JPWO2015093499A1 - the film - Google Patents

Abstract

Disclosed is a film containing polyvinyl alcohol, which is less colored by heating and excellent in dispersion even when it contains a surfactant. SOLUTION: Polyvinyl alcohol having a saponification degree of 50 to 99.99 mol% and a viscosity average polymerization degree of 200 to 5,000 is contained, and the content of alkali metal salt of carboxylic acid is 0. 0 in terms of mass of alkali metal. A peak top molecular weight (A) measured with a differential refractive index detector when the film is 5% by mass or less and the polyvinyl alcohol heated at 120 ° C. for 3 hours is subjected to gel permeation chromatography measurement, The peak top molecular weight (B) measured with an absorptiometric detector (measurement wavelength: 280 nm) satisfies the following formula (1) (AB) / A <0.75 (1) and the peak top molecular weight (B) A film having an absorbance of 0.25 × 10 −3 to 3.00 × 10 −3. [Selection] Figure 1

Description

  The present invention relates to a film containing specific polyvinyl alcohol and a method for producing the same.

  Polyvinyl alcohol (hereinafter sometimes abbreviated as “PVA”) is known as a water-soluble synthetic polymer. PVA is particularly excellent in strength characteristics and film-forming properties as compared with other synthetic polymers, and is frequently used in various applications such as films. On the other hand, PVA is easily colored by heating.

  Patent Document 1 proposes a method for producing PVA using a peroxyester compound having a predetermined structure as an initiator used for polymerization of vinyl ester. Patent Document 1 describes that the manufactured PVA is difficult to be colored by heating.

  Patent Document 2 discloses a method for producing PVA in which a polyvinyl acetate monomer having a content of an inhibitor (polymerization inhibitor) of 10 ppm or less is polymerized to obtain polyvinyl acetate, and then the polyvinyl acetate is hydrolyzed. Have been described. Patent Document 2 describes that the produced PVA is less colored.

JP-A-5-320219 Special table 2011-508802 gazette

  However, even when the methods described in Patent Documents 1 and 2 are used, the effect of reducing coloration when PVA or a film containing the same is heated is still inadequate. There was a problem of poor dispersibility and poor surface properties.

  The present invention has been made in order to solve the above-described problems, and provides a film containing PVA, which is less colored by heating and excellent in dispersion even when it contains a surfactant. For the purpose.

  As a result of intensive studies to solve the above problems, the present inventors have found that a specific film using PVA that satisfies specific requirements is less colored by heating and includes a surfactant. The present inventors have found that it is excellent in a dispersed state, and further studied based on the knowledge to complete the present invention.

That is, the above-described problem includes PVA having a saponification degree of 50 to 99.99 mol% and a viscosity average polymerization degree of 200 to 5,000, and the content of the alkali metal salt of the carboxylic acid is in terms of the mass of the alkali metal. A differential refractive index detector when the film is 0.5% by mass or less and the PVA heated at 120 ° C. for 3 hours is measured by gel permeation chromatography (hereinafter sometimes abbreviated as GPC). The peak top molecular weight (A) measured by (1) and the peak top molecular weight (B) measured by an absorptiometric detector (measurement wavelength: 280 nm) are represented by the following formula (1):
(AB) / A <0.75 (1)
And a film having an absorbance at a peak top molecular weight (B) of 0.25 × 10 ^{−3 to} 3.00 × 10 ⁻³ is solved.

However, in the GPC measurement,
Mobile phase: 20 mmol / L sodium trifluoroacetate-containing hexafluoroisopropanol (hereinafter, hexafluoroisopropanol may be abbreviated as HFIP.)
Sample concentration: 1.00 mg / mL
Sample injection volume: 100 μL
Column: “GPC HFIP-806M” manufactured by Showa Denko KK
Column temperature: 40 ° C
Flow rate: 1 mL / min Absorbance detector cell length: 10 mm
It is.

  According to this invention, it is a film containing PVA, and there is little coloring by heating, and even if it is a case where surfactant is included, the film excellent in the dispersion state is obtained.

In the PVA of Example 1, the relationship between the molecular weight and the value measured by the differential refractive index detector (RI), and the relationship between the molecular weight and the absorbance measured by the absorptiometric detector (UV) (measurement wavelength 280 nm). It is the graph which showed.

The PVA in the present invention is a PVA having a saponification degree of 50 to 99.99 mol% and a viscosity average polymerization degree of 200 to 5,000, and when the PVA heated at 120 ° C. for 3 hours is measured by GPC. The peak top molecular weight (A) measured with a differential refractive index detector and the peak top molecular weight (B) measured with an absorptiometric detector (measurement wavelength 280 nm) are expressed by the following formula (1).
(AB) / A <0.75 (1)
And the absorbance at the peak top molecular weight (B) is 0.25 × 10 ^{−3 to} 3.00 × 10 ⁻³ .

However, in the GPC measurement,
Mobile phase: HFIP containing 20 mmol / L sodium trifluoroacetate
Sample concentration: 1.00 mg / mL
Sample injection volume: 100 μL
Column: “GPC HFIP-806M” manufactured by Showa Denko KK
Column temperature: 40 ° C
Flow rate: 1 mL / min Absorbance detector cell length: 10 mm
It is.

  In the GPC measurement in the present invention, a GPC apparatus having a differential refractive index detector and an absorptiometric detector and capable of performing measurement by these detectors at the same time is used. It is necessary to use an absorptiometric detector that can measure the absorbance at a wavelength of 280 nm, and it is preferable to use an absorptivity detector that can simultaneously measure the absorbance at a wavelength of 280 nm and the absorbance at a wavelength of 320 nm. A cell having a cell length (optical path length) of 10 mm is used as the cell of the detection unit of the absorptiometer. The absorptiometric detector may measure the absorption of ultraviolet light having a specific wavelength, or may measure the absorption of ultraviolet light having a specific range of wavelengths. The PVA subjected to the measurement is separated into each molecular weight component by a GPC column. The signal intensity by the differential refractive index detector is approximately proportional to the concentration of PVA (mg / mL). On the other hand, the PVA detected by the absorptiometric detector is only PVA having absorption at a predetermined wavelength. By the GPC measurement, the concentration and absorbance at a predetermined wavelength can be measured for each molecular weight component of PVA.

  HFIP containing sodium trifluoroacetate at a concentration of 20 mmol / L is used as a solvent and mobile phase used for dissolving PVA measured in the GPC measurement. HFIP can dissolve PVA and polymethyl methacrylate (hereinafter abbreviated as PMMA). Further, by adding sodium trifluoroacetate, the adsorption of PVA to the column filler is prevented. The flow rate in the GPC measurement is 1 mL / min, and the column temperature is 40 ° C.

  In the GPC measurement, monodisperse PMMA (hereinafter referred to as standard PMMA) is used as a standard. Several types of standard PMMA with different molecular weights are measured, and a calibration curve is created from the GPC elution volume and the molecular weight of the standard PMMA. In the present invention, a calibration curve created using the detector is used for measurement by the differential refractive index detector, and a calibration curve created using the detector is used for measurement by the absorptiometric detector. Using these calibration curves, the GPC elution volume is converted into the molecular weight, and the peak top molecular weight (A) and the peak top molecular weight (B) are determined.

  Prior to the GPC measurement, the PVA is heated at 120 ° C. for 3 hours. In the present invention, PVA is heated by the following method. That is, first, an aqueous solution in which PVA powder is dissolved is cast, and then dried at 23 ° C. and 50% RH to obtain a film. The thickness of the film is 30 to 75 μm, and preferably 40 to 60 μm. Next, the film is heated at 120 ° C. for 3 hours using a hot air dryer. From the viewpoint of suppressing heat treatment errors between samples, a gear oven is preferable as the hot air dryer.

  A heated PVA (film) is dissolved in the aforementioned solvent to obtain a measurement sample. The concentration of PVA in the measurement sample is 1.00 mg / mL, and the injection volume is 100 μL. However, when the viscosity average degree of polymerization of PVA exceeds 2400, the excluded volume increases, and therefore the PVA concentration may not be measured with good reproducibility at 1.00 mg / mL. In that case, an appropriately diluted sample (injection amount 100 μL) is used. Absorbance is proportional to the concentration of PVA. Therefore, the absorbance when the PVA concentration is 1.00 mg / mL is obtained using the concentration of the diluted sample and the actually measured absorbance.

  FIG. 1 shows the relationship between the molecular weight obtained by GPC measurement of PVA and the value measured by the differential refractive index detector, and the molecular weight and the absorptiometric detector (measurement wavelength). It is the graph which showed the relationship with the light absorbency measured by 280 nm. The GPC measurement in the present invention will be further described with reference to FIG. In FIG. 1, the chromatogram indicated by “RI” is a plot of the value measured by the differential refractive index detector against the molecular weight (horizontal axis) of PVA converted from the elution volume. In the present invention, the molecular weight at the peak position in the chromatogram is defined as peak top molecular weight (A). When there are a plurality of peaks in the chromatogram, the molecular weight at the peak position where the peak height is the highest is the peak top molecular weight (A).

  In FIG. 1, the chromatogram indicated by “UV” is a plot of the absorbance measured by an absorptiometric detector (measurement wavelength 280 nm) against the molecular weight (horizontal axis) of PVA converted from the elution volume. . In the present invention, the molecular weight at the peak position in the chromatogram is defined as peak top molecular weight (B). When there are a plurality of peaks in the chromatogram, the molecular weight at the peak position where the peak height is the highest is the peak top molecular weight (B).

The PVA has a peak top molecular weight (A) measured with a differential refractive index detector and a peak top molecular weight (B) measured with an absorptiometric detector (measurement wavelength 280 nm) when GPC measurement is performed by the above-described method. ) Satisfies the following formula (1).
(AB) / A <0.75 (1)

  The peak top molecular weight (A) is a value serving as an index of the molecular weight of PVA. On the other hand, the peak top molecular weight (B) is derived from a component present in PVA and having absorption at 280 nm. Usually, since the peak top molecular weight (A) is larger than the peak top molecular weight (B), (AB) / A becomes a positive value. If the peak top molecular weight (B) increases, (AB) / A decreases, and if the peak top molecular weight (B) decreases, (AB) / A increases. That is, when (A−B) / A is large, it means that there are many components that absorb ultraviolet rays having a wavelength of 280 nm in the low molecular weight components in PVA.

  When (A-B) / A is 0.75 or more, as described above, the component that absorbs ultraviolet light having a wavelength of 280 nm increases in the low molecular weight component. In this case, it is difficult to obtain a film that is less colored by heating and that is excellent in its dispersed state even if it contains a surfactant. From such a viewpoint, (A−B) / A is preferably less than 0.70, and more preferably less than 0.65.

The PVA needs to have an absorbance (measurement wavelength of 280 nm) at a peak top molecular weight (B) of 0.25 × 10 ^{−3 to} 3.00 × 10 ⁻³ when GPC measurement is performed by the method described above. When the absorbance is less than 0.25 × 10 ⁻³ , it is difficult to obtain a film excellent in the dispersion state of the surfactant. On the other hand, when the absorbance exceeds 3.00 × 10 ⁻³ , it is difficult to obtain a film that is less colored by heating. The absorbance is preferably 0.50 × 10 ^{−3 to} 2.80 × 10 ^{−3, and} more preferably 0.75 × 10 ^{−3 to} 2.50 × 10 ⁻³ .

From the viewpoint of the balance between the effect of reducing the colorability by heating and the effect of improving the dispersion state of the surfactant, the peak top molecular weight (A) measured by the differential refractive index detector and the spectrophotometric detection in the GPC measurement. The peak top molecular weight (C) measured by a vessel (measurement wavelength: 320 nm) is represented by the following formula (2)
(AC) / A <0.75 (2)
It is preferable to satisfy.

  The peak top molecular weight (C) is measured in the same manner as the peak top molecular weight (B) except that the measurement wavelength in the absorptiometric detector is 320 nm. The peak top molecular weight (C) is derived from a component present in PVA and having an absorption at 320 nm. Usually, since the peak top molecular weight (A) is larger than the peak top molecular weight (C), (AC) / A becomes a positive value. If the peak top molecular weight (C) increases, (AC) / A decreases, and if the peak top molecular weight (C) decreases, (AC) / A increases. That is, when (AC) / A is large, it means that there are many components that absorb ultraviolet rays having a wavelength of 320 nm among low molecular weight components in PVA.

  When (AC) / A is 0.75 or more, as described above, the low molecular weight component contains more components that absorb ultraviolet light having a wavelength of 320 nm. From the viewpoint of the balance between the effect of reducing the colorability by heating and the effect of improving the dispersion state of the surfactant, (AC) / A is more preferably less than 0.70, and even more preferably 0.65. Is less than.

From the viewpoint of the balance between the effect of reducing the colorability due to heating and the effect of improving the dispersion state of the surfactant, the PVA has an absorbance (measurement) at the peak top molecular weight (C) when GPC measurement is performed by the method described above. The wavelength 320 nm) is preferably 0.20 × 10 ^{−3 to} 2.90 × 10 ⁻³ . From the above viewpoint, the absorbance is more preferably 0.40 × 10 ^{−3 to} 2.70 × 10 ^{−3, and} still more preferably 0.60 × 10 ^{−3 to} 2.40 × 10 ⁻³ .

  Further, the PVA is the number average of the PVA obtained by the differential refractive index detector in the GPC measurement from the viewpoint of the balance between the effect of reducing the colorability by heating and the effect of improving the dispersion state of the surfactant. The ratio Mw / Mn of the weight average molecular weight Mw to the molecular weight Mn is preferably 2.2 to 6.0. Mw and Mn are obtained from a chromatogram obtained by plotting the values measured by the differential refractive index detector with respect to the molecular weight of PVA described above. Mw and Mn in the present invention are values in terms of PMMA.

  In general, Mn is an average molecular weight that is strongly influenced by a low molecular weight component, and Mw is an average molecular weight that is strongly influenced by a high molecular weight component. Mw / Mn is generally used as an index of molecular weight distribution of a polymer. When Mw / Mn is small, it indicates that the polymer has a small proportion of low molecular weight component, and when Mw / Mn is large, it indicates that the polymer has a large proportion of low molecular weight component.

  Therefore, in this invention, when Mw / Mn is less than 2.2, it shows that the ratio of a low molecular weight component is small in PVA. From the viewpoint of obtaining a film that is more excellent in the dispersed state of the surfactant, Mw / Mn is more preferably 2.3 or more. On the other hand, when Mw / Mn exceeds 6.0, it shows that the ratio of a low molecular weight component is large in PVA. From the viewpoint of obtaining a film with less coloring by heating, Mw / Mn is more preferably 3.5 or less, and further preferably 3.0 or less. It is considered that the low molecular weight component in PVA affects the colorability of the film by heating and the dispersion state of the surfactant.

The viscosity average degree of polymerization of the PVA is measured according to JIS-K6726. That is, after re-saponifying and purifying PVA to a saponification degree of 99.5 mol% or more, it can be obtained from the intrinsic viscosity [η] measured in water at 30 ° C. by the following equation.
P = ([η] × 10,000 / 8.29) ^{(1 / 0.62)}

  The viscosity average polymerization degree of the PVA is 200 to 5,000. When the viscosity average polymerization degree is less than 200, the strength of the formed film is insufficient. On the other hand, when the viscosity average degree of polymerization exceeds 5,000, the viscosity of the aqueous solution containing the PVA becomes high and film formation becomes difficult. The viscosity average degree of polymerization is preferably 250 to 4,500, more preferably 300 to 4,000, and still more preferably 400 to 3,500.

  The degree of saponification of the PVA is measured according to JIS-K6726. The saponification degree of the PVA is 50 to 99.99 mol%. When the degree of saponification is less than 50 mol%, the water solubility of PVA is significantly reduced. On the other hand, when the degree of saponification exceeds 99.99 mol%, PVA cannot be produced stably. The saponification degree is preferably 60 to 99.8 mol%, more preferably 70 to 99.7 mol%, and still more preferably 80 to 99.6 mol%.

  Examples of the vinyl ester used in the production of the PVA include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and versatic. Examples thereof include vinyl acid, and vinyl acetate is particularly preferable.

  The PVA is produced by polymerizing a vinyl ester in the presence of a thiol compound such as 2-mercaptoethanol, n-dodecyl mercaptan, mercaptoacetic acid, 3-mercaptopropionic acid, and saponifying the resulting polyvinyl ester. You can also. By this method, PVA in which a functional group derived from a thiol compound is introduced at the terminal is obtained.

  Examples of the method for polymerizing vinyl ester include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these methods, a bulk polymerization method performed without a solvent or a solution polymerization method performed using a solvent such as alcohol is usually employed. In terms of enhancing the effect of the present invention, a solution polymerization method in which polymerization is performed together with a lower alcohol is preferable. The lower alcohol is not particularly limited, but alcohols having 3 or less carbon atoms such as methanol, ethanol, propanol and isopropanol are preferable, and methanol is usually used. When performing the polymerization reaction by the bulk polymerization method or the solution polymerization method, either a batch method or a continuous method can be adopted as the reaction method. Examples of the initiator used for the polymerization reaction include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy- 2,4-dimethylvaleronitrile) and other azo initiators; organic peroxide initiators such as benzoyl peroxide and n-propyl peroxycarbonate, and the like, which are known initiators within a range not impairing the effects of the present invention. It is done. Among these, organic peroxide initiators having a half-life at 60 ° C. of 10 to 110 minutes are preferable, and it is particularly preferable to use peroxydicarbonate. Although there is no restriction | limiting in particular about the polymerization temperature at the time of performing a polymerization reaction, The range of 5 to 200 degreeC is suitable.

  When the vinyl ester is polymerized by a technique such as radical polymerization, a copolymerizable monomer can be copolymerized as necessary as long as the effects of the present invention are not impaired. Such monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, 1-hexene; carboxylic acids such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride or the like Derivatives; acrylic acid or salts thereof, acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate; methacrylic acid or salts thereof, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate Methacrylic acid esters such as isopropyl methacrylate; acrylamide; acrylamide derivatives such as N-methyl acrylamide and N-ethyl acrylamide; methacrylamide; methacrylamide derivatives such as N-methyl methacrylamide and N-ethyl methacrylamide; Vinyl ethers such as ruether, 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; 3-buten-1-ol, 4-penten-1-ol, 5-hexene-1 Hydroxy group-containing α-olefins such as ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3-buten-1-ol; Monomers having a sulfonic acid group such as acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyl Monomers having cationic groups such as roxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine Body: Vinyltrimethoxysilane, Vinylmethyldimethoxysilane, Vinyldimethylmethoxysilane, Vinyl Triethoxysilane, vinyl methyl diethoxy silane, vinyl dimethyl ethoxy silane, 3- (meth) acrylamido propyl trimethoxy silane, 3- (meth) monomers include having a silyl group such as acrylamide-propyltriethoxysilane. The amount of monomers copolymerizable with these vinyl esters varies depending on the purpose and application of use, but is usually 20 moles based on all monomers used for copolymerization. % Or less, preferably 10 mol% or less.

  PVA can be obtained by saponifying the polyvinyl ester obtained by the above-mentioned method in an alcohol solvent.

  As the catalyst for the saponification reaction of the polyvinyl ester, an alkaline substance is usually used, and examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. The amount of the alkaline substance used is preferably within a range of 0.002 to 0.2 in a molar ratio based on the vinyl ester monomer unit of the polyvinyl ester, and within a range of 0.004 to 0.1. It is particularly preferred. The catalyst for the saponification reaction may be added all at once in the early stage of the saponification reaction, or a part thereof may be added in the early stage of the saponification reaction and the rest may be added during the saponification reaction.

  Examples of the solvent that can be used for the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, diethyl sulfoxide, dimethylformamide, and the like. Of these solvents, methanol is preferably used. At this time, the moisture content of methanol is preferably adjusted to 0.001 to 1% by mass, more preferably 0.003 to 0.9% by mass, and particularly preferably 0.005 to 0.8% by mass.

  The saponification reaction is preferably performed at a temperature of 5 to 80 ° C, more preferably 20 to 70 ° C. The saponification reaction is preferably performed for 5 minutes to 10 hours, more preferably for 10 minutes to 5 hours. The saponification reaction can be performed by either a batch method or a continuous method. After completion of the saponification reaction, the remaining catalyst may be neutralized as necessary. Usable neutralizing agents include organic acids such as acetic acid and lactic acid, and esters such as methyl acetate.

  The alkaline substance containing an alkali metal added during the saponification reaction is usually neutralized by an ester such as methyl acetate generated by the progress of the saponification reaction, or neutralized by a carboxylic acid such as acetic acid added after the reaction. At this time, an alkali metal salt of a carboxylic acid such as sodium acetate is formed. As will be described later, in the film of the present invention, the content of the alkali metal salt of the carboxylic acid needs to be 0.5% by mass or less in terms of the mass of the alkali metal. To obtain such a film, the PVA may be washed after saponification.

  Examples of the cleaning liquid used in this case include a lower alcohol such as methanol, a solution composed of 100 parts by weight of the lower alcohol and 20 parts by weight or less of water, and a solution composed of the lower alcohol and an ester such as methyl acetate produced in the saponification step. It is done. The content of the ester in the solution composed of the lower alcohol and the ester is not particularly limited, but is preferably 1,000 parts by mass or less with respect to 100 parts by mass of the lower alcohol. The addition amount of the cleaning liquid is preferably 100 to 10,000 parts by mass, more preferably 150 to 5,000 parts by mass, and more preferably 200 to 1 with respect to 100 parts by mass of the gel obtained by saponification and PVA swollen with alcohol. Is more preferable. When the addition amount of the cleaning liquid is less than 100 parts by mass, the content of the alkali metal salt of the carboxylic acid may exceed the above range in the obtained film. On the other hand, when the addition amount of the cleaning liquid exceeds 10,000 parts by mass, it is difficult to expect improvement of the cleaning effect by increasing the addition amount. Although there is no particular limitation on the washing method, for example, a step of adding a gel (PVA) and a washing liquid in a tank, stirring or standing at 5 to 100 ° C. for about 5 to 180 minutes, and then removing the liquid is performed. A batch system that repeats until the content of the alkali metal salt of the acid is in a desired range is exemplified. Further, there is a continuous method in which PVA is continuously added from the top of the column at the same temperature and for the same time as the batch method, and a lower alcohol is continuously added from the bottom of the column, and the two are brought into contact with each other.

  In preparing the PVA, the peak top molecular weight (A), the peak top molecular weight (B), the absorbance at the peak top molecular weight (B), the peak top molecular weight (C), and the absorbance at the peak top molecular weight (C) are as described above. As a method of adjusting so as to satisfy, for example, the following methods can be mentioned.

  A) A vinyl ester from which a radical polymerization inhibitor contained in the raw vinyl ester has been removed in advance is used for the polymerization.

  B) A vinyl ester having a total content of impurities contained in the raw material vinyl ester of preferably 1 to 1,200 ppm, more preferably 3 to 1,100 ppm, and still more preferably 5 to 1,000 ppm is used for radical polymerization. . Impurities include aldehydes such as acetaldehyde, crotonaldehyde, and acrolein; acetaldehyde such as acetaldehyde dimethyl acetal, crotonaldehyde dimethyl acetal, and acrolein dimethyl acetal obtained by acetalizing the aldehyde with a solvent alcohol; ketones such as acetone; methyl acetate and ethyl acetate Ester etc. are mentioned.

  C) In order to suppress alcoholic decomposition and hydrolysis of vinyl ester due to alcohol or a small amount of water in a series of steps in which raw material vinyl ester is radically polymerized in alcohol solvent and unreacted vinyl ester is recovered and reused, Organic acids, specifically hydroxycarboxylic acids such as glycolic acid, glyceric acid, malic acid, citric acid, lactic acid, tartaric acid, salicylic acid; malonic acid, succinic acid, maleic acid, phthalic acid, oxalic acid, glutaric acid A carboxylic acid or the like is added to suppress the generation of aldehydes such as acetaldehyde generated by decomposition as much as possible. The addition amount of the organic acid is preferably 1 to 500 ppm, more preferably 3 to 300 ppm, and still more preferably 5 to 100 ppm with respect to the raw material vinyl ester.

  D) As a solvent used for polymerization, a solvent having a total content of impurities of preferably 1 to 1,200 ppm, more preferably 3 to 1,100 ppm, and still more preferably 5 to 1,000 ppm. Examples of the impurities contained in the solvent include those described above as the impurities contained in the raw material vinyl ester.

  E) When the vinyl ester is radically polymerized, the ratio of the solvent to the vinyl ester is increased.

  F) An organic peroxide is used as a radical polymerization initiator used for radical polymerization of vinyl ester. Organic peroxides include acetyl peroxide, isobutyl peroxide, diisopropyl peroxycarbonate, diallyl peroxydicarbonate, di-n-propyl peroxydicarbonate, dimyristyl peroxydicarbonate, di (2-ethoxyethyl) And peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, di (methoxyisopropyl) peroxydicarbonate, di (4-tert-butylcyclohexyl) peroxydicarbonate, and the like. It is preferable to use peroxydicarbonate having a half-life of 10 to 110 minutes.

  G) When an inhibitor is added after radical polymerization of the vinyl ester in order to suppress polymerization, an inhibitor of 5 molar equivalents or less is added to the remaining undecomposed radical polymerization initiator. As a kind of inhibitor, a compound having a conjugated double bond having a molecular weight of 1,000 or less and stabilizing a radical to inhibit a polymerization reaction can be mentioned. Specifically, for example, isoprene, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-t-butyl-1,3-butadiene, 1,3-pentadiene 2,3-dimethyl-1,3-pentadiene, 2,4-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-pentadiene, 3-ethyl-1,3-pentadiene, 2-methyl -1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 2,5-dimethyl-2,4-hexadiene 1,3-octadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-methoxy-1,3-butadiene, 2-methoxy-1,3-butadiene, 1-ethoxy- , 3-butadiene, 2-ethoxy-1,3-butadiene, 2-nitro-1,3-butadiene, chloroprene, 1-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-bromo -1,3-butadiene, fulvene, tropone, osymene, ferrandrene, myrcene, farnesene, semblene, sorbic acid, sorbic acid ester, sorbic acid salt, abietic acid, etc. Conjugated dienes; from conjugated structures of three carbon-carbon double bonds such as 1,3,5-hexatriene, 2,4,6-octatriene-1-carboxylic acid, eleostearic acid, tung oil, cholecalciferol Conjugated triene: cyclooctatetraene, 2,4,6,8-decatetraene-1-carboxylic acid, retinol, retinoic acid, etc. Carbon - include polyenes such as conjugated polyene consisting of carbon-carbon double bond of four or more conjugated structure. Any of those having a plurality of stereoisomers such as 1,3-pentadiene, myrcene, and farnesene may be used. Further, p-benzoquinone, hydroquinone, hydroquinone monomethyl ether, 2-phenyl-1-propene, 2-phenyl-1-butene, 2,4-diphenyl-4-methyl-1-pentene, 3,5-diphenyl-5 Methyl-2-heptene, 2,4,6-triphenyl-4,6-dimethyl-1-heptene, 3,5,7-triphenyl-5-ethyl-7-methyl-2-nonene, 1,3- Diphenyl-1-butene, 2,4-diphenyl-4-methyl-2-pentene, 3,5-diphenyl-5-methyl-3-heptene, 1,3,5-triphenyl-1-hexene, 2,4 , 6-triphenyl-4,6-dimethyl-2-heptene, 3,5,7-triphenyl-5-ethyl-7-methyl-3-nonene, 1-phenyl-1,3-butadiene, 1,4 -Diff Aromatic compounds such-1,3-butadiene and the like.

  H) An alcohol solution of polyvinyl ester from which the remaining vinyl ester is removed as much as possible is used for the saponification reaction. Preferably, the residual monomer removal rate is 99% or more, more preferably 99.5% or more, still more preferably 99.8% or more.

  A desired PVA can be obtained by appropriately combining A) to H). By producing a film in which the content of the alkali metal salt of the carboxylic acid is in a specific range using the PVA thus obtained, there is little coloring due to heating, and even in the case of containing a surfactant, the dispersion state is excellent. A film is easily obtained.

  The film of the present invention contains an alkali metal salt of a carboxylic acid, and the content thereof is 0.5% by mass or less, preferably 0.37% by mass or less, more preferably 0.8% by mass in terms of alkali metal mass. It is 28 mass% or less, More preferably, it is 0.23 mass% or less. When the said content exceeds 0.5 mass%, it becomes difficult to obtain a film with little coloring by heating. A film having such a content can be obtained by adjusting the content of an alkali metal salt of a carboxylic acid contained in a raw material such as PVA used for production.

  In the present invention, the content of the alkali metal salt of the carboxylic acid (the alkali metal mass conversion value) is obtained by ashing the PVA or film with a platinum crucible and then measuring the obtained ash content by ICP emission analysis. It can be determined from the amount of metal ions.

  Examples of the alkali metal salt of carboxylic acid include those obtained by neutralizing an alkali catalyst used in the above saponification step, such as sodium hydroxide, potassium hydroxide, sodium methylate, etc. with carboxylic acid, and the above polymerization step. Carboxylic acid added for the purpose of suppressing the alcoholysis of vinyl esters such as vinyl acetate used in saponification is obtained by neutralization in the saponification process, and as a inhibitor added to stop radical polymerization. When a carboxylic acid having a heavy bond is used, it includes those obtained by neutralizing the carboxylic acid in a saponification step, or those intentionally added. Specific examples include sodium acetate, potassium acetate, sodium propionate, potassium propionate, sodium glycerate, potassium glycerate, sodium malate, potassium malate, sodium citrate, potassium citrate, sodium lactate, potassium lactate, tartaric acid Sodium, potassium tartrate, sodium salicylate, potassium salicylate, sodium malonate, potassium malonate, sodium succinate, potassium succinate, sodium maleate, potassium maleate, sodium phthalate, potassium phthalate, sodium oxalate, potassium oxalate , Sodium glutarate, potassium glutarate, sodium abietic acid, potassium abietic acid, sodium sorbate, potassium sorbate, 2,4,6-octatri Sodium -1-carboxylate, potassium 2,4,6-octatriene-1-carboxylate, sodium eleostearate, potassium eleostearate, sodium 2,4,6,8-decatetraene-1-carboxylate 2,4,6,8-decatetraene-1-carboxylate, sodium retinoate, potassium retinoate and the like, but are not limited thereto.

  The film of the present invention may contain a plasticizer. Although there is no restriction | limiting in particular in the kind of plasticizer, Polyhydric alcohol type plasticizers, such as glycerol, trimethylene glycol, propylene glycol, diethylene glycol, are preferable, and glycerol is especially preferable. The plasticizer content is preferably 30 parts by mass or less and more preferably 25 parts by mass or less with respect to 100 parts by mass of PVA. If the plasticizer content exceeds 30 parts by mass, the plasticizer may ooze out on the surface of the film.

  The film of the present invention can contain a surfactant. Examples of the surfactant include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant, and one or more of these can be used.

  Examples of the anionic surfactant include carboxylic acid types such as potassium laurate; sulfate ester types such as octyl sulfate; sulfonic acid types such as dodecylbenzenesulfonate and sodium alkylbenzenesulfonate; polyoxyethylene lauryl ether phosphate mono Ethanolamine salt, octyl phosphate potassium salt, lauryl phosphate potassium salt, stearyl phosphate potassium salt, octyl ether phosphate potassium salt, dodecyl phosphate sodium salt, tetradecyl phosphate sodium salt, dioctyl phosphate Ester sodium salt, Trioctyl phosphate sodium salt, Polyoxyethylene aryl phenyl ether phosphate potassium salt, Polyoxyethylene aryl ester Such as alkenyl ether phosphate amine salts.

  Examples of nonionic surfactants include alkyl ether types such as polyoxyethylene oleyl ether and polyoxyethylene lauryl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate. Alkylamine type such as polyoxyethylene lauryl amino ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; lauric acid diethanolamide, oleic acid diethanolamide, etc. Examples include alkanolamide type; allyl phenyl ether type such as polyoxyalkylene allyl phenyl ether.

  Examples of the cationic surfactant include amines such as laurylamine hydrochloride; quaternary ammonium salts such as lauryltrimethylammonium chloride; and pyridium salts such as laurylbiridinium chloride.

  Examples of amphoteric surfactants include N-alkyl-N, N-dimethylammonium betaine.

  The content of the surfactant is preferably in the range of 0.01 to 5 parts by mass and more preferably in the range of 0.02 to 3 parts by mass with respect to 100 parts by mass of PVA.

  The film of the present invention can contain an inorganic filler. Examples of the inorganic filler include silica, heavy or light calcium carbonate that may be surface-treated, aluminum hydroxide, aluminum oxide, titanium oxide, diatomaceous earth, mica, magnesium carbonate, kaolin, halosite, viroferrite, selenium. Examples include clays such as sites, talc, and the like, and one or more of these can be used. Among these, silica and talc are preferable from the viewpoint of dispersibility in PVA. It is preferable that content of an inorganic filler is 10 mass parts or less with respect to 100 mass parts of PVA.

  In addition to those described above, the film of the present invention has a crosslinking agent, a colorant, a fragrance, an extender, an antifoaming agent, a release agent, an ultraviolet absorber, starch, and a resin other than PVA (for example, a water-soluble high-performance material other than PVA). Other components such as molecules) can be further included as necessary. The ratio of the total mass of PVA, plasticizer, surfactant and inorganic filler to the total mass of the film of the present invention is preferably in the range of 50 to 100% by mass, and in the range of 80 to 100% by mass. It is more preferable that the content is within the range of 90 to 100% by mass.

  There is no restriction | limiting in particular in the thickness of the film of this invention, Although it can set suitably according to the use, usage aspect, etc. of the film of this invention, it is preferable to exist in the range of 1-100 micrometers, The range of 3-50 micrometers More preferably, it is within. In addition, the thickness of a film can measure the thickness of arbitrary 5 places, and can obtain | require it as those average values.

  Although there is no restriction | limiting in particular in the manufacturing method of the film of this invention which content of the alkali metal salt of carboxylic acid exists in the said range, According to the manufacturing method of this invention which has the process of drying the film forming stock solution containing the said PVA, The film of the present invention can be efficiently produced, which is preferable.

  Examples of the liquid medium used for preparing the membrane forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, Trimethylolpropane, ethylenediamine, diethylenetriamine and the like can be mentioned, and one or more of these can be used. Among these, water is preferable from the viewpoint of a small environmental load and recoverability. There is no restriction | limiting in particular in the density | concentration of PVA in a film forming undiluted | stock solution, For example, it can be 0.1-50 mass%.

  There is no particular limitation on the method of mixing the PVA with additives such as the above-mentioned plasticizer, surfactant, inorganic filler and other components when preparing the film forming stock solution. For example, PVA pellets and additives are mixed. Then, this is mixed with the liquid medium as a mixture; the PVA dissolved in the liquid medium is mixed with the additive; the additive is dispersed in the surfactant and then mixed with the PVA; And a method of dispersing the product in a plasticizer and then mixing with PVA. Among these, since it is possible to easily obtain a film in which the additive is more uniformly dispersed, it is preferable to adopt a method in which the additive is dispersed in a surfactant and then mixed with PVA. It is more preferable to adopt a method in which PVA and a liquid medium are mixed after being dispersed in the agent.

  When one or more of additives such as the above-mentioned plasticizer, surfactant, inorganic filler, and other components are blended in the film, these components are added in advance before film formation. It is preferable to make it contain in the film-forming stock solution. There is no particular limitation on the blending time of these components, and further blending into the mixture of PVA and surfactant as described above, or before mixing of PVA and surfactant, The method of mix | blending in advance in one or both of these is mentioned.

  In the step of drying the film-forming stock solution, the specific drying method is not particularly limited, and a drying method generally employed when producing a cast film can be employed. The formed film can be heat-treated as necessary. The temperature of the heat treatment is preferably in the range of 70 to 145 ° C, and more preferably in the range of 100 to 135 ° C. Examples of the heat treatment time include a range of 1 second to 1 hour. In addition, in the process of manufacturing the film including the heat treatment, the water swellability of the obtained film may be reduced when exposed to a temperature that is too high, and thus until the film is manufactured using the film forming stock solution. It is preferable to keep the film forming stock solution and the film at a temperature of 180 ° C. or lower, preferably 150 ° C. or lower, more preferably 145 ° C. or lower, and particularly preferably 135 ° C. or lower.

  If necessary, uniaxial or biaxial stretching may be performed at any one or two or more stages before, during or after drying. The stretching temperature is preferably in the range of 20 to 120 ° C. In addition, the draw ratio is preferably in the range of 1.05 to 5 times, more preferably in the range of 1.1 to 3 times, based on the length before drawing. Further, if necessary, the residual stress can be reduced by heat fixing the film after stretching.

  The film of the present invention is less colored by heating. The YI value of the film of the present invention when heated at 120 ° C. for 3 hours is preferably 7 or less, more preferably 5 or less, further preferably 4 or less, and preferably 2 or less. Particularly preferred is 0.3 or more. The YI value can be determined according to JIS K 7105, and specifically can be determined by the method described later in the examples.

  The use of the film of the present invention is not particularly limited, but the film of the present invention is less colored by heating and is excellent in its dispersed state even when it contains a surfactant. (Films for warming vegetables, growing vegetables, etc.), gas barrier materials, filters, optical films such as polarizing films, hydraulic transfer, packaging, agriculture, civil engineering, medical, industrial, Japan It can be preferably used for water-soluble films and biodegradable films for household goods and toys.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified. “Polymerization degree” means “viscosity average polymerization degree”.

[Polymerization degree and saponification degree of PVA]
The degree of polymerization and saponification of PVA were determined by the method described in JIS-K6726.

[Content of sodium acetate in PVA and film]
The content of sodium acetate in the PVA and film (mass converted value of sodium) was determined by using the Jerrel Ash ICP emission analyzer “IRIS AP” after ashing the PVA or film. This was determined by measuring the amount of sodium.

[GPC measurement of PVA]
(PVA heating)
The PVA powder was put in water, heated at 95 ° C. for 1 hour to dissolve, and then cooled to room temperature to obtain a 2% aqueous solution of PVA. Next, the obtained aqueous solution was cast on a polyethylene terephthalate film (20 cm × 20 cm) and dried for 2 weeks under the conditions of 23 ° C. and 50% RH to obtain a film having a thickness of 50 μm. The obtained film was fixed with a clip to a stainless steel metal mold (20 cm × 20 cm, 1 cm wide metal frame), and heated in a gear oven at 120 ° C. for 3 hours.

(measuring device)
GPC measurement was performed using “GPCmax” manufactured by VISCOTECH. As a differential refractive index detector, “TDA305” manufactured by VISCOTECH was used. “UV Detector 2600” manufactured by VISCOTECH was used as an ultraviolet-visible absorption detector. The optical path length of the detection cell of the absorptiometric detector is 10 mm. “GPC HFIP-806M” manufactured by Showa Denko KK was used for the GPC column. Moreover, OmniSEC (Version 4.7.0.406) attached to the apparatus was used as analysis software.

(Measurement condition)
A sample was collected from the vicinity of the center of the heated film obtained by the above method. The sample was dissolved in 20 mmol / L sodium trifluoroacetate-containing HFIP to prepare a 1.00 mg / mL solution of PVA. The solution was filtered through a 0.45 μm polytetrafluoroethylene filter and used for measurement.

  As the mobile phase, HFIP containing 20 mmol / L sodium trifluoroacetate was used. The mobile phase flow rate was 1.0 mL / min. The sample injection amount was 100 μL, and measurement was performed at a GPC column temperature of 40 ° C.

In addition, in the case of the sample whose viscosity average polymerization degree of PVA exceeds 2400, GPC measurement was performed using the solution (100 microliters) diluted suitably. The absorbance at a sample concentration of 1.00 mg / mL was calculated from the measured value by the following formula. α (mg / mL) is the concentration of the diluted sample.
Absorbance at a sample concentration of 1.00 mg / mL = (1.00 / α) × measured value of absorbance

(Create a calibration curve)
As a standard, PMMA (peak top molecular weight: 1,944,000, 790,000, 467,400, 271,400, 144,000, 79,250, 35,300, 13,300, 7, manufactured by Agilent Technologies 100, 1,960, 1,020, 690), and a calibration curve for converting the elution volume into the PMMA molecular weight was prepared for each of the differential refractive index detector and the absorptiometric detector. The analytical software was used to create each calibration curve.
In this measurement, a column capable of separating peaks of standard samples having both molecular weights of 1,944,000 and 271400 was used in the measurement of PMMA. Moreover, in this apparatus, the peak intensity obtained from the differential refractive index detector is expressed in mV (millivolt), and the peak intensity obtained from the ultraviolet-visible absorbance detector is expressed in absorbance (abs unit: Absorbance unit).

[Colorability of film]
A film containing PVA was prepared and heated by the method described above in “GPC measurement of PVA” — “PVA heating”. And about the film after a heating, yellowness (YI value) was calculated | required according to JISK7105 using SM color computer "SM-TH" by Suga Test Instruments Co., Ltd., and it was set as the index of the coloring property of the film by heating. .

[Dispersed state of surfactant in film]
100 parts of PVA and 0.1 part of lauric acid diethanolamide were heated at 95 ° C. for 1 hour and dissolved in water, and then cooled to room temperature to obtain a 4% aqueous solution of PVA. The obtained aqueous solution was cast on a polyethylene terephthalate film (20 cm × 20 cm) and dried for 1 week under conditions of 23 ° C. and 50% RH to obtain a film having a thickness of 50 μm. The obtained film was observed with a 200-fold optical microscope, and the dispersion state of the surfactant (presence of aggregates) was evaluated.

[Synthesis of polyvinyl acetate]
(PVAc-1)
A 6-liter separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a reflux tube was previously deoxygenated and contained vinyl acetate (VAM) 2 containing 500 ppm of acetaldehyde (AA) and 50 ppm of acetaldehyde dimethyl acetal (DMA). 555 g; methanol (MeOH) 945 g containing 50 ppm of acetaldehyde dimethyl acetal and acetaldehyde content of less than 1 ppm; a 1% methanol solution of tartaric acid in an amount of 20 ppm of tartaric acid in vinyl acetate was charged. While blowing nitrogen into the flask, the temperature in the flask was kept at 60 ° C. In addition, -10 degreeC ethylene glycol / water solution was circulated through the reflux pipe. A 0.55 mass% methanol solution of di-n-propyl peroxydicarbonate was prepared, and 18.6 mL was added to the flask to initiate polymerization. The amount of di-n-propyl peroxydicarbonate added at this time was 0.081 g. A methanol solution of di-n-propyl peroxydicarbonate was sequentially added at a rate of 20.9 mL / hour until the completion of polymerization. During the polymerization, the temperature in the flask was kept at 60 ° C. Four hours after the start of polymerization, when the solid content concentration of the polymerization solution reached 25.1%, 0.0141 g of sorbic acid (3% of di-n-propyl peroxydicarbonate remaining undecomposed in the polymerization solution) was obtained. After adding 1200 g of contained methanol (corresponding to a molar equivalent), the polymerization liquid was cooled to terminate the polymerization. When the polymerization was stopped, the polymerization rate of vinyl acetate was 35.0%. After the polymerization solution was cooled to room temperature, the pressure in the flask was reduced using a water flow aspirator to distill off vinyl acetate and methanol, thereby precipitating polyvinyl acetate. After 3,000 g of methanol was added to the precipitated polyvinyl acetate and the polyvinyl acetate was dissolved while heating at 30 ° C., the pressure in the flask was reduced again using a water aspirator, so that the vinyl acetate and methanol were retained. And polyvinyl acetate was precipitated. The operation of dissolving polyvinyl acetate in methanol and then precipitating it was further repeated twice. Methanol was added to the precipitated polyvinyl acetate to obtain a 40% by mass methanol solution of polyvinyl acetate (PVAc-1) with a vinyl acetate removal rate of 99.8%.

  The viscosity average degree of polymerization was measured using a part of the obtained methanol solution of PVAc-1. To a methanol solution of PVAc-1, a 10% methanol solution of sodium hydroxide was added so that the molar ratio of sodium hydroxide to vinyl acetate monomer units in polyvinyl acetate was 0.1. When the gelled product was formed, the gel was pulverized and subjected to Soxhlet extraction with methanol for 3 days. The obtained PVA was dried and subjected to measurement of the viscosity average polymerization degree. The viscosity average degree of polymerization was 1700.

(PVAc-2 to PVAc-20)
Polyvinyl acetate (PVAc-2 to PVAc-20) was obtained by the same method as PVAc-1, except that the conditions described in Table 1 were changed. In Table 1, “ND” means less than 1 ppm. Viscosity average polymerization degree of each obtained polyvinyl acetate was calculated | required similarly to PVAc-1. The results are shown in Table 1.

[Example 1]
The total solid concentration (saponification concentration) is 30% by mass with respect to a 40% by mass methanol solution of PVAc-1, and the molar ratio of sodium hydroxide to the vinyl acetate monomer unit in PVAc-1 is 0. The saponification reaction was started at 40 ° C. by adding methanol and an 8% methanol solution of sodium hydroxide with stirring so that the ratio became 0.02. The gel is pulverized when the gelated product is generated as the saponification reaction proceeds, and the crushed gel is transferred to a container at 40 ° C. When 60 minutes have elapsed from the start of the saponification reaction, methanol / methyl acetate / water ( 25/70/5 mass ratio) solution and neutralized. The obtained swollen gel was centrifuged, immersed in methanol twice the weight of the swollen gel, allowed to stand for 30 minutes, and then centrifuged four times and dried at 60 ° C. for 1 hour. And dried at 100 ° C. for 2 hours to obtain PVA.

  The obtained PVA had a viscosity average polymerization degree of 1,700, a saponification degree of 99.1 mol%, and a sodium acetate content of 0.7% (0.20% in terms of mass of sodium (Na)). . These data are also shown in Table 2.

GPC measurement was performed by the said method using obtained PVA. FIG. 1 is a graph showing the relationship between the molecular weight and the value measured with a differential refractive index detector, and the relationship between the molecular weight and the absorbance measured with an absorptiometric detector (measurement wavelength 280 nm). The molecular weight at this time is one converted from the elution volume using a calibration curve (PMMA equivalent molecular weight). The peak top molecular weight (A) measured with the differential refractive index detector obtained from FIG. 1 was 100,000, and the peak top molecular weight (B) measured with the absorptiometric detector (280 nm) was 53,000. It was. The obtained value is expressed by the following formula (AB) / A
The value obtained by substituting for was 0.47. The absorbance at the peak top molecular weight (B) was 1.30 × 10 ⁻³ . These results are also shown in Table 2.

The peak top molecular weight (C) measured with an absorptiometric detector (320 nm) determined in the same manner as the method for determining the peak top molecular weight (B) was 50,000. The peak top molecular weight (A) and the peak top molecular weight (C) are expressed by the following formula (AC) / A
The value obtained by substituting for was 0.50. The absorbance at the peak top molecular weight (C) was 1.05 × 10 ⁻³ . These results are also shown in Table 2.

  Each measurement or evaluation of the content of sodium acetate (mass conversion value of sodium (Na)), the colorability of the film, and the dispersion state of the surfactant in the film was performed by the method described above using the obtained PVA. . The results are shown in Table 2.

[Examples 2 to 20, 22 to 24, Comparative Examples 1 to 21 and 23 to 28]
Except having changed into the conditions shown in Table 2 and 3, each PVA was synthesize | combined like Example 1, and each measurement or evaluation was performed like Example 1 using obtained PVA. The results are shown in Tables 2 and 3.

[Example 21]
The total solid concentration (saponification concentration) is 40% by mass with respect to a 55% by mass methanol solution of PVAc-3, and the molar ratio of sodium hydroxide to the vinyl acetate monomer unit in PVAc-3 is 0. A saponification reaction was started at 40 ° C. by adding methanol and an 8% methanol solution of sodium hydroxide under stirring so as to obtain 0.005. Note that saponification reaction was performed by adding distilled water so that the water content in the system was 1.2%. One hour after adding the sodium hydroxide methanol solution, 0.8 molar equivalent of 1% acetic acid aqueous solution of sodium hydroxide and a large amount of distilled water were added to stop the saponification reaction. The obtained solution was transferred to a dryer, dried at 65 ° C. for 12 hours, and then dried at 100 ° C. for 2 hours to obtain PVA.

  Each measurement or evaluation was performed in the same manner as in Example 1 using the obtained PVA. The results are shown in Table 3.

[Comparative Example 22]
The total solid concentration (saponification concentration) is 40% by mass with respect to a 55% by mass methanol solution of PVAc-3, and the molar ratio of sodium hydroxide to the vinyl acetate monomer unit in PVAc-3 is 0. A saponification reaction was started at 40 ° C. by adding methanol and an 8% methanol solution of sodium hydroxide under stirring so as to obtain 0.005. Note that saponification reaction was performed by adding distilled water so that the water content in the system was 3.0%. One hour after adding the sodium hydroxide methanol solution, 0.8 molar equivalent of 1% acetic acid aqueous solution of sodium hydroxide and a large amount of distilled water were added to stop the saponification reaction. The obtained solution was transferred to a dryer, dried at 65 ° C. for 12 hours, and then dried at 100 ° C. for 2 hours to obtain PVA.

  Although each measurement or evaluation was attempted in the same manner as in Example 1 using the obtained PVA, since the obtained PVA was insoluble in water, a film for GPC measurement could not be prepared. Therefore, only some evaluation results are shown in Table 2.

  As is clear from the above results, the film of the present invention is less colored by heating and is excellent in its dispersed state even when it contains a surfactant.

Claims (11)

It contains polyvinyl alcohol having a saponification degree of 50 to 99.99 mol% and a viscosity average polymerization degree of 200 to 5,000, and the content of alkali metal salt of carboxylic acid is 0.5% by mass or less in terms of mass of alkali metal. A film that is
When the polyvinyl alcohol heated at 120 ° C. for 3 hours is measured by gel permeation chromatography, the peak top molecular weight (A) measured by a differential refractive index detector and measured by an absorptiometric detector (measurement wavelength: 280 nm) The peak top molecular weight (B) is expressed by the following formula (1)
(AB) / A <0.75 (1)
And the absorbance at the peak top molecular weight (B) is 0.25 × 10 ^{−3 to} 3.00 × 10 ⁻³ . In the gel permeation chromatography measurement, the peak top molecular weight (A) measured with a differential refractive index detector and the peak top molecular weight (C) measured with an absorptiometric detector (measurement wavelength 320 nm) are expressed by the following formula (2). )
(AC) / A <0.75 (2)
The film according to claim 1, wherein In the gel permeation chromatography measurement, the absorbance at the peak top molecular weight (C) measured by an absorptiometric detector (measurement wavelength: 320 nm) is 0.20 × 10 ^{−3 to} 2.90 × 10 ^−3. Item 3. The film according to Item 1 or 2.   The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the polyvinyl alcohol obtained by a differential refractive index detector in the gel permeation chromatography measurement is 2.2 to 6.0. The film in any one of -3.   The film according to any one of claims 1 to 4, further comprising a surfactant.   The film in any one of Claims 1-5 whose YI value when heated at 120 degreeC for 3 hours is 7 or less. The content of the alkali metal salt of the carboxylic acid has a step of drying a film-forming stock solution containing polyvinyl alcohol having a saponification degree of 50 to 99.99 mol% and a viscosity average polymerization degree of 200 to 5,000. It is a manufacturing method of the film which is 0.5 mass% or less in terms of mass,
When the polyvinyl alcohol heated at 120 ° C. for 3 hours is measured by gel permeation chromatography, the peak top molecular weight (A) measured by a differential refractive index detector and measured by an absorptiometric detector (measurement wavelength: 280 nm) The peak top molecular weight (B) is expressed by the following formula (1)
(AB) / A <0.75 (1)
And the absorbance at the peak top molecular weight (B) is 0.25 × 10 ^{−3 to} 3.00 × 10 ⁻³ . In the gel permeation chromatography measurement, the peak top molecular weight (A) measured with a differential refractive index detector and the peak top molecular weight (C) measured with an absorptiometric detector (measurement wavelength 320 nm) are expressed by the following formula (2). )
(AC) / A <0.75 (2)
The manufacturing method of Claim 7 which satisfy | fills. In the gel permeation chromatography measurement, the absorbance at the peak top molecular weight (C) measured by an absorptiometric detector (measurement wavelength: 320 nm) is 0.20 × 10 ^{−3 to} 2.90 × 10 ^−3. Item 9. The manufacturing method according to Item 7 or 8.   The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the polyvinyl alcohol obtained by a differential refractive index detector in the gel permeation chromatography measurement is 2.2 to 6.0. The manufacturing method in any one of -9.   The manufacturing method in any one of Claims 7-10 in which the said film-forming stock solution further contains surfactant.

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