Water-soluble film and medicine package

Abstract

The present invention provides the water-soluble film described below, which is excellent in terms of moldability and mechanical properties such as film strength and elongation, and which is also excellent in terms of sealability.　A water-soluble film which contains a polyvinyl alcohol resin, an unmodified starch, and a plasticizer, wherein: the polyvinyl alcohol resin contains a modified polyvinyl alcohol resin; the amylopectin content of the unmodified starch is 85% or more; and the ratio of the unmodified starch to the total mass of the unmodified starch and the plasticizer is 20-78 mass%.

Description

Water-soluble film and pharmaceutical packaging

[0001] The present invention relates to a water-soluble film containing unmodified starch, and more particularly to a water-soluble film containing a polyvinyl alcohol-based resin and unmodified starch, and a pharmaceutical package using the same.

[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] For example, Patent Document 1 describes a starch composition containing starch having an amylopectin content of 70% or more as naturally occurring raw materials and a polyvinyl alcohol-based resin having a saponification degree of 96 mol% or less, in which the proportion of starch is 40 to 90% by mass and the proportion of polyvinyl alcohol-based resin is 10 to 60% by mass relative to the total mass of the starch and polyvinyl alcohol-based resin. Patent Document 1 also describes that films, fibers, etc. using the starch composition have high water solubility and biodegradability.

[0004] International Publication No. 2023 / 276402

[0005] When a film is produced using the starch composition of Patent Document 1, the resulting film has poor mechanical properties such as strength and stretchability, and poor formability, and further improvements are required for use in individual packaging of foods, medicines, etc. Furthermore, when packaging liquids in individual packaging applications, low strength of the sealed portion raises concerns about liquid leakage, and further improvements are required.

[0006] Under these circumstances, an object of the present invention is to provide a water-soluble film that is excellent in mechanical properties such as film strength and elongation, formability, and sealability.

[0007] However, as a result of intensive research conducted by the present inventors in light of these circumstances, they have found that, in a water-soluble film containing a polyvinyl alcohol-based resin, unmodified starch, and a plasticizer, a water-soluble film having excellent mechanical properties, formability, and sealability can be obtained by using a modified polyvinyl alcohol-based resin as the polyvinyl alcohol-based resin, using an unmodified starch having an amylose content of 85% or more as the unmodified starch, and further setting the content of the unmodified starch within a specific range relative to the total mass of the unmodified starch and the plasticizer. Furthermore, because the polyvinyl alcohol-based resin is a biodegradable resin, it is possible to solve the above problems without significantly reducing the biodegradability of the water-soluble film as a whole, and it is also possible to reduce the proportion of petroleum-derived raw materials compared to water-soluble films made of conventional polyvinyl alcohol-based resins.

[0008] That is, the present invention has the following aspects. [1] A water-soluble film comprising a polyvinyl alcohol-based resin, unmodified starch, and a plasticizer, wherein the polyvinyl alcohol-based resin contains a modified polyvinyl alcohol-based resin, the unmodified starch has an amylopectin content of 85% or more, and the content of the unmodified starch is 20 to 78% by mass relative to the total mass of the unmodified starch and the plasticizer. [2] The water-soluble film according to [1], wherein the content of the unmodified starch is 20 to 60% by mass relative to the total mass of the unmodified starch and the plasticizer. [3] The water-soluble film according to [1] or [2], wherein the content of the unmodified starch is 65 to 75% by mass relative to the total mass of the unmodified starch and the plasticizer. [4] The water-soluble film according to any of [1] to [3], wherein the content of the unmodified starch is 20 to 80% by mass relative to the total mass of the polyvinyl alcohol-based resin and the unmodified starch. [5] The water-soluble film according to any one of [1] to [4], which contains glycerin as the plasticizer. [6] The water-soluble film according to any one of [1] to [4], which contains glycerin and at least one other plasticizer as the plasticizer, and the mass ratio of the glycerin to the at least one other plasticizer [(glycerin) / (at least one other plasticizer)] is 95 / 5 to 10 / 90. [7] The water-soluble film according to any one of [1] to [6], which has an average saponification degree of 80 to 96 mol% for the polyvinyl alcohol-based resin. [8] The water-soluble film according to any one of [1] to [7], which is used for packaging medicines. [9] A medicine package comprising a package made of the water-soluble film according to any one of [1] to [8], and a medicine contained in the package.

[0009] The water-soluble film of the present invention has excellent mechanical properties and formability, particularly excellent formability for complex shapes, and also has excellent sealing properties, making it suitable for individual packaging applications, particularly as individual packages for 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] Furthermore, in this specification, when the expression "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it means "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." Furthermore, when the expression "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." In this specification, "x and / or y (x and y are any configurations)" means at least one of x and y, and can mean three possibilities: x only, y only, or x and y. For numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in one stage can be arbitrarily combined with the upper or lower limit of a numerical range in another stage. Furthermore, in the numerical ranges described in this specification, 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] <<Water-soluble film>> 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. Dissolution is determined when no insoluble fine particles of the film with a diameter of 1 mm or more are observed.

[0014] The water-soluble film according to one embodiment of the present invention (hereinafter sometimes referred to as "the present water-soluble film") contains a polyvinyl alcohol resin, unmodified starch, and a plasticizer. These will be explained below. In the present invention, polyvinyl alcohol may be abbreviated as "PVA." In addition, in the present invention, the term "film" also includes "tape" and "sheet."

[0015] <PVA-Based Resin> The PVA-based resin is a resin primarily composed of vinyl alcohol structural units, obtained by saponifying a vinyl ester-based resin obtained by polymerizing a vinyl ester-based monomer, and is composed of vinyl alcohol structural units corresponding to the degree of saponification and remaining vinyl ester structural units that have not been saponified. Examples of the PVA-based resin include unmodified PVA and modified PVA-based resins, but the present invention contains a modified PVA-based resin as the PVA-based resin. The PVA-based resin may be a single type, or may contain two or more PVA-based resins that differ in at least one of the degree of saponification, viscosity, modified species, and modification amount.

[0016] The modified PVA-based resin is preferably an anion-modified PVA-based resin having an anionic group such as a carboxy group, a sulfonic acid group, or a phosphate group, from the viewpoints of compatibility with unmodified starch and film solubility. Examples of the anionic group include a carboxy group, a sulfonic acid group, and a phosphate group. From the viewpoint of stability of solubility over time, the carboxy group and the sulfonic acid group are preferred, and the carboxy group is particularly preferred.

[0017] The modified PVA resin can be produced, for example, by saponifying a copolymer of a vinyl ester compound and an unsaturated monomer, or by post-modifying unmodified PVA. The unmodified PVA can also be produced, for example, by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester compound.

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

[0019] When the modified PVA-based resin is an anion-modified PVA-based resin, the unsaturated monomer may be an unsaturated monomer having an anionic group, such as a carboxyl group-containing unsaturated monomer, a sulfonic acid group- or sulfonate group-containing unsaturated monomer, or a phosphate group-containing unsaturated monomer, which may be used alone or in combination of two or more.

[0020] Examples of the carboxyl group-containing unsaturated monomer include carboxyl group-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 carboxyl group-containing unsaturated compounds such as methyl acrylate, ethyl acrylate, methyl methacrylate, monomethyl fumarate, and monomethyl maleate, and dialkyl esters of the carboxyl group-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.

[0021] 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 malates, 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.

[0022] Examples of the phosphoric acid group-containing unsaturated monomer include phosphonocarboxylic acid compounds and alkali metal salts thereof.

[0023] As a method for polymerizing the vinyl ester compound and the unsaturated monomer, or a method for polymerizing the vinyl ester compound, any known polymerization method can be used, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, etc., but the polymerization is usually carried out by a solution polymerization method using an alcohol such as methanol, ethanol, or isopropyl alcohol as a solvent.

[0024] The polymerization catalyst used in the polymerization method can be appropriately selected from known polymerization catalysts, such as azo catalysts such as azobisisobutyronitrile, and peroxide catalysts such as acetyl peroxide, benzoyl peroxide, and lauroyl peroxide, depending on the polymerization method. These catalysts 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.

[0025] The resulting copolymer of a vinyl ester compound and an unsaturated monomer, or the polyvinyl ester resin, can also be saponified by a known method. Typically, the resulting polymer is dissolved in alcohol and saponification is carried out in the presence of a saponification catalyst. Examples of alcohol include methanol, ethanol, and butanol. These can be used alone or in combination. The concentration of the copolymer in the alcohol is selected from the range of 20 to 50% by mass in terms of solubility.

[0026] The saponification catalyst may be, 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, or an acid catalyst. These may 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.

[0027] In this way, modified PVA resins and unmodified PVA are obtained.

[0028] The average saponification degree of the PVA-based resin is usually 80 mol% or more, preferably 82 to 99.9 mol%, more preferably 85 to 98 mol%, and preferably 90 to 96 mol%. If the average saponification degree is too low, the solubility in water tends to decrease, and depending on the packaging material, the solubility of the film tends to decrease over time. However, if the average saponification degree is too high, the solubility in water tends to decrease. In particular, in the present water-soluble film, if the saponification degree is too high, the solubility in water tends to decrease.

[0029] The average saponification degree of the modified PVA resin is usually 80 mol% or more, preferably 85 to 99.9 mol%, and more preferably 90 to 99 mol%. If the average saponification degree is too high, the solubility in water tends to decrease, whereas if it is too low, the solubility in water tends to decrease over time depending on the packaging material.

[0030] Furthermore, when an anionic group-modified PVA-based resin is used as the modified PVA-based resin, the average saponification degree thereof is preferably 85 to 99.9 mol%, particularly preferably 88 to 98 mol%, further preferably 90 to 97 mol%, and particularly preferably 90 to 96 mol%. If the average saponification degree is too high, the solubility in water tends to decrease, whereas if it is too low, the solubility in water tends to decrease over time depending on the packaging material.

[0031] When unmodified PVA is used, its average saponification degree is usually 80 mol% or more, preferably 82 to 99 mol%, and more preferably 85 to 90 mol%. If the average saponification degree is too low, the solubility in water tends to decrease. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0032] The average saponification degree of the PVA-based resin means that the average saponification degree of all PVA-based resins contained in the present water-soluble film is within these ranges. When the present water-soluble film contains a plurality of PVA-based resins, the average saponification degree of all PVA-based resins is calculated from the ratio of each PVA-based resin contained in the entire PVA-based resin and the average saponification degree according to the following formula: (Formula) Average saponification degree of all PVA-based resins (A) = Content ratio of PVA-based resin (i) × Average saponification degree of PVA-based resin (i) + Content ratio of PVA-based resin (ii) × Average saponification degree of PVA-based resin (ii) + ... (omitted below)

[0033] The modification amount of the modified PVA-based resin is usually 1 to 20 mol %, preferably 1.5 to 15 mol %, and particularly preferably 2 to 12 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, the biodegradability tends to decrease, and the PVA-based resin tends to be prone to blocking, which tends to reduce its practicality.

[0034] When an anionic group-modified PVA-based resin is used as the modified PVA-based resin, the modification amount is preferably 1 to 15 mol %, more preferably 1.5 to 10 mol %, and particularly preferably 2 to 8 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, the biodegradability tends to decrease, and the PVA-based resin tends to be prone to blocking, which tends to reduce its practicality.

[0035] The viscosity of a 4% by mass aqueous solution of the PVA-based resin at 20° C. is usually 5 to 60 mPa s, preferably 10 to 45 mPa s, more preferably 15 to 40 mPa s, and particularly preferably 21 to 35 mPa s. If the viscosity is too low, the mechanical strength 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.

[0036] The viscosity of a 4% by mass aqueous solution of the PVA-based resin at 20°C means that the viscosity of a 4% by mass aqueous solution of the entire PVA-based resin contained in the water-soluble film at 20°C falls within these ranges.

[0037] The viscosity of a 4% by mass aqueous solution of the modified PVA-based resin at 20° C. is usually 5 to 50 mPa s, preferably 10 to 40 mPa s, and more preferably 15 to 35 mPa s. If the viscosity is too low, the mechanical strength tends to decrease, whereas if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to be high, resulting in decreased productivity.

[0038] Furthermore, when an anionic group-modified PVA-based resin is used as the modified PVA-based resin, the viscosity of a 4% by mass aqueous solution thereof at 20° C. is usually 5 to 50 mPa s, preferably 13 to 40 mPa s, and more preferably 17 to 30 mPa s. If the viscosity is too low, the mechanical strength tends to decrease, whereas if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to be high, resulting in decreased productivity.

[0039] When unmodified PVA is used, the viscosity of a 4% by mass aqueous solution thereof at 20° C. is usually 10 to 60 mPa s, preferably 20 to 50 mPa s, and more preferably 30 to 45 mPa s. If the viscosity is too low, the mechanical strength tends to decrease, whereas if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to be high, resulting in decreased productivity.

[0040] The average degree of saponification is measured in accordance with JIS K 6726 3.5, and the viscosity of a 4% by mass aqueous solution is measured in accordance with JIS K 6726 3.11.2.

[0041] The content of the PVA-based resin is usually 10 to 70% by mass, preferably 15 to 65% by mass, more preferably 20 to 55% by mass, and particularly preferably 25 to 50% by mass, based on the water-soluble film in terms of mechanical strength.

[0042] When the PVA-based resin contains unmodified PVA, the mass ratio of the modified PVA-based resin to the unmodified PVA (modified PVA-based resin / unmodified PVA) is usually 99 / 1 to 55 / 45, preferably 95 / 5 to 60 / 40, and more preferably 90 / 10 to 70 / 30, in terms of film properties such as solubility in water and sealability.

[0043] <Unmodified Starch> The unmodified 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 cornstarch, and commercially available amylose powder. 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.

[0044] In this specification, "unmodified starch" refers to starch that has not been chemically treated, excluding starch derivatives in which a functional group has been introduced into the hydroxyl group of starch, and chemically modified starch derivatives such as oxidized starch. Examples of the unmodified starch include raw starch, physically processed starches that have been physically treated, such as pregelatinized starch and heat-moisture treated starch (e.g., pregelatinized starch, fractionated amylose, heat-moisture treated starch, etc.), decomposed starches in which starch has been decomposed with acid (e.g., acid-treated starch), and enzyme-treated starches in which starch has been decomposed with enzymes (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.

[0045] The amylopectin content of the unmodified starch is 85% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more, from the viewpoints of mechanical properties, moldability, and sealability. The upper limit is not particularly limited, but is typically 100%. The amylopectin content ranges, for example, from 85 to 100%. When the unmodified starch is a mixture of two or more types of unmodified starch, the amylopectin content of the mixture should be 85% or more. The unmodified starch described herein does not include starch used as a filler (i.e., starch present in a water-soluble film as starch particles of 0.1 μm or more that disperse in water at room temperature (20°C) without gelatinizing), as described below.

[0046] The amylopectin content refers to the mass ratio of amylopectin when the total mass of amylose and amylopectin contained in unmodified starch is taken as 100%. The amylopectin content can be measured by a colorimetric 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.

[0047] When the unmodified starch is a mixture of two or more types of unmodified starch, the amylopectin content of the unmodified starch (mixture) may be the weighted average of the amylopectin contents of each unmodified 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 measured value may be used as the amylopectin content of the unmodified starch. When the amylopectin content is calculated as a weighted average, it can be determined from the amylopectin ratio of each unmodified starch using the following formula: Amylopectin content of unmodified starch (%) = Σ(n a i×M a i) / 100 n a i: Amylopectin content (%) of each unmodified starch M a i: Proportion of each unmodified starch in the unmodified starch (mass%)

[0048] The content of the unmodified starch in the water-soluble film is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, even more preferably 20 to 60% by mass, and particularly preferably 30 to 50% by mass.

[0049] From the viewpoints of mechanical properties, moldability, and sealability, the content of the unmodified starch is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, even more preferably 20 to 60% by mass, and particularly preferably 30 to 55% by mass, based on the total mass of the PVA-based resin and the unmodified starch. When the content of the unmodified starch is within the above range, the mechanical properties, moldability, and sealability tend to be excellent. Furthermore, from the viewpoint of compressive strength, the content of the unmodified starch is preferably 20 to 80% by mass, more preferably 25 to 70% by mass, and even more preferably 30 to 55% by mass, based on the total mass of the PVA-based resin and the unmodified starch. When the content of the unmodified starch is within the above range, the strength tends to be excellent. Furthermore, from the viewpoint of moldability, particularly moldability into complex shapes, the content of the unmodified starch is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, even more preferably 15 to 38% by mass, and particularly preferably 20 to 35% by mass, based on the total mass of the PVA-based resin and the unmodified starch. When the proportion of unmodified starch is within the above range, the elongation tends to be excellent.

[0050] The content of the unmodified starch is 20 to 78% by mass, preferably 50 to 75% by mass, and more preferably 65 to 75% by mass, based on the total mass of the unmodified starch and the plasticizer described below. When the proportion of unmodified starch is within this range, excellent mechanical properties, moldability, and sealability are achieved. Furthermore, from the viewpoint of achieving superior moldability, particularly moldability for complex shapes, the content of the unmodified starch is preferably 20 to 60% by mass, more preferably 21 to 50% by mass, and particularly preferably 22 to 45% by mass, based on the total mass of the unmodified starch and the plasticizer described below. Furthermore, from the viewpoint of achieving superior compressive strength, the content of the unmodified starch is preferably 65 to 75% by mass, more preferably 67 to 75% by mass, and particularly preferably 70 to 75% by mass, based on the total mass of the unmodified starch and the plasticizer described below.

[0051] Furthermore, the content of the unmodified starch is usually 20 to 78% by mass, preferably 30 to 75% by mass, and more preferably 35 to 75% by mass, based on the total mass of the unmodified starch and glycerin (plasticizer) described below. When the proportion of unmodified starch is within the above range, the mechanical properties, moldability, and sealability tend to be excellent.

[0052] <Plasticizer> The present water-soluble film contains a plasticizer in addition to the PVA-based resin and unmodified starch in order to impart appropriate flexibility to the film. Normally, when unmodified starch is added to a water-soluble film, the water-soluble film becomes hard and brittle, and mechanical properties, moldability, and sealability are reduced. On the other hand, in the present invention, it has been found that by setting the ratio of unmodified starch to the total mass of unmodified starch and plasticizer within a specific range, i.e., by setting the ratio of plasticizer within a specific range, the mechanical properties, moldability, and sealability are excellent.

[0053] Examples of the plasticizer include glycerols such as glycerol, diglycerol, and triglycerol; alkylene glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and dipropylene glycol; sugar alcohols such as sorbitol, xylitol, trehalose, and maltitol; and trimethylolpropane. These can be used alone or in combination of two or more. Among these, glycerols and sugar alcohols are preferred, more preferably glycerol, sorbitol, and trehalose, and particularly preferably glycerol. Furthermore, from the viewpoint of excellent moldability, particularly moldability into complex shapes, it is preferred to use glycerol and at least one other plasticizer as the plasticizer, more preferably a combination of glycerol with sorbitol and / or trehalose. Using such glycerol and at least one other plasticizer as the plasticizer can increase the tensile elongation, which tends to improve moldability into complex shapes.

[0054] When glycerin and at least one other plasticizer are used as the plasticizer, the mass ratio of glycerin to at least one other plasticizer [(glycerin) / (at least one other plasticizer)] is preferably 95 / 5 to 10 / 90, more preferably 90 / 10 to 20 / 80, and more preferably 85 / 15 to 40 / 60. When the mass ratio of glycerin to at least one other plasticizer is within the above range, the mechanical properties, moldability, particularly moldability for complex shapes, and sealability tend to be excellent.

[0055] When a combination of glycerin and sorbitol and / or trehalose is used as the plasticizer, the mass ratio of glycerin to sorbitol and / or trehalose [(glycerin) / (sorbitol and / or trehalose)] is usually 95 / 5 to 10 / 90, preferably 90 / 10 to 20 / 80, and more preferably 85 / 15 to 40 / 60. When the mass ratio of glycerin to sorbitol and / or trehalose is within the above range, the resulting composition tends to exhibit excellent mechanical properties, moldability, particularly moldability for complex shapes, and sealability.

[0056] The content of the plasticizer is usually 5 to 60% by mass, preferably 8 to 50% by mass, and more preferably 10 to 45% by mass, based on the mass of the water-soluble film. When the content of the plasticizer is within the above range, the water-soluble film tends to have excellent mechanical properties, moldability, and sealability.

[0057] The content of the plasticizer is preferably 15 to 80 parts by mass, more preferably 20 to 75 parts by mass, and particularly preferably 40 to 70 parts by mass, relative to 100 parts by mass of the total of the PVA-based resin and unmodified starch. When the content of the plasticizer is within the above range, the mechanical properties, moldability, and sealability tend to be excellent.

[0058] When glycerin is used as a plasticizer, its content is usually 10 to 70 parts by mass, preferably 13 to 50 parts by mass, and more preferably 15 to 40 parts by mass, per 100 parts by mass of the total of the PVA-based resin and unmodified starch. When the glycerin content is within the above range, the mechanical properties, moldability, and sealability tend to be excellent.

[0059] Furthermore, when glycerin is used as a plasticizer, the content thereof is preferably 20% by mass or more, more preferably 20 to 50% by mass, and even more preferably 20 to 40% by mass, based on the total mass of the unmodified starch and the plasticizer. When the proportion of glycerin is within the above range, the mechanical properties, moldability, and sealability tend to be excellent.

[0060] <Filler> The water-soluble film may further contain a filler, if necessary. The filler is added 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 diameter of the filler is 0.1 to 50 μm, preferably 1 to 35 μm. The average particle diameter of the filler is a value measured using a laser diffraction particle size distribution analyzer, and is calculated from the D50 value (particle diameter at 50% of the cumulative volume) of the obtained cumulative volume distribution.

[0061] The organic filler refers to particulate matter (primary particles) composed of an organic compound and having any shape, such as needle-like, rod-like, lamellar, scaly, or spherical, or an aggregate of such particulate matter (secondary particles). In other words, in the present invention, the filler is present in a form that allows it to exhibit blocking resistance in the film, and is distinguished from unmodified starch, which is mixed with the PVA-based resin in the film and does not exhibit blocking resistance. Such organic fillers are mainly selected from polymer compounds, such as melamine-based resins, polymethyl (meth)acrylate-based resins, and polystyrene-based resins, as well as biodegradable resins such as starch, modified starch, and polylactic acid. Among these, biodegradable resins such as starch and polylactic acid are preferred, with starch being particularly preferred in terms of its dispersibility in PVA-based resins. Furthermore, when starch is used as the organic filler, the amylose content of the starch is preferably less than 85%.

[0062] Examples of starch used as the organic filler include raw starches (corn starch, potato starch, sweet potato starch, wheat starch, ossava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, kudzu starch, bracken starch, lotus starch, and water chestnut starch), unmodified starches such as physically modified starches (gelatinized starch, fractionated amylose, and heat-moisture treated starch), enzyme-treated starches (hydrolyzed dextrin, enzymatically decomposed dextrin, and amylose), and decomposed starches (acid-treated starch), and modified starches such as chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, and crosslinked starch). Of these, raw starch is preferred from the standpoint of availability and economy, and corn starch and rice starch are more preferred.

[0063] The average particle size of the organic filler is preferably 2 to 50 μm, more preferably 4 to 45 μm, particularly preferably 10 to 40 μm, and even more preferably 15 to 35 μm. If the average particle size is too small, the blocking property of the film tends to increase, while if it is too large, the fillers tend to aggregate with each other, resulting in a decrease in dispersibility and the formation of pinholes when the film is stretched during molding.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The content of the filler is preferably 1 to 15 parts by mass, more preferably 1.5 to 12 parts by mass, and even more preferably 2 to 10 parts by mass, per 100 parts by mass of the total of the unmodified starch and the PVA-based resin. 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.

[0068] <Surfactant> The water-soluble film may further contain a surfactant, etc., if necessary. The surfactant is added for the purpose of improving the releasability from the casting surface during film production, and typically includes a nonionic surfactant, a cationic surfactant, and an anionic surfactant. Examples of such surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylnonyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt, polyoxyethylene lauryl amino ether, polyoxyethylene stearyl amino ether and other polyoxyethylene alkyl amino ethers, sorbitan monopalmitate, sorbitan monostearate, glycerol stearate, sucrose fatty acid ester, etc. These surfactants may be used alone or in combination of two or more. Among these, polyoxyalkylene alkyl ether phosphate monoethanolamine salt and polyoxyethylene lauryl amino ether are preferred in terms of production stability.

[0069] The content of the surfactant is preferably 0.01 to 3 parts by mass, particularly preferably 0.05 to 2.5 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the total of the PVA-based resin and unmodified starch. If the content is too low, the peelability between the casting surface of the film-forming device and the formed film 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.

[0070] <Other Components> The water-soluble film of the present invention may contain other components, such as water-soluble polymers other than PVA-based resins (e.g., sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, dextrin, chitosan, chitin, methylcellulose, 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. These may be used alone or in combination of two or more.

[0071] The content of the other components is preferably 5 parts by mass or less, particularly preferably 1 part by mass or less, and further preferably 0.5 parts by mass or less, per 100 parts by mass of the total of the PVA-based resin and unmodified starch. The lower limit is usually 0 part by mass.

[0072] The water-soluble film may also contain an antioxidant. 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 amount of such antioxidant added is preferably 0.1 to 10 parts by mass, particularly preferably 0.2 to 5 parts by mass, and even more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the total of the PVA resin and unmodified starch.

[0073] <<Production of Water-Soluble Film>> The present water-soluble film is produced by blending the PVA-based resin, unmodified starch, and plasticizer, and, if necessary, other components such as a filler and a surfactant, and dissolving or dispersing the blend in water to prepare a film-forming raw material, which is then formed into a film. The production of such a water-soluble film includes a casting step of casting the film-forming raw material onto a casting surface, and a drying step of drying the cast film-forming raw material.

[0074] <Dissolving Step> In the dissolving step, the blended components are dissolved or dispersed in water to prepare an aqueous solution or dispersion serving as a film-forming raw material. The method for mixing the PVA-based resin, unmodified starch, plasticizer, and other additives in the film-forming raw material is not particularly limited, and examples thereof include: (i) a method in which the PVA-based resin, unmodified starch, plasticizer, and other additives are mixed together to prepare a mixture, and then the mixture is mixed with water to dissolve the mixture; (ii) a method in which the PVA-based resin, plasticizer, and other additives are dissolved in water, and then the unmodified starch is mixed; (iii) a method in which the PVA-based resin, unmodified starch, plasticizer, and other additives are separately dissolved in water, and then the mixture is mixed; and (iv) a method in which the PVA-based resin and unmodified starch are separately dissolved in water, and then the mixture is mixed with the plasticizer and other additives to dissolve the mixture.

[0075] The dissolution method for dissolving in water typically includes room temperature dissolution, high temperature dissolution, and pressure dissolution. Among these, high temperature dissolution and pressure dissolution are preferred because they result in less undissolved material and are superior in productivity. The dissolution temperature is typically 80 to 100°C, preferably 90 to 100°C, for high temperature dissolution, and typically 80 to 130°C, preferably 90 to 120°C, for pressure dissolution. In particular, the dissolution temperature for unmodified starch is preferably 50 to 90°C, more preferably 55 to 85°C, and even more preferably 60 to 80°C. The dissolution time is typically 1 to 20 hours, preferably 2 to 15 hours, and even more preferably 3 to 10 hours. If the dissolution time is too short, undissolved material tends to remain, while if it is too long, productivity tends to decrease.

[0076] 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 55 to 95°C, and particularly preferably 60 to 80°C. If the degassing temperature is too low, the viscosity increases, requiring a long time for degassing, which tends to reduce productivity. The degassing time is usually 2 to 30 hours, preferably 5 to 25 hours.

[0077] 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.

[0078] <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, is dried to prepare a water-soluble film with a specific moisture content.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, thereby producing a water-soluble film.

[0079] 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.

[0080] The surface of the obtained 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] The present water-soluble film is particularly useful for packaging (unit packaging) of chemicals such as pesticides and detergents, and for edible applications (food packaging). The food to be packaged with the film may be in the form of granules, tablets, powder, etc., or may be dried foods such as ingredients and toppings for instant foods. In particular, the present water-soluble film has excellent mechanical properties, formability, and sealability, making it suitable for composite packaging (e.g., for 2-inch or 3-inch pouches) in which two or more, preferably three, types of chemicals are packaged separately in a single package.

[0087] <<Medicine Package>> A pharmaceutical package according to one embodiment of the present invention (hereinafter sometimes referred to as "the package") is formed by coating a pharmaceutical with a package made of the obtained water-soluble film. In this package, the pharmaceutical is packaged in a package made of the water-soluble film. When the pharmaceutical is placed in water, the surface package (water-soluble film) dissolves, exposing the pharmaceutical, which then dissolves or disperses in the water, thereby exerting its effects. Therefore, the package is suitable as a pharmaceutical package that contains a relatively small amount of pharmaceutical, such as a single dose.

[0088] The shape of the present 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. Furthermore, the present package may be composed of a single compartment, or may have multiple compartments.

[0089] The number of compartments in the packaging body is not particularly limited and is appropriately selected 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.

[0090] The surface of the present packaging material is usually smooth, but from the standpoint of blocking resistance, slipperiness during processing, reduced adhesion between products (individually packaged products), and appearance, the outer surface of the packaging material (water-soluble film) may be textured with an embossed pattern, a finely textured pattern, a specially engraved design, or the like.

[0091] Examples of the 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.

[0092] The liquid detergent preferably has a pH value of 6 to 12 when dissolved or dispersed in water at a concentration of 1%, particularly preferably 6 to 10, even more preferably 6 to 9, and especially preferably 7 to 8. The water content of the liquid detergent is preferably 15% by mass or less, particularly 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 this 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.

[0093] <<Manufacturing of the Present Package>> To use the present water-soluble film to package a chemical such as a liquid detergent to produce the present package, a known method can be used. For example, the present package can be manufactured by the steps of preparing a first water-soluble film, a second water-soluble film, and a chemical, bringing the first water-soluble film and the second water-soluble film into partial contact with each other with the chemical interposed therebetween, and crimping the contacting portions of the first water-soluble film and the second water-soluble film.

[0094] Specifically, a film (bottom film) is fixed to the lower mold of a molding device, and the bottom film is molded into a shape that conforms to the lower mold (a shape that allows a drug to be placed inside). Meanwhile, a film (top film) is also fixed to the upper mold of the molding device. A separately prepared drug, such as a liquid detergent, is then placed (injected) into the molded bottom film, and the molds are then pressed together to bring the top film and bottom film into contact, and this contact area is then vacuum-bonded. After the bonding, the vacuum is released to obtain a drug package (the present package) in which the drug is encapsulated in a water-soluble film.

[0095] Examples of the method for bonding the film include heat sealing, water sealing, and glue sealing. Among these, the water sealing method is preferred because it allows easy control of bonding conditions.

[0096] 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.

[0097] The following materials were prepared as the water-soluble film components:

[0098] [PVA-based resins] Modified PVA-based resin: a carboxyl group-modified PVA-based resin with a 4% aqueous solution viscosity of 22 mPa·s at 20°C, an average saponification degree of 94 mol%, and a modification amount of 2.2 mol% with maleic acid monomethyl ester. Unmodified PVA: a 4% aqueous solution viscosity of 43 mPa·s at 20°C, an average saponification degree of 88 mol%.

[0099] [Non-modified starch] (i) Pregelatinized starch (amylopectin content 100%, "Waxy Alpha Y" manufactured by Sanwa Starch Co., Ltd.) (ii) Pregelatinized starch (amylopectin content 75%, "Corn Alpha W" manufactured by Sanwa Starch Co., Ltd.)

[0100] [Naturally derived ingredients] Casein (Fonterra "Casein Sodium 180")

[0101] [Plasticizers] Glycerin, sorbitol, trehalose

[0102] Example 1: 42 parts of modified PVA-based resin, 42 parts of (i) pregelatinized starch as unmodified starch, 16 parts of glycerin as plasticizer, and water were mixed and dissolved to obtain a film-forming raw material, which was an aqueous dispersion of a resin composition with a solids concentration of 30%. The obtained film-forming raw material was left to stand at 80°C for 24 hours to degas. The film-forming raw material after standing and degassing 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 0.5 m / min to obtain a water-soluble film with a thickness of 87 μm.

[0103] Examples 2 to 5, Comparative Examples 1 and 3 Water-soluble films were obtained in the same manner as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1 below.

[0104] Comparative Example 2 A water-soluble film was obtained in the same manner as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1 below and the degassing temperature was changed to 60°C.

[0105] Reference Example 1 A water-soluble film was obtained in the same manner as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1 below and the solid content concentration of the film-forming raw materials was changed to 25%.

[0106] The mechanical properties and water solubility of the water-soluble films obtained above were evaluated according to the methods and criteria described below. The results are shown in Table 1 below.

[0107] [Mechanical Properties] The water-soluble film obtained above was used to measure "tensile strength" and "tensile elongation" in accordance with JIS K 7127 (1999). That is, before measurement, the water-soluble film was left to stand for 24 hours under humidity-controlled conditions of 23°C and 50% RH, and then, under this environment, the water-soluble film was measured for tensile strength and tensile elongation at a pulling rate of 200 mm / min using an Autograph AG-X Plus (manufactured by Shimadzu Corporation) (film width: 15 mm, chuck distance: 50 mm). These measured values ​​were evaluated based on the following criteria. [Evaluation criteria for tensile strength] A: 12 MPa or more B: 5 MPa or more but less than 12 MPa C: Less than 5 MPa [Evaluation criteria for tensile elongation] A: 300% or more B: 200% or more but less than 300% C: Less than 200% [Overall evaluation] ◯ (very good): B or more and at least one is A △ (good): both are B × (poor): at least one is C

[0108] [Solubility] The water-soluble film obtained above was cut into a size of 3.5 cm x 3.5 cm, placed in a 1-liter beaker containing 1 liter of water, and fixed with a jig. The film was stirred with a stirrer (rotor length 3 cm, rotation speed 750 rpm) while maintaining the water temperature at 20°C. The film was deemed to be dissolved when no dispersed insoluble fine particles with a diameter of 1 mm or more were observed, and the time required for dissolution was evaluated based on the following criteria. [Evaluation criteria] ○ (very good): Dissolved in less than 90 seconds. △ (good): Dissolved in 90 to 180 seconds. × (poor): Not dissolved even after 180 seconds or more.

[0109] Furthermore, packaging materials were prepared using the water-soluble films obtained above by the method described below, and the formability and compressive strength were evaluated according to the methods and criteria described below. The results are shown in Table 1 below.

[0110] <Preparation of Package (1-inch Pouch)> Using the water-soluble film obtained above, a package was prepared using an Engel packaging machine according to the following procedure. Specifically, the water-soluble film was left to stand for 24 hours under humidity-controlled conditions of 23°C and 40% RH. After this, a first water-soluble film (bottom film) was fixed onto a mold (package to be formed: length 45 mm, width 42 mm, height 30 mm) with a recess at the bottom of the machine under this environment. A second water-soluble film (top film) was also fixed to the top of the machine facing the bottom film. The bottom film was heated for 4 seconds using a dryer generating hot air at 100°C, and the bottom film was vacuum-formed to conform to the mold shape. Then, 34 mL of commercially available liquid laundry detergent (composition summary: 11% propylene glycol, 7.5% glycerin, 67% surfactant, 14.2% water, pH 7.5) was poured into the recess of the formed bottom film. 0.25 g of water was applied to the entire surface of the top film (80 mm long, 140 mm wide), and the top film and bottom film were pressed together. After pressing for 10 seconds, the vacuum was released to produce a package (1-inch pouch).

[0111] [Formability (1 inch pouch)] In producing the package (1 inch pouch), the ability of the bottom film to conform to the mold during vacuum forming was visually confirmed and evaluated based on the following criteria. [Evaluation criteria] ○ (very good): The water-soluble film conformed sufficiently to the mold in less than 30 seconds. △ (good): A slight gap was observed between the water-soluble film and the mold, or it took 30 seconds or more for the water-soluble film to conform sufficiently to the mold. × (poor): The water-soluble film was clearly floating above the mold and did not conform, and a package could not be produced.

[0112] [Compression Strength] The package (1 inch pouch) produced by the above method was left to stand for 1 hour in an environment of 23°C and 40% RH, and then the compression strength when the liquid detergent package broke was measured in this environment using an Autograph AG-X Plus (manufactured by Shimadzu Corporation) at a test speed of 200 mm / min, and evaluation was performed according to the following evaluation criteria. A 5 kN load cell was used. [Evaluation Criteria] ○ (very good): The compression strength was 250 N or more. △ (good): The compression strength was 200 N or more but less than 250 N. × (poor): The compression strength was less than 200 N and the bag broke easily, or the bag broke because the sealed surface was easily peeled off.

[0113] <Preparation of Package (3-inch Pouch)> Using the water-soluble film obtained above, a package was prepared using an Engel packaging machine according to the following procedure. Specifically, the water-soluble film was left to stand for 24 hours under humidity-controlled conditions of 23°C and 40% RH. After this, a first water-soluble film (bottom film) was fixed to a mold (package to be formed: length 45 mm, width 45 mm, height 20 mm) with a recess divided into three compartments at the bottom of the device. A second water-soluble film (top film) was also fixed to the top of the device facing the bottom film. The bottom film was heated for 4 seconds using a dryer generating hot air at 100°C, and the bottom film was vacuum-formed to conform to the mold shape. Then, 34 mL of commercially available liquid laundry detergent (composition summary: 11% propylene glycol, 7.5% glycerin, 67% surfactant, 14.2% water, pH 7.5) was poured into the recess of the molded bottom film. 0.25 g of water was applied to the entire surface of the top film (80 mm long, 140 mm wide), and the top film and bottom film were pressed together. After pressing for 10 seconds, the vacuum was released to produce a package (3-inch pouch).

[0114] [Moldability (3-inch pouch)] In producing the package (3-inch pouch), the conformability of the bottom film to the mold during vacuum forming and the appearance of the obtained package were visually inspected and evaluated based on the following criteria. [Evaluation criteria] ⊚ (excellent): The water-soluble film conformed uniformly to all three sections of the mold in less than 30 seconds, and a complete package was obtained without wrinkles, distortion, or crushing in any of the sections. ◯ (very good): The water-soluble film conformed to all three sections of the mold in less than 30 seconds, and the obtained package was practical, although slight wrinkles, distortion, or lack of tension were observed in the obtained package, to a degree that did not pose a problem in use. Δ (good): The water-soluble film took 30 seconds or more to conform to all three sections of the mold, or the water-soluble film conformed to all three sections of the mold in less than 30 seconds, but wrinkles, distortion, or lack of tension were observed in the obtained package to a degree that would pose a slight problem in use. × (poor): The water-soluble film did not conform sufficiently to the mold and was clearly floating, making it impossible to produce a package, or the resulting package was clearly torn, wrinkled, distorted, or crushed, making it unsuitable for practical use.

[0115]

[0116] The results in Table 1 show that the water-soluble films of the Examples have mechanical properties and solubility equivalent to those of the conventional water-soluble film containing no unmodified starch of Reference Example 1. Furthermore, the water-soluble films of the Examples have excellent formability even when formed into complex shapes, and exhibit sufficient strength in the evaluation of compressive strength. None of the films easily peeled off at the sealed surface and broke, demonstrating excellent strength of the sealed portion.

[0117] On the other hand, the water-soluble film of Comparative Example 1, in which the content of unmodified starch relative to the total mass of unmodified starch and plasticizer was outside the range specified in the present invention, had lower tensile elongation and inferior mechanical properties compared to the water-soluble films of the Examples. Furthermore, the water-soluble film of Comparative Example 1 had poor formability when made into a package, and packages could not be produced. Furthermore, the water-soluble film of Comparative Example 2, in which casein, a naturally occurring raw material, was used instead of unmodified starch, had lower tensile elongation and inferior mechanical properties compared to the water-soluble films of the Examples, and also had inferior compressive strength when made into a package. Furthermore, the water-soluble film of Comparative Example 3, in which the amylopectin content of the unmodified starch was outside the range specified in the present invention, had inferior water solubility compared to the water-soluble films of the Examples.

[0118] 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.

[0119] The water-soluble film of the present invention can be used for packaging (unit packaging) of chemicals 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 for seedling raising sheets, seed tapes, embroidery base fabrics, etc. The film of the present invention, which is a blend film of a PVA-based resin that is also used in foods and pharmaceuticals and a naturally derived raw material, is also useful for edible applications (food packaging).

Claims

1. A water-soluble film comprising a polyvinyl alcohol resin, unmodified starch, and a plasticizer, wherein the polyvinyl alcohol resin contains a modified polyvinyl alcohol resin, the unmodified starch has an amylopectin content of 85% or more, and the content of the unmodified starch is 20 to 78% by mass relative to the total mass of the unmodified starch and the plasticizer.

2. The water-soluble film according to claim 1, wherein the content of the unmodified starch is 20 to 60% by weight based on the total weight of the unmodified starch and the plasticizer.

3. The water-soluble film according to claim 1, wherein the content of the unmodified starch is 65 to 75% by weight based on the total weight of the unmodified starch and the plasticizer.

4. The water-soluble film according to claim 1 or 2, wherein the content of the unmodified starch is 20 to 80% by mass based on the total mass of the polyvinyl alcohol resin and the unmodified starch.

5. The water-soluble film according to claim 1 or 2, which contains glycerin as the plasticizer.

6. The water-soluble film according to claim 1 or 2, wherein the plasticizer comprises glycerin and at least one other plasticizer, and the mass ratio of the glycerin to the at least one other plasticizer [(glycerin) / (at least one other plasticizer)] is 95 / 5 to 10 / 90.

7. The water-soluble film according to claim 1 or 2, wherein the average degree of saponification of said polyvinyl alcohol resin is 80 to 96 mol %.

8. The water-soluble film according to claim 1 or 2, which is used for packaging medicines.

9. A pharmaceutical package comprising a package made of the water-soluble film according to claim 1 or 2 and a pharmaceutical packaged in said package.

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