Molded body, film, masking material, water-soluble transfer coating material for forming coating material layer having uneven structure, support material for molding, and method for using molded body

Abstract

Provided is a molded body which is molded from a composition containing a modified poly(vinyl alcohol)-based polymer having a vinyl alcohol structural unit and a structural unit represented by formula (1). If the mass of the molded body after being heat treated for 10 minutes at 200°C is denoted by M1 (parts by mass) and the mass of the heat-treated molded body after being immersed for 16 hours in a quantity of water which corresponds to 500 times the mass M1 and which is 10°C and then vacuum dried for 16 hours at 40ºC and 10 Pa is denoted by M2 (parts by mass), then the elution rate, as defined by [1-(M2 / M1)]×100 (mass%), is 90 mass% or more.

Description

Molded body, film, masking material, water-soluble transfer coating material for forming a coating material layer having a concave-convex structure, modeling support material, and method of using the molded body

[0001] The present invention relates to a molded article, a film, a masking material, a water-soluble transfer coating material for forming a coating material layer having a textured structure, a support material for modeling, and a method for using the molded article.

[0002] Vinyl alcohol polymers are one of the few crystalline, water-soluble polymers. Taking advantage of their excellent water solubility and film properties (strength, oil resistance, film-forming ability, oxygen gas barrier property, etc.), vinyl alcohol polymers are widely used in emulsifiers, suspending agents, surfactants, fiber processing agents, various binders, paper processing agents, adhesives, films, etc.

[0003] In recent years, vinyl alcohol-based polymers have been used as protective films or laminated films composed of the film and a substrate, for example, in the processing of products or the manufacturing process of functional components, etc., to temporarily protect the products or functional components during processing. For example, vinyl alcohol-based polymers are sometimes used as surface protection films for metals or glass during transport or processing, surface protection films for resin molded products, masking materials, or water-soluble transfer sheets for transferring textured structures. In these cases, films formed from vinyl alcohol-based polymers may be subjected to thermal history in processes after being attached to products, etc. However, the water solubility of the vinyl alcohol-based polymers constituting the films decreases when subjected to thermal history, and they may not be sufficiently peeled or removed even when contacted with water or hot water after a predetermined process is performed. For this reason, films formed from vinyl alcohol-based polymers may be required to be easily peeled or completely removed with water or hot water after thermal history, to the extent that the performance of the products, functional components, etc. is not impaired.

[0004] Patent Document 1 discloses a film obtained from a resin composition containing PVA (A) obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester compound, a polybasic acid or an alkali metal salt thereof (B), and a hydrazine compound (C).

[0005] Japanese Patent Application Laid-Open No. 2003-171521

[0006] However, the film of Patent Document 1 has a problem in that it is not sufficiently water-soluble in low-temperature water after heat treatment.

[0007] An object of the present invention is to provide a molded body formed from a composition containing a modified polyvinyl alcohol-based polymer, which can maintain its water solubility before heat treatment even after heat treatment; a film formed from a composition containing the modified polyvinyl alcohol-based polymer; a masking material formed from the molded body; a water-soluble transfer coating material for forming a coating material layer having a concave-convex structure, which includes the molded body; a support material for modeling, which includes the molded body; and a method for using the molded body.

[0008] As a result of extensive investigations, the present inventors have discovered a molded article formed from a composition containing a modified polyvinyl alcohol-based polymer having a vinyl alcohol structural unit and a structural unit represented by the following formula (1), The inventors have found that a molded product having an elution rate defined as [1-(M2 / M1)]×100 (mass%) of 90 mass% or more can maintain its water solubility before heat treatment even after heat treatment, where M1 (parts by mass) is the mass of the molded product after heat treatment at 200°C for 10 minutes, and M2 (parts by mass) is the mass of the molded product after immersion treatment for 16 hours in 10°C water having 500 parts by mass of M1 and vacuum drying for 16 hours at 40°C and 10 Pa. More specifically, the inventors have found that a molded product having an elution rate defined as [1-(M2 / M1)]×100 (mass%) of 90 mass% or more can maintain its water solubility before heat treatment even after heat treatment, and have completed the present invention. More specifically, allyl monomers usually have a reactivity ratio with vinyl acetate (r ＶＡｃ ) and the reactivity ratio of the comonomer (r ＣＯＭ) are roughly the same value, and the charge ratio of vinyl acetate to the allyl type monomer is often the same as the composition ratio of vinyl acetate to the allyl type monomer in the polymer. However, although 2-methylene-1,3-propanediol diacetate (MPDAc) is an allyl type monomer, the reactivity ratio with vinyl acetate (r ＶＡｃ ) and the reactivity ratio of the comonomer (r ＣＯＭ ) are significantly different, so when MPDAc and vinyl acetate are polymerized by the "bulk addition method," the resulting polymer will have different compositional ratios of MPDAc structural units and vinyl acetate structural units in the portion formed at the beginning of the polymerization and the portion formed at the end of the polymerization. The present inventors have discovered that by adding 2-methylene-1,3-propanediol diacetate (MPDAc) to vinyl acetate using the "dropping polymerization method" rather than the "bulk addition method," it is possible for the first time to adjust the compositional ratio of vinyl acetate to 2-methylene-1,3-propanediol diacetate (MPDAc) in the polymer to a desired value, and have completed the present invention.

[0009] That is, the present invention is as follows: [1] A molded article formed from a composition containing a modified polyvinyl alcohol-based polymer having a vinyl alcohol structural unit and a structural unit represented by the following formula (1), A molded product having an elution rate defined by [1-(M2 / M1)] x 100 (% by mass) of 90% by mass or more, where M1 (parts by mass) is the mass of the molded product after heat-treating the molded product at 200°C for 10 minutes, and M2 (parts by mass) is the mass of the molded product after immersing the heat-treated molded product in 10°C water having an amount 500 times the mass of M1 for 16 hours and vacuum-drying the molded product at 40°C and 10 Pa for 16 hours. [2] The molded product according to [1] above, wherein the content of the structural unit represented by formula (1) is 0.1 to 40 mol% relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer. [3] The molded product according to [1] above, wherein the content of the structural unit represented by formula (1) is 0.8 to 10 mol% relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer. [4] The molded article according to any one of [1] to [3] above, wherein the modified polyvinyl alcohol-based polymer has a degree of saponification of 80.0 to 99.9 mol%. [5] The molded article according to any one of [1] to [4] above, wherein the distribution of the modification rate of the structural unit represented by formula (1) relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer is 0.5 mol% or less. [6] A film formed from a composition containing the modified polyvinyl alcohol-based polymer according to any one of [1] to [5] above. [7] The film according to [6] above, wherein the film has a thickness of 1 to 1000 μm. [8] A masking material formed from the molded article according to any one of [1] to [5] above. [9] A water-soluble transfer coating material for forming a coating material layer having a concavo-convex structure, comprising the molded article according to any one of [1] to [5] above.

[10] A support material for modeling, comprising the molded article according to any one of [1] to [5] above.

[11] A method for using the molded article according to any one of [1] to [5] above, wherein a molded article formed from a composition containing the modified polyvinyl alcohol-based polymer is heat-treated at a temperature higher than 100°C and not higher than 330°C, and then dissolved in water at 0 to 70°C.

[0010] According to the present invention, it is possible to provide a molded body formed from a composition containing a modified polyvinyl alcohol-based polymer, which can maintain its water solubility before heat treatment even after heat treatment; a film formed from a composition containing the modified polyvinyl alcohol-based polymer; a masking material formed from the molded body; a water-soluble transfer coating material for forming a coating material layer having a concave-convex structure, which includes the molded body; a support material for modeling, which includes the molded body; and a method for using the molded body.

[0011] An example of an embodiment of the present invention will be described below. However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the following description. In this specification, preferred embodiments are shown, but a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters indicated as numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. In this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less." In this specification, "structural unit" means "a repeating unit constituting a polymer." In this specification, "room temperature" means 20 to 25°C. In this specification, "degree of polymerization" means the number-average degree of polymerization measured by size exclusion chromatography (SEC).

[0012] [Molded Article] The molded article of the present invention is a molded article formed from a composition containing a modified polyvinyl alcohol-based polymer having a vinyl alcohol structural unit and a structural unit represented by the following formula (1): The present invention is characterized in that the elution rate, defined as [1-(M2 / M1)] x 100 (% by mass), is 90% by mass or more, where M1 (parts by mass) is the mass of the molded body after heat treatment at 200°C for 10 minutes, and M2 (parts by mass) is the mass of the molded body after immersion treatment for 16 hours in 10°C water containing 500 parts by mass of M1 and vacuum drying for 16 hours at 40°C and 10 Pa. The reason why the effects of the present invention are obtained is not clear, but the modified polyvinyl alcohol polymer used in the present invention is nonionically modified, the modified units are randomly introduced, and it has low crystallinity, so that even when heated, the primary structure does not change due to crosslinking or the like, and crystallization does not proceed, and therefore it is presumed that the water solubility before heat treatment can be maintained.

[0013] In the present invention, the elution rate is 90% by mass or more. If the elution rate is less than 90%, for example, defects, failures, or performance degradation due to non-eluted components are likely to occur. The elution rate is preferably 92% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more, and may be 100% by mass.

[0014] <Composition> The composition used in the present invention contains a modified polyvinyl alcohol polymer having a vinyl alcohol structural unit and a structural unit represented by the following formula (1).

[0015] (Modified Polyvinyl Alcohol Polymer) The modified polyvinyl alcohol polymer has a vinyl alcohol structural unit and a structural unit represented by the following formula (1), and may further have other structural units as necessary.

[0016] The arrangement order of the structural unit represented by formula (1), the vinyl alcohol structural unit, and other arbitrary structural units in the modified polyvinyl alcohol polymer is not particularly limited, and may be random, block, alternating, or the like.

[0017] The total of the vinyl alcohol structural units and the structural units represented by formula (1) relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer is not particularly limited, but is preferably 70 mol% or more, more preferably 80 mol% or more, particularly preferably 90 mol% or more, and may be 100 mol%. The total of the vinyl alcohol units and the structural units represented by formula (1) relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer is １ It can be measured by H-NMR.

[0018] <Structural Unit Represented by Formula (1)> The modified polyvinyl alcohol polymer has a structural unit represented by the above formula (1) (i.e., a structure having a 1,3-diol structure in the main chain of the polymer), which reduces the crystallinity of the modified polyvinyl alcohol polymer and improves its handleability, such as solubility and viscosity stability. Furthermore, when the modified polyvinyl alcohol polymer of the present invention is processed into a film, the high hydrogen bonding strength of the 1,3-diol structure can reduce a decrease in film strength due to a decrease in crystallinity, and the film can maintain toughness even under high humidity. Another factor that is presumed to be due to the presence of a quaternary carbon in the modified polyvinyl alcohol polymer is its low molecular mobility, making it less susceptible to crystallization upon heat treatment.

[0019] <<Modification Rate of Structural Unit Represented by Formula (1)>> The modification rate (content) of the structural unit represented by formula (1) relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer is not particularly limited, but from the viewpoint of cold water solubility, it is preferably 0.1 mol% or more, more preferably 0.8 mol% or more, and particularly preferably 2.0 mol% or more, while from the viewpoint of biodegradability, it is preferably 40.0 mol% or less, more preferably 20.0 mol% or less, even more preferably 15.0 mol% or less, even more preferably 10.0 mol% or less, and particularly preferably 9.0 mol% or less. The modification rate of the structural unit represented by formula (1) relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer can be measured by the method used in the examples described later.

[0020] <<Distribution of Modification Rate of Structural Unit Represented by Formula (1)>> The distribution of the modification rate of the structural unit represented by formula (1) relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer is not particularly limited as long as it is 0.5 mol% or less. From the viewpoint of solvent resistance, it is preferably 0.4 mol% or less, more preferably 0.3 mol% or less, even more preferably 0.2 mol% or less, particularly preferably 0.1 mol% or less, and most preferably 0.0 mol%. The distribution of the modification rate of the structural unit represented by formula (1) relative to 100 mol% of all structural units in the modified polyvinyl alcohol-based polymer can be measured by the method used in the examples described below. When the modification rate distribution is 0.5 mol% or less, the amount of components that swell excessively in a solvent is reduced, resulting in a lower overall swelling degree, thereby improving solvent resistance. By adding an "unsaturated monomer convertible to a structural unit represented by formula (1)" such as 2-methylene-1,3-propanediol diacetate (MPDAc), which will be described later, using a "dropping polymerization method" rather than a "bulk addition method," the modification rate distribution can be reduced to 0.5 mol% or less. That is, when polymerization is performed using the "bulk addition method," the resulting modified polyvinyl alcohol-based polymer will contain areas where the ratio of MPDAc structural units to vinyl alcohol structural units is relatively high and areas where it is low, and the low areas will have poor cold water solubility. Therefore, when the modified polyvinyl alcohol-based polymer is immersed in water using the measurement method described in the Examples, the water solubility ratio (modification rate distribution) will decrease. In contrast, when polymerization is performed using the "dropping polymerization method," the variation (distribution) in the ratio of MPDAc structural units to vinyl alcohol structural units will be small throughout the resulting modified polyvinyl alcohol-based polymer, and the areas where this ratio is low and therefore poor cold water solubility will be reduced. Therefore, when the modified polyvinyl alcohol polymer is immersed in water according to the measurement method described in the Examples, the proportion of the polymer dissolved in water (modification rate distribution) is improved.

[0021] <Saponification degree of modified polyvinyl alcohol polymer> The saponification degree of the modified polyvinyl alcohol polymer is not particularly limited, but from the viewpoint of biodegradability, it is preferably 80.0 mol% or more, more preferably 82.0 mol% or more, and particularly preferably 85.0 mol% or more. From the viewpoint of solvent resistance and barrier property, it is preferably 95.0 mol% or more, more preferably 98.0 mol% or more, and particularly preferably 98.5 mol% or more. On the other hand, from the viewpoint of cold water solubility, it is preferably 99.9 mol% or less, more preferably 99.5 mol% or less, and particularly preferably 99.2 mol% or less. The saponification degree of the modified polyvinyl alcohol polymer refers to the number of vinyl alcohol units (-CH ２ The degree of saponification is the ratio (mol %) of the number of moles of vinyl alcohol units to the total number of moles of structural units (typically vinyl ester units) that can be converted to —CH(OH)— and vinyl alcohol units (i.e., the molar fraction of hydroxyl groups to the total of hydroxyl groups and ester bonds in the modified polyvinyl alcohol-based polymer). The degree of saponification is determined by taking into account the amount of the structural unit represented by formula (1) and its derivatives. １ It can be measured by H-NMR, more specifically, by the method used in the examples described below.

[0022] The modified polyvinyl alcohol polymer can be obtained by saponifying a vinyl ester copolymer, and the saponification of the vinyl ester copolymer is carried out, for example, in a state where the vinyl ester copolymer is dissolved in alcohol or aqueous alcohol.

[0023] The alcohol used for saponification is not particularly limited, and examples thereof include lower alcohols such as methanol and ethanol. These may be used alone or in combination of two or more. Among these, methanol is preferred from an economical viewpoint.

[0024] The alcohol used for saponification may contain other solvents such as acetone, methyl acetate, ethyl acetate, benzene, etc., as long as the amount of the other solvents is 40% by mass or less of the mass of the alcohol.

[0025] Examples of catalysts used for saponification include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; alkali catalysts such as sodium methylate; and acid catalysts such as mineral acids. These may be used alone or in combination of two or more. Among these, sodium methoxide is preferred from an economical viewpoint.

[0026] The temperature at which the saponification is carried out is not particularly limited, but is preferably in the range of 20 to 60°C. If a gel-like product precipitates as the saponification proceeds, the product can be pulverized, washed, and dried to obtain a modified polyvinyl alcohol polymer. The saponification method is not limited to the above-mentioned method, and known methods can be used.

[0027] <Degree of polymerization of modified polyvinyl alcohol polymer> The degree of polymerization of the modified polyvinyl alcohol polymer is not particularly limited, but from the viewpoint of film strength, it is preferably 100 or more, more preferably 200 or more, and particularly preferably 300 or more, and from the viewpoint of industrial production, it is preferably 7,000 or less, more preferably 5,000 or less, and particularly preferably 4,000 or less. The degree of polymerization of the modified polyvinyl alcohol polymer can be measured by the method used in the examples described later.

[0028] <Other Structural Units> The modified polyvinyl alcohol-based polymer may further contain structural units other than the structural unit represented by formula (1), the vinyl alcohol unit, and the vinyl ester unit, as long as the effects of the present invention are obtained. The other structural units are not particularly limited, and examples thereof include structural units derived from ethylenically unsaturated monomers copolymerizable with vinyl esters. The modified polyvinyl alcohol-based polymer of the present invention may also contain structural units derived from unsaturated monomers copolymerizable with vinyl ester monomers and convertible into the structural unit represented by formula (1) (structural units that were not converted into the structural unit represented by formula (1) by saponification). The total proportion of the structural unit represented by formula (1), the vinyl alcohol unit, and the vinyl ester unit in the modified polyvinyl alcohol-based polymer is not particularly limited, but is preferably 80 mol% or more, more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may even be 99 mol% or more, based on 100 mol% of the total number of moles of all structural units constituting the modified polyvinyl alcohol-based polymer.The ethylenically unsaturated monomer is not particularly limited, and examples thereof include α-olefins such as ethylene, propylene, n-butene, isobutylene, and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylic ester group; methacrylic acid and its salts; unsaturated monomers having a methacrylic ester group; acrylamide derivatives such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts; acrylamidopropyldimethylamine and its salts (e.g., quaternary salts); methacrylamide; methacrylamido derivatives such as N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and its salts; and methacrylamidepropyldimethylamine and its salts (e.g., quaternary salts). vinyl amide derivatives; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, and 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinyl halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarboxylic acids and salts or esters thereof such as maleic acid, itaconic acid, and fumaric acid; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; etc. These may be used alone or in combination of two or more.

[0029] <Other Components> The composition containing the modified polyvinyl alcohol polymer can be further formulated as needed with additives such as fillers, processing stabilizers such as copper compounds, weathering stabilizers, colorants, UV absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, plasticizers, other thermoplastic resins, lubricants, fragrances, antifoaming agents, deodorizers, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, mildew inhibitors, preservatives, and crystallization rate retarders. These may be used alone or in combination of two or more.

[0030] By utilizing its properties, the modified polyvinyl alcohol polymer can be used in various applications where vinyl alcohol polymers are used, either alone or as a composition with other components, according to known methods such as molding, spinning, emulsification, etc. The modified polyvinyl alcohol polymer of the present invention can be used, for example, in the following applications: (1) Adhesives: Adhesives for wood, paper, aluminum foil, plastics, etc., pressure-sensitive adhesives, rewetting agents, binders for nonwoven fabrics, binders for various building materials such as gypsum board and fiberboard, binders for various powder granulations, battery binders, additives for cement and mortar, hot-melt adhesives, pressure-sensitive adhesives, fixing agents for anionic paints, adhesives for polarizing plates, water-based vinyl adhesives, honeymoon adhesives, etc. (2) Molded products: Fibers, long-fiber nonwoven fabrics, composite fibers, films for hollow fibers (especially water-soluble films for packaging agricultural chemicals, detergents, laundry clothes, civil engineering additives, disinfectants, dyes, pigments, etc.), water-soluble fibers, water-soluble materials for composite fibers (hollow fibers), barrier packaging materials (biodegradable barrier materials for coffee capsules, etc., barrier packaging materials, etc.), support materials for 3D printers, masking materials, temporary protective materials, sanitary products such as napkins and disposable diapers, waste disposal products such as ostomy bags, medical products such as blood-absorbing sheets, seedling raising sheets, high-pressure gas transfer hoses, etc. (3) Coating Agents: Paper clear coating agents, paper pigment coating agents, paper sizing agents, textile sizing agents, warp sizing agents, textile processing agents, leather finishing agents, paints, anti-fogging agents, metal corrosion inhibitors, zinc plating brighteners, antistatic agents, conductive agents, temporary paints, etc. (4) Emulsifiers: Emulsifiers for emulsion polymerization of ethylenically unsaturated compounds, butadiene compounds, and various acrylic monomers, post-emulsifiers for hydrophobic resins such as polyolefins and polyester resins, epoxy resins, paraffin, and bitumen, etc. (5) Suspension Agents: Pigment dispersion stabilizers for paints, India ink, water-based colors, and adhesives, dispersion stabilizers for suspension polymerization of various vinyl compounds such as vinyl chloride, vinylidene chloride, styrene, (meth)acrylate, and vinyl acetate, etc. (6) Thickeners: Thickeners for various aqueous solutions and emulsions, etc. (7) Resin Raw Materials: Raw materials for polyvinyl acetal resins, raw materials for photosensitive resins, etc.(8) Others: Flocculants for suspended and dissolved matter in water, drainage aids for pulp and slurry, soil conditioners, ion exchange resins, ion exchange membranes, surfactants, textile processing agents, drilling fluid conditioners, diverting agents, etc.

[0031] (Molding Method) The molding method for molding the composition containing the modified polyvinyl alcohol polymer of the present invention is not particularly limited, and examples thereof include a method of molding from a solution state in which the polymer is dissolved in a solvent such as water or dimethyl sulfoxide (e.g., cast molding), a method of plasticizing the polymer by heating and molding (e.g., extrusion molding, injection molding, inflation molding, press molding, blow molding), etc. By these molding methods, molded articles having any shape such as films, sheets, tubes, bottles, etc. can be obtained.

[0032] Polyvinyl alcohol-based polymers have high film strength even under high humidity conditions, making them particularly suitable for applications as internal additives for paper and various water-soluble binders. In addition, for these applications, the high water solubility of polyvinyl alcohol-based polymers is advantageous and useful, since the solubility of the vinyl alcohol-based polymer in water affects the simplification of the process.

[0033] [Method for Producing Modified Polyvinyl Alcohol-Based Polymer] The method for producing the modified polyvinyl alcohol-based polymer is not particularly limited, and examples thereof include a method of copolymerizing a vinyl ester-based monomer with an unsaturated monomer copolymerizable therewith and convertible into a structural unit represented by formula (1), converting the vinyl ester units of the obtained vinyl ester-based copolymer into vinyl alcohol units, and converting the units derived from the unsaturated monomer convertible into the structural unit represented by formula (1) into the structural unit represented by formula (1).

[0034] <Unsaturated Monomers Convertible to Structural Units Represented by Formula (1)> A specific example of an unsaturated monomer convertible to a structural unit represented by formula (1) is represented by the following formula (2).

[0035] In formula (2), R represents an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms. Specific examples of the alkyl group having 1 to 5 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and pentyl. Substituents that R may have include alkoxy groups, halogen atoms, and hydroxyl groups. Multiple R may be the same or different. The structure of R is not particularly limited, and it may have a branched or cyclic structure in part, or may be substituted in part with another functional group.

[0036] Examples of the unsaturated monomer represented by formula (2) include hydroxymethylvinylidene diacetate, and specific examples include 2-methylene-1,3-propanediol diacetate (1,3-diacetoxy-2-methylenepropane), 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyronyloxy-2-methylenepropane. These may be used alone or in combination of two or more. Among these, 2-methylene-1,3-propanediol diacetate (1,3-diacetoxy-2-methylenepropane) is preferred from the viewpoint of ease of production.

[0037] The unsaturated monomer represented by formula (2) generally undergoes a copolymerization reaction with a vinyl ester monomer more easily than other allylic unsaturated monomers (e.g., allyl glycidyl ether) used in modifying polyvinyl alcohol polymers. Therefore, the modified polyvinyl alcohol polymer has fewer restrictions on the modification rate and polymerization degree during polymerization, and can achieve a high modification rate and polymerization degree. Furthermore, since the amount of unreacted unsaturated monomer remaining at the end of polymerization can be reduced, the modified polyvinyl alcohol polymer is also excellent in terms of the environment and cost during industrial production.

[0038] The vinyl ester monomer used in the production of the modified polyvinyl alcohol polymer is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate. These may be used alone or in combination of two or more. Among these, vinyl acetate is preferred from an economical viewpoint.

[0039] <Polymerization method> The polymerization method when copolymerizing the unsaturated monomer represented by formula (2) with the vinyl ester-based monomer is not particularly limited, and may be, for example, any of batch polymerization, semi-batch polymerization, continuous polymerization, semi-continuous polymerization, etc., and known methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. can be applied as the polymerization method. Bulk polymerization or solution polymerization, in which polymerization proceeds without a solvent or in a solvent such as alcohol, is usually used. When obtaining a vinyl ester-based copolymer with a high degree of polymerization, emulsion polymerization is preferred.

[0040] The solvent for the solution polymerization method is not particularly limited, and examples thereof include lower alcohols such as methanol, ethanol, and propanol. These may be used alone or in combination of two or more. Among these, methanol is preferred from an economical viewpoint.

[0041] The amount of solvent used in the polymerization system may be selected in consideration of chain transfer of the solvent depending on the polymerization degree of the target modified polyvinyl alcohol-based polymer. For example, when the solvent is methanol, the mass ratio of the solvent to the total monomers contained in the polymerization system {= (solvent) / (total monomers)} is preferably selected within the range of 0.01 to 10, more preferably within the range of 0.02 to 5, and particularly preferably within the range of 0.05 to 3.

[0042] <Polymerization initiator> The polymerization initiator used for copolymerization of the unsaturated monomer represented by formula (2) and the vinyl ester monomer is not particularly limited, and examples thereof include known polymerization initiators selected from azo initiators, peroxide initiators, and redox initiators depending on the polymerization method. These may be used alone or in combination of two or more.

[0043] <<Azo Initiator>> The azo initiator is not particularly limited, and examples thereof include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), etc. These may be used alone or in combination of two or more.

[0044] <<Peroxide Initiator>> The peroxide initiator is not particularly limited, and examples thereof include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanate and α-cumyl peroxyneodecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; and acetyl peroxide. These may be used alone or in combination with two or more. Potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like may be combined with the above initiators to form a polymerization initiator.

[0045] <<Redox Initiator>> The redox initiator is not particularly limited, and examples thereof include polymerization initiators that combine the above-mentioned peroxide initiators with a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, Rongalit, etc. These may be used alone or in combination of two or more.

[0046] The amount of the polymerization initiator used is not particularly limited, but is appropriately selected depending on the polymerization catalyst and polymerization rate. For example, when 2,2'-azobisisobutyronitrile or acetyl peroxide is used as the polymerization initiator, the amount is preferably 0.01 to 0.20 mol %, more preferably 0.02 to 0.15 mol %, based on the vinyl ester monomer.

[0047] The polymerization temperature is not particularly limited, but is preferably from room temperature to about 150° C., more preferably 40° C. or higher and not higher than the boiling point of the solvent used.

[0048] The copolymerization of the unsaturated monomer represented by formula (2) and the vinyl ester monomer may be carried out in the presence of a chain transfer agent, as long as the effects of the present invention can be obtained.

[0049] The chain transfer agent is not particularly limited, and examples thereof include aldehydes such as acetaldehyde and propionaldehyde, ketones such as acetone and methyl ethyl ketone, mercaptans such as 2-hydroxyethanethiol, phosphinates such as sodium phosphinate hydrate, etc. These may be used alone or in combination of two or more.

[0050] The amount of the chain transfer agent to be added to the polymerization system can be determined depending on the chain transfer coefficient of the chain transfer agent to be added and the degree of polymerization of the desired modified polyvinyl alcohol polymer, and is not particularly limited, but is preferably 0.1 to 10 parts by mass per 100 parts by mass of the vinyl ester monomer.

[0051] The modified polyvinyl alcohol polymer of the present invention can be obtained by saponifying a vinyl ester copolymer obtained by copolymerizing an unsaturated monomer represented by formula (2) with a vinyl ester monomer. By saponifying the vinyl ester copolymer, the vinyl ester units in the vinyl ester copolymer are converted into vinyl alcohol units. Furthermore, the ester bonds of the structural units derived from the unsaturated monomer represented by formula (2) are also saponified, converting them into structural units having a 1,3-diol structure represented by formula (1). Therefore, the modified polyvinyl alcohol polymer of the present invention can be produced without further reactions such as hydrolysis after saponification.

[0052] A preferred example of the method for producing a modified polyvinyl alcohol-based polymer includes a method in which a vinyl ester-based monomer and 2-methylene-1,3-propanediol diacetate (1,3-diacetoxy-2-methylenepropane) are copolymerized by dropwise polymerization, and the resulting vinyl ester-based copolymer is saponified to produce a modified polyvinyl alcohol-based polymer.

[0053] [Film] The film of the present invention is formed from a composition containing the modified polyvinyl alcohol-based polymer of the present invention. The film formed from the composition containing the modified polyvinyl alcohol-based polymer of the present invention can be suitably used for various film applications, taking advantage of its excellent water solubility.

[0054] The film of the present invention has improved water solubility because the modified polyvinyl alcohol polymer contained therein contains a structural unit having a 1,3-diol structure represented by the above formula (1). Although this does not limit the present invention, it is thought that the reason for the above advantages is that the structural unit represented by formula (1) reduces crystallinity, etc.

[0055] The content of the modified polyvinyl alcohol-based polymer of the present invention in the film of the present invention is not particularly limited, but from the viewpoint of the mechanical properties of the film, it is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, while from the viewpoint of water solubility, it is preferably 100% by mass or less, more preferably 95% by mass or less, and particularly preferably 90% by mass or less.

[0056] The film of the present invention may contain a plasticizer in addition to the modified polyvinyl alcohol polymer. The plasticizer is not particularly limited, and polyhydric alcohols are preferred. Specific examples of the plasticizer are not particularly limited, and include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. These may be used alone or in combination of two or more. Among these, glycerin is preferred from an economical viewpoint.

[0057] The content of the plasticizer in the film of the present invention is not particularly limited, but is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and particularly preferably 40 parts by mass or less, relative to 100 parts by mass of the modified polyvinyl alcohol-based polymer in the film. By making the content 50 parts by mass or less, it is possible to prevent the film from becoming too flexible and reducing handleability.

[0058] The film of the present invention may also contain starch and / or other water-soluble polymers for the purposes of imparting mechanical strength, maintaining moisture resistance when handling the film, or adjusting the speed of softening due to water absorption when dissolving the film and the time required for diffusion in water.

[0059] The starch is not particularly limited, and examples thereof include natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, and sago starch; processed starches that have been subjected to etherification processing, esterification processing, oxidation processing, etc. These may be used alone or in combination of two or more.

[0060] The starch content in the film of the present invention is not particularly limited, but is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, per 100 parts by mass of the modified polyvinyl alcohol-based polymer in the film. When the starch content in the water-soluble film of the present invention is 15 parts by mass or less, the impact resistance of the film is improved, and the processability is also improved.

[0061] The other water-soluble polymers are not particularly limited and include, for example, dextrin, gelatin, glue, casein, shellac, gum arabic, polyacrylic acid amide, sodium polyacrylate, polyvinyl methyl ether, a copolymer of methyl vinyl ether and maleic anhydride, a copolymer of vinyl acetate and itaconic acid, polyvinylpyrrolidone, cellulose, acetyl cellulose, acetyl butyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, sodium alginate, etc. These may be used alone or in combination of two or more.

[0062] The content of the other water-soluble polymer in the film of the present invention is not particularly limited, but is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of the modified polyvinyl alcohol-based polymer in the film. When the content of the other water-soluble polymer in the film of the present invention is 15 parts by mass or less, the water solubility and dispersibility of the film are improved.

[0063] The film of the present invention may further contain additives such as fillers, processing stabilizers such as copper compounds, weathering stabilizers, colorants, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, other thermoplastic resins, lubricants, fragrances, antifoaming agents, deodorizers, extenders, peeling agents, release agents, reinforcing agents, crosslinking agents, mildew inhibitors, preservatives, and crystallization rate retarders, as required.

[0064] The total proportion of the modified polyvinyl alcohol-based polymer, plasticizer, starch, and other water-soluble polymer in the film of the present invention is not particularly limited, but is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the mass of the film.

[0065] The thickness of the film of the present invention is not particularly limited, but from the viewpoint of achieving both strength and water solubility, it is preferably 1 to 1000 μm, more preferably 1 to 500 μm, even more preferably 1 to 100 μm, and particularly preferably 10 to 100 μm.

[0066] The length and width of the film of the present invention are not particularly limited, but from the viewpoint of productivity during processing, the length is preferably 1 m or more, more preferably 100 m or more, and particularly preferably 1,000 m or more, and the width is preferably 0.5 m or more, more preferably 0.8 m or more, and particularly preferably 1.0 m or more.

[0067] The method for producing the film of the present invention is not particularly limited, and a production method that results in a more uniform thickness and width of the film after film formation can be preferably used. For example, the film can be produced using a film-forming solution in which a modified polyvinyl alcohol-based polymer constituting the film, and optionally at least one of a plasticizer, starch, other water-soluble polymer, additive, and surfactant, is dissolved in a liquid medium; or a film-forming solution in which a modified polyvinyl alcohol-based polymer, and optionally at least one of a plasticizer, starch, other water-soluble polymer, additive, surfactant, and liquid medium, is dissolved, and the modified polyvinyl alcohol-based polymer is dissolved. When the film-forming solution contains at least one of a plasticizer, starch, other water-soluble polymer, additive, and surfactant, it is preferable that these components are uniformly mixed.

[0068] [Masking Material] The masking material of the present invention is formed from the molded article of the present invention. Taking advantage of its excellent water solubility, the molded article of the present invention can be suitably used in various masking material applications. For example, an aqueous solution is applied to an object to be masked, dried, and then washed away with water. Specific applications include use as a masking material during the painting of various office supplies and household items, such as various industrial products such as automobiles and aircraft, office equipment such as printers and personal computers, and various consumer products such as furniture and plastic models; use as a primary surface protective material during various manufacturing processes such as 3D measurement and surface inspection; temporary protective material during various processes involving surface damage, such as the assembly, molding, and cutting of fine parts and large parts, such as rocket engines and automobile parts; and temporary protective material during various surface treatments, surface treatments, and surface modifications, such as surface plating, antifouling treatment, hydrophilization treatment, and antibacterial treatment. The molded article of the present invention can be used in applications where various masking tapes are used. The substrate can be various plastic substrates and metal substrates.

[0069] The content of the modified polyvinyl alcohol polymer in the composition of the masking material of the present invention is not particularly limited, but from the viewpoint of formability, it is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, while from the viewpoint of water solubility, it is preferably 100% by mass or less, more preferably 95% by mass or less, and particularly preferably 90% by mass or less.

[0070] [Water-Soluble Transfer Coating Material] The water-soluble transfer coating material of the present invention includes the molded article of the present invention. Taking advantage of its excellent water solubility, the molded article of the present invention can be suitably used in various water-soluble transfer coating material applications. For example, it can be used as a water-soluble transfer coating material for forming coating material layers with an uneven structure, such as a transfer sheet for libretto. Specific applications include coating materials that transfer complex shapes to curved surfaces, such as the surfaces of rockets, aircraft, automobiles, railroad cars, automobile interior parts, home appliance parts, mobile devices, aquariums, bathtubs, ships, vehicle parts, decorative panels, and housing equipment.

[0071] The content of the modified polyvinyl alcohol polymer in the composition of the transfer coating material of the present invention is not particularly limited, but from the viewpoint of formability, it is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, while from the viewpoint of water solubility, it is preferably 100% by mass or less, more preferably 95% by mass or less, and particularly preferably 90% by mass or less.

[0072] [Support Material for Modeling] The support material for modeling of the present invention includes the molded article of the present invention. The molded article of the present invention can be suitably used for various support materials for modeling, taking advantage of its excellent water solubility. For example, it can be used as a support material for 3D printers in the modeling of automobile parts, aerospace parts, train parts, medical devices, and electronic parts, or as a filament for 3D printers.

[0073] The content of the modified polyvinyl alcohol polymer in the composition of the support material for molding of the present invention is not particularly limited, but from the viewpoint of formability, it is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, while from the viewpoint of water solubility, it is preferably 100% by mass or less, more preferably 95% by mass or less, and particularly preferably 90% by mass or less.

[0074] [Water-soluble mold] The water-soluble mold of the present invention includes the molded article of the present invention. Taking advantage of its excellent water solubility and thermoplasticity, the molded article of the present invention can be suitably used as various water-soluble molds. Examples include water-soluble molds for obtaining ceramic articles of desired shapes, water-soluble molds used in molding ophthalmic devices, water-soluble molds for obtaining silicone resin molded articles, water-soluble molds for obtaining thermoplastic resin molded articles, cores used to create internal cavities during thermoplastic resin molding, and molded articles obtained by dispersing modified polyvinyl alcohol in a thermoplastic elastomer matrix and then rinsing off only the modified polyvinyl alcohol with water.

[0075] The content of the modified polyvinyl alcohol polymer in the composition for the water-soluble mold of the present invention is not particularly limited, but from the viewpoint of moldability, it is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, while from the viewpoint of water solubility, it is preferably 100% by mass or less, more preferably 95% by mass or less, and particularly preferably 90% by mass or less.

[0076] [Method of Using the Molded Article] The method of using the molded article of the present invention is characterized by heat-treating a molded article formed from a composition containing a modified polyvinyl alcohol-based polymer at a temperature higher than 30° C. and not higher than 330° C., and then dissolving the molded article in water at 0 to 70° C. The heat-treatment method also includes treatment outdoors by solar heat at 30° C. or higher.

[0077] The heat treatment is preferably carried out on the molded body at a temperature of more than 100° C. and not more than 330° C. The temperature of the water used to dissolve the molded body after the heat treatment depends on the heat treatment temperature, the object, etc., but is preferably 0 to 70° C., more preferably 5 to 60° C., even more preferably 10 to 50° C., and still more preferably 10 to 40° C., from the viewpoints of shortening the takt time and facilitating water treatment at low temperatures, within a range that does not damage the object.

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, "%" represents "% by mass" unless otherwise specified. The measurement methods and evaluation methods employed in the examples and comparative examples are shown below.

[0079] [Primary Structure of Modified Polyvinyl Alcohol-Based Polymer (Saponification Degree, Modification Rate)] The primary structure (saponification degree, modification rate) of the modified polyvinyl alcohol-based polymer obtained in the following synthesis examples was １ Analysis was carried out using H-NMR. １ Deuterated DMSO was used as the solvent for H-NMR measurement. Note that the primary structure refers to the exact arrangement of monomers and chemical bonds.

[0080] [Method for measuring the distribution of modification rate] (1) 0.5 g of the modified polyvinyl alcohol polymer obtained in each synthesis example was dissolved in 5 mL of water, and then added to 20 mL of three types of solutions of ethanol / water with a mass ratio of 65 / 35, 70 / 30, and 77 / 23 to cause precipitation. (2) The precipitate was separated and dried, and then measured using a 270 MHz １ (3) The solution after separating the precipitate was dried to solidify the solution, and the dissolved components were recovered. １ The modification rate (B mole %) was measured by H-NMR. (4) From the obtained values, (B-A) mole % was defined as the modification rate distribution. The largest value among the measured values ​​for each of the three solvent compositions was adopted as the modification rate of the modified polyvinyl alcohol-based polymer.

[0081] [Evaluation of Solvent Resistance] The swelling degree of a film in ethanol / water was measured as an index of solvent resistance. A 10% by mass aqueous solution of a modified polyvinyl alcohol polymer was prepared, cast onto a PET film, and dried at 20°C for 1 week to obtain a 70 μm thick polyvinyl alcohol resin film. The obtained film was cut into a 30 mm x 30 mm piece, added to 10 mL of an 80 / 20 (mass ratio) ethanol / water mixed solution, and held at 50°C for 3 hours before being removed. The mass A of the swollen film was measured. The film was then dried at 80°C for 24 hours, and the mass B of the bone-dry film was measured. The swelling degree was calculated according to the following formula. Since the swelling property in the above solvents is largely dependent on the content of structural units other than the vinyl alcohol structural unit, the content of structural units other than the vinyl alcohol structural unit was classified into the following cases and evaluated accordingly. In both cases, a lower swelling degree indicates higher solvent resistance. (1) When the content of structural units other than vinyl alcohol is less than 10 mol%, A: Swelling degree is less than 150%. C: Swelling degree is 150% or more. (2) When the content of structural units other than vinyl alcohol is 10 mol% or more but less than 20 mol%, A: Swelling degree is less than 200%. C: Swelling degree is 200% or more. (3) When the content of structural units other than vinyl alcohol is 20 mol% or more, B: Swelling degree is less than 250%. C: Swelling degree is 250% or more.

[0082] [Heat Treatment of Film] A 10% by mass aqueous solution of a modified polyvinyl alcohol polymer was prepared, cast onto a PET film, and dried at 20°C for 1 week to obtain a 70 μm thick polyvinyl alcohol resin film. The obtained film was cut into 35 mm x 45 mm pieces and subjected to heat treatment under the conditions shown in Table 2 (110°C for 1 day, 200°C for 10 minutes, and 300°C for 5 minutes).

[0083] [Evaluation of Film Dissolution Rate] The dissolution rate of the film was measured as an index of water solubility after heat treatment. The mass of the film after heat treatment was designated as M1 (parts by mass). The film was immersed in M1 x 500 parts by mass of water at 10°C for 16 hours, recovered, and then completely dried (after vacuum drying at 40°C and 10 Pa for 16 hours). The mass of the film was designated as M2 (parts by mass). The dissolution rate was defined as ([1 - (M2 / M1)] x 100 (% by mass), and the dissolution rate was evaluated. Similarly, the dissolution rates of films immersed for 16 hours in water at 25°C (M1 x 500 parts by mass) and 70°C (M1 x 500 parts by mass) were evaluated according to the following criteria. In Table 2, the dissolution rates when water at 10°C was used are shown as numerical values ​​(% by mass). A: Dissolution rate is 95% by mass or more B: Dissolution rate is 80% by mass or more but less than 95% by mass C: Dissolution rate is less than 80% by mass

[0084] [Evaluation of Biodegradability] A 10% by mass aqueous solution of modified polyvinyl alcohol polymer was prepared, cast onto a PET film, and dried at 20°C for 1 week to obtain a 70 μm thick polyvinyl alcohol resin film. The obtained film was cut into 35 mm x 45 mm pieces and heat-treated at 200°C for 10 minutes. Using this film, biodegradability was evaluated using a biodegradability test method in accordance with OECD 301B. The test conditions are shown below. The biodegradation rate (mass%) was calculated based on the theoretical oxygen demand calculated from the polymer composition. Apparatus: OXI TOP (manufactured by WTW) Sludge used: Return sludge from a general sewage treatment plant Test medium: 200 mL Sample concentration: Approximately 30 mass ppm (15 mg DOC / L) Sludge concentration: 30 mg / L Temperature: 22°C Period: 28 days Biodegradation rate (mass%) = {(actual amount of oxygen consumed) / (theoretical oxygen demand)} x 100

[0085] [Evaluation of Barrier Properties] Oxygen transmission rate (OTR) is an index of oxygen gas barrier properties, and it can be said that the lower the OTR value, the higher the oxygen gas barrier properties. The unit of the OTR value is [cc / (m ２ ·day·atm)]. Specific measurements were carried out as follows. A 10% by mass concentration aqueous solution of a modified polyvinyl alcohol polymer was prepared, and this was applied to a 12 μm thick PET film using a variable applicator (manufactured by YOSHIMITSU). The film was then dried at a drying temperature of 60°C for 1 hour to form a modified vinyl alcohol polymer layer, thereby obtaining a PET laminated film consisting of a PET film and a modified vinyl alcohol polymer layer. The obtained film was cut into a 15 cm x 15 cm piece and measured under conditions of 20°C and 65% RH using an oxygen gas transmission rate measuring device OX-TRAN2 / 21 (manufactured by Mocon), and the oxygen transmission rate (OTR) of the film was calculated as F1 [cc / (m ２ ·day·atm)] was obtained. After the measurement, the film thickness T (μm) of the film was measured using an electromagnetic film thickness meter SAMAC-PRO manufactured by Sanko Electronics Laboratory Co., Ltd. Then, the OTR value A [cc. 20 μm / (m ２ A = F1 × T / 20 (1) When measuring the oxygen gas barrier property of the laminate, the measured OTR value of the entire laminate was calculated as F [cc / (m ２ ·day·atm)], and F1 is calculated from the following formula (2), and then, using formula (1), the value A [cc. 20 μm / (m ２ The meaning of each symbol in the following formula (2) is as follows: OTR actual measurement value of the entire PET laminated film: F [cc / (m ２ · day · atm)] · OTR of modified vinyl alcohol polymer layer: F1 [cc / (m ２ · day · atm)] · PET film OTR actual measurement value: F2 [cc / (m ２ ・day・atm)] (1 / F)=(1 / F1)+(1 / F2) (2)

[0086] <Synthesis of modified polyvinyl alcohol polymer> (Synthesis Example 1) Synthesis of modified polyvinyl alcohol polymer (PVOH-1) A reaction vessel equipped with a reflux condenser, a stirrer, a nitrogen inlet, an initiator addition port, and a solution feed port was charged with 60 parts by mass of vinyl acetate, 25.5 parts by mass of 2-methylene-1,3-propanediol diacetate, and 0 parts by mass of methanol, and the temperature was increased under a nitrogen stream while stirring to stabilize the internal temperature at 60 ° C., and then 0.15 parts by mass of 2,2'-azobisisobutyronitrile (0.13 mol% relative to vinyl acetate) was added to initiate polymerization. Thereafter, 18.3 parts by mass of a 50% by mass methanol solution of 2-methylene-1,3-propanediol diacetate was added dropwise at 2.6 parts by mass / h, and the conversion rate of vinyl acetate ("polymerization rate" in Table 1) was reacted for 7 hours until it reached 40 mol%. 0.43 parts by mass of sorbic acid was added as a polymerization inhibitor to terminate the polymerization. Subsequently, unreacted vinyl acetate monomer was removed from the system by adding methanol and distilling off under reduced pressure at 40 ° C. to obtain a methanol solution of the copolymer. Next, the methanol solution was diluted with methanol to a concentration of 20% by mass, and while maintaining the solution temperature at 40 ° C., a 13% by mass methanol solution of sodium hydroxide was added at a ratio of 0.03 moles of sodium hydroxide per mole of the total amount of vinyl acetate structural units and 2-methylene-1,3-propanediol diacetate structural units in the copolymer, to perform saponification. As the saponification proceeded, a saponified product precipitated, and a gel was formed about 7 minutes after addition. This was pulverized and left to stand at 40 ° C. for 60 minutes to allow saponification to proceed, after which methyl acetate was added to neutralize the remaining alkali. After confirming the completion of neutralization using a phenolphthalein indicator, the product was filtered to obtain a white solid, to which 25 parts by mass of methanol was added and heated under reflux for 1 hour. The above washing procedure was repeated three times, and the white solid obtained by centrifugal dehydration was then dried in a vacuum dryer at 40° C. for 24 hours to obtain a modified polyvinyl alcohol polymer.

[0087] Synthesis Examples 2 to 10 Synthesis of Modified Polyvinyl Alcohol Polymers (PVOH-2 to PVOH-10) Modified polyvinyl alcohol polymers (PVOH-2 to PVOH-10) were produced in the same manner as in Synthesis Example 1, except that the polymerization conditions, such as the charged amounts of vinyl acetate, methanol, and 2-methylene-1,3-propanediol diacetate, and the feed rates, and the saponification conditions, such as the concentration of modified PVAc during saponification and the molar ratio of sodium hydroxide to vinyl acetate units, shown in Table 1, were changed as shown in Table 1 (however, some of the same values ​​were included).

[0088] (Synthesis Example 11) Synthesis of Unmodified Polyvinyl Alcohol Polymer (PVOH-11) An unmodified polyvinyl alcohol polymer (PVOH-11) was produced in the same manner as in Synthesis Example 1 (but without modification), except that the modifying species (comonomer) shown in Table 1 was not added and the saponification conditions, such as methanol, polymerization time, and the molar ratio of sodium hydroxide to vinyl acetate units during saponification, were changed as shown in Table 1.

[0089] Example 1 A polyvinyl alcohol resin film having a thickness of 70 μm was obtained by the method described above using the modified polyvinyl alcohol polymer (PVOH-1) obtained in Synthesis Example 1, and the obtained film was cut into a piece of 35 mm × 45 mm, which was subjected to a heat treatment at 200°C for 10 minutes, and the film elution rate in water at 10°C, 25°C, and 70°C was evaluated. The evaluation results are shown in Table 2.

[0090] The degree of saponification and the modification rate of the modified polyvinyl alcohol polymer obtained in Synthesis Example 1 were: １Analysis by H-NMR (solvent: deuterated DMSO) revealed that the degree of saponification was 99.9 mol % and the degree of modification was 30.5 mol %. The distribution of the degree of modification was measured by the above-mentioned measurement method and was found to be 0.3 mol %. The degree of polymerization was measured by the following polymerization degree measurement and was found to be 500. The physical properties of the obtained modified polyvinyl alcohol polymer are shown in Table 2. (Number-average degree of polymerization) The number-average molecular weight (Mn) of the polymer was measured using a size-exclusion high-performance liquid chromatography apparatus "HLC-8320GPC" manufactured by Tosoh Corporation. The measurement conditions were as follows: Column: Two HFIP columns "GMHHR-H(S)" manufactured by Tosoh Corporation connected in series Standard sample: Polymethyl methacrylate Solvent and mobile phase: Sodium trifluoroacetate-HFIP solution (concentration 20 mM) Flow rate: 0.2 mL / min Temperature: 40°C Sample solution concentration: 0.1 mass% (filtered through a filter with an opening diameter of 0.45 μm) Injection volume: 10 μL Detector: RI The number-average degree of polymerization DPn of the polymer was calculated using the following formula: DPn = Mn × 100 / (44 × a + 88 × b) a: Content (mol%) of polyvinyl alcohol structural units b: Content (mol%) of 2-methylene-1,3-propanediol structural units

[0091] Example 2 The film dissolution rate was evaluated in the same manner as in Example 1, except that the heat treatment conditions were changed to 300° C. for 5 minutes. The evaluation results are shown in Table 2.

[0092] (Example 3) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to a modified polyvinyl alcohol polymer (PVOH-2), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0093] (Example 4) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to the modified polyvinyl alcohol polymer (PVOH-3), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0094] Example 5 The film dissolution rate was evaluated in the same manner as in Example 4, except that the heat treatment conditions were changed to 300° C. for 5 minutes. The evaluation results are shown in Table 2.

[0095] Example 6 The film dissolution rate was evaluated in the same manner as in Example 4, except that the heat treatment conditions were changed to 110° C. for 1 day. The evaluation results are shown in Table 2.

[0096] (Example 7) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to the modified polyvinyl alcohol polymer (PVOH-4), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0097] Example 8 The film dissolution rate was evaluated in the same manner as in Example 7, except that the heat treatment conditions were changed to 110° C. for 1 day. The evaluation results are shown in Table 2.

[0098] (Example 9) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to the modified polyvinyl alcohol polymer (PVOH-5), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0099] (Example 10) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to a modified polyvinyl alcohol polymer (PVOH-6), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0100] Example 11 The film elution rate was evaluated in the same manner as in Example 10, except that the heat treatment conditions were changed to 300° C. for 5 minutes. The evaluation results are shown in Table 2.

[0101] Example 12 The film dissolution rate was evaluated in the same manner as in Example 10, except that the heat treatment conditions were changed to 110° C. for 1 day. The evaluation results are shown in Table 2.

[0102] (Example 13) Except for using a modified polyvinyl alcohol polymer (PVOH-7) instead of the modified polyvinyl alcohol polymer (PVOH-1), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0103] (Example 14) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to the modified polyvinyl alcohol polymer (PVOH-8), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0104] (Example 15) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to the modified polyvinyl alcohol polymer (PVOH-9), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0105] (Example 16) Except for changing the modified polyvinyl alcohol polymer (PVOH-1) to a modified polyvinyl alcohol polymer (PVOH-10), the physical properties and film elution rate of the modified polyvinyl alcohol polymer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0106] Comparative Example 1 The unmodified polyvinyl alcohol polymer (PVOH-11) obtained in Synthesis Example 11 was evaluated for its physical properties and film elution rate in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0107] Comparative Example 2 The film elution rate was evaluated in the same manner as in Comparative Example 1, except that the heat treatment conditions were changed to 300° C. for 5 minutes. The evaluation results are shown in Table 2.

[0108] Comparative Example 3 The film dissolution rate was evaluated in the same manner as in Comparative Example 1, except that the heat treatment conditions were changed to 110° C. for 1 day. The evaluation results are shown in Table 2.

[0109]

[0110]

[0111] As is clear from the above results (comparison between Examples 1 to 16 and Comparative Examples 1 to 3), the elution rate is 90 mass% or more, which satisfies the requirements of the present invention, and it can be seen that the water solubility of the molded body before the heat treatment is maintained.

[0112] According to the present invention, a molded article formed from a composition containing a modified polyvinyl alcohol-based polymer, which maintains its water solubility before heat treatment, can be provided. Therefore, the molded article can be used, for example, as a water-soluble film, a masking material, a temporary protective material, a water-soluble transfer coating material for forming a coating material layer having an uneven structure, a support material for a 3D printer, etc.

Claims

1. A molded article formed from a composition containing a modified polyvinyl alcohol polymer having a vinyl alcohol structural unit and a structural unit represented by the following formula (1): The molded body has a dissolution rate of 90% by mass or more, as defined by [1-(M2 / M1)]×100 (% by mass), where M1 (parts by mass) is the mass of the molded body after heat-treating the molded body at 200° C. for 10 minutes, M2 (parts by mass) is the mass of the molded body after immersing the heat-treated molded body in 10° C. water having 500 parts by mass times M1 for 16 hours and vacuum-drying the molded body at 40° C. and 10 Pa for 16 hours.

2. The molded article according to claim 1, wherein the content of the structural unit represented by formula (1) is 0.1 to 40 mol % relative to 100 mol % of all structural units in the modified polyvinyl alcohol polymer.

3. The molded article according to claim 1, wherein the content of the structural unit represented by formula (1) is 0.8 to 10 mol % relative to 100 mol % of all structural units in the modified polyvinyl alcohol polymer.

4. The molded article according to claim 1 or 2, wherein the modified polyvinyl alcohol polymer has a degree of saponification of 80.0 to 99.9 mol %.

5. A molded article according to claim 1 or 2, wherein the distribution of the modification rate of the structural unit represented by formula (1) relative to 100 mol % of all structural units in the modified polyvinyl alcohol polymer is 0.5 mol % or less.

6. A film formed from a composition containing the modified polyvinyl alcohol polymer according to claim 1 or 2.

7. The film according to claim 6, wherein the thickness of the film is 1 to 1000 μm.

8. A masking material formed from the molded article according to claim 1 or 2.

9. A water-soluble transfer coating material for forming a coating layer having a concave-convex structure, comprising the molded article according to claim 1 or 2.

10. A support material for modeling, comprising the molded article according to claim 1 or 2.

11. A method for using the molded article according to claim 1 or 2, comprising heat-treating a molded article formed from a composition containing the modified polyvinyl alcohol-based polymer at a temperature higher than 100°C and not higher than 330°C, and then dissolving the molded article in water at a temperature of 0 to 70°C.