Gas barrier laminate and production thereof

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a gas barrier laminate and a method for producing the same, and more particularly, it is formed from a mixture containing polyvinyl alcohol (PVA) and a poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid. The present invention relates to a multi-layered gas-barrier laminate containing a film insoluble in water and excellent in oxygen-gas-barrier property as a gas-barrier layer, and a method for producing the same. In the gas barrier laminate of the present invention, the layer of the gas barrier film does not contain chlorine atoms, and heat resistance, moisture resistance, mechanical strength, sealing property, etc. are imparted by other layers, so that food packaging is provided. Suitable for applications such as materials.

【0002】

[Conventional technology]

Packaging materials are generally required to have a function of preventing quality deterioration of the contents, but particularly in fields such as food packaging materials in which the contents are liable to be oxidatively deteriorated, they are required to have excellent oxygen gas barrier properties. Currently, in the field of packaging materials, as a film having excellent oxygen gas barrier properties, for example, a PVA film, a partially saponified (EVOH) film of an ethylene / vinyl acetate copolymer, a vinylidene chloride (PVDC) film, etc. are widely used. There is. Among these, PVDC film has the characteristic that it does not have a gas barrier property of humidity dependence, unlike PVA film and EVOH film, but it has an environmental problem because chlorine gas is generated during incineration. ..

【0003】

The PVA film has flexibility, non-chargeability, and oxygen gas barrier property, and is particularly characterized by having the best oxygen gas barrier property in a dry state among general synthetic resins. Under high humidity conditions, the oxygen gas barrier property is significantly reduced due to moisture absorption, and there is a drawback that it dissolves in boiling water. Therefore, as a general-purpose PVA film, a film having heat treatment at the final stage of film processing to improve crystallinity or biaxial stretching to improve crystallinity and mechanical strength is commercially available. As a multi-layered laminated film, the gas barrier property of humidity dependence is reduced. However, the conventional method is still insufficient in preventing the deterioration of gas barrier property due to moisture absorption of the PVA film and improving the water resistance.

【0004】

By the way, according to US Pat. No. 2,169,250, a film or fiber is formed from a mixed aqueous solution of PVA and polycarboxylic acid, and heat treatment is performed to react PVA and polycarboxylic acid into water or most solvents. A method of introducing an insoluble crosslinked structure is disclosed. In this document, as a specific example, a methacrylic acid monomer is polymerized in an aqueous PVA solution, the obtained mixture is cast on a glass plate, dried, and then heated at 140 ° C. for 5 minutes to be transparent. It is described that a cross-linked film was obtained (Example I). However, under the heat treatment conditions disclosed in this document, it is not possible to obtain a film having excellent oxygen gas barrier properties under high humidity conditions.

【0005】

On the other hand, films and sheets made using a mixture of PVA and polyacrylic acid have been proposed (Japanese Patent Laid-Open No. 63-47743, Tokuhei 2-14376, Tokuhei 2-27941, etc.). All of these films and sheets are water-soluble or water-absorbent, not water-resistant and gas-barrier films. Poly (meth) acrylic acid (ie, polyacrylic acid or polymethacrylic acid) or a partially neutralized salt thereof is a water-soluble polymer, which can be formed from the solution by the casting method, but is obtained. Although the film has good oxygen gas barrier properties under dry conditions, it has strong hydrophilicity and is not suitable for packaging materials such as foods containing a large amount of water.

【0006】

As a result of repeated studies to produce a film having excellent oxygen gas barrier properties of PVA film even under high humidity conditions and excellent water resistance, the present inventors have conducted PVA and poly ( It has been found that these objectives can be achieved by forming a film from a specific ratio mixture of meta) acrylic acid or a partially neutralized salt thereof by a casting method or the like and then performing heat treatment under specific conditions (Japanese Patent Application No. Hei 5-31404, Japanese Patent Application No. 5-262958). However, the film alone obtained in this way does not have sufficient sealing properties, mechanical strength, moisture resistance, etc. required as a packaging material, and therefore further improvement has been required.

【0007】

[Problems to be Solved by the Invention]

An object of the present invention is to provide a multi-layer gas barrier laminate containing a film insoluble in water and excellent in oxygen gas barrier as a gas barrier layer even under high humidity conditions, and a method for producing the same. More specifically, an object of the present invention is water-insoluble and excellent oxygen gas barrier property formed from a mixture containing PVA and a poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid. It is an object of the present invention to provide a gas barrier laminate containing a film as a gas barrier layer and a method for producing the same.

【0008】

As a result of diligent research to achieve the above object, the present inventors have formed and specified a film from a mixture containing PVA and a poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid. A laminated structure of at least two layers in which a film formed by heat treatment under conditions, which is insoluble in water and has excellent oxygen gas barrier properties, is used as a gas barrier layer, and a layer formed of a thermoplastic resin is provided adjacent thereto. It has been found that a multi-layered laminate having the above purpose is suitable for the above purpose.

【0009】

If a film having various performances and functions such as toughness, heat resistance, chemical resistance, oil resistance, and sealing property is arranged as a layer of the thermoplastic resin, it has gas barrier property and is laminated with these characteristics. You can get a body. In particular, since the gas barrier film lacks sealing properties, it can be laminated with a thermoplastic resin having sealing properties such as heat sealing properties to impart sealing properties, making it suitable as a packaging material. ..

【0010】

Further, if other layers are arranged in addition to these two layers to form a laminated body of three or more layers, heat resistance, toughness, moisture resistance, water resistance, sealing property, etc. are further improved or imparted. A multi-layered laminate can be obtained. The present invention has been completed based on these findings.

【0011】

[Means for solving problems]

Thus, according to the present invention, polyvinyl alcohol is formed from a mixture containing poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid in a weight ratio of 95: 5 to 10:90. The oxygen permeability coefficient of the film was 1.25 × 10 measured under the conditions of a temperature of 30 ° C and a relative humidity of 80%.^-3ml (STP) cm / m²-A gas characterized in that the gas barrier film (A) having h · atm {Pa} or less has a laminated structure of at least two layers laminated adjacent to a layer (B) formed of a thermoplastic resin. A barrier laminate is provided.

【0012】

Further, according to the present invention, polyvinyl alcohol and a partially neutralized product of poly (meth) acrylic acid or poly (meth) acrylic acid are placed on a layer (B) formed of a thermoplastic resin in a weight ratio. A solution contained in the range of 95: 5 to 10:90 is cast, dried to form a film, and then heat-treated at a temperature of 100 ° C (373K) or higher to a temperature of 30 ° C, relative to the temperature. Oxygen permeation coefficient measured under 80% humidity is 1.25 x 10^-3ml (STP) cm / m²A method for producing a gas barrier laminated body having a laminated structure of at least two layers including a step of forming a gas barrier film (A) of h · atm {Pa} or less is provided.

【0013】

Hereinafter, the present invention will be described in detail. Gas barrier film In the present invention, a film formed from a mixture containing PVA and a poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid in a weight ratio of 95: 5 to 10:90. The oxygen permeability coefficient measured under the conditions of a temperature of 30 ° C and a relative humidity of 80% is 1.25 × 10.^-3ml (STP) cm / m²-Use a gas barrier film of h · atm {Pa} or less as the gas barrier layer of the laminate.

【0014】

The PVA used in the present invention preferably has a saponification degree of usually 95% or more, preferably 98% or more, and an average degree of polymerization of usually 300 to 2500, preferably 300 to 1500. The poly (meth) acrylic acid used in the present invention is a compound containing two or more carboxyl groups, and specifically, polyacrylic acid, polymethacrylic acid, a copolymer of acrylic acid and methacrylic acid, and the like. Alternatively, it may be a mixture of two or more of these. Suitable examples include homopolymers of acrylic acid or methacrylic acid and copolymers of both. The average molecular weight of poly (meth) acrylic acid is preferably in the range of 2000 to 250,000.

【0015】

The partially neutralized product of poly (meth) acrylic acid used in the present invention is obtained by partially neutralizing the carboxyl group of poly (meth) acrylic acid as described above with an alkali (that is, making it a carboxylate). Obtainable. Examples of the alkali include sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia (including aqueous ammonia) and the like. The partially neutralized product is usually prepared by adding an alkali to an aqueous solution of poly (meth) acrylic acid. The desired degree of neutralization can be obtained by adjusting the amount ratio of poly (meth) acrylic acid to alkali.

【0016】

When a partially neutralized product of poly (meth) acrylic acid is used, the coloration of the film due to heat treatment can be significantly reduced as compared with the case where poly (meth) acrylic acid is used, and the degree of neutralization can be reduced. By selecting it, the gas barrier property can be further improved. When the degree of neutralization exceeds 20%, the gas barrier property tends to decrease. Therefore, the partially neutralized product of poly (meth) acrylic acid preferably has a degree of neutralization of 20% or less. The degree of neutralization is more preferably 1 to 20%, and most preferably 3 to 15%.

【0017】

The degree of neutralization can be calculated by the following formula. Neutralization = (A / B) x 100 (%) A: The total number of moles of neutralized carboxyl groups in 1 g of partially neutralized poly (meth) acrylic acid. B: Total number of moles of carboxyl groups in 1 g of poly (meth) acrylic acid before partial neutralization.

【0018】

The mixed system of PVA with a high degree of saponification and poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid has excellent compatibility. For example, when it is made into an aqueous solution, it is a uniform mixed solution. Is obtained. To make a film of these mixtures, an aqueous solution of the mixture is cast on a support such as a glass plate or a plastic film and dried to form a film (solution casting method), or a high concentration of the mixture. There is a method (extrusion method) in which the water-containing solution of No. 1 is spread in a film shape through a gap while applying discharge pressure with an extruder, and the water-containing film is dried on a rotating drum or a belt. Among these film forming methods, the solution casting method is particularly preferable because a dry film having excellent transparency can be easily obtained.

【0019】

A mixture of PVA and poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid can be prepared by dissolving each polymer in water, mixing an aqueous solution of each polymer, or in an aqueous solution of PVA (meth). It can be prepared by a method of polymerizing an acrylic acid monomer, a method of polymerizing a (meth) acrylic acid monomer in a PVA aqueous solution, and then neutralizing with alkali. The mixture may be prepared using a solvent other than water. When the solution casting method is adopted, the polymer concentration is usually about 5 to 30% by weight. When preparing an aqueous solution or a water-dissolved solution, a solvent other than water such as alcohol, a softener, or the like may be appropriately added, if desired. The thickness of the film can be appropriately determined according to the purpose of use and is not particularly limited, but is usually 0.1 to 500 μm, preferably 0.5 to 100 μm, and more preferably about 0.5 to 50 μm.

【0020】

The mixing ratio of PVA with poly (meth) acrylic acid or partially neutralized poly (meth) acrylic acid is 95: 5 to 10:90 by weight from the viewpoint of gas barrier properties under high humidity conditions. is there. Outside the range of this mixing ratio, good gas barrier properties cannot be obtained under high humidity conditions as compared with the case of the PVA single film. This mixing ratio is preferably 90:10 to 10:90, more preferably 80:20 to 20:80.

【0021】

To form a film with excellent water resistance and gas barrier properties from a mixture of PVA and a partially neutralized product of poly (meth) acrylic acid or poly (meth) acrylic acid, the mixture is manufactured by a solution casting method or the like. After the film is formed, it is necessary to perform heat treatment under specific conditions. As a result of heat-treating the PVA single film and the mixture film at various temperatures and times after film formation, in the case of the PVA single film (thickness 3 μm), the temperature was 30 ° C and the relative humidity was 80% (80%). Oxygen permeability at RH) is 100 ml (STP) / m² It turned out that it was about day atm {Pa}. This oxygen permeability is 1.25 x 10 when converted to the oxygen permeability coefficient.^-3ml (STP) cm / m² H atm {Pa}.

【0022】

When a film composed of a mixture of PVA and poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid is heat-treated, a gas barrier property superior to that of a PVA simple substance film can be obtained. The conditions were found to be as follows. When PVA and poly (meth) acrylic acid are used as starting materials for the gas barrier film, heat treatment of the film under the conditions satisfying the following relational expressions (a) and (b) is 30 ° C, 80%. The oxygen permeability coefficient measured under RH conditions is 1.25 x 10^-3ml (STP) cm / m²-A gas barrier film of h · atm {Pa} or less can be obtained. (a) 373 T 573 (b) logt -0.0282 × T + 14.14 [In the formula, T is the heat treatment temperature (K) and t is the heat treatment time (minutes).

【0023】

A film consisting of a mixture of PVA and poly (meth) acrylic acid with a thickness of 3 μm, 30 ° C, and an oxygen permeability of 50 ml (STP) / m at 80% RH.²-In order to obtain a gas barrier film having day · atm {Pa} or less, heat treatment may be performed under conditions that satisfy the following relational expression (b') instead of the above equation (b). (b') logt -0.0278 × T + 14.14 Under these heat treatment conditions (a) and (b'), the oxygen permeability coefficient measured under the conditions of 30 ° C and 80% RH was 6.25 × 10.^-4ml (STP) cm / m²-A gas barrier film of h · atm {Pa} or less can be obtained.

【0024】

When a partially neutralized product of PVA and poly (meth) acrylic acid is used as the starting material of the gas barrier film, the film is heat-treated under the conditions satisfying the following relational expressions (a) and (c). , 30 ° C, 80% RH, oxygen permeability coefficient is 1.25 × 10^-3ml (STP) cm / m²-A gas barrier film of h · atm {Pa} or less can be obtained. (a) 373 T 573 (c) logt -0.0582 × T + 26.06 [In the formula, T is the heat treatment temperature (K) and t is the heat treatment time (minutes).

【0025】

A film consisting of a mixture of PVA and a partially neutralized poly (meth) acrylic acid with an oxygen permeability of 50 ml (STP) / m at a thickness of 3 μm, 30 ° C and 80% RH.²-In order to obtain a gas barrier film having day · atm {Pa} or less, heat treatment may be performed under conditions that satisfy the following relational expression (c') instead of the above equation (c). (c ) logt -0.0564 × T + 25.53 Under these heat treatment conditions (a) and (c'), the oxygen permeability coefficient measured under the conditions of 30 ° C and 80% RH was 6.25 × 10.^-4ml (STP) cm / m²-A gas barrier film of h · atm {Pa} or less can be obtained.

【0026】

In each case, the heat treatment temperature T is selected from the range of 373K (100 ° C) to 573K (300 ° C). Even within this range, when the heat treatment temperature is low, a very long heat treatment time is required to obtain the desired gas barrier property, and the productivity is lowered. For example, a mixture film with a thickness of 3 μm and an oxygen permeability of 100 ml (STP) / m at 30 ° C and 80% RH.²-In order to obtain a gas barrier film of day · atm {Pa} or less, when the heating temperature is 120 ° C, it is necessary to heat for 30 hours or more. On the other hand, the higher the heat treatment temperature, the shorter the heat treatment time required to obtain a film having a high degree of gas barrier property. However, if the heat treatment temperature is too high, there is a risk of discoloration or decomposition of the film. The preferred heat treatment temperature is about 433K (160 ° C) to 503K (230 ° C).

【0027】

A film formed from a mixture of PVA and a poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid by performing such a heat treatment, at a temperature of 30 ° C. and a relative humidity of 80%. Oxygen permeability coefficient measured under the conditions of 1.25 × 10^-3ml (STP) cm / m²-A gas barrier film of h · atm {Pa} or less can be obtained. This gas barrier property is the same as or better than that of the heat-treated PVA simple substance film. Moreover, the film formed from the mixture can acquire water resistance by heat treatment and becomes insoluble in boiling water.

【0028】

Gas barrier laminate In the gas barrier laminate of the present invention, the gas barrier film (A) formed from a mixture of the above-mentioned PVA and a poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid is thermoplastic. It has a laminated structure of at least two layers laminated adjacent to a layer (B) formed of a resin. The thermoplastic resin is not particularly limited, but for example, polyethylene terephthalate (PET), nylon 6, nylon 66, nylon 12, nylon 6/66 copolymer, polyamide such as nylon 6/12 copolymer, low density polyethylene, etc. , Polyethylene such as high density polyethylene, linear low density polyethylene, ethylene / vinyl acetate copolymer, polypropylene, ethylene / acrylic acid copolymer, ethylene / acrylate copolymer, ethylene / ethyl acrylate copolymer, etc. Examples thereof include polyvinyl chloride, polyvinylidene chloride, and polyphenylene sulfide.

【0029】

By laminating these various thermoplastic resin layers (B) (film, sheet, etc.) on the gas barrier film (A), it has excellent gas barrier properties, as well as heat resistance, chemical resistance, and oil resistance. It is possible to obtain a gas barrier laminate having various performances and functions such as mechanical strength, sealing property, weather resistance, moisture resistance, protection of a gas barrier film, and impartation of mechanical suitability in secondary processing. For example, when laminated with a thermoplastic resin film having heat-sealing properties such as polyolefin, a laminated body having both gas barrier properties and heat-sealing properties can be obtained. Further, when laminated with a heat-resistant film, a laminated body having heat resistance and toughness can be obtained.

【0030】

In order to laminate the gas barrier film (A) and the layer (B) formed of the thermoplastic resin, known laminations such as a coating method, a dry lamination method, and an extrusion coating method are performed with or without an adhesive layer. The law can be adopted. In coating methods (including casting methods), a solution of a mixture of PVA and a poly (meth) acrylic acid or a partially neutralized product of poly (meth) acrylic acid is used, for example, in an air knife coater, kiss roll coater, or metering. A device such as a bar coater, a gravure roll coater, a reverse roll coater, a dip coater, a die coater, or a combination thereof is used to coat a layer of thermoplastic resin to a desired thickness, and then an arch. Using a device such as a dryer, a straight bath dryer, a tower dryer, or a drum dryer, or a device in which they are combined, water is evaporated and dried by blowing hot air or irradiating infrared rays to form a film. After that, the film is heat-treated. In the dry laminating method, a gas barrier film and a film or sheet formed of a thermoplastic resin are bonded together. In the extrusion coating method, a thermoplastic resin is melt-extruded onto a gas barrier film to form a layer.

【0031】

However, the layer of the gas barrier film (A) is usually heat-treated at a high temperature after the solution of the mixture is cast on the support and dried to form a film by a solution casting method. Considering that the toughness of the gas barrier film (A) alone is insufficient, a heat-resistant film such as a stretched PET film, a stretched nylon film, or a stretched polypropylene film is used as a support, and moreover. In addition, it is preferable to form the gas barrier film (A) by the solution casting method and the subsequent heat treatment. Among the heat-resistant films, in particular, the heat-resistant film formed of a thermoplastic resin such as PET or nylon 6 having a melting point or a Vicat softening point of 180 ° C or higher has good dimensional stability during heat treatment and is a gas barrier. This is preferable from the viewpoint that a laminated body in which the property film (A) and the heat-resistant film are in close contact with each other can be obtained.

【0032】

The laminate of the present invention is not limited to a two-layer structure consisting of a gas barrier film (A) and a thermoplastic resin layer (B), and other layers may be further laminated if desired. For example, a glass plate, a plastic plate, and the like can be mentioned. Further, by laminating the gas barrier film (A) in a sandwich shape with the same or different layers of thermoplastic resin, a laminate having improved gas barrier property such as humidity dependence, mechanical strength, and moisture resistance can be obtained. be able to. Further, various films, coating layers and the like may be provided in order to impart functions such as gloss, antifogging property and ultraviolet ray blocking property.

【0033】

When the sealability of the heat-resistant film is insufficient in the laminate of the gas barrier film and the heat-resistant film, a layer of a thermoplastic resin having the sealability is further laminated to impart the sealability to the laminate. can do. Generally, as a sealing method for packaging materials, there are methods such as heat sealing, impulse sealing, high frequency sealing, and ultrasonic sealing. Therefore, it is desirable that the sealing layer is formed of a thermoplastic resin suitable for each applicable sealing method.

【0034】

The heat-sealing method is generally used for packaging materials, and examples of the heat-sealing sealable layer include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene / vinyl acetate copolymer, and the like. Polypropylene, ethylene / acrylic acid copolymer, ethylene / acrylate copolymer, polyolefin such as ethylene / ethyl acrylate copolymer, nylon 6.66 copolymer, nylon 6/12 copolymer, etc. Examples include layers formed from coalescence and the like.

【0035】

A high-frequency sealing method is also preferably used as the sealing method, and examples of the sealing layer capable of high-frequency sealing include polyvinyl chloride, polyvinylidene chloride, nylon 6, and nylon 66. The thermoplastic resin having a sealing property can be appropriately selected according to the purpose, and in the case of using a thermoplastic resin having a melting point or a Vicat softening point of less than 180 ° C, it is usually 2 kg · f or more (15 mm width). It is preferable in that it is easy to obtain a product having the sealing strength of.

【0036】

When a sealing layer is further laminated on the laminate of the gas barrier film and the heat-resistant film, the sealing layer is adjacent to the gas barrier film or the heat-resistant film with or without an adhesive layer. And stack. If desired, another layer may be laminated on the surface on the side where the sealing layer is not laminated. If the adhesiveness between the layers is insufficient, an adhesive layer is provided. As the adhesive for that purpose, various adhesives such as urethane, acrylic, and polyester, which are generally used for dry laminating various films, are provided. Adhesives can be mentioned. If desired, various additives such as antioxidants, lubricants, ultraviolet absorbers, pigments, fillers, and antistatic agents can be added to each layer of the present invention.

【0037】

In the laminate of the present invention, the thickness of the gas barrier film (A) is as described above. The thickness of the layer (B) formed of the thermoplastic resin is not particularly limited, but is usually 5 to 1000 μm, preferably 10 to 100 μm from the viewpoint of mechanical strength, flexibility, economy, and the like. When the layer (B) formed of the thermoplastic resin serves as the seal layer, or when the seal layer is arranged separately from the layer (B) formed of the thermoplastic resin, the thickness thereof is not particularly limited. From the viewpoint of seal strength, flexibility, economy, etc., it is usually 5 to 1000 μm, preferably 10 to 100 μm.

【0038】

The laminated structure of the laminated body of the present invention is as described above, but typical ones are a gas barrier film / thermoplastic resin layer, a heat resistant film / gas barrier film / sealing layer, and a sealing property. Layers / heat-resistant films / gas barrier films and the like can be mentioned, but the present invention is not limited to these. The method for producing the laminate of the present invention is as described above, but in a particularly preferable embodiment, PVA and poly (meth) acrylic acid or poly (meth) acrylic acid or poly (meth) are formed on the layer (B) formed from the thermoplastic resin. A solution containing a partially neutralized meta) acrylic acid in a weight ratio of 95: 5 to 10:90 was cast and dried to form a film, and then 100 ° C (373K) or higher. By heat-treating at the temperature of, the oxygen permeability coefficient measured under the conditions of temperature 30 ° C and 80% RH is 1.25 × 10.^-3ml (STP) cm / m²-A method for producing a gas barrier laminate having a laminated structure of at least two layers including a step of forming a gas barrier film (A) of h · atm {Pa} or less can be mentioned.

【0039】

The heat treatment conditions are as described above. Further, in order to carry out the heat treatment quickly, it is preferable to use a heat-resistant film as the layer (B) formed of the thermoplastic resin. The laminated body composed of the gas barrier film (A) thus obtained and the layer (B) formed of the thermoplastic resin is sealed if the layer (B) has no or insufficient sealing property. By the step of further laminating the layers having the property, a laminated body having a three-layer structure can be produced. The sealing layer is laminated adjacent to the gas barrier film (A) or the layer (B) with or without an adhesive layer by a dry laminating method or the like. Of course, another layer may be laminated together with the sealing layer or in place of the sealing layer.

【0040】

[Example]

Hereinafter, the present invention will be described in more detail with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples.

【0041】

[Reference Example 1] In this Reference Example 1, the effect of the mixing ratio of PVA and a partially neutralized product of poly (meth) acrylic acid or poly (meth) acrylic acid on the gas barrier property of the heat-treated film is shown. Kuraray Co., Ltd.'s Poval 105 (saponification degree 98.5%, average degree of polymerization 500) is used as PVA, and Wako Pure Chemical Industries, Ltd.'s polyacrylic acid 25 wt% aqueous solution (average molecular weight) is used as polyacrylic acid (PAA). 150000) was used. For the partially neutralized product of PAA, PAA partially neutralized product (PAANa) having a neutralization degree (DN) of 5%, 10% and 20% was prepared by adding a calculated amount of sodium hydroxide to the PAA aqueous solution.

【0042】

Each aqueous solution (concentration: 10% by weight) was prepared by mixing PVA and PAA or PAANa at various mixing ratios shown in Table 1. Each of these aqueous solutions is coated on a stretched polyethylene terephthalate film (stretched PET film with a thickness of 16 μm) with a tabletop coater (K303 PROOFER manufactured by RK Print-Coat Instruments) with a mayer bar, and then water is evaporated using a dryer. A dry film having a thickness of 3 μm was obtained. The stretched PET film on which this dry film was formed was heat-treated in an oven at 200 ° C. for 15 minutes. Table 1 shows the oxygen permeability of each heat-treated film measured under the conditions of 30 ° C and 80% RH. The results in Table 1 are shown in a graph in Fig. 1.

【0043】

<Measurement method of oxygen permeability> Using the oxygen permeability tester OX-TRAN 2/20 and 100TWIN manufactured by Modern Control, the oxygen permeability of the stretched film (laminate) on which the stretched PET film and the heat-treated film are formed can be measured. Measure and use the following formula to measure the oxygen permeability of the heat-treated film P_filmWas calculated. 1 / P_total = 1 / P_film+ 1 / P_PETP_total: Oxygen permeability of laminate P_film: Oxygen permeability of heat treatment film P_PET: Oxygen permeability of stretched PET film [0044]

[table 1]

<img file="JPH07205379A_D0001.tif" />【0045】

From the results in Table 1, the mixing ratio of PVA: PAA (DN = 0%) or PVA: PAANa (DN = 5%, 10% and 20%) is 95: 5 to 10:90, preferably 90: 10 to. In the case of a weight ratio of 10:90, more preferably 80:20 to 20:80, a film having excellent gas barrier properties can be obtained even under high humidity conditions of 80% RH at 30 ° C. In addition, the gas barrier property is improved by partially neutralizing PAA (DN = 5% and 10%), but the gas barrier property tends to decrease as the degree of neutralization increases (DN = 20%). Shown. Therefore, the degree of neutralization is preferably 20% or less. The PVA single film and the PAANa single film were dissolved in boiling water, but all the heat-treated films except these were insoluble in boiling water.

【0046】

[Reference Example 2] In this Reference Example 2, the influence of the heat treatment conditions (heat treatment temperature and heat treatment time) on the gas barrier property of the heat treatment film formed from the mixture of PVA and PAA is shown. In the same manner as in Reference Example 1, a dry film having a composition of PVA: PAA = 60: 40 (weight ratio) and a thickness of 3 μm was formed on the stretched PET film. The stretched PET film on which this dry film was formed was heat-treated in an oven by changing the heat treatment temperature and the heat treatment time as shown in Table 2. For each heat-treated film, the oxygen permeability at 30 ° C and 80% RH was measured by the same method as in Reference Example 1. The results are shown in Table 2.

【0047】

[Table 2]

<img file="JPH07205379A_D0002.tif" />(Footnote) ND indicates that the measurement was not possible because the oxygen permeability of the stretched PET film of the support and the oxygen permeability of the stretched PET film on which the heat treatment film was laminated are close to each other.

【0048】

The data in Table 2 are graphed in Fig. 2 for the relationship between the heat treatment time and oxygen permeability for each heat treatment temperature. Specifically, from the data in Table 2, a linear regression line between logP and logt was created by a conventional method for each heat treatment temperature regarding the relationship between oxygen permeability (P) and heat treatment time (t). Next, at each heat treatment temperature, the oxygen permeability is 0.1, 1.0, 5.0, 10, 50, 100, 500, and 1000 ml (STP) / m.² The heat treatment time logt that becomes day · atm {Pa} was calculated, and based on this calculation result, a linear regression line was created for the relationship between the heat treatment temperature (T) and logt. The oxygen permeability of the heat-treated PVA single film with a thickness of 3 μm is 100 ml (STP) / m.² It is about day atm {Pa}. Therefore, in order to obtain a mixture film with better gas barrier properties than the PVA simple substance film, the oxygen permeability is 100 ml (STP) / m.²-It is necessary to perform heat treatment under heat treatment conditions of day · atm {Pa} or less. From the results of the regression analysis obtained above, it was found that this heat treatment condition has the following equation. logt -0.0282 × T + 14.14 [0049]

[Reference Example 3] In Reference Example 3, the effect of the heat treatment conditions (heat treatment temperature and heat treatment time) on the gas barrier property of the heat treatment film formed from the mixture of PVA and PAANa is shown. In the same manner as in Reference Example 1, a dry film having a composition of PVA: PAANa (DN = 10%) = 30:70 (weight ratio) and a thickness of 3 μm was formed on the stretched PET film. The stretched PET film on which this dry film was formed was heat-treated in an oven by changing the heat treatment temperature and the heat treatment time as shown in Table 3. For each heat-treated film, the oxygen permeability at 30 ° C and 80% RH was measured by the same method as in Reference Example 1. The results are shown in Table 3.

【0050】

[Table 3]

<img file="JPH07205379A_D0003.tif" />(Footnote) ND has the same meaning as above.

【0051】

The data in Table 3 are graphed in Fig. 3 for the relationship between the heat treatment time and oxygen permeability for each heat treatment temperature. Specifically, from the data in Table 3, a linear regression line between logP and logt was created by a conventional method for each heat treatment temperature regarding the relationship between oxygen permeability (P) and heat treatment time (t). Next, at each heat treatment temperature, the oxygen permeability is 0.1, 1.0, 5.0, 10, 50, 100, 500, and 1000 ml (STP) / m.² The heat treatment time logt that becomes day · atm {Pa} was calculated, and based on this calculation result, a linear regression line was created for the relationship between the heat treatment temperature (T) and logt. Oxygen permeability is 100 ml (STP) / m²-The heat treatment conditions below day · atm {Pa} were found to be the following equations from the results of the regression analysis obtained above. logt -0.0582 × T + 26.06 [0052]

[Examples 1 to 9, Comparative Examples 1 to 2] Poval 105 (saponification degree 98.5%, average degree of polymerization 500) manufactured by Kuraray Co., Ltd. was used as PVA, and Wako Pure Chemical Industries, Ltd. as polyacrylic acid (PAA). ), A 25 wt% aqueous solution of polyacrylic acid (average molecular weight 150,000) was used. PAANa (DN = 10%) was prepared by partially neutralizing PAA with sodium hydroxide (NaOH) to a degree of neutralization of 10%, and then an aqueous solution of a mixture of PVA: PAANa = 30: 70 (weight ratio) (concentration 10). Weight%) was prepared. This aqueous solution is coated on a stretched PET film (melting point 264 ° C) or a stretched nylon 6 (ONy) film (melting point 220 ° C) using a mayer bar, and then water is evaporated using a dryer to a thickness of 3 μm. A dry film was obtained. Next, the stretched PET film on which the dry film was formed and the ONy film on which the dry film was formed were heat-treated in an oven. Further, an aqueous solution of a mixture of PVA: PAA = 50: 50 (weight ratio) was prepared, a dry film was formed on the stretched PET film in the same manner as described above, and heat treatment was performed.

【0053】

Furthermore, as polymethacrylic acid (PMAA), a 20% by weight aqueous solution of polymethacrylic acid (AC-30H; average molecular weight 50000) manufactured by Nippon Pure Chemical Industries, Ltd. was used, and PMAA partial neutralization with a degree of neutralization of 10% with NaOH was used. A product (PMAANa) was prepared. Then, an aqueous solution (concentration 10% by weight) of a mixture of PVA: PMAANa = 80: 20 (weight ratio) was prepared, coated on an ONy film, and then water was evaporated to obtain a dry film having a thickness of 3 μm. Heat treatment was performed.

【0054】

A linear low-density polyethylene (LLDPE) film (melting point 121 ° C) or unstretched polypropylene (CPP) film (melting point 165 ° C) was further applied to a part of the obtained two-layer structure laminate (Toyo). It was dry-laminated via a Morton Adcoat 335A, hardener = CAT-10) layer. For comparison, an aqueous solution of the mixture of PVA and PAANa was cast on a glass plate to form a dry film, then heat-treated, and then the heat-treated film was peeled off to prepare a single film. Table 4 shows the laminated structure of each laminate, the heat treatment conditions, the oxygen permeability measured under the conditions of 30 ° C and 80% RH, the oxygen permeability after the gelbo test, and the seal strength.

【0055】

<Seal strength> Heat sealing was performed using a degassing sealer V-300 device manufactured by Fuji Impulse. The sealing surface was the third layer (Examples 1 to 5), the first layer (Examples 6 to 9), or the second layer (Comparative Example 2). For the seal strength, the tensile strength of the film cut to a width of 15 mm was measured using Tencilon RTM100 manufactured by Toyo Baldwin. The tensile speed was 500 mm / min. <Bending fatigue resistance: Oxygen permeability after gelbo test> Using a gelboflex tester manufactured by Rigaku Kogyo Co., Ltd., the oxygen permeability after bending a sample piece 10 times at 25 ° C and 50% RH was measured. ..

【0056】

[Table 4]

<img file="JPH07205379A_D0004.tif" />(* 1) Unit: ml (STP) / m² Day atm {Pa} (* 2) Unit: kg f (15mm width) [0057]

The laminated film of the present invention in which PET, ONy, CPP, LLDPE, etc. are laminated on one side or both sides of the gas barrier film has high oxygen gas barrier property even after a gelbo test in which the film is bent 10 times. Laminated films, particularly films laminated with polyolefin (Examples 1 to 5), had good heat-sealing properties and had appropriate performance as a packaging film. On the other hand, when the gas barrier film layer (second layer) was heat-sealed, the sealing could not be performed. Moreover, since this gas barrier film single layer (Comparative Example 2) was brittle, the film was torn during the gelbo test.

【0058】

[Effect of the invention]

According to the present invention, there is provided a gas barrier laminate containing a film that is insoluble in water and has excellent oxygen gas barrier properties as a gas barrier layer even under high humidity conditions, and a method for producing the same. The gas barrier film used in the present invention has an excellent gas barrier property equal to or higher than that of the PVA film, has a small humidity dependence of the gas barrier property, and has good water resistance. The laminate containing this gas barrier film has gas barrier properties as well as sealing properties and toughness, and is easily denatured by oxygen gas, such as meat products such as livestock meat, ham and sausage, juice, cider and the like. Suitable for packaging materials for medical products such as beverages and infusions.

[Simple explanation of drawings]

[Figure 1]

The relationship between the PAA (Na) content and the oxygen permeability of the heat-treated film obtained by changing the mixing ratio of PVA and PAA or the partially neutralized product (PAANa) of PAA and the degree of neutralization (DN), respectively. It is a graph which shows.

[Figure 2]

It is a graph which shows the relationship between the heat treatment condition (temperature and time) of the mixture film of PVA and PAA, and oxygen permeability.

[Fig. 3]

It is a graph which shows the relationship between the heat treatment condition (temperature and time) of the mixture film of PVA and PAANa, and oxygen permeability.