JPH05295299A - Liquid composition for forming gas-barrier film and surface-coated formed material - Google Patents

Abstract

PURPOSE:To provide a liquid composition giving a coating film having excellent flexibility, transparency and property as a gas-barrier to gases such as oxygen, nitrogen and carbon dioxide gas and to provide a molded material coated with the composition to improve the property as a gas-barrier. CONSTITUTION:The objective film-forming liquid composition is composed of an aqueous solution containing a water-soluble polymer having plural acidic functional groups in one molecule [e.g. (meth)acrylic polymer or copolymer] and water glass at a ratio A/B of preferably 1-0.01 wherein A is acid equivalent of the water-soluble polymer and B is base equivalent of the water glass. A molded material having improved gas-barrierness can be produced by coating a molded material with the above composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid resin composition for forming a gas barrier coating film and a molded article provided with a gas barrier property by applying the composition.
This liquid composition is transparent and has an excellent gas barrier property against gases such as oxygen, nitrogen, carbon dioxide, and steam, and is used as a resin molded product in a film shape, a sheet shape, a bottle shape, or the like. By coating on one side or both sides, a resin molded body having excellent gas barrier properties can be obtained. Further, when the liquid composition is applied to the surface of a metal molding to form a gas barrier coating, a metal molding having excellent corrosion resistance and weather resistance can be obtained.

[0002]

2. Description of the Related Art Conventionally, thermoplastic resins such as polyolefin resins, polystyrene resins, polyvinyl chloride resins and polyester resins have excellent moldability and transparency. Is widely used as. However, all of these resins have a large gas permeability, and when used in food packaging, for example, the contents of the resins are likely to be deteriorated due to oxidative deterioration. Therefore, a method of imparting a gas barrier property by laminating or laminating a gas barrier resin or a gas barrier layer such as a metal foil or a metal oxide is adopted.

On the other hand, examples of the gas barrier resin include ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH), vinylidene chloride copolymer (hereinafter abbreviated as PVDC), polymethaxylene adipamide (hereinafter, MXD
6) and the like are known.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since OH and MXD6 have poor physical properties as a thin film, it is difficult to use as a coating type, and it is difficult to form them into a film. Further, PVDC contains chlorine and may cause pollution.

Although a method of laminating an aluminum foil on the surface of a thermoplastic film or vapor-depositing a metal oxide is also known, the problem with the aluminum foil is that the contents cannot be seen from the outside. However, the method of vapor-depositing a metal oxide, the vapor deposition apparatus is expensive and has low productivity, and the flexibility of the vapor-deposition layer is poor as compared with the thermoplastic film of the base material, so that the vapor-deposition layer easily cracks, This causes a decrease in gas barrier ability.

The present invention has been made by paying attention to the above circumstances, and an object thereof is a liquid resin composition which gives a film which is transparent and has excellent flexibility and film forming property and excellent gas barrier property. And a molded article having excellent gas barrier properties.

[0007]

The composition of the liquid composition for forming a gas barrier film according to the present invention comprises an aqueous solution containing a water-soluble polymer having a plurality of acidic functional groups in the molecule and water glass. It has a gist. In the above structure, the water-soluble polymer is a homopolymer of a radical-polymerizable monomer having at least one acidic functional group in the molecule or a copolymer of the radical-polymerizable monomer and a polymerizable monomer copolymerizable with the homopolymer. Polymers are preferable, carboxyl groups and phosphoric acid groups are most preferable as the acidic functional groups, and acrylic acid and methacrylic acid are most preferable among the radical-polymerizable monomers. The ratio A / B of the acid equivalent (A) of the water-soluble polymer and the base equivalent (B) of water glass is preferably in the range of 1 to 0.01. Then, by coating the liquid composition for forming a gas barrier coating film on one side or both sides of a film-shaped, sheet-shaped, or bottle-shaped resin molded body, a resin molded body having excellent gas barrier properties can be obtained. By applying this liquid composition to the surface of a metal molded body to form a gas barrier coating, a metal molded body excellent in corrosion resistance and weather resistance can be obtained.

[0008]

The liquid composition for forming a gas barrier film of the present invention comprises an aqueous solution containing a specific water-soluble polymer and water glass, and the water-soluble polymer referred to herein is a plurality of molecules in the molecule. The type is not particularly limited as long as it is a polymer having an acidic functional group and soluble in water, such as poly (meth)
Examples thereof include water-soluble homopolymers such as acrylic acid, copolymers of (meth) acrylic acid and a polymerizable monomer that can be copolymerized, and those partially neutralized with a base.

The type of copolymerizable polymerizable monomer is not particularly limited, but preferred examples include methyl (meth) acrylate, butyl (meth) acrylate,
Cyclohexyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-tricyclo [5,2,1, 0 ^2,6 ] -3-decenyloxyethyl (meth) acrylate, methyl-2-chloroacrylate, methyl-2-bromoacrylate, cyclohexyl-2-chloroacrylate, cyclohexyl-2-
Bromoacrylate, 2-tricyclo [5,2,1,0
^2,6 ] -3-decenyloxyethyl-2-chloroacrylate and other monofunctional (meth) acrylic acid esters, styrene, α-methylstyrene, p-methylstyrene and their nucleus-substituted derivatives, and benzoic acid Aromatic vinyl compounds such as (meth) acrylic can be used, and one or more of these can be used.

There is no limitation on the method of polymerizing the above-mentioned polymerizable or copolymerizable monomer, and any known method may be used. Generally, solution polymerization or emulsion polymerization is carried out in the presence of a radical polymerization initiator. Suspension polymerization or bulk polymerization. It is also possible to polymerize or copolymerize by thermal polymerization, photopolymerization, radiation polymerization or the like.

The preferred molecular weight of the polymer is in the range of 500 to 500,000 in terms of weight average molecular weight. If the molecular weight is too small, the water resistance and gas barrier properties of the coating tend to be insufficient, while if the molecular weight is too large, Not only does the viscosity become too high and the coatability deteriorates, but in some cases gelation occurs when mixed with water glass.

The radical-polymerizable monomer having an acidic functional group constituting the above-mentioned polymer is not particularly limited in its type as long as it is a radical-polymerizable monomer having at least one acidic functional group in the molecule. However, preferred examples include (meth) acrylic acid and 2- (meth) acryloyloxyethyl acid phosphate.
These may be used alone or in combination of two or more.

As the water glass used in the present invention, composite compositions composed of silicon oxide and alkali oxides having various molar ratios can be used, and as the kind of alkali, sodium, potassium, lithium, ammonium and the like can be used. Is mentioned. Specific examples of water glass include sodium silicate, potassium silicate, lithium silicate, colloidal silica, ammonium silicate, etc. These alkali silicates may be used alone or in combination of two or more. Is. It may also be a mixture of silicon oxide and an alkali oxide and / or hydroxide.

The liquid composition for forming a gas barrier coating of the present invention comprises an aqueous solution containing the above water-soluble polymer having a plurality of acidic functional groups in the molecule and water glass,
It can be obtained by containing these in an appropriate ratio. The above water-soluble polymer and water glass are preferably mixed at a ratio A / B of acid equivalent (A) of water-soluble polymer / base equivalent (B) of water glass of 1 to 0.01, more preferably 1 to 0.01.
When the A / B is too large, the aqueous liquid tends to cause gelation and the storage stability tends to deteriorate, and conversely, when the A / B becomes too small, the water resistance of the coating film formed. Properties and gas barrier properties tend to be insufficient.

The preferred concentration of the aqueous solution containing the water-soluble polymer and water glass is 0.01 to 50% by weight, more preferably 0.1 to 20% by weight. If the concentration of the aqueous solution is too low, 1 Since the thickness of the coating formed by the single coating is too thin, the coating must be repeated many times to form a sufficient gas barrier coating, resulting in poor work efficiency. On the other hand, when the concentration of the aqueous liquid is too high, the coating film thickness per coating becomes too thick, and thus the coating film is likely to be cracked.

In the liquid composition of the present invention, in addition to the above-mentioned water-soluble polymer and water glass, a wettability improver, an antistatic agent, and various other additives are added within a range not impairing the characteristics of the present invention. It is possible to add.

In the present invention, solvents other than water, for example, alcohols such as methanol, ethanol and isopropanol, ketones such as acetone and methyl ethyl ketone,
Alternatively, it is also possible to add one kind or a combination of two or more kinds of diethyl ether, tetrahydrofuran and the like, if necessary.

The thus obtained liquid composition for forming a gas barrier film is applied to one surface or both surfaces of a resin molded product such as a film, a sheet or a bottle, or the surface of a metal molded product to form a film having a gas barrier property. To form. The coating method is not particularly limited, and examples thereof include a roll coating method, a dipping method, a bar coating method, a nozzle coating method, a spray coating method, and the like, and it is also possible to appropriately combine these methods.

In this case, it is also effective to subject the molded base material to a corona discharge treatment or other surface activation treatment or an anchor treatment with a known surface treatment agent such as urethane resin prior to coating. Curing and drying after coating may be carried out at room temperature, but appropriate heating is effective for completing curing and drying in a short time. In this case, it goes without saying that the heating temperature should be set below the heat-resistant temperature of the molded body as the base material.

The film thickness may be appropriately selected in consideration of the required degree of gas barrier property, etc.
The thickness is in the range of 0.001 to 20 μm, and more generally 0.01 to 10 μm. If the coating thickness is too thin, defects such as pinholes are likely to occur in the coating, and conversely if the coating thickness is too thick, cracking is likely to occur in the coating.

There is no particular limitation on the type of the molded product as the coated substrate, and examples thereof include polyolefin resins such as polyethylene and polypropylene, polyethylene terephthalate, polyethylene isophthalate, polyethylene-2,6 naphthalate, polybutylene terephthalate, or these. Polyester resins such as copolymers of the above, polyether resins such as polyoxymethylene, nylon-6, nylon-6
6, polyamide-based resins such as polymeta-xylene adipamide, polystyrene, poly (meth) acrylic acid ester,
Polyacrylonitrile, polyvinyl acetate, polycarbonate, cellophane, polyimide, polyetherimide,
Thermoplastic resin such as polyphenylene sulfone, polyether sulfone, polysulfone, polyether ketone, ionomer, fluorine resin; melamine resin, polyurethane resin, epoxy resin, phenol resin, unsaturated polyester resin, alkyd resin, urea Examples thereof include thermosetting resins such as series resins and silicon series resins; metals such as steel, aluminum, copper, nickel and zinc, and various alloys thereof.

Examples of the shape thereof include molded bodies of various shapes such as a film shape, a sheet shape and a bottle shape. In the case of a resin film, a resin sheet, a resin bottle, etc., one side or both sides thereof can be mentioned. It is possible to impart a gas barrier property to them by applying to the resin, and in the case of a resin molded product or a metal molded product, by coating on the surface thereof, the corrosion resistance and weather resistance of the molded product can be enhanced.

Accordingly, the gas barrier film-forming liquid composition of the present invention utilizes various gas foods by utilizing its excellent gas barrier property.
It can be widely used as a coating agent for imparting a gas barrier property to packaging materials such as pharmaceuticals, electronic parts and machine parts, or as a weather resistant surface treatment agent for machine materials and the like.

[0024]

EFFECTS OF THE INVENTION The present invention is constituted as described above, and by combining a water-soluble polymer having a plurality of acidic functional groups in the molecule with water glass, it is transparent and excellent in flexibility, It is possible to provide a liquid composition that gives a film having excellent gas barrier properties against gases such as nitrogen, carbon dioxide gas, and steam, and by applying this composition, a molded article having excellent gas barrier properties can be provided. Can be obtained.

[0025]

EXAMPLES The present invention will be specifically described with reference to the following examples, but the present invention is not limited by the following examples. The characteristic test method used in the examples is as follows. (1) Oxygen permeability: Measured by a gas permeability measuring device manufactured by Toyo Seiki Seisakusho according to JIS K 7126. (2) Flexibility: A film-forming liquid composition having a thickness of 25 μm
After coating on an ET film by a dipping method, the coating film was folded 180 degrees after drying, and the film without cracks was marked with ◯, and the film with cracks was marked with x. (3) A film-forming liquid composition is applied to a PET film having a thickness of 25 μm by a dipping method, and the resulting coated film is compared with a PET film having a thickness of 25 μm. Those in which the above are recognized are marked with x.

Example 1 20 g of a 5% aqueous solution of polyacrylic acid (molecular weight 2000) and 40 g of a 4% aqueous solution of sodium silicate (No. 3) were mixed together, and polyvinyl alcohol (88% saponified product) 1 was added as a wettability improver.
% Of 0.6% aqueous solution to give an aqueous coating solution. This coating solution was applied to a 25 μm PET film by a dipping method and dried at 21 ° C. for 24 hours. The obtained coating was transparent, did not crack even when bent at 180 degrees, and had an oxygen permeability of 6.73 cc / m ² · 24 hrs · atm, which was very good. The oxygen permeability of PET film is 7
It was 0.1 cc / m ² · 24hrs · atm.

Example 2 (Polymerization of Methacrylic Acid) 8.6 g of methacrylic acid was dissolved in 200 g of deionized water, heated to 60 ° C. and heated to 0.048 g of sodium persulfate and 0.002 g of L-ascorbic acid.
Then, hold at 60 ° C for 20 minutes with stirring, and further 8
The temperature was raised to 0 ° C. and the temperature was maintained for 2 hours to obtain an aqueous polymethacrylic acid solution having a molecular weight of 5000. (Preparation of coating composition and coating) An aqueous coating liquid was prepared in the same manner as in Example 1 except that the polyacrylic acid in Example 1 was changed to the polymethacrylic acid obtained above. The coating solution thus obtained was dip-coated on a PET film in the same manner as in Example 1 to form a gas barrier coating. The obtained coating is transparent, does not crack even when bent to 180 degrees, and has an oxygen permeability of 2.91 cc / m ² · 24hr.
It showed a good value of s ・ atm.

Examples 3 to 10 Preparation of an aqueous coating solution and evaluation of film performance were carried out in the same manner as in Example 1 except that the acidic functional group-containing polymer and water glass were changed as shown in Table 1. The results are shown in Table 1, and it can be seen that all have excellent flexibility and oxygen barrier properties.

[0029]

[Table 1]

Example 11 20 g of a 5% aqueous solution of polyacrylic acid (molecular weight 2000), 30 g of a 4% aqueous solution of sodium silicate (No. 3), and a 4% aqueous solution of silica sol (“Snowtex-UP” manufactured by Nissan Chemical Co., Ltd.) 1
0 g was mixed, and 0.6 g of a 1% aqueous solution of polyvinyl alcohol (88% saponified product) was further added as a wettability improver to obtain a coating liquid. This coating solution was applied to a 25 μm polyester film by a dipping method and dried at 21 ° C. for 24 hours. The obtained film was transparent, did not crack even when bent at 180 °, and had an oxygen permeability of 7.11 cc / m ² · 24 hrs · atm, which was very good.

Comparative Example 1 A 25% aqueous solution of 5% polyacrylic acid (molecular weight 2000) was used.
m PET film by dipping method
It was dried at 1 ° C. for 24 hours. The resulting coating is transparent,
No crack was generated even when bent at 180 degrees. However, the oxygen permeability was 24.98 cc / m ² · 24 hrs · atm, and the oxygen barrier property was poor.

Comparative Examples 2 to 8 In Comparative Example 1, a coated PET film was obtained in the same manner as in Comparative Example 1 except that the 5% aqueous solution of polyacrylic acid was changed to that shown in Table 2, and its performance was similarly obtained. An evaluation was done. The results are shown in Table 2, and the oxygen barrier properties were poor in all cases.

[0033]

[Table 2]

Comparative Example 9 0.1 g of 5% aqueous solution of polyacrylic acid (molecular weight 2000)
And 5 g of a 4% aqueous solution of sodium silicate (No. 3) are mixed together, and polyvinyl alcohol (88% saponified product) 1 is used as a wettability improver.
When 0.6 g of a 100% aqueous solution was added and mixed, precipitation occurred.

Comparative Example 10 0.1 g of 5% polyacrylic acid (molecular weight 2000) aqueous solution
And sodium silicate (No. 3) 10% aqueous solution 100 g are mixed,
As a wettability improver, 1.0 g of a 1% aqueous solution of polyvinyl alcohol (88% saponified product) was added and mixed, and then a thickness of 2
It was applied to a 5 μm PET film by a dipping method and dried at 21 ° C. for 24 hours. The resulting coating was transparent, but cracked when bent 180 degrees. The oxygen permeability was 67.10 cc / m ² · 24 hrs · atm, which was extremely poor.

Comparative Example 11 Polyacrylic acid (molecular weight 2000) 30% aqueous solution 20 g
And 40 g of a 40% aqueous solution of sodium silicate (No. 3) were mixed, and 0.6 g of a 1% aqueous solution of polyvinyl alcohol (88% saponified product) as a wettability improver was added and mixed, whereby the liquid gelled.

Comparative Example 12 20 g of a 5% aqueous solution of polyacrylic acid (molecular weight of 1,000,000) and 40 g of a 4% aqueous solution of sodium silicate (No. 3) were mixed to prepare a polyvinyl alcohol (88% saponified product) 1 as a wettability improver.
When 0.6 g of a 0.1% aqueous solution was added and mixed, the liquid gelled.

Comparative Example 13 20 g of a 5% aqueous solution of polyacrylic acid (molecular weight 500) and 40 g of a 4% aqueous solution of sodium silicate (No. 3) were mixed, and 1% of polyvinyl alcohol (88% saponified product) was used as a wettability improver.
0.6 g of an aqueous solution was added and mixed, and the obtained aqueous solution was applied to a PET film having a thickness of 25 μm by a dipping method and dried at 21 ° C. for 24 hours. The film obtained was transparent and did not crack when bent 180 degrees, but its oxygen permeability was 57.65 cc / m ² · 24 hrs ·
It was very bad with atm.

The abbreviations in Tables 1 and 2 have the following meanings. PAA: polyacrylic acid PMAA: polymethacrylic acid PPM: poly-2-methacryloyloxyethyl acid phosphate PMMA: polymethyl methacrylate AA: acrylic acid MAA: methacrylic acid MMA: methyl methacrylate PM: 2-methacryloyloxyethyl acid phosphate

Continuation of front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C09D 1/04 PCM 6770-4J 133/02 PGB 7921-4J 143/02 PGL 7921-4J 201/06 PDP 7415- 4J 201/08 PDH 7415-4J

Claims (6)

[Claims] 1. A liquid composition for forming a gas barrier film, comprising an aqueous solution containing a water-soluble polymer having a plurality of acidic functional groups in the molecule and water glass. 2. A water-soluble polymer comprising a homopolymer of a radical-polymerizable monomer having at least one acidic functional group in the molecule or a polymerizable monomer copolymerizable with the homopolymer. The liquid composition for forming a gas barrier film according to claim 1, which is a copolymer. 3. The liquid composition for forming a gas barrier film according to claim 1, wherein the acidic functional group is a carboxyl group or a phosphoric acid group. 4. The liquid composition for forming a gas barrier film according to claim 2, wherein the radically polymerizable monomer having an acidic functional group is acrylic acid and / or methacrylic acid. 5. The gas barrier property according to claim 1, wherein the ratio A / B of the acid equivalent (A) of the water-soluble polymer and the base equivalent (B) of water glass is in the range of 1 to 0.01. Liquid composition for forming a film. 6. A surface-coated molded article, which is coated with the liquid composition for forming a gas barrier coating according to any one of claims 1 to 5.