Water-soluble film, packaging, drug packaging, and production method therefor

Abstract

Provided is a water-soluble film that exhibits superior basic material properties such as tensile strength, tensile elongation, and elastic modulus at 8% elongation.　Specifically provided is a water-soluble film comprising a polyvinyl alcohol resin and a plasticizer, said water-soluble film containing at least 13 parts by mass of the plasticizer with respect to 100 parts by mass of the polyvinyl alcohol resin, and having a pMC value for radiocarbon C14 as measured in accordance with ASTM D6866 (Method B) of at least 60%.

Description

Water-soluble film, packaging, pharmaceutical packaging, and manufacturing method thereof

[0001] The present invention relates to a water-soluble film, and more particularly to a water-soluble film containing a polyvinyl alcohol resin containing radioactive carbon C14 and a specific amount of a plasticizer.

[0002] Polyvinyl alcohol-based resins are thermoplastic resins that are water-soluble, and when made into films, their physical properties and texture are significantly different from those of hydrophobic thermoplastic resins such as polyethylene terephthalate films and polyolefin films.

[0003] Taking advantage of its water solubility, polyvinyl alcohol resins are used for a wide range of applications, such as in unit packaging, in which various chemicals such as pesticides and detergents are placed in bags made of polyvinyl alcohol resin film.

[0004] For example, Patent Document 1 discloses a water-soluble film used for a water-soluble unit packaging bag, which is obtained by blending 5 to 30 parts by weight of a plasticizer, 1 to 10 parts by weight of starch, and 0.01 to 2 parts by weight of a surfactant with 100 parts by weight of a polyvinyl alcohol-based resin.

[0005] Japanese Patent Application Laid-Open No. 2001-329130

[0006] The water-soluble film disclosed in Patent Document 1 can be used as a package for packaging chemicals such as liquid detergents. However, when packaging liquid detergents or the like, the water-soluble film needs to be processed using a dedicated mold, and the film needs to maintain tension even after packaging processing. Therefore, basic physical properties such as tensile strength, tensile elongation, and 8% elastic modulus are still insufficient, and further improvement is required. Therefore, the present invention provides a water-soluble film that is excellent in basic physical properties such as tensile strength, tensile elongation, and 8% elastic modulus.

[0007] However, in light of these circumstances, the present inventors have conducted extensive research and found that by setting the pMC value of radioactive carbon C14 of a water-soluble film containing a polyvinyl alcohol resin and a specific amount of plasticizer within a specific range, basic physical properties such as tensile strength, tensile elongation, and 8% modulus of elasticity can be improved.

[0008] That is, the present invention has the following aspects. [1] A water-soluble film containing a polyvinyl alcohol-based resin and a plasticizer, wherein the plasticizer is contained in an amount of 13 parts by mass or more per 100 parts by mass of the polyvinyl alcohol-based resin, and wherein the pMC value of the radiocarbon C14 of the water-soluble film measured by ASTM D6866 (Method B) is 60% or more. [2] The water-soluble film according to [1], wherein the pMC value of the radiocarbon C14 of the polyvinyl alcohol-based resin measured by ASTM D6866 (Method B) is 55% or more. [3] The water-soluble film according to [1] or [2], wherein the polyvinyl alcohol-based resin contains a modified polyvinyl alcohol-based resin. [4] The water-soluble film according to [3], wherein the modified polyvinyl alcohol-based resin is a carboxy group-modified polyvinyl alcohol-based resin. [5] The water-soluble film according to any one of [1] to [4], wherein the content of the plasticizer is 13 to 55 parts by mass relative to 100 parts by mass of the polyvinyl alcohol-based resin. [6] The water-soluble film according to any one of [1] to [5], wherein the plasticizer contains glycerin. [7] The water-soluble film according to any one of [1] to [6], wherein the plasticizer contains a plasticizer derived from natural materials. [8] The water-soluble film according to any one of [1] to [7], wherein the content of the polyvinyl alcohol-based resin is 75 to 85% by mass relative to 100% by mass (non-volatile content) of the water-soluble film. [9] The water-soluble film according to any one of [1] to [8], wherein the ratio of the pMC value (%) of radioactive carbon C14 of the polyvinyl alcohol-based resin measured by ASTM D6866 (Method B) to the content (parts by mass) of the plasticizer per 100 parts by mass of the polyvinyl alcohol-based resin (pMc of radioactive carbon C14 / content of plasticizer) is 0.5 to 10.

[10] A package comprising the water-soluble film according to any one of [1] to [9].

[11] A drug package comprising a package comprising the water-soluble film according to any one of [1] to [9] and a drug encapsulated in the package.

[12] The drug package according to

[11] , wherein the drug is a liquid detergent.

[13] A method for producing the drug package described in

[11] or

[12] , 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 abutting and pressing the first water-soluble film and the second water-soluble film together.

[0009] The water-soluble film of the present invention can be a water-soluble film having improved basic physical properties such as tensile strength, elongation, and 8% elastic modulus compared to a water-soluble film containing the same amount of plasticizer, and therefore can be suitably used as a water-soluble film that requires secondary processing such as packaging formation.

[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] In this specification, the term "film" also includes "sheet" and "tape." In this specification, the term "main component" refers to a component that has a significant effect on the properties of the target object, 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, and even more preferably 80% by mass or more, and may even be 100% by mass.

[0013] <Water-Soluble Film> A water-soluble film according to one embodiment of the present invention (hereinafter sometimes referred to as "the water-soluble film") is a water-soluble film containing a polyvinyl alcohol-based resin (hereinafter sometimes referred to as "PVA-based resin") and a plasticizer, wherein the plasticizer is contained in an amount of 13 parts by mass or more per 100 parts by mass of the PVA-based resin, and the pMC value of radiocarbon C14 of the water-soluble film measured according to ASTM D6866 (Method B) is 60% or more. The "pMC of radiocarbon C14" means Percent Modern Carbon of radiocarbon C14 and is a unit expressing the relative concentration ratio of radiocarbon C14 of a measurement sample to a modern reference standard (NIST 4990C).

[0014] As used herein, the term "water-soluble film" refers to a film that dissolves in water at room temperature (20°C). In this specification, 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 1 liter of water 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.

[0015] The pMC value of radioactive carbon C14 of the water-soluble film, as measured by ASTM D6866 (Method B), is 60% or more, preferably 65% ​​or more, more preferably 70% or more, and particularly preferably 80% or more. It is also preferably less than 100%, more preferably 95% or less, and particularly preferably 90% or less. When the pMC value of radioactive carbon C14 of the water-soluble film is within the above range, basic physical properties such as tensile strength, tensile elongation, and 8% modulus of elasticity are improved. The pMC value of radioactive carbon C14 of the water-soluble film can be adjusted, for example, by adjusting the mass content ratio of the bio-PVA-based resin and the fossil-PVA-based resin described below, or by adjusting the content of the plasticizer derived from natural materials described below.

[0016] Furthermore, the present water-soluble film contains radioactive carbon C14 because the pMC value of radioactive carbon C14 is 60% or more. Here, in this specification, "containing radioactive carbon C14" means that the pMC value of C14 measured by ASTM D6866 (Method B) specified by the American Society of Testing and Materials is greater than 0. In other words, the present water-soluble film containing radioactive carbon C14 is one in which all or part of the carbon constituting the water-soluble film is derived from a living organism. Note that the "living organism" derived from a living organism is preferably a plant.

[0017] The reason why the effects of the present invention are achieved is not clear, but it is presumed that the pMC value of radioactive carbon C14 in this water-soluble film is within a specific range, i.e., the water-soluble film contains a specific amount of radioactive carbon C14, which causes an interaction between the PVA-based resin and the plasticizer, thereby improving the basic physical properties of the water-soluble film.

[0018] The tensile strength of the water-soluble film, measured in accordance with JIS K 7127 (1999), is usually 15 to 70 MPa, preferably 20 to 60 MPa, and more preferably 25 to 50 MPa. When the tensile strength is within the above range, the film tends to have excellent secondary processability, such as packaging formability.

[0019] The tensile elongation of the water-soluble film, measured in accordance with JIS K 7127 (1999), is usually 200 to 700%, preferably 250 to 600%, and more preferably 300 to 500%. When the tensile elongation is within the above range, the film tends to have excellent secondary processability, such as formability into a package.

[0020] The water-soluble film has a modulus of elasticity at 8% elongation (8% modulus of elasticity) measured in accordance with JIS K 7127 (1999) of usually 10 to 100 MPa, preferably 15 to 80 MPa, and more preferably 20 to 50 MPa. When the 8% modulus of elasticity is within the above range, the film tends to have excellent secondary processability, such as formability into a package.

[0021] The water content of the water-soluble film is preferably 3 to 15% by mass, particularly 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.

[0022] Each component contained in the water-soluble film will be described below.

[0023] [PVA-Based Resin] The PVA-based resin used in this embodiment will be described. 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. The PVA-based resin 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, with modified PVA-based resins being preferred in terms of water solubility. The PVA-based resin may be used alone, 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.

[0024] The modified PVA resin may be an anion-modified PVA resin, a pyrrolidone ring-modified PVA resin, or an amino group-modified PVA resin, and the anion-modified PVA resin is preferred from the viewpoint of the solubility of the film. The anionic group may be, for example, a carboxy group, a sulfonic acid group, or a phosphate group, and the carboxy group or sulfonic acid group is preferred from the viewpoint of the stability of solubility over time, with the carboxy group being particularly preferred.

[0025] 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 be produced, for example, by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester compound.

[0026] The PVA-based resin preferably contains radioactive carbon C14. That is, the PVA-based resin is preferably a "PVA-based resin in which all or part of the carbon constituting the PVA-based resin is made of vinyl ester monomers of biological origin." The "organism" of biological origin is preferably a plant.

[0027] The PVA-based resin containing radioactive carbon C14 may be, for example, composed solely of a PVA-based resin in which all or part of the carbon constituting the PVA-based resin is made from vinyl ester monomers derived from living organisms (hereinafter, this may be referred to as a "bio-PVA-based resin"), or may be a mixture of a bio-PVA-based resin and a PVA-based resin obtained solely from raw materials derived from fossil fuels (hereinafter, this may be referred to as a "fossil-PVA-based resin").

[0028] There are no particular limitations on the method for obtaining such a "bio-PVA-based resin," and examples thereof include: (1) a method of saponifying a polyvinyl ester obtained by polymerizing only bio-derived vinyl ester monomers (bio-vinyl ester monomers) using biologically derived ethylene (bioethylene) as a raw material; (2) a method of saponifying a polyvinyl ester obtained by polymerizing a bio-vinyl ester monomer using a mixture of bioethylene and fossil fuel-derived ethylene as a raw material; (3) a method of saponifying a polyvinyl ester obtained by copolymerizing a bio-vinyl ester monomer using bioethylene as a raw material with a vinyl ester monomer using fossil fuel-derived ethylene; (4) a method of saponifying a mixture of a polyvinyl ester obtained by polymerizing only bio-vinyl ester monomers using bioethylene as a raw material and a polyvinyl ester obtained by polymerizing only fossil fuel-derived vinyl ester monomers; and (5) a method of combining the above methods (2) to (4). Among these methods, method (1) or (2) is preferred in that it allows for efficient production of a bio-PVA-based resin.

[0029] Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. These may be used alone or in combination of two or more. It is preferable to use one or more vinyl esters, and it is particularly preferable to use one vinyl ester monomer. Among these vinyl ester monomers, vinyl acetate is preferred.

[0030] The method for producing the vinyl ester monomer is not particularly limited, and can be obtained, for example, by reacting ethylene with a compound having a carboxy group represented by R-COOH. For example, vinyl acetate can usually be obtained by subjecting ethylene, acetic acid, and oxygen to a gas-phase reaction in the presence of a catalyst. In this case, vinyl acetate containing a predetermined amount of radioactive C14 carbon (biovinyl acetate) can be obtained by using ethylene containing a predetermined amount of radioactive C14 carbon or acetic acid containing a predetermined amount of radioactive C14 carbon as the compound having a carboxy group. An example of ethylene containing a predetermined amount of radioactive C14 carbon is bioethylene.

[0031] In the production of vinyl ester monomers, it is preferable to use raw materials other than ethylene, such as carboxylic acids, that are derived from living organisms. However, the carboxyl group is released from the polymer backbone of the polyvinyl ester during saponification and is usually recovered and reused. Therefore, even if fossil fuel-derived materials are used, they do not increase the amount of carbon dioxide present in the global environment and do not contribute to global warming.

[0032] 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. These may be used alone or in combination of two or more. Among these, a carboxyl group-containing unsaturated monomer is preferred. The unsaturated monomer may be derived from a fossil fuel or a biological source.

[0033] 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, these esters typically have 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 4 carbon atoms. Of these, maleic acid compounds are preferred, with monomethyl maleate being more preferred.

[0034] 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.

[0035] Examples of the phosphoric acid group-containing unsaturated monomer include phosphonocarboxylic acid compounds and alkali metal salts thereof.

[0036] The modified polyvinyl alcohol resin is usually obtained by saponifying a copolymer obtained by polymerizing the vinyl ester monomer and an unsaturated monomer in the presence of a polymerization catalyst. The unmodified PVA is obtained by saponifying a polyvinyl ester obtained by polymerizing the vinyl ester monomer in the presence of a polymerization catalyst. The polymerization method of the vinyl ester monomer and the unsaturated monomer, or the polymerization method of the vinyl ester monomer, can be any known polymerization method, such as solution polymerization, emulsion polymerization, or suspension polymerization. Solution polymerization using an alcohol, such as methanol, ethanol, or isopropyl alcohol, as a solvent is usually used.

[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. 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.

[0038] The resulting copolymer of vinyl ester monomer and unsaturated monomer, or the polyvinyl ester, 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.

[0039] 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 monomer.

[0040] In this way, a modified PVA-based resin or an unmodified PVA is obtained. Furthermore, when the modified PVA-based resin or the unmodified PVA contains a biovinyl ester monomer as a polymerization component, it will contain radioactive carbon C14.

[0041] The pMC value of radioactive carbon C14 of the PVA-based resin, as measured by ASTM D6866 (Method B), is preferably 55% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more. It is also preferably less than 100%, even more preferably 95% or less, and particularly preferably 90% or less. When the pMC value of radioactive carbon C14 of the PVA-based resin is within the above range, the basic physical properties of the water-soluble film, such as tensile strength, tensile elongation, and 8% modulus of elasticity, tend to be improved. The pMC value of radioactive carbon C14 of the PVA-based resin can be adjusted, for example, by adjusting the ratio of biovinyl ester monomer used in polymerization or by adjusting the mass content ratio of the bio-PVA-based resin to the fossil PVA-based resin.

[0042] The mass ratio of the bio-PVA-based resin to the fossil PVA-based resin in the PVA-based resin (bio-PVA-based resin / fossil PVA-based resin) is usually 100 / 0 to 65 / 35, preferably 100 / 0 to 70 / 30, more preferably 100 / 0 to 75 / 25, and even more preferably 100 / 0 to 80 / 20. When the mass ratio of the bio-PVA-based resin to the fossil PVA-based resin is within the above range, the basic physical properties of the water-soluble film, such as tensile strength, tensile elongation, and 8% elastic modulus, tend to be improved.

[0043] When the PVA-based resin is a modified PVA-based resin, the modification amount is usually 0.1 to 20 mol %, preferably 0.5 to 15 mol %, and more preferably 1 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.

[0044] When the modified PVA-based resin is an anionic group-modified PVA-based resin, the modification amount is usually 1 to 15 mol %, preferably 1.5 to 10 mol %, and more 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.

[0045] 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 even more 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.

[0046] When the PVA-based resin is a modified PVA-based resin, its average saponification degree is usually 80 mol% or more, preferably 85 to 99.9 mol%, 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.

[0047] When the modified PVA-based resin is an anionic group-modified PVA-based resin, the average saponification degree thereof is usually 85 to 99.9 mol%, preferably 88 to 98 mol%, more preferably 90 to 97 mol%, and even more 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.

[0048] When the PVA-based resin is an unmodified PVA, 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.

[0049] The average saponification degree of the PVA-based resin means that the average saponification degree of all the 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 the 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 = 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)

[0050] The weight-average molecular weight of the PVA-based resin is usually 20,000 to 150,000, preferably 30,000 to 120,000, and more preferably 50,000 to 100,000. If the weight-average molecular weight is too small, the mechanical strength tends to decrease, while if it is too large, the productivity tends to decrease. The weight-average molecular weight of the polyvinyl alcohol-based resin is a weight-average molecular weight measured by GPC.

[0051] The degree of polymerization of a PVA-based resin can be expressed not only by the weight-average molecular weight but also by the viscosity of a 4% by mass aqueous solution at 20° C. The viscosity of a 4% by mass aqueous solution of a 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 reduced productivity.

[0052] 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.

[0053] When the PVA-based resin is a modified PVA-based resin, its viscosity as a 4% by mass aqueous solution 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.

[0054] When the modified PVA-based resin is an anionic group-modified PVA-based resin, its 4% by mass aqueous solution viscosity 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.

[0055] When the PVA-based resin is an unmodified PVA, its viscosity as a 4% by mass aqueous solution 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.

[0056] 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.

[0057] The PVA-based resin is preferably the main component of the water-soluble film from the viewpoints of mechanical strength and processability during secondary processing of the film. The content of the PVA-based resin is usually 50 to 88% by mass, preferably 60 to 87% by mass, more preferably 65 to 86% by mass, even more preferably 70 to 85% by mass, and particularly preferably 75 to 85% by mass, based on 100% by mass (non-volatile content) of the water-soluble film. In this specification, the term "non-volatile content" refers to the solid content excluding water and solvents.

[0058] [Plasticizer] The water-soluble film contains a specific amount of plasticizer. 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. In particular, it is preferable to contain two or more plasticizers in order to achieve excellent mechanical properties and moldability of the water-soluble film. Furthermore, in terms of the effects of the present invention, it is preferable that the plasticizer contains a plasticizer derived from natural materials. Examples of the plasticizer derived from natural materials include glycerin, sorbitol, xylitol, and maltitol, with glycerin and sorbitol being more preferred.

[0059] In this specification, "derived from natural materials" refers to raw materials (natural raw materials) of plant, animal, or microbial origin obtained by physical treatment such as drying or grinding without chemical synthesis, or raw materials obtained by processing natural materials through chemical synthesis without introducing carbon atoms derived from non-natural raw materials. Therefore, plasticizers derived from natural materials contain radioactive carbon C14.

[0060] When the plasticizer is derived from natural materials, i.e., contains radioactive carbon C14, and the PVA-based resin also contains radioactive carbon C14, it is presumed that a stronger interaction occurs between them, resulting in further improvements in the basic physical properties of the water-soluble film, such as tensile strength, tensile elongation, and 8% modulus of elasticity.

[0061] The content of the plasticizer is 13 parts by mass or more, preferably 13 to 60 parts by mass, more preferably 13 to 55 parts by mass, and even more preferably 14 to 50 parts by mass, based on 100 parts by mass of the PVA-based resin. When the content of the plasticizer is within the above range, the basic physical properties of the water-soluble film, such as tensile strength, tensile elongation, and 8% elastic modulus, can be improved.

[0062] The content of the plasticizer is 13% by mass or more, preferably 13 to 55% by mass, more preferably 14 to 45% by mass, and even more preferably 15 to 40% by mass, based on 100% by mass (non-volatile content) of the water-soluble film. When the content of the plasticizer is within the above range, the basic physical properties of the water-soluble film, such as tensile strength, tensile elongation, and 8% elastic modulus, tend to be improved.

[0063] When the PVA-based resin contains radioactive carbon C14, the ratio of the pMC value (%) of radioactive carbon C14 measured by ASTM D6866 (Method B) to the content (parts by mass) of the plasticizer relative to 100 parts by mass of the PVA-based resin (pMC value of radioactive carbon C14 / content of plasticizer) is preferably 0.5 to 10, more preferably 1 to 8, even more preferably 1.5 to 7, particularly preferably 2 to 6, and especially preferably 2 to 4. When the ratio of the pMC value (%) of radioactive carbon C14 to the content (parts by mass) of the plasticizer is within the above range, basic physical properties of the water-soluble film, such as tensile strength, tensile elongation, and 8% elastic modulus, tend to be improved.

[0064] [Filler] The water-soluble film may further contain a filler, if necessary. The filler is added for the purpose of improving blocking resistance. Such fillers are not particularly limited, and either organic or inorganic fillers 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 0.1 to 50 μm, 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 volume) of the obtained cumulative volume distribution.

[0065] 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, and biodegradable resins such as starch, modified starch, and polylactic acid. Among these, biodegradable resins such as starch and polylactic acid are preferred, and starch is particularly preferred in terms of its dispersibility in PVA-based resins.

[0066] Examples of starch used as the organic filler 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.), unmodified starches such as physically modified starches (gelatinized starch, fractionated amylose, heat-moisture treated starch, etc.), enzyme-treated starches (hydrolyzed dextrin, enzymatically decomposed dextrin, amylose, etc.), and decomposed starches (acid-treated starch, etc.), and modified starches such as chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, cross-linked starch, etc.) and oxidized starch. Of these, raw starch is preferred from the standpoint of availability and economy, and corn starch and rice starch are more preferred.

[0067] 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.

[0068] 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.

[0069] Among these, it is preferable to use an oxide-based inorganic compound or talc, and it is particularly preferable to use titanium oxide, talc or silica, and it is further preferable to use silica.

[0070] The average particle size of the inorganic filler is preferably 1 to 20 μm, particularly preferably 2 to 15 μm, and further preferably 3 to 10 μm. If the average particle size is too small, the 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.

[0071] When the water-soluble film contains a filler, the content thereof is usually 1 to 15 parts by mass, preferably 1.5 to 12 parts by mass, and more preferably 2 to 10 parts by mass, based on 100 parts by mass of 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.

[0072] [Surfactant] The water-soluble film may further contain a surfactant, etc., if necessary. The surfactant 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, 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.

[0073] When the water-soluble film contains a surfactant, the content thereof is usually 0.01 to 3 parts by mass, preferably 0.05 to 2.5 parts by mass, and more preferably 0.1 to 2 parts by mass, relative to 100 parts by mass of the PVA-based resin. If the content is too low, the peelability between the casting surface of the film-forming device and the formed 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.

[0074] [Antioxidant] The water-soluble film may 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.

[0075] When the present water-soluble film contains an antioxidant, the content thereof is usually 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the PVA-based resin.

[0076] [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.

[0077] When the water-soluble film contains the other components, the content thereof is usually 5 parts by mass or less, preferably 1 part by mass or less, and more preferably 0.5 parts by mass or less, based on 100 parts by mass of the PVA-based resin. The lower limit is usually 0 part by mass.

[0078] <Production of Water-Soluble Film> The present water-soluble film is produced by dissolving or dispersing the PVA-based resin, plasticizer, and, if necessary, additives such as fillers, surfactants, and other components 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 film-forming raw material preparation step of preparing the film-forming raw material and a film-forming step of forming the film-forming raw material into a film shape to obtain a water-soluble film.

[0079] [Membrane-forming raw material preparation step] In the membrane-forming raw material preparation step, the components are dissolved or dispersed in water to prepare an aqueous solution or aqueous dispersion serving as a membrane-forming raw material. The preparation of the membrane-forming raw material is not particularly limited, and may be prepared by dissolving or dispersing a PVA-based resin, a plasticizer, and an additive in water according to a known method.

[0080] The dissolution method for dissolving the components 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 produce 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. The dissolution time is typically 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, while if it is too long, productivity tends to decrease.

[0081] 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, and productivity tends to decrease. The degassing time is usually 2 to 30 hours, preferably 5 to 25 hours.

[0082] The solids concentration of the film-forming raw material is preferably 10 to 60% by mass, particularly 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, preferably 4.8 to 7.5.

[0083] [Film-forming process] In the film-forming process, the film-forming raw material prepared in the film-forming raw material preparation process is formed into a film, and if necessary, a drying treatment is performed to prepare a water-soluble film. As a method for forming the film-forming raw material into a film, 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 a metal surface of an endless belt or a drum roll, or a plastic substrate surface such as a polyethylene terephthalate film, dried, and if necessary, further heat-treated to produce a water-soluble film.

[0084] 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.

[0085] 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.

[0086] The thickness of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 10 to 120 μm, particularly 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 slow down and the film-forming efficiency also tends to decrease.

[0087] The width of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 300 to 5000 mm, particularly preferably 500 to 4000 mm, and further preferably 600 to 3000 mm. If the width is too narrow, productivity tends to decrease, while if the width is too wide, it tends to become difficult to control slack and film thickness.

[0088] The length of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 100 to 20,000 m, particularly preferably 800 to 15,000 m, and even more preferably 1,000 to 10,000 m. If the length is too short, productivity tends to decrease because of the time and effort required to switch films, while if the length is too long, poor appearance tends to occur due to tight winding.

[0089] 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.

[0090] The water-soluble film is particularly useful for packaging chemicals such as pesticides and detergents (unit packaging) and for edible food packaging. The food to be packaged with 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.

[0091] <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.

[0092] 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.

[0093] 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 to have excellent water solubility. 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.

[0094] <Manufacturing of Drug Package> A known method can be used to package a drug such as a liquid detergent using the water-soluble film to form a drug package. For example, the drug package can be manufactured by the steps of preparing a first water-soluble film, a second water-soluble film, and a drug, placing the first water-soluble film and the second water-soluble film opposite each other with the drug interposed therebetween and partially abutting the first water-soluble film and the second water-soluble film, and crimping the abutting portion of the first water-soluble film and the second water-soluble film.

[0095] 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, after which the molds are pressed together to bring the top film and bottom film into contact, and the contact area is vacuum-bonded. After the pressure is applied, the vacuum is released to obtain a drug package in which the drug is encapsulated in a water-soluble film.

[0096] 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.

[0097] The present invention will be explained in more detail below by way of 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.

[0098] The following materials were prepared as the water-soluble film components:

[0099] <PVA-Based Resin> [Synthesis of Carboxy-Modified PVA-Based Resin Containing Radioactive Carbon C14] 300 parts by mass of vinyl acetate, the carbon of which is derived from biomass, 87 parts by mass of methanol, and 0.15 parts by mass of monomethyl maleate were added to a reactor equipped with a reflux condenser, a sample inlet, and a stirring blade. The reactor was then immersed in a water bath and heated. With the reactor refluxing (internal temperature approximately 60°C), 1.05 parts by mass of 2,2'-azobis(isobutyronitrile) was added as a polymerization catalyst to initiate polymerization. Simultaneously with the initiation of polymerization, the dropwise addition of a 5% by mass solution of monomethyl maleate, consisting of 5% by mass of monomethyl maleate, 5% by mass of methanol, and 90% by mass of vinyl acetate, the carbon of which is derived from biomass, was initiated. The dropwise addition of the monomethyl maleate solution was carried out continuously from the start to the end of polymerization, gradually decreasing the dropwise addition rate as the polymerization progressed until a total of 200 parts by mass of the solution was added dropwise. The reactor was maintained in a reflux state during the polymerization. After 6 hours of polymerization, 0.12 parts by mass of m-dinitrobenzene and 500 parts by mass of methanol were added as polymerization terminators to terminate the polymerization. At the end of the polymerization, the vinyl acetate conversion rate was 62%, and the monomethyl maleate modification rate was 2.2 mol%. Methanol and vinyl acetate were distilled off from the resulting post-polymerization solution under reduced pressure. When the viscosity increased appropriately, methanol was added to expel the remaining vinyl acetate, yielding a methanol solution of polyvinyl acetate. The resulting methanol solution of polyvinyl acetate was diluted with methanol to a concentration of 9% by mass, and 1,500 parts by mass of this polyvinyl acetate methanol solution (135 parts by mass as polyvinyl acetate) was charged into a reactor similar to the one described above. The reactor was immersed in a water bath and heated to an internal temperature of 50°C. 90.1 parts by mass of a 3.5% by mass solution of sodium hydroxide in methanol was added to initiate the saponification reaction. 50 minutes after the addition of the methanol solution of sodium hydroxide, 1.5 parts by mass of acetic acid and 500 parts by mass of methanol were added to terminate the saponification reaction, and the resulting saponified product was crushed and filtered off.The obtained saponified product was washed with methanol and then dried in a vacuum dryer at 50°C for 20 hours to obtain a carboxyl group-modified PVA-based resin containing radioactive carbon C14 (pMC value of radioactive carbon C14: 85%, viscosity of a 4% by mass aqueous solution at 20°C: 22 mPa s, average degree of saponification: 94 mol%, monomethyl maleate modification rate: 2.2 mol%).

[0100] [Synthesis of fossil fuel-derived carboxyl group-modified PVA-based resin] A fossil fuel-derived carboxyl group-modified PVA-based resin (pMC value of radioactive carbon C14: 0%, viscosity of 4% by mass aqueous solution at 20°C: 22 mPa s, average degree of saponification: 94 mol%, monomethyl maleate modification rate: 2.2 mol%) was obtained in the same manner as in the synthesis of the carboxyl group-modified PVA-based resin containing radioactive carbon C14, except that vinyl acetate in which the carbon of the vinyl group moiety is derived from biomass (that initially charged into the reactor and that used for the added monomethyl maleate solution) was changed to vinyl acetate in which all carbon is derived from petroleum.

[0101] Fossil fuel-derived unmodified PVA (saponification degree 88 mol%, viscosity of 4% by mass aqueous solution at 20°C 43 mPa s)

[0102] <Plasticizers> ・Glycerin (plasticizer derived from natural ingredients) ・Sorbitol (plasticizer derived from natural ingredients)

[0103] Example 1: To a composition containing 100 parts by mass of a carboxy-modified PVA-based resin containing radioactive carbon C14, 15 parts by mass of glycerin as a plasticizer, and 15 parts by mass of sorbitol, ion-exchanged water was added so that the concentration of the composition became 25% by mass, and the mixture was dissolved at 90° C. for 90 minutes to obtain an aqueous PVA-based resin composition solution. The obtained aqueous PVA-based resin composition solution was degassed at 80° C., cast onto a polyethylene terephthalate film, and dried by passing it through a drying chamber (105° C.). The dried film was peeled off from the polyethylene terephthalate film to obtain a water-soluble film with a thickness of 78 μm and a moisture content of 7.6% by mass.

[0104] Examples 2 and 3, Comparative Examples 1 to 3 Water-soluble films of Examples 2 and 3 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the formulations of the compositions were changed as shown in Table 1 below.

[0105] The water-soluble films thus obtained were evaluated as follows, and the results are shown in Table 1 below.

[0106] [Radiocarbon C14 pMC Value] The radiocarbon C14 pMC value of the water-soluble film obtained above was measured according to ASTM D6866-22 (Method B).

[0107] [Tensile Strength, Tensile Elongation, and Elastic Modulus] Using the water-soluble film obtained above, measurements were made in accordance with JIS K 7127 (1999). That is, the water-soluble film was left to stand for 24 hours under humidity conditions of 23°C and 50% RH, and then, under this environment, the water-soluble film was measured at a pulling rate of 200 mm / min (film width: 15 mm, chuck distance: 50 mm) using an Autograph AGS-H manufactured by Shimadzu Corporation (analysis software: Factory SHiKiBU2000 manufactured by Shimadzu Corporation), to determine the tensile strength (MPa), tensile elongation (%), and elastic modulus (measured at an elongation of 8%) at the time of film break.

[0108]

[0109] From the results in Table 1, the water-soluble films of the examples, which contained a PVA-based resin and a specific amount of plasticizer and had a radioactive carbon C14 pMC value of 60% or more, had higher tensile strength, tensile elongation, and 8% modulus of elasticity than the water-soluble films of the comparative examples, which contained the same amount of plasticizer but had a radioactive carbon C14 pMC value of less than 60%.

[0110] 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.

[0111] This water-soluble film 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 such as seedling sheets, seed tapes, and embroidery base fabrics.

Claims

1. A water-soluble film comprising a polyvinyl alcohol resin and a plasticizer, wherein the plasticizer is contained in an amount of 13 parts by mass or more per 100 parts by mass of the polyvinyl alcohol resin, and the pMC value of radiocarbon C14 of the water-soluble film measured according to ASTM D6866 (Method B) is 60% or more.

2. The water-soluble film according to claim 1, wherein the pMC value of radiocarbon C14 of said polyvinyl alcohol resin measured according to ASTM D6866 (Method B) is 55% or more.

3. The water-soluble film according to claim 1 or 2, wherein the polyvinyl alcohol resin contains a modified polyvinyl alcohol resin.

4. The water-soluble film according to claim 3, wherein the modified polyvinyl alcohol resin is a carboxy group-modified polyvinyl alcohol resin.

5. The water-soluble film according to claim 1 or 2, wherein the content of the plasticizer is 13 to 55 parts by mass per 100 parts by mass of the polyvinyl alcohol resin.

6. The water-soluble film according to claim 1 or 2, wherein the plasticizer comprises glycerin.

7. The water-soluble film according to claim 1 or 2, wherein the plasticizer comprises a plasticizer derived from natural sources.

8. The water-soluble film according to claim 1 or 2, wherein the content of the polyvinyl alcohol resin is 75 to 85% by mass relative to 100% by mass (non-volatile content) of the water-soluble film.

9. The water-soluble film according to claim 1 or 2, wherein the ratio of the pMC value (%) of radioactive carbon C14 of the polyvinyl alcohol-based resin measured by ASTM D6866 (Method B) to the content (parts by mass) of the plasticizer per 100 parts by mass of the polyvinyl alcohol-based resin (pMC of radioactive carbon C14 / content of plasticizer) is 0.5 to 10.

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

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

12. The pharmaceutical package of claim 11, wherein the pharmaceutical is a liquid detergent.

13. A method for producing a drug package according to claim 11, 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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