WO2011132592A1 - Polyvinyl alcohol film - Google Patents

Abstract

Disclosed is a polyvinyl alcohol film containing a polyvinyl alcohol polymer (A), and 0.001 to 1 parts by mass of a surfactant (B) with respect to 100 parts by mass of the polyvinyl alcohol polymer (A). The color of the polyvinyl alcohol film, which has a pH of 2.0 to 8.0 at 20°C when dissolved in water at a concentration of 7 mass%, does not easily take on a yellow tinge, even after being stored for several months in a temperature-controlled warehouse, or the like, at near normal temperature. The polyvinyl alcohol polymer is preferably obtained using an acidic substance (C).

Description

Polyvinyl alcohol polymer film

The present invention relates to a polyvinyl alcohol (hereinafter, “polyvinyl alcohol” may be abbreviated as “PVA”) polymer film, a method for producing the same, and a method for storing the PVA polymer film.

PVA polymer films formed from PVA polymers are used for optical applications such as polarizing film manufacturing raw materials, chemicals such as agricultural chemicals and detergents, taking advantage of the unique characteristics of water solubility and various other excellent physical properties. It is used in various applications such as medicine packaging and textile packaging.

By the way, a method of adding a nonionic surfactant as a method for suppressing the generation of die lines and foreign matters when forming a PVA polymer film using a T die or the like and improving the film forming property has been proposed. (See Patent Document 1). In addition, as a method of providing a PVA polymer film that has excellent optical characteristics without optical streaks and optical color unevenness and can exhibit an effect of excellent blocking resistance, a specific surfactant is used. A method of blending a plurality of types has been proposed (see Patent Document 2).

JP 2001-253993 A JP 2005-206809 A

However, when the PVA polymer film produced by blending the surfactant is rolled up and stored in a warehouse where the temperature is controlled near room temperature for about several months, the color of the roll is extremely yellowish. It has become clear in recent years that there is a problem with This yellowing hardly affects the physical properties of the PVA polymer film such as mechanical strength, stretchability, haze, etc., but when used as a packaging material, the color of the contents becomes yellowish, or the polarizing film The light transmitted through the polarizing film obtained when used as a raw material for producing the product may be yellowish, and may give a bad impression to consumers and users.

An object of the present invention is to provide a PVA polymer film in which the color of the film is hardly yellowish even after being stored for about several months in a warehouse whose temperature is controlled near room temperature.

As a result of intensive studies to achieve the above object, the present inventor is a PVA polymer film containing a PVA polymer and a surfactant, and the pH when dissolved in water is within a certain range. The present inventors have found that the above object can be achieved by a certain PVA polymer film, and have further studied based on the findings to complete the present invention.

That is, the present invention
[1] A PVA polymer film containing 0.001 to 1 part by mass of a surfactant (B) with respect to 100 parts by mass of the PVA polymer (A) and the PVA polymer (A), A PVA polymer film having a pH of 2.0 to 8.0 at 20 ° C. when dissolved in water at a concentration of 7% by mass;
[2] The PVA polymer film of the above [1], wherein the saponification degree of the PVA polymer (A) is 90 mol% or more,
[3] The PVA polymer film of [1] or [2], which is obtained using the acidic substance (C),
[4] The pKa (acid dissociation constant) at 25 ° C. of the acidic substance (C) is 3.5 or more, and the boiling point of the acidic substance (C) under normal pressure exceeds 120 ° C. PVA polymer film,
[5] The PVA polymer film according to any one of [1] to [4], wherein the surfactant (B) is a nonionic surfactant,
[6] The PVA polymer film of the above [5], wherein the nonionic surfactant is an alkanolamide type surfactant,
[7] The PVA polymer film as described in any one of [1] to [6] above, containing 0.01 to 3% by mass of the antioxidant (D) with respect to the surfactant (B).
[8] A step of preparing a film-forming stock solution containing 0.001 to 1 part by mass of the surfactant (B) with respect to 100 parts by mass of the PVA polymer (A) and the PVA polymer (A); A process for forming a film-forming stock solution, wherein the film-forming stock solution is obtained using a mixture containing 70% by mass or more of the surfactant (B). A method for producing any one PVA polymer film,
[9] The method according to [8] above, wherein the film-forming stock solution is obtained using an acidic substance (C).
[10] The method according to [8] or [9] above, wherein the mixture has a pH at 20 ° C. of 8.0 or more when dissolved in water at a concentration of 0.1% by mass,
[11] A PVA polymer, wherein the PVA polymer film according to any one of the above [1] to [7] is stored under conditions of a temperature of 0 to 40 ° C. and a humidity of 75% RH or less. Film storage method,
About.

Even if the PVA polymer film of the present invention is stored in a warehouse or the like for a long time, the color of the film is hardly yellowish. Therefore, even when the PVA polymer film is used as a raw material for producing a packaging material or a polarizing film, it is difficult to give a bad impression to consumers and users. Moreover, according to the manufacturing method of this invention, said PVA-type polymer film can be manufactured easily and cheaply.
Furthermore, if the PVA polymer film is stored by the storage method of the present invention, yellowing of the film can be more effectively suppressed.

The present invention is described in further detail below.
The PVA polymer film of the present invention contains a PVA polymer (A) and a surfactant (B).

As the PVA polymer (A), a polymer produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer can be used. Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Among these, vinyl acetate is preferable.

The vinyl ester polymer is preferably obtained by using only one or two or more vinyl ester monomers as a monomer, and using only one vinyl ester monomer as a monomer. Although what was obtained is more preferable, the copolymer of 1 type, or 2 or more types of vinyl-ester type monomers and the other monomer copolymerizable with this may be sufficient.

Other monomers copolymerizable with such vinyl ester monomers include, for example, ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene and isobutene; acrylic acid or salts thereof; methyl acrylate, acrylic Such as ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc. Acrylic acid ester; methacrylic acid or salt thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, methacrylic acid 2-ethylhexyl, dodecyl methacrylate Methacrylic acid esters such as octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid or salt thereof, acrylamidopropyldimethylamine or salt thereof, N Acrylamide derivatives such as methylolacrylamide or derivatives thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or salts thereof, methacrylamidepropyldimethylamine or salts thereof, N-methylolmethacrylamide or Methacrylamide derivatives such as derivatives thereof; N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, etc. -Vinyl amide; 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; acrylonitrile, methacrylonitrile, etc. Vinyl cyanide; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salt, ester or acid anhydride; itaconic acid or its salt , Esters or acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like. The vinyl ester polymer can have a structural unit derived from one or more of these other monomers.

The proportion of structural units derived from the other monomers in the vinyl ester polymer is preferably 15 mol% or less based on the number of moles of all structural units constituting the vinyl ester polymer, More preferably, it is 5 mol% or less.

The degree of polymerization of the PVA polymer (A) is not particularly limited, but is preferably 200 or more from the viewpoint of film strength and the like, more preferably in the range of 200 to 15,000, and 300 to 5, More preferably, it is within the range of 000. Here, the degree of polymerization means an average degree of polymerization measured according to the description of JIS K6726-1994. After re-saponifying and purifying a PVA polymer, the intrinsic viscosity [η measured in water at 30 ° C. [η ] (Unit: deciliter / g).
Po = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

The saponification degree of the PVA polymer (A) is preferably 90 mol% or more, and more preferably 93 mol% or more. When the degree of saponification is less than 90 mol%, the water resistance and durability of the PVA polymer film may be insufficient. Here, the degree of saponification of the PVA polymer is the total number of moles of structural units (typically vinyl ester monomer units) that can be converted into vinyl alcohol units by saponification and the vinyl alcohol units of the PVA polymer. On the other hand, the ratio (mol%) occupied by the number of moles of the vinyl alcohol unit. The degree of saponification of the PVA polymer can be measured according to the description of JIS K6726-1994.

When producing the PVA polymer film of the present invention, one type of PVA polymer may be used alone as the PVA polymer (A), and the degree of polymerization, the degree of saponification, or the degree of modification may be used. Two or more different PVA polymers may be blended and used. However, the PVA polymer film of the present invention has a PVA polymer having an acidic functional group such as a carboxyl group or a sulfonic acid group; a PVA polymer having an acid anhydride group; a basic functional group such as an amino group. When a PVA polymer having a functional group that promotes a crosslinking reaction, such as a neutralized product thereof, is included, the secondary processability of the PVA polymer film is increased by a crosslinking reaction between PVA polymer molecules. May decrease. Therefore, in particular, when excellent secondary processability is required as typified by optical applications, the PVA polymer film is composed of a PVA polymer having an acidic functional group and a PVA polymer having an acid anhydride group. It is preferable that neither a polymer, a PVA polymer having a basic functional group, or a neutralized product thereof is contained, and the PVA polymer (A) is obtained using only a vinyl ester monomer as a monomer. PVA polymer produced by saponifying the obtained vinyl ester polymer and / or using only vinyl ester monomer and ethylene and / or olefin having 3 to 30 carbon atoms as monomers. It is more preferable to include only the PVA polymer produced by saponifying the vinyl ester polymer. Glycol ester-based monomer alone it is more preferable to contain only PVA polymer produced by saponifying a vinyl ester polymer obtained by using the monomer.

The type of the surfactant (B) used in the present invention is not particularly limited, and examples thereof include an anionic surfactant and a nonionic surfactant.

Examples of the anionic surfactant include carboxylic acid types such as potassium laurate; sulfate ester types such as octyl sulfate; and sulfonic acid types such as dodecylbenzene sulfonate.

Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene laurylamino Alkylamine type such as ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as lauric acid diethanolamide and oleic acid diethanolamide; polyoxy Examples include allyl phenyl ether type such as alkylene allyl phenyl ether.

Surfactant may be used alone or in combination of two or more. Among these surfactants, nonionic surfactants are preferred because they are excellent in reducing the abnormalities of the film surface during film formation, and the effects of the present invention are more prominent. A surfactant is more preferable, and a dialkanolamide (for example, diethanolamide) of an aliphatic carboxylic acid (for example, a saturated or unsaturated aliphatic carboxylic acid having 8 to 30 carbon atoms) is more preferable.

Since the surfactant (B) is easily available and inexpensive, it is preferably used in the form of a mixture containing the surfactant (B). The content of the surfactant (B) in the mixture is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. Moreover, as an upper limit of the content rate of surfactant (B) in the said mixture, 99.99 mass% is mentioned, for example. Although there is no restriction | limiting in particular in components other than surfactant (B) which the said mixture contains, For example, the raw material, catalyst, solvent which were used when manufacturing surfactant (B); surfactant (B) decomposes | disassembles And, for example, a stabilizer added to improve the stability of the surfactant (B). More specifically, the surfactant (B) is an alkanolamide type nonionic interface. In the case of activators, the corresponding alkanolamines are mentioned.

Since the mixture containing the surfactant (B) exhibits the effects of the present invention more remarkably, the pH at 20 ° C. when dissolved in water at a concentration of 0.1% by mass (the resulting aqueous solution) PH) is preferably 8.0 or more, more preferably in the range of 8.5 to 12.0. In addition, the mixture containing the surfactant (B) is added to water so as to be 0.1% by mass and stirred (may be further heated and / or cooled if necessary), and then the mixture is heated to 20 ° C. Even when a part of the components contained in the mixture containing the surfactant (B) is not completely dissolved and is in the form of a dispersion when the temperature is maintained, the pH of the dispersion The value obtained by measuring can be regarded as the above pH.

The content of the surfactant (B) in the PVA polymer film needs to be in the range of 0.001 to 1 part by mass with respect to 100 parts by mass of the PVA polymer, and is 0.01 to 0.00. It is preferably in the range of 7 parts by mass, and more preferably in the range of 0.05 to 0.5 parts by mass. If the content is less than 0.001 part by mass, the effect of reducing the abnormality of the film surface during film formation hardly appears, and if it exceeds 1 part by mass, it elutes on the film surface and causes blocking, resulting in poor handling.

The PVA polymer film of the present invention has a pH at 20 ° C. (pH of the resulting aqueous solution) in the range of 2.0 to 8.0 when dissolved in water at a concentration of 7% by mass. This is extremely important for suppressing yellowing of the film during long-term storage. When said pH is less than 2.0, yellowing considered to be due to deterioration of the PVA polymer itself tends to occur. In addition, the film having a pH of less than 2.0 requires special film-forming equipment that has been subjected to antiseptic processing during film formation. From this viewpoint, the pH is preferably 2.5 or more, and more preferably 3.0 or more. On the other hand, when the above pH exceeds 8.0, a sufficient yellowing suppression effect cannot be obtained. From this viewpoint, the pH is preferably 7.5 or less, more preferably 7.0 or less, further preferably 6.8 or less, and particularly preferably 6.5 or less. And most preferably 6.0 or less. In addition, when the PVA polymer film is added to water so as to be 7% by mass and stirred (may be further heated and / or cooled as necessary), and then the temperature is maintained at 20 ° C. Even when some of the components contained in the PVA polymer film are not completely dissolved and are in the form of a dispersion, the value obtained by measuring the pH of the dispersion is the above value. It can be regarded as the pH.

For the PVA polymer film of the present invention, the method of controlling the pH at 20 ° C. when dissolved in water at a concentration of 7% by mass within the range of 2.0 to 8.0 is not necessarily limited. Since it is easy, the method of mix | blending an appropriate quantity of acidic substance (C) in the manufacture process of a PVA-type polymer film is suitable.

Although there is no restriction | limiting in particular in the kind of acidic substance (C), It is preferable that it is an acidic substance whose pKa (acid dissociation constant) in 25 degreeC is 3.5 or more. When a strong acidic substance having a pKa of less than 3.5 is used, the pH of the PVA polymer film obtained by dissolving the obtained PVA polymer film in water due to slight fluctuations in the amount of the acidic substance used may change significantly. If it becomes difficult to obtain the desired PVA polymer film, or if the concentration of such strong acidic substances varies in the PVA polymer film, yellowing occurs in the high concentration region. It may cause problems such as.

Also, it is preferable that the boiling point of the acidic substance (C) under normal pressure (1 atm in absolute pressure) exceeds 120 ° C. When the boiling point under normal pressure is 120 ° C. or lower, the acidic substance gradually volatilizes from the PVA polymer film during long-term storage, which may reduce the yellowing suppression effect. In the present specification, it is assumed that an acidic substance having substantially no volatility at 120 ° C. under normal pressure also has a boiling point exceeding 120 ° C. under normal pressure. Here, as the acidic substance having substantially no volatility, for example, about 1 g of the acidic substance precisely weighed in an evaporating dish is placed, and the acidic substance is kept even at 10 minutes at 120 ° C. under normal pressure. Examples include an acidic substance in which the mass reduction amount of the substance is 10% by mass or less. The boiling point of the acidic substance (C) is more preferably 125 ° C. or higher, and further preferably 130 ° C. or higher.

Examples of acidic substances having a pKa at 25 ° C. of 3.5 or more and a boiling point under atmospheric pressure exceeding 120 ° C. include organic acids such as lactic acid, succinic acid, adipic acid, benzoic acid, capric acid, citric acid, and lauric acid; Examples include inorganic acidic substances such as boric acid, potassium dihydrogen phosphate, and sodium dihydrogen phosphate; amino acids such as aspartic acid and glutamic acid, but are not necessarily limited thereto. These acidic substances may be used alone or in combination of two or more. Among these, inorganic acidic substances are preferable because dissipation due to volatilization can be substantially ignored.

The amount of the acidic substance (C) preferably used in the production process of the PVA polymer film of the present invention is 20 when the finally obtained PVA polymer film is dissolved in water at a concentration of 7% by mass. The amount at which the pH at 2.0 ° C. is in the range of 2.0 to 8.0. The content of the acidic substance (C) used in the PVA polymer film (however, in the form of a conjugate base, the acidic substance (C) having the same number of moles as the conjugate base is included. Cannot be determined in general depending on the type of acidic substance (C) used, but, for example, 0.0001 to 0.05 mol per 100 g of PVA polymer (A) The ratio becomes.

As described above, the PVA polymer film of the present invention has a pH at 20 ° C. in the range of 2.0 to 8.0 when dissolved in water at a concentration of 7% by mass, but was dissolved in water. When the PVA polymer film of the present invention showing such a pH further contains an antioxidant (D), the reason is not clear, but the yellowing suppression effect can be sustained for a longer period of time. . Such an effect of the antioxidant (D) is hardly observed in the case of a PVA polymer film in which the pH at 20 ° C. when dissolved in water at a concentration of 7% by mass is out of the above range.
Although there is no restriction | limiting in particular in the kind of antioxidant (D), Organic type antioxidants, such as a phenol type, a phosphite type, a thioester type, a benzotriazole type, a hindered amine type, are illustrated as a suitable thing.

The content of the antioxidant (D) in the PVA polymer film of the present invention is preferably in the range of 0.01 to 3% by mass based on the mass of the surfactant (B). More preferably, it is in the range of ˜1% by mass. When the said content rate is less than 0.01 mass% based on the mass of surfactant (B), it may become impossible to maintain the yellowing suppression effect over a longer period, and when it exceeds 3 mass% There exists a possibility that antioxidant (D) may aggregate and it may appear as a fault on a PVA-type polymer film, and an external appearance may be impaired.

The PVA polymer film is more rigid than other plastic films when it does not contain a plasticizer, and may have problems such as mechanical properties such as impact strength and process passability during secondary processing. In order to prevent these problems, it is preferable that the PVA polymer film of the present invention contains a plasticizer (E). Preferred plasticizers include polyhydric alcohols, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. These plasticizers (E) may be used alone or in combination of two or more. Among these plasticizers, ethylene glycol or glycerin is preferable from the viewpoint of an effect of improving stretchability when the PVA polymer film of the present invention is stretched and used. The content of the plasticizer (E) in the PVA polymer film is preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of the PVA polymer contained in the PVA polymer film. It is more preferably in the range of ˜25 parts by mass, and still more preferably in the range of 5 to 20 parts by mass. When the content is less than 1 part by mass, the above-described problem tends to occur. When the content exceeds 30 parts by mass, the film becomes too flexible, and the handleability may deteriorate.

Even if the PVA polymer film of the present invention comprises only the PVA polymer (A) and the surfactant (B), the PVA polymer (A) and the surfactant (B) and the above-mentioned acidic substance (C) (However, when it is in the form of a conjugate base, it includes a salt containing the conjugate base), an antioxidant (D), and a plasticizer (E). However, PVA (A), surfactant (B), acidic substance (C) (however, in the case of a conjugate base, as long as the effects of the present invention are not inhibited as necessary) Other components other than the antioxidant (D) and the plasticizer (E) may be further included. Examples of such other components include moisture, ultraviolet absorbers, lubricants, colorants, fillers, preservatives, antifungal agents, and other polymer compounds other than those described above. However, a PVA polymer film containing a chelating agent typified by polycarboxylic acid or polyamine or a chelate compound in which a metal is coordinated to it tends to form a gel in the production process. Therefore, it is preferable that the PVA polymer film contains neither a chelating agent nor a chelating compound.

PVA polymer (A), surfactant (B), acidic substance (C) (however, when it is in the form of a conjugated base, a salt containing the conjugated base is included), antioxidant (D) The ratio of the total mass of the plasticizer (E) to the total mass of the PVA polymer film of the present invention is preferably in the range of 60 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.

In the PVA polymer film of the present invention, the surfactant (B) is added in an amount of 0.001 to 1 part by mass (preferably 0 to 100 parts by mass of the PVA polymer (A) and the PVA polymer (A). 0.01 to 0.7 parts by mass, and more preferably 0.05 to 0.5 parts by mass). Specific examples of the film-forming stock solution include, for example, a PVA polymer solution in which the PVA polymer (A) is dissolved in a solvent and contains the surfactant (B) in the above ratio, or a PVA system in a water-containing state. Examples thereof include a melt obtained by melting the polymer (A) (which may further contain an organic solvent or the like) and the surfactant (B) in the above ratio.

As a specific method for producing the PVA polymer film, for example, using the above PVA polymer solution, a casting film forming method, a wet film forming method (discharging into a poor solvent), a wet and dry method, A film forming method, a gel film forming method (a method in which a PVA polymer solution is once cooled and gelated, and then a solvent is extracted and removed to obtain a PVA polymer film), or a combination thereof, Arbitrary methods, such as the melt extrusion film-forming method of obtaining the said melt using an extruder etc. and forming this by extruding this from T dies etc., are employable. Among these, the casting film forming method and the melt extrusion film forming method are preferable because a PVA polymer film having high transparency and little coloring can be obtained.

The concentration of volatile components in the above stock solution for forming a film (concentration of a volatile component such as a solvent removed by volatilization or evaporation during film formation) is preferably in the range of 50 to 90% by mass, and 55 to 80% by mass. % Is more preferable. If the volatile concentration is less than 50% by mass, the viscosity may increase and film formation may be difficult. On the other hand, if the concentration of volatile components exceeds 90% by mass, the viscosity becomes low and the thickness uniformity of the resulting film tends to be impaired, which is not preferable.

There is no restriction | limiting in particular in the preparation method of said film forming undiluted | stock solution, For example, what dissolved PVA-type polymer (A) in water, surfactant (B), and also acidic substance (C) as needed , A method of adding at least one of the antioxidant (D), the plasticizer (E) and the other components described above, and melt-kneading the PVA polymer (A) in a water-containing state using an extruder When melting, the surfactant (B) and, if necessary, at least one of the acidic substance (C), the antioxidant (D), the plasticizer (E) and the other components described above are melted together. Examples thereof include a kneading method. Among these, in the case of producing a PVA polymer film by a casting film forming method, a surfactant (B) and, if necessary, a solution obtained by dissolving a PVA polymer (A) in water. Furthermore, the method of adding at least 1 sort (s) of an acidic substance (C), antioxidant (D), a plasticizer (E), and said other component is preferable.

In addition, when the surfactant (B) is blended in the preparation of the membrane forming stock solution, if it is used in the form of a mixture containing the surfactant (B), the complicated purification work of the surfactant (B) is not required. In addition, it is preferable because it is not necessary to use a more expensive high-purity surfactant (B), and the film-forming stock solution can be easily and inexpensively prepared. Furthermore, when the said film forming undiluted | stock solution is what was obtained using acidic substance (C), the PVA polymer film obtained by adjusting the compounding quantity at the time of the mixing | blending of acidic substance (C) is water. It is preferable because the pH at the time of dissolution in can be easily adjusted to the above range.

The thickness of the PVA polymer film of the present invention is not particularly limited, and can be set to an appropriate thickness depending on the application. Specifically, for example, for packaging materials, the average thickness is preferably in the range of 5 to 500 μm, and when used as a raw material for the polarizing film, the average thickness is preferably in the range of 5 to 150 μm. . In addition, the average thickness of a PVA polymer film measures the thickness of arbitrary 10 places (for example, arbitrary 10 places on the straight line drawn in the width direction of the PVA polymer film), and calculates | requires it as those average values. be able to.

The present invention also includes a method for storing a PVA polymer film, wherein the PVA polymer film of the present invention is stored under conditions of a temperature of 0 to 40 ° C. and a humidity of 75% RH or less. The PVA polymer film of the present invention is characterized by less yellowing when stored for a long period of time compared to conventional PVA polymer films, but tends to be more likely to yellow as the temperature during storage increases. Therefore, it is preferable to store at a temperature of 40 ° C. or lower. On the other hand, if the temperature during storage is too low, condensation may occur on the surface of the film when it is taken out from the storage place for use, which may cause abnormalities such as film blocking or tarmi. From this viewpoint, the temperature during storage is preferably 0 ° C. or higher. Similarly, if it is stored under conditions where the humidity exceeds 75% RH, abnormalities such as film blocking and tarmi may occur due to moisture absorption of the PVA polymer film. There is no particular limitation on the storage period when storing the PVA polymer film, but if it is too long, yellowing may proceed gradually especially when stored at high temperatures, etc. It is preferably within 2 years, more preferably from 1 month to 1.5 years, and even more preferably from 3 months to 1 year.

The use of the PVA polymer film of the present invention is not particularly limited. For example, packaging materials; raw materials for producing optical films such as polarizing films and retardation films; water-soluble films such as laundry bags; The PVA polymer film of the present invention can be used as a release film, etc., but the color of the film is hardly yellowish even when stored in a warehouse for a long period of time. Therefore, it is preferable to use as a raw material for producing a packaging material, a polarizing film or a retardation film. Further, the PVA polymer film of the present invention containing the surfactant (B) in the above ratio and having a pH at 20 ° C. within the above range when dissolved in water at a concentration of 7% by mass, Even in the case of continuous production for a long time (preferably 72 hours or more, more preferably 120 hours or more, and further preferably 180 hours or more), a streak-like shape presumed to be caused by the aggregate of the surfactant (B) Since the occurrence of defects (defects caused by fine irregularities in the film that occur continuously or intermittently in parallel with the film flow direction) can be suppressed to a high degree, it can be applied to final products such as polarizing films and retardation films. When high quality is required, it can be particularly preferably used as a raw material for producing them.

EXAMPLES The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to these examples.
In addition, each measuring method of the pH at the time of dissolving the PVA film which was employ | adopted in the following Examples and Comparative Examples and the yellowness (YI value) of a PVA film is shown below.

[Measurement of pH when PVA film is dissolved in water]
7 g of PVA film was placed in 93 g of deionized water at room temperature and heated to about 90 ° C. with stirring to completely dissolve the film. The resulting aqueous solution was then cooled to 20 ° C., and a pH meter (METTLER TOLEDO) The pH of the aqueous solution was measured using “MP230” manufactured by the manufacturer.

[Measurement of Yellowness (YI Value) of PVA Film]
Eight film samples were stacked, and the YI value of the film was measured as a value for the entire eight sheets using a color difference meter (Model “NF-902” manufactured by Nippon Denshoku Industries Co., Ltd.).

[Example 1]
After dipping 100 parts by mass of PVA (polyvinyl saponified saponified product) having a saponification degree of 99.9 mol%, a polymerization degree of 2400, and a sodium acetate content of 2.4% by mass in 2500 parts by mass of distilled water at 35 ° C. for 24 hours. Then, centrifugal dehydration was performed to obtain a PVA water-containing chip. The sodium acetate content in the obtained PVA water-containing chip was 0.1% by mass relative to PVA, and the volatile content in the PVA water-containing chip was 70% by mass.
A mixture containing glycerin 12 parts by mass and a surfactant (95% by mass of lauric acid diethanolamide) with respect to 333 parts by mass of the PVA water-containing chip (100 parts by mass in terms of dry PVA), and diethanolamine as an impurity The pH of the mixture at 20 ° C. when dissolved in water at a concentration of 0.1% by mass (measured by the same method as described above for the PVA film) is 9.64.) 3 parts by weight, 0.003 part by weight of 4,4′-butylidenebis (6-tert-butyl-3-methylphenol) (phenolic antioxidant) was added, and 1 mol / l potassium dihydrogen phosphate aqueous solution was further added. After adding at a ratio of 10 ml to 100 g of PVA, mix well to make a mixture, and heat this with a twin-screw extruder with a maximum temperature of 130 ° C. Melted. After cooling to 100 ° C. with a heat exchanger, a PVA film having a film width of 1.2 m and an average thickness of 60 μm was obtained by melt-extrusion film formation on a 95 ° C. metal drum and drying. In the obtained PVA film, no defects such as streaks were found, and the appearance was good. Using the obtained PVA film, the pH when dissolved in water was measured by the method described above and found to be 6.0.

The obtained PVA film was cut into A4 size, and the yellowness (YI value) in the initial state was measured by the method described above to be 4.6. This PVA film was suspended and left in a hot air dryer adjusted to 80 ° C. Then, the yellowness (YI value) of the film after 3 days, 5 days and 10 days from the standing was measured by the above-mentioned method, and they were 7.6, 9.0 and 10.1, respectively. Therefore, the yellowing degree (ΔYI), which is the amount of increase from the initial value of the yellowness (YI value), was calculated as 3.0, 4.4, and 5.5, respectively.
The results of the above various evaluations are shown in Table 1. In addition, although said film forming was performed continuously for 240 hours, generation | occurrence | production of the stripe-shaped defect was not recognized.

[Example 2]
In Example 1, instead of adding 1 mol / l potassium dihydrogen phosphate aqueous solution at a rate of 10 ml to 100 g of PVA, 1 mol / l aqueous lactic acid solution was added at a rate of 5 ml to 100 g of PVA. Except for this, a PVA film was obtained in the same manner as in Example 1. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Example 3]
In Example 1, instead of adding 1 mol / l potassium dihydrogen phosphate aqueous solution at a rate of 10 ml per 100 g of PVA, 1 mol / l aqueous acetic acid solution was added at a rate of 10 ml per 100 g of PVA. Except for this, a PVA film was obtained in the same manner as in Example 1. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Example 4]
In Example 2, a PVA film was obtained in the same manner as in Example 2 except that the addition amount of the lactic acid aqueous solution was changed from a ratio of 5 ml to 100 g of PVA to a ratio of 2 ml to 100 g of PVA. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Example 5]
A PVA chip having a degree of saponification of 88.0 mol%, a degree of polymerization of 2400, and a sodium acetate content of 2.0% by mass was used as the PVA chip in the same manner as in Example 1. A hydrous chip was obtained. The sodium acetate content in the obtained PVA water-containing chip was 0.08% by mass relative to PVA, and the volatile content in the PVA water-containing chip was 86% by mass. This PVA water-containing chip was dried under reduced pressure at 20 ° C. to adjust the volatile content concentration to 70% by mass.
A PVA film was obtained in the same manner as in Example 1 except that the obtained PVA water-containing chip was used instead of the PVA water-containing chip having a volatile content concentration of 70% by mass used in Example 1. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Example 6]
A PVA film was obtained in the same manner as in Example 1, except that 4,4′-butylidenebis (6-tert-butyl-3-methylphenol) was not added. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Example 7]
In Example 1, the amount of 4,4′-butylidenebis (6-tert-butyl-3-methylphenol) added was 0.003 with respect to 333 parts by mass of PVA water-containing chips (100 parts by mass in terms of dry state PVA). A PVA film was obtained in the same manner as in Example 1 except that the mass was changed to 0.018 parts by mass. Although the obtained PVA film does not become a practical problem, when it is observed under strong light such as sunlight, it is estimated that it is caused by 4,4′-butylidenebis (6-tert-butyl-3-methylphenol). The agglomerated defects that were observed were seen thin.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Example 8]
In Example 1, a PVA film was obtained in the same manner as in Example 1 except that the addition amount of the potassium dihydrogen phosphate aqueous solution was changed from a ratio of 10 ml to 100 g of PVA to a ratio of 5 ml to 100 g of PVA. It was. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1. In addition, when said film formation was performed continuously for 240 hours, generation | occurrence | production of the stripe-like defect was recognized slightly.

[Example 9]
A PVA film was obtained in the same manner as in Example 8, except that 4,4′-butylidenebis (6-tert-butyl-3-methylphenol) was not added. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Comparative Example 1]
Example 1 was conducted except that none of glycerin, a mixture containing a surfactant, 4,4′-butylidenebis (6-t-butyl-3-methylphenol), and an aqueous potassium dihydrogen phosphate solution was added. In the same manner as in Example 1, a PVA film was obtained. The obtained PVA film had many defects such as streaks and was poor in appearance.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Comparative Example 2]
A PVA film was prepared in the same manner as in Example 1 except that neither 4,4′-butylidenebis (6-tert-butyl-3-methylphenol) nor aqueous potassium dihydrogen phosphate solution was added. Got. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Comparative Example 3]
In Example 1, the PVA film was obtained like Example 1 except not having added potassium dihydrogen phosphate aqueous solution. In the obtained PVA film, no defects such as streaks were found, and the appearance was good.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1. In addition, when said film formation was performed continuously for 240 hours, generation | occurrence | production of the stripe-like defect was recognized.

[Comparative Example 4]
In Example 2, instead of adding a 1 mol / l lactic acid aqueous solution at a rate of 5 ml with respect to 100 g of PVA, the lactic acid was used as it was without diluting in water, and the proportion was 0.1 mol with respect to 100 g of PVA. A mixture of the PVA water-containing chip and various additives was obtained in the same manner as in Example 1 except that the mixture was added in step 1. By adding water to this mixture, an aqueous solution having a solid content concentration of 7% by mass was prepared. It was 1.7 when pH of the obtained aqueous solution was measured by the method similar to having mentioned above about the case of a PVA film. When this mixture was melt-cast using an extruder, the plating applied to the molten resin flow path might corrode, so the film-forming was abandoned.

[Comparative Example 5]
In Example 1, except that the addition amount of the mixture containing the surfactant was changed from 0.3 parts by mass to 3 parts by mass with respect to 333 parts by mass of the PVA water-containing chip (100 parts by mass in terms of dry state PVA). A PVA film was obtained in the same manner as Example 1. The obtained PVA film had many defects such as streaks and was poor in appearance.
Various measurements were performed in the same manner as in Example 1 using the obtained PVA film. The results are shown in Table 1.

[Example 10]
The PVA film obtained in Example 1 was wound up in a roll shape by 50 m in a paper tube having a diameter of 3 inches, and stored in a thermo-hygrostat adjusted to a temperature of 30 ° C. and a humidity of 50% RH. It was taken out after 6 months and the yellowness (YI value) of the PVA film was measured by the method described above. As a result, it was 5.4 with respect to 4.6 before the start of storage, and the yellowing degree (ΔYI) was 0.8. It was small. Also, the film surface was good with no change from before storage. The evaluation results are shown in Table 2.

[Comparative Example 6]
In Example 10, instead of using the PVA film obtained in Example 1, the PVA film was stored in the same manner as in Example 10 except that the PVA film obtained in Comparative Example 3 was used. The evaluation results of the PVA film taken out after 6 months are shown in Table 2.

According to the present invention, since the PVA polymer film can be obtained in which the color of the film is hardly yellowish even when stored in a warehouse or the like for a long time, the PVA polymer film is, for example, a packaging material; It can be preferably used as a raw material for producing an optical film such as a film or retardation film; a water-soluble film such as a laundry bag; a release film for producing artificial marble.

Claims (11)

A polyvinyl alcohol polymer film comprising 0.001 to 1 part by mass of a surfactant (B) with respect to 100 parts by mass of the polyvinyl alcohol polymer (A) and the polyvinyl alcohol polymer (A), A polyvinyl alcohol polymer film having a pH of 2.0 to 8.0 at 20 ° C. when dissolved in water at a concentration of 7% by mass. The polyvinyl alcohol polymer film according to claim 1, wherein the saponification degree of the polyvinyl alcohol polymer (A) is 90 mol% or more. The polyvinyl alcohol polymer film according to claim 1 or 2, which is obtained using an acidic substance (C). 4. The polyvinyl alcohol according to claim 3, wherein the acidic substance (C) has a pKa (acid dissociation constant) at 25 ° C. of 3.5 or more and the boiling point of the acidic substance (C) under normal pressure exceeds 120 ° C. 5. Polymer film. The polyvinyl alcohol polymer film according to any one of claims 1 to 4, wherein the surfactant (B) is a nonionic surfactant. The polyvinyl alcohol polymer film according to claim 5, wherein the nonionic surfactant is an alkanolamide type surfactant. The polyvinyl alcohol polymer film according to any one of claims 1 to 6, comprising 0.01 to 3% by mass of an antioxidant (D) based on the surfactant (B). Preparing a film-forming stock solution containing 0.001 to 1 part by mass of a surfactant (B) with respect to 100 parts by mass of the polyvinyl alcohol-based polymer (A) and the polyvinyl alcohol-based polymer (A); A film forming solution is formed, and the film forming solution is obtained by using a mixture containing 70% by mass or more of the surfactant (B). The manufacturing method of the polyvinyl alcohol-type polymer film of description. The production method according to claim 8, wherein the film-forming stock solution is obtained using an acidic substance (C). The production method according to claim 8 or 9, wherein the mixture has a pH at 20 ° C of 8.0 or more when dissolved in water at a concentration of 0.1% by mass. The polyvinyl alcohol polymer film according to any one of claims 1 to 7, wherein the polyvinyl alcohol polymer film is stored under conditions of a temperature of 0 to 40 ° C and a humidity of 75% RH or less. Storage method.