Polyvinyl alcohol-based film

Abstract

The present invention provides a polyvinyl alcohol-based film in which occurrence of wrinkles can be prevented when the film is wound on a core tube. Provided is a polyvinyl alcohol-based film comprising a polyvinyl alcohol-based resin (A), wherein the difference (|α-β|) between the arithmetic mean height (Sa)α of a first surface of said polyvinyl alcohol-based film and the arithmetic mean height (Sa)β of a second surface of said polyvinyl alcohol-based film is not more than 0.10 μm.

Description

Polyvinyl alcohol film

[0001] The present invention relates to a polyvinyl alcohol-based film containing a polyvinyl alcohol-based resin as a main component, and more particularly to a polyvinyl alcohol-based film that can suppress the occurrence of winding wrinkles when the film is wound around a core tube.

[0002] Polyvinyl alcohol films have been used in many applications as films with excellent transparency and dyeability, for example, as optical polyvinyl alcohol films used as raw films for polarizing films, etc. In addition, by adjusting the degree of saponification of the polyvinyl alcohol resin or by introducing (modifying) anionic functional groups or the like into the polyvinyl alcohol molecular chain, they have been used as water-soluble films characterized by their water-solubility, i.e., solubility in water. In particular, in unit packaging applications for chemicals such as pesticides and detergents, they have the advantages of eliminating the need to measure the amount of chemical at the time of use and preventing hand staining, and therefore, unit packaging applications for liquid products such as liquid detergents are expanding.

[0003] After being formed, a polyvinyl alcohol film is usually wound around a core tube to form a film roll, which is then stored and transported. For this reason, for example, Patent Document 1 proposes a water-soluble film that is processed so that the surface roughness (Ra) and maximum height (Rz) of the film fall within a predetermined range, in order to prevent blocking that occurs when the polyvinyl alcohol film is stored for a long period of time at high temperatures, such as in a warehouse in summer, in relation to the storage of the polyvinyl alcohol film, which is generally stored in a wound state.

[0004] Japanese Patent Application Laid-Open No. 2021-178514

[0005] However, the technology of Patent Document 1 enhances blocking resistance by utilizing the difference in surface roughness between a film surface that has been processed so that its surface roughness (Ra) and maximum height (Rz) fall within a predetermined range and a back surface that has not been processed in this manner. Therefore, although the technology has excellent blocking resistance, it tends to cause poor air escape when the film is wound onto a core tube, making it more susceptible to winding wrinkles. A film roll with winding wrinkles has problems such as the side edges of the roll not being aligned, making it look unattractive, and making it difficult to unwind the film smoothly. Furthermore, when a film unwound from a film roll with winding wrinkles is used for subsequent secondary processing, the processed product will have a poor appearance due to distortion and wrinkles, and this problem needs improvement.

[0006] The present invention has been made in view of the above circumstances, and provides a polyvinyl alcohol film that can suppress the occurrence of wrinkles when the film is wound around a core tube.

[0007] However, the present inventors have conducted extensive research in light of these circumstances and have found that, in a polyvinyl alcohol-based film that is stored in a wound state, if the difference (|α-β|) between the arithmetic mean height (Sa)α of the first surface and the arithmetic mean height (Sa)β of the second surface is set to 0.10 μm or less, air can be easily removed when the film is wound onto a core tube, and the occurrence of winding wrinkles can be suppressed.

[0008] That is, the present invention has the following aspects [1] to

[13] . [1] A polyvinyl alcohol-based film containing a polyvinyl alcohol-based resin (A), wherein the difference (|α - β|) between the arithmetic mean height (Sa)α of the first side and the arithmetic mean height (Sa)β of the second side of the polyvinyl alcohol-based film is 0.10 μm or less. [2] The polyvinyl alcohol-based film according to [1], wherein the arithmetic mean height (Sa)α of the first side and the arithmetic mean height (Sa)β of the second side are both 2 μm or less. [3] The polyvinyl alcohol-based film according to [1] or [2], wherein the difference (|γ - δ|) between the maximum height (Sz)γ of the first side and the maximum height (Sz)δ of the second side of the polyvinyl alcohol-based film is 3 μm or less. [4] The polyvinyl alcohol-based film according to any one of [1] to [3], wherein the maximum height (Sz)γ of the first side and the maximum height (Sz)δ of the second side are both 2 μm or more. [5] The polyvinyl alcohol-based film according to any one of [1] to [4], which contains a filler. [6] The polyvinyl alcohol-based film according to [5], wherein the content of the filler is 1 to 30 parts by mass per 100 parts by mass of the polyvinyl alcohol-based resin (A). [7] The polyvinyl alcohol-based film according to any one of [1] to [6], wherein the water content is 3 to 15% by mass. [8] The polyvinyl alcohol-based film according to any one of [1] to [7], which is a water-soluble film. [9] A pharmaceutical package comprising a package formed from the polyvinyl alcohol-based film according to any one of [1] to [8], and a pharmaceutical packaged in the package.

[10] The pharmaceutical package according to [9], wherein the pharmaceutical is a detergent.

[11] The pharmaceutical package according to

[10] , wherein the detergent is a liquid detergent.

[12] A method for producing the polyvinyl alcohol-based film according to any one of [1] to [8], wherein in the step of casting a film-forming raw material containing the polyvinyl alcohol-based resin (A) onto a casting surface to form a polyvinyl alcohol-based film, after the film-forming raw material has been cast onto the casting surface, the polyvinyl alcohol-based film has a water content of 40 mass% or less when peeled from the casting surface.

[13] A method for producing the polyvinyl alcohol-based film according to any one of [1] to [8], wherein in the step of casting a film-forming raw material containing the polyvinyl alcohol-based resin (A) onto a casting surface to form a polyvinyl alcohol-based film, the time from casting the film-forming raw material onto the casting surface to peeling the polyvinyl alcohol-based film from the casting surface is 180 seconds or less.

[0009] The polyvinyl alcohol-based film of the present invention can suppress the occurrence of wrinkles when the film is wound around a core tube. Therefore, a film roll with fewer wrinkles and with even side edges can be obtained, resulting in a good appearance. The present invention can achieve a greater improvement effect in polyvinyl alcohol-based films with a relatively high moisture content.

[0010] The present invention will be described in more detail below based on embodiments of the present invention, but the present invention is not limited to the following embodiments. In the present invention, when "Y to Z" (Y and Z are any numbers) is expressed, unless otherwise specified, it means "Y or more and Z or less", and also includes the meaning of "preferably larger than Y" or "preferably smaller than Z". Furthermore, when "Y or more" (Y is any number) or "Z or less" (Z is any number) is expressed, it also includes the meaning of "preferably larger than Y" or "preferably less than Z".

[0011] In the present specification, when numerical ranges are described in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, 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 polyvinyl alcohol film of the present invention is a film containing a polyvinyl alcohol resin (A), characterized in that the difference (|α−β|) between the arithmetic mean height (Sa)α of a first surface (e.g., the front surface) of the polyvinyl alcohol film and the arithmetic mean height (Sa)β of a second surface (e.g., the back surface) of the polyvinyl alcohol film is 0.10 μm or less.

[0013] Hereinafter, polyvinyl alcohol may be abbreviated as "PVA," a film primarily composed of polyvinyl alcohol-based resin may be abbreviated as "PVA-based film," and a water-soluble film primarily composed of polyvinyl alcohol-based resin may be abbreviated as "PVA-based water-soluble film."

[0014] In the present invention, the term "water-soluble film" refers to a film that dissolves in water at about room temperature (20°C). The solubility of the film can be evaluated as follows: A water-soluble film is cut into a size of 3 cm x 5 cm, placed in a 1-liter beaker containing 1 liter of water and fixed with a jig, and stirred with a stirrer (rotor length: 3 cm, rotation speed: 750 rpm) while maintaining the water temperature at 20°C. When no dispersion of insoluble fine particles having a diameter of 1 mm or more is visually observed in the water-soluble film, the film is deemed dissolved.

[0015] <PVA-Based Film> [Arithmetic Mean Height (Sa)] It is important that the difference (|α-β|) between the arithmetic mean height (Sa)α of the first surface and the arithmetic mean height (Sa)β of the second surface of the PVA-based film is 0.10 μm or less. This difference (|α-β|) is preferably 0.085 μm or less, more preferably 0.07 μm or less, even more preferably 0.06 μm or less, and particularly preferably 0.05 μm or less. The lower limit of the difference (|α-β|) is preferably 0.0005 μm or more, more preferably 0.0001 μm or more, and even more preferably 0.00001 μm or more; the closer to zero the value, the better. When the difference (|α-β|) is within the above range, the films slide appropriately against each other during winding, allowing for good air release, and preventing wrinkles from forming when winding.

[0016] In the present PVA-based film, the arithmetic mean height (Sa)α of the first side and the arithmetic mean height (Sa)β of the second side are both preferably 2 μm or less, more preferably 1.5 μm or less, even more preferably 1.2 μm or less, particularly preferably 1 μm or less, and especially preferably 0.9 μm or less. Furthermore, the arithmetic mean height (Sa)α of the first side and the arithmetic mean height (Sa)β of the second side are both preferably 0.1 μm or more, more preferably 0.2 μm or more, particularly preferably 0.3 μm or more, particularly preferably 0.4 μm or more, and even more preferably 0.5 μm or more. When the arithmetic mean height (Sa)α of the first side and the arithmetic mean height (Sa)β of the second side are within the above ranges, air escapes more smoothly during film winding, which tends to further reduce the occurrence of winding wrinkles.

[0017] In the present invention, the arithmetic mean height (Sa)α of the first surface of the PVA-based film and the arithmetic mean height (Sa)β of the second surface of the PVA-based film refer to three-dimensional arithmetic mean heights defined in accordance with JIS B0681-2 (2018).

[0018] [Maximum Height (Sz)] In the present PVA-based film, the difference (|γ-δ|) between the maximum height (Sz)γ of the first side and the maximum height (Sz)δ of the second side is preferably 3 μm or less, more preferably 2.5 μm or less, even more preferably 1.8 μm or less, particularly preferably 1.5 μm or less, and especially preferably 1 μm or less. The lower limit of the difference (|γ-δ|) is preferably 0.01 μm or more, more preferably 0.001 μm or more; the closer to 0 the better. If the difference (|γ-δ|) is too large, the balance of sliding between the films during film winding will be poor, air will escape unevenly, and winding wrinkles will be more likely to occur.

[0019] In this PVA-based film, the maximum height (Sz)γ of the first side and the maximum height (Sz)δ of the second side are preferably both 2 μm or more, more preferably 2.5 μm or more, particularly preferably 3 μm or more, especially preferably 4 μm or more, even more preferably 5 μm or more, even more preferably 5.5 μm or more, and even more preferably 6 μm or more. Furthermore, the maximum height (Sz)γ of the first side and the maximum height (Sz)δ of the second side are both preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and especially preferably 9 μm or less. When the maximum height (Sz)γ of the first side and the maximum height (Sz)δ of the second side are within the above ranges, blocking of the film tends to be more effectively suppressed. Furthermore, if the maximum height (Sz)γ of the first surface and the maximum height (Sz)δ of the second surface are too small, the film is prone to blocking, the peel position of the film is unstable when unwound from the film roll, and the winding speed and tension become unstable, causing misalignment of the end face of the wound film roll. If they are too large, the balance with the suppression of winding wrinkles tends to be reduced.

[0020] In the present invention, the maximum height (Sz)γ of the first surface of the PVA-based film and the maximum height (Sz)δ of the second surface of the PVA-based film refer to the three-dimensional maximum heights defined in accordance with JIS B0681-2 (2018).

[0021] Next, each component constituting the PVA-based film will be described.

[0022] [PVA-based resin (A)] The present PVA-based film is a water-soluble film mainly composed of a PVA-based resin (A). Here, "mainly composed of a PVA-based resin (A)" means that the PVA-based resin (A) is contained in an amount of typically 50% by mass or more, preferably 55% by mass or more, and particularly preferably 60% by mass or more, based on the entire PVA-based film. If the content is too low, the solubility in water and the mechanical properties of the film tend to decrease. The upper limit of the content is typically 99% by mass or less, preferably 95% by mass or less, and particularly preferably 90% by mass or less, in terms of the shape stability over time when the PVA-based film is used as a liquid detergent package.

[0023] The PVA-based resin (A) used in the present PVA-based film may be an unmodified PVA or a modified PVA-based resin.

[0024] The unmodified PVA and modified PVA-based resins can be produced by a production method known in the art, for example, as follows.

[0025] The unmodified PVA can be produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester compound.

[0026] 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 may be used alone or in combination of two or more.

[0027] The modified PVA resin can be produced by copolymerizing the vinyl ester compound with an unsaturated monomer copolymerizable with the vinyl ester compound, followed by saponification.

[0028] Examples of unsaturated monomers copolymerizable with the vinyl ester compound include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, and 5-hexen-1-ol, and derivatives thereof such as acylated products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid, as well as their salts, monoesters, and dialkyl esters; amides such as diacetone acrylamide, acrylamide, and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, as well as their salts; and N-vinyl pyrrolidone. These may be used alone or in combination of two or more.

[0029] In addition to the above, the modified PVA-based resin may also include, for example, a resin having primary hydroxyl groups in the side chain, typically having 1 to 5, preferably 1 to 2, and particularly preferably 1 primary hydroxyl group in the side chain, and preferably having secondary hydroxyl groups in addition to the primary hydroxyl groups. Examples of such modified PVA-based resins include PVA-based resins having hydroxyalkyl groups in the side chain and PVA-based resins having 1,2-diol structural units in the side chain. PVA-based resins having 1,2-diol structural units in their side chains can be produced by, for example, (1) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (2) a method of saponifying and decarboxylating a copolymer of vinyl acetate and vinyl ethylene carbonate, (3) a method of saponifying and deketalizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane, or (4) a method of saponifying a copolymer of vinyl acetate and glycerin monoallyl ether.

[0030] The modified PVA-based resin used in the present PVA-based film is preferably modified with at least one hydrophilic group selected from the group consisting of a carboxy group, a sulfonic acid group, a phosphate group, a pyrrolidone ring group, etc., from the viewpoint of solubility. These modifying groups also include salts of these functional groups, such as sodium and potassium salts. Among these, an anionic group-modified PVA-based resin is preferred. 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, a carboxy group or a sulfonic acid group is particularly preferred, with a carboxy group being even more preferred.

[0031] The carboxyl group-modified PVA-based resin can be produced by any method, and examples of the production method include (i) a method of copolymerizing an unsaturated monomer having a carboxyl group with a vinyl ester-based compound, followed by saponification, and (ii) a method of polymerizing a vinyl ester-based compound in the presence of an alcohol, aldehyde, or thiol having a carboxyl group as a chain transfer agent, followed by saponification.

[0032] The unsaturated monomer having a carboxy group in the method (i) above may be an ethylenically unsaturated dicarboxylic acid (maleic acid, fumaric acid, itaconic acid, etc.), an ethylenically unsaturated dicarboxylic acid monoester (maleic acid monoalkyl ester, fumaric acid monoalkyl ester, itaconic acid monoalkyl ester, etc.), an ethylenically unsaturated dicarboxylic acid diester (maleic acid dialkyl ester, fumaric acid dialkyl ester, itaconic acid dialkyl ester, etc.) (however, it is necessary that these diesters are converted to a carboxy group by hydrolysis during saponification of the copolymer), or an ethylenically unsaturated carboxylic acid anhydride (maleic anhydride, Examples of suitable monomers include monomers such as maleic acid, maleic acid monoalkyl esters, maleic acid dialkyl esters, maleic acid salts, maleic anhydride, itaconic acid, itaconic acid monoalkyl esters, itaconic acid dialkyl esters, (meth)acrylic acid, and the like, and it is particularly preferred to use maleic acid, maleic acid monoalkyl esters, maleic acid dialkyl esters, maleic acid salts, and maleic anhydride, with maleic acid monoalkyl esters being even more preferred. These may be used alone or in combination of two or more.

[0033] In the method (ii) above, compounds derived from thiols, which have a particularly large chain transfer effect, are effective, and examples thereof include compounds represented by the following general formulas (1) to (3).

[0034]

[0035]

[0036]

[0037] Further, salts of the compounds represented by the general formulas (1) to (3) above may also be used. Specific examples include mercaptoacetate, 2-mercaptopropionate, 3-mercaptopropionate, 2-mercaptostearate, etc. These compounds may be used alone or in combination of two or more.

[0038] In addition to the unsaturated monomer having a carboxy group and the vinyl ester compound, other general monomers may be added to the polymerization to the extent that water solubility is not impaired, and examples of such monomers include alkyl esters of ethylenically unsaturated carboxylic acids, allyl esters of saturated carboxylic acids, α-olefins, alkyl vinyl ethers, alkyl allyl ethers, as well as (meth)acrylamide, (meth)acrylonitrile, styrene, vinyl chloride, etc. These may be used alone or in combination of two or more.

[0039] The method for producing the carboxyl group-modified PVA-based resin is not limited to the above-mentioned method. For example, a method of post-reacting a PVA-based resin (partially saponified or completely saponified) with a carboxyl group-containing compound having a functional group reactive with a hydroxyl group, such as a dicarboxylic acid, an aldehydecarboxylic acid, or a hydroxycarboxylic acid, can also be employed.

[0040] When a sulfonic acid-modified PVA-based resin modified with a sulfonic acid group is used, the resin can be produced by, for example, a method of copolymerizing a copolymerization component such as vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, or 2-acrylamido-2-methylpropanesulfonic acid with a vinyl ester-based compound, followed by saponification, or a method of subjecting vinyl sulfonic acid or a salt thereof, 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof, or the like, to Michael addition to a PVA-based resin.

[0041] On the other hand, methods for post-modifying the unmodified PVA include methods of acetoacetic esterification, acetalization, urethanization, etherification, grafting, phosphate esterification, and oxyalkylenation of the unmodified PVA.

[0042] The PVA-based film preferably contains a modified PVA-based resin, particularly an anionic group-modified PVA-based resin, and more preferably a carboxy group-modified PVA-based resin, in order to improve the film's solubility in water, particularly in cold water (e.g., 10°C or lower), and to suppress a decrease in solubility over time when the substance to be packaged is alkaline.

[0043] When a carboxyl group-modified PVA-based resin is used in the present PVA-based film, maleic acid-modified PVA-based resin and itaconic acid-modified PVA-based resin are preferred in terms of ease of handling, high polymerizability with vinyl ester monomers, and excellent productivity. In particular, maleic acid-modified PVA-based resin is preferred in terms of stability over time of the solubility of the film when a drug is packaged and in terms of being less susceptible to the pH of the drug.

[0044] The average saponification degree of the PVA-based resin (A) is preferably 80 mol% or more, particularly preferably 82 to 99.9 mol%, even more preferably 85 to 98.5 mol%, and especially preferably 90 to 97 mol%. If the average saponification degree is too low, the solubility of the film in water tends to decrease. If the average saponification degree is too high, the water solubility tends to decrease. From the viewpoint of a balance between solubility and excellent moldability (mold conformability), the average saponification degree is more preferably 90 to 99.9 mol%, particularly preferably 91 to 98.5 mol%, and even more preferably 92 to 97 mol%. The average saponification degree of the PVA-based resin (A) means that the average saponification degree of the entire PVA-based resin contained in the PVA-based film falls within these ranges. When a PVA-based film contains a plurality of PVA-based resins, the average saponification degree of all PVA-based resins (A) is calculated from the ratio of each PVA-based resin contained in all PVA-based resins (A) and the average saponification degree thereof 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)

[0045] In particular, when unmodified PVA is used as the PVA-based resin (A), the average saponification degree is preferably 80 mol% or more, particularly preferably 82 to 99 mol%, and even more preferably 85 to 90 mol%. If the average saponification degree is too low, water solubility, particularly the solubility over time of the film used to package medicines and the like, tends to decrease. However, if the average saponification degree is too high, water solubility tends to decrease.

[0046] On the other hand, when a modified PVA-based resin is used as the PVA-based resin (A), the average saponification degree thereof is preferably 80 mol% or more, particularly preferably 85 to 99.9 mol%, and further preferably 90 to 98 mol%. If the average saponification degree is too low, the solubility of the film, particularly the solubility over time of the film when used to package medicines and the like, tends to decrease. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0047] Furthermore, when an anionic group-modified PVA-based resin is used as the PVA-based resin (A), the average saponification degree thereof is preferably 85 mol% or more, particularly 88 to 99 mol%, further preferably 90 to 98 mol%, and especially preferably 92 to 97 mol%. A saponification degree within this range inhibits the film from decreasing in solubility over time and provides superior moldability. If the average saponification degree is too low, the solubility of the PVA-based film in water tends to decrease over time depending on the pH of the drug to be packaged. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0048] The average degree of saponification is measured in accordance with JIS K 6726 3.5.

[0049] The degree of polymerization of the PVA-based resin (A) used in the present PVA-based film can generally be expressed by its aqueous solution viscosity, and the viscosity of a 4% by weight aqueous solution at 20°C is preferably 5 to 55 mPa·s, more preferably 10 to 50 mPa·s, particularly 15 to 45 mPa·s, especially 17 to 43 mPa·s, 21 to 40 mPa·s, or even 21.5 to 38 mPa·s. The viscosity of the 4% by weight aqueous solution of the PVA-based resin (A) at 20°C means that the viscosity of the 4% by weight aqueous solution of the entire PVA-based resin contained in the PVA-based film at 20°C falls within this range. Furthermore, when unmodified PVA is used as the PVA-based resin (A), the viscosity of the 4% by weight aqueous solution at 20°C is preferably 5 to 60 mPa·s, more preferably 10 to 50 mPa·s, especially 15 to 45 mPa·s. When a modified PVA-based resin is used as the PVA-based resin (A), the viscosity of a 4% by mass aqueous solution at 20°C is preferably 5 to 50 mPa·s, more preferably 15 to 45 mPa·s, particularly 17 to 40 mPa·s, especially 21 to 38 mPa·s, and even more preferably 21.5 to 35 mPa·s. A viscosity within this range results in a PVA-based film with excellent mechanical strength and moldability. If the viscosity is too low, the mechanical strength of the PVA-based film used as a packaging material tends to decrease, while if the viscosity is too high, productivity tends to decrease.

[0050] The viscosity of the 4 mass % aqueous solution is measured in accordance with JIS K 6726 3.11.2.

[0051] The modification amount of the modified PVA-based resin is preferably 1 to 15 mol%, particularly preferably 1.5 to 12 mol%, further preferably 2 to 8 mol%, and particularly preferably 2 to 5 mol%. If the modification amount is too small, the solubility in water tends to decrease, whereas if the modification amount is too large, the productivity of the PVA-based resin tends to decrease, biodegradability tends to decrease, and blocking tends to occur easily.

[0052] In the present PVA-based film, the PVA-based resin (A) may be used alone or in combination of two or more types differing in at least one of the degree of saponification, viscosity, modified species, modification amount, etc. For example, two or more types of unmodified PVAs may be used in combination, two or more types of modified PVA-based resins may be used in combination, or one or more types of unmodified PVA and one or more types of modified PVA-based resin may be used in combination, etc. Among these, from the viewpoint of solubility, it is preferable that the PVA-based resin (A) contains a modified PVA-based resin, and from the viewpoint of water-tightness and compressive strength when made into a package, it is preferable to use one or more types of unmodified PVA and one or more types of modified PVA-based resin in combination.

[0053] [Plasticizer (B)] The PVA-based film preferably contains a plasticizer (B) in order to provide the film with appropriate flexibility when used as a package. The plasticizer (B) may be used alone or in combination of two or more.

[0054] Examples of such plasticizers (B) include glycerins such as glycerin, diglycerin, and triglycerin, alkylene glycols such as triethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, and propylene glycol, and sugar alcohols such as trimethylolpropane, sorbitol, xylitol, and maltitol. Among these, glycerin, polyethylene glycol, and diglycerin are preferably used because they are easily available and can achieve a plasticizing effect with a small amount. In addition, sorbitol is also preferred in terms of the stability of the package over time.

[0055] In the present PVA-based film, it is preferable to use a polyhydric alcohol (b1) (hereinafter sometimes abbreviated as "plasticizer (b1)") having a melting point of 50°C or less in terms of mold conformability during film molding and mechanical properties. Examples of the plasticizer (b1) include aliphatic alcohols, preferably ethylene glycol (-13°C), diethylene glycol (-11°C), triethylene glycol (-7°C), propylene glycol (-59°C), tetraethylene glycol (-5.6°C), 1,3-propanediol (-27°C), 1,4-butanediol (20°C), 1,6-hexanediol (40°C), tripropylene glycol, and dihydric alcohols such as polyethylene glycols with a molecular weight of 2000 or less, and trihydric or higher alcohols such as glycerin (18°C), diglycerin, and triethanolamine (21°C). These may be used alone or in combination of two or more. The values ​​in parentheses indicate melting points. Among these, in terms of flexibility of the PVA-based film, those having a melting point of 30° C. or less are particularly preferred, and those having a melting point of 20° C. or less are even more preferred. The lower limit of the melting point is usually −80° C., preferably −10° C., and particularly preferably 0° C.

[0056] Furthermore, among the plasticizers (b1), those having four or less hydroxyl groups in one molecule are preferred, and those having three or less hydroxyl groups in particular are preferred in that flexibility at around room temperature (25°C) can be easily controlled. Specifically, for example, glycerin is suitable.

[0057] Furthermore, the plasticizer (b1) preferably has a molecular weight of 100 or less, particularly preferably 50 to 100, and even more preferably 60 to 95, in terms of ease of controlling flexibility. Specifically, for example, glycerin is suitable.

[0058] When two or more plasticizers (B) are used in combination in the PVA-based film, it is preferable to use a polyhydric alcohol (b2) (hereinafter sometimes abbreviated as "plasticizer (b2)") having a melting point of 80°C or higher, in terms of the toughness of the PVA-based film and the shape stability over time when used as a package.

[0059] As the plasticizer (b2), many sugar alcohols, monosaccharides, and polysaccharides can be used. Among them, for example, dihydric alcohols such as salicylic alcohol (83°C), catechol (105°C), resorcinol (110°C), hydroquinone (172°C), bisphenol A (158°C), bisphenol F (162°C), and neopentyl glycol (127°C), trihydric alcohols such as phloroglucinol (218°C), erythritol (121°C), threitol (88°C), and pentaerythritol (121°C), are particularly suitable. Examples include tetrahydric alcohols such as rhythritol (260°C); pentahydric alcohols such as xylitol (92°C), arabitol (103°C), fucitol (153°C), glucose (146°C), and fructose (104°C); hexahydric alcohols such as mannitol (166°C), sorbitol (95°C), and inositol (225°C); octahydric alcohols such as lactitol (146°C), sucrose (186°C), and trehalose (97°C); and nonahydric or higher alcohols such as maltitol (145°C). These may be used alone or in combination of two or more. The parentheses indicate melting points. Among these, those with a melting point of 85°C or higher are preferred, particularly 90°C or higher, in terms of the tensile strength of the PVA-based film. The upper limit of the melting point is preferably 300°C, and particularly preferably 200°C.

[0060] Furthermore, among the plasticizers (b2), those having 4 or more hydroxyl groups in one molecule are preferred in terms of compatibility with the PVA-based resin (A), particularly preferably 5 to 10 hydroxyl groups, and further preferably 6 to 8 hydroxyl groups in one molecule. Specific examples of suitable plasticizers include sorbitol, sucrose, and trehalose.

[0061] In addition, from the viewpoint of the toughness of the PVA-based film, the plasticizer (b2) preferably has a molecular weight of 150 or more, particularly preferably 160 to 500, and further preferably 180 to 400. Specific examples of suitable plasticizers include sorbitol and sucrose.

[0062] The content of the plasticizer (B) used in the present PVA-based film is preferably 3 to 25 parts by mass, more preferably 5 to 22 parts by mass, particularly preferably 7 to 20 parts by mass, even more preferably 8 to 18 parts by mass, and especially preferably 8.5 to 16 parts by mass, per 100 parts by mass of the PVA-based resin (A). If the content of the plasticizer (B) is too low, the mechanical properties tend to be insufficient, the film tends to be too hard, become brittle in low-humidity environments, the conformability of the film during molding tends to be reduced, resulting in poor appearance of the package, and the tension of the package tends to decrease over time. On the other hand, if the content is too high, the film tends to be too soft, prone to blocking, and the dimensional stability of the package tends to decrease.

[0063] The content of the plasticizer (b1) is preferably 3 to 25 parts by mass, particularly preferably 5 to 20 parts by mass, further preferably 7 to 18 parts by mass, and particularly preferably 8 to 16 parts by mass, based on 100 parts by mass of the PVA-based resin (A). If the content of the plasticizer (b1) is too low, the mechanical properties and the conformability of the film during molding tend to deteriorate, resulting in a poor appearance of the package.

[0064] The content of the plasticizer (b1) is preferably more than 50% by mass, particularly preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 85% by mass or more, even more preferably 90% by mass or more, or even more preferably 97% by mass or more, based on the total amount of the plasticizer (B). If the content of the plasticizer (b1) is too low, the mechanical properties tend to deteriorate, and the conformability of the film during molding tends to deteriorate, resulting in a poor appearance of the package.

[0065] When the plasticizer (b2) is used, the content thereof is preferably 1 to 25 parts by mass, particularly preferably 1 to 20 parts by mass, further preferably 1.5 to 10 parts by mass, and particularly preferably 2 to 8 parts by mass, based on 100 parts by mass of the PVA-based resin (A). If the content of the plasticizer (b2) is too low, the tension of the film when made into a package tends to decrease, whereas if the content is too high, the mechanical properties of the film and the followability during molding tend to decrease, resulting in a poor appearance of the package.

[0066] [Filler (C)] The PVA-based film may further contain a filler (C) as needed.

[0067] The filler (C) is contained for the purpose of blocking resistance, and examples thereof include organic fillers and inorganic fillers, among which organic fillers are preferably used. These can be used alone or in combination of two or more.

[0068] The average particle size of the filler (C) is preferably 0.1 to 50 μm, particularly preferably 1 to 35 μm. The average particle size of the filler (C) is a value measured with a laser diffraction particle size distribution analyzer, and is calculated from the D50 value (particle size at 50% of the cumulative size) of the obtained cumulative volume distribution.

[0069] The organic filler used in the present PVA-based film refers to particulate matter (primary particles) composed of organic compounds and having any shape, such as needle-like, rod-like, lamellar, scaly, or spherical, or an aggregate of such particulate matter (secondary particles). Such organic fillers are mainly selected from polymer compounds, such as melamine-based resins, polymethyl(meth)acrylate-based resins, polystyrene-based resins, and biodegradable resins such as starch and polylactic acid. These can be used alone or in combination of two or more. Among these, biodegradable resins such as polymethyl(meth)acrylate-based resins, polystyrene-based resins, and starch are preferred, with starch being particularly preferred in terms of its dispersibility in the PVA-based resin (A).

[0070] Examples of the starch include raw starches (corn starch, potato starch, sweet potato starch, wheat starch, cassava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, kudzu starch, bracken starch, lotus starch, and water chestnut starch), physically modified starches (α-starch, fractionated amylose, and heat-moisture treated starch), enzyme-modified starches (hydrolyzed dextrin, enzymatically decomposed dextrin, and amylose), chemically decomposed and modified starches (acid-treated starch, hypochlorite-oxidized starch, and dialdehyde starch), and chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, and cross-linked starch). These starches can be used alone or in combination of two or more. Among these, raw starches, particularly corn starch and rice starch, are preferred from the viewpoints of availability and economy.

[0071] The average particle size of the organic filler is preferably 2 to 50 μm, particularly preferably 4 to 45 μm, further preferably 10 to 40 μm, and particularly preferably 15 to 35 μm. If the average particle size is too small, the blocking tendency of the film tends to increase, while if it is too large, the fillers tend to aggregate with each other, reducing dispersibility and tending to form pinholes when stretched during film molding.

[0072] The inorganic filler used in the present PVA-based film refers to particulate matter (primary particles) composed of inorganic compounds 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.

[0073] Among the above, it is preferable to use an oxide-based inorganic compound or talc, more preferably titanium oxide, talc or silica, and particularly preferably silica.

[0074] 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 blocking tendency of the film tends to increase, and the flexibility and toughness of the film tends to decrease, while if the average particle size is too large, the water sealing property tends to decrease.

[0075] The content of the filler (C) is preferably 1 to 30 parts by mass, particularly preferably 2 to 25 parts by mass, and even more preferably 2.5 to 20 parts by mass, per 100 parts by mass of the PVA-based resin (A). If the content is too low, blocking tends to increase, while if the content is too high, the flexibility and toughness of the film tend to decrease. From the viewpoints of achieving both blocking resistance and wrinkle reduction of the film and balancing blocking resistance and moldability of the film, the content of the filler (C) is preferably 8 parts by mass or less, particularly 6 parts by mass or less, even more preferably 0.1 to 5.5 parts by mass, more preferably 0.5 to 5.0 parts by mass, even more preferably 1 to 4.5 parts by mass, particularly preferably 1.5 to 4.0 parts by mass, and especially preferably 2 to 3.5 parts by mass, per 100 parts by mass of the PVA-based resin (A).

[0076] [Surfactant (D)] The PVA-based film may contain a surfactant (D) as needed.

[0077] The surfactant (D) is contained for the purpose of improving the releasability from the cast surface during production of the PVA-based film, and includes nonionic surfactants, cationic surfactants, anionic surfactants, etc. Examples include polyoxyethylene nonylphenyl ether, polyoxyethylene octylnonyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene alkylamino ethers such as polyoxyalkylene alkyl ether phosphate monoethanolamine salts, polyoxyethylene lauryl amino ethers, and polyoxyethylene stearyl amino ethers, and the like, and these surfactants may be used alone or in combination of two or more. Among these, polyoxyalkylene alkyl ether phosphate monoethanolamine salts and polyoxyethylene lauryl amino ether are preferred in terms of production stability.

[0078] The content of the surfactant (D) is preferably 0.1 to 5 parts by mass, particularly preferably 0.2 to 4.5 parts by mass, and further preferably 0.3 to 4 parts by mass, per 100 parts by mass of the PVA-based resin (A). If the content is too low, the peelability between the casting surface of the film-forming apparatus and the formed PVA-based film tends to decrease, resulting in a decrease in productivity, whereas if the content is too high, the adhesive strength during sealing tends to decrease.

[0079] The PVA-based film may contain an antioxidant to inhibit yellowing. 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, catechol, and Rongalite. These can be used alone or in combination. Of these, sulfites, particularly sodium sulfite, are preferred. The amount of antioxidant added is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, and particularly preferably 0.3 to 3 parts by mass, per 100 parts by mass of the PVA-based resin (A).

[0080] The PVA-based film may further contain, to the extent that the object of the invention is not impaired, fragrances, rust inhibitors, mildew inhibitors, colorants, extenders, antifoaming agents, ultraviolet absorbers, fluorescent brighteners, liquid paraffins, bitter components (e.g., denatonium benzoate, etc.), etc. These may be used alone or in combination of two or more.

[0081] <Production of PVA-based film> The PVA-based film is produced by a dissolution step in which the PVA-based resin (A), preferably a plasticizer (B), and optionally a filler (C) and a surfactant (D) are blended and dissolved or dispersed in water to prepare a film-forming raw material, and a film-forming step in which the film-forming raw material is shaped into a film and dried as necessary to form a film, and the produced film is wound up into a film roll. The process for producing the PVA-based film is described below.

[0082] In the dissolving step, the PVA-based resin composition containing the blended components is dissolved or dispersed in water to prepare an aqueous solution or aqueous dispersion as a film-forming raw material. The PVA-based resin composition is usually dissolved in water by a method such as room temperature dissolution, high temperature dissolution, or pressure dissolution. Among these, high temperature dissolution is preferred because it leaves less undissolved material and is highly productive.

[0083] The solids concentration of the film-forming raw material is preferably 10 to 65% by mass, particularly preferably 12 to 60% by mass, and further preferably 15 to 55% by mass. If the concentration is too low, the productivity of the film tends to decrease, whereas 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.

[0084] [Film-forming process] In the film-forming process, the film-forming raw material prepared in the dissolving process is shaped into a film, and if necessary, dried to form a film. For film formation, methods such as melt extrusion and casting can be used, but casting is preferred in terms of film thickness accuracy. When performing the casting method, for example, the film-forming raw material is extruded through a slit such as a T-slit die, cast onto a casting surface such as the metal surface of an endless belt or drum roll, a polyethylene terephthalate film, or a plastic substrate such as polypropylene, and then dried to produce the PVA-based film. It is preferable to use an endless belt or drum roll as the target for casting the film-forming raw material, and particularly, it is more preferable to use a drum roll because it is easy to control the moisture content of the film when peeled off from the casting surface.

[0085] In the present PVA-based film, the difference (|α-β|) between the arithmetic mean height (Sa)α of the first surface and the arithmetic mean height (Sa)β of the second surface satisfies a specific range. The arithmetic mean height can be adjusted to the specific range by, for example, controlling the moisture content of the film at the time of peeling from the casting surface, the time in contact with the casting surface (contact time), the temperature of the casting surface (casting temperature), etc.

[0086] In the film-forming process of the present PVA-based film, it is preferable to set the moisture content of the film at the time of peeling from the casting surface higher than in the past. By further drying the film that is not dry to the inside to the target moisture content without contacting the casting surface, the solid matter contained in the film, such as filler, flows inside and is dispersed evenly on both surfaces of the film, making it possible to prepare a film with a small difference in roughness between the two surfaces.

[0087] For this reason, the moisture content of the PVA-based film at the time of peeling from the cast surface is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. Furthermore, the moisture content of the PVA-based film at the time of peeling from the cast surface is preferably 5% by mass or more, particularly 8% by mass or more, and even more preferably 12% by mass or more. That is, the moisture content of the PVA-based film at the time of peeling from the cast surface is preferably 5 to 40% by mass, more preferably 8 to 30% by mass, and even more preferably 12 to 25% by mass. By setting the moisture content of the PVA-based film at the time of peeling from the cast surface within the above range, it becomes possible to distribute fillers, etc., on the cast surface side, and the difference in roughness between the two surfaces of the film tends to be smaller. The moisture content is measured in accordance with JIS K 6726 3.4, and the obtained value of the volatile content is taken as the moisture content.

[0088] Furthermore, the contact time between the film-forming raw material and the cast surface of the film after being cast on the cast surface and before being peeled off is preferably 180 seconds or less, more preferably 120 seconds or less, and even more preferably 90 seconds or less, in order to adjust the moisture content of the film at the time of peeling from the cast surface. Furthermore, the contact time between the film-forming raw material and the cast surface of the film is preferably 10 seconds or more, and particularly preferably 20 seconds or more. That is, the contact time between the film-forming raw material and the cast surface of the film after being cast on the cast surface and before being peeled off is preferably 10 to 180 seconds, more preferably 20 to 120 seconds, and even more preferably 20 to 90 seconds. By setting the contact time between the film and the cast surface of the film within the above range, the difference in roughness between the two surfaces of the film tends to be smaller.

[0089] From the viewpoint of adjusting the moisture content of the film at the time of peeling from the casting surface, the casting temperature is preferably 60° C. to 100° C., more preferably 65° C. to 95° C., and even more preferably 70° C. to 90° C. When the casting temperature is within this range, filler and the like can be distributed on the casting surface as well, which tends to reduce the difference in roughness between the two surfaces of the film, and thus makes it possible to suppress wrinkles and blocking.

[0090] In addition, if a drying process is further performed after peeling the film from the cast surface, it is preferable to use a drying roll (a device that dries the film by passing it between multiple metal rolls set at a predetermined temperature), as this makes it easier to adjust the roughness of both sides of the film to a specific range.

[0091] Conventionally, when producing a film by the casting method, the roughness of the film surface has been adjusted by setting the surface of the casting surface to a predetermined roughness, or the film has been dried on the casting surface until the moisture content is relatively low in order to shorten the labor and drying time required for the drying process between peeling the film from the casting surface and winding. Therefore, at the time of peeling from the casting surface, the film has already dried to the inside, and fillers and the like are fixed without flowing inside the film, and the roughness of the film surface that was in contact with the casting surface tends to depend on the roughness of the casting surface, while the film surface not in contact with the casting surface (the surface exposed to air) has unevenness due to the fillers and the like dispersed during the drying process on the casting surface. Therefore, films with a large difference in roughness between the two surfaces of the film have tended to be obtained.

[0092] In this manner, the PVA film can be produced.

[0093] The moisture content of the PVA-based film is preferably 3 to 15% by mass, particularly preferably 5 to 12% by mass, and even more preferably 6 to 10% by mass, from the viewpoint of mechanical strength and sealing ability. If the moisture content is too low, the film becomes too hard, which can lead to, for example, reduced formability when forming a package during secondary processing, reduced impact resistance of the package, and poor sealing. If the moisture content is too high, blocking and winding wrinkles tend to occur. The moisture content can be adjusted by appropriately setting the film-forming conditions, drying conditions, and humidity control conditions. The moisture content is measured in accordance with JIS K 6726 3.4, and the value of the volatile content obtained is taken as the moisture content.

[0094] The thickness of the PVA-based film is appropriately selected depending on the application, etc., but is preferably 10 to 130 μm, particularly preferably 20 to 110 μm, further preferably 30 to 100 μm, and particularly preferably 45 to 90 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.

[0095] The width of the PVA-based 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, production efficiency tends to decrease, while if the width is too wide, it tends to be difficult to control slack and film thickness.

[0096] The length of the PVA-based 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, switching between films tends to be time-consuming, while if the length is too long, the film tends to become too heavy and have a poor appearance due to tight winding.

[0097] The PVA-based film is transported and typically wound around a core tube to form a film roll. The difference in arithmetic mean height (Sa) of the contact surfaces between the wound film and the film stacked on top of it is always controlled to a constant, small value, allowing for adequate slippage between the already wound film and the film to be wound, allowing for adequate air escape between the two, resulting in a film roll without wrinkles and suppressing blocking during unwinding. Therefore, the PVA-based film can be used to obtain a film roll with excellent appearance.

[0098] The obtained film roll can be supplied as a product as it is, but preferably can also be supplied as a film roll slit into a film width of a desired size.

[0099] The PVA-based film thus obtained is useful for various packaging applications, such as 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 raising sheets, seed tapes, and embroidery base fabrics, and is particularly suitable for use in unit packaging of chemicals such as laundry detergents and dishwashing detergents.

[0100] <Medicine Package> A pharmaceutical package according to one embodiment of the present invention is formed by coating a pharmaceutical with a package made of the obtained PVA-based film. Because the pharmaceutical package contains a pharmaceutical packaged in a package made of the water-soluble PVA-based film, when the pharmaceutical package is placed in water, the surface package (the PVA-based film) dissolves, exposing the pharmaceutical, which then dissolves or disperses in water, thereby exerting its effects. Therefore, the pharmaceutical package according to one embodiment of the present invention is suitable as a pharmaceutical package containing a relatively small amount of pharmaceutical, such as a single dose.

[0101] Examples of the above-mentioned chemicals include agricultural chemicals such as insecticides, fungicides, and herbicides, fertilizers, detergents, etc., and detergents such as laundry detergents and dishwashing detergents are particularly preferred. Such chemicals may be liquid or solid, and if solid, may be in the form of granules, tablets, powder, etc. The chemicals are preferably those that are dissolved or dispersed in water, and are particularly preferably those that contain liquid detergents. The pH of such chemicals may be alkaline, neutral, or acidic.

[0102] The liquid detergent preferably has a pH value of 6 to 12 when dissolved or dispersed in water, particularly 6.5 to 11, and even more preferably 7 to 8. The liquid detergent also preferably has a water content of 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 the above range, the PVA-based film tends to be free from gelation or insolubilization and exhibit 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.

[0103] Such drug packages can be obtained by known methods. For example, they can be produced by placing a drug between two opposing PVA-based films (a first PVA-based film and a second PVA-based film) and then crimping and bonding the overlapping portions (contact portions) of the PVA-based films around the drug. Specifically, a lower mold of a molding machine is prepared, which has a recess shaped to accommodate the drug. A first PVA-based film (bottom film) is fixed to the lower mold, and the bottom film is molded to a shape that conforms to the lower mold. Meanwhile, a second PVA-based film (top film) is also fixed to the upper mold of the molding machine. A separately prepared drug, such as a liquid detergent, is then placed (introduced) into the molded bottom film, and the upper and lower molds are clamped together to bring the top and bottom films around the drug into contact with each other, and the contact portions are crimped under vacuum. After the pressure bonding, the vacuum is released to obtain a drug package in which the drug is encapsulated in the PVA-based film.

[0104] Examples of methods for bonding the film include heat sealing, water sealing, and glue sealing. Of these, water sealing is preferred because it is easy to control the bonding conditions.

[0105] 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" and "%" are based on mass.

[0106] First, the following materials were prepared as raw materials for the PVA-based films of the Examples and Comparative Examples. These were then used to produce the PVA-based films of the Examples and Comparative Examples described below. The arithmetic mean height (Sa) and maximum height (Sz) of the films were measured, and film rolls using the films were evaluated for winding wrinkles and blocking as described below. The evaluation results are also shown in Table 1 below.

[0107] [Raw materials for PVA-based film] The following two types of PVA-based resins were used as the PVA-based resin (A): (a1): a carboxyl-modified PVA-based resin with a 4% aqueous solution viscosity of 22 mPa·s at 20°C, an average degree of saponification of 94 mol%, and a modification amount with maleic acid monomethyl ester of 2.0 mol%; and (a2): an unmodified PVA with a 4% aqueous solution viscosity of 43 mPa·s at 20°C and an average degree of saponification of 88 mol%. The following two types of plasticizers were used as the plasticizer (B): (b1): glycerin and (b2): sorbitol. Cornstarch (average particle size 20 μm) was used as the filler (C).

[0108] Example 1: 90 parts of PVA-based resin (a1) and 10 parts of PVA-based resin (a2) as PVA-based resin (A), 20 parts of plasticizer (b1) and 20 parts of plasticizer (b2) as plasticizer (B), 8 parts of filler (C), 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 25%. The obtained film-forming raw material was cast onto a metal casting surface, heated to a casting temperature of 85°C, held on the casting surface for 70 seconds, and then peeled from the casting surface (the film had a water content of 15 to 20% at the time of peeling), and further dried to obtain a water-soluble PVA-based film with a thickness of 87 μm and a water content of 9%.

[0109] Examples 2 to 6, Comparative Examples 1 and 2 The same procedures as in Example 1 were carried out except that the film composition, contact time with the casting surface, and casting temperature were changed as shown in Table 1, to obtain water-soluble PVA-based films.

[0110] [Arithmetic Mean Height (Sa), Maximum Height (Sz)] The arithmetic mean height (Sa) and maximum height (Sz) of the PVA-based films obtained in Examples 1 to 6 and Comparative Examples 1 and 2 were measured in accordance with JIS B0681 using a shape analysis laser microscope VK-X-1000 (manufactured by Keyence Corporation) at three arbitrary locations on each of the first and second surfaces of the PVA-based film, and the average values ​​were calculated.

[0111] Furthermore, film rolls were produced using the PVA-based films obtained in Examples 1 to 6 and Comparative Examples 1 and 2, and were evaluated according to the methods described below.

[0112] [Wrinkles during winding] The obtained PVA-based film was slit into a width of 0.5 m and wound up to 500 m around a core tube having an inner diameter of 3 inches to prepare a film roll. The wound state of the PVA-based film was visually observed and evaluated based on the following index. Evaluation criteria ◯ (very good): No wrinkles occurred during winding. Δ (good): Slight wrinkles occurred during winding. × (poor): Many wrinkles occurred during winding.

[0113] [Blocking] The appearance of the film roll produced above was visually observed and evaluated based on the following criteria: Evaluation criteria ◯ (very good): The end faces of the film roll were aligned. △ (good): There were some areas where the end faces of the film roll were slightly misaligned. × (poor): The end faces of the film roll were significantly misaligned.

[0114]

[0115] As described above, Examples 1 to 6, which satisfied the ranges prescribed in the present invention, all received good evaluations for winding wrinkles and blocking. In contrast, Comparative Examples 1 and 2, which did not satisfy the ranges prescribed in the present invention, received poor evaluations for winding wrinkles, and Comparative Example 2 in particular also received poor evaluations for blocking.

[0116] 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.

[0117] The polyvinyl alcohol film of the present invention is useful for various packaging applications, such as unit packaging applications for 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 raising sheets, seed tapes, and embroidery base fabrics. It is particularly suitable for use in unit packaging applications for chemicals such as laundry detergents and dishwashing detergents.

Claims

1. A polyvinyl alcohol-based film containing a polyvinyl alcohol-based resin (A), wherein the difference (|α-β|) between the arithmetic mean height (Sa)α of a first surface of the polyvinyl alcohol-based film and the arithmetic mean height (Sa)β of a second surface of the polyvinyl alcohol-based film is 0.10 μm or less.

2. The polyvinyl alcohol film according to claim 1, wherein the arithmetic mean height (Sa)α of the first surface and the arithmetic mean height (Sa)β of the second surface are both 2 μm or less.

3. A polyvinyl alcohol-based film according to claim 1 or 2, wherein the difference (|γ-δ|) between the maximum height (Sz) γ of the first surface of the polyvinyl alcohol-based film and the maximum height (Sz) δ of the second surface of the polyvinyl alcohol-based film is 3 μm or less.

4. A polyvinyl alcohol film according to claim 1 or 2, wherein the maximum height (Sz) γ of the first surface and the maximum height (Sz) δ of the second surface are both 2 μm or more.

5. The polyvinyl alcohol film according to claim 1 or 2, which contains a filler.

6. The polyvinyl alcohol-based film according to claim 5, wherein the content of the filler is 1 to 30 parts by mass per 100 parts by mass of the polyvinyl alcohol-based resin (A).

7. A polyvinyl alcohol film according to claim 1 or 2, having a moisture content of 3 to 15% by mass.

8. The polyvinyl alcohol film according to claim 1 or 2, which is a water-soluble film.

9. A pharmaceutical package comprising a package formed from the polyvinyl alcohol film according to claim 1 or 2 and a pharmaceutical packaged in said package.

10. The pharmaceutical package of claim 9, wherein the pharmaceutical is a detergent.

11. The pharmaceutical package of claim 10, wherein the detergent is a liquid detergent.

12. A method for producing a polyvinyl alcohol-based film as described in claim 1 or 2, wherein in the process of casting a film-forming raw material containing the polyvinyl alcohol-based resin (A) onto a casting surface to form a polyvinyl alcohol-based film, after the film-forming raw material is cast onto the casting surface, the water content of the polyvinyl alcohol-based film when peeled off from the casting surface is 40 mass% or less.

13. A method for producing a polyvinyl alcohol-based film as described in claim 1 or 2, wherein in the process of casting a film-forming raw material containing the polyvinyl alcohol-based resin (A) onto a casting surface to form a polyvinyl alcohol-based film, the time from casting the film-forming raw material onto the casting surface to peeling the polyvinyl alcohol-based film from the casting surface is 180 seconds or less.

Images