JP2001105543A - Coated plastic film and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coated plastic film which is excellent in transparency, slidability, and especially gas-barrier properties in high humidity. SOLUTION: In a coated plastic film, at least one layer of a composition comprising a swellable silicate compound in the form of a colloidal water- containing layer (A) and a saponified ethylene-vinyl acetate copolymer of 2-19 mole % ethylene unit, 200-2000 degree of polymerization, and 80.0-99.99 mole % degree of saponification (B) is formed at least on one side of a base material film of a thermoplastic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated plastic film suitable as a packaging material having excellent transparency and transparency to gases such as oxygen, nitrogen, carbon dioxide and water vapor, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyolefin, polystyrene,
Films made of thermoplastic resins such as polyvinyl chloride, polyester, and polyamide, especially oriented polypropylene, polyester, and polyamide films have excellent mechanical properties, heat resistance, and transparency, and are widely used as packaging materials. Used. However, when these films are used for food packaging, their gas permeability is too large and their oxygen barrier properties are insufficient, resulting in deterioration of the contents due to oxidative deterioration or propagation of aerobic microorganisms. In many cases, a method of easily stacking another layer having good oxygen barrier properties is often employed.

[0003] The most typical means are a method of laminating a metal foil such as aluminum, and a method of depositing such a metal on the surface of the thermoplastic resin film. An excellent gas barrier property, particularly an oxygen barrier property, is effective. It is used for

However, these aluminum laminates and vapor-deposited films are opaque, and when they are used for packaging foods, there is a drawback that the contents cannot be seen. Along with the trend of fashion, there is an increasing demand for films that are transparent and have excellent gas barrier properties.

[0005] On the other hand, various transparent plastic film materials having small gas permeability are conventionally known, and examples thereof include films made of polyvinyl alcohol, polyacrylonitrile resin, and polyvinylidene chloride resin.
However, these films alone are insufficient in physical properties such as strength, elongation, water resistance and heat resistance as compared to films of oriented polypropylene, polyester, polyamide and the like. It cannot be used alone as a packaging material film at all, and at present, it is generally used by laminating such a film having a thickness of about 20 to 40 μm together with the polypropylene film or polyester film. Moreover, these films are all expensive alone, and by making them into multiple layers, not only become more expensive but also the total layer thickness becomes very thick, and it is difficult to obtain a high degree of transparency. There are problems such as.

Further, polyvinylidene chloride-based resins and polyacrylonitrile-based resins generate toxic substances when heated / burned, so that not only is it difficult to dispose of used packaging materials, but also when recycling used packaging materials. However, they also have the property of having an effect of significantly lowering product quality, and there is also a demand to avoid use as much as possible.

[0007] On the other hand, polyvinyl alcohol is extremely excellent in preventing gas permeation during drying, but has a very large hygroscopic property, and has a drawback that the intended gas barrier property is greatly reduced by moisture absorption.

As an improvement over the above problems, an ethylene-vinyl alcohol copolymer obtained by copolymerizing 25 to 60 mol% of ethylene is used. However, this has a problem that although its resistance to moisture absorption is improved, it is still not sufficient, and there is a problem that the gas barrier properties tend to slightly decrease due to copolymerization of ethylene.

Further, since the level of gas barrier properties obtained by these films is still not sufficient as compared with the above-mentioned aluminum laminated film, it has high transparency and high gas barrier properties, and it can be used alone. At present, there is a strong demand for low-cost films that can be used.

On the other hand, in order to solve these problems, a method of applying a barrier resin such as polyvinyl alcohol, polyethylene vinyl alcohol, polyvinylidene chloride or the like to oriented polypropylene, polyester or polyamide has been studied. Vinylidene chloride is widely used. However, such gas barrier properties are not yet sufficient, and are used by increasing the coating thickness, but the level is far from the level of aluminum vapor deposition and the like,
The above environmental problems have not been improved at all.

[0011]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a high gas barrier property, particularly, a high gas barrier property under a high humidity environment. To provide a coated plastic film which simultaneously satisfies the above-mentioned transparency and a method for producing the same.

[0012]

That is, the coated plastic film of the present invention comprises a swellable layered silicate compound (hereinafter referred to as component (A)) on at least one surface of a base film made of a thermoplastic resin. Containing 2 to 19 mol% of ethylene units, and having a degree of polymerization of 200 to 2000;
It has at least one layer of a composition (hereinafter, also referred to as the coating layer) composed of a vinyl alcohol-based polymer having a saponification degree of 80.0 to 99.99 mol% [hereinafter, referred to as a component (B)]. A coated plastic film to be coated, and an aqueous composition containing the composition, coated on at least one surface of a base film, and dried.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The substrate film used for the coating film of the present invention is not particularly limited as long as it is a thermoplastic resin having a transparent film forming ability. Polyolefin resins such as polyethylene and polypropylene, Polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate and copolymers thereof, polyether resins such as polyoxymethylene, nylon-6 Polyamide resins such as nylon, nylon-6,6, polymeta-xylene adipamide, polystyrene, poly (meth)
Acrylic esters, polyacrylonitrile, vinyl resins such as polyvinyl acetate and copolymers thereof, cellulose resins such as polycarbonate resins and cellophane, acetate and the like, and cellulose resins such as polyimide, and furthermore, polyimides and polyethers Imide, polyphenylene sulfide, polyether sulfone, polysulfone,
Polyether ketone, a fluorine-containing polymer, a simple substance of many other resins, a copolymer, a mixture, composed of a composite, unstretched or uniaxially or an oriented film stretched in a biaxial direction perpendicular to or the like. it can.

In particular, for the purpose of the present invention, the base film is made of a biaxially stretched film of polypropylene, polyester, polyamide, or the like from the viewpoints of heat resistance dimensional change, mechanical strength, moldability, and economic efficiency. A certain case is preferable, and a polyester film such as polyethylene terephthalate as a main component is most preferable in terms of transparency, heat resistance, and mechanical strength.

Although the thickness of the film is not particularly limited,
Usually 1 ~ 250μm, 3 ~ 50μ as packaging material
m is particularly preferred.

The substrate film may be a single layer or a composite multilayer film, and the composite method and the number of layers in the multilayer film are arbitrary.

The present invention is characterized in that at least one surface of such a thermoplastic resin film is coated with at least one layer of a composition comprising the components (A) and (B).

In the present invention, the swellable layered silicate component (A) is a hydrous silicate of aluminum, magnesium or iron, and among clay minerals.
It is a compound having a layered structure with repeating units based on tetrahedral crystalline SiO ₄ . The compound having this layered structure is composed of SiO ₄ tetrahedrons connected in a hexagonal mesh plate-like form, and ions forming an octahedral coordination between the upper and lower two plates.
For example, it has a multilayer structure such as a sandwich-like three-layer structure in which Al ³⁺ , Fe ²⁺ , Mg ^{3+ and the} like are ion-bonded. In the present invention, the swelling property means that the layered silicate compound absorbs polar molecules such as carboxylic acids, alcohols, and water molecules between the layers, so that the interlayer distance is expanded or further swelling is performed, and the ultrafine It refers to the property of becoming particles. Examples of the swellable layered silicate compound include those that swell indefinitely, such as smectite, that is, those that disperse in a colloidal form, and those that swell in a limited manner, such as vermiculite. For the purpose of the invention, the former, which swells indefinitely, is effective and preferred. There are several types of such unrestricted swollen smectite groups, with the difference in the number of octahedral sites in the occupied central layer resulting in dioctahedral with trivalent and divalent substituted central cations. It is classified into smectite and trioctahedral smectite having monovalently substituted divalent cations.

Examples of dioctahedral smectite include montmorillonite, beederite and nontronite, and trioctahedral smectite includes
Hectorite, sabonite, teniolite, and the like. These minerals include those produced from natural clays, semi-synthetic products obtained by subjecting layers extracted from natural products to an interlayer ion exchange treatment, and pure synthetic products synthesized to have a structure similar to that of natural products.

Among these, trioctahedral smectite, which is a synthetic product, is preferable in terms of purity, uniformity, and the like. From the viewpoints of transparency when formed into a film and gas impermeability, [Si
_{8 (Mg 5.34 Li 0.66) O} 20 (OH) 4 ] ^M +0.66 (However, M ⁺ interlayer cations such as Na ^+), as indicated by, and most preferably when using a synthetic hectorite.

Each layer of the crystal structure in the layered structure of such a synthetic hectorite forms a two-dimensional platelet having a thickness of about 1 mm. Magnesium atoms present in this platelet unit are converted to lower valent cations. And the platelet unit is negatively charged. In the dry state, this negative charge is balanced by displaceable cations (usually sodium ions) outside the lattice structure on the plate surface, and in the solid phase, these particles bind to each other by van der Waals forces and It is a bunch of. When this is dispersed in water, the replaceable cations are hydrated, the particles swell and the platelets separate. This completely separated state gives an unlimited swelling state, that is, a transparent colloidal dispersion sol, which is the most preferable application form of the present invention.

In the ionic state, such as in water, the platelets have a negative surface charge and the ends have a positive charge. Under the condition that the surface negative charge is considerably larger than the edge positive charge, a stable sol state is formed by interparticle repulsion. However, under conditions where the ion concentration increases, such as when the particle concentration increases or when salt is added, the repulsion decreases,
A so-called card house structure is formed by suction of surface negative charges and edge positive charges, resulting in thickening or gelling. Conventionally, there are many uses of this synthetic hectorite utilizing the card house structure and the resulting thixotropy.However, in order to provide better air barrier properties, this card house structure is used. It is preferable not to do so. In order to obtain a sol with a high particle concentration without taking this card house structure, it is preferable to use a so-called deflocculant using a polyphosphate such as hexamethanate, tripolyphosphate, pyrophosphate, etc. Powder grades, such as those to which the deflocculant has been previously applied, can be particularly preferably used.

On the other hand, it is important that the vinyl alcohol polymer (B) used as the component (B) used in the present invention contains 2 to 19 mol% of ethylene units. The content is preferably 2.5 to 17 mol%, more preferably 3 to 15 mol%, and particularly preferably 3.5 to 13 mol%.

When the ethylene content is less than 2 mol%, the moisture resistance of the component (B) is remarkably reduced.
Even if the components are added, not only does the gas barrier property in a high-humidity environment become inadequate, but also the stability of the coating solution is lowered, and the productivity of the coating layer is lowered. .
When the content of ethylene is more than 19 mol%,
The barrier property level of the component (B) is reduced, and the gas barrier properties are not only inferior to those in the case where the ethylene content is 19 mol% or less over the entire humidity range, but also a special solvent such as an alcohol / water mixed solvent is used as a solvent. Therefore, there is a problem that the solution stability when the component (A) is added is remarkably deteriorated.

The ethylene content of the PVA polymer of the present invention was determined by proton NMR of ethylene-containing polyvinyl ester which is a precursor of the PVA. That is, the obtained polyvinyl ester is sufficiently purified by reprecipitation with n-hexane / acetone three times or more, and then dried under reduced pressure at 80 ° C. for 3 times.
After a period of days, polyvinyl esters were prepared for analysis. The polymer was dissolved in DMSO-D6 and measured at 80 ° C. using 500 MHz proton NMR (JEOLX-500). Peaks derived from the main chain methine of the vinyl ester (4.7 to 5.2 ppm) and peaks derived from ethylene, the vinyl ester and the main chain methylene of the third component (0.
8 to 1.6 ppm) to calculate the ethylene content.

The viscosity-average degree of polymerization (hereinafter abbreviated as polymerization degree) of the PVA polymer of the present invention is from 200 to 2,000, preferably from 220 to 1,800, more preferably from 240 to 1600, particularly preferably from 250 to 1500. . If the degree of polymerization is less than 200, the workability in the production of the coat layer is reduced, and not only a satisfactory product is not obtained, but also the obtained product has low mechanical strength and is liable to cause problems such as cracks. If the degree of polymerization exceeds 2,000, the solution viscosity at the time of processing becomes high, so that workability and workability deteriorate, and at the same time, problems such as pinholes in products tend to occur.

The degree of polymerization (P) of the PVA polymer is determined according to JIS.
-Measured according to K6726. That is, after the PVA-based polymer is re-saponified and purified, the intrinsic viscosity [η] measured in water at 30 ° C. is determined by the following equation. P = ([η] × 103 / 8.29) × (1 / 0.62)

The degree of saponification of the PVA polymer of the present invention is 80.
It must be ~ 99.99 mol%. 84-99.
9 mol% is preferable, 87 to 99.7 mol% is more preferable, and 90 to 99.5 mol% is particularly preferable. If the degree of saponification is less than 80 mol%, the crystallinity of the PVA-based polymer is extremely reduced, and the high gas barrier properties and water vapor barrier properties intended by the present invention cannot be obtained. On the other hand, the degree of saponification is 99.9.
PVA-based polymers larger than 9 mol% cannot be produced stably, and film formation cannot be carried out stably.

The content of the carboxylic acid and lactone ring of the PVA polymer of the present invention is not particularly limited.
It is preferably in the range of 0.020 to 0.40 mol%, more preferably 0.022 to 0.37 mol%,
024 to 0.33 mol% is particularly preferred, and 0.025 to 0.35 mol%.
0.30 mol% is most preferred. The carboxylic acid in the present invention includes an alkali metal salt thereof, and examples of the alkali metal include potassium and sodium. When the content of the carboxylic acid and the lactone ring is small, the viscosity stability of the aqueous solution at a low temperature and the viscosity stability of the high-concentration aqueous solution may be reduced, while the content of the carboxylic acid and the lactone ring is 0.40 mol. %, The affinity with water is increased, so that the gas barrier property and the water vapor barrier property in a high humidity environment may be deteriorated.

Further, when the PVA-based polymer of the present invention has a carboxylic acid and lactone ring content satisfying the following formula, the effect of the present invention is remarkably increased, which is preferable. −1.94 × 10-5 × P + 0.044 ≦ content ≦ −1.39 × 10-4 × P
+0.42 (Here, the content (unit: mol%) represents the content of the carboxylic acid and lactone rings, and P represents the viscosity average degree of polymerization of the vinyl alcohol polymer.)

As a method for producing a PVA polymer having a specific amount of ethylene units and having a carboxylic acid and a lactone ring, a vinyl ester monomer such as vinyl acetate and a monomer having the ability to form a carboxylic acid and a lactone ring are used. A method of saponifying a vinyl ester polymer obtained by copolymerization with a monomer in an alcohol or dimethyl sulfoxide solution, in the presence of a thiol compound containing a carboxylic acid such as mercaptoacetic acid or 3-mercaptopropionic acid , A method of saponifying a vinyl ester monomer after polymerizing it.When polymerizing a vinyl ester monomer such as vinyl acetate, the vinyl ester monomer and the alkyl group of the vinyl ester polymer are A method of causing a chain transfer reaction and saponifying after obtaining a hyperbranched vinyl ester polymer, with an epoxy group Of saponification after reacting a copolymer of a monomer and a vinyl ester monomer with a thiol compound having a carboxyl group, and a method of acetalizing PVA with an aldehyde having a carboxyl group. Can be

The vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate. Etc., and among them, P
From the viewpoint of obtaining VA, vinyl acetate is preferred. Examples of the monomer having an ability to form a carboxylic acid and a lactone ring of the present invention include a monomer having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride or itaconic anhydride, acrylic acid And its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylates such as i-propyl acrylate, methacrylic acid and its salts, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, Methacrylic acid esters such as i-propyl methacrylate; acrylamide derivatives such as acrylamide, N-methylacrylamide and N-ethylacrylamide; and methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide. .

The content of the carboxylic acid and lactone rings of the PVA polymer can be determined from the peak of proton NMR. After complete saponification to a degree of saponification of 99.95 mol% or more, washing with methanol was sufficient, followed by drying at 90 ° C. under reduced pressure for 2 days to prepare PVA for analysis. In the above case, the prepared analytical PVA is dissolved in DMSO-D6,
500 MHz proton NMR (JEOL GX-50
0) at 60 ° C. The monomers of acrylic acid, acrylic esters, acrylamide and acrylamide derivatives have peaks (2.0 p.
pm), the monomer (methacrylic acid ester, methacrylic acid ester, acrylamide and methacrylamide derivative) has a peak (0.pm) derived from a methyl group directly connected to the main chain.
6 to 1.1 ppm), and the content was calculated by an ordinary method. A monomer having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, or the like can be obtained by adding the prepared analytical PVA to DMSO.
-After dissolving in D6, add a few drops of trifluoroacetic acid and add 500M
It measured at 60 degreeC using the proton NMR (JEOL GX-500) of Hz. For quantification, the content was calculated by an ordinary method using the methine peak of the lactone ring attributed to 4.6 to 5.2 ppm. In the cases of and, the content was calculated using the peak (2.8 ppm) derived from methylene bonded to the sulfur atom. In the case of, the created analytical P
VA was dissolved in methanol-D4 / D2O = 2/8, and 5
00 MHz proton NMR (JEOL GX-50
0) at 80 ° C. The peak derived from methylene of the terminal carboxylic acid or an alkali metal salt thereof (the following structural formulas (I) and (II)) belongs to 2.2 ppm (integral value A) and 2.3 ppm (integral value B). , The methylene-derived peak of the terminal lactone ring is represented by the following structural formula (I
II)｝ belongs to 2.6 ppm (integral value C), the peak derived from methine in the vinyl alcohol unit belongs to 3.5 to 4.15 ppm (integral value D), and the content of carboxylic acid and lactone ring is calculated by the following formula. calculate. Here, △ indicates the amount of modification (mol%).

Content (mol%) of carboxylic acid and lactone rings = 50 × (A + B + C) × (100− △) / (10
0 × D)

[0035]

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[0036]

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[0037]

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In the case of (1), the prepared analysis PVA is
It was dissolved in O-D6 and proton NMR at 500 MHz (J
EOL GX-500) at 60 ° C. Peak 4.8 to 5.2 derived from methine in the acetal moiety
The content was calculated by a conventional method using ppm {the following structural formula (IV)}.

[0039]

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As long as the effects of the present invention are not impaired,
It may contain a monomer unit other than a vinyl alcohol unit, an ethylene, a vinyl ester unit, and a monomer capable of forming a carboxylic acid and a lactone ring described above.
Such units include propylene, 1-butene, isobutene, α-olefins such as 1-hexene, acrylamide, N-methylacrylamide, acrylamide derivatives such as N-ethylacrylamide, methacrylamide, N-methylmethacrylamide, Methacrylamide derivatives such as N-ethyl methacrylamide, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, vinyl ethers such as n-butyl vinyl ether, ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1, Hydroxy group-containing vinyl ethers such as 4-butanediol vinyl ether, allyl acetate,
Allyl ethers such as propyl allyl ether, butyl allyl ether and hexyl allyl ether, monomers having an oxyalkylene group, vinyl silyls such as vinyl trimethoxysilane, isopropenyl acetate, 3-butene-
Hydroxy such as 1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, and 3-methyl-3-buten-1-ol; Group-containing α-olefins, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2
Monomers having a sulfonic acid group derived from acrylamide-2-methylpropanesulfonic acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine,
N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine,
Examples include monomers having a cationic group derived from allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine and the like. The content of these monomers is
The amount is usually 20 mol% or less, and preferably 10 mol% or less, although it varies depending on the purpose and use of the composition.

The PVA-based polymer of the present invention can be prepared by reacting a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as 2-mercaptoethanol or n-dodecylmercapto except for the above-mentioned carboxylic acid-containing mercaptan. To
A terminal-modified product obtained by copolymerizing with ethylene and saponifying it may be used.

Examples of the method for copolymerizing the vinyl ester monomer with ethylene include known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or in a solvent such as an alcohol is usually employed. Examples of the alcohol used as a solvent during the solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. Examples of the initiator used for the copolymerization include α, α′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), benzoyl peroxide, and n-propyl peroxycarbonate And known initiators such as azo initiators and peroxide initiators. The polymerization temperature is not particularly limited, but is suitably in the range of 0 ° C to 150 ° C.

The melting point of the PVA polymer of the present invention is preferably 160 or more, more preferably 170 ° C. or more, and
The above is more preferable, and 180 ° C. or higher is particularly preferable. If the melting point is lower than 160 ° C., the crystallinity of the PVA polymer tends to decrease, and the water resistance and the gas and water vapor barrier properties tend to decrease.

The melting point of the PVA-based polymer was raised to 250 ° C. in nitrogen at a heating rate of 10 ° C./min, cooled to room temperature using a DSC, and then to 250 ° C. again at a heating rate of 10 ° C./min. It means the temperature at the peak top of the endothermic peak indicating the melting point of the PVA-based polymer when the temperature is raised.

The PVA polymer used in the present invention preferably contains an alkali metal. The content ratio of the alkali metal (C) to 100 parts by weight of the PVA-based polymer (B) is such that the alkali metal (C) is 0.0% in terms of sodium.
003 to 1 part by weight, preferably 0.0003 to 0.8 part by weight, more preferably 0.0005 to 0.6 part by weight, and particularly preferably 0.0005 to 0.5 part by weight. Examples of the alkali metal include potassium and sodium, which are mainly salts of lower fatty acids such as acetic acid and propionic acid, and PVA containing a specific amount of the carboxylic acid of the present invention.
It may be present as a salt of a carboxylic acid and a salt of a sulfonic acid contained in a comonomer, and even in an additive. When the content ratio of the alkali metal is less than 0.0003 parts by weight, the water solubility of the PVA tends to decrease when the PVA-based polymer is used as an aqueous solution. On the other hand, if it exceeds 1 part by weight, the barrier properties against gas and water vapor tend to be reduced, probably because the crystallinity of the PVA-based polymer is reduced. Hereinafter, in the present invention, unless otherwise specified, the PVA-based polymer (B) refers to a state containing an alkali metal (C).

In the present invention, the method of adding a specific amount of the alkali metal (C) to the PVA-based polymer is not particularly limited, and a method of once adding a compound containing an alkali metal after obtaining the PVA-based polymer, When saponifying a vinyl ester polymer in a solvent, a PVA-based polymer obtained by blending an alkali metal into a PVA-based polymer by using an alkali metal-containing alkaline material as a saponification catalyst and saponifying the polymer. Is washed with a washing solution to control the alkali metal contained in the PVA-based polymer. The latter is more preferred.
The content of the alkali metal can be determined by an atomic absorption method.

As a method for producing the specific ethylene-containing PVA polymer of the present invention, a vinyl ester polymer obtained by copolymerizing ethylene and the above-mentioned vinyl ester monomer is prepared by using an alcohol or dimethyl sulfoxide. Known methods such as a method of saponification in a solution can be used.

The alkaline substance used as the saponification catalyst includes potassium hydroxide or sodium hydroxide. The molar ratio of the alkaline substance used in the saponification catalyst is preferably from 0.004 to 0.5, particularly preferably from 0.005 to 0.05, based on the vinyl acetate unit. The saponification catalyst may be added all at once in the early stage of the saponification reaction, or may be additionally added during the saponification reaction. Examples of the solvent for the saponification reaction include methanol, methyl acetate, diethylsulfoxide, dimethylformamide and the like. Of these solvents, methanol is preferred, and the water content is 0.1%.
Methanol controlled at 001 to 1% by weight is more preferable, methanol controlled at a water content of 0.003 to 0.9% by weight is more preferable, and methanol controlled at a water content of 0.005 to 0.8% by weight is preferable. Particularly preferred. The temperature of the saponification reaction is preferably 5 to 80 ° C, more preferably 20 to 70 ° C.
Is more preferred. The saponification time is preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours. Known methods such as a batch method and a continuous method can be applied as the saponification method.

As the cleaning solution, methanol, acetone,
Examples thereof include methyl acetate, acetate, hexane, and water. Among them, methanol, methyl acetate, and water alone or a mixed solution are more preferable. The amount of the cleaning liquid is set so as to satisfy the content ratio of the alkali metal (C), and usually, 30 to 10 parts by weight based on 100 parts by weight of PVA.
000 parts by weight are preferred, and 50 to 3000 parts by weight are more preferred. The washing temperature is preferably 5 to 80C,
20-70 degreeC is more preferable. The washing time is preferably from 20 minutes to 10 hours, more preferably from 1 hour to 6 hours. Known methods such as a batch method and an AC cleaning method can be applied as the cleaning method.

In the present invention, the mixing ratio of the component (A) and the component (B) is important in terms of obtaining an effective gas blocking effect. That is, the weight ratio of component (A) / component (B) is preferably in the range of 0.5 / 99.5 to 70/30, and particularly preferably 5/95 to 50/50. By adopting these compounding ratios, besides the original gas barrier effect, the properties such as the transparency and slip property of the coating film, the antistatic property, and the durability of the coating layer are all improved. Is done.

When the mixing ratio is less than 0.5 / 99.5, the effect of adding the component (A) is not sufficient,
In the case where the ratio exceeds 2, the interaction between the component (B) and the inorganic substance is strong, so that the compounded composition sharply thickens, gelation is caused, the coating film layer becomes extremely brittle, and cracks are caused. It is easy to cause a decrease in gas barrier properties and the like, and it is difficult to exhibit a substantially effective effect.

As a compounding method for obtaining a composition comprising the components (A) and (B), any known mixing method can be used, but the mixing of the components (A) and (B) can be performed. To obtain the effect most effectively, the component (A) is preliminarily swelled in water by interlayer hydration, and then the component (B) or its solution or the production process of the component (B), ie, polymerization A method of adding and mixing at an arbitrary stage in the process of polymerizing, such as a reaction, is preferably used. Above all, in order to obtain a coating liquid composition having excellent transparency and stability, a method in which both the component (A) and the component (B) are sufficiently diluted and then mixed while stirring can be particularly preferably used.

The composition comprising the components (A) and (B) may be used alone, but can be used in combination with other resins which can be mixed as long as the object of the present invention is not impaired. As such a resin, for example, non-copolymerized polyvinyl alcohol or polyacrylic acid or esters thereof, polyester-based resin, polyurethane-based resin,
Examples include polyamide-based resins, epoxy resins, melamine resins, and many others.

It is also possible to incorporate a crosslinking agent comprising a high-molecular or low-molecular compound having a reactive group capable of reacting with these resin compositions into these resin compositions. In general, the incorporation of a crosslinking agent often improves the durability and adhesion of the coating layer. As the cross-linking agent, conventionally known ones can be arbitrarily used, but from the viewpoint of gas blocking effect, it is more preferable to use a compound having a low molecular weight as much as possible in order to minimize the molecular gap of the coating layer. Preferred examples of such a compound include boric acid compounds such as boric acid, and low-molecular polyaldehydes such as glutaraldehyde. It is also possible to include a carboxylic acid component in the modified polymer molecule and perform ionic crosslinking with a polyvalent metal.

The resin composition of the present invention is usually dissolved, dispersed or emulsified in water or an aqueous medium mixed with any water-miscible organic solvent (eg, lower alcohols such as methyl alcohol and isopropyl alcohol). Used as The composition of the aqueous medium is not particularly limited, but it is more preferable to use a water / alcohol-based mixed solvent from the viewpoints of coatability, drying properties, etc. as long as the solubility and dispersibility of the resin are not impaired. .

As a method for forming a layer of such a composition on the base film, any method such as a solution coating method and a laminating method can be used. In particular, an aqueous solution or an aqueous dispersion of the resin composition can be used. The coating method of applying the aqueous resin composition of Example 1 to the surface of the base film, drying and, if necessary, heat-treating is effectively used. The coating liquid composed of such an aqueous composition has little change with time,
Very little aggregation / precipitation. Therefore, a coated plastic film having stable performance can be obtained. As a coating method, a usual method such as a roll coating method such as gravure or reverse, a doctor knife method, an air knife, a nozzle coating method, a bar coating method, and a coating method combining these can be used.

The thickness of the coating layer varies depending on the base film, the desired level, and the like. Usually, the thickness after drying is 10 μm or less, preferably 5 μm or less, and most preferably 3 μm or less. It is preferable in terms of properties, economy and the like. There is no particular lower limit, but if it is 0.05 μm or less, it is difficult to obtain a substantially sufficient effect.

The conditions for drying and heat treatment during coating are as follows:
Although it depends on the coating thickness and the conditions of the apparatus, it is usually preferable to select from the range of about 70 to 170 ° C. Drying. The heat treatment may be performed in one step, or the drying step and the heat treatment step may be performed in separate steps. If performed in a separate process, the drying
It is preferable that the temperature is 70 to 90 ° C., the temperature of the heat treatment step is 90 to 170 ° C., and the time is 5 seconds to 10 minutes.

It is preferred that the base film is subjected to a corona treatment or other surface activation treatment or an anchor treatment using a known anchor treatment material before forming the coating layer. In addition, antistatic agents and slip agents in the composition to be coated,
The addition of various known inorganic and organic additives such as an anti-blocking agent is optional as long as the object of the present invention is not hindered.

[0060]

The present invention will be described in more detail with reference to the following examples. In addition, the density | concentration display in an example is a weight reference | standard unless there is particular notice, and evaluated by the following method.

[Oxygen permeability] MODERN CONTR
OLS INC. MOCONOX Oxygen Permeation Analyzer
-Measured according to the method described in JIS K7126 (isobaric method) under the conditions of 20 ° C., 65% RH and 20 ° C., 100% RH using Model TRAN2 / 20. The oxygen permeability referred to in the present invention is a value obtained by removing the contribution of the base layer by calculation and converting the contribution of the coat layer into an oxygen transmission amount at a film thickness of 2 μm (ml · 2 μm / m ² ···). day ・
atm). Further, the oxygen transmission amount V (CC / m ² · day · atm) of the entire coated film is 1 / V = 1 / VB + 1 / VC VB: The oxygen transmission amount (CC / m ² · day · atm) of the base film VC : Calculated from the oxygen permeation amount (CC / m ² · day · atm) of the coat layer.

[Haze] A part of the sample film was cut out and coated with silicone oil, and HR manufactured by Murakami Color Research Laboratory was used.
The haze value was measured using -100 according to ASTM D1003-61.

[Coefficient of Friction] Based on ASTM-D-1894, the coefficient of friction was determined based on the coefficient of static friction between the coating layer surface and the substrate film surface (back surface).

[Coating Liquid Stability] The prepared coating liquid was stored in a closed state at room temperature for 3 days, and the presence or absence of formation of aggregation, precipitation, etc. was visually observed.

Example 1 (Preparation of Coating Solution) [Preparation of Component A]
w% of synthetic hectorite [Si ₈ (Mg _5.34 Li
_0.66 ) O ₂₀ (OH) ₄ ] Na ⁺ _0.66 ( ^Laponite XLS manufactured by Nippon Silica Kogyo Co., Ltd.) was added to water with stirring to ^obtain a 10% swollen water-absorbing sol, which was used as the component (A).

[Preparation of ethylene-modified PVA (component B)]
In a 250-L pressure reactor equipped with a stirrer, a nitrogen inlet, an ethylene inlet, an initiator addition port, and a delay solution addition port, 107.2 kg of vinyl acetate, 42.8 kg of methanol and 15 g of maleic anhydride were charged, and the temperature was raised to 60 ° C. After heating 3
The system was replaced with nitrogen by bubbling nitrogen for 0 minutes. Then, ethylene was introduced and charged so that the pressure in the reaction tank was 5.9 kg / cm2. 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) as an initiator
A solution of (AMV) in methanol was prepared at a concentration of 2.8 g / L, followed by bubbling with nitrogen gas and purging with nitrogen. A 5% solution of maleic anhydride dissolved in methanol was prepared as a delay solution, followed by bubbling with nitrogen gas and purging with nitrogen. After adjusting the inside temperature of the polymerization tank to 60 ° C., 204 ml of the initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to maintain the reaction vessel pressure at 5.9 kg / cm 2 and the polymerization temperature at 60 ° C., AMV was used at 640 ml / hr using the above initiator solution, and the delay solution was used at the same time. The polymerization was carried out by continuously adding maleic anhydride while keeping the ratio of vinyl acetate and maleic anhydride in the polymerization system constant.
After 4 hours, when the polymerization rate reached 30%, the polymerization was stopped by cooling. At this point, the total amount of the maleic anhydride delay solution added by delay was 1400 ml. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled through to completely remove ethylene. Next, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate. To 333 g of methanol solution of polyvinyl acetate (100 g of polyvinyl acetate in the solution) prepared by adding methanol to the obtained polyvinyl acetate solution so as to have a concentration of 30%, 46.5 g (polyvinyl acetate in polyvinyl acetate) was added. Molar ratio (MR) to vinyl acetate unit
(0.10) of an alkaline solution (a 10% methanol solution of NaOH) was added for saponification. About 1 minute after the addition of the alkali, the gelled system was pulverized with a pulverizer,
After letting it saponify for 1 hour at room temperature, methyl acetate 1
000 g was added to neutralize the remaining alkali. After confirming the completion of the neutralization using a phenolphthalein indicator, methanol 1000 was added to the white solid PVA obtained by filtration.
g was added and washed at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal dewatering was left in a dryer at 70 ° C. for 2 days to obtain dry ethylene-modified PVA. When the obtained ethylene-modified PVA resin was analyzed, the degree of saponification was 98.5 mol%, and the content of the alkali metal was 0.36 parts by weight with respect to 100 parts by weight of the modified PVA.
The ethylene content was 7 mol%, the average degree of polymerization was 1,000, the carboxylic acid and lactone ring content was 0.246 mol%,
The amount of 2-glycol bond was 1.61 mol%, the content of three hydroxyl groups was 87%, and the melting point was 210 ° C. Met.

The obtained ethylene-modified PVA resin was dissolved in warm water so as to have a solid content of 2%, and then cooled to room temperature.
The ingredients.

The component (A) and the component (B) are mixed so that the respective solid fractions are (A) / (B) = 30/70, and an aqueous solution having a solid content of 2% is prepared. It was a working liquid.

(Preparation of Coated Film) The obtained coating solution was applied using a bar coater on the corona-treated surface of a biaxially stretched polyethylene terephthalate film having a thickness of 25 μm which had been subjected to corona discharge treatment, and dried at 80 ° C. for 5 minutes. Later, 150
Heat treatment was performed at 5 ° C. for 5 minutes to obtain a coated film. The dry thickness of the coating layer was 4.0 μm. Table 1 shows the evaluation results of the obtained films.

Example 2 As a base film, a corona discharge-treated film having a thickness of 20 μm was used.
And a coated film was obtained in the same manner as in Example 1 except that the heat treatment temperature was set to 100 ° C. Table 1 shows the evaluation results of the obtained films.

Example 3 The polymerization conditions of ethylene-modified PVA were changed and the degree of saponification was 9
7 mol%, sodium content is 0.25 parts by weight based on 100 parts by weight of modified PVA, ethylene content is 3 mol%, average polymerization degree is 500, carboxylic acid and lactone ring content is 0.277 mol%, 1 , 2-glycol bond amount 1.6
An ethylene-modified PVA having a melting point of 207 ° C. and a mole of 6% by mole and a content of three hydroxyl groups of 88% was obtained. A coated film was obtained in exactly the same manner as in Example 1 except that this was used as the component (B).
Table 1 shows the evaluation results of the obtained films.

Example 4 The polymerization conditions of ethylene-modified PVA were changed and the degree of saponification was 9
8 mol%, sodium content is 0.01 part by weight based on 100 parts by weight of the modified PVA, ethylene content is 13 mol%, average degree of polymerization is 300, carboxylic acid and lactone ring content is 0.267 mol%, , 2-glycol binding amount
46 mol%, content of three hydroxyl groups 78%, melting point 196 ° C.
Of ethylene-modified PVA was obtained. A coated film was obtained in exactly the same manner as in Example 1 except that this was used as the component (B). Table 1 shows the evaluation results of the obtained films.

Example 5 Except that the ratio of component (A) to component (B) was changed so that component (A) / component (B) = 5/95, the procedure was exactly the same as in Example 1. A coated film was obtained. Table 1 shows the evaluation results of the obtained films.

Example 6 Example 6 was repeated except that the ratio of component (A) to component (B) was changed so that component (A) / component (B) was 50/50 and the solid content was 1.5%. A coated film was obtained in exactly the same manner as in Example 1. Table 1 shows the evaluation results of the obtained films.

Comparative Example 1 Evaluation was made using only the base polyester film without coating the resin composition for a coating layer. Table 1 shows the results.
The oxygen permeability of the base material alone was 40 CC / m2 at 65% RH.
It was 43 CC / m 2 · day · atm at day / atm and 85% RH (thickness conversion was not performed).

Comparative Example 2 A coated film was prepared in the same manner as in Example 1 except that polyvinyl alcohol (Kuraray Povar (TM) 110 manufactured by Kuraray Co., Ltd.) was used as the resin composition for a coating layer. Obtained. Table 1 shows the evaluation results of the obtained films.

Comparative Example 3 As the resin composition for the coating layer, an ethylene-modified PVA resin having an ethylene content of 27 mol% (Eval (TM) EP-L101 manufactured by Kuraray Co., Ltd.) was used.
A coated film was obtained in exactly the same manner as in Example 1 except that n-propanol = 1/1 liquid was used. Table 1 shows the evaluation results of the obtained films.

Comparative Example 4 A coated film was obtained in exactly the same manner as in Example 1, except that the coating layer was formed only with the component (A) without the component (B). Table 1 shows the evaluation results of the obtained films.

Comparative Example 5 A coated polyester film was obtained in exactly the same manner as in Example 1, except that the coating layer was formed only with the component (B) without the component (A). Table 1 shows the evaluation results of the obtained films.

Comparative Example 6 A coated film was obtained in the same manner as in Example 1 except that a non-swellable spherical silica colloid sol was used instead of the component (A) in Example 1. Table 1 shows the evaluation results of the obtained films.

[0081]

[Table 1]

[0082]

As described above, the coated film of the present invention is excellent in transparency, gas barrier properties, especially gas barrier properties in a high humidity environment, and further has excellent slip properties. . Further, according to the method of the present invention, the coating liquid has little change with time, and aggregation and precipitation are little generated, so that not only coating is easy but also a coated plastic film having stable performance can be obtained. it can.

Continued on front page F-term (reference) 4F006 AA02 AA12 AA15 AA18 AA20 AA22 AA32 AA35 AA36 AA38 AA39 AA40 AB20 AB76 BA00 BA05 CA07 DA03 DA04 EA05 4F100 AA03B AK01A AK21B AK42A BA02 DJ04 J02B02 J04B03 J02B04 JH2J04A DJ006 GH00 HA03 HA06

Claims (4)

[Claims] 1. A swellable layered silicate compound (A) and an ethylene unit are contained in at least one surface of a base film made of a thermoplastic resin in an amount of 2 to 19 mol%, the degree of polymerization is 200 to 2000, and the degree of saponification is 1. Is 80.0-99.
A coated plastic film having at least one layer of a composition comprising 99 mol% of a vinyl alcohol polymer (B). 2. The coated plastic film according to claim 1, wherein the swellable layered silicate compound is a colloidal layered silicate compound. 3. The coated plastic film according to claim 1, wherein the swellable layered silicate compound is synthetic hectorite. 4. A swellable layered silicate compound (A) and ethylene units are contained in at least one surface of a base film made of a thermoplastic resin in an amount of 2 to 19 mol%, the degree of polymerization is 200 to 2,000, and the degree of saponification is 4. Is 80.0-99.
A method for producing a coated plastic film, comprising coating and drying an aqueous composition containing 99 mol% of a vinyl alcohol polymer (B).