Water-soluble film for liquid detergent capsule packaging

Abstract

Provided is a water-soluble film that is for a liquid detergent-packaging capsule and that is free from discoloration such as yellowing due to heating and coloring due to contact with a liquid detergent contained in the capsule, and can prevent deposition of inorganic salts such as sulfites and sulfates contained in the packaging capsule or the liquid detergent, and prevent whitening due to such deposition, and can maintain the tensional texture of the packaging capsule containing the liquid detergent and keep good appearance thereof over time. This water-soluble film for a liquid detergent-packaging capsule is a water-soluble film for a packaging capsule in which a liquid detergent is sealed, and is characterized by containing an anionic-group modified polyvinyl alcohol resin, a plasticizer including glycerin and sorbitol at a mass ratio of 1 : 2.1 to 5.3, and a sulfite, and is characterized in that the total contained amount of the glycerin and the sorbitol is 21-39 parts by mass, and the contained amount of the sulfite is 0.1-1.9 parts by mass, with respect to 100 parts by mass of the anionic-group modified polyvinyl alcohol resin.

Description

[Technical Field]

[0001] The present invention relates to a water-soluble film for use in packaging capsules for liquid detergents, which is used as packaging capsules for enclosing liquid detergents. [Background technology]

[0002] Polyvinyl alcohol resins are preferably used as water-soluble films for molding one-dose packaging capsules that enclose liquid detergent and are dispensed during laundry. However, these water-soluble films have problems such as yellowing due to heating during film formation or when the film is drawn by vacuum molding or the like to fill the liquid detergent and form the packaging capsule, and discoloration due to deterioration over time during storage due to prolonged contact with the components of the encapsulated liquid detergent. Therefore, in order to prevent such discoloration, mainly due to heat, it is known to add sulfite as an antioxidant to the water-soluble film.

[0003] The sulfite in the water-soluble film may precipitate from the surface of the water-soluble film over time, causing a bleed-out phenomenon, which may result in whitening of the water-soluble film.

[0004] As a method for preventing discoloration and bleed-out of such water-soluble films, Patent Document 1 discloses a water-soluble film containing a polyvinyl alcohol resin, at least two types of plasticizers, such as glycerin and diglycerin and / or trimethylolpropane, and a sulfite, in which the plasticizer is contained in an amount of 5 to 50 parts by weight per 100 parts by weight of the polyvinyl alcohol resin, and the weight ratio of the sulfite to the plasticizer is more than 0.02 and not more than 0.35.

[0005] Sulfites are not only used as antioxidants for water-soluble films, but are also sometimes used as stabilizers for enclosed liquid detergents. In addition to sulfites, sulfates can also be used as stabilizers. Inorganic salts such as sulfites and sulfates in liquid detergents are dissolved or dispersed, but they gradually penetrate the water-soluble film using the water or solvent contained in the liquid detergent as a carrier. As a result, they may precipitate on the surface of the water-soluble film over time, similar to sulfites that were previously incorporated as antioxidants in the water-soluble film. These precipitates cause a bleed-out phenomenon, resulting in the problem of whitening the film.

[0006] It is necessary to prevent not only the precipitation of sulfites contained in the water-soluble film as antioxidants, but also the precipitation of inorganic salts contained in the enclosed liquid detergent onto the film surface, and further to suppress whitening caused by these bleed-out phenomena.

[0007] In recent years, when washing laundry, dishes, etc., liquid detergent capsules have become common. These capsules are made by deep-drawing or other processes to form a water-soluble film, and contain a single dose of liquid detergent. Safety regulations, etc., have led to the dilution of liquid detergents to prevent serious illness caused by accidentally ingesting high-concentration detergents if young children accidentally ingest these capsules.

[0008] Liquid detergents are diluted by adding water as a solvent, dispersants, stabilizers, etc. to increase the volume. Compounds that can be used as dispersants or stabilizers may also be used as plasticizers in the water-soluble film for packaging capsules that encapsulate the liquid detergent. When a liquid detergent containing a large amount of such solvents or plasticizers is encapsulated, the water-soluble film for packaging capsules softens, and the packaging capsules swell due to absorption of the solvents or plasticizers. When the packaging capsules soften or swell in this way, the packaging capsules stretch, losing their firmness and impairing the appearance of the liquid detergent packaging capsules.

[0009] Furthermore, when the packaging capsules soften or swell, the gas barrier properties are reduced, making the liquid detergent packaging capsules susceptible to the humidity and temperature of their storage environment. When the gas barrier properties are reduced and the liquid detergent packaging capsules are susceptible to the storage environment, for example, in a low-humidity environment, the amount of water contained in the packaging capsules evaporates more, resulting in a decrease in the amount of solvent that dissolved inorganic salts such as sulfites and sulfates, which then precipitate on the surface of the packaging capsules, causing a bleed-out phenomenon and making the capsules susceptible to whitening.

[0010] There is a need for a water-soluble film for liquid detergent packaging capsules that is useful for liquid detergent packaging capsules, which prevents discoloration, does not cause the bleed-out phenomenon in which sulfites contained in the water-soluble film for packaging capsules that enclose liquid detergent or inorganic salts contained in the enclosed liquid detergent precipitate on the film surface, suppresses the resulting whitening, and can maintain the tension of the packaging capsules that enclose liquid detergent, thereby maintaining a good appearance. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-179390 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made to solve the above-mentioned problems, and aims to provide a water-soluble film for liquid detergent packaging capsules that does not undergo discoloration such as yellowing due to heating or coloring due to contact with the enclosed liquid detergent, can prevent the precipitation of inorganic salts such as sulfites and sulfates contained in the packaging capsules and liquid detergent and the resulting whitening, and can maintain the tension of the packaging capsules containing the liquid detergent, thereby maintaining a good appearance over time. [Means for solving the problem]

[0013] The water-soluble film for liquid detergent packaging capsules of the present invention, which has been made to achieve the above-mentioned object, is a water-soluble film for packaging capsules for enclosing liquid detergent, and is a water-soluble film for liquid detergent packaging capsules, which is a water-soluble film for liquid detergent packaging capsules, and is made by mixing an anionic group-modified polyvinyl alcohol resin with glycerin and sorbitol in a ratio of 1:2.1 to 5. 0 (excluding the case where the weight ratio is 1:5.0 and the case where the saponification degree of the anionic group-modified polyvinyl alcohol resin is 97 mol% and the weight ratio is 1:2.5) and a sulfite, wherein the total content of the glycerin and the sorbitol is 21 to 39 parts by mass, and the content of the sulfite is 0. 5 ~1.9 parts by mass (However, 0.5 parts by mass is excluded) Yes The maximum haze value after storage for two weeks in an environment of 23°C and 33% RH was 5.4%. It is something.

[0014] In the water-soluble film for liquid detergent packaging capsules, the sulfite is preferably sodium sulfite.

[0015] In the water-soluble film for liquid detergent packaging capsules, the anion-modified polyvinyl alcohol may contain maleic acid-modified polyvinyl alcohol.

[0016] The water-soluble film for a liquid detergent packaging capsule may be one in which the liquid detergent contains at least one selected from sulfites, sulfates, and other inorganic salts.

[0017] The water-soluble film for liquid detergent packaging capsules preferably has a yellowness index of 1.5 at most after storage at 90°C for 2 days.

[0018] The water-soluble film for liquid detergent packaging capsules preferably has a maximum haze value of 10.0% after storage for two weeks in an environment of 23°C and 33% RH.

[0019] The water-soluble film for liquid detergent packaging capsules preferably has an adhesion strength of up to 200 gf after storage for two days in an environment of 23°C and 50% RH.

[0020] It is preferable that the water-soluble film for liquid detergent packaging capsules is one in which the difference between the haze value of the ear portion of a liquid detergent packaging capsule formed by sealing the sheet pieces of the water-soluble film for liquid detergent packaging capsules together at their edges and the haze value of the ear portion of the liquid detergent-encapsulated capsule after storing the liquid detergent in the hollow formed between the sheet pieces by sealing and then storing it at 45°C for 3 days is at most 15.0%.

[0021] It is preferable that when the water-soluble film for liquid detergent packaging capsules is used as a liquid detergent-encapsulated capsule containing liquid detergent, the capsule height retention rate (%) calculated as the post-storage height relative to the initial height after storage in an environment of 23°C and 50% RH for one week is at least 90%, where the post-storage height is the height after storage and the height before storage is the initial height. [Effects of the Invention]

[0022] The water-soluble film for liquid detergent packaging capsules of the present invention contains a plasticizer containing glycerin and sorbitol in a specific mass ratio in a specific amount relative to the content of anionic group-modified polyvinyl alcohol resin, and therefore can be used for packaging capsules that enclose liquid detergents, without causing precipitation of sulfites that prevent discoloration or inorganic salts contained in liquid detergents on the film surface and resulting whitening.

[0023] Furthermore, since the water-soluble film for liquid detergent packaging capsules contains sulfite when the liquid detergent is sealed into the packaging capsules to form the packaging capsules, discoloration such as yellowing due to heating can be prevented. When the water-soluble film for liquid detergent packaging capsules encapsulates the liquid detergent into the packaging capsules, the water contained in the liquid detergent acts as a carrier and moves over time to be absorbed and incorporated into the packaging capsules together with the sulfite contained in the liquid detergent, thereby absorbing and incorporating some of the sulfite contained in the liquid detergent for use. The water-soluble film for liquid detergent packaging capsules can exhibit the same discoloration prevention effect whether the sulfite is already contained in the film or whether it is subsequently migrated and incorporated as described above. This allows the water-soluble film for liquid detergent packaging capsules to exhibit a sufficient discoloration prevention effect while suppressing the amount of sulfite already contained in the film for liquid detergent packaging capsules.

[0024] Furthermore, in the past, when a liquid detergent contained a component such as glycerin, which could act as a plasticizer in the packaging capsule, it acted as a carrier, similar to water, and over time, sulfite was absorbed into the packaging capsule, easily resulting in a large amount of sulfite migrating from the liquid detergent to the packaging capsule. However, the water-soluble film for liquid detergent packaging capsules of the present invention, when used to encapsulate liquid detergent into a packaging capsule, can suppress the absorption of such components and the associated sulfite, while minimizing the amount of sulfite migrating from the liquid detergent to the packaging capsule. This allows the packaging capsule to contain enough sulfite to prevent discoloration, while preventing the sulfite from increasing over time to the point where it precipitates on the surface of the packaging capsule. Furthermore, the film can suppress the incorporation of not only sulfite but also other inorganic salts contained in the liquid detergent into the packaging capsule, thereby preventing the bleed-out phenomenon in which they precipitate on the surface of the packaging capsule.

[0025] The water-soluble film for liquid detergent packaging capsules can be used to encapsulate liquid detergents containing large amounts of solvents, etc., as packaging capsules, and can also inhibit the absorption and migration of plasticizers contained in such liquid detergents, which can also be compounds that cause the packaging capsules to swell.This prevents the packaging capsules from losing their firmness due to swelling and stretching, and can be used for liquid detergent packaging capsules that maintain a good appearance over time.

[0026] The water-soluble film for liquid detergent packaging capsules does not undergo discoloration such as yellowing due to heating or staining due to the liquid detergent contained therein, and does not cause bleeding or whitening due to precipitation of sulfites, which prevent discoloration, or inorganic salts contained in the liquid detergent onto the surface of the packaging capsule.It is useful as a liquid detergent packaging capsule that can maintain a firm feel and good appearance over time, while preventing the packaging capsule from becoming susceptible to the effects of the temperature and humidity of the storage environment due to a decrease in gas barrier properties due to swelling, etc. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments for carrying out the present invention will be described in detail, but the scope of the present invention is not limited to these embodiments.

[0028] The water-soluble film for liquid detergent packaging capsules of the present invention is intended for use in packaging capsules that enclose liquid detergent, and contains at least an anionic group-modified polyvinyl alcohol resin, a plasticizer containing glycerin and sorbitol in a mass ratio of 1:2.1 to 5.3, and a sulfite, with the plasticizer being 21 to 39 parts by mass and the sulfite being 0.1 to 1.9 parts by mass per 100 parts by mass of the anionic group-modified polyvinyl alcohol resin.

[0029] The plasticizer contained in the water-soluble film for liquid detergent packaging capsules preferably has a mass ratio of glycerin to sorbitol of 1:2.1 to 5.3, more preferably 1:2.5 to 5.0, and even more preferably 1:2.5 to 4.0. Glycerin and sorbitol impart appropriate flexibility to the water-soluble film for liquid detergent packaging capsules, facilitating processes such as vacuum forming (thermoforming) when producing the liquid detergent packaging capsules. If the plasticizer contains more glycerin than sorbitol, it may become sticky, improving the adhesion of the water-soluble film for liquid detergent packaging capsules, or may increase the risk of bleeding out and whitening due to the precipitation of sulfites and inorganic salts contained in the liquid detergent on the surface of the packaging capsules. If the adhesion is too high, for example, when the water-soluble film for liquid detergent packaging capsules is wound into a roll during film production, the films may adhere to each other, making them difficult to handle. If the mass ratio of sorbitol exceeds the above range, the amount of sorbitol will be too excessive, resulting in sorbitol being precipitated on the surface of the water-soluble film for liquid detergent packaging capsules.

[0030] The plasticizer may consist of glycerin and sorbitol, or may contain glycerin and sorbitol together with other plasticizers exemplified below.

[0031] Examples of plasticizers other than glycerin and sorbitol include diglycerin, polyglycerol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, erythritol, xylitol, mannitol, glucose, fructose, maltitol, lactose, triethanolamine, triethanolamine acetate, ethanolacetamide, bisphenol A, bisphenol S, N-methylpyrrolidone, pentaerythritol, and compounds in which ethylene oxide is added to polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol. When plasticizers other than glycerin and sorbitol are contained, the total amount of all plasticizers may be up to 60 parts by mass per 100 parts by mass of the anionic group-modified polyvinyl alcohol resin.

[0032] The total mass of glycerin and sorbitol is preferably 21 to 39 parts by mass, more preferably 25 to 35 parts by mass, and even more preferably 28 to 35 parts by mass, per 100 parts by mass of the anion-modified polyvinyl alcohol resin. By incorporating a plasticizer containing glycerin and sorbitol at a specific mass ratio within the above range relative to the content of the anion-modified polyvinyl alcohol resin, when the water-soluble film for liquid detergent packaging capsules is used as a packaging capsule, it is possible to somewhat suppress the penetration of components that could serve as the plasticizer contained in the encapsulated liquid detergent into the film packaging capsule. This prevents the packaging capsule from absorbing these components and swelling. In contrast, the sulfite contained in the liquid detergent is appropriately absorbed and incorporated into the film packaging capsule.

[0033] Furthermore, although this will vary depending on the type and amount of ingredients contained in the enclosed liquid detergent, for example, if the liquid detergent contains glycerin as an ingredient that can act as a plasticizer, there will be a tendency for an equilibrium to be reached between the plasticizer contained in the packaging capsule and the ingredient contained in the liquid detergent that can act as a plasticizer for the packaging capsule.

[0034] If the amount of glycerin contained in this liquid detergent is greater than the amount of glycerin contained in the water-soluble film for liquid detergent packaging capsules, some of the glycerin contained in the liquid detergent will migrate to the film, which is the packaging capsule, and be absorbed into the film. Meanwhile, some of the sorbitol, a plasticizer contained in the packaging capsule, will migrate from the film to the liquid detergent and be released. In this case, glycerin can act as a carrier to transfer sulfites and inorganic salts in the liquid detergent to the film, while sorbitol can act as a carrier to transfer sulfites and inorganic salts in the film to the liquid detergent. Thus, if the sorbitol releases more sulfites and inorganic salts in the film to the liquid detergent due to the film containing more sorbitol than glycerin, the amount of sulfites and inorganic salts in the film can be prevented from increasing over time to the point where they precipitate. This prevents sulfites, inorganic salts, etc. from precipitating on the film surface when the liquid detergent is encapsulated.

[0035] Although a specific example in which glycerin migrates to the film side and sorbitol migrates to the liquid detergent side has been shown, the present invention is not limited to this example, and if the amount of glycerin contained in the liquid detergent is less than the amount of glycerin contained in the water-soluble film for liquid detergent packaging capsules, the glycerin in the film acts as a carrier for transferring sulfites, inorganic salts, etc. to the detergent side. In this way, depending on the types and amounts of components contained in the liquid detergent, plasticizers, particularly glycerin and sorbitol, migrate between the packaging capsule and the liquid detergent, respectively, and release and / or absorb the sulfites, inorganic salts, etc. contained therein, thereby suppressing the precipitation of sulfites, inorganic salts, etc.

[0036] The sulfite contained in the water-soluble film for liquid detergent packaging capsules is preferably 0.1 to 1.9 parts by mass, more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the anion-modified polyvinyl alcohol resin. If the sulfite content exceeds 1.9 parts by mass, the sulfite is likely to precipitate on the surface of the water-soluble film for liquid detergent packaging capsules and the packaging capsules containing the liquid detergent. Furthermore, the sulfite content in the water-soluble film for liquid detergent packaging capsules is preferably 0.1 to 1.3% by mass. The sulfite can prevent discoloration, such as yellowing or coloring, of the water-soluble film for liquid detergent packaging capsules and the packaging capsules containing the liquid detergent.

[0037] Examples of sulfites include sodium sulfite, potassium sulfite, calcium sulfite, and ammonium sulfite. Among them, sodium sulfite is preferred. These sulfites may be used alone or in combination. The sulfite contained in the water-soluble film for liquid detergent packaging capsules may be the same as or different from the sulfite contained in the liquid detergent to be encapsulated.

[0038] The water-soluble film for liquid detergent packaging capsules may contain an anionic group-modified polyvinyl alcohol resin as a film-constituting resin.

[0039] The anionic group-modified polyvinyl alcohol resin is preferably an anionic group-modified polyvinyl alcohol copolymer, more preferably a carboxylic acid-modified polyvinyl alcohol copolymer into which a carboxyl group has been introduced, and even more preferably a maleic acid-modified polyvinyl alcohol copolymer.

[0040] The anionic group-modified polyvinyl alcohol resin may be a carboxylic acid-modified polyvinyl alcohol obtained by copolymerizing an anionic comonomer, for example, an unsaturated carboxylic acid and a vinyl ester compound, and then saponifying the resulting copolymer, or may be a polyvinyl alcohol or a vinyl alcohol copolymer in which some of the hydroxyl groups have been esterified with an acid anhydride.

[0041] Examples of vinyl ester compounds include vinyl acetate, vinyl formate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, etc. These may be used alone or in combination.

[0042] Examples of anionic comonomers include maleic acid, itaconic acid, fumaric acid, crotonic acid, acrylic acid, methacrylic acid, vinylsulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid, anhydrides thereof, and esters thereof.

[0043] The anionic group-modified polyvinyl alcohol resin may contain repeating units of other monomers in addition to the repeating units of the unsaturated carboxylic acid. Examples of the other monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; alkyl vinyl ethers; dimethylallyl vinyl ketone; N-vinylpyrrolidone; vinyl chloride; vinylidene chloride; polyoxyalkylene (meth)allyl ethers such as polyoxyethylene (meth)allyl ether and polyoxypropylene (meth)allyl ether; and polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate. polyoxyalkylene (meth)acrylamides such as polyoxyethylene (meth)acrylamide and polyoxypropylene (meth)acrylamide; polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester; polyoxyalkylene vinyl ethers such as polyoxyethylene vinyl ether and polyoxypropylene vinyl ether; polyoxyalkylene allylamines such as polyoxyethylene allylamine and polyoxypropylene allylamine; polyoxyalkylene vinylamines such as polyoxyethylene vinylamine and polyoxypropylene vinylamine; diacrylacetonamide, etc.

[0044] Further examples include cationic group-containing monomers such as N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidopropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, 3-butenetrimethylammonium chloride, dimethyldiallylammonium chloride, and diethyldiallylammonium chloride.

[0045] These other monomers may be used alone or in combination, and may be contained in an amount that does not impair the object of the present invention, for example, 0.01 to 10 mol %.

[0046] The degree of polymerization of the anionic group-modified polyvinyl alcohol resin is preferably 700 or more, more preferably 900 or more, and even more preferably 1200 or more. If the degree of polymerization is lower than 700, the mechanical properties of the water-soluble film for liquid detergent packaging capsules tend to deteriorate. The degree of polymerization may be up to 2500, more preferably 2200 or less, and even more preferably 2000 or less. If the degree of polymerization is higher than 2500, the water solubility of the water-soluble film for liquid detergent packaging capsules tends to deteriorate. The degree of saponification of the anionic group-modified polyvinyl alcohol resin is preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 99 mol% or less, and even more preferably 87 mol% or more and 98 mol% or less. If the degree of saponification is lower than 70 mol%, the water solubility tends to deteriorate. The degree of saponification is measured in accordance with JIS K6726 (1994).

[0047] The viscosity of a 4% by mass aqueous solution of the anionic group-modified polyvinyl alcohol resin at 20°C is not particularly limited, but is preferably 7.0 to 50 mPa·s, more preferably 9.0 to 40 mPa·s, and even more preferably 12 to 35 mPa·s. The viscosity of a 4% by mass aqueous solution is measured in accordance with JIS K6726 (1994).

[0048] The degree of modification of the anionic group-modified polyvinyl alcohol resin is preferably 0.1 to 10 mol%, more preferably 0.5 to 8 mol%, and even more preferably 1 to 6 mol%. If the degree of modification of the anionic group-modified polyvinyl alcohol resin is less than 0.1 mol%, the solubility in water decreases, and if it exceeds 10 mol%, the productivity of the resin decreases.

[0049] The water-soluble film for liquid detergent packaging capsules may contain multiple types of anion-modified polyvinyl alcohol resins, which may differ in one or more of molecular weight, degree of polymerization, viscosity, degree of saponification, degree of modification, and modified species.

[0050] The water-soluble film for liquid detergent packaging capsules may further contain unmodified polyvinyl alcohol, other water-soluble polymers, surfactants and additives as required, within the range that does not impair its physical properties.

[0051] Examples of water-soluble polymers include sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, dextrin, chitosan, chitin, methyl cellulose, and hydroxyethyl cellulose.

[0052] Examples of surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, and zwitterionic surfactants. Among these, polyoxyethylene lauryl ether sodium acetate and polyoxyethylene secondary alkyl ether phosphate metal salts are preferred. These may be used alone or in combination. The content of the surfactant is preferably 0.17 to 0.60 parts by mass per 100 parts by mass of the polyvinyl alcohol resin. The surfactant can impart peelability from the cast surface during water-soluble film production and facilitate processing such as sealing (water-sealing, heat sealing) during the production of liquid detergent packaging capsules.

[0053] Examples of additives include fillers, colorants, fragrances, extenders, antifoaming agents, release agents, ultraviolet absorbers, rust inhibitors, liquid paraffins, fluorescent brighteners, chelating agents, bittering agents such as denatonium benzoate, fatty acid substances, inorganic powders, etc.

[0054] The water-soluble film for liquid detergent packaging capsules is produced by a known method such as solution casting, wet extrusion, or melt extrusion using a water-soluble film composition prepared by kneading a specified amount of an anionic group-modified polyvinyl alcohol resin, a plasticizer containing glycerin and sorbitol, a sulfite, and optionally a surfactant and water. The water-soluble film composition may also contain the water-soluble polymers and additives exemplified above, as needed.

[0055] The water-soluble film for liquid detergent packaging capsules preferably has a moisture content of 5.5 to 8.0% by mass, more preferably 6.0 to 7.0% by mass.

[0056] The thickness of the water-soluble film for liquid detergent packaging capsules can be set appropriately within the range of 20 to 100 μm, but from the standpoint of robustness to prevent leakage of the liquid detergent when encapsulated, robustness to prevent breakage during processing and molding, and maintaining the tautness of the packaging capsule, it is preferably 25 to 95 μm, more preferably 30 to 90 μm, and even more preferably 75 to 90 μm.

[0057] The water-soluble film for liquid detergent packaging capsules preferably has a maximum yellowness index of 1.5 as measured in accordance with JIS Z8722 (2009) after storage at 90°C for two days. Furthermore, the water-soluble film for liquid detergent packaging capsules preferably has a maximum haze value of 10.0% as measured in accordance with JIS K7136 (2000) after storage for two weeks in an environment of 23°C and 33% RH. Furthermore, after storing the water-soluble film for liquid detergent packaging capsules in an environment of 23°C and 50% RH for two days, the water-soluble film for liquid detergent packaging capsules is placed on a glass plate, aluminum foil, and a 3 kg glass plate are placed on top. After five minutes have passed, the upper glass plate and aluminum foil are removed, and a digital force gauge (IMADA: DS2-50N) is attached to a clip attached to the center of one side of the water-soluble film for liquid detergent packaging capsules. The clip is then pulled perpendicular to the lower glass plate. The maximum strength measured when the film peels off from the lower glass plate is preferably a maximum adhesion strength of 200 gf.

[0058] When the water-soluble film for liquid detergent packaging capsules is used as a packaging capsule for enclosing liquid detergent, by sealing the four sides of two sheets of the film together to form a capsule shape with a hollow for enclosing liquid detergent, the initial haze value of the ear portion around the periphery of the packaging capsule without liquid detergent enclosed, and the post-storage haze value of the ear portion around the periphery of the liquid detergent-enclosed capsule after enclosing liquid detergent and storing it at 45°C for three days, are each measured in accordance with JIS K7136 (2000), and it is preferable that the difference obtained by subtracting the initial haze value from the post-storage haze value is a maximum of 15.0%.

[0059] When the water-soluble film for liquid detergent packaging capsules is used as a liquid detergent-encapsulated capsule containing liquid detergent, the capsule height retention rate (%) is calculated by dividing the height of the liquid detergent-encapsulated capsule after storage for one week in an environment of 23°C and 50% RH by the initial height of the liquid detergent-encapsulated capsule before storage and multiplying the result by 100. The capsule height retention rate (%) is preferably at least 90%, and more preferably 95% or more.

[0060] When the liquid detergent encapsulated as a packaging capsule contains sulfite, the water-soluble film for the liquid detergent packaging capsule of the present invention may absorb and incorporate a part of the sulfite.

[0061] Liquid detergent packaging capsules can be manufactured using the water-soluble film for liquid detergent packaging capsules of the present invention, for example, as follows. A vacuum-forming deep-draw packaging capsule manufacturing machine is used to pull out the water-soluble film for liquid detergent packaging capsules from a bottom water-soluble film roll. The water-soluble film for liquid detergent packaging capsules is guided onto a molding die having cavities corresponding to the depressions for containing the liquid detergent. This bottom water-soluble film is heated to 70 to 120°C and brought into contact with the openings of a plurality of aligned cavities. A vacuum pump connected to the cavities is used to suction the interior of the cavities, reducing the pressure. The bottom water-soluble film is stretched to the shape of the cavities, resulting in a packaging capsule bottom sheet with depressions formed therein. A predetermined amount of liquid detergent is filled into the depressions in the packaging capsule bottom sheet. The water-soluble film for liquid detergent packaging capsules is pulled out from a top water-soluble film roll, and after applying water if necessary, the liquid detergent is covered over the packaging capsule bottom sheet. When the edge portions corresponding to the periphery of the recess are heat-sealed and / or pressure-sealed, the bottom water-soluble film for the liquid detergent packaging capsule and the top water-soluble film for the liquid detergent packaging capsule are sealed at the edge portions. When the middle of the edge portions is cut, individually wrapped deep-draw packaged capsules are obtained.

[0062] When the liquid detergent packaging capsule contains a sulfite in the hollow space of the water-soluble film for liquid detergent packaging capsules, the liquid detergent packaging capsule can absorb and incorporate some of the sulfite into the packaging capsule. This makes it difficult for the water-soluble film for liquid detergent packaging capsules to undergo discoloration, such as yellowing or staining caused by the liquid detergent, not only due to the sulfite already contained in the film but also due to sulfite that subsequently migrates from the liquid detergent, thereby maintaining a good appearance over time. The mechanism behind this is not entirely clear, but is presumed to be as follows.

[0063] In a packaging capsule made of a water-soluble film for liquid detergent packaging capsules and the liquid detergent enclosed therein, a tendency for the plasticizer contained in the packaging capsule to reach equilibrium with components contained in the liquid detergent that can act as plasticizers for the capsules occurs, or the water contained in the packaging capsule evaporates due to exposure to air and the effects of temperature and humidity, resulting in a phenomenon in which some of the water contained in the liquid detergent migrates to the packaging capsule over time. Because the water and plasticizer act as carriers, some of the sulfite and other inorganic salts contained in the liquid detergent migrate to the packaging capsule along with the water and plasticizer, penetrate, and are absorbed into the packaging capsule. However, depending on the type and amount of the specific plasticizer in the water-soluble film, sulfite and other inorganic salts do not bleed out and appear to remain incorporated within the water-soluble film. Therefore, packaging capsules made of a water-soluble film for liquid detergent packaging capsules appear to be able to exhibit the same antioxidant effect of preventing discoloration, whether the sulfite is originally contained in the water-soluble film for liquid detergent packaging capsules or is incorporated later as described above.

[0064] The liquid detergent packaging capsule does not discolor over time during storage or whiten due to a bleed-out phenomenon because the liquid detergent is enclosed in the packaging capsule, is not easily affected by the storage environment, and maintains a firm feel and good appearance over time.

[0065] The liquid detergent to be enclosed in the liquid detergent packaging capsule is not particularly limited, and commercially available products can be used, and may contain at least one selected from sulfites, sulfates, and other inorganic salts. The content of these substances in the liquid detergent is not particularly limited, but when sulfites, particularly sodium sulfite, are contained, it is preferable that the total amount of sulfate-based substances (sulfites, bisulfites, sulfates, etc.) contained in the water-soluble film for liquid detergent packaging capsules and sulfate-based substances (sulfites, bisulfites, sulfates, etc.) contained in the liquid detergent per liquid detergent packaging capsule is 0.498 to 0.506 mass%. [Example]

[0066] Examples of the present invention will be described in detail below, but the scope of the present invention is not limited to these examples. The polyvinyl alcohol resins (PVA) used in the examples and comparative examples are as follows. A1: 4% by mass aqueous solution viscosity 28 mPa·s, polymerization degree 1700, average saponification degree 88 mol%, modification degree 1.9 mol%, maleic acid-modified polyvinyl alcohol A2: 4% by mass aqueous solution viscosity 28 mPa·s, degree of polymerization 1700, average degree of saponification 93 mol%, degree of modification 1.9 mol%, maleic acid-modified polyvinyl alcohol A3: 4% by mass aqueous solution viscosity 29 mPa·s, polymerization degree 1700, average saponification degree 97 mol%, modification degree 1.9 mol%, maleic acid-modified polyvinyl alcohol A4: 4% by mass aqueous solution viscosity 29 mPa·s, polymerization degree 1700, average saponification degree 94 mol%, modification degree 3.6 mol%, maleic acid-modified polyvinyl alcohol A5: 4% by mass aqueous solution viscosity 25 mPa·s, degree of polymerization 1800, average degree of saponification 88 mol%, unmodified polyvinyl alcohol

[0067] Example 1 (Preparation of Water-Soluble Film Composition) A water-soluble film composition was prepared by kneading 100 parts by mass of an anionic-modified polyvinyl alcohol (4% by mass aqueous solution viscosity 28 mPa·s, degree of saponification 88 mol%, degree of maleic acid modification 1.9 mol%), which was a polyvinyl alcohol resin, with 0.5 parts by mass of sodium sulfite as a sulfate-based substance, 7 parts by mass of glycerin and 23 parts by mass of sorbitol as plasticizers, 0.5 parts by mass of polyoxyethylene lauryl ether sodium acetate, an anionic surfactant, as a surfactant, and water.

[0068] (Preparation of water-soluble film for liquid detergent packaging capsules) The viscosity of this composition was approximately 3000 mPa·s when measured at 85°C using a Brookfield viscometer. A metal roll was prepared as a casting surface, and its surface was cleaned by wiping it with a cloth dampened with pure water. The water-soluble film composition was cast onto the metal roll while the surface temperature of the metal roll was heated to approximately 80°C. The metal roll was dried for 8 minutes while rotating, producing a 75 μm-thick water-soluble film for liquid detergent packaging capsules.

[0069] Examples 2 to 11 For Examples 2 to 11, each water-soluble film composition was prepared according to the formulation shown in Table 1. Using each of the obtained water-soluble film compositions, each water-soluble film for liquid detergent packaging capsules was produced in the same manner as in Example 1. It should be noted that Examples 1, 7, and 10 are reference examples.

[0070] (Comparative Examples 1 to 21) For Comparative Examples 1 to 21, each water-soluble film composition was prepared according to the formulation shown in Table 1. Each water-soluble film composition obtained was used to produce each water-soluble film for liquid detergent packaging capsules in the same manner as in Example 1.

[0071] [Table 1]

[0072] The water-soluble films for liquid detergent packaging capsules obtained in each Example and Comparative Example were subjected to the following evaluation tests. The preferable ranges in each evaluation test are shown in Table 2 below as evaluation criteria. The results of each evaluation test are also summarized in Table 2 below.

[0073] (Yellowing resistance evaluation test) One sheet of the water-soluble film for liquid detergent packaging capsules obtained in each Example and Comparative Example was cut to a size of 180 mm x 75 mm and stored for two days in an environment at 90°C. Thereafter, the YI (yellowness index) was measured in accordance with JIS Z8722 (2009) using a spectrophotometer (Nippon Denshoku Industries Co., Ltd.: SD 7000).

[0074] (Bleeding resistance evaluation test) One sheet of the water-soluble film for liquid detergent packaging capsules obtained in each Example and Comparative Example was cut to a size of 100 mm x 100 mm and stored in an environment of 23 ° C and 33% RH for 2 weeks. Thereafter, the haze was measured according to JIS K7136 (2000) using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.: NDH 5000). By measuring the haze value, the bleeding resistance of the components contained in the water-soluble film for liquid detergent packaging capsules can be evaluated.

[0075] (Adhesion evaluation test) A sheet of water-soluble film for liquid detergent packaging capsules obtained in each Example and Comparative Example was cut to a size of 330 mm x 330 mm and stored at 23°C and 50% RH for two days. The water-soluble film for liquid detergent packaging capsules was placed on a glass plate, the surface of which had been wiped clean with a lab towel (manufactured by Unichemy) moistened with methanol, so that the air side of the film for liquid detergent packaging capsules was in contact with the surface when cast. A sheet of aluminum foil was placed on top of the water-soluble film for liquid detergent packaging capsules, and a 3 kg glass plate was then placed on top of the aluminum foil. After 5 minutes, the glass plate and aluminum foil placed on top of the water-soluble film for liquid detergent packaging capsules were removed, and the adhesion strength between the lower glass plate and the water-soluble film for liquid detergent packaging capsules was measured using the following procedure. A clip was attached to the center of one side of the water-soluble film for liquid detergent packaging capsules, and the clip was hooked onto the tip of a digital force gauge (manufactured by Imada Co., Ltd.: DS2-50N). With the clip still attached, the digital force gauge was pulled perpendicular to the glass plate to measure the maximum strength at which the film peeled from the glass plate.

[0076] (Preparation of liquid laundry detergent) A liquid laundry detergent was prepared consisting of 37% by mass of linear alkyl (C10-C15) benzenesulfonic acid, 5.5% by mass of monoethanolamine, 21% by mass of glycerin, 28% by mass of propylene glycol, 0.5% by mass of sodium sulfite, and 8% by mass of distilled water, for a total of 100% by mass.

[0077] (Precipitation and whitening evaluation test) One sheet of water-soluble film for liquid detergent packaging capsules obtained in each Example and Comparative Example was cut to a size of 206 mm x 115 mm, and the long edge was folded in half so that the air surface during casting was on the inside. The two opposite edges were heat-sealed using a heat seal tester (TP-701B manufactured by Tester Sangyo Co., Ltd.) to a seal width of 25 mm to produce a flat bag measuring 103 mm x 115 mm. At this time, the initial haze (H0) of the seal portion of the flat bag, i.e., the edge, was measured using a haze meter (NDH 5000 manufactured by Nippon Denshoku Industries Co., Ltd.). Approximately 17 mL of the prepared liquid laundry detergent was poured into the flat bag, and the remaining edge was heat-sealed to produce a packaged capsule containing the liquid detergent. This liquid detergent packaging capsule was placed in a PET 15 μm / PE 50 μm laminated bag, sealed, and stored at 45°C for 3 days. At this time, the post-storage haze (H1) of the seal portion of the liquid detergent packaging capsule was measured using a haze meter (NDH 5000 manufactured by Nippon Denshoku Industries Co., Ltd.). The heat-sealing conditions were as follows: Each haze value was measured in accordance with JIS K7136 (2000). Upper seal: 10mm wide Teflon coated aluminum seal bar (Teflon is a registered trademark), 160℃ Lower seal: Rubber plate with Teflon tape (Teflon is a registered trademark), 30℃ Sealing time: 1 second Sealing pressure: 0.2 MPa

[0078] The Δ deposition haze (%) was determined as follows. Δ Deposition haze (%) = Haze of sealed area after storage (H1) - Initial haze of sealed area (H0) Since each water-soluble film has different transparency after heat sealing and bleed-out before storage, resulting in different initial haze values, the difference in haze values ​​before and after storage can be determined to evaluate only the precipitation and whitening that occurs when each water-soluble film encapsulates the liquid detergent.

[0079] (Capsule tightness evaluation test) The water-soluble film for liquid detergent packaging capsules obtained in each Example and Comparative Example was used as the bottom film, stretched without wrinkles or sagging, and placed in a cavity (opening area 2000 mm 2 The water-soluble film for liquid detergent packaging capsules was placed on a mold having a box-shaped cavity with rounded corners and a depth of 15 mm. The water-soluble film for liquid detergent packaging capsules was heated to about 90°C for 5 seconds, and the water-soluble film for liquid detergent packaging capsules was made to conform to the cavity by vacuum forming, forming a recessed water-soluble film sheet for liquid detergent packaging capsules. The recess in the water-soluble film sheet for liquid detergent packaging capsules on the cavity was filled with about 22 mL of the prepared liquid laundry detergent. Next, the water-soluble film for liquid detergent packaging capsules obtained in the same manner was used as a top water-soluble film, and a water coating amount of 44 to 54 g / m was applied to it. 2 The water-soluble film for the top was immediately pressed and bonded to the water-soluble film sheet at the edge of the recess that would become the bottom side using a 1.5 kg metal roll, and after holding for about 1 minute and 30 seconds, the vacuum was stopped, and the capsule row was removed from the cavity and cut to produce liquid detergent packaging capsules.

[0080] After removing the liquid detergent packaging capsule from the cavity, it was left to stand at room temperature for approximately 7 minutes. At this time, the initial height (h0) of the liquid detergent-enclosed capsule was measured using a height gauge (Mitutoyo Corporation: Absolute Digimatic Height Gage). This liquid detergent packaging capsule was then stored for another week in an environment of 23°C and 50% RH. At this time, the height (h1) of this liquid detergent packaging capsule after storage was measured using a height gauge (Mitutoyo Corporation: Absolute Digimatic Height Gage).

[0081] The capsule height retention rate (%) was calculated as follows. Capsule height retention rate (%) = height after storage (h1) / initial height (h0) x 100 The capsule height retention rate was evaluated on a three-point scale: 95% or more = ◎, 90% or more but less than 95% = ◯, and less than 90% = ×. ◎ means that the capsule has particularly good tension and has an appearance that is more preferred by consumers.

[0082] [Table 2]

[0083] As shown in Table 2, Examples 1 to 11 met all the evaluation criteria, and were found to have resistance to yellowing and bleeding, adequate adhesion, and the ability to maintain a good capsule tightness and appearance without causing precipitation or whitening when a liquid detergent was encapsulated. On the other hand, Comparative Examples 1 to 21 did not meet the evaluation criteria in any of the evaluation tests, making them unsatisfactory.

[0084] Specifically, when the sulfite content was 0.1 to 1.9 parts by mass relative to 100 parts by mass of anionic group-modified polyvinyl alcohol resin as in Examples 1 to 11, the evaluation criteria of YI of 1.5 or less, haze of 10.0% or less, adhesion strength (gf / 330 mm) of 200 gf or less, precipitation and whitening (Δprecipitation haze) of 15.0% or less, and capsule height retention of 90% or more were satisfied. In contrast, when the sulfite content was less than 0.1 parts by mass as in Comparative Example 1, YI became too large, and when the sulfite content exceeded 1.9 parts by mass as in Comparative Examples 2 and 3, precipitation and whitening (Δprecipitation haze) became too high.

[0085] When the total content of glycerin and sorbitol was 21 to 39 parts by mass per 100 parts by mass of the anionic group-modified polyvinyl alcohol resin as in Examples 1 to 11, all evaluation items met the evaluation criteria. In contrast, when the total content of glycerin and sorbitol exceeded 39 parts by mass as in Comparative Examples 4 and 5, the haze and adhesion strength were too high. When the total content of glycerin and sorbitol was less than 21 parts by mass as in Comparative Examples 6 and 7, the precipitation and whitening (Δprecipitation haze) were too high. Furthermore, even when the total content of glycerin and sorbitol was 21 to 39 parts by mass, when the mass ratio was below the range of 1:2.1 to 5.3, the adhesion strength was too high, and the smaller the mass ratio, the higher the precipitation and whitening (Δprecipitation haze) tended to be. On the other hand, when the mass ratio exceeded the range of 1:2.1 to 5.3, the haze was too high, and the higher the mass ratio, the higher the precipitation and whitening (Δprecipitation haze) tended to be.

[0086] All evaluation items satisfied the evaluation criteria even when the degree of maleic acid modification, average degree of saponification, and viscosity in the anionic group-modified polyvinyl alcohol resin varied as in Examples 1 to 11. In contrast, when unmodified polyvinyl alcohol was used as in Comparative Example 16, the haze and adhesion strength were too high, and precipitation and whitening (Δ precipitation haze) were too high.

[0087] When sodium hydrogen sulfite or sodium sulfate was used instead of sulfite as in Comparative Examples 17 and 18, not only did the precipitation and whitening (Δ precipitation haze) become too high, but the adhesion strength also became too high, and when sodium sulfate was used, the YI and haze became too high.

[0088] When sorbitol and trimethylolpropane were used without glycerin as in Comparative Example 19, precipitation and whitening (Δ precipitation haze) became too high; when glycerin and mannitol were used without sorbitol as in Comparative Example 20, not only did precipitation and whitening (Δ precipitation haze) become too high, but the haze and adhesion strength also became too high; and when glycerin and xylitol were used without sorbitol as in Comparative Example 21, precipitation and whitening (Δ precipitation haze) became too high.

[0089] By using predetermined amounts of components as in Examples 1 to 11, excellent YI, haze, adhesion strength, precipitation and whitening (Δ precipitation haze), and capsule height retention rate were exhibited. [Industrial Applicability]

[0090] The water-soluble film for liquid detergent packaging capsules of the present invention can be used as packaging capsules for enclosing various liquid detergents used for washing, cleaning, etc. Liquid detergent packaging capsules using the water-soluble film for liquid detergent packaging capsules can be used as detergents for commercial or household use.

Claims

1. A water-soluble film for a packaging capsule for enclosing a liquid detergent, 1. A water-soluble film for liquid detergent packaging capsules, comprising: an anion-modified polyvinyl alcohol resin; a plasticizer containing glycerin and sorbitol in a mass ratio of 1:2.1 to 5.0 (excluding the case where the weight ratio is 1:5.0 and the case where the anion-modified polyvinyl alcohol resin has a degree of saponification of 97 mol % and the weight ratio is 1:2.5); and a sulfite; wherein the total content of the glycerin and the sorbitol is 21 to 39 parts by mass and the content of the sulfite is 0.5 to 1.9 parts by mass (excluding the 0.5 part by mass part) per 100 parts by mass of the anion-modified polyvinyl alcohol resin; and wherein the haze value after two weeks of storage in an environment of 23°C and 33% RH is 5.4% at most.

2. 2. The water-soluble film for liquid detergent packaging capsules according to claim 1, wherein the sulfite is sodium sulfite.

3. 3. The water-soluble film for liquid detergent packaging capsules according to claim 1, wherein the anionic group-modified polyvinyl alcohol resin contains maleic acid-modified polyvinyl alcohol.

4. 4. The water-soluble film for liquid detergent packaging capsules according to claim 1, wherein the liquid detergent contains a sulfite and / or a sulfate.

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