JP2000319415A - Gas barrier film coated with high nitrile-content copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas barrier film coated with a high nitrile-content copolymer latex having an excellent film-forming ability and gas barrier properties. SOLUTION: At least one surface of a plastic film is coated with a latex comprising as a main component a high nitrile-content copolymer obtained by emulsion polymerization of 100 pts.wt. of a monomer mixture comprising 70-95 wt.% of acrylonitrile and 5-30 wt.% of at least one vinyl monomer copolymerizable therewith in the presence of 3-25 pts.wt. of a polyvinyl alcohol having a viscosity of 2-50 mPa.s and a saponification degree of at least 95.5 mole %.

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 obtained by coating a plastic film with a high nitrile copolymer latex having excellent coating film forming ability and gas barrier properties.

[0002]

2. Description of the Related Art Acrylonitrile resins exhibit excellent gas barrier properties based on the intermolecular bonds specific to nitrile groups, and have chemical resistance to acids, alkalis, organic solvents, and the like, flexural modulus, strength, creep resistance, and the like. Is a thermoplastic resin having excellent mechanical properties. In recent years, its value as a packaging material in films, sheets, and containers has been recognized in the fields of foods, agricultural drugs, cosmetics, and the like. However, the gas barrier property and the melt moldability of the acrylonitrile resin are contradictory properties. As the content of the acrylonitrile component increases, the gas barrier property increases, but the melt moldability decreases.

[0003] The same is true for coating, and the gas barrier property and the film forming ability are contradictory properties, and the film forming ability decreases as the content of the acrylonitrile component increases. On the other hand, if the content of the acrylonitrile component is high, the polymerization stability becomes poor, and a latex cannot be obtained stably. Techniques for obtaining a latex stably at a high acrylonitrile content include, for example, Japanese Patent Publication No. 54-41.
No. 638 and Japanese Patent Publication No. 55-2207 disclose a production method for introducing a certain amount or more of acidic groups into a polymer produced when polymerizing under specific pressure and temperature conditions. The ability to form a coating film is not sufficient.

Japanese Patent Application Laid-Open No. 57-195770 discloses a nitrile barrier resin latex coating to which a specific thickener is added, and Japanese Patent Application Laid-Open No. 59-213773 discloses that at least a film forming property and a dry film property are different. Although a coating film forming composition containing a mixture of two aqueous nitrile resins has been proposed, baking at a high temperature and for a long time is required to develop barrier properties, and a base material having a low heat-resistant temperature such as a plastic film is required. It cannot be used for wood.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and is intended to provide a high nitrile copolymer having excellent film-forming ability and gas barrier properties. It is an object to provide a gas barrier film coated with latex.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to overcome the above-mentioned problems of the prior art and, surprisingly, have found that by carrying out emulsion polymerization in the presence of a specific polyvinyl alcohol, high acrylonitrile can be obtained. The content can be polymerized stably, and in the nitrile copolymer latex,
Although the film forming ability and the barrier property are contradictory properties, the film forming ability of the latex is significantly improved,
In addition, they have found that a coating film having high barrier properties can be obtained, and have completed the present invention.

That is, the present invention relates to (1) 100 parts by weight of a monomer mixture comprising 70 to 95% by weight of acrylonitrile and 5 to 30% by weight of at least one vinyl monomer copolymerizable therewith. On the other hand, at least one surface is coated with a high nitrile copolymer latex obtained by emulsion polymerization in the presence of 3 to 25 parts by weight of polyvinyl alcohol having a viscosity of 2 to 50 mPa · s and a degree of saponification of 95.5 mol% or more. A high-nitrile copolymer latex according to claim 1 and a solid content of 100%.
A gas barrier film coated on at least one surface with a high nitrile copolymer latex containing 2 to 50 mPa · s in viscosity per part by weight and 25 parts by weight or less of polyvinyl alcohol having a saponification degree of 95.5 mol% or more, 3)
A laminated film comprising at least two or more film layers, including the gas barrier film according to claim 1 or 2.

The details of the present invention will be described below. The monomer mixture used in the present invention has acrylonitrile of 7%.
0-95% by weight, preferably 80-90% by weight;
At least one vinyl monomer copolymerizable therewith;
%, Desirably 10 to 20% by weight. If acrylonitrile is less than 70% by weight, sufficient gas barrier properties cannot be obtained. On the other hand, when the content exceeds 95% by weight, the polymerization stability becomes poor.

The vinyl monomer copolymerizable with acrylonitrile used in the present invention is not particularly limited.
It is a known or well-known compound having a carbon-carbon unsaturated double bond, and includes (meth) acrylates, (meth) acrylamides, (meth) acrylates having a functional group bonded thereto, vinyls, olefins, and unsaturated carboxylic acids. Acid esters, vinylidenes, urethanes having an unsaturated bond,
Silicones having an unsaturated bond and fluorine-based unsaturated monomers can be used. Preferably, unsaturated carboxylic acid esters, specific examples include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like.

In the present invention, the polyvinyl alcohol used at the time of emulsion polymerization has a viscosity of 2 to 50 mPa · s, preferably 2 to 10 mP at 20 ° C. and 4% by a B-type viscometer.
a.s, and the degree of saponification is 95.5 mol% or more, preferably 98 mol% or more. If the viscosity exceeds 50 mPa · s, the viscosity of the system during polymerization becomes too high, and the polymerization stability cannot be ensured in order to increase the solid content of the latex to 10% or more. In order to increase the solid content of the latex, it is desirable that the viscosity be low. In addition, the degree of saponification is 95.5 mol%.
If it is less than 10, the polymerization stability is lowered, and a yield of 90% or more cannot be obtained.

The polyvinyl alcohol is used in an amount of 3 to 25 parts by weight, preferably 6 to 25 parts by weight, based on 100 parts by weight of the monomer mixture.
It is preferable that the content be 15 to 15 parts by weight. If the amount of the polyvinyl alcohol is less than 3 parts by weight, it is difficult to obtain a good ability to form a coating film. If the amount exceeds 25 parts by weight, the viscosity of the system becomes too high, and it is difficult to secure polymerization stability. The type of polymerization initiator, surfactant, and the like used for the polymerization of the high nitrile copolymer latex of the present invention is not particularly limited, but these substances remain in the coating film formed from the latex and remain as gas and steam. It is preferable that the amount used is as small as possible, because it may be a factor of deteriorating the barrier property. Particularly for the emulsifier, it is more preferable to use a reactive emulsifier, for example, sulfoethyl methacrylate, sodium p-styrenesulfonate and the like.

Further, since a high molecular weight high nitrile copolymer is inferior in melt fluidity, fusion of latex particles and molecular diffusion after fusion hardly occur. Therefore, a low molecular weight is added by adding a molecular weight modifier. It is desirable to do. The method for producing a high nitrile copolymer latex of the present invention is performed by a generally known emulsion polymerization method using the above-described raw materials,
It can be manufactured without using a special reactor. The method of adding various additives such as a polymerization initiator, a surfactant, and a monomer mixture to the polymerization system, and the polymerization temperature are not particularly limited. In the present invention, it is preferable to further mix polyvinyl alcohol to the high nitrile copolymer latex obtained above from the viewpoint that a coating film can be formed at a lower temperature.

The polyvinyl alcohol to be mixed with the high nitrile copolymer latex has the above-mentioned properties.
It is preferably at most 5 parts by weight, more preferably at most 15 parts by weight. When the amount of polyvinyl alcohol exceeds 25 parts by weight, the water resistance of the coated film after coating is significantly reduced. The high nitrile copolymer latex of the present invention can be used as a barrier coating agent. The substrate film layer coated with the barrier coating agent of the present invention and used as a barrier layer is not particularly limited, for example, polyester, polyamide, polyimide, polypropylene, polyethylene, polyvinyl alcohol, cellophane, polystyrene, polyvinyl chloride,
Examples include ethylene-vinyl alcohol copolymer, polycarbonate, and the like, and multilayer films thereof.

Further, the barrier layer of the present invention may be provided on a substrate film layer, and the film layer may be provided on the barrier layer. The method of coating the high nitrile copolymer latex coating agent of the present invention is not particularly limited, and includes known methods such as an air knife coat, a gravure coat, a reverse gravure coat, a bar coat, and a comma coat. Further, after coating the unstretched film by the coating method, the film may be stretched simultaneously with the barrier layer to prepare a laminated film including the barrier layer composed of the latex of the present invention. The drying temperature and stretching temperature vary depending on the acrylonitrile content in the monomer mixture, the mixing ratio of polyvinyl alcohol and the heat resistance of the base film, but are determined in the range of room temperature to 210 ° C. according to the transparency and water resistance of the coating film. Can be

[0015]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and the like, but the present invention is not limited to these examples and the like. Parts and percentages are by weight unless otherwise specified. The analysis means used in the embodiments of the present invention are as follows. (A) Amount of aggregate generated during polymerization After the completion of emulsion polymerization, the total amount of latex in the polymerization vessel was reduced to 400 m.
After filtration through an ash wire mesh, the solid matter remaining on the wire mesh was washed with water and dried to dryness, the weight was measured, and the weight was expressed as a weight fraction with respect to the monomer mixture used for the polymerization. (B) Preparation of a coated film A stretched polyester film or a stretched nylon film or a stretched polypropylene film subjected to a corona discharge treatment was dried with a high nitrile copolymer latex using a Mayer rod, and the coating weight was 2.5 g / m2. ² and dried in a hot air circulating drier at 100 to 200 ° C. for 30 seconds.

(C) Oxygen Permeability A coated film prepared by using the stretched polyester film (12 μm), the stretched nylon film (15 μm), and the stretched polypropylene film (22 μm) according to the above item (b) at 20 ° C. and a relative humidity of 55 %,
OX-TRAN100 (Modern Control
Was measured at 20 ° C. and a relative humidity of 60%.
It is a value at a coating amount of 2.5 g / m ² . (D) Viscosity Measured according to the method of 3.5 of JIS K6726. (E) Degree of saponification Measured according to the method of 3.11.1 of JIS K6726.

Example 1 A high nitrile copolymer latex was produced by the following method. 220 parts of water and 0.04 sodium persulfate in a pressure-resistant reactor lined with glass
After the parts were charged and degassed, the temperature of the contents was kept at 80 ° C. In a separate container, 80 parts of acrylonitrile, 18 parts of methyl acrylate, and 2 parts of methacrylic acid were measured and mixed to prepare a monomer mixture. The monomer mixture was continuously metered into the pressure-resistant reactor over 5 hours. In parallel, 0.6 part of sodium persulfate (however, the concentration is 1.48%
Added as an aqueous solution. ), Polyvinyl alcohol (hereinafter referred to as PVA) (manufactured by Kuraray: trade name PVA-103,
Completely saponified type, degree of saponification 98.4 mol%, viscosity 3.5 m
10 Pa · s (4%, 20 ° C.) (provided that the concentration is 7.
Added as a 69% aqueous solution. ) And 2 parts of sulfoethyl methacrylate (hereinafter referred to as SEM; manufactured by Nippon Emulsifier: trade name Antox MS-2N) (provided that the concentration is 4.76)
% Aqueous solution. ) Was metered in continuously over 5 hours. During this time, the content was maintained at 80 ° C., and the reaction was allowed to proceed until the internal pressure was sufficiently reduced.

Table 1 shows the polymerization yield of the obtained high nitrile copolymer latex, the amount of aggregates, and the oxygen permeability of the film coated on the stretched polyester film. The obtained latex has excellent coating film forming ability to obtain a transparent film at the above-mentioned coating conditions and the drying temperature shown in Table 1,
Moreover, the gas barrier property of the coated film was also high. Example 2 The monomer mixture was converted to acrylonitrile 80
Parts, 18 parts of ethyl acrylate, and 2 parts of methacrylic acid. Table 1 shows the results. Example 3 The monomer mixture was converted to acrylonitrile 80
Parts, 18 parts of butyl acrylate, and 2 parts of methacrylic acid. Table 1 shows the results.

(Example 4) 100% by weight of the solid content of the latex of Example 1 was mixed with PVA (manufactured by Kuraray, trade name PV
A-103, completely saponified type, degree of saponification 98.4 mol%,
10 parts of a viscosity of 3.5 mPa · s (4%, 20 ° C.) (however, added as a 11% aqueous solution) was added.
The oxygen permeability of a film obtained by coating the obtained latex on a stretched polyester film was measured. Table 1 shows the results.

Example 5 The procedure was the same as in Example 4 except that the base film was a stretched nylon film. Table 1 shows the results. (Example 6) The procedure was the same as in Example 4 except that the base film was a stretched polypropylene film. Table 1 shows the results
Shown in (Comparative Example 1) Except that PVA was not added, the procedure was exactly the same as in Example 1. Table 1 shows the results.

(Comparative Example 2) No PVA was added, and instead of the SEM aqueous solution, sodium alkyldiphenyl ether sulfonate (manufactured by Sanyo Chemical Industries, trade name: Eleminol MO)
N-2) Except that 2 parts (added as a 6.25% aqueous solution) was the same as Example 1. Table 1 shows the results. (Comparative Example 3) No PVA was added, and 2 parts of polyoxyethylene nonylphenyl ether (trade name: Emulgen 935, manufactured by Kao Corporation) was used instead of the SEM aqueous solution (however, added as a 6.25% aqueous solution). Except for this, the procedure was exactly the same as in Example 1. Table 1 shows the results.

Example 7 The procedure was the same as in Example 4 except that the drying temperature was 100 ° C. Table 1 shows the results. (Comparative Example 4) PVA (manufactured by Kuraray, trade name: PVA-103, fully saponified type, saponification degree 98.4 mol%, viscosity 3.5 mPa ·) was added to 100 parts by weight of the solid content of the latex of Comparative Example 1.
s (4%, 20 ° C.)) of 10 parts (but added as an 11% concentration aqueous solution). The oxygen permeability of a film obtained by coating the obtained latex on a stretched polyester film was measured. Table 1 shows the results.

Example 8 In a SUS pressure-resistant reactor,
0.64 parts of sodium persulfate (added as a 1.06% aqueous solution), 2 parts of SEM (provided that the concentration is 1.
Added as a 41% aqueous solution. ), PVA (Kuraray:
Trade name PVA-105, fully saponified type, degree of saponification
5 mol%, viscosity 5.6 mPa · s (4%, 20 ° C.)) 1
0 parts (however, added as a 4.54% aqueous solution), acrylonitrile 93 parts, methyl acrylate 5
Parts, a monomer mixture of 2 parts of methacrylic acid was added at room temperature, and the temperature was raised to 80 ° C. for 1 hour. Then, the content was kept at 80 ° C. for 1 hour, and the reaction was allowed to proceed until the internal pressure was sufficiently reduced. .

Table 2 shows the polymerization yield of the obtained high nitrile copolymer latex, the amount of aggregates, and the oxygen permeability of the film coated on the stretched polyester film. The obtained latex had excellent coating film forming ability to obtain a transparent film under the above-mentioned coating conditions and the drying temperature shown in Table 2, and also had high gas barrier properties of the coated film. Example 9 The monomer mixture was converted to acrylonitrile 88
Parts, 10 parts of methyl acrylate and 2 parts of methacrylic acid. Table 2 shows the results.

Example 10 The procedure of Example 8 was repeated except that the monomer mixture was changed to 80 parts of acrylonitrile, 18 parts of methyl acrylate and 2 parts of methacrylic acid. Table 2 shows the results. (Example 11) Except that the amount of PVA added was 8 parts, the procedure was exactly the same as in Example 10. Table 2 shows the results. Example 12 The procedure was the same as Example 10 except that the amount of PVA added was changed to 6 parts. Table 2 shows the results.

Example 13 The procedure of Example 8 was repeated except that the monomer mixture was changed to 70 parts of acrylonitrile, 28 parts of methyl acrylate and 2 parts of methacrylic acid. Table 2 shows the results. (Comparative Example 5) Acrylonitrile 60 was used as the monomer mixture.
Parts, methyl acrylate 38 parts, and methacrylic acid 2 parts, except that they were the same as in Example 8. Table 2 shows the results. (Comparative Example 6) Acrylonitrile 50 was used as the monomer mixture.
Parts, 48 parts of methyl acrylate and 2 parts of methacrylic acid. Table 2 shows the results.

Comparative Example 7 The procedure of Example 8 was repeated except that the monomer mixture was changed to 40 parts of acrylonitrile, 58 parts of methyl acrylate, and 2 parts of methacrylic acid. Table 2 shows the results. (Comparative Example 8) PVA was partially saponified and had a saponification degree of 80.0
The procedure was exactly the same as that of Example 9 except that the mol% and the viscosity were 5.0 mPa · s (4%, 20 ° C.) (manufactured by Nippon Chemical Synthesis: Gohsenol KL-01). Table 2 shows the results.

Comparative Example 9 PVA is partially saponified, the degree of saponification is 88 mol%, and the viscosity is 45 mPa · s (4%, 20 ° C.)
(Except for Unitika: trade name UP240G). Table 2 shows the results. (Comparative Example 10) Example 9 except that PVA was not added.
It was exactly the same. Table 2 shows the results. In the above Examples 1 to 13 and Comparative Examples 1 to 10,
As shown in Table 1 and Table 2, when the monomer composition and the PVA satisfy the conditions of the present invention, excellent film-forming ability, high barrier properties and polymerization stability can be obtained.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

The high nitrile copolymer latex of the present invention is stable and can be dried at a lower temperature and in a shorter time than conventional high nitrile copolymer latex when applied in latex state to plastic films, sheets, metal plates, etc. It is possible and has excellent film forming ability. Particularly, a gas barrier film coated on a plastic film can provide a gas barrier packaging material containing no chlorine atom.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 133/20 C09D 133/20 F term (Reference) 4F071 AA14X AA29 AA33X AA34 AA34X AA35X AA88 AF08 AH04 AH05 BA05 BB13 BC02 4F100 AK01B AK02A AK02C AK07 AK21A AK21C AK21J AK25 AK25J AK27A AK27C AK27J AK42 AK48 AK55 AK55J AL01 AL01A AL01C AL05A AL05C AT00B BA02 BA03 BA06 BA10A BA10C BA13 BA15 EH46 EJ37 GB15 GB23 JA06A JA06C JD02 JD03 YY00A YY00C 4J002 BE022 BG101 GF00 GH00 HA07 4J011 AA05 DA01 KA09 KA16 KB04 KB29 PA67 PB40 PC02 PC06 4J038 CE021 MA13 PB03 PC08

Claims (3)

[Claims] 1. A viscosity of 2 to 100 parts by weight of a monomer mixture composed of 70 to 95% by weight of acrylonitrile and 5 to 30% by weight of at least one vinyl monomer copolymerizable therewith. A gas barrier film having at least one surface coated with a high nitrile copolymer latex obtained by emulsion polymerization in the presence of 3 to 25 parts by weight of polyvinyl alcohol having a saponification degree of 50 mPa · s and 95.5 mol% or more. 2. The high nitrile copolymer latex according to claim 1, which has a viscosity of 2 to 100 parts by weight of a solid content thereof.
A gas barrier film comprising at least one surface coated with a high nitrile copolymer latex containing 50 mPa · s and 25 parts by weight or less of polyvinyl alcohol having a saponification degree of 95.5 mol% or more. 3. A laminated film comprising at least two or more film layers, comprising the gas barrier film according to claim 1.