Composition, Film, and Package

Abstract

Provided are a composition having excellent water solubility and chemical resistance, and a film and a package containing said composition. A composition comprising a vinyl alcohol-based polymer (A) and a plasticizing agent, wherein the block character of residual vinylester units of the vinyl alcohol-based polymer (A) is 0.55-1.

Description

Technical Field

[0001] The present disclosure relates to a composition, a film, and a package.

Background Art

[0002] In recent years, as a form of using various chemicals such as agricultural chemicals, laundry detergents, bleaching agents, toiletry products, and industrial chemicals, a package formed by sealing a certain amount of each chemical in a water-soluble film is put into water, and the chemicals are dissolved or dispersed in water together with the water-soluble film for use. Generally, such a packaging form is called unit packaging. The advantages of unit packaging include that the user can use it without directly touching dangerous chemicals, the work is simple because there is no need to measure when using because a certain amount of contents is packaged, and there is no need to process the container used for packaging the chemicals after use.

[0003] Among the chemicals packaged in such water-soluble films, there are substances with high oxidizing power such as acidic substances, chlorine-based substances (such as disinfectants), and agricultural chemicals. When a substance with high oxidizing power is stored in a state of being packaged in a water-soluble film, there is a problem that the water solubility of the film decreases over time and the film becomes insoluble or hardly soluble in water. As films for packaging substances with high oxidizing power, polyethylene oxide-based films, cellulose-based films, etc. are known, but these films have the disadvantages that the dissolution rate in water is very slow, the mechanical physical properties are insufficient, and the impact resistance at low temperatures is small because they are hard and brittle.

[0004] Recently, a vinyl alcohol-based polymer (hereinafter, may be abbreviated as "PVA") that has excellent interfacial properties and strength properties as one of the few crystalline water-soluble polymers and is used as a stabilizer for various binders, paper processing, fiber processing, and emulsions has been increasingly used as a raw material for water-soluble films.

[0005] Examples of PVA films for packaging substances with high oxidizing power as described above include water-soluble films obtained by blending polyethylene glycol with carboxylic acid ester-modified PVA (Patent Document 1), water-soluble films for pesticide packaging obtained by forming a film from a modified polyvinyl alcohol containing a sulfonic acid group-containing unit (Patent Document 2), and water-soluble films composed of a modified polyvinyl alcohol having a sulfonic acid group and gallic acid or its alkyl ester (Patent Document 3), etc.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] In water-soluble films as described above, it is required to be excellent in water solubility and to have little decrease in water solubility when stored in a state of packaging a drug (hereinafter referred to as "excellent in drug resistance").

[0008] An object of the present disclosure is to provide a composition excellent in water solubility and drug resistance, a film and a package containing the same.

Means for Solving the Problems

[0009] As a result of intensive studies by the present inventor, it has been found that a composition containing a vinyl alcohol-based polymer in which the block character of the residual vinyl ester unit is in a specific range and a plasticizer can solve the above problems.

[0010] One aspect of the present disclosure is a composition containing a vinyl alcohol polymer (A) and a plasticizer, wherein the block character of the residual vinyl ester units of the vinyl alcohol polymer (A) is 0.55 or more and 1 or less.

[0011] The content of the plasticizer with respect to 100 parts by mass of the vinyl alcohol polymer (A) is preferably 0.1 part by mass or more and 30 parts by mass or less.

[0012] The plasticizer contains glycerin and sorbitol, and the content of glycerin with respect to 100 parts by mass of the vinyl alcohol polymer (A) is preferably 1 part by mass or more and 15 parts by mass or less, and the content of sorbitol with respect to 100 parts by mass of the vinyl alcohol polymer (A) is preferably 1 part by mass or more and 15 parts by mass or less.

[0013] The viscosity of a 4% aqueous solution of the vinyl alcohol polymer (A) is preferably 2 mPa·s or more and 20 mPa·s or less.

[0014] The saponification degree of the vinyl alcohol polymer (A) is preferably 60 mol% or more and 99 mol% or less.

[0015] It is preferable that the composition further contains an antioxidant.

[0016] The vinyl alcohol polymer (A) preferably has a sulfonic acid group or a salt thereof in the side chain.

[0017] The modification amount of the sulfonic acid group or a salt thereof in the vinyl alcohol polymer (A) is preferably 0.01 mol% or more and 10 mol% or less.

[0018] The vinyl alcohol polymer (A) is an unmodified vinyl alcohol polymer, and it is also preferable that the block character of the residual vinyl ester units of the vinyl alcohol polymer (A) is 0.55 or more and 0.75 or less.

[0019] Another aspect of the present disclosure is a film containing the above-described composition.

[0020] Yet another aspect of the present disclosure is a package containing a chemical in the above-described composition or the above-described film.

[0021] It is preferable that the above chemical is a pesticide, a bactericide or a detergent.

Advantages of the Invention

[0022] The composition, film and package of the present disclosure are excellent in water solubility and chemical resistance.

Embodiments for Carrying Out the Invention

[0023] <Composition> The composition contains a vinyl alcohol polymer (A) (hereinafter, may be abbreviated as "PVA(A)") and a plasticizer, and the block character of the residual vinyl ester unit of PVA(A) (hereinafter, may be simply referred to as "block character") is 0.55 or more and 1 or less.

[0024] The composition can be suitably used as a composition for preparing a film for drug packaging.

[0025] <Vinyl alcohol polymer (A)> Since the block character of the residual vinyl ester unit of PVA(A) is within the above specific range, the water solubility of PVA(A) is improved as compared with a vinyl alcohol polymer having a block character outside the above range. The reason is not necessarily clear, but it is presumed that the crystallinity of PVA(A) is reduced due to the reduction of the block property of the residual vinyl ester unit, and as a result, the water solubility is improved.

[0026] Hereinafter, a vinyl alcohol polymer in a stage prior to PVA(A) that still has the characteristics of PVA(A) may be referred to as a "vinyl alcohol polymer (B)" (hereinafter sometimes abbreviated as "PVA(B)") for distinction from PVA(A). For example, PVA(B) may be a vinyl alcohol polymer having a block character of less than 0.55 obtained by polymerizing a vinyl ester monomer to obtain a vinyl ester polymer and then saponifying this vinyl ester polymer.

[0027] In PVA(A), the lower limit of the block character of the residual vinyl ester unit is 0.55, preferably 0.58, more preferably 0.6. The upper limit of the block character is 1, preferably 0.9, more preferably 0.85, even more preferably 0.8, and still more preferably 0.75. Also, the block character is 0.55 or more and 1 or less, preferably 0.58 or more and 0.9 or less, more preferably 0.6 or more and 0.8 or less, and even more preferably 0.6 or more and 0.75 or less. Further, when PVA(A) is an unmodified vinyl alcohol polymer, the block character is preferably within the above range and preferably 0.55 or more and 0.75 or less. By satisfying the above for the block character, a composition excellent in water solubility, chemical resistance, and production efficiency can be obtained.

[0028] The "unmodified vinyl alcohol polymer" is a vinyl alcohol polymer that does not have a sulfonic acid group or its salt in the side chain as described later. As one embodiment, the unmodified vinyl alcohol polymer may be a saponified product of a polymer of a vinyl ester monomer and may be a vinyl alcohol polymer having substantially only an ester group and a hydroxy group remaining in its side chain.

[0029] The "block character of residual vinyl ester units" is a numerical value representing the distribution of residual ester groups and hydroxy groups generated by saponification of ester groups in a vinyl alcohol-based polymer, and takes a value from 0 to 2. When the block character is 0, it indicates that the residual ester groups or hydroxy groups are completely block-distributed in the vinyl alcohol-based polymer. As the value of the block character increases, the alternation between the residual ester groups and the hydroxy groups increases. When the block character is 1, the residual ester groups and the hydroxy groups exist completely randomly, and when the block character is 2, the residual ester groups and the hydroxy groups exist completely alternately. The "residual ester group" means an ester group (-O-C(=O)-Q (Q represents a hydrocarbon group other than the CH2=CH-O-C(=O) part contained in the vinyl ester-based monomer)) contained in the vinyl ester-based monomer unit in the vinyl alcohol-based polymer obtained through saponification treatment. The block character can be determined by 13 C-NMR measurement described later. When the vinyl alcohol-based polymer contains repeating units other than vinyl ester-based monomer units and / or vinyl alcohol units, the block character is calculated for all sites where the vinyl ester-based monomer units and / or vinyl alcohol units in the vinyl alcohol-based polymer are continuous.

[0030] The above-mentioned block character can be adjusted by the type of vinyl ester-based monomer, saponification conditions such as catalysts and solvents, heat treatment after saponification, etc. When saponification is carried out by a general method, usually, the block character is less than 0.55, but the block character can be made to have a value of 0.55 or more by heat treatment such as heating thereafter.

[0031] The lower limit of the viscosity of the 4 mass% aqueous solution of PVA(A) is preferably 2 mPa·s, more preferably 2.5 mPa·s, and even more preferably 3 mPa·s. The upper limit of the viscosity of the 4 mass% aqueous solution is preferably 20 mPa·s, more preferably 15 mPa·s, and even more preferably 10 mPa·s. The viscosity of the 4 mass% aqueous solution of PVA(A) is preferably 2 mPa·s or more and 20 mPa·s or less, more preferably 2.5 mPa·s or more and 15 mPa·s or less, and even more preferably 3 mPa·s or more and 10 mPa·s or less. When the viscosity of the 4 mass% aqueous solution is within the above range, the mechanical strength of the film containing the composition is better, and it does not gel even during heating including heat treatment in the manufacturing process, and the manufacturing efficiency is better. The viscosity of the 4 mass% aqueous solution is a value measured using a B-type viscometer under the conditions of a rotor rotation speed of 60 rpm and a temperature of 20°C. As the B-type viscometer, commercially available products such as B-type viscometer BLII (manufactured by Toki Sangyo Co., Ltd.), digital B-type viscometer BASE (trade name, manufactured by ATAGO CO., LTD.), and digital B-type viscometer PRO (trade name, manufactured by ATAGO CO., LTD.) can be used.

[0032] The lower limit of the saponification degree of PVA(A) is preferably 60 mol%, more preferably 65 mol%, even more preferably 70 mol%, and in some cases even more preferably 80 mol%, and in some cases even more preferably 85 mol%. The upper limit of the saponification degree is preferably 99 mol%, more preferably 98 mol%, even more preferably 97 mol%, in some cases even more preferably 95 mol%, and particularly preferably 90 mol%. The saponification degree of PVA(A) is preferably 60 mol% or more and 99 mol% or less, more preferably 65 mol% or more and 97 mol% or less, and even more preferably 70 mol% or more and 90 mol% or less. By setting the saponification degree of PVA(A) to be not less than the above lower limit, the effect of improving water solubility can be enhanced more, and PVA(A) can be manufactured more stably industrially. For example, the composition can be formed into a film more stably. The saponification degree of PVA(A) is measured by the method described in JIS-K6726-1994.

[0033] PVA(A) is a polymer having vinyl alcohol units as the main repeating units. The lower limit of the content ratio of vinyl alcohol units in all the repeating units in PVA(A) is preferably, for example, 60 mol%, more preferably 70 mol%, and even more preferably 80 mol%. The upper limit of the above content ratio is preferably, for example, 99.9 mol%, and more preferably 99 mol%.

[0034] PVA(A) preferably has a sulfonic acid group or a salt thereof in its side chain. The "salt of a sulfonic acid group" refers to a group in which the hydrogen ion of the sulfonic acid group (-SO3H) is substituted with a cation such as a metal ion or an ammonium ion. As the above salt, an alkali metal salt (-SO3M: M is an alkali metal atom) is preferable, and a sodium salt (-SO3Na) is more preferable. PVA(A) may have both a sulfonic acid group and a salt of a sulfonic acid group in its side chain. The "side chain" refers to an atomic chain other than the main chain when the longest atomic chain among the polymer chains is defined as the main chain.

[0035] PVA(A) preferably further has an aromatic ring bonded to the sulfonic acid group or a salt thereof. Examples of the aromatic ring include carbon rings such as a benzene ring and a naphthalene ring, and heterocyclic rings such as a furan ring and a pyridine ring. As the aromatic ring, a carbon ring is preferable, and a benzene ring is more preferable. The sulfonic acid group or a salt thereof and the aromatic ring are preferably bonded via the sulfur atom of the sulfonic acid group. At this time, the sulfonic acid group or a salt thereof and the aromatic ring may be directly bonded via the sulfur atom of the sulfonic acid group, or may be bonded via another bonding chain (linking group). The sulfonic acid group or a salt thereof and the aromatic ring are preferably directly bonded.

[0036] As a method for introducing a sulfonic acid group or its salt into the side chain of a vinyl alcohol-based polymer, for example, as described below, a method of acetalizing PVA(B) using an aldehyde having a sulfonic acid group or its salt can be mentioned. PVA(A) preferably has a structural unit represented by the following formula (I). Usually, in PVA(B) after saponification using an alkali catalyst, a trace amount of the alkali catalyst used during saponification in the production process may remain. For this reason, even if the aldehyde having a sulfonic acid group used during acetalization is not a salt, the sulfonic acid group of the resulting PVA(A) can be in the form of a salt such as an alkali metal salt.

[0037]

Chemical formula

[0038] In the above formula (I), X 1 and X 2 is such that at least one of them is -Z-SO3Y and the other is a hydrogen atom, a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms or -Z-SO3Y. Y is, independently of each other, a hydrogen atom, a metal atom or an ammonium group. Z is, independently of each other, a single bond or a linking group.

[0039] Examples of the metal atom represented by the above Y include an alkali metal atom (such as a lithium atom, a sodium atom, a potassium atom, etc.), an alkaline earth metal atom (such as a calcium atom, etc.). Among them, from the viewpoint of the solubility of the resulting film, etc., Y is preferably a hydrogen atom or an alkali metal atom, more preferably a hydrogen atom or a sodium atom, and even more preferably a sodium atom. When Y is a divalent or higher metal atom such as an alkaline earth metal atom, Y may form a crosslinked structure bonded to two or more -SO3 - groups.

[0040] Examples of the linking group represented by the above Z include, in addition to a divalent hydrocarbon group, -O-, -CO-, -COCO-, -CO(CH2) mCO-, -CH(OH)-, -S-, -CS-, -SO-, -SO2-, -NR 1 -, -CONR 1 -, -NR 1 CO-, -CSNR 1 -, -NR 1 CS-, -NR 1 NR 1 -, -HPO4-, -Si(OR 1 )2-, -OSi(OR 1 )2-, -OSi(OR 1 )2O-, -Ti(OR 1 )2-, -OTi(OR 1 )2-, -OTi(OR 1 )2O-, -Al(OR 1 )-, -OAl(OR 1 )-, -OAl(OR 1 )O- and other divalent groups such as these can be mentioned. Here, R 1 is each independently an arbitrary substituent, and a hydrogen atom or an alkyl group is preferred. m is a natural number from 1 to 10. Examples of the above divalent hydrocarbon group include divalent aliphatic hydrocarbon groups such as an alkylene group, an alkenylene group, and an alkynylene group, and divalent aromatic hydrocarbon groups such as a phenylene group and a naphthylene group. Some or all of the hydrogen atoms of these hydrocarbon groups may be substituted with halogen atoms such as a fluorine atom, a chlorine atom, and a bromine atom. As the above Z, a single bond is preferred.

[0041] The above X 1 and X 2 From the viewpoint of the reactivity of the aldehyde used for acetalization, X 1 is -Z-SO3Y, and X 2 is preferably a hydrogen atom, a halogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, or -Z-SO3Y. The above X 1-Z-SO3Y represented by the formula is bonded to the carbon atom at the ortho position with respect to the aromatic ring carbon atom to which the aldehyde is bonded, so that -Z-SO3Y acts as an intramolecular acidic catalyst, and it is presumed that the reactivity of the aldehyde is further improved. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., and among them, a chlorine atom and a bromine atom are preferable. The alkyl group having 1 to 4 carbon atoms may be linear or branched, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, etc., and among them, a methyl group and an ethyl group are preferable. X 2 is more preferably a hydrogen atom, a chlorine atom, a hydroxy group, a methyl group or -SO3Y, and even more preferably a hydrogen atom.

[0042] In the aspect where PVA(A) has a sulfonic acid group or a salt thereof in its side chain, the lower limit of the modification amount of the sulfonic acid group or a salt thereof is preferably 0.01 mol%, more preferably 0.05 mol%, further preferably 0.1 mol%, even more preferably 0.2 mol%, and particularly preferably 0.3 mol%. The upper limit of the above modification amount is preferably 10 mol%, more preferably 7 mol%, and further preferably 5 mol%. When the modification amount of the sulfonic acid group or a salt thereof is in the above range in the aspect where PVA(A) has a sulfonic acid group or a salt thereof in its side chain, the water solubility and chemical resistance can be further improved, and the mechanical strength of a film or the like containing the composition can be further improved.

[0043] The "modified amount of sulfonic acid group or its salt" refers to the ratio of the total number of moles of the sulfonic acid group and its salt to the number of moles of all repeating units of PVA(A). In this specification, the structure represented by -CR2-CR2- is regarded as one repeating unit. Each of the above R2 is independently a hydrogen atom or an arbitrary substituent, and two R2 contained in the same or different structural units may be bonded to each other. For example, it is assumed that the structural unit represented by the above formula (I) consists of two repeating units. On the other hand, it is assumed that the vinyl alcohol unit, the residual vinyl ester unit, the structural unit derived from other monomers, etc. each consist of one repeating unit. In other words, the structure derived from the monomer having a carbon-carbon double bond used in the polymerization is the repeating unit.

[0044] In the aspect where PVA(A) has a sulfonic acid group or its salt in its side chain, the modified amount of the sulfonic acid group or its salt is that of PVA(A) 1 It can be determined by 1H-NMR measurement. For example, in the case of PVA(A) obtained by acetalization reaction using sodium 2-benzaldehydesulfonate, this PVA(A) is dissolved in DMSO-d6 and measured using 1H-NMR at 400 MHz. 1 The peak derived from the methine of the vinyl alcohol unit is attributed to 4.2 to 5.2 ppm (integration value α), and the peak derived from the benzene ring of sodium 2-benzaldehydesulfonate is attributed to around 7.0 to 8.0 ppm (integration value β), and the modified amount of the sulfonic acid group or its salt is calculated by the following formula. Modified amount of sulfonic acid or its salt (mol%) = {(β / 4) / α} × 100

[0045] <Method for producing vinyl alcohol polymer (A)> PVA(A) can be produced, for example, by polymerizing a vinyl ester monomer to obtain a vinyl ester polymer, saponifying the obtained vinyl ester polymer using an alkali catalyst in an alcohol solution to obtain PVA(B), and heat-treating the obtained PVA(B).

[0046] In the case where PVA(A) has a sulfonic acid group or a salt thereof in its side chain, PVA(A) can be produced, for example, by polymerizing a vinyl ester monomer to obtain a vinyl ester polymer, saponifying the obtained vinyl ester polymer with an alkali catalyst in an alcohol solution to obtain PVA(B), and heat-treating the obtained PVA after or while mixing it with an aldehyde having a sulfonic acid group or a salt thereof.

[0047] Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Among them, vinyl acetate is preferable.

[0048] Examples of the method for polymerizing the vinyl ester monomer include known methods such as bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc. Among these methods, the bulk polymerization method carried out without a solvent and the solution polymerization method carried out using a solvent such as alcohol are preferable, and in terms of enhancing the effects of the present disclosure, the solution polymerization method carried out in the presence of a lower alcohol is more preferable. As the lower alcohol, an alcohol having 3 or less carbon atoms is preferable, methanol, ethanol, n-propanol and isopropanol are more preferable, and methanol is even more preferable. When carrying out the polymerization reaction by the bulk polymerization method or the solution polymerization method, either a batch system or a continuous system can be adopted as the reaction method.

[0049] Examples of the initiator used in the polymerization reaction include known initiators such as azo-based initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); organic peroxide-based initiators such as benzoyl peroxide, n-propyl peroxycarbonate, etc. There is no particular limitation on the polymerization temperature when carrying out the polymerization reaction, but a range of 5°C or higher and 200°C or lower is appropriate.

[0050] When polymerizing the vinyl ester monomer, a copolymerizable monomer can be further copolymerized as long as the gist of the present disclosure is not impaired. Such monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, 1-hexene; acrylamide derivatives such as N-methylacrylamide, N-ethylacrylamide; methacrylamide derivatives such as N-methylmethacrylamide, N-ethylmethacrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether; hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1,4-butanediol vinyl ether; allyl acetate; allyl ethers such as propyl allyl ether, butyl allyl ether, hexyl allyl ether; monomers having an oxyalkylene group; isopropenyl acetate; hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3-buten-1-ol; monomers having a silyl group such as vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, 3-(meth)acrylamidopropyltrimethoxysilane, 3-(meth)acrylamidopropyltriethoxysilane, etc. The upper limit of the amount of these monomers used varies depending on the purpose and use for which they are used, etc., but 20 mol% is preferable, 10 mol% is more preferable, 5 mol% is further preferable, 3 mol% is even more preferable, and 2 mol% is particularly preferable with respect to the total monomers. It is preferable that the amount of the monomer other than the vinyl ester monomer used is 0 mol%, that is, it is preferable to polymerize substantially only the vinyl ester monomer.

[0051] For the saponification reaction of the vinyl ester polymer obtained in the above polymerization step, an alcoholysis reaction or a hydrolysis reaction using a conventionally known basic catalyst (alkali catalyst) such as sodium hydroxide, potassium hydroxide, sodium methoxide, etc. can be applied. As the solvent used in the saponification reaction, alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene, etc. can be mentioned, and these can be used alone or in combination of two or more. Among them, it is preferable to use methanol or a mixed solution of methanol and methyl acetate as the solvent and carry out the saponification reaction in the presence of sodium hydroxide which is a basic catalyst because it is simple. By such a method, PVA (B) can be obtained.

[0052] The PVA (B) obtained in the above saponification reaction is heat-treated alone or after or while mixing with an aldehyde having a sulfonic acid group or its salt (hereinafter, may be abbreviated as "heat treatment step") to obtain PVA (A) having a specific block character. At this time, from the viewpoint of suppressing gelation during heating, the viscosity of a 4 mass% aqueous solution of PVA (B) obtained in the above saponification reaction is preferably 20 mPa·s or less. The range of the preferred 4 mass% aqueous solution viscosity and saponification degree of PVA (B) is the same as the range of the above-mentioned PVA (A).

[0053] In the aspect where PVA (A) has a sulfonic acid group or its salt in its side chain, there is no particular limitation on the aldehyde having a sulfonic acid group or its salt (salt of sulfonic acid group), but for example, a compound represented by the following formula (II) can be used.

[0054]

Chemical formula

[0055] In the above formula (II), X 1 and X 2 are defined and have the same preferred range as in the above formula (I).

[0056] Examples of the compound represented by the formula (II) include 2-benzaldehydesulfonic acid, 2,4-benzaldehydedisulfonic acid, 4-chlorobenzaldehyde-2-sulfonic acid, 4-methylbenzaldehyde-2-sulfonic acid, 4-hydroxylbenzaldehyde-2-sulfonic acid, or salts thereof. Among them, from the viewpoint of easy availability, 2-benzaldehydesulfonic acid or 2,4-benzaldehydedisulfonic acid is preferable. Examples of the salt include alkali metal salts, alkaline earth metal salts, ammonium salts, etc. Among them, alkali metal salts are preferable, and sodium salts are more preferable. That is, preferable aldehydes having a salt of a sulfonic acid group include sodium 2-benzaldehydesulfonate, sodium 2,4-benzaldehydedisulfonate, etc.

[0057] The lower limit of the addition amount of the aldehyde having the sulfonic acid group or its salt is preferably 0.1 part by mass, more preferably 0.5 part by mass, and further preferably 1 part by mass with respect to 100 parts by mass of PVA (B). The upper limit of the addition amount is preferably 50 parts by mass, more preferably 40 parts by mass, and further preferably 30 parts by mass with respect to 100 parts by mass of PVA (B).

[0058] There is no particular limitation on the temperature of the above heat treatment. As the lower limit of the heat treatment temperature, 80°C is preferable, 100°C is more preferable, 120°C is further preferable, 130°C is even more preferable, and 150°C is particularly preferable. As the upper limit of the heat treatment temperature, 240°C is preferable, 230°C is more preferable, 220°C is further preferable, and 210°C is even more preferable. At this time, it is preferable to mix PVA(B) alone or, in the case where PVA(A) has a sulfonic acid group or a salt thereof in its side chain, PVA(B) and an aldehyde having a sulfonic acid group or a salt thereof in a molten state. When the heat treatment temperature is less than the above lower limit, the reaction may not proceed sufficiently, and it may not be possible to produce PVA(A) that satisfies the block character of the present disclosure. When the heat treatment temperature exceeds the above upper limit, PVA(B) may decompose or a gel may be generated. The "molten state" only needs to be a state in which at least PVA(B) is confirmed to be molten.

[0059] There is no particular limitation on the time for heat treatment with PVA(B) alone or for heat treatment while mixing PVA(B) and an aldehyde having a sulfonic acid group or a salt thereof. As the lower limit of the heat treatment time, 1 minute is preferable, 3 minutes is more preferable, and 4 minutes is further preferable. As the upper limit of the heat treatment time, 3 hours is preferable, 2 hours is more preferable, 1 hour is further preferable, and 30 minutes is even more preferable. When the heat treatment time is less than the above lower limit, the reaction may not proceed sufficiently. When the heat treatment time exceeds the above upper limit, PVA(B) may decompose or a gel may be generated.

[0060] In the case where PVA(A) has a sulfonic acid group or a salt thereof in its side chain, there is no particular limitation on the method of mixing PVA(B) and an aldehyde having a sulfonic acid group or a salt thereof. For example, after dry blending using a ribbon blender, Henschel mixer, V blender, etc., known mixing devices or kneading devices such as a kneader extruder, single-screw or twin-screw extruder, mixing roll, Banbury mixer, etc. can be used. Among them, a method of mixing in a molten state using a single-screw or twin-screw extruder having sufficient kneading power is preferable.

[0061] In the step of mixing the above-mentioned PVA(B) and an aldehyde having a sulfonic acid group or a salt thereof, it is preferable to carry out the mixing substantially in the absence of a solvent. In this case, for example, a method of mixing a powder composed of PVA(B) and a powder composed of an aldehyde having a sulfonic acid group or a salt thereof in the above-mentioned heat treatment step is preferable. At this time, depending on the heat treatment temperature (the temperature at the time of mixing), the powder composed of PVA(B) and the powder composed of an aldehyde having a sulfonic acid group or a salt thereof may be mixed in a powder state or in a molten state. From the viewpoint of improving reactivity, it is preferable to mix in a molten state. According to the production method of the present disclosure, since mixing can be carried out substantially in the absence of a solvent, a drying step such as solvent removal is unnecessary, and PVA(A) can be produced more easily. "Substantially in the absence of a solvent" means that no solvent is intentionally added to the mixture of PVA(B) and an aldehyde having a sulfonic acid group or a salt thereof.

[0062] In the step of mixing the above-mentioned PVA(B) and an aldehyde having a sulfonic acid group or a salt thereof, it is preferable to substantially not use a catalyst. Usually, in an acetalization reaction carried out in a solution, an acid catalyst such as an inorganic acid such as sulfuric acid, hydrochloric acid, phosphoric acid or an ammonium salt thereof is used to advantageously carry out the reaction, and it is added so that the pH of the reaction system becomes 5 or less. Therefore, after the reaction is completed, a step of neutralizing with an alkaline substance is required as necessary. According to the production method of the present disclosure, acetalization can proceed without substantially using a catalyst, so a neutralization step or the like is unnecessary, and PVA(A) can be produced more easily. "Substantially not using a catalyst" means that no catalyst is intentionally added in the heat treatment step.

[0063] In the production of PVA(A), the block character of PVA(A) increases compared to that of PVA(B) by undergoing the above heat treatment step. The lower limit of the difference between the block character of the residual vinyl ester units in PVA(B) and the block character of the residual vinyl ester units in PVA(A) is preferably 0.05, more preferably 0.08, and even more preferably 0.1. The upper limit of the difference in the above block character is preferably 0.4, more preferably 0.35, and even more preferably 0.3. By setting the difference in the block character of the residual vinyl ester units within the above range, a composition with further improved water solubility can be obtained compared to the raw material vinyl alcohol-based polymer.

[0064] <Method for producing the composition> The composition can be produced, for example, by mixing PVA(A) and a plasticizer.

[0065] The timing of mixing PVA(A) and the plasticizer is not particularly limited in the production process of the composition. For example, the plasticizer may be mixed with PVA(B) in advance and then the above heat treatment step may be performed, or the plasticizer may be mixed with PVA during the above heat treatment step, or the plasticizer may be added to and mixed with PVA(A) after the heat treatment step. The plasticizer may be added all at once or added in portions.

[0066] When using two or more types of plasticizers, they may be mixed with PVA(A) or PVA(B) as a blend in which the plasticizers are pre-mixed with each other, or each plasticizer may be separately added to and mixed with PVA(A) or PVA(B), or each plasticizer may be added at different times in the production process of the composition.

[0067] The composition may be, for example, an aqueous solution composition in which PVA(A) and a plasticizer are dissolved in water, or a composition in which the plasticizer is sprinkled and added to solid PVA(A), or a composition obtained by melt-kneading PVA(A) and a plasticizer.

[0068] <Plasticizer> Examples of the plasticizer include polyhydric alcohols such as glycerin, diglycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, pentaerythritol, sorbitol, 1,3 - butanediol, 2 - methyl - 1,3 - propanediol; polyethers such as polyethylene glycol and polypropylene glycol; polyvinylamides such as polyvinylpyrrolidone; amide compounds such as N - methylpyrrolidone and dimethylacetamide; compounds obtained by adding ethylene oxide or propylene oxide to the above polyhydric alcohols, etc. Among these, from the viewpoints of water solubility, chemical resistance, strength and processability of the film containing the composition, a plasticizer obtained by combining two or more polyhydric alcohols is preferable, a plasticizer obtained by combining sorbitol and at least one of the above polyhydric alcohols is more preferable, and a plasticizer obtained by combining sorbitol and one of the above polyhydric alcohols is even more preferable. From the viewpoint of achieving both chemical resistance and film strength, a plasticizer containing glycerin and sorbitol is preferable, and a plasticizer consisting only of glycerin and sorbitol is more preferable. Among polyhydric alcohols, by combining glycerin and sorbitol, the balance between water solubility and chemical resistance can be further improved.

[0069] As the lower limit of the content of the plasticizer in the composition, 0.1 part by mass is preferable, 1 part by mass is more preferable, and 2 parts by mass is even more preferable with respect to 100 parts by mass of PVA(A). As the upper limit of the above content, 30 parts by mass is preferable, 20 parts by mass is more preferable, and 10 parts by mass is even more preferable with respect to 100 parts by mass of PVA(A). The content of the plasticizer is preferably 0.1 part by mass or more and 30 parts by mass or less, more preferably 0.1 part by mass or more and less than 10 parts by mass, even more preferably 1 part by mass or more and less than 5 parts by mass, and even more preferably 2 parts by mass or more and less than 3 parts by mass with respect to 100 parts by mass of PVA(A). When the plasticizer is a combination of two or more kinds, it is preferable that the total content of the plasticizer is within the above range.

[0070] When using a plasticizer containing glycerin and sorbitol, it is preferable that the total content of glycerin and sorbitol is within the above range. The content of glycerin is preferably 1 to 15 parts by mass, and the content of sorbitol is more preferably 1 to 15 parts by mass. It is even more preferable that the content of glycerin is more than 1 part by mass and less than 10 parts by mass, and the content of sorbitol is more than 1 part by mass and less than 10 parts by mass. It is still more preferably that the content of glycerin is 2 to 5 parts by mass, and the content of sorbitol is 2 to 5 parts by mass. It is particularly preferable that the content of glycerin is 2 to less than 3 parts by mass, and the content of sorbitol is 2 to less than 3 parts by mass. When the content of the plasticizer is within the above range, the water solubility and chemical resistance of the composition and films containing the same can be further improved. Note that the above contents of glycerin and sorbitol are values relative to 100 parts by mass of PVA(A).

[0071] In addition to the effects of the above plasticizer, when the block character of PVA(A) is within a specific range, a composition excellent in water solubility, chemical resistance, and film strength can be obtained. The reason for this is not necessarily clear, but when packaging chemicals with high oxidizing power, the lower the block character, that is, the more locally the ester residues are present, the ester residue oxidation reaction, which is a cause of the oxidative degradation of PVA, may proceed chain-reactionally. Since the ester residues are dispersed due to the block character being within a specific range, the progress of the oxidation reaction can be slowed down, which is presumed to contribute to the improvement of chemical resistance.

[0072] Furthermore, when the block character is within a specific range, it is presumed that the functional groups of PVA(A) (hydroxy groups when PVA(A) is unmodified) are arranged more randomly, improving water solubility, and the synergistic effect with the plasticizer contained in the composition improves chemical resistance and film strength.

[0073] In one embodiment of the present disclosure, from the viewpoint of improving both chemical resistance and film strength, it is preferable to use glycerin and sorbitol in combination as plasticizers. The reason for this is not clear, but in a composition containing PVA (A) with a block character of 0.55 or more and 1 or less, glycerin contributes to the balance between water solubility and film strength, and it is presumed that sorbitol suppresses the migration of glycerin in the film to the chemical which is the content of the package and the resulting decrease in film strength. Furthermore, by setting the content of the plasticizer within the above range, it is possible to further improve the balance of water solubility, chemical resistance, and film strength.

[0074] The composition may contain an antioxidant. Examples of the antioxidant include hydroxycarboxylic acids such as citric acid, tartaric acid, L - ascorbic acid, malic acid, and salts thereof (sulfites, bisulfites, thiosulfates, nitrites), gallic acid and its salts, and esters of gallic acid such as methyl, ethyl, propyl, and isoamyl gallates.

[0075] As the lower limit of the content of the antioxidant in the composition, 0.3 parts by mass is preferable, 0.5 parts by mass is more preferable, and 1 part by mass is even more preferable with respect to 100 parts by mass of PVA (A). As the upper limit of the content, 5 parts by mass is preferable, 3 parts by mass is more preferable, and 2 parts by mass is even more preferable with respect to 100 parts by mass of PVA (A). When the addition amount of the antioxidant is within the above range, the chemical resistance of the composition, films containing the same, etc. is further improved.

[0076] <Film> The film contains the above - mentioned composition. The film is a water - soluble film. Note that the water - soluble film in the present disclosure may be a film with a size of 40 mm × 40 mm and an average film thickness of 40 μm that can completely dissolve in 1 liter of water at 20°C.

[0077] In the production of the film, in the production raw materials, saccharides, inorganic fillers and other components may be blended with the above-described composition as necessary within a range that does not impair the effects of the present disclosure. These components may be mixed and prepared by known methods such as a method of dissolving or dispersing them in a solvent in a stirring tank, a method of melt-kneading them in an extruder, or the like.

[0078] The method for producing the film is not particularly limited, and it can be produced by known methods such as a casting method or a melt extrusion method.

[0079] In the case of the casting method, for example, the above-described composition and, if necessary, various additives (for example, surfactants, saccharides) are dissolved in an aqueous solvent (for example, water), and the resulting solution is allowed to stand on a smooth casting surface. After the aqueous solvent has evaporated, when it is peeled off from the casting surface, a transparent and uniform water-soluble film can be obtained. Water is preferred as the aqueous solvent. The casting surface is not particularly limited as long as it is a smooth and hard material such as steel, aluminum, glass, polymers (for example, polyolefins, polyethylene, polyamides, polyvinyl chloride, polycarbonates, polyhalocarbons, etc.). The evaporation rate of the aqueous solvent can be increased by methods such as heating the casting surface or exposing the deposited solution to heated air, infrared rays, or the like.

[0080] In the case of the melt extrusion method, for example, a plasticizer may be sprinkled on the powdery PVA(A) at a stage before introducing PVA(A) into the extruder, or a plasticizer may be added when introducing PVA(A) into the extruder.

[0081] The lower limit of the average film thickness of the film is preferably 10 μm, more preferably 20 μm, and even more preferably 30 μm. On the other hand, the upper limit of the average film thickness is preferably 200 μm, more preferably 150 μm, and even more preferably 120 μm. By setting the average film thickness within the above range, a film with a better balance of film strength (film strength), water solubility, and chemical resistance can be obtained.

[0082] <Package> The package is a package that contains a drug with the above-described composition or the above-described film.

[0083] The method for manufacturing the package is not particularly limited, and it can be manufactured by any known suitable method. For example, the above-described composition may be formed into a molded body having a shape capable of supporting a drug, such as a capsule shape, to accommodate the drug, and the package may be manufactured. Further, for example, two sheets of the film may be overlapped, sealed leaving a portion to be an inlet for the drug, the drug may be accommodated through the inlet, and then the inlet may be sealed to manufacture the package.

[0084] The package is excellent in chemical resistance, and the drug to be accommodated is not particularly limited. For example, various drugs such as agricultural chemicals, bactericides, detergents such as laundry detergents, bleaching agents, toiletries, and industrial chemicals can be preferably used. In particular, since the package is excellent in chemical resistance even when it contains a substance with a high oxidizing power, it can also be preferably used as a package for accommodating a substance with a high oxidizing power as a drug. Examples of the substance with a high oxidizing power include oxidizing agents composed of sodium carbonate, sodium hypochlorite, calcium hypochlorite, lithium hypochlorite, dichloroisocyanuric acid, trichloroisocyanuric acid, trichloroisocyanurate, salts and hydrates thereof, 1,3-dibromo-5,5-dimethylhydantoin, 2,2-dibromo-3-nitrilopropionamide, dibromocyanacetamide, 1-bromo-3-chloro-5,5-dimethylhydantoin, 2-bromo-2-nitro-1,3-propanediol, and combinations thereof.

Example

[0085] Hereinafter, the present disclosure will be described more specifically using examples. In the following, "parts" and "%" mean mass basis unless otherwise specified.

[0086] [Viscosity of 4 mass% aqueous solution of PVA] The viscosity of the 4 mass% aqueous solution of PVA was measured using a B-type viscometer BLII (manufactured by Toki Sangyo Co., Ltd.) under the conditions of a rotor rotation speed of 60 rpm and a temperature of 20°C.

[0087] [Degree of saponification of PVA] The degree of saponification of PVA was determined by the method described in JIS-K6726-1994.

[0088] [Amount of modification of sulfonic acid group or its salt in PVA(A)] The amount of modification of sulfonic acid group or its salt in PVA(A) was determined according to the method using the above-mentioned 1 1H-NMR.

[0089] [Block character of residual vinyl ester unit of PVA] The block character of the residual vinyl ester unit of PVA was determined from the integral values of the peaks by analyzing three peaks related to the dyad structure of two units appearing in the methylene region for a sample in which PVA was dissolved in a mixed solvent of heavy water / heavy methanol at a measurement temperature of 70°C and an integration number of 18,000 times. The above three peaks correspond to the methylene carbon sandwiched between the carbon atom of the main chain bonded to the residual ester group (-O-C(=O)-Q (Q has the same meaning as above)) and the carbon atom of the main chain bonded to the hydroxy group; the methylene carbon sandwiched between the carbon atom of the main chain bonded to the residual ester group and the carbon atom of the main chain bonded to the residual ester group adjacent to this carbon atom; and the methylene carbon sandwiched between the carbon atom of the main chain bonded to the hydroxy group and the carbon atom of the main chain bonded to the hydroxy group adjacent to this carbon atom. The measuring method and calculation method are described in "Poval" (published by Kobunshi Kankokai, 1984, pages 246-249) and Macromolecules, 10, 532 (1977). 13 13C-NMR measurement was carried out, and it was determined from the integral values of the peaks by analyzing three peaks related to the dyad structure of two units appearing in the methylene region. The above three peaks correspond to the methylene carbon sandwiched between the carbon atom of the main chain bonded to the residual ester group (-O-C(=O)-Q (Q has the same meaning as above)) and the carbon atom of the main chain bonded to the hydroxy group; the methylene carbon sandwiched between the carbon atom of the main chain bonded to the residual ester group and the carbon atom of the main chain bonded to the residual ester group adjacent to this carbon atom; and the methylene carbon sandwiched between the carbon atom of the main chain bonded to the hydroxy group and the carbon atom of the main chain bonded to the hydroxy group adjacent to this carbon atom. The measuring method and calculation method are described in "Poval" (published by Kobunshi Kankokai, 1984, pages 246-249) and Macromolecules, 10, 532 (1977).

[0090] [Production Example 1] (Production of PVA2) As the raw material PVA, PVA (B) (hereinafter referred to as "PVA1") with an aqueous solution viscosity of 8.0 mPa·s at 4 mass%, a saponification degree of 88 mol%, and a block character of 0.52 for the residual vinyl ester unit, which was obtained by saponifying a vinyl ester polymer using an alkali catalyst, was used. After melt-kneading (heat treatment) PVA1 under the following conditions and then cooling, non-modified PVA (A) (hereinafter referred to as "PVA2") was obtained. The 4 mass% aqueous solution viscosity of the obtained PVA2 was 7.4 mPa·s, the saponification degree was 88 mol%, and the block character of the residual vinyl ester unit was 0.68.

[0091] <Melt-kneading conditions> Apparatus: "Laboplast Mill 4C150" manufactured by Toyo Seiki Seisakusho, Ltd. Jacket temperature during kneading: 180 °C Kneading time: 5 minutes

[0092] [Production Example 2] (Production of PVA3) 100 parts by mass of PVA1 as PVA (B) and 21.2 parts by mass of sodium 2-benzaldehydesulfonate as an aldehyde having a sulfonic acid group or its salt were dry-blended to obtain a mixture. The obtained mixture was melt-kneaded (heat treated) under the same conditions as in Production Example 1 and then cooled to obtain pellets of PVA (A) (hereinafter referred to as "PVA3") in which a sulfonate (salt of a sulfonic acid group) was introduced into the side chain. The 4 mass% aqueous solution viscosity of the obtained PVA3 was 7.5 mPa·s, the saponification degree was 88 mol%, the modification amount of the sulfonate was 2 mol%, and the block character of the residual vinyl ester unit was 0.65.

[0093] [Production Examples 3 and 4] (Production of PVA4 and 5) PVA (A) (hereinafter referred to as "PVA4" and "PVA5") in which a sulfonate (salt of a sulfonic acid group) was introduced into the side chain was obtained in the same manner as in Production Example 2, except that the type of PVA (B) used, the type and amount of the aldehyde having a sulfonic acid group or its salt as the modification species, and the melt-kneading conditions were changed as shown in Table 1 below.

[0094] [Production Example 5] (Production of PVA6) Using 100 parts by mass of PVA1 as PVA(B), an aqueous solution with a concentration of 10% by mass was prepared. While maintaining the temperature of the aqueous solution at 50 °C, 5.3 parts by mass of sodium 2-benzaldehydesulfonate was added and stirred well. Then, 1.0 N hydrochloric acid was added to adjust the pH of the aqueous solution to 2.0. After maintaining this state for 6 hours to allow the reaction to proceed, sodium hydroxide was added for neutralization. The resulting reaction product was purified to obtain PVA(A) (hereinafter referred to as "PVA6") with a sulfonate (salt of sulfonic acid group) introduced into the side chain. The viscosity of a 4% by mass aqueous solution of PVA6 was 8.0 mPa·s, the saponification degree was 92 mol%, the modification amount of the sulfonic acid group or its salt was 0.5 mol%, and the block character of the residual vinyl ester unit was 0.52.

[0095] [Production Example 6] (Production of PVA8) As PVA(B), PVA(B) (hereinafter referred to as "PVA7") with a viscosity of 5.0 mPa·s in a 4% by mass aqueous solution, a saponification degree of 74 mol%, and a block character of 0.43 for the residual vinyl ester unit, which was obtained by saponifying a vinyl ester polymer using an alkali catalyst, was used. PVA7 was melt-kneaded (heat-treated) in the same manner as in Production Example 1 and then cooled to obtain unmodified PVA(A) (hereinafter referred to as "PVA8").

[0096] [Production Examples 7 to 9] (Production of PVA9 to PVA11) Except that the type of PVA(B) used, the type and amount of the aldehyde having a sulfonic acid group or its salt as the modification species, and the melt-kneading conditions were changed as shown in Table 1 below, in the same manner as in Production Example 2, PVA(A) (hereinafter referred to as "PVA9", "PVA10", and "PVA11") with a sulfonate (salt of sulfonic acid group) introduced into the side chain were obtained respectively.

[0097] [Production Example 10] As PVA(B), PVA(B) (hereinafter referred to as "PVA12") having a 4% by mass aqueous solution viscosity of 22.0 mPa·s, a saponification degree of 88 mol%, and a block character of residual vinyl ester units of 0.50 was used. An attempt was made to produce PVA(A) under the conditions shown in Table 1 below using 100 parts by mass of PVA12. However, since the 4% by mass aqueous solution viscosity of PVA(B) exceeded 20 mPa·s, it gelled during melt-kneading, and PVA(A) could not be obtained.

[0098]

Table 1

[0099] [Example 1] (Preparation of Composition) 95 parts of PVA2 as PVA(A), 2.5 parts of glycerin (2.6 parts per 100 parts by mass of PVA2) and 2.5 parts of sorbitol (2.6 parts per 100 parts by mass of PVA2) as plasticizers were added to water to prepare a 10% by mass aqueous solution of the composition.

[0100] (Preparation of Film) Using the aqueous solution of the above composition, a film was prepared under the conditions described in the section of the following "Method for Evaluating Improvement in Water Solubility", and the degree of improvement in water solubility of the obtained film was evaluated. Separately, using the aqueous solution of the above composition, a film was prepared under the conditions described in the section of the following "Method for Evaluating Chemical Resistance 1", and the chemical resistance of the obtained film was evaluated. The results are shown in Table 2 below.

[0101] [Example 2, Comparative Examples 1 and 2] A composition was prepared in the same manner as in Example 1 except that the PVA shown in Table 2 below was used instead of PVA2. Then, a film was prepared, and the degree of improvement in water solubility and the chemical resistance of the obtained film were evaluated. The results are shown in Table 2 below.

[0102] [Method for Evaluating Improvement in Water Solubility] An aqueous solution of the obtained composition was cast and dried at 20 °C to obtain a film with an average film thickness of 76 μm. This film was cut into a 40 mm × 40 mm square and sandwiched in a slide mount. Separately, a 1-liter glass beaker filled with 1 liter of distilled water was placed in a thermostatic bath adjusted to 20 °C, and stirring was carried out at 250 rpm using a 5 cm rotor. After the distilled water in the beaker reached 20 °C, the above slide mount was immersed in the stirred cold water to start the measurement of water solubility. At this time, the dissolution state of the film was visually observed, and the dissolution time δ (seconds) until the film of PVA(A) was completely dissolved was measured. Separately, a film with an average film thickness of 76 μm of PVA(B), which is the raw material of each PVA(A), was also prepared in the same manner, and the dissolution time γ (seconds) until the film was completely dissolved was measured for the obtained PVA(B) film in the same manner. The difference between the dissolution time γ (seconds) of the raw material PVA(B) and the dissolution time δ (seconds) of PVA(A) was taken, and the degree to which the dissolution time of PVA(A) was shortened with respect to the raw material PVA(B) was used as the value of water solubility improvement. The larger the value, the better the water solubility improvement.

[0103] [Evaluation Method of Chemical Resistance 1] An aqueous solution of the obtained composition was cast and dried at 20 °C to obtain a film with an average film thickness of 40 μm. This film was cut into a 50 mm × 50 mm square, and two pieces of this film were heat-sealed on three sides so that the four corners overlapped, 10 g of sodium carbonate was put inside, and the inlet was heat-sealed to produce a package. This package was stored under the conditions of 20 °C and 65% RH for 30 days. After storage, a 40 mm × 40 mm square film piece was cut out from the package, sandwiched in a slide mount, and the dissolution time (seconds) until the film was completely dissolved was measured in the same manner as the above [Water Solubility Improvement Evaluation Method] to evaluate Chemical Resistance 1. The shorter the dissolution time, the better the chemical resistance. In Table 2 below, ">180" means that most of the film was undissolved at the time when 180 seconds had passed.

[0104]

Table 2

[0105] From the results in Table 2, it can be seen that the films prepared using the composition (Examples 1 and 2) containing PVA (A) with a block character of the residual vinyl ester unit being 0.55 or more and 1 or less and a plasticizer have improved water solubility and significantly superior chemical resistance compared to the films prepared using PVA (B) (Comparative Examples 1 and 2) with a block character of less than 0.55.

[0106] [Example 3] (Preparation of composition) 95 parts of PVA3 as PVA (A), 2.5 parts of glycerin (2.6 parts based on 100 parts by mass of PVA2) and 2.5 parts of sorbitol (2.6 parts based on 100 parts by mass of PVA2) as plasticizers were added to water to prepare a 10% by mass aqueous solution of the composition.

[0107] (Preparation of film) Using the aqueous solution of the above composition, a film was prepared under the conditions described in the section of the above "Method for evaluating improvement in water solubility", and the water solubility improvement of the obtained film was evaluated. Separately, using the aqueous solution of the above composition, a film was prepared under the conditions described in the section of the following "Method for evaluating chemical resistance 2", and the chemical resistance of the obtained film was evaluated. The results are shown in Table 3 below.

[0108] [Examples 4 to 9, Comparative Example 3] A composition was prepared in the same manner as in Example 3 except that the PVA and plasticizers shown in Table 3 below were used instead of PVA3. Then, a film was prepared, and the degree of improvement in water solubility and chemical resistance of the obtained film were evaluated. The results are shown in Table 3 below.

[0109] [Method for evaluating chemical resistance 2] An aqueous solution of the obtained composition was cast and dried at 20°C to obtain a film with an average film thickness of 40 μm. This film was cut into a 50 mm × 50 mm square, and two pieces of this film were heat-sealed on three sides so that the four corners overlapped. 10 g of trichloroisocyanuric acid was put inside, and the inlet was heat-sealed to produce a package. This package was stored under the conditions of 20°C and 65% RH for 30 days. After storage, a 40 mm × 40 mm square film piece was cut out from the package, sandwiched between slide mounts, and the dissolution time (seconds) until the film was completely dissolved was measured by the same method as the above [Water Solubility Improvement Evaluation Method] to evaluate Chemical Resistance 2. The shorter the dissolution time, the better the chemical resistance. In Table 3 below, ">180" means that most of the film was undissolved at the time point of 180 seconds.

[0110] [Table 3]

[0111] From the results of Examples 3 to 9 in Table 3, it can be seen that a film prepared using a composition containing PVA (A) having a sulfonic acid group or its salt in its side chain and a block character of 0.55 or more and 1 or less and a plasticizer shows a significant improvement in water solubility compared to the film prepared using the raw material PVA (B), and also shows significantly excellent chemical resistance against trichloroisocyanuric acid with higher oxidizing power. On the other hand, a film prepared using PVA6 having a sulfonic acid group or its salt in its side chain but a block character of less than 0.55 (Comparative Example 3) shows an improvement in water solubility compared to the film prepared using the raw material PVA (B), but the degree is smaller compared to Examples 3 to 9, and in the chemical resistance evaluation, most of the film was undissolved at the time point of 180 seconds, indicating poor chemical resistance.

[0112] [Examples 10 to 16] A composition was prepared in the same manner as in Example 3 except that the PVA and plasticizer shown in Table 4 below were used. After that, a film was produced, and the degree of improvement in water solubility and the chemical resistance evaluation of the obtained film were carried out. The results are shown in Table 4 below.

[0113]

Table 4

[0114] In the results of Examples 10 to 16 in Table 4, the effects of improved water solubility and chemical resistance were observed in all cases. Here, from the viewpoint of the balance between improved water solubility and chemical resistance, it can be said that Example 3 is more excellent than Examples 10 to 13 and 16, and it can be seen that a combination of glycerin and sorbitol is preferable as the plasticizer. Also, from the same viewpoint, it can be said that Example 3 is more excellent than Examples 14 and 15, and it can be seen that it is preferable that the content of glycerin in the plasticizer is 2 parts by mass or more and 5 parts by mass or less, and the content of sorbitol is 2 parts by mass or more and 5 parts by mass or less.

Industrial Applicability

[0115] Since the composition is excellent in water solubility and chemical resistance, the water-soluble film made from the composition has little deterioration in water solubility even when it comes into contact with a chemical having a high oxidizing power, and the composition can be suitably used for a wide range of applications such as unit packaging of chemicals.

Claims

1. A composition containing a vinyl alcohol polymer (A) and a plasticizer, wherein the block character of the residual vinyl ester units of the vinyl alcohol polymer (A) is 0.55 or more and 1 or less, the plasticizer contains glycerin and sorbitol, the total content of the plasticizer relative to 100 parts by mass of the vinyl alcohol polymer (A) is 4 parts by mass or more and less than 10 parts by mass, the content of glycerin relative to 100 parts by mass of the vinyl alcohol polymer (A) is 2 parts by mass or more and 5 parts by mass or less, the content of sorbitol relative to 100 parts by mass of the vinyl alcohol polymer (A) is 2 parts by mass or more and 5 parts by mass or less, the vinyl alcohol polymer (A) has a sulfonic acid group or a salt thereof in the side chain, and the modification amount of the sulfonic acid group or a salt thereof in the vinyl alcohol polymer (A) is 2 mol% or more and 10 mol% or less.

2. The composition according to claim 1, wherein the viscosity of a 4% by mass aqueous solution of the vinyl alcohol polymer (A) at 20 °C is 2 mPa·s or more and 20 mPa·s or less.

3. The composition according to claim 1 or claim 2, wherein the saponification degree of the vinyl alcohol polymer (A) is 60 mol% or more and 99 mol% or less.

4. The composition according to any one of claims 1 to 3, further containing an antioxidant.

5. A film containing the composition according to any one of claims 1 to 4.

6. A package containing the chemical substance and formed by using the composition according to any one of claims 1 to 4 or the film according to claim 5.

7. The package according to claim 6, wherein the chemical substance is a pesticide, a bactericide or a detergent.

Images