JPH05302010A - Aqueous dispersion - Google Patents

Abstract

PURPOSE:To obtain an aqueous dispersion of a copolymer insoluble in water at ordinary temp. which dispersion has excellent storage stability by bonding an ionizable compound to an ethylene-vinyl alcohol copolymer to form a block or other copolymer and dispersing the resulting copolymer into water. CONSTITUTION:An ionizable compound (e.g. sodium acrylate) is block- copolymerized with or grafted onto an ethylene-vinyl alcohol copolymer (a) having an ethylene content of 15-65mol% in an amount of 0.1-5mol% based on the copolymer (a). The resulting block or graft copolymer (b) is dispersed into an aqueous medium (e.g. a water/alcohol mixture) to give a stable aqueous dispersion of the copolymer (b) which has fine particle diameters and a high solid content. Applying and drying the dispersion gives a film excellent in gas- barrier property, flavor preservation, etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aqueous dispersion of an ethylene-vinyl alcohol copolymer, and more particularly to an emulsion dispersion having a small particle size and excellent dispersion stability.

[0002]

2. Description of the Related Art Ethylene-vinyl ester copolymers,
In particular, an ethylene-vinyl alcohol-based copolymer obtained by saponifying an ethylene-vinyl acetate copolymer (abbreviated as EVOH) has excellent gas barrier properties against oxygen and the like, oil resistance, and chemical resistance. It has attracted attention as a protective coating material for plastic moldings, metal surfaces, paper, wood and the like.

A high gas barrier property is required particularly for food packaging films, sheets, laminates, hollow containers and the like, which are required to prevent the contents from being oxidized or to retain the scent. Further, for vinyl chloride wallpaper, vinyl chloride leather, sheets and the like made of soft vinyl chloride, a coating material for preventing bleeding of a plasticizer is required. Therefore, it is widely practiced to provide EVOH excellent in gas barrier property, aroma retaining property, and oil / chemical resistance in the outer layer or the intermediate layer to highly satisfy these required performances.

Generally, as a method of forming an EVOH layer, a method by melt extrusion or injection molding, a method of laminating an EVOH film, etc. are widely practiced.
On the other hand, a method of applying an EVOH solution or an aqueous dispersion and drying it has been proposed. This method is noteworthy because it can form a relatively thin film and can easily form a film on a complex shape such as a hollow container.

However, in the method of applying an EVOH solution, it is basically difficult to use a solution having a high concentration because of the viscosity, and the solvent is an organic solvent such as dimethyl sulfoxide or a mixed solvent with water containing a large amount of alcohol. Therefore, there are problems such as economical disadvantage such as deterioration of working environment due to volatilization of the organic solvent in the film formation process and a device for recovering the organic solvent is required. On the other hand, the method of applying the EVOH aqueous dispersion is expected to be considered to be advantageous from the viewpoint of the above-mentioned working environment and economy because the solvent is an aqueous system.

As an aqueous dispersion of EVOH, an ordinary EV is used.
JP-A No. 54-54, wherein OH is emulsified and dispersed in the presence of a usual surfactant or a usual polymer protective colloid such as polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose and polyvinyl alcohol.
No. 101844, JP-A-56-61430 and the like. However, according to the study by the present inventors, the aqueous dispersion of EVOH obtained by these known methods has insufficient dispersion stability and is difficult to be practically used for coating.

Further, in JP-A-54-101844, a carboxylic acid group-containing monomer such as acrylic acid or maleic anhydride is terpolymerized with ethylene and vinyl acetate and terpolymerized to obtain a so-called random copolymer. It has been shown that EVOH containing a carboxyl anion group is emulsified and dispersed by using an ordinary surfactant as an emulsion dispersion stabilizer.

However, in this so-called random carboxyl anionic EVOH, the ionic group component is randomly contained, so that unless the content is increased, the emulsion dispersion stability cannot be sufficiently achieved, and the EVOH structure is disturbed. Is large, the crystallinity is greatly reduced, and the barrier performance of the formed film is low.

[0009]

An object of the present invention is to provide an EVOH-based aqueous dispersion having excellent dispersion stability, particularly stability during storage or use, and particularly to an aqueous emulsion dispersion.

[0010]

The above-mentioned object is to provide a component containing 0.1 to 5 mol% of an ionic group with respect to EVOH, which is bound in a block or graft form and is insoluble in water at room temperature. This can be achieved by dispersion using a specific ionic EVOH-based block or graft copolymer, especially by emulsion dispersion.

[0011]

More detailed description of the invention The greatest feature of the present invention is EVO
The stability of the H-based aqueous dispersion during storage or use is remarkably improved and the dispersion stability is excellent. In addition to having a small particle size, the dispersion stability is excellent, and there is almost no significant increase in the particle size due to the aggregation of the particles during storage or use. Therefore, the small particle size is also a great feature. Due to this feature, the EVOH-based aqueous dispersion of the present invention has good film-forming properties, a thinner film can be applied, and a dried film has excellent barrier properties. Since the ionic group component is bonded to the EVOH component in block or graft form,
It is considered that the excellent crystallinity of the EVOH component is not significantly disturbed and the barrier property is excellent, which contributes to the high barrier performance.

EVOH used in the present invention is 0.1-0.1%.
The component (B) containing a specific amount of ionic groups of 5 mol% has a block or graft form and an ethylene content of 15
~ 65 mol% ethylene with a saponification degree of 90 mol% or more
An ethylene-vinyl alcohol block or graft copolymer (hereinafter referred to as ionic EVO) which is bound to the vinyl alcohol copolymer component (A) and is insoluble in water at room temperature.
Abbreviated as H), and there is no limitation on the manufacturing method and the like. The term "insoluble in water at room temperature" means that the content of insoluble matter when dissolved in water of 30% at a concentration of 1% for 1 day is 50% or more. The insoluble content is preferably high, and is preferably 80% or more, more preferably 90% or more.

The ionic group includes a group which dissociates in water and exhibits ionicity, that is, an anionic group, a cationic group and an amphoteric group. Examples of the anionic group include groups such as sulfonic acid, sulfonate, sulfuric acid ester, sulfuric acid ester salt, phosphoric acid, phosphoric acid salt, carboxylic acid, and carboxylic acid salt, and these acid groups and salts are also included. Is also good. Sulfonic acid or the base, or carboxylic acid or the base is preferable in terms of excellent dispersion stabilizing effect, and sulfonic acid or the base is particularly desirable.

Examples of the cationic group include groups such as amine salts, quaternary ammonium salts, phosphonium salts and sulfonium salts. Particularly, a quaternary ammonium salt is preferable because it has a large dispersion stabilizing effect. Examples of the amphoteric group include an aminocarboxylic acid salt (betaine type), an aminosulfonic acid salt (sulfobetaine type), an aminosulfate salt (sulfate betaine type) and the like.

The content of the component (B) containing an ionic group is in the range of 0.1 to 5 mol% with respect to the ethylene-vinyl alcohol copolymer component (A) unit and is insoluble in water at room temperature. There is a need. If it is less than 0.1 mol%, the dispersion stability is poor, and if it exceeds 5 mol%, the gas barrier performance of the formed film is extremely deteriorated, which is unsuitable. Preferably 0.
5 to 4 mol% is desirable. It is preferable that the content of the ionic group-containing unit in the component containing an ionic group is higher from the viewpoint of the dispersion stabilizing effect, but other units containing no ionic group within a range that does not significantly impair the dispersion stabilizing effect. May be included.

The composition of the EVOH component of the ionic EVOH has an ethylene content of 15 to 65 mol% and a saponification degree of 90 mol%.
(The degree of saponification referred to in the present invention indicates the degree of saponification of vinyl ester units).

If it is less than 15 mol%, the stability of the dispersion becomes poor, and if it exceeds 65 mol%, the gas barrier property of the polymer itself becomes unsatisfactory, which is unsuitable. From the viewpoint of stability of the dispersion liquid and barrier performance, the ethylene content is preferably 20 to 50 mol%.

If the saponification degree is less than 90 mol%, the gas barrier property of the polymer will be insufficient, so that it is necessary to use a polymer having a saponification degree of 90 mol% or more. The higher the degree of saponification, the higher the barrier performance, and it is preferably 95 mol% or more, more preferably 97 mol% or more.

The EVOH component is obtained by copolymerizing and saponifying ethylene with a vinyl ester such as vinyl acetate, vinyl formate, vinyl propionate, vinyl benzoate, vinyl trifluoroacetate and vinyl pivalate, especially vinyl acetate. Any vinyl alcohol copolymer can be used.

The structure of the ionic EVOH is not particularly limited as long as it is a so-called block or graft copolymer, and it is a diblock body, a triblock body or a multiblock body of more than that shown schematically, or EV.
Examples thereof include a graft body in which the ionic component (B) is grafted to the OH component (A), a graft body in which the EVOH component (A) is grafted to the ionic component (B), and the like. A star-shaped one can also be used.

(A) Ionic EVOH block

[0022]

[Chemical 1]

[0023]

[Chemical 2]

[0024]

[Chemical 3]

(B) Ionic EVOH grafted product A product obtained by grafting an ionic component to oEVOH.

[0026]

[Chemical 4]

EVOH grafted to an ionic component.

[0028]

[Chemical 5]

There are no restrictions on the method for producing ionic EVOH, but examples thereof include the following.

(I) Ionic EVOH block (i) Having an ionic group by radical copolymerization of ethylene and a vinyl ester, particularly vinyl acetate, in the presence of an ionic group-containing polymer having a thiol group at the terminal. A block copolymer of a polymer and an ethylene-vinyl ester copolymer is obtained, and then the vinyl ester unit is saponified to form a vinyl alcohol unit, whereby a block copolymer in which the polymer having an ionic group and EVOH are bonded via S A polymer can be obtained.

The ionic group-containing polymer having a thiol group at the terminal is obtained by polymerizing an ionic group-containing vinyl monomer in the presence of thiocarboxylic acid such as thioacetic acid to synthesize an ionic group-containing polymer having a thioester group at the terminal, Then, the terminal thioester group is decomposed and converted into a thiol group, whereby it can be synthesized. In addition, a condensation type polymer having a hydroxyl group at the terminal, which is obtained by condensing a component containing an ionic group, and a condensation type polymer having an ionic group containing a thiol at the terminal obtained by thiolating the hydroxyl group at the terminal with hydrogen sulfide, etc. Can also be used.

(Ii) Reversely, ethylene and vinyl ester are radically copolymerized in the presence of a thiocarboxylic acid such as thioacetic acid, and then saponified to obtain an ionic group in the presence of EVOH having a thiol group at the terminal. By radical polymerization of the vinyl monomer to be obtained, a block copolymer in which a polymer having an ionic group and EVOH are bonded via S can be obtained.

(Iii) Polyperoxide, for example, polyphthaloperoxide is used as a polymerization initiator to radically copolymerize ethylene-vinyl ester. Then, the resulting ethylene-vinyl ester copolymer containing a peroxide group in the molecule is brought into contact with an ionic vinyl monomer as a polymer initiator to carry out heating radical polymerization to block the ethylene-vinyl ester copolymer and the ionic polymer. A copolymer is obtained. An ionic EVOH block can be obtained by saponifying a vinyl ester unit of this copolymer and converting it into a vinyl alcohol unit by a conventional method.

(Iv) Organic disulfides such as tetraethylthiuram disulfide are used as an initiator or a chain transfer agent to polymerize an ionic vinyl monomer, and R ₂ NC is added to the terminal.
(S) S-group {R represents a hydrocarbon group having 1 to 20 carbon atoms (for example, an alkyl group). } Which has an ionic group is synthesized. Next, by using this polymer as a polymerization initiator to copolymerize ethylene and vinyl ester by light irradiation polymerization, an ionic polymer and ethylene-
A block copolymer with vinyl ester is obtained. An ionic EVOH block can be obtained by saponifying a vinyl ester unit of this block copolymer by a conventional method and converting it into a vinyl alcohol unit.

(B) Ionic EVOH graft product (a) Polymerizing a vinyl monomer having an ionic group onto EVOH by a conventional method, that is, a method by radiation or ultraviolet irradiation, a method in which a peroxide coexists. Thus, an ionic EVOH graft body obtained by grafting a polymer having an ionic group onto EVOH is obtained.

(B) A method of radical copolymerizing a macromonomer containing EVOH and a vinyl monomer having an ionic group, or a macromonomer containing an ethylene-vinyl ester copolymer and a radical monomer containing an ionic group. By a method of polymerizing and then saponifying to convert vinyl ether units into vinyl alcohol, an ionic EVOH graft product obtained by grafting an ionic polymer with EVOH is obtained.

Ionic EV can be obtained by various methods as described above.
Although OH can be produced, the production efficiency (block or graft efficiency) of block- or graft-type ionic EVOH is not 100% theoretically, and ionic polymers that are homopolymers of each and EVOH are by-produced.

It is preferable that the efficiency is high, but it is usually difficult to strictly separate and distinguish the by-produced homopolymer, and EVOH may be mixed, and the ionic polymer is too much. Unless it is not necessary to remove the homopolymer,
The thing containing the homopolymer can be used as it is.

Therefore, the ionic EVOH of the present invention includes the entire block or graft reaction product containing the ionic component by-produced at the time of its production and the homopolymer of EVOH. The content of the functional group component means the mol% of the apparent block or graft component including the homopolymer with respect to the EVOH unit.

However, it is preferable that the content of the homopolymer, particularly the homopolymer of the ionic component, is small, and the homopolymer may be removed as necessary. From this point of view, (i), (ii), and (b) can be mentioned as preferable production methods having high efficiency.

As the vinyl monomer forming the ionic component, a radical homopolymerizable or copolymerizable radical having an ionic functional group or an ionically convertible group can be used. An example is shown below.

O Monomers that form an anionic component Acrylamide sulfonate monomers such as sodium 2-acrylamido-2-methylpropane sulfonate, Styrene sulfonate monomers such as potassium styrene sulfonate, Sodium allyl sulfonate Examples thereof include allyl sulfonate monomer, vinyl sulfonate monomer such as sodium vinyl sulfonate, and these acid monomers. Also, these sulfonic acid esters can be used by converting the ester into a salt or an acid after polymerization.

As the carboxylic acid anion monomer, acrylic acid, methacrylic acid, maleic anhydride, itaconic acid,
Examples thereof include mono-, di-, and polycarboxylic acid-based vinyl monomers such as fumaric acid, and alkali metal salts and ammonium salts thereof. Further, these esters can also be used because the ester group can be converted to the acid or base after polymerization.

O Monomers forming a cationic component Amino group-containing (meth) acrylamide monomers such as aminopropyl acrylamide or methacrylamide, and amino group-containing (meth) acrylates such as aminoethyl acrylate or methacrylate or salts thereof are also polymerizable. Good and preferable. Particularly, the quaternary salt thereof is preferable because the coloring of the polymer is small. For example, acrylamidopropyltrimethylammonium chloride, methacroylethyltriethylammonium bromide, and the like.

These monomers can be used alone or in combination. It is also possible to copolymerize with another monomer that does not contain an ionic group.

The degree of polymerization of the EVOH of the present invention is selected according to the application, but an extremely low EVOH is not preferred because the strength of the formed film is low, and therefore an EVOH of usually 500 or more, preferably 700 or more is used. The higher the degree of polymerization is, the more advantageous it is to apply and use as an aqueous dispersion, and usually about 5000 can be used. If necessary, 5 mol% or less of a copolymerizable monomer other than ethylene and vinyl ester may be copolymerized.

There is no limitation on the method of dispersing the ionic EVOH, and known methods can be used. For example, a solution of ionic EVOH is contacted with water, which is a non-solvent for EVOH, with stirring to precipitate EVOH particles as fine particles of 3 μm or less, preferably 2 μm or less, optimally 1 μm or less, and then the solvent is removed. Thus, an aqueous dispersion can be obtained. Here, the diameter of the fine particles is the number average particle diameter.

The solid content concentration of the aqueous dispersion is appropriately determined depending on the production conditions and uses, but the feature of the present invention is that a stable dispersion having a high concentration can be obtained. The solid content concentration is preferably 10% by weight or more, more preferably 15% by weight or more, and most preferably 20% by weight or more.
The upper limit of the solid content concentration is not particularly limited, but if the concentration is too high, the stability of the aqueous dispersion may be slightly poor. Therefore, it is preferably 60% by weight or less, more preferably 50% by weight. % Or less, optimally 40% by weight or less.

Examples of the solvent include methyl alcohol,
Ethyl alcohol, propyl alcohol, butyl alcohol and other monohydric alcohols, ethylene glycol, propylene glycol and other dihydric alcohols, glycerin and other 3
Dihydric alcohol, phenol, phenols such as cresol, amines such as ethylenediamine and trimethylenediamine, dimethyl sulfoxide, dimethylacetamide,
N-methylpyrrolidone and the like, or hydrates thereof and the like can be used alone or in admixture of two or more. Particularly preferred solvents are alcohol-water mixed solvents such as water-methyl alcohol, water-normal propyl alcohol and water-isopropyl alcohol.

The organic solvent in the solvent can be removed by an appropriate method such as an evaporation method, an extraction method or a dialysis method. It is desirable that the degree of removal is high, but it is possible to leave a small proportion of the organic solvent in balance with economic efficiency.

As another method, the ionic EVOH is heated and dissolved in a solvent which dissolves at a high temperature but becomes insoluble at a low temperature, and then the solution is cooled in the presence of the ionic EVOH to precipitate and emulsify the fine particles. A method of dispersing can also be adopted. Thereafter, the solvent is replaced with water to obtain an aqueous dispersion.

As the solvent which dissolves at a high temperature and precipitates at a low temperature, the above-mentioned alcohols alone or a mixed solvent with water can be used.

As yet another method, ionic EVOH
It is also possible to bring the solution of (1) into contact with a non-solvent or to cool the solution to precipitate and emulsify and disperse the particles, and then disperse the particles in water.

A method in which ionic EVOH is stirred at high speed in water or dispersed and emulsified by a ball mill or the like can also be adopted.

A preferred method for producing an aqueous dispersion in the present invention is to disperse ionic EVOH in this common solvent, for example, a water-alcohol mixed solvent, while stirring at a temperature of 5
Dissolve at 0-75 ° C to give a solution, then cool (temperature -1
EVOH particles are precipitated and dispersed (emulsified), and then under reduced pressure (temperature 10 to 30 ° C. pressure 1
The method includes obtaining an aqueous dispersion having a desired solid content concentration by removing alcohol to 0 to 150 mmHg) and further removing a desired amount of water.

The aqueous dispersion of the present invention contains alkali metal compounds such as sodium hydroxide, sodium chloride, sodium acetate, sodium sulfate and sodium nitrate, calcium hydroxide, calcium chloride, calcium acetate and calcium sulfate for the purpose of decreasing the viscosity. , Alkaline earth metal compounds such as calcium nitrate, and other electrolytes from 0.01 to
0.5 wt% (based on the polymer) may be blended.
It may be before or after atomizing the EVOH of the dispersoid.

If necessary, it is possible to add a usual surfactant or protective colloid in addition to the ionic EVOH to the aqueous dispersion of the present invention within a range not hindering the achievement of the object of the present invention. It is also possible to add an aqueous dispersion of another resin, a stabilizer against light or heat, a pigment, a lubricant, a mildew-proofing agent, a film-forming aid or the like.

The aqueous dispersion obtained by the method of the present invention is useful as a coating material for forming a film having an excellent gas barrier property, but by utilizing its excellent mechanical performance and chemical performance, it can be used for other purposes. For example, it can be atomized and dried into fine powder,
It can also be used in a wide range of applications such as paints and binders for adhesives and vehicles.

As described above, according to the present invention, an aqueous dispersion having a high solid content and excellent in stability during storage or use can be obtained, and since it is aqueous, there is no problem of environmental pollution. It can be applied to the surface of various substrates as a useful coating agent which has an advantage and can form a thin film having excellent gas barrier property, aroma retaining property and oil / chemical resistance by coating and drying.
Here, as the base material, in particular, thermoplastic resin (polyolefin (polyethylene, polypropylene, etc.), polyester, polyamide, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polystyrene, polyvinyl alcohol, vinyl acetate resin (ethylene-vinyl acetate copolymer, etc. ) Etc.), various molded products (films, sheets, cups, bottles, etc.) are preferable, and fiber aggregates (paper, non-woven fabric, woven fabric, fibrous casing, etc.), inorganic substances (cement, etc.), Other examples include metal, polyvinyl chloride resin wallpaper, and photographic paper.

The method of applying the aqueous dispersion of the present invention to the surface of a substrate includes discharging from a casting head,
Any means such as roll coating, doctor roll coating, doctor knife coating, curtain flow coating, spraying, dipping, and brush coating is exemplified. Examples of the method of drying and heat treating the substrate thus coated include a dry heat treatment method such as an infrared irradiation method and a hot air drying method. These infrared irradiation and hot-air drying may be used alone or in combination. Also dry
The temperature of the heat treatment is preferably 30 to 180 ° C,
The lower limit is preferably 50 ° C or higher, and optimally 80
℃ or above. The drying / heat treatment time is preferably 5 seconds to 10 minutes, more preferably 1 to 5 minutes. During the drying and heat treatment, conditions such as increasing or decreasing the temperature, for example, treating at a low temperature at the beginning and gradually raising the temperature are free. By performing such drying and heat treatment, a film having an excellent gas barrier property is formed on the surface of the base material. The thickness of the film after coating, drying and heat treatment of the aqueous dispersion of the present invention is preferably 0.5 to 15 μm, more preferably 1 to 10 μm, and most preferably 2 to 6 μm.
m.

Next, synthesis examples of ionic EVOH graft and block are shown. Unless otherwise specified, parts indicate parts by weight.

1. Carboxyl anionic EVOH graft product Ethylene content of 33 mol% obtained by copolymerizing ethylene and vinyl acetate and further saponification, saponification degree of 99.6 mol%,
10 parts of EVOH having a degree of polymerization of 1000, 40 parts of water and 40 parts of methyl alcohol were placed in a reaction vessel equipped with a stirrer, a reflux condenser and a thermometer, replaced with nitrogen gas, and heated in a water bath at 80 ° C. to dissolve EVOH.

Then, 0.5 part of a nitrogen-substituted acrylic acid monomer and 0.1 part of ammonium persulfate as a polymerization initiator.
5 parts was added, and heat graft polymerization was carried out at 80 ° C. for 4.5 hours in a nitrogen atmosphere. As a result of analyzing the unreacted acrylic acid monomer by the double bond quantitative method by the bromine method, the polymerization rate of acrylic acid was 99%.

10% sodium hydroxide in water / methyl alcohol = 5 was added to the resulting acrylic acid-grafted EVOH solution.
Anionic property in which 2.8 parts of a 0/50 (weight ratio) mixed solvent solution (equal mol of sodium hydroxide to acrylic acid) was added and neutralized, and apparent sodium acrylate was grafted to EVOH at 2.6 mol% 11% of EVOH graft
A solution containing in concentration was obtained.

2. Sulfonic acid anionic EVOH graft product Ethylene content of 44 mol% obtained by copolymerizing ethylene and vinyl acetate and further saponification, saponification degree of 99.5 mol%,
10 parts of EVOH having a degree of polymerization of 900, 32 parts of water, and 48 parts of ethyl alcohol were placed in a reactor equipped with a stirrer, a reflux condenser and a thermometer, and after nitrogen substitution, they were heated and dissolved in a water bath at 70 ° C.

Next, 0.8 part of cerium ammonium nitrate was added with 0.5 part of nitrogen-substituted potassium styrenesulfonate as a polymerization initiator, and graft polymerization was carried out by heating at 70 ° C. for 6 hours in a nitrogen atmosphere. When the unreacted potassium styrenesulfonate monomer was analyzed by double bond quantification by the bromine method, the polymerization rate was 97%. That is, potassium styrenesulfonate is 0.8 mol% relative to the apparent EVOH.
A grafted anionic EVOH graft was obtained.

3. Carboxyl anionic EVOH graft product The amino group of aminoethanethiol was treated with di-tert. Butyl dicarbonate protected tert. Radical copolymerization of ethylene and vinyl acetate using butoxycarbonylaminoethanethiol as a chain transfer agent was performed by reacting the resulting copolymer with formic acid to convert to amino formate salt, and then obtained by reacting with methacrylic acid chloride, Ethylene content 5
0 mol%, a polymerization degree of 500 ethylene - macromonomers {average structure of methacrylamide type vinyl acetate copolymer type _{CH 2 = C (CH 3)} CONHCH 2 CH 2 S (-CH 2 CH 2
_{-) 250 (-CH 2 C (} OCOCH 3) H-) 250} 3000
Parts, methacrylic acid 86 parts and methyl alcohol 700
0 part and 0 parts were placed in a polymerization reactor, the temperature was raised to 65 ° C. after nitrogen substitution,
12 parts of azobisisobutyronitrile as a polymerization initiator was added and polymerization was carried out for 3.5 hours. After the completion of the polymerization, the unreacted monomer was analyzed by a gas chromatographic method to determine the polymerization rate.

10% sodium hydroxide was added to the solution after polymerization.
400 parts of methyl alcohol solution was added and heated at 60 ° C. for 1 hour. The precipitated polymer was thoroughly washed with methyl alcohol and then dried to obtain 3100 parts of a powder polymer. Nuclear magnetic resonance spectrum analysis of this polymer revealed that the content of sodium methacrylate component was 2 mol% based on EVOH.
The degree of saponification of EVOH was 98 mol%, and it was an anionic EVOH graft body of the type in which EVOH was grafted to a sodium methacrylate polymer.

4. Sulphonic acid anionic EVOH block thioacetic acid as chain transfer agent 2-acrylamido-2-
Ethylene and vinyl acetate using, as a chain transfer agent, a sodium 2-acrylamido-2-methylpropanesulfonate polymer having a degree of polymerization of 15 and having a thiol group at the terminal, which is obtained by radical polymerization of methylpropanesulfonic acid and treatment with sodium hydroxide. And ethylene content 25 mol%,
Copolymerization was performed so that the degree of polymerization was 1000.

Next, by saponification, the ethylene content is 25 mol%, the saponification degree is 99.3 mol%, and the polymerization degree is 100.
1.5 mol% 2-acrylamido-2 in 0 EVOH
-A sulfonate anionic EVOH block product was obtained in which sodium methylpropanesulfonate was block-copolymerized via S.

5. Sulfonic acid anionic EVOH block body 2-acrylamido-2-methylpropanesulfone is the same as 4 except that the polymerization degree of the 2-acrylamido-2-methylpropanesulfonic acid sodium polymer having a thiol group at the terminal of 4 is changed. An ionic EVOH block was synthesized in which the amount of sodium acid was 0.5, 1, and 3.5 mol% of block copolymerized with EVOH.

6. Carboxyl anionic EVOH block: A methyl acrylate polymer having a thioester group at the terminal is synthesized by polymerizing methyl acrylate in the presence of thioacetic acid, and then the terminal thioester group is decomposed with ammonia to give a thiol at the terminal. A methyl acrylate polymer having a group and a polymerization degree of 20 was synthesized.

In the presence of this polymer, ethylene and vinyl pivalate were added to an ethylene content of 3 in a tetrahydrofuran solvent.
A block copolymer of a methyl acrylate polymer and an ethylene-vinyl pivalate copolymer was synthesized by radical copolymerization at 5 mol% and a polymerization degree of 900. Next, by saponifying with potassium hydroxide as a catalyst, the ethylene content is 35 mol%, the saponification degree is 97 mol%,
An anionic EVOH block was synthesized by block-copolymerizing EVOH having a degree of polymerization of 900 with potassium acrylate-methyl acrylate copolymer having a degree of polymerization of 20 (potassium acrylate content 80 mol%) via S.

7. Cationic EVOH block body In the same manner as described in 5 above, a cationic vinyl monomer such as methacrylamidopropyltrimethylammonium chloride was used in place of sodium 2-acrylamido-2-methylpropanesulfonate, and radical polymerization was similarly performed to EVOH via S. A cationic EVOH block was synthesized by block-copolymerizing a cationic polymer.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. The parts in the examples are parts by weight unless otherwise specified.

Example 1 was synthesized according to Synthesis Example 1,
Ethylene content of 33 mol%, saponification degree of 99.6 mol%, polymerization degree of 1000 EVOH, sodium acrylate 2.6 mol% grafted, water-insoluble content is 90
A mixed solvent solution of water / methyl alcohol = 50/50 (weight ratio, the same applies below) containing 11% of anionic EVOH graft product was heated and dissolved at 65 ° C.

When this solution was cooled to room temperature with stirring, it was stably emulsified and dispersed to obtain a uniform emulsion dispersion. The average particle diameter was 0.8 μm. Next, this emulsion dispersion was evaporated under reduced pressure with stirring to distill off methyl alcohol.
Agglomeration of particles was hardly observed even in the process of distilling methyl alcohol, and it was stable, and an aqueous emulsion dispersion having an average particle diameter of 0.8 μm was obtained. Further, the storage stability was good, and almost no aggregation was observed in the storage test at 40 ° C. for 30 days.

On the other hand, for comparison, when emulsified and dispersed only with a normal EVOH, an ethylene oxide adduct of a nonyl phenyl ether of a normal nonionic surfactant, sodium dodecylbenzenesulfonate as an anionic surfactant, or polymer protection is used. As a colloid, a partially saponified polyvinyl alcohol having a saponification degree of 80 mol% and a polymerization degree of 600 was also used as an emulsion dispersion stabilizer (5% by weight based on EVOH), and an ordinary EVOH was tried under the same conditions as in Example 1, but In any case, the solution that was heated and dissolved was cooled with stirring and agglomerated and blocked at the stage where particles were precipitated, and a stable emulsion dispersion was not obtained.

As described above, it can be seen that the anionic group component grafted to EVOH of the present invention has a remarkable effect in stabilizing the emulsion dispersion of EVOH, and a stable aqueous emulsion dispersion can be obtained. Then, the aqueous emulsion dispersion is applied to the primer-treated surface of the biaxially stretched polypropylene film, and then 110
Oxygen gas barrier property of the obtained formed film was measured at 4 ° C / m ² · 24 hr ·
Atm (film thickness 5 μm, 20 ° C., 0% RH), it showed excellent performance as a food packaging material.

Example 2 Synthesized according to Synthesis Example 2,
0.8 mol% of potassium styrenesulfonate was grafted to EVOH having an ethylene content of 44 mol%, a saponification degree of 99.5 mol% and a polymerization degree of 900, and the insoluble content in water was 9%.
A 2% water / ethyl alcohol = 40/60 mixed solvent solution of anionic EVOH graft (concentration 11%) was heated to 70 ° C. with stirring.

Then, the solution was cooled to room temperature with stirring to obtain a stable emulsion dispersion having a particle size of 0.7 μm.
This emulsion dispersion was evaporated under reduced pressure at 25 ° C. to remove ethyl alcohol by distillation to obtain a stable aqueous emulsion dispersion having a solid content concentration of 24% and an average particle diameter of 0.7 μm.

Example 3 was synthesized according to Synthesis Example 3,
An ethylene-insoluble component of a type in which EVOH having an ethylene content of 50 mol%, a saponification degree of 98 mol% and a polymerization degree of 500 was grafted on a sodium methacrylate polymer having a molality of 2 mol% had a water-insoluble content of 9%.
To 150 parts of 3% anionic EVOH graft, 1 part of water is added.
00 parts and 250 parts of isopropyl alcohol were added and dissolved by heating. This solution is 5,000 rp with a high speed stirrer
When added dropwise to 500 parts of water kept at 20 ° C. with stirring at m, it was uniformly emulsified and a stable dispersion was obtained. The average particle diameter was 0.7 μm.

Next, this emulsified dispersion was evaporated under reduced pressure at 20 ° C. to remove isopropyl alcohol by evaporation to obtain a solid content of 2
A 2% aqueous emulsion dispersion was obtained. The average particle size of this aqueous emulsion dispersion was 0.7 μm, and there was almost no particle enlargement due to the vacuum evaporation treatment, and a stable aqueous emulsion dispersion was obtained.

Example 4 Synthesized according to Synthesis Example 4,
2-acrylamide-based on EVOH having an ethylene content of 25 mol%, a saponification degree of 99.3 mol% and a polymerization degree of 1000.
Water / methyl alcohol = 1.5 mol% sodium 2-methylpropanesulfonate block-copolymerized, anionic EVOH block with 96% insoluble matter in water =
A 50/50 mixed solvent solution (concentration 12%) was dissolved by heating at 70 ° C.

Then, when the mixture was cooled to room temperature with stirring, the particles were precipitated and emulsified and dispersed. The average particle diameter was 0.7 μm.
By evaporating this dispersion under reduced pressure, methyl alcohol was removed by evaporation to obtain a stable aqueous emulsion dispersion. The solid content concentration was 23% and the average particle diameter was 0.8 μm. Even when the aqueous emulsion dispersion was left at 40 ° C. for 30 days, neither sedimentation nor enlargement of particles was observed and the stability was good.

[Examples 5 to 7] 2-acrylamido-2-methylpropanesulfonic acid was synthesized according to Synthesis Example 5 with respect to EVOH having an ethylene content of 25 mol%, a saponification degree of 99.5 mol% and a polymerization degree of 1000. Sodium is 0.
The 5,1 and 3.5 mol% block copolymerized anionic EVOH block was emulsified and dispersed and methyl alcohol was distilled off in the same manner as in Example 4 to obtain a stable aqueous emulsified dispersion. The properties of the aqueous emulsion dispersion were good as shown in Table 1 below.

[0087]

[Table 1]

Example 8 Synthesized according to Synthesis Example 6,
The ethylene-vinyl pivalate copolymer saponified product has an ethylene content of 35 mol%, a saponification degree of 99 mol%, and a polymerization degree of 90.
EVOH of 0 and degree of polymerization of 20 potassium acrylate-methyl acrylate copolymer (potassium acrylate content 80
In mol%, the block content of potassium acrylate is EVO
Anionic EVOH block 50 in which the amount of insoluble matter in water is 96%, which is a block copolymerized with 1.8% by mole of H).
40 parts of a mixed solvent of water / methyl alcohol = 50/50
It was dissolved in 0 parts by heating at 70 ° C. Then, the mixture was cooled to room temperature with stirring to obtain an emulsion dispersion. The emulsified dispersion was evaporated under reduced pressure to remove methyl alcohol to obtain an aqueous emulsified dispersion having a solid content concentration of 21% and an average particle diameter of 0.8 μm.

Example 9 Synthesized according to Synthesis Example 7,
2 mol% of acrylamidopropyldimethylbenzylammonium chloride with respect to EVOH having an ethylene content of 25 mol%, a saponification degree of 99.5 mol% and a polymerization degree of 1000
The block copolymerized cationic EVOH block having a water-insoluble content of 94% was treated with water / methyl alcohol = 5.
It was heated and dissolved at 70 ° C. in a mixed solvent of 0/50 so that the solid content concentration became 10%.

Then, this solution was cooled to room temperature with stirring to obtain a stable emulsion dispersion. By evaporating this dispersion liquid under reduced pressure at room temperature to remove methyl alcohol,
A stable aqueous dispersion having a solid content concentration of 21% and an average particle diameter of 1.1 μm was obtained.

[Example 10] Insoluble in water, which was block-copolymerized with 2 mol% to EVOH, using methacryloyloxyethyltrimethylammonium chloride instead of acrylamidopropyldityltylbenzylammonium chloride of Example 9. 93% cationic E
By emulsifying and dispersing under the same conditions as in Example 9 except for using the VOH block, and distilling off methanol, a stable aqueous emulsion dispersion having a solid content concentration of 22% and an average particle diameter of 1.2 μm was obtained.

[0092]

As described above, by dispersing the anionic EVOH graft or block body of the present invention, particularly aqueous dispersion, a high solid content concentration having a small particle size and excellent stability during storage or use is obtained. It has the advantage of being free from problems such as environmental pollution because it is an aqueous dispersion, and is useful for forming a thin film showing high gas barrier properties, aroma retention and oil / chemical resistance by coating and drying. It has high industrial value and can be used as a coating agent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Sato 1 Kuraray Co., Ltd., 2045 Sakazu, Kurashiki City, Okayama Prefecture (72) Inventor Hiromitsu Hiroto 1621 Sakazu, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd.

Claims (1)

[Claims] 1. An ethylene-vinyl alcohol copolymer component having an ethylene content of 15 to 65 mol% and a component containing an ionic group of 0.1 to 5 mol% based on the copolymer component are block-shaped. Alternatively, an aqueous dispersion of a copolymer that is bound in a graft form and is insoluble in water at room temperature.