JP2003171468A - Gas-barrier resin composition and gas-barrier film made thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas-barrier film keeping the gas-barrierness even in a highly humid atmosphere, having high productivity and resistant to discoloration. <P>SOLUTION: A polycarboxylic acid polymer is made to react with (1) a carboxyl-reactive polymer having ≥5 nitrogen-containing functional groups reactive with carboxy group in the structure and (2) a ≥2-valent metal ion to form a crosslinked site in the polycarboxylic acid polymer by the reaction with the carboxyl-reactive polymer and a crosslinked site formed by the ≥2- valent metal ion. The weight ratio of the polycarboxylic acid polymer to the carboxyl-reactive polymer is 99.9/0.1-60/40. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas barrier resin composition and a gas barrier film using the same.

[0002]

2. Description of the Related Art In the field of packaging foods and medicines, packaging materials having excellent gas barrier properties such as oxygen gas barrier properties are used for the purpose of preventing quality deterioration of contents. As such a gas barrier film, a film in which polyvinylidene chloride is laminated, a film using a polyvinyl alcohol resin, and the like are known. In particular, a film obtained by laminating the above polyvinylidene chloride is widely used for food packaging.

[0003]

However, the film in which the above polyvinylidene chloride is laminated tends to be refrained from use due to recent environmental problems such as dioxin.

The film using the polyvinyl alcohol resin has a problem that the gas barrier property under high humidity is deteriorated because the polyvinyl alcohol resin contains a hydroxyl group. On the other hand, for example, Japanese Patent Laid-Open No. 10-2
Japanese Patent No. 37180 discloses a film coated with a resin obtained by ester-crosslinking and ion-crosslinking a polyalcohol-based resin and a partially neutralized product of polyacrylic acid or polymethacrylic acid. Although this film has improved gas barrier properties under high humidity, it requires high-temperature and long-time reaction to carry out the esterification reaction, and also has a problem of productivity. Further, there is a problem that the obtained coat layer is colored.

Further, Japanese Patent Laid-Open No. 2001-310425 discloses a gas barrier film composed of polyacrylic acid and a cross-linking agent component, but the gas barrier property of the obtained film is not always sufficient. There is.

[0006] Therefore, an object of the present invention is to provide a gas barrier film which retains gas barrier properties even under high humidity and is excellent in productivity and in which coloring is less likely to occur.

[0007]

The present invention relates to a polycarboxylic acid-based polymer, (1) a carboxyl group-reactive polymer having five or more nitrogen-containing functional groups which react with a carboxyl group in the structure, and (2) By reacting with a divalent or higher valent metal ion, the polycarboxylic acid-based polymer is caused to form a cross-linking site by the reaction with the carboxyl group reactive polymer and a cross-linking site with the divalent or higher valent metal ion. The weight ratio of the polycarboxylic acid-based polymer and the carboxyl group-reactive polymer is 99.9 / 0.
By setting it as 1-60 / 40, the said subject was solved.

Since a predetermined carboxyl group-reactive polymer is reacted with a polycarboxylic acid type polymer to form a cross-linking site, the hot water resistance of the resulting resin composition can be improved. Further, since the polycarboxylic acid-based polymer is provided with a cross-linking site by a metal ion having a valence of 2 or more, the hot water resistance of the obtained resin composition can be further improved, and the gas barrier property under high humidity can be improved. it can.

Further, since the amount of the carboxyl group-reactive polymer used is within a predetermined range, the gas barrier property under high humidity can be enhanced without impairing the appearance of the resin composition finally obtained. Furthermore, by using a specific carboxyl group-reactive polymer, the reaction conditions can be milder than those of the esterification reaction, and the productivity can be improved. Further, since the specific carboxyl group-reactive polymer is crosslinked with a metal ion having a valence of 2 or more, the productivity can be improved and the hot water resistance and the gas barrier property can be further improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The gas barrier resin composition according to the present invention comprises a polycarboxylic acid-based polymer, (1) a carboxyl group-reactive polymer having 5 or more nitrogen-containing functional groups that react with a carboxyl group in the structure, and (2) a divalent polymer. It is a composition in which a cross-linking site by the carboxyl group-reactive polymer and a cross-linking site by the divalent or higher valent metal ion are formed in the polycarboxylic acid-based polymer by reacting with the above metal ions.

As the above polycarboxylic acid type polymer,
Polyacrylic acid, polymethacrylic acid, polymaleic acid,
A homopolymer or copolymer of a monomer having a carboxyl group such as polyitaconic acid or acrylic acid-methacrylic acid copolymer. Further, partially neutralized products of homopolymers or copolymers of monomers having a carboxyl group such as the above polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymer and the like can be mentioned. Among these, polyacrylic acid, polymethacrylic acid and their partially neutralized products are preferable.

As the alkaline substance for partially neutralizing the homopolymer or copolymer of the above-mentioned monomer having a carboxyl group, sodium hydroxide, potassium hydroxide,
Examples thereof include metal hydroxide salts such as lithium hydroxide and ammonia. The partially neutralized product can be obtained by adding the metal hydroxide salt to an aqueous solution of a polycarboxylic acid polymer and reacting them.

The degree of neutralization of the partially neutralized product is not particularly limited, but is preferably 2 to 30% and more preferably 5 to 20% in terms of molar ratio to the carboxyl group. If it is less than 2%, the reactivity with the above-mentioned carboxyl group-reactive polymer tends to decrease, and the productivity tends to decrease. On the other hand, when it is more than 30%, the number of reaction points itself with the carboxyl group-reactive polymer decreases, and the gas barrier property of the final resin composition tends to deteriorate.

The weight average molecular weight of the above polycarboxylic acid type polymer is not particularly limited, but is 2000 to 500,0.
00 is preferable, and 20,000 to 400,000 is more preferable. If it is less than 2000, the gas barrier property of the finally obtained resin composition tends to deteriorate. on the other hand,
When it is more than 500,000, the viscosity of the aqueous solution becomes too high, which is not preferable.

The above-mentioned carboxyl group-reactive polymer is
It refers to a polymer having 5 or more nitrogen-containing functional groups that easily react with a carboxyl group in the structure, and refers to a polymer that forms a cross-linking site in the polycarboxylic acid-based polymer. When the number of the nitrogen-containing functional groups is less than 5, the flexibility of the finally obtained composition may deteriorate.

The above-mentioned carboxyl group-reactive polymer has the above-mentioned nitrogen-containing functional group only in the side chain in the main chain, has the above-mentioned nitrogen-containing functional group in the side chain in the main chain, and has a terminal portion. Also have the above-mentioned nitrogen-containing functional group.

The degree of polymerization of the above-mentioned carboxyl group-reactive polymer having a nitrogen-containing functional group in the side chain of the main chain is 5 to 5.
200,000 is preferable, 10-180,000 is preferable, and 100-150,000 is more preferable. If the degree of polymerization is less than 5, the flexibility of the finally obtained composition may deteriorate. On the other hand, when the degree of polymerization is higher than 200,000, the viscosity of the solution tends to be too high.

As the nitrogen-containing functional group, a carbamoyl group, a carbodiimide group, an oxazoline group, an amino group,
Examples thereof include acetamide group and isocyanate group. At least one kind of these is contained, and only one kind may be contained or two or more kinds may be contained.

Examples of the carboxyl group-reactive polymer are as follows. First, examples of the polymer containing a carbamoyl group include acrylamide, methacrylamide polymer or copolymer, amide-ammonium salt-modified maleic acid-based copolymer, and the like. Polyacrylamide, polymethacrylamide, amide-ammonium salt-modified maleic acid. Copolymer (Kuraray Co., Ltd .:
Product names ISOBAN 104, 110, etc.) are preferably used.

Further, as the polymer containing an amino group,
Examples thereof include polyallylamine, polyvinylamine, polyvinylaniline, branched polyethyleneimine and the like. Further, examples of the polymer containing an acetamide group include polymers obtained by subjecting the above-mentioned polymer containing an amino group to modification such as acetylation.

In addition to the above-mentioned carboxyl group-reactive polymer, a catalyst or the like may be appropriately added in order to enhance the reactivity between the above-mentioned polycarboxylic acid type polymer and the carboxyl group-reactive polymer.

The weight ratio of the above polycarboxylic acid type polymer to the carboxyl group reactive polymer is such that polycarboxylic acid type polymer / carboxyl group reactive polymer = 99.9.
/0.1 to 60/40 is preferable, and 99/1 to 80/20 is preferable. If the amount of the carboxyl group-reactive polymer is less than 0.1% by weight, the water resistance of the resin composition will be low. On the other hand, when it is higher than 40% by weight, the gas barrier property of the final product tends to be deteriorated.

The above-mentioned divalent or higher valent metal ions are those which form an ionic bond with the carboxyl group of the aforementioned polycarboxylic acid type polymer and have divalent or higher valent cations. Since this metal ion has a positive ion with a valence of 2 or more,
An ionic bond can be formed with one or more carboxyl groups, and a crosslinking site can be formed in the carboxylic acid-based polymer.

The divalent or higher valent metal ions include magnesium ions, calcium ions, barium ions,
Examples thereof include zinc ion, copper ion, cobalt ion, nickel ion, aluminum ion and iron ion. Among these, magnesium ion, calcium ion, and barium ion are preferably used. At least one of these may be used, and only one may be used or two or more may be used in combination.

The divalent metal ion is preferably used in the state of an alkaline aqueous solution. When used in this state, the exchange reaction between the metal ion and the counter ion of the carboxyl group proceeds, the ionic cross-linking site is formed, and the composition is stabilized. Examples of the alkaline aqueous solution include aqueous solutions of metal salt hydroxides and the like, and alcoholic aqueous solutions containing alcohol and the like may be used. Specifically, a magnesium hydroxide aqueous solution, a calcium hydroxide aqueous solution, a barium hydroxide aqueous solution and the like are preferably used.

The above gas barrier resin composition can be produced by reacting a polycarboxylic acid type polymer with the above carboxyl group-reactive polymer and then reacting it with an alkaline aqueous solution of a divalent or higher valent metal ion. The reaction conditions in the reaction with the carboxyl group-reactive polymer are preferably 100 to 230 ° C. and 1 second to 60 minutes, though depending on the kind of the carboxyl group reactive polymer.

The reaction with the divalent or higher valent metal ion may be carried out by applying an aqueous solution of the divalent or higher valent metal ion to the reaction polymer of the polycarboxylic acid type polymer and the carboxyl group-reactive polymer. The above crosslinked product is converted to the above 2
It is performed by immersing in an aqueous solution of a metal ion having a valency or more. The reaction conditions at this time are 10 to 120 ° C. and 1
Seconds to 60 minutes are preferred.

The above gas barrier resin composition is molded by
It is preferable to carry out up to the stage of mixing the carboxyl group-reactive polymer with the polycarboxylic acid polymer. This is because, if the polycarboxylic acid-based polymer and the carboxyl group-reactive polymer are subjected to a crosslinking reaction by heating to form a crosslinking site, molding is often difficult.

For preparing a mixed solution of the above polycarboxylic acid type polymer and the above carboxyl group-reactive polymer, a method of dissolving each component in water, a method of mixing an aqueous solution of each component, or the like can be applied. In addition to water, a solvent such as alcohol,
A mixed solvent such as water / alcohol may be used.

As a molding method, the above mixed solution is extruded from a T-die or the like and heated to form a film into a film, or the mixed solution is cast onto a glass plate, a plastic film or the like. A method of forming into a film, a method of producing a laminate in which a film is laminated on a substrate by applying the mixture on at least one surface of a substrate and heating the mixture, and a raw material resin for the substrate. A method for producing a laminate in which a film is laminated on a substrate by heating while coextruding, extruding from the above T die or the like, and joining the film obtained by heating to the substrate to form the film on the substrate. The method of manufacturing the laminated body laminated | stacked on.

The obtained film or laminate is coated with the aqueous solution of divalent or higher valent metal ions on the mixed solution coating layer side, or the film or laminate is dipped in the aqueous solution of divalent or higher valent metal ions. And reacting to form a cross-linking site by a metal ion having a valence of 2 or more, and a film or laminate having a gas barrier property is obtained.

The base material is not particularly limited as long as the gas barrier property is imparted to the entire laminate by laminating the gas barrier resin composition, and examples thereof include polyester resins and polyamide resins. resin,
Examples thereof include synthetic resins such as polyolefin resins and cellulosic materials such as cellophane and paper. Further, as the shape of the base material, any shape such as a film shape, a sheet shape, and a molded body such as various containers can be adopted.

In the present invention, water-swellable inorganic tabular grains such as vermiculite and montmorillonite can be added to the solution containing the above polycarboxylic acid type polymer and the carboxy group-reactive polymer. By molding this, the performance of the final gas barrier composition can be further enhanced.

[0034]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. First, the substances used are shown below. -Polyacrylic acid: manufactured by Wako Pure Chemical Industries, Ltd., first-class reagent, weight average molecular weight of about 250,000-Polyacrylamide: manufactured by Kishida Chemical Co., Ltd., reagent, weight average molecular weight of 9,000,000-10,000,000 (degree of polymerization: 12.7) 10,000 ~
1410,000) (hereinafter abbreviated as "PAM")-Amide-modified maleic acid-based copolymer: manufactured by Kuraray Co., Ltd.
Product name Isoban 110 (weight average molecular weight 160,000 to 170,000 (hereinafter abbreviated as "isoban")-Polyvinyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd .; polyvinyl alcohol 1000, completely saponified type) (hereinafter, " P
Abbreviated as "VA". ) ・ Starch: Soluble starch (Kishida Chemical Co., Ltd .; reagent)

[Preparation of partially neutralized polyacrylic acid] Polyacrylic acid was dissolved in ion-exchanged water so that the solid content was 5% by weight. Add 10 mol% sodium hydroxide to the carboxyl group of polyacrylic acid, and neutralize to 1
0% partially neutralized polyacrylic acid (hereinafter referred to as "PAA-N
Abbreviated as a ". ) Was prepared.

(Examples 1 to 8) PAA-N was mixed so that the solid content of PAA-Na was as shown in Table 1.
The aqueous solution of the carboxyl group-reactive polymer shown in Table 1 was mixed with the aqueous solution a. PAM is 1% by weight when dissolved in water
Used as an aqueous solution. Further, isoban was dissolved in water and used as a 5% by weight aqueous solution. These mixed aqueous solutions were stretched polyester film (manufactured by Toyobo Co., Ltd .: E51
00, thickness: 12 μm) was coated with a Mayer bar so that the thickness of the coating film after drying was 1 μm.
After drying at 100 ° C. for 2 minutes, the heat treatment temperature shown in Table 1
Heat treatment was performed in a hot air dryer for 5 minutes. Then, Table 1
Is immersed in a 0.2% by weight aqueous solution of the metal ion hydroxide (Wako Pure Chemical Industries, Ltd .; reagent) for 30 minutes,
After washing with water, it was dried at 100 ° C. for 2 minutes to obtain a laminate film. Using the obtained laminated film, the oxygen permeability, hot water resistance, and appearance were measured or judged according to the following methods.

[Oxygen permeability] Oxygen permeability tester (Mode
RN Control; OX-TRAN2 / 2
0), the target film is 23 ℃, relative humidity 80%
The oxygen permeability in the atmosphere was measured. Since the oxygen permeability changes depending on the thickness of the film, the thickness of the gas barrier resin composition layer, etc., the oxygen permeability per 1 μm of the gas barrier resin composition layer was calculated according to the following formula. 1 / P _total = 1 / P _sample + 1 / P _{base In the} above formula, P _total is the measurement result, P _sample is the oxygen permeability of the gas barrier resin composition layer, and P _base is the oxygen permeability of the base film. Show.

[Hot Water Resistance] The target film was immersed in warm water of 80 ° C. for 30 minutes, and the weight reduction of the gas barrier resin composition layer was measured. The results were evaluated according to the following criteria. ◯: Weight remaining ratio is 100% Δ: Weight remaining ratio is 50% or more and less than 100% ×: Weight remaining ratio is less than 50%

[Appearance] The appearance of the target film was evaluated according to the following criteria. ◯: No difference compared to the base film alone x: Colored xx: Gas barrier resin composition layer peels off / swells

(Comparative Examples 1 to 3) PVA or starch was used as the polymer to be mixed with the polycarboxylic acid-based polymer, and the compounding ratios shown in Table 1 were used in the same manner as in Example 2 or Example 6. A laminate film was obtained. Note that P
VA was dissolved in water and used as a 5% by weight aqueous solution.
The starch was dissolved in water and used as a 5% by weight aqueous solution. Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

(Comparative Example 4) A laminate film was obtained in the same manner as in Example 5 except that the compounding ratio of the partially neutralized polyacrylic acid and isoban was changed to 40/60. Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

(Comparative Example 5) A laminate film was obtained in the same manner as in Example 5 except that the metal ion hydroxide was not used to form the crosslinking site. Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

Comparative Example 6 A laminate film was obtained in the same manner as in Example 5 except that the above polycarboxylic acid polymer was not used and no heat treatment was performed. Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

Comparative Example 7 A laminate film was obtained in the same manner as in Example 1 except that the above carboxyl group-reactive polymer was not used and no heat treatment was performed. Using the obtained laminate film, according to the above method, the oxygen permeability,
The hot water resistance and appearance were measured or judged.

[0045]

[Table 1]

[0046]

The gas barrier resin composition according to the present invention and the film or laminate obtained therefrom have a cross-linking site in the polycarboxylic acid-based polymer by the carboxyl group-reactive polymer, so that the cross-linked polycarboxylic acid obtained is obtained. The hot water resistance of the base polymer can be improved.

Since the polycarboxylic acid type polymer is provided with a cross-linking site with a metal ion having a valence of 2 or more, the hot water resistance can be further improved and the gas barrier property under high humidity can be improved.

Furthermore, since the amount of the carboxyl group-reactive polymer used is within the predetermined range, the gas barrier property under high humidity can be enhanced without impairing the appearance of the resin composition finally obtained.

Furthermore, by using a specific carboxyl group-reactive polymer, the reaction conditions can be milder than those of the esterification reaction, and the productivity can be improved. Moreover, since the specific carboxyl group-reactive polymer is crosslinked with a metal ion having a valence of 2 or more,
It is possible to further improve the hot water resistance and the gas barrier property as well as the productivity.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C08L 101: 00 C08L 101: 00 (72) Inventor Susumu Sakata 4-1-1 Daikai, Fukushima-ku, Osaka No. Rengo Co., Ltd. Central Research Institute (72) Inventor Masao Fujita 4-1-1, Daikai, Fukushima-ku, Osaka Rengo Co., Ltd. Central Research Center F-term (reference) 4F006 AA02 AA12 AA35 AA38 AB24 AB38 BA05 CA07 4F071 AA09 AA14 AA43 AA54 AA75 AA78 AB18 AF08 AH04 BA01 BB06 BC01 4F100 AB09B AH03B AJ04A AK03A AK24B AK25B AK41A AK46A AK70B AL01B AL05B AL07B AC02A25 AF02A25 AF02A25 AF02A25 A02A25 AF02A25A02A25A02A25A02A25A02A25A25A25A25A22A25A22A25A02A25A22A25A22A25A25A22A25A22A25A22A25A22A25A22A25A22A25A02A25A25A25A22A25A22A25A02A25A22A22A25A22A25A22A25A22A02A25A22A25A22A25A01A02

Claims (11)

[Claims] 1. A polycarboxylic acid-based polymer, (1) a carboxyl group-reactive polymer having 5 or more nitrogen-containing functional groups which react with a carboxyl group in the structure, and (2)
By reacting with a divalent or higher valent metal ion, the polycarboxylic acid-based polymer is caused to form a cross-linking site by the reaction with the carboxyl group reactive polymer and a cross-linking site with the divalent or higher valent metal ion. A gas barrier resin composition in which the weight ratio of the polycarboxylic acid-based polymer to the carboxyl group-reactive polymer is 99.9 / 0.1 to 60/40. 2. The nitrogen-containing functional group in the carboxyl group-reactive polymer is at least one selected from a carbamoyl group, a carbodiimide group, an oxazoline group, an amino group, an acetamide group and an isocyanate group. The gas barrier resin composition of. 3. The gas barrier resin composition according to claim 1, wherein the divalent or higher valent metal ion is at least one selected from magnesium ion, calcium ion and barium ion. 4. The polycarboxylic acid-based polymer is at least one selected from polyacrylic acid, polymethacrylic acid, polyacrylic acid or a partially neutralized product of polymethacrylic acid.
The gas barrier resin composition according to claim 1 or 2, which is a seed. 5. A gas barrier film formed from the gas barrier resin composition according to claim 1. 6. A gas barrier film in which the gas barrier resin composition according to claim 1 is applied to at least one surface of a substrate. 7. The gas barrier film according to claim 6, wherein the substrate is at least one selected from polyester resins, polyamide resins, and polyolefin resins. 8. The gas barrier film according to claim 6, wherein the base material is made of a cellulose material. 9. A gas barrier laminate having the gas barrier film according to claim 5 laminated thereon. 10. A method for producing a gas barrier resin composition, which comprises reacting a polycarboxylic acid-based polymer with a carboxyl group-reactive polymer, and then reacting it with an alkaline aqueous solution of a divalent or higher valent metal ion. 11. A method for producing a gas barrier film, which comprises reacting a polycarboxylic acid-based polymer with a carboxyl group-reactive polymer, forming a film, and then reacting it with an alkaline aqueous solution of a divalent or higher valent metal ion.