RU2825863C1 - Film of polyvinyl alcohol resin, method of distinguishing film of polyvinyl alcohol resin and method of producing film of polyvinyl alcohol resin - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to films made from polyvinyl alcohol resin. Disclosed is a film of polyvinyl alcohol resin containing polyvinyl alcohol resin (A), in which content of carbon 14 (¹⁴C) in total amount of carbon contained in polyvinyl alcohol resin (A), that is ¹⁴C/C, is equal to 1.0 × 10^-14 or more, where the polyvinyl alcohol resin (A) has 1,2-glycol bond content of 0.2 mol.% or more and less than 2.0 mol.%, and where polyvinyl alcohol resin (A) is obtained from polyvinyl ether, wherein said polyvinyl ester is a copolymer of one, two or more types of vinyl ester monomers and other monomers capable of copolymerisation with it, and a proportion of a structural unit obtained from another monomer capable of copolymerisation with a vinyl ester monomer, in relation to the number of moles of all structural units of monomers in polyvinyl ether is 15 mol.% or less. Invention also discloses an optical and water-soluble film based on the disclosed film and a package made from a water-soluble film.

EFFECT: disclosed PVA film 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 or combustion and can be reliably identified by the manufacturer.

12 cl, 2 tbl, 6 ex

Description

[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.

LEVEL OF TECHNOLOGY

[0002]

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

[0003]

PVA is also known as synthetic resin, which has the unusual property of being biodegradable for a synthetic resin and creates a low environmental burden. However, most of the raw materials for PVA are produced using compounds derived from fossil fuels such as oil, coal and natural gas as inputs. Fossil fuels contain carbon that has been locked in the ground for many years. Therefore, PVA is biodegraded by microorganisms or treated by burning, like a normal synthetic resin, releasing carbon dioxide into the atmosphere, causing the carbon that was locked deep in the ground and not present in the atmosphere to be released into the atmosphere as carbon dioxide and can cause global warming.

[0004]

On the other hand, if the raw material used for the synthetic resin is a material obtained from a living organism (plant, animal) that absorbs carbon dioxide circulating in the global environment and is grown using a nutrient source in which the carbon dioxide is converted into organic matter, then even if the material is subjected to 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 reaction using carbon dioxide and water as raw materials, assimilate and fix carbon dioxide as an organic body, and thus attract attention as a carbon source. For example, an alcohol component, particularly ethyl alcohol, is distilled and separated from the fermentation product of sugar extracted from plant raw materials such as sugar cane or corn, or the fermentation product of cellulose, and ethylene as an alkene can be obtained by its 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 in the environment does not increase even if this bio-PVA is subjected to biodegradation treatment or incineration to generate 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, stable carbon 12 (hereinafter may be referred to as ¹² C), and metastable carbon 13 (hereinafter may be referred to as ¹³ C), and its mass ratio is known to be 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. The ratio of ¹² C and ¹³ C is stable. Since radioactive ^14C is produced when a neutron contained in a secondary cosmic ray generated by a primary cosmic ray in the upper atmosphere collides with a nitrogen atom ( ^14N ) in the atmosphere, radioactive ^14C is continuously supplied although its amount fluctuates slightly due to the change in sunspot activity; but on the other hand, the amount of radioactive ^14C decreases with a half-life of 5730 years.

[0007]

Because the carbon that makes up the body of a living organism, growing by continually absorbing carbon dioxide circulating in the global environment, continues to be renewed during its lifetime, 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. The half-life of ¹⁴ C is 5,730 years, and the mass fraction of ¹⁴ C in 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 of ¹⁴ C in the carbon dioxide circulating in the global environment, because the fossil fuels are isolated from the modern carbon dioxide circulating in the global environment.

[0008]

Therefore, since the value of the proportion of ¹⁴ C in the carbon constituting the conventional PVA obtained using fossil fuel as feedstock is also significantly less than the proportion of ¹⁴ C content in the carbon constituting the bio-PVA, that is, essentially 0%, bio-PVA and PVA obtained from fossil fuel can be distinguished from each other by measuring the proportion of ¹⁴ C in the carbon contained.

[0009]

As an application of the polyvinyl alcohol resin film (hereinafter referred to as the PVA film) containing the polyvinyl alcohol resin, mention may be made of the raw material fabric film in the production of optical film such as the polarizing film which is a component of the LCD monitor such as the liquid crystal television or the film for individual packaging of household chemical goods and the like in the amount intended for one-time 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, such as having very few defects and having almost no unevenness in thickness.

ESSENCE OF THE INVENTION

TECHNICAL PROBLEM

[0010]

As described above, the PVA film is used in various applications such as raw material fabric film for producing optical film and film for packaging household chemicals, but problems related to the quality of the PVA film may occur in the market in the final products such as liquid crystal TV and packaging household chemicals including optical film using the PVA film. In this case, it is necessary to identify whether the PVA film that causes the problem is produced by the company itself or by another company. However, in the conventionally known method, it is very difficult to identify the manufacturer of the PVA film by analyzing the PVA film used for the final product that has a problem. Therefore, there has been a need for a method for easily and reliably identifying the manufacturer of the PVA film used for the final product that has a problem in the market.

[0011]

Thus, firstly, the object 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 slightly, even when carbon dioxide is formed as a result of biodegradation or combustion treatment. Secondly, the object of the present invention is to provide a method for simple and reliable identification of the manufacturer of the PVA film.

SOLVING THE PROBLEM

[0012]

The National Institute of Standards and Technology (NIST) standard ASTM D6866 is known for distinguishing between plant-derived 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 the radiocarbon dating method, and the current version of the standard is ASTM D6866-20, which was implemented in February 2020. This method can differentiate between a film containing bio-PVA and a film that does not contain bio-PVA and contains only fossil fuel-derived PVA.

[0013]

Thus, the present invention relates to the following:

[1] A polyvinyl alcohol resin film comprising a polyvinyl alcohol resin (A) in which the content of carbon 14 ( ¹⁴ C) 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.

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

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

[4] A polyvinyl alcohol resin film according to any one of paragraphs [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-based ethylene (Bb).

[5] 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%.

[6] 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.

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

[8] 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%.

[9] 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%.

[10] An optical film in which the polyvinyl alcohol resin film according to any one of paragraphs [1] to [9] is used.

[11] A water-soluble film in which a polyvinyl alcohol resin film according to any one of paragraphs [1] to [9] is used.

[12] Packaging in which a detergent, agrochemical or disinfectant is packed in a water-soluble film according to paragraph [11].

[13] 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 of ¹⁴ C/C carbon 14 ( ¹⁴ C) to the total amount of carbon.

[14] 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 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-derived ethylene (Bb), by measuring a relative content of ¹⁴ C/C carbon 14 ( ¹⁴ C) to the total amount of carbon.

[15] 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 of the stable isotope of carbon 13 ( ¹³ C) for the polyvinyl alcohol resin film containing a polyvinyl alcohol resin (Ab) in which all or part of the carbon comes from ethylene of biological origin (Bb).

[16] The method for distinguishing a polyvinyl alcohol resin film according to item [15], wherein when the proportion of δ ¹³ C of the stable isotope carbon 13 ( ¹³ C) is -20‰ or more, the biologically derived ethylene (Bb) is classified as plant-derived C4 ethylene (Bb), and when the proportion of δ ¹³ C of the stable isotope carbon 13 ( ¹³ C) is less than -20‰, the biologically derived ethylene (Bb) is classified as plant-derived C3 ethylene (Bb).

[17] 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-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 ¹³ C fraction of the stable isotope carbon 13 ( ¹³ C).

[18] A method for distinguishing a polyvinyl alcohol resin film, comprising distinguishing 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 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-derived ethylene (Bb), by measuring a proportion of δ ¹³ C of the stable isotope carbon 13 ( ¹³ C).

[19] A method for producing a film from polyvinyl alcohol resin, comprising:

synthesis of a vinyl alcohol ester monomer by reacting a compound having a carboxyl group with ethylene of biological origin (Bb), or synthesis of a vinyl alcohol ester monomer by reacting a compound having a carboxyl group with ethylene (Bb);

polymerization of the obtained vinyl alcohol ester monomer to obtain a polyvinyl ester;

saponification of the resulting polyvinyl ester to obtain a polyvinyl alcohol resin (Ab); and

using the obtained polyvinyl alcohol resin (Ab) to produce a polyvinyl alcohol resin film.

BENEFICIAL 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 slightly, even when carbon dioxide is generated as a result of biodegradation or combustion processing. According to the present invention, secondly, it is possible to provide a method for simple and reliable identification of the manufacturer of the PVA film.

DESCRIPTION OF IMPLEMENTATION OPTIONS

[0015]

The present invention will now be described in detail.

[0016]

< ¹⁴ C content percentage>

The PVA film of the present invention contains PVA (A) which is a saponified product of polyvinyl ester, and the content ratio of ¹⁴ C in the total number of carbon atoms constituting PVA (A), that is, ¹⁴ C/C (which may be simply referred to as ¹⁴ C/C hereinafter), is 1.0×10 ^-14 or more. The total amount of carbon is the sum of all carbon isotopes, and ¹⁴ C/C is the ratio of the amount of 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 perform an accurate measurement and it is difficult to distinguish whether the origin of PVA (A) contained in the PVA film is biological. In addition, a small value of ¹⁴ C/C indicates that the proportion of biologically 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 of ¹⁴ C/C is preferably 2.0×10 ^-14 or more, more preferably 5.0×10 ^-14 or more, and still more preferably 1.0×10 ^-13 or more. On the other hand, the upper limit of ¹⁴ C/C is not particularly limited, but since biologically derived raw materials are usually more expensive than fossil fuel raw materials, the value of ¹⁴ C/C is preferably 1.0×10 ^-11 or less, more preferably 7.0×10 ^-12 or less, and still more preferably 5.0×10 ^-12 or less.

[0017]

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

[0018]

<Proportion of δ ¹³ C stable isotope of carbon>

The proportion δ ¹³ C of the stable isotope of carbon ¹³ C (hereinafter may be simply referred to as δ ¹³ C) in the present invention refers to the ratio of ¹³ C to ¹² C among three types of isotopes of carbon atoms existing in nature (the percentage abundance ratio of ¹² C: ¹³ C: ¹⁴ C=98.9:1.11:1.2×10 ^-12 ), and the proportion of the stable isotope of carbon is expressed as a deviation with respect to a standard substance and means a value (δ value) defined 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 stable isotope in the measured sample and [( ¹³ C/ ¹² C) _PDB ] represents the fraction of stable isotope in the standard substance. PDB is an abbreviation for "Pee Dee Belemnite" and refers to a calcium carbonate fossil of arrowhead (as the standard substance, an arrowhead fossil from the PeeDee Bed in South Carolina) and is used as the standard body with the ¹³ C/ ¹² C ratio. The "δ ¹³ C stable isotope fraction of carbon" is measured by accelerator mass spectrometry. Since the standard substance is rare, a working standard in which the ratio of stable isotope to 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 its raw material, 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 the δ ¹³ C values of both groups are very different. In the case of PVA using bioethylene derived from C3 plants as raw material, δ ¹³ C is less than -20‰, and in the case of PVA using bioethylene derived 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 the PVA is derived from fossil fuel.

[0022]

Plants are classified into three types: C3 plants, C4 plants, and cloverleaf photosynthetic plants (CAM/Crassulacean acid metabolism) according to the types of initial fixed products of carbon dioxide in the carbonic acid fixation pathway of photosynthesis. In culture, maize and various cereal crops are C4 plants, major crops such as rice and wheat are C3 plants, and cacti, Crassulaceae, Euphorbiaceae, etc. are CAM plants.

[0023]

More than 90% of the plants on Earth are C3 plants and include, for example, agriculturally useful plants such as rice, wheat, tobacco, potato and oil palm. The enzyme involved in carbon dioxide fixation in the C3 plant photosynthetic pathway is ribulose-1,5-diphosphate carboxylase, which has a low affinity for carbon dioxide and, conversely, a high affinity for oxygen, so that the efficiency of the carbon dioxide fixation reaction is reduced and thus the efficiency of the photochemical synthesis reaction is low.

[0024]

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

[0025]

A C4 plant is a plant that performs C4 photosynthesis, which is a form of photosynthesis that has a C4 pathway for carbon dioxide concentration in addition to the Calvin-Benson cycle, which is the overall cycle of carbon dioxide reduction in photosynthesis. The enzyme involved in carbon dioxide fixation in the C4 plant photosynthesis pathway is phosphoenolpyruvate carboxylase. This enzyme is characterized by the fact that its activity is not inhibited by oxygen, and it has a high ability to fix carbon dioxide and has a developed chloroplast in the vascular wall cell as well. Representative C4 plants include maize, sugarcane, cassava, sorghum, miscanthus sinensis, guinea grass, Rhodes grass, Urochloa subquadripara, foxtail grass, barnyard grass, Eleusinia coraciana, and Chamaecyparis paniculata, which is also known as burning bush, broom, or Kochia scoparia . These C4 plants use extra energy to fix carbon dioxide, and thus can fix carbon dioxide more efficiently than other non-C4 plants. In addition, other plants find it difficult to collect carbon dioxide at high temperatures, unlike C4 plants. In addition, photosynthesis can be carried out sufficiently even with little water. This is a physiological adaptation of the plants to harsh climatic conditions such as high temperatures, dry soils with low carbon dioxide, and nitrogen-poor soils.

[0026]

In the PVA film of the present invention, the proportion of δ ¹³ C of the stable isotope carbon 13 ( ¹³ C) measured by the accelerator mass spectrometry method is preferably -20‰ or more. The value of δ ¹³ C is more preferably -18‰ or more, still more preferably -15‰ or more, and particularly preferably -13‰ or more. The value of δ ¹³ C is more preferably -1‰ or less, still more preferably -4‰ or less, and particularly preferably -7‰ or less. The fact that the proportion of δ ¹³ C of the stable isotope carbon in the PVA film of the present invention is in the above-mentioned range indicates that PVA using bioethylene obtained from C4 plants as a raw material was used as the PVA (A) contained in the PVA film. Bioethylene obtained from C4 plants is generally less available than bioethylene obtained from C3 plants, and thus the manufacturer of the PVA film can be more easily and reliably identified when the proportion of δ ¹³ C stable carbon isotope in the PVA film of the present invention is in the above-mentioned range. In addition, corn, sugar cane and cassava are preferable as C4 plants from the viewpoint of production volume and cost.

[0027]

In addition, as plants different from C3 and C4 plants, CAM plants have a photosynthetic system adapted to a dry environment, and this photosynthetic system is considered to be an advanced form of the C3 photosynthesis variety. The ^δ13C value 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 a biomass raw material, 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 ¹⁴ C/C or δ ¹³ C values can be used as a starting material, provided that ¹⁴ C/C and, if necessary, δ ¹³ C are within the above-mentioned range.

[0029]

For example, not only the PVA film showing δ ¹³ C is obtained by using the C3 plant raw material, but also a specified δ ¹³ C value is obtained by mixing PVAs having different δ ¹³ C, that is, a δ ¹³ C value that cannot be achieved by a simple C3 plant substance, and a more specific δ ¹³ C value is obtained, so that the recognition accuracy of the obtained PVA film can be further improved. Therefore, when a raw material having a different δ ¹³ C value is used, 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, the δ ¹³ C of the PVA 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-derived ethylene (Bb). Thus, 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 only from raw materials produced from fossil fuels.

[0031]

The method for obtaining PVA (Ab) is not particularly limited, and, for example, can be used

(1) a method in which only polyvinyl ether (Db1) obtained by polymerizing only biovinyl ether monomer (Cb1) is saponified to obtain PVA (Ab1),

(2) a method for saponifying a polyvinyl ether (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 produce PVA (Ab2),

(3) a method for saponifying a polyvinyl ether (Db2) obtained by copolymerizing a biovinyl ether monomer (Cb1) and a vinyl ether monomer (Cp) using fossil fuel-derived ethylene (Bp) as a raw material to produce PVA (Ab3),

(4) a method in which a mixture of a polyvinyl ester (Db1) and a polyvinyl ester (Dp) obtained by polymerizing only a fossil fuel-derived vinyl ester monomer (Cp) is saponified to obtain PVA (Ab4), and

(5) a method that combines methods (2) - (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 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 carboxyl group R-COOH. Vinyl acetate can be synthesized as follows. Generally, vinyl acetate can be obtained by a gas-phase reaction of ethylene, acetic acid and oxygen in the presence of a catalyst. Here, by using ethylene containing a predetermined amount of ¹⁴ C or acetic acid containing a predetermined amount of ¹⁴ C as the compound having a carboxyl group, vinyl acetate containing a predetermined amount of ¹⁴ C is obtained. Examples of ethylene containing a predetermined amount of ¹⁴ C include bioethylene.

[0034]

In the production of vinyl ester monomer, it is preferable to use biological raw materials other than ethylene such as carboxylic acid as raw materials, but the carboxylic acid group is removed from the polyvinyl ester polymer backbone during saponification, and is usually recovered and reused. Therefore, even when using raw materials derived from fossil fuels, the carbon dioxide content in 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 copolymerizing therewith.

[0036]

Other monomers capable of copolymerizing with the vinyl ester monomer are preferably ethylene. That is, 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, t-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 a salt thereof, methacrylamidopropyl dimethylamine or a salt thereof, and N-methylol methacrylamide 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, 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 kinds 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 obtained 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 fuels may be used, or a monomer of plant origin may 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 still 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 still more preferably less than 3000. Here, the polymerization degree of PVA (A) means an average polymerization degree Po measured according to the specification of JIS K6726-1994, and is defined by the limiting viscosity [η] (unit: deciliter/g) measured in water at 30°C after re-saponification and purification of PVA, according to the following formula.

[0041]

Po=([η]×10 ⁴ /8.29) ^(1/0.62)

[0042]

In the PVA film of the present invention, the saponification degree of the 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 film for packaging household chemicals, 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 still 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 still more preferably less than 99.995 mol%. Here, the saponification degree of PVA refers to the ratio (mol%) of the number of moles of vinyl alcohol block to the total number of moles of the structural block (usually vinyl ester monomer block) that can be converted into vinyl alcohol block by saponification and into vinyl alcohol block in PVA. The saponification degree of PVA can be measured according to the description of JIS K6726-1994.

[0043]

In the PVA film of the present invention, the content of the 1,2-glycol bond in the PVA (A) is preferably 0.2 mol% or more. The content of the 1,2-glycol bond in the PVA (A) is preferably less than 2.0 mol%. When the content of the 1,2-glycol bond is less than 2.0 mol%, good optical properties and mechanical strength are easily achieved when using the PVA film as a raw material fabric film for producing an optical film. On the other hand, when the content of the 1,2-glycol bond is 0.2 mol% or more, it is possible to improve the productivity in producing the PVA (A) and reduce the production cost. The content of the 1,2-glycol bond in the PVA (A) is more preferably 0.4 mol% or more, and still more preferably 0.6 mol% or more. The content of the 1,2-glycol bond in the PVA (A) is more preferably less than 1.9 mol%, and still 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) are deposited in the processing liquid due to the occurrence of 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 obtained polarizing film, which may cause a problem. 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%, the defects of foreign impurities on the surface of the polarizing film obtained from the PVA fine particles (A) cannot be sufficiently reduced. 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 still 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 still more preferably less than 0.05 mol%.

[0046]

In the PVA film of the present invention, one kind of PVA may be used as the PVA (A), or a mixture of two or more kinds of PVA having different degrees of polymerization, saponification and modification may be used. When two or more kinds of PVA are mixed and used, PVA (A) and PVA obtained from biomass such as bioethylene different from PVA (A), PVA (A) and PVA obtained from oil or fossil fuel 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 mass% or more, more preferably 80 mass% or more, and still more preferably 85 mass% or more. In addition, the content may be 100 mass%, but is preferably 99 mass% or less, and may be 95 mass% or less and or 90 mass% or less in consideration of 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 physical properties such as impact strength and processability during secondary processing may be a problem. In order 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 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 sweating on the surface of the film. In addition, it is preferable to use a plasticizer obtained from a raw material 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 still 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 still 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 be deteriorated or bleeding may occur on the surface of the film.

[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, to maintain moisture resistance when handling the PVA film, or to adjust the softening rate by absorbing water when dissolving the PVA film.

[0051]

Examples of the 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 preferred.

[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 amount of starch is more than 15 phr, the processability during the production of the PVA film may be deteriorated.

[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, cellulose acetate 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 from the viewpoint of its convenient processing and improving the ability to separate from the film-forming device when producing the PVA film. Examples of the surfactant include an anionic surfactant and a nonionic surfactant.

[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 dodecylbenzene sulfonate.

[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 may 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 it does not interfere with the effect of the present invention. The ratio of the total weight of PVA, the plasticizer, starch, the water-soluble polymer other than PVA (A), and the surfactant to the total weight of the PVA film of the present invention is preferably in the range of 60-100 mass%, more preferably 80-100 mass%, and even more preferably 90-100 mass%.

[0059]

<Form>

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, still more preferably 100 µm or less, and still more preferably 50 µm or less, because if the thickness is too large, the secondary processability 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, still 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 preferable. Examples of the water-soluble film include a film for packaging household chemicals, a base film for hydraulic transfer, a base film for embroidery, an anti-adhesive film for molding artificial marble, a film for packaging seeds, and a film for waste storage bags, and the film for packaging household chemicals is preferable. Examples of household chemicals include detergents, agricultural chemicals, and disinfectants. The form of the household chemicals may be any of a powder form, a lump form, a gel form, and a liquid form. The package can be obtained by packaging the household chemicals using the PVA film of the present invention as a film for packaging household chemicals. Using this package, you can easily and safely use a certain amount of the preparation when washing clothes with detergent in normal household conditions or when spraying pesticide on fields during agricultural work.

[0061]

<Production method of 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 (ejection 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 the PVA (A). Among these, the flow-cast film forming method and the melt extrusion film forming method are preferable because a uniform film can be obtained with high productivity. The following describes a method for forming a PVA film using a flow-casting method and a method for forming a film using melt extrusion.

[0062]

When the PVA film is formed by the flow casting method or the melt extrusion method, the above-mentioned film-forming raw material is poured in the form of a film onto a support such as a metal roller or a metal belt, and heated to remove the solvent, thereby curing and forming the film. The cured film is separated from the support, dried by a drying roller, a drying oven, etc. as required, further heat-treated as required, and wound up, whereby a long PVA film in the form of a roll can be obtained.

[0063]

The concentration of volatile components (such as solvent removed by volatilization or evaporation during film formation) and the like) in the film-forming solution is preferably 50 mass% or more, and more preferably 55 mass% or more. The concentration of volatile components in the film-forming solution is preferably 90 mass% or less, and more preferably 80 mass% or less. When the concentration of volatile components is less than 50 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 mass%, the viscosity becomes low, and the uniformity of the thickness of the obtained film is easily disturbed.

[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 the film forming solution = {(Wa - Wb)/Wa} × 100

where Wa represents the weight (g) of the film-forming solution, and Wb represents the weight (g) of the film after drying Wa (g) of the film-forming solution in an electrothermal dryer at 105°C for 16 h.

[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 cast-in-place or melt extrusion method, the film-forming feedstock solution 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 solution for forming the film 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 solution for forming the film 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 too hard.

[0069]

While the PVA film is heated on the substrate, hot air having a speed of 1-10 m/s can uniformly blow over the entire free surface area of the PVA film to control 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 from the viewpoint of drying efficiency, drying uniformity, etc. 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 from the viewpoint of drying efficiency, drying uniformity, etc.

[0070]

The PVA film separated from the support is dried on the support preferably to a volatile content of 5-50 mass%, 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 a plurality of drying rollers, it is preferable to bring one and the other surface of the film into contact with the drying rollers alternately 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 temperature of the drying oven and the drying roller is too high, the film may become too hard. On the other hand, the lower limit of the temperature of the drying oven and the drying roller is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher. When the temperature of the drying oven and the drying roller is too low, the productivity may decrease.

[0071]

The dried PVA film can be further subjected to heat treatment as necessary. By performing 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 60°C or higher. The upper limit of the heat treatment temperature is preferably 135°C or lower, and more preferably 130°C or lower. If the heat treatment 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 finally obtained PVA film is not necessarily limited to the series of treatments described above. The volatile fraction of the PVA film is preferably 1 mass% or more, and more preferably 2 mass% or more. The volatile fraction of the PVA film is preferably 5 mass% or less, and more preferably 4 mass% or less.

[0074]

<Method of distinction>

The PVA film obtained by the above-described 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 14 carbon ( ¹⁴ C) to the total amount of carbon, i.e., ¹⁴ C/C.

[0075]

In the present invention, PVA (Ap) obtained only from ethylene obtained 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 obtained 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 14 carbon ( ¹⁴ C) to the total carbon, that is, ¹⁴ C/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 raw materials is different, the ¹⁴ C/C ratio is different. For example, when a PVA film produced by one's own company is produced so that the proportion of carbon 14 ( ¹⁴ C) in the total amount of carbon, that is, ¹⁴ C/C, is constant, it can be determined whether the 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, the production is carried out so that the proportion of carbon 14 ( ¹⁴ C) in the total amount of carbon, that is, ¹⁴ C/C, varies depending on the production location, production date, and production batch, as a result of which the production location, production date, and production batch of the PVA film can be determined by measuring the proportion of carbon 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, is 1.0×10 ^-14 or more, more preferably 5.0×10 ^-14 or more, and still more preferably 2.0×10 ^-14 or more. In addition, since biologically derived raw materials are usually more expensive than raw materials derived from fossil fuels, in order to distinguish the PVA film, it is preferable to produce the PVA film so that the proportion of carbon 14 ( ¹⁴ C) in the total amount of carbon, that is, ¹⁴ C/C, is 1.0×10 ^-11 or less, more preferably 5.0×10 ^-12 or less, and still more preferably 0.1×10 ^-14 or less.

[0078]

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

[0079]

In the above description, the proportion of carbon 14 ( ¹⁴ C) in the total amount of carbon, that is, ¹⁴ C/C, is measured, and then the proportion δ ¹³ C of the stable isotope of carbon 13 ( ¹³ C) is measured for the film identified as the 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, is not measured, the proportion δ ¹³ C of the stable isotope of carbon 13 ( ¹³ C) is measured, and as a result, the 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 from fossil fuel-derived raw materials. However, since the proportion of δ ¹³ C stable carbon isotope in PVA (Ap) derived from fossil fuel-derived raw materials is generally less than -20‰, it may be difficult to distinguish a PVA film containing PVA (Ab) derived from plant-based C3 ethylene (Bb) as raw materials from a PVA film containing only PVA (Ap) derived 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 is possible to determine 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 a polarizing film. It can also be suitably used for a water-soluble film such as a package for household chemicals and a seed tape.

Examples

[0083]

Hereinafter, 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]

[Cleaning PVA Film]

The roll of PVA film obtained in the following Examples or Comparative Examples was unwound to collect approximately 5 g of the film, and the film was cut into small pieces. Then, the cut PVA film was extracted with a Soxhlet abstractor using chloroform. By sufficiently removing the components other than PVA in the PVA film in this way, the PVA film was purified to obtain PVA in the PVA film.

[0085]

[Measurement of the proportion of carbon 14 ( ¹⁴ C) in the total amount of PVA carbon in PVA film, i.e. ¹⁴ C/C]

The PVA obtained in the above section [Purification of PVA Film] 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 total reduction using an iron catalyst. Then, the carbon isotope ratio ( ^14C / ^12C ratio, ^13C / ^12C ratio) of the purified PVA film and the standard substance was measured by accelerator mass spectrometry, and ^{the 12C} concentration, ^13C concentration, and ^14C concentration were determined from the measurement results. Then, the obtained ^14C concentration was divided by the total carbon concentration (the sum of the ^12C , ^13C , and ^14C concentrations) to calculate the ^14C /C value of PVA in the PVA film. Here, graphite synthesized from the oxalic acid standard substance (HOxII) provided by the National Institute of Standards and Technology was used as the standard substance. ^{The 14} C/C measurement limit in this measurement was less than 1.0 × 10 ^-14 .

[0086]

[Measurement of δ ¹³ C fraction of stable carbon isotope of PVA in PVA film]

The PVA obtained in the above section [Purification of PVA Film] 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 total reduction using an iron catalyst. Then, the carbon isotope ratio ( ^13C / ^12C ratio) of the purified PVA film and the standard substance was measured by accelerator mass spectrometry. Then, the proportion δ ^13C of the stable carbon isotope was calculated by 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, [( ^13C / ^12C ) _sample ] represents the carbon isotope ratio ( ^13C / ^12C ratio) of the measured purified PVA film, and [( ^13C / ^12C ) _PDB ] represents the carbon isotope ratio ( ^13C / ^12C ratio) of PDB as a standard substance.

[0089]

[Measurement of ethylene block content, alkoxyl group content, 1,2-glycol bond content and saponification degree of PVA in PVA film]

The PVA obtained in the above section [PVA Film Cleaning] was dissolved in dimethyl sulfoxide (DMSO-d ₆ ), and then the solution was added to acetone to precipitate the PVA, thereby further purifying the PVA. One or two drops of trifluoroacetic acid (TFA) were added dropwise to the PVA solution in DMSO-d ₆ , and the resulting sample was immediately subjected to NMR measurement under the following conditions. From the obtained NMR spectrum, the ethylene block content, the alkoxyl group content, the 1,2-glycol bond content, and the saponification degree of PVA in the PVA film were determined.

[0090]

(NMR measurement conditions)

Device used: Superconducting Nuclear Magnetic Resonance Device "Lambda 500" manufactured by JEOL Ltd.

Solvent: DMSO-d ₆ (with dropwise addition of TFA)

Concentration: 5 wt%.

Temperature: 80°C

Resonant frequency: 1H 500 MHz

Rotation angle: 45°

Pulse delay time: 4.0 s

Number of integrations: 6000

[0091]

[Measurement of the ultimate tensile temperature of PVA film]

A rectangular test specimen having a width of 30 mm and a length of 60 mm was taken from the center portion in the width direction of the roll of the PVA film obtained in the following Examples or Comparative Examples. 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 extension at the time of rupture. This procedure was repeated 3 times, and the average value of the percentage of extension at the time of rupture was determined. When the average value was 6.5 times or more, the constant temperature of the water bath was lowered by 1°C, and when the average value was less than 6.5, the constant temperature of the water bath was raised by 1°C, and the limit temperature at which the average value of the percentage of extension 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 inclusions in 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 bodies existing on the surface of the cut polarizing film were visually observed, and the amount of foreign bodies having the longest diameter of 5-500 μm (no./600 cm ² ) was determined. This procedure was repeated 3 times to obtain an average value (no./600 cm ² ) of the amount of foreign bodies. The longest diameter of the foreign bodies was measured using a differential interference microscope (magnification: 200×). In the following Examples or Comparative Examples, since the polarizing film after the drying treatment was continuously wound for 6 hours, the cut polarizing film is a sample of about 6 hours from the start of the production of the polarizing film.

[0093]

[Measuring the degree of polarization of polarizing film]

A 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 light transmittance (Y ^'' ) in the case of superimposing the samples so that their length directions (stretching directions) were 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 ^⊥ )/(Y ^'' + Y ^⊥ )} 1/2 × 100

[0095]

<Example 1>

(1) Synthesis of vinyl acetate

After impregnating 23 g (water absorption 19.7 g) of the silica spherical carrier "HSV-I" (manufactured by Shanghai Haiyuan Chemical Industry Technology Co., Ltd.) (sphere diameter: 5 mm, specific surface area: 160 ^m2 /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.% was added, the resulting mixture was maintained 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/support composition was immersed in 60 ml of a 1.7 wt.% aqueous solution of acetic acid and left for 16 hours. Then the composition was 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 support 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 sugar cane (manufactured by Braskem S. A.) 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 in a known manner, and then 2,4-diphenyl-4-methyl-1-pentene (DPMP) as a compound having a conjugated double bond and a molecular weight of 1,000 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 polymerization degree. A 6 mass% methanol solution of sodium hydroxide was added to the obtained methanol solution of polyvinyl acetate with stirring so that the molar ratio of sodium hydroxide to the vinyl acetate units of the polyvinyl acetate was 0.023, and the saponification reaction was started at 30°C. As the saponification reaction proceeded, a gelled product was obtained. After 50 min from the start of the saponification reaction, the gelled product was crushed to obtain PVA (PVA-1) swollen in methanol. This PVA-1 was washed with 5 times its weight of methanol, and then dried with hot air at 55°C for 1 hour and at 100°C for 2 hours.

[0098]

(3) Production of PVA film and PVA film roll

An 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 stock solution for forming a PVA film. The stock solution for forming a film was discharged from a slot die onto a first metal roller of 2 m in diameter with a surface temperature of 90°C, and dried to separate a 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 having 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: 1m) 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 0.6m in width, 1000m in length and 30μm in thickness.

[0099]

(4) Production of polarizing film

The 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 treatment liquid (pure water) at 30°C and uniaxially stretching the film by 1.72 times in the length direction during the immersion. The dyeing was performed by immersing the PVA film in a swelling treatment tank with a treatment 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 the immersion. Crosslinking was performed by immersing the PVA film in a swelling treatment tank with a crosslinking treatment liquid (an aqueous solution of 2.6 wt % boric acid) 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 (an 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 (an 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 resulting roll of PVA film was then unwound to continuously produce polarizing film.

[0100]

(5) Production of a roll of polarizing film

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

[0101]

For another polarizing film sample, the light transmittance when the sample is tilted at 45 degrees and the light 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-obtained 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 up for 6 hours to obtain a polarizing film roll product (polarizing film roll).

[0103]

The thus obtained PVA film roll and polarizing film roll were measured and evaluated in the manner described above. 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.

[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 the 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 results of the measurement and evaluation are shown in Table 2. The raw materials and polymerization conditions of 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 the 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 results of the measurement and evaluation are shown 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 “(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 the 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 the 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 in 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 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-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, which is 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 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 “(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 results of the measurement and evaluation are shown in Table 2. The raw materials and polymerization conditions of PVA are shown in Table 1.

[0111]

*1) AMV: 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile);

AIBN: Azobisisobutyronitrile;

*2) Weight relative to 100 m.h. vinyl acetate.

[0112]

*) Use of PVA obtained by mixing PVA-1 and PVA-4 in a weight ratio of 1:1.

Claims (13)

1. A polyvinyl alcohol resin film for use as a raw material fabric film for producing an optical film, a household chemical packaging film, a base film for hydraulic transfer, a base film for embroidery, an anti-adhesive film for molding artificial marble, a seed packaging film or a film for waste storage bags, comprising a polyvinyl alcohol resin (A) in which the content of carbon 14 ( ¹⁴ C) 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, 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%, and wherein the polyvinyl alcohol resin (A) is obtained from a polyvinyl ether, wherein the polyvinyl ether is a copolymer of one, two or more kinds of vinyl ether monomers and other monomers capable of copolymerizing with it, and the proportion of the structural block obtained from another monomer capable of copolymerizing with the vinyl ether monomer, in relation to the number of moles of all the structural blocks of the monomers in the polyvinyl ether is 15 mol% or less. 2. The polyvinyl alcohol resin film according to claim 1, wherein the proportion of δ ¹³ C of the stable isotope carbon 13 ( ¹³ C) is -20‰ or more. 3. A film made of polyvinyl alcohol resin according to claim 1, in which the proportion of δ ¹³ C of the stable isotope of carbon 13 ( ¹³ C) is less than -20‰. 4. A film of polyvinyl alcohol resin according to any one of claims 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-based ethylene (Bb). 5. The polyvinyl alcohol resin film according to any one of claims 1 to 3, 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%. 6. The polyvinyl alcohol resin film according to any one of claims 1 to 3, wherein the polyvinyl alcohol resin (A) has a saponification degree of 80 mol% or more. 7. The polyvinyl alcohol resin film according to any one of claims 1 to 3, wherein the polyvinyl alcohol resin (A) has a degree of polymerization of 200 or more and less than 8000. 8. The polyvinyl alcohol resin film according to any one of claims 1 to 3, 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%. 9. An optical film for use as a raw material for a polarizing film, a viewing angle improving film, a retention film or a brightness improving film, wherein the optical film uses a polyvinyl alcohol resin film according to any one of claims 1 to 3. 10. A water-soluble film for packaging household chemicals, for hydraulic transfer, for embroidery, for molding artificial marble, for packaging seeds or for waste storage bags, wherein the water-soluble film uses a polyvinyl alcohol resin film according to any one of paragraphs 1-3. 11. Packaging of household chemicals in which the detergent, agrochemical or disinfectant is packed in a water-soluble film according to paragraph 10.