阅读说明：本技术 水溶性薄膜及其制造方法、以及药剂包装体 (Water-soluble film, method for producing same, and drug package ) 是由 中原耕一郎 市来隼哉 于 2019-03-28 设计创作，主要内容包括：作为即使长期保管后卷曲的产生也得到抑制的水溶性薄膜,提供一种水溶性薄膜,其为含有聚乙烯醇系树脂(A)的水溶性薄膜,上述薄膜两面基于通过利用衰减全反射法的红外光谱分析进行的测定分别具有下述式(1)所示的结晶度指数X,将薄膜的一面的结晶度指数设为Xa、将另一面的结晶度指数设为Xb,其中,Xa≥Xb的情况下,薄膜两面的结晶度指数之差Xa-Xb为0.015～0.10。X＝ABS<Sub>1141</Sub>/ABS<Sub>1093</Sub>(1)ABS<Sub>1141</Sub>：波数1141cm<Sup>-1</Sup>的吸光度ABS<Sub>1093</Sub>：波数1093cm<Sup>-1</Sup>的吸光度。(As a water-soluble film in which the occurrence of curling is suppressed even after long-term storage, there is provided a water-soluble film comprising a polyvinyl alcohol resin (A), wherein both surfaces of the film have a crystallinity index X represented by the following formula (1) as measured by infrared spectroscopic analysis by attenuated total reflection, and the crystallinity index of one surface of the film is Xa and the crystallinity index of the other surface is Xb, wherein Xa is not less than XbThe difference Xa-Xb between the crystallinity indexes of both sides of the film is 0.015 to 0.10. X is ABS 1141 /ABS 1093 (1)ABS 1141 : wave number of 1141cm ‑1 Absorbance of ABS 1093 : wave number 1093cm ‑1 Absorbance of (b).)

1. A water-soluble film comprising a polyvinyl alcohol resin A, both surfaces of which have a crystallinity index X represented by the following formula (1) as measured by infrared spectroscopic analysis by attenuated total reflection, wherein Xa represents the crystallinity index of one surface of the film and Xb represents the crystallinity index of the other surface of the film, and when Xa is not less than Xb, the difference Xa-Xb between the crystallinity indexes of both surfaces of the film is 0.015 to 0.10,

X＝ABS₁₁₄₁/ABS₁₀₉₃(1)

ABS₁₁₄₁: wave number of 1141cm^-1Absorbance of (A)

ABS₁₀₉₃: wave number 1093cm^-1Absorbance of (b).

2. The water-soluble film according to claim 1, further comprising a plasticizer B.

3. The water-soluble film according to claim 2, wherein the content of the plasticizer B is 5 parts by weight or more based on 100 parts by weight of the polyvinyl alcohol resin a.

4. The water-soluble film according to any one of claims 1 to 3, further comprising a filler C.

5. The water-soluble film according to claim 4, wherein the content of the filler C is 1 to 30 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin A.

6. The water-soluble film according to any one of claims 1 to 5, wherein the polyvinyl alcohol resin A contains an anionic group-modified polyvinyl alcohol resin a 1.

7. A drug package comprising a package formed from the water-soluble film according to any one of claims 1 to 6 and a drug packaged in the package.

8. The pharmaceutical package of claim 7, wherein the pharmaceutical is a detergent.

9. The pharmaceutical package according to claim 7 or 8, wherein the pharmaceutical is a liquid detergent.

10. A method for producing a water-soluble film according to any one of claims 1 to 6, comprising: the method comprises a step of producing a polyvinyl alcohol film containing a polyvinyl alcohol resin A, a step of applying water to the surface of the polyvinyl alcohol film, and a heat treatment step.

Technical Field

The present invention relates to a water-soluble film containing a polyvinyl alcohol resin as a main component, and more particularly, to a water-soluble film in which occurrence of curling is suppressed even after long-term storage, a method for producing the same, and a drug package.

Background

The polyvinyl alcohol film is a film made of a water-soluble polyvinyl alcohol resin although it is a thermoplastic resin, and has various physical properties, hand feeling, and the like greatly different from those of a hydrophobic film which is generally used for a packaging film such as a polyethylene terephthalate film and a polyolefin film.

In the past, packaging (unit packaging) of a drug has been proposed, which is widely used by adding various drugs such as agricultural chemicals and detergents to a bag made of a film of a polyvinyl alcohol resin by effectively utilizing the water solubility of the polyvinyl alcohol resin.

As the water-soluble film used in the above applications, a water-soluble film is known which is mainly composed of a polyvinyl alcohol resin, and which contains a relatively large amount of plasticizer in combination with a plasticizer having a high melting point and a plasticizer having a low melting point as plasticizers (for example, see patent document 1); a water-soluble film having excellent solubility and reduced curling (for example, see patent document 2).

Disclosure of Invention

Problems to be solved by the invention

The water-soluble film disclosed in patent document 1 can provide a package excellent in appearance characteristics without causing a decrease in mechanical characteristics and tension with time, but on the other hand, the film may curl depending on the production conditions. If the water-soluble film is curled, for example, when a package is produced using the water-soluble film, handling becomes difficult and displacement is likely to occur at the time of sealing, which causes a problem of lowering the production efficiency of the package, and further improvement is desired.

In addition, although the water-soluble film disclosed in patent document 2 is reduced in the occurrence of curling after being left standing for 24 hours in an environment of 23 ℃ and 40% RH by heat-treating the dried water-soluble film at 95 to 135 ℃, the problem of curling remaining when stored for a long period of time in a product warehouse or the like is expected to be further improved.

Therefore, under such a background, the present invention proposes a water-soluble film in which the occurrence of curling is suppressed even after long-term storage.

Means for solving the problems

However, the present inventors have intensively studied in view of the above-mentioned problems, and as a result, they have found that the above-mentioned object can be achieved by a water-soluble film in which the difference in crystallinity index (degree of crystallization) between the surface layer portions on both sides of the water-soluble film is larger than that of the conventional film, by making detailed studies on the relationship between the crystal state and the occurrence of curling in the surface layer portions on both sides of the polyvinyl alcohol-based film.

Specifically, the present invention provides a water-soluble film comprising a polyvinyl alcohol resin (A), wherein each of both surfaces of the film has a crystallinity index X represented by the following formula (1) as measured by infrared spectroscopic analysis by attenuated total reflection, and the crystallinity index of one surface of the film is Xa and the crystallinity index of the other surface is Xb, wherein when Xa is not less than Xb, the difference Xa-Xb between the crystallinity indexes of both surfaces of the film is 0.015 to 0.10.

X＝ABS₁₁₄₁/ABS₁₀₉₃(1)

ABS₁₁₄₁: wave number of 1141cm^-1Absorbance of (A)

ABS₁₀₉₃: wave number 1093cm^-1Absorbance of (A)

In addition, the present invention provides a method for producing a water-soluble film, comprising: a step of producing a polyvinyl alcohol film containing a polyvinyl alcohol resin (A), a step of applying water to the surface of the polyvinyl alcohol film, and a heat treatment step.

ADVANTAGEOUS EFFECTS OF INVENTION

The water-soluble film of the present invention is reduced in curl when formed into a package from a film stored for a long period of time, and therefore, is less likely to cause misalignment, exhibits good sealability, and is excellent in productivity of the package, and is useful for various packaging applications, particularly for unit packaging applications of medicines and the like.

When the water-soluble film of the present invention further contains a plasticizer (B), flexibility is provided by the film, and ease of molding when forming a drug package is improved.

In the water-soluble film of the present invention, when the content of the plasticizer (B) is 5 parts by weight or more based on 100 parts by weight of the polyvinyl alcohol resin (a), when a liquid such as a liquid detergent is packaged in a water-soluble film to form a package, the shape stability of the package over time can be maintained without causing a decrease in the toughness of the water-soluble film.

Further, when the water-soluble film of the present invention further contains a filler (C), the water-soluble film is excellent in blocking resistance.

In the water-soluble film of the present invention, when the content of the filler (C) is 1 to 30 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin (a), the water-soluble film has not only excellent blocking resistance but also excellent flexibility and toughness.

In the water-soluble film of the present invention, when the polyvinyl alcohol resin (a) contains the anionic group-modified polyvinyl alcohol resin (a1), the water-soluble film has more excellent solubility.

Further, the present invention provides a drug package comprising a package formed of the water-soluble film and a drug packaged in the package. In this case, the medicine can be used without breaking the package.

In addition, in the medicine package of the present invention, when the medicine is a detergent, the detergent can be used more easily with less time and effort for metering.

Further, in the medicine package of the present invention, if the medicine is a liquid detergent, the liquid detergent does not contaminate the surroundings, and the medicine package can be used more easily.

It is considered that according to the method for producing a water-soluble film comprising the step of producing a polyvinyl alcohol film containing a polyvinyl alcohol resin (a), the step of applying water to the surface of the polyvinyl alcohol film, and the heat treatment step of the present invention, by applying water to the surface of the dried polyvinyl alcohol film and performing the heat treatment, a difference in crystallinity is formed on each surface of the film, and the balance of swelling and shrinking actions on both surfaces of the film is maintained, and as a result, improvement in curling over a long period of time is achieved.

Detailed Description

The present invention will be specifically described below.

The water-soluble film of the present invention is a film containing a polyvinyl alcohol resin (A), and has a specific difference in crystallinity index between both surfaces of the film.

The most important feature of the present invention is that by providing a specific difference in the crystallinity index of the front and back of the film, the balance of swelling and shrinking actions on the film surface is maintained, and as a result, the curling of the water-soluble film is suppressed for a long period of time.

Hereinafter, polyvinyl alcohol is sometimes referred to as "PVA", a film containing a polyvinyl alcohol resin as a main component is sometimes referred to as "PVA film", and a water-soluble film containing a polyvinyl alcohol resin as a main component is sometimes referred to as "PVA water-soluble film".

The film surface in the present invention refers to at least one of the front and back surfaces of the film other than the film thickness surface.

Specifically disclosed is a water-soluble film, which is characterized in that when the crystallinity indexes X of both surfaces of the film represented by the following formula (1) are measured by infrared spectroscopic analysis using an attenuated total reflection method (ATR method) on both surfaces of the film, the difference Xa-Xb between the crystallinity indexes of both surfaces of the film (wherein Xa represents the crystallinity index of one surface and Xb represents the crystallinity index of the other surface, and Xa is not less than Xb) is 0.015 to 0.10.

X＝ABS₁₁₄₁/ABS₁₀₉₃(1)

ABS₁₁₄₁: wave number of 1141cm^-1Absorbance of (A)

ABS₁₀₉₃: wave number 1093cm^-1Absorbance of (A)

First, a method for measuring the crystallinity index X of the film surface represented by the above formula (1) by infrared spectroscopic analysis using Attenuated Total Reflection (ATR) method will be described in detail.

The infrared spectroscopic analysis in the present invention refers to an analysis method for measuring an infrared absorption spectrum by a primary reflection type ATR method using Attenuated total reflection (Attenuated total reflection). This analysis method uses a method in which an ATR prism having a high refractive index is brought into close contact with a sample, infrared light is irradiated to the sample through the ATR prism, and the light emitted from the ATR prism is spectrally analyzed.

In infrared spectroscopic analysis by attenuated total reflectance (ATR method), there is a simplicity in that a spectrum can be measured only by bringing a sample into close contact with an ATR prism, and it is generally known that 1000cm is used^-1Since the depth of penetration by the diamond ATR crystal at an incident angle of 45 ° in the vicinity is about 2 μm, evaluation concerning the PVA crystallinity focused on the surface layer portion of the thin film can be performed.

The crystallinity index X of the PVA-based film surface means 1141cm in the infrared absorption spectrum measured by infrared spectroscopic analysis by ATR method^-1Absorbance of (2) relative to 1093cm^-1The ratio of absorbance of (b). Here, 1141cm^-1The absorption of (A) is a peak derived from the skeletal oscillation of an elongated carbon zigzag chain in a PVA crystal region, and is generally known as a peak corresponding to a crystal band of PVA, and is known to be 1141cm as the crystallinity of PVA increases^-1The peak intensity of (a) is enhanced. On the other hand, 1093cm^-1Is derived from PVAPeak of C-O stretching vibration at 1093cm^-1Is 1141cm based on the peak intensity of^-1The peak intensity of (a) is normalized to calculate X which is the crystallinity index of the film surface.

That is, when the crystallinity index X shows a large value, it indicates a property that the crystallinity of the surface layer portion of the film is high and dimensional change due to moisture absorption is less likely to occur. Conversely, when the crystallinity index X is a small value, it indicates that the crystallinity of the surface layer portion of the film is low and dimensional change such as swelling and shrinkage due to moisture absorption is likely to occur.

[ method for measuring crystallinity index X of film surface ]

The crystallinity index X of the film surface was measured by the following method.

Specifically, an infrared absorption spectrum was obtained by Attenuated Total Reflection (ATR) using the following measurement apparatus and measurement conditions for 5 spots (1. 40mm in the vertical direction: 30mm in the horizontal direction, 2.40 mm in the vertical direction: 90mm in the horizontal direction, 3. 120mm in the vertical direction: 30mm in the horizontal direction, 4. 120mm in the vertical direction: 90mm in the horizontal direction, and 5. 80mm in the vertical direction: 60mm in the horizontal direction) on the front and back surfaces of a water-soluble film cut to have a vertical width of 160mm and a horizontal width of 120 mm.

The measurement device: fourier transform Infrared Spectroscopy FT/IR-6600 (manufactured by Nippon spectral Co., Ltd.), and polarization type 1 st reflection ATR PRO610P-S (manufactured by Nippon spectral Co., Ltd.)

ATR prism: PKS-D615P (manufactured by Nippon spectral Co., Ltd.) [ material: diamond, sample contact area: 2.0mm φ, incident angle (center): 45 degree ]

Assay method: 1-reflection ATR method

Determination of wavenumber region: 4000-400 cm^-1

ATR correction: implementation (anomalous dispersion mode) [ range: 4000-400 cm^-1And the repetition times are as follows: 1 time, incident angle: 45.0 °, prism refractive index: 2.400 (diamond), sample refractive index: 1.500, zero-base correction: is effective]

The detector: DLATGS

A beam splitter: Ge/KBr

Resolution power: 4cm^-1

Cumulative number of times: 32 times (16 times when measuring background)

From the obtained infrared absorption spectrum, the Absorbance (ABS) depending on the crystallinity of PVA was obtained in the following manner₁₁₄₁) And Absorbance (ABS) as a reference for PVA₁₀₉₃)。

ABS₁₁₄₁The wave number in the infrared absorption spectrum curve is 1163cm^-1±7.5cm^-1The lowest absorption position of (C), and a wave number of 993cm in an infrared absorption spectrum curve^-1±7.5cm^-1Wave number of 1141cm with straight line connecting the lowest absorption positions as base line^-1±7.5cm^-1The maximum value of the absorbance difference from the baseline (measured absorbance-absorbance at baseline) in the infrared absorption spectrum curve of the region (1) was defined as the wave number of 1141cm^-1Absorbance of ABS₁₁₄₁。

In addition, ABS₁₀₉₃Refers to wave number 1163cm in infrared absorption spectrum curve^-1±7.5cm^-1The lowest absorption position of (C), and a wave number of 993cm in an infrared absorption spectrum curve^-1±7.5cm^-1Wave number of 1093cm using straight line connecting the lowest absorption positions as base line^-1±7.5cm^-1The maximum value of the absorbance difference from the baseline (measured absorbance-absorbance at baseline) in the infrared absorption spectrum curve of the region (2) was defined as the wave number of 1093cm^-1Absorbance of ABS₁₀₉₃。

From ABS obtained by the above measurement₁₁₄₁、ABS₁₀₉₃The crystallinity indexes X at the front 5 points and the back 5 points were calculated, and the values obtained by averaging the 5 points were obtained as the crystallinity indexes Xa and Xb (Xa.gtoreq.Xb) of the surface of the PVA based water-soluble film.

That is, when the measured crystallization index of the film front surface is higher than that of the film back surface, Xa is the crystallization index of the film front surface, and Xb is the crystallization index of the film back surface. When the crystallization index of the film front surface is lower than that of the film back surface, the crystallization index of the film back surface is Xa, and the crystallization index of the film front surface is Xb. When the crystallization index of the front surface of the film is equal to that of the back surface of the film, Xa-Xb is 0.

In the present invention, when the crystallinity indexes X of both surfaces of the film represented by the following formula (1) are measured by infrared spectroscopic analysis by attenuated total reflectance (ATR method), the difference Xa-Xb between the crystallinity indexes of both surfaces of the film (here, the crystallinity index of one surface is Xa and the crystallinity index of the other surface is Xb, wherein Xa is not less than Xb) is 0.015 to 0.10.

X＝ABS₁₁₄₁/ABS₁₀₉₃(1)

ABS₁₁₄₁: wave number of 1141cm^-1Absorbance of (A)

ABS₁₀₉₃: wave number 1093cm^-1Absorbance of (A)

The difference Xa-Xb in crystallinity index is in the range of 0.015 to 0.10, preferably 0.020 to 0.080, and more preferably 0.030 to 0.060.

When Xa to Xb are too small, the film tends to curl when stored for a long period of time, and the effect of the present invention cannot be obtained. When Xa to Xb is too large, the surface properties such as sealing property and printability tend to be poor.

The water-soluble film can be produced by, for example, dissolving and producing a film-forming raw material containing a PVA-based resin (A), casting and drying the film-forming raw material to produce a PVA-based film, and subjecting the PVA-based film to a wet heat treatment in the subsequent step, as a method for obtaining a water-soluble film having a difference Xa-Xb in crystallinity index between both sides of the film of 0.015 to 0.10. Examples of the wet heat treatment method include (i) a method in which the surface of the PVA-based film after drying is coated with water and then heat-treated; (ii) a method of immersing the dried PVA based film in a water bath and then performing heat treatment; (iii) a method of performing a humidity conditioning treatment and then a heat treatment on the dried PVA based film in a chamber in a high humidity state; (iv) and a method of subjecting the dried PVA-based film to a water vapor treatment in a water vapor chamber in a high temperature state and simultaneously performing a heat treatment while performing a water treatment.

Among them, the method (i) is preferable from the viewpoint of easy control of crystallinity by being limited to only one surface of the film. (i) The details of the method (2) are described later.

The water-soluble film of the present invention contains the PVA-based resin (A) as a main component.

The PVA-based resin (a) used in the present invention may be an unmodified PVA or a modified PVA-based resin, and a modified PVA-based resin is preferable.

In addition, 2 or more PVA resins different in at least one of saponification degree, viscosity, type of modification, and amount of modification may be used in combination. Specific examples thereof include 2 or more kinds of unmodified PVA combined with each other, 2 or more kinds of modified PVA resins combined with each other, 2 or more kinds of unmodified PVA and modified PVA resins combined with each other, and the like.

In the present invention, the main component means a component that accounts for 50 wt% or more, preferably 55 wt% or more, particularly preferably 60 wt% or more of the entire water-soluble film, and further includes a case where the entire water-soluble film is formed only of the PVA-based resin (a).

The unmodified PVA is a resin mainly composed of a vinyl alcohol structural unit obtained by saponifying a polyvinyl ester resin obtained by polymerizing a vinyl ester compound, and is composed of a vinyl alcohol structural unit having a comparable saponification degree and a vinyl ester structural unit remaining without saponification.

Examples of the vinyl ester compound include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl decanoate, vinyl laurate, vinyl versatate, vinyl palmitate, and vinyl stearate, but vinyl acetate is preferably used. The vinyl ester compounds can be used alone or in combination of 2 or more.

As a method for copolymerizing the vinyl ester compound with an unsaturated monomer copolymerizable with the vinyl ester compound, any known polymerization method such as solution polymerization, emulsion polymerization, suspension polymerization, etc. can be used, and the copolymerization is usually carried out by solution polymerization using an alcohol such as methanol, ethanol, or isopropanol as a solvent.

The modified PVA-based resin is a resin obtained by introducing a modifying group into a polyvinyl ester-based resin mainly composed of a vinyl alcohol structural unit obtained by saponifying a polyvinyl ester-based resin obtained by polymerizing a vinyl ester-based compound, by copolymerization, post-reaction, or the like, and is composed of an unsaturated monomer structural unit formed by copolymerization or a structural unit formed by post-reaction, in addition to the vinyl alcohol structural unit corresponding to the degree of saponification and the vinyl ester structural unit remaining without saponification.

As the vinyl ester compound, the same compounds as in the case of the unmodified PVA as the PVA resin (a) can be used.

The modified PVA-based resin formed by copolymerization (copolymerization-modified PVA-based resin) can be produced by a method in which the vinyl ester-based compound and an unsaturated monomer copolymerizable with the vinyl ester-based compound are copolymerized and then saponified.

Examples of the unsaturated monomer copolymerizable with the vinyl ester compound include, for example, olefins such as ethylene, propylene, isobutylene, α -octene, α -dodecene and α -octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic anhydride and itaconic acid, salts, monoesters and dialkyl esters thereof, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid and methallylsulfonic acid or salts thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethyl ammonium chloride, allyl trimethyl ammonium chloride, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyalkylene (meth) allyl ether such as polyoxypropylene (meth) allyl ether, and the like, 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) acrylamido-1, 1-dimethylpropyl) ester, polyoxyethylene vinyl ether, and polyoxypropylene vinyl ether, and unsaturated monomers obtained by copolymerization of hydroxyl group-containing α -olefins such as polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, 3-buten-1-ol, 4-penten-1-ol, and 5-hexen-1-ol, and derivatives thereof such as acylates thereof. These may be used alone or in combination of 2 or more.

Examples of the modified PVA-based resin formed by the post-reaction (post-modified PVA-based resin) include, for example, a post-modified PVA-based resin having an acetoacetyl group formed by the reaction with diketene; a post-modified PVA-based resin having a polyoxyalkylene group formed by a reaction with ethylene oxide; a post-modified PVA-based resin having a hydroxyalkyl group formed by a reaction with an epoxy compound or the like; or a post-modified PVA-based resin obtained by reacting a PVA-based resin with an aldehyde compound having various functional groups or the like through esterification, acetalization, urethanization, etherification, grafting, phosphorylation, oxyalkylene, or the like. These may be used alone or in combination of 2 or more.

The modified PVA resin has a primary hydroxyl group in a side chain, and examples thereof include modified PVA resins having a primary hydroxyl group in a side chain in an amount of usually 1 to 5, preferably 1 to 2, and particularly preferably 1, and further preferably having a secondary hydroxyl group in addition to the primary hydroxyl group. Examples of the modified PVA resin include a modified PVA resin having a hydroxyalkyl group in a side chain thereof, a modified PVA resin having a1, 2-diol structural unit in a side chain thereof, and the like.

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

The carboxyl group-modified PVA resin as the modified PVA resin may be produced by any method, and examples thereof include (I) a method in which an unsaturated monomer having a carboxyl group and a vinyl ester compound are copolymerized and then saponified; (II) a method of polymerizing a vinyl ester compound and then saponifying the polymerized vinyl ester compound by allowing an alcohol, an aldehyde, a thiol or the like having a carboxyl group to coexist as a chain transfer agent.

As the vinyl ester compound in the method (I) or (II), the aforementioned vinyl ester compound can be used, but vinyl acetate is preferably used.

Examples of the unsaturated monomer having a carboxyl group in the method (I) include ethylenically unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, and the like), ethylenically unsaturated dicarboxylic monoesters (maleic acid monoalkyl ester, fumaric acid monoalkyl ester, itaconic acid monoalkyl ester, and the like), ethylenically unsaturated dicarboxylic diesters (maleic acid dialkyl ester, fumaric acid dialkyl ester, itaconic acid dialkyl ester, and the like) [ these diesters need to be converted into a carboxyl group by hydrolysis at the time of saponification of the copolymer ], ethylenically unsaturated carboxylic anhydrides (maleic anhydride, itaconic anhydride, and the like), ethylenically unsaturated monocarboxylic acids ((meth) acrylic acid, crotonic acid, and the like), and salts thereof. These may be used alone or in combination of 2 or more.

Among them, maleic acid, monoalkyl maleate, dialkyl maleate, maleic anhydride, itaconic acid, monoalkyl itaconate, dialkyl itaconate, (meth) acrylic acid, and the like are preferably used, and maleic acid, monoalkyl maleate, dialkyl maleate, and maleic anhydride are particularly preferably used, and monoalkyl maleate is more preferably used.

In the method (ii), a compound derived from a thiol having a large chain transfer effect is particularly effective, and specific examples thereof include thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, and 2-mercaptostearic acid.

In addition to the above-mentioned unsaturated monomer having a carboxyl group and vinyl ester compound, other general monomers may be contained and polymerized within a range not impairing water solubility. Examples of the monomer include alkyl esters of ethylenically unsaturated carboxylic acids, allyl esters of saturated carboxylic acids, α -olefins, alkyl vinyl ethers, alkyl allyl ethers, (meth) acrylamides, (meth) acrylonitriles, styrenes, and vinyl chlorides. These may be used alone or in combination of 2 or more.

The method for producing the carboxyl group-modified PVA-based resin is not limited to the above-described method, and for example, the following method may be performed: post-reacting polyvinyl alcohol (partially or completely saponified) with a carboxyl group-containing compound having a functional group reactive with a hydroxyl group, such as dicarboxylic acid, aldehyde carboxylic acid, hydroxycarboxylic acid, etc.; and the like.

In the case of using a sulfonic acid group-modified PVA-based resin, for example, a method of copolymerizing a copolymerizable component such as vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, or 2-acrylamido-2-methylpropanesulfonic acid with a vinyl ester-based compound and then saponifying the copolymer; a method of adding Michael addition of vinyl sulfonic acid or a salt thereof, 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof, or the like to PVA, and the like.

The average saponification degree of the PVA-based resin (a) used in the present invention is preferably 80 mol% or more, particularly preferably 82 to 99.8 mol%, and further preferably 85 to 99.5 mol%. If the average degree of saponification is too small, the solubility of the film tends to decrease with time depending on the pH of the drug to be packaged.

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%, and further preferably 85 to 90 mol%. If the average saponification degree is too small, the water solubility tends to decrease. In addition, the average degree of saponification tends to be too large, and the water solubility also tends to decrease.

The average saponification degree of the modified PVA resin used in the present invention is preferably 80 mol% or more, particularly preferably 85 to 99.9 mol%, and more preferably 90 to 99.5 mol%. If the average degree of saponification is too small, the solubility of the film tends to decrease with time depending on the pH of the drug to be packaged. When the average saponification degree is too high, the solubility to water tends to be greatly lowered by the thermal history at the time of film formation.

Further, when an anionic group-modified PVA resin is used as the modified PVA resin, the average saponification degree is preferably 85 mol% or more, particularly preferably 88 to 99.9 mol%, more preferably 90 to 99.8 mol%, and particularly preferably 92 to 99.5 mol%.

The average degree of saponification is measured according to JIS K67263.5, and the viscosity of the 4 wt% aqueous solution is measured according to JIS K67263.11.2.

The polymerization degree of the PVA based resin can be generally expressed by the viscosity of an aqueous solution, and the 4 wt% aqueous solution viscosity at 20 ℃ of the PVA based resin (A) used in the present invention is preferably 10 to 50 mPas, more preferably 15 to 45 mPas, and particularly preferably 20 to 40 mPas. If the viscosity is too low, the mechanical strength of the film as a packaging material tends to be reduced, and if it is too high, the viscosity of the aqueous solution at the time of film formation tends to be high, and the productivity tends to be reduced.

When an unmodified PVA is used as the PVA based resin (A), the unmodified PVA preferably has a 4 wt% aqueous solution viscosity at 20 ℃ of 5 to 50 mPas, particularly preferably 10 to 45 mPas, and further preferably 15 to 40 mPas.

When a modified PVA-based resin is used as the PVA-based resin (A), the modified PVA-based resin preferably has a 4 wt% aqueous solution viscosity at 20 ℃ of 5 to 50 mPas, particularly preferably 10 to 45 mPas, and further preferably 15 to 40 mPas.

If the viscosity is too low, the mechanical strength of the water-soluble film as a packaging material tends to be reduced, while if it is too high, the viscosity of the aqueous solution at the time of film formation tends to be high, and the productivity tends to be reduced.

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

In the present invention, when an anionic group-modified PVA resin is used as the modified PVA resin, the modification amount of the anionic group-modified PVA resin is preferably 1 to 10 mol%, particularly preferably 1.5 to 9 mol%, and further preferably 2 to 8 mol%. If the amount of modification is too small, the solubility in water tends to be low, and if it is too large, the productivity or biodegradability of the PVA-based resin tends to be low, and blocking tends to be easily caused.

In the present invention, the PVA-based resin (a) preferably contains an unmodified PVA and a modified PVA-based resin, particularly preferably contains an unmodified PVA and an anionic group-modified PVA-based resin, and further preferably contains an unmodified PVA and a carboxyl group-modified PVA-based resin, from the viewpoint of solubility and film strength.

When the unmodified PVA and the modified PVA resin are contained, the content ratio of the unmodified PVA to the modified PVA resin is, by weight, 1/99 to 99/1, particularly 5/95 to 95/5, and further 10/90 to 90/10, for the unmodified PVA and the modified PVA resin.

In particular, from the viewpoint of film physical properties such as solubility and water-tightness, the unmodified PVA/modified PVA resin is preferably 5/95 to 40/60, more preferably 6/94 to 30/70, and still more preferably 7/93 to 20/80. When the content ratio of the unmodified PVA is too small, the water-tightness tends to be lowered, and when the content ratio of the modified PVA resin is too small, the solubility tends to be lowered.

When the modified PVA-based resin and the unmodified PVA are contained, the viscosity of a 4 wt% aqueous solution of the unmodified PVA at 20 ℃ is preferably 5 to 50 mPas, particularly preferably 10 to 45 mPas, further preferably 12 to 40 mPas, and particularly preferably 15 to 35 mPas. If the viscosity is too low, the mechanical strength of the film as a packaging material tends to be reduced, while if it is too high, the viscosity of the aqueous solution at the time of film formation tends to be high, and the productivity tends to be reduced.

[ plasticizer (B) ]

The PVA film of the present invention preferably further contains a plasticizer (B) from the viewpoint of imparting flexibility to the film and ease of molding. The plasticizer (B) may be used alone in 1 kind or in combination of 2 or more kinds, and the combination of 2 or more kinds is preferable from the viewpoint of toughness of the film itself when used as a package, particularly shape stability over time of the package when a liquid detergent is packaged.

Examples of the plasticizer (B) include glycerol such as glycerol, diglycerol, and triglycerol, alkylene glycols such as triethylene glycol, polyethylene glycol, polypropylene glycol, and dipropylene glycol, ethers such as trimethylolpropane and dibutyl ether, carboxylic acids such as stearic acid, oleic acid, linoleic acid, linolenic acid, sorbic acid, citric acid, and adipic acid, ketones such as cyclohexanone, amines such as monoethanolamine, triethanolamine, ethylenediamine, and imidazole compounds, and amino acids such as alanine, glycine, aspartic acid, glutamic acid, histidine, lysine, and cysteine.

Sugar alcohols, monosaccharides, and polysaccharides may also be used, and examples thereof include 2-membered alcohols such as salicyl alcohol, catechol, resorcinol, hydroquinone, bisphenol a, bisphenol F, and neopentyl glycol, 3-membered alcohols such as phloroglucinol, 4-membered alcohols such as erythritol, threitol, and pentaerythritol, 5-membered alcohols such as xylitol, arabitol, fucotol, glucose, and fructose, 6-membered alcohols such as mannitol, sorbitol, and inositol, 8-membered alcohols such as lactitol, sucrose, and trehalose, and 9-or more-membered alcohols such as maltitol. These may be used alone or in combination of 2 or more.

From the viewpoint of excellent curl resistance and a good balance between strength and flexibility, glycerin and sorbitol are preferably used in combination.

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, further preferably 8 to 60 parts by weight, and particularly preferably 10 to 50 parts by weight, based on 100 parts by weight of the PVA-based resin (a). When the content of the plasticizer (B) is too small, the shape stability over time tends to be lowered when a liquid such as a liquid detergent is packed to form a package. If the amount is too large, the mechanical strength tends to be reduced or blocking tends to occur.

The content ratio (glycerin/sorbitol) of glycerin to sorbitol is preferably 0.1 to 5, particularly preferably 0.2 to 4.5, further preferably 0.5 to 4, and particularly preferably 0.7 to 1.3 in terms of a weight ratio. If the content ratio is too small, the PVA-based film tends to be too soft and easily cause blocking, and if it is too large, the PVA-based film tends to be too hard and tends to become brittle in a low humidity environment.

In the present invention, a filler (C), a surfactant (D), and the like may be further contained as necessary.

The filler (C) is contained for the purpose of blocking resistance, and examples thereof include an organic filler and an inorganic filler, and among them, an organic filler is preferably used. In addition, from the viewpoint of improving the water-tightness at the time of producing the package, it is also preferable to use both the organic filler and the inorganic filler in combination.

The organic filler is a particulate matter (primary particles) composed of an organic compound and having any shape such as a needle shape, a rod shape, a layer shape, a flake shape, or a sphere shape, or an aggregate (secondary particles) of the particulate matter.

The organic filler is mainly selected from polymer compounds, and examples thereof include melamine resins, polymethyl (meth) acrylate resins, polystyrene resins, and biodegradable resins such as starch and polylactic acid. These may be used alone or in combination of 2 or more. Among them, biodegradable resins such as polymethyl (meth) acrylate resins, polystyrene resins, and starches are preferable, and starches are particularly preferable from the viewpoint of dispersibility in the PVA resin (a).

Examples of the starch include raw starch (corn starch, potato starch, sweet potato starch, wheat starch, tapioca starch (cassava starch), sago starch, tapioca starch (tapioca starch), sorghum starch, rice starch, bean starch, arrowroot starch, fern starch, lotus starch, water caltrop starch, etc.), physically modified starch (α -starch, fractionated amylose (fractionated amylose), heat-treated starch, etc.), enzymatically modified starch (hydrolyzed dextrin, enzymatically hydrolyzed dextrin, amylose, etc.), chemically decomposed modified starch (acid-treated starch, hypochlorous oxidized starch, dialdehyde starch, etc.), chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, crosslinked starch, etc.), and the like. Among them, raw starch, particularly corn starch and rice starch are preferably used from the viewpoint of ease of obtaining and economy.

The average particle diameter of the organic filler is preferably 5 to 50 μm, particularly preferably 10 to 40 μm, and further preferably 15 to 35 μm. If the average particle diameter is too small, the blocking property of the film tends to be high, and if it is too large, the filler tends to aggregate with each other, the dispersibility tends to be low, or pinholes tend to be formed when the film is stretched during molding.

The average particle diameter of the organic filler is a value measured by a laser diffraction particle size distribution measuring apparatus, and is calculated from the D50 value (particle diameter at 50% accumulation) of the obtained cumulative volume distribution.

The inorganic filler refers to a particulate matter (primary particles) composed of an inorganic compound and having any shape such as a needle shape, a rod shape, a layer shape, a flake shape, or a sphere shape, or an aggregate (secondary particles) of the particulate matter.

Examples of the inorganic filler include silica (silica), diatomaceous earth, titanium oxide, calcium oxide, magnesium oxide, aluminum oxide, barium oxide, germanium oxide, tin oxide, zinc oxide, and other oxide-based inorganic compounds, talc, clay, kaolin, mica, asbestos, gypsum, graphite, 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 hollow sphere, bentonite, montmorillonite, copper powder, sodium sulfate, potassium sulfate, zinc sulfate, copper sulfate, ferric sulfate, magnesium sulfate, aluminum sulfate, potassium aluminum sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, aluminum nitrate, ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium phosphate, potassium nitrate, aluminum sulfate, zinc sulfate, copper sulfate, magnesium sulfate, aluminum sulfate, potassium nitrate, ammonium nitrate, sodium chloride, potassium chloride, magnesium chloride, calcium, Potassium chromate, and the like. These may be used alone or in combination of 2 or more.

Among them, from the viewpoint of excellent hydrogen bonding with the PVA-based resin (a) and an increase in the water-tightness improving effect, it is preferable to use an oxide-based inorganic compound and talc, and it is particularly preferable to use titanium oxide, talc, silica, and further more preferable to use silica.

The average particle diameter of the inorganic filler is preferably 1 to 20 μm, particularly preferably 2 to 15 μm, and further preferably 3 to 10 μm. If the average particle size is too small, the blocking property of the film tends to be high, and the flexibility and toughness of the film tend to be low, while if it is too large, the effect of improving the water-tightness tends to be difficult to obtain.

The average particle diameter of the inorganic filler is a value measured by a laser diffraction particle size distribution measuring apparatus, and is calculated from the D50 value (particle diameter at 50% accumulation) 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, and further preferably 2.5 to 20 parts by weight, based on 100 parts by weight of the PVA based resin (A). If the content ratio is too small, blocking property tends to be high, and if it is too large, flexibility and toughness of the film tend to be low.

The surfactant (D) used in the present invention is contained for the purpose of improving the releasability from the casting surface in the production of the PVA-based film, and generally includes a nonionic surfactant, a cationic surfactant and an anionic surfactant. Examples thereof include polyoxyethylene alkyl amino ethers such as polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl nonyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyalkylene alkyl ether phosphate monoethanol amine salt, polyoxyethylene lauryl amino ether, and polyoxyethylene stearyl amino ether, and these may be used alone or in combination of 2 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, and further preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the PVA based resin (A). If the content is too small, the releasability between the casting surface of the film-forming apparatus and the PVA-based film to be formed tends to be low, and the productivity tends to be low, and if it is too large, there is a tendency to cause a problem such as a decrease in the adhesive strength at the time of sealing performed when the water-soluble film is formed into a package.

The composition may further contain other water-soluble polymers (for example, sodium polyacrylate, polyethylene oxide, polyvinyl pyrrolidone, dextrin, chitosan, chitin, methyl cellulose, hydroxyethyl cellulose, and the like), perfumes, rust inhibitors, colorants, extenders, antifoaming agents, ultraviolet absorbers, liquid paraffins, fluorescent whitening agents, bitter components (for example, denatonium benzoate, and the like) within a range not to impair the object of the present invention. These may be used alone or in combination of 2 or more.

In the present invention, it is preferable to add an antioxidant in order to suppress yellowing. Examples of the antioxidant include sulfites such as sodium sulfite, potassium sulfite, calcium sulfite and ammonium sulfite, tartaric acid, ascorbic acid, sodium thiosulfate, catechol and sodium hydrosulfite, and among them, sulfites, particularly sodium sulfite, are preferable. The amount of the antioxidant to be blended 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).

< production of Water-soluble film >

The water-soluble film of the present invention can be produced, for example, by the following method.

The water-soluble film of the present invention can be produced by first producing a PVA-based film through a film-forming step including a dissolving step of a film-forming raw material for producing a PVA-based resin (a), a casting step, and a drying step, and then, after the drying step of the film-forming step, passing through a step (i) of applying water to the surface of the obtained PVA-based film and a step (ii) of heat-treating the film.

The respective steps will be specifically described below.

[ dissolving Process ]

In the dissolving step, a PVA resin composition containing the PVA resin (a), preferably further containing a plasticizer (B), and if necessary further containing a filler (C), a surfactant (D), and the like is dissolved or dispersed with water to produce an aqueous solution or an aqueous dispersion to be a film-forming raw material.

The dissolving step means a step until the PVA resin composition is dissolved or dispersed in water to obtain a film-forming raw material free from undissolved matter.

As a method for dissolving the PVA resin composition in water, ordinary temperature dissolution, high temperature dissolution, pressurized dissolution, and the like are generally employed, and among them, high temperature dissolution and pressurized dissolution are preferred from the viewpoint of a small amount of undissolved matter and excellent productivity.

The dissolution temperature is usually 80 to 100 ℃ and preferably 90 to 100 ℃ in the case of high-temperature dissolution, and 80 to 130 ℃ and preferably 90 to 120 ℃ in the case of pressurized dissolution. The dissolution time may be suitably adjusted depending on the dissolution temperature and the pressure at the time of dissolution, and is usually 1 to 20 hours, preferably 2 to 15 hours, and particularly 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 the dissolving step, examples of the stirring blade include a paddle, FULLZONE, MAXBLEND, TWINSTAR, anchor, screw, and propeller.

Further, the PVA-based resin aqueous solution obtained after dissolution is subjected to a defoaming treatment, and examples of the defoaming method include standing defoaming, vacuum defoaming, twin-screw extrusion defoaming, and the like. Among them, standing defoaming and twin-screw extrusion defoaming are preferable. The temperature for the standing deaeration is usually 50 to 100 ℃, preferably 70 to 95 ℃, and the deaeration time is usually 2 to 30 hours, preferably 5 to 20 hours.

The solid content concentration of the film-forming raw material is preferably 10 to 50 wt%, particularly preferably 15 to 40 wt%, and further preferably 20 to 35 wt%. If the concentration is too low, the productivity of the film tends to be low, and if it is too high, the viscosity becomes too high, and it takes time to defoam the film-forming raw material or a die mark tends to be generated during film formation.

[ casting step and drying step ]

In the film forming step, the PVA-based film having a moisture content of 15 wt% or less is adjusted by passing through a casting step of shaping the film forming material produced in the dissolving step into a film shape and a drying step of drying the film forming material as necessary.

In the case of film formation, for example, a melt extrusion method, a casting method, or the like can be used, and the casting method is preferable from the viewpoint of film thickness accuracy.

The temperature of the film-forming raw material immediately before casting (the discharge section) is preferably 60 to 98 ℃, and particularly preferably 70 to 95 ℃. If the temperature is too low, the viscosity of the film-forming raw material tends to increase, and the productivity of the PVA film tends to decrease, and if it is too high, foaming tends to occur.

In the drying step of drying the film-forming raw material on the casting surface after casting, the surface temperature of the casting surface is preferably 50 to 110 ℃, particularly preferably 70 to 100 ℃. If the surface temperature is too low, drying is insufficient, the moisture content of the film tends to increase, and blocking tends to occur, and if it is too high, the film-forming raw material tends to foam, and film-forming defects tend to form.

In the drying during film formation, drying by a hot roll, drying by blowing hot air to a film by a floating dryer, drying by a far infrared device, a medium heating device, and the like may be used in combination.

The film-forming raw material is dried by the above-mentioned drying step until the moisture content is 15 wt% or less, and then peeled off from the casting surface (in the case where the film is further dried by a heat roll after being peeled off from the casting surface, the film is peeled off from the drying heat roll), thereby obtaining a PVA-based film. The PVA film peeled from the casting surface (or the dry heat roller) is cooled at 10 to 35 ℃.

The surface of the PVA film of the present invention may be flat, and it is preferable to perform unevenness processing such as embossing, fine unevenness pattern, special engraving pattern on one surface or both surfaces of the PVA film from the viewpoints of blocking resistance, sliding property during processing, reduced adhesion between products, and appearance.

The processing temperature in the above-mentioned embossing is usually 60 to 150 ℃, preferably 80 to 140 ℃. The working pressure is usually 2 to 8MPa, preferably 3 to 7 MPa. The processing time depends on the processing pressure and the film forming speed, but is usually 0.01 to 5 seconds, preferably 0.1 to 3 seconds.

If necessary, after the embossing treatment, a cooling treatment may be performed to prevent unwanted stretching of the film due to heat.

In the present invention, the PVA-based film is subjected to a wet heat treatment after the drying step in the film-forming step, and water is applied to the surface of the PVA-based film and heat treatment is performed, in particular, in the wet heat treatment, whereby the water-soluble film of the present invention satisfying a specific difference in crystallinity index on the front and back of the film can be produced.

The method of applying water to the surface of the PVA based film and heat treating the film will be described in detail below.

First, a step of applying water to the surface of the dried PVA based film will be described.

The coating of water on the surface of the PVA-based film may be water alone or a coating solution containing water as a main component. In order to control the crystallinity of the surface of the PVA-based film, the coating liquid needs to contain water as a main component, and the water content of the coating liquid is usually 80% by weight or more, preferably 90% by weight or more, and more preferably 99% by weight or more. If the water content of the coating liquid is too small, the curl suppression effect is difficult to be exhibited, and thus the action and effect of the present invention tend to be difficult to obtain.

Examples of the components other than water include organic solvents such as PVA-based resins, water-soluble polymers different from the PVA-based resins, plasticizers, surfactants, fillers, antioxidants, perfumes, rust inhibitors, colorants, extenders, antifoaming agents, ultraviolet absorbers, fluorescent brighteners, liquid paraffins, bitter components (e.g., denatonium benzoate), and alcohols. These may be used alone or in combination of 2 or more.

As a method for applying water to the surface of the PVA-based film, there may be mentioned methods such as gravure offset printing, gravure coating, roll coating, bar coating, and spray coating, and from the viewpoint of uniformly applying an appropriate amount of water to the surface and preventing dissolution and perforation of the water-soluble film due to the application, a spray coating method and a roll coating method are preferable, and a method of applying water while spraying it by a spray coating method is particularly preferable.

The temperature of the water or the coating liquid is usually about 0 to 60 ℃, preferably 5 to 50 ℃, and particularly preferably 10 to 40 ℃.

If the temperature is too low, the water impregnation action in the film surface is reduced and the curl suppression effect tends to be difficult to be exhibited, and if it is too high, the water-soluble film tends to be dissolved and to be opened.

The coating weight is usually 0.1 to 50g/m²Degree of preferably 0.5 to 10g/m²Particularly preferably 1.0 to 4g/m²。

If the amount is too small, the curl suppressing effect is hard to be exhibited, and the effect of the present invention tends to be hard to be obtained, and if it is too large, the water-soluble film tends to be dissolved, to be opened, or to generate bubbles.

In the case of the spray coating method, the distance between the spray nozzle and the film is usually about 5 to 100cm, preferably 10 to 80cm, and particularly preferably 20 to 60 cm.

If the distance is too short, the water-soluble film tends to be dissolved and to open pores, and if the distance is too long, the curl suppression effect is difficult to be exhibited, and the effect of the present invention tends to be difficult to obtain.

The size of the water droplets at the time of spraying is usually 1 to 1000. mu.m, preferably 5 to 500. mu.m, and particularly preferably 10 to 300. mu.m.

If the size of the droplets is too small, the droplets tend to be easily volatilized, and the amount of moisture supplied to the surface of the film tends to decrease, while if the size of the droplets is too large, uneven application tends to be formed, and it is difficult to obtain a sufficient curl suppression effect.

In the present invention, when water is applied to the surface of the PVA-based film after the drying step, it is preferable to apply water to the surface of the film on the opposite side to the side of the film in contact with the casting surface (e.g., the metal surface of the endless belt or the drum roll) out of the 2 surfaces of the film.

Next, the heat treatment process after the water application on the surface will be described.

The heat treatment in the present invention is different from the drying at the time of film formation, and aims to stabilize the crystal state of the film surface controlled by the surface coating in the previous stage by providing an appropriate thermal history after the surface coating with water.

In the case of the conventional heat treatment method, the crystallinity is controlled in a state where the crystalline state of PVA formed in advance in the production process remains, and therefore, the curling improvement effect in the short term is obtained, but the curling improvement effect in the long term is not sufficient.

Therefore, in the present invention, it is important to provide an appropriate thermal history after the surface is coated with water.

The time from the application of water to the heat treatment is preferably 1 to 120 seconds, particularly preferably 2 to 60 seconds, and further preferably 3 to 40 seconds. If the time is too long, the water-soluble film tends to dissolve and open pores, and if the time is too short, the effect of surface coating is weak, and the curl suppression effect tends to be difficult to exhibit.

The heat treatment temperature is preferably 80 to 130 ℃, particularly preferably 85 to 125 ℃, and further preferably 90 to 120 ℃. If the heat treatment temperature is too high, the sealing strength tends to be insufficient and the solubility of the film tends to be lowered, and if the heat treatment temperature is too low, the amount of heat supplied to the film tends to be reduced and the long-term curl suppression effect tends to be difficult to obtain.

The heat treatment time is preferably 0.1 to 60 seconds, particularly preferably 0.5 to 20 seconds, and further preferably 1 to 10 seconds. If the heat treatment time is too long, the sealing strength tends to be insufficient and the solubility of the film tends to decrease, and if the heat treatment time is too short, the amount of heat supplied to the film tends to decrease and the long-term curl suppression effect tends to be difficult to obtain.

From the viewpoint of suppressing the decrease in film solubility and improving productivity, the heat treatment temperature and time are preferably a high temperature heat treatment for a short time, preferably 85 to 125 ℃ for 0.5 to 20 seconds, and particularly preferably 90 to 120 ℃ for 1 to 10 seconds.

The moisture content of the film after heat treatment is usually 3 to 15% by weight, preferably 5 to 14% by weight, and particularly preferably 8 to 11% by weight. When the water content is high, blocking tends to occur easily, and when the water content is too low, the film tends to be too hard.

As a method of performing heat treatment after water is applied to the surface, there can be applied (a) a method of contacting with a heated metal roll (hot roll) after water is applied to the surface; (b) a method of contacting with a heated metal plate after the surface is coated with water; (c) a method of spraying hot air after applying water on the surface; (d) and a method of applying water to the surface and then heating the surface by infrared irradiation, far infrared irradiation, or high-frequency induction. Among them, the contact heat treatment method (a) and (b) is preferable from the viewpoint of easy direct control of the heat treatment on the coated surface. In the case of a heat roller, a plurality of rollers may be used.

In the present invention, when the heat treatment is performed after the water is applied to the surface, the heat treatment is preferably performed on the same surface of the film as the surface-coated surface, and particularly, the heat treatment is preferably performed by bringing the surface-coated surface of the film into contact with a portion of a heat treatment apparatus such as a heat roll or a metal plate.

[ other Processes ]

In the production of the water-soluble film of the present invention, after the above-mentioned production step, a winding step, packaging, storage, transportation, and the like are carried out as necessary.

In the winding step, the PVA-based film (water-soluble film) subjected to the wet heat treatment after film formation is conveyed and wound up, and wound up on a core tube (S1) to produce a film roll. The obtained film roll may be supplied as it is as a product, but it is preferable that the rolled PVA type water-soluble film is slit into a desired width and then rewound on a core tube having a length corresponding to the width of the film (S2), or may be supplied as a film roll having a desired size.

The water-soluble film of the present invention thus obtained is suppressed in the occurrence of curling even after long-term storage, is reduced in the occurrence of sealing defects, and is useful for various packaging applications such as unit packaging applications of pharmaceuticals such as agricultural chemicals and detergents.

< Water-soluble film for packaging drug >

The water-soluble film of the present invention can be particularly suitably used as a water-soluble film for pharmaceutical packaging. The water-soluble film for packaging a drug is preferably a water-soluble film for packaging a detergent, a water-soluble film for packaging an agricultural chemical, and particularly preferably a water-soluble film for packaging a liquid detergent.

Examples of the chemical include pesticides such as insecticides, bactericides, and herbicides, fertilizers, detergents such as clothes detergents and dish washing detergents, and detergents are particularly preferred. The shape of the drug may be liquid or solid, and in the case of liquid, the drug is liquid, and the viscosity of the liquid drug is not particularly limited as long as the drug is liquid and the drug has fluidity and changes shape in accordance with the shape of the container, but is preferably 10 to 200mPa · s. The viscosity of the liquid drug is measured at room temperature by a B-type rotational viscometer. In the case of a solid, granules, tablets, powders, and the like can be mentioned. The drug is preferably used as dissolved or dispersed in water.

The pH of the agent may be any of alkaline, neutral, and acidic. The liquid detergent preferably has a pH value of 6 to 12, particularly preferably 7 to 11 when dissolved or dispersed in water, and the liquid detergent preferably has a water content of 15 wt% or less, particularly preferably 0.1 to 10 wt%, and further 0.1 to 7 wt%.

The pH value is measured according to JIS K33628.3. The water content was measured according to JIS K33627.21.3.

< medicinal preparation Package >

The drug package of the present invention is a package formed of a water-soluble film and the drug contained therein. Since it is packaged in a water-soluble film, it is used for applications in which the drug is dissolved or dispersed in water after the water-soluble film is dissolved, and the effect of the drug is exhibited when it is put into water together with the package. And is therefore suitable for unit dose packages in which a relatively small amount of a medicament is packed 1 time.

The medicine package of the present invention in which a liquid detergent is packed is particularly suitable for a single package of a liquid detergent, and the package (water-soluble film) of the present invention in which the liquid detergent is packed is kept in a shape in which the liquid detergent is packed during storage, and when the package is used (during washing), the package is dissolved by contacting water, and the packed liquid detergent flows out from the package.

The medicine package of the present invention is manufactured by, for example, sealing a medicine in a package formed by bonding end portions of 2 pieces of water-soluble film cut out in a square or circular shape. The medicament package has a dimension such that the length (diameter) of one side is usually 10 to 50mm, preferably 20 to 40 mm. The thickness of the water-soluble film used for the package is usually 10 to 120 μm, preferably 15 to 110 μm, and more preferably 20 to 100 μm. The amount of the drug such as liquid detergent to be contained is usually 5 to 50mL, preferably 10 to 40 mL.

When a package in which a medicament is packaged is formed using the water-soluble film of the present invention, a known method can be used. Examples thereof include a method of heat-sealing the water-soluble film (1), (2) a method of water-sealing, and (3) a method of paste-sealing, and among them, the method of water-sealing (2) is generally used and is preferable.

The pharmaceutical package of the present invention generally has a smooth surface. However, from the viewpoints of blocking resistance, slidability during processing, reduced adhesion between products (packages), and appearance, the outer surface of the package (water-soluble film) may be subjected to embossing, fine uneven patterns, special engraved patterns, and other uneven processes.