Water-soluble film and package

Abstract

Provided is a water-soluble film that has excellent high-speed printability and excellent moisture resistance. The water-soluble film of the present invention contains a polyvinyl alcohol resin, and has a surface on at least one side in which the proportion of carbon-oxygen single bonds (C-O) in the total carbon element bonds obtained by X-ray photoelectron spectroscopy is 75 to 85%.

Description

TECHNICAL FIELD

[0001] The present application relates to a water-soluble film suitable for packaging of various agents and the like, and a package using the same. BACKGROUND

[0002] Conventionally, a water-soluble film has been used in a wide range of fields such as packaging of various agents such as liquid detergents and agricultural chemicals, and seed tapes containing seeds, by virtue of its water-solubility.

[0003] Among water-soluble films for such use, a film mainly using polyvinyl alcohol resin (hereinafter, sometimes referred to as PVA) has been proposed, which improves water-solubility by compounding various additives such as plasticizers, or using modified polyvinyl alcohol (for example, Patent Document 1).

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-078166 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] A water-soluble film using PVA has good affinity with ink for printing, and can be printed without special formulation / treatment or the like. However, in recent years, it has been confirmed that if the line speed of printing is increased in order to further improve productivity, even with a water-soluble film using PVA, omission of printing, peeling of ink, or the like sometimes occurs. That is, in a water-soluble film using PVA, there is room for improvement in high-speed printability of the film.

[0009] As a method of improving the high-speed printability of a water-soluble film using PVA, the following methods can be cited: (i) adding a hydrophilic plasticizer to the water-soluble film; and (ii) subjecting the water-soluble film to surface modification such as ozone treatment or corona treatment. However, with either of the above (i) and (ii), the high-speed printability of the film can be improved, but sometimes the moisture resistance of the film decreases, the form stability of a package packed with the film decreases, or the package is broken due to blocking between films. That is, in a water-soluble film using PVA, it is difficult to balance the high-speed printability and the moisture resistance of the film.

[0010] Therefore, an object of the present application is to provide a water-soluble film which is excellent in high-speed printability, and is also excellent in moisture resistance.

[0011] MEANS FOR SOLVING THE PROBLEMS

[0012] As a method for quantifying the amount of elements present on the surface of a film or the like, there is X-ray photoelectron spectroscopy analysis (hereinafter, sometimes referred to as XPS). In the case of a water-soluble film using PVA, by XPS measurement, each element such as fluorine (F), silicon (Si), in addition to carbon (C), oxygen (O), or the like, can be quantified.

[0013] Further, it is also possible to determine the bonding state of each element and the proportion thereof present based on detailed analysis of each element based on XPS. For example, it is possible to distinguish each bonding state of carbon and find the proportion of each bond in the total carbon bond.

[0014] As a result of further research repeated based on the insight of the above detailed analysis of each element based on XPS, the present inventors found that by adjusting the proportion of carbon-oxygen single bond (hereinafter, sometimes referred to as C-O) in the total carbon element bond obtained by analyzing the surface portion of one side or both sides of a water-soluble film by X-ray photoelectron spectroscopy analysis within a specific range, the above problem can be solved, and the present application was completed based on this insight.

[0015] That is, the present application relates to the following: [1]

[0017] A water-soluble film containing a polyvinyl alcohol resin, having a surface on at least one side in which the proportion of carbon-oxygen single bond (C-O) in the total carbon element bond obtained by X-ray photoelectron spectroscopy analysis is 75 to 85%.

[0018] Further, the present application relates to the following: [2]

[0020] The water-soluble film according to the above [1], wherein

[0021] the ratio (C-C / C-O) of the proportion of carbon-carbon single bond (C-C) obtained by X-ray photoelectron spectroscopy analysis to the proportion of C-O on the surface in which the proportion of C-O in the total carbon bond is within the range is 0.1 to 0.3; [3]

[0023] The water-soluble film according to the above [1] or [2], wherein

[0024] the proportion of carbon among all elements obtained by X-ray photoelectron spectroscopy analysis is 50 to 70%, the proportion of oxygen is 20 to 35%, and the ratio of carbon to oxygen (C / O) is 1.5 to 3.5 on the surface in which the proportion of C-O in the total carbon bond is within the range; [4]

[0026] The water-soluble film according to any one of the above [1] to [3], wherein

[0027] the surface having the proportion of C-O in the total carbon element bond present in the range is surface-modified; and [5]

[0029] The water-soluble film according to the above [4], wherein

[0030] The surface modification is based on any one of ultraviolet treatment, ozone treatment, corona treatment, plasma treatment.

[0031] Also, the present application relates to the following: [6]

[0033] The method for producing the water-soluble film according to any one of the above [1] to [5], wherein

[0034] The film-forming dope solution is cast onto a support surface having a wetting tension in the range of 20 to 60 mN / m and dried.

[0035] Also, the present application relates to the following: [7]

[0037] A package, wherein

[0038] The water-soluble film according to any one of the above [1] to [5] contains a medicament; [8]

[0040] The package according to the above [7], wherein

[0041] The medicament is a pesticide, a detergent, or a disinfectant; [9]

[0043] The package according to the above [7] or [8], wherein

[0044] The medicament is in a liquid form; and

[10]

[0046] The package according to any one of the above [7] to [9], wherein

[0047] The surface having the proportion of C-O in the total carbon element bond present in the range of 75 to 85% is a printed surface.

[0048] Effects of the Invention

[0049] According to the present application, a water-soluble film having excellent high-speed printability and also excellent moisture resistance can be provided. DETAILED DESCRIPTION

[0050] Next, the present application will be described in detail.

[0051] <XPS measurement>

[0052] In the present application, the amount of elements on the surface of the water-soluble film is measured by XPS. XPS measurement refers to the identification and quantification of elements present on the surface of a sample, and the analysis of the chemical bonding state, by exciting the core electrons of atoms on the surface of the sample by irradiating X-rays, and detecting the kinetic energy of photoelectrons released therefrom. In XPS analysis, elements present at a depth of about 2 to 8 nm from the surface can be measured.

[0053] Furthermore, in the XPS measurement, when the horizontal axis is set as the kinetic energy and the vertical axis is set as the intensity, a peak called Cls can be obtained from photoelectrons originating from carbon atoms present on the surface of the sample. This peak is a composite of various peaks depending on the bonding state of the carbon atoms. The positions of these various peaks are determined according to the bonding state of the carbon atoms. For example, a carbon-carbon single bond (hereinafter sometimes referred to as C-C) or a carbon-hydrogen bond (hereinafter sometimes referred to as C-H) shows a peak at a position of 285 eV, C-O shows a peak at a position of 286.6 eV, a carbon-nitrogen single bond (hereinafter sometimes referred to as C-N) shows a peak at a position of 285.7 eV, a carbonyl group (hereinafter sometimes referred to as C=O) shows a peak at a position of 287.7 eV, an ester bond (hereinafter sometimes referred to as C(=O)-O) shows a peak at a position of 289.4 eV, and a carbonate bond (hereinafter sometimes referred to as O-C(=O)-O) shows a peak at a position of 290 eV. The Cls peak, which is a composite of these peaks, can be separated into individual peaks, for example, by automatic waveform separation fitting attached to the XPS analysis device (see Patent Document: Japanese Patent Application Publication No. 2007-302740).

[0054] The peaks attributed to each of the above bonds are obtained by detailed analysis (narrow scan) of Cls. Narrow scan refers to an analysis method in which a narrow range of energy is scanned under high energy resolution conditions, and the chemical state of the element of interest is determined from the peak position and peak shape.

[0055] The water-soluble film of the present application is a water-soluble film in which the presence ratio of C-O in the total carbon bonds on at least one surface shows 75 to 85%. In the case where the presence ratio of C-O is less than 75%, high-speed printability becomes insufficient, and problems such as omission of printing and peeling of ink are easily caused at high-speed printing. On the other hand, in the case where it exceeds 85%, the moisture resistance is poor, and thus the adhesion of films to each other and the form stability of the package tend to be poor.

[0056] The proportion of C-O present is preferably 76% or more, more preferably 77% or more, and further preferably 78% or more. Also, the proportion of C-O present is preferably 84.5% or less.

[0057] In addition, the "proportion of C-O present in the total carbon bonds" is the proportion of the peak attributed to C-O in the Cls peak obtained by detailed analysis of the Cls peak by the above-described narrow scanning and by the above-described automatic waveform separation fitting, and this proportion (%) is taken as the proportion of C-O present.

[0058] In the present application, the proportion of C-O present on the surface is 75 to 85% in either one of the single surface or both surfaces of the water-soluble film, but in the case of only the single surface, it is preferable to use this surface as the printing surface when printing is performed on the film.

[0059] As described above, in the water-soluble film of the present application, the proportion of C-O present on at least the surface of the single surface is 75 to 85%, and further, from the viewpoint of improving the high-speed printability and the moisture resistance of the film, the ratio of the proportion of C-C present to the proportion of C-O present (hereinafter, sometimes referred to simply as C-C / C-O) obtained by X-ray photoelectron spectroscopy analysis of the surface is preferably 0.1 to 0.3. The proportion of C-C present is the proportion (%) of the peak attributed to carbon-carbon single bonds in the Cls peak obtained by detailed analysis of the Cls peak by the above-described narrow scanning and by the above-described automatic waveform separation fitting, and this proportion (%) is taken as the proportion of C-C present.

[0060] Also, the value obtained by dividing the proportion of C-O present by the proportion of C-C present is taken as C-C / C-O.

[0061] If C-C / C-O is large, it indicates that the proportion of C-C that becomes hydrophobic is large, and the surface of the film becomes hydrophobic. If the hydrophobicity of the surface of the film is high, the high-speed printability of the film can decrease. On the other hand, if C-C / C-O is small, it indicates that the proportion of hydrophilic groups on the surface of the film is large, and the moisture resistance can decrease, and the adhesion of the films to each other and the form stability of the packaging body are poor. From the above viewpoint, C-C / C-O is preferably 0.1 to 0.3, more preferably 0.11 to 0.27, and further preferably 0.12 to 0.24.

[0062] Also, in the surface in which the proportion of C-O present is 75 to 85%, from the viewpoint of improving the high-speed printability and the moisture resistance of the film, the proportion of carbon present in all of the elements obtained by XPS measurement is preferably 50 to 70%, the proportion of oxygen present is preferably 20 to 35%, and the ratio of carbon to oxygen is preferably 1.5 to 3.5.

[0063] In the XPS measurement, almost all kinds of elements can be measured, but in the present application, the result of the XPS measurement of the surface of the film is quantified for the measured carbon, nitrogen, oxygen, fluorine, sodium, silicon, phosphorus and sulfur (hereinafter, these all measured elements are sometimes referred to as all measured elements), and the proportion of the carbon element and the proportion of the oxygen element with respect to the total amount thereof are respectively taken as the existence proportion of carbon and the existence proportion of oxygen.

[0064] In addition, generally, in the case where the surface of the PVA film is subjected to the XPS measurement, the measured elements are caused by the PVA, the plasticizer as described later, the additive and the like. That is, depending on the kind of the plasticizer, the additive material and the like contained in the PVA film, elements other than the above-mentioned carbon, nitrogen, oxygen, fluorine, sodium, silicon, phosphorus and sulfur can also be measured, but in the present application, the proportion of the carbon element and the proportion of the oxygen element with respect to the total amount of the above-mentioned all measured elements are respectively taken as the existence proportion (%) of carbon and the existence proportion (%) of oxygen.

[0065] Further, the proportion of carbon to oxygen (hereinafter, sometimes simply referred to as C / O) means a value obtained by dividing the existence proportion of oxygen by the above-mentioned existence proportion of carbon.

[0066] In the case where the existence proportion of carbon is less than 50% or in the case where it exceeds 70%, both of which tend to deteriorate the high-speed printability of the film. The existence proportion of carbon in all elements is more preferably 52 to 68%, and further preferably 50 to 66%.

[0067] In the case where the existence proportion of oxygen is less than 20%, the high-speed printability of the film tends to deteriorate, and in the case where it exceeds 35%, the moisture resistance tends to decrease. The existence proportion of oxygen in all elements is more preferably 22.5 to 32.5%, and further preferably 25 to 30%.

[0068] Further, in the case where C / O is less than 1.5, the moisture resistance of the film tends to deteriorate, and in the case where it exceeds 3.5, the high-speed printability tends to deteriorate. C / O is more preferably 1.7 to 3.3, and further preferably 1.8 to 3.1.

[0069] In addition, in the case where the existence proportion of C-O in the water-soluble film of the present application is 75 to 85% on one side, the existence proportion of elements other than carbon and oxygen, that is, nitrogen, fluorine, sodium, silicon, phosphorus, sulfur elements is 0.1 to 30% in total.

[0070] That is, in the water-soluble film of the present application, the existence proportion of C-O on at least one side of the surface is 75 to 85%, but it is further preferable to satisfy both of the following:

[0071] (1) From the viewpoint of taking into consideration both of the high-speed printability and the moisture resistance, C-C / C-O of the surface is 0.1 to 0.3, and more preferably 0.13 to 0.27; and

[0072] (2) From the viewpoint of balancing high-speed printability and moisture resistance, the proportion of carbon present in all elements of the surface is 50 to 70%, and the proportion of oxygen present is 20 to 35%, and the ratio of carbon to oxygen (C / O) is 1.5 to 3.5.

[0073] In the present application, it is important to adjust the proportion of C-O present in the surface of the water-soluble film, and further, as necessary, the proportions of C-C / C-O, carbon present, oxygen present, C / O, within the above-mentioned ranges. As to the method, for example, the proportion of C-O present within the above-mentioned ranges can be adjusted by, for example, adjusting the treatment conditions of UV treatment, ozone treatment, corona treatment, plasma treatment, and the like, and treating the surface of the film; or applying a liquid medicine containing a surfactant onto the surface of the film; adding an appropriate surfactant to the water-soluble film; adjusting various conditions in the process of allowing the solvent to evaporate when manufacturing the water-soluble film.

[0074] For example, as described later, in the process of allowing the solvent to evaporate when manufacturing the water-soluble film, the proportion of C-O present can be appropriately controlled by, for example, adjusting the wetting tension (hydrophilicity) of the surface of the support on which the film-forming original solution is cast; adjusting the temperature of the support when the film-forming original solution is dried; and adjusting the humidity when dried by blowing hot air of a prescribed moisture content when drying on the support.

[0075] Further, in the case of performing corona treatment on the surface of the film, if the amount of corona discharge is increased, the proportion of C-O present tends to increase. This tendency is considered to be the same in other surface treatment methods such as UV treatment, ozone treatment, plasma treatment, and the like, and the proportion of C-O present can be adjusted by adjusting the irradiation intensity, the amount of discharge, and the like in each treatment.

[0076] Of these, from the viewpoint of manufacturing cost, solvent treatment, and the like, it is preferable to perform treatment on the surface of the film by a method such as UV treatment, ozone treatment, corona treatment, plasma treatment, and the like.

[0077] The total dissolution time when the water-soluble film of the present application is immersed in water at 10°C is preferably 120 seconds or less. By having a total dissolution time of 120 seconds or less, it is possible to suitably use it as a film for packaging a medicine or the like. The total dissolution time is more preferably 90 seconds or less, further preferably 60 seconds or less, and particularly preferably 45 seconds or less. On the other hand, the lower limit of the total dissolution time is not particularly limited, and in a water-soluble film in which the total dissolution time is too short, problems such as blocking between films, reduction in film strength, and the like caused by moisture absorption of moisture in the atmosphere tend to occur. Therefore, the total dissolution time is preferably 5 seconds or more, more preferably 10 seconds or more, further preferably 15 seconds or more, and particularly preferably 20 seconds or more.

[0078] The total dissolution time when the water-soluble film is immersed in water at 10°C can be measured as follows. In addition, deionized water is used as the water in the measurement of the total dissolution time.

[0079] <1> The water-soluble film is left in a constant temperature and humidity chamber adjusted to 20°C-65% RH for 16 hours or more to adjust the humidity.

[0080] <2> After a rectangular sample of 40 mm in length by 35 mm in width is cut from the water-soluble film after the humidity adjustment, the sample is fixed between two 50 mm by 50 mm plastic plates with the length direction of the sample parallel to the length direction of the window (hole) and the window located approximately in the center of the width direction of the sample.

[0081] <3> 300 mL of deionized water is added to a 500 mL beaker, and the water temperature is adjusted to 10°C while stirring with a magnetic stirrer equipped with a 3 cm long rod at a rotation speed of 280 rpm.

[0082] <4> While taking care not to contact the rod of the magnetic stirrer, the sample fixed to the plastic plates in <2> above is completely immersed in the deionized water in the beaker.

[0083] <5> The time from the start of immersion in the deionized water until the sample pieces are completely dispersed in the deionized water and the pieces are no longer visible to the naked eye is measured.

[0084] The total dissolution time measured by the above method depends on the thickness of the sample, but in the present specification, the time until the sample of the above size is completely dissolved is set as the total dissolution time regardless of the thickness.

[0085] <Polyvinyl Alcohol Resin>

[0086] The water-soluble film of the present application contains PVA. As the PVA, a polymer produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer can be used. As the vinyl ester monomer, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl 2,2-dimethylpropionate, and vinyl versatate, etc. can be given, and among these, vinyl acetate is preferred.

[0087] The above vinyl ester polymer is preferably a polymer obtained using only one or two or more kinds of vinyl ester monomers as the monomer, and more preferably a polymer obtained using only one kind of vinyl ester monomer as the monomer, but can also be a copolymer of one or two or more kinds of vinyl ester monomers and other monomers copolymerizable therewith.

[0088] As other monomers copolymerizable with such a vinyl ester monomer, for example, there can be mentioned ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene, isobutene, and the like; acrylic acid or a salt thereof; acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, and the like; methacrylic acid or a salt thereof; methacrylic esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, and the like; acrylamide derivatives such as acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N,N-dimethyl acrylamide, diacetone acrylamide, acrylamidopropyl sulfonic acid or a salt thereof, dimethylaminopropyl acrylamide or a salt thereof, N-hydroxymethyl acrylamide or a derivative thereof, and the like; methacrylamide derivatives such as methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamidopropyl sulfonic acid or a salt thereof, dimethylaminopropyl methacrylamide or a salt thereof, N-hydroxymethyl methacrylamide or a derivative thereof, and the like; N-vinyl amides such as N-vinyl formamide, N-vinyl acetamide, N-vinyl pyrrolidone, and the like; vinyl ethers such as methyl vinyl ether, vinyl ethyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, and the like; vinyl cyanides such as acrylonitrile, methacrylonitrile, and the like; halogenated ethylenes such as chloroethylene, vinylidene chloride, fluoroethylene, vinylidene fluoride, and the like; propenyl compounds such as allyl acetate, allyl chloride, and the like; maleic acid or a salt, ester, or anhydride thereof; itaconic acid or a salt, ester, or anhydride thereof; vinyl silyl compounds such as vinyltrimethoxysilane, and the like; isopropenyl acetate, and the like. The above-mentioned vinyl ester-based polymer can have structural units derived from one or more than two of these other monomers.

[0089] From the viewpoint of water solubility and film strength of the obtained water-soluble film, the proportion of structural units derived from the above-mentioned other monomers in the above-mentioned vinyl ester-based polymer is preferably 15 mol% or less, more preferably 5 mol% or less, based on the total number of moles of all structural units constituting the vinyl ester-based polymer.

[0090] From the viewpoint of film strength, the polymerization degree of PVA is preferably 200 or more, more preferably 300 or more, and further preferably 500 or more. On the other hand, from the viewpoint of productivity of PVA, productivity of water-soluble film, and the like, the polymerization degree is preferably 8,000 or less, more preferably 5,000 or less, and further preferably 3,000 or less. Here, the polymerization degree refers to the average polymerization degree measured according to the description of JIS K 6726-1994, and the limiting viscosity [η] (unit: deciliter / g) measured in water at 30°C after resaponification and purification of PVA is calculated from the following formula.

[0091] Po = ([η] x 10 4 / 8.29) (1 / 0.62)

[0092] In the present application, the saponification degree of PVA is preferably 64 to 99.99 mol%. By adjusting the saponification degree within this range, it is easy to balance the water-solubility and the mechanical physical properties of the film. The saponification degree is more preferably 70 mol% or more, and further preferably 75 mol% or more. On the other hand, the saponification degree is more preferably 99.9 mol% or less, and further preferably 99.5 mol% or less. Here, the saponification degree of PVA refers to the proportion (mol%) of the number of moles of vinyl alcohol units with respect to the total number of moles of structural units (typically, vinyl ester monomer units) of PVA that can be converted to vinyl alcohol units by saponification. The saponification degree of PVA can be measured in accordance with the description of JIS K 6726-1994.

[0093] The water-soluble film in the present application can use one PVA as PVA, or two or more kinds of PVA having different polymerization degrees, saponification degrees, or modification degrees, etc. can be mixedly used.

[0094] In the present application, the content ratio of PVA in the water-soluble film is not particularly limited, and is preferably 50 mass% or more, more preferably 80 mass% or more, and further preferably 85 mass% or more.

[0095] <Plasticizer>

[0096] The water-soluble film of the present application is hard in the absence of a plasticizer, and the mechanical physical properties such as impact strength, processability during secondary processing, and the like can sometimes become problematic. In order to prevent these problems, it is preferable to include a plasticizer in the water-soluble film of the present application. As a preferable plasticizer, polyhydric alcohols can be given, and specifically, for example, polyhydric alcohols such as ethylene glycol, glycerol, diglycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, sorbitol, and the like can be given. These plasticizers can be used singly or in combination with two or more. Of these plasticizers, from the viewpoint of not easily exuding to the surface of the film and the like, ethylene glycol or glycerol is preferable, and glycerol is more preferable.

[0097] 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 further preferably 5 parts by mass or more, relative to 100 parts by mass of the PVA contained in the water-soluble film. Also, the amount of the plasticizer is preferably 70 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 40 parts by mass or less. If the amount of the plasticizer is less than 1 part by mass, the improvement effect on the mechanical physical properties such as impact strength can be insufficient. On the other hand, if the content exceeds 70 parts by mass, the film becomes excessively soft, and the handleability can sometimes be reduced, or exudation to the surface of the film can occur.

[0098] <Starch / Water-soluble Polymer>

[0099] In order to impart mechanical strength to the water-soluble film, maintain the moisture resistance during handling of the film, or adjust the speed of softening caused by absorption of water during dissolution of the film, and the like, a starch and / or a water-soluble polymer other than PVA can be contained in the film of the present application.

[0100] As the starch, for example, natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, sago starch, and the like; processed starches to which etherification processing, esterification processing, oxidation processing, and the like have been applied, and the like can be given, and processed starches are particularly preferable.

[0101] The content of the starch in the water-soluble film is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the PVA. If the amount of the starch is greater than 15 parts by mass, the processability can deteriorate.

[0102] As the water-soluble polymer other than PVA, for example, dextrin, gelatin, animal glue, casein, shellac, gum arabic, polyacrylamide, sodium polyacrylate, polyvinyl methyl ether, a copolymer of methyl vinyl ether and maleic anhydride, a copolymer of vinyl acetate and itaconic acid, polyvinylpyrrolidone, cellulose, acetyl cellulose, acetyl butyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, sodium alginate, and the like can be given.

[0103] The content of the water-soluble polymer other than PVA in the water-soluble film is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of PVA. If the content is more than 15 parts by mass, the water-solubility of the water-soluble film can be insufficient.

[0104] <Surfactant>

[0105] In the film formation of the water-soluble film, a surfactant is preferably added to the water-soluble film from the viewpoint of improving the operability thereof and the peelability of the self-made film device at the time of manufacturing the water-soluble film. Furthermore, by adding an appropriate surfactant to the water-soluble film, the presence ratio of C-O on the surface of the water-soluble film of the present application and further the presence ratio of C-C / C-O, carbon, oxygen, C / O, as needed, can be set within the desired range. As the kind of the surfactant, anionic surfactants, nonionic surfactants, and the like can be exemplified.

[0106] As the anionic surfactant, for example, carboxylic acid types such as potassium laurate; sulfates such as octyl sulfate; sulfonic acid types such as dodecylbenzenesulfonate; and the like can be exemplified.

[0107] As the nonionic surfactant, for example, polyoxyalkylene alkyl ether types such as polyoxyethylene lauryl ether, polyoxyethylene oleyl ether; polyoxyalkylene alkyl phenyl ether types such as polyoxyethylene octyl phenyl ether; polyoxyalkylene alkyl ester types such as polyoxyethylene laurate; polyoxyalkylene alkyl amine types such as polyethylene glycol dodecanamide; polyoxyalkylene alkyl amide types such as polyoxyethylene lauramide; polyoxyalkylene polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether; alkanolamide types such as lauric acid diethanolamide, oleic acid diethanolamide; polyoxyalkylene allyl phenyl ether types such as polyoxyalkylene allyl phenyl ether; and the like can be exemplified.

[0108] The surfactant can be used singly or in combination of two or more.

[0109] The surfactant in the present application has a tendency to aggregate on the surface of the film rather than to be uniformly dispersed in the water-soluble film, and the effect is obtained by a small amount of addition, and thus is preferred. Therefore, a surfactant having appropriate affinity with PVA is preferably selected. A surfactant having excessively high affinity with PVA has a tendency to be uniformly dispersed, and a surfactant having excessively low affinity with PVA forms droplets in the film by phase separation, and easily reduces the transparency of the film or easily exudes to the surface of the film.

[0110] Furthermore, a surfactant having appropriate affinity with PVA tends to easily aggregate on the surface of the water-soluble film at the time of film formation, and thus, by adjusting the kind and amount of the surfactant, the presence ratio of C-O on the surface of the film and the like can be controlled.

[0111] As an example of the surfactant having an appropriate affinity with PVA, a nonionic surfactant is preferable, and particularly, a polyoxyalkylene alkyl ether surfactant is more preferable, and further, a polyoxyalkylene alkyl ether of a fatty acid (e.g., a saturated or unsaturated fatty acid having 8 to 30 carbon atoms, etc.) is still more preferable.

[0112] From the viewpoints of the film-forming property and the peelability of the obtained film, the content of the surfactant in the water-soluble film is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and further preferably 0.05 parts by mass or more, relative to 100 parts by mass of PVA. On the other hand, from the viewpoints of bleeding to the surface of the obtained film and aggregation of the surfactant, the content of the surfactant is preferably 10 parts by mass or less, more preferably 1 part by mass or less, further preferably 0.5 parts by mass or less, and particularly preferably 0.3 parts by mass or less. If the content is less than 0.01 parts by mass, the film-forming property tends to be poor. Also, the peelability of the film-forming device at the time of manufacturing the water-soluble film tends to be reduced, or agglomerates tend to be generated between the films. On the other hand, if the content is more than 10 parts by mass, bleeding to the surface of the film and deterioration of the appearance of the film due to aggregation of the surfactant tend to occur.

[0113] <Other Components>

[0114] The water-soluble film of the present application can contain, in addition to the plasticizer, the starch, the water-soluble polymer other than PVA, and the surfactant, components such as moisture, an antioxidant, an ultraviolet absorber, a lubricant, a crosslinking agent, a coloring agent, a filler, a preservative, a mold inhibitor, other polymer compounds, and the like, within a range not impairing the effects of the present application. The total of the respective amounts of PVA, the plasticizer, the starch, the water-soluble polymer other than PVA, and the surfactant is preferably within a range of 60 to 100% by mass, more preferably within a range of 80 to 100% by mass, and further preferably within a range of 90 to 100% by mass, relative to the total mass of the water-soluble film of the present application.

[0115] From the viewpoint of the secondary processability of the obtained film, the thickness of the water-soluble film of the present application is preferably 200 μm or less, more preferably 150 μm or less, further preferably 100 μm or less, and particularly preferably 50 μm or less. Also, from the viewpoint of the mechanical strength of the water-soluble film, the thickness of the water-soluble film is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, and particularly preferably 20 μm or more. In addition, the thickness can be measured at any 10 points (e.g., any 10 points on a straight line drawn in the length direction of the water-soluble film) and the average value thereof can be taken as the thickness of the water-soluble film.

[0116] <Method for producing water-soluble film>

[0117] In the present application, the method for producing a water-soluble film is not particularly limited, and the film can be produced by any method, such as a method in which a film-forming raw solution in which a solvent, an additive, or the like is added to PVA and homogenized is subjected to film formation by a casting method, a wet film formation method (discharge into a poor solvent), a dry-wet film formation method, a gel film formation method (a method in which a film-forming raw solution is temporarily cooled and gelled, and then the solvent is extracted and removed to obtain a water-soluble film), or a combination thereof; a melt extrusion film formation method or a blow molding method in which the above film-forming raw solution is obtained using an extruder or the like and extruded from a T die or the like. Among these, the casting method and the melt extrusion film formation method are preferable because a homogeneous film can be obtained at a high production rate. Hereinafter, the casting method or the melt extrusion film formation method for a water-soluble film will be described.

[0118] In the case where a water-soluble film is produced by the casting method or the melt extrusion film formation method, the above film-forming raw solution is extruded in a film shape onto a support such as a metal roll or a metal belt, and the solvent is removed by heating, whereby the film is solidified and filmized. The solidified film is peeled from the support, dried as necessary by a drying roll, a drying furnace, or the like, further heat-treated as necessary, and wound, whereby a long water-soluble film in a roll shape can be obtained.

[0119] The volatile component concentration of the above film-forming raw solution (the concentration of volatile components such as solvents removed by volatilization or evaporation at the time of film formation) is preferably in the range of 50 to 90% by mass, and more preferably in the range of 55 to 80% by mass. If the volatile component concentration is less than 50% by mass, the viscosity of the film-forming raw solution becomes high, and film formation can sometimes be difficult. On the other hand, if the volatile component concentration exceeds 90% by mass, the viscosity becomes low, and the thickness uniformity of the obtained film is easily impaired.

[0120] Herein, the "volatile fraction of the film-forming raw solution" in the present specification refers to the volatile fraction calculated from the following formula.

[0121] Volatile fraction of film-forming raw solution (% by mass) = {(Wa - Wb) / Wa} x 100

[0122] (In the formula, Wa represents the mass (g) of the film-forming raw solution, and Wb represents the mass (g) of the film-forming raw solution dried for 16 hours at 105°C.)

[0123] The method for adjusting the film-forming raw solution is not particularly limited, and examples include a method in which PVA and additives such as a plasticizer and a surfactant are dissolved in a dissolving tank or the like; a method in which PVA in a water-containing state is melt-kneaded together with a plasticizer, a surfactant, or the like using a single-screw or twin-screw extruder; and the like.

[0124] The film of the film-formation raw solution that is slobbered onto the support is heated and dried on the support and in the subsequent drying step to be solidified, but the hydrophilicity of the surface of the support at this time greatly influences the surface state of the film, and the higher the hydrophilicity of the support, the higher the proportion of the presence of C-O in the total carbon element bond on the surface of the film in contact with the support. It is inferred that this is because the hydroxyl group of PVA and the hydrophilic surfactant easily gather on the surface in contact with the support. In addition, as described later, the hydrophilicity of the surface of the support can be evaluated by measuring the wetting tension of the surface of the support.

[0125] The drying conditions on the support also greatly influence the surface state of the film. For example, if the drying temperature is set to a high temperature, the drying speed becomes fast, and thus the movement of the surfactant is hindered, and it is not easy for the surfactant to gather on the surface of the film, which influences the proportion of the presence of C-O in the total carbon element bond on the surface of the film, and the like. Also, if the film of the film-formation raw solution is blown with hot air having a low moisture content to reduce the humidity at the time of drying while being dried on the support, the hydrophobic group tends to gather on the surface of the film in contact with the air, and, on the contrary, if hot air having a high moisture content is blown to increase the humidity at the time of drying, the hydrophilic group tends to gather on the surface of the film.

[0126] Therefore, adjusting the drying conditions at the time of film-formation is also one of the methods of controlling the proportion of the presence of C-O on the surface of the film and the like.

[0127] The drying conditions at the time of film-formation influence the production speed of the film, and it is possible that the use of raw materials such as surfactants will be limited. Therefore, in order to make the proportion of the presence of C-O on the surface of the film within the range of the present application, it is preferable to adjust not only the hydrophilicity (wetting tension) of the support and the drying conditions at the time of film-formation, but also to use a method of performing surface modification on the film manufactured, as described later.

[0128] From the viewpoint that the proportion of the presence of C-O from at least one surface of the water-soluble film satisfies the above range, the wetting tension of the surface of the first drying roller or the first drying belt (hereinafter, sometimes referred to as the first drying roller or the like) as the support on which the film-formation raw solution is cast is preferably within the range of 20 to 60 mN / m. In the case where the wetting tension of the surface of the first drying roller or the like is less than 20 mN / m, the proportion of the presence of C-O in the total carbon element bond cannot be sufficiently high, and the high-speed printability can be poor, and, in the case where it exceeds 60 mN / m, the adhesion of the film to the surface of the first drying roller or the like is too high, and it can be difficult to peel the film from the first drying roller or the like. The wetting tension of the surface of the first drying roller or the like is preferably within the range of 23 to 50 mN / m, more preferably within the range of 25 to 40 mN / m, and further preferably within the range of 28 to 32 mN / m.

[0129] As a method of adjusting the wetting tension of the surface of the first drying roll or the like, a method in which a hydrophilic surfactant is continuously applied to the surface, a method in which a coating film of a hydrophilic resin is applied to the surface, and a method in which the surface is treated with an aqueous acid solution can be exemplified. Among these, from the viewpoints of cost, stability of the quality of the film obtained, and the like, the method in which the hydrophilic surfactant is continuously applied to the surface of the first drying roll or the like is preferred.

[0130] In addition, in the present application, the wetting tension of the surface of the first drying roll or the like can be measured in accordance with JIS K 6768.

[0131] The surface temperature of the first drying roll or the like is preferably from 50 to 110°C. In the case where the surface temperature is less than 50°C, the high-speed printability of the film and the productivity tend to decrease. In the case where it exceeds 110°C, film surface abnormalities such as bubbling tend to occur and the crystallinity tends to decrease and the mechanical strength of the film tends to decrease. The above-mentioned surface temperature is preferably from 60 to 100°C, and more preferably from 65 to 95°C.

[0132] The film of the film-forming raw solution can be heated on the first drying roll or the like while hot air having a wind speed of from 1 to 10 m / sec is blown uniformly to the entire region of the non-contact surface side of the film of the film-forming raw solution, and the drying speed is adjusted. From the viewpoints of drying efficiency, uniformity of drying, and the like, the temperature of the hot air blown to the non-contact surface side is preferably from 50 to 150°C, and more preferably from 70 to 120°C.

[0133] From the viewpoint that the proportion of the presence of C-O on the surface of the film can be easily adjusted within the range of the present application, the moisture content of the hot air is preferably from 4 to 90 g / m 3 , more preferably from 5 to 70 g / m 3 , and further preferably from 6 to 50 g / m 3 .

[0134] The film peeled from the first drying roll or the like is preferably dried to a volatile matter content of 5 to 50 mass% on a subsequent support (hereinafter, sometimes referred to as a drying roll or the like, and in the case where there are two or more subsequent supports, sometimes referred to as a second drying roll, a third drying roll, or a second drying belt, a third drying belt, in order). After drying to a volatile matter content within the preferable range, peeling is performed, and further drying is performed as necessary. The drying method is not particularly limited, and in addition to a method in which the film is brought into contact with a drying roll or the like, a method in which a drying oven is used can be given. In the case where drying is performed using a plurality of drying rolls or the like, the one side surface and the other side surface of the film are brought into contact with the second drying roll or the second drying belt alternately after the first drying roll, which makes the both surfaces uniform, and thus is preferable. For example, the number of the second drying roll and the subsequent drying rolls, including the second drying roll, is preferably three or more, more preferably four or more, and further preferably five to thirty. The temperature of the drying oven and the second drying roll and the subsequent drying rolls is preferably 40°C or higher and 110°C or lower. The upper limit of the temperature of the drying oven and the second drying roll and the subsequent drying rolls is more preferably 100°C, and further preferably 90°C. If the temperature of the drying oven and the second drying roll and the subsequent drying rolls is too high, the high-speed printability can decrease. On the other hand, the lower limit of the temperature of the drying oven and the second drying roll and the subsequent drying rolls is more preferably 45°C, and further preferably 50°C. If the temperature of the drying oven and the second drying roll and the subsequent drying rolls is too low, the mechanical strength of the film can decrease.

[0135] The obtained water-soluble film can be further subjected to heat treatment as necessary. By performing heat treatment, the strength, water-solubility, and the like of the film can be adjusted. The temperature of the heat treatment is preferably 60°C to 135°C. The heat treatment temperature is more preferably 130°C or lower. If the heat treatment temperature is too high, the amount of heat applied is too much, and the water-solubility can decrease.

[0136] The water-soluble film thus produced is subjected to humidity conditioning, cutting of both end portions (ear portions), and the like as necessary, wound in a roll shape on a cylindrical core, and subjected to moisture-proof packaging to become a product.

[0137] The volatile matter content of the water-soluble film finally obtained by the above series of processes is preferably within the range of 1 to 5 mass%, and more preferably within the range of 2 to 4 mass%.

[0138] As described above, the water-soluble film subjected to surface modification is one of the preferable embodiments of the present application. The method of surface modification is not particularly limited, and is preferably any one of ultraviolet treatment, ozone treatment, corona treatment, and plasma treatment, of which the corona treatment is more preferable in terms of the treatment speed, safety, easiness of adjustment of the degree of treatment, and the like.

[0139] From the viewpoint of high-speed printability of the film and coloring of the film, reduction of damage such as perforation, the condition of the corona treatment is preferably in the range of 100 to 400 W • min / m 2 , more preferably in the range of 120 to 350 W • min / m 2 , further preferably in the range of 150 to 300 W • min / m 2 . In the case where the condition of the corona treatment is less than 100 W • min / m 2 , improvement in high-speed printability can be insufficient, on the other hand, in the case where it exceeds 400 W • min / m 2 , perforation, coloring and the like can occur in the film.

[0140] In addition, the discharge amount is calculated by the following formula (1).

[0141] Discharge amount (W • min / m 2 ) = output (W / m) / treatment speed (m / min) (1)

[0142] <Use>

[0143] The water-soluble film of the present application is excellent in high-speed printability and moisture resistance, and can be suitably used for various uses of water-soluble films. As such water-soluble films, for example, there can be mentioned a film for packaging of a medicament, a base film for hydraulic transfer, a base film for embroidery, a release film for artificial marble molding, a film for packaging of seeds, and a film for a bag for storing dirt, and the like. Among these, from the viewpoint of more significantly exerting the effects of the present application, the water-soluble film of the present application is preferably used as a film for packaging of a medicament.

[0144] As the kind of medicament in the case where the water-soluble film of the present application is used as a film for packaging of a medicament, there can be mentioned a pesticide, a detergent (including a bleaching agent), a disinfectant, and the like. The physical property of the medicament is not particularly limited, and can be acidic, neutral, or alkaline. Furthermore, a boron-containing compound can be contained in the medicament. As the shape of the medicament, any one of powder, block, gel, and liquid can be mentioned. The packaging method is not particularly limited, and a unit packaging method in which the medicament is packaged (preferably, sealed) in a unit amount is preferred. By packaging the medicament using the film of the present application as a film for packaging of a medicament, a package of the present application can be obtained.

[0145] Example

[0146] Hereinafter, the present application will be specifically described by way of examples, but the present application is not limited by the following examples in any way. In addition, the evaluation items and methods employed in the following examples and comparative examples are as follows.

[0147] (1) Measurement conditions of X-ray photoelectron spectroscopy (XPS)

[0148] The film was cut to a size of 5 mm x 5 mm and disposed on a measurement base via a conductive double-sided tape. At the time of measurement, both sides of the film were measured. Regarding XPS, each sample was measured under the following measurement conditions.

[0149] Measurement device: Ohi Quantera SXM (ULVAX-PHI. INC.)

[0150] Analysis software: Multi Pack ver 9.0 (ULVAX-PHI. INC.)

[0151] X-ray source: Monochromatic Al Kα (1486.6 eV)

[0152] X-ray beam diameter: 100 μm φ (25 W, 15 kV)

[0153] Measurement range: 100 μm x 300 μm

[0154] Signal capture angle: 45°

[0155] Charging neutralization conditions: Neutralizing electron gun, Ar + Ion gun

[0156] Vacuum degree: 1 x 10 -6 Pa

[0157] In addition, in the following examples and comparative examples, the following elements were measured.

[0158] Measured elements: Cls, Nls, Ols, Fls, Nals, Si2p, P2p, S2p

[0159] The obtained spectrum was analyzed, and the contents of Cls, Ols were quantified.

[0160] Further, the obtained peak of Cls was automatically fitted using the above analysis software, and the amounts of the bonding states of carbon, C-C, C-O were quantified.

[0161] (2) High-speed printability

[0162] An ink for building materials containing a mixture of a dye and barium sulfate at 70% by weight and a mixture of an alkyd resin and nitrocellulose at 30% by weight was used in three colors to gravure print a wood grain on a base film in an atmosphere of 20°C, 72% RH. The thickness of the printed layer was set to 2 μm each, the release tension was set to 1 kg / m, and the printing speed was set to 80 m / minute. After printing, the multilayer film was dried in a drying zone of 1 m heated with a hot air of 60°C. The printed surface after drying was observed, and evaluated according to the following criteria.

[0163] A: Even if observed with a magnifying glass, it is difficult to identify the printing omission.

[0164] B: Although it is difficult to identify the printing omission by the naked eye, it can be identified if observed with a magnifying glass.

[0165] C: A little printing omission can be identified by the naked eye.

[0166] D: The printing omission can be clearly identified by the naked eye.

[0167] (3) Moisture resistance

[0168] A water-soluble film was cut into 3 cm x 20 cm, and after being rolled into a cylindrical shape with an inner diameter of about 1 cm with the short side as the axis, both end portions were cut off. Thus, a small water-soluble film roll with an inner diameter of 1 cm and a width of 1 cm was produced. The center axis of the obtained roll was gripped with a double clip (manufactured by KOKUYO Co., Ltd., product name: Scel-bo) having a mouth width of 15 mm in such a manner that the direction of the portion gripped by the clip coincided with the axial direction of the roll, and the roll was stored under conditions of 60°C - 90% RH for 16 hours. The film roll after storage was unwound, and the adhesion state of the contact surfaces of the end portions to each other was evaluated according to the following criteria.

[0169] A: There was no adhesion of the contact surfaces to each other at the end portions, and the water-soluble film was unwound without resistance.

[0170] B: Although resistance was felt at the time of unwinding, the water-soluble film was unwound if force was applied.

[0171] C: The contact surfaces adhered to each other at the end portions, and the water-soluble film could not be unwound.

[0172] (4) Total dissolution time of water-soluble film

[0173] The total dissolution time of the water-soluble film in deionized water at 10°C was found by the method.

[0174] <Example 1>

[0175] A film-forming solution having a volatile matter rate of 60% by mass was prepared by adjusting 100 parts by mass of a methyl maleate (MA)-modified PVA (saponification degree: 99 mol%, polymerization degree: 1700, MA modification degree: 5 mol%) obtained by saponifying polyvinyl acetate, 20 parts by mass of glycerol as a plasticizer, 0.05 parts by mass of polyoxyethylene lauryl ether as a surfactant, and water.

[0176] On a first drying roll having a surface temperature adjusted to 85°C, the film-forming solution was coated so that the coating amount became 2.5 g / m 2A 0.1% by mass aqueous solution of polyoxyethylene dodecyl ether, used as a hydrophilic surfactant, was continuously coated using a roller coater, followed by hot air blowing at 85°C and drying. The wetting tension of the surface of the first drying roller, on which the hydrophilic surfactant (polyoxyethylene dodecyl ether) was continuously coated, was 31.2 mN / m. On this first drying roller (surface temperature 85°C), the liquid obtained by filtering the film-forming solution was expelled as a film, and the entire surface of the film containing the film-forming solution that was not in contact with the first drying roller was sprayed with air at a speed of 5 m / s, with a moisture content of 24.9 g / m. 3 It was dried by hot air at 85°C.

[0177] Next, the film is peeled off from the first drying roller, and the other side of the film containing the film-forming solution, different from the side that contacted the first drying roller, is brought into contact with the surface of a subsequent first drying roller (hereinafter referred to as the second drying roller) at a surface temperature of 85°C and dried. Then, the film is dried by alternately contacting one side and the other side of the film containing the film-forming solution with six drying rollers, including the second drying roller (hereinafter referred to as the third drying roller, the fourth drying roller, and the last drying roller as the seventh drying roller), thereby obtaining a thin film. The surface temperature of the third drying roller and subsequent drying rollers is 75°C, and no surfactant is coated on the surface of the drying rollers after the second drying roller. The obtained film is then heat-treated by alternately contacting both sides of multiple heat-treatment rollers at 90°C for a total of 30 seconds, and wound onto a polyvinyl chloride tube to obtain a water-soluble film (thickness 35 μm, length [film flow direction] 1200 m, width 1 m).

[0178] The results of XPS measurements on both sides of the obtained water-soluble film showed that on one side, the proportion of carbon-oxygen single bonds (CO) in the total carbon elemental bonds was 81.6%, the ratio of carbon-carbon single bonds to CO (CC / C=O) was 0.23, and the carbon content was 72.8% of the total elements. Similarly, the oxygen content was 26.8%, and the carbon-oxygen ratio (C / O) was 2.7. On the other side, the proportion of carbon-oxygen single bonds (CO) in the total carbon elemental bonds was 82.2%, the ratio of carbon-carbon single bonds to CO (CC / C=O) was 0.22, the carbon content was 72.8% of the total elements, and the oxygen content was 27.0%, and the carbon-oxygen ratio (C / O) was 2.7.

[0179] The film has a total melting time of 73 seconds, a high-speed printability rating of B, and a moisture resistance rating of A.

[0180] The composition of the film-forming stock solution, the film-forming conditions, the XPS analysis results of the obtained water-soluble film, and the evaluation results are summarized in Table 1. In Table 1, the surface in contact with the first drying roll is referred to as surface 1, and the surface on the side opposite to surface 1 (the surface in contact with the second drying roll) is referred to as surface 2.

[0181] <Example 2>

[0182] A portion of the film obtained in Example 1 was discharged, and both surfaces thereof were treated using a corona treatment device at 200 W minute / m 2 , and then wound up. The XPS analysis results of the water-soluble film and the evaluation results are shown in Table 1.

[0183] <Example 3>

[0184] PVA was changed to unmodified PVA (saponification degree: 88 mol%, polymerization degree: 1700) obtained by saponification of polyvinyl acetate, and the moisture content of the hot air blown to the entire surface of the film of the film-forming stock solution on the side not in contact with the first drying roll was changed to 202.1 g / m 3 , and otherwise, in the same manner as in Example 2, a water-soluble film was obtained. The XPS analysis results of the water-soluble film and the evaluation results are shown in Table 1.

[0185] <Example 4>

[0186] A water-soluble film was obtained in the same manner as in Example 3, except that the first drying roll was not coated with a hydrophilic surfactant (polyoxyethylene lauryl ether). The wetting tension of the surface of the first drying roll was 55.2 mN / m. The XPS analysis results of the water-soluble film and the evaluation results are shown in Table 1.

[0187] <Example 5>

[0188] A water-soluble film was obtained in the same manner as in Example 2, except that the surfactant in the film-forming stock solution was changed to lauric acid diethanolamide. The XPS analysis results of the water-soluble film and the evaluation results are shown in Table 1.

[0189] <Comparative Example 1>

[0190] A water-soluble film was obtained in the same manner as in Example 2, except that the moisture content of the hot air blown to the entire surface of the film of the film-forming stock solution on the side not in contact with the first drying roll was changed to 202.1 g / m 3 . The XPS analysis results of the water-soluble film and the evaluation results are shown in Table 1.

[0191] <Comparative Example 2>

[0192] A water-soluble film was obtained in the same manner as in Example 1, except that the first drying roll was not coated with the hydrophilic surfactant (polyoxyethylene dodecyl ether) and that the wetting tension of the surface of the first drying roll was 55.2 mN / m. The results of XPS analysis and evaluation of the water-soluble film are shown in Table 1.

[0193] <Comparative Example 3>

[0194] A water-soluble film was obtained in the same manner as in Comparative Example 2, except that the PVA was changed to unmodified PVA (saponification degree: 88 mol%, polymerization degree: 1700) obtained by saponifying polyvinyl acetate. The results of XPS analysis and evaluation of the water-soluble film are shown in Table 1.

[0195]

[0196] From the above results, it was found that the water-soluble film of the present application is excellent in high-speed printability and also excellent in moisture resistance. Since the moisture resistance is excellent, it is considered that the form stability as a packaging body is also maintained.

[0197] Therefore, the water-soluble film of the present application can be suitably used for various uses of water-soluble films, such as a film for packaging of a medicament, a base film for hydraulic transfer, a base material film for embroidery, a release film for artificial marble molding, a film for packaging of seeds, and a film for a dirt storage bag, and the like. Among these, the water-soluble film of the present application is more suitably used as a film for packaging of a medicament, and can be used as a film for packaging of a medicament having oxidizing properties, such as a pesticide, a detergent (including a bleaching agent), and the like.

Claims

1. A water-soluble film containing a polyvinyl alcohol resin, having a surface with a proportion of carbon-oxygen single bonds (C-O) in total carbon element bonds obtained by X-ray photoelectron spectroscopic analysis of 75 to 85% on at least one side, and a total dissolution time when the water-soluble film is immersed in water at 10°C being 120 seconds or less.

2. The water-soluble film according to claim 1, wherein the proportion of C-O in the total carbon element bonds is 75 to 85% on the surface.

3. The water-soluble film according to claim 1 or 2, wherein the proportion of C-O in the total carbon element bonds is 75 to 85% on the surface.

4. The water-soluble film according to claim 1 or 2, wherein the surface on which the proportion of C-O in the total carbon element bonds is in the range is surface-modified.

5. The water-soluble film according to claim 4, wherein the surface modification is based on any one of ultraviolet treatment, ozone treatment, corona treatment, and plasma treatment.

6. A method for producing the water-soluble film according to any one of claims 1 to 5, wherein a film-forming dope solution is cast onto a support surface having a wetting tension in the range of 20 to 60 mN / m and dried.

7. A package, wherein the water-soluble film according to any one of claims 1 to 5 contains a medicament.

8. The package according to claim 7, wherein the medicament is a pesticide, a detergent, or a disinfectant.

9. The package according to claim 7 or 8, wherein the medicament is in a liquid form.

10. The package according to claim 7 or 8, wherein the surface with a proportion of C-O in total carbon element bonds of 75 to 85% is a printed surface. ​ ​ ​ ​ ​ ​ ​ ​ ​

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