JP2005220154A - Multilayer film and bag for heavy packaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer film having excellent flex resistance and gas barrier properties and to provide a bag for heavy packaging. <P>SOLUTION: The multilayer film has a gas barrier layer prepared by coating at least one surface of a substrate layer composed of a thermoplastic resin with a dispersion containing an inorganic layer compound having 200-3,000 aspect ratio and polyvinyl alcohol and a layer obtained by coating the top surface of the gas barrier layer with a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid. The bag for the heavy packaging is composed of the multilayer film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a multilayer film and a heavy packaging bag.

Conventionally, films made of thermoplastic resins such as polypropylene, polyester, polyamide, etc., due to their excellent mechanical properties, heat resistance, transparency, etc., in many fields such as food field, cosmetic field, agricultural chemical field, medical field, Widely used as packaging material.
When a thermoplastic resin film is used as a packaging material, gas barrier properties are often required to prevent the contents from being deteriorated by oxygen. As a packaging material having such a gas barrier property, for example, in Patent Document 1, a sealant film, a base film, a gas barrier layer composed only of an inorganic layered compound and a resin, and a protective layer composed only of polyurethane and an isocyanate compound are sequentially laminated. A packaging material is disclosed (see Patent Document 1).

Japanese Patent Laid-Open No. 11-171237

However, such a packaging material has insufficient bending resistance. For example, when it is used as a heavy packaging bag, pinholes are generated and gas barrier properties are often lowered.

The present invention provides a multilayer film and a heavy packaging bag excellent in flex resistance and gas barrier properties.

That is, the present invention has a gas barrier layer formed by applying a dispersion containing an inorganic layered compound having an aspect ratio of 200 to 3000 and polyvinyl alcohol on at least one surface of a base material layer made of a thermoplastic resin, A multilayer film and a heavy packaging bag having a layer formed by coating a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid on a gas barrier layer.

The multilayer film and heavy packaging bag of the present invention are excellent in flex resistance and gas barrier properties.

The multilayer film of the present invention has a gas barrier layer formed by coating a dispersion containing an inorganic layered compound having an aspect ratio of 200 to 3000 and polyvinyl alcohol on at least one surface of the base material layer.
As the polyvinyl alcohol used in the present invention, polyvinyl alcohol obtained by a known method can be used. For example, a copolymer of vinyl alcohol and vinyl acetate, or an acetate ester portion of a vinyl acetate polymer can be hydrolyzed. Polymers obtained by transesterification (saponification), polymers obtained by saponifying vinyl trifluoroacetate polymer, vinyl formate polymer, vinyl pivalate polymer, t-butyl vinyl ether polymer, trimethylsilyl vinyl ether polymer, etc. Can be mentioned.

From the viewpoint of gas barrier properties, the saponification rate of the polyvinyl alcohol used is preferably 70 mol% or more, more preferably 85 mol% or more, particularly preferably 98 mol% or more, and a completely saponified product. Most preferably it is. Moreover, it is preferable that the polymerization degree of polyvinyl alcohol exists in the range of 100-5000, and it is more preferable that it exists in the range of 200-3000.

As the dispersion for forming the gas barrier layer, it is preferable to use a dispersion containing a chelate compound in addition to the inorganic layered compound and polyvinyl alcohol from the viewpoint of water resistance of the gas barrier layer. The multilayer film of the present invention having such a gas barrier layer can be used as a packaging material for boil or retort. A chelate compound is a compound in which a bidentate or more multidentate ligand is coordinated to a metal ion, and is a compound that can undergo a crosslinking reaction with polyvinyl alcohol. By cross-linking polyvinyl alcohol using a chelate compound, a gas barrier layer excellent in balance between flexibility and water resistance, that is, gas barrier properties after hydrothermal treatment can be obtained. In addition, by using a chelate compound as a crosslinking agent, gelation of the dispersion can be suppressed, and a dispersion having excellent coating properties can be obtained.

Examples of chelate compounds used in the present invention include titanium chelate compounds, zirconium chelate compounds, and aluminum chelate compounds. Only one kind of these chelate compounds may be used, or two or more kinds may be appropriately mixed and used. It is particularly preferable to use a titanium chelate compound from the viewpoint of suppressing the gelation of the dispersion and from the viewpoint of the water resistance of the resulting gas barrier layer.

Examples of titanium chelate compounds include titanium acetylacetonate, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamate, titanium ethylacetoacetate, and the like.

Examples of the zirconium chelate compound include zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate, and zirconium acetylacetonate bisethylacetoacetate.

Examples of the aluminum chelate compound include aluminum acetylacetonate, aluminum organic acid chelate, aluminum propionylpropionate, aluminum butylacetonate, and aluminum ethylacetoacetate.

As the inorganic layered compound in the present invention, a clay mineral having a swelling property to a solvent and a cleavage property is particularly preferably used. The clay mineral is generally (i) a type having a two-layer structure having an octahedral layer mainly composed of aluminum, magnesium, or the like on the upper part of a tetrahedral layer of silica, and (ii) a tetrahedral layer of silica, It is classified into a type having a three-layer structure in which an octahedral layer having a central metal such as aluminum or magnesium is narrowed from both sides. Examples of the two-layer structure type (i) include clay minerals such as kaolinite group and antigolite group. Examples of the three-layer structure type (ii) include clay minerals such as smectite group, vermiculite group, and mica group depending on the number of interlayer cations.

More specifically, these clay minerals include kaolinite, dickite, nacrite, halloysite, antigolite, chrysotile, pyrophyllite, montmorillonite, beidellite, nontronite, saponite, sauconite, stevensite hectorite, tetracite. Examples include lyric mica, sodium teniolite, muscovite, margarite, talc, vermiculite, phlogopite, xanthophyllite, chlorite. In addition, these clay minerals treated with organic substances such as ion exchange and improved dispersibility (see Asakura Shoten, “Encyclopedia of Clay”; hereinafter may be referred to as organically modified clay minerals) are also used as inorganic layered compounds. Can be used.

Among the clay minerals, smectite group, vermiculite group and mica group clay minerals are preferable, and smectite group is particularly preferable. Examples of the smectite group include, but are not limited to, montmorillonite, beidellite, nontronite, saponite, soconite, stevensite, and hectorite.

The aspect ratio of the inorganic layered compound used in the present invention is 200 to 3,000. When the aspect ratio of the inorganic layered compound is too small, the gas barrier property tends to be insufficient. When the aspect ratio is too large, it is difficult to swell and cleave, and the gas barrier property tends to be insufficient. .
The inorganic layered compound used preferably has an average particle size of 5 μm or less. If the average particle size is too large, gas barrier properties, transparency and film-forming properties tend to be inferior, and in applications where transparency is required, it is preferably 1 μm or less.

In the present invention, the aspect ratio (Z) of the inorganic layered compound is a value determined using the formula: Z = L / a, and the average particle size is the particle size in the dispersion medium determined by the diffraction / scattering method. (Volume-based median diameter) L.
a is the unit thickness of the inorganic layered compound determined by the powder X-ray diffraction method (“Guide to Instrumental Analysis (a)” (1985, published by Kagaku Dojinsha, supervised by Jiro Shiokawa), page 69), The thickness of the unit crystal layer of the inorganic layered compound is shown.

The average particle size of the inorganic layered compound is a particle size obtained by a known method using a diffraction / scattering method in a dispersion medium. That is, it can be obtained by calculating the particle size distribution most consistent with the above diffraction / scattering pattern from the diffraction / scattering pattern obtained when light is passed through the dispersion of the inorganic layered compound by Mie scattering theory or the like. it can.
When the inorganic layered compound is sufficiently swollen and cleaved with the same type of dispersion medium as used in the diffraction / scattering method and then mixed with polyvinyl alcohol, the particle size of the swollen and cleaved inorganic layered compound in polyvinyl alcohol Can be considered to be approximately equal to the particle size of the inorganic layered compound swollen and cleaved in the dispersion medium.

In the present invention, the dispersion applied to the base material layer to form the gas barrier layer is obtained by dispersing polyvinyl alcohol and an inorganic layered compound in a dispersion medium. The inorganic layered compound in the present invention is a compound that swells and cleaves in the dispersion medium. Specifically, those having a swelling value of 5 or more according to the following swellability test are preferred, and those having a swelling value of 20 or more are more preferred. Further, those having a cleavage value of 5 or more by cleavage test described below are preferred, and those having a cleavage value of 20 or more are more preferred.

(Swellability test)
Into a 100 ml graduated cylinder is placed 100 ml of a dispersion medium, and 2 g of the inorganic layered compound is gradually added thereto. After standing at 23 ° C. for 24 hours, the volume (ml) of the inorganic layered compound dispersion layer is read from the scale of the interface between the inorganic layered compound dispersion layer and the supernatant in the graduated cylinder. It shows that swelling property is so high that this numerical value (swelling value) is large.

[Cleavage test]
Gradually add 30 g of inorganic layered compound into 1,500 ml of dispersion medium, disperser (Asada Tekko Co., Ltd., Despa MH-L, blade diameter 52 mm, rotation speed 3,100 rpm, container capacity 3 L, distance between bottom surface and blades 28 mm) at a peripheral speed of 8.5 m / min for 90 minutes at 23 ° C., and 100 ml of this dispersion is collected in a graduated cylinder.
After standing for 60 minutes, the volume (ml) of the inorganic layered compound dispersion layer is read from the scale of the interface between the layered compound dispersion layer and the supernatant in the graduated cylinder. The larger this numerical value (cleavage value), the higher the cleavage property.

As a dispersion medium for swelling and cleaving the inorganic layered compound, when the inorganic layered compound is a natural swellable clay mineral, water, alcohols (methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, etc.), dimethylformamide , Dimethyl sulfoxide, acetone and the like, among which water, alcohol, and a water-alcohol mixture are particularly preferable.

When the inorganic layered compound is an organically modified clay mineral, aromatic hydrocarbons such as benzene, toluene and xylene, ethers such as ethyl ether and tetrahydrofuran, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, n -Aliphatic hydrocarbons such as pentane, n-hexane, n-octane, halogenated hydrocarbons such as chlorobenzene, carbon tetrachloride, chloroform, dichloromethane, 1,2-dichloroethane, perchloroethylene, ethyl acetate, methacrylic acid Methyl, dioctyl phthalate, dimethylformamide, dimethyl sulfoxide, methyl cellosolve, silicon oil and the like can be used as a dispersion medium.

The contents of the inorganic layered compound and polyvinyl alcohol in the dispersion of the present invention are not particularly specified, but from the viewpoint of coating properties, the total weight of polyvinyl alcohol and inorganic layered compound in the dispersion is usually 0.1. It is -70%, and it is preferable that it is 1-15%. From the viewpoint of gas barrier properties, the weight of the inorganic layered compound is usually from 3 to 70% when the total of the inorganic layered compound and polyvinyl alcohol is 100% by weight.

When the dispersion of the present invention contains a chelate compound, the blending ratio of polyvinyl alcohol and chelate compound is the number of moles of crosslinkable functional groups in polyvinyl alcohol (that is, the total moles of hydrogen bonding groups and ionic groups). Number) is HN, and the number of moles of the crosslinkable group containing the ligand in the chelate compound is CN, the ratio of the number of moles of the crosslinkable group in the chelate compound to the number of moles of the crosslinkable functional group in polyvinyl alcohol It is preferable to mix | blend so that K (K = CN / HN) may be 0.001-10, and it is more preferable to set it as 0.01-1. When the blending ratio of the chelate compound is too small, the water resistance tends to be insufficient, and when it is too large, the dispersion is easily gelled.

The dispersion in the present invention preferably contains a surfactant. By applying a dispersion containing a surfactant to form a gas barrier layer, the adhesion between the gas barrier layer and the base material layer made of a thermoplastic resin can be improved. The content of the surfactant is usually 0.001 to 5% by weight in 100% by weight of the dispersion. When the surfactant content is too low, the effect of improving the adhesion between the gas barrier layer and the base material layer made of the thermoplastic resin tends to be insufficient, and when the surfactant content is too high. Tends to lower the gas barrier properties.

As the surfactant, a known surfactant such as an anionic surfactant, a cationic surfactant, a zwitterionic surfactant, a nonionic surfactant, or the like can be used. In particular, an alkali metal salt of a carboxylic acid having an alkyl chain of 6 to 24 carbon atoms, an ether type nonionic surfactant such as a polydimethylsiloxane-polyoxyethylene copolymer (silicone-based nonionic surfactant) ) And fluorine-type nonionic surfactants (fluorine-based nonionic surfactants) such as perfluoroalkylethylene oxide compounds and the like, and effectively, a gas barrier layer and a base material layer made of a thermoplastic resin Adhesion can be improved.

The method for preparing the dispersion containing the inorganic layered compound and polyvinyl alcohol used for forming the gas barrier layer is not particularly limited. For example, a method of mixing a polyvinyl alcohol solution obtained by dissolving polyvinyl alcohol in a solvent and an inorganic layered compound dispersion in which an inorganic layered compound is previously swollen and cleaved in a dispersion medium, and a method in which the inorganic layered compound is previously swollen and cleaved in a dispersion medium. Examples thereof include a method of mixing the inorganic layered compound dispersion liquid and polyvinyl alcohol, and a method of mixing the polyvinyl alcohol solution and the inorganic layered compound.

From the viewpoint of dispersibility of the inorganic layered compound, the dispersion containing the inorganic layered compound and polyvinyl alcohol is preferably subjected to high-pressure dispersion treatment using a high-pressure dispersion apparatus. Examples of the high-pressure dispersing device include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation, a nanomizer manufactured by Nanomizer, a Manton Gorin type high-pressure dispersing device, and a homogenizer manufactured by Izumi Food Machinery. The high-pressure dispersion treatment is a method in which a dispersion is passed through a plurality of capillaries at high speed, and a dispersion containing an inorganic layered compound and polyvinyl alcohol is collided with each other or the dispersion and the inner wall of the capillaries to cause high shear and This is a processing method for applying high pressure.

In the high-pressure dispersion treatment, it is preferable that the dispersion is passed through a thin tube having a tube diameter of about 1 μm to 1000 μm, and at this time, treatment is performed so that a maximum pressure of 100 kgf / cm ² or more is applied. Maximum pressure is more preferably at 500 kgf / cm ² or more, and particularly preferably 1000 kgf / cm ² or more. In addition, when the dispersion containing the inorganic layered compound and polyvinyl alcohol passes through the narrow tube, the maximum arrival speed of the dispersion is preferably 100 m / s or more, and the heat transfer rate due to pressure loss is 100 kcal / hr or more. Preferably there is.

When the chelate compound is blended in the dispersion for forming the gas barrier layer, the blending method is not particularly limited, but usually a chelate prepared by previously dissolving the chelate compound in a solvent such as alcohol in an amount of 10 to 90% by weight. It adjusts by the method of adding a solution to the dispersion liquid containing polyvinyl alcohol and an inorganic layered compound.

The dispersion containing the inorganic layered compound, polyvinyl alcohol and chelate compound is preferably acidic from the viewpoint of the stability of the dispersion, more preferably 5 or less, and particularly preferably 3 or less. There is no particular lower limit to the pH of the dispersion, but it is usually 0.5 or more. The dispersion can be made acidic by adding an acidic solution such as hydrochloric acid or subjecting the dispersion to an ion exchange treatment.

The multilayer film of the present invention has a gas barrier layer formed by coating a dispersion containing an inorganic layered compound having an aspect ratio of 200 to 3000 and polyvinyl alcohol on at least one surface of a base material layer made of a thermoplastic resin. On the gas barrier layer, there is a layer formed by coating a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid. By having a layer formed by coating a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid on the gas barrier layer, a multilayer film having excellent bending resistance and gas barrier properties can be obtained.

Examples of the isocyanate compound include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 4,4'-methylenebiscyclohexyl isocyanate, and isophorone diisocyanate.

The active hydrogen compound is a compound having two or more hydroxyl groups as active hydrogen groups in the molecule and having no carboxyl group, such as ethylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol. Low molecular weight polyols such as 1,6-hexanediol, neopentyl glycol, trimethylolpropane, polyether polyols such as polyethylene glycol, polyoxypropylene glycol, ethylene oxide / propylene oxide copolymer, polytetramethylene ether glycol, poly- Examples include polyester polyols such as polyesters from β-methyl-δ-valerolactone, polycaprolactone, diol / dibasic acid.
As the active hydrogen compound, it is more preferable to use a compound having a number average molecular weight of 300 to 100,000.

The mixing ratio of the isocyanate compound and the active hydrogen compound is preferably determined in consideration of the equivalent relationship between the isocyanate group and the hydroxyl group contained in the active hydrogen compound. For example, assuming that the number of moles of isocyanate groups is AN and the number of moles of active hydrogen groups in the active hydrogen compound is BN, the ratio R (R = AN / BN) of the number of moles of isocyanate groups to the number of moles of active hydrogen groups is the gas barrier. It is preferably 0.001 or more from the viewpoint of adhesion to the layer, pinhole resistance, etc., and preferably 1000 or less from the viewpoint of blocking prevention. The number of moles of isocyanate groups and active hydrogen groups can be quantified by ¹ H-NMR and ¹³ C-NMR.

The polyoxycarboxylic acid in the present invention is a compound having at least one carboxyl group and at least two hydroxyl groups in the molecule. For example, dimethylolpropionic acid, dimethylolbutanoic acid, glyceric acid, erythronic acid, threon Acid, ribbon acid, alabonic acid, xylonic acid, lyxonic acid, gluconic acid, aroonic acid, altronic acid, mannonic acid, gulonic acid, idonic acid, galactonic acid, talonic acid, glucoheptonic acid, polylactic acid, polyhydroxybutyric acid, polyhydroxy Examples include valeric acid and polycaprolactone. The polyoxycarboxylic acid is preferably contained in the coating solution in an amount of 0.01 to 50% by weight, more preferably 0.1 to 20% by weight, based on the total weight of the isocyanate compound and the active hydrogen compound. If the content of polyoxycarboxylic acid is too small, the bending resistance effect is insufficient, and if it is too large, the viscosity of the coating liquid tends to be high and the workability tends to decrease.

As a solvent for a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid, usually alcohols, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, esters, ketones, Ethers, halogenated hydrocarbons, mixed solvents thereof and the like are used.

The method for adjusting the coating liquid is not particularly limited. For example, a method of mixing a polyoxycarboxylic acid solution in which a polyoxycarboxylic acid is dissolved in a solvent and a solution in which an active hydrogen compound and an isocyanate compound are dissolved in a solvent are mixed. Is mentioned. Usually, the solvent for dissolving the polyoxycarboxylic acid and the solvent for dissolving the active hydrogen compound and the isocyanate compound are the same compound.

A well-known thing can be used as a thermoplastic resin which comprises the base material layer in this invention. For example, low density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, polypropylene, ethylene-acetic acid Polyolefin resins such as vinyl copolymer, ethylene-methyl methacrylate copolymer, ionomer resin, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, nylon-6, nylon-6,6, metaxylenediamine -Adipic acid condensation polymer, amide resin such as polymethylmethacrylamide, acrylic resin such as polymethyl methacrylate, polystyrene, styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadiene Copolymers, Styrene-acrylonitrile resins such as polyacrylonitrile, hydrophobic cellulose resins such as cellulose triacetate and cellulose diacetate, halogen-containing resins such as polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride, polyvinyl alcohol, ethylene -Hydrogen bonding resins such as vinyl alcohol copolymers, cellulose derivatives, polycarbonate resins, polysulfone resins, polyether sulfone resins, polyether ether ketone resins, polyphenylene oxide resins, engineering plastic resins such as polymethylene oxide resins, etc. can give.
In particular, a biaxially stretched film made of any one of polypropylene, polyethylene terephthalate and nylon is preferably used from the viewpoint of strength.

The multilayer film of the present invention may have a gas barrier layer on one surface of the base material layer, or may have a gas barrier layer on both surfaces. In the case where the gas barrier layers are provided on both surfaces of the base material layer, a layer formed by applying a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid is provided on both gas barrier layers.

An anchor coat layer may be provided between the base material layer and the gas barrier layer. The anchor coat layer is preferably formed by coating the base material layer with a coating liquid containing an isocyanate compound and an active hydrogen compound.

The method of providing a gas barrier layer on the base material layer and the method of providing a layer formed by coating a coating liquid containing an isocyanate compound, an active hydrogen compound and polyoxycarboxylic acid on the gas barrier layer are not particularly limited, For example, gravure methods such as direct gravure method, reverse gravure method, micro gravure method, etc .; roll coating method such as two roll beat coat method, bottom feed three reverse coat method; doctor knife method; die coating method; bar coating method; A gas barrier layer and a protective layer can be provided by a coating method combining the above. After applying the dispersion liquid for forming the gas barrier layer on the base material layer by the method as described above, drying and volatilizing the dispersion medium, the isocyanate compound and active hydrogen are further applied on the gas barrier layer by the method as described above. The multilayer film of the present invention can be obtained by coating and drying a coating solution containing a compound and polyoxycarboxylic acid to form a layer. It is preferable to heat-treat the multilayer film at 110 ° C. or higher and 220 ° C. or lower from the viewpoint of improving the gas barrier property after the hot water treatment. The heat source used for the heat treatment is not particularly limited, and various methods such as hot roll contact, heat medium contact (air, etc.), infrared heating, microwave heating and the like can be applied.

The thickness of the gas barrier layer or the layer formed by coating a coating solution containing an isocyanate compound, an active hydrogen compound and polyoxycarboxylic acid is not particularly limited. Usually, the thickness of the gas barrier layer after drying is about 1 nm to 10 μm, and the thickness after drying of the layer formed by applying a coating solution containing an isocyanate compound, an active hydrogen compound and polyoxycarboxylic acid is 1 nm to 10 μm. is there. When it has an anchor coat layer, its thickness is usually 0.01 to 5 μm.

When the gas barrier layer is provided on one surface of the base material layer, the heat seal layer is formed on the layer formed by coating with a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid on the gas barrier layer. You may have. In this case, the heat seal layer and the gas barrier layer can be bonded by a layer formed by applying a coating liquid containing an isocyanate compound, an active hydrogen compound and polyoxycarboxylic acid.

From the viewpoint of bending resistance, when the gas barrier layer is provided on one surface of the base material layer, the heat barrier layer is provided on the surface of the base material layer not adjacent to the gas barrier layer, and is provided on the gas barrier layer. It is preferable that the layer formed by coating a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid is a multilayer film having a surface layer.

As the resin constituting the heat seal layer, low density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-4- Methyl-1-pentene copolymer, ethylene-octene copolymer, polypropylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-acrylic acid copolymer Examples thereof include polyolefin resins such as coalescence and ionomer resins, polyacrylonitrile resins, and polyester resins.

The method for laminating the heat seal layer and the base material layer is not particularly limited. For example, a method in which a solution in which the resin constituting the heat seal layer is dissolved is applied to the base material layer. Examples thereof include a method of extruding and laminating a resin constituting the seal layer, a method of dry laminating the heat seal layer and the base material layer, and the like. The interface between the heat seal layer and the base material layer may be subjected to treatment such as corona treatment, ozone treatment, electron beam treatment, and application of an anchor coating agent.

Each layer which comprises the multilayer film of this invention may contain various additives, such as a ultraviolet absorber, a coloring agent, and antioxidant, as needed to such an extent that the effect of this invention is not impaired. Moreover, the multilayer film of this invention may have layers other than the layer mentioned above.

The multilayer film of the present invention can be suitably used as a packaging material in many fields such as the food field, cosmetic field, agricultural chemical field, and medical field. The multilayer film of the present invention is excellent in bending resistance and gas barrier properties. Such a multilayer film of the present invention is preferably used as a packaging material for heavy packaging.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these. Measurement methods for various physical properties are described below.

[Thickness Measurement] The thickness of 0.5 μm or more was measured with a commercially available digital thickness gauge (contact thickness gauge, trade name: Ultra High Precision Deci-Microhead MH-15M, manufactured by Nippon Optical Co., Ltd.). On the other hand, the thickness of less than 0.5 μm was determined from the calibration curve by creating a calibration curve between the actual coating thickness and IR absorption by the IR method.

[Particle Size Measurement] Using a laser diffraction / scattering type particle size distribution measuring device (LA910, manufactured by HORIBA, Ltd.), the volume-based median diameter of particles considered to be inorganic layered compounds present in polyvinyl alcohol is determined as the particle size L As measured. In addition, the dispersion liquid stock solution containing polyvinyl alcohol and the inorganic stratiform compound was measured by a paste cell with an optical path length of 50 μm, and the diluted solution of the dispersion liquid was measured by an optical path length of 4 mm by a flow cell method.

[Aspect Ratio Calculation] Using an X-ray diffractometer (XD-5A, manufactured by Shimadzu Corporation), an inorganic layered compound alone and a dried coating liquid containing polyvinyl alcohol and the inorganic layered compound are powdered. The diffraction measurement by was carried out. As a result, the unit thickness a of the inorganic layered compound was obtained, and further, from the diffraction measurement of the dried coating liquid for forming the gas barrier layer, it was confirmed that there was a portion where the interplanar spacing of the inorganic layered compound was widened. Using the particle diameter L obtained by the above method, the aspect ratio Z was calculated by the equation Z = L / a.

[Boil treatment] Heat seal layers of the multilayer film are heat sealed using a heat sealer (FUJI IMPULSE T230: manufactured by FUJI IMPULSE CO.LTD) at a temperature of 150 ° C for 1 second and a heat seal width of 10 mm. A bag of × 150 mm was produced. 50 cc of water was put into this bag and boiled at 98 ° C. for 60 minutes.

[Bend Resistance Test] A 210 mm × 297 mm multilayer film was aged in an environment of 23 ° C. and 50% RH for 24 hours in accordance with ASTM F392. The multi-layer film is formed into a cylindrical shape with 210 mm sides aligned, and using a gel bath flex tester with a thermostatic bath [Tester Sangyo Co., Ltd.], the central axis in the length direction of the cylindrical film is set to 440 °. After twisting, the test of returning to the original was repeated 100 times.

[Measurement of Oxygen Permeation] Based on JIS K7126, measurement was performed with an ultrasensitive oxygen permeability measuring device (OX-TRANML, manufactured by MOCON) at 23 ° C. and 50% RH.

[Example 1] Dispersion kettle (trade name: Despa MH-L, manufactured by Asada Tekko Co., Ltd.), ion-exchanged water (specific electric conductivity 0.7 μs / cm or less) 1300 g and polyvinyl alcohol (PVA117H; ) Kuraray, degree of saponification; 99.6%, degree of polymerization 1,700) was mixed with 130 g, and the temperature was raised to 95 ° C. under low speed stirring (1500 rpm, peripheral speed 4.1 m / min). The mixed system was stirred at the same temperature for 30 minutes to dissolve the polyvinyl alcohol, and then cooled to 60 ° C. to obtain an aqueous polyvinyl alcohol solution.

While stirring the polyvinyl alcohol aqueous solution (60 ° C.) under the same conditions as described above, an alcohol aqueous solution obtained by mixing 122 g of 1-butanol, 122 g of isopropyl alcohol and 520 g of ion-exchanged water was dropped over 5 minutes. After completion of the dropping, switching to high-speed stirring (3,000 rpm, peripheral speed = 8.2 m / min), 65 g of high-purity montmorillonite (trade name: Kunipia G; manufactured by Kunimine Industry Co., Ltd.) was gradually added to the stirring system, After completion of the addition, stirring was continued at 60 ° C. for 60 minutes. Thereafter, 243 g of isopropanol was further added over 15 minutes, and then the mixed system was cooled to room temperature to obtain a dispersion liquid (1) containing an inorganic layered compound and polyvinyl alcohol. Non-ionic surfactant (polydimethylsiloxane-polyoxyethylene copolymer, trade name: SH3746, manufactured by Toray Dow Corning Co., Ltd.) 0.1% by weight (with respect to the dispersion) And a high-pressure dispersion apparatus (trade name: ultrahigh-pressure homogenizer M110-E / H, manufactured by Microfluidics Corporation) under the condition of 1100 kgf / cm ² to treat the inorganic layered compound and polyvinyl. A dispersion (2) containing alcohol was obtained.
The cleaved montmorillonite average particle size was 560 nm, the a value obtained from powder X-ray diffraction was 1.2156 nm, and the aspect ratio was 460.

To 2000 g of the dispersion (2) containing the above inorganic layered compound and polyvinyl alcohol, 5.33 g of titanium acetylacetonate (trade name: TC100, manufactured by Matsumoto Pharmaceutical Co., Ltd.) as a chelate compound was stirred at a low speed (1500 rpm, At a peripheral speed of 4.1 m / min), a dispersion (3) containing polyvinyl alcohol, an inorganic layered compound and a chelate compound is prepared by gradually adding it while adjusting with hydrochloric acid so that the pH of the system is 3 or less. did.

A biaxially stretched nylon (ONy) film (trade name: ON-U; manufactured by Unitika Ltd.) having a thickness of 15 μm is treated as a base layer (base film), and one of the base films An anchor coat agent (EL510-1 / CAT-RT87 = 5/1 (weight ratio): manufactured by Toyo Morton Co., Ltd.) was used on the surface by a microgravure coating method using a test coater (manufactured by Yasui Seiki). Gravure coating was performed at a coating speed of 3 m / min and a drying temperature of 80 ° C. to form an anchor coat layer. The dry thickness of the anchor coat layer was 0.05 μm.

Furthermore, the dispersion liquid (3) containing the above-mentioned polyvinyl alcohol, inorganic layered compound and chelate compound was applied at a coating speed of 3 m / min and a drying temperature of 100 ° C. by a microgravure coating method using a test coater (manufactured by Yasui Seiki). Gravure coating was performed to obtain a coated film in which a film (gas barrier layer) based on the coating liquid was formed on the base material layer via an anchor coat layer. The film thickness (dry thickness) of the gas barrier layer was 0.2 μm.

Next, a coating solution was applied onto the gas barrier layer of the coating film to form a layer. In the coating liquid, a mixture of an active hydrogen compound and an isocyanate compound (trade name: AD335AE / CAT-10L = 10/4 (weight ratio): manufactured by Toyo Morton Co., Ltd.), dimethylolbutanoic acid (Nippon Kasei ( Co., Ltd.) 2% by weight (based on the solid content of the active hydrogen compound and the isocyanate compound) was used. The coating solution was subjected to gravure coating at a coating speed of 3 m / min and a drying temperature of 100 ° C. by a micro gravure coating method using a test coater (manufactured by Yasui Seiki Co., Ltd.) to form a layer. The dry thickness of the layer was 0.2 μm.

Next, a urethane adhesive (trade name: TM250 / CAT-RT86-60L = 15/2, Toyo Morton (on the surface opposite to the gas barrier layer of the coated film formed by coating the coating solution) The product is dry laminated with a linear corona-treated linear low density polyethylene ((LLDPE), trade name: TUX-FCD, manufactured by Tosero Co., Ltd., thickness 70 μm) as a heat seal layer, and a multilayer film. Got. Using the multilayer film, the boil treatment and the bending resistance test were performed by the method described above. The results are shown in Table 1. The multilayer film was excellent in gas barrier properties even after the bending resistance test. In addition, the gas barrier property was excellent even after the boil treatment.

Example 2 Example of Example 1 except that dispersion (2) containing polyvinyl alcohol and inorganic layered compound was used instead of dispersion (3) containing polyvinyl alcohol, inorganic layered compound and chelate compound of Example 1. In the same manner as in Example 1, a comparative multilayer film was obtained. Using the multilayer film, a boil treatment and a bending resistance test were performed in the same manner as in Example 1. The results are shown in Table 1. The multilayer film was excellent in gas barrier properties even after the bending resistance test, but was slightly inferior in gas barrier properties after boil treatment.

[Comparative Example 1] Instead of the coating liquid containing the isocyanate compound, active hydrogen compound and polyoxycarboxylic acid of Example 1, the coating liquid containing an isocyanate compound and active hydrogen compound which does not contain polyoxycarboxylic acid (product) A multilayer film for comparison was obtained in the same manner as in Example 1 except that AD335AE / CAT-10L = 10/4 (weight ratio): manufactured by Toyo Morton Co., Ltd. was used. Using the multilayer film, a boil treatment and a bending resistance test were performed in the same manner as in Example 1. The results are shown in Table 1. The multilayer film was inferior in gas barrier properties after the bending resistance test, and somewhat inferior in gas barrier properties after boil treatment.

Claims (5)

On at least one surface of a base material layer made of a thermoplastic resin, it has a gas barrier layer formed by applying a dispersion containing an inorganic layered compound having an aspect ratio of 200 to 3000 and polyvinyl alcohol, and on the gas barrier layer, A multilayer film having a layer formed by coating a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid. On one surface of a base material layer made of a thermoplastic resin, a gas barrier layer is formed by applying a dispersion containing an inorganic layered compound having an aspect ratio of 200 to 3000 and polyvinyl alcohol, and an isocyanate is formed on the gas barrier layer. A multilayer film having a layer formed by coating a coating solution containing a compound, an active hydrogen compound and polyoxycarboxylic acid. The multilayer film according to claim 1 or 2, which is a gas barrier layer formed by coating a dispersion containing an inorganic layered compound having an aspect ratio of 200 to 3,000, polyvinyl alcohol and a chelate compound. The surface layer is a surface layer having a heat seal layer on the surface of the base material layer not adjacent to the gas barrier layer and coated with a coating liquid containing an isocyanate compound, an active hydrogen compound and a polyoxycarboxylic acid. 3. The multilayer film as described in 3. A heavy packaging bag comprising the multilayer film according to claim 4.