Water-soluble film and package

Abstract

The present invention relates to a water-soluble film and a package. The present invention provides a water-soluble film having good transparency and good peelability from a support with a small amount of surfactant. The water-soluble film of the present invention contains a polyvinyl alcohol resin and a surfactant, the content of the surfactant being 0.005 to 1 parts by mass per 100 parts by mass of the polyvinyl alcohol resin, and the ratio S(0) / S(32) of the amount S(0) of the surfactant present on at least one surface of the water-soluble film to the amount S(32) of the surfactant present on a surface at a depth position 32 nm away from the surface of the water-soluble film, measured from the count number of fragment ions derived from the surfactant detected by time-of-flight secondary ion mass spectrometry, is in the range of 100 to 500.

Description

[0001] This invention application is a divisional application of PCT patent application PCT / JP2021 / 022538, entitled "Water-soluble film and packaging body", and the parent application number in China is 202180046093.X. Technical Field

[0002] This invention relates to a water-soluble film containing polyvinyl alcohol resin suitable for use in packaging various pharmaceuticals, and to a packaging body using the same. Background Technology

[0003] Water-soluble films are used in a wide range of applications, such as packaging liquid detergents, pesticides, and seed strips containing seeds, due to their excellent solubility in water.

[0004] In water-soluble films used for the purposes described above, polyvinyl alcohol resin (hereinafter, sometimes referred to as PVA) is mainly used. Furthermore, a water-soluble film whose water solubility is improved by incorporating various additives such as plasticizers or by using modified polyvinyl alcohol is disclosed (for example, see Patent Document 1).

[0005] Previous technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2017-078166. Summary of the Invention

[0006] The technical problem to be solved by the invention In the manufacture of water-soluble films, the film is typically obtained by pouring a film-forming solution containing PVA and solvent onto a support such as a metal roller or drum, and then evaporating and removing the solvent. Compared to resins such as polyolefins, hydrophilic PVA generally has a higher affinity for metals and tends to be less prone to peeling from the support. Poor peeling from the support results in uneven film thickness, inconsistent mechanical strength, solubility, and other physical properties.

[0007] To improve the peelability of self-supporting structures in water-soluble films, it is known to add surfactants to the film-forming solution of water-soluble films.

[0008] However, when a surfactant with high affinity for PVA is added to the film-forming solution of a water-soluble film, a large amount of surfactant is required to obtain sufficient peelability, which is not preferable from an economic point of view. Furthermore, by adding a large amount of surfactant, the surfactant easily seeps to the surface of the water-soluble film, causing the film to clump together. On the other hand, when a surfactant with low affinity for PVA is added to the film-forming solution of a water-soluble film, even if the amount of surfactant added is small, the peelability of the film is improved. However, PVA and the surfactant undergo phase separation in the film-forming solution, causing surfactant particles to disperse in the film, thereby tending to reduce the transparency of the film. Therefore, even by reducing the amount of surfactant added to the film-forming solution and reducing the surfactant content in the water-soluble film, a water-soluble film with excellent peelability from the support and good transparency is desired.

[0009] The object of the present invention is to provide a water-soluble film with good peelability from the support and good transparency with a lower surfactant content.

[0010] means for solving technical problems As a method for analyzing components present on the surface of thin films and components present in the depth direction of the thin film, time-of-flight secondary ion mass spectrometry (hereinafter, sometimes referred to as TOF-SIMS) is employed. In this analytical method, the distribution of various additive components on the surface of the thin film can be determined by identifying fragment ions originating from various additives. Furthermore, by etching and analyzing the surface of the thin film, the distribution of various additive components in the depth direction of the thin film can also be determined.

[0011] For example, if the analysis focuses on the signal of fragment ions of surfactants contained in the film, the segregation state of the surfactant in the surface portion of the film can be estimated by comparing the signal intensity, that is, the segregation state on the surface obtained by etching in the direction of the film surface and the depth direction of the film.

[0012] Based on the insights gained from detailed analysis of the segregation state of surfactants in various water-soluble films using the aforementioned TOF-SIMS, the inventors conducted in-depth research and discovered that the above-mentioned objective can be achieved by water-soluble films in which the segregation state of surfactants in the film surface satisfies a specific relationship. Based on this insight, the inventors further conducted research and completed the present invention.

[0013] That is, the present invention relates to the following: [1] A water-soluble film comprising polyvinyl alcohol resin and a surfactant, wherein the water-soluble film, The content of the surfactant is 0.005 to 1 part by mass relative to 100 parts by mass of the polyvinyl alcohol resin, and the ratio of the amount of surfactant S(0) on at least one surface of the water-soluble film, measured by the count of fragment ions originating from the surfactant as detected by time-of-flight secondary ion mass spectrometry, to the amount of surfactant S(32) on the surface of the water-soluble film at a depth of 32 nm from the surface, is in the range of 100 to 500.

[0014] Furthermore, the present invention relates to the following: [2] According to the water-soluble film described in [1], wherein, The surfactant is a nitrogen-containing surfactant; [3] According to the water-soluble film described in [2], wherein, The nitrogen-containing surfactant comprises at least one selected from the group consisting of alkylamine surfactants, alkylamide surfactants and alkylalkanolamide surfactants; [4] According to the water-soluble film described in [3], wherein, The alkylamine surfactant is a polyoxyethylene alkylamine surfactant, and the alkylamide surfactant is a higher fatty acid diethanolamide surfactant. [5] The water-soluble film according to any one of [1] to [4] contains a filler; and [6] According to the water-soluble film described in [5], wherein, The filler is made of inorganic particles.

[0015] Furthermore, the present invention relates to the following: [7] A type of packaging, wherein, The water-soluble film described in any one of [1] to [6] contains a pharmaceutical agent; [8] According to the packaging body described in [7], wherein, The agent is a pesticide, detergent, or disinfectant; and [9] According to the packaging body described in [7] or [8], wherein, The medicine is in liquid form.

[0016] Invention Effects According to the present invention, a water-soluble film with good peelability from the support and good transparency can be provided with a lower surfactant content. Detailed Implementation

[0017] The present invention will now be described in detail.

[0018] The water-soluble film of the present invention contains PVA and a surfactant. Furthermore, the water-soluble film may contain other resins, components, or additives other than PVA, such as plasticizers.

[0019] <surfactants> In this invention, the water-soluble film contains a surfactant to obtain good peelability from the support.

[0020] The surfactant content in the water-soluble film needs to be 0.005 to 1 part by weight relative to 100 parts by weight of PVA. If the surfactant content is less than 0.005 parts by weight, problems such as poor peelability of the self-support of the water-soluble film during manufacturing or agglomeration between water-soluble films may easily occur. From this point of view, the surfactant content in the water-soluble film is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, and even more preferably 0.05 parts by weight or more. On the other hand, when the surfactant content exceeds 1 part by weight, surfactant seepage to the surface of the water-soluble film and reduced transparency of the water-soluble film due to surfactant aggregation may easily occur. From this point of view, the surfactant content in the water-soluble film is preferably 0.8 parts by weight or less, more preferably 0.6 parts by weight or less, even more preferably 0.4 parts by weight or less, and particularly preferably 0.3 parts by weight or less.

[0021] Here, the surfactant content in the water-soluble film refers to the ratio of the mass of surfactant to the mass of PVA contained in the entire water-soluble film. Typically, the surfactant is non-volatile, and the surfactant content in the water-soluble film is substantially the same as the mass of surfactant relative to the mass of PVA in the film-forming solution. If the surfactant is volatile, the surfactant content in the water-soluble film can be measured by methods such as dissolving the water-soluble film in a good solvent for PVA, such as hexafluoroisopropanol, adding a poor solvent for PVA, such as methanol, to cause the PVA to redefine and remove it, and then quantifying the surfactant concentration in the solvent by liquid chromatography or similar methods.

[0022] There are no particular restrictions on the type of surfactant; for example, anionic surfactants and nonionic surfactants can be used. However, it is preferable that the surfactant has an appropriate affinity for the PVA contained in the water-soluble film. If the affinity for PVA is too high, the surfactant is easily dispersed uniformly in the PVA, resulting in insufficient surfactant on the surface of the water-soluble film, which may lead to poor peelability of the self-supporting structure of the water-soluble film.

[0023] On the other hand, when the affinity with PVA is too low, in the film-forming solution of water-soluble films, or during the drying and curing process of the film-forming solution on the support, the surfactant separates from PVA to form droplets, which can easily lead to a decrease in the transparency of the film and a roughness of the film surface.

[0024] As a surfactant with suitable affinity for PVA, a nitrogen-containing surfactant is preferred, exemplified by alkylamine surfactants, alkylamide surfactants, and alkylalkanolamide surfactants. Therefore, the water-soluble film of the present invention preferably contains at least one surfactant selected from the group consisting of alkylamine surfactants, alkylamide surfactants, and alkylalkanolamide surfactants.

[0025] Examples of alkylamine surfactants include higher fatty acid amine salts such as oleylamine acetate and polyoxyethylene alkylamine surfactants such as polyoxyethylene laurylamine.

[0026] Examples of alkylamide surfactants include polyoxyethylene laurylamide and other polyoxyethylene alkylamide surfactants.

[0027] Examples of alkyl alkanolamide surfactants include higher fatty acid alkanolamide surfactants such as laurylamide alkanol.

[0028] From the viewpoint that it is easier to obtain a water-soluble film with excellent peelability from the support under a wider range of manufacturing conditions, polyoxyethylene alkylamine surfactants or higher fatty acid alkanolamide surfactants are more preferred, and polyoxyethylene alkylamine surfactants are even more preferred.

[0029] These surfactants can be used alone or in combination of two or more.

[0030] <TOF-SIMS Measurement> In this invention, the ratio of the amount of surfactant S(0) on at least one surface of the water-soluble film, measured by the count of fragment ions derived from surfactant in the water-soluble film as detected by TOF-SIMS, to the amount of surfactant S(32) on a surface of the water-soluble film at a depth of 32 nm from the surface, is in the range of 100 to 500. However, the ratio of the amount of surfactant S(0) on the surface to the amount of surfactant S(32) on a surface of the water-soluble film at a depth of 32 nm from the surface refers to the value obtained by dividing S(32) by S(0) (hereinafter, sometimes referred to as S(0) / S(32)).

[0031] S(0) is the amount of surfactant present on at least one surface, measured by the count of fragment ions originating from surfactant, when analyzing at least one surface of a water-soluble film using TOF-SIMS. On the other hand, S(32) is the amount of surfactant present on the surface at a depth of 32 nm from the surface of the water-soluble film (the same surface as the surface where S(0) is measured) after 32 nm etching along the depth direction from the surface of the water-soluble film (hereinafter, sometimes referred to as the etched surface), measured by TOF-SIMS at a depth of 32 nm from the surface of the water-soluble film exposed by etching (hereinafter, sometimes referred to as the etched surface), measured by the count of fragment ions originating from surfactant. A S(0) / S(32) of 100 or higher indicates that the amount of surfactant present on the surface of the water-soluble film is more than 100 times the amount of surfactant present on the surface at a depth of 32 nm from the surface of the water-soluble film.

[0032] If S(0) / S(32) is small, it indicates insufficient segregation of surfactant on the surface of the water-soluble film, which can easily lead to a decrease in the peelability of the self-support of the water-soluble film or a decrease in the transparency of the water-soluble film. S(0) / S(32) is preferably 150 or more, more preferably 200 or more, and even more preferably 250 or more.

[0033] On the other hand, if S(0) / S(32) is large, it indicates that the surfactant segregation on the surface of the water-soluble film is large, the surface of the water-soluble film is sticky and prone to agglomeration between films, and the transportability is reduced. S(0) / S(32) is preferably 450 or less, more preferably 400 or less, and even more preferably 350 or less.

[0034] There are no particular restrictions on the counts of S(0) and S(32) as long as they can be distinguished from other fragment ions. In order to achieve a level that can ignore interference and other effects, it is preferred to be 50 or more, more preferably 100 or more, and even more preferably 1000 or more.

[0035] As described above, the water-soluble film of the present invention ensures good peelability from the support by suppressing the amount of surfactant added, causing the surfactant to segregate on the surface of the film. Furthermore, it avoids the reduction in film transparency that occurs with excessive surfactant addition.

[0036] As a method for controlling S(0) / S(32) within the above-mentioned range, the following method can be cited: in addition to selecting the type and content of surfactants with appropriate affinity to the above-mentioned PVA, the film-forming conditions of the water-soluble film, such as the adjustment conditions of the film-forming stock solution, extrusion conditions, and drying conditions described later, are also selected. By combining these methods, the water-soluble film of the present invention can be obtained.

[0037] The following describes the specific implementation method of TOF-SIMS measurement.

[0038] <Sample Adjustment> The water-soluble thin film was cut into 5mm × 5mm pieces and attached to the measurement base using conductive double-sided tape. During measurement, the surface of the unetched film and the etched surface (obtained by etching the film surface) at a depth of 32nm from the film surface were used as measurement targets. TOF-SIMS measurements were performed under the conditions described below. Furthermore, the depth of 32nm from the film surface was defined as the 200th analysis point during the etching process under the conditions described below.

[0039] <TOF-SIMS Measurement Conditions> Measuring device: TOF-SIMS 5 (manufactured by ION-TOF) Analysis software: Surface Lab 6 (manufactured by ION-TOF) Primary ion source: Bi3 ++ Measuring current: 0.2pA at 25keV (10kHz) Measurement range: 200μm × 200μm Pixel count measured: 128Pix × 128Pix Neutralization conditions: Neutralization electron gun not used Count measurement: the number of fragments captured by the detector (detector strength). <Etching Processing Conditions> Etching mode: GCIB Etching source: Ar cluster Raster Size: 500μm × 500μm Current: 0.26nA The following cycle was repeated: under the aforementioned etching conditions, a total depth of 0.16 nm was etched from the surface of the water-soluble film along the depth direction through three etching passes, followed by one TOF-SIMS measurement. Therefore, the value at a depth of 32 nm from the surface of the water-soluble film during each TOF-SIMS measurement, after etching to a depth of 0.16 nm, became the analysis result for the 200th point (etching rate: 0.16 nm / scan). Furthermore, this etching rate (0.16 nm / scan) was calculated assuming it was the same as the etching rate (0.16 nm / scan) when etching a sample of a known water-soluble film with a known thickness, whose thickness was measured individually using an ellipsometry or similar instrument, under the same conditions.

[0040] <Selection Methods for Fragment Ions Derived from Surfactants> If a TOF-SIMS measurement is performed on a water-soluble film, a variety of fragment ions are counted. Among these, fragment ions unique to the surfactant contained in the water-soluble film are selected, and their counts are measured. Fragment ions unique to surfactants are, for example, fragment ions with high strength that are not considered to be generated from other components in the water-soluble film. As a specific selection method, a TOF-SIMS measurement is performed on a water-soluble film without surfactants under the same conditions as described above. Fragment ions with high strength or fragment ions that are independent of other fragment ions are selected from those that are almost not present in the water-soluble film without surfactants but are present in the water-soluble film containing surfactants. For the selected fragment ions, the counts on the surface of the water-soluble film and on the etched surface at a depth of 32 nm from the surface of the water-soluble film are measured, and these are taken as S(0) and S(32), respectively.

[0041] <Polyvinyl alcohol resin> The water-soluble film of the present invention contains PVA. As PVA, a polymer manufactured by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer can be used. Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, 2,2-dimethylpropionate, and vinyl tert-carbonate, among which vinyl acetate is preferred.

[0042] The aforementioned vinyl ester polymers are preferably polymers obtained using only one or more vinyl ester monomers as monomers, more preferably polymers obtained using only one vinyl ester monomer as monomers, but may also be copolymers of one or more vinyl ester monomers and other monomers that can copolymerize with them.

[0043] Other monomers that can copolymerize with this vinyl ester monomer include, for example, ethylene; olefins with 3 to 30 carbon atoms such as propylene, 1-butene, and isobutene; acrylic acid or its salts; acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid or its salts; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid or its salts, dimethylaminopropylacrylamide or its salts, and N-hydroxymethylacrylamide. Acrylamide derivatives such as methylacrylamide or its derivatives; methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid or its salts, dimethylaminopropylmethacrylamide or its salts, N-hydroxymethylmethacrylamide or its derivatives; N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone or other N-vinylamides; vinyl ethers such as methyl vinyl ether, vinyl ethyl ether, n-propyl vinyl ether, isopropyl vinyl ether, vinyl n-butyl ether, vinyl isobutyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether or other vinyl ethers; vinyl cyanides such as acrylonitrile and methacrylonitrile; halogenated vinylides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; propylene compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters or anhydrides; itaconic acid or its salts, esters or anhydrides; vinyl silyl compounds such as vinyltrimethoxysilane; isopropyl acetate, etc. The above-mentioned vinyl ester polymers can have one or more structural units derived from these other monomers.

[0044] From the viewpoints of water solubility and film strength, based on the molar number of all structural units constituting the vinyl ester polymer, the proportion of structural units derived from the other monomers in the vinyl ester polymer is preferably 15 mol% or less, more preferably 5 mol% or less.

[0045] There is no particular limitation on the degree of polymerization of PVA. From the viewpoint of film strength, a lower limit for the degree of polymerization is preferably 200 or higher, more preferably 300 or higher, and even more preferably 500 or higher. On the other hand, from the viewpoint of PVA productivity and water-soluble film productivity, an upper limit for the degree of polymerization is preferably 8,000 or lower, more preferably 5,000 or lower, and even more preferably 3,000 or lower. Here, the degree of polymerization refers to the limiting viscosity [η] (unit: deciliters / g) measured in water at 30°C after resaponification and purification of PVA, based on the average degree of polymerization (Po) measured according to JIS K6726-1994, calculated by the following formula.

[0046] Po = ([η] × 10) 4 (8.29) （1 / 0.62） In this invention, the degree of saponification of PVA is preferably 64 to 99.9 mol%. By adjusting the degree of saponification within this range, it is easy to balance the water solubility and mechanical and physical properties of the film. The degree of saponification is more preferably 70 mol% or more, and even more preferably 75 mol% or more. On the other hand, the degree of saponification is more preferably 99.6 mol% or less, and even more preferably 99.3 mol% or less. Here, the degree of saponification of PVA refers to the proportion (mol%) of the number of moles of the vinyl alcohol unit relative to the total number of moles of the structural units (typically vinyl ester monomer units) and vinyl alcohol units in PVA that can be converted into vinyl alcohol units through saponification. The degree of saponification of PVA-based polymers can be measured according to the description in JIS K 6726-1994.

[0047] The water-soluble film of this invention can use only one type of PVA as the PVA, or it can use two or more PVAs with different degrees of polymerization, saponification, or modification.

[0048] In this invention, the upper limit of the PVA content in the water-soluble film is preferably 100% by mass. On the other hand, the lower limit of the PVA content is preferably 50% by mass, more preferably 80% by mass, and even more preferably 85% by mass.

[0049] <Packaging> In this invention, to improve the peelability of the self-supporting structure of the water-soluble film, it is preferable to contain filler in the water-soluble film. The average particle size of the filler is preferably 0.5 to 50 μm. When the average particle size of the filler is less than 0.5 μm, the improvement in peelability is sometimes insufficient; when it exceeds 50 μm, the transparency of the water-soluble film may sometimes decrease. The average particle size of the filler is more preferably 1 to 30 μm, and even more preferably 1.5 to 15 μm.

[0050] The material of this filler is not particularly limited; it can be either inorganic or organic, such as clay, talc, alumina, starch, or acrylic resin microparticles. Among these, inorganic microparticles are preferred from the perspectives of cost and operability.

[0051] The filler content in the water-soluble film is preferably 15 parts by weight or less, more preferably 10 parts by weight or less, relative to 100 parts by weight of PVA. If the content is greater than 15 parts by weight, the process passability may deteriorate. On the other hand, if the content is too low, sufficient effect may not be obtained. The filler content is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more.

[0052] <Plasticizers> PVA-containing films, when not containing plasticizers, are more rigid than other plastic films, and their mechanical and physical properties, such as impact strength, and processability during secondary processing may sometimes deteriorate. To prevent this, it is preferable to include a plasticizer in the water-soluble film of the present invention. Preferred plasticizers include polyols, specifically, ethylene glycol, glycerol, diglycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, sorbitol, and other polyols. These plasticizers can be used alone or in combination of two or more. From the viewpoint of minimizing leakage to the surface of the water-soluble film, ethylene glycol or glycerol is preferred, and glycerol is more preferred.

[0053] When the water-soluble film of the present invention contains a plasticizer, the content of the plasticizer in the water-soluble film is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of PVA contained in the water-soluble film. Furthermore, the content of the plasticizer is preferably 70 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. If the above content is less than 1 part by mass, the improvement effect on the mechanical and physical properties of the water-soluble film, such as impact strength, may be insufficient. On the other hand, if the above content exceeds 70 parts by mass, the water-soluble film becomes excessively soft, which may sometimes lead to reduced operability and seepage to the surface of the water-soluble film.

[0054] <Water-soluble polymers> In order to impart mechanical strength to the water-soluble film, maintain the moisture resistance during film handling, or regulate the rate of softening caused by water absorption during film dissolution, the water-soluble film of the present invention may contain water-soluble polymers other than PVA.

[0055] Other water-soluble polymers besides PVA include dextrin, gelatin, animal glue, casein, shellac, gum arabic, polyacrylamide, sodium polyacrylate, polyvinyl methyl ether, copolymers of methyl vinyl ether and maleic anhydride, copolymers of vinyl acetate and itaconic acid, polyvinylpyrrolidone, cellulose, acetylcellulose, acetylbutylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, sodium alginate, etc.

[0056] The content of water-soluble polymers other than PVA in the water-soluble film is preferably 15 parts by weight or less, more preferably 10 parts by weight or less, relative to 100 parts by weight of PVA. If the content is greater than 15 parts by weight, the water solubility of the film may decrease.

[0057] <Other Ingredients> In addition to surfactants, plasticizers, and water-soluble polymers other than PVA, the water-soluble film of the present invention may also contain water, antioxidants, ultraviolet absorbers, lubricants, crosslinking agents, colorants, fillers, preservatives, fungicides, and other polymeric compounds, to a extent that does not impair the effects of the present invention. The total mass of PVA, surfactants, the aforementioned plasticizers, and water-soluble polymers other than PVA constitutes a proportion of 60 to 100% by mass in the total mass of the water-soluble film of the present invention, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass.

[0058] <Water-soluble film> The complete dissolution time of the water-soluble film of the present invention when immersed in water at 10°C is preferably 150 seconds or less. If the complete dissolution time is 150 seconds or less, it is suitable for use as a packaging film for pharmaceuticals, etc. The complete dissolution time is more preferably 90 seconds or less, even more preferably 60 seconds or less, and particularly preferably 45 seconds or less. On the other hand, there is no particular limitation on the lower limit of the complete dissolution time. From the viewpoint that water-soluble films with excessively short complete dissolution times tend to easily experience clumping between films due to moisture absorption from the atmosphere, and a decrease in film strength, it is preferable to have 5 seconds or more, more preferably 10 seconds or more, even more preferably 15 seconds or more, and particularly preferably 20 seconds or more.

[0059] There is no particular limitation on the thickness of the water-soluble film of the present invention. If the thickness is too thick, the secondary processability of the water-soluble film tends to deteriorate. Therefore, it is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and especially preferably 50 μm or less. Furthermore, if the thickness is too thin, the mechanical strength of the water-soluble film may decrease. Therefore, it is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and especially preferably 20 μm or more. In addition, the thickness can be measured at any 10 points (for example, any 10 points on a straight line drawn along the length direction of the water-soluble film), and their average value can be obtained as the thickness of the water-soluble film.

[0060] <Method for manufacturing water-soluble thin films> In this invention, the method for manufacturing water-soluble films can utilize a film-forming stock solution in which solvents, surfactants, etc., are added to PVA and homogenized. Film can be formed using any of the following methods: (i) casting film formation, (ii) wet film formation by extruding the film-forming stock solution into a poor solvent, (iii) wet-dry film formation, (iv) gel film formation by temporarily cooling and gelling the film-forming stock solution and then extracting and removing the solvent to obtain a PVA film, (v) a combination of these methods, (vi) melt extrusion film formation by extruding the film-forming stock solution from a T-die using an extruder, or (vii) blow molding. From the viewpoint of obtaining homogeneous water-soluble films with high productivity, (i) casting film formation or (vi) melt extrusion film formation is preferred. Hereinafter, (i) casting film formation or (vi) melt extrusion film formation for water-soluble films will be described.

[0061] In the case of manufacturing water-soluble films by (i) casting or (vi) melt extrusion, the film-forming solution is cast onto a support such as a metal roller or metal strip in a film-like form, heated to remove the solvent, and then cured to form a film. The cured film is peeled off from the support, dried as needed by a drying roller or drying oven, further heat-treated as needed, and then wound to obtain a roll of long-length water-soluble film.

[0062] It is believed that, apart from surfactants with a very high affinity for PVA, the surfactants in the film-forming solution gradually undergo phase separation within the solution, forming tiny droplets. If this film-forming solution is allowed to flow within a pipe, the surfactants tend to move towards the pipe wall due to the shear rate distribution from the center to the pipe wall. Furthermore, the concentration of surfactants near the pipe wall tends to increase, resulting in a higher concentration of surfactants on the surface of the film formed by the film-forming solution cast on the support. Consequently, the amount of surfactant present on the surface of the obtained water-soluble film, S(0) and S(32), tends to increase. Therefore, by adjusting the movement speed of the surfactants within the pipe, the amount of surfactant present on the surface of the obtained water-soluble film, S(0) and S(32), can be adjusted. Here, the migration speed of the surfactant is influenced not only by the surfactant's affinity for PVA, but also by the dispersion of the surfactant after adjusting the film-forming solution, the temperature (viscosity) of the film-forming solution, the shear rate in the flow path piping, the presence or absence of mixing devices such as static mixers, the drying rate of the dripping film-forming solution, and the film-forming conditions. Therefore, by adjusting these main factors, the amount of surfactant S(0) and S(32) present on the surface of the water-soluble film of the present invention can be adjusted.

[0063] Regarding methods for adjusting the film-forming solution, examples include dissolving PVA, surfactants, and additives such as plasticizers as needed in a dissolving tank; or melting and blending PVA in a aqueous state with surfactants and plasticizers as needed when using a single-screw or twin-screw extruder.

[0064] If the shear rate of the film-forming solution is too low, the surfactant dispersion will be poor, and the transparency of the water-soluble film may decrease. On the other hand, if the shear rate is too high, the surfactant will be over-dispersed, and the segregation of surfactant on the surface of the water-soluble film may be insufficient. The preferred shear rate for adjusting the film-forming solution is 10 to 300 s. -1 More preferably 20 to 250 seconds -1 More preferably 30 to 200 seconds -1 Furthermore, the aforementioned shear rate refers to the maximum shear rate of the film-forming solution adjustment device. For example, in the case of stirring and adjusting simultaneously in a tank using stirring blades, it becomes the value obtained by dividing the distance between the tip of the stirring blade and the tank wall by the speed of the tip of the stirring blade. In the case of a single-screw extruder, it becomes the value obtained by dividing the groove depth by the linear velocity of the bottom surface of the groove in the screw metering section (usually the front end of the screw).

[0065] The volatile content concentration of the film-forming solution is preferably in the range of 50 to 90% by mass, and more preferably in the range of 55 to 80% by mass. Volatile content concentration refers to the concentration of volatile components such as solvents that are removed through evaporation or volatilization during film formation. If the volatile content concentration is less than 50% by mass, the viscosity of the film-forming solution becomes high, sometimes making film formation difficult. On the other hand, if the volatile content concentration exceeds 90% by mass, the viscosity becomes low, and the uniformity of the thickness of the obtained film is easily compromised. Here, the "volatile content of the film-forming solution" in this specification is calculated using the following formula.

[0066] The volatile fraction (mass%) of the film-forming solution = {(Wa-Wb) / Wa} × 100 (In the formula, Wa represents the mass (g) of the film-forming stock solution, and Wb represents the mass (g) of Wa (g) of the film-forming stock solution after drying in an electric dryer at 105℃ for 16 hours.) The adjusted film-forming solution is fed to a T-mold or similar device via piping and is extruded as a film. Filters can be installed in the piping to remove surfactant droplets, or static mixers can be used to alter the dispersion state of the surfactant droplets. However, as mentioned above, if the dispersion state of the surfactant droplets is excessively homogenized, the degree of surfactant segregation on the surface of the water-soluble film may decrease.

[0067] Regarding the temperature of the film-forming solution in the piping and T-die, if it is too high, the surfactant will excessively segregate on the surface of the water-soluble film, potentially reducing the transparency of the film. If it is too low, the segregation of surfactant on the surface of the water-soluble film may be insufficient. The temperature of the film-forming solution in the piping and T-die is preferably 70 to 130°C, more preferably 80 to 120°C, and even more preferably 85 to 110°C.

[0068] The shear rate in the T-die significantly affects the segregation state of surfactants on the surface of the water-soluble film. If the rate is too high, excessive surfactant segregation may occur, potentially reducing the film's transparency. Conversely, if the rate is too low, insufficient surfactant segregation may result in inadequate peelability of the self-supporting structure. The preferred shear rate in the T-die is between 100 and 1000 s⁻¹. -1 More preferably 150 to 850 seconds -1 Further preferred to be 200 to 700 seconds -1 .

[0069] The film-forming solution, which is poured into the support in a film-like form from a T-mold, is dried and cured on the support and in subsequent drying processes. During this period, the segregation of surfactants on the surface of the water-soluble film gradually occurs.

[0070] The surface temperature of the first drying roller or first drying belt (hereinafter sometimes referred to as the first drying roller, etc.), which serves as the first support for the film-forming solution, is preferably 50 to 110°C. When the surface temperature is less than 50°C, drying is performed slowly, which may lead to excessive segregation of surfactants on the surface of the water-soluble film and poor peelability of the water-soluble film due to insufficient drying. On the other hand, when the surface temperature exceeds 110°C, abnormalities in the surface of the water-soluble film due to foaming or the like may easily occur, and insufficient segregation of surfactants on the surface of the water-soluble film may result from rapid drying. The surface temperature of the first drying roller is preferably 60 to 100°C, more preferably 65 to 95°C.

[0071] While heating the film-shaped PVA on the first drying roller, hot air at a speed of 1 to 10 m / s can be uniformly blown onto the entire area of ​​the film-shaped PVA on the non-contact side of the first drying roller, etc., to adjust the drying speed. From the viewpoints of drying efficiency and drying uniformity, the temperature of the hot air blown onto the non-contact side is preferably 50 to 150°C, more preferably 70 to 120°C.

[0072] The water-soluble film peeled off from the first drying roller, etc., continues to be dried on subsequent supports (hereinafter, sometimes referred to as drying rollers, etc., and in the case of two or more, sometimes referred to sequentially as the second drying roller, the third drying roller, or the second drying belt, the third drying belt) preferably to a volatile content of 5 to 50% by mass. After drying to a volatile content within the preferred range, peeling is performed, and further drying is carried out as needed. There are no particular limitations on the drying method; in addition to methods involving contact with drying rollers, etc., methods using a drying oven are also possible. When using multiple drying rollers, etc., alternating contact between one side and the other side of the film with the second drying roller and subsequent sections is preferable, as it homogenizes both sides. For example, the number of subsequent drying rollers, including the second drying roller, is preferably three or more, more preferably four or more, and even more preferably five to 30. The temperature of the drying oven, the second drying roller, or the second drying belt and subsequent sections is preferably 40°C or higher and 110°C or lower. The upper limit of the temperature after the drying oven, the second drying roller or the second drying belt is more preferably 100°C or less, more preferably 90°C or less, and even more preferably 85°C or less.

[0073] The water-soluble film can be further heat-treated as needed. Heat treatment can adjust the film's strength, water solubility, birefringence, etc. The preferred heat treatment temperature is 60°C or higher and 135°C or lower. More preferably, the upper limit of the heat treatment temperature is 130°C or lower. If the heat treatment temperature is too high, the water solubility of the water-soluble film may decrease.

[0074] As needed, the water-soluble film thus manufactured is further subjected to moisture conditioning treatment, cutting of both ends (ears) of the film, etc., and then wound into a cylindrical core and packaged in a moisture-proof manner to become a product.

[0075] The volatile content of the water-soluble film finally obtained through the above series of processes is preferably in the range of 1 to 5% by mass, and more preferably in the range of 2 to 4% by mass.

[0076] <Uses> The water-soluble film of the present invention is suitable for various applications. Examples of such water-soluble films include pharmaceutical packaging films, base films for hydraulic transfer printing, substrate films for embroidery, release films for artificial marble molding, seed packaging films, and films for waste collection bags. Among these, the water-soluble film of the present invention is preferably used as a pharmaceutical packaging film.

[0077] Examples of pharmaceutical agents that can be used when the water-soluble film of the present invention is used as a pharmaceutical packaging film include pesticides, detergents (including bleach), and disinfectants. The physical properties of the pharmaceutical agent are not particularly limited; it can be acidic, neutral, or alkaline. Furthermore, the pharmaceutical agent may contain boron-containing compounds. The form of the pharmaceutical agent can be any of the following: powder, block, gel, or liquid. There are no particular limitations on the packaging method; a unit package method is preferred, where the pharmaceutical agent is packaged in a single unit quantity (preferably sealed). By using the water-soluble film of the present invention as a pharmaceutical packaging film to package the pharmaceutical agent, the packaging body of the present invention can be obtained. Example

[0078] The present invention will now be specifically described through examples, etc., but the present invention is not limited to any of the following examples. Furthermore, the evaluation items and methods used in the following examples and comparative examples are as follows.

[0079] [TOF-SIMS Measurement] Using the aforementioned apparatus and conditions, the S(0) and S(32) of the thin films obtained in the following embodiments or comparative examples are measured, and the S(0) / S(32) is determined.

[0080] [Peelability of water-soluble films] The peelability of the film self-support during the manufacture of water-soluble films in the examples and comparative examples was evaluated according to the following criteria. Furthermore, the support used for peelability evaluation was the first drying roller.

[0081] A: In the circumferential direction of the support, the position where the film separates from the film-forming support is approximately the same in the width direction. When viewed from the width direction, the peeling position is roughly on a straight line, which allows for stable film formation.

[0082] B: The position where the film separates from the support varies slightly in the width direction. When viewed from the width direction, the peeling position appears uneven, but film formation can be carried out stably.

[0083] C: The position where the film separates from the support varies greatly in the width direction, and obvious thickness unevenness is observed in the film, but film production can be carried out continuously.

[0084] D: It is difficult to peel the film off the support stably, and film production cannot be carried out continuously.

[0085] [Haze value of water-soluble films] On the water-soluble film obtained in the following examples or comparative examples, a straight line was drawn perpendicular to the film ends along the width direction (TD) of the film. 5 cm was removed from each end of the film along this line, dividing the remaining portion into 20 equal parts. The center of each of the 20 divisions was used as the measurement point, and the haze value at this measurement point was measured according to ASTM D1003-61 using a haze meter “HZ-1” manufactured by Suga Test Instruments Co., Ltd. In the following examples and comparative examples, a film with a width of 170 cm was manufactured; therefore, the center of each 8 cm wide section, divided into 20 equal parts from 160 cm with 5 cm removed from both ends, was measured. The average of the 20 measured haze values ​​was calculated and used as the haze value of the water-soluble film.

[0086] <Example 1> 100 parts by weight of methyl maleate (MA) modified PVA (saponification degree 99 mol%, polymerization degree 1700, MA modification degree 5 mol%) obtained by saponification of polyvinyl acetate, 10 parts by weight of glycerol as plasticizer, 0.2 parts by weight of polyoxyethylene laurylamine as surfactant, and water were added to a dissolving tank and stirred with a paddle stirrer at a speed of 150 s. -1 The film-forming stock solution was mixed at its highest shear rate, and the volatile content was adjusted to 60% by mass. The obtained film-forming stock solution was filtered, and the temperature was adjusted to 95°C, with a reaction time of 360 seconds. -1 The film is ejected in a film form from the T-die onto the first drying roller, which has a surface temperature of 85°C. Hot air at 85°C is then sprayed onto the surface of the film not in contact with the first drying roller at a speed of 5 m / s for drying. The film is then peeled off from the first drying roller. The peelability of the water-soluble film is rated as A.

[0087] The film, peeled from the first drying roller, is dried by alternating contact between one side and the other side of the film with subsequent drying rollers, and then wound to obtain a water-soluble film (35 μm thick and 170 cm wide). The surface temperature of each subsequent drying roller is adjusted to 75°C.

[0088] The TOF-SIMS measurements of the obtained water-soluble film characteristically detected C3H7N2O compared to a water-soluble film obtained in the same manner without the addition of surfactant (hereinafter, sometimes referred to as the control film). + Based on the ion count, S(0) is 1,980,000 and S(32) is 6,390. Therefore, S(0) / S(32) is 310. Furthermore, the haze of this water-soluble film is 0.6%.

[0089] <Comparative Example 1> In Example 1, the shape of the paddle agitator blades during film-forming was adjusted to change the maximum shear rate to 350 s. -1 The temperature of the film-forming solution in the T-die was changed to 85℃, and the lip opening of the T-die was changed, thereby changing the maximum shear rate in the T-die to 80s. -1 In addition, a water-soluble film was manufactured in the same manner as in Example 1. The TOF-SIMS measurement results, the peelability of the water-soluble film, and the haze are shown in Table 1. Furthermore, in the TOF-SIMS measurement, C3H7N2O was characteristically detected compared to the control film. + ion.

[0090] <Comparative Example 2> The amount of surfactant was changed to 0.001 parts by mass. Otherwise, the film-forming solution was adjusted in the same manner as in Example 1 to manufacture a film. However, the peelability of the water-soluble film from the first drying roller was D, and a stable water-soluble film could not be obtained. As a result, TOF-SIMS measurement and haze measurement could not be performed.

[0091] <Comparative Example 3> The amount of surfactant was changed to 3 parts by mass, and a water-soluble film was manufactured in the same manner as in Example 1. The TOF-SIMS measurement results, the peelability of the water-soluble film, and the haze are shown in Table 1. Furthermore, in the TOF-SIMS measurement, C3H7N2O was characteristically detected compared to the control film. + ion.

[0092] <Example 2> The surfactant was changed to lauric acid diethanolamide, and the water-soluble film was manufactured in the same manner as in Example 1. TOF-SIMS measurements of the obtained water-soluble film characteristically detected C4H compared to the control film. 10 NO2 + The ion count, based on which the ion count is, is S(0) / S(32) = 440. The peelability and haze of the water-soluble film are shown in Table 1.

[0093] <Example 3> The PVA was replaced with unmodified PVA obtained by saponifying polyvinyl acetate (88 mol% saponification, 1700 degree of polymerization). Otherwise, a water-soluble film was manufactured in the same manner as in Example 1. The TOF-SIMS measurement results, the peelability, and the haze of the water-soluble film are shown in Table 1. Furthermore, in the TOF-SIMS measurement, C3H7N2O was characteristically detected compared to the control film. + ion.

[0094] <Example 4> The amount of surfactant was changed to 0.08 parts by mass, and a water-soluble film was manufactured in the same manner as in Example 2. The TOF-SIMS measurement results, the peelability of the water-soluble film, and the haze are shown in Table 1. Furthermore, in the TOF-SIMS measurement, C4H was characteristically detected compared to the control film. 10 NO2 + ion.

[0095] <Example 5> Three parts by mass of talc with an average particle size of 3 μm were added as filler to the film-forming solution. Otherwise, a water-soluble film was manufactured in the same manner as in Example 4. The TOF-SIMS measurement results, the peelability of the water-soluble film, and the haze are shown in Table 1. Furthermore, in the TOF-SIMS measurement, C4H was characteristically detected compared to the control film. 10 NO2 + ion.

[0096] <Comparative Example 4> In Example 2, the amount of surfactant was changed to 0.8 parts by mass, and the shape of the paddle stirring blades during film-forming was changed to alter the maximum shear rate to 75 s. -1 The shearing speed in the T-die was changed to 1030s by altering the lip opening of the T-die. -1In addition, a water-soluble film was manufactured in the same manner as in Example 2. The TOF-SIMS measurement results, the peelability of the water-soluble film, and the haze are shown in Table 1. Furthermore, in the TOF-SIMS measurement, C4H was characteristically detected compared to the control film. 10 NO2 + ion.

[0097] As clearly shown in Table 1, the water-soluble film of the present invention exhibits good peelability and low haze even with a relatively low surfactant content, thus demonstrating good transparency. The obtained water-soluble film is suitable for various applications. In particular, the water-soluble film of the present invention is suitable for pharmaceutical packaging films, and is suitable for packaging pesticides, detergents (including bleach), disinfectants, etc.

Claims

1. A water-soluble film comprising polyvinyl alcohol resin and a surfactant, wherein the water-soluble film, The content of the surfactant is 0.005 to 1 part by mass relative to 100 parts by mass of the polyvinyl alcohol resin, and the ratio of the amount of surfactant S(0) on at least one surface of the water-soluble film, measured by the count of fragment ions originating from the surfactant as detected by time-of-flight secondary ion mass spectrometry, to the amount of surfactant S(32) on the surface of the water-soluble film at a depth of 32 nm from the surface, is in the range of 100 to 500.

2. The water-soluble film according to claim 1, wherein, The surfactant is a nitrogen-containing surfactant.

3. The water-soluble film according to claim 2, wherein, The nitrogen-containing surfactant comprises at least one selected from the group consisting of alkylamine surfactants, alkylamide surfactants and alkylalkanolamide surfactants.

4. The water-soluble film according to claim 3, wherein, The alkylamine surfactant is a polyoxyethylene alkylamine surfactant, and the alkylamide surfactant is a higher fatty acid diethanolamide surfactant.

5. The water-soluble film according to any one of claims 1 to 4, wherein it contains a filler.

6. The water-soluble film according to claim 5, wherein, The filler is made of inorganic particles.

7. A packaging body, wherein, The water-soluble film according to any one of claims 1 to 6 contains a pharmaceutical agent.

8. The packaging body according to claim 7, wherein, The agent is a pesticide, detergent, or disinfectant.

9. The packaging body according to claim 7 or 8, wherein, The medicine is in liquid form.

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