JP2019151004A - Transparent gas barrier film and method for producing the same - Google Patents

Abstract

To provide a transparent gas barrier film having excellent oxygen and water vapor barrier performance.SOLUTION: A transparent gas barrier film has a metal oxide layer and an organic/inorganic mixing layer obtained by condensation polymerization of a vinyl alcohol-based resin and alkoxysilane laminated on at least one surface of a base material plastic film, in which a chlorine content layer (A) per 1 cmobtained by the following expression (1) in the organic/inorganic mixing layer is 50-150 μg/cm. The expression (1): A=a chlorine detection amount (μg/cm)/a thickness (μm) of the organic/inorganic mixing layer×10.SELECTED DRAWING: None

Description

  The present invention relates to a transparent gas barrier film having excellent oxygen and water vapor barrier performance and a method for producing the same.

  Various packaging materials have been used to wrap various items such as food and drinks, pharmaceuticals, and daily necessities, but these packaging materials have oxygen barrier performance and water vapor barrier performance to prevent deterioration of the contents. Needed. In particular, having excellent gas barrier performance can contribute to extending the shelf life and improving food safety. Aluminum foil is an example of a packaging material having excellent gas barrier performance, but the aluminum foil is prone to pinholes and is not transparent, so the contents cannot be visually recognized. Moreover, since aluminum foil has high electroconductivity, there exists a fault that it cannot be used for a microwave oven use.

  In order to solve these problems, a deposition film in which a deposition film of a metal oxide such as aluminum oxide or silicon oxide is provided on a film of polyester or the like by a vacuum deposition method or the like has been proposed. These metal oxide vapor-deposited films are transparent and can be used for cooking using a microwave oven. However, since the metal oxide layer is hard, cracks and pinholes due to bending occur, and there is a problem that the gas barrier performance is remarkably lowered.

  Therefore, a gas barrier film is disclosed in which a metal oxide layer such as silicon oxide or aluminum oxide is provided on a resin film such as polyester, and a protective layer having gas barrier performance is further laminated thereon by coating a polymer. However, gas barrier performance may deteriorate due to swelling of the protective layer under humidified conditions or by retort sterilization.

  On the other hand, as a gas barrier film with reduced barrier deterioration due to high-temperature humidification conditions or retort sterilization, a vapor-deposited film of a metal oxide such as aluminum oxide or silicon oxide is provided on a plastic substrate film by vacuum vapor deposition or the like. Furthermore, a method for producing a transparent gas barrier laminate film by applying a coating agent containing a metal alkoxide such as alkoxysilane and a polyvinyl alcohol resin and / or an ethylene / vinyl alcohol copolymer is disclosed (for example, Patent Documents 1 and 2).

JP 2007-290292 A Japanese Patent Laying-Open No. 2015-193194

  However, in Patent Documents 1 and 2, it is necessary to heat-treat the gas barrier film in order to advance the crosslinking reaction such as siloxane bond by condensation polymerization of the coat layer and to express the gas barrier performance. If the gas barrier film is to be heat-treated, a large-scale facility is required, and the process becomes longer, leading to an increase in cost. Also, when this heat treatment is performed at a high temperature, troubles such as film roll winding and tightening may occur, or the flatness of the film may deteriorate, and the gas barrier performance after the heat treatment is insufficient. There was something wrong.

  An object of this invention is to provide the transparent gas-barrier film which has the outstanding gas barrier performance, and its manufacturing method, without performing an advanced heat processing.

In order to solve the above-mentioned problems, the present invention laminates an organic-inorganic hybrid layer obtained by condensation polymerization of a metal oxide layer and a vinyl alcohol-based resin and an alkoxysilane on at least one surface of a base plastic film, The organic-inorganic hybrid layer has a chlorine content (A) per cm ³ obtained by the following formula (1) of 50 to 150 μg / cm ³ , thereby forming a transparent gas barrier film.

A = Amount of detected chlorine (μg / cm ² ) / Thickness of organic-inorganic hybrid layer (μm) × 10 ⁴ (1)
In the present invention, the metal oxide layer is preferably a layer made of aluminum oxide, and the organic-inorganic hybrid layer preferably has a thickness of 0.2 μm to 2 μm.

  In the present invention, a metal oxide layer is formed on a base plastic film, a coating solution comprising a polyvinyl alcohol resin and an alkoxysilane is applied on the metal oxide layer, dried and solidified, and then contacted with an aqueous hydrochloric acid solution. And drying the transparent gas barrier film.

  According to the present invention, it is possible to easily provide a transparent gas barrier film having excellent oxygen and water vapor barrier performance without performing a heat treatment for a long time at a high temperature.

  The transparent gas barrier film of the present invention basically has a layer structure in which a metal oxide layer and a specific organic-inorganic hybrid layer are sequentially laminated on at least one surface of a base plastic film.

(Base plastic film)
The base plastic film used for the transparent gas barrier film of the present invention is not particularly limited as long as the properties such as mechanical strength, heat resistance, and light resistance are taken into consideration depending on the use, but typical examples include polyethylene terephthalate and polyethylene naphthalate. Polyester such as phthalate, polybutylene terephthalate, polybutylene 2,6-naphthalate, polyvinyl alcohol, saponified ethylene / vinyl acetate copolymer, polyolefin such as polystyrene, polycarbonate, polyethylene, polypropylene, polyamide such as 6 nylon and 12 nylon, aromatic Examples thereof include films and sheets made of homopolymers or copolymers such as group polyamide and polyimide. Preferably, it is superior in suitability for vapor deposition processing, and has dimensional stability and heat resistance. As the base plastic film used in the gas barrier film of the present invention, a polyethylene terephthalate film arbitrarily stretched in a biaxial direction is more preferably used, and a biaxially stretched polyethylene terephthalate film is most preferably used from the viewpoint of economy. . Further, the surface of these base plastic films may be subjected to surface modification treatment such as corona treatment, flame treatment, plasma treatment, and anchor coating. Furthermore, the thickness of these plastic films is selected in the range of 6 to 250 μm depending on the purpose from the viewpoint of vapor deposition processability and economy, but in the range of 8 to 50 μm from the viewpoint of economy and handleability. Is done.

(Metal oxide layer)
In the present invention, a metal oxide layer is formed on the substrate plastic film. The metal oxide layer is made of a vapor deposition layer such as aluminum oxide, silicon oxide, magnesium oxide, or a mixture thereof, and is transparent and has gas barrier performance. Of these, aluminum oxide is more preferable in consideration of processability and gas barrier performance. The method for laminating the aluminum oxide layer on the base plastic film is not particularly limited, but the reactive evaporation method in which the aluminum metal layer is directly heated and evaporated to form the aluminum oxide layer by reaction with oxygen gas. Well-known methods such as ion plating under an oxygen gas atmosphere, sputtering using an aluminum oxide target, reactive sputtering using a metal aluminum target to react with oxygen gas, and chemical vapor deposition can be used. .

(Organic / inorganic hybrid layer)
In the present invention, the organic / inorganic hybrid layer is formed by applying a gas barrier resin obtained by condensation polymerization of vinyl alcohol resin and alkoxysilane. Thereby, the metal oxide layer which is a base layer can be protected and gas barrier performance can be improved.

  A specific method for forming the organic-inorganic hybrid layer is an aqueous solution or alcohol containing a vinyl alcohol resin having a high affinity for the metal oxide layer as a main component and containing either or both of alkoxysilane and a hydrolyzate thereof. It is formed from a mixed aqueous solution.

  The vinyl alcohol resin as the main agent for forming the organic-inorganic hybrid layer is not particularly limited as long as it is a vinyl alcohol resin such as polyvinyl alcohol, ethylene / vinyl alcohol copolymer, and modified polyvinyl alcohol. Among them, particularly when polyvinyl alcohol is used in the coating composition of the present invention, the gas barrier performance is excellent, which is more preferable. Polyvinyl alcohol as used herein is generally obtained by saponifying polyvinyl acetate, and may be partially saponified or completely saponified by saponifying a part of the acetate group. It is not limited.

In the present invention, alkoxysilane is an organosilicon compound having an alkoxy group. An alkoxy group has a structure of RO— in which an alkyl group R is bonded to oxygen, and is converted to a silanol group through a dealcoholization reaction by hydrolysis, and a representative one is a methoxy group or an ethoxy group It is. Specifically, these silicon compounds having an alkoxy group include tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetrapropoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxylane, dimethyldisilane. Examples include ethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, and hexyltriethoxysilane. Tetraalkoxysilane having a (RO) ₄ Si structure is highly developed in the process of condensation polymerization. It is preferable because a strong siloxane network cross-linked is easily formed, and tetraethoxysilane is relatively stable in an aqueous solvent after hydrolysis.

  In the present invention, alkoxysilane may be used as a hydrolyzate obtained by converting an alkoxy group to a silanol group by hydrolysis in advance, or as an oligomer that is partially condensation-polymerized by a siloxane bond, or together with these. Is preferable in order to complete the process in a short time. In order to promote hydrolysis of alkoxysilane, it is preferable to use an acid catalyst, and hydrochloric acid is generally used. In order to hydrolyze the alkoxysilane, about 0.001 to 0.05 mol of hydrochloric acid is added to 1 mol of alkoxysilane.

  In the present invention, the organic / inorganic hybrid layer is formed by using a coating agent comprising an aqueous solution or an alcohol mixed aqueous solution containing the vinyl alcohol resin and the alkoxysilane and / or a hydrolyzate thereof. With the above vinyl alcohol resin alone, the hydroxyl chain in the molecular chain is bound by hydrogen bonds in the process of solidifying as a coating film, the molecular chain is restrained, and excellent barrier performance against gases such as oxygen and nitrogen However, since water bonds are plasticized with respect to water molecules, the barrier performance cannot be expressed. By using a resin composition consisting of a vinyl alcohol resin and an alkoxysilane, an inorganic structure having a siloxane bond as a skeleton formed by condensation polymerization of alkoxysilanes, a hydrogen bond at each hydroxyl group of a polyvinyl alcohol resin, and a dehydration reaction Thus, a so-called organic-inorganic hybrid (hybrid) structure having a Si—O— covalent bond via oxygen appears. In such a structure, the molecular chain is more restrained than a single vinyl alcohol resin, and water vapor barrier performance can be exhibited. In addition, bonding with polar groups on the surface of the metal oxide layer improves adhesion, and a dense structure is formed by filling and reinforcing defects such as pinholes, cracks, and grain boundaries in the metal oxide layer. And can exhibit excellent gas barrier performance.

(Method for forming organic-inorganic hybrid layer)
There is no restriction | limiting in particular as a method of forming the organic-inorganic hybrid layer in this invention, It can form by the method according to a base film. For example, printing methods such as offset printing method, gravure printing method, silk screen printing method, roll coating method, dip coating method, bar coating method, die coating method, knife edge coating method, gravure coating method, kiss coating method, spin coating method The coating liquid may be coated using a method such as a combination of these.

  The film thickness of the organic-inorganic hybrid layer provided on the metal oxide layer is preferably 0.2 to 2 μm, more preferably 0.3 to 1 μm. If the thickness of the organic / inorganic hybrid layer is less than 0.2 μm, the gas barrier performance cannot be sufficiently exhibited. If the thickness of the organic / inorganic hybrid layer is 2 μm or more, the gas barrier performance due to cohesive failure in the organic / inorganic hybrid layer. There may be a problem such as a decrease in adhesion and a decrease in adhesion after processing into a laminate.

(Method of contact with hydrochloric acid)
In the transparent gas barrier film of the present invention, the chlorine content (A) per cm ^{3 of the} organic-inorganic hybrid layer obtained by condensation polymerization of vinyl alcohol resin and alkoxysilane is 50 to 150 μg / cm ^3. is important. A is given by the following equation (1).

A = Amount of detected chlorine (μg / cm ² ) / Thickness of organic-inorganic hybrid layer (μm) × 10 ⁴ (1)
In order to set A to 50 to 150 μg / cm ³ , after forming the organic-inorganic hybrid layer of the present invention, a hydrochloric acid aqueous solution (including a water / alcohol mixed solution) is applied or immersed in a hydrochloric acid aqueous solution, and then the solution Can be achieved by drying.

  As described above, for hydrolysis of alkoxysilane, it is preferable to add 0.001 to 0.05 mol of hydrochloric acid in advance to 1 mol of alkoxysilane to silanolate the alkoxy group. After application of the organic-inorganic hybrid layer, the hydrochloric acid evaporates with the solvent during drying and solidification, and hardly remains in the organic-inorganic hybrid layer. After the formation of the organic-inorganic hybrid layer of the present invention, the remaining silanol group in the organic-inorganic hybrid layer is coated or immersed in an aqueous hydrochloric acid solution or a water / alcohol mixed solution of hydrochloric acid and then dried. By promoting condensation polymerization to a siloxane bond, excellent gas barrier performance can be exhibited without additional heat treatment.

This effect is exhibited to the maximum when A is 50 to 150 μg / cm ³ . That is, if it is less than 30 μg / cm ³ , the condensation polymerization reaction is insufficient, and if it exceeds 150 μg / cm ³ , the condensation polymerization reaction is suppressed and the gas barrier performance becomes insufficient.

  The hydrochloric acid contact method in the method for producing a transparent gas barrier film of the present invention is not particularly limited as long as it can be immersed, applied, and dried by a method according to the base plastic film. For example, roll coating method, dip coating method, bar coating method, die coating method, knife edge coating method, gravure coating method, kiss coating method, spin coating method, etc., a combination method of these, or a film in a water tank filled with hydrochloric acid What is necessary is just to dry after using the method of conveying.

The concentration of hydrochloric acid applied on the organic-inorganic hybrid layer in the present invention is preferably selected to be 0.1 to 0.4 mol / L, but 0.1 to 0 in terms of hydrochloric acid residue and handling properties. The range of 2 mol / L is more preferable. Moreover, there is no restriction | limiting in particular in the coating amount of hydrochloric acid, However, When the drying of hydrochloric acid is considered, the range of 0.1-6.0 g / m < ² > is preferable. Furthermore, drying conditions should just dry the hydrochloric acid apply | coated to the transparent gas barrier film, and 80-200 degreeC is preferable, and 100-180 degreeC is more preferable from the point of the residue of hydrochloric acid and the thermal deformation of a transparent gas barrier film. .

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these. The physical properties in Examples and Comparative Examples were measured as follows.

(1) Oxygen permeability (cc / m ² · 24 hr · atm)
Based on the isobaric method described in JIS K7126-2: 2006, using a transparent gas barrier film under conditions of a temperature of 23 ° C. and a humidity of 90% RH using an oxygen transmission meter (OXTRAN 2/20) manufactured by MOCON of the United States. The oxygen transmission rate was measured.

(2) Water vapor transmission rate (g / m ² · 24 hr)
The infrared gas sensor described in Appendix B of JIS K7129: 2008, using a transparent gas barrier film under conditions of a temperature of 40 ° C. and a humidity of 90% RH, using an oxygen transmission meter (PERMATRAN W3 / 31) manufactured by MOCON, USA The water vapor transmission rate was measured based on the method.

(3) Thickness of organic / inorganic hybrid layer (μm)
Regarding the thickness of the organic-inorganic hybrid layer, the transparent gas barrier film was cut in the thickness direction with a microtome, and the cross section was observed with a scanning electron microscope (SEM). SEM used Hitachi scanning electron microscope S-3400N manufactured by Hitachi High-Technologies Corporation, and three points were imaged at a magnification of 50,000 times. In the obtained three images, the thickness of the organic-inorganic hybrid layer was measured, and the average value of them was taken as the thickness of the organic-inorganic hybrid layer.

(4) Chlorine content (μg / cm ³ )
A transparent gas barrier film is cut into 100 mm × 100 mm to prepare a cut sample, immersed in 100 mL of water at 25 ° C. for 20 minutes, and then the ion is made by DIONEX using a sodium carbonate / sodium bicarbonate mixed aqueous solution as a mobile phase. Chlorine content (A) (μg / cm ³ ) per 1 cm ³ of the organic / inorganic hybrid layer was calculated by quantifying the detected amount of chlorine ions using the chromatography system ICS1500. A = Amount of detected chlorine (μg / cm ² ) / Organic / inorganic hybrid layer thickness (μm) × 10 ⁴ .

Example 1
<Metal oxide layer>
A biaxially stretched polyethylene terephthalate film (P60 manufactured by Toray Industries, Inc.) having a thickness of 12 μm was used as the base plastic film, and an aluminum oxide layer having a thickness of 15 nm was formed by a reactive vacuum deposition method to form a metal oxide layer.

<Vinyl alcohol resin solution>
As a vinyl alcohol resin, polyvinyl alcohol (hereinafter also abbreviated as PVA. Polymerization degree 1,700, saponification degree 98.5%) was put into a solvent of water / isopropyl alcohol = 97/3 by weight ratio. The mixture was heated and stirred at 90 ° C. to obtain a polyvinyl alcohol solution having a solid content of 10% by weight.

<Alkoxysilane solution>
To a solution obtained by mixing 5.4 g of tetraethoxysilane (hereinafter sometimes abbreviated as TEOS) and 2.2 g of methanol, 9.9 g of a 0.02 mol / L hydrochloric acid aqueous solution (0.007 hydrochloric acid with respect to 1 mol of TEOS). Mol) was dropped while stirring to obtain a tetraethoxysilane hydrolyzed solution.

<Organic / inorganic hybrid layer>
Mix the polyvinyl alcohol solution and the alkoxy run solution so that the weight ratio of the solid content of PVA and the solid content of TEOS in terms of SiO ₂ (solid weight of PVA / weight of solid content of TEOS in terms of SiO ₂ ) is 35/65. -It stirred and diluted with water and the coating liquid of 5.4 weight% of solid content was obtained. This coating solution was applied onto the aluminum oxide layer and dried at 120 ° C. to form a 0.39 μm organic-inorganic hybrid layer to obtain a laminate.

<Coating of hydrochloric acid solution>
A 0.1 mol / L hydrochloric acid aqueous solution was applied onto the gas barrier film on which the organic-inorganic hybrid layer was formed by a gravure coating method so that the hydrochloric acid coating amount was 3.0 g / m ² , Dry for 2 seconds.

(Example 2)
A transparent gas barrier film was obtained in the same manner as in Example 1 except that a 0.2 mol / L hydrochloric acid aqueous solution was used.

(Example 3)
A transparent gas barrier film was obtained in the same manner as in Example 1 except that the thickness of the organic / inorganic mixed layer was 0.22 μm.

Example 4
A transparent gas barrier film was obtained in the same manner as in Example 2 except that the thickness of the organic / inorganic mixed layer was 0.22 μm.

(Example 5)
A transparent gas barrier film was obtained in the same manner as in Example 1 except that the thickness of the organic / inorganic mixed layer was 0.52 μm.

(Example 6)
A transparent gas barrier film was obtained in the same manner as in Example 2 except that the thickness of the organic / inorganic mixed layer was 0.52 μm.

(Comparative Example 1)
A transparent gas barrier film was obtained in the same manner as in Example 1 except that the hydrochloric acid aqueous solution was not applied.

(Comparative Example 2)
A transparent gas barrier film was obtained in the same manner as in Comparative Example 1 except that heat treatment was performed at 60 ° C. for 72 hours after forming the organic-inorganic hybrid layer.

(Comparative Example 3)
A transparent gas barrier film was obtained in the same manner as in Comparative Example 1 except that the heat treatment was performed at 80 ° C. for 168 hours after the organic-inorganic hybrid layer was formed.

(Comparative Example 4)
A transparent gas barrier film was obtained in the same manner as in Example 1 except that 0.05 mol / L hydrochloric acid aqueous solution was used.

(Comparative Example 5)
A transparent gas barrier film was obtained in the same manner as in Example 1 except that 0.5 mol / L hydrochloric acid aqueous solution was used.

(Comparative Example 6)
When the alkoxysilane solution of Example 1 was prepared, 9.9 g of 0.15 mol / L hydrochloric acid aqueous solution (0.05 mol of hydrochloric acid with respect to 1 mol of TEOS) was added dropwise with stirring, so that tetraethoxysilane hydrolyzed. A decomposition solution was obtained. In the same manner as in Example 1, a 0.41 μm organic-inorganic hybrid layer was laminated, and no aqueous hydrochloric acid solution was applied.

As is clear from the results of the above examples, the transparent gas barrier film of the present invention was a good transparent gas barrier film that exhibited stable gas barrier performance without heat treatment. On the other hand, in Comparative Examples 1 and 2, chlorine is below the detection limit and cannot exhibit sufficient gas barrier performance. In Comparative Example 3, the gas barrier performance is insufficient and the film is thermally deformed by high-temperature heat treatment. A bug also occurred. In Comparative Example 4, the concentration of the aqueous hydrochloric acid solution was low, so the chlorine content was low and sufficient gas barrier performance was not exhibited. In Comparative Example 5, the concentration of the aqueous hydrochloric acid solution was high, condensation polymerization was suppressed, and the gas barrier performance was sufficient. I didn't. In Comparative Example 6, hydrochloric acid sufficient to hydrolyze TEOS was added, but after application, the organic / inorganic hybrid layer was mixed with the organic / inorganic hybrid layer because the hydrochloric acid evaporated when dried at 120 ° C. to form the organic / inorganic hybrid layer. The chlorine in the layer was below the detection limit, and the gas barrier performance was insufficient.

Claims (3)

An organic-inorganic hybrid layer obtained by condensation polymerization of a metal oxide layer and a vinyl alcohol-based resin and an alkoxysilane is laminated on at least one surface of the base plastic film. In the organic-inorganic hybrid layer, the following formula (1) A transparent gas barrier film, wherein the chlorine content (A) per cm ³ obtained in step 1 is 50 to 100 μg / cm ³ .
A = Amount of detected chlorine (μg / cm ² ) / Thickness of organic-inorganic hybrid layer (μm) × 10 ⁴ (1)   The transparent gas barrier film according to claim 1, wherein the metal oxide layer is a layer made of aluminum oxide, and the thickness of the organic-inorganic hybrid layer is 0.2 μm to 2 μm. Forming a metal oxide layer on a base plastic film, applying a coating liquid comprising a polyvinyl alcohol-based resin and an alkoxysilane on the metal oxide layer, and after drying and solidifying, contacting with an aqueous hydrochloric acid solution and drying A method for producing a transparent gas barrier film.