Water-soluble film and pharmaceutical packaging

Abstract

The present invention provides the following as a water-soluble film which is useful in a package which makes it possible to improve breakage resistance upon immersion in water in the case of a package molded by deep drawing, or in other words, prevent a chemical agent from leaking or dissolving too early, when packaging a chemical agent such as a liquid detergent.　A polyvinyl alcohol-based water-soluble film in which a polyvinyl alcohol resin (A) is a main component, wherein said polyvinyl alcohol resin (A) contains a polyvinyl alcohol resin (a1) which is a main component of the component (A) and exhibits a viscosity as a 4 mass% aqueous solution at 20°C of 21 mPa·s or higher, and also contains a polyvinyl alcohol resin (a2) which satisfies formula (α) and formula (β) in its relationship with the component (a1). (α) The viscosity as a 4 mass% aqueous solution at 20°C of the polyvinyl alcohol resin (a2) is greater than the viscosity as a 4 mass% aqueous solution at 20°C of the polyvinyl alcohol resin (a1), and (β) the absolute value of the difference in the average degree of saponification between the polyvinyl alcohol resin (a1) and the polyvinyl alcohol resin (a2) is no more than 5 mol%.

Description

[Technical Field]

[0001] The present invention relates to a water-soluble film and a drug package containing a polyvinyl alcohol resin as a main component, and more specifically to a water-soluble film and a drug package that, when used in packaging drugs such as liquid detergents, improves resistance to bag rupture when immersed in water when the package is deep-drawn, i.e., can prevent early leakage or dissolution of the packaged drug such as liquid detergent. [Background technology]

[0002] Polyvinyl alcohol films are thermoplastic resins that are water-soluble. Taking advantage of the water-solubility of polyvinyl alcohol, they have traditionally been used as water-soluble films, and are used in a wide range of applications, including packaging (unit packaging) for pesticides, detergents, and other chemicals, hydraulic transfer films, sanitary products such as napkins and disposable diapers, waste disposal products such as ostomy bags, medical products such as blood-absorbing sheets, and temporary substrates for seedling raising sheets, seed tape, and embroidery fabrics.

[0003] Among these, unit packaging applications for pesticides, detergents, and other chemicals have the advantage of eliminating the need to measure the amount of chemical each time they are used and not getting your hands dirty, and so unit packaging (individual packaging) applications are expanding, especially for liquid products such as liquid detergents.

[0004] For example, a water-soluble film has been proposed that is useful for individual packaging, not only because it is soluble in water, but also because it has high peel strength at the sealed portion and prevents leakage of liquid even when used to package liquids such as liquid detergents (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 043511 Summary of the Invention [Problem to be solved by the invention]

[0006] Such individual packages usually have one or more compartments and are of various shapes and sizes. In recent years, particularly in the case of individual packages for liquid detergents, packages with compartments of more complex shapes and sizes have been designed from the viewpoints of improving cleaning performance and design, and deep drawing molding has been used to form such individual packages. However, when deep drawing molding is performed using conventional water-soluble films, there is a concern that when the obtained individual package is immersed in water, the time until the bag breaks is short, and chemicals such as liquid detergents may leak out early, which may prevent the cleaning effect from being properly exerted or may cause problems if the individual package is accidentally ingested, and therefore further improvement is required.

[0007] Therefore, in light of this background, the present invention provides a water-soluble film useful for packaging chemicals such as liquid detergents, which has improved resistance to tearing when immersed in water when the package is made by deep drawing, i.e., which can prevent early leakage or dissolution of the packaged chemicals such as liquid detergents, and a chemical package in which various chemicals are packaged in the water-soluble film. [Means for solving the problem]

[0008] In view of these circumstances, the present inventors conducted extensive research into the causes of early breakage (dissolution) of individual packages when immersed in water, and discovered that deep drawing can cause partial overstretching, resulting in thinned portions of the film, and therefore that uniform stretchability of the film is important. Based on this knowledge, the present inventors conducted further research aimed at achieving uniform film elongation even during deep drawing. As a result, they discovered that the compatibility state of the polyvinyl alcohol-based resin in the film and the balance of the polyvinyl alcohol-based resin in the polymer chain are important for the uniform stretchability of the film (in the present invention, mainly meaning reducing localized thinning of the film thickness), and that by incorporating a polyvinyl alcohol-based resin with a high viscosity and a small difference in average saponification degree relative to the polyvinyl alcohol-based resin that serves as the main component in the polyvinyl alcohol-based resin used, uniform film stretchability can be imparted even during deep drawing, resulting in individual packages that have excellent resistance to breakage when immersed in water.

[0009] That is, the gist of the present invention is as follows. <1> A water-soluble polyvinyl alcohol-based film containing a polyvinyl alcohol-based resin (A) as a main component, the polyvinyl alcohol-based resin (A) being a main component of the (A) component, the water-soluble film containing: a polyvinyl alcohol-based resin (a1) having a 4 mass% aqueous solution viscosity at 20°C of 21 mPa·s or more; and a polyvinyl alcohol-based resin (a2) that satisfies the following (α) and (β) in its relationship with the (a1) component: (α) The viscosity of a 4% by mass aqueous solution of the polyvinyl alcohol-based resin (a2) at 20°C is higher than the viscosity of a 4% by mass aqueous solution of the polyvinyl alcohol-based resin (a1) at 20°C. (β) The absolute value of the difference in average saponification degree between the polyvinyl alcohol-based resin (a1) and the polyvinyl alcohol-based resin (a2) is 5 mol% or less <2> The content mass ratio (a1 / a2) of the polyvinyl alcohol-based resin (a1) to the polyvinyl alcohol-based resin (a2) is 99 / 1 to 50 / 50. <1> The water-soluble film described above. <3> The polyvinyl alcohol resin (a1) is a modified polyvinyl alcohol resin. <1> or <2> The water-soluble film described above. <4> The polyvinyl alcohol resin (a2) is unmodified polyvinyl alcohol. <1> ~ <3> 1. The water-soluble film according to any one of the preceding claims. <5> The polyvinyl alcohol resin (a2) has an average saponification degree of 90 to 99.9 mol%. <1> ~ <4> 1. The water-soluble film according to any one of the preceding claims. <6> The filler (C) is contained in an amount of 6 parts by mass or less relative to 100 parts by mass of the polyvinyl alcohol-based resin (A). <1> ~ <5> 1. The water-soluble film according to any one of the preceding claims. <7> <1> ~ <6> 1. A pharmaceutical package comprising a package formed from the water-soluble film according to any one of the preceding items and a pharmaceutical packaged in the package. [Effects of the Invention]

[0010] When the water-soluble film of the present invention is used to package chemicals such as liquid detergents, it can improve the resistance to bag rupture when immersed in water when the package is formed by deep drawing, i.e., it can prevent the chemicals from leaking or dissolving early. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be specifically described below.

[0012] In the present invention, when the expression "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it means "X or more and Y or less," and also includes the meaning of "preferably larger than X" or "preferably smaller than Y." Furthermore, when it is expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y."

[0013] In addition, in the present invention, polyvinyl alcohol may be abbreviated as "PVA," a film having a polyvinyl alcohol-based resin as its main component may be abbreviated as "PVA-based film," and a water-soluble film having a polyvinyl alcohol-based resin as its main component may be abbreviated as "PVA-based water-soluble film."

[0014] The water-soluble film of the present invention is a PVA film containing a PVA resin (A) as a main component. Here, "containing PVA resin (A) as the main component" means that the PVA 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 water-soluble 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, from the viewpoint of shape stability over time when used as a liquid detergent package.

[0015] Here, the term "water-soluble film" refers to a film that dissolves in water at room temperature (20°C). In the present invention, the solubility of the film can be evaluated as follows. The PVA film was cut into pieces measuring 3 cm x 5 cm, placed in a 1-liter beaker containing 1 liter of water, and secured with a jig. The water was kept at a temperature of 20°C and stirred with a stirrer (rotor length 3 cm, rotation speed 750 rpm). The film was deemed dissolved when no insoluble particles with a diameter of 1 mm or more were visible.

[0016] [PVA resin (A)] First, the PVA resin (A) used in the present invention will be described. The PVA resin (A) used in the present invention is selected from unmodified PVA and modified PVA resins and contains two or more PVA resins that differ in at least one of the average saponification degree, viscosity, modified species, and modification amount. The PVA resin (A) contains a first PVA resin (a1) that is the main component of the PVA resin (A) and a second PVA resin (a2) that satisfies the following conditions (α) and (β) in relation to the first PVA resin (a1): (α) The viscosity of a 4% by mass aqueous solution of the PVA resin (a2) at 20°C is higher than the viscosity of a 4% by mass aqueous solution of the PVA resin (a1) at 20°C. (β) The absolute value of the difference in average saponification degree between the PVA resin (a1) and the PVA resin (a2) is 5 mol % or less.

[0017] Here, the PVA resin (a1) that is the main component of the PVA resin (A) refers to the PVA resin with the highest content (mass%) in the PVA resin (A). When two or more PVA resins with the same highest content are present, if any of the PVA resins is defined as the PVA resin (a1) that is the main component of the PVA resin (A), the other PVA resins that satisfy the relationship between (α) and (β) are defined as PVA resin (a2), and the other PVA resins that do not satisfy the relationship between (α) and (β) are defined as PVA resin (a3). In other words, when any of the PVA resins is defined as the PVA resin (a1), the PVA resin (a2) that satisfies the viscosity and degree of saponification requirements for the PVA resin (a1) falls within the scope of the present invention. In this case, even when the other PVA-based resin is designated as (a1), there may be another PVA-based resin (a2) that satisfies the relationship between (α) and (β) (if such a PVA-based resin exists, it will be designated as (a2)), and one that does not satisfy the relationship between (α) and (β) will be designated as PVA-based resin (a3).

[0018] The PVA resin (a2) may be any PVA resin that satisfies the above-mentioned specific viscosity and degree of saponification (α) and (β) in relation to the PVA resin (a1), and the PVA resin (a2) may be used alone or in combination of two or more. That is, when the PVA resin (A) contains three or more PVA resins, the PVA resin (a2) may contain only one or two or more, and when two or more are contained, each of them may satisfy the viscosity and degree of saponification requirements relative to the PVA resin (a1).

[0019] In the present invention, the PVA resin (A) may contain a PVA resin (a3) ​​other than the PVA resin (a1) and the PVA resin (a2). The PVA resin (a3) ​​is selected from unmodified PVA and modified PVA resins, and is different from the PVA resins (a1) and (a2) in at least one of the average saponification degree, viscosity, modified species, and modification amount. The PVA resin (a3) ​​may be used alone or in combination of two or more kinds.

[0020] In the present invention, from the viewpoint of uniform stretchability of the film, it is necessary that the viscosity of a 4 mass% aqueous solution of the PVA-based resin (a2) at 20°C is higher than the viscosity of a 4 mass% aqueous solution of the PVA-based resin (a1) at 20°C. The difference between the viscosity of a 4 mass% aqueous solution of the PVA-based resin (a2) at 20°C and the viscosity of a 4 mass% aqueous solution of the PVA-based resin (a1) at 20°C is preferably 0.1 mPa·s or more, more preferably 0.5 mPa·s or more, 1 mPa·s or more, 1.5 mPa·s or more, 2 mPa·s or more, 3 mPa·s or more, 5 mPa·s or more, or 10 mPa·s or more. The upper limit of the viscosity difference is preferably 45 mPa·s or less, more preferably 40 mPa·s or less, or 35 mPa·s or less. If the difference in viscosity of a 4% by mass aqueous solution at 20° C. is too small, the effects of the present invention tend to be difficult to achieve, whereas if it is too large, film formability tends to decrease in the film production process.

[0021] In the present invention, it is important that the absolute value of the difference in average saponification degree between the PVA resin (a1) and the PVA resin (a2) is 5 mol % or less, preferably 4.5 mol % or less, particularly preferably 4 mol % or less. By reducing the absolute value of this difference in average saponification degree, the compatibility of the PVA-based resin is improved, improving the uniform stretchability of the film, and ultimately preventing early leakage or dissolution of the drug when immersed in water when used as a drug package.

[0022] The average degree of saponification is measured in accordance with JIS K 6726 3.5, and the viscosity of a 4 mass % aqueous solution is measured in accordance with JIS K 6726 3.11.2.

[0023] The PVA resin (a1) used in the present invention preferably has an average saponification degree of 80 mol% or more, particularly preferably 82 to 99.9 mol%, further preferably 85 to 99 mol%, and particularly preferably 86 to 98 mol%. If the average saponification degree is too low, the solubility of the PVA film in water tends to decrease. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0024] The viscosity of a 4% by mass aqueous solution of the PVA resin (a1) at 20° C. is 21 mPa·s or more, preferably 21 to 50 mPa·s, particularly preferably 21.5 to 45 mPa·s, and even more preferably 22 to 40 mPa·s. If the viscosity is too low, the mechanical strength of the film as a packaging material tends to decrease, while if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to be high, reducing productivity.

[0025] The PVA resin (a2) used in the present invention preferably has an average saponification degree of 80 mol% or more, particularly preferably 83 to 99.9 mol%, further preferably 85 to 99 mol%, and particularly preferably 86 to 98 mol%. If the average saponification degree is too low, the solubility of the PVA film in water tends to decrease. Also, the uniform stretchability of the film tends to decrease. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0026] From the viewpoint of improving the mechanical properties of the film and the solubility of the film during deep drawing, it is also preferred that the average saponification degree of the PVA resin (a2) is equal to or greater than the average saponification degree of the PVA resin (a1), and further that the average saponification degree of the PVA resin (a2) is larger than the average saponification degree of the PVA resin (a1).

[0027] The viscosity of a 4% by mass aqueous solution of the PVA resin (a2) at 20°C is greater than 21 mPa·s, preferably 21.5 to 60 mPa·s, and particularly preferably 25 to 55 mPa·s. If the viscosity is too low, the uniform stretchability of the film tends to decrease. On the other hand, if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to be high, which tends to decrease productivity.

[0028] The mass ratio of the PVA-based resin (a1) to the PVA-based resin (a2) (PVA-based resin (a1) / PVA-based resin (a2)) is preferably 99 / 1 to 50 / 50, particularly preferably 99 / 1 to 51 / 49, further preferably 95 / 5 to 55 / 45, and particularly preferably 94 / 6 to 60 / 40. If the content is too small, uniform stretchability tends to be difficult to obtain, whereas if it is too large, film-forming properties tend to deteriorate, resulting in a decrease in productivity.

[0029] The content of the PVA resin (a2) in the PVA resin (A) is preferably 1 to 50% by mass, particularly preferably 3 to 40% by mass, and further preferably 5 to 30% by mass. If the content is too small, uniform stretchability tends to be difficult to obtain, whereas if it is too large, film-forming properties tend to deteriorate, resulting in a decrease in productivity.

[0030] The content of the PVA resin (a3) ​​in the PVA resin (A) is preferably 49% by mass or less, particularly preferably 5% by mass or less, with the lower limit usually being 0% by mass. If the content is too high, it tends to be difficult to achieve the effects of the present invention.

[0031] The PVA resin (a1) and the PVA resin (a2) used in the present invention are selected from unmodified PVA and modified PVA resins.

[0032] The unmodified PVA is a resin mainly composed of vinyl alcohol structural units, which can be produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester compound, and is composed of vinyl alcohol structural units corresponding to the degree of saponification and vinyl ester structural units remaining unsaponified.

[0033] 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 above vinyl ester compounds may be used alone or in combination of two or more.

[0034] 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. The modified PVA resin is a resin obtained by introducing a modifying group by copolymerization or post-reaction into a resin mainly composed of vinyl alcohol structural units obtained by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester compound, and is composed of vinyl alcohol structural units corresponding to the degree of saponification, vinyl ester structural units remaining without saponification, and unsaturated monomer structural units obtained by copolymerization or structural units obtained by post-reaction.

[0035] Examples of unsaturated monomers copolymerizable with the vinyl ester compounds include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl-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, 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 methallyl sulfonic acid, or their salts. These can be used alone or in combination of two or more.

[0036] The modified PVA resin may have primary hydroxyl groups in the side chain. For example, the number of primary hydroxyl groups in the side chain is typically 1 to 5, preferably 1 to 2, and particularly preferably 1. Furthermore, it is preferable that the modified PVA resin has a secondary hydroxyl group in addition to the primary hydroxyl group. Examples of such modified PVA resins include PVA resins having hydroxyalkyl groups in the side chain and PVA resins having 1,2-diol structural units in the side chain. PVA resins having 1,2-diol structural units in the side chain can be produced, for example, by (1) saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (2) saponifying and decarboxylating a copolymer of vinyl acetate and vinyl ethylene carbonate, (3) saponifying and deketalizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane, or (4) saponifying a copolymer of vinyl acetate and glycerin monoallyl ether.

[0037] In terms of solubility, the modified PVA resin used in the present invention is preferably an anionic group-modified PVA resin. Examples of the anionic group include a carboxy group, a sulfonic acid group, and a phosphate group. In terms of chemical resistance and stability over time, the carboxy group and the sulfonic acid group are preferred, and the carboxy group is particularly preferred.

[0038] When a carboxyl group-modified PVA resin is used in the present invention, maleic acid-modified PVA resin or itaconic acid-modified PVA resin is preferred in terms of ease of handling, high polymerizability with vinyl ester monomers, and excellent productivity, and maleic acid-modified PVA resin is particularly preferred in terms of the stability over time of the solubility of the film when a drug is packaged (particularly, the fact that it is less susceptible to the pH of the drug).Furthermore, acrylic acid-modified PVA resin is preferred in terms of the mechanical properties of the film.

[0039] The unmodified PVA and modified PVA-based resins can be obtained using production methods known in the art, such as those described in WO 2017 / 043511.

[0040] The average saponification degree of the unmodified PVA used in the present invention is preferably 80 mol% or more, particularly preferably 80 to 99.9 mol%, further preferably 82 to 99 mol%, and particularly preferably 85 to 98 mol%. If the average saponification degree is too low, the solubility of the PVA film in water tends to decrease. However, if the average saponification degree is too high, the solubility in water tends to decrease.

[0041] The viscosity of a 4% by mass aqueous solution of the unmodified PVA used in the present invention at 20° C. is preferably 8 to 60 mPa s, and particularly preferably 10 to 60 mPa s. If the viscosity is too low, the mechanical strength of the PVA film used as a packaging material tends to decrease, while if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to increase, reducing productivity.

[0042] The average saponification degree of the modified PVA resin used in the present invention is preferably 80 mol% or more, particularly preferably 85 to 99.9 mol%, further preferably 90 to 99 mol%, and particularly preferably 92 to 99 mol%. If the average saponification degree is too low, the solubility of the 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 of the film in water tends to decrease significantly.

[0043] The viscosity of a 4% by mass aqueous solution of the modified PVA resin used in the present invention at 20° C. is preferably 8 to 50 mPa·s, particularly preferably 15 to 45 mPa·s, and even more preferably 20 to 40 mPa·s. If the viscosity is too low, the mechanical strength of the PVA film used as a packaging material tends to decrease, while if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to be high, resulting in reduced productivity.

[0044] The modification amount of the modified PVA resin used in the present invention is preferably 1 to 20 mol%, more preferably 1.5 to 15 mol%, particularly preferably 2 to 12 mol%, and especially preferably 2 to 6 mol%. If the modification amount is too small, the solubility of the PVA film in water tends to decrease, while if it is too large, the productivity of the PVA resin tends to decrease, biodegradability tends to decrease, and the film tends to be prone to blocking.

[0045] In the present invention, from the viewpoint of solubility, it is preferred that at least one of the PVA resins (A) is a modified PVA resin. It is particularly preferred that the PVA resin (a1) is a modified PVA resin, and among these, from the viewpoint of the stability of the solubility of the film over time, it is preferred that it is an anionic group-modified PVA resin, and more preferably a carboxy group-modified PVA resin.

[0046] In the present invention, from the viewpoints of mechanical properties and water-sealing property as well as uniform stretchability of the film, it is preferred that at least one of the PVA resins (A) is unmodified PVA, and it is particularly preferred that the PVA resin (a2) is unmodified PVA.

[0047] Here, as specific embodiments of the present invention, for example, it is preferable that (1) both the PVA-based resin (a1) and the PVA-based resin (a2) are modified PVA-based resins, (2) the PVA-based resin (a1) is a modified PVA-based resin and the PVA-based resin (a2) is an unmodified PVA, or (3) both the PVA-based resin (a1) and the PVA-based resin (a2) are unmodified PVA. From the viewpoint of the stability of solubility over time, the above (1) and (2) are preferable, and the above (2) is particularly preferable.

[0048] In the above (1) and (2), that is, when the PVA-based resin (a1) is a modified PVA-based resin, the average saponification degree is preferably 85 mol% or more, particularly preferably 90 to 99.9 mol%, further preferably 92 to 99.5 mol%, and particularly preferably 93 to 99 mol%. If the average saponification degree is too low, the solubility of the PVA-based film in water tends to decrease, and the solubility of the film 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. The viscosity of a 4% by mass aqueous solution of the PVA resin (a1) at 20° C. is preferably 21 to 50 mPa·s, particularly preferably 21.5 to 45 mPa·s, and even more preferably 22 to 40 mPa·s. If the viscosity is too low, the mechanical strength of the film as a packaging material tends to decrease, while if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to increase, reducing productivity. Furthermore, the PVA resin (a1) is preferably an anionic group-modified PVA, particularly a carboxy group-modified PVA, and even more preferably a maleic acid-modified PVA. The modification amount is preferably 1 to 15 mol%, more preferably 1.5 to 12 mol%, particularly preferably 2 to 6 mol%, and especially preferably 2 to 4 mol%. If the modification amount is too small, the solubility of the film in water tends to decrease, while if it is too large, the productivity of the PVA resin tends to decrease, biodegradability tends to decrease, and the film tends to be prone to blocking.

[0049] In the above (1), the modified PVA of the PVA resin (a2) can be a modified PVA resin that satisfies the relationship between viscosity and degree of saponification specified in the present invention for the modified PVA resin of (a1). The PVA resin (a2) is preferably an anionic group-modified PVA, particularly a carboxy group-modified PVA, and more preferably a maleic acid-modified PVA.

[0050] Furthermore, in the above (2), that is, when the PVA-based resin (a2) is unmodified PVA, the average saponification degree is preferably 85 mol% or more, particularly preferably 87 to 99.9 mol%, and from the viewpoint of improving the solubility of the film during deep drawing, it is even more preferably 90 to 99.5 mol%, particularly preferably 92 to 99 mol%, and more preferably 93 to 98 mol%. If the average saponification degree is too low, the solubility of the PVA-based film in water tends to decrease. Also, the uniform stretchability of the film tends to decrease. However, if the average saponification degree is too high, the solubility in water tends to decrease. The viscosity of a 4% by mass aqueous solution of the PVA resin (a2) at 20°C is greater than 21 mPa·s, preferably 21.5 to 60 mPa·s, particularly preferably 22 to 55 mPa·s, further preferably 23 to 50 mPa·s, and particularly preferably 25 to 45 mPa·s. If the viscosity is too low, the uniform stretchability of the film tends to decrease. On the other hand, if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to increase, reducing productivity.

[0051] In the above (2), the mass ratio of the PVA resin (a1) to the PVA resin (a2) (PVA resin (a1) / PVA resin (a2)) is preferably 98 / 2 to 55 / 45, particularly preferably 95 / 5 to 60 / 40, further preferably 94 / 6 to 70 / 30, and particularly preferably 93 / 7 to 80 / 20, from the viewpoint of the balance between the uniform stretchability of the film and the film properties such as solubility in water and water sealability. If the content of the PVA-based resin (a2) is too low, it is difficult to obtain the effect of uniform stretchability, and the water-sealing property tends to decrease. If the content of the PVA-based resin (a1) is too low, the solubility tends to decrease over time.

[0052] In the above (3), that is, when the PVA resin (a1) is unmodified PVA, the average saponification degree is preferably 80 to 98 mol%, particularly preferably 82 to 95 mol%, further preferably 85 to 93 mol%, and particularly preferably 86 to 90 mol%, from the viewpoints of the solubility and mechanical properties of the film. If the average saponification degree is too low or too high, the solubility in water tends to decrease.

[0053] In the above (3), the unmodified PVA of the PVA-based resin (a2) can be an unmodified PVA that satisfies the relationship between viscosity and degree of saponification specified in the present invention relative to the unmodified PVA of the above (a1).

[0054] The average saponification degree of the PVA resin (A) of the present invention is preferably 85 mol% or more, particularly preferably 86 to 99.9 mol%, further preferably 88 to 99.5 mol%, particularly preferably 90 to 99.0 mol%, more preferably 92 to 98.5 mol%, and more preferably 93 to 98 mol%. If the average saponification degree is too low, the solubility of the PVA film in water tends to decrease, or the solubility of the film 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.

[0055] The viscosity of a 4% by mass aqueous solution of the PVA resin (A) used in the present invention at 20°C is preferably 10 to 60 mPa·s, particularly preferably 15 to 55 mPa·s, even more preferably 20 to 50 mPa·s, particularly preferably 21 to 45 mPa·s, and even more preferably 22 to 40 mPa·s. If the viscosity is too low, the mechanical strength of the PVA film used as a packaging material tends to decrease, while if the viscosity is too high, the viscosity of the aqueous solution during film formation tends to increase, reducing productivity.

[0056] The PVA resin (A) used in the present invention preferably has a modification amount of 0.5 to 20 mol%, particularly preferably 1 to 15 mol%, further preferably 1.5 to 12 mol%, and particularly preferably 1.5 to 6 mol%. If the modification amount is too small, the solubility in water tends to decrease, while if it is too large, the productivity of the PVA resin tends to decrease, biodegradability tends to decrease, and the PVA film tends to be prone to blocking.

[0057] [Plasticizer (B)] In the present invention, it is preferable to add a plasticizer (B) to the PVA resin (A) in order to impart flexibility to the film when used as a package. The plasticizer (B) can be used alone or in combination of two or more, but it is preferable to use at least two types in combination in order to provide a strong film when used as a package, to enable sealing at low temperatures, and to achieve high strength in the sealed portion.

[0058] One of the plasticizers (B) is a polyhydric alcohol (b1) (hereinafter sometimes abbreviated as "plasticizer (b1)") having a melting point of 80°C or higher, and the other is a polyhydric alcohol (b2) (hereinafter sometimes abbreviated as "plasticizer (b2)") having a melting point of 50°C or lower, which is preferable in terms of toughness during the production of the water-soluble film and the packaging, shape stability over time when made into a packaging for liquid detergent, sealability, etc.

[0059] As the polyhydric alcohol (b1) having a melting point of 80°C or higher, 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 (8 Examples of suitable alcohols include tetrahydric alcohols such as xylitol (92°C), arabitol (103°C), fucitol (153°C), glucose (146°C), and fructose (104°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 numbers in parentheses indicate melting points. Among the above, from the viewpoint of the tensile strength of the water-soluble film, those having a melting point of 85°C or higher are preferred, and those having a melting point of 90°C or higher are particularly preferred. The upper limit of the melting point is preferably 300°C, and particularly preferably 200°C.

[0060] Furthermore, among the plasticizers (b1), those having 4 or more hydroxyl groups in one molecule are preferred in terms of compatibility with the PVA resin (A), with 5 to 10 being particularly preferred, and 6 to 8 being even more preferred. Specific examples of suitable plasticizers include sorbitol, sucrose, and trehalose.

[0061] Furthermore, from the viewpoint of the toughness of the water-soluble film, the plasticizer (b1) preferably has a molecular weight of 150 or more, particularly preferably 160 to 500, and even more preferably 180 to 400. Specific examples of suitable plasticizers include sorbitol and sucrose.

[0062] On the other hand, examples of polyhydric alcohols (b2) having a melting point of 50°C or less include aliphatic alcohols, such as dihydric alcohols such as 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 polyethylene glycols having 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 parentheses indicate the melting point. Among the above, 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, in terms of the flexibility of the water-soluble film. The lower limit of the melting point is usually -80°C, preferably -10°C, and particularly preferably 0°C.

[0063] Furthermore, among the plasticizers (b2), those having four or less hydroxyl groups in one molecule are preferred, and those having three or less hydroxyl groups in particular are preferred, as this makes it easier to control flexibility at around room temperature (25°C). Specifically, for example, glycerin is suitable.

[0064] Furthermore, the plasticizer (b2) preferably has a molecular weight of 100 or less, particularly preferably 50 to 100, and even more preferably 60 to 95, in order to make it easier to control flexibility. Specifically, for example, glycerin is suitable.

[0065] Plasticizers (b3) other than the above-mentioned plasticizers (b1) and (b2) can be used in combination, and examples of such plasticizers (b3) include alcohols such as trimethylolpropane (58°C), diethylene glycol monomethyl ether, cyclohexanol, carbitol, and polypropylene glycol, ethers such as dibutyl ether, carboxylic acids such as stearic acid, oleic acid, linoleic acid, linolenic acid, sorbic acid, citric acid, and adipic acid, ketones such as cyclohexanone, amines such as monoethanolamine, triethanolamine, ethylenediamine, and imidazole compounds, and amino acids such as alanine, glycine, aspartic acid, glutamic acid, histidine, lysine, and cysteine. These can be used alone or in combination of two or more.

[0066] The content of the plasticizer (B) is preferably 20 parts by mass or more, particularly preferably 25 to 70 parts by mass, even more preferably 30 to 60 parts by mass, and especially preferably 35 to 50 parts by mass, per 100 parts by mass of the PVA resin (A). If the content of the plasticizer (B) is too low, the toughness of the water-soluble film tends to be impaired over time when used to package a liquid such as a liquid detergent. However, if the content is too high, the mechanical strength tends to decrease.

[0067] Furthermore, the mass ratio (b1 / b2) of the plasticizer (b1) to the plasticizer (b2) is preferably 0.1 to 5, particularly preferably 0.2 to 4.5, even more preferably 0.3 to 4, especially preferably 0.4 to 3.5, more preferably 0.5 to 3, and even more preferably 0.7 to 2. If the mass ratio is too small, the water-soluble film tends to be too soft and prone to blocking, whereas if it is too large, the water-soluble film tends to be too hard and prone to brittleness in low-humidity environments. Furthermore, when used as a package for a liquid detergent, the shape stability over time tends to decrease.

[0068] The content of the plasticizer (b1) and the plasticizer (b2) is preferably 5 to 40 parts by mass, particularly preferably 8 to 30 parts by mass, and even more preferably 10 to 25 parts by mass, of the plasticizer (b1) relative to 100 parts by mass of the PVA resin (A), and is preferably 5 to 40 parts by mass, particularly preferably 10 to 35 parts by mass, and even more preferably 15 to 30 parts by mass of the plasticizer (b2). If the amount of plasticizer (b1) is too small, the water-soluble film tends to become too hard, and the shape stability over time when used as a package for a liquid detergent tends to decrease. If the amount is too large, the water-soluble film tends to become too soft. If the amount of plasticizer (b2) is too small, the water-soluble film tends to become too hard and brittle in a low-humidity environment, and if the amount is too large, the water-soluble film tends to become too soft and prone to blocking.

[0069] Furthermore, the total amount of plasticizer (b1) and plasticizer (b2) relative to the total amount of plasticizer (B) is preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 87% by mass or more, even more preferably 90% by mass or more, and especially preferably 95% by mass or more, and most preferably the entire plasticizer (B) consists solely of plasticizer (b1) and plasticizer (b2). If the total amount of plasticizer (b1) and plasticizer (b2) is too small, the mechanical strength tends to decrease. Furthermore, when used as a package for liquid detergent, the shape stability over time tends to decrease.

[0070] [Filler (C)] In the present invention, a filler (C) may further be contained, if necessary.

[0071] The filler (C) is contained for the purpose of blocking resistance, and includes organic fillers (c1) and inorganic fillers (c2), which can be used alone or in combination of two or more. Of these, organic fillers (c1) are preferably used. The average particle size of the filler (C) is preferably 0.1 to 50 μm, and 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 volume) of the obtained cumulative volume distribution.

[0072] The organic filler (c1) refers to particulate matter (primary particles) composed of organic 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). Such organic filler (c1) is mainly selected from polymer compounds, and examples thereof include melamine-based resins, polymethyl (meth)acrylate-based resins, polystyrene-based resins, as well as biodegradable resins such as starch and polylactic acid. Among these, biodegradable resins such as polymethyl (meth)acrylate-based resins, polystyrene-based resins, and starch are preferred, and starch is particularly preferred from the viewpoint of dispersibility in the PVA-based resin (A).

[0073] Examples of the starch include raw starches (corn starch, potato starch, sweet potato starch, wheat starch, ossava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, kudzu starch, bracken starch, lotus starch, water chestnut starch, etc.), physically modified starches (α-starch, fractionated amylose, moist heat-treated starch, etc.), enzyme-modified starches (hydrolyzed dextrin, enzymatically decomposed dextrin, amylose, etc.), chemically decomposed modified starches (acid-treated starch, hypochlorite-oxidized starch, dialdehyde starch, etc.), and chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, cross-linked starch, etc.). Of these, raw starches, particularly corn starch and rice starch, are preferably used from the standpoints of availability and economy.

[0074] The average particle size of the organic filler (c1) is preferably 5 to 50 μm, particularly preferably 10 to 40 μm, and further preferably 15 to 35 μm. If the average particle size is too small, the blocking property of the PVA film tends to increase, while if it is too large, the fillers tend to aggregate with each other, reducing dispersibility and causing pinholes when the film is stretched during molding.

[0075] The inorganic filler (c2) 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 (c2) 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.

[0076] Among these, it is preferable to use an oxide-based inorganic compound or talc, since it has excellent hydrogen bonding activity with the PVA-based resin (A) and improves water sealing properties. In particular, it is preferable to use titanium oxide, talc, or silica, and it is even more preferable to use silica.

[0077] The inorganic filler (c2) preferably has an average particle size of 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 PVA 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.

[0078] The content of the filler (C) is preferably 1 to 30 parts by mass, particularly preferably 1.5 to 25 parts by mass, and further preferably 2 to 20 parts by mass, per 100 parts by mass of the PVA resin (A). If the content is too low, the blocking property of the PVA film tends to increase, while if it is too high, the flexibility and toughness of the PVA film tend to decrease. Furthermore, from the viewpoint of resistance to bag rupture when immersed in water when a package is formed by deep drawing molding, the amount is preferably 6 parts by mass or less per 100 parts by mass of the PVA-based resin (A), and more preferably 5.5 parts by mass or less, 5.0 parts by mass or less, 4.5 parts by mass or less, 4.0 parts by mass or less, 3.5 parts by mass or less, 3.0 parts by mass or less, 2.5 parts by mass or less, 2.0 parts by mass or less, 1.5 parts by mass or less, 1.0 parts by mass or less, or 0.5 parts by mass or less, while the lower limit is 0 part by mass, and more preferably 0.01 parts by mass or more, 0.05 parts by mass or more, or 0.1 parts by mass or more.

[0079] [Surfactant (D)] In the present invention, if necessary, a surfactant (D) and the like may further be contained. The surfactant (D) used in the present invention is incorporated for the purpose of improving releasability from the cast surface during production of the PVA-based film, and typically includes nonionic surfactants, cationic surfactants, and anionic surfactants. 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 ether, and polyoxyethylene stearyl amino ether. These can 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. The surfactant (D) may be used alone or in combination of two or more kinds.

[0080] The content of the surfactant (D) is preferably 0.01 to 3 parts by mass, particularly preferably 0.05 to 2.5 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the modified PVA resin (A). If the content is too low, the peelability between the casting surface of the film-forming device and the formed PVA film tends to decrease, resulting in a decrease in productivity, while if the content is too high, problems such as a decrease in adhesive strength during sealing when the PVA film is used as a package tend to occur.

[0081] In addition, within a range that does not inhibit the object of the invention (for example, 5% by mass or less), other water-soluble polymers other than the PVA-based resin (A) (for example, sodium polyacrylate, polyethylene oxide, polyvinyl pyrrolidone, dextrin, chitosan, chitin, methyl cellulose, hydroxyethyl cellulose, etc.), fragrances, rust inhibitors, colorants, extenders, defoamers, ultraviolet absorbers, liquid paraffins, fluorescent brighteners, bitter components (for example, sodium benzoate, etc.), etc. can also be contained. These can be used alone or in combination of two or more.

[0082] In addition, in the present invention, it is preferable to blend an antioxidant in terms of suppressing yellowing. Examples of such antioxidants include sulfites such as sodium sulfite, potassium sulfite, calcium sulfite, ammonium sulfite, tartaric acid, ascorbic acid, sodium thiosulfate, techol, Rongalit, etc. Among them, sulfites, particularly sodium sulfite, are preferable. The blending amount of such an antioxidant is preferably 0.1 to 10 parts by mass, particularly preferably 0.2 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the modified PVA-based resin (A).

[0083] <Production of PVA-based water-soluble film> In the present invention, as described above, a PVA-based resin composition containing the PVA-based resin (A), preferably further a plasticizer (B), and optionally further a filler (C), a surfactant (D), etc. is obtained, and such a PVA-based resin composition is produced in the order of [I] dissolution step, [II] film-forming step, [III] winding step to obtain a PVA-based water-soluble film.

[0084] 〔[I] Dissolution step〕 In the dissolution step, the above PVA-based resin composition is dissolved or dispersed in water to prepare an aqueous solution or a water dispersion as a film-forming raw material. As the dissolution method when dissolving the above PVA-based resin composition in water, usually, normal temperature dissolution, high temperature dissolution, pressure dissolution, etc. are adopted. Among them, high temperature dissolution and pressure dissolution are preferable from the viewpoints of having less undissolved matter and excellent productivity. The dissolution temperature is usually 80 to 100°C, preferably 90 to 95°C in the case of high-temperature dissolution, and usually 80 to 130°C, preferably 90 to 120°C in the case of pressure dissolution. The dissolution time may be adjusted appropriately depending on the dissolution temperature and pressure during dissolution, but is usually 1 to 20 hours, preferably 2 to 15 hours, and particularly preferably 3 to 10 hours. If the dissolution time is too short, undissolved materials tend to remain, while if it is too long, productivity tends to decrease.

[0085] In the dissolving step, examples of stirring blades include paddle, full zone, max blend, twin star, anchor, ribbon, and propeller. Furthermore, after dissolution, the resulting PVA resin aqueous solution is subjected to a degassing treatment. Examples of such a degassing method include static degassing, vacuum degassing, twin-screw extrusion degassing, etc. Among these, static degassing and twin-screw extrusion degassing are preferred. The temperature for static defoaming is usually 50 to 100°C, preferably 70 to 95°C, and the defoaming time is usually 2 to 30 hours, preferably 5 to 20 hours.

[0086] The solids concentration of the film-forming raw material is preferably 10 to 60% by mass, particularly preferably 12 to 50% by mass, and further preferably 15 to 40% by mass. If the concentration is too low, film productivity tends to decrease, while if it 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.

[0087] [[II] Film forming process] In the film-forming process, the film-forming raw materials prepared in the dissolving process are formed into a film, and if necessary, dried to prepare a PVA-based water-soluble film with a water content of less than 15% by mass. For film formation, methods such as melt extrusion and casting can be used, with the casting method being preferred in terms of precision of film thickness. In the casting method, for example, the above-mentioned film-forming raw material is extruded from a slit such as a T-slit die, cast onto a casting surface such as an endless belt or the metal surface of a drum roll, and dried to produce a PVA-based water-soluble film.

[0088] The temperature of the film-forming raw material at the film-forming raw material discharge section of a T-slit die or the like is preferably 60 to 98° C., particularly preferably 70 to 95° C. If the temperature is too low, the viscosity of the film-forming raw material increases, which tends to reduce the productivity of the PVA-based water-soluble film, while if the temperature is too high, foaming and the like tend to occur. After casting, the film-forming raw material is dried on the casting surface. Drying is usually carried out by heating the casting surface, such as the metal surface of an endless belt or drum roll. The surface temperature of the casting surface is preferably 50 to 150°C, and particularly preferably 60 to 140°C. If the surface temperature is too low, the film tends to have a high moisture content due to insufficient drying, which can lead to blocking. If the surface temperature is too high, the film-forming raw material tends to foam, resulting in poor film formation. In addition, drying during film formation can be performed using a heated roll, drying by blowing hot air onto the film using a floating dryer, drying by a far-infrared device, a dielectric heating device, or the like.

[0089] After drying the film-forming raw material to a moisture content of less than 25% by mass in the above drying process, the PVA-based water-soluble film is obtained by peeling it off from the casting surface (or from the drying heat roll if further drying with a heat roll is performed after peeling it off from the casting surface). The PVA-based water-soluble film peeled off from the casting surface (or the drying heat roll) is conveyed while being cooled in an environment of 10 to 35°C.

[0090] In order to prevent the film from curling, it is also preferable to carry out a heat treatment after the film-forming step [II]. The heat treatment can usually be carried out using a heated roll, but other methods include a heat treatment in which hot air is blown onto the film using a floating dryer, a heat treatment using a far-infrared device, a dielectric heating device, etc. In the present invention, the use of a heated roll is preferred from the viewpoint of productivity. Note that multiple heated rolls can also be used.

[0091] [[III] Winding process] In the winding process, the PVA-based water-soluble film peeled off from the cast surface in the film-forming process is transported and wound up around a core tube (S1) to prepare a film roll. The obtained film roll can be supplied as a product as it is, but it can also be rewound onto a core tube (S2) having a length that corresponds to the width of the desired size of PVA-based water-soluble film and supplied as a film roll of the desired size.

[0092] In this manner, the PVA-based water-soluble film of the present invention can be produced. The manufacturing process of the PVA-based water-soluble film is preferably carried out in an environment of, for example, 10 to 35° C., particularly preferably 15 to 30° C. The humidity is usually 70% RH or less, with the lower limit being 0% RH.

[0093] The thickness of the PVA-based 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.

[0094] The width of the PVA-based 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, production efficiency tends to decrease, while if it is too wide, it tends to become difficult to control slack and film thickness.

[0095] The length of the PVA-based 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, switching between films tends to be time-consuming, while if it is too long, tight winding tends to result in poor appearance and excessive weight.

[0096] The surface of the PVA-based 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. In such uneven processing, the processing temperature is usually 60 to 150° C., preferably 80 to 140° C. The processing pressure is usually 2 to 8 MPa, preferably 3 to 7 MPa. The processing time, although it depends on the processing pressure and film formation speed, is usually 0.01 to 5 seconds, preferably 0.1 to 3 seconds. If necessary, after the unevenness processing, a cooling treatment may be carried out to prevent unintended stretching of the film due to heat.

[0097] The water content of the resulting PVA-based 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, in terms 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, while if the water content is too high, blocking tends to occur. Adjusting the water content to this range can be achieved by appropriately setting the 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.

[0098] The PVA-based water-soluble film thus obtained has excellent shape stability during long-term storage and impact resistance at low temperatures, making it useful for a variety of packaging applications, including unit packaging for pesticides, detergents, and other chemicals, (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 base materials for seedling raising sheets, seed tape, and embroidery fabrics. In particular, it can be suitably used for unit packaging of medicines such as laundry detergents and dishwashing detergents.

[0099] <Medicine packaging> The pharmaceutical package according to one embodiment of the present invention is a package in which a pharmaceutical is encapsulated in the obtained PVA-based water-soluble film. Because the pharmaceutical is packaged in the water-soluble film, the entire package can be placed in water, and after the water-soluble film dissolves, the pharmaceutical dissolves or disperses in the water, thereby exerting its effects. Therefore, the pharmaceutical package is suitable for packaging a relatively small amount of pharmaceutical, such as a single dose.

[0100] Examples of the chemicals to be encapsulated include agricultural chemicals such as insecticides, fungicides, and herbicides, fertilizers, detergents, etc., with detergents such as laundry detergents and dishwashing detergents being particularly preferred. The chemicals may be in the form of liquid or solid, and in the case of liquids, they may be in the form of liquids, and in the case of solids, they may be in the form of granules, tablets, powders, etc. The chemicals to be used by dissolving or dispersing them in water are preferred, and in the present invention, it is particularly preferred to encapsulate liquid detergents. The pH of the chemicals may be alkaline, neutral, or acidic.

[0101] The liquid detergent preferably has a pH value of 6 to 12 when dissolved or dispersed in water, particularly preferably 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, which prevents the water-soluble film from gelling or becoming insoluble and ensures excellent water solubility. The pH value is measured in accordance with JIS K 3362 8.3, and the water content is measured in accordance with JIS K 3362 7.21.3.

[0102] During storage, the drug package maintains its shape, containing a drug such as a liquid detergent, and during use (e.g., during cleaning), the package (water-soluble film) comes into contact with water, dissolving the package and causing the drug contained therein to flow out.

[0103] When using the PVA-based water-soluble film of the present invention to package a drug such as a liquid detergent into a drug package, a known method can be used. For example, it is manufactured by laminating two PVA-based water-soluble films together. One film (bottom film) is fixed onto a mold at the bottom of a molding device, and another film (top film) is fixed onto the top of the device. After that, a liquid detergent or other agent is poured into the molded film, and the top and bottom films are pressed together. After pressing, the vacuum is released to obtain the package. Typically, deep drawing occurs when the film is stretched 2.5 times or more when molded into a package, or when the thickness of the thinnest part of the package is 35% or less, preferably 30% or less, of the original film thickness.

[0104] Methods for sealing the film after adding the drug include, for example, (1) heat sealing, (2) water sealing, and (3) glue sealing, and among these, the water sealing method (2) is the most versatile and advantageous.

[0105] The surface of the above-mentioned pharmaceutical packaging is usually smooth, but from the standpoint of blocking resistance, slipperiness during processing, reduced adhesion between products (packagings), and appearance, the outer surface of the packaging (PVA-based water-soluble film) may be textured with an embossed pattern, a finely textured pattern, a specially engraved design, or the like.

[0106] The drug retention time (time until the bag is broken) of the drug packaging body of the present invention usually exceeds 30 seconds, preferably 33 seconds or more, more preferably 35 seconds or more, and can suppress early leakage and dissolution of the liquid. The upper limit depends on the type of drug and the method of use, but in the case of the packaging body of the liquid detergent for washing, it is preferably usually 300 seconds or less.

[0107] The bag-breaking time of the drug packaging body is obtained by measuring the time from when the drug packaging body is left standing in an environment of 23°C and 50% RH for 1 day and then floating it in ion-exchanged water at 20°C until the packaging body breaks and the drug begins to leak.

Examples

[0108] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, “parts” and “%” mean mass basis.

[0109] The following materials were prepared as the material components of the water-soluble film. <PVA-based resin> · PVA-based resin (a-1): A carboxy group-modified PVA-based resin with a 4% aqueous solution viscosity of 24 mPa·s at 20°C, an average saponification degree of 94 mol%, and a modification amount of 2.0 mol% with maleic acid monomethyl ester · PVA-based resin (a-2): An unmodified PVA with a 4% aqueous solution viscosity of 27.5 mPa·s at 20°C and an average saponification degree of 97.7 mol% · PVA-based resin (a-3): An unmodified PVA with a 4% aqueous solution viscosity of 18 mPa·s at 20°C and an average saponification degree of 88 mol% · PVA-based resin (a-4): A carboxy group-modified PVA-based resin with a 4% aqueous solution viscosity of 22 mPa·s at 20°C, an average saponification degree of 94 mol%, and a modification amount of 2.0 mol% with maleic acid monomethyl ester · PVA-based resin (a-5): An unmodified PVA with a 4% aqueous solution viscosity of 43 mPa·s at 20°C and an average saponification degree of 88 mol% PVA resin (a-6): Unmodified PVA with a viscosity of 54 mPa·s in a 4% aqueous solution at 20°C and an average saponification degree of 98 mol% PVA resin (a-7): Unmodified PVA with a viscosity of 6.6 mPa·s in a 4% aqueous solution at 20°C and an average degree of saponification of 92.5 mol% PVA resin (a-8): A carboxyl-modified PVA resin with a viscosity of 30 mPa·s in a 4% aqueous solution at 20°C, an average degree of saponification of 94 mol%, and a modification amount of 2.0 mol% with maleic acid monomethyl ester. PVA resin (a-9): Unmodified PVA with a 4% aqueous solution viscosity of 22.5 mPa·s at 20°C and an average saponification degree of 88 mol%

[0110] <Other ingredients> Plasticizer (b1): Sorbitol Plasticizer (b2): Glycerin Filler (c1): Corn starch (average particle size 20 μm) Surfactant (d1): Polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt

[0111] Example 1 As the PVA-based resin (A), 90 parts of modified PVA (a-1), 10 parts of unmodified PVA (a-2), as the plasticizer (B), 20 parts of sorbitol (b1) and 20 parts of glycerin (b2), as the surfactant (D), 0.2 parts of polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt (d1), 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 22%. The obtained film-forming material was cast onto a polyethylene terephthalate film and dried by passing it through a 3 m long drying chamber (105°C) at a speed of 0.350 m / min to obtain a PVA-based film (water-soluble film) with a thickness of 87 μm.

[0112] Using the PVA-based water-soluble film of Example 1 obtained above, a drug package was produced using a package manufacturing machine manufactured by Engel according to the following procedure. Specifically, a PVA-based water-soluble film (bottom film) was fixed onto the mold (the package to be formed: approximately 45 mm long, 42 mm wide, and 30 mm high) at the bottom of the device, and a PVA-based water-soluble film (top film) was also fixed onto the top of the device. The bottom film was heated for 10 seconds using a dryer generating hot air at 90°C, and the bottom film was vacuum-molded into the mold. Then, 34 mL of P&G's Ariel Bioscience Gel Ball liquid detergent solution (composition: 12.7% propylene glycol, 7.5% glycerin, 12.7% ethanolamine, 57% surfactant, 9.3% water, pH 6.9) was poured into the molded PVA-based film. 0.25 g of water was applied to the entire surface of the top film (80 mm long, 140 mm wide), the top film and bottom film were pressed together, and after 30 seconds of pressing, the vacuum was released to obtain a pharmaceutical package that was a liquid detergent package (thinnest part film thickness: 20 μm).

[0113] <Example 2, Comparative Examples 1 to 3> The same procedure as in Example 1 was carried out except for the changes shown in Table 1 to obtain a PVA-based water-soluble film, and a liquid detergent package was obtained using this film.

[0114] The obtained liquid detergent package was used to measure and evaluate the physical properties of the liquid detergent package according to the methods described below. The results are shown in Table 1 below.

[0115] [Bag bursting time] The resulting liquid detergent package was left to stand for one day in an environment of 23°C and 50% RH, and then floated in ion-exchanged water at 20°C to measure the time until the capsule broke and the detergent began to leak.

[0116] [Table 1]

[0117] The results in Table 1 above show that the liquid detergent packages obtained using the films of Examples 1 and 2 are suitable for practical use, as the liquid detergent comes out after a certain amount of time has passed since they were immersed in water, and there is no concern about premature leakage of chemicals such as liquid detergent. Note that, after immersion in water, the time from when the package breaks and when the chemicals are released (chemical retention time) is preferably 30 seconds or more. In contrast, in the liquid detergent packages using the films of Comparative Examples 1 and 2 containing PVA-based resins (a1) and (a3) ​​with a difference in average saponification degree exceeding 5 mol%, which does not satisfy the range specified in the present invention, the time until the package broke after immersion in water was short, making them unsuitable for practical use.

[0118] Example 3 As the PVA-based resin (A), 90 parts of modified PVA (a1), 10 parts of unmodified PVA (a2), as the plasticizer (B), 20 parts of sorbitol (b1) and 20 parts of glycerin (b2), as the filler (C), 2 parts of corn starch (average particle size 20 μm) (c1), as the filler (C), 0.2 parts of polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt (d1), as the surfactant (D), 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 22%. The obtained film-forming material was cast onto a polyethylene terephthalate film and dried by passing it through a 3 m long drying chamber (105°C) at a speed of 0.350 m / min to obtain a PVA-based film (water-soluble film) with a thickness of 87 μm.

[0119] Using the PVA-based water-soluble film of Example 3 obtained above, a drug package was produced using a package manufacturing machine manufactured by Engel according to the following procedure. Specifically, a PVA-based water-soluble film (bottom film) was fixed onto the mold at the bottom of the device (the dimensions of the molded package: approximately 45 mm length, 42 mm width, and 30 mm height), and a PVA-based water-soluble film (top film) was also fixed onto the top of the device. The bottom film was heated for 10 seconds using a dryer generating hot air at 80°C, and the bottom film was vacuum-molded into the mold. Then, 34 mL of commercially available laundry detergent (composition: 11% propylene glycol, 7.5% glycerin, 67% surfactant, 14.2% water, pH 7.5) was poured into the molded PVA-based film. 0.25 g of water was applied to the entire top film (80 mm length, 140 mm width), and the top and bottom films were pressed together. After 30 seconds of pressing, the vacuum was released to obtain a pharmaceutical package (liquid detergent package) (thinnest part thickness: 23 μm).

[0120] <Examples 4 to 8, Comparative Examples 3 and 4> A PVA-based water-soluble film was obtained in the same manner as in Example 3, except for the changes shown in Table 2. A liquid detergent package was produced using this film, and the physical properties of the liquid detergent package were measured and evaluated in the same manner as above. The results are shown in Table 2 below. [Table 2]

[0121] The results in Table 2 above show that the liquid detergent packages obtained using the films of Examples 3 to 8 are suitable for practical use, as the liquid detergent comes out after a certain amount of time has passed since they were immersed in water, and there is no concern that chemicals such as liquid detergent will leak out prematurely. In contrast, in the liquid detergent packages using the films of Comparative Examples 3 and 4, which do not meet the range specified in the present invention, the time until the bag broke after being immersed in water was short, making them unsuitable for practical use.

[0122] 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. [Industrial Applicability]

[0123] The water-soluble film of the present invention can be used for various packaging applications, particularly for individual packaging of chemicals such as liquid detergents, because it improves resistance to bag rupture when immersed in water when the package is formed by deep drawing, i.e., it can prevent early leakage or dissolution of the chemicals.

Claims

1. A water-soluble polyvinyl alcohol-based film containing a polyvinyl alcohol-based resin (A) as a main component, the polyvinyl alcohol-based resin (A) being a main component of the (A) component, comprising: a modified polyvinyl alcohol-based resin (a1) having a 4% by mass aqueous solution viscosity at 20°C of 21 mPa s or more; and an unmodified polyvinyl alcohol-based resin (a2) that satisfies the following (α) and (β) in relation to the (a1) component, and the content mass ratio (a1 / a2) of the modified polyvinyl alcohol-based resin (a1) to the unmodified polyvinyl alcohol-based resin (a2) is 99 / 1 to 50 / 50: (α) The viscosity of a 4% by mass aqueous solution of the unmodified polyvinyl alcohol-based resin (a2) at 20°C is higher than the viscosity of a 4% by mass aqueous solution of the modified polyvinyl alcohol-based resin (a1) at 20°C. (β) The absolute value of the difference in average saponification degree between the modified polyvinyl alcohol-based resin (a1) and the unmodified polyvinyl alcohol-based resin (a2) is 5 mol % or less

2. 2. The water-soluble film according to claim 1, wherein the mass ratio (a1 / a2) of the modified polyvinyl alcohol resin (a1) to the unmodified polyvinyl alcohol resin (a2) is 95 / 5 to 55 / 45.

3. 3. The water-soluble film according to claim 1, wherein the unmodified polyvinyl alcohol resin (a2) has an average degree of saponification of 90 to 99.9 mol %.

4. 4. The water-soluble film according to claim 1, wherein the filler (C) is contained in an amount of 6 parts by mass or less per 100 parts by mass of the polyvinyl alcohol-based resin (A).

5. A pharmaceutical package comprising a package formed from the water-soluble film according to any one of claims 1 to 4 and a pharmaceutical packaged in the package.

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