JP4065266B2 - Gas barrier film and method for producing the same - Google Patents

Description

  The present invention relates to a transparent gas barrier film used in the field of packaging foods, pharmaceuticals, precision electronic parts and the like.

  In recent years, packaging materials used in the packaging field of foods, pharmaceuticals, precision electronic components, etc. are used to maintain the taste and freshness by suppressing the alteration of contents, especially the oxidation of fats and oils and the alteration of proteins in foods. In addition, in pharmaceuticals, the effects of oxygen permeating through packaging materials are prevented in order to suppress the deterioration of active ingredients and maintain their efficacy, and in precision electronic parts, to suppress the corrosion of metal parts and prevent poor insulation. Therefore, it is required to have a gas barrier property to block gas (gas).

For this purpose, polymer films that are generally said to have a relatively high gas barrier property such as polypropylene (KOP), polyethylene terephthalate (KPET), or ethylene vinyl alcohol copolymer (EVOH) coated with vinylidene chloride resin are used as gas barrier materials. Generally used is a packaging film using a gas barrier material or a deposited film in which a silicon oxide thin film such as silicon oxide (SiO _x ) is provided on a transparent polymer substrate by means of vacuum deposition or the like. It has been.

  However, the packaging film using the above-mentioned EVOH is easily affected by temperature and humidity, and the gas barrier property may be further lowered depending on the change. In addition, packaging films using vinylidene chloride resins such as KOP and KPET are said to be one of the causes of acid rain because they generate chlorine gas when incinerated after disposal. There is. In addition, a vapor deposition film in which a silicon oxide thin film is provided on a substrate made of a transparent polymer by means such as vacuum vapor deposition is likely to crack the vapor deposition film due to bending or the like, and as a result, gas barrier properties may be lowered.

Therefore, as a packaging film that overcomes these drawbacks, as a method for coating a film with a liquid composition comprising a water-soluble inorganic substance or polymer and developing a high gas barrier property, a hydrophilic polymer solution such as polyvinyl alcohol (PVA) There has been proposed a method of imparting gas barrier properties by mixing a hydrolyzed solution of a metal alkoxide, coating the film, drying and heat-treating it, and causing the hydrophilic polymer and the metal alkoxide to interact with each other (Patent Document 1). These methods combine the excellent gas barrier properties of metal oxides with the flexibility of polymers, and have high gas barrier properties and practicality that can withstand rough handling such as bending.
However, it is not easy to highly complex the hydrophilic polymer and the metal oxide, and there is a problem that the gas barrier property is impaired particularly when exposed to a high humidity for a long time.

  Therefore, in place of polyvinyl alcohol, those using a mixture of ethylene / vinyl alcohol copolymer in polyvinyl alcohol (Patent Document 2), those using modified polyvinyl alcohol as polyvinyl alcohol (Patent Document 3), etc. have been reported. In addition, a method of using an alkoxysilane having an imino group as a silane compound and aging after drying to form a gas barrier layer has been reported (Patent Document 4). As a result, although the gas barrier property showed a certain improvement, it was difficult to say that the gas barrier property was sufficiently improved especially when exposed to high humidity for a long time.

Further, a gas barrier layer provided with an overcoat layer (Patent Document 5) has also been proposed, which is effective for long-time exposure under high humidity, but the manufacturing process becomes complicated. was there.
JP-A-4-345841 and JP-A-6-192454 JP 2001-219506 A JP 2004-143197 A JP 2002-292810 A JP 2002-67214 A

  The present invention solves the above-mentioned conventional drawbacks, and is transparent and has a substantially sufficient gas barrier property without providing an overcoat layer, and the gas barrier property is lowered with the passage of time under high humidity. Provides a gas barrier film having a small thickness and a method for producing the same.

The present inventors have found that the problem can be solved by a film having a specific oxygen permeability, and have completed the present invention.
That is, the invention described in claim 1 is represented by the general formula [1] (wherein R represents the same or different alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 10). The alkoxysilane and / or the alkoxycondensate polycondensate is 6 to 10 moles of water relative to the silicon atoms of the alkoxysilane and / or alkoxysilane polycondensate , and the mass of the water is 0.3 to 3 It hydrolyzes to a hydrolysis rate of 90% or more without gelation in a solution having a pH of 0.5 to 3.5 containing an organic solvent and an acid in double amount , and 100 weight of silicon oxide in the hydrolyzed solution 25 to 100 parts by weight of polyvinyl alcohol solution mixed coating liquid temper made against part, after performing coating layer by coating the coating solution on a substrate of plastic film, 1 at 100 ° C. below the temperature Dry for ~ 30 seconds, then 80 ° C or higher The oxygen permeability measured under the same condition after conditioned at 20 ° C.-90% RH for 48 hours is 10 cc / m ² · 24 Hr · atm or less A method for producing a gas barrier film,
Invention of Claim 2 is obtained by the manufacturing method of Claim 1, does not have an overcoat layer on the said coat layer, and after humidity-conditioning for 48 hours on 20 degreeC-90% RH conditions, A gas barrier film characterized by having an oxygen permeability measured in (10) of 10 cc / m ² · 24 Hr · atm or less,
According to a third aspect of the invention, having a further adhesive layer between the plastic film and the coating layer, the gas barrier film according to claim 2,
The invention according to claim 4 is the gas barrier film according to claim 2 or 3 , wherein the plastic film is a stretched polyamide film, a stretched polypropylene film or a stretched polyester film.
It is.

  The present invention is excellent in flexibility, transparency, moisture resistance, solvent resistance, etc., and without providing an overcoat layer, it is excellent in gas barrier properties, particularly oxygen barrier properties, and for a long time under high humidity, for example, 90 Even if it is 1 month or more in% RH, there exists an effect that oxygen barrier property does not fall. Therefore, for example, in food packaging applications, the oxygen concentration can be maintained at 0% for a long time even under high humidity in the bag, and food discoloration, microbial growth, and the like can be prevented.

Hereinafter, the present invention will be described in detail.
The alkoxysilane and its polycondensate used in the present invention (hereinafter also simply referred to as “alkoxysilane”) are represented by the above general formula [1] (wherein R represents the same or different alkyl group having 1 to 4 carbon atoms, n represents an integer of 0 to 10.), and these can be used alone or in combination.
Polyvinyl alcohol is not particularly limited, but 80% or more of a saponified product is preferable, and a completely saponified product is more preferably used. The completely saponified product is more compatible with the hydrolyzed product obtained by hydrolyzing the alkoxysilane and forms a denser barrier layer. The degree of polymerization of polyvinyl alcohol is preferably 200 to 3,500.
The polyvinyl alcohol is 25 to 100 parts by weight, preferably 60 to 100 parts by weight with respect to 100 parts by weight of silicon oxide (SiO ₂ equivalent) in the hydrolyzate of alkoxysilane. When the weight ratio of polyvinyl alcohol is lower than 25 parts by weight, not only the flexibility of the barrier layer is sufficient and cracks are easily generated, but also the gas barrier property is lowered. On the other hand, when it is larger than 100 parts by weight, the gas barrier property is lowered, which is not preferable.

  The plastic film of the base material used in the present invention is a polyolefin resin such as polyethylene or polypropylene; a polyester resin such as polyethylene terephthalate, polyethylene isophthalate, polyethylene-2,6-naphthalate, or polybutylene terephthalate; Polyether resins; Polyamide resins such as polyamide-6, polyamide-6,6, polymetaxylene adipamide; Vinyl resins such as polystyrene, poly (meth) acrylate, polyacrylonitrile, polyvinyl acetate; Polycarbonate Cellulose resin such as cellulose acetate; Polyimide; Polyetherimide; Polyphenylene sulfide; Polyethersulfone; Polysulfone; Ton; a films mainly composed of thermoplastic resins such as polyether ketone ketone. These thermoplastic resins may be a homopolymer or a copolymer. In addition, the plastic film used for this invention is not limited to the said thermoplastic resin, The non-thermoplastic film represented by the cellophane can also be used. As the film, either an unstretched film or a uniaxially or biaxially stretched film can be used. However, a stretched polyamide film, a stretched polypropylene film or a stretched film is used from the viewpoint of ease of coating when coating a barrier layer and the strength of the barrier film. A polyester film is most preferred.

The gas barrier film of the present invention has an oxygen permeability of 10 cc / m ² · 24 Hr · atm or less measured under the same condition after humidity conditioning at 20 ° C.-90% RH for 48 hours.
The oxygen permeability under high humidity reaches almost saturation in 24 to 48 hours when measured at 20 ° C. and 90% RH. Therefore, after conditioning for 48 hours under the condition of 20 ° C.-90% RH, if the oxygen permeability measured under the same condition is 10 cc / m ² · 24 Hr · atm or less, under high humidity, for example, 90% RH, Even if it is kept for at least one month for a long time, it shows a practically sufficient oxygen barrier property.

The gas barrier film of the present invention hydrolyzes alkoxysilane to a hydrolysis rate of 90% or more without gelation in a solution containing water , an acid and an organic solvent , and mixes a polyvinyl alcohol solution to prepare a coating solution. The coating liquid is coated on a plastic film substrate, dried at a temperature of 100 ° C. or lower for 1 to 30 seconds , and then aged at 80 ° C. or lower for at least 24 hours.

  Hydrolysis of the alkoxysilane is carried out by heating the alkoxysilane in a solution containing water, an acid and an organic solvent. At this time, polycondensation of the alkoxysilane hydrolyzate also occurs simultaneously. The amount of water used is 6 to 10 moles per silicon atom of alkoxysilane. When the amount is more than 10 mol, polycondensation of the hydrolyzed silicate proceeds too much and the solution gels. The gelled liquid cannot be uniformly mixed with the polyvinyl alcohol solution. On the other hand, when the amount is less than 6 mol, it is substantially difficult to achieve a hydrolysis rate of 90% or more of alkoxysilane.

The acid acts as a catalyst for alkoxysilane hydrolysis and polycondensation. As the acid used, mineral acids such as hydrochloric acid and nitric acid and other inorganic acids are preferably used. The pH during hydrolysis is 0.5 to 3.5, preferably 2 to 2.7. If the pH is greater than 3.5, hydrolysis does not proceed. When the pH is less than 0.5, hydrolysis proceeds sufficiently, but at the same time, polycondensation proceeds remarkably and the solution gels.
The temperature at the time of hydrolysis is 30 to 60 ° C, preferably 40 to 55 ° C. If it is higher than 60 ° C., polycondensation proceeds and the solution gels. On the other hand, if the temperature is lower than 30 ° C., hydrolysis does not proceed sufficiently and a longer time is required, which is not practical. The hydrolysis time varies depending on the pH and temperature of the solution, but is generally 30 to 400 minutes.

Examples of the organic solvent to be used include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butanol and the like, and ethyl alcohol and isopropyl alcohol are particularly preferably used. The amount of the organic solvent is 0.3 to 3 parts based on the weight of water used for hydrolysis. When the amount is more than 3 parts, it is difficult to recover the organic solvent, and when the amount is less than 0.3 part, the solution gels during the hydrolysis of the alkoxysilane.
By the above method, it is possible to obtain a solution that does not gel despite the hydrolysis rate of 90% or more of alkoxysilane.

The hydrolyzed liquid of alkoxysilane is mixed with a polyvinyl alcohol solution to prepare a coating liquid. Polyvinyl alcohol is 25 to 100 parts by weight, preferably 60 to 100 parts by weight with respect to 100 parts by weight of silicon oxide (SiO ₂ equivalent) in the hydrolyzed solution. When the weight ratio of polyvinyl alcohol is lower than 25 parts by weight, not only the flexibility of the barrier layer is sufficient and cracks are easily generated, but also the gas barrier property is lowered. When it is larger than 100 parts by weight, the gas barrier property is lowered, which is not preferable.

  In order to apply the coating liquid thus prepared to a substrate made of a plastic film, a normal coating method can be used. Examples include reverse roll coating, dip coating, Mayer bar coating, knife coating, nozzle coating, die coating, spray coating, curtain coating, screen printing, gravure coating, and other printing methods. It is done. These may be combined. The coating layer thickness after drying is 0.1 to 3.0 μm, preferably 0.5 to 1.5 μm. When the thickness after drying is less than 0.1 μm, sufficient gas barrier properties are not exhibited. On the other hand, if the coating layer thickness after drying exceeds 3.0 μm, the gas barrier property is lowered due to the occurrence of cracks and insufficient adhesion strength, and the cost is increased.

  In the method of the present invention, an adhesive layer can be provided between the substrate made of a plastic film and the coating layer as necessary. The adhesive layer contains a compound containing an isocyanate group, a carboxyl group, an acid anhydride group, an oxazolinyl group, a thioisocyanate group, and an epoxy group, and can be coated and dried by the coating method described above. .

After coating, the coating layer is dried and aged to form a barrier layer having high gas barrier properties even under high humidity.
Drying is performed at a dryer internal temperature of 100 ° C. or lower, preferably 50 to 100 ° C. for 1 to 30 seconds. When it is dried at a temperature higher than 100 ° C., fine voids are formed in the barrier layer due to rapid evaporation of the solvent, and the gas barrier property is lowered. When the drying time is longer than 30 seconds, the volumetric shrinkage of the coating film becomes remarkable. As a result, cracks are generated in the coating film and the appearance is not only impaired, but also the gas barrier property is lowered.
After drying, aging is performed at an ambient temperature of 20 to 80 ° C. for 24 hours or longer, preferably at 40 to 60 ° C. for 36 hours or longer. When the temperature is higher than 80 ° C., the flatness of the base material made of a plastic film is impaired, and processing suitability such as printability is deteriorated. Moreover, when it is lower than 20 ° C., a sufficient aging effect cannot be obtained.

In the method of the present invention, the hydrolysis rate of the alkoxysilane and / or alkoxysilane polycondensate is high, and the presence of many silanol groups in the hydrolyzate allows the silicate and polyvinyl alcohol to be mixed with each other with high compatibility. As a result, a coated film having a high oxygen barrier property even under high humidity can be obtained.
Further, the aging treatment forms a strong interaction mainly consisting of densification of the barrier layer and hydrogen bonding of silicate and polyvinyl alcohol. Thereby, a highly practical transparent gas barrier film in which the deterioration of the gas barrier property is small with the passage of time under high humidity can be obtained.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, the apparatus and conditions used for the measurement of each physical property are as follows.
(1) Oxygen permeability measurement An oxygen permeability measuring apparatus model 8000 manufactured by Illinois was used. The measurement was performed at 20 ° C.-90% RH for 48 hours.
(2) Measurement of hydrolysis rate The alcohol component was analyzed and quantified using a gas chromatograph G-3810 manufactured by Yanaco and a gas chromatography column Gaskuropack 54 60/80 mesh, and the hydrolysis rate of alkoxysilane was determined based on the yield.
(3) Peel strength Peel strength was measured using a dry laminate adhesive TM-265 / CAT-RT37 (manufactured by Toyo Morton Co., Ltd.) and laminated with 50 μm polyethylene (FC-D; manufactured by Toh Cello Co., Ltd.), followed by a tensile test. Using a machine (TENSILON RTA-100 manufactured by ORIENTEC), measurement was performed at a tensile speed of 100 mm / min and a film width of 15 mm.

Example 1
8.3 times moles of pure water with respect to 1 atom of silicon of ethyl silicate 40 (Colcoat, SiO ₂ min 40% pentamer), and 1.2 times of ethanol with respect to the weight of silicon oxide, After adjusting the pH to 2.3 using 1N hydrochloric acid, hydrolysis was performed at 50 ° C. for 3.5 hours with stirring. After cooling, pure water was added to this solution to obtain a transparent solution having a silicon oxide concentration of 8% by weight. At this time, the hydrolysis rate of the silicate was 97%.
On the other hand, polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA-110, saponification degree 98-99%, average polymerization degree 1000) was dissolved in pure water to obtain an aqueous solution having a concentration of 7% by weight. The above solution was mixed and stirred so that the weight ratio of silicon oxide to polyvinyl alcohol was 60/40 to obtain a coating solution.
The resulting coating solution was coated on a stretched nylon film (Kohjin biaxially stretched polyamide film “Bonyl”, thickness 15 μm) with a Mayer bar and dried at 80 ° C. for 15 seconds. The temperature of the film at this time was 46 ° C. with an infrared thermometer. After returning the film to room temperature, it was aged at 55 ° C. for 96 hours to obtain a gas barrier film. The thickness of the coat layer of this film was 1.0 μm.
The obtained film was conditioned at 20 ° C.-90% RH for 1 hour and 48 hours, and then the oxygen gas permeability measured under the same conditions is shown in Table 1.

Example 2
Example 1 is the same as Example 1 except that ethyl silicate 28 (SiO ₂ min 28% monomer manufactured by Colcoat Co.) is used instead of ethyl silicate 40 (Col coat SiO ₂ min 40% pentamer). To obtain a film.
The obtained film was conditioned at 20 ° C.-90% RH for 1 hour and 48 hours, and then the oxygen gas permeability measured under the same conditions is shown in Table 1.

Comparative Example 1
In Example 1, the silicon oxide of ethyl silicate 40 was hydrolyzed with 2 moles of pure water. The hydrolysis rate at this time was 60%. Otherwise, a film was obtained in the same manner as described in Example 1, and the values obtained by measuring the oxygen gas permeability are shown in Table 1.

Comparative Example 2
In Example 1, the silicon oxide of ethyl silicate 40 was hydrolyzed using 12 times moles of pure water. This solution gradually became cloudy and the whole solution was gelled, so that it could not be mixed with the aqueous polyvinyl alcohol solution. The hydrolysis rate at this time was 98%.

Comparative Example 3
In Example 1, a film was obtained in the same manner as in Example 1 except that after coating the coating solution, drying was performed at 110 ° C. for 10 minutes, and then aging was not performed.
Table 1 shows values obtained by measuring the oxygen gas permeability of the obtained film.

The gas barrier film of Example 1 did not have high oxygen gas permeability even under a long period of high humidity, and was maintained at 10 cc / m ² · 24 Hr · atm or less. On the other hand, in Comparative Example 1 in which the hydrolysis rate of the silicate was low and in Comparative Example 3 in which the coating layer was dried at 110 ° C., the gas barrier property was maintained under high humidity conditions for a long time although the oxygen gas permeability at the initial stage of high humidity was low. Decreased significantly.

Examples 3 and 4 and Comparative Examples 4 and 5
A silicate hydrolysis solution and an aqueous solution of polyvinyl alcohol were prepared in the same manner as in Example 1, and the mixing ratio was changed as shown in Table 2, and the rest was carried out in the same manner as in Example 1 to obtain a film. Table 2 shows the measured values of transmittance.

  It can be seen that a coating layer having a composition ratio of polyvinyl alcohol and silicate, that is, a weight ratio of polyvinyl alcohol / silicon oxide of 50/50 to 20/80, has a high gas barrier property even under a long period of time under high humidity.

Examples 5 and 6
Weight of 1.3 times of ethanol added to the pure water and the silicon oxide of 8.3 mols per mol of the silicon 1 atom of ethyl silicate 40 (Colcoat Co. SiO ₂ min 40%), with aluminum sulfate Then, the pH was adjusted to 2.5, followed by hydrolysis at 55 ° C. for 3 hours with stirring. After cooling this solution, pure water was added to obtain a transparent solution containing 8% by weight of silicon oxide. On the other hand, polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA-110, saponification degree 98-99%, average polymerization degree 1000) was dissolved in pure water to obtain a 7% by weight aqueous solution. The above solution was mixed and stirred so that the weight ratio of polyvinyl alcohol to silicon oxide was 40/60 to obtain a coating solution.
OPP (manufactured by Nimura Chemical Co., Ltd.) and PET film (manufactured by Mitsubishi Chemical Polyester Co., Ltd.) were coated with urethane anchor coating material AD-335AE / CAT-60 (manufactured by Toyo Morton Co., Ltd.) and dried at 90 ° C. for 10 seconds. The thickness of the adhesive layer at that time was 0.2 μm. Each substrate was coated with the prepared coating solution and dried at 80 ° C. for 15 seconds. After returning the film to room temperature, it was aged at 55 ° C. for 96 hours to obtain a gas barrier film. The thickness of the barrier layer was 1.0 μm.
The obtained film was conditioned at 20 ° C. and 90% RH for 1 hour and 48 hours, and the measured oxygen gas permeability and peel strength under the same conditions are shown in Table 3.

Comparative Example 5
19.9 g of ethyl silicate cake, 18.77 g of ethanol, 0.27 g of 2N hydrochloric acid and 1.6 g of water were mixed and stirred at room temperature for 30 minutes to 1 hour. At this time, the molar ratio of ethyl silicate to water in the mixture was 1: 1.95. Subsequently, 30 L of Soarnol (isopropyl alcohol aqueous solution containing 30% by weight of ethylene / vinyl alcohol random copolymer, Nippon Synthetic Chemical Co., Ltd.) 6.26 g, polyvinyl alcohol aqueous solution (concentration: 10% by weight) 31.37 g, water 17. 69 g, 6.26 g of methanol, 6.10 g of n-butanol and 0.02 g of cetyl alcohol were added and stirred at 70 ° C. for 20 to 30 minutes to obtain a coating solution. After applying a methyl chloroform solution of metal acetylacetone complex salt (manufactured by Nippon Synthetic Chemical Co., Ltd., Aron Polyprimer) as an anchor coating agent in advance on one side of a polypropylene film (thickness 25 μm), and drying at 80 ° C. for 10 seconds, The coating solution was applied and dried at 80 ° C. for 4 minutes. The surface opposite to the coated surface of the obtained film was thermally shielded and aged at 115 ° C. for 4 minutes to obtain a laminated film having a thickness of 30 μm.
The obtained film was conditioned at 20 ° C. and 90% RH for 1 hour and 48 hours, and the measured oxygen gas permeability and peel strength under the same conditions are shown in Table 3.

  Even when OPP or PET is used as the substrate, a practical barrier film can be obtained in which the decrease in gas barrier properties is small under high humidity and the adhesion of the barrier layer is high.

  As described above, according to the present invention, it is excellent in flexibility, transparency, moisture resistance, solvent resistance, etc., and without providing an overcoat layer, for a long time under high humidity, gas barrier properties, particularly A gas barrier film having excellent oxygen barrier properties is provided and can be used as a packaging material in various fields such as foods, pharmaceuticals, and precision electronic parts.

Claims (4)

Of alkoxysilane and / or alkoxysilane represented by the general formula [1] (wherein R represents the same or different alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 10). The polycondensate contains 6 to 10 moles of water, 0.3 to 3 times the amount of the organic solvent, and an acid with respect to the silicon atoms of the alkoxysilane and / or the polycondensate of alkoxysilane. In a solution having a pH of 0.5 to 3.5, it hydrolyzes to a hydrolysis rate of 90% or more without gelation, and 25 to 100 parts by weight with respect to 100 parts by weight of silicon oxide in the hydrolyzed solution. polyvinyl alcohol solution mixed coating solution adjustment made to, after performing a coating layer by coating the coating solution on a substrate of plastic film, and dried 30 seconds at 100 ° C. or less of the temperature, and then 80 ° C. or less At least 24 hours A method for producing a gas barrier film having an oxygen permeability of 10 cc / m ² · 24 Hr · atm or less measured under the same conditions after humidity conditioning at 20 ° C.-90% RH for 48 hours .

It is obtained by the production method according to claim 1 and does not have an overcoat layer on the coat layer, and after adjusting the humidity for 48 hours at 20 ° C.-90% RH, the oxygen permeability measured under the same condition is 10 cc. / M ² A gas barrier film characterized by being 24 Hr · atm or less. The gas barrier film according to claim 2 , further comprising an adhesive layer between the plastic film and the coating layer.
The gas barrier film according to claim 2 or 3 , wherein the plastic film is a stretched polyamide film, a stretched polypropylene film or a stretched polyester film.