JP3131505B2 - Multi-layer structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer structure in which an aqueous dispersion of a saponified ethylene-vinyl ester copolymer is applied to a thermoplastic substrate.

[0002]

2. Description of the Related Art Ethylene-vinyl ester copolymers, especially ethylene-vinyl alcohol copolymers (hereinafter abbreviated as EVOH) obtained by saponifying ethylene-vinyl acetate copolymers, have a gas barrier property against oxygen and the like and an oil-resistant property. Due to its excellent chemical resistance, it is widely used as a protective coating material for packaging materials, plastic molded products, metal surfaces, paper, wood and the like.

[0003] In particular, high gas barrier properties are required for films, sheets, laminates, hollow containers, and the like for food packaging, for which it is important to prevent oxidation of the contents or to maintain the flavor. PVC wallpaper made of soft vinyl chloride,
For PVC leather, sheets and the like, a coating material for preventing bleeding of the plasticizer is required. Therefore, it has been widely practiced to meet these required properties to a high degree by providing EVOH having excellent gas barrier properties, fragrance retention properties and oil / chemical resistance in the inner layer, the outer layer or the intermediate layer.

In general, as a method for forming an EVOH layer, a method by melt extrusion or injection molding, a method of laminating an EVOH film, and the like are widely practiced.
On the other hand, a method has been proposed in which an EVOH solution or an aqueous dispersion is applied and dried. This method attracts attention because a relatively thin film can be formed, and a film having a complicated shape such as a hollow container can be easily formed.

However, in the method of applying an EVOH solution, it is basically difficult to use a solution having a high concentration because of viscosity, and the solvent is an organic solvent such as dimethyl sulfoxide or a mixed solvent of a large amount of alcohol and water. In the formation process, there is a problem that the working environment is deteriorated due to the volatilization of the organic solvent and equipment for recovering the organic solvent is required. On the other hand, the method of applying the EVOH aqueous dispersion is advantageous in terms of working environment and economy because the solvent is water.

[0006] As an aqueous dispersion of EVOH, conventional EOH
VOH is emulsified and dispersed in the presence of an ordinary surfactant or an ordinary polymer colloid, for example, polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, etc.
-101844 and JP-A-56-61430. However, according to studies by the present inventors, the aqueous dispersion of EVOH obtained by these known methods has insufficient dispersion stability, and EVOH is applied to a film formed by coating and drying a thermoplastic substrate. Since a large number of fish eyes of particle aggregates were generated, a multilayer structure having good appearance was not obtained.

Japanese Patent Application Laid-Open No. 54-101844 discloses a so-called randomly copolymerized random copolymer obtained by terpolymerizing a vinyl monomer such as acrylic acid or acrylamide with ethylene-vinyl acetate and saponifying it. Combined EVO
H itself has been shown to disperse a conventional surfactant as a dispersion stabilizer.

However, according to the studies by the present inventors, no improvement in dispersion stability was observed for EVOH by simple ternary random copolymerization, and a practical aqueous dispersion could not be obtained. In the case where acrylic acid having an ionic group is copolymerized, the dispersion stability is improved by the ionic group, but since the ionic group is randomly contained,
If the content is not increased, the dispersion stability cannot be sufficiently achieved, and if the content is increased, the disorder of the EVOH structure becomes large, the crystallinity is reduced, and the gas barrier property is significantly reduced. Therefore, a practical multilayer structure cannot be obtained.

[0009]

SUMMARY OF THE INVENTION The present invention relates to an appearance which is obtained by applying a specific EVOH aqueous dispersion having excellent dispersion stability to a thermoplastic substrate and drying it, and having an excellent barrier property and having no fish eyes. It relates to a good multilayer structure.

[0010]

According to the present invention, the multilayer structure comprises a saponified ethylene-vinyl ester copolymer having an ionic group as a dispersion stabilizer and an ethylene content of 15 to 65 mol%.
An aqueous dispersion having a saponified ethylene-vinyl ester copolymer as a dispersoid, and a saponified ethylene-vinyl ester copolymer having an ethylene content of 15 to 65 mol% having an ionic group at the terminal and being insoluble in water at ordinary temperature. Aqueous dispersion as a dispersoid, aqueous solution containing a saponified ethylene-vinyl ester copolymer having an ethylene content of 15 to 65 mol%, in which a sulfonic acid group or a salt thereof is randomly introduced and insoluble in water at ordinary temperature, It is obtained by applying and drying at least one aqueous dispersion selected from dispersions on a thermoplastic substrate.

The aqueous dispersion of EVOH used in the present invention has good dispersion stability and hardly agglomerates particles during storage or use. Therefore, a thin homogeneous film free of fish eyes can be formed on a thermoplastic substrate. It is formed on top and develops high barrier properties.

An aqueous dispersion using EVOH having an ionic group as a dispersion stabilizer and EVOH as a dispersoid will be specifically described below. The ionic group of EVOH having an ionic group used as a dispersion stabilizer includes a group showing ionicity in water, that is, an anionic group, a cationic group, and an amphoteric group. Anionic groups are more preferred from the viewpoint of the dispersion stabilizing effect.

Examples of the anionic group include sulfonic acid or a salt thereof, carboxylic acid or a salt thereof, phosphoric acid or a salt thereof,
Examples include groups such as a sulfate ester or a salt thereof, and these acids and salts may be contained at the same time. Sulfonic acid or carboxylic acid or a salt thereof is preferable in terms of excellent dispersion stabilizing effect, and sulfonic acid or a salt thereof is particularly preferable.

Examples of the cationic group include amines and salts thereof, quaternary ammonium salts, phosphonium salts, and sulfonium salts. In particular, quaternary ammonium salts are preferred because of their high dispersion stabilizing effect. Examples of the amphoteric group include aminocarboxylates (betaine type), aminosulfonates (sulfobetaine type), and aminosulfate salts (sulfate-betaine type).

The content of the ionic group is appropriately selected within a range having a dispersion stabilizing effect.
It is preferably 0.05 to 50 mol% based on the VOH component unit. More preferably 0.1 to 30 mol%, especially 0.2
-10 mol%, more preferably 0.2-10 mol%. If it is less than 0.05 mol%, the dispersion stabilizing effect is small,
If it exceeds 50 mol%, the water resistance and gas barrier properties of the film obtained by applying and drying the aqueous dispersion become poor,
Not practical. The ion-modified EVOH may contain another unit containing no ionic group as long as the dispersion stabilizing effect is not significantly impaired.

The composition of the EVOH component in the ion-modified EVOH is preferably at least ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% (the saponification degree in the present invention indicates the saponification degree of the vinyl ester component). . A preferred range of the ethylene content is 12 mol% or more, more preferably 1 mol% or more.
It is at least 5 mol%, and more preferably at least 20 mol%. The upper limit is preferably at most 65 mol%, more preferably at most 60 mol%. The preferred degree of saponification is 9
It is 0 mol% or more, and more preferably 95 mol% or more.

The degree of polymerization of the ion-modified EVOH is not particularly limited, but is preferably 100 or more from the viewpoint of the dispersion stabilizing effect. The upper limit of the degree of polymerization is not particularly limited, but a too large one is usually used in an amount of 2,000 or less because the solution viscosity is high and the dispersibility is lowered. Here, the polymerization degree of the ion-modified EVOH is determined from the intrinsic viscosity measured at 30 ° C. in a water / phenol-based mixed solvent (weight ratio 15/85) containing 1 mol / l ammonium thiocyanate.

Regarding the structure of the ion-modified EVOH, those in which an ionic group is randomly introduced are preferably used, and there is no particular limitation on the production method.

For example, a method in which a monomer containing an ionic group is radically copolymerized with ethylene and a vinyl ester, and a vinyl ester unit in the obtained copolymer is saponified to be converted into a vinyl alcohol. A method in which an ionic group-containing component is introduced through an addition reaction of an ionic group-containing component, or a method in which an ionic group-containing component is added to an ethylene-vinyl ester copolymer, followed by saponification of a vinyl ester unit in the copolymer to form a vinyl alcohol unit. And the like. The polymerization, saponification, addition reaction and the like can be carried out by a known method.

The vinyl ester can be copolymerized with ethylene such as vinyl formate, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl trifluoroacetate, vinyl pivalate, and the like. Although a monomer which can be converted into a compound can be used, vinyl acetate is particularly preferable.

As the ionic group-containing monomer copolymerized with ethylene and vinyl ester, those capable of radical homopolymerization or radical copolymerization having an ionic group or a group convertible to ion can be used. An example is shown below.

Anionic group-containing monomer The sulfonic acid anion group-containing monomer includes 2-
(Meth) acrylamide sulfonate monomers such as sodium (meth) acrylamide-2-methylpropanesulfonate, styrene sulfonate monomers such as potassium styrenesulfonate, and allyl sulfonates such as sodium allyl sulfonate Monomers, vinyl sulfonates, ammonium salts thereof, and acid monomers thereof. Esters of these sulfonic acids can also be used by converting the esters into their salts or acids after polymerization.

Examples of the carboxylic acid anionic group-containing monomer include mono-, di-, and polycarboxylic acid-based vinyl monomers such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, and fumaric acid, or alkali metal salts and ammonium salts thereof. And the like. These esters can also be used because the ester group can be converted into a salt after polymerization.

A cationic group-containing monomer; an amino group-containing (meth) acrylamide monomer such as aminopropylacrylamide or methacrylamide; an amino group-containing (meth) acrylate such as aminoethyl acrylate or methacrylate; or a salt thereof. The polymerizability is also favorable and preferable. Particularly, the quaternary salt is preferable because the coloring of the polymer is small. For example, trimethylacrylamidopropyl ammonium chloride, triethyl methacryloyl ethyl ammonium bromide, and the like.

These monomers can be used alone or in combination. Copolymerization with other monomers is also possible as long as the dispersion stabilizing effect is not impaired.

Examples of the addition reaction to EVOH include a Michael addition reaction of an ionic group-containing vinyl monomer to its hydroxyl group, an acetalization or ketalization with an ionic group-containing aldehyde or ketone, and an ionic group-containing epoxy. Addition of a base compound, addition of a carboxylic anhydride, esterification with sulfuric acid and the like can be mentioned. In addition, introduction of a monomer having an ionic group having low radical homopolymerizability such as maleic anhydride by a radical addition reaction may be mentioned.

Further, the ethylene-vinyl ester copolymer is subjected to a radical addition reaction of an ionic group-containing monomer having low radical homopolymerizability such as maleic anhydride, and then saponified to convert the vinyl ester unit into vinyl alcohol. It is also possible to manufacture.

The dispersoid EVOH is obtained by copolymerizing and saponifying ethylene with the vinyl ester, particularly vinyl acetate, and it is necessary that the ethylene content is in the range of 15 to 65 mol%. If the ethylene content is less than 15 mol%, the stability of the aqueous dispersion becomes poor, and 65 mol%
If it exceeds, the gas barrier property becomes poor and is not practical. From both aspects of aqueous dispersion stability and gas barrier properties,
A more preferred range for the ethylene content is 20-55 mol%. The saponification degree is preferably at least 90 mol%. If it is less than 90 mol%, the gas barrier property is insufficient, preferably 95 mol%, more preferably 97 mol% or more. If necessary, a copolymerizable monomer other than ethylene and vinyl ester may be introduced in an amount of 5 mol% or less.

[0029] The degree of polymerization of the dispersoid EVOH is selected according to the intended use, but if it is extremely low, the strength of the formed film is unpreferably low. Usually, 400 or more, preferably 700 or more are used. The higher the degree of polymerization, the more advantageous it is to apply and use as an aqueous dispersion, and usually up to about 5,000. Here, the degree of polymerization of the dispersoid is water /
30 ° C in a phenolic mixed solvent (weight ratio 15/85)
It is determined from the intrinsic viscosity measured in the above.

The amount of the ion-modified EVOH used as a dispersion stabilizer is appropriately selected in consideration of the type and content of the ionic group, and the preferred range is 2 to 200 parts by weight per 100 parts by weight of the dispersoid EVOH. Parts, more preferably 3 to 100
Parts by weight, more preferably 5 to 50 parts by weight. If the amount is too small, the dispersion stability becomes poor, and if it is too large, the gas barrier properties of the formed film may be insufficient, which is not preferable.

The method for dispersing EVOH as a dispersoid using ion-modified EVOH as a dispersion stabilizer is not limited.
Known methods can be used.

For example, after a mixture of EVOH as a dispersoid and ion-modified EVOH as a dispersion stabilizer is dissolved in a solvent, the solution is brought into contact with water, which is a non-solvent for EVOH, under stirring to reduce the EVOH particles. 3 μm or less, preferably 2 μm
An aqueous dispersion can be obtained by precipitating as fine particles having a particle size of 1 μm or less, optimally 1 μm or less, and then removing a desired amount of the solvent. Here, the diameter of the fine particles is the number average particle diameter.

The solid content concentration of the aqueous dispersion is appropriately determined depending on the application and the like, but is 10% by weight or more, preferably 15% by weight or more, and most preferably 20% by weight or more. The upper limit of the solid content concentration is not particularly limited. However, if the concentration is too high, the storage stability of the aqueous dispersion may become slightly poor. Therefore, it is usually preferably 60% by weight or less, more preferably 50% by weight. %, Optimally up to 40% by weight.

As the solvent, for example, methyl alcohol,
Monohydric alcohols such as ethyl alcohol, propyl alcohol and butyl alcohol; dihydric alcohols such as ethylene glycol and propylene glycol;
Polyhydric alcohols, phenols, phenols such as cresol, ethylenediamine, amines such as trimethylenediamine, dimethylsulfoxide, dimethylacetamide,
N-methylpyrrolidone or the like, or a hydrate thereof may be used alone or in combination of two or more. Particularly preferred solvents are alcohol-water mixed solvents such as water-methyl alcohol, water-normal propyl alcohol, water-isopropyl alcohol and the like.

The organic solvent in the solvent can be removed by an appropriate method such as an evaporation method, an extraction method or a dialysis method. It is desirable that the degree of removal be high, but a small proportion of the organic solvent may be left in consideration of economy.

As another method, a mixture of EVOH as a dispersoid and ion-modified EVOH as a dispersion stabilizer is heated and dissolved in a solvent that dissolves at a high temperature but becomes insoluble at a low temperature, and then cools the solution. Thereby, a method of depositing and dispersing the fine particles can also be adopted. Thereafter, the aqueous dispersion can be obtained by replacing the organic solvent with water. As the solvent that dissolves at a high temperature but becomes insoluble at a low temperature, alcohols alone or a mixed solvent with water among the solvents described above can be used.

As still another method, the dispersoid EV
A solution of a mixture of OH and ion-modified EVOH, which is a dispersion stabilizer, is contacted with a non-solvent or cooled and the particles precipitated and dispersed are separated by filtration, and the particles are mixed with water in the presence of ion-modified EVOH. Can also be dispersed.

In the present invention, a suitable method for producing an aqueous dispersion includes EVOH as a dispersoid and ionic modification of a dispersion stabilizer.
VOH is dissolved in a common solvent, for example, a mixed solvent of water / alcohol at a temperature of 50 to 75 ° C. with stirring to form a solution.
The particles are precipitated and dispersed (emulsified),
A method of obtaining an aqueous dispersion having a desired solid content concentration by removing an alcohol at 0 to 30 ° C. under reduced pressure (pressure of 10 to 150 mmHg) and further removing a desired amount of water.

For the purpose of lowering the viscosity of the aqueous dispersion, alkali metal compounds such as sodium hydroxide, sodium chloride, sodium acetate, sodium sulfate and sodium nitrate, calcium hydroxide, calcium chloride, calcium acetate, calcium sulfate, calcium nitrate 0.01 to 0.5% by weight of alkaline earth metal compounds such as
(To polymer) may be blended. Mixing is EVO of dispersoid
It may be before or after H is made finer (dispersed). If necessary, ordinary surfactants and protective colloids can be added to the aqueous dispersion as long as the object of the present invention is not hindered. In addition, an aqueous dispersion of another resin, a stabilizer against light or heat, a pigment, a lubricant, a fungicide, a film-forming aid, or an inorganic substance such as talc can also be added.

As described above, the EVOH having an ionic group includes an EVO into which an ionic group is randomly introduced.
H is preferred, but EVOH having an ionic group at the terminal of the EVOH molecule, and optionally having a crosslinkable group can also be used. EV having an ionic group at the terminal
OH is, for example, a compound having an active group such as an alcohol, an aldehyde or a thiol having a sulfonic acid group or a salt thereof, a carboxylic acid group or a salt thereof, an ammonium group or the like coexisting as a chain transfer agent; And then saponifying the vinyl ester unit, or introducing a compound containing a sulfonic acid group or a salt thereof, a carboxylic acid group or a salt thereof, an ammonium group, etc. at the terminal of EVOH by a chemical reaction, or the like. Manufactured. Among these methods, a method for economically and efficiently introducing an ionic group into the terminal to obtain EVOH exhibiting excellent stability as an aqueous dispersion includes a sulfonic acid group or a salt thereof, and a carboxylic acid group. Alternatively, a method is preferred in which ethylene and vinyl ester are copolymerized in the presence of a thiol containing a salt thereof, an ammonium group, or the like, followed by saponification.

Next, an aqueous dispersion using EVOH having an ionic group as a dispersoid used in the present invention, that is, an aqueous dispersion of a self-dispersion type will be described. In this case, as the EVOH having an ionic group, particularly the EVOH into which the ionic group is randomly introduced, those having a sulfonic acid group or a salt thereof as the above-described ionic group are preferable. As the EVOH having an ionic group at the terminal used as a dispersoid, those described above are preferable.

When EVOH having these ionic groups is used as a dispersoid, it is necessary that the EVOH be insoluble in water at ordinary temperature and have an ethylene content of 15 to 65 mol%. Insoluble in water at normal temperature, 30% at 1% concentration
Insoluble in water for one day. The higher the insoluble content, the better, 80% or more,
More preferably, it is 90% or more. On the other hand, if the ethylene content is less than 15 mol%, the stability of the aqueous dispersion becomes poor, and if it exceeds 65 mol%, the gas barrier properties become poor, which is not practical. From the viewpoint of both the stability of the aqueous dispersion and the gas barrier property, the more preferable range of the ethylene content is 20 to 55 mol%. The content of an ionic group such as a sulfonic acid group or a salt thereof is determined from the viewpoint of dispersion stability.
0.1 to 10 mol% with respect to EVOH component unit in VOH
And more preferably 0.3 to 7
Mol%, optimally 0.5 to 5 mol%. If it is less than 0.1 mol%, the dispersion stability is low, and if it exceeds 10 mol%, the affinity for water becomes too strong and the dispersion stability becomes poor, so that it cannot be used. The degree of saponification and the degree of polymerization are the same as in the case of EVOH used as the above-mentioned dispersoid.

In the present invention, the EV having an ionic group used as the above-mentioned dispersion stabilizer or dispersoid is used.
As OH, a block or graft copolymer of an EVOH component and a component having an ionic group can also be used.

Further, an aqueous dispersion containing a block or graft copolymer of EVOH and a polyvinyl alcohol component as a dispersion stabilizer or dispersoid, and a block or graft copolymer of EVOH and a polyether component as a dispersion stabilizer or An aqueous dispersion as a dispersoid can also be used.

The aqueous EVOH dispersion described above has a good dispersion stability and hardly any agglomeration of particles during storage or use. Therefore, when applied and dried on the surface of a thermoplastic substrate, it has no fish eyes and good appearance. A thin, homogeneous film is formed, and is most suitable for producing a multilayer structure having high barrier properties.

As the thermoplastic substrate, polyolefin (polypropylene, branched or linear polyethylene,
Ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, etc., polyester (polyethylene terephthalate, etc.), polyamide (polyamide 6, polyamide 6)
6, polyamide 6/12, etc.), various molded articles (films, sheets, cups, bottles, etc.) made of thermoplastic resin alone or a mixture such as polyvinyl chloride, polyvinylidene chloride, polycarbonate, polystyrene, polyvinyl alcohol, etc. Are preferred.

The multilayer structure of the present invention comprises at least two layers of the above-mentioned thermoplastic base material layer and an EVOH layer formed by coating and drying the EVOH aqueous dispersion. Specific examples of typical layer configurations include a thermoplastic substrate layer /
EVOH layer, thermoplastic base layer / EVOH layer / sealant layer, thermoplastic base layer (A) / adhesive resin layer / thermoplastic base layer (B) / EVOH layer, thermoplastic base layer (A ) / Adhesive resin layer / thermoplastic substrate layer (B) / EVOH layer / sealant layer etc. (where A and B are different kinds of thermoplastic substrates). The thickness of the thermoplastic base material layer varies depending on the type and use of the molded product, but is usually selected from the range of 5 to 1000 μm. The thickness of the EVOH layer is usually 0.5 to 1
It is selected from the range of 5 μm. If the thickness of the EVOH layer is 0.
If it is less than 5 μm, the gas barrier properties may be insufficient. On the other hand, if it exceeds 15 μm, cracks may occur in the process of applying and drying the aqueous dispersion, and a continuous film may not be formed. A more preferable range of the thickness of the EVOH layer is 1 to 1
0 μm, optimally 2-6 μm. Adhesive resin layer having a function of adhering different thermoplastic base material layers and heat sink
The thickness of the sealant layer having a sealing property (layer of low-density linear polyethylene or the like) is usually 1 to 10 μm, respectively.
m, selected from the range of 3 to 100 μm.

The method for producing the multilayer structure is not particularly limited. Preferably, an anchor coat is applied to the surface of a thermoplastic substrate which has been subjected to a primer treatment (corona treatment, flame treatment, etc.), and an EVOH aqueous dispersion is applied to the surface. Is applied, followed by drying and, if necessary, heat treatment.

As the anchor coating agent, a polyurethane compound, a polyester / isocyanate compound or the like is used, and a polyurethane compound is particularly preferable. The practical thickness of the anchor coat layer is in the range of 0.1 to 3 μm. The method of applying the anchor coat includes a Meyer bar coat, discharge from a casting head,
Any means such as roll coating, doctor roll coating, doctor knife coating, spraying, dipping, brushing and the like are exemplified. After the anchor coating, a drying treatment is performed if necessary. Examples of the drying method include a dry heat treatment method such as an infrared irradiation method and a hot air drying method. Drying temperature is 3
0 to 140 ° C is preferable, and the lower limit is 50 ° C or more,
Particularly, 80 ° C. or higher is preferable. The drying time is preferably from 5 seconds to 5 minutes.

The method of applying the aqueous EVOH dispersion to the surface of the anchor coat layer includes air knife coating, Meyer bar coating, discharging from a casting head, and roasting.
Arbitrary means such as coating, doctor roll coating, doctor knife coating, spraying, dipping, brushing and the like are exemplified. Examples of the drying method after the application include a dry heat treatment method such as an infrared irradiation method and a hot air drying method. Drying may be performed by one method or a combination of a plurality of methods. The drying temperature is preferably 30 to 180 ° C., and the lower limit is 50 ° C. or higher, more preferably 80 ° C. or higher, and most preferably 100 ° C. or higher.
° C or higher. The drying time is preferably 5 seconds to 10 minutes, more preferably 1 to 5 minutes. It is free to increase or decrease the temperature during drying, for example, to lower the temperature at the beginning after coating and then gradually increase the temperature.

According to the above method, a thin uniform EVOH continuous film is formed on the surface of the thermoplastic substrate via the anchor coat layer. In the present invention, as described above, EVO
H aqueous dispersion, the dispersion stability is significantly better than conventionally known EVOH aqueous dispersion, and substantially no agglomerates of EVOH particles, so almost no fish eyes are observed in the formed film, The multilayer structure is beautiful. In addition, the adhesiveness between the base material layer and the EVOH layer is high. Particularly, in the case of a film-shaped molded product, peeling between the layers does not occur even when the film is bent, and the EVOH layer does not break (generate a crack or the like). It has the feature of maintaining its properties.

The multilayer structure of the present invention has a gas barrier property,
It is extremely useful as a packaging material or container for fields requiring oil and chemical resistance, for example, foods, pharmaceuticals, industrial chemicals, agricultural chemicals, and the like.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. “Parts” or “%” in the examples are expressed on a weight basis unless otherwise specified. The solvent composition is also shown by weight ratio.

[0054]

【Example】

Example 1 An ethylene content of 33 mol%, a saponification degree of 99.6 mol%, and a polymerization degree of 800 (in which 1.2 mol% of sodium 2-acrylamido-2-methylpropanesulfonate unit was randomly introduced with respect to the EVOH component) A solution of sodium sulfonate-modified EVOH having an intrinsic viscosity of 0.91 deciliters / g (measured at 30 ° C.) dissolved in a water / phenol-based mixed solvent (15/85 by weight) containing 1 mol / l of ammonium thiocyanate was dissolved in 10%. % Of water / methyl alcohol = 50/50 mixed solvent solution, ethylene content 32 mol%, saponification degree 99.5 mol%, polymerization degree 10
00 (water / phenol-based mixed solvent (weight ratio 15/85))
Was added to 28 parts of ordinary EVOH having an intrinsic viscosity of 1.06 deciliter / g measured at 30 ° C., 100 parts of methyl alcohol and 100 parts of water, and the mixture was heated and dissolved at 65 ° C.

When this solution was cooled at 10 ° C. with stirring, particles were precipitated, and a stable dispersion was obtained. The average particle size was 0.7 μm. The dispersion is then stirred for 2 hours.
Evaporation at 0 ° C. under reduced pressure removed methyl alcohol. No aggregation of particles was observed in the process of distilling off methyl alcohol, and an aqueous dispersion having an average particle diameter of 0.7 μm and a solid concentration of 25% was obtained. The storage stability was good, and almost no aggregation was observed in the storage test at 40 ° C. for 10 days.

A biaxially-stretched polypropylene film (thickness: 20 μm) treated with a primer (corona treatment) is coated with a polyurethane-based adhesive main agent (AD335A, manufactured by Toyo Motor Corporation).
Mixed solution (solvent: toluene / methyl ethyl ketone = 50/5) of a polymer and a curing agent (Cat-10, manufactured by Toyo Motor Corporation)
0) so that the coating amount is about 1 g (solid content) / m2,
After coating with a wire bar, the coating was dried with hot air at 80 ° C. for 3 minutes to provide an anchor coat layer. Next, 3.5 g (solid content) / m of the EVOH aqueous dispersion was applied to the surface of the anchor coat layer.
2 was applied with a Meyer bar, dried with hot air at 110 ° C. for 5 minutes, and then aged at 40 ° C. for 3 days.

The oxygen permeability of the multilayer structure comprising the biaxially stretched polypropylene layer (20 μm) / EVOH layer (3 μm) thus obtained was measured at 20 ° C. and 0% RH. / M 2 · day · atm showed good gas barrier properties as a food packaging material.
The measurement conditions and units for the amount of oxygen transmission are the same). Further, the number of fish eyes in the EVOH layer was as small as 2 / m 2, and the appearance was good (the haze value, which is a measure of transparency, was 5%).

Next, the amount of oxygen permeation after bending the multilayer structure was measured. The bending test uses a gelbo flex tester (manufactured by Rigaku Corporation) under the conditions of 20 ° C. and 65% RH, and turns a 12-inch × 8-inch sample into a 3.5-inch cylindrical shape. , Grip both ends, initial gripping interval 7 inches, gripping interval at maximum bending 1 inch,
A twist of 440 degrees was applied at the first 3.5 inches of the stroke, followed by a reciprocating motion of linear and horizontal motion at a rate of 40 times / min for the next 2.5 inches.
The oxygen permeation amount after 3.2 reciprocations was 3.2, and almost no decrease in the barrier property due to bending was observed.

A biaxially stretched polypropylene layer and an EVO
When the delamination strength with the H layer was measured under the conditions of 20 ° C. and 65% RH, a practical adhesive strength was obtained at 240 g / 15 mm.

Example 2 Copolymerization of ethylene and vinyl acetate by adding sodium 3-mercaptopropanoate as a chain transfer agent, removal of unreacted monomer (ethylene and vinyl acetate), saponification, washing, and An ethylene content having a terminal sodium carboxylate content of 32 mol% and a saponification degree of 9 obtained by drying.
9.9 mol%, degree of polymerization 430 (intrinsic viscosity 0.62 deciliter / g), concentration of 1%, water-insoluble content of 99% when dissolved in water at 30 ° C. for 1 day, using EVOH. A dispersion type aqueous dispersion was prepared. That is, first, 50 parts of the terminal ion-modified EVOH is dissolved in 600 parts of a mixed solvent of water / methyl alcohol = 30/70 by heating at 65 ° C., and then cooled at 20 ° C. with stirring to obtain water / methyl alcohol having an average particle diameter of 0.9 μm. A system dispersion was obtained. Next, this dispersion was evaporated under reduced pressure at 20 ° C. with stirring to remove methyl alcohol. No agglomeration of particles was observed in the process of distilling off methyl alcohol, the average particle diameter was 0.9 μm, and the solid concentration was 24%.
Was obtained. Good storage stability, 1 at 40 ° C
Almost no agglomeration was observed even after standing for 0 days.

In the same manner as in Example 1, an anchor coat layer was provided on a biaxially stretched polypropylene film that had been subjected to a corona treatment, and the above EVOH aqueous dispersion was applied to the surface thereof, dried and aged to form a multilayer structure (EVOH). Layer thickness 4μ
m) were prepared and various physical properties were evaluated. As a result, the amount of oxygen permeation measured without bending was 4.3, and the amount of oxygen permeation measured with 100 reciprocations of bending was 4.5.
The number of fish eyes in the EVOH layer was as small as 3 / m 2, and the appearance was good (haze value: 5%). The interlayer peel strength between the biaxially oriented polypropylene layer and the EVOH layer was 220 g / 15 mm.

Comparative Example 1 Ethylene, vinyl acetate and acrylic acid were obtained by copolymerization, removal of unreacted monomer, saponification, washing and drying.
Ternary random copolymer EVOH having an acrylic acid content of 1.0 mol%, an ethylene content of 32 mol%, a saponification degree of 99.5 mol%, a polymerization degree of 430 (intrinsic viscosity of 0.62 deciliter / g) and a water-insoluble content of 98% When the dispersion was carried out under the same conditions as in Example 2 except that the above was used, aggregation of particles was observed in the process of distilling off methyl alcohol. The aqueous dispersion (concentration 2)
0%) and the multilayer structure (E
(VOH layer thickness 3 μm) was prepared, but the EVOH layer
Many fish eyes (1
50 pieces / m 2) were observed, the appearance was extremely poor, and the oxygen permeation amount was very large at 35, which was not practical.

Example 3 Sodium 2-acrylamido-2-methylpropanesulfonate unit was randomly introduced at 0.2 mol% with respect to the EVOH component, ethylene content 27 mol%, saponification degree 99.6 mol%, polymerization 100 parts of sodium sulfonate-modified EVOH having a degree of 1000 (intrinsic viscosity of 1.09 deciliters / g) and a water-insoluble content of 99% were converted to water / methyl alcohol =
After heating and dissolving in 2400 parts of a 35/65 mixed solvent at 65 ° C., the mixture was cooled at 15 ° C. with stirring to obtain a water / methyl alcohol dispersion having an average particle size of 0.5 μm. Next, this dispersion was evaporated under reduced pressure at 30 ° C. with stirring to remove methyl alcohol. No agglomeration of particles was observed even in the process of distilling off methyl alcohol.
Was obtained. Good storage stability, 1 at 40 ° C
Almost no agglomeration was observed even after standing for 0 days.

Primer-treated (corona-treated) biaxially stretched polyethylene terephthalate film (12 μm thick)
m), a polyurethane-based adhesive main agent (manufactured by Toyo Moton,
AD503A) and a curing agent (manufactured by Toyo Morton, Cat-1)
0) with a solution (solvent: ethyl acetate) of about 1
After coating with a gravure coater to give g (solid content) / m @ 2, the coating was dried with hot air at 90 DEG C. for 10 seconds to form an anchor coat layer. Next, the EVOH aqueous dispersion was applied on the surface of the anchor coat layer with an air knife coater so as to have a coating amount of 3.5 g (solid content) / m @ 2, and then was applied at 80 DEG C. for 3 minutes, and then 1 hour.
After drying with hot air at 20 ° C. for 1 minute, it was aged at 40 ° C. for 3 days.

The biaxially stretched polyethylene terephthalate layer (12 μm) / EVOH layer (3 μm)
Various physical properties of the multilayer structure composed of m) were evaluated in the same manner as in Example 1. As a result, the amount of oxygen permeation measured without bending was 2.8, and the amount of oxygen permeation measured with 100 reciprocations of bending was 3.0. The number of fish eyes in the EVOH layer was as small as 2 / m 2, and the appearance was good (haze value: 5%). The delamination strength between the biaxially stretched polyethylene terephthalate layer and the EVOH layer is 250 g.
/ 15 mm.

Comparative Example 2 A multilayer structure was prepared in the same manner as in Example 3 except that no anchor coat was applied, and various physical properties were evaluated. As a result, the oxygen permeation amount measured without bending was 3.0 and the barrier property was good, but the oxygen permeation amount measured with 100 reciprocations of bending was 18.
When it was more than 00, it could not be put to practical use. The delamination strength between the biaxially stretched polyethylene terephthalate layer and the EVOH layer was 0 g / 15 mm, and the remarkably low adhesiveness was considered to have caused the EVOH layer to break (crack, etc.) due to bending.

Example 4 EVO having sodium carboxylate at the end of Example 2
H, benzaldehyde to the hydroxyl group of EVOH
By the acetalization reaction with potassium p-sulfonate, the sulfonic acid anion group was added to the EVOH component at a concentration of 0.1%.
8 mol% introduced, ethylene content 38 mol%, saponification degree 99.5 mol%, polymerization degree 1100 (intrinsic viscosity 1.12
Deciliter / g), ion-modified E with a water-insoluble content of 94%
EVO was performed in the same manner as in Example 2 except that VOH was used.
An H aqueous dispersion was obtained. The average particle size was 0.6 μm, and the solid content concentration was 19%. The storage stability was also good, and almost no aggregation was observed even after the storage at 40 ° C. for 10 days.

A primer-treated (corona-treated) biaxially stretched polyamide 6 film (thickness: 20 μm) is coated with a polyurethane-based adhesive main agent (AD335A, manufactured by Toyo Moton) and a curing agent (Cat-, manufactured by Toyo Moton). 10) (solvent: toluene / methyl ethyl ketone = 50/50)
Was coated with a wire bar so that the coating amount was about 1 g (solid content) / m @ 2, and then dried with hot air at 80 DEG C. for 3 minutes to provide an anchor coat layer. Next, the E was placed on the surface of the anchor coat layer.
The aqueous VOH dispersion was applied with a Meyer bar so as to give a coating amount of 3.5 g (solid content) / m 2, dried with hot air at 100 ° C. for 3 minutes, further at 130 ° C. for 1 minute, and then aged at 40 ° C. for 3 days.

When the various physical properties of the multilayer structure (EVOH layer thickness 3 μm) were evaluated, the oxygen permeation amount measured without bending was 3.5, and the oxygen permeation amount was measured with 100 reciprocating bends. Was 3.8. In addition, the number of fish eyes in the EVOH layer was as small as 2 / m, and the appearance was good (haze value: 4%). The interlayer peel strength between the biaxially stretched polyamide 6 layer and the EVOH layer was 230 g / 15 mm.

[0070]

According to the multilayer structure obtained by applying the specific EVOH aqueous dispersion of the present invention to a thermoplastic substrate, almost no fish eyes are observed in the formed film because there is substantially no aggregate of EVOH particles. And the appearance is beautiful. Also,
The adhesiveness between the substrate layer and the EVOH layer is high, and in particular, in the case of a film-shaped molded product, separation between the layers does not occur even when the film is bent.
Since the VOH layer is not destroyed (cracks or the like), it has a feature of maintaining high barrier properties. Therefore, the multilayer structure of the present invention is extremely useful as a field in which gas barrier properties, oil resistance and chemical resistance are required, for example, as packaging materials or containers for foods, pharmaceuticals, industrial chemicals, agricultural chemicals and the like.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Li, Hiroto 1621 Sazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. Examiner Hiroaki Hirai (56) References JP-A-5-93009 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 7/04 C08F 8/12

Claims (2)

(57) [Claims] An aqueous dispersion comprising a saponified ethylene-vinyl ester copolymer having an ionic group as a dispersion stabilizer and a saponified ethylene-vinyl ester copolymer having an ethylene content of 15 to 65 mol%. Having an ionic group at the end, an ethylene content insoluble in water at room temperature of 15 to 65.
Aqueous dispersion having a mol% of a saponified ethylene-vinyl ester copolymer as a dispersoid, an ethylene-containing monomer having a sulfonic acid group or a salt thereof introduced at random and having an ethylene content of 15 to 65 mol% which is insoluble in water at ordinary temperature. A multilayer structure in which at least one aqueous dispersion selected from aqueous dispersions containing a saponified vinyl ester copolymer as a dispersoid is applied to a thermoplastic substrate. 2. An ethylene-vinyl alcohol having an ionic group.
The saponified steal copolymer is used as a dispersion stabilizer and contains ethylene.
Ethylene-vinyl ester copolymer in an amount of 15 to 65 mol%
Aqueous dispersion with saponified dispersoid, ionic at the end
Content of ethylene insoluble in water at room temperature
Mole percent of a saponified ethylene-vinyl ester copolymer.
Aqueous dispersion as a dispersoid, sulfonic acid group or salt thereof
Ethylene randomly introduced and insoluble in water at room temperature
Ethylene-vinyl ester copolymer having a content of 15 to 65 mol%
Selected from aqueous dispersions with coalesced saponified
At least one aqueous dispersion applied to a thermoplastic substrate
Then, a method for producing a multilayer structure obtained by drying.