JP2556940B2 - Barrier laminated film and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a laminated film having excellent gas barrier properties.

[0002]

2. Description of the Related Art Thermoplastic resin films, particularly polyester films, are widely used because they are excellent in mechanical strength, chemical resistance and transparency and are inexpensive. For example, it is used as a base film for photography, a base film for magnetic tapes, a film for drawing, a film for electric devices such as capacitors, industrial materials such as membrane switches, touch panels, keyboards and labels. Further, it is also used as a packaging agent for food packaging.

However, when the polyester film is used as a packaging material such as food packaging, the gas barrier property is generally insufficient. For example, Table 1 shows the permeability of oxygen and water vapor between a polyethylene terephthalate (PET) film most commonly used as a polyester film and a polyvinylidene chloride (PVDC) film which is a film having excellent gas barrier properties.

[0004]

[Table 1]

1) The amount of oxygen gas which permeated the film at 1 atm for 24 hours using a 20 μm film.

2) The amount of water that has permeated the film at 40 ° C. and 90% RH for 24 hours using a 20 μm film.

As is clear from Table 1, the PET film is highly permeable to oxygen gas and water vapor and has a low gas barrier property.

In general, the gas barrier property of a substrate is a property in which adsorption, diffusibility and desorption of gas to the substrate are combined, and the following tendency tends to occur for a polymeric substrate: Polymers do not have the gas barrier properties of metals because they are not completely crystalline, as found in metals. In a film or sheet composed of a crystalline polymer,
The lower the affinity of the polymer with the gas, the smaller the intermolecular gap, and the better the barrier property, the more polar groups the polymer has in the gas adsorption, diffusion and desorption.

2. The higher the crystallinity of the polymer substrate, the better the gas barrier property.

3. Generally, a polymer having a symmetric molecular structure has a good gas barrier property.

4. The larger the crystal orientation of the polymer, the better the gas barrier property.

5. The higher the rigidity of the polymer chain, the better the gas barrier property.

6. The higher the cohesive energy density of the polymer, the larger the bonding force between the polymer chains and the better the gas barrier property. This is the case for polymers with polar groups.

The above properties 2 to 6 indicate that a substrate composed of a polymer having a dense molecular structure has a higher gas barrier property.

As described above, a polymer having a polar group generally has a good gas barrier property. However, polar groups such as hydroxyl groups and amide groups are likely to bond with water molecules, and their gas barrier properties decrease with increasing humidity. Therefore, a film made of such a resin having a polar group is laminated with a PVCD film whose gas barrier property is not affected by humidity, and is used as a laminate film having excellent gas barrier property independent of humidity.
Other types include a copolymer of vinyl alcohol and ethylene (trade name Eval), a copolymer of PVCD and acrylonitrile, and the like, which have excellent oxygen gas barrier properties that are not affected by humidity. Widely used as a film for food packaging.

However, since most of these gas barrier films use chlorine-based polymers, there are various causes such as carcinogenicity due to organic chlorine generated in the manufacturing process and disposal route, destruction of the ozone layer due to chlorine gas, and the like. I have a problem.

[0017]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned conventional drawbacks, and its object is to:
It is to provide a laminated film having excellent gas barrier properties. A further object of the present invention is to provide a method for producing a laminated film having such excellent properties.

[0018]

The laminated film of the present invention comprises a base film made of a thermoplastic resin; a composition containing an alkoxysilane, a silane coupling agent, and polyvinyl alcohol, which is polycondensed by a sol-gel method. The main component is a composite polymer having a linear polymer as a main component, and at least one composite polymer layer laminated on at least one surface of the base film is achieved, thereby achieving the above object. To be done.

In the method for producing a laminated film of the present invention, a composition containing an alkoxysilane, a silane coupling agent, and polyvinyl alcohol is mixed in the presence of a sol-gel method catalyst, a mineral acid, water and an organic solvent. A step of preparing a coating solution containing a composite polymer of the composition which is condensed and whose main component is a linear polymer; a step of applying the coating solution to at least one surface of a base film made of a thermoplastic resin And a step of forming a composite polymer layer on the surface of the base film by heat-treating the base film at a temperature of 120 ° C. or higher and at a temperature not higher than the melting point of the thermoplastic resin; The above object is achieved by the above.

According to a preferred embodiment, the composition further contains one or more metal alkoxides.

A transparent thermoplastic resin film is used as the base film of the present invention. Examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene-2,6-naphthalate and polybutylene terephthalate; polyether resins such as polyoxymethylene;
Polyamide resins such as nylon-6, nylon-6,6, polymethaxylene adipamide; polystyrene, poly (meth) acrylic acid ester, polyacrylonitrile,
Vinyl-based resins such as polyvinyl acetate; polycarbonate-based resins; cellulosic resins such as cellophane and acetate; polyimides; polyetherimides; polyphenylene sulfides; polyether sulfones; polysulfones; polyether ether ketones; polyether ketone ketones . These resins may be homopolymers or copolymers. Particularly, in consideration of mechanical strength, moldability and economy, polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate are preferable. Further, preferably, a copolymerized polyester containing 80 mol% or more of terephthalic acid as a dicarboxylic acid component and 80 mol% or more of ethylene glycol as a glycol component,
Alternatively, a mixture of polyesters containing polyethylene terephthalate in a proportion of 80% by weight or more is used.

As the other dicarboxylic acid component used in the polyester other than the copolymerized polyester and polyethylene terephthalate, any of aromatic, aliphatic and alicyclic dicarboxylic acids can be used. Aromatic dicarboxylic acids include isophthalic acid, orthophthalic acid,
2,6-naphthalenedicarboxylic acid or the like is used. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, sebacic acid, oxalic acid and the like. As the alicyclic dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid,
1,4-cyclohexanedicarboxylic acid or the like is used. As the glycol component, an aliphatic glycol having 2 to 8 carbon atoms or an alicyclic glycol having 6 to 12 carbon atoms is preferable. As such glycol,
1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1, 4-cyclohexane dimethacrylate, p-xylene glycol, diethylene glycol, triethylene glycol and the like. Polyether glycol may also be used as the glycol component, for example polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. may be used. Oxyacids such as p-hydroxybenzoic acid may also be used as part of the copolymerization component.

The dicarboxylic acid component and the glycol component are polymerized (or copolymerized) by a usual method to prepare a polyester.

As the substrate film, such a thermoplastic resin may be used alone, or one or more kinds of resins may be melt-mixed and formed into a film shape. Such a base film may be an unstretched film or a uniaxially or biaxially oriented film. Furthermore, a laminate in which two or more such films are laminated can also be used.

The alkoxysilane used in the present invention is
It is represented by Si (OR ¹ ) ₄ and R ¹ is a lower alkyl group. Specifically _{Si (O-CH 3) 4} , Si (O-C 2 H
₅ ) ₄ etc. are used. You may mix and use these alkoxysilanes.

In the present invention, the above-mentioned alkoxy is optionally used.
Zirconium alkoxide, Titanium with silane
Metal alkoxides such as
You. Zirconium alkoxide is Zr (OR²)_FourIndicated by
And R²Is a lower alkyl group. Specifically, Zr
(O-CH₃)_Four, Zr (O-C₂H_Five)_Four, Zr (O-i
so-C₃H₇)_Four, Zr (O-C_FourH₉)_FourUsed by
Can be done. Mix two or more of these alkoxides
You may use. Using zirconium alkoxide
Improves the toughness and heat resistance of the resulting laminated film
I do. The amount used is 100 weight of the above alkoxysilane.
10 parts by weight or less, preferably about
5 parts by weight. If it exceeds 10 parts by weight, the compound formed
The combined polymer becomes easier to gel, and the brittleness of the composite polymer
Of the composite polymer when the base film is coated.
-The layer is easily peeled off. Titanium alkoxide
Ti (OR³)_FourIndicated by R³Is a lower alkyl group
You. Specifically, Ti (O-CH₃)_Four, Ti (O-C₂
H_Five)_Four, Ti (O-C₃H₇)_Four, Ti (O-C_FourH₉)_Four
Etc. can be used. Two or more of these alkoxides
You may mix and use. For titanium alkoxide
The thermal conductivity of the resulting coating is low.
Therefore, the heat resistance of the base material is significantly improved. The usage amount is
5 parts by weight or less based on 100 parts by weight of alkoxysilane
Range, preferably about 3 parts by weight. 5 parts by weight
Above, the brittleness of the formed composite polymer increases.
The composite polymer peels off when the base film is coated.
It will be easier.

As the silane coupling agent used together with the above alkoxide, known organic reactive group-containing organoalkoxysilanes can be used. In particular, an organoalkoxysilane having an epoxy group is suitable. For example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β- (3,4-epoxycyclohexyl)
There is ethyltrimethoxysilane. Two or more kinds of such silane coupling agents may be mixed and used. The amount of such a silane coupling agent used is in the range of 1 to 20 parts by weight with respect to 100 parts by weight of the alkoxysilane. If 20 parts by weight or more is used, the rigidity and brittleness of the formed composite polymer increases, and the insulating properties and processability of the composite polymer layer decrease.

In the present invention, the composition constituting the composite polymer contains polyvinyl alcohol (PVA).
By adding PVA, the gas barrier property of the obtained composite polymer is significantly improved. The content of PVA is in the range of 50 to 200 parts by weight, preferably about 100 parts by weight, based on 100 parts by weight of the total amount of the above-mentioned alkoxysilane and metal alkoxide. When it exceeds 200 parts by weight, the brittleness of the composite polymer becomes large, and the water resistance of the obtained laminated film also decreases. If it is less than 50% by weight, the gas barrier property is deteriorated.

As the sol-gel method catalyst used in the method of the present invention, mainly as a polycondensation catalyst, a tertiary amine which is substantially insoluble in water and soluble in an organic solvent is used.
Examples thereof include N, N-dimethylbenzylamine, tripropylamine, tributylamine, tripentylamine and the like, and N, N-dimethylbenzylamine is particularly preferable. The total amount of alkoxysilane, metal alkoxide, and silane coupling agent is 1
It is 0.01 to 1 part by weight, preferably about 0.03 part by weight, per 00 parts by weight. The mineral acid used in the method of the present invention is used not only as a catalyst for the sol-gel method, but also as an acetalization catalyst (mainly a hydrolysis catalyst) described later. As the mineral acid, sulfuric acid, hydrochloric acid, nitric acid or the like is used. The amount of the mineral acid used is 0.001 to the total molar amount of the alkoxysilane, the metal alkoxide and the alkoxide component (silicate portion) of the silane coupling agent.
0.05 mol, preferably about 0. It is 01 mol.

In the method of the present invention, based on 1 mol of the total molar amount of the above-mentioned alkoxysilane and metal alkoxide,
0.8-2 mol of water is used. When the amount of water exceeds 2 moles, the polymer obtained from the alkoxysilane and the metal alkoxide becomes spherical particles, and the spherical particles are three-dimensionally crosslinked with each other to become a low density, porous polymer. . Porous polymers cannot improve the gas barrier properties of the base film. When the amount of water is less than 0.8 mol, the hydrolysis reaction is difficult to proceed.

As the organic solvent used in the method of the present invention, ethyl alcohol, isopropyl alcohol, butyl alcohol and the like are used. The amount of the solvent used is usually 30 to 100 parts by weight per 100 parts by weight of the total amount of the above-mentioned alkoxysilane, metal alkoxide, silane coupling agent, PVA, mineral acid and sol-gel method catalyst.

According to the method of the present invention, the laminated film of the present invention is formed, for example, as follows. First, the above-mentioned alkoxysilane, silane coupling agent, PVA,
A sol-gel method catalyst, a mineral acid, water, an organic solvent, and optionally a metal alkoxide are mixed to prepare a coating solution.
The polycondensation reaction gradually progresses in this coating liquid. Then, the coating liquid is applied to the base film by a conventional method and dried. By drying, the polycondensation of the above-mentioned alkoxysilane, metal alkoxide, silane coupling agent and PVA further progresses to form a layer of the composite polymer. Preferably, the above operation is repeated to laminate a plurality of composite polymer layers. Finally, the film coated with the above coating solution is heated at a temperature of 120 ° C. or higher and a melting point of the base film or lower, preferably in the range of 150 to 200 ° C. for 30 seconds to 10 minutes to obtain the present invention. A laminated film of is obtained. The laminated film of the present invention thus obtained has excellent gas barrier properties. The laminated film on which the single or plural composite polymer layers are formed in this manner is subjected to an acetalization treatment, if necessary. Specifically, this laminated film is immersed in an aldehyde solution containing an acid. Formaldehyde, acetaldehyde, butyraldehyde, etc. are used as the aldehyde. By applying an acetalization treatment, the unreacted hydroxyl groups derived from PVA present in the composite polymer in a trace amount react with the aldehyde to be acetalized, and the water resistance of the composite polymer is improved. (Moisture resistance) is further improved.

[0033]

In the method of the present invention, the alkoxysilane and metal alkoxide are hydrolyzed by the added water. Next, by the action of the sol-gel method catalyst, protons are taken from the generated hydroxyl groups, and the hydrolysis products are dehydrated and polycondensed. At this time, the silane coupling agent is also hydrolyzed at the same time, and the alkoxy group becomes a hydroxyl group. A ring-opening of the epoxy group also occurs due to the function of the catalyst to generate a hydroxyl group. The polycondensation reaction between the hydrolyzed silane coupling agent and the hydrolyzed alkoxide also proceeds.
Furthermore, since PVA is present in the reaction system, a reaction with the hydroxyl group of PVA also occurs. The polycondensate produced is Si
It is a composite polymer containing an inorganic part composed of a bond such as -O-Si, Si-O-Zr, and Si-O-Ti, and an organic part derived from a silane coupling agent. In the above reaction, for example, a linear polymer having a partial structural formula represented by the formula (II) and further having a part derived from the silane coupling agent is first produced. This polymer has an OR group (alkoxy group such as ethoxy group) branched from a linear polymer. This OR group is hydrolyzed by the existing mineral acid as a catalyst to become an OH group,
This undergoes a polycondensation reaction with PVA represented by the formula (I) to produce Si
It is believed that a composite polymer represented by the formula (III) having an —O—Si bond is formed. In the polycondensation reaction, the sol-gel method catalyst (base catalyst) works firstly
The H group is deprotonated and then polycondensation proceeds.

[0034]

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[0035]

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[0036]

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The above reaction proceeds at room temperature, and the viscosity of the coating solution increases during preparation. When this coating solution is applied to a base film and heated to remove the solvent and the alcohol produced by the polycondensation reaction, the polycondensation reaction is completed and a transparent composite polymer layer is formed on the base film. . When a plurality of composite polymer layers are laminated, the composite polymers between the layers also condense and the layers are firmly bonded. Furthermore, since the organic reactive group of the silane coupling agent and the hydroxyl group generated by hydrolysis are bonded to the hydroxyl group on the surface of the base material film, the adhesion between the base material film surface and the composite polymer layer is also good.

In the method of the present invention, the amount of water added is adjusted to 0.8 mol to 2 mol, preferably 1.5 mol, relative to 1 mol of the alkoxides, so that the above linear chain is used. A polymer is formed. Such a linear polymer has crystallinity and has a structure in which a large number of minute crystals are embedded in an amorphous portion. Such a crystal structure is a crystalline organic polymer (for example, vinylidene chloride or PVA).
In addition, a polar group (OH group) is partially present in the molecule, the cohesive energy of the molecule is high, and the rigidity of the molecular chain is also high, so that a good gas barrier property is exhibited. The Si-O-CH bond of the polymer represented by the formula (III) is the same as the stable bond state formed by acetylation or formalization of PVA.

The laminated film thus obtained is excellent in water resistance, but the water resistance is further improved by further performing the acetalization treatment as described above. As described above, the laminated film of the present invention exhibits sufficient barrier properties against H ₂ O permeation as well as barrier properties against oxygen and N _2, etc., and is also excellent in solvent resistance and chemical resistance. There is.

Since the laminated film of the present invention has the above-mentioned excellent properties, it is useful as a packaging material, and particularly excellent in gas barrier properties (O ₂ , N ₂ , H ₂ O, etc.).
It is preferably used as a film for food packaging.

[0041]

EXAMPLES Examples of the present invention will be described below.

(Example 1) 25 g of ethyl silicate, 25 g of ethanol, 1.86 g of 2N hydrochloric acid and 1.5 of water
1 g was mixed and stirred at 80 ° C. for 1-2 hours. At this time, the molar ratio of ethyl silicate and water of the above mixture is 1: 1.51. Then epoxy silane SH604
2.5 g of Toray Dow Corning Co., Ltd. was added and stirred.

To this was added 17.4 g of an aqueous solution containing 10% of PVA polymerization degree (2000; manufactured by Kuraray Co., Ltd.) and stirred for 1 to 2 hours, at which point N, N-dimethylbenzylamine 32% by weight ethanol became transparent. When 0.1 g of the solution was added and stirred, a viscous coating liquid was obtained.

The above coating solution was applied to a polyethylene terephthalate film having a thickness of 12 μm and dried at 150 ° C. for 5 minutes to obtain a laminated film having a thickness of 20 μm. As a result of evaluating the gas barrier properties of the obtained laminated film, the results obtained by measuring two samples are shown in Table 2.

[0045]

[Table 2]

1) Amount of O ₂ gas that has permeated the film at 1 atm for 24 hours.

2) The amount of H ₂ O that has passed through the film at 40 ° C. and 90% RH for 24 hours.

3) The amount of N ₂ gas that has permeated the film at 1 atm for 24 hours.

As is clear from the comparison of the results in Table 2 with Table 1, the laminated film of the present invention has a very low oxygen, water vapor and nitrogen permeability, and is a Saran film (manufactured by Asahi Kasei Kogyo KK; mainly composed of vinylidene chloride). It has a better gas barrier than acrylonitrile copolymer).

Example 2 The coating solution obtained in Example 1 was applied to a polyethylene terephthalate film having a thickness of 12 μm, dried at 150 ° C. for 5 minutes, cooled once to 25 ° C. or lower, and then in an acetaldehyde solution. Acetalized. In this way, the same thickness as in Example 1 was 20 μm.
A laminated film of m was obtained. The evaluation results of the gas barrier properties of the obtained laminated film were almost the same as in Example 1.

Example 3 In order to add toughness to the composite polymer, 1 g of zirconium isopropoxide was added to the coating liquid of Example 1 and a laminated film of the present invention was obtained in the same manner as in Example 2. . The obtained film had improved flexibility and toughness as compared with the films of Examples 1 and 2.

Example 4 A 5% aqueous solution of PVA was added to 25.
A viscous coating liquid was obtained in the same manner as in Example 1 except that 0 g was used. This coating solution is applied to a polypropylene film having a thickness of 20 μm and dried at 120 ° C. for 5 minutes,
After cooling once to 25 ° C. or less, acetalization treatment was performed in an acetaldehyde solution. Thickness 27
A μm laminated film was obtained. This film was evaluated in the same manner as in Example 1. Table 3 shows the results.

[0053]

[Table 3]

[0054]

According to the present invention, a laminated film having an extremely good gas barrier property can be obtained. The gas barrier property of the laminated film of the present invention is higher than that of the conventional PVDC film and the like, and is excellent in water resistance. It is also highly flexible and has excellent solvent resistance and chemical resistance. There is no concern about environmental pollution because it does not use chlorine compounds. Such a film can be used in various fields including packaging materials,
It is particularly suitable as a film for food packaging.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C08J 7/04 C08J 7/04 P (56) Reference JP-A-3-93542 (JP, A) JP-A 4-80030 (JP, A)

Claims (7)

(57) [Claims] 1. A linear polymer whose main component is obtained by polycondensing a base film made of a thermoplastic resin and a composition containing an alkoxysilane, a silane coupling agent and polyvinyl alcohol by a sol-gel method. And at least one composite polymer layer laminated on at least one side of the substrate film.
Having a laminated film 2. The laminated film according to claim 1, wherein the composition further contains one or more metal alkoxides. 3. A composition containing an alkoxysilane, a silane coupling agent, and polyvinyl alcohol is polycondensed in the presence of a sol-gel method catalyst, a mineral acid, water, and an organic solvent, and the main component is linear. Preparing a coating solution containing a composite polymer of the composition comprising a polymer;
At least one side of the base film made of a thermoplastic resin,
The step of applying the coating liquid; and the laminate at 120 ° C.
The method for producing a laminated film, which includes the step of forming a composite polymer layer on the surface of the base film by heat treatment at a temperature not lower than the melting point of the thermoplastic resin. 4. The method of claim 3, wherein the composition further contains one or more metal alkoxides. 5. The sol-gel method catalyst is a tertiary amine which is substantially insoluble in water and soluble in an organic solvent.
The method according to claim 3. 6. The water is used in a ratio of 0.8 to 2 mol per mol of the alkoxysilane.
The method described in. 7. The method further comprises the step of acetalizing the base film having the composite polymer layer formed thereon.
The method according to claim 3.