JP2021006598A - Composite containing ethylene-modified polyvinyl alcohol - Google Patents

Abstract

To provide a composite containing ethylene modified polyvinyl alcohol having high moisture barrier property.SOLUTION: A composite contains ethylene-modified polyvinyl alcohol (A) and graphene (B), in which a content of an ethylene unit of the ethylene-modified polyvinyl alcohol(A) is 2 to 20 mol%.SELECTED DRAWING: None

Description

The present invention relates to ethylene-modified polyvinyl alcohol-containing composites. More specifically, the present invention relates to a composite containing ethylene-modified polyvinyl alcohol (A) and graphene (B) and a method for producing the same.

In food packaging materials, barrier films based on a polymer base, which have advantages in weight reduction, cost reduction, handling safety, etc., are widely used as compared with materials such as glass bottles and metal cans. Among them, polyvinyl alcohol (hereinafter, may be abbreviated as "PVA") is in a state of being laminated with a film such as polyolefin as a thin film for reasons such as high oxygen barrier property, high film strength, and high transparency. , Used as a barrier film. However, since PVA is a hydrophilic resin having a hydroxyl group, it has a problem that it exhibits a high oxygen barrier property and a low water vapor barrier property.

On the other hand, graphenes are attracting attention as a two-dimensional carbon material that exhibits characteristic electromagnetic properties and mechanical properties. In particular, graphene oxide, which can be synthesized by oxidative exfoliation of graphite represented by the Hummers method, has a characteristic of being easily dispersed in water. Utilizing this feature, it is possible to prepare a composite material of graphene oxide and PVA by mixing a dispersion of PVA dissolved in water and graphene oxide. Patent Document 1 discloses a PVA-based composite fiber having a high Young's modulus containing graphene oxide particles. In addition, efforts are being made to enhance the barrier properties of polymer materials by compositing, taking advantage of the characteristic of graphene that does not allow substances to permeate. Patent Document 2 discloses a transparent nanocomposite barrier film containing graphene, a polymer, and a cross-linking group.

Further, Non-Patent Document 1 reports that the water vapor barrier property is improved in the composite material of PVA and graphene oxide, but in order to sufficiently improve the barrier property, a large amount of graphene oxide must be added. There is a problem that the transparency of the composite material is impaired. On the other hand, in Non-Patent Document 2, the monomer component of PVA and graphene oxide are mixed by the in-situ polymerization method, polymerized and saponified to prepare a composite, so that even a small amount of graphene oxide is added. It is disclosed that it exhibits a high water vapor barrier property. However, in order to manufacture a composite by the same method, it is necessary to add graphene in the PVA polymerization process, which makes it difficult to handle in small lots, and it costs money to switch brands because foreign substances are mixed in the polymerization process. There was the above problem.

Japanese Unexamined Patent Publication No. 2013-155461 Special Table 2018-503541

“High barrier graphene oxide nanosheet / poly (vinyl alcohol) nanocomposite films,” Hua-Dong Huang, Peng-Gang Ren, Jun Chen, Wei-Qin Zhang, Xu Ji, Zhong-Ming Li, Journal of Membrane Science Vol.409- 410 (2012) Pages.156-163 “Poly (vinyl alcohol) / graphene oxide nanocomposites prepared by in situ filtration with enhanced mechanical properties and water vapor barrier properties,” Jiaojiao Ma, Ying Li, Xiande Yin, Yu Xu, Jia Yue, Jianjun Bao and Tao zhou, RSC Advances, 2016, 6, 49448-49458

The present invention has been made to solve the above problems, and an object of the present invention is to provide an ethylene-modified polyvinyl alcohol-containing composite having a high water vapor barrier property. In the present invention, a composite can be produced by a simple method using industrially manufactured PVA.

As a result of diligent studies to solve the above problems, the present inventors have found that a high water vapor barrier property can be obtained by adding a small amount of graphene in PVA having a content of ethylene units in a specific range. Completed the invention.

The present invention includes the following inventions.
[1] A composite containing ethylene-modified polyvinyl alcohol (A) and graphene (B), wherein the ethylene unit content of the ethylene-modified polyvinyl alcohol (A) is 2 to 20 mol%.
[2] The composite according to [1], wherein the ethylene-modified polyvinyl alcohol (A) has a viscosity average degree of polymerization in the range of 300 to 4000.
[3] The composite according to [1] or [2], wherein the degree of saponification of the ethylene-modified polyvinyl alcohol (A) is 90 mol% or more.
[4] The composite according to any one of [1] to [3], wherein graphene (B) is graphene oxide.
[5] The composite according to any one of [1] to [4], wherein the graphene (B) has an average particle size of 0.01 μm or more and 300 μm or less.
[6] The composite according to any one of [1] to [5], wherein the mass ratio (B / A) of graphene (B) to ethylene-modified polyvinyl alcohol (A) is 0.01 to 1.
[7] A film composed of the composite according to any one of [1] to [6].
[8] A multi-layer film comprising the composite film according to [7] and a substrate film.
[9] A step of preparing a mixed solution of graphene (B) and ethylene-modified polyvinyl alcohol (A) to obtain a composite, and a step of coating the obtained composite on a substrate film are provided in [7]. The film according to the above or the method for producing a multilayer film according to [8].

The composite of the present invention has a high water vapor barrier property. Further, it is possible to maintain the high transparency and the physical characteristics of the coating film, which are the characteristics of the conventional PVA-based resin. Therefore, taking advantage of such characteristics, the composite of the present invention is suitably used for various applications as a coating film having a barrier property. Further, according to the production method of the present invention, a multi-layer barrier film can be efficiently produced by a method such as mixing ethylene-modified PVA (A) and graphene (B) in a solution system and coating and drying on a substrate film. ..

The composite of the present invention is preferably in a form in which graphene (B) is dispersed in a polymer mainly composed of ethylene-modified PVA (A). The form in which the ethylene-modified PVA (A) and graphene (B) are mixed in a solution and the graphene (B) is dispersed in the solution may be used, and the solid form is contained in the solid ethylene-modified PVA (A). Graphene (B) may be in a dispersed form. Graphene (B) is a two-dimensional material that has the property of impermeable to gas by itself. Therefore, it is possible to suppress the permeation due to the diffusion and movement of water molecules in the polymer and improve the water vapor barrier property. On the other hand, by adding a small amount of graphene (B), it is possible to maintain the physical characteristics and optical properties of the film originally possessed by PVA.

[Ethylene-modified polyvinyl alcohol (A)]
The ethylene-modified polyvinyl alcohol (A) (hereinafter, also referred to as ethylene-modified PVA (A)) used in the composite of the present invention can be obtained by saponifying an ethylene-vinyl ester copolymer.

Examples of the vinyl ester-based monomer used in the production of the ethylene-vinyl ester copolymer include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatic acid, and capron. Examples thereof include vinyl acetate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate and the like. Of these, vinyl acetate is most preferable from the viewpoint of cost.
The ethylene-modified PVA (A) may contain the above-mentioned vinyl ester-based monomer unit, or may contain the above-mentioned saponified product of the above-mentioned vinyl ester-based monomer unit. For example, examples of the ethylene-modified PVA (A) include those containing a vinyl acetate monomer unit and a vinyl alcohol unit. The content of the vinyl ester-based monomer unit in the ethylene-modified PVA (A) is preferably 10 mol% or less, more preferably 5 mol% or less.

It is important that the content of ethylene units with respect to all the monomer units constituting the ethylene-modified PVA (A) is in the range of 2 to 20 mol% from the viewpoint of water vapor barrier property when combined with graphene (B). It is preferably in the range of 2 to 18 mol%, more preferably in the range of 2 to 15 mol%, and further preferably in the range of 2 to 10 mol%. When the content of the ethylene unit is 2 mol% or more, the affinity with graphene (B) is improved, and a composite having excellent water vapor barrier property can be obtained. Further, since the content of the ethylene unit is 20 mol% or less, the water vapor barrier property is excellent and the handling as a solution is excellent.

The content of the ethylene unit can be determined, for example, from ¹ H-NMR of an ethylene-vinyl ester copolymer which is a precursor or a revinegared product of the ethylene-modified PVA. That is, the ethylene-vinyl ester copolymer was sufficiently reprecipitated with n-hexane / acetone (for example, 3 times or more), and then dried under reduced pressure at 80 ° C. for 3 days to analyze ethylene-vinyl. An ester copolymer is prepared. The polymer is dissolved in DMSO-d ₆ and measured at 80 ° C. using ¹ H-NMR (eg 500 MHz). Ethylene unit using a peak derived from the main chain methylene of vinyl ester (4.7 to 5.2 ppm) and a peak derived from ethylene, vinyl ester and the main chain methylene of the third component (0.8 to 1.6 ppm). Content rate can be calculated.

The ethylene-modified PVA (A) may contain monomeric units derived from other copolymerizable monomers. The content of the monomer unit derived from the other copolymerizable monomer with respect to all the monomer units constituting the ethylene-modified PVA (A) is preferably 10 mol% or less, preferably 5 mol% or less. More preferably. Examples of the other copolymerizable monomer include a vinyl ester-based monomer such as vinyl pivalate, a (meth) acrylate-based monomer such as methyl (meth) acrylate, and (meth). ) Examples thereof include (meth) acrylamide-based monomers such as acrylamide. Such a monomer introduction method may be a copolymerization method or a post-reaction introduction method.

The ethylene-modified PVA (A) can be obtained, for example, by subjecting an ethylene-vinyl ester copolymer to a saponification reaction with a saponification catalyst (for example, an alkali saponification catalyst). The ethylene-modified PVA (A) has a low-polarity moiety derived from an ethylene unit and a vinyl ester-based monomer and a high-polarity moiety derived from a saponified vinyl alcohol unit in the molecule. Therefore, the polarity of the polymer can be controlled according to the content of ethylene units. By selecting the content of ethylene units to match the solubility parameter of graphene (B), the affinity between graphene (B) and ethylene-modified PVA (A) is enhanced, and the ethylene-modified PVA (A) of graphene (B) is enhanced. ), The dispersion stability in the medium can be improved, and the water vapor barrier property can be improved with a low addition amount.

The viscosity average degree of polymerization P (hereinafter, may be abbreviated as "degree of polymerization") of the ethylene-modified PVA (A) used in the present invention is measured according to JIS K 6726 (1994). That is, the ethylene-modified PVA can be re-saponified to a saponification degree of 99.5 mol% or more, purified, and then obtained from the ultimate viscosity [η] (liter / g) measured in water at 30 ° C. by the following formula.
P = ([η] x 10000 / 8.29) ^{(1 / 0.62)}
The degree of polymerization of the ethylene-modified PVA (A) is preferably 300 or more and less than 4000, and more preferably 500 or more and less than 3000. The degree of polymerization of the ethylene-modified PVA (A) may be 900 or more, or 1000 or more. If the degree of polymerization is less than 300, the physical properties of the film will be low, and if the degree of polymerization is 4000 or more, the viscosity of the solution when combined with graphene (B) will be too high, and the concentration of the aqueous solution will have to be lowered. There is a problem that productivity is reduced.

The saponification degree of ethylene-modified PVA (A) used in the present invention is measured according to JIS K 6726 (1994). The saponification degree of the ethylene-modified PVA (A) is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 98 mol% or more. When the saponification degree of the ethylene-modified PVA (A) is 90 mol% or more, the composite of the present invention having excellent water vapor barrier property and transparency can be obtained. The ethylene-modified PVA (A) may be used alone or in combination of two or more.

[Graphene (B)]
Graphene (B) can be obtained by various methods, and for example, commercially available graphene may be used. As a method for producing graphene, mechanical peeling of highly oriented pyrolytic graphite, pyrolytic chemical vapor deposition, or the like may be used. Further, for example, graphene oxide produced by oxidizing graphite by a specific method or reduced graphene oxide obtained by chemically reducing the graphene oxide may be used as graphene (B). Known methods for oxidizing graphite to obtain graphene oxide include the known Brodie method (using nitrate and potassium chlorate), the Studio method (using nitrate, sulfuric acid and potassium chlorate), and the Hummers method (using sulfuric acid, sodium nitrate and excess). (Using potassium manganate) and other methods with improvements to these methods can be used. Of these, the Hummers method (WS Hummers, Offeman, RE Preparation of Graphitic Oxide. J Am Chem Soc, 1958 80 (6) pp.1339-1339) or an improved method thereof (Patent No. 5098064), in which oxidation is particularly likely to proceed. Is especially recommended. Among graphene (B), graphene oxide is preferable. For example, graphene oxide manufactured by Tokyo Chemical Industry Co., Ltd. can be mentioned.

The graphene (B) in the present invention includes, in addition to graphene itself, a treatment typified by graphene oxide that causes compositional changes and structural changes (for example, reduction treatment, chemical modification (functionality such as carboxy group contained in graphene oxide). It also includes graphene that has undergone) (such as chemically binding organic substances using groups). The treatment that causes the composition change and the structural change can be performed before combining graphene (B) and ethylene-modified PVA (A) or after combining with ethylene-modified PVA (A). Examples of the treatment before conjugating graphene oxide include heat treatment performed on a graphene oxide-containing solution, light irradiation treatment, and heat treatment after adding a reducing agent. Examples of the treatment performed after combining with ethylene-modified PVA (A) include heat treatment, treatment of exposure to a reducing atmosphere, and light irradiation treatment.

Graphene (B) may have an oxygen-containing group such as a hydroxyl group, an epoxy group, or a carbonyl group. In graphene (B), the content of oxygen atoms by elemental analysis can be, for example, in the range of 5 to 60% by mass. When the content of oxygen atoms is less than 5% by mass, it tends to be difficult to obtain a strong interaction with ethylene-modified PVA (A), preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably. It is 30% by mass or more. On the other hand, if the oxygen atom content of graphene (B) exceeds 60% by mass, the structure of graphene oxide tends to be unmaintainable. However, it is not intended to be limited to these ranges. The oxygen atom content can be evaluated by energy dispersive X-ray analysis combined with XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope), and TEM (transmission electron microscope).

Graphene (B) is said to have a portion that retains a graphite structure derived from graphite and an amorphous structure portion, and it is considered that the presence of the amorphous structure portion causes a function different from that of graphite. The presence of the amorphous structure can be confirmed by Raman spectrum.

When the graphene (B) is plate-shaped, it is preferable that the thickness is as thin as possible because the effect of improving the barrier property of the graphene (B) per unit addition amount is enhanced. Therefore, in order to reduce the thickness of the plate-shaped graphene (B), the graphene (B) may be mechanically treated with an ultrasonic irradiator, a precision emulsifier, or the like. In other words, the graphene (B) may be a graphene (B) after mechanical treatment such as an ultrasonic irradiator or a precision emulsifier.

The average particle size of the graphene (B) particles (preferably graphene oxide particles) is preferably 0.01 μm or more and 300 μm or less, more preferably 0.5 μm or more and 200 μm or less, and 1 μm or more and 100 μm or less. .. If the particle size is smaller than 0.01 μm, there is a problem that the effect of improving the water vapor barrier property becomes small. On the other hand, when the particle size is larger than 300 μm, it is necessary to use a large graphite as a raw material, and there is a problem that the time required for oxidation becomes long. Here, the average particle diameter means the median diameter (d ₅₀ ) measured by the laser diffraction method. The method for measuring the average particle size in the present specification is as described in Examples described later. Graphene (B) can be reduced by mechanical treatment such as ultrasonic treatment.

The thickness of the graphene (B) single layer is preferably about 1 nm, and since it is a two-dimensional material having an extremely high aspect ratio, a very high effect of improving the water vapor barrier property can be obtained by adding a small amount in combination with ethylene-modified PVA (A). can get.

The mass ratio (B / A) of graphene (B) to ethylene-modified PVA (A) is preferably 0.005 or more, more preferably 0.01 or more, further preferably 0.015 or more, and particularly 0.02 or more. Preferably, it is preferably 1 or less, more preferably 0.8 or less, further preferably 0.6 or less, and particularly preferably 0.5 or less. When the mass ratio (B / A) is 0.005 or more, the composite of the present invention having excellent water vapor barrier properties can be obtained. On the other hand, when the mass ratio (B / A) is less than 1, the high transparency of the composite and the film obtained from the composite can be maintained.

The composite of the present invention can be produced, for example, by removing a solvent from a mixed solution obtained by mixing ethylene-modified PVA (A) and graphene (B) in a solution system. The solvent is not particularly limited as long as it dissolves the polymer and disperses graphene (B), but is limited to water, polar solvents such as dimethyl sulfoxide, dimethylformamide, and N-methylpyrrolidone, methanol, ethanol, n-propanol, and the like. An aliphatic alcohol such as i-propyl alcohol and a mixed solvent thereof can be used. Further, water is preferably used because of its ease of handling.

The mixing method of the ethylene-modified PVA (A) and the graphene (B) as a solution system is not particularly limited as long as the two are uniformly mixed, but ethylene is added to the dispersion of the graphene (B). A method of mixing a solution of the modified PVA (A); a method of adding a solid (for example, powder) ethylene-modified PVA (A) to a dispersion of the graphene (B) and dissolving the solution; the solid graphene (B) is ethylene. Examples include a method of adding to a solution of modified PVA (A). Further, in order to disperse uniformly in a shorter time, an apparatus such as an ultrasonic irradiator, a precision dispersion emulsifier or a homogenizer can be used.

In addition to the ethylene-modified PVA (A), graphene (B) and solvent, various additives may be added to the mixed solution of the ethylene-modified PVA (A) and graphene (B) in a required amount depending on the purpose. Examples of the additive include a dispersant, a colorant such as a pigment, an antioxidant, an antioxidant, a cross-linking agent, an ultraviolet absorber, a surfactant, a reducing agent, a pH adjuster and the like. The amount of the additive in the composite is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less of the whole. Examples of the cross-linking agent include alkyldialdehyde, adipaldehyde, orthoalkyl silicate and the like. Examples of the alkyldialdehyde include glutaraldehyde and succinaldehyde. Examples of the orthoalkyl silicate include tetraalkyl orthosilicate (for example, tetramethyl orthosilicate, tetraethyl orthosilicate, tetraisopropyl orthosilicate, and / or tetra-t-butyl orthosilicate, etc.). In certain embodiments of the present invention, the composite of the present invention may be free of the cross-linking agent. In other words, the composite of the present invention does not have to have a cross-linking group (for example, a cross-linking group containing a Si—O bond) between the ethylene-modified polyvinyl alcohol (A) and graphene (B). Therefore, in the manufacturing process, no electromagnetic beam irradiation or cross-linking reaction step for cross-linking is required.

The composite of the present invention preferably contains ethylene-modified PVA (A) in an amount of 80% by mass or more, more preferably 90% by mass or more, and preferably 99.99% by mass or less. Further, graphene (B) is preferably contained in an amount of 0.01% by mass or more, and preferably 1% by mass or less.

Other embodiments of the present invention include molded articles made of the composite of the present invention. The molded product is not particularly limited, but a film is preferable. In addition, another embodiment of the present invention includes a multilayer film including a layer made of the composite of the present invention and a substrate film. The method for producing the film or the multilayer film of the present invention is not particularly limited, and is, for example, a step of preparing a mixed solution of graphene (B) and ethylene-modified polyvinyl alcohol (A) to obtain a composite. Examples thereof include a manufacturing method including a step of coating the composite on a substrate film. The method for producing the film or the multilayer film of the present invention is not particularly limited as a means for forming a film on the substrate film, and examples thereof include a coat film forming method and a cast film forming method. After coating the composite on the substrate film, it may be dried if necessary. For example, a single-layer film can be obtained by peeling a film made of a composite from a substrate film after the above step.

The substrate film used for the multilayer film of the present invention is not particularly limited, but a polyester film such as polyethylene terephthalate, a polyolefin film such as polyethylene and polypropylene, and a polyamide film such as nylon are used. The substrate film may be stretched, corona-treated, smoothed, or the like, depending on the required physical properties. Further, the multilayer film may be a multilayer film including a layer (for example, an adhesive layer) for improving adhesion in addition to the composite film and substrate film of the present invention.

The composite of the present invention can be used for packaging materials (for example, food packaging materials, pharmaceutical packaging materials, cosmetic packaging materials), electronic component materials, battery materials, etc. that require water vapor barrier properties, and can be used as food packaging materials and pharmaceutical packaging materials. Can be suitably used.

The present invention includes embodiments in which the above configurations are variously combined within the scope of the technical idea of the present invention as long as the effects of the present invention are exhibited.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples, and many modifications are applicable within the scope of the technical idea of the present invention. It is possible by someone with ordinary knowledge in the field. Unless otherwise specified, "%" and "part" in Examples and Comparative Examples represent "% by mass" and "part by mass", respectively. The analysis and evaluation in the following examples and comparative examples were performed as follows.

[Calculation of average particle size]
The average particle size of graphene (median size (d ₅₀ ), volume basis) was determined using a laser diffraction / scattering type particle size distribution measuring device LA-950 (HORIBA, Ltd.). Specifically, using a batch cell, the solution of ethylene-modified PVA (A) and graphene (B) obtained in each example was mixed with ion-exchanged water so that the light transmittance was 90% or more. It was diluted and measured.

[Water vapor barrier improvement rate]
JIS Z 0208: 1976 With reference to the moisture permeability test method (cup method) for moisture-proof packaging materials, the amount of water vapor that passed through the film per unit time under the conditions of 23 ° C and 90% RH was adsorbed on calcium chloride in the cup. The moisture permeability was calculated by measuring by mass. The value at the time when it was measured every 24 hours and became stable was adopted (n = 2 average value). The water vapor barrier property improvement rate (%) was calculated by the following formula.
Water vapor barrier improvement rate (%) = 100-100 x (Wa / Wb)
Wa: Moisture permeability of composite film (g / day / m ² )
Wb: Moisture permeability (g / day / m ² ) of a film made of a vinyl alcohol-based resin used as a composite material to which graphene (B) is not added.

[Total light transmittance]
The total light transmittance of the film conforms to the method described in JIS K 7361 (1997), and a film having a thickness of 100 μm is measured using a haze meter NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd., and the measured values are measured three times. The average value of was adopted.

〔Tensile strength〕
The tensile strength of the film conforms to the method described in JIS K 7161 (1994), and a film having a thickness of 100 μm is subjected to a chuck distance of 70 mm and a speed using a precision universal testing machine Autograph AG-Xplus manufactured by Shimadzu Corporation. The measurement was performed under the condition of 500 mm / min, and the average value of the measured values of 5 times was adopted.

[Degree of polymerization]
The viscosity average degree of polymerization of each ethylene-modified PVA (A) was determined by the method described in JIS K 6726 (1994).

[Saponification degree]
The degree of saponification of each ethylene-modified PVA (A) was determined by the method described in JIS K 6726 (1994).

[Vinyl alcohol resin]
The following materials were used:
-Ethylene-modified PVA1 (ethylene unit content 4 mol%, polymerization degree 1700, saponification degree 98 mol%)
-Ethethylene modified PVA2 (ethylene unit content 7 mol%, polymerization degree 1000, saponification degree 99 mol%)
-PVA3 (ethylene unit content 0 mol%, polymerization degree 1700, saponification degree 98 mol%)
PVA4 (ethylene unit content 0 mol%, polymerization degree 1700, saponification degree 88 mol%)
Ethylene-vinyl alcohol copolymer 5 (ethylene unit content 32 mol%, degree of polymerization 800, degree of saponification 99.9 mol%)
The degree of polymerization of the ethylene-modified PVA1 to 4 is a value measured according to JIS K 6726 (1994). The degree of polymerization of the ethylene-vinyl alcohol copolymer 5 is a value measured by using GPC (gel permeation chromatography).

[Graphene (B)]
The following materials were used.
-Graphene oxide 1: Graphene oxide (having hydroxyl groups, epoxy groups, and carbonyl groups, oxygen atom content is 45 to 55% (elemental analysis value); manufactured by Tokyo Kasei Kogyo Co., Ltd.) (10 mg / ml dispersion)
-Graphene oxide 2: Graphene oxide (oxygen atom content less than 58% (carbon atom content is 42 to 52%) (elemental analysis value); manufactured by Sigma-Aldrich) (2 mg / ml dispersion)
-Graphene oxide 3: Graphene oxide nanocolloid (oxygen atom content less than 58% (elemental analysis value); manufactured by Sigma-Aldrich) (2 mg / ml dispersion)

[Example 1]
Using graphene oxide 1, a composite was prepared so that the amount of graphene was 0.04% by mass.
Specifically, 0.4 ml of a 10 mg / ml dispersion of graphene oxide 1 was added to 90 ml of ion-exchanged water, then 10 g of ethylene-modified PVA1 powder was added, and the mixture was heated to 95 ° C. to completely dissolve the polymer. It was. A part of the obtained solution was diluted 10-fold separately, and the average particle size of graphene was measured with a laser diffraction / scattering type particle size distribution measuring device and found to be 8.8 μm. The results are shown in Table 1.
A part of the obtained solution was coated on a PET film having a thickness of 100 μm, dried in a hot air dryer at 40 ° C. for 10 minutes, and then peeled off from the PET film to obtain a film composed of a composite of 30 μm. In the same manner, one more film of the same was produced. As a result of measuring the moisture permeability of each of the two films, the average value was 165 g / day / m ² . On the other hand, as a result of preparing two films by the same method except that graphene was not added and measuring the moisture permeability, the average value was 380 g / day / m ² . The result of comparing the measurement results and calculating the water vapor barrier property improvement rate was 57%. The results are shown in Table 1.
Further, a film having a thickness of 100 μm made of the composite obtained in the same manner was produced. When the tensile strength was measured, it was 58 MPa, and when the total light transmittance was measured, it was 92%.

[Example 2]
Using graphene oxide 1, a composite was prepared so that the amount of graphene was 0.08% by mass.
Specifically, in Example 1, the amount of the dispersion liquid of graphene oxide 1 used was changed from 0.4 ml to 0.8 ml. A film was obtained and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1. Moreover, when the tensile strength was measured, it was 59 MPa, and when the total light transmittance was measured, it was 87%.

[Example 3]
Using graphene oxide 1, a composite was prepared so that the amount of graphene was 0.25% by mass.
Specifically, in Example 1, the amount of the dispersion liquid of graphene oxide 1 used was changed from 0.4 ml to 2.5 ml. A film was obtained and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[Example 4]
Using graphene oxide 1, a composite was prepared so that the amount of graphene was 0.5% by mass.
Specifically, in Example 1, the amount of the dispersion liquid of graphene oxide 1 used was changed from 0.4 ml to 5.0 ml. A film was obtained and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[Example 5]
Using graphene oxide 2, a composite was prepared so that the amount of graphene was 0.04% by mass.
Specifically, 2.0 ml of a 2 mg / ml dispersion of graphene oxide 2 was used instead of 0.4 ml of the 10 mg / ml dispersion of graphene oxide 1 in Example 1. A film was obtained and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[Example 6]
Using graphene oxide 3, a composite was prepared so that the amount of graphene was 0.04% by mass.
Specifically, 2.0 ml of a 2 mg / ml dispersion of graphene oxide 3 was used instead of 0.4 ml of the 10 mg / ml dispersion of graphene oxide 1 in Example 1. A film was obtained and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[Example 7]
Using graphene oxide 1, a composite was prepared so that the amount of graphene was 0.04% by mass.
In Example 7, the polymer was completely dissolved by heating to 95 ° C. in the same manner as in Example 1, and then an additional treatment was performed at 20,000 rpm for 5 minutes using the precision emulsion disperser ClearMix to prepare the solution. Obtained. A film was obtained and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[Example 8]
Using modified PVA2 and graphene oxide 1, a composite was prepared so that the amount of graphene was 0.04% by mass.
Specifically, ethylene-modified PVA2 was used instead of ethylene-modified PVA1 in Example 1. A film was obtained and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[Comparative Example 1]
The same operation as in Example 1 was carried out except that PVA3 was used instead of the ethylene-modified PVA1 in Example 1, and a film was obtained and evaluated. The results are shown in Table 1. Further, the bending strength of the obtained film was measured to be 55 MPa, and the total light transmittance was measured to be 93%.

[Comparative Example 2]
The same operation as in Comparative Example 1 was carried out except that PVA4 was used instead of the ethylene-modified PVA1 in Example 1, and a film was obtained and evaluated. The results are shown in Table 1. Further, when the bending strength of the obtained film was measured, it was 39 MPa, and when the total light transmittance was measured, it was 92%.

[Comparative Example 3]
The same operation as in Example 5 was carried out except that PVA4 was used instead of ethylene-modified PVA1 in Example 5, and a film was obtained and evaluated. The results are shown in Table 1. Further, when the bending strength of the obtained film was measured, it was 40 MPa, and when the total light transmittance was measured, it was 92%.

[Comparative Example 4]
The same operation as in Example 7 except that the ethylene-vinyl alcohol copolymer 5 was used instead of the ethylene-modified PVA1 in Example 7 and water / propanol mixed solvent was used instead of the ion-exchanged water. Was carried out, a film was obtained, and evaluation was performed. The results are shown in Table 1.

[Comparative Example 5]
The same operation as in Comparative Example 2 was carried out except that the amount of the dispersion liquid of graphene oxide 1 used was changed from 0.4 ml to 1.8 ml in Comparative Example 2, and a film was obtained and evaluated. The results are shown in Table 1.

As shown in Table 1, the films made of the composites of Examples 1 to 8 were excellent in water vapor barrier property and also in the improvement rate of water vapor barrier property. In Comparative Examples 1 to 3 and 5, the improvement rate of the water vapor barrier property was low, and the water vapor barrier property of the obtained film was also low. In Comparative Example 4, the water vapor barrier property was high, but the addition of graphene (B) did not improve the water vapor barrier property.

From the above results, it was confirmed that the composite of the present invention has a high water vapor barrier property.

The composite of the present invention is useful as a film having a water vapor barrier property. In particular, it is useful for packaging materials (for example, food packaging materials, pharmaceutical packaging materials, cosmetic packaging materials), electronic component materials, battery materials, etc. that require a water vapor barrier property.

Claims (9)

A composite containing ethylene-modified polyvinyl alcohol (A) and graphene (B), wherein the ethylene unit content of ethylene-modified polyvinyl alcohol (A) is 2 to 20 mol%. The composite according to claim 1, wherein the ethylene-modified polyvinyl alcohol (A) has a viscosity average degree of polymerization in the range of 300 to 4000. The composite according to claim 1 or 2, wherein the ethylene-modified polyvinyl alcohol (A) has a saponification degree of 90 mol% or more. The composite according to any one of claims 1 to 3, wherein the graphene (B) is graphene oxide. The composite according to any one of claims 1 to 4, wherein the graphene (B) has an average particle size of 0.01 μm or more and 300 μm or less. The composite according to any one of claims 1 to 5, wherein the mass ratio (B / A) of graphene (B) to ethylene-modified polyvinyl alcohol (A) is 0.01 to 1. A film comprising the composite according to any one of claims 1 to 6. A multi-layer film comprising the composite film according to claim 7 and a substrate film. The film according to claim 7, further comprising a step of preparing a mixed solution of graphene (B) and ethylene-modified polyvinyl alcohol (A) to obtain a composite, and a step of coating the obtained composite on a substrate film. Alternatively, the method for producing a multilayer film according to claim 8.