JP2000319478A - Production of high-nitrile content copolymer latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-nitrile content copolymer latex excellent in emulsion stability, film-forming capability and gas barrier properties by subjecting a monomer mixture comprising acrylonitrile and a vinyl monomer in a specified ratio to emulsion polymerization in the presence of a polyvinyl alcohol having specified viscosity and degree of saponification. SOLUTION: This copolymer latex is produced by subjecting 100 pts.wt. monomer mixture comprising 70-95 pts.wt. acrylonitrile and 30-5 pts.wt. at least one copolymerizable vinyl monomer to emulsion polymerization in the presence of 3-25 pts.wt. polyvinyl alcohol having a viscosity (at 20 deg.C with a Brookfield viscometer) of 2-50 mPa.s and a degree of saponification of 95.5 mol% or higher, a polymerization initiator, a surfactant, a reactive emulsifier (e.g. sulfoethyl methacrylate), etc. Examples of the copolymerizable vinyl monomer are (meth)acrylates, (meth)acrylamides, vinyl compounds, olefins, unsaturated carboxylic esters and vinylidene compounds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high nitrile copolymer latex coating agent having excellent film forming ability and gas barrier properties, and a method for stably producing the same.

[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 has excellent emulsion stability and excellent coating film forming ability and gas barrier property. An object of the present invention is to provide a production method for stably polymerizing a high nitrile copolymer latex coating agent having the same.

[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) 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 with a viscosity of 2 to 30% by weight. Emulsion polymerization in the presence of a polyvinyl alcohol having a saponification degree of 95.5 mol% or more at 50 mPa · s or less, and a method for producing a high nitrile copolymer latex, wherein (3) A method for producing a high nitrile copolymer latex according to (1), wherein (3) acrylonitrile 7 is present in an amount of 3 to 25 parts by weight based on 100 parts by weight of the body mixture.
A monomer mixture comprising 0 to 95% by weight and 5 to 30% by weight of at least one vinyl monomer copolymerizable therewith has a viscosity of 2 to 50 mPa · s and a saponification degree of 95.5 mol%. After emulsion polymerization in the presence of the above polyvinyl alcohol, the resulting high nitrile copolymer latex has a viscosity of 2 to 50 mPa · s per 100 parts by weight of its solid content.
s, a method for producing a high nitrile copolymer latex, comprising adding an amount of 25 parts by weight or less of polyvinyl alcohol having a degree of saponification of 95.5 mol% or more,

(4) 70-95% by weight of acrylonitrile
And one or more vinyl monomers 5 to 3 copolymerizable therewith
0% by weight and 100 parts by weight of the monomer mixture
A high nitrile copolymer latex obtained by emulsion polymerization in the presence of 3 to 25 parts by weight of a polyvinyl alcohol having a viscosity of 2 to 50 mPa · s and a degree of saponification of 95.5 mol% or more, (5) The latex described above has a viscosity of 2 to 50 mPa.
s, a high nitrile copolymer latex containing 25 parts by weight or less of polyvinyl alcohol having a saponification degree of 95.5 mol% or more, and (6) a latex as described in (4) or (5) above. High nitrile copolymer latex barrier coating agent.

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.

The polyvinyl alcohol used in the emulsion polymerization in the present invention has a viscosity at 20 ° C. and 4% of 2 to 50 mPa · s, preferably 2 to 10 mP, measured 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 flowability, fusion of latex particles and molecular diffusion after fusion are unlikely to occur. 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 that polyvinyl alcohol is further mixed with 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 properties described above, and is preferably 25 parts by weight or less, and more preferably 15 parts by weight or less, based on 100 parts by weight of the solid content of the latex. . 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,
Examples include polyvinyl chloride, 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 base film layer, and the film layer may be provided on the barrier layer. There is no particular limitation on the method of coating the high nitrile copolymer latex coating agent of the present invention, and known methods, for example, air knife coating, gravure coating,
Reverse gravure coat, bar coat, comma coat and the like can be mentioned.

Further, a laminated film including a barrier layer composed of the latex of the present invention may be prepared by coating an unstretched film by the above-mentioned coating method and stretching the film at the same time as the barrier layer. 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

[0017]

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 Coated Film A high-nitrile copolymer latex was dried on a stretched polyester film, a stretched nylon film, or a stretched polypropylene film that had been subjected to corona discharge treatment using a Mayer rod to give a coating weight of 2. It was applied so as to be 5 g / m ² and dried in a hot air circulating drier at 100 to 200 ° C. for 30 seconds. (C) Oxygen permeability The 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) is left at 20 ° C. and 55% relative humidity. After doing
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 procedure was the same as in Example 1 except that the monomer mixture was changed to 80 parts of acrylonitrile, 18 parts of butyl acrylate and 2 parts of methacrylic acid. Table 1 shows the results. (Example 4) PVA (manufactured by Kuraray: trade name PVA-103, 100 parts by weight of solid content of the latex of Example 1)
Completely saponified type, degree of saponification 98.4 mol%, viscosity 3.5 m
Pa · s (4%, 20 ° C.)) 10 parts (however, concentration 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 stretched nylon film was used as the base 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 Chemicals Co., Ltd., 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 was the same as in Example 8 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 was partially saponified, the degree of saponification was 88 mol%, and the viscosity was 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.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

According to the production method of the present invention, a high nitrile copolymer latex can be produced stably. Also,
The obtained high nitrile copolymer latex is stable, and can be dried at a lower temperature and shorter time than conventional high nitrile copolymer latex when applied in a latex state to a plastic film, a sheet, a metal plate, etc., and is excellent. It has a coating film forming ability and can form a film having a high barrier property. The high nitrile copolymer latex of the present invention can be used for barrier packaging materials, metal rust preventive paints, and the like.

Claims (6)

[Claims] 1. 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 with a viscosity of 2 to 50 mPa.multidot.
s. A process for producing a high nitrile copolymer latex, which comprises carrying out emulsion polymerization in the presence of polyvinyl alcohol having a degree of saponification of 95.5 mol% or more. 2. The method for producing a high nitrile copolymer latex according to claim 1, wherein the polyvinyl alcohol is present in an amount of 3 to 25 parts by weight based on 100 parts by weight of the monomer mixture. 3. 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, having a viscosity of 2 to 50 mPa.multidot.
s, after emulsion polymerization in the presence of polyvinyl alcohol having a degree of saponification of 95.5 mol% or more, the resulting high nitrile copolymer latex has a viscosity of 2 to 50 mPa · s per 100 parts by weight of its solid content. s, saponification degree is 95.
A method for producing a high nitrile copolymer latex, comprising adding 5 mol% or more of polyvinyl alcohol to 25 parts by weight or less. 4. 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, has a viscosity of 2 to 50 mPa.multidot. s, a high nitrile copolymer latex obtained by emulsion polymerization in the presence of 3 to 25 parts by weight of polyvinyl alcohol having a degree of saponification of 95.5 mol% or more. 5. A high nitrile copolymer latex according to claim 4, which has a viscosity of 2 to 100 parts by weight per solid content.
A high nitrile copolymer latex containing 50 mPa · s and a polyvinyl alcohol having a saponification degree of 95.5 mol% or more and 25 parts by weight or less. 6. A high nitrile copolymer latex barrier coating agent comprising the latex according to claim 4 or 5.