JP3096318B2 - Composite film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite film suitable as a packaging film and a method for producing the same.

[0002]

2. Description of the Related Art Packaging films, especially food packaging films, are required to have high barrier properties against water vapor, oxygen gas, etc. in order to protect the contents. However, it is generally difficult to secure a barrier property against all of water vapor, oxygen gas, aroma, and the like by using the base film alone.

Therefore, as a film having a high barrier property against oxygen gas and water vapor, a film in which a gas barrier layer made of a vinylidene chloride-based polymer is formed on a base film is known. However, this film has poor weather resistance and tends to yellow.

As a film having a high oxygen gas barrier property,
A packaging film in which a gas barrier layer made of an ethylene-vinyl alcohol copolymer is formed on a base film has also been proposed. For example, JP-A-2-202929 discloses a method in which a solution of an ethylene-vinyl alcohol copolymer is applied to a polyamide film and then stretched to enhance oxygen gas barrier properties. JP-A-2-2271
No. 74 discloses a method of applying a solution of an ethylene-vinyl alcohol copolymer to a base material and subjecting the solution to a heat treatment to enhance oxygen gas barrier properties. Further, JP-A-2-231138 discloses that when a polymer layer having high moisture permeability is formed as an outer layer and an ethylene-vinyl alcohol copolymer layer is formed as an intermediate layer, at the time of forced drying after the retort treatment, It has been proposed to increase the drying rate of the layer of the ethylene-vinyl alcohol copolymer to recover the oxygen gas barrier property at an early stage.

[0005] However, the ethylene-vinyl alcohol copolymer has low adhesion to the substrate film. In particular,
Since the ethylene-vinyl alcohol copolymer has a hygroscopic property, in a packaging film to be subjected to a retort treatment or the like, the adhesive force is greatly reduced by the retort treatment or the like, and the oxygen gas barrier property is also reduced due to the moisture absorption.

Accordingly, an object of the present invention is to provide a composite film which is excellent in adhesion to a substrate film and gas barrier properties while using an ethylene-vinyl alcohol copolymer as a constituent material of the film.

Another object of the present invention is to provide a composite film which does not discolor for a long time.

It is still another object of the present invention to provide a method for producing a composite film having the above-mentioned excellent properties simply and with good productivity.

[0009]

The present inventors have achieved the above object by attaining
Result of extensive studies, the substrate film, an ethylene - vinyl alcohol copolymer (hereinafter, referred to as EVOH), aqueous U
Choose from urethane adhesives and polybutadiene adhesives
The coating solution or coating containing at least one member, after applying the anchor coating agent to the substrate film, when coating the coating liquid, adhesion between the substrate film and the coating layer is significantly improved gas barrier properties The present inventors have found that a composite film having excellent weather resistance can be obtained, and have completed the present invention.

[0010] That is, the present invention relates to a method for producing a base film, comprising: attaching at least one surface of EVOH to an aqueous urethane-based adhesive;
And at least one selected from polybutadiene adhesives
The kind seen free and provides a composite film coating layer formed by coating is formed.

Further, the composite film, on at least one surface of the base film, through an anchor coating agent layer, co computing layer may be formed.

Further, the present invention provides a method for producing a base film, comprising the steps of: providing EVOH, an aqueous urethane adhesive,
Method for producing a composite film for applying a coating solution containing at least one <br/> selected from polybutadiene based adhesive; on at least one surface of a substrate film was applied an anchor coat agent, the coating liquid Provided is a method for producing a composite film to be applied.

Examples of the substrate film include polyethylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer, polypropylene, ethylene-propylene copolymer, and poly-4-methylpentene-1. Olefin-based polymers such as polyvinyl chloride; polyvinylidene chloride; vinylidene chloride-vinyl chloride copolymer; vinylidene chloride-based polymers such as vinylidene chloride-acrylonitrile copolymer; polystyrene, styrene-acrylonitrile copolymer, styrene-acrylonitrile- Styrene-based polymers such as butadiene copolymers; polyesters such as polyethylene terephthalate, modified polyethylene terephthalate and polybutylene terephthalate; nylons or polyamides such as nylon 6, nylon 11, and nylon 66 De; polycarbonates; polyimides; polyvinyl alcohol; cellophane; cellulose-based polymers such as acetyl cellulose; various film to material and rubber hydrochloride and the like can be used.

Among these base films, films excellent in transparency, mechanical strength, and packaging suitability, particularly, polypropylene film, polyethylene terephthalate film, and nylon film are preferable. Since EVOH has excellent oxygen gas barrier properties, as a base film,
A polypropylene film having insufficient oxygen gas barrier properties as compared with a polyethylene terephthalate film is frequently used.

The base film may be unstretched,
It may be uniaxially or biaxially stretched. The uniaxially or biaxially stretched base film has high mechanical strength. The stretched base film is also suitable as a heat-shrinkable packaging film and an easily-openable packaging film.
For stretching the substrate film, for example, a conventional stretching method such as roll stretching, rolling stretching, belt stretching, tenter stretching, tube stretching, or a combination thereof can be applied. The stretching ratio can be appropriately set according to the desired film properties, and is, for example, about 1.5 to 20 times, and preferably about 2 to 15 times.

Further, the substrate film may be surface-treated. Examples of the surface treatment include conventional surface treatments such as corona discharge treatment, high-frequency treatment, flame treatment, electron beam irradiation treatment, chromic acid treatment, and solvent treatment. Further, a film subjected to a surface treatment other than the above may be used. Of these surface treatments, corona discharge treatment is preferred.

The base film may be a single-layer film or a composite film in which two or more films are laminated. The thickness of the base film is not particularly limited,
Usually, it is about 5 to 250 μm, preferably about 10 to 100 μm.

The base film comprises an antistatic agent, a lubricant,
Various additives such as an antiblocking agent, an antioxidant, an ultraviolet absorber, a crystal nucleus growth agent, a heat stabilizer, a tackifier, a plasticizer, and a filler may be contained.

In the composite film of the present invention, one or both surfaces of the base film may be provided with EVOH and aqueous urethane.
Adhesives selected from adhesives based on polybutadiene
Even without looking it contains a kind, Koti <br/> ring layer is formed which is formed by coating.

The EVOH is not particularly limited as long as it is a solvent-soluble copolymer, but is a copolymer having an ethylene content of 10 to 65 mol%, preferably 25 to 45 mol%.
The molecular weight of EVOH is, for example, 1 × 10 ⁴ to 10 × 10
⁴ , preferably about 4 × 10 ^{4 to} 5 × 10 ⁴ . In addition, MFI under the conditions of temperature 210 ° C. and load 2160 g
(Melt flow index) is about 5 to 10 g / 10 minutes, temperature is 210 ° C., load is 50 kg, 1 mmΦ × 10 mm
Has an apparent melt viscosity of 5,000 to 15,000 poise, preferably about 7,500 to 12,500 poise. The saponification degree is 90% or more, preferably 94% or more,
More preferably, it is 99.5% or more. Such an E
VOH is, for example, soluble in a mixed solvent of water and alcohol.

[0021] As the adhesive, contact the film adhesive Chakuzai, for example, polyisocyanate compound and a polyester polyol and / or aqueous urethane adhesives obtained by reacting a polyether polyol, Po Li butadiene adhesive [e.g. , Nippon Soda Co., Ltd., Titabond T-1
80 etc.] . These adhesives may be either one-part adhesives or two-part reactive adhesives. The adhesive can be used by mixing one kind or two or more kinds.

[0022] Preferred adhesives include water soluble urethane adhesive [e.g., Nippon Soda Co., Chitabondo T-185 and the like curing agent] include. Since this aqueous urethane-based adhesive exhibits the same dissolution characteristics as EVOH, it is preferable from the viewpoint of preparation of a coating agent, workability, and the like. It should be noted that a curing agent is not always necessary in the two-part reaction type aqueous urethane-based adhesive. That is, the adhesion between the base film and the coating layer can be increased without using a curing agent, probably because the EVOH reacts with the isocyanate groups of the aqueous urethane-based adhesive.

The content of the adhesive can be selected within a range that does not impair the adhesion of the EVOH to the base film and the gas barrier property.
0.1 to 25 parts by weight, preferably 0.5 to 20 parts by weight,
More preferably, it is about 1 to 15 parts by weight. When the amount of the adhesive is less than 0.1 part by weight, the adhesion to the substrate film is not sufficient, and when the amount exceeds 25 parts by weight, the gas barrier property may be reduced.

The thickness of the coating layer can be set within a range that does not impair the gas barrier properties, transparency and the like.
It is about 10 μm, preferably about 0.5 to 7.5 μm, and more preferably about 0.75 to 5 μm.

[0025] In multi case film of the present invention, the one or both surfaces of a substrate film via an anchor coating agent layer may be formed the coating layer.

Examples of the anchor coating agent include a titanium anchor coating agent, a polyethyleneimine anchor coating agent, and a urethane anchor coating agent. Preferred anchor coating agents include urethane-based anchor coating agents, particularly two-part reactive urethane-based anchor coating agents.

The thickness of the anchor coating agent layer can be selected in a wide range that can ensure adhesion, for example, 0.01 to 5 μm.
m, preferably about 0.05 to 2.5 μm.

In the above-mentioned composite film, the coating
The layer preferably contains a lubricant such as a wax or a fine powdery lubricant in order to impart slipperiness and blocking resistance. Examples of the wax include hydrocarbon waxes;
Various waxes such as a fatty acid wax, a fatty acid amide wax, and an ester wax can be used. At least one of the above waxes is used. The content of the wax is usually 0.1 part with respect to 100 parts by weight of the EVOH.
10 to 10 parts by weight, preferably about 0.25 to 5 parts by weight, more preferably about 0.5 to 2.5 parts by weight.

Examples of the fine powder lubricant include silica fine powder, alumina fine powder, polyethylene fine powder, acrylic fine powder, silicone fine powder, and melamine fine powder. The particle size of the fine powdery lubricant is preferably in a range that does not impair the transparency and gas barrier properties of the coating film, for example, 5 μm or less. The content of the fine powdery lubricant is EV
It is usually about 0.01 to 5 parts by weight, preferably about 0.05 to 2.5 parts by weight, based on 100 parts by weight of OH.

The coating layer may be made of another polymer, for example, olefin polymer, acrylic polymer, styrene polymer, polyester, polyacetal, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyvinyl chloride, vinyl chloride-acetic acid. It may contain a vinyl copolymer, polyamide, polyurethane, polycarbonate, chlorinated polyolefin, cellulosic polymer, or the like. In addition, the coating layer may contain various additives such as an antistatic agent, an antioxidant, an ultraviolet absorber, a heat stabilizer, a tackifier, a plasticizer, a filler, a dye and a pigment.

Further, the composite film of the present invention only needs to include the above-mentioned layer constitution.
The base film may be further laminated on the layer. In this case, the coating layer and the base film are
They may be directly laminated by extrusion lamination or the like, or may be laminated by dry lamination or the like using an adhesive or an anchor coat agent. In addition, coating
A heat seal layer may be formed on the layer. The heat seal layer is a film having a heat seal property among the base films, a conventional polymer having a heat seal property, for example, a styrene-butadiene copolymer,
It can be formed of a vinyl chloride-vinyl acetate copolymer, an ethylene-vinyl acetate copolymer, or the like.

[0032] In the present invention, on at least one side of the base film, it is sufficient that the coating layer is formed, an antistatic layer on the other surface, slipping layer or blocking layer may be formed .

A composite film [0033] The present invention (1) to the base film, a method for applying a coating solution containing a EVOH and adhesive, (2) the substrate film was applied an anchor coat agent, and EVOH It can be obtained by a method of applying a coating solution containing an adhesive . In addition, after an application process, it is normally provided to a drying process.

In the above methods (1) and (2), the coating solution containing EVOH can be usually prepared using a mixed solvent of water and alcohol. Examples of the alcohol include methanol, ethanol, propanol, isopropanol, cyclohexanol and the like. In addition, EV
Other organic solvents may be used in combination as long as the stability of the solution containing OH is not impaired. Further, the coating liquid may contain, for example, an aliphatic carboxylic acid or the like. EV in coating liquid
The concentration of OH can be set within a range that does not hinder the coatability, and is, for example, about 2.5 to 25% by weight, and preferably about 5 to 15% by weight. When the concentration of EVOH is less than 2.5% by weight, the number of times of application may increase to form a predetermined film, and when it exceeds 25% by weight, the viscosity is high and the coating property is deteriorated. Easy to do.

In the above method (2), the anchor coating agent is usually used as an organic solvent solution. The organic solvent is selected according to the type of the anchor coating agent. Examples of the organic solvent include alcohols, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, esters, ketones, ethers, and mixed solvents thereof.

Each of the above-mentioned coating liquids may contain conventional additives, for example, an antifoaming agent, a viscosity adjusting agent, a leveling agent and the like in order to enhance the coating property.

Each coating solution is applied so that the film thickness after drying becomes the film thickness of the coating layer and the anchor coating agent layer .

The coating means is not particularly limited, and is a conventional means such as a comma coater, a lip coater, a dip coater, a roll coater, a gravure coater, an air knife coater, a reverse coater, a kiss coater, a T-die coater, and a myrbar. Coaters, spray coaters and the like can be used.

An aging treatment after the coating / drying step can enhance gas barrier properties. The aging treatment can be performed in a temperature range that does not impair the properties of the composite film, for example, 20 to 150 ° C, preferably about 30 to 75 ° C. When performing the aging treatment under such a temperature condition, the treatment time is, for example, about 1 minute to 5 days, preferably about 1 hour to 3 days.

In the production method of the present invention, a high gas barrier property can be imparted only by coating and drying the coating liquid on the base film, and the adhesion between the base film and the coating layer can be enhanced. Further, the coating layer formed by application has better barrier properties per unit thickness than the coating layer formed by extrusion lamination or the like.

[0041]

According to the composite film of the present invention, since the coating layer contains an adhesive or the coating layer is formed on the base film via an anchor coating agent layer, EVOH is used as a constituent material of the film. However, it has excellent adhesion to the substrate film and gas barrier properties.

Further, the composite film of the present invention exhibits high gas barrier properties without forming a gas barrier layer of a vinylidene chloride-based polymer and does not discolor for a long time.

Further, according to the method of the present invention, a composite film having the above-mentioned excellent properties can be easily produced with good productivity.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments.

Example 1 A mixed solvent of water and isopropanol (mixing weight ratio 1:
To 1), EVOH [manufactured by Nippon Gohsei Chemical Co., Ltd., trade name: Soarnol, ethylene content 29 mol%] was added and dissolved by heating, and an aqueous urethane-based adhesive [Nippon Soda ( Co., Ltd., Citabond T-185]
0 to 7 parts by weight, fine silica powder having an average particle size of 1.6 μm.
3 parts by weight were added to prepare a coating solution having a solid content of 15% by weight. In using the aqueous urethane-based adhesive, a curing agent was not used.

The coating solution after drying was applied to the corona discharge treated surface of a biaxially stretched polypropylene film having a thickness of 20 μm (trade name: Seneshi POP, OPP, manufactured by Daicel Chemical Industries, Ltd.) using a comma coater. 3.2g /
The composition was applied under the condition of m ² and dried to form a coating layer.

An anchor coating agent [AD-563A / AD-56, manufactured by Toyo Morton Co., Ltd.] on the coating layer.
3B = 100/15 (Wet weight ratio), solvent: ethyl acetate] was applied under the condition of an applied amount of 2.5 g / m ² after drying,
60 μm thick CPP [P114 manufactured by Toyobo Co., Ltd.
3] to form a layer structure of OPP / E
A composite film of VOH / AC / CPP was prepared. Unless otherwise specified, the symbol AC means an anchor coating agent layer, and the symbol EVOH means a layer containing EVOH.

Example 2 0 to 7 parts by weight of a butadiene-based adhesive [Nippon Soda Co., Ltd., Titabond T-180] based on 100 parts by weight of the EVOH, and 0.3 part by weight of a fine silica powder having an average particle diameter of 1.6 μm. Except that OPP was added, the layer configuration was changed to OPP in the same manner as in Example 1.
A composite film of / EVOH / AC / CPP was prepared.

The composite films obtained in Examples 1 and 2 were subjected to a boil treatment at 95 ° C. for 30 minutes, and the peel strength between the OPP and the EVOH layer before and after the boil was measured. The results are shown in FIG.

FIG. 1 shows that the addition of an adhesive, particularly an aqueous urethane-based adhesive, to EVOH allows OPP and EVO to be added.
The adhesion to the H layer is significantly improved even after boiling.

Example 3 Of the coating solutions prepared in Example 1, 100 parts by weight of EVOH and 7 parts by weight of an adhesive were added (temperature: 30 parts).
The viscosity at 200 ° C.) was applied to the biaxially stretched polypropylene film used in Example 1 by an amount of 3.0 g /
It was applied under the conditions of m ² to prepare a composite film having a layer configuration of OPP / EVOH.

Example 4 The composite film obtained in Example 3 was treated in the same manner as in Example 1 by using an anchor coat agent (a coating amount of 2.5 g after drying).
/ M ² ) to prepare a composite film (layer structure OPP / EVOH / AC / CPP) laminated with CPP.

Reference Example 1 A mixed solvent of water and isopropanol (mixing weight ratio 1:
In 1), the EVOH used in Example 1 was dissolved, and EVOH was dissolved.
0.3 parts by weight of silica fine powder having an average particle size of 1.6 μm was added to 100 parts by weight to prepare a coating solution for an EVOH layer.

The biaxially oriented polypropylene film used in Example 1 was coated with a two-component reaction type urethane anchor coating agent [AD-335A / CAT-10, manufactured by Toyo Morton Co., Ltd.]
= 100/20 (Wet weight ratio), solvent: ethyl acetate, solid content 35% by weight] under the condition of a coating amount of 1.0 g / m ² after drying, and drying. Coating was performed under the condition of a coating amount of 3.0 g / m ² after drying, and the coating was dried to produce a composite film having a layer configuration of OPP / AC / EVOH.

Reference Example 2 The composite film obtained in Reference Example 1 was treated in the same manner as in Example 1 with an anchor coat agent (coating amount after drying: 2.5 g).
/ M ² ) to prepare a composite film (layer structure OPP / AC / EVOH / AC / CPP) laminated with CPP.

With respect to the composite films obtained in Examples 3 and 4 and Reference Examples 1 and 2 , OPP and E
Peel strength between VOH layer, gas barrier property, yellowing resistance,
The slip property and the blocking property were evaluated. The results are shown in the table.

[0057]

[Table 1] Unless otherwise specified, the oxygen gas barrier property was measured by OX-T manufactured by MODERN CONTROLS, INC.
Measured at a temperature of 20 ° C. with PAN TWIN using oxygen gas with a humidity of 70% and helium gas as a compensation gas,
Water vapor barrier properties are available from MODERN CONT
ROLS, INC.) PERMATRAN-WIA, temperature 40 ℃,
The measurement was performed under the condition of a relative humidity of 90%. The yellowing resistance was determined by comparing the composite film of Example 3 and Reference Example 1 with a standard sample [thickness 20].
μm biaxially oriented polypropylene film coated with a vinylidene chloride-based polymer (KOP, manufactured by Daicel Chemical Industries, Ltd.)] is irradiated with light for 24 hours using a fade meter, and the degree of yellowing is visually determined as follows. Evaluation was based on criteria.

Excellent: Almost no discoloration Good: Some discoloration Not possible: Significant yellow discoloration (standard sample) The slip property was evaluated by measuring the dynamic friction coefficient.

The blocking property is measured by superposing the EVOH surface and the biaxially oriented polypropylene film on each other at 45 g / cm.
A load of ² was applied, and this was left for 24 hours in an atmosphere of 40 ° C. and 90% relative humidity, and evaluated according to the following criteria.

Excellent: Almost no blocking Good: Slightly blocking Not possible: Remarkable blocking Example 5 Ethylene content 38 instead of EVOH used in Example 1
OPP in the same manner as in Example 3 except that mol% of EVOH (trade name: Soarnol, manufactured by Nippon Synthetic Chemical Co., Ltd.) was used.
Was applied under the condition of a coating amount of 3.0 g / m ² after drying to prepare a composite film having a layer configuration of OPP / EVOH.

Reference Example 3 An ethylene content of 38 was used in place of EVOH used in Example 1.
A composite film having a layer configuration of OPP / AC / EVOH was prepared in the same manner as in Reference Example 1 except that mol% of EVOH (trade name: Soarnol, manufactured by Nippon Synthetic Chemical Co., Ltd.) was used.

Using the KOP as a standard sample, the composite films of Examples 3 and 5 and Reference Examples 1 and 3 were irradiated with light using a fade meter, and the degree of yellowing with irradiation time was examined. . The results are shown in FIG.

FIG. 2 shows that the composite films of Examples 3 and 5 are excellent in weather resistance.

Example 6 The OPP / EVOH composite film having a layer structure obtained in Example 3 was stored at a temperature of 40 ° C., and the change in oxygen gas permeability with the aging time was measured. The oxygen gas permeability was measured at a temperature of 20 ° C. and a relative humidity of 60%. The results are shown in FIG.

FIG. 3 shows that the aging treatment enhances the oxygen gas barrier property.

[Brief description of the drawings]

FIG. 1 is a graph showing the results in Example 1 and Example 2.

FIG. 2 shows a standard sample KOP, Examples 3 and 5, and a reference example.
It is a graph which shows the result of weather resistance in Examples 1 and 3 .

FIG. 3 is a graph showing the results of oxygen gas barrier properties in Example 6 .

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI B32B 27/28 102 B32B 27/28 102 (58) Investigated field (Int.Cl. ⁷ , DB name) C08J 7/04-7 / 06 B05D 7/00-7/24 B32B 7/00-7/14 B32B 27/00-27/42

Claims (6)

(57) [Claims] Claims: 1. At least one surface of a substrate film,
Ethylene-vinyl alcohol copolymer and aqueous urethane
Adhesives selected from adhesives based on polybutadiene
Composite film without even looking contains a one, and code <br/> coating layer formed by coating is formed. 2. The method according to claim 1, wherein at least one surface of the base film has
Via the anchor coating agent layer, the composite film of claim 1, wherein the co computing layer is formed. 3. An ethylene-vinyl alcohol copolymer having an ethylene content of 10 to 65 mol%.
The composite film according to the above. 4. At least one surface of the base film,
Ethylene-vinyl alcohol copolymer and aqueous urethane
Adhesives selected from adhesives based on polybutadiene
A method for producing a composite film in which a coating liquid containing at least one kind is applied. 5. On at least one surface of the base film,
After applying the anchor coating agent, wherein for applying the coating coating solution
Item 5. The method for producing a composite film according to Item 4 . 6. After the coating coating solution was applied, method for producing a composite film according to claim 4 or 5, wherein the d <br/> Jingu treated at 30 to 75 ° C..