JP7234625B2 - POLYVINYL ALCOHOL-BASED FILM, METHOD FOR MANUFACTURING SAME, AND DRUG PACKAGE - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyvinyl alcohol film and a method for producing the same. More particularly, it relates to a polyvinyl alcohol-based film with few bubble defects and a method for producing the same. After

BACKGROUND ART Conventionally, polyvinyl alcohol-based films have been used in many applications as films having excellent transparency and dyeability, and are used as optical polyvinyl alcohol-based films for polarizing films and the like. Such a polarizing film is used as a basic component of a liquid crystal display, and in recent years, its use has expanded to high-luminance, high-definition liquid crystal televisions. In addition to liquid crystal televisions, they are also widely used in smartphones, tablets, personal computers, projectors, and automotive panels. In such an optical polyvinyl alcohol film, a polarizing film with less display defects is required as the screens of liquid crystal televisions and the like become thinner and larger. In order to produce such a polarizing film, it is necessary to improve the original polyvinyl alcohol film.

In addition, the polyvinyl alcohol film is characterized by water solubility by adjusting the degree of saponification of the polyvinyl alcohol resin and introducing (denaturing) an anionic functional group into the polyvinyl alcohol molecular chain. It is also used as a water-soluble film. Specifically, packaging (unit packaging) for chemicals such as agricultural chemicals and detergents, (hydraulic) transfer film, sanitary products such as napkins and paper diapers, waste treatment products such as ostomy bags, medical supplies such as blood absorbing sheets, and seedling raising. It is used for temporary substrates such as sheets, seed tapes, and embroidery base fabrics. In particular, in unit packaging applications for chemicals such as agricultural chemicals and detergents, there is an advantage that the labor of measuring the amount of each chemical at the time of use can be saved and hands are not soiled. Such a polyvinyl alcohol-based water-soluble film is increasingly used for packaging liquid products such as liquid detergents, and from the viewpoint of preventing liquid leakage, there is a need for drug packages with few air bubbles. In order to manufacture such a drug package, it is necessary to improve the polyvinyl alcohol-based film that serves as the original fabric.

As a polyvinyl alcohol-based film used for such optical film applications, a polyvinyl alcohol-based film containing two or more surfactants in a polyvinyl alcohol-based resin (see, for example, Patent Documents 1 and 2) and the like are known. ing.

Further, as a polyvinyl alcohol film used for such a water-soluble film, for example, 5 to 30 parts by weight of a plasticizer, 1 to 10 parts by weight of starch and 0.01 to 2 parts by weight of a surfactant are added to 100 parts by weight of polyvinyl alcohol. a water-soluble film (see, for example, Patent Document 3) obtained by blending parts, and a polyvinyl alcohol-based film made of a resin composition containing two or more polyvinyl alcohols with different degrees of saponification (for example, see Patent Document 4.) Or, a polyvinyl alcohol resin containing 1 to 10 mol% of carboxyl groups and a polyvinyl alcohol resin containing no carboxyl groups and having a 4 wt% aqueous solution viscosity at 20 ° C. of 1 to 10 mPa s A polyvinyl alcohol film (see, for example, Patent Document 5) and the like are known.

Japanese Patent Application Laid-Open No. 2005-206809 Japanese Patent Application Laid-Open No. 2005-206810 Japanese Patent Application Laid-Open No. 2001-329130 JP 2003-261694 A Japanese Patent Application Laid-Open No. 2003-206380

However, although the polyvinyl alcohol-based films disclosed in Patent Documents 1 and 2 have few optical streaks, optical spots and the like and are excellent in blocking properties, they are insufficient as countermeasures against air bubble defects generated in the film. However, there are concerns about quality problems such as the occurrence of display defects when used as a polarizing film, and further improvements have been desired.

In addition, the polyvinyl alcohol-based film disclosed in Patent Document 3 has excellent water solubility, blocking resistance, and impact burst strength, and the polyvinyl alcohol-based film disclosed in Patent Document 4 has excellent cold water solubility and durability. The polyvinyl alcohol-based film disclosed in Patent Document 5 is excellent in heat seal strength and water solubility when packaging an alkaline substance. There are concerns about quality issues such as liquid leakage when packaging liquid products using this method and storing them for a long period of time, and appearance defects due to ink splashing at air bubble defects when printed on packaging film, and further improvements are desired. It was something that could be done.

Under such circumstances, an object of the present invention is to provide a polyvinyl alcohol-based film with few air bubbles and a method for producing the polyvinyl alcohol-based film.

However, as a result of intensive research in view of such circumstances, the present inventors have studied in detail the relationship between the constituent components of the polyvinyl alcohol film and the blending method, and found that at least one of the degree of saponification, viscosity, modified species, and modified amount is The inventors have found that a polyvinyl alcohol-based film containing a trace amount of a lower monohydric alcohol component in a polyvinyl alcohol-based resin containing two or more different polyvinyl alcohol-based resins can achieve the above object, and completed the present invention.

That is, the gist of the present invention is polyvinyl alcohol containing polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of saponification degree, viscosity, modified species, and modified amount as a main component system film, wherein the polyvinyl alcohol-based resin (A) contains an unmodified polyvinyl alcohol resin and a carboxyl group-modified polyvinyl alcohol-based resin, and the unmodified polyvinyl alcohol resin and the carboxyl group-modified polyvinyl alcohol-based resin The content ratio by weight is unmodified polyvinyl alcohol resin/carboxyl group-modified polyvinyl alcohol resin = 1/99 to 99/1, contains 1 to 500 ppm of monohydric alcohol having 1 to 3 carbon atoms, and has 1 carbon atom. The present invention relates to a polyvinyl alcohol film characterized in that the monohydric alcohol of 1 to 3 is at least one selected from methanol and ethanol.
And, the present invention provides (I) a polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of saponification degree, viscosity, modification type, and modification amount as a main component. a step of dissolving an alcohol-based resin composition to obtain a polyvinyl alcohol-based resin aqueous solution; , (III) a step of forming a film using the polyvinyl alcohol resin aqueous solution obtained in the step (II), in this order, wherein the polyvinyl alcohol resin (A) is an unmodified polyvinyl alcohol resin and a carboxyl group and a modified polyvinyl alcohol-based resin, and the content ratio of the unmodified polyvinyl alcohol resin and the carboxyl group-modified polyvinyl alcohol-based resin is the unmodified polyvinyl alcohol resin/carboxyl group-modified polyvinyl alcohol-based resin=1/ 99 to 99/1 and the monohydric alcohol having 1 to 3 carbon atoms is at least one selected from methanol and ethanol.

Since the polyvinyl alcohol-based film of the present invention suppresses air bubble defects, it has few display defects when used as a polarizing film, and when used as a liquid product package, it has excellent liquid leakage resistance during long-term storage. Become.

The present invention will be specifically described below.
The polyvinyl alcohol-based film of the present invention is mainly composed of a polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of the degree of saponification, viscosity, modified species, and modified amount, and carbon It is necessary to contain 1 to 2000 ppm of monohydric alcohol of number 1 to 3.
Hereinafter, polyvinyl alcohol may be abbreviated as "PVA", and a film containing a polyvinyl alcohol-based resin as a main component may be abbreviated as "PVA-based film".

The content of monohydric alcohol having 1 to 3 carbon atoms is preferably 5 to 1000 ppm, particularly preferably 10 to 500 ppm. If the content of the monohydric alcohol having 1 to 3 carbon atoms is less than the lower limit, large bubbles are likely to be generated in the solution due to stirring during film production, and those that remain without disappearing until film formation form the film. It becomes a bubble defect. On the other hand, if the content exceeds the upper limit, a large amount of the lower alcohol component is vaporized when the film is dried at a high temperature after forming the film, resulting in the generation of fine air bubbles, resulting in air bubble defects in the film. I don't get it.
In addition, a monohydric alcohol having 4 or more carbon atoms is not preferable because the water solubility of the monohydric alcohol is low and the hydrophilicity is insufficient, so that the turbidity and viscosity stability of the aqueous PVA-based resin solution may decrease.

Such monohydric alcohols having 1 to 3 carbon atoms may contain an ether bond in their structure, and specific examples include methanol, ethanol, 1-propanol, 2-propanol, cyclopropanol, methoxymethanol, ethoxymethanol. , 2-methoxyethanol, and the like.

Among these, monohydric alcohols containing no ether bond in the structure are preferred from the viewpoint of safety, methanol and ethanol are particularly preferred from the viewpoint of hydrophilicity, and ethanol is more preferred from the viewpoint of environmental toxicity.

Moreover, these monohydric alcohols can be used alone, or two or more of them can be used in combination.

The content of monohydric alcohol having 1 to 3 carbon atoms in the PVA-based film is quantitatively measured by gas chromatography/mass spectrometry (GC/MS) equipped with a dynamic headspace device.
Specifically, a film sample (approximately 5 mg) was volatilized at 120°C for 60 minutes in a dynamic headspace device to evaporate the monohydric alcohol component, and the gas components collected by the agglomeration device were transferred to the GC/MS device. identification and quantification. Identify the monohydric alcohol component from the MS spectrum of GC, determine the volatilization amount from the peak area of the abundance intensity obtained by GC based on the calibration curve of each alcohol component, and from the weight of the film sample subjected to measurement By conversion, the content of monohydric alcohol having 1 to 3 carbon atoms in the PVA-based film can be obtained.
When two or more types of monohydric alcohols having 1 to 3 carbon atoms are contained together, the total value of the detected alcohol contents is calculated as the content of monohydric alcohols having 1 to 3 carbon atoms. be able to.

The PVA-based film of the present invention is mainly composed of a PVA-based resin (A) containing two or more PVA-based resins different in at least one of saponification degree, viscosity, modification type, and modification amount.
Here, the PVA-based resin (A) as a main component means that the PVA-based resin (A) is usually 50% by weight or more, preferably 55% by weight or more, and particularly preferably 60% by weight or more, relative to the entire water-soluble film. means to contain
First, the PVA-based resin (A) containing two or more PVA-based resins differing in at least one of the degree of saponification, viscosity, modification type, and modification amount used in the present invention will be described.
Hereinafter, "polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of saponification degree, viscosity, modified species, and modified amount" is simply referred to as "PVA-based resin (A)". may be abbreviated.

[PVA-based resin (A)]
The PVA-based resin (A) used in the present invention is selected from unmodified PVA and modified PVA-based resins, and two or more PVA-based resins differing in at least one of saponification degree, viscosity, modified species, and modified amount. It is the contained PVA-based resin. Specific examples include the combined use of two or more types of unmodified PVAs, the combined use of two or more types of modified PVA-based resins, and the combined use of two or more types of unmodified PVA and modified PVA-based resins.

Unmodified PVA is a resin mainly composed of vinyl alcohol structural units, which is obtained by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester compound. It is composed of vinyl ester structural units remaining without conversion.

Examples of such vinyl ester compounds include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, and vinyl stearate. Among them, it is preferable to use vinyl acetate. The above vinyl ester compounds may be used alone or in combination of two or more.

As the method for copolymerizing the vinyl ester compound, known polymerization methods such as solution polymerization method, emulsion polymerization method and suspension polymerization method can be arbitrarily used. It is carried out by a solution polymerization method using alcohol as a solvent.

As the polymerization catalyst, a known polymerization catalyst such as an azo catalyst such as azobisisobutyronitrile, a peroxide catalyst such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, etc., is appropriately selected according to the polymerization method. be able to. Also, the reaction temperature for polymerization is selected from the range of about 50° C. to the boiling point.

Saponification can be carried out by a known method, usually by dissolving the resulting copolymer in alcohol in the presence of a saponification catalyst. Alcohols include methanol, ethanol, butanol, and the like. The concentration of the copolymer in alcohol is selected from the range of 20 to 50% by weight from the viewpoint of solubility.

As the saponification catalyst, alkali catalysts such as alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate, and alcoholates can be used, and acid catalysts can be used. is also possible. The amount of the saponification catalyst used is preferably 1 to 100 millimol equivalents relative to the vinyl ester compound.

The average saponification degree of the unmodified PVA used in the present invention is preferably 80 mol% or more, particularly preferably 82 to 99 mol%, further preferably 85 to 90 mol%. be. If the average degree of saponification is too small, the water solubility tends to decrease. In addition, even if the average degree of saponification is too large, the water solubility tends to decrease.

In addition, the unmodified PVA used in the present invention preferably has a 4% by weight aqueous solution viscosity at 20° C. of 10 to 50 mPa·s, particularly preferably 15 to 45 mPa·s, and still more preferably 20 to 40 mPa·s. . If the viscosity is too low, the mechanical strength of the film as a packaging material tends to decrease, and if it is too high, the viscosity of the aqueous solution during film formation tends to be high, resulting in a decrease in productivity.

The above average saponification degree is measured according to JIS K 6726 3.5, and the 4% by weight aqueous solution viscosity is measured according to JIS K 6726 3.11.2.

Modified PVA-based resin is a resin mainly composed of vinyl alcohol structural units obtained by saponifying a polyvinyl ester-based resin obtained by polymerizing a vinyl ester-based compound. It is an introduced resin composed of vinyl alcohol structural units corresponding to the degree of saponification and vinyl ester structural units remaining unsaponified, as well as unsaturated monomer structural units by copolymerization or structural units by post-reaction. be.

As such a vinyl ester compound, the same compound as in the unmodified PVA can be used.

Modified PVA-based resins by copolymerization (copolymerization-modified PVA-based resins) include vinyl ester monomers and unsaturated monomers copolymerizable with vinyl ester monomers such as ethylene, propylene, isobutylene, α- Olefins such as octene, α-dodecene, and α-octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, their salts, monoesters, dialkylesters, etc., acrylonitrile , methacrylonitrile and other nitriles, acrylamide, methacrylamide and other amides, ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid and other olefin sulfonic acids or salts thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride , allyltrimethylammonium chloride, dimethyl allyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyalkylene (meth) allyl ether such as polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate; polyoxyalkylene (meth)acrylamides such as polyoxyethylene (meth)acrylamide and polyoxypropylene (meth)acrylamide; Polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinyl Those obtained by copolymerization with hydroxy group-containing α-olefins such as amines, 3-buten-1-ol, 4-penten-1-ol, 5-hexene-1-ol, and derivatives such as acylated products thereof is mentioned.

Examples of modified PVA-based resins (post-modified PVA-based resins) by post-reaction include those having acetoacetyl groups due to reaction with diketene, those having polyalkylene oxide groups due to reaction with ethylene oxide, epoxy compounds, and the like. Reaction with PVA resin by esterification, acetalization, urethanization, etherification, grafting, phosphate esterification, oxyalkylenation, etc. with hydroxyalkyl groups or aldehyde compounds with various functional groups. I can mention what I got.

Further, the modified PVA-based resin has a primary hydroxyl group in the side chain, for example, the number of the primary hydroxyl group in the side chain is usually 1 to 5, preferably 1 to 2, particularly preferably 1. Furthermore, it is preferable to have a secondary hydroxyl group in addition to the primary hydroxyl group. Examples of such modified PVA include modified PVA resins having hydroxyalkyl groups in side chains and modified PVA resins having 1,2-diol structural units in side chains. A modified PVA resin having a 1,2-diol structural unit in a side chain can be produced by, for example, (a) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (b) acetic acid (c) saponification and decarboxylation of a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane; It can be produced by a method of ketalization, (d) a method of saponifying a copolymer of vinyl acetate and glycerin monoallyl ether, and the like.

As the method for copolymerizing the vinyl ester-based compound and the unsaturated monomer copolymerizable with the vinyl ester-based compound, the same method as in the case of the unmodified PVA can be used. It is carried out by a solution polymerization method using a solvent. In addition, the same polymerization catalyst, saponification method, saponification catalyst, etc. as in the case of the unmodified PVA can be appropriately selected.

As the modified PVA-based resin used in the present invention, it is preferable to use an anionic group-modified PVA-based resin in terms of solubility. Examples of the anionic group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. From the viewpoint of chemical resistance and stability over time, a carboxyl group and a sulfonic acid group are preferred, and a carboxyl group is particularly preferred. .

The carboxyl group-modified PVA-based resin can be produced by any method. For example, (I) a method of copolymerizing an unsaturated monomer having a carboxyl group and a vinyl ester compound and then saponifying it ) A method of polymerizing a vinyl ester compound in the presence of an alcohol, aldehyde, thiol, or the like having a carboxyl group as a chain transfer agent and then saponifying the polymer.

As the vinyl ester compound in method (I) or (II), the above-mentioned compounds can be used, but it is preferable to use vinyl acetate.

Examples of the unsaturated monomer having a carboxyl group in the above method (I) include ethylenically unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.) or ethylenically unsaturated dicarboxylic acid monoesters (maleic acid monoesters). alkyl esters, monoalkyl fumarate, monoalkyl itaconate, etc.), or ethylenically unsaturated dicarboxylic acid diesters (dialkyl maleate, dialkyl fumarate, dialkyl itaconate, etc.) [however, these diesters are It is necessary to change to a carboxyl group by hydrolysis during saponification of the polymer], ethylenically unsaturated carboxylic anhydride (maleic anhydride, itaconic anhydride, etc.), or ethylenically unsaturated monocarboxylic acid ( (Meth)acrylic acid, crotonic acid, etc.) and salts thereof.

Among them, it is preferable to use maleic acid, maleic acid monoalkyl ester, maleic acid dialkyl ester, maleic acid salt, maleic anhydride, itaconic acid, itaconic acid monoalkyl ester, itaconic acid dialkyl ester, (meth)acrylic acid, and the like. is preferably maleic acid, maleic acid monoalkyl ester, maleic acid dialkyl ester, maleic acid salt, maleic anhydride, more preferably maleic acid monoalkyl ester.

In the method (II) above, thiol-derived compounds having a particularly large chain transfer effect are effective, and examples thereof include the following compounds and salts thereof.

[In general formulas (1) and (2) above, n is an integer of 0 to 5, and R1, R2 and R3 each represent a hydrogen atom or a lower alkyl group (which may contain a substituent). ]

[However, in the general formula (3), n is an integer of 0 to 20. ]

Specific examples include mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 2-mercaptostearic acid and the like.

In addition to the unsaturated monomer having a carboxyl group and the vinyl ester compound, the polymerization may be carried out by containing other general monomers within a range that does not impair the water solubility. As the base, for example, allyl ester of saturated carboxylic acid, α-olefin, alkyl vinyl ether, alkyl allyl ether, (meth)acrylamide, (meth)acrylonitrile, styrene, vinyl chloride and the like can be used.

In addition, the method for producing the carboxyl group-modified PVA resin is not limited to the above method. A method of post-reacting a carboxyl group-containing compound having a certain functional group can also be implemented.

When using a sulfonic acid-modified PVA resin modified with a sulfonic acid group, examples include vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and the like. is copolymerized with a vinyl ester compound and then saponified; a method of Michael addition of vinylsulfonic acid or its salt, 2-acrylamido-2-methylpropanesulfonic acid or its salt, etc. to PVA; can be manufactured by

The average degree of saponification of the modified PVA-based resin used in the present invention is preferably 80 mol % or more, particularly preferably 85 to 99.9 mol %, still more preferably 90 to 99.0 mol %. If the average degree of saponification is too small, the solubility of the film tends to decrease over time depending on the pH of the drug to be packaged. In addition, when the average degree of saponification is too large, the solubility in water tends to greatly decrease due to the heat history during film formation.

Furthermore, when an anionic group-modified PVA-based resin is used as the modified PVA-based resin, the average degree of saponification is preferably 85 mol% or more, particularly preferably 88 to 99.9 mol%, and further It is preferably 90 to 99.5 mol %, particularly preferably 90 to 99.0 mol %.

Further, the modified PVA-based resin used in the present invention preferably has a 4% by weight aqueous solution viscosity at 20° C. of 10 to 50 mPa·s, particularly preferably 15 to 45 mPa·s, further preferably 20 to 40 mPa·s. be. If the viscosity is too low, the mechanical strength of the film as a packaging material tends to decrease, and if it is too high, the viscosity of the aqueous solution during film formation tends to be high, resulting in a decrease in productivity.

The above average saponification degree is measured according to JIS K 6726 3.5, and the 4% by weight aqueous solution viscosity is measured according to JIS K 6726 3.11.2.

The modified amount of the modified PVA-based resin used in the present invention is preferably 1 to 20 mol %, particularly preferably 1.5 to 15 mol %, still more preferably 2 to 12 mol %. If the modified amount is too small, the solubility in water tends to decrease, and if it is too large, the productivity of the resin tends to decrease, the biodegradability tends to decrease, and blocking tends to occur easily. be.

In the present invention, when an anionic group-modified PVA-based resin is used as the modified PVA-based resin, the amount of modification of the anionic group-modified PVA-based resin is preferably 1 to 10 mol%, particularly preferably 1.5 to 9 mol %, more preferably 2 to 8 mol %. If the amount of such modification is too small, the solubility in water tends to decrease, and in particular, the solubility of the film tends to decrease over time when used as a drug package. On the other hand, if the amount of modification is too large, the productivity of the resin tends to decrease, the biodegradability tends to decrease, and blocking tends to occur easily.

In the present invention, from the viewpoint of film physical properties such as solubility and mechanical properties, PVA-based resin containing two or more PVA-based resins that differ in at least one of saponification degree, viscosity, modified species, and modified amount (A ) is the main component of the PVA-based film. The content of the PVA-based resin (A) in the PVA-based film is preferably 35% by weight or more, particularly preferably 50% by weight or more, and still more preferably 60% by weight or more. If the content is too small, the solubility in water and the mechanical properties of the film tend to deteriorate. The upper limit of the content is usually 99% by weight or less, preferably 95% by weight or less, and particularly preferably 90% by weight or less, from the viewpoint of the shape stability over time when the liquid detergent package is formed. is preferred.

In the present invention, since the PVA-based resin (A) containing two or more PVA-based resins can maintain the solubility for a long time, at least one PVA-based resin is preferably a modified PVA-based resin. Furthermore, it is preferably an anionic group-modified PVA-based resin, and particularly preferably a carboxyl group-modified PVA-based resin.
From the viewpoint of film strength, it is preferable to contain unmodified PVA and modified PVA-based resin, more preferably to contain unmodified PVA and anionic group-modified PVA-based resin, particularly unmodified PVA and modified PVA-based resin. It is preferable to contain a carboxyl group-modified PVA-based resin.

When unmodified PVA and modified PVA-based resin are contained, the content ratio (weight ratio) of unmodified PVA and modified PVA-based resin is unmodified PVA/modified PVA-based resin=1/99 to 99/1. is preferred, particularly preferably 5/95 to 95/5, more preferably 10/90 to 90/10.
In particular, from the viewpoint of film physical properties such as solubility and water sealability, unmodified PVA/modified PVA resin is preferably 5/95 to 40/60, particularly preferably 6/94 to 30/70, and more preferably It is preferably 7/93 to 20/80. If the content of the unmodified PVA is too low, the water-sealing property tends to be lowered, and if the content of the modified PVA-based resin is too low, the solubility tends to be lowered.

In addition, when the modified PVA-based resin and the unmodified PVA are contained, the unmodified PVA preferably has a 4% by weight aqueous solution viscosity at 20° C. of 5 to 50 mPa·s, particularly preferably 10 to 45 mPa·s. s, more preferably 12 to 40 mPa·s, particularly preferably 15 to 35 mPa·s. If the viscosity is too low, the mechanical strength of the film as a packaging material tends to be low.

The average degree of saponification of the PVA-based resin (A) used in the present invention is preferably 80 mol % or more, particularly preferably 85 to 99 mol %, still more preferably 90 to 98 mol %. If the average degree of saponification is too small, the water solubility of the PVA-based film tends to decrease. In addition, even if the average degree of saponification is too large, the solubility in water tends to decrease.

The viscosity of the 4% by weight aqueous solution of the PVA-based resin (A) used in the present invention at 20° C. is preferably 10 to 50 mPa·s, particularly preferably 15 to 45 mPa·s, and still more preferably 20 to 40 mPa·s. is s. If the viscosity is too low, the mechanical strength of the PVA-based film as a packaging material tends to decrease, and if it is too high, the viscosity of the aqueous solution during film formation tends to be high, resulting in a decrease in productivity.

The PVA-based resin (A) used in the present invention preferably has a modification amount of 1 to 20 mol%, particularly preferably 1.5 to 15 mol%, and still more preferably 2 to 12 mol%. . When the amount of such modification is small, the solubility in water tends to decrease, and when the amount of modification is large, the productivity of the PVA resin tends to decrease, the biodegradability tends to decrease, and the PVA-based film tends to cause blocking. tend to become

[Plasticizer (B)]
In the PVA-based film of the present invention, it is preferable to further contain a plasticizer (B) from the viewpoint of imparting flexibility and moldability to the film. The plasticizer (B) may be used alone or in combination of two or more. Using two or more in combination improves the toughness of the film itself when used as a package, and especially the liquid detergent. It is preferable in terms of the shape stability of the package over time when packaged.

When two or more such plasticizers (B) are used in combination, a polyhydric alcohol (B1) having a melting point of 80° C. or higher (hereinafter sometimes abbreviated as “plasticizer (B1)”) and a melting point of 50 ° C. or less polyhydric alcohol (B2) (hereinafter sometimes abbreviated as “plasticizer (B2)”). It is preferable in terms of toughness and shape stability over time when used as a package for liquid drugs.

As the polyhydric alcohol (B1) having a melting point of 80° C. or higher, that is, the plasticizer (B1), many sugar alcohols, monosaccharides, and polysaccharides can be applied. Among them, for example, salicyl alcohol ( 83°C), catechol (105°C), resorcinol (110°C), hydroquinone (172°C), bisphenol A (158°C), bisphenol F (162°C), neopentyl glycol (127°C), dihydric alcohols such as Trihydric alcohols such as loglucinol (218°C), tetrahydric alcohols such as erythritol (121°C), threitol (88°C), pentaerythritol (260°C), xylitol (92°C), arabitol (103°C), fucitol (153°C), glucose (146°C), fructose (104°C) and other pentahydric alcohols, mannitol (166°C), sorbitol (95°C), inositol (225°C) and other hexahydric alcohols, lactitol (146°C) , sucrose (186° C.), trehalose (97° C.) and other octahydric alcohols, and 9-hydric or higher alcohols such as maltitol (145° C.). These can be used alone or in combination of two or more. The numbers in parentheses above indicate the melting point of each compound.
Among the above, those having a melting point of 85° C. or higher, particularly 90° C. or higher are preferable from the viewpoint of the tensile strength of the PVA-based film. The upper limit of the melting point is usually 300°C, preferably 200°C.

Furthermore, in the present invention, among the plasticizer (B1), it is preferable that the number of hydroxyl groups in one molecule is 4 or more in terms of compatibility with the PVA-based resin (A), and particularly preferably 5 to The number is 10, more preferably 6 to 8. Specific examples include sorbitol, sucrose, trehalose, and the like.

Further, in the present invention, the molecular weight of the plasticizer (B1) is preferably 150 or more, particularly preferably 160 to 500, further preferably 180 to 400, from the viewpoint of the tension of the PVA-based film. Suitable examples include sorbitol and sucrose.

On the other hand, as the polyhydric alcohol (B2) having a melting point of 50° C. or less, that is, the plasticizer (B2), many aliphatic alcohols can be applied. For example, ethylene glycol (−13° C.) and diethylene glycol are preferred. (-11°C), triethylene glycol (-7°C), propylene glycol (-59°C), tetraethylene glycol (-5.6°C), 1,3-propanediol (-27°C), 1,4- Butanediol (20°C), 1,6-hexanediol (40°C), tripropylene glycol, dihydric alcohol such as polyethylene glycol with a molecular weight of 2000 or less, glycerin (18°C), diglycerin, triethanolamine (21°C) trihydric or higher alcohols such as From the viewpoint of the flexibility of the PVA-based film, the melting point is preferably 30° C. or lower, particularly 20° C. or lower. The lower limit of the melting point is usually -80°C, preferably -10°C, particularly preferably 0°C. These can be used alone or in combination of two or more. The numbers in parentheses above indicate the melting point of each compound.

Furthermore, in the present invention, among the plasticizer (B2), the number of hydroxyl groups in one molecule is 4 or less, particularly 3 or less, so that the flexibility near room temperature (25 ° C.) is easy to control. Specifically, for example, glycerin is preferable.

In the present invention, the plasticizer (B2) preferably has a molecular weight of 100 or less, particularly 50 to 100, and further preferably 60 to 95, in terms of easy control of flexibility. Specifically, for example, glycerin is suitable.

In the present invention, a plasticizer (B3) other than the above plasticizers (B1) and (B2) can also be used in combination. Examples of such plasticizers (B3) include trimethylolpropane (58°C) and diethylene glycol. Alcohols such as monomethyl ether, cyclohexanol, carbitol, polypropylene glycol, ethers such as dibutyl ether, carboxylic acids such as stearic acid, oleic acid, linoleic acid, linolenic acid, sorbic acid, citric acid, adipic acid, cyclohexanone, etc. ketones, amines such as monoethanolamine, triethanolamine, ethylenediamine and imidazole compounds, and amino acids such as alanine, glycine, aspartic acid, glutamic acid, histidine, lysine and cysteine.
In terms of excellent curl resistance and a good balance between strength and flexibility, in addition to the plasticizers (B1) and (B2), the plasticizer (B3) has a melting point greater than 50°C and less than 80°C. It is preferable to use three kinds of plasticizers, polyhydric alcohols, and it is particularly preferable to use trimethylolpropane as the plasticizer (B3).

In the present invention, the content of the plasticizer (B) is preferably 5 parts by weight or more, particularly preferably 5 to 70 parts by weight, more preferably 8 parts by weight, based on 100 parts by weight of the PVA resin (A). to 60 parts by weight, particularly preferably 10 to 50 parts by weight. If the content of the plasticizer (B) is too small, the shape stability over time tends to deteriorate when a liquid such as a liquid detergent is packaged to form a package. In addition, when it is too large, there is a tendency that the mechanical strength is lowered and blocking is likely to occur.

Further, the content weight ratio (B1/B2) of the plasticizer (B1) and the plasticizer (B2) is preferably 0.1 to 5, particularly preferably 0.2 to 4.5, and more preferably 0.2 to 4.5. It is preferably 0.5 to 4, particularly preferably 0.7 to 3. If the content is too small, the PVA-based film tends to be too soft, and blocking tends to occur.

Further, the content of the plasticizer (B1) and the plasticizer (B2) is preferably 5 to 40 parts by weight of the plasticizer (B1) with respect to 100 parts by weight of the PVA resin (A). , Particularly preferably 8 to 30 parts by weight, more preferably 10 to 25 parts by weight, and the plasticizer (B2) is preferably 5 to 40 parts by weight, particularly preferably 10 to 35 parts by weight, more preferably is 15 to 30 parts by weight.
If the amount of the plasticizer (B1) is too small, the PVA-based film tends to be too hard, and if it is too large, the PVA-based film tends to be too soft. Also, if the plasticizer (B2) is too small, the PVA-based film tends to become too hard and tends to become brittle in a low-humidity environment. There is

Furthermore, the total amount of the plasticizer (B1) and the plasticizer (B2) is preferably 70% by weight or more, particularly 80% by weight or more, and further 85% by weight or more, relative to the total plasticizer (B). is preferably If the total amount of plasticizers (B1) and (B2) is too small, mechanical strength tends to decrease.

In addition to the plasticizer (B1) and the plasticizer (B2), when the plasticizer (B3) is used in combination, the ratio of the plasticizers (B1), (B2), and (B3) to each other is The content of the plasticizer (B3) with respect to the total amount of the plasticizers (B1), (B2), and (B3) is preferably 20% by weight or less. From the standpoint of tearability, the content is preferably 0.5 to 18% by weight, more preferably 2 to 15% by weight, particularly preferably 4 to 13% by weight. If the content of the plasticizer (B3) is too large, the change in the state of the film between room temperature and high temperature may become large, and the pinhole resistance and bag breakage resistance may deteriorate.

In the present invention, a filler (C), a surfactant (D), etc. can be further contained as necessary.

[Filler (C)]
The filler (C) is contained for the purpose of anti-blocking property, and includes organic filler (C1) and inorganic filler (C2), among which organic filler (C1) is preferably used. Moreover, from the viewpoint of improving the water-sealing property at the time of preparing the package, it is preferable to use both the organic filler (C1) and the inorganic filler (C2) together.

The organic filler (C1) used in the present invention is a particulate matter (primary particles) composed of an organic compound and having an arbitrary shape such as a needle-like, rod-like, layered, scale-like, or spherical shape, or a particulate matter thereof. Indicates an aggregate of substances (secondary particles).
Such an organic filler (C1) is mainly selected from polymer compounds, and examples thereof include melamine-based resins, polymethyl (meth)acrylate-based resins, polystyrene-based resins, and biodegradable resins such as starch and polylactic acid. etc. Among these, biodegradable resins such as polymethyl (meth)acrylate-based resins, polystyrene-based resins and starch are preferred, and starch is particularly preferred from the viewpoint of dispersibility in the PVA-based resin (A).

Examples of the above starch include raw starch (corn starch, potato starch, sweet potato starch, wheat starch, kisava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, arrowroot starch, bracken starch, lotus starch, watermelon starch, etc.), physically modified starch (α-starch, fractionated amylose, heat-moisture treated starch, etc.), enzymatically modified starch (hydrolyzed dextrin, enzymatically degraded dextrin, amylose, etc.), chemically modified starch (acid-treated starch, sodium hypochlorite, etc.) chlorinated oxidized starch, dialdehyde starch, etc.), chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, crosslinked starch, etc.), and the like. Among them, it is preferable to use raw starch, particularly corn starch and rice starch, from the viewpoint of availability and economy.

The average particle size of the organic filler (C1) is preferably 5 to 50 μm, particularly preferably 10 to 40 μm, still more preferably 15 to 35 μm. If the average particle size is too small, the blocking property of the film tends to increase. There is

The average particle size of the organic filler (C1) is a value measured with a laser diffraction particle size distribution measuring device, and is calculated from the D50 value (accumulated 50% particle size) of the obtained cumulative volume distribution. .

The inorganic filler (C2) used in the present invention is a particulate matter (primary particles) composed of an inorganic compound and having an arbitrary shape such as a needle-like, rod-like, layered, scale-like, or spherical shape, or a particulate matter thereof. Indicates an aggregate of substances (secondary particles).
Examples of the inorganic filler (C2) include oxide-based inorganic compounds such as silica (silicon dioxide), diatomaceous earth, titanium oxide, calcium oxide, magnesium oxide, aluminum oxide, barium oxide, germanium oxide, tin oxide and zinc oxide, Talc, clay, kaolin, mica, asbestos, gypsum, graphite, glass balloons, glass beads, calcium sulfate, barium sulfate, ammonium sulfate, calcium sulfite, calcium carbonate, whisker-like calcium carbonate, magnesium carbonate, dawsonite, dolomite, potassium titanate, Carbon black, glass fiber, alumina fiber, boron fiber, processed mineral fiber, carbon fiber, carbon hollow sphere, bentonite, montmorillonite, copper powder, sodium sulfate, potassium sulfate, zinc sulfate, copper sulfate, iron sulfate, magnesium sulfate, aluminum sulfate , aluminum potassium sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, aluminum nitrate, ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium phosphate, potassium chromate and the like. These can be used alone or in combination of two or more.

Among them, it is preferable to use an oxide-based inorganic compound and talc, and particularly preferably titanium oxide, talc, Silica is preferably used, and more preferably silica is used.

The inorganic filler (C2) preferably has an average particle size of 1 to 20 μm, particularly preferably 2 to 15 μm, further preferably 3 to 10 μm. If the average particle size is too small, the blocking property of the film tends to increase, and the flexibility and toughness of the film tend to decrease.

The average particle size of the inorganic filler (C2) is a value measured with a laser diffraction particle size distribution measuring device, and is calculated from the D50 value (accumulated 50% particle size) of the obtained cumulative volume distribution. .

The content of the filler (C) is preferably 1 to 30 parts by weight, particularly preferably 2 to 25 parts by weight, more preferably 2.5 to 20 parts by weight, based on 100 parts by weight of the PVA resin (A). weight part. If the content is too low, the blocking property tends to increase, and if it is too high, the flexibility and toughness of the film tend to decrease.

When the organic filler (C1) and the inorganic filler (C2) are used together, the content ratio (weight ratio) of the organic filler (C1) and the inorganic filler (C2) is preferably C1/C2 = 2 to 15. Especially preferably 3-13, more preferably 4-10. If the content of the organic filler (C1) with respect to the inorganic filler (C2) is too small, the flexibility and toughness of the film tend to decrease, making it difficult to obtain a good package. If the content of the filler (C1) is too large, there is a tendency for the water sealability to deteriorate.

[Surfactant (D)]
The surfactant (D) used in the present invention is contained for the purpose of improving releasability from the cast surface during PVA-based film production, and is usually a nonionic surfactant, a cationic surfactant, or an anionic surfactant. Surfactants are included. For example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl nonyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkylallyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyalkylene alkyl ether phosphate monoethanolamine salt, polyoxyethylene lauryl amino ether, polyoxyethylene alkyl amino ether such as polyoxyethylene stearyl amino ether, and the like. , these can be used alone or in combination of two or more. Among them, polyoxyalkylene alkyl ether phosphate monoethanolamine salt and polyoxyethylene lauryl amino ether are preferable from the viewpoint of production stability.

The content of the surfactant (D) is preferably 0.01 to 3 parts by weight, particularly preferably 0.05 to 2.5 parts by weight, per 100 parts by weight of the PVA resin (A). , more preferably 0.1 to 2 parts by weight. If the content is too small, the peelability between the cast surface of the film forming apparatus and the formed PVA-based film tends to decrease, resulting in a decrease in productivity. There is a tendency to cause problems such as a decrease in adhesive strength when sealing is performed.

In addition, other water-soluble polymers (e.g., sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, dextrin, chitosan, chitin, methylcellulose, hydroxyethylcellulose, etc.), fragrances, and rust preventives are added to the extent that the objects of the invention are not hindered. Agents, coloring agents, bulking agents, antifoaming agents, ultraviolet absorbers, liquid paraffins, fluorescent whitening agents, bitter components (eg, denatonium benzoate, etc.), etc., may also be incorporated. These can be used alone or in combination of two or more.

Moreover, in the present invention, it is preferable to blend an antioxidant from the viewpoint of suppressing yellowing. Such antioxidants include, for example, sulfites such as sodium sulfite, potassium sulfite, calcium sulfite and ammonium sulfite, tartaric acid, ascorbic acid, sodium thiosulfate, techol, rongarite, etc. Among them, sulfites, particularly sulfites Sodium is preferred. Such a compounding amount is preferably 0.1 to 10 parts by weight, particularly preferably 0.2 to 5 parts by weight, and further preferably 0.3 to 3 parts by weight based on 100 parts by weight of the PVA-based resin (A). is.

<Production of PVA-based film>
The PVA-based film of the present invention can be produced by the following method.
Polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of the saponification degree, viscosity, modified species, and modified amount, preferably further a plasticizer (B), if necessary Furthermore, a PVA-based resin composition containing a filler (C), a surfactant (D), etc. is obtained, and (I) at least one of saponification degree, viscosity, modified species, and modified amount is different 2 (II) a dissolution step of dissolving a polyvinyl alcohol-based resin composition containing polyvinyl alcohol-based resin (A) containing at least one polyvinyl alcohol-based resin as a main component to obtain a polyvinyl alcohol-based resin aqueous solution; (III) a step of adding 0.001 to 5% by weight of a monohydric alcohol having 1 to 3 carbon atoms to the aqueous solution to prepare a film-forming raw material; A PVA-based film is produced by a production method characterized by including a film-forming step of forming a film using a film-forming raw material) in this order.

The PVA-based resin (A), which is the raw material of the PVA-based film, may use a lower alcohol as a solvent in the polymerization process and the saponification process. System solvent may remain. However, in the dissolution process in film production, dissolution is generally performed for a long time at a temperature higher than the boiling point of the alcohol solvent, so the alcohol solvent remaining in the raw material volatilizes and is discharged outside the system. No alcohol-based solvent remains in the normally produced PVA-based film.
In the present invention, focusing on the effect of the solvent, the PVA-based aqueous solution after dissolution, in which the alcohol-based solvent usually disappears and does not remain, is dared to contain a monohydric alcohol to form a film, thereby forming air bubbles in the film. We have newly found that the generation can be controlled.
Each step will be specifically described below.

[[I] dissolving step]
In the dissolving step, the PVA-based resin composition is dissolved or dispersed in water to prepare an aqueous PVA-based resin solution.
The dissolution step refers to the step of dissolving or dispersing the PVA-based resin composition in water to obtain an aqueous solution free of undissolved matter.
As the dissolution method for dissolving the PVA-based resin composition in water, normal temperature dissolution, high temperature dissolution, pressurized dissolution, etc. are usually adopted. Dissolution and pressurized dissolution are preferred.

The dissolution temperature is usually 80 to 100°C, preferably 90 to 100°C, in the case of high temperature dissolution, and is usually 80 to 130°C, preferably 90 to 120°C, in the case of pressure dissolution.
The dissolution time may be appropriately adjusted depending on the dissolution temperature and pressure during dissolution, and is usually 1 to 20 hours, preferably 2 to 15 hours, more preferably 3 to 10 hours. If the dissolution time is too short, undissolved matter tends to remain, and if it is too long, productivity tends to decrease.

In addition, in the dissolving step, examples of the stirring impeller include a paddle, full zone, Maxblend, twister, anchor, ribbon, propeller and the like.
Further, after dissolution, the obtained PVA-based resin aqueous solution is subjected to a defoaming treatment. be done. Among them, stationary defoaming and twin-screw extrusion defoaming are preferable. The temperature for stationary defoaming is usually 50 to 100° C., preferably 70 to 95° C., and the defoaming time is usually 2 to 30 hours, preferably 5 to 20 hours.

[[II] Monohydric alcohol compounding step having 1 to 3 carbon atoms]
The PVA-based film of the present invention is prepared by adding a monohydric alcohol having 1 to 3 carbon atoms to the aqueous PVA-based resin solution after the dissolution step, that is, after preparing the aqueous PVA-based resin solution in which the PVA-based resin composition is dissolved. It can be obtained by preparing a raw material for film formation with the content of 0.001 to 5% by weight, and then manufacturing in the order of film formation.

In the present invention, it is important to add a monohydric alcohol having 1 to 3 carbon atoms to the aqueous PVA-based resin solution after the dissolution step. When a monohydric alcohol having 1 to 3 carbon atoms is blended before the dissolving step, the alcoholic solvent volatilizes and is discharged outside the system during the dissolving step, so the desired PVA-based film cannot be obtained. do not have. In addition, since an explosion-proof reaction vessel is required to dissolve the PVA-based resin aqueous solution containing the alcohol-based solvent at a high temperature for a long time, it is not preferable in terms of equipment cost and safety.

Such monohydric alcohols having 1 to 3 carbon atoms may contain an ether bond in their structure, and specific examples include methanol, ethanol, 1-propanol, 2-propanol, cyclopropanol, methoxymethanol, ethoxymethanol. , 2-methoxyethanol, and the like. A monohydric alcohol having 4 or more carbon atoms is not preferable because the water solubility of the monohydric alcohol is low and the hydrophilicity is insufficient, which may reduce the turbidity and viscosity stability of the PVA-based aqueous solution.

Among these, monohydric alcohols containing no ether bond are preferred from the viewpoint of safety, methanol and ethanol having good hydrophilicity are preferred, and ethanol is particularly preferred from the viewpoint of environmental toxicity.

Moreover, these monohydric alcohols can be used alone, or two or more of them can be used in combination.

The content of monohydric alcohol having 1 to 3 carbon atoms in the aqueous PVA resin solution is preferably 0.001 to 5% by weight, particularly preferably 0.01 to 3% by weight, and more preferably 0.1%. ~2% by weight. If the concentration is too low, there is a tendency that the effect of suppressing the generation of air bubbles during solution preparation cannot be obtained, and if it is too high, fine air bubbles tend to be generated during film drying.

The solid content concentration of the film-forming raw material is preferably 10 to 50% by weight, particularly preferably 15 to 40% by weight, further preferably 20 to 35% by weight. If the concentration is too low, the productivity of the film tends to decrease, and if it is too high, the viscosity becomes too high, and it takes time to degas the film-forming raw material, and there is a tendency for die lines to occur during film formation. There is

[[III] film forming process]
In the film-forming process, the film-forming raw material prepared in the dissolving process and the C1-3 monohydric alcohol compounding process is shaped into a film, and if necessary, dried to achieve a moisture content of 15% by weight. The following PVA-based film is prepared.
In forming the film, for example, a method such as a melt extrusion method or a casting method can be employed, and the casting method is preferable in terms of film thickness accuracy.
When performing the casting method, for example, (i) a method in which the film-forming raw material is passed through a gap using an applicator, bar coater, or the like, and cast onto a casting surface such as a metal surface; The PVA-based film of the present invention is produced by casting the film-forming raw material by a method of discharging it from a slit such as a slit die and casting it on a casting surface such as an endless belt or a metal surface of a drum roll, and then drying it. be able to.

The temperature of the film-forming raw material at the film-forming raw material discharge portion of a T-shaped slit die or the like is preferably 60 to 98°C, particularly preferably 70 to 95°C. If the temperature is too low, the viscosity of the film-forming raw material tends to increase and the productivity of the PVA-based film tends to decrease.
After casting, the raw material for film formation is dried on the casting surface. The surface temperature of the casting surface is preferably 50 to 110°C, particularly preferably 70 to 100°C. If the surface temperature is too low, the moisture content of the film tends to increase due to insufficient drying, and blocking tends to occur.
In addition, for drying during film formation, drying using hot rolls, drying by blowing hot air onto the film using a floating dryer, drying using a far-infrared device, dielectric heating device, or the like can be used in combination.

After drying the film-forming raw material until the moisture content becomes 15% by weight or less by the above drying treatment, peel it off from the cast surface (if further drying with a hot roll after peeling from the cast surface, peel off from the dry heat roll to obtain a PVA-based film. The PVA-based film peeled off from the cast surface (or dry heat roll) is cooled in an environment of 10 to 35°C.

The surface of the PVA-based film of the present invention may be plain, but from the viewpoints of anti-blocking properties, slipperiness during processing, reduced adhesion between products, and appearance, an embossed pattern is applied to one or both sides of the PVA-based film. It is also preferable to apply uneven processing such as a fine uneven pattern, a special engraving pattern, or the like.
The processing temperature is usually 60 to 150.degree. C., preferably 80 to 140.degree. The working pressure is usually 2-8 MPa, preferably 3-7 MPa. The processing time is usually 0.01 to 5 seconds, preferably 0.1 to 3 seconds, although it depends on the processing pressure and film forming speed.
In addition, if necessary, after the roughening treatment, a cooling treatment may be performed in order to prevent unintended stretching of the film due to heat.

[Other processes]
In the case of producing a long PVA-based film, a winding process, packaging, storage, transportation, and the like are carried out as necessary after the above-described film-forming process.
In the winding process, the PVA-based film separated from the cast surface or the like in the film forming process is transported and wound up, and is wound around a core tube (S1) to prepare a film roll. The obtained film roll can be supplied as a product as it is, but preferably the wound PVA-based water-soluble film is slit into a desired size width, and then a core tube (S2) having a length corresponding to the film width is cut. It can also be rewound and supplied as a roll of film of the desired size.

The core tube (S1) around which the PVA-based film is wound is cylindrical, and its material can be appropriately selected from metals, plastics, and the like, but metals are preferable from the standpoint of robustness and strength.
The inner diameter of the core tube (S1) is preferably 3-30 cm, more preferably 10-20 cm. The thickness of the core tube (S1) is preferably 1-30 mm, more preferably 2-25 mm. The length of the core tube (S1) must be longer than the width of the PVA-based film, and preferably protrudes from the end of the film roll by 1 to 50 cm.

The core tube (S2) is cylindrical, and its material can be appropriately selected from paper, metal, plastic, and the like, but paper is preferable from the viewpoint of weight reduction and handling.
The inner diameter of the core tube (S2) is preferably 3-30 cm, more preferably 10-20 cm. The thickness of the core tube (S2) is preferably 1-30 mm, more preferably 3-25 mm. The length of the core tube (S2) may be equal to or longer than the width of the PVA-based film of the product, preferably equal to 50 cm longer.

When wound around the core tube (S2), the PVA-based film is slit to a desired width.
For such slitting, a shear blade, a razor blade, or the like is used to slit, but slitting with a shear blade is preferable from the viewpoint of smoothness of the cross section of the slit.

In the present invention, the PVA-based film is preferably produced in an environment of 10 to 35° C., particularly 15 to 30° C., and the humidity is usually 70% RH or less.
Thus, the PVA-based film of the present invention can be produced.

The thickness of the PVA-based film of the present invention is preferably 10-120 μm, particularly preferably 30-110 μm, further preferably 60-100 μm. If the thickness is too thin, the mechanical strength of the film tends to decrease, and if it is too thick, the dissolution rate in water tends to decrease, and the film-forming efficiency tends to decrease.

The width of the PVA-based film of the present invention is preferably 100 to 5000 mm, particularly preferably 200 to 2000 mm, still more preferably 300 to 1000 mm. If the width is too narrow, production efficiency tends to decrease, and if it is too wide, it tends to be difficult to control slack and film thickness.

Furthermore, the length of the PVA-based film of the present invention is appropriately selected depending on the application, etc., but is preferably 100 to 20,000 m, particularly preferably 800 to 15,000 m, and still more preferably 1,000 to 10,000 m. If the length is too short, switching the film tends to be troublesome, and if it is too long, the appearance tends to be poor due to tight winding and the weight tends to be too heavy.

Moreover, the moisture content of the PVA-based film is particularly preferably 1 to 12% by weight, more preferably 4 to 10% by weight. If the moisture content of the film is too low, the film will become too hard, and the formability of the package and the impact resistance of the package will tend to decrease.

The film roll obtained by winding the PVA-based water-soluble film of the present invention around a core tube is preferably packaged with a packaging film made of a water vapor barrier resin. Such a packaging film is not particularly limited, but has a moisture permeability of 10 g. /m ² /day (measured according to JIS Z 0208) or less can be used. Specific examples include, for example, single-layer films such as high-density polyethylene, low-density polyethylene, polypropylene, polyester, polyvinylidene chloride-coated polypropylene, and glass-deposited polyester, or laminated films thereof, split cloth, paper, and non-woven fabric. Laminated films with and the like. Examples of laminated films include laminated films of glass-deposited polyester and polyethylene, and laminated films of polyvinylidene chloride-coated polypropylene and polyethylene.

Such a film is preferably subjected to antistatic treatment from the viewpoint of preventing contamination by foreign matter, and the antistatic agent may be kneaded into the film or coated on the surface. In the case of kneading, about 0.01 to 5% by weight of the antistatic agent is used with respect to the resin, and in the case of surface coating, about 0.01 to 1 g/m ² of antistatic agent is used.
Examples of antistatic agents include alkyldiethanolamines, polyoxyethylenealkylamines, higher fatty acid alkanolamides, sorbitan fatty acid esters, and the like.

Next, the film roll is preferably wrapped with a wrapping film made of a water vapor barrier resin, and then further wrapped with a wrapping film made of an aluminum material. Film (e.g. laminated film of aluminum foil and polyethylene film), laminated film of aluminum vapor-deposited film and moisture-resistant plastic film (e.g. laminated film of aluminum-deposited polyester film and polyethylene film), laminated film of alumina vapor-deposited film and moisture-resistant plastic film ( For example, a laminated film of an alumina-deposited polyester film and a polyethylene film), etc., and in the present invention, a laminated film of an aluminum foil and a polyolefin film, a laminated film of an aluminum-deposited film and a polyolefin film are particularly useful. Laminated films having a configuration of polyethylene film/aluminum foil/polyethylene film, laminated films having a configuration of oriented polypropylene film/low-density polyethylene film/aluminum foil, and the like are useful.

For packaging, it is preferred that the inner wrapping film of the water vapor barrier resin and the outer wrapping film made of the aluminum material are sequentially wrapped, and the excess portion in the width direction is pushed into the core tube.

In order to prevent the ends of the film roll from being scratched or foreign matter such as dust from adhering thereto, protective pads having core tube through-holes can be attached to both ends of the film roll directly or after packaging.
As for the shape of the protective pad, a disk-shaped sheet or film is practical in accordance with the film roll. In order to enhance the protective effect, it is preferable to add a cushioning function such as foam, woven fabric, or non-woven fabric. Moreover, in order to protect the film roll from humidity, a desiccant may be enclosed separately, or may be laminated or mixed with the protective pad. The material of the protective pad is preferably plastic, and specific examples thereof include polystyrene, polyethylene, polypropylene, polyester, polyvinyl chloride, and the like.

The protective pad containing a desiccant includes, for example, calcium chloride, silica gel, molecular sieves, saccharides, particularly saccharides with high osmotic pressure, desiccants or water absorbing agents such as water absorbent resins, natural celluloses, synthetic celluloses, Glass cloth, non-woven fabric, and other moldable materials dispersed, impregnated, coated, and dried to form a moisture-absorbing layer. (registered trademark) film or the like sandwiched between thermoplastic resin films.
Examples of commercially available sheet-like desiccants include "Id Sheet" manufactured by I.D., "Arrow Sheet" and "Zeo Sheet" manufactured by Shinagawa Kasei Co., Ltd., and "Hi Sheet Dry" manufactured by Hi Sheet Kogyo Co., Ltd. .

The film roll wrapped by such means is supported by providing brackets (supporting plates) on both end protrusions of the core tube, or by placing the both end protrusions on a pedestal, so that the film roll does not come into contact with the ground, but is suspended in the air. Storage and transportation are preferably carried out in a floating state. Brackets are used when the width of the film is relatively small, and pedestals are used when the width of the film is relatively large.
The bracket is made of plywood or plastic plate, and its size is usually such that four sides of the bracket are larger than the diameter of the film roll.

Then, a pair of brackets are arranged on the core tube projecting portions at both ends of the film roll so as to face each other, and are fitted to the film roll. For fitting, a hole slightly larger than the diameter of the core pipe is usually provided in the center of the bracket, or a U-shaped hole is cut from the upper part of the bracket to the center so that the core pipe can be easily inserted.

Film rolls supported by brackets are stored and transported in cartons such as corrugated cardboard boxes. When using rectangular brackets, the four corners should be cut off in order to facilitate storage work. preferable. In addition, it is preferable to fix the pair of brackets with a binding tape so that they do not wobble.At that time, the side surface (thickness part) of the bracket is approximately the same as the tape width so that the tape does not move or loosen. It is also practical to provide tape deviation prevention grooves.

When storing or transporting the wrapped film roll, it is desirable to avoid extreme high temperature, low temperature, low humidity, and high humidity conditions. .

Since the PVA-based film of the present invention thus obtained is characterized by having few bubble defects, it is used for polarizing film applications (liquid crystal televisions, smartphones, tablets, personal computers, projectors, vehicle-mounted panels, etc.) with strict requirements for display defects, Water-soluble film applications that require resistance to perforation by liquids (unit packaging applications for chemicals such as agricultural chemicals and detergents, (hydraulic) transfer films, sanitary products such as napkins and paper diapers, filth disposal products such as ostomy bags, blood-absorbing sheets and other medical supplies, seedling sheets, seed tapes, temporary substrates such as embroidery base fabrics, etc.).
Among them, the PVA-based film of the present invention is mainly composed of a polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of saponification degree, viscosity, modified species, and modified amount. As a result, it has excellent solubility and water-sealing properties, and has good leakage resistance when liquid is packaged, so it is useful for individual packaging of drugs (drug packages).

<Drug package>
The drug package of the present invention is a package in which a drug is enclosed in the PVA-based film of the present invention.
The drug to be encapsulated is not particularly limited, and examples thereof include pesticides such as insecticides, fungicides and herbicides, fertilizers, detergents and the like, with detergents being particularly preferred.
The drug may be in the form of liquid or solid, and the liquid may be liquid, and the solid may be granular, tablet, powder, or the like. The drug is preferably dissolved or dispersed in water for use, and in the present invention, it is particularly preferred to include a liquid detergent.
Also, the pH of the drug may be alkaline, neutral or acidic.

The surface of the drug package is usually smooth. The outer surface of the PVA-based film) may be subjected to uneven processing such as an embossed pattern, a fine uneven pattern, a special engraving pattern, or the like.

A liquid detergent package, which is an example of the drug package of the present invention, will be described below.
The liquid detergent package retains a shape in which the liquid detergent is contained during storage. During use (during washing), the package (PVA-based film) comes into contact with water, causing the package to dissolve and the contained liquid detergent to flow out of the package.
The size of the liquid detergent package is usually 10-50 mm in length, preferably 20-40 mm. Moreover, the thickness of the package made of the PVA-based film is usually 10 to 120 μm, preferably 15 to 110 μm, more preferably 20 to 100 μm. The amount of liquid detergent contained is usually 5-50 mL, preferably 10-40 mL.

A well-known method can be employed to package a liquid detergent using the PVA-based film of the present invention to form a drug package.
For example, it is manufactured by bonding two PVA-based films, the film (bottom film) is fixed on the mold at the bottom of the molding device, and the film (top film) is also placed on the top of the device. fixed. The bottom film is heated with a drier and vacuum-molded into a mold. After that, a liquid detergent is added to the molded film, and the top and bottom films are pressure-bonded. After pressing, the vacuum can be released to obtain a package.
Examples of methods for crimping films include (1) heat sealing, (2) water sealing, and (3) glue sealing. It is preferable in terms of excellent productivity.

There are no restrictions on the liquid detergent, and it may be alkaline, neutral, or acidic, but from the viewpoint of the water solubility of the film, the pH value when dissolved or dispersed in water should be 6 to 14. 7 to 11 are particularly preferred. The above pH value is measured according to JIS K 3362 8.3. Also, the water content is measured according to JIS K 3362 7.21.3.
In addition, the water content of the liquid detergent is preferably 15% by weight or less, particularly 0.1 to 10% by weight, and more preferably 0.1 to 7% by weight. It is excellent in water solubility without being insolubilized.
The viscosity of the liquid medicine is not particularly limited as long as it is fluid and can change its shape according to the container, but it is preferably 10 to 200 mPa·s. The viscosity of such a liquid drug is measured with a B-type rotational viscometer at room temperature.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, "parts" and "%" mean weight standards.

<Example 1>
As the PVA-based resin (A), 90 parts of carboxyl group-modified PVA (A1) having a 4% aqueous solution viscosity of 22 mPa s at 20 ° C., an average saponification degree of 94 mol%, and a modification amount of 2.0 mol% with maleic acid monomethyl ester. , 10 parts of unmodified PVA (A2) with a viscosity of 4% aqueous solution at 20 ° C. of 18 mPa s and an average degree of saponification of 88 mol%, 20 parts of sorbitol (b1) as a plasticizer (B) and 20 parts of glycerin (b2) Part, 8 parts of starch (average particle size 20 μm) as filler (C), 0.2 part of polyoxyalkylene alkyl ether phosphate monoethanolamine salt as surfactant (D), and 525 parts of water. and 90° C. for 90 minutes to dissolve the PVA-based resin composition, thereby obtaining an aqueous PVA-based resin solution having a solid concentration of 22%. After adjusting the temperature of the above PVA-based resin aqueous solution to 80 ° C., 2 parts of ethanol (0.3% by weight with respect to the PVA-based resin aqueous solution) is added to the above PVA-based resin aqueous solution, and a stirrer (AS ONE Stirring and mixing for 30 minutes was performed using MIX-ROTAR "MR-5" manufactured by the company. Next, the PVA-based resin aqueous solution mixed with ethanol was heated to 80° C. and left to stand for 30 minutes, and then the surface temperature was adjusted to 85° C. using an applicator with a gap of 740 μm. flowed upwards. After drying the casted PVA-based resin aqueous solution on a metal plate at a temperature of 85° C. for 7 minutes and 30 seconds, the dry film was peeled off from the metal plate at a rate of 25 mm/sec to obtain a length of 20 cm, a width of 15 cm, and a thickness of 85 μm. A PVA-based film having a moisture content of 5.8% by weight was obtained. As a result of measuring the ethanol content of the obtained PVA-based film, it was 110 ppm.

< Reference example 1 >
A PVA-based film was obtained in the same manner as in Example 1, except that the amount of ethanol added was changed to 15 parts (2.2% by weight with respect to the PVA-based resin aqueous solution). As a result of measuring the ethanol content of the obtained PVA-based film, it was 830 ppm.

<Comparative Example 1>
A PVA-based film was obtained in the same manner as in Example 1, except that ethanol was not added. As a result of measuring the ethanol content of the obtained PVA-based film, it was 0 ppm.

<Comparative Example 2>
A PVA-based film was obtained in the same manner as in Example 1, except that the amount of ethanol added was changed to 40 parts (5.6% by weight with respect to the PVA-based resin aqueous solution). As a result of measuring the ethanol content of the obtained PVA-based film, it was 2200 ppm.

<Comparative Example 3>
A PVA-based film was obtained in the same manner as in Example 1, except that the modified PVA (A1) was changed to only 100 parts as the PVA-based resin (A). As a result of measuring the ethanol content of the obtained PVA-based film, it was 110 ppm.

Using the PVA-based films obtained in Example 1 , Reference Example 1 , and Comparative Examples 1, 2 and 3, the physical properties of the films were measured and evaluated according to the methods described below. The results are shown in Table 1 below.

[Moisture content of PVA-based film]
A 5 cm×5 cm sample for moisture content measurement was cut out from the obtained PVA-based film at the central portion in the width direction. After weighing the film weight (W) of the cut film sample with an electronic balance, the film sample was immersed in 15 ml (S) of dehydrated methanol having a moisture content of 0.03% or less, and the inside of the film was allowed to stand at room temperature for 1 hour. of water was extracted. Using a Karl Fischer moisture meter (manufactured by Kyoto Electronics Industry Co., Ltd., "MKA-610"), the water content of 10 ml of the extract (E) is measured by volumetric titration, and the film moisture content (% by weight) is calculated from the following formula. Calculated.

Ｆ： カールフィッシャー試薬の力価（ｍｇ／ｍｌ）
Ｖ： 抽出液１０ｍｌの滴定に用いたカールフィッシャー試薬量（ｍｌ）
Ｂ： 脱水メタノール１０ｍｌの滴定に用いたカールフィッシャー試薬量（ｍｌ）
Ｗ： ５ｃｍ×５ｃｍサイズにしたフィルム試料の重量（ｇ）
Ｅ： カールフィッシャー測定に使用した抽出液の量（ｍｌ）
Ｓ： フィルム試料の水分抽出に使用した脱水メタノールの量（ｍｌ）

F: Potency of Karl Fischer reagent (mg/ml)
V: Karl Fischer reagent amount (ml) used for titration of 10 ml of extract
B: Amount of Karl Fischer reagent used for titration of 10 ml of dehydrated methanol (ml)
W: Weight (g) of film sample with a size of 5 cm x 5 cm
E: Amount of extract used for Karl Fischer measurement (ml)
S: Amount (ml) of dehydrated methanol used to extract moisture from the film sample

[Content of monohydric alcohol having 1 to 3 carbon atoms in PVA-based film]
The content of monohydric alcohol having 1 to 3 carbon atoms in the PVA-based film was measured under the following conditions using GC/MS analysis equipped with a dynamic headspace device.
<Dynamic headspace conditions>
・ Thermal desorption device: TDS-3 (manufactured by Gestel)
・ Sample amount: about 5 mg
・ Heating conditions: 120 ° C., 60 minutes <GC / MS measurement conditions>
・ GC device: Agilent 7890GC (manufactured by Agilent Technologies)
・Column: DB-WAX (crosslinked PEG capillary column)
・Column temperature: 40°C x 5 minutes - 10°C/minute - 250°C x 10 minutes ・Inlet temperature: -150°C (collection) → 250°C
・Carrier gas: helium ・Column flow rate: 1.0 mL/min ・Split ratio: 1/30
・ MS unit device: Agilent 5977MSD (manufactured by Agilent Technologies)
・Mode: SCAN mode

[Bubble generation state after film drying]
(Evaluation method)
A sample having a size of 5 cm×5 cm was cut out from the obtained PVA-based film at the central portion in the width direction. Regarding the cut film sample, regarding the remaining state of bubbles generated during stirring (bubble diameter in the length direction or width direction is 250 μm or more) and small bubbles generated during drying (bubble diameter in the length direction or width direction is less than 250 μm) It was observed with a digital microscope and evaluated according to a five-grade evaluation standard.
(Evaluation criteria)
5: Good with no bubbles observed 4: Small bubbles with a bubble diameter of less than 250 μm are slightly present (1 or more and less than 3)
3: Small bubbles with a bubble diameter of less than 250 μm exist (3 or more and less than 10)
2: Only bubbles with a bubble diameter of 250 μm or more exist (one or more)
Alternatively, only small bubbles with a bubble diameter of less than 250 μm exist in large quantities (10 or more)
1: Bubbles with a bubble diameter of 250 μm or more exist (one or more),
In addition, small bubbles with a bubble diameter of less than 250 μm also exist (10 or more)

[Cold water solubility]
The obtained PVA-based film was cut into a size of 3 cm×5 cm and fixed to a jig. Next, put water (1 liter) in a 1-liter beaker, stir with a stirrer (rotor length 3 cm, rotation speed 750 rpm) while maintaining the water temperature at 5 ° C., and put the PVA-based film fixed to the jig into the water. After immersion, the time (seconds) until the film dissolved was measured. As a standard of "dissolution", dissolution was determined when no dispersion of insoluble fine particles having a diameter of 1 mm or more was observed.

[Peel strength of water seal part]
After the PVA-based film was subjected to humidity conditioning at 23° C. and 50% RH for 24 hours, the PVA-based film was stretched 50 mm from the center in the width direction so that one side of the PVA-based film was parallel to the MD direction (machine direction). The film is cut into a square of 50 mm to obtain a PVA-based film (1). In addition, from the central portion of the PVA-based film in the width direction, the film was cut into a rectangle having a side parallel to the MD direction (flow direction) of 70 mm and a side parallel to the TD direction (width direction) of 15 mm. (2).
(Measurement of peel strength)
The above PVA-based film (1) cut into 50 mm × 50 mm is placed on a 30 cm square glass plate, and a PVA sponge roller (“Cygnus Roller” manufactured by Aion Co., Ltd.) is sufficiently moistened with water from above, and the entire roller is The PVA-based film (1) was rolled with a roller having a total weight of 110 g and water to impregnate the PVA-based film with water. After that, another sheet of the PVA-based film (2) cut to 15 mm × 70 mm was placed on the PVA-based film (1) wetted with water, and another rubber roller (width 250 mm, diameter 60 mm, weight 2750 g) was rolled twice to adhere two PVA-based films.
After leaving this for 1 minute, the lower PVA-based film (1) was fixed to the substrate glass, a spring scale was attached to the end face of the upper PVA-based film (2), and pulled upward at a speed of 10 cm/sec. Thus, the peel strength (g/15 mm) was measured. In addition, the measurement was performed under the environment of 23° C. and 50% RH.

[Evaluation of drug package]
Using the PVA-based film obtained above, a total of 20 liquid detergent packages were produced in the following procedure using a package manufacturing machine manufactured by Engel.
That is, on the mold (length 41.5 mm, width 46.5 mm, depth 20 mm) at the bottom of the device, TD (width direction) is set vertically and a film (bottom film, size: length 120 mm x width 150 mm) was fixed, and a film (top film, size: length 80 mm x width 120 mm) was also fixed in the upper part of the device with the MD (flow direction) horizontal. After that, the bottom film was heated for 10 seconds with a dryer that generates hot air at 90° C., and the bottom film was vacuum-molded into a mold. Next, take out the liquid detergent (part of the ingredients: glycerin 5.4%, propylene glycol 22.6%, water 10.4%) packaged in a P & G power gel ball and apply it to the molded film 20 mL was added. Subsequently, 1.5 g of water was applied to the entire surface of the top film, and the top film and the bottom film were pressed together. After pressing for 30 seconds, the vacuum was released to obtain liquid detergent packages (2 pieces).
(Evaluation method)
The ratio of the number of specimens in which liquid leakage occurred among the obtained drug packages was calculated, and the defect rate (%) of the drug packages was obtained.
Defective rate (%) = Number of specimens with liquid leakage/20 x 100
All of the specimens in which liquid leaked were due to the generation of small holes due to air bubble defects in the film, and no specimens that leaked from the water seal portion or the like were observed.

From the results in Table 1 above, the PVA-based film of Example 1 satisfies the specific conditions for the content of the monohydric alcohol having 1 to 3 carbon atoms in the PVA-based film. It can be seen that the generation of air bubbles during drying of the film is suppressed, and a PVA-based film with few air bubble defects can be obtained. In addition, it can be seen that the rate of occurrence of defective products (liquid leakage) of the liquid drug package produced using the obtained PVA-based film is low, and a good drug package can be obtained. In addition, the obtained PVA-based film dissolves in cold water at 5°C in a very short time of less than 2 minutes, and the peel strength of the water-sealed portion is high. It can be seen that the suitability for liquid detergent packaging, which requires strength, is good.

On the other hand, in Comparative Example 1, in which the content of the monohydric alcohol having 1 to 3 carbon atoms in the PVA-based film is less than 1 ppm, air bubbles are easily generated after the solution is adjusted, and air bubbles generated during dissolution are also present in the film after drying. As a result, a bubble defect with a bubble diameter of 250 μm or more remained. In addition, in Comparative Example 2, in which the content of monohydric alcohol having 1 to 3 carbon atoms in the PVA-based film exceeds 2000 ppm, the generation of air bubbles during dissolution is suppressed, but small air bubbles with a diameter of less than 250 μm due to high-temperature drying during drying. was found to exist in large quantities. Thus, it can be seen that the drug package produced using the PVA-based film having the air bubble defect causes liquid leakage due to the air bubble defect and is inferior in the productivity of the drug package. Moreover, in Comparative Example 3, which does not contain two or more different PVA-based resins, the peel strength of the water-sealing portion was insufficient compared to the Examples.

Since the PVA-based film of the present invention is characterized by having few air bubble defects, it can be used for polarizing films with strict requirements for display defects (liquid crystal televisions, smartphones, tablets, personal computers, projectors, vehicle-mounted panels, etc.) and liquid holes. Water-soluble film applications that require resistance to opening (unit packaging applications for chemicals such as agricultural chemicals and detergents, (hydraulic) transfer films, sanitary products such as napkins and disposable diapers, filth disposal products such as ostomy bags, medical care such as blood-absorbing sheets supplies, seedling sheets, seed tapes, temporary substrates for embroidery, etc.).
Among them, the PVA-based film of the present invention is mainly composed of a polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of saponification degree, viscosity, modified species, and modified amount. Therefore, it has excellent solubility and water sealability, and has good liquid leakage resistance when packaging liquid products, so it is useful for individual packaging applications such as medicine (drug packaging).

Claims (5)

A polyvinyl alcohol-based film mainly composed of a polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of the degree of saponification, viscosity, modified species, and modified amount, wherein the polyvinyl The alcohol-based resin (A) contains an unmodified polyvinyl alcohol resin and a carboxyl group-modified polyvinyl alcohol resin, and the content ratio of the unmodified polyvinyl alcohol resin and the carboxyl group-modified polyvinyl alcohol resin is a weight ratio, Modified polyvinyl alcohol resin/carboxyl group-modified polyvinyl alcohol resin = 1/99 to 99/1, contains 1 to 500 ppm of a monohydric alcohol having 1 to 3 carbon atoms, and the monohydric alcohol having 1 to 3 carbon atoms is A polyvinyl alcohol film characterized by being at least one selected from methanol and ethanol. A drug package comprising: a package formed by laminating the polyvinyl alcohol film according to claim 1 ; and a drug contained in the package. 3. A drug package according to claim 2 , wherein the drug is detergent. 4. A drug package according to claim 2 or 3 , wherein the drug is a liquid detergent. (I) a polyvinyl alcohol-based resin composition mainly composed of a polyvinyl alcohol-based resin (A) containing two or more polyvinyl alcohol-based resins different in at least one of saponification degree, viscosity, modified species, and modified amount; a step of dissolving to obtain a polyvinyl alcohol-based resin aqueous solution;
(II) a step of adding 0.001 to 2% by weight of a monohydric alcohol having 1 to 3 carbon atoms to the polyvinyl alcohol-based resin aqueous solution;
(III) a step of forming a film using the polyvinyl alcohol-based resin aqueous solution obtained in the step (II);
in this order, the polyvinyl alcohol resin (A) contains an unmodified polyvinyl alcohol resin and a carboxyl group-modified polyvinyl alcohol resin, and the unmodified polyvinyl alcohol resin and the carboxyl group-modified polyvinyl alcohol resin is a weight ratio of unmodified polyvinyl alcohol resin/carboxyl group-modified polyvinyl alcohol resin = 1/99 to 99/1, and the monohydric alcohol having 1 to 3 carbon atoms is at least one selected from methanol and ethanol. A method for producing a polyvinyl alcohol film, characterized in that