JPH107824A - Gas barrier film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare the subject film comprising an inorganic layered compound having a specific particle diameter and a water-soluble polymer and having high gas barrier property, adhesiveness, etc., under high moisture by formation of coating film whose surface parameter is controlled. SOLUTION: This film is obtained by forming a coating film composed mainly of (A) an inorganic layered compound having >=1μm, preferably >=5μm particle diameter and (B) a water-soluble polymer (preferably polyvinyl alcohol-based polymer) onto at least one face of a thermoplastic resin substrate (preferably an olefin-based resin) and has <=25, preferably <=20 surface roughness parameter Rt/Ra. The coating film preferably contains a crosslinking agent in an amount of 0.01-10% based on its weight ratio to the coating film component. The film can be used as every packaging materials, because the film has gas barrier property, after preparing a bag, and adhesiveness of coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas barrier film, and more particularly to a gas barrier film excellent in high gas barrier properties under high humidity, adhesion to a substrate, and gas barrier properties after bag making. is there.

[0002]

2. Description of the Related Art In the field of packaging of foods and medicines, if oxygen or the like enters from the outside air, the contents cannot be stored for a long period of time due to deterioration of the contents. Therefore, a film having a gas barrier property capable of preventing entry of outside air. Is being developed.

[0003] Polymer Engineering and
According to Science, Vol. 20, No. 22, pp. 1543-1546 (December 1986), polyvinylidene chloride, polyvinylidene chloride,
Examples include polyacrylonitrile and polyvinyl alcohol. However, since polyvinylidene chloride contains a chlorine atom and polyacrylonitrile contains a -CN group, environmental problems at the time of disposal have been raised in recent years. Further, since polyvinyl alcohol contains an -OH group, the humidity dependence of gas barrier properties is large, and the gas barrier properties are significantly reduced at high humidity. Even an ethylene-vinyl alcohol copolymer in which the humidity dependence of polyvinyl alcohol has been improved, gas barrier properties at high humidity are not yet sufficient.

On the other hand, silicon oxide (JP-B-53-12953)
And aluminum oxide (JP-A-62-1799).
A film in which an inorganic substance such as No. 35 is vapor-deposited on the surface of a substrate has been developed. However, the formation of these films involves a vapor deposition process, which results in extremely high costs, the lack of flexibility of the inorganic coating, and poor adhesion to the substrate due to poor adhesion to the substrate. There is a problem.

As means for solving these problems, a film in which a base material is provided with a coating film composed of a metal oxide and polyvinyl alcohol (JP-A-56-4563, etc.) has been developed. As for the gas barrier property at the time, it is not yet at a satisfactory level. Further, a film having a gas barrier layer composed of an inorganic layered compound and a high hydrogen bonding compound (JP-A-6-93133, JP-A-7-41)
However, there is a great disadvantage in terms of productivity because long time drying or heat treatment is required in the process of forming the gas barrier layer in order to obtain high barrier properties, and the adhesion between the coating material and the base material is also low. Low. If the adhesion to the base material is high, a highly reliable packaging material that does not break the bag or deform the bag when processed into a packaging bag or the like can be obtained.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the conventional gas barrier film, to have gas barrier properties even under high humidity, to have an adhesive property to a substrate, and to improve the performance after bag making. An object of the present invention is to provide a gas barrier film having gas barrier properties.

[0007]

According to the present invention, in order to achieve the above-mentioned object, an inorganic layered compound having a particle diameter of 1 μm or more and a water-soluble polymer are mainly provided on at least one surface of a thermoplastic resin substrate. A film on which a coating film as a component is formed, wherein the surface roughness parameter Rt / Ra of the coating film is 25.
It consists of a gas barrier film characterized by the following.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention forms a coating film composed of an inorganic layered compound having a specific particle size and a water-soluble polymer, and controls the surface parameters of the coating film to obtain a high coating film under high humidity. A gas barrier film having both gas barrier properties, adhesiveness, and gas barrier properties after bag making has been developed, and is promising as a packaging material having high storage stability and high reliability.

In the present invention, in consideration of gas barrier properties under high humidity, adhesion and gas barrier properties after bag making,
It is necessary that the particle diameter of the inorganic layered compound is 1 μm or more. Preferably, it is larger than 5 μm. The particle diameter in the present invention is a volume average particle diameter determined by a laser scattering method based on light scattering theory.

In the present invention, the term "inorganic layered compound" refers to an inorganic compound in which ultrathin unit crystal layers overlap to form one layered particle, and those which swell and cleave in a solvent are preferred. Among them, a clay compound having a swelling property in a solvent is particularly preferably used. Distribution and clay compound having swelling property to solvent in the present invention is a clay compound having the property of unit crystal layers in a coordination water absorption and swelling of the ultra-thin, generally Si ⁴⁺ is O ^2- against and A layer forming a tetrahedral structure and a layer forming an octahedral structure in which Al ³⁺ , Mg ²⁺ , Fe ²⁺ , Fe ³⁺ , Li ^+, etc. are coordinated to O ²⁻ and OH ⁻ . Are combined in a one-to-one or two-to-one relationship and stacked to form a layered structure, which may be natural or synthetic. Representative examples include kaolinite, halloysite, montmorillonite, vercurite, saponite, dickite, nacrite, antigolite, pyrophyllite, hectorite, beidellite, margarite, talc, tetrasilyl mica,
Examples include muscovite, phlogopite, and chlorite.

The water-soluble polymer in the present invention refers to a polymer which can be completely dissolved or finely dispersed in water at normal temperature.
For example, polyvinyl alcohol-based polymers or derivatives thereof, carboxymethylcellulose, cellulose derivatives such as hydroxyethylcellulose, oxidized starch, etherified starch, starches such as dextrin, polyvinylpyrrolidone, copolymers containing polar groups such as sulfoisophthalic acid Polyester, vinyl polymer such as polyhydroxyethyl methacrylate or a copolymer thereof,
Examples include acrylic polymer, urethane polymer, ether polymer, and functional group modified polymers such as carboxyl group, amino group, and methylol group of these various polymers. It is preferably a polyvinyl alcohol polymer or a derivative thereof, and particularly preferably a saponification degree of 80 mol%.
The above polyvinyl alcohol is a copolymerized polyvinyl alcohol having a vinyl alcohol unit of 60 mol% or more.
The degree of polymerization of the polyvinyl alcohol-based polymer or a derivative thereof is preferably 100 to 5000, and is 1200 to 250.
0 is more preferred.

Further, in the present invention, it is preferred that the coating film contains a crosslinking agent in a weight ratio of 0.01 to 10%, since the gas barrier property under high humidity is improved. More preferably, 0.
05 to 8%.

The crosslinking agent used in the present invention is not particularly limited as long as it has reactivity with a water-soluble polymer, but an epoxy-based crosslinking agent, an isocyanate-based crosslinking agent,
Melamine-based crosslinking agents, oxazoline-based crosslinking agents, silane coupling agents, and the like are used. Preferably, it is a low-temperature curing type crosslinking agent. The low-temperature curing type cross-linking agent reacts with a water-soluble polymer at a temperature of 100 ° C. or lower, and oxazoline-based cross-linking agents, silane coupling agents, and the like are preferably used.

The mixing ratio of the inorganic layered compound to the water-soluble polymer in the present invention is preferably in the range of 5/95 to 60/40 by weight.

In the present invention, the thickness of the coating film is not particularly limited.
10 μm is preferred, and 0.3 to 6 μm is particularly preferred.

In order to improve the dispersibility of the inorganic layer compound in the coating film, the coating film may contain an amine compound represented by the following general formula.

[0017]

Embedded image In the formula, R1 and R2 are hydrogen or a hydrocarbon group having 1 to 6 carbon atoms, and R3 is a hydrocarbon group having 1 or more carbon atoms or a hydrocarbon group having 1 or more polar groups shown below and having 1 or more polar groups. Group. What is the polar group

Embedded image And so on. Specific examples of the amine compound include alkylamines such as butylamine and hexylamine; aminoalcohols such as aminoethyl alcohol, aminopropyl alcohol and aminoethylaminoethanol; and amino acids such as aminohexanoic acid and aminododecanoic acid.

The coating film may contain various additives as long as the gas barrier properties are not impaired. For example, antioxidants, weathering agents, heat stabilizers, lubricants, nucleating agents, ultraviolet absorbers, coloring agents and the like. Further, inorganic or organic particles may be contained as long as the transparency and gas barrier properties are not impaired. For example, talc, kaolin, calcium carbonate, titanium oxide, silicon oxide, calcium fluoride, lithium fluoride, alumina, barium sulfate, zirconia, mica, calcium phosphate, crosslinked polystyrene-based particles, and the like.

Further, a divalent or higher valent metal salt, a catalyst component, etc. may be added in order to enhance the interaction between the layered compound and the polymer, between the polymers or between the layered compounds in forming the coating film. . It is desirable to use an acetate, a sulfate, a nitrate, or the like containing calcium, magnesium, aluminum, or the like because moisture resistance is improved. The amount is about 1 to 10000 ppm based on the coating film.

In the present invention, defining the surface roughness parameter Rt / Ra of the coating film surface improves the process abrasion resistance and the gas barrier property when laminating an unstretched propylene film or the like with an adhesive therebetween. Is preferred. Rt is the maximum height, the distance between the maximum peak and the deepest valley of the surface roughness curve, and Ra is the center line average roughness. It is necessary that the surface roughness parameter Rt / Ra is 25 or less. More preferably, it is 20 or less. If the surface roughness parameter Rt / Ra exceeds 25, the gas barrier properties will decrease. This is considered to be because when the coating film was formed at a high speed, the coating film surface was shaved due to contact with a roll or contact between the films during winding. As a method of setting the surface roughness parameter Rt / Ra to 25 or less, the inorganic layered compound and the water-soluble polymer may be coated on a smooth thermoplastic resin base material by reducing the ratio of the inorganic layered compound. A method of applying a coating material in a uniformly dispersed state, drying the coating film surface at a temperature of 160 ° C. or less, and drying for 60 seconds or less to form a coating film is used. The details of the parameters are shown in "Measurement / Evaluation Method of Surface Roughness" by Jiro Nara (General Technology Center, 1983).

The thermoplastic resin substrate used in the present invention is necessary mainly for imparting mechanical properties and film processability, and includes various commercially available thermoplastic resin films. Although not particularly limited, typical examples include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, nylon 6, and nylon 12
Such as polyamide, polyvinyl chloride, ethylene vinyl acetate copolymer or saponified product thereof, polystyrene, polycarbonate, polysulfone, polyphenylene oxide, polyphenylene sulfide, aromatic polyamide,
Polyimide, polyamide imide, cellulose, cellulose acetate, polyvinylidene chloride, polyacrylonitrile,
Polyvinyl alcohol and the like, and copolymers thereof. Polyesters such as polyethylene terephthalate and polyolefins such as polyethylene and polypropylene are preferred from the viewpoints of cost performance, transparency, gas barrier properties and the like.

These thermoplastic resin substrates may be unstretched, uniaxially stretched, or biaxially stretched, but from the viewpoint of dimensional stability and mechanical properties, those stretched biaxially are particularly preferred. The thermoplastic resin base material may contain various additives. For example, antioxidants, weathering agents, heat stabilizers, lubricants, nucleating agents, ultraviolet absorbers, coloring agents and the like.
Further, inorganic or organic particles may be contained as long as the transparency is not impaired. For example, talc, kaolin, calcium carbonate, titanium oxide, silicon oxide, calcium fluoride, lithium fluoride, alumina, barium sulfate,
Zirconia, mica, calcium phosphate, crosslinked polystyrene-based particles, and the like. The average particle size is preferably 0.001 to 10 μm, more preferably 0.003 to
5 μm. The average particle diameter is a particle diameter obtained by taking a photograph at a magnification of 10,000 to 100,000 using a transmission microscope or the like and calculating the number average.

Further, these thermoplastic resin substrates are preferably transparent. The light transmittance is preferably 40% or more, more preferably 60% or more. The thermoplastic resin substrate is preferably smooth. The thickness of the thermoplastic resin substrate is not particularly limited, but is preferably 2 to 1000 μm.

Next, a typical method for producing the gas barrier film of the present invention will be described.

The method for forming a coating film on the thermoplastic resin substrate is not particularly limited, and an extrusion lamination method or a melt coating method may be used. However, since a thin film can be coated at a high speed, the coating method can be used. It is preferable to apply a gravure coat, a reverse coat, a spray coat, a kiss coat, a die coat, an air knife coat, or a metaling bar coat to a dispersion solution in which the components of the film are dispersed in various solvents. Thermoplastic resin substrate is a known adhesion promoting treatment before application,
For example, a corona discharge treatment in air, a nitrogen gas, a mixed gas of nitrogen / carbon dioxide gas, or another atmosphere, a plasma treatment under reduced pressure, a flame treatment, an ultraviolet treatment, or the like may be performed. When a biaxially stretched film of a polyester such as polyethylene terephthalate or a polyolefin such as polypropylene is used as the thermoplastic resin substrate, either an off-line coating method or an in-line coating method may be used.

The method for drying the coating film is not particularly limited, and a hot roll contact method, a heat medium (air, oil, etc.) contact method, an infrared heating method, a microwave heating method, and the like can be used. Drying of the coating film
From the viewpoint of gas barrier properties, the drying is preferably performed within the range of 60 ° C to 160 ° C, and the drying time is 1 to 60 ° C.
Seconds, preferably 3 to 30 seconds.

The coating containing the components of the coating film is preferably a solution in which the inorganic layered compound is uniformly dispersed or swelled in the solvent and the water-soluble polymer is uniformly dissolved or dispersed.
As the solvent, water or a mixed solution of water / lower alcohol is used, but a mixed solution of water / lower alcohol is preferably used from the viewpoint of gas barrier properties, adhesion and productivity under high humidity. The lower alcohol is an alcoholic compound having a linear or branched aliphatic group having 1 to 3 carbon atoms. For example, methanol, ethanol, n- or iso-propanol is preferably used. The mixing ratio of water / alcohol is 99/1 to 20/8 by weight.
0 is preferred. If the mixing ratio is more than 99/1, the gas barrier property under high humidity is insufficient, the adhesion between the coating layer and the substrate is poor,
There is a problem such as a decrease in productivity. If the ratio is less than 20/80, the dispersibility of the constituents of the coating film in a solvent is deteriorated.

In order to impart coatability to the film, the mixed solvent may contain another water-soluble organic compound as the third component as long as the stability of the dispersion solution is maintained. Is also good. Examples of the water-soluble organic compound include alcohols such as methanol, ethanol, n- or iso-propanol, glycols such as ethylene glycol and propylene glycol, methyl cellosolve,
Glycol derivatives such as ethyl cellosolve and n-butyl cellosolve; polyhydric alcohols such as glycerin and wax; ethers such as dioxane; esters such as ethyl acetate; and ketones such as methyl ethyl ketone.
Further, the pH of the dispersion solution is from 2 to 11 in view of the stability of the solution.
Is preferred.

The method of preparing the coating agent is not particularly limited,
A method in which a water-soluble polymer is uniformly dissolved in a solvent and then mixed with a solution in which the layered compound is uniformly dispersed is effectively used. Further, the solution may contain a crosslinking agent, particles, and the like.

[0030]

[Evaluation method of characteristics] The evaluation method of characteristics used in the present invention is as follows.

(1) Particle Size The inorganic layered compound is dispersed in water using a laser diffraction / scattering type particle size distribution analyzer LA-700 manufactured by HORIBA, Ltd., and the volume average particle size is measured at room temperature. did.

(2) Surface Parameters The maximum height Rt and the center line average roughness Ra of the coated surface were measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The measurement conditions were as follows, and the average value of 20 measurements was taken as a value, and the ratio of Rt to Ra was calculated.

Stylus tip radius: 0.5 μm Stylus load: 5 mg Measurement length: 1 mm Cutoff: 0.08 mm

(3) Gas barrier property Oxygen permeability measuring apparatus (OX-TRAN 2/20, manufactured by Modern Control Co., Ltd.) according to ASTM D-3985.
Was used to measure oxygen permeability. Measurement condition is temperature 23
° C and a relative humidity of 80%.

(4) Adhesion between Coating Film and Substrate Unstretched polypropylene film (CPP, T350 manufactured by Toray Synthetic Film Co., Ltd.) using a polyurethane adhesive
1, 50 μm) and the coating surface of this film.
After aging at 0 ° C. for 48 hours, the surfaces opposite to the surface in contact with the adhesive are reinforced with cellophane tape, cut to a width of 15 mm, and the CPP and the film are peeled at 180 ° using tensilon, and the peel strength at that time I asked. The peeling was performed at a peeling speed of 10 cm / min, at 23 ° C. and in an atmosphere of 65% relative humidity.

(5) Gas barrier property after bag making The film aged by the above method was cut into a 20 cm square, the CPP side was overlapped, and the four sides were heat-sealed with an impulse sealer to prepare a bag filled with air. . The bag was cut open, and the gas barrier properties of the film were measured by the method described above.

[0037]

【Example】

Example 1 3 wt% of sodium tetrasilyl mica (manufactured by Topy Industries, particle size: 24.2 μm) as an inorganic layered compound
Water / isopropyl alcohol (IPA)
It was dispersed in a mixed solvent (weight ratio 90/10) (Solution A).
98.5 mol% saponification degree as water-soluble polymer, polymerization degree 1
700 polyvinyl alcohol (hereinafter abbreviated as PVOH)
Water / IPA mixed solvent (weight ratio 90
/ 10) (liquid B). A such that the mixing ratio of the inorganic layered compound / water-soluble polymer is 30/70 by weight.
Liquid A and Liquid B were mixed, and IPA was 1% by weight based on all coating materials.
A coating composition was prepared so as to have a solid content of 0% and a solid concentration of 2.5%. The coating was subjected to corona discharge treatment (in a mixed gas of carbon dioxide / nitrogen (volume ratio 83:17), treatment intensity = 60 W · min /
m ² ) applied to a biaxially stretched polypropylene film (“Torayfan” manufactured by Toray, thickness: 20 μm) using a reverse coater (coating speed: 12 m / min), guided into a hot-air drying dryer, and heated to 120 ° C. under low tension. After drying for 20 seconds, the film was wound up. Table 1 shows the properties of the obtained film. A film excellent in gas barrier properties, adhesion, and gas barrier properties after bag making was obtained.

Examples 2 to 4 Films were obtained in the same manner as in Example 1 except that the coating composition, coating thickness, and substrate were changed. Table 1 shows the properties of the obtained film.

In Example 2, a cross-linking agent (γ- (2-aminoethyl) aminopropyltrimethoxysilane) was used together with polyvinyl alcohol and an inorganic layered compound.
Was obtained in the same manner as in Example 1. As a result, a film having excellent gas barrier properties, adhesion, and gas barrier properties after bag making was obtained.

In Example 3, sodium hectorite (manufactured by Topy Industries, particle size 1.5 μm) was used as the inorganic layered compound.
m), a coating film having the composition shown in Table 1 was formed in the same manner as in Example 1 using a biaxially stretched polyester film (“Lumirror” manufactured by Toray, thickness: 12 μm) that had been subjected to corona discharge treatment (in air). As a result, a film having excellent gas barrier properties, adhesion, and gas barrier properties after bag making was obtained.

In Example 4, a coating film was formed on a polypropylene film in the same manner as in Example 1 by changing the coating composition using PVOH having a saponification degree of 88.0 mol% and a polymerization degree of 500 as a water-soluble polymer. However, a film having excellent gas barrier properties was obtained.

Comparative Example 1 A film using montmorillonite (particle diameter 0.8 μm, manufactured by Toyohyun Yoko Co., Ltd.) as an inorganic layered compound and PVOH having a saponification degree of 88.0 mol% and a polymerization degree of 500 as a water-soluble polymer. I got As is clear from Table 1, the obtained film was found to be inferior in gas barrier properties and adhesion.

Comparative Example 2 The ratio of the inorganic layered compound / water-soluble polymer was 80 by weight.
/ 20, a coating composition adjusted to a solid content concentration of 6 wt% was applied to PET, and dried at 180 ° C. for 30 seconds with a hot air drier to obtain a film having a surface roughness parameter of 27.2. It was found that the obtained film had significantly poor gas barrier properties and adhesion.

[0044]

[Table 1] The meanings of the abbreviations in the table are as follows.

PP is a biaxially oriented polypropylene film (thickness: 20 μm, mixed gas of nitrogen gas / carbonic acid (volume ratio: 8
3:17) Corona discharge treatment (treatment intensity = 60 W · m)
in / m ² )), PET is a biaxially stretched polyethylene terephthalate film (thickness: 12 μm, corona discharge treatment in air), PVOH1 is a polyvinyl alcohol having a saponification degree of 98.5 mol%, polymerization degree is 1700, and PVOH2 is a saponification degree of 88. 0.0 mol%, polyvinyl alcohol having a polymerization degree of 500, a crosslinking agent of γ- (2-aminoethyl) aminopropyltrimethoxysilane, particles 1 of sodium tetrasilyl mica having a particle diameter of 24.2 μm, and particles 2 having a particle diameter of 1 .
5 μm sodium hectorite, particle 3 has a particle size of 0.
8 μm montmorillonite.

[0046]

The film obtained by the present invention can be used as any packaging material because it has not only excellent gas barrier properties but also gas barrier properties after bag making and adhesion of the coating film.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C08L 29/04 LGM C08L 29/04 LGM // C08K 3:00

Claims (7)

[Claims] 1. A film comprising a thermoplastic resin substrate on at least one surface of which a coating film mainly composed of an inorganic layered compound having a particle diameter of 1 μm or more and a water-soluble polymer is formed. A gas barrier film having a roughness parameter Rt / Ra of 25 or less. 2. The gas barrier film according to claim 1, wherein the particle diameter of the inorganic layered compound is larger than 5 μm. 3. The surface roughness parameter Rt / R of the coating film.
The gas barrier film according to claim 1 or 2, wherein a is 20 or less. 4. The gas barrier film according to claim 1, wherein the water-soluble polymer is a polyvinyl alcohol polymer or a derivative thereof. 5. The gas barrier film according to claim 1, wherein a cross-linking agent is contained in the coating film in an amount of 0.01 to 10% by weight relative to the components of the coating film. 6. The gas barrier film according to claim 5, wherein the crosslinking agent is a low-temperature curing type crosslinking agent. 7. The gas barrier film according to claim 1, wherein the thermoplastic resin substrate is made of an olefin resin.