Patent Description:
A film containing a polyvinyl alcohol resin (hereinafter, it may be referred to as PVA) has unique properties such as water solubility and optical characteristics, and is therefore used in various applications that take advantage of its characteristics, such as a water-soluble film for drug packaging and a seed tape, and an optical film as used a raw material for a polarizing film for a liquid crystal display.

The PVA is also known as a synthetic resin which has an unusual biodegradability as a synthetic resin and has a small environmental load. However, most of raw materials for producing the PVA are produced using fossil fuel-derived compounds such as petroleum, coal, and natural gas as a starting material. Fossil fuel contains carbon that has been fixed in the ground for many years. Therefore, the PVA is subjected to biodegradation treatment by microorganisms or incineration treatment like a usual synthetic resin to release carbon dioxide into the atmosphere, which causes carbon that was fixed deep in the ground and did not exist in the atmosphere is released into the atmosphere as carbon dioxide, and may cause global warming.

On the other hand, if a material obtained from a living organism (a plant, an animal) that absorbs carbon dioxide circulating in the global environment and is grown by a nutrient source in which the carbon dioxide is converted into an organic substance is used as a raw material of a synthetic resin, even if the material is subjected to biodegradation treatment or incineration treatment to generate carbon dioxide, the carbon dioxide existing in the global environment circulates, and thus the total amount of carbon constituting the carbon dioxide does not change.

In particular, plants are living organisms that absorbs carbon dioxide circulating in the global environment, performs a photosynthesis reaction using carbon dioxide and water as raw materials, and assimilates and immobilizes carbon dioxide as an organic body, and thus are attracting attention as a carbon source. For example, an alcohol component, particularly ethyl alcohol, is distilled and separated from a fermentation product of sugar extracted from a plant raw material such as sugar cane or corn or a cellulose fermentation product, and ethylene as an alkene can be obtained by a dehydration reaction thereof. When a vinyl ester monomer (hereinafter, it may be referred to as a bio-vinyl ester monomer) is synthesized using the bio-derived ethylene (hereinafter, it may be referred to as bio-ethylene) as a raw material, and a polyvinyl ester obtained by polymerizing this bio-vinyl ester monomer is saponified to produce a PVA (hereinafter, it may be referred to as a bio-PVA), carbon dioxide existing in the global environment is not increased even if this bio-PVA is subjected to a biodegradation treatment or an incineration treatment to generate carbon dioxide, and this does not cause global warming.

Carbon constituting carbon dioxide circulating in the global environment is a mixture of radioactive carbon <NUM> (hereinafter, it may be referred to as <NUM>C) that is an isotope, stable carbon <NUM> (hereinafter, it may be referred to as <NUM>C), and metastable carbon <NUM> (hereinafter, it may be referred to as <NUM>C), and it is known that the mass ratio thereof is <NUM> mass% for <NUM>C, <NUM> mass% for <NUM>C, and <NUM> × <NUM>-<NUM> mass% to <NUM> × <NUM>-<NUM> mass% (trace amount) for <NUM>C. The ratio between <NUM>C and <NUM>C is stable. Since radioactive <NUM>C is generated when a neutron contained in a secondary cosmic ray generated by a primary cosmic ray in the upper layer of the atmosphere collides with a nitrogen atom (<NUM>N) in the atmosphere, the radioactive <NUM>C is continuously supplied although it slightly fluctuates due to the intensity of the sunspot activity of the sun, but on the other hand, the radioactive <NUM>C decreases with a half-life of <NUM> years.

Since carbon constituting the body of a living organism that grows by constantly absorbing carbon dioxide circulating in the global environment continues to be updated during its survival, carbon continues to take over the mass ratio of the three types of carbon isotopes constituting carbon dioxide circulating in the global environment. When a living organism is killed, the mass ratio of the three types of carbon isotopes inside the living organism is fixed at the ratio at the time of death. The half-life of <NUM>C is <NUM> years, and the mass ratio of <NUM>C in the fossil fuel formed over a long period of time after the death of a living organism that lived in ancient times long before this is very small compared to the mass ratio of <NUM>C in carbon dioxide circulating in the global environment since the fossil fuel is isolated from modern carbon dioxide circulating in the global environment.

Therefore, since a value of the abundance ratio of <NUM>C in carbon constituting a normal PVA using a fossil fuel as a raw material is also significantly smaller than the abundance ratio of <NUM>C in carbon constituting a bio-PVA, that is, substantially <NUM>%, the bio-PVA and the fossil fuel-derived PVA can be distinguished from each other by measuring the abundance ratio of <NUM>C in contained carbon.

As applications of a polyvinyl alcohol resin film (hereinafter, the film may be referred to as a PVA film) containing a polyvinyl alcohol resin, a raw fabric film in the production of an optical film such as a polarizing film, which is a component of an LCD such as a liquid crystal television, or a film for drug packaging in individual packaging of a drug or the like in a single use amount is exemplified, and the demand has been continuously expanding in recent years. The PVA film used for these applications is required to have very high quality such as very few defects and almost no unevenness in thickness.

As described above, a PVA film is used in various applications such as a raw fabric film for producing an optical film and a film for drug packaging, but in the market, problems caused by the quality of the PVA film may occur in end products such as a liquid crystal television and a drug package including an optical film using the PVA film. In that case, it is necessary to identify whether the PVA film that is the cause of the problem is produced by own company or produced by another company. However, in the conventionally known technique, it is very difficult to identify the manufacturer of the PVA film by analyzing the PVA film used for the end product in which the problem has occurred. Therefore, there has been a demand for a method for easily and reliably discriminating the manufacturer of the used PVA film for the end product in which the problem has occurred in the market.

Therefore, first, an object of the present invention is to provide a PVA film using PVA that does not increase carbon dioxide existing in the global environment or has a small increase amount even when carbon dioxide is generated by a biodegradation treatment or an incineration treatment. Secondly, an object of the present invention is to provide a method for easily and reliably discriminating a manufacturer of a PVA film.

ASTM D6866 by the National Institute of Standards and Technology (NIST) is known for distinguishing between a plant-derived organic substance and a fossil fuel-derived organic substance. ASTM D6866 is an ASTM (American Society for Testing and Materials) standard for determining biogenic carbon concentrations in solid, liquid and gas samples utilizing a radiocarbon dating method, and the currently effective version of the standard is ASTM D6866-<NUM> which was implemented in February <NUM>. According to this method, it is possible to discriminate between a film containing bio-PVA and a film that does not contain bio-PVA and contains only fossil fuel-derived PVA.

Using <NUM>C as indicator for bio-PVA was also proposed on the "<NPL>.

That is, the present invention is set out in the appended set of claims.

According to the present invention, it is possible to provide a method for easily and reliably discriminating a manufacturer of a PVA film.

Hereinafter, the invention will be specifically described.

A PVA film for instance contains PVA (A) which is a saponified product of a polyvinyl ester, and the abundance ratio of <NUM>C in the total carbon atoms constituting the PVA (A), that is, <NUM>C/C (Hereinafter, it may be referred to as <NUM>C/C. ), is <NUM> × <NUM>-<NUM> or more. Total carbon is the sum of all carbon isotopes, and <NUM>C/C is the ratio of <NUM>C to total carbon. When <NUM>C/C is less than <NUM> × <NUM>-<NUM>, it is close to the measurement lower limit of the measurement method in accordance with ASTM D6866, it is difficult to perform accurate measurement, and it is difficult to discriminate whether PVA (A) contained in the PVA film is bio-PVA. In addition, the small <NUM>C/C indicates that the ratio of bio-derived raw material used in the production of the PVA (A) is small, and the effect of reducing the increase amount of carbon dioxide existing in the global environment becomes insufficient. <NUM>C/C is preferably <NUM> × <NUM>-<NUM> or more, more preferably <NUM> × <NUM>-<NUM> or more, and still more preferably <NUM> × <NUM>-<NUM> or more. On the other hand, the upper limit of <NUM>C/C is not particularly limited, but since a bio-derived raw material is generally more expensive than a fossil fuel-derived raw material, <NUM>C/C is preferably <NUM> × <NUM>-<NUM> or less, more preferably <NUM> × <NUM>-<NUM> or less, and still more preferably <NUM> × <NUM>-<NUM> or less.

In the present invention, the method for measuring <NUM>C/C is not particularly limited, and for example, a sample (for example, vinyl acetate) is converted into carbon dioxide or graphite as necessary, and then subjected to accelerator mass spectrometry (AMS method) to compare and measure the content of <NUM>C with respect to a standard substance (for example, oxalic acid in U. <NUM>C/C can be calculated by dividing the amount of <NUM>C in the sample by the total amount of carbon in the sample.

The carbon stable isotope ratio δ<NUM>C of <NUM>C (hereinafter, it may be referred to as δ<NUM>C) in the present invention refers to the ratio of <NUM>C to <NUM>C among the three types of isotopes of carbon atoms existing in nature (abundance ratio <NUM>C : <NUM>C: <NUM>C = <NUM> : <NUM> : <NUM> × <NUM>-<NUM>, units; %), and the carbon stable isotope ratio is expressed as a deviation with respect to a standard substance, and means the value (δ value) defined by the following formula.

Here, [(<NUM>C/<NUM>C)sample] represents a stable isotope ratio of a sample to be measured, and [(<NUM>C/<NUM>C)PDB] represents a stable isotope ratio of a standard substance. PDB is an abbreviation of "Pee Dee Belemnite" and means a fossil of arrowheads made of calcium carbonate (as a standard substance, a fossil of arrowheads unearthed from a PeeDee layer in South Carolina State), and is used as a standard body having a <NUM>C/<NUM>C ratio. The "carbon stable isotope ratio δ<NUM>C" is measured by an accelerator mass spectrometry method. Since the standard substance is rare, a working standard in which a stable isotope ratio with respect to the standard substance is known can also be used.

Bio-ethylene is roughly divided into two groups depending on the plant as a raw material thereof, and there are bio-ethylene derived from C3 plants such as sweet potato, sugar beet, rice, a tree, and an alga, and bio-ethylene derived from C4 plants such as corn, sugar cane, and cassava, and the δ<NUM>C of both groups are greatly different. In the case of a PVA using C3 plant-derived bio-ethylene as a raw material, δ<NUM>C is less than -<NUM> ‰, and in the case of a PVA using C4 plant-derived bio-ethylene as a raw material, δ<NUM>C is -<NUM> ‰ or more. Therefore, the PVA using C3 plant-derived bio-ethylene as a raw material and the PVA using C4 plant-derived bio-ethylene as a raw material can be discriminated by measuring δ<NUM>C after the above <NUM>C/C is measured to exclude the possibility of being a fossil fuel-derived PVA.

Plants are classified into three types of a C3 plant, a C4 plant, and a suckling plant type photosynthesis (CAM/Crassulacean Acid Metabolism) plant from the types of initial fixed products of carbon dioxide in the photosynthesis carbonic acid fixation route. In the crop, corn and miscellaneous grain crops are the C4 plant, main crops such as rice and wheat are the C3 plant, and Cactaceae, Crassulaceae, Euphorbiaceae, and the like are the CAM plant.

More than <NUM>% of the plants on the earth belong to the C3 plant, and include, for example, agriculturally useful plants such as rice, wheat, tobacco, wheat, potato, and oil palm. The enzyme involved in the fixation of carbon dioxide in the photosynthesis pathway of the C3 plant is ribulose-<NUM>,<NUM>-diphosphate carboxylase, which has low affinity for carbon dioxide and conversely high affinity for oxygen, so that the efficiency of the carbon dioxide fixation reaction and thus the photosynthesis reaction is low.

The PVA film preferably has a carbon stable isotope ratio δ<NUM>C of carbon <NUM> (<NUM>C) of less than -<NUM> ‰ as measured by an accelerator mass spectrometry. δ<NUM>C is more preferably -<NUM> ‰ or more, still more preferably -<NUM> ‰ or more, and particularly preferably -<NUM> ‰ or more. δ<NUM>C is more preferably -<NUM> ‰ or less, still more preferably -<NUM> ‰ or less, and particularly preferably -<NUM> ‰ or less. The fact that the carbon stable isotope ratio δ<NUM>C in the PVA film is in the above range indicates that a PVA using C3 plant-derived bio-ethylene as a raw material is used as a PVA (A) contained in the PVA film, and it is preferable from the viewpoint of cost of a raw material and suppliability. As the C3 plant, rice, wheat, potato, and palm oil are preferable.

The C4 plant is a plant that performs C4 type photosynthesis, and is a form of photosynthesis having a C4 pathway for concentration of carbon dioxide in addition to a Calvin-Benson's cycle which is a general carbon dioxide reduction cycle in the process of photosynthesis. The enzyme involved in carbon dioxide fixation in the photosynthesis pathway of the C4 plant is phosphoenolpyruvate carboxylase. This enzyme is characterized in that it is not inhibited in activity by oxygen, has a high ability to fix carbon dioxide, and has a developed chloroplast also in a vascular sheath cell. Representative C4 plants include corn, sugar cane, cassava, sorghum, miscanthus sinensis, guineagrass, rhodes grass, urochloa subquadripara, setaria italica, barnyard millet, eleusine coracana, broom cypress, and the broom cypress is also referred to as burning bush, a broom tree, or Kochia scoparia. Such C4 plants use extra energy to fix carbon dioxide, and thus can fix carbon dioxide more efficiently than other plants other than C4 plants. In addition, it is difficult for other plants other than the C4 plant to collect carbon dioxide at a high temperature, but the C4 plant does not. In addition, photosynthesis can be sufficiently performed even when the amount of water is small. This is a physiological adaptation to cope with harsh climates for plants such as high temperature, dry, low carbon dioxide, and poor nitrogen soil.

In the PVA film, the carbon stable isotope ratio δ<NUM>C of carbon <NUM> (<NUM>C) measured by an accelerator mass spectrometry method is preferably -<NUM> ‰ or more. δ<NUM>C is more preferably -<NUM> ‰ or more, still more preferably -<NUM> ‰ or more, and particularly preferably -<NUM> ‰ or more. δ<NUM>C is more preferably -<NUM> ‰ or less, still more preferably -<NUM> ‰ or less, and particularly preferably -<NUM> ‰ or less. The fact that the carbon stable isotope ratio δ<NUM>C in the PVA film is in the above range indicates that PVA using C4 plant-derived bio-ethylene as a raw material was used as PVA (A) contained in the PVA film. Here, C4 plant-derived bio-ethylene tends to be less easily available than C3 plant-derived bio-ethylene, and thus the manufacturer of the PVA film can be more easily and reliably discriminated when the carbon stable isotope ratio δ<NUM>C in the PVA film is in the above range. In addition, as the C4 plant, corn, sugar cane, and cassava are preferable from the viewpoint of production amount and cost.

In addition, as plants other than the C3 plant and the C4 plant, the CAM plant has a photosynthesis system adapted to a dry environment, and this photosynthesis system is considered to be an evolved form of a kind of C3 photosynthesis. The δ<NUM>C of the CAM plant is generally in a range of about -<NUM> ‰ to about -<NUM> ‰, and these CAM plants can be used in combination as a biomass raw material as long as the effect of the present invention is not hindered as necessary.

As the PVA film, a mixture of a PVA having different <NUM>C/C or δ<NUM>C may be used as a raw material as long as <NUM>C/C and, if necessary, δ<NUM>C are within the above range.

For example, not only a PVA film showing δ<NUM>C is obtained using a C3 plant-derived raw material, but also a predetermined δ<NUM>C is obtained by mixing PVAs having different δ<NUM>C, that is, δ<NUM>C that cannot be achieved by a simple substance of a C3 plant is included, and more specific δ<NUM>C is obtained, whereby the discrimination accuracy of the obtained PVA film can be further enhanced. That is, when a raw material having a different δ<NUM>C is used, a statistical analysis value obtained by analyzing the carbon stable isotope ratio is unique, and thus the raw material can be distinguished from other raw materials. Therefore, the δ<NUM>C of a PVA film produced from such a raw material also has a unique analysis value, and identification and tracking become easy.

In the PVA film, all or a part of the PVA (A) is preferably a polyvinyl alcohol resin (Ab) in which all or a part of carbon constituting the PVA (A) is derived from bio-derived ethylene (Bb). That is, in the PVA film, the PVA (A) may be PVA (Ab) alone, or may be a mixture of a PVA (Ab) and PVA (Ap) obtained only from a fossil fuel-derived raw material.

A method for obtaining PVA (Ab) is not particularly limited, and for example,.

Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate, and among these, vinyl acetate is preferable.

The method for producing the vinyl ester monomer is not particularly limited, and for example, the vinyl ester monomer can be obtained by reacting ethylene with a compound having a carboxy group represented by R-COOH. Vinyl acetate can be synthesized as follows. Normally, vinyl acetate can be obtained by gas-phase reaction of ethylene, acetic acid, and oxygen in the presence of a catalyst. At this time, by using ethylene containing a predetermined amount of <NUM>C or acetic acid containing a predetermined amount of <NUM>C as the compound having a carboxy group, vinyl acetate containing a predetermined amount of <NUM>C is obtained. Examples of ethylene containing the predetermined amount of <NUM>C include bio-ethylene.

In the production of the vinyl ester monomer, it is preferable to use a bio-derived raw material as raw materials other than ethylene such as carboxylic acid, but the carboxylic acid group is removed from the polymer main chain of the polyvinyl ester at the time of saponification, and is usually recovered and reused. Therefore, even when using a fossil fuel-derived raw material, carbon dioxide existing in the global environment does not increase, and does not cause global warming.

The polyvinyl ester is preferably obtained using one kind or two or more kinds of vinyl ester monomers, and more preferably obtained using only one kind of vinyl ester monomer. In addition, the polyvinyl ester may be a copolymer of one kind or two or more kinds of vinyl ester monomers and other monomers copolymerizable with the same.

The other monomers copolymerizable with the vinyl ester monomer are preferably ethylene. That is, the PVA contained in the PVA film preferably contains an ethylene unit. In addition, the content of the ethylene unit is preferably <NUM> mol% or more, and more preferably <NUM> mol% or more, based on the number of moles of all structural units constituting the vinyl ester polymer. In addition, the content of the ethylene unit is preferably less than <NUM> mol%, and more preferably less than <NUM> mol%, based on the number of moles of all structural units constituting the vinyl ester polymer. When the content of the ethylene unit is within the above range, water resistance and the like can be improved without significantly impairing optical characteristics of the PVA film when the PVA film is used as a raw fabric film for producing an optical film. The reason for this is not necessarily clear, but it is presumed that while the hydrophilicity is weakened by introducing an ethylene unit into the polymer main chain, the volume occupied by the ethylene unit in the crystal is not greatly different from that of the vinyl alcohol unit, so that the crystal structure of a PVA is not greatly disturbed.

Examples of other monomers copolymerizable with the vinyl ester monomer include olefins having <NUM> to <NUM> carbon atoms, such as propylene, <NUM>-butene, and isobutene, in addition to ethylene; acrylic acid or a salt thereof; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, <NUM>-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid or a salt thereof; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, <NUM>-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate; acrylamide derivatives such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamide propane sulfonic acid or a salt thereof, acrylamide propyl dimethylamine or a salt thereof, and N-methylol acrylamide or a derivative thereof; methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidopropyldimethylamine or a salt thereof, and N-methylolmethacrylamide or a derivative thereof; N-vinylamide such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; 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, and stearyl vinyl ether; vinyl cyanide such as acrylonitrile and methacrylonitrile; 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 a salt, ester or acid anhydride thereof; itaconic acid or a salt thereof, ester or acid anhydride; vinylsilyl compound such as vinyltrimethoxysilane; and isopropenyl acetate. The vinyl ester-based polymer can have a structural unit derived from one kind or two or more kinds among these other monomers.

The ratio of the structural unit derived from another monomer to the polyvinyl ester is preferably <NUM> mol% or less, and more preferably <NUM> mol% or less based on the number of moles of all structural units constituting the polyvinyl ester from the viewpoint of the strength of the obtained PVA film, optical performance in the case of using the PVA film as a raw fabric film for producing an optical film.

As another monomer copolymerizable with the vinyl ester monomer, a fossil fuel-derived monomer may be used, or a plant-derived monomer may be used.

In the PVA film, the degree of polymerization of a PVA (A) is preferably <NUM> or more. The degree of polymerization of the PVA (A) is preferably less than <NUM>,<NUM>. From the viewpoint of the strength of the PVA film, the degree of polymerization of the PVA (A) is more preferably <NUM> or more, and still more preferably <NUM> or more. On the other hand, from the viewpoint of productivity of the PVA (A) or the PVA film, the degree of polymerization of the PVA (A) is more preferably less than <NUM>,<NUM>, and still more preferably less than <NUM>,<NUM>. Here, the degree of polymerization of a PVA (A) means an average degree of polymerization Po measured according to the description of JIS K6726-<NUM>, and is determined from a limiting viscosity [η] (unit: deciliter/g) measured in water at <NUM> after re-saponification and purification of a PVA by the following formula.

In the PVA film, the degree of saponification of the PVA (A) is preferably <NUM> mol% or more. When the degree of saponification is less than <NUM> mol%, water solubility is easily impaired when the PVA film is used as a film for drug packaging, and optical characteristics are easily impaired when the PVA film is used as a raw fabric film for producing an optical film. The degree of saponification is more preferably <NUM> mol% or more, and still more preferably <NUM> mol% or more. On the other hand, the degree of saponification is preferably less than <NUM> mol%, more preferably less than <NUM> mol%, and still more preferably less than <NUM> mol%. Here, the degree of saponification of a PVA refers to a ratio (mol%) of the number of moles of the vinyl alcohol unit to the total number of moles of a structural unit (typically, a vinyl ester monomer unit) that can be converted into a vinyl alcohol unit by saponification and the vinyl alcohol unit that the PVA has. The degree of saponification of a PVA can be measured according to the description of JIS K6726-<NUM>.

In the PVA film, the content of the <NUM>,<NUM>-glycol bond in the PVA (A) is preferably <NUM> mol% or more. The content of the <NUM>,<NUM>-glycol bond in the PVA (A) is preferably less than <NUM> mol%. When the content of the <NUM>,<NUM>-glycol bond is less than <NUM> mol%, good optical characteristics and mechanical strength are easily obtained when the PVA film is used as a raw fabric film for producing an optical film. On the other hand, when the content of the <NUM>,<NUM>-glycol bond is <NUM> mol% or more, productivity in the production of the PVA (A) can be increased, and the production cost can be reduced. The content of the <NUM>,<NUM>-glycol bond in the PVA (A) is more preferably <NUM> mol% or more, and still more preferably <NUM> mol% or more. The content of the <NUM>,<NUM>-glycol bond in the PVA (A) is more preferably less than <NUM> mol%, and still more preferably less than <NUM> mol%.

In the PVA film, it is preferable that the PVA (A) has an alkoxyl group at the polymer terminal, and the content of the alkoxyl group with respect to total monomer units (hereinafter, it may be referred to as the content of the terminal alkoxyl group) is <NUM> mol% or more. The content of the terminal alkoxyl group is preferably less than <NUM> mol%. The method for introducing an alkoxyl group into the polymer terminal is not particularly limited, and examples thereof include a method in which a vinyl ester is polymerized using a polymerization initiator having an alkoxyl group.

When the PVA film is used as a raw fabric film for producing an optical film, for example, when a polarizing film is produced using a PVA film as a raw fabric film, if the PVA (A) is eluted into a treatment liquid in a production process and the concentration of the PVA (A) in the treatment liquid is increased, fine particles of the PVA (A) are precipitated in the treatment liquid due to progress of boric acid crosslinking and adhere to the PVA film, and foreign matters derived from the PVA fine particles remain on the surface of the resulting polarizing film, which may cause a problem. In the PVA film, since the PVA (A) has an alkoxyl group at the polymer terminal and the content thereof with respect to total monomer units is <NUM> mol% or more and less than <NUM> mol%, the occurrence of this problem can be suppressed. When the content of the terminal alkoxyl group is less than <NUM> mol%, foreign matter defects on the surface of the polarizing film derived from the fine particles of a PVA (A) may not be sufficiently reduced. When the content of the terminal alkoxyl group is more than <NUM> mol%, the polarizing performance of the resulting polarizing film may be insufficient when the PVA film is used as a raw fabric film for producing an optical film. The content of the terminal alkoxyl group with respect to total monomer units is more preferably <NUM> mol% or more, and still more preferably <NUM> mol% or more. The content of the terminal alkoxyl group with respect to total monomer units is more preferably less than <NUM> mol%, and still more preferably less than <NUM> mol%.

In the PVA film, one kind of a PVA may be used as the PVA (A), or two or more kinds of a PVA having different degrees of polymerization, saponification, and modification be blended and used. When two or more kinds of a PVA are blended and used, PVA derived from biomass such as bio-ethylene other than PVA (A) and PVA (A) may be blended, PVA (A) and PVA derived from petroleum or fossil may be blended, or both may be combined.

Generally, the content of the PVA (A) in the PVA film is not particularly limited, but is preferably <NUM> mass% or more, more preferably <NUM> mass% or more, and still more preferably <NUM> mass% or more. In addition, the content may be <NUM> mass%, but is preferably <NUM> mass% or less, and may be <NUM> mass% or less, and further <NUM> mass% or less in consideration of compatibility between the availability of biomass and the performance as a polarizing film.

The PVA film is more rigid than other plastic films in a state of not containing a plasticizer, and mechanical physical properties such as impact strength and process passability at the time of secondary processing may be a problem. In order to prevent these problems, the PVA film contains a plasticizer. Preferable examples of the plasticizer include a polyhydric alcohol, and specific examples thereof include polyhydric alcohols such as ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, and sorbitol. These plasticizers may be used singly or in combination of two or more kinds thereof. Among these plasticizers, ethylene glycol or glycerin is preferable, and glycerin is more preferable from the viewpoint of difficulty in bleeding out to the film surface. In addition, it is preferable to use a plasticizer produced from a bio-derived raw material.

The content of the plasticizer in the PVA film is preferably <NUM> part by mass or more, more preferably <NUM> parts by mass or more, and still more preferably <NUM> parts by mass or more with respect to <NUM> parts by mass of the PVA contained in the PVA film. In addition, the content of the plasticizer is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less, and still more preferably <NUM> parts by mass or less. When the content of the plasticizer is less than <NUM> part by mass, the effect of improving mechanical physical properties such as impact strength of the PVA film may not be sufficient. On the other hand, when the content of the plasticizer is more than <NUM> parts by mass, the PVA film becomes too soft, so that the handleability may be deteriorated or bleeding out may occur on the film surface.

The PVA film may contain starch and/or a water-soluble polymer other than the PVA (A). Containing such a water-soluble polymer makes it possible to impart mechanical strength to the PVA film, maintain moisture resistance when handling the PVA film, or adjust the rate of softening due to absorption of water when dissolving the PVA film.

Examples of the starch include natural starches such as a corn starch, a potato starch, a sweet potato starch, a wheat starch, a rice starch, a tapioca starch, and a sago starch; and processed starches subjected to etherification processing, esterification processing, and oxidation processing, and particularly, the processed starches are preferable.

The content of starch in the PVA film is preferably <NUM> parts by mass or less, and more preferably <NUM> parts by mass or less, with respect to <NUM> parts by mass of the PVA (A). When the amount of starch is more than <NUM> parts by mass, there is a possibility that the process passability at the time of producing a PVA film is deteriorated.

Examples of the water-soluble polymer other than PVA (A) include dextrin, gelatin, glue, casein, shellac, gum arabic, polyacrylic acid amide, sodium polyacrylate, polyvinyl methyl ether, a copolymer of methyl vinyl ether and maleic anhydride, a copolymer of vinyl acetate and itaconic acid, polyvinyl pyrrolidone, cellulose, acetyl cellulose, acetyl butyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and sodium alginate.

The content of the water-soluble polymer other than the PVA (A) in the PVA film is preferably <NUM> parts by mass or less, and more preferably <NUM> parts by mass or less, with respect to <NUM> parts by mass of the PVA (A). When the content of the water-soluble polymer other than the PVA (A) is more than <NUM> parts by mass, the physical properties of the PVA film may be impaired.

In film forming of a PVA film, it is preferable to add a surfactant to the PVA film from the viewpoint of handleability thereof and improvement of releasability from a film forming apparatus in the production of the PVA film. Examples of the surfactant include an anionic surfactant and a nonionic surfactant.

Examples of the anionic surfactant include carboxylic acid type surfactants such as potassium laurate; sulfuric acid ester type surfactants such as octyl sulfate; and a sulfonic acid type surfactants such as dodecylbenzenesulfonate.

Examples of the nonionic surfactant include alkyl ether type surfactants such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether; alkylphenyl ether type surfactants such as polyoxyethylene octylphenyl ether; alkyl ester type surfactants such as polyoxyethylene laurate; alkylamine type surfactants such as polyoxyethylene laurylamino ether; alkylamide type surfactants such as polyoxyethylene lauric acid amide; polypropylene glycol ether type surfactants such as polyoxyethylene polyoxypropylene ether; alkanolamide type surfactants such as lauric acid diethanolamide and oleic acid diethanolamide; and allyl phenyl ether type surfactants such as polyoxyalkylene allyl phenyl ether.

The surfactant may be used singly or in combination of two or more kinds thereof.

The PVA film may contain components such as moisture, an antioxidant, an ultraviolet absorber, a lubricant, a crosslinking agent, a colorant, a filler, an antiseptic, an antifungal agent, and other polymer compounds in addition to a plasticizer, starch, a water-soluble polymer other than the PVA (A), and a surfactant as long as the effect of the present invention is not hindered. The ratio of the total mass of a PVA, plasticizer, starch, water-soluble polymer other than PVA (A), and surfactant to the total mass of the PVA film is preferably within the range of <NUM> to <NUM> mass%, more preferably within the range of <NUM> to <NUM> mass%, and still more preferably within the range of <NUM> to <NUM> mass%.

The thickness of the PVA film is not particularly limited, but the thickness of the PVA film is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and still more preferably <NUM> or less because if the thickness is too thick, secondary processability tends to be deteriorated. When the thickness is too thin, there is a possibility that a problem occurs in the mechanical strength of the PVA film. Therefore, the thickness of the PVA film is preferably <NUM> or more, more preferably <NUM> or more, still more preferably <NUM> or more, and particularly preferably <NUM> or more. The thickness of the PVA film can be obtained as an average value of thicknesses measured at <NUM> arbitrary positions (for example, <NUM> arbitrary points on a straight line drawn in the length direction of the PVA film).

The PVA film is used as a raw fabric film for producing an optical film or a water-soluble film. Examples of the optical film include a polarizing film, a viewing angle improving film, a retardation film, and a brightness improving film, and the polarizing film is preferable. Examples of the water-soluble film include a film for drug packaging, a base film for hydraulic transfer, a base film for embroidering, a release film for molding artificial marble, a film for seed packaging, and a film for waste storage bag, and the film for drug packaging is preferable. Examples of the type of the drug include detergents, agricultural chemicals, and disinfectants. The form of the drug may be any of a powder form, a lump form, a gel form, and a liquid form. A package can be obtained by packaging a drug using the PVA film as a film for drug packaging. By using this package, it is possible to use a certain amount of a drug easily and safely when washing clothes using a detergent in general households or spraying a pesticide on a paddy field in agricultural works.

Generally, a PVA film can be produced by any method, such as a method for film forming by a flow-casting film forming method, a wet film forming method (ejection into a poor solvent), a dry-wet film forming method, a gel film forming method (method in which the film forming stock solution is once cooled and gelled, and then the solvent is extracted and removed to obtain a PVA film) or a combination of these methods, a melt extrusion film forming method, in which an extruder is used to obtain the above film forming stock solution, and the film is extruded from a T-die, or an inflation molding method using a film forming stock solution homogenized by adding solvent and additives to PVA (A). Among them, a flow-casting film forming method and a melt extrusion film forming method are preferable because a homogeneous film can be obtained with high productivity. Hereinafter, a flow-casting film forming method or a melt extrusion film forming method for a PVA film is described.

When a PVA film is formed by a flow-casting film forming method or a melt extrusion film forming method, the above-mentioned film forming stock solution is spilled onto a support such as a metal roll or a metal belt in the form of a film, and is heated to remove a solvent, thereby solidifying and forming a film. The solidified film is released from the support, dried by a drying roll, a drying furnace, or the like as necessary, further heat-treated as necessary, and wound up, whereby a long PVA film in a roll shape can be obtained.

The volatile content concentration (concentration of volatile components such as a solvent removed by volatilization or evaporation during film forming or the like) of the film forming stock solution is preferably <NUM> mass% or more, and more preferably <NUM> mass% or more. The volatile content concentration of the film forming stock solution is preferably <NUM> mass% or less, and more preferably <NUM> mass% or less. When the volatile content concentration is less than <NUM> mass%, the viscosity of the film forming stock solution increases, and film forming may be difficult. On the other hand, when the volatile content concentration exceeds <NUM> mass%, the viscosity becomes low, and the thickness uniformity of the resulting film is easily impaired.

Here, the "volatile fraction of the film forming stock solution" in the present specification refers to a volatile fraction determined by the following formula. <MAT> (In the formula, Wa represents the mass (g) of the film forming stock solution, and Wb represents the mass (g) when the film forming stock solution of Wa (g) is dried in an electrothermal dryer at <NUM> for <NUM> hours.

The method for adjusting the film forming stock solution is not particularly limited, and examples thereof include a method in which PVA and additives such as a plasticizer and a surfactant are dissolved in a dissolution tank, and a method in which PVA in a water-containing state is melt-kneaded together with a plasticizer, a surfactant, and the like when the PVA is melt-kneaded using a single screw extruder or a twin screw extruder.

When a PVA film is formed by a flow-casting film forming method or a melt extrusion film forming method, the film forming stock solution is spilled from a film-like discharge device onto a support such as a metal roll or a metal belt in the form of a film, and is heated to remove a solvent, thereby solidifying and forming a film.

The surface temperature of the support on which the film forming stock solution is spilled is preferably <NUM> or higher, more preferably <NUM> or higher, and still more preferably <NUM> or higher. The surface temperature of the support on which the film forming stock solution is spilled is preferably <NUM> or lower, more preferably <NUM> or lower, and still more preferably <NUM> or lower. When the surface temperature is lower than <NUM>, the time required for drying becomes long, and productivity tends to decrease. When the surface temperature exceeds <NUM>, there are tendencies that the film surface abnormality such as foaming is likely to occur and the film becomes too hard.

While the PVA film is heated on the support, hot air having an air velocity of <NUM> to <NUM>/s may be uniformly blown to the entire region on the non-contact surface side of the PVA film to adjust the drying rate. The temperature of the hot air blown onto the non-contact surface side is preferably <NUM> or higher, and more preferably <NUM> or higher from the viewpoint of drying efficiency, uniformity of drying, and the like. The temperature of the hot air blown onto the non-contact surface side is preferably <NUM> or lower, and more preferably <NUM> or lower from the viewpoint of drying efficiency, uniformity of drying, and the like.

The PVA film released from the support is dried on the support preferably to a volatile fraction of <NUM> to <NUM> mass%, then released, and further dried if necessary. The drying method is not particularly limited, and examples thereof include a method of contacting with a drying furnace or a drying roll. In the case of drying with a plurality of drying rolls, it is preferable to bring one surface and the other surface of the film alternately into contact with the drying rolls in order to make both surfaces uniform. The number of the drying rolls is preferably <NUM> or more, more preferably <NUM> or more, and still more preferably <NUM> or more. The number of drying rolls is preferably <NUM> or less. The upper limit of the temperature of the drying furnace and the drying roll is preferably <NUM> or lower, more preferably <NUM> or lower, more preferably <NUM> or lower, and still more preferably <NUM> or lower. If the temperature of the drying furnace and the drying roll is too high, the film may become too hard. On the other hand, the lower limit of the temperature of the drying furnace and the drying roll is preferably <NUM> or higher, more preferably <NUM> or higher, and still more preferably <NUM> or higher. When the temperature of the drying furnace and the drying roll is too low, productivity may be deteriorated.

The dried PVA film can be further subjected to heat treatment as necessary. By performing the heat treatment, physical properties such as strength, water solubility, and birefringence of the PVA film can be adjusted. The lower limit of the heat treatment temperature is preferably <NUM> or higher. The upper limit of the heat treatment temperature is preferably <NUM> or lower, and more preferably <NUM> or lower. If the heat treatment temperature is too high, the film may become too hard.

If necessary, the PVA film produced in this way is further subjected to a humidity control treatment, cut at both ends (lugs) of the film, and wound into a roll shape on a cylindrical core, and is subjected to moisture-proof packaging to obtain a product.

The volatile fraction of the finally obtained PVA film by the series of treatments described above is not necessarily limited. The volatile fraction of the PVA film is preferably <NUM> mass% or more, and more preferably <NUM> mass% or more. The volatile fraction of the PVA film is preferably <NUM> mass% or less, and more preferably <NUM> mass% or less.

The PVA film obtained by the above method containing a plasticizer, cut, and extracted with a Soxhlet extractor sdstrreter- using chloroform thereby removing components other than the PVA resin can be discriminated between a PVA film containing a PVA (Ab) in which all or a part of carbon is derived from bio-derived ethylene (Bb) and a PVA film containing only a PVA (Ap) derived only from fossil fuel-derived ethylene (Bp) by measuring the abundance ratio of carbon <NUM> (<NUM>C) in total carbon, that is, <NUM>C/C.

In the present invention, the PVA (Ap) derived only from fossil fuel-derived ethylene (Bp) means that the PVA (Ab) is not contained in which all or a part of carbon is derived from bio-derived ethylene (Bb), and is not a concept of excluding the PVA (Ap) containing monomer units other than fossil fuel-derived ethylene (Bp). In the present invention, the PVA film containing only the PVA (Ap) means not containing the PVA (Ab) derived from bio-derived ethylene (Bb), and is not a concept of excluding a PVA film containing components other than the PVA (Ap).

In addition, by measuring the abundance ratio <NUM> (<NUM>C) of carbon in the total carbon, that is, <NUM>C/C, it is possible to discriminate a PVA film containing a plasticizer produced, cut, and extracted with a Soxhlet extractor using chloroform thereby removing components other than the PVA resin containing a PVA (Ab) in which all or a part of carbon is derived from bio-derived ethylene (Bb) from a PVA film, different from the PVA film, containing a PVA (Ab) in which a part of carbon is derived from bio-derived ethylene (Bb). For example, even in a PVA film partially containing a PVA (Ab) derived from the same plant-derived ethylene (Bb), if the ratio of a PVA (Ab) derived from bio-derived ethylene (Bb) and PVA (Ap) obtained only from a fossil fuel-derived raw material is different, the abundance ratio <NUM>C/C is different. For example, when a PVA film produced by own company is produced so that the abundance ratio of carbon <NUM> (<NUM>C) in the total carbon, that is, <NUM>C/C is constant, it is possible to discriminate whether the PVA film is a PVA film produced by own company or a PVA film produced by another company. In addition, even in the same company, production is performed so that the abundance ratio of carbon <NUM> (<NUM>C), that is, <NUM>C/C varies depending on the production site, the production date, and the production lot, whereby the production site, the production date, and the production lot of the PVA film can be specified by measuring the abundance ratio of carbon <NUM> (<NUM>C), that is, <NUM>C/C.

In order to discriminate the PVA film, the PVA film is preferably produced so that the abundance ratio of <NUM>C in the total carbon, that is, <NUM>C/C is <NUM> × <NUM>-<NUM> or more, more preferably <NUM> × <NUM>-<NUM> or more, and still more preferably <NUM> × <NUM>-<NUM> or more. In addition, since a bio-derived raw material is generally more expensive than a fossil fuel-derived raw material, in order to discriminate a PVA film, it is preferable to produce a PVA film so that the abundance ratio of <NUM>C in total carbon, that is, <NUM>C/C, is <NUM> × <NUM>-<NUM> or less, more preferably <NUM> × <NUM>-<NUM> or less, and still more preferably <NUM> × <NUM>-<NUM> or less.

Furthermore, by measuring the abundance ratio of carbon <NUM> (<NUM>C) in the total carbon, that is, <NUM>C/C, it is possible to discriminate whether bio-derived ethylene (Bb) is C3 plant-derived ethylene (Bb) or C4 plant-derived ethylene (Bb) by measuring the carbon stable isotope ratio δ<NUM>C of carbon <NUM> (<NUM>C) for a PVA film that has been discriminated to contain PVA (Ab) derived from bio-derived ethylene (Bb). More specifically, bio-derived ethylene (Bb) is discriminated as C4 plant-derived ethylene (Bb) when a carbon stable isotope ratio δ<NUM>C of (<NUM>C) of carbon <NUM> is -<NUM> ‰ or more, and bio-derived ethylene (Bb) is discriminated as C3 plant-derived ethylene (Bb) when the carbon stable isotope ratio δ<NUM>C is less than -<NUM> ‰. By measuring the abundance ratio of carbon <NUM> (<NUM>C) in the total carbon, that is, <NUM>C/C, and the carbon stable isotope ratio of carbon <NUM> (<NUM>C), that is, δ<NUM>C, PVA films can be discriminated with higher accuracy.

In the above description, the abundance ratio of carbon <NUM> (<NUM>C) in total carbon, that is, <NUM>C/C is measured, and then the carbon stable isotope ratio δ<NUM>C of carbon <NUM> (<NUM>C) is measured for one that is discriminated to be a PVA film containing a PVA (Ab) derived from bio-derived ethylene (Bb). However, the abundance ratio of carbon <NUM> (<NUM>C), that is, <NUM>C/C is not measured, the carbon stable isotope ratio δ<NUM>C of carbon <NUM> (<NUM>C) is measured, and as a result, a PVA film containing a PVA (Ab) in which all or a part of carbon is derived from bio-derived ethylene (Bb) can be discriminated from other PVA films different from the PVA film. For example, it is possible to discriminate a PVA film containing a PVA (Ab) derived from bio-derived ethylene (Bb) from a PVA film containing only PVA (Ap) obtained from only a fossil fuel-derived raw material. However, since the carbon stable isotope ratio δ<NUM>C of a PVA (Ap) obtained only from a fossil fuel-derived raw material is generally less than -<NUM> ‰, it may be difficult to discriminate a PVA film containing a PVA (Ab) obtained from C3 plant-derived ethylene (Bb) as a raw material from a PVA film containing only PVA (Ap) obtained only from a fossil fuel-derived raw material.

Further, it is also possible to discriminate a PVA film containing a PVA (Ab) derived from bio-derived ethylene (Bb) from a PVA film containing a PVA (Ab) different from the PVA film and derived from bio-derived ethylene (Bb).

As described above, when the mixing ratio of a bio-PVA and a fossil fuel-derived PVA of a PVA to be used is changed for each production line of a PVA film, it is possible to specify which production line of a PVA film is used as a raw material for the polarizing film used by analyzing a polarizing plate of an LCD product available in a consumer market.

As described above, the PVA film can be suitably used for optical applications such as a raw material of a polarizing film. It can also be suitably used for the application of a water-soluble film such as drug packaging and a seed tape.

Hereinafter, the present invention is specifically described with reference to Examples and the like, but the present invention is not limited by the following Examples at all.

A PVA film roll obtained in the following Examples or Comparative Examples was unwound to collect about <NUM> of a film, and the film was cut into a small piece. Then, the cut PVA film was extracted with a Soxhlet extractor using chloroform. By sufficiently removing components other than a PVA in the PVA film in this manner, the PVA film was purified to obtain a PVA in the PVA film.

The PVA obtained in the above [Purification of PVA Film] was subjected to CO<NUM> conversion by a pretreatment method (ASTM D6866/Method B) specified by American Society of Testing and Materials, and then subjected to C (graphite) conversion by a complete reduction treatment using an iron catalyst. Next, the carbon isotope ratio (<NUM>C/<NUM>C ratio, <NUM>C/<NUM>C ratio) of the purified PVA film and the standard substance was measured by an accelerator mass spectrometry, and the <NUM>C concentration, the <NUM>C concentration, and the <NUM>C concentration were determined from the measurement results. Then, the obtained <NUM>C concentration was divided by the total carbon concentration (total of <NUM>C concentration, <NUM>C concentration, and <NUM>C concentration) to calculate <NUM>C/C of a PVA in the PVA film. Here, as a standard substance, graphite synthesized from an oxalic acid standard substance (HOxII) provided by National Institute of Standards and Technology was used. The measurement limit of <NUM>C/C in this measurement is less than <NUM> × <NUM>-<NUM>.

The PVA obtained in the above [Purification of PVA Film] was subjected to CO<NUM> conversion by a pretreatment method (ASTM D6866/Method B) specified by American Society of Testing and Materials, and then subjected to C (graphite) conversion by a complete reduction treatment using an iron catalyst. Next, the carbon isotope ratio (<NUM>C/<NUM>C ratio) of the purified PVA film and the standard substance was measured by an accelerator mass spectrometry. Then, the carbon stable isotope ratio δ<NUM>C was calculated by the following formula. Here, PDB ("Pee Dee Belemnite") was used as the standard substance.

In the above formula, [(<NUM>C/<NUM>C)sample] represents a carbon isotope ratio (<NUM>C/<NUM>C ratio) of the purified PVA film to be measured, and [(<NUM>C/<NUM>C)PDB] represents a carbon isotope ratio (<NUM>C/<NUM>C ratio) of PDB as a standard substance.

The PVA obtained in the above [Purification of PVA Film] was dissolved in dimethyl sulfoxide (DMSO-d<NUM>), and then the solution was added to acetone to precipitate a PVA, thereby further purifying the PVA. One to two drops of trifluoroacetic acid (TFA) was added dropwise to the DMSO-d<NUM> solution of the PVA, and the obtained sample was immediately subjected to NMR measurement under the following conditions. From the obtained NMR spectrum, the ethylene unit content, the alkoxyl group content, the <NUM>,<NUM>-glycol bond content, and the degree of saponification of a PVA in the PVA film were determined.

A rectangular test piece having a width direction of <NUM> and a flow direction of <NUM> was taken from the central part in the width direction of the PVA film roll obtained in the following Examples or Comparative Examples. This test piece was set in a tensile tester at a chuck interval of <NUM>, and then stretched in a constant-temperature water bath set at a predetermined temperature to measure a percent of stretch at the time of breaking. This procedure was repeated <NUM> times, and the average value of the percent of stretch at the time of breaking was determined. When the average value was <NUM> times or more, the temperature of the constant-temperature water bath was lowered by <NUM>, and when the average value was less than <NUM> times, the temperature of the constant-temperature water bath was raised by <NUM>, and a limit temperature at which the average value of the percent of stretch at the time of breaking was <NUM> times or more (minimum temperature at which the average value was <NUM> times or more) was determined.

A polarizing film roll obtained in the following Examples or Comparative Examples was unwound and cut into a size of <NUM> in the length direction (stretching direction) and <NUM> in the width direction. The blue foreign matter existing on the surface of the cut polarizing film was visually observed, and the number of foreign matters having a longest diameter of <NUM> to <NUM> (pieces/<NUM><NUM>) was determined. This procedure was repeated <NUM> times to obtain an average value (pieces/<NUM><NUM>) of the number of foreign matters. The longest diameter of the foreign matter was measured using a differential interference microscope (magnification: <NUM> times). In the following Examples or Comparative Examples, since the polarizing film after the drying treatment is continuously wound for <NUM> hours, the cut polarizing film is a sample after about <NUM> hours from the start of production of the polarizing film.

A polarizing film roll obtained in the following Examples or Comparative Examples was unwound and cut into a size of <NUM> in the length direction (stretching direction) and <NUM> in the width direction. Two square samples of <NUM> in the length direction (stretching direction) and <NUM> in the width direction of the cut polarizing film were taken from the central part in the width direction of the polarizing film, and the light transmittance (Y//) in the case of overlapping the samples such that the length direction (stretching direction) was parallel and the light transmittance (Y⊥) in the case of overlapping the samples such that the length direction (stretching direction) was orthogonal were measured by the same method as the above transmittance measurement method, and the degree of polarization (V) (%) was determined from the following formula.

After impregnating <NUM> (water absorption <NUM>) of the silica sphere carrier "HSV-I" (manufactured by Shanghai Haiyuan Chemical Industry Technology Co. ) (sphere diameter: <NUM>, specific surface area: <NUM><NUM>/g, water absorption: <NUM>/g) with an aqueous solution equivalent to the amount of water absorbed by the carrier, which contains <NUM> of a <NUM> mass% sodium tetrachloropallastate aqueous solution and <NUM> of a <NUM> mass% hydrogen tetrachloroaurate tetrahydrate aqueous solution, and then the silica sphere carrier was immersed in <NUM> of an aqueous solution containing <NUM> of sodium metasilicate nonahydrate and allowed to stand for <NUM> hours. Subsequently, <NUM> of a <NUM> mass% hydrazine hydrate aqueous solution was added, and the resulting mixture was allowed to stand at room temperature for <NUM> hours, then washed with water until chloride ions disappeared from water, and dried at <NUM> for <NUM> hours. The resulting palladium/gold/carrier composition was immersed in <NUM> of a <NUM> mass% acetic acid aqueous solution and allowed to stand for <NUM> hours. Then, the composition was washed with water for <NUM> hours and dried at <NUM> for <NUM> hours. Thereafter, <NUM> of an aqueous solution equivalent to the amount of water absorbed by the carrier of potassium acetate was impregnated, and dried at <NUM> for <NUM> hours to obtain a vinyl acetate synthesis catalyst.

The obtained catalyst (<NUM>) was diluted with <NUM> of glass beads and filled in a SUS316L reaction tube (inner diameter <NUM>, length <NUM>, and then the reaction was carried out by circulating a gas mixed at a reaction temperature of <NUM>. and a reaction pressure of <NUM> MPaG at a ratio of ethylene/oxygen/water/acetic acid/nitrogen = <NUM>/<NUM>/<NUM>/<NUM>/ <NUM> (mol%) at a flow rate of <NUM> NL/hour. Here, bio-ethylene derived from a sugar cane (manufactured by Braskem S. ) was used as ethylene. The obtained reaction gas containing vinyl acetate was purified to obtain vinyl acetate.

Using the obtained vinyl acetate as a monomer, <NUM>,<NUM>'-azobis-(<NUM>-methoxy-<NUM>,<NUM>-dimethylvaleronitrile) as a polymerization initiator, and methanol as a solvent, polymerization was performed at a polymerization temperature of <NUM> by a known method, and then <NUM>,<NUM>-diphenyl-<NUM>-methyl-<NUM>-pentene (DPMP) as a compound having a conjugated double bond and a molecular weight of <NUM> or less was added in an amount of <NUM> mol per <NUM> mol of the polymerization initiator used. The polymerization time was adjusted in accordance with the target degree of polymerization. A <NUM> mass% methanol solution of sodium hydroxide was added to the obtained methanol solution of polyvinyl acetate under stirring so that the molar ratio of sodium hydroxide to vinyl acetate units of polyvinyl acetate was <NUM>, and a saponification reaction was started at <NUM>. As the saponification reaction proceeded, a gelated product was produced. When <NUM> minutes had elapsed from the start of the saponification reaction, the gelated product was pulverized to obtain a PVA (PVA-<NUM>) swollen with methanol. This PVA-<NUM> was washed with <NUM> times its mass of methanol and then dried with hot air at <NUM> for <NUM> hour and at <NUM> for <NUM> hours.

An aqueous solution (PVA concentration: <NUM> mass%) containing <NUM> parts by mass of the obtained PVA-<NUM>, <NUM> parts by mass of glycerin, and <NUM> parts by mass of lauric acid diethanolamide was prepared as a film forming stock solution of the PVA film. The film forming stock solution was discharged from a slit die onto a first metal roll having a diameter of <NUM> and adjusted to a surface temperature of <NUM>, and dried to release the film having a moisture content of <NUM> mass% from the metal roll. Subsequently, the film surface not in contact with the first metal roll was brought into contact with a second metal roll having a surface temperature of <NUM> and a diameter of <NUM>, and the film was dried. Further, the film was sequentially brought into contact with a third to sixth metal rolls (surface temperature: <NUM> to <NUM>, diameter: <NUM>) so that one surface and the other surface of the film were alternately brought into contact with the metal rolls, dried, and wound up to obtain a roll-shaped product of the PVA film (PVA film roll) having a width of <NUM>, a length of <NUM>, and a thickness of <NUM>.

The obtained PVA film roll was unwound, and subjected to a swelling treatment, a dyeing treatment, a crosslinking treatment, a stretching treatment, a washing treatment, and a drying treatment in this order to continuously produce a polarizing film. The swelling treatment was performed by immersing the PVA film in a swelling treatment tank with a treatment liquid (pure water) at <NUM> and uniaxially stretching the film <NUM> times in the length direction during the immersion. The dyeing treatment was performed by immersing the PVA film in a swelling treatment tank with a treatment liquid (aqueous solution of <NUM> mass% of boric acid and <NUM> mass% of potassium iodide) at <NUM>, and uniaxially stretching the film <NUM> times in the length direction during the immersion. The crosslinking treatment was performed by immersing the PVA film in a swelling treatment tank with a crosslinking treatment liquid (aqueous solution of <NUM> mass% boric acid) at <NUM>, and uniaxially stretching the film <NUM> times in the length direction during the immersion. The stretching treatment was performed by uniaxially stretching the PVA film <NUM> times in the length direction in a swelling treatment tank with a stretching treatment liquid (aqueous solution of <NUM> mass% of boric acid and <NUM> mass% of potassium iodide) at <NUM>. The washing treatment was performed by immersing the PVA film in a washing treatment tank with a washing treatment liquid (aqueous solution of <NUM> mass% of boric acid and <NUM> mass% of potassium iodide) at <NUM> for <NUM> seconds. The drying treatment was performed by drying the PVA film at <NUM> for <NUM> minutes. Here, the PVA film was not stretched between the washing treatment and the drying treatment. In this way, the obtained PVA film roll was unwound to continuously produce a polarizing film.

Two square samples of <NUM> in the length direction (stretching direction) and <NUM> in the width direction of the obtained polarizing film were collected from the central part in the width direction of the polarizing film, and for each sample, the visibility correction of the visible light region of the C light source and the visual field of <NUM> degrees was performed in accordance with JIS Z8722 (Method for measuring object color) using a spectrophotometer V-<NUM> (with integrating sphere) manufactured by Hitachi, Ltd. , and for one polarizing film sample, the light transmittance when the sample is tilted <NUM> degrees with respect to the stretching axis direction and the light transmittance when the sample is tilted -<NUM> degrees were measured, and the average value (Y1) thereof was obtained.

For the other polarizing film sample, the light transmittance when the sample is tilted <NUM> degrees and the light transmittance when the sample is tilted -<NUM> degrees were measured in the same manner as described above, and the average value (Y2) thereof was obtained. The value of Y1 and Y2 obtained above were averaged to obtain the transmittance (Y) (%) of the polarizing film.

The concentrations of iodine and potassium iodide in the swelling treatment tank were adjusted so that the transmittance was <NUM>%, and then the polarizing film after the drying treatment was continuously wound for <NUM> hours to obtain a roll-shaped product of the polarizing film (polarizing film roll).

The PVA film roll and the polarizing film roll thus obtained were measured and evaluated by the method described above. The measurement and evaluation results are shown in Table <NUM>. The raw materials and polymerization conditions of a PVA are shown in Table <NUM>.

The same procedure as in Example <NUM> was carried out to obtain a PVA (PVA-<NUM>) except that the polymerization initiator used in the "(<NUM>) Synthesis of PVA" was changed to azobisisobutyronitrile. Then, a PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as in Example <NUM> except that PVA-<NUM> was used. The measurement and evaluation results are shown in Table <NUM>. The raw materials and polymerization conditions of a PVA are shown in Table <NUM>.

The same procedure as in Example <NUM> was carried out to obtain a PVA (PVA-<NUM>) except that the polymerization temperature of a PVA was changed to <NUM> in "(<NUM>) Synthesis of PVA". Then, a PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as in Example <NUM> except that PVA-<NUM> was used. The measurement and evaluation results are shown in Table <NUM>. The raw materials and polymerization conditions of a PVA are shown in Table <NUM>.

The same procedure as in Example <NUM> was carried out to obtain a PVA (PVA-<NUM>) except that ethylene used in the "(<NUM>) Synthesis of vinyl acetate" was changed to petroleum-derived ethylene (manufactured by AIR LIQUIDE Kogyo Gas Ltd. Then, a PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as in Example <NUM> except that PVA-<NUM> was used. The measurement and evaluation results are shown in Table <NUM>. The raw materials and polymerization conditions of a PVA are shown in Table <NUM>.

A PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as in Example <NUM> except that the PVA used in the above "(<NUM>) Production of a PVA film and PVA film roll" is changed to the PVA obtained by mixing the PVA-<NUM> obtained in Comparative Example <NUM> and the PVA-<NUM> obtained in Example <NUM> at a mass ratio of <NUM> : <NUM>. The measurement and evaluation results are shown in Table <NUM>. The raw materials and polymerization conditions of a PVA are shown in Table <NUM>.

PVA (PVA-<NUM>) was obtained in the same manner as in Example <NUM> except that <NUM> parts by mass of sugar cane-derived bio-ethylene (manufactured by Braskem S. ) was added as a monomer used in the above "(<NUM>) Synthesis of PVA", with respect to <NUM> parts by mass of vinyl acetate, and a polymerization reaction was performed while the pressure in the reaction vessel was maintained at <NUM> MPaG. Then, a PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as in Example <NUM> except that PVA-<NUM> was used. The measurement and evaluation results are shown in Table <NUM>. The raw materials and polymerization conditions of a PVA are shown in Table <NUM>.

Rice, a C3 plant, was subjected to an alkali treatment step, a saccharification treatment step, and an ethanolization step to obtain rice-derived ethanol. The ethanol was subjected to a dehydration reaction treatment at <NUM> using mordenite as a catalyst to produce rice-derived bio-ethylene.

Then, PVA (PVA-<NUM>) was obtained in the same manner as in Example <NUM> except that ethylene used in the "(<NUM>) Synthesis of vinyl acetate" was changed to rice-derived bio-ethylene. Then, a PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as in Example <NUM> except that PVA-<NUM> was used. The measurement and evaluation results are shown in Table <NUM>. The raw materials and polymerization conditions of a PVA are shown in Table <NUM>.

Claim 1:
A method for discriminating a polyvinyl alcohol resin film, the method comprising discriminating a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or a part of carbon is derived from bio-derived ethylene (Bb) from a polyvinyl alcohol resin film containing only a polyvinyl alcohol resin (Ap) derived only from fossil fuel-derived ethylene (Bp) by
producing a polyvinyl alcohol resin film containing a plasticizer from a polyvinyl alcohol resin,
obtaining a cut polyvinyl alcohol resin film by cutting the polyvinyl alcohol resin film and extracting the cut polyvinyl alcohol resin film with a Soxhlet extractor using chloroform thereby removing components other than the polyvinyl alcohol resin from the cut polyvinyl alcohol resin film, and
measuring an abundance ratio <NUM>C/C of carbon <NUM> (<NUM>C) in total carbon for the obtained cut polyvinyl alcohol resin film.