Polyvinyl alcohol resin film, method for distinguishing polyvinyl alcohol resin film and method for producing polyvinyl alcohol resin film

Abstract

FIELD: PVA resins.SUBSTANCE: invention is a film made of polyvinyl alcohol resin, containing a polyvinyl alcohol resin (A), in which the content of carbon 14 (14C) in the total amount of carbon included in the composition of the polyvinyl alcohol resin (A), that is, 14C / C, is 1.0×10-14 or more. The present invention is a method for distinguishing a polyvinyl alcohol resin film, comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb), and a polyvinyl alcohol resin film containing only a polyvinyl alcohol resin (Ap) obtained only from fossil fuel-derived ethylene (Bp), by measuring the relative content of 14C / C carbon 14 (14C) to the total amount of carbon.EFFECT: providing a PVA film that does not increase the amount of carbon dioxide present in the environment, or increases it insignificantly, even when carbon dioxide is formed as a result of biodegradation treatment or incineration, in addition, a method for simple and reliable identification of the manufacturer of the PVA film is provided.6 cl, 2 tbl

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001] The present invention relates to a polyvinyl alcohol resin film, a method for distinguishing a polyvinyl alcohol resin film, and a method for producing a polyvinyl alcohol resin film.BACKGROUND

[0002] The film containing polyvinyl alcohol resin (also referred to as PVA hereinafter) has unique properties such as water solubility and optical performance, and is therefore used in various applications where such characteristics are important, such as water-soluble film for packaging medicines and seed tapes, and optical film used as a raw material for polarizing film of liquid crystal display.

[0003] PVA is also known as a synthetic resin, which has the unusual ability for a synthetic resin to be biodegradable and has a low environmental impact. However, most of the raw materials used to produce PVA are derived from fossil fuels such as oil, coal, and natural gas. Fossil fuels contain carbon that has been locked up in the ground for many years. Therefore, PVA is biodegraded by microorganisms or burned, like a conventional synthetic resin, releasing carbon dioxide into the atmosphere. This releases carbon that was locked up deep in the ground and not present in the atmosphere as carbon dioxide, potentially contributing to global warming.

[0004] On the other hand, if the raw material of a synthetic resin is a material obtained from a living organism (plant, animal) that absorbs carbon dioxide circulating in the global environment and is grown with a nutrient source in which the carbon dioxide is converted into organic matter, then even if the material is processed by biodegradation or combustion to produce carbon dioxide, the carbon dioxide present in the environment is circulated, and thus the total amount of carbon that constitutes carbon dioxide does not change.

[0005] In particular, plants are living organisms that absorb carbon dioxide circulating in the environment, carry out photosynthesis using carbon dioxide and water as raw materials, and assimilate and fix carbon dioxide as an organic substance. Thus, plants are attractive as a carbon source. For example, the alcohol component, particularly ethyl alcohol, is distilled and separated from the fermentation product of sugar extracted from plant materials such as sugarcane or corn, or the fermentation product of cellulose. Ethylene, as an alkene, can be obtained through a dehydration reaction.When a vinyl alcohol ester monomer (hereinafter also referred to as a biovinyl ether monomer) is synthesized using bio-derived ethylene (hereinafter also referred to as bioethylene), and a polyvinyl ether obtained by polymerizing this biovinyl ether monomer is saponified to produce PVA (hereinafter also referred to as bio-PVA), the carbon dioxide content of the environment does not increase even if this bio-PVA is subjected to biodegradation treatment or incineration to produce carbon dioxide, and it does not cause global warming.

[0006] The carbon that makes up the carbon dioxide circulating in the environment is a mixture of radioactive carbon 14 (hereinafter may be referred to as 14 C), which is an isotope of stable carbon 12 (hereinafter may be designated as 12 C) and metastable carbon 13 (hereinafter may be designated as 13C), and it is known that its mass ratio is 98.892 wt.% for 12 C, 1.108 wt.% for 13 C and 1.2×10 -12 -1.2×10 -10 wt.% (trace amount) for 14 C. Ratio 12 C and 13 C is stable. Since it is radioactive 14 C is formed when a neutron contained in a secondary cosmic ray generated by a primary cosmic ray in the upper atmosphere collides with a nitrogen atom ( 14 N) in the atmosphere, radioactive 14 C is supplied continuously, although its amount fluctuates slightly due to changes in sunspot activity; but, on the other hand, the amount of radioactive 14 C decreases with a half-life of 5730 years.

[0007] As the carbon that makes up the body of a living organism, growing by constantly absorbing carbon dioxide circulating in the global environment, continues to be renewed throughout its life, the carbon continues to assume the mass ratio of the three types of carbon isotopes that make up the carbon dioxide circulating in the global environment. When a living organism dies, the mass ratio of the three types of carbon isotopes within the living organism is fixed at the ratio at the time of death. Half-life 14 C is 5730 years old, and the mass fraction is 14 The C content of fossil fuels formed over a long period of time after the death of an ancient organism long before is very small compared to the mass fraction 14 C in carbon dioxide circulating in the global environment because fossil fuels are isolated from modern carbon dioxide circulating in the global environment.

[0008] Therefore, since the value of the share 14 The C content of conventional PVA produced using fossil fuels as feedstock is also significantly less than the proportion of the content 14 With the carbon content of bio-PVA being essentially 0%, bio-PVA and fossil fuel derived PVA can be distinguished from each other by measuring the proportion 14 C in the contained carbon.

[0009] As an application of the polyvinyl alcohol resin film (hereinafter referred to as the PVA film) containing the polyvinyl alcohol resin, mention can be made of a raw material fabric film in the production of optical film, such as a polarizing film, which is a component of an LCD monitor such as a liquid crystal television, or a film for individual packaging of a medicine, etc. in a quantity intended for single use, and the demand for them has been continuously increasing in recent years. The PVA film used for these purposes must have very high quality, for example, have very few defects and almost no unevenness in thickness. SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[0010] As described above, PVA film is used in various applications, such as raw fabric film for optical film production and pharmaceutical packaging film. However, quality issues with PVA film may arise in the marketplace in end products such as LCD TVs and pharmaceutical packaging, including optical film using PVA film. In this case, it is necessary to identify whether the PVA film causing the problem is manufactured by the company itself or by another company. However, in the conventional method, it is very difficult to identify the manufacturer of the PVA film by analyzing the PVA film used for the end product in question. Therefore, a need has arisen for a simple and reliable method for identifying the manufacturer of the PVA film used for the end product in question.

[0011] Thus, firstly, the objective of the present invention is to provide a PVA film using PVA that does not increase the amount of carbon dioxide present in the environment, or increases it only slightly, even when carbon dioxide is generated as a result of biodegradation or incineration. Secondly, the objective of the present invention is to provide a method for simple and reliable identification of the manufacturer of PVA film. SOLUTION TO THE PROBLEM

[0012] ASTM D6866, a standard from the National Institute of Standards and Technology (NIST), is known for distinguishing between plant-based organic matter and fossil fuel-derived organic matter. ASTM D6866 is an ASTM (American Society for Testing and Materials) standard for determining biogenic carbon concentrations in solid, liquid, and gaseous samples using radiocarbon dating. The current version of the standard is ASTM D6866-20, which was implemented in February 2020. This method can distinguish films containing bio-based PVA from films that do not contain bio-based PVA and contain only fossil fuel-derived PVA.

[0013] Thus, the present invention relates to the following:

[0001] A polyvinyl alcohol resin film containing a polyvinyl alcohol resin (A) in which the carbon content is 14 ( 14C) in the total amount of carbon contained in the polyvinyl alcohol resin (A), that is 14 C / C is 1.0 × 10 -14 or more.

[0002] The polyvinyl alcohol resin film according to item [1], in which the proportion δ 13 C stable isotope of carbon 13 ( 13 C) is -20‰ or more.

[0003] The polyvinyl alcohol resin film according to item [1], in which the proportion δ 13 C stable isotope of carbon 13 ( 13 C) is less than -20‰.

[0004] The polyvinyl alcohol resin film according to any one of [1] to [3], wherein all or part of the polyvinyl alcohol resin (A) is a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-derived ethylene (Bb).

[0005] The polyvinyl alcohol resin film according to any one of [1] to [4], wherein the polyvinyl alcohol resin (A) contains an ethylene unit, and the content of the ethylene unit relative to the total amount of monomer units of the polyvinyl alcohol resin (A) is 1 mol% or more and less than 15 mol%.

[0006] The polyvinyl alcohol resin film according to any one of [1] to [5], wherein the polyvinyl alcohol resin (A) has a saponification degree of 80 mol% or more.

[0007] The polyvinyl alcohol resin film according to any one of [1] to [6], wherein the polyvinyl alcohol resin (A) has a polymerization degree of 200 or more and less than 8000.

[0008] The polyvinyl alcohol resin film according to any one of [1] to [7], wherein the polyvinyl alcohol resin (A) has a 1,2-glycol bond content of 0.2 mol% or more and less than 2.0 mol%.

[0009] The polyvinyl alcohol resin film according to any one of [1] to [8], wherein the polyvinyl alcohol resin (A) has an alkoxy group at the polymer end, and the content of the alkoxy group relative to the total amount of monomer units of the polyvinyl alcohol resin (A) is 0.0005 mol% or more and less than 1 mol%.

[0010] An optical film that uses a polyvinyl alcohol resin film according to any one of [1] to [9].

[0011] A water-soluble film that uses a polyvinyl alcohol resin film according to any one of [1] to [9].

[0012] A package in which a detergent, agrochemical or disinfectant is packed in a water-soluble film according to item

[11] .

[0013] A method for distinguishing a polyvinyl alcohol resin film, comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-derived ethylene (Bb) and a polyvinyl alcohol resin film containing only a polyvinyl alcohol resin (Ap) derived only from fossil fuel-derived ethylene (Bp), by measuring the relative content 14 C / C carbon 14 ( 14 C) to the total amount of carbon.

[0014] A method for distinguishing a polyvinyl alcohol resin film, comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb), and a polyvinyl alcohol resin film other than the above-mentioned polyvinyl alcohol resin film and containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb), by measuring the relative content 14 C / C carbon 14 ( 14 C) to the total amount of carbon.

[0015] The method for distinguishing a polyvinyl alcohol resin film according to

[13] or

[14] , wherein the discrimination of whether the ethylene of biological origin (Bb) is C3 ethylene of plant origin (Bb) or C4 ethylene of plant origin (Bb) is carried out by measuring the proportion δ 13 C stable isotope of carbon 13 ( 13C) for a polyvinyl alcohol resin film comprising a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb).

[0016] The method for distinguishing a polyvinyl alcohol resin film according to item

[15] , wherein, when the proportion δ 13 C stable isotope of carbon 13 ( 13 C) is -20‰ or more, bio-based ethylene (Bb) is classified as plant-based C4 ethylene (Bb), and when the proportion δ 13 C stable isotope of carbon 13 ( 13 C) is less than -20‰, biologically derived ethylene (Bb) is classified as plant-derived C3 ethylene (Bb).

[0017] A method for distinguishing a polyvinyl alcohol resin film, comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-derived ethylene (Bb), and a polyvinyl alcohol resin film containing only a polyvinyl alcohol resin (Ap) derived only from fossil fuel-derived ethylene (Bp), by measuring a δ fraction 13 C stable isotope of carbon 13 ( 13 C).

[0018] A method for distinguishing a polyvinyl alcohol resin film, comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb), and a polyvinyl alcohol resin film different from the above-mentioned polyvinyl alcohol resin film and containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb), by measuring the proportion δ 13 C stable isotope of carbon 13 ( 13 C).

[0019] A method for producing a film of polyvinyl alcohol resin, comprising: synthesizing a vinyl alcohol ester monomer by reacting a compound having a carboxyl group with ethylene of biological origin (Bb), or synthesizing a vinyl alcohol ester monomer by reacting a compound having a carboxyl group with ethylene (Bb); polymerizing the obtained vinyl alcohol ester monomer to obtain a polyvinyl ester; saponifying the obtained polyvinyl ester to obtain a polyvinyl alcohol resin (Ab); and using the obtained polyvinyl alcohol resin (Ab) to produce a film of polyvinyl alcohol resin. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0014] According to the present invention, firstly, it is possible to provide a PVA film that does not increase the amount of carbon dioxide present in the environment, or increases it only slightly, even when carbon dioxide is generated as a result of biodegradation or incineration treatment. Secondly, according to the present invention, it is possible to provide a method for simple and reliable identification of the manufacturer of the PVA film. DESCRIPTION OF EMBODIMENTS

[0015] Next, the present invention will be described in detail.

[0016] <Content share 14 C>The PVA film of the present invention contains PVA (A), which is a saponified product of polyvinyl ester, and the content proportion 14 C in the total number of carbon atoms that make up PVA (A), that is 14 C / C (which may be referred to simply as 14 C / C) is 1.0 × 10 -14or more. The total amount of carbon is the sum of all carbon isotopes, and 14 C / C is the ratio of the amount 14 C to the total amount of carbon. When 14 C / C is less than 1.0 × 10 -14 , it is close to the lower limit of measurement of the measurement method according to ASTM D6866, so it is difficult to make an accurate measurement and it is difficult to distinguish whether the origin of PVA (A) contained in the PVA film is biological. In addition, the small value 14 C / C indicates that the proportion of bio-derived raw materials used in the production of PVA(A) is small and the effect of reducing the increase in the amount of carbon dioxide in the global environment becomes insufficient. The value 14 C / C is preferably 2.0 x 10 -14 or more, more preferably 5.0 × 10 -14 or more, and even more preferably 1.0 × 10 -13or more. On the other hand, the upper limit 14 C / C is not particularly limited, but since biologically derived feedstocks are generally more expensive than fossil fuel feedstocks, the value 14 C / C is preferably 1.0 × 10 -11 or less, more preferably 7.0 × 10 -12 or less, and even more preferably 5.0 × 10 -12 or less.

[0017] In the present invention, a measuring method 14 C / C is not particularly limited, and for example, the sample (e.g. vinyl acetate) is converted to carbon dioxide or graphite as needed, and then subjected to accelerator mass spectrometry (AMS method) to compare and measure the content 14 C relative to a standard substance (for example, oxalic acid in the US NIST). The value 14 C / C can be calculated by dividing the quantity 14 C in the sample per total amount of carbon in the sample.

[0018] <Proportion δ 13C stable isotope of carbon>Proportion δ 13 C stable isotope of carbon 13 C (hereinafter may be denoted simply as δ 13 C) in the present invention refers to the relationship 13 C to 12 C among the three types of isotopes of carbon atoms existing in nature (percentage abundance 12 C: 13 C: 14 C=98.9:1.11:1.2×10 -12 ), and the fraction of the stable isotope of carbon is expressed as a deviation from the standard substance and denotes a value (δ value) determined by the following formula:

[0019] δ 13 C[‰]={( 13 C / 12 C) sample / ( 13 C / 12 C) PDB - 1.0} × 1.000

[0020] where [( 13 C / 12 C) sample ] represents the fraction of the stable isotope in the measured sample, and [( 13 C / 12 C) PDB] represents the proportion of a stable isotope in the standard substance. PDB is an abbreviation for "Pee Dee Belemnite" and refers to an arrowhead fossil composed of calcium carbonate (as the standard substance, an arrowhead fossil from the PeeDee Bed in South Carolina) and is used as the standard body with the ratio 13 C / 12 C. "Share δ 13 The ratio of stable isotope carbon to standard is measured using accelerator mass spectrometry. Since the standard substance is rare, a working standard in which the ratio of the stable isotope to the standard substance is known can also be used.

[0021] <C3 Plants and C4 Plants>Bioethylene is roughly divided into two groups according to the plant used as raw material for it, and there are bioethylene derived from C3 plants such as sweet potato, sugar beet, rice, wood and algae, and bioethylene derived from C4 plants such as corn, sugarcane and cassava, and δ values 13 The C values ​​of both groups differ significantly. In the case of PVA, which uses bioethylene derived from C3 plants as a raw material, δ 13 C is less than -20‰, and in the case of PVA, which uses bioethylene obtained from C4 plants as raw material, δ 13 C is -20‰ or more. Therefore, PVA using bioethylene derived from C3 plants as feedstock and PVA using bioethylene derived from C4 plants as feedstock can be distinguished by measuring δ 13 C after measuring the above 14 C / C to exclude the possibility that PVA is derived from fossil fuels.

[0022] Plants are classified into three types: C3 plants, C4 plants, and plants with clover-type photosynthetic pathways (CAM / Crassulacean acid metabolism). These types are based on the types of carbon dioxide products they produce in the carbon dioxide fixation pathway during photosynthesis. In culture, maize and various cereal crops are classified as C4 plants, major crops such as rice and wheat are classified as C3 plants, and cacti, Crassulaceae, Euphorbiaceae, and other plants are classified as CAM plants.

[0023] More than 90% of plants on Earth are C3 plants, including agriculturally useful crops such as rice, wheat, tobacco, potatoes, and oil palm. The enzyme involved in carbon dioxide fixation in the photosynthetic pathway of C3 plants is ribulose-1,5-diphosphate carboxylase, which has a low affinity for carbon dioxide and, conversely, a high affinity for oxygen. This reduces the efficiency of the carbon dioxide fixation reaction, thereby reducing the efficiency of photochemical synthesis.

[0024] The PVA film of the present invention preferably has a proportion of δ 13 C stable isotope of carbon 13 ( 13 C) less than -20‰, measured using accelerator mass spectrometry. The δ value 13 C is more preferably -50‰ or more, even more preferably -45‰ or more, and particularly preferably -40‰ or more. The value of δ 13C is more preferably -22‰ or less, even more preferably -25‰ or less, and particularly preferably -26‰ or less. The fact that the proportion δ 13 The stable carbon isotope C in the PVA film of the present invention is within the above-mentioned range, indicating that PVA using bioethylene derived from C3 plants as a raw material is used as the PVA (A) contained in the PVA film, which is preferable in terms of raw material cost and processability. Preferred C3 plants include rice, wheat, potato, and palm oil.

[0025] A C4 plant is a plant that performs C4 photosynthesis, a form of photosynthesis that utilizes the C4 pathway for carbon dioxide concentration in addition to the Calvin-Benson cycle, which is the overall cycle of carbon dioxide reduction during photosynthesis. The enzyme involved in carbon dioxide fixation in the C4 plant photosynthetic pathway is phosphoenolpyruvate carboxylase. This enzyme is characterized by its activity not being inhibited by oxygen, its high capacity for carbon dioxide fixation, and its well-developed chloroplast, also found in the choroidal cell. Representative C4 plants include maize, sugarcane, cassava, sorghum, Chinese miscanthus, Guinea grass, Rhodes grass, Urochloa subquadripara, Italian foxtail, barnyard grass, Eleusis coraciana, and Chamaecyparis paniculata, also known as burning bush, broom, or Kochia scoparia.These C4 plants use additional energy to fix carbon dioxide, and thus can fix carbon dioxide more efficiently than other non-C4 plants. Furthermore, other plants have difficulty capturing carbon dioxide at high temperatures, unlike C4 plants. Furthermore, photosynthesis can be carried out to a sufficient degree even with little water. This is a physiological adaptation of the plants to harsh climatic conditions, such as high temperatures, dry soil with low carbon dioxide levels, and nitrogen-poor soil.

[0026] In the PVA film of the present invention, the proportion δ 13 C stable isotope of carbon 13 ( 13 C), measured by accelerator mass spectrometry, is preferably -20‰ or greater. The value of δ 13C is more preferably -18‰ or more, even more preferably -15‰ or more, and particularly preferably -13‰ or more. The value of δ 13 C is more preferably -1‰ or less, even more preferably -4‰ or less, and particularly preferably -7‰ or less. The fact that the proportion δ 13 The stable carbon isotope C in the PVA film of the present invention is in the above-mentioned range, indicating that PVA using bioethylene derived from C4 plants as a raw material was used as the PVA (A) contained in the PVA film. Bioethylene derived from C4 plants is generally less accessible than bioethylene derived from C3 plants, and thus the manufacturer of the PVA film can be more easily and reliably identified when the proportion δ 13The stable carbon isotope C in the PVA film of the present invention is within the above-mentioned range. Furthermore, corn, sugarcane, and cassava are preferred C4 crops in terms of production volume and cost.

[0027] In addition, as plants different from C3 and C4 plants, CAM plants have a photosynthetic system adapted to dry environments, and this photosynthetic system is considered to be an advanced form of the C3 photosynthesis variety. The δ value 13 The C of CAM plants is generally in the range of about -35‰ to about -10‰, and these CAM plants can be used as needed in combination as biomass raw materials, provided that the effect of the present invention is not deteriorated.

[0028] As the PVA film of the present invention, a mixture of PVA with different values ​​can be used as the raw material 14 C / C or δ 13 C, provided that14 C / C and δ if necessary 13 C are in the above range.

[0029] For example, not only the PVA film showing δ 13 C is obtained using plant material C3, but also a given value of δ 13 C is obtained by mixing PVAs with different δ 13 C, that is, the value of δ 13 C, which cannot be achieved by the simple plant substance C3, and a more specific value of δ is obtained 13 C, which allows for further improvement in the recognition accuracy of the resulting PVA film. Thus, when using raw materials with a different δ value 13 C, the statistical analysis value obtained by analyzing the proportion of stable carbon isotope is unique, and thus the raw material can be distinguished from other raw materials. Therefore, δ 13PVA film produced from such raw materials also has a unique analysis value, and identification and tracking become easy.

[0030] <Polyvinyl alcohol resin>In the PVA film of the present invention, all or part of the PVA (A) is preferably a polyvinyl alcohol resin (Ab), in which all or part of the carbon constituting the PVA (A) is derived from bio-based ethylene (Bb). Therefore, in the PVA film of the present invention, the PVA (A) may be only PVA (Ab), or may be a mixture of PVA (Ab) and PVA (Ap) obtained solely from raw materials produced from fossil fuels.

[0031] The method for producing PVA (Ab) is not particularly limited, and for example, (1) a method in which only a polyvinyl ester (Db1) obtained by polymerizing only a biovinyl ether monomer (Cb1) is saponified to obtain PVA (Ab1), (2) a method of saponifying a polyvinyl ester (Db2) obtained by polymerizing a biovinyl ether monomer (Cb2) using a mixture of bioethylene (Bb) and fossil fuel-derived ethylene (Bp) as a raw material to obtain PVA (Ab2), (3) a method of saponifying a polyvinyl ester (Db2) obtained by copolymerizing a biovinyl ether monomer (Cb1) and a vinyl ester monomer (Cp) using fossil fuel-derived ethylene (Bp) as a raw material to obtain PVA can be used (Ab3),(4) a method in which a mixture of a polyvinyl ether (Db1) and a polyvinyl ether (Dp),obtained by polymerization of only fossil fuel derived vinyl ester monomer (Cp), is saponified to produce PVA (Ab4), and (5) a process that combines processes (2) to (4).,

[0032] 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 them, vinyl acetate is preferred.

[0033] The method for producing 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 carboxyl group R-COOH. Vinyl acetate can be synthesized as follows. Generally, vinyl acetate can be obtained by the gas-phase reaction of ethylene, acetic acid, and oxygen in the presence of a catalyst. In this case, when using ethylene containing a predetermined amount 14C, or acetic acid containing a predetermined amount 14 C, as a compound having a carboxyl group, vinyl acetate is obtained containing a predetermined amount 14 C. Examples of ethylene containing a predetermined amount 14 C, include bioethylene.

[0034] When producing vinyl ester monomer, it is preferable to use bio-based raw materials other than ethylene, such as carboxylic acid, as raw materials. However, the carboxylic acid group is removed from the polyvinyl ester polymer backbone during saponification and is usually recovered and reused. Therefore, even when using fossil fuel-derived raw materials, the carbon dioxide content of the environment does not increase and does not cause global warming.

[0035] The polyvinyl ester is preferably produced using one, two, or more kinds of vinyl ester monomers, and more preferably using only one kind of vinyl ester monomer. In addition, the polyvinyl ester may be a copolymer of one, two, or more kinds of vinyl ester monomers and other monomers capable of copolymerization with it.

[0036] Other monomers capable of copolymerizing with the vinyl ester monomer are preferably ethylene. Therefore, the PVA contained in the PVA film of the present invention preferably contains an ethylene block. In addition, the content of the ethylene block is preferably 1 mol% or more, and more preferably 1.5 mol% or more, based on the number of moles of all structural blocks constituting the vinyl ester polymer. In addition, the content of the ethylene block is preferably less than 15 mol%, and more preferably less than 10 mol%, based on the number of moles of all structural blocks constituting the vinyl ester polymer. When the content of the ethylene block is in the above-mentioned range, water resistance and the like can be improved without significantly deteriorating the optical characteristics of the PVA film when the PVA film of the present invention is used as a raw material fabric film for producing an optical film.The reason for this is unclear, but it is suggested that although the hydrophilicity is weakened by the introduction of the ethylene block into the polymer backbone, the volume occupied by the ethylene block in the crystal is not very different from that of the vinyl alcohol block, so that the crystalline structure of PVA is not greatly disturbed.

[0037] Examples of other monomers copolymerizable with the vinyl ester monomer, in addition to ethylene, include olefins having 3 to 30 carbon atoms such as propylene, 1-butene, and isobutene; acrylic acid or a salt thereof; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid or a salt thereof; methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate and octadecyl methacrylate; acrylamide derivatives such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, propanesulfonic acid acrylamide or a salt thereof, propyldimethylamine acrylamide or a salt thereof, and N-methylolacrylamide or a derivative thereof;methacrylamide derivatives such as methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamidopropanesulfonic acid or its salt, methacrylamidopropyl dimethylamine or its salt, and N-methylol methacrylamide or its derivative; 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, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-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 its salt, ester or anhydride; itaconic acid or its salt, ester or anhydride; a vinylsilyl compound such as vinyltrimethoxysilane;and isopropenyl acetate. The vinyl ester polymer may have a structural unit derived from one, two, or more of these other monomers.

[0038] The proportion of the structural block derived from another monomer in the polyvinyl ester is preferably 15 mol% or less, and more preferably 5 mol% or less based on the number of moles of all the structural blocks constituting the polyvinyl ester, from the viewpoint of the strength of the resulting PVA film and the optical characteristics in the case of using the PVA film as a raw material fabric film for producing an optical film.

[0039] As another monomer copolymerizable with the vinyl ester monomer, a monomer derived from fossil fuel can be used, or a plant-derived monomer can be used.

[0040] In the PVA film of the present invention, the polymerization degree of PVA (A) is preferably 200 or more. The polymerization degree of PVA (A) is preferably less than 8000. From the viewpoint of the strength of the PVA film, the polymerization degree of PVA (A) is more preferably 300 or more, and even more preferably 500 or more. On the other hand, from the viewpoint of the performance of PVA (A) or the PVA film, the polymerization degree of PVA (A) is more preferably less than 5000, and even more preferably less than 3000. Here, the polymerization degree of PVA (A) means the average polymerization degree Po measured in accordance with the description of JIS K6726-1994, and is defined by the limiting viscosity [ƞ] (unit: deciliter / g) measured in water at 30°C after re-saponification and purification of PVA, according to the following formula.

[0041] Po=([ƞ] × 10 4 / 8.29) (1 / 0,62)

[0042] In the PVA film of the present invention, the saponification degree of PVA (A) is preferably 80 mol% or more. When the saponification degree is less than 80 mol%, water solubility is easily deteriorated when the PVA film is used as a drug packaging film, and optical performance is easily deteriorated when the PVA film is used as a raw material fabric film for producing an optical film. The saponification degree is more preferably 84 mol% or more, and even more preferably 88 mol% or more. On the other hand, the saponification degree is preferably less than 100 mol%, more preferably less than 99.999 mol%, and even more preferably less than 99.995 mol%. Here, the saponification degree of PVA refers to the ratio (mol%) is the ratio of the number of moles of vinyl alcohol block to the total number of moles of the structural block (usually a vinyl ester monomer block) that can be converted into a vinyl alcohol block by saponification and into a vinyl alcohol block in PVA. The saponification degree of PVA can be measured according to the description in JIS K6726-1994.

[0043] In the PVA film of the present invention, the content of 1,2-glycol bond in PVA (A) is preferably 0.2 mol% or more. The content of 1,2-glycol bond in PVA (A) is preferably less than 2.0 mol%. When the content of 1,2-glycol bond is less than 2.0 mol%, good optical performance and mechanical strength are easily achieved when using the PVA film as a raw material film for producing an optical film. On the other hand, when the content of 1,2-glycol bond is 0.2 mol% or more, it is possible to improve the productivity of PVA (A) production and reduce the production cost. The content of 1,2-glycol bond in PVA (A) is more preferably 0.4 mol% or more, and even more preferably 0.6 mol% or more. The content of 1,2-glycol bond in PVA (A) is more preferably less than 1.9 mol% and even more preferably less than 1.8 mol%.

[0044] In the PVA film of the present invention, it is preferable that the PVA (A) has an alkoxy group at the end of the polymer, and the content of the alkoxy group relative to the total amount of monomer units (hereinafter, may be referred to as the content of the terminal alkoxy group) is 0.0005 mol% or more. The content of the terminal alkoxy group is preferably less than 1 mol%. The method for introducing the alkoxy group to the end of the polymer is not particularly limited, and examples thereof include a method in which a vinyl ester is polymerized using a polymerization initiator containing an alkoxy group.

[0045] When the PVA film of the present invention is used as a raw material film for producing an optical film, for example, when a polarizing film is produced using the PVA film as a raw material film, if PVA (A) is eluted into a processing liquid during the production process and the concentration of PVA (A) in the processing liquid increases, fine particles of PVA (A) precipitate in the processing liquid due to the crosslinking with boric acid and adhere to the PVA film, and foreign substances derived from the fine particles of PVA remain on the surface of the resulting polarizing film, which may cause problems. In the PVA film of the present invention, since PVA (A) has an alkoxy group at the end of the polymer and its content relative to the total amount of monomer units is 0.0005 mol% or more and less than 1 mol%, the occurrence of this problem can be suppressed. When the content of the terminal alkoxy group is less than 0.0005 mol.% foreign impurity defects on the surface of the polarizing film obtained from the PVA fine particles (A) cannot be reduced sufficiently. When the content of the terminal alkoxy group is more than 1 mol%, the polarizing characteristics of the obtained polarizing film may be insufficient when the PVA film of the present invention is used as a raw material fabric film for producing an optical film. The content of the terminal alkoxy group relative to the total amount of monomer units is more preferably 0.001 mol% or more, and even more preferably 0.005 mol% or more. The content of the terminal alkoxy group relative to the total amount of monomer units is more preferably less than 0.1 mol%, and even more preferably less than 0.05 mol%.

[0046] In the PVA film of the present invention, the PVA (A) may be a single type of PVA, or a mixture of two or more types of PVA having different degrees of polymerization, saponification, and modification may be used. When two or more types of PVA are mixed and used, PVA (A) and PVA derived from biomass, such as bioethylene, other than PVA (A), PVA (A) and PVA derived from petroleum or fossil fuels may be mixed, or both may be combined.

[0047] In the present invention, the content of PVA (A) in the PVA film is not particularly limited, but is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more. In addition, its content may be 100% by mass, but preferably 99% by mass or less, and may be 95% by mass or less and 90% by mass or less in consideration of the compatibility between the availability of biomass and the performance as a polarizing film.

[0048] <Plasticizer>The PVA film of the present invention is more rigid than other plastic films in a state without a plasticizer, and mechanical and physical properties such as impact strength and processability during secondary processing may be problematic. To prevent these problems, the PVA film of the present invention preferably contains a plasticizer. Preferred examples of the plasticizer include a polyhydric alcohol, and specific examples include polyhydric alcohols such as ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, and sorbitol. These plasticizers can be used alone or in combination of two or more kinds. Among these plasticizers, ethylene glycol or glycerin are preferable, and glycerin is more preferable from the viewpoint of sweating on the film surface.In addition, it is preferable to use a plasticizer obtained from raw materials of biological origin.

[0049] The content of the plasticizer in the PVA film of the present invention is preferably 1 phr or more, more preferably 3 phr or more, and even more preferably 5 phr or more per 100 phr of PVA contained in the PVA film. In addition, the content of the plasticizer is preferably 70 phr or less, more preferably 50 phr or less, and even more preferably 40 phr or less. When the content of the plasticizer is less than 1 phr, the effect of improving the mechanical physical properties such as the impact strength of the PVA film may be insufficient. On the other hand, when the content of the plasticizer is more than 70 phr, the PVA film becomes too soft, so that the processability may deteriorate or bleeding on the film surface may occur.

[0050] <Starch / Water-Soluble Polymer>The PVA film of the present invention may contain starch and / or a water-soluble polymer other than PVA (A). The presence of such a water-soluble polymer makes it possible to impart mechanical strength to the PVA film, maintain moisture resistance during handling of the PVA film, or adjust the softening rate by absorbing water during dissolution of the PVA film.

[0051] Examples of starch include natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch and sago starch; and processed starches subjected to esterification, esterification and oxidation, and in particular, processed starches are preferable.

[0052] The starch content of the PVA film is preferably 15 phr or less, and more preferably 10 phr or less per 100 phr of PVA (A). When the starch amount is more than 15 phr, the processability of the PVA film may deteriorate.

[0053] 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, methyl vinyl ether-maleic anhydride copolymer, vinyl acetate-itaconic acid copolymer, polyvinylpyrrolidone, cellulose, cellulose acetate, acetyl butyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose and sodium alginate.

[0054] The content of the water-soluble polymer other than PVA (A) in the PVA film is preferably 15 phr or less, and more preferably 10 phr or less per 100 phr of PVA (A). When the content of the water-soluble polymer other than PVA (A) is more than 15 phr, the physical properties of the PVA film may deteriorate.

[0055] <Surfactant>When forming a PVA film, it is preferable to add a surfactant to the PVA film for its ease of processing and to improve the ability to separate from the film-forming device during PVA film production. Examples of surfactants include anionic surfactants and nonionic surfactants.

[0056] Examples of the anionic surfactant include carboxylic acid type surfactants such as potassium laurate; sulfuric acid ester type surfactants such as octyl sulfate; and sulfonic acid type surfactants such as dodecylbenzenesulfonate.

[0057] Examples of the nonionic surfactant include alkyl ether type surfactants such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether; alkyl phenyl ether type surfactants such as polyoxyethylene octyl phenyl ether; alkyl ester type surfactants such as polyoxyethylene laurate; alkyl amine type surfactants such as polyoxyethylene lauryl amine ether; alkyl amide 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 can be used alone or in combination of two or more of its types.

[0058] <Other Components>The PVA film of the present invention 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 PVA (A), and a surfactant, as long as this does not interfere with the effect of the present invention. The ratio of the total weight of PVA, plasticizer, starch, a water-soluble polymer other than PVA (A), and a surfactant to the total weight of the PVA film of the present invention is preferably in the range of 60-100% by weight, more preferably 80-100% by weight, and even more preferably 90-100% by weight.

[0059] <Shape>The thickness of the PVA film of the present invention is not particularly limited, but is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and even more preferably 50 μm or less, because if the thickness is too large, the secondary workability tends to deteriorate. When the thickness is too small, there is a possibility that problems with the mechanical strength of the PVA film will occur. Therefore, the thickness of the PVA film is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and particularly preferably 20 μm or more. The thickness of the PVA film can be obtained as the average value of the thicknesses measured at 10 arbitrary positions (for example, at 10 arbitrary points on a straight line drawn in the length direction of the PVA film).

[0060] (Application) The PVA film of the present invention is used as a raw material 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 retention film, and a brightness improving film, and the polarizing film is preferred. Examples of the water-soluble film include a drug packaging film, a hydraulic transfer base film, an embroidery base film, an anti-adhesive film for molding artificial marble, a seed packaging film, and a film for waste storage bags, and the drug packaging film is preferred. Examples of drugs include detergents, agricultural chemicals, and disinfectants. The drug form can be any of powder form, lump form, gel form, and liquid form.The packaging can be produced by packaging a medicinal product using the PVA film of the present invention as the medicinal product packaging film. This packaging allows for easy and safe use of a certain amount of the drug when washing laundry with detergent under normal household conditions or when spraying pesticides on fields during agricultural work.

[0061] <Method for producing a PVA film>In the present invention, the PVA film can be produced by any method such as a flow-cast film forming method, a wet film forming method (ejecting into a weak solvent), a dry wet film forming method, a gel film forming method (a method in which a film-forming stock solution is cooled and turned into a gel, 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-mentioned film-forming stock solution and the film is extruded from a T-die, or a blow molding method using a film-forming stock solution homogenized by adding a solvent and additives to PVA (A).Among these, the in-line casting method and the melt extrusion method are preferred because uniform films can be produced with high productivity. The in-line casting method and the melt extrusion method for PVA film are described below.

[0062] When PVA film is formed by the flow-casting or melt extrusion method, the above-mentioned film-forming precursor is cast onto a substrate, such as a metal roller or metal strip, and heated to remove the solvent, thereby curing and forming the film. The cured film is separated from the substrate, dried on a drying roller, in a drying oven, etc. as needed, further heat-treated as needed, and then wound up, resulting in a long PVA film in roll form.

[0063] The concentration of volatile components (such as the solvent removed by volatilization or evaporation during film formation, etc.) in the film-forming solution is preferably 50% by mass or more, and more preferably 55% by mass or more. The concentration of volatile components in the film-forming solution is preferably 90% by mass or less, and more preferably 80% by mass or less. When the concentration of volatile components is less than 50% by mass, the viscosity of the film-forming solution increases, and film formation may be difficult. On the other hand, when the concentration of volatile components exceeds 90% by mass, the viscosity becomes low, and the uniformity of the thickness of the resulting film is easily disrupted.

[0064] The term "volatile fraction of a film-forming solution" in the present description refers to a volatile fraction defined by the following formula.

[0065] Volatile fraction (wt%) of film-forming solution={(Wa - Wb) / Wa} × 100where Wa represents the mass (g) of the film-forming solution, and Wb represents the mass (g) of the film after drying Wa (g) of the film-forming solution in an electrothermal dryer at 105°C for 16 hours.

[0066] The method for controlling the solution for forming a film 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 dissolving tank, and a method in which PVA in a water-containing state is melt-kneaded together with a plasticizer, a surfactant, etc. when PVA is produced using a single-screw extruder or a twin-screw extruder.

[0067] When PVA film is formed by the flow casting method or melt extrusion method, the film forming raw material is poured from a film-shaped discharge device onto a substrate such as a metal roller or metal belt and heated to remove the solvent, thereby curing and forming the film.

[0068] The surface temperature of the substrate onto which the film-forming solution is poured is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 65°C or higher. The surface temperature of the substrate onto which the film-forming solution is poured is preferably 110°C or lower, more preferably 100°C or lower, and even more preferably 95°C or lower. When the surface temperature is less than 50°C, the time required for drying increases and the productivity tends to decrease. When the surface temperature exceeds 110°C, film surface abnormalities such as foaming tend to occur, and the film becomes excessively hard.

[0069] While the PVA film is heated on the substrate, hot air at a speed of 1-10 m / s can be uniformly blown over the entire free surface area of ​​the PVA film to regulate the drying speed. The temperature of the hot air blowing over the free surface of the film is preferably 50°C or higher, and more preferably 70°C or higher, in terms of drying efficiency and drying uniformity. The temperature of the hot air blowing over the free surface of the film is preferably 150°C or lower, and more preferably 120°C or lower, in terms of drying efficiency and drying uniformity.

[0070] The PVA film separated from the substrate is dried on the substrate preferably to a volatile content of 5-50% by weight, and then removed and further dried if necessary. The drying method is not particularly limited, and examples thereof include a method of contacting with a drying oven or a drying roller. In the case of drying using multiple drying rollers, it is preferable to alternately contact one and the other surface of the film with the drying rollers so that both surfaces are uniform. The number of drying rollers is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. The number of drying rollers is preferably 30 or less. The upper limit of the temperature of the drying oven and the drying roller is preferably 110°C or lower, more preferably 100°C or lower, even more preferably 90°C or lower, and even more preferably 85°C or lower.If the oven and drying roller temperatures are too high, the film may become too hard. On the other hand, the lower limit of oven and drying roller temperatures is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher. If the oven and drying roller temperatures are too low, productivity may decrease.

[0071] The dried PVA film can be further heat-treated as needed. Heat-treating can adjust the physical properties of the PVA film, such as strength, water solubility, and birefringence. The lower limit of the heat-treating temperature is preferably 60°C or higher. The upper limit of the heat-treating temperature is preferably 135°C or lower, and more preferably 130°C or lower. If the heat-treating temperature is too high, the film may become too hard.

[0072] If necessary, the PVA film produced in this way is further subjected to moisture control treatment, cut at both ends of the film and wound into a roll on a cylindrical core, and then packed in moisture-proof packaging to obtain the product.

[0073] The volatile fraction of the final PVA film is not necessarily limited to the series of treatments described above. The volatile fraction of the PVA film is preferably 1% by mass or more, and more preferably 2% by mass or more. The volatile fraction of the PVA film is preferably 5% by mass or less, and more preferably 4% by mass or less.

[0074] <Distinction Method>The PVA film obtained by the above method can be distinguished between a PVA film containing PVA (Ab) in which all or part of the carbon is derived from bio-derived ethylene (Bb) and a PVA film containing only PVA (Ap) derived only from fossil fuel-derived ethylene (Bp) by measuring the ratio of the amount of carbon 14 ( 14 C) to the total amount of carbon, that is 14 C / C.

[0075] In the present invention, the PVA (Ap) obtained only from ethylene derived from fossil fuels (Bp) means that it does not contain PVA (Ab) in which all or part of the carbon is obtained from ethylene of biological origin (Bb), and is not a concept of excluding PVA (Ap) containing monomer units other than ethylene derived from fossil fuels (Bp). In the present invention, a PVA film containing only PVA (Ap) means that it does not contain PVA (Ab) obtained from ethylene of biological origin (Bb), and is not a concept of excluding a PVA film containing components other than PVA (Ap).

[0076] In addition, by measuring the ratio of the amount of carbon 14 ( 14 C) to the total amount of carbon, that is 14C / C, it is possible to distinguish a PVA film containing PVA (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb) from a PVA film other than a PVA film containing PVA (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb). For example, even in a PVA film partially containing PVA (Ab) derived from the same plant-based ethylene (Bb), if the ratio of PVA (Ab) derived from bio-based ethylene (Bb) and PVA (Ap) derived only from fossil fuel-derived feedstock is different, the ratio 14 C / C varies. For example, when a PVA film produced by a company is produced so that the carbon content is 14 ( 14 C) in the total amount of carbon, that is 14C / C, was constant, it is possible to determine whether a PVA film is a PVA film produced by one's own company or a PVA film produced by another company. In addition, even in the same company, production is carried out in such a way that the carbon fraction 14 ( 14 C) in the total amount of carbon, that is 14 C / C varied depending on the production location, manufacturing date and production lot, as a result the production location, manufacturing date and production lot of PVA film can be determined by measuring the carbon fraction 14 ( 14 C), that is 14 C / C.

[0077] In order to distinguish the PVA film, the PVA film is preferably produced so that the proportion of carbon 14 ( 14 C) in the total amount of carbon, that is 14 C / C was 1.0 × 10 -14 or more, more preferably 5.0 × 10 -14 or more, and even more preferably 2.0 × 10 -14or more. In addition, since biologically derived raw materials are generally more expensive than fossil fuel-derived raw materials, in order to distinguish PVA film, it is preferable to produce PVA film so that the carbon fraction is 14 ( 14 C) in the total amount of carbon, that is 14 C / C was 1.0 × 10 -11 or less, more preferably 5.0 × 10 -12 or less, and even more preferably 0.1 × 10 -14 or less.

[0078] In addition, by measuring the proportion of carbon 14 ( 14 C) in the total amount of carbon, that is 14 C / C, it is possible to distinguish whether ethylene of biological origin (Bb) is C3 ethylene of plant origin (Bb) or C4 ethylene of plant origin (Bb) by measuring the δ fraction 13 C stable isotope of carbon 13 ( 13C) for PVA film that has been identified as containing PVA (Ab) derived from bio-based ethylene (Bb). More specifically, bio-based ethylene (Bb) is classified as C4 plant-derived ethylene (Bb) when the fraction δ 13 C stable isotope of carbon 13 ( 13 C) is -20‰ or more, or as plant-derived C3 ethylene (Bb), when the fraction δ 13 C stable isotope of carbon 13 ( 13 C) is less than -20‰. Measuring the proportion of carbon 14 ( 14 C) in the total amount of carbon, that is 14 C / C, and the proportion of the stable isotope carbon 13 ( 13 C), that is, δ 13 C, PVA films can be distinguished with higher accuracy.

[0079] The above description measures the proportion of carbon 14 ( 14 C) in the total amount of carbon, that is 14 C / C, and then the fraction δ 13 C stable isotope of carbon 13 ( 13C) is measured for the film identified as a PVA film containing PVA (Ab) derived from bio-based ethylene (Bb). However, the proportion of carbon 14 ( 14 C) in the total amount of carbon, that is 14 C / C, not measured, fraction δ 13 C stable isotope of carbon 13 ( 13 C) is measured, and as a result, a PVA film containing PVA (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb) can be distinguished from other PVA films that are different from it. For example, it is possible to distinguish a PVA film containing PVA (Ab) derived from bio-based ethylene (Bb) from a PVA film containing only PVA (Ap) derived only from fossil fuel-derived feedstock. However, since the fraction δ 13Since the stable carbon isotope C of PVA (Ap) produced only from fossil fuel-derived raw materials is generally less than -20‰, it may be difficult to distinguish a PVA film containing PVA (Ab) produced from plant-derived C3 ethylene (Bb) as raw materials from a PVA film containing only PVA (Ap) produced only from fossil fuel-derived raw materials.

[0080] In addition, it is also possible to distinguish a PVA film containing PVA (Ab) derived from bio-derived ethylene (Bb) from a PVA film containing another PVA (Ab) derived from bio-derived ethylene (Bb).

[0081] As described above, when the mixing ratio of bio-PVA and fossil fuel PVA in the PVA used is changed for each PVA film production line, it can be determined which PVA film production line was used as the raw material for the polarizing film used in the analysis of the polarizing plate of the liquid crystal product available in the consumer market.

[0082] <Application>As described above, the PVA film of the present invention can be suitably used for optical applications, such as a raw material for polarizing film. It can also be suitably used for water-soluble films, such as drug packaging and seed tape. Examples

[0083] Next, the present invention is specifically described with reference to Examples and the like, but the present invention is in no way limited to the following Examples.

[0084] [Purification of PVA Film]The PVA film roll obtained in the following Examples or Comparative Examples was unwound to collect approximately 5 g of film and cut into small pieces. The cut PVA film was then extracted with a Soxhlet extractor using chloroform. By sufficiently removing non-PVA components from the PVA film, the PVA film was purified to obtain PVA within the PVA film.

[0085] [Measurement of the proportion of carbon 14 ( 14 C) in the total amount of PVA carbon in the PVA film, that is 14The C / C]PVA obtained in the [PVA Film Cleaning] section above was converted to CO2 by the pretreatment method (ASTM D6866 / Method B) specified by the American Society for Testing and Materials, and then converted to C (graphite) by complete reduction using an iron catalyst. The carbon isotope ratio (C isotope ratio) was then measured by accelerator mass spectrometry. 14 WITH / 12 C, ratio 13 WITH / 12 C) purified PVA film and standard substance, and the concentration was determined from the measurement results 12 C, concentration 13 C and concentration 14 C. Then the obtained concentration 14 C was divided by the total carbon concentration (the sum of the concentrations 12 WITH, 13 With and 14 C) to calculate the value 14C / C PVA in PVA film. Here, graphite synthesized from the standard substance oxalic acid (HOxII) provided by the National Institute of Standards and Technology was used as the standard substance. The measurement limit 14 The C / C ratio in this measurement was less than 1.0 × 10 -14 .

[0086] [Measurement of the δ fraction 13 [C stable carbon isotope of PVA in PVA film]The PVA obtained in the above section [PVA film cleaning] was converted to CO2 by the pretreatment method (ASTM D6866 / Method B) specified by the American Society for Testing and Materials, and then converted to C (graphite) by complete reduction using an iron catalyst. Then, the carbon isotope ratio (C isotope ratio) was measured by accelerator mass spectrometry. 13 WITH / 12 C) purified PVA film and standard substance. Then the fraction δ 13The stable carbon isotope concentration was calculated using the following formula. Here, PDB ("Pee Dee Belemnite") was used as the standard substance.

[0087] δ 13 C[‰]={( 13 C / 12 C) sample / ( 13 C / 12 C) PDB - 1.0} × 1.000

[0088] In the above formula [( 13 C / 12 C) sample ] represents the carbon isotope ratio (ratio 13 WITH / 12 C) the measured purified PVA film, and [( 13 C / 12 C) PDB ] represents the carbon isotope ratio (ratio 13 WITH / 12 C) PDB as a standard substance.

[0089] [Measurement of Ethylene Block Content, Alkoxy Group Content, 1,2-Glycol Linkage Content, and Saponification Degree of PVA in PVA Film]The PVA obtained in the [PVA Film Cleaning] section above was dissolved in dimethyl sulfoxide (DMSO-d6), and then the solution was added to acetone to precipitate PVA, thereby further purifying PVA. One or two drops of trifluoroacetic acid (TFA) were added dropwise to the PVA solution in DMSO-d6, and the resulting sample was immediately subjected to NMR measurement under the following conditions. From the obtained NMR spectrum, the ethylene block content, alkoxy group content, 1,2-glycol linkage content, and saponification degree of PVA in the PVA film were determined.

[0090] (NMR measurement conditions)Used device: Superconducting nuclear magnetic resonance device "Lambda 500" manufactured by JEOL Ltd.Solvent: DMSO-d6 (with TFA dropwise addition)Concentration: 5 wt%.Temperature: 80°CResonance frequency: 1H 500 MHzFlip angle: 45°Pulse delay time: 4.0 sNumber of integrations: 6000

[0091] [Measurement of the Tensile Breaking Temperature of PVA Film]A rectangular test specimen with a width of 30 mm and a length of 60 mm was taken from the center of the PVA film roll obtained in the following examples or comparative examples in the width direction. This test specimen was placed in a tensile testing apparatus with a clamp interval of 15 mm and then stretched in a water bath with a constant set temperature to measure the percentage of elongation at break. This procedure was repeated three times, and the average percentage of elongation at break was determined.When the average value was 6.5 times or more, the constant temperature of the water bath was decreased by 1°C, and when the average value was less than 6.5, the constant temperature of the water bath was increased by 1°C, and the limit temperature at which the average value of the percentage of elongation at the time of rupture was 6.5 times or more (the minimum temperature at which the average value was 6.5 times or more) was determined.

[0092] [Evaluation of the amount of foreign matter in the polarizing film]The roll of polarizing film obtained in the following Examples or Comparative Examples was unwound and cut into pieces measuring 30 cm in the length direction (in the stretching direction) and 20 cm in the width direction. Blue foreign matter existing on the surface of the cut polarizing film was visually observed, and the number of foreign matter having the longest diameter of 5-500 μm (pcs / 600 cm) was determined. 2). This procedure was repeated 3 times to obtain the average value (pcs. / 600 cm 2 ) the amount of foreign inclusions. The longest diameter of foreign inclusions was measured using a differential interference microscope (magnification: 200x). In the following examples or comparative examples, since the polarizing film is continuously wound for 6 hours after drying treatment, the cut polarizing film is a sample approximately 6 hours after the start of polarizing film production.

[0093] [Measurement of the polarization degree of polarizing film]The roll of polarizing film obtained in the following Examples or Comparative Examples was unwound and cut into pieces measuring 30 cm in the length direction (stretching direction) and 20 cm in the width direction. Two square samples measuring 1.5 cm in the length direction (stretching direction) and 1.5 cm in the width direction of the cut polarizing film were taken from the central portion in the width direction of the polarizing film, and the luminous transmittance ( ) in the case of superposition of samples in such a way that their length directions (directions of extension) are parallel, and the light transmittance (Y ┴ ) in the case of superimposing the samples so that their length directions (stretching directions) were orthogonal, were measured in the same manner as the above-mentioned method for measuring transparency, and the degree of polarization (V) (%) was determined by the following formula.

[0094] Degree of polarization (V) (%)={( - Y ┴ ) / ( + Y ┴ )}1 / 2 × 100

[0095] <Example 1>(1) Synthesis of vinyl acetate After impregnation of 23g (water absorption 19.7g) of silica spherical carrier “HSV-I” (manufactured by Shanghai Haiyuan Chemical Industry Technology Co., Ltd.) (sphere diameter: 5mm, specific surface area: 160m 2 / g, water absorption: 0.75 g / g) with an aqueous solution equivalent to the amount of water absorbed by the carrier, which contains 1.5 g of a 56 wt.% aqueous solution of sodium tetrachloropallastate and 1.5 g of a 17 wt.% aqueous solution of hydrogen tetrachloroaurate tetrahydrate, the silica sphere carrier was immersed in 40 ml of an aqueous solution containing 2.5 g of sodium metasilicate nonahydrate and left for 20 hours. Then, 3.3 ml of an aqueous solution of hydrazine hydrate with a concentration of 52 wt.% were added, the resulting mixture was kept at room temperature for 4 hours, then washed with water until the chloride ions disappeared from the water and dried at 110 °C for 4 hours. The resulting palladium / gold / carrier composition was immersed in 60 ml of a 1.7 wt% aqueous acetic acid solution and left for 16 hours. The composition was then washed with water for 16 hours and dried at 110°C for 4 hours.After this, impregnation with 2 g of an aqueous solution equivalent to the amount of water absorbed by the potassium acetate carrier was performed and drying at 110°C for 4 hours to obtain a catalyst for the synthesis of vinyl acetate.

[0096] The obtained catalyst (3 ml) was diluted with 75 ml of glass beads and placed in a SUS316L reaction tube (inner diameter 22 mm, length 480 mm), after which the reaction was carried out by circulating the gas mixture at a reaction temperature of 150 °C and a pressure of 0.6 MPa g at an ethylene / oxygen / water / acetic acid / nitrogen ratio of 47.3 / 6.1 / 5.6 / 26.3 / 14.7 (mol%) and a flow rate of 20 L / h. Here, bioethylene obtained from sugarcane (manufactured by Braskem SA) was used as ethylene. The resulting reaction gas containing vinyl acetate was purified to obtain vinyl acetate.

[0097] (2) Synthesis of PVA Using the obtained vinyl acetate as a monomer, 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile) as a polymerization initiator, and methanol as a solvent, polymerization was carried out at a polymerization temperature of 60°C according to a known method. Then, 2,4-diphenyl-4-methyl-1-pentene (DPMP), a compound having a conjugated double bond and a molecular weight of 1000 or less, was added in an amount of 2 mol per 1 mol of the polymerization initiator used. The polymerization time was adjusted according to the target degree of polymerization. A 6 wt.% methanol solution of sodium hydroxide was added to the resulting methanol solution of polyvinyl acetate with stirring so that the molar ratio of sodium hydroxide to vinyl acetate units of polyvinyl acetate was 0.023, and the saponification reaction began at 30°C. As the saponification reaction progressed, a gelled product was obtained.After 50 minutes of saponification, the gelled product was ground to yield methanol-swollen PVA (PVA-1). This PVA-1 was washed with 5 times its mass of methanol and then dried in hot air at 55°C for 1 hour and at 100°C for 2 hours.

[0098] (3) Production of PVA Film and PVA Film RollAn aqueous solution (PVA concentration: 15 wt%) containing 100 phr of the obtained PVA-1, 12 phr of glycerin, and 0.1 phr of lauric acid diethanolamide was prepared as a PVA film stock solution. The film stock solution was discharged from a slit die onto a first metal roller with a diameter of 2 m and a surface temperature of 90°C and dried to separate the film with a moisture content of 12 wt% from the metal roller. Then, the surface of the film not in contact with the first metal roller was brought into contact with a second metal roller with a surface temperature of 70°C and a diameter of 1 m, and the film was dried.Then, the film was sequentially brought into contact with the third to sixth metal rollers (surface temperature: 80-120°C, diameter: 1 m) so that one surface and the other surface of the film were alternately brought into contact with the metal rollers, dried, and wound up to obtain a product in the form of a PVA film roll (PVA film roll) of 0.6 m in width, 1000 m in length, and 30 μm in thickness.

[0099] (4) Production of Polarizing FilmThe obtained PVA film roll was unwound and subjected to swelling, dyeing, crosslinking, stretching, washing, and drying in this order to continuously obtain a polarizing film. The swelling treatment was performed by immersing the PVA film in a swelling treatment tank with a processing liquid (pure water) at 30°C and uniaxially stretching the film by 1.72 times in the length direction during immersion. The dyeing was performed by immersing the PVA film in a swelling treatment tank with a processing liquid (an aqueous solution of 2.8 wt% boric acid and 5 wt% potassium iodide) at 32°C and uniaxially stretching the film by 1.37 times in the length direction during immersion. Crosslinking was performed by immersing the PVA film in a swelling treatment tank with a crosslinking treatment liquid (aqueous solution of boric acid with a concentration of 2.6 wt.%) at 32°C and uniaxially stretching the film by 1.12 times in the length direction during immersion. Stretching treatment was performed by uniaxially stretching the PVA film by 2.31 times in the length direction in a swelling treatment tank with a stretching treatment liquid (aqueous solution of 2.8 wt% boric acid and 5 wt% potassium iodide) at 55°C. Washing was performed by immersing the PVA film in a washing tank with a washing liquid (aqueous solution of 1.5 wt% boric acid and 5 wt% potassium iodide) at 22°C for 12 s. Drying was performed by drying the PVA film at 60°C for 1.5 min. Here, the PVA film was not stretched between washing and drying. The thus obtained PVA film roll was unwound to continuously produce the polarizing film.

[0100] (5) Production of Polarizing Film RollTwo square specimens measuring 1.5cm in the length direction (in the stretching direction) and 1.5cm in the width direction of the obtained polarizing film were taken from the center portion in the width direction of the polarizing film, and for each specimen, the visibility correction of the visible light region of illuminant C and the visual field of 2 degrees was performed in accordance with the JIS Z8722 (Method for Measuring the Color of an Object) standard using a V-7100 spectrophotometer (with integrating sphere) manufactured by Hitachi Co., Ltd., and for one specimen of the polarizing film, the luminous transmittance when the specimen was tilted at 45 degrees with respect to the stretching axis direction and the luminous transmittance when the specimen was tilted at -45 degrees were measured, and their average value (Y1) was obtained.

[0101] For another polarizing film sample, the luminous transmittance when the sample is tilted at 45 degrees and the luminous transmittance when the sample is tilted at -45 degrees were measured in the same manner as described above, and their average value (Y2) was obtained. The above Y1 and Y2 values ​​were averaged to obtain the transmittance (Y) (%) of the polarizing film.

[0102] The concentrations of iodine and potassium iodide in the swelling treatment tank were adjusted so that the transmittance was 43.5%, and then the polarizing film after drying treatment was continuously wound for 6 hours to obtain a polarizing film roll product (polarizing film roll).

[0103] The resulting PVA film roll and polarizing film roll were measured and evaluated in the manner described above. The measurement and evaluation results are presented in Table 2. The raw materials and PVA polymerization conditions are shown in Table 1.

[0104] <Example 2>The same procedure as in Example 1 was carried out to obtain PVA (PVA-2), except that the polymerization initiator used in Section “(2) Synthesis of PVA” was replaced with azobisisobutyronitrile. Then, a roll of PVA film and a roll of polarizing film were produced, measured, and evaluated in the same manner as in Example 1, except that PVA-2 was used. The measurement and evaluation results are presented in Table 2. The raw materials and polymerization conditions for PVA are shown in Table 1.

[0105] <Example 3>The same procedure as in Example 1 was carried out to obtain PVA (PVA-3), except that the polymerization temperature of PVA was changed to 90°C in Section “(2) Synthesis of PVA”. Then, a roll of PVA film and a roll of polarizing film were produced, measured, and evaluated in the same manner as in Example 1, except that PVA-3 was used. The measurement and evaluation results are presented in Table 2. The raw materials and polymerization conditions of PVA are shown in Table 1.

[0106] <Comparative Example 1>The same procedure as in Example 1 was carried out to obtain PVA (PVA-4), except that the ethylene used in the section “(1) Synthesis of vinyl acetate” was replaced with petroleum-derived ethylene (manufactured by AIR LIQUIDE Kogyo Gas Ltd.). Then, a roll of PVA film and a roll of polarizing film were produced, measured, and evaluated in the same manner as in Example 1, except that PVA-4 was used. The results of measurement and evaluation are shown in Table 2. The raw materials and polymerization conditions of PVA are shown in Table 1.

[0107] <Example 4>A PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as in Example 1, except that the PVA used in the above-mentioned section “(3) Production of PVA film and PVA film roll” was replaced with PVA obtained by mixing PVA-4 obtained in Comparative Example 1 and PVA-1 obtained in Example 1 at a mass ratio of 1:1. The results of measurement and evaluation are shown in Table 2. The raw materials and polymerization conditions of PVA are shown in Table 1.

[0108] <Example 5>PVA (PVA-5) was obtained in the same manner as Example 1, except that 5.7 phr of sugarcane-derived bioethylene (manufactured by Braskem S.A.) was added as the monomer used in the above-mentioned section “(2) Synthesis of PVA” per 100 phr of vinyl acetate, and the polymerization reaction was carried out at a reactor pressure of 0.03 MPaG. Then, a PVA film roll and a polarizing film roll were produced, measured, and evaluated in the same manner as Example 1, except that PVA-5 was used. The results of the measurement and evaluation are shown in Table 2. The raw materials and polymerization conditions of PVA are shown in Table 1.

[0109] <Example 6>Rice, a C3 plant, was subjected to an alkali treatment step, a saccharification treatment step, and an ethanolization step to produce rice-derived ethanol. This ethanol was then subjected to a dehydration reaction at 190°C using mordenite as a catalyst to produce rice-derived bioethylene.

[0110] Then, PVA (PVA-6) was obtained in the same manner as in Example 1, except that the ethylene used in Section “(1) Synthesis of Vinyl Acetate” was replaced with rice-derived bioethylene. Then, a roll of PVA film and a roll of polarizing film were produced, measured, and evaluated in the same manner as in Example 1, except that PVA-6 was used. The measurement and evaluation results are presented in Table 2. The raw materials and polymerization conditions for PVA are shown in Table 1.

[0111] [Table 1] Ethylene as a raw material for vinyl acetate PVA polymerization conditions Origin Plant Polymerization catalyst*1 Polymerization temperature Amount of ethylene for copolymerization*2 Units of measurement °C m.h. PVA-1 Bio Sugar cane AMV 60 - PVA-2 Bio Sugar cane AIBN 60 - PVA-3 Bio Sugar cane AMV 90 - PVA-4 Oil - AMV 60 - PVA-5 Bio Sugar cane AMV 60 5,7 PVA-6 Bio Rice AMV 60 - *1) AMV: 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile)AIBN: Azobisisobutyronitrile*2) Weight relative to 100 phr vinyl acetate

[0112] [Table 2] PVA film Polarizing film PVA Evaluation of PVA film Evaluation of polarizing film View Degree of polymerization Degree of saponification Ethylene block content Alkoxyl group content 1,2-glycol bond content 14C / C δ13C Ultimate tensile temperature Average value of the number of foreign inclusions Degree of polarization Units of measurement mol.% mol.% mol.% mol.% ‰ °C pcs. / 600 cm2 % Example 1 PVA-1 2430 99,9 0 0,01 1,4 9,5 × 10-13 -11 63 0 99,99 Example 2 PVA-2 2400 99,9 0 0 1,4 9,1 × 10-13 -13 63 2,6 99,99 Example 3 PVA-3 2420 99,9 0 0,01 1,6 9,4 × 10-13 -12 62 0,3 99,98 Example 4* PVA-1+PVA-4 2430 99,9 0 0,01 1,4 4,8 × 10-13 -18 63 0 99,99 Example 5 PVA-5 2400 99,9 3,8 0,01 1,3 9,6 × 10-13 -11 68 0,3 99,99 Example 6 PVA-6 2420 99,9 0 0,01 1,4 1,1 × 10-12 -36 63 0 99,99 Comparative example 1 PVA-4 2430 99,9 0 0,01 1,4 Below the measurement limit -26 63 0 99,99 *) Use of PVA obtained by mixing PVA-1 and PVA-4 in a weight ratio of 1:1

Claims

1. A method for distinguishing between a polyvinyl alcohol resin film comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb) and a polyvinyl alcohol resin film containing only a polyvinyl alcohol resin (Ap) derived only from fossil fuel-derived ethylene (Bp) by measuring the relative content 14 C / C carbon 14 ( 14 C) to the total amount of carbon.

2. A method for distinguishing between a polyvinyl alcohol resin film according to claim 1, further comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb) and a polyvinyl alcohol resin film different from the above-mentioned polyvinyl alcohol resin film and containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb), based on the measured relative content 14 C / C.

3. A method for distinguishing a polyvinyl alcohol resin film according to claim 1 or 2, wherein the discrimination of whether the ethylene of biological origin (Bb) is C3 ethylene of plant origin (Bb) or C4 ethylene of plant origin (Bb) is carried out by measuring the fraction δ 13 C stable isotope of carbon 13 ( 13C) for a polyvinyl alcohol resin film comprising a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb).

4. The method for distinguishing a film of polyvinyl alcohol resin according to claim 3, in which, when the proportion δ 13 C stable isotope of carbon 13 ( 13 C) is -20 or more, bio-based ethylene (Bb) is classified as plant-based ethylene C4 (Bb), and when the proportion δ 13 C stable isotope of carbon 13 ( 13 C) is less than -20 , bio-based ethylene (Bb) is classified as plant-based C3 ethylene (Bb).

5. A method for distinguishing between a polyvinyl alcohol resin film comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb) and a polyvinyl alcohol resin film containing only a polyvinyl alcohol resin (Ap) derived only from fossil fuel-based ethylene (Bp) by measuring a δ fraction 13 C stable isotope of carbon 13 ( 13 C).

6. A method for distinguishing a polyvinyl alcohol resin film according to claim 5, comprising distinguishing between a polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb) and a polyvinyl alcohol resin film different from the above-mentioned polyvinyl alcohol resin film and containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon is derived from bio-based ethylene (Bb), based on the measured fraction δ 13 C stable isotope of carbon 13 ( 13 C).