size 20 μm (disperses but does not dissolve in water at about 20°C, functions as a filler)

[0126] (Plasticizers) Plasticizer 1: Glycerin Plasticizer 2: Sorbitol

[0127] [Non-naturally derived ingredients] (Surfactants) Polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt

[0128] Example 1: 40 parts of a carboxyl-modified PVA-based resin (PVA1), 10 parts of an unmodified PVA (PVA2), 50 parts of starch 1 as a naturally-occurring material, 20 parts of glycerin as a plasticizer, 0.2 parts of a polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt as a surfactant, and water were mixed to obtain a film-forming raw material, which was an aqueous dispersion of a resin composition with a solids concentration of 25% by mass. The film-forming raw material was cast onto a polyethylene terephthalate film and dried by passing it through a 3-m long drying chamber (105°C) at a speed of 0.40 m / min to obtain a water-soluble film with a thickness of 87 μm (water content: 7% by mass).

[0129] Example 2 A film-forming raw material was obtained by mixing 65 parts of a carboxyl-modified PVA-based resin (PVA1) as a PVA-based resin, 35 parts of pullulan as a naturally-occurring raw material, 8 parts of cornstarch (starch 2) as a filler, 20 parts of glycerin and 20 parts of sorbitol as plasticizers, 0.2 parts of a polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt as a surfactant, and water. The remaining steps were the same as in Example 1, and a water-soluble film with a thickness of 100 μm (water content: 7.5% by mass) was obtained.

[0130] Example 3: 50 parts of a carboxyl-modified PVA-based resin (PVA1) as a PVA-based resin, 50 parts of pregelatinized starch (Starch 1) as a naturally-derived raw material, 20 parts of glycerin as a plasticizer, and water were mixed to obtain a film-forming raw material, which was an aqueous dispersion of a resin composition with a solid content of 30% by mass. Otherwise, the same procedure as in Example 1 was repeated to obtain a water-soluble film with a thickness of 87 μm (water content: 7.1% by mass).

[0131] Example 4 A water-soluble film having a thickness of 89 μm (water content: 7.5% by mass) was obtained in the same manner as in Example 3, except that the components and amounts of the resin composition were changed to those shown in Table 1 below.

[0132] Comparative Examples 1 to 3 Water-soluble films having a thickness of 86 μm (water content: 7% by mass) were obtained in the same manner as in Example 1, except that the components and amounts of the resin composition were changed to those shown in Table 1 below.

[0133]

[0134] The viscosity of a 1% by mass aqueous solution of each of the water-soluble films obtained was measured by the method described below, and the results are also shown in Table 1. The mechanical properties and water-sealing properties of the water-soluble films were evaluated according to the methods and criteria described below. The results are shown in Table 2 below.

[0135] <Aqueous Solution Viscosity> The viscosity of the aqueous solution obtained by dissolving 0.7 g of the water-soluble film obtained above in 69.3 g of water at 23°C was measured. That is, an aqueous solution was prepared to have a concentration of 1% by mass based on the mass of the film, and the viscosity was measured at 20°C using a falling-ball viscometer as described in "JIS Z 8803:2011 Method for measuring viscosity of liquids." The water-soluble film used was allowed to stand for 24 hours under humidity conditions of 23°C and 50% RH before being dissolved in water. The entire process from preparation of the aqueous solution to viscosity measurement was carried out within 8 hours. Note that after dissolving the water-soluble film in water, the film was allowed to stand for 3 hours at 20°C, and any insoluble matter that precipitated (e.g., starch as a filler) was removed before the viscosity measurement.

[0136] <Mechanical Properties> [Tensile Strength, Tensile Elongation] Using the water-soluble film obtained above, the "tensile strength" and "tensile elongation" were measured in accordance with JIS K 7127 (1999). That is, before measurement, the water-soluble film was allowed to stand for 24 hours under humidity-controlled conditions of 23°C and 50% RH, and then, under these conditions, the tensile strength and tensile elongation of the water-soluble film were measured using an Autograph AG-X Plus (manufactured by Shimadzu Corporation) at a pulling rate of 200 mm / min (film width: 15 mm, chuck distance: 50 mm). These measured values ​​were evaluated based on the following criteria. [Evaluation Criteria] ⊚ (excellent): The tensile strength was 10 MPa or more and the tensile elongation was greater than 300%. ◯ (very good): The tensile strength was 10 MPa or more and the tensile elongation was 200 to 300%, or the tensile strength was 5 MPa or more but less than 10 MPa and the tensile elongation was greater than 300%. △ (good): The tensile strength was 5 MPa or more and less than 10 MPa, and the tensile elongation was 200 to 300%. × (poor): The tensile strength was 0 to less than 5 MPa and / or the tensile elongation was less than 200%.

[0137] <Water sealing property> The water-soluble film obtained above was cut into a size of 100 mm × 200 mm (top film) and 100 mm × 100 mm (bottom film), and a water sealing test was performed. That is, the water-soluble film was left to stand for 24 hours under humidity conditions of 23°C and 40% RH, and then, under this environment, the water-soluble film (bottom film) was fixed to a 30 cm square glass plate, and water was applied using a water-soaked PVA sponge roller ("Cygnus Roller" manufactured by Ion Co., Ltd.). Thereafter, the water-soluble film (top film) was placed on the water-coated water-soluble film (bottom film), and another rubber roller (width 250 mm, diameter 60 mm, weight 2750 g) was rolled twice from above to press the top film and bottom film together, thereby preparing a test specimen. After 2 minutes, the test piece was subjected to measurement of the peel strength of the sealed portion using an Autograph AG-X Plus (Shimadzu Corporation) at a pulling rate of 100 mm / min (film width 15 mm, chuck distance 20 mm). The state of failure of the sealed portion in the water seal test, or the average test force over a stroke of 50 to 100 mm, was evaluated based on the following criteria: [Evaluation criteria] ○ (Very good): The average test force was 5 N / 15 mm or more, and cohesive failure occurred at the sealed portion. △ (Good): The average test force was 3 N / 15 mm or more but less than 5 N / 15 mm, and cohesive failure occurred at the sealed portion. × (Poor): The average test force was less than 3 N / 15 mm, or interfacial peeling occurred at the sealed portion.

[0138]

[0139] The results in Table 2 above show that the films of Examples 1 to 4, whose 1% by mass aqueous solution viscosities (dilute solution viscosities) were within the specified viscosity range, had excellent mechanical properties and also excellent water-tightness. In contrast, the films of Comparative Examples 1 to 3, whose 1% by mass aqueous solution viscosities (dilute solution viscosities) were outside the specified viscosity range, all had poor water-tightness.

[0140] The water-soluble films of the examples have excellent mechanical properties and water-sealing properties, making them suitable for packaging applications, and packages made using such water-soluble films also have excellent mechanical properties and water-sealing properties.

[0141] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0142] This water-soluble film can be used for packaging (unit packaging) of pharmaceuticals such as pesticides and detergents, (hydraulic) transfer films, sanitary products such as napkins and disposable diapers, waste disposal products such as ostomy bags, medical products such as blood-absorbing sheets, and temporary substrates such as seedling raising sheets, seed tape, and embroidery base fabrics. This water-soluble film, a blend film of PVA-based resin, which is also used in food and pharmaceuticals, and naturally derived raw materials, is also useful for edible applications (food packaging).

Claims

1. A water-soluble film comprising a polyvinyl alcohol resin and at least one naturally occurring raw material selected from the group consisting of sugars, sugar alcohols, lipids, proteins, and salts thereof, wherein the content of the naturally occurring raw material is 40% by mass or more relative to 100% by mass (solid content) of the water-soluble film, and a 1% by mass aqueous solution of the water-soluble film has a viscosity of 2.00 to 2.60 mPa·s at 20°C.

2. The water-soluble film according to claim 1, wherein the naturally occurring raw material comprises a naturally occurring raw material having a weight-average molecular weight of 10,000 or more.

3. A method for producing the water-soluble film according to claim 1 or 2, comprising the steps of: preparing a film-forming raw material containing the polyvinyl alcohol resin and the naturally occurring raw material; casting the film-forming raw material onto a casting surface; and drying the film-forming raw material cast onto the casting surface.

4. A package containing the water-soluble film according to claim 1 or 2.

5. A pharmaceutical package comprising a package containing the water-soluble film according to claim 1 or 2 and a pharmaceutical packaged in the package.

6. The pharmaceutical package of claim 5, wherein the pharmaceutical is a liquid detergent.

7. A method for producing a drug package as described in claim 5, comprising the steps of: preparing a first water-soluble film, a second water-soluble film, and the drug; placing the drug between the first water-soluble film and the second water-soluble film; and abutting and pressing the first water-soluble film and the second water-soluble film together.

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