Method for producing water-soluble film, water-soluble film, packaging, and drug packaging

Abstract

A method for producing a water-soluble film that forms a film by extruding from a die a resin composition (Z) obtained by mixing and dissolving a water-soluble polymer (A) and water by a multi-screw extruder as a method for producing a water-soluble film that has excellent blocking resistance, no undissolved water-soluble polymer, and no coloration of the film, wherein the multi-screw extruder has a plurality of temperature-adjustable cylinders and a plurality of screws configured by combining a plurality of screw elements; when the temperature-adjustable cylinders are each designated as C1, C2, C3… from upstream, the cylinder equipped with a raw material supply port that supplies a raw material composed mainly of the water-soluble polymer (A) is designated as CS, and the cylinder equipped with a raw material supply port furthest upstream of the raw material supply ports that supply a raw material containing water is designated as CT, 0≤T−S≤6; and the ratio of the effective length of the screws and the diameter of the screws is from more than 50 to 100.

Description

Method for producing water-soluble film, water-soluble film, package, and drug package

[0001] The present invention relates to a method for producing a water-soluble film, which comprises mixing and dissolving a water-soluble polymer (A) and water in a multi-screw extruder to obtain a resin composition (Z) containing a mixture of the water-soluble polymer (A) and water as main components, and extruding the resin composition (Z) from a die to form a film, and to a water-soluble film obtained by the production method.

[0002] Water-soluble films have been used in a wide range of fields, and among them, water-soluble films made of polyvinyl alcohol-based resins are widely used for individual packaging (unit packaging) of pharmaceuticals such as pesticides and detergents, as well as for food packaging.

[0003] A commonly known method for producing a water-soluble film involves dissolving or dispersing a raw material composition containing a water-soluble polymer such as a polyvinyl alcohol-based resin in a solvent such as water, mixing, and degassing to prepare a mixture (film-forming raw material), and then discharging the film-forming raw material from a die and casting it onto a casting surface such as the metal surface of an endless belt or a drum roll or the surface of a plastic substrate, followed by drying to form a film. Methods for mixing and dissolving a water-soluble polymer in a solvent include a method in which the mixture is stirred with a stirring blade while heated in a container such as a tank, or a method in which the mixture is mixed and dissolved with a screw while heated in an extruder.

[0004] Known methods for producing a water-soluble film in which a water-soluble polymer and a solvent are mixed and dissolved in an extruder include, for example, a production method having a step of supplying a powdered polyvinyl alcohol resin to a twin-screw extruder and a step of supplying a solvent for liquefying the polyvinyl alcohol resin (see Patent Document 1), and a production method using a multi-screw extruder without a vent, in which the temperatures of the head, the mold outlet, and the boiling point of the liquid are controlled, and the back pressure in the mold is adjusted to within a predetermined range (see Patent Document 2).

[0005] JP 2002-254492 A JP 2015-182372 A

[0006] However, water-soluble films used particularly for pharmaceutical packaging applications are required to satisfy various physical properties, such as excellent cold water solubility and storage stability for various pharmaceuticals, and there are a wide variety of types of water-soluble polymers and additives as main components. However, in conventionally known production methods such as those disclosed in Patent Documents 1 and 2, undissolved water-soluble polymers remain in the resin composition (film-forming raw material), which reduces the formability of the resulting water-soluble film and the mechanical properties of packages made using the water-soluble film, and the blocking resistance is insufficient, so further improvement is required. In addition, the resin composition may become discolored, impairing the appearance of the resulting water-soluble film, so further improvement is required.

[0007] Therefore, in this context, the present invention provides a method for producing a water-soluble film by mixing and dissolving a water-soluble polymer and water in a multi-screw extruder, which method produces a water-soluble film without coloring, without undissolved water-soluble polymer, and with excellent blocking resistance.

[0008] However, in light of these circumstances, the present inventors have conducted extensive research and found that the above-mentioned problems can be solved by using a multi-screw extruder in which the ratio of the effective length to the diameter of the screws is in a specific range that is larger than conventional ones, and by specifying the positional relationship between the cylinder of the raw material supply port that supplies a raw material mainly composed of a water-soluble polymer and the cylinder of the raw material supply port that is located most upstream of the raw material supply ports that supply a raw material containing water.

[0009] That is, the present invention has the following aspects: [1] A method for producing a water-soluble film, which comprises extruding a resin composition (Z) obtained by mixing and dissolving a water-soluble polymer (A) and water in a multi-screw extruder through a die to form a film, wherein the multi-screw extruder has a plurality of temperature-controllable cylinders and a plurality of screws formed by combining a plurality of screw elements, and when the temperature-controllable cylinders are designated C1, C2, C3, ... from the upstream side, a cylinder provided with a raw material supply port for supplying a raw material mainly composed of the water-soluble polymer (A) is designated C1, C2, C3, ... S The cylinder in which the most upstream raw material supply port is installed among the raw material supply ports for supplying raw materials containing water is designated as C.T [2] A method for producing a water-soluble film, wherein, when the ratio of the effective length (L) of the screw to the diameter (D) of the screw (L / D) is greater than 50 and less than 100, the ratio is 0≦T−S≦6 (where S and T are each an integer of 1 or greater), and the ratio of the effective length (L) of the screw to the diameter (D) of the screw (L / D) is greater than 50 and less than 100. [3] A method for producing a water-soluble film, wherein the screw has a kneading disk region, and the kneading disk region is respectively arranged in the order of K1, K2, K3, ..., K4 from the upstream of the multi-screw extruder. m (K m is the kneading area located at the most downstream side.) When the upstream end of the kneading disc area K1 is T [3] The method for producing a water-soluble film according to [1], wherein the cylinder has a plurality of raw material supply ports for supplying the raw material containing water, and the cylinder having the most downstream raw material supply port is designated as C u When the kneading disc area K m The upstream end of the cylinder portion C u [4] The method for producing a water-soluble film according to [2], wherein the cylinder has a plurality of raw material supply ports for supplying the raw material containing water, and the cylinder having the most downstream raw material supply port is designated as C u When the kneading disc area K m-1 (where m is an integer of 2 or more) is connected to the downstream end of the cylinder portion C u [5] A method for producing a water-soluble film according to [2] or [3], wherein the water-soluble polymer (A) comprises a polyvinyl alcohol-based resin. [6] A method for producing a water-soluble film according to any one of [1] to [5], wherein the resin composition (Z) extruded from the die has a water content of 20 to 60 mass%. [7] A method for producing a water-soluble film according to any one of [1] to [6], wherein the resin composition (Z) extruded from the die contains 10 to 60 parts by mass of a plasticizer (B) per 100 parts by mass of the water-soluble polymer (A). [8] A water-soluble film produced by the method for producing a water-soluble film according to any one of [1] to [7]. [9] A package formed from the water-soluble film according to [8].

[10] A drug package comprising a package formed from the water-soluble film according to [8], and a drug packaged in the package.

[0010] According to the method for producing a water-soluble film of the present invention, the resin composition does not become discolored, and the obtained water-soluble film is free of undissolved water-soluble polymer and has excellent mechanical properties, moldability, blocking resistance, and transparency. Furthermore, the obtained water-soluble film does not break or leak contents when used for packaging medicines, etc.

[0011] FIG. 1 is an explanatory diagram of a multi-screw extruder used in one embodiment of the present invention.

[0012] The present invention will be described in more detail below based on exemplary embodiments of the present invention, but the present invention is not limited to these embodiments. In the present invention, when "X to Y" (X and Y are any numbers) is used, it means "X or more and Y or less" unless otherwise specified, and also includes "preferably greater than X" or "preferably smaller than Y." Furthermore, when "X or more" (X is any number) or "Y or less" (Y is any number) is used, it also includes "preferably greater than X" or "preferably less than Y." In the present invention, "x and / or y (x and y are any configurations or components)" refers to three combinations: x only, y only, and x and y. Furthermore, the term "major component" refers to the component that accounts for the largest amount in a target substance, and typically accounts for 50% by mass or more, preferably 60% by mass or more, and particularly preferably 70% by mass or more of the target substance.

[0013] The present invention is a method for producing a water-soluble film, which comprises mixing and dissolving a water-soluble polymer (A) and water in a multi-screw extruder to obtain a resin composition (Z) containing a mixture of the water-soluble polymer (A) and water as main components, and extruding the resin composition (Z) from a die to form a film.

[0014] <Multi-screw extruder> An example of a multi-screw extruder used in the present invention is shown in Figure 1. In Figure 1, the multi-screw extruder 1 has multiple screws 3 inside a cylinder 4 to which multiple temperature-controllable cylinders 2 are connected. A head 25 is located downstream of the multi-screw extruder 1, and a breaker plate 26 can be installed in the flow path of the head 25. A mesh for capturing foreign matter can also be installed in the breaker plate 26. Furthermore, a conduit 27, a gear pump 28, a filtration device 29 such as a filter pack or a screen changer, etc. can be appropriately connected downstream of the head 25. A die 30 is located at the most downstream end. Here, "downstream" refers to the direction in which the composition flows within the multi-screw extruder 1, and "upstream" refers to the opposite direction.

[0015] In the present invention, a twin-screw extruder or an extruder with three or more screws can be used as the multi-screw extruder 1, but a twin-screw extruder is preferred in terms of equipment installation costs and maintenance. The configuration of the multi-screw extruder 1 will be described below.

[0016] [Screw] The screw 3 is configured by combining screw elements divided in the direction of the effective screw length. The dimensions of the screw 3 can be expressed by the effective screw length (L) (unit: mm) and the screw diameter (D) (unit: mm).

[0017] In the present invention, the ratio (L / D) of the effective screw length (L) (unit: mm) to the screw diameter (D) (unit: mm) is more than 50 and not more than 100, preferably 52 to 95, particularly preferably 55 to 90, and even more preferably 60 to 85. If the (L / D) ratio is too small, mixing may be insufficient, resulting in the formation of undissolved water-soluble polymer (A) or backflow of steam within the extruder. On the other hand, if the (L / D) ratio is too large, coloration of the film-forming raw material mixture may occur or the blocking resistance of the resulting film may decrease.

[0018] Examples of the screw elements include a kneading disc element 11 and a full flight element 12.

[0019] The kneading disc element 11 is a screw element capable of kneading and mixing raw materials in an extruder. Examples of the kneading disc element 11 include a kneading disc, a rotor, a twist kneading disc, and a gear kneader.

[0020] The kneading disc is configured by arranging multiple plate-shaped kneading discs in a row in the axial direction, each having a cross section perpendicular to the axial direction of the screw that is formed into a substantially elliptical shape. The kneading disc rotates as the screw rotates, and the material is introduced between the kneading disc and the inner wall of the cylinder, where it is kneaded. The kneading intensity of the kneading disc can be adjusted by the mounting method (mounting angle relative to the screw axis). For example, in the present invention, a feed kneading disc can be used, in which multiple kneading discs are mounted in succession with a phase difference of a predetermined pitch of 30 to 60 degrees in the reverse rotation direction of the screw. A neutral kneading disc can also be used, in which multiple kneading discs are mounted in succession with a phase difference of 90 degrees. Furthermore, a return kneading disc can also be used, in which multiple kneading discs are mounted in succession with a phase difference of a predetermined pitch of 30 to 60 degrees in the rotation direction of the screw.

[0021] The feed kneading discs have the ability to feed the material because the kneading discs are arranged in a twisted arrangement in the axial direction, but the neutral kneading discs have almost no ability to feed the material. Therefore, with the neutral kneading discs, the material tends to remain in the kneading section and be sufficiently kneaded, and the degree of kneading can be increased compared to the feed kneading discs. In addition, the return kneading discs have the ability to return the kneaded resin composition (Z) from downstream to upstream, and can further increase the degree of kneading.

[0022] The full-flight element 12 is a screw element having a spiral groove, and the wings (flights) that form the groove are spiral. When the full-flight element 12 rotates, the composition in the groove of the full-flight element 12 is transported to other flight grooves at the intermeshing portion and extruded downstream.

[0023] The number of flights (number of threads) of the full flight element 12 may be one, two, or three or more, but two is preferable for efficient transportability. There are no particular restrictions on the length or flight pitch of the full flight element 12, but it is preferable to shorten the pitch of the full flight elements 12 located before and after the kneading disk area described below in order to increase the filling rate.

[0024] In the present invention, the screw 3 preferably has a kneading disc region 13 in which the kneading disc elements 11 are connected in series. By having the kneading disc region 13, the water-soluble polymer (A) and water can be mixed and dissolved more efficiently.

[0025] The kneading disc region 13 may be one or more, but it is preferable to have more than one. When there are more than one kneading disc region 13, they are respectively designated as K1, K2, K3, ..., K4 from the upstream of the multi-screw extruder 1. m (K m is the kneading disc region located at the most downstream side. ) Further, full flight elements 12 are arranged between each kneading disc region 13.

[0026] In the present invention, the upstream end of the kneading disc region K1 is preferably located within 55% of the upstream position in the direction of the effective screw length (L), more preferably within 50%, and particularly preferably within 45%. By having the upstream end of the kneading disc region K1 located within the above-mentioned range from the upstream position in the direction of the effective screw length (L), strong shear and kneading can be applied from the beginning in the multi-screw extruder system, allowing efficient mixing and dissolution of the water-soluble polymer (A), and tending to prevent undissolved material from remaining in the water-soluble film. Here, the upstream end of the kneading disc region K1 refers to the position of the upstream end of the kneading disc element located most upstream of the kneading disc elements 11 constituting the kneading disc region K1. Furthermore, the position X% from the upstream position in the direction of the effective screw length (L) refers to the relative position when the upstream end of the screw element located most upstream of all the screw elements constituting the screw 3 is set to 0% and the downstream end of the screw element located most downstream is set to 100%.

[0027] In the present invention, the kneading disc region K m The downstream end of the kneading disc region K is preferably located at a position 50% or more from the upstream side in the direction of the effective screw length (L), more preferably 55% or more, and particularly preferably 60% or more. m Since the downstream end of the kneading disc region K is within the above range from the upstream side in the direction of the effective screw length (L), the small amount of undissolved matter remaining in the system of the multi-screw extruder at the end of the process can be subjected to strong shearing and kneading, thereby efficiently mixing and dissolving the water-soluble polymer (A), and there is a tendency that no undissolved matter remains in the water-soluble film. m The downstream end of the kneading disc area K m The downstream end position is the position of the downstream end of the kneading disc element arranged on the most downstream side among the kneading disc elements constituting the kneading disc element.

[0028] In the present invention, the total length (L) of each kneading disc area 13 relative to the screw effective length (L) KD) ratio (L KD / L) is preferably 0.15 or more, more preferably 0.17 or more, and even more preferably 0.19 or more. The upper limit is usually 0.90 or less, preferably 0.80 or less, and more preferably 0.75 or less. KD ) refers to the above-mentioned K1, K2, K3, ..., K m The total axial length of the above (L KD By setting the ratio (mm / L) within the above range, it is possible to ensure time for applying strong shear and kneading in the multi-screw extruder, and there is a tendency that the water-soluble polymer (A) can be efficiently mixed and dissolved.

[0029] Furthermore, it is preferable that the kneading disc region 13 has a certain length. Specifically, the axial length of the kneading disc region 13 is preferably 2% or more of the effective screw length (L), more preferably 3% or more, and even more preferably 4% or more. It is also preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less. When there are multiple kneading disc regions 13, it is preferable that each kneading disc region 13 is in the above range. When the axial length of the kneading disc region 13 is in the above range, the resin composition tends to be more likely to remain in the kneading section and the water-soluble polymer (A) tends to be more easily dissolved.

[0030] [Cylinder] As described above, the cylinder 4 is formed by connecting a plurality of temperature-controllable cylinders 2, and is provided with at least two raw material supply ports: a raw material supply port for supplying a raw material containing the water-soluble polymer (A) as a main component, and a raw material supply port for supplying a raw material containing water.

[0031] In the present invention, it is also preferable to have a plurality of raw material supply ports for supplying raw materials containing water. By having a plurality of raw material supply ports for supplying the raw materials containing water, it is possible to adjust the water content of the resin composition (Z) extruded from the die. Furthermore, by dissolving various additives described below, such as a plasticizer (B), a filler (C), a surfactant (D), etc., in water after the water-soluble polymer (A) has been mixed and dissolved in water and supplying the resulting solution to the multi-screw extruder, it is possible to reduce thermal history and shear stress, which is effective when adding additives that are relatively sensitive to heat and shear stress and are easily decomposed or dissolved.

[0032] The upstream side of the cylinder 4 is provided with a raw material supply port 21. Furthermore, the cylinder 4 downstream of the raw material supply port 21 may be provided with a plurality of raw material supply ports, such as a raw material supply port 22 and a raw material supply port 23.

[0033] The raw material supply port 22 can supply a liquid from a liquid addition pump 32 connected to a liquid tank 31. Furthermore, the raw material supply port 23 can supply a liquid from the liquid addition pump 32 connected to the liquid tank 31, or supply a solid into the multi-screw extruder 1 by a feeder 33 (including a side feeder).

[0034] The screw element used in the cylinder 2 having a raw material supply port for supplying raw materials containing water installed therein can be either a kneading disc element 11 or a full-flight element 12, but it is preferable to use a full-flight element 12 for the purpose of suppressing water overflow at the water supply section and backflow upstream. It is also preferable that a full-flight element 12 is used between the raw material supply port for supplying raw materials mainly composed of the water-soluble polymer (A) and the raw material supply port arranged most upstream among the raw material supply ports for supplying raw materials containing water.

[0035] As described above, the cylinder 4 is connected to the temperature-controllable cylinder 2. When the temperature-controllable cylinders 2 are designated C1, C2, C3, ... from the upstream side, the cylinder 2 having the raw material supply port for supplying the raw material mainly composed of the water-soluble polymer (A) is designated as C1. SThe cylinder 2 in which the most upstream raw material supply port among the raw material supply ports for supplying raw materials containing water is installed is designated as C T When T-S is set as above, it is most important that 0≦T-S≦6 (where S and T are each an integer of 1 or greater). Preferably, 1≦T-S≦5, and particularly preferably, 1≦T-S≦4. When T-S≧7, the water-soluble polymer (A) is subjected to a large amount of thermal history, and the resulting resin composition (Z) is colored yellow. Furthermore, the region in which the water-soluble polymer (A) is conveyed within the cylinder 4 without being plasticized by water becomes longer, which increases the load and shear heat on the multi-screw extruder 1, making the multi-screw extruder 1 more likely to stop, and promoting coloration of the resin composition (Z). Furthermore, when there are multiple raw material supply ports for supplying a raw material mainly composed of the water-soluble polymer (A), the positional relationship between the cylinder 2 in which the most upstream raw material supply port is installed and the cylinder 2 in which the most upstream raw material supply port among the raw material supply ports for supplying a water-containing raw material is installed may be within the above-mentioned range.

[0036] In the present invention, the raw material supply port for supplying a raw material containing the water-soluble polymer (A) as a main component is preferably raw material supply port 21, and the raw material supply ports for supplying a raw material containing water are preferably raw material supply ports 22 and 23. Furthermore, the raw material supply port 21 is preferably installed in the cylinder C1.

[0037] When there are a plurality of raw material supply ports for supplying the raw material containing water, the cylinder in which the most downstream raw material supply port is installed is designated as C u When the kneading disc area K m The upstream end of the cylinder C u It is preferable that the nozzle is located downstream of the nozzle. m The upstream end of the cylinder C u By being located downstream of the cylinder section C u This allows the added water and additives to be dispersed uniformly in the resin composition (Z).

[0038] In addition, when there are a plurality of raw material supply ports for supplying the raw material containing water, the cylinder in which the most downstream raw material supply port is installed is designated as C u When the kneading disc area Km-1 (where m is an integer of 2 or more) is connected to the downstream end of the cylinder C u As described above, the screw element in the water supply section preferably uses a full-flight element 12, and the cylinder C u Within the kneading disc area K m-1 If the downstream end of the water supply pipe is included, it is likely to cause water to overflow at the water supply section or backflow upstream, which is undesirable.

[0039] Furthermore, the cylinder 2 can be provided with a vent hole 24, and in the present invention, it is preferable to have the vent hole 24 in order to degas volatile components such as moisture and gases generated in the extruder. The vent hole 24 can be used to degas steam generated in the cylinder 4 or to connect to a vacuum pump to draw a vacuum. Furthermore, the number of raw material supply ports and vent holes may be increased beyond the number shown in FIG. 1 as needed.

[0040] <Resin composition (Z)> As described above, the present invention provides a method for producing a water-soluble film, which comprises extruding a resin composition (Z) containing a water-soluble polymer (A) and water as main components, obtained by mixing and dissolving the water-soluble polymer (A) and water in a multi-screw extruder, through a die to form a film. Each component contained in the resin composition (Z) will be described below.

[0041] [Water-soluble polymer (A)] Examples of the water-soluble polymer (A) include polyvinyl alcohol-based resins, polyethylene glycol-based resins, carboxymethyl cellulose-based resins, sodium acrylate-based resins, polyvinylpyrrolidone, dextrin, chitosan, chitin, methyl cellulose, hydroxyethyl cellulose, casein, and pullulan. The water-soluble polymer (A) may be used alone or in combination of two or more. Among these, those containing a polyvinyl alcohol-based resin are preferred.

[0042] [Polyvinyl Alcohol-Based Resin] In the present invention, a polyvinyl alcohol (hereinafter abbreviated as "PVA")-based resin is a resin in which vinyl alcohol units are the main unit component among the repeating units constituting the polymer. The main unit component refers to a unit component that occupies 50 mol % or more and 100 mol % or less in the resin. PVA-based resins are thermoplastic resins that are water-soluble, and films containing PVA-based resins as the main component are also used as water-soluble films and are used in a wide range of fields. Examples of PVA-based resins used in the present invention include unmodified PVA and modified PVA-based resins.

[0043] The average saponification degree of the PVA-based resin used in the present invention is preferably 80 mol% or more, particularly 82 to 99.9 mol%, further 85 to 98.5 mol%, and especially 90 to 97 mol%. When an unmodified PVA is used as the PVA-based resin, the average saponification degree is preferably 80 mol% or more, particularly 82 to 99 mol%, and even more preferably 85 to 90 mol%. When a modified PVA-based resin is used as the PVA-based resin, the average saponification degree is preferably 80 mol% or more, particularly 85 to 99.9 mol%, and even more preferably 90 to 98 mol%. When an anionic group-modified PVA-based resin is used as the PVA-based resin, the average saponification degree is preferably 85 mol% or more, particularly 88 to 99 mol%, further 90 to 97 mol%, and especially preferably 91 to 94 mol%. If the average saponification degree is too low, the solubility of the water-soluble film in water tends to decrease over time depending on the pH of the drug to be packaged, whereas if the average saponification degree is too high, the solubility in water tends to decrease significantly.

[0044] The degree of polymerization of the PVA-based resin used in the present invention can generally be expressed by the viscosity of its aqueous solution, and the viscosity of a 4% by weight aqueous solution at 20°C is preferably 5 to 50 mPa·s, more preferably 13 to 45 mPa·s, and particularly preferably 17 to 40 mPa·s. When an unmodified PVA is used as the PVA-based resin, the viscosity of the unmodified PVA in a 4% by weight aqueous solution at 20°C is preferably 5 to 50 mPa·s, more preferably 13 to 45 mPa·s, and particularly preferably 17 to 40 mPa·s. When a modified PVA-based resin is used as the PVA-based resin, the viscosity of the modified PVA-based resin in a 4% by weight aqueous solution at 20°C is preferably 5 to 50 mPa·s, more preferably 13 to 40 mPa·s, and particularly preferably 17 to 30 mPa·s. If the viscosity is too low, the mechanical strength of the water-soluble film used as a packaging material tends to decrease, whereas if the viscosity is too high, the viscosity of the film-forming material tends to increase, resulting in decreased productivity.

[0045] The average degree of saponification is measured in accordance with JIS K 6726 3.5, and the viscosity of a 4% by mass aqueous solution is measured in accordance with JIS K 6726 3.11.2.

[0046] When a modified PVA-based resin is used as the PVA-based resin, the modification amount is preferably 1 to 10 mol%, more preferably 1.5 to 8 mol%, particularly preferably 2 to 6 mol%, and particularly preferably 2 to 5 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-based resin tends to decrease, the biodegradability tends to decrease, and blocking tends to occur easily.

[0047] In the present invention, the above-mentioned PVA-based resins may be used alone, or an unmodified PVA and a modified PVA-based resin may be used in combination. Furthermore, two or more PVA-based resins having different saponification degrees, viscosities, modified species, modification amounts, etc. may be used in combination.

[0048] In particular, in water-soluble films for packaging medicines (especially for packaging laundry detergents), the PVA-based resin preferably contains a modified PVA-based resin, and more preferably contains an anionic group-modified PVA-based resin, from the viewpoint of solubility. Examples of the anionic group include a carboxy group, a sulfonic acid group, and a phosphate group. From the viewpoint of solubility in water and chemical resistance, the carboxy group and the sulfonic acid group are preferred, and the carboxy group is particularly preferred.

[0049] The carboxyl group of the carboxyl group-modified PVA is derived from a monomer having a carboxyl group, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, or itaconic acid; or a carboxyl group-containing unsaturated compound such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, or itaconic acid; or a compound in which the carboxyl group has been fully or partially neutralized with a base such as an alkali compound (e.g., sodium hydroxide or potassium hydroxide); or a monoalkyl ester of the above carboxyl group-containing unsaturated compound such as methyl acrylate, ethyl acrylate, methyl methacrylate, monomethyl fumarate, or monomethyl maleate; or a dialkyl ester of the above carboxyl group-containing unsaturated compound such as diethyl fumarate or diethyl maleate. From the standpoints of economy and practicality, the carbon number of these esters is typically 1 to 20, preferably 1 to 10, and particularly preferably 1 to 4. Among these, maleic acid compounds are preferred, with monomethyl maleate being even more preferred.

[0050] The PVA-based resin can be produced by a conventional method described in, for example, JP-A-2017-95679.

[0051] [Water] The water used in the present invention is not particularly limited, but it is preferable to use ion-exchanged water or RO water. The water preferably has a silica content of 50 μg / L or less, preferably 5.0 μg / L or less, and a chloride ion content of 2 μg / L or less, preferably 1 μg / L.

[0052] In the present invention, the resin composition (Z) may contain a plasticizer (B), a filler (C), a surfactant (D), and other additives.

[0053] [Plasticizer (B)] In the present invention, it is preferable to contain a plasticizer (B) in order to impart appropriate flexibility to the film. The plasticizer (B) can be used alone or in combination of two or more. It is also preferable to use two or more in combination in terms of the mechanical properties and moldability of the film.

[0054] Examples of such plasticizers (B) include glycerins such as glycerin, diglycerin, and triglycerin; alkylene glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and dipropylene glycol; and sugar alcohols such as trimethylolpropane, sorbitol, xylitol, and maltitol. Among these, glycerin, diglycerin, and polyethylene glycol are preferred because they are easily available and can achieve a plasticizing effect with a small amount, and sorbitol is preferred in terms of the stability of the package over time. These may be used alone or in combination of two or more. When two or more such plasticizers are used in combination, it is preferable to use a polyhydric alcohol (b1) having a melting point of 80°C or higher (hereinafter sometimes abbreviated as "plasticizer (b1)") in combination with a polyhydric alcohol (b2) having a melting point of 50°C or lower (hereinafter sometimes abbreviated as "plasticizer (b2)"). Furthermore, from the viewpoints of productivity and the mechanical properties of the resulting film, the plasticizer (b2) is preferably a compound that is liquid at about room temperature, and preferably has a melting point of 30° C. or lower, particularly preferably 20° C. or lower. The lower limit of the melting point is usually −95° C., preferably −40° C., particularly preferably −15° C., and even more preferably −5° C.

[0055] The content of the plasticizer (B) is preferably 10 to 60 parts by mass, particularly preferably 15 to 55 parts by mass, and even more preferably 20 to 50 parts by mass, per 100 parts by mass of the water-soluble polymer (A). If the content of the plasticizer (B) is too low, the plasticizing effect is low, resulting in poor processability, and when used as a package, the toughness of the water-soluble film tends to be impaired over time. If the content of the plasticizer (B) is too high, the strength of the film tends to be reduced and blocking tends to occur easily.

[0056] [Filler (C)] In the present invention, a filler (C) can be further contained as needed. The filler (C) is contained for the purpose of blocking resistance, and includes organic fillers (c1) and inorganic fillers (c2), with organic filler (c1) being particularly preferred. The average particle diameter of the filler (C) is preferably 0.1 to 50 μm, and particularly preferably 1 to 35 μm. The average particle diameter of the filler (C) is a value measured using a laser diffraction particle size distribution analyzer, and is calculated from the D50 value (particle diameter at 50% of the cumulative volume) of the obtained cumulative volume distribution.

[0057] The organic filler (c1) refers to particulate matter (primary particles) composed of an organic compound and having any shape, such as needle-like, rod-like, layer-like, scale-like, or spherical, or an aggregate of such particulate matter (secondary particles). Such organic 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 in terms of dispersibility in the water-soluble polymer (A).

[0058] Examples of the starch include raw starches (corn starch, potato starch, sweet potato starch, wheat starch, cassava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, kudzu starch, bracken starch, lotus starch, 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 viewpoints of biodegradability, availability, and economy.

[0059] 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 tendency of the 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.

[0060] As the inorganic filler (c2), it is preferable to use an oxide-based inorganic compound or talc, and it is particularly preferable to use titanium oxide, talc or silica, and it is further preferable to use silica.

[0061] The average particle size of the inorganic filler (c2) is preferably 1 to 20 μm, particularly preferably 2 to 15 μm, and further preferably 3 to 10 μm. If the average particle size is too small, the flexibility and toughness of the film tend to decrease and blocking tends to increase, while if the average particle size is too large, pinholes tend to form when the film is stretched during molding.

[0062] The content of the filler (C) is preferably 1 to 30 parts by mass, particularly preferably 1.5 to 25 parts by mass, and even more preferably 2 to 20 parts by mass, per 100 parts by mass of the water-soluble polymer (A). If the content is too low, the blocking tendency of the film tends to increase, while if the content is too high, the flexibility and toughness of the film tend to decrease.

[0063] [Surfactant (D)] In the present invention, a surfactant (D) or the like can be further contained as necessary. The surfactant (D) used in the present invention is contained for the purpose of improving releasability from the casting surface during film production, 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, polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt, polyoxyethylene lauryl amino ether, polyoxyethylene stearyl amino ether and other polyoxyethylene alkyl amino ethers, sorbitan monopalmitate, sorbitan monostearate, glycerol stearate, sucrose fatty acid esters, etc., which can be used alone or in combination of two or more. Among these, polyoxyalkylene alkyl ether phosphate monoethanolamine salt and polyoxyethylene lauryl amino ether are preferred in terms of production stability. The surfactant (D) may be used alone or in combination of two or more thereof.

[0064] 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 water-soluble polymer (A). If the content is too low, the peelability between the casting surface of the film-forming apparatus and the formed film tends to decrease, resulting in a decrease in productivity. If the content is too high, blocking tends to occur easily, and when the film is used to form a package, the adhesive strength at the time of sealing tends to decrease.

[0065] The resin composition (Z) may also contain solvents, fragrances, rust inhibitors, colorants, extenders, antifoaming agents, ultraviolet absorbers, liquid paraffins, fluorescent brighteners, bitter components (e.g., denatonium benzoate, etc.), etc., within the scope of not impairing the object of the invention. These may be used alone or in combination of two or more.

[0066] Examples of the solvent include ethanol, methanol, propanol, isopropanol, acetone, methyl ethyl ketone, acetic acid, methyl acetate, ethyl acetate, butyl acetate, benzene, toluene, etc. The solvents may be used alone or in combination of two or more.

[0067] In the present invention, an antioxidant may be blended. Examples of such antioxidants include sulfites such as sodium sulfite, potassium sulfite, calcium sulfite, and ammonium sulfite, as well as tartaric acid, ascorbic acid, sodium thiosulfate, techol, and Rongalit. Of these, sulfites, particularly sodium sulfite, are preferred. The blending amount is preferably 0.1 to 10 parts by mass, particularly preferably 0.2 to 5 parts by mass, and even more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the water-soluble polymer (A).

[0068] <Method of manufacturing water-soluble film> Next, the method of manufacturing a water-soluble film of the present invention will be described. The manufacturing method of the present invention preferably comprises at least the following steps: Step [I]: A step of supplying a raw material mainly composed of a water-soluble polymer (A) to a multi-screw extruder; Step [II]: A step of supplying a raw material containing water from at least one location of the multi-screw extruder; Step [III]: A step of mixing and dissolving the raw materials in the multi-screw extruder to prepare a resin composition (Z); Step [IV]: A step of extruding the resin composition (Z) from a die onto a casting surface to form a water-soluble film.

[0069] [Step [I]: Step of Supplying a Raw Material Comprising a Water-Soluble Polymer (A) as a Main Component to a Multi-Screw Extruder] A method for supplying the raw material comprising the water-soluble polymer (A) as a main component can be, for example, a method of supplying the raw material from a raw material supply port installed in the cylinder 2 of the multi-screw extruder 1 shown in FIG. 1 . The raw material supply port for supplying the raw material comprising the water-soluble polymer (A) as a main component to the multi-screw extruder may be one or two or more. In the present invention, from the viewpoint of production efficiency, it is preferable that the raw material comprising the water-soluble polymer (A) as a main component be supplied from the raw material supply port 21 located at the most upstream of the multiple raw material supply ports. It is also preferable to supply a portion of the raw material comprising the water-soluble polymer (A) as a main component from the raw material supply port 21 located at the most upstream of the multiple raw material supply ports, and then dissolve the remaining water-soluble polymer (A) in water and supply it as a water-containing raw material, as described below.

[0070] The form of the water-soluble polymer (A) supplied is not particularly limited and may be, for example, powder, granules, pellets, etc. Furthermore, the raw material containing the water-soluble polymer (A) as a main component may contain a plasticizer (B), a filler (C), a surfactant (D), other additives, and a solvent.

[0071] [Step [II]: Step of Supplying a Water-Containing Raw Material from at Least One Location of the Multi-Screw Extruder] Next, the step of supplying a water-containing raw material from at least one location of the multi-screw extruder 1 will be described. The water-containing raw material may contain, in addition to water, a water-soluble polymer (A), a plasticizer (B), a filler (C), a surfactant (D), other additives, and a solvent. In particular, the water-containing raw material preferably contains a plasticizer (B), a filler (C), and a surfactant (D).

[0072] As described above, the water-containing raw material is fed into the cylinder C equipped with a raw material feed port for feeding the raw material mainly composed of the water-soluble polymer (A). S and a cylinder C in which the most upstream raw material supply port among the raw material supply ports for supplying raw materials containing water is installed. T The raw material is supplied from a raw material supply port that is within a specific range of positional relationship with the raw material. The method for supplying the raw material containing water is not particularly limited, but may be, for example, by using a liquid addition pump 32 or the like.

[0073] The temperature of the cylinder 2 in which the raw material supply port is installed is preferably 15 to 105°C, more preferably 20 to 100°C, and even more preferably 25 to 95°C. If the cylinder temperature is less than 15°C, a lot of energy will be consumed when heating the mixture on the downstream side, which tends to reduce productivity. On the other hand, if the cylinder temperature exceeds 105°C, steam will return to the upstream side and rise from the supply port for the water-soluble polymer (A), blocking the water-soluble polymer (A), which tends to reduce productivity.

[0074] When the plasticizer (B), filler (C), surfactant (D), other additives, and solvent are not blended with the raw material mainly composed of the water-soluble polymer (A) or the raw material containing water, these raw materials may be individually fed from the raw material feed port to the multi-screw extruder 1 using, for example, a hydrogenation pump 32, a feeder, a side feeder 33, etc. In this case, it is preferable to feed them downstream of the raw material containing water.

[0075] When the filler (C) is contained, as described above, it may be blended into a raw material mainly composed of the water-soluble polymer (A) or a raw material containing water, but it is also preferable in terms of dispersibility to blend it after dispersing it in the plasticizer (B).

[0076] Furthermore, when the filler (C) is supplied to the multi-screw extruder 1, the supply position is preferably at a position 50% or more from the upstream of the screw, more preferably at a position 60% or more, particularly preferably at a position 70% or more, and even more preferably at a position 75% or more. By supplying the filler (C) to the multi-screw extruder 1 at a position 50% or more from the upstream of the screw, there is a tendency that the filler (C) can be contained in the film in a size that can impart the unevenness necessary to maintain blocking resistance. In particular, when an organic filler (c1) is used as the filler (C), this is preferred in terms of obtaining a film with excellent blocking resistance and water sealing properties.

[0077] [Step [III]: Step of mixing and dissolving the raw materials in a multi-screw extruder to prepare the resin composition (Z)] The step of mixing and dissolving the raw materials in the multi-screw extruder 1 to prepare the resin composition (Z) is carried out by rotating the screw 3 installed inside the cylinder 4 of the multi-screw extruder 1. In this step, the water-soluble polymer (A) is dissolved in water, and the resin composition (Z) is prepared as a mixture (film-forming raw material).

[0078] The rotation speed of the screw 3 is usually 50 to 1000 rpm, preferably 100 to 800 rpm, and more preferably 150 to 600 rpm. If the rotation speed of the screw 3 is too low, discharge tends to become unstable, while if it is too high, the resulting film may become discolored. In addition, it is preferable for the screws to rotate in the same direction, as this allows for adequate shearing to achieve sufficient kneading.

[0079] The temperature of each cylinder 2 is preferably 10 to 170°C, more preferably 30 to 150°C, particularly preferably 40 to 130°C, and especially preferably 50 to 110°C. If the temperature is too low, mixing and dissolution will be insufficient, and undissolved water-soluble polymer (A) will tend to be produced or air bubbles will remain. On the other hand, if the temperature is too high, the mixture will tend to become discolored, reducing the transparency of the resulting film and deteriorating its blocking resistance.

[0080] In the present invention, the water content of the resin composition (Z) in the multi-screw extruder is preferably 20 to 60% by mass. The water content of the resin composition (Z) is more preferably 25 to 55% by mass, and even more preferably 30 to 50% by mass. If the water content is too low, the water-soluble polymer may not dissolve sufficiently, resulting in undissolved material, or the viscosity of the film-forming raw materials may increase, leading to insufficient degassing and the occurrence of die lines during film formation. If the water content is too high, the film thickness accuracy may decrease, or the drying efficiency during film formation may decrease, leading to reduced productivity of the water-soluble film.

[0081] In the present invention, the pH of the resin composition (Z) in the multi-screw extruder is preferably 4 to 10, and more preferably 4.8 to 9.5.

[0082] [Step [IV]: Step of extruding resin composition (Z) from a die onto a casting surface to form a water-soluble film] In step [IV], the resin composition (Z) prepared in step [III] is extruded from a die 30 onto a casting surface to form a film, and if necessary, a drying treatment is performed to form a water-soluble film.

[0083] Any conventionally known die can be used as the die 30, but a T-slit die is preferred. Also, a gear pump 28 is preferably connected between the multi-screw extruder and the die 30. Use of the gear pump 28 is preferred because it makes it easier to achieve a uniform thickness distribution in the film flow direction.

[0084] The temperature of the resin composition (Z) at the discharge portion of the 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, tending to reduce the productivity of the water-soluble film, whereas if the temperature is too high, bubbles and the like tend to form.

[0085] In the present invention, the water content of the resin composition (Z) extruded from the spinneret 30 is preferably 20 to 60% by mass. The water content of the resin composition (Z) is more preferably 25 to 55% by mass, and even more preferably 30 to 50% by mass. The water content is measured in accordance with JIS K 6726 3.4 by recovering the resin composition (Z) immediately after extrusion from the spinneret, and the value of the volatile content of the recovered material is taken as the water content.

[0086] Furthermore, it is preferable that the resin composition (Z) extruded from the die 30 be extruded onto a casting surface, such as the metal surface of an endless belt or drum roll, or the surface of a plastic substrate such as a polyethylene terephthalate film, and then dried on the casting surface. Drying is usually performed by heating the casting surface. 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, making it prone to blocking. If the surface temperature is too high, the resin composition (Z) tends to foam, resulting in poor film formation. Furthermore, drying during film formation can be performed using a heated roll, a floating dryer blowing hot air onto the film, a far-infrared device, a dielectric heating device, or other similar methods.

[0087] The water-soluble film thus formed is peeled from the casting surface, transported, and wound around a core tube to form a film roll. The resulting film roll can be supplied as a finished product as is, but it is also preferable to supply the water-soluble film as a film roll obtained by slitting it to a desired film width.

[0088] The water-soluble film may be given a textured finish such as an embossed pattern, a fine textured pattern, or a special engraved pattern on one or both sides of the film in terms of blocking resistance, slipperiness during processing, reduced adhesion between products, and appearance.

[0089] <Water-soluble film> The water-soluble film of the present invention is a film that contains a water-soluble polymer (A) as a main component and dissolves in water at room temperature (20° C.). Since the water-soluble film is obtained by the characteristic production method of the present invention, it is free from undissolved water-soluble polymer (A) and is excellent in mechanical properties, formability, blocking resistance, etc.

[0090] The thickness of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 10 to 120 μm, particularly preferably 15 to 110 μm, and even more preferably 20 to 100 μm. If the thickness is too thin, the mechanical strength of the film tends to decrease, while if the thickness is too thick, the dissolution rate in water tends to slow down and the film-forming efficiency also tends to decrease.

[0091] The width of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 300 to 5000 mm, particularly preferably 500 to 4000 mm, and further preferably 600 to 3000 mm. If the width is too narrow, production efficiency tends to decrease, while if it is too wide, it tends to become difficult to control slack and film thickness.

[0092] The length of the water-soluble film is appropriately selected depending on the application, etc., but is preferably 100 to 20,000 m, particularly preferably 800 to 15,000 m, and even more preferably 1,000 to 10,000 m. If the length is too short, film switching is time-consuming and production efficiency tends to decrease, while if the length is too long, poor appearance tends to occur due to tight winding.

[0093] The water content of the resulting 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. If the water content is too high, blocking tends to occur. Adjusting the water content to this level can be achieved by appropriately setting the drying conditions and humidity control conditions. The water content is measured in accordance with JIS K 6726 3.4, and the value of the volatile content obtained is taken as the water content.

[0094] The surface roughness (Ra) of the obtained water-soluble film is preferably 0.2 to 1.0 μm, particularly preferably 0.25 to 0.8 μm, and even more preferably 0.3 to 0.6 μm. If the surface roughness is too small, blocking resistance tends to decrease, while if it is too large, sealing ability tends to decrease. The maximum height difference (Rz) is also preferably 2 to 10 μm, particularly preferably 3 to 8 μm, and even more preferably 4 to 7 μm. The surface roughness (Ra) and (Rz) can be measured using a laser microscope in accordance with JIS B0601-2001.

[0095] The water-soluble film of the present invention may be used as a single layer, or may be used as a multilayer structure in which other films or resin layers are laminated.

[0096] <Package / Drug Package> A package according to one embodiment of the present invention is formed from the obtained water-soluble film. Furthermore, a drug package according to one embodiment of the present invention is a package in which a drug is enclosed in the obtained water-soluble film. According to this drug package, the drug is packaged in the water-soluble film. Therefore, when the entire package is placed in water, the drug dissolves or disperses in the water after the water-soluble film dissolves, thereby exerting the effects of the drug. Therefore, this drug package is suitable for drug packages that contain a relatively small amount of drug, such as a single dose.

[0097] Examples of the chemical 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 chemical may be in the form of a liquid or solid, and in the case of a liquid, it is in the form of a liquid, and in the case of a solid, it may be in the form of a granule, tablet, powder, etc. The chemical is preferably one that is dissolved or dispersed in water for use, and in the present invention, it is particularly preferred to encapsulate a liquid detergent. The pH of the chemical may be alkaline, neutral, or acidic.

[0098] The liquid detergent preferably has a pH value of 6 to 12 when dissolved or dispersed in water, particularly 6.5 to 11, and especially 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. The water content is measured in accordance with JIS K 3362 7.21.3.

[0099] When using the water-soluble film of the present invention to package a chemical such as a liquid detergent to form a chemical package, a known method can be used. For example, the product is produced by laminating two water-soluble films together, with one film (bottom film) fixed to a mold at the bottom of a molding device and another film (top film) fixed to the top of the device. After that, the chemical such as a liquid detergent is poured into the molded film, and the top and bottom films are then crimped together. After crimping, the vacuum is released to obtain the package.

[0100] Methods for laminating the film after the drug has been added include, for example, (1) heat sealing, (2) water sealing, and (3) glue sealing, and among these, the water sealing method (2) is versatile and advantageous.

[0101] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" means parts by mass.

[0102] The following materials were prepared as the material components of the water-soluble film. [Water-soluble polymer (A)] PVA-based resin (a1): a carboxyl-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 with maleic acid monomethyl ester of 2.0 mol% [Water] Ion-exchanged water [Plasticizer (B)] Plasticizer (b1): sorbitol Plasticizer (b2): glycerin [Filler (C)] Organic filler (c1): corn starch [Surfactant (D)] Surfactant (d1): phosphate ester surfactant

[0103] <Example 1> A cylinder capable of controlling the temperature at 15 points along the effective length of the screw (C1, C2, C3, ..., C 15 A head section, a conduit, and a T-die were installed at the downstream tip of a twin-screw extruder having a screw diameter (D). The screw configuration was as follows: kneading disk region K1 at a position 45-51% from the upstream in the screw effective length direction; kneading disk region K2 at a position 54-60% from the upstream; kneading disk region K3 at a position 63-69% from the upstream; kneading disk region K4 at a position 72-78% from the upstream; and kneading disk region K5 at a position 81-87% from the upstream. The ratio (L / D) of the screw effective length (L) to the screw diameter (D) was 52.5, and the total length (L KD ) ratio (L KD / L) was 0.30. Furthermore, raw material supply ports were installed in cylinders C1 and C2. The position of cylinder C1 was 1 to 8% from the upstream side in the direction of the effective length of the screw, and the position of cylinder C2 was 8 to 14% from the upstream side. A raw material mixture of 100 parts of PVA-based resin (a1), 20 parts of plasticizer (b2), 8 parts of filler (c1), and 1 part of surfactant (d1) was supplied from the raw material supply port of cylinder C1 using a feeder. In addition, an aqueous solution of plasticizer (b1) with a concentration of 24% by mass was prepared, and the aqueous solution was added from the raw material supply port of C2 using a liquid addition pump. At this time, the feed rate and the pump rate were adjusted to supply PVA-based resin (a1) / plasticizer (b1) / plasticizer (b2) / filler (c1) / surfactant (d1) / water = 40.5% by mass / 8.1% by mass / 8.1% by mass / 3.3% by mass / 0.4% by mass / 39.6% by mass. The feeder for the PVA-based resin (a1), the tank for the aqueous solution, and the pump were kept at room temperature. 15 Set temperature (T1 to T 15 ) are T1 = 30°C, T2 = 30°C, T3 to T 15 = 90°C, and the set temperatures of the head, conduit, and T-die were also set to 90°C, and extrusion was performed to obtain a film-like resin composition from the die. The water content of the resin composition extruded from the die was 40% by mass. The film-like resin composition extruded from the die was then taken up with a chill roll to obtain a water-soluble film with a thickness of 100 μm. The appearance of the obtained water-soluble film was visually inspected, and a white, transparent film was obtained, with no undissolved matter observed. Furthermore, when a random location of the obtained water-soluble film was observed with a digital microscope (200x magnification), it was confirmed that fillers of a size sufficient to maintain blocking resistance were present.

[0104] Example 2: Extrusion was performed in the same manner as in Example 1, except that a 24% by mass aqueous solution of plasticizer (b1) was added using a liquid pump through the raw material supply port installed on cylinder C4 instead of cylinder C2. A film-like resin composition was obtained from the die. Note that cylinder C4 was located 21 to 27% upstream in the direction of the effective screw length. The water content of the resin composition extruded from the die was 40% by mass. The film-like resin composition extruded from the die was then collected with a chill roll to obtain a water-soluble film with a thickness of 100 μm. Visual inspection of the appearance of the obtained water-soluble film revealed a white, transparent film, with no undissolved material. Furthermore, observation of a random location on the obtained water-soluble film using a digital microscope (200x magnification) confirmed the presence of fillers large enough to maintain blocking resistance.

[0105] Example 3: Extrusion was performed in the same manner as in Example 1, except that a 24% by mass aqueous solution of plasticizer (b1) was added using a liquid pump through the raw material supply port installed on cylinder C6 instead of cylinder C2. A film-like resin composition was obtained from the die. Note that cylinder C6 was located 34 to 41% upstream in the direction of the effective screw length. The water content of the resin composition extruded from the die was 40% by mass. The film-like material extruded from the die was then collected with a chill roll to obtain a water-soluble film with a thickness of 100 μm. Visual inspection of the appearance of the obtained water-soluble film revealed a white, transparent film, with no undissolved material. Furthermore, observation of a random location on the obtained water-soluble film using a digital microscope (200x magnification) confirmed the presence of fillers large enough to maintain blocking resistance.

[0106] <Example 4> A cylinder capable of controlling the temperature at 15 points along the effective length of the screw (C1, C2, C3, ..., C 15A head section, a conduit, and a T-die were installed at the downstream tip of a twin-screw extruder having a screw diameter (D). The screw configuration was as follows: kneading disk region K1 at a position 45-51% from the upstream in the screw effective length direction; kneading disk region K2 at a position 54-60% from the upstream; kneading disk region K3 at a position 63-69% from the upstream; kneading disk region K4 at a position 72-78% from the upstream; and kneading disk region K5 at a position 90-93% from the upstream. The ratio (L / D) of the screw effective length (L) to the screw diameter (D) was 52.5, and the total length (L KD ) ratio (L KD / L) was 0.27. 13 The position of cylinder C1 was 1 to 8% from the upstream side in the direction of the effective length of the screw, and the position of cylinder C4 was 21 to 27% from the upstream side in the direction of the effective length of the screw. 13 The position of the filler (c1) is 80 to 87% from the upstream in the direction of the effective length of the screw. A raw material prepared by blending 100 parts of PVA resin (a1), 20 parts of plasticizer (b2), and 1 part of surfactant (d1) in advance was supplied to the twin-screw extruder through the raw material supply port of cylinder C1 by a feeder. In addition, an aqueous solution of plasticizer (b1) with a concentration of 19.8% by mass was prepared, and the aqueous solution was supplied to the twin-screw extruder through the raw material supply port of cylinder C4 by using a liquid addition pump. Furthermore, an aqueous solution of filler (c1) with a concentration of 33% by mass was prepared, and the aqueous solution was supplied to the twin-screw extruder through the raw material supply port of cylinder C5 by using a liquid addition pump. 13 The aqueous solution was fed into the twin-screw extruder from the raw material feed port using a liquid addition pump. At this time, the feed rate and the pump feed rate were adjusted so that the PVA-based resin (a1) / plasticizer (b1) / plasticizer (b2) / filler (c1) surfactant (d1) / water ratio was 40.5% by mass / 8.1% by mass / 8.1% by mass / 3.3% by mass / 0.4% by mass / 39.6% by mass. The feeder for the PVA-based resin (a1), the tank for the aqueous solution, and the pump were kept at room temperature. 15 Set temperature (T1 to T 15 ) are T1 to T2 = 30°C, T3 to T 12 = 90 ° C., T 13~T 15 = 70°C, and the set temperatures of the head, conduit, and T-die were set to 70°C, and extrusion was performed to obtain a film-like resin composition from the die. The water content of the resin composition extruded from the die was 40% by mass. The film-like resin composition extruded from the die was then taken up with a chill roll to obtain a water-soluble film with a thickness of 100 μm. The appearance of the obtained water-soluble film was visually inspected, and a white, transparent film was obtained, with no undissolved matter observed. Furthermore, when a random location of the obtained water-soluble film was observed with a digital microscope (200x magnification), it was confirmed that fillers of a size sufficient to maintain blocking resistance were present.

[0107] <Example 5> Temperature-controllable cylinders (C1, C2, C3, ..., C 18 A head section, a conduit, and a T-die were installed at the downstream tip of a twin-screw extruder having 18 kneading discs. The screw configuration was as follows: kneading disc region K1 was located at 23-35% from the upstream in the direction of the effective screw length; kneading disc region K2 was located at 36-48% from the upstream; kneading disc region K3 was located at 49-60% from the upstream; kneading disc region K4 was located at 62-70% from the upstream; kneading disc region K5 was located at 71-79% from the upstream; and kneading disc region K6 was located at 80-87% from the upstream; and full-flight elements were installed elsewhere. The ratio (L / D) of the screw effective length (L) to the screw diameter (D) was 63, and the total length (L) of each kneading disc region was 100%. KD ) ratio (L KDThe flow rate (flow rate / L) was 0.58. Furthermore, raw material supply ports were installed in cylinders C1, C3, and C4. The position of cylinder C1 was 3 to 5% upstream in the direction of the effective screw length, the position of cylinder C3 was 13 to 16%, and the position of cylinder C4 was 19 to 22%. A raw material composition consisting of 100 parts by mass of PVA-based resin (a1), 8 parts by mass of filler (C1-1), and 1 part by mass of surfactant (d1) was supplied via a feeder through the raw material supply port of cylinder C1. Furthermore, water was supplied via the raw material supply port of cylinder C3 using a liquid addition pump, and aqueous solutions containing 41% by mass of plasticizer (b1) and 41% by mass of plasticizer (b2) were added via the raw material supply port of cylinder C4 using a liquid addition pump. At this time, the feed rate and pump rate were adjusted to supply PVA-based resin (a1) / plasticizer (b1) / plasticizer (b2) / filler (c1-1) surfactant (d1) / water = 40.5% by mass / 8.1% by mass / 8.1% by mass / 3.3% by mass / 0.4% by mass / 39.6% by mass. The feeder for PVA-based resin (a1), the tank for the aqueous solution, and the pump were kept at room temperature (23°C). The set temperatures of cylinders C1 to C5 were 90°C, and those of cylinders C6 to C7 were 100°C. 16 Set the temperature to 110℃, cylinder C 17 ~C 18 The set temperature of the extrusion head was 70°C, and the set temperatures of the head, conduit, and T-die were also 70°C. The extrusion was performed at a screw rotation speed of 200 rpm, and a film-like resin composition was obtained from the die. The water content of the resin composition extruded from the die was 40% by mass. The film-like resin composition extruded from the die was then taken up with a chill roll to obtain a water-soluble film with a thickness of 100 μm. The appearance of the obtained water-soluble film was visually inspected, and a white, transparent film was obtained, with no undissolved matter observed. Furthermore, when a random location of the obtained water-soluble film was observed with a digital microscope (200x magnification), the presence of fillers of a size sufficient to maintain blocking resistance was confirmed.

[0108] Comparative Example 1: Extrusion was performed in the same manner as in Example 1, except that a 24% by mass aqueous solution of plasticizer (b1) was added using a liquid pump through the raw material supply port installed on cylinder C8 instead of cylinder C2. A film-like resin composition was obtained from the die. Note that cylinder C8 was located 47-54% upstream in the effective screw length direction. The water content of the resin composition extruded from the die was 40% by mass. The film-like resin composition extruded from the die was then collected with a chill roll to obtain a water-soluble film with a thickness of 100 μm. Visual inspection of the appearance of the obtained water-soluble film revealed a yellow color and a large amount of undissolved material. Furthermore, observation of a random location of the obtained water-soluble film using a digital microscope (200x magnification) confirmed the presence of fillers large enough to maintain blocking resistance.

[0109] The production conditions for the water-soluble films of Examples 1 to 5 and Comparative Example 1, and the results of the appearance evaluation of the obtained water-soluble films are shown in Table 1 below.

[0110]

[0111] The water-soluble films produced in Examples 1 to 5 were found to have excellent appearances, with no discoloration or undissolved PVA-based resin. Furthermore, the films contained fillers, which provided excellent blocking resistance. On the other hand, the water-soluble film produced in Comparative Example 1 was yellowish, contained a large amount of undissolved material, and had a significantly poor appearance. When the water-soluble film obtained in Comparative Example 1 was used as a package, there was a risk of the film breaking or pinholes or the like being formed, which could cause leakage of the contents from the package, making it unsuitable for practical use.

[0112] 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 all intended to fall within the scope of the present invention.

[0113] The water-soluble film produced by the production method of the present invention can be used for various packaging applications, and is particularly useful for unit packaging of medicines and the like, and for packaging food.

Claims

1. A method for producing a water-soluble film, which comprises mixing and dissolving at least a water-soluble polymer (A) and water in a multi-screw extruder to obtain a resin composition (Z), and extruding the resin composition (Z) from a die to form a film, The multi-screw extruder has a plurality of temperature-controllable cylinders and a plurality of screws formed by combining a plurality of screw elements, The temperature-controllable cylinders are respectively 1 , C 2 , C 3 ..., the cylinder having a raw material supply port for supplying the raw material containing the water-soluble polymer (A) as the main component is designated as C. S The cylinder in which the most upstream raw material supply port is installed among the raw material supply ports for supplying raw materials containing water is designated as C. T where 0≦T−S≦6 (where S and T are integers of 1 or more), A method for producing a water-soluble film, wherein the ratio (L / D) of the effective length (L) of the screw to the diameter (D) of the screw is more than 50 and 100 or less.

2. The screw has one or more kneading disc regions, and the kneading disc regions are arranged in the order of K from the upstream of the multi-screw extruder. 1 , K. 2 , K. 3 , ..., K m (K m is the kneading area located at the most downstream side. 1 The upstream end of the cylinder C T 2. The method for producing a water-soluble film according to claim 1, wherein the water-soluble film is located downstream of the water-soluble film.

3. The cylinder has a plurality of raw material supply ports for supplying raw materials containing water, and the cylinder having the most downstream raw material supply port installed therein is designated as C. u When the kneading disc area K m The upstream end of the cylinder portion C u 3. The method for producing a water-soluble film according to claim 2, wherein the water-soluble film is located downstream of the water-soluble film.

4. The cylinder has a plurality of raw material supply ports for supplying raw materials containing water, and the cylinder having the most downstream raw material supply port installed therein is designated as C. u When the kneading disc area K m-1 (where m is an integer of 2 or more) is connected to the downstream end of the cylinder portion C u 4. The method for producing a water-soluble film according to claim 2, wherein the water-soluble film is located upstream of the water-soluble film.

5. 3. The method for producing a water-soluble film according to claim 1, wherein the water-soluble polymer (A) comprises a polyvinyl alcohol-based resin.

6. 3. The method for producing a water-soluble film according to claim 1, wherein the resin composition (Z) extruded from the die has a water content of 20 to 60% by mass.

7. 3. The method for producing a water-soluble film according to claim 1, wherein the resin composition (Z) contains 10 to 60 parts by mass of a plasticizer (B) per 100 parts by mass of the water-soluble polymer (A).

8. A water-soluble film produced by the method for producing a water-soluble film according to claim 1 or 2.

9. A package formed from the water-soluble film according to claim 8.

10. A pharmaceutical package comprising a package formed from the water-soluble film according to claim 8 and a pharmaceutical packaged in the package.