JP3257695B2 - Aqueous dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. 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 copolymer obtained by saponifying an ethylene-vinyl acetate copolymer (abbreviated as EVOH) is excellent in gas barrier properties such as oxygen, oil resistance, and chemical resistance. It is attracting attention as a protective coating material for plastic molded products, metal surfaces, paper, wood, and the like.

[0003] In particular, high gas barrier properties are required for films, sheets, laminates, hollow containers, and the like for food packaging, which require prevention of oxidation of contents or retention of aroma. Further, a coating material for preventing bleeding of a plasticizer is required for a PVC wallpaper, a PVC leather, a sheet and the like made of soft vinyl chloride. Accordingly, it is widely practiced to provide EVOH having excellent gas barrier properties, fragrance retention properties, and oil / chemical resistance in an outer layer or an intermediate layer to satisfy these required performances to a high degree.

In general, as a method of forming an EVOH layer, a method of melt extrusion or injection molding, a method of laminating an EVOH film, and the like are widely practiced.
On the other hand, a method has been proposed in which an EVOH solution or an aqueous dispersion is applied and dried. This method is attracting attention because a relatively thin film can be formed and a film having a complicated shape such as a hollow container can be easily formed.

However, in the method of applying an EVOH solution, it is basically difficult to use a solution having a high concentration because of viscosity, and the solvent is a mixed solvent with an organic solvent such as dimethyl sulfoxide or water containing a large amount of alcohol. Therefore, there is a problem that the working environment is deteriorated due to the volatilization of the organic solvent in the process of forming the film, and a device for recovering the organic solvent is required. On the other hand, the method of applying the EVOH aqueous dispersion liquid is a solvent based on water, and is considered to be advantageous from the viewpoint of the working environment and economy, and is expected.

[0006] As an aqueous dispersion of EVOH, a conventional EV is used.
OH is emulsified and dispersed in the presence of an ordinary surfactant or an ordinary polymer protective colloid such as polyethylene oxide, carboxymethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, etc.
101844 and JP-A-56-61430. However, according to the study of 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.

Japanese Patent Application Laid-Open No. 54-101844 discloses a so-called random copolymer obtained by terpolymerizing a carboxylic acid group-containing monomer such as acrylic acid or maleic anhydride with ethylene and vinyl acetate and saponifying it. It is disclosed that EVOH containing a carboxyl anion group is emulsified and dispersed using a usual surfactant as an emulsification dispersion stabilizer.

However, since the so-called random carboxyl anionic EVOH contains an ionic group component at random, the emulsification dispersion stability cannot be sufficiently achieved unless the content is increased, and the structure of the EVOH is disordered. And the crystallinity is greatly reduced, and the barrier properties of the formed film are low.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous dispersion of an EVOH-based aqueous dispersion, particularly an aqueous emulsified dispersion, which has remarkably improved stability during storage or use and has excellent dispersion stability.

[0010]

An object of the present invention is to provide a method in which a component containing an ionic group in an amount of 0.1 to 5 mol% with respect to EVOH is bound in a block or graft form and is insoluble in water at room temperature. It is achieved by dispersing using a specific ionic EVOH-based block or graft copolymer, and particularly by emulsifying and dispersing.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The most important 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. A small particle size is also a major feature because, in addition to having a small particle size from the beginning, the dispersion stability is excellent and there is almost no significant increase in the particle size due to the aggregation of particles during storage or use. Due to this feature, the EVOH-based aqueous dispersion of the present invention has a good film-forming property, a thinner film can be applied, and a dried film has excellent barrier properties. Because the ionic group component is bonded to the EVOH component in a block or graft form,
It is considered that the fact that the crystallinity of the EVOH component is not significantly disturbed and the barrier property is excellent contributes to high barrier performance.

The EVOH used in the present invention is 0.1 to 0.1.
The component (B) containing a specific amount of ionic group of 5 mol% is block-like or graft-like and has an ethylene content of 15%.
Ethylene having a saponification degree of 90 mol% or more.
Ethylene-vinyl alcohol-based block or graft copolymer (hereinafter referred to as ionic EVO) which is bound to the vinyl alcohol-based copolymer component (A) and is insoluble in water at ordinary temperature.
H), and there is no limitation on the production method and the like. The term "insoluble in water at normal temperature" refers to a substance having a concentration of 1% and an insoluble content of 50% or more when dissolved in water at 30 ° C for 1 day. The higher the insoluble content, the better, preferably 80% or more, more preferably 90% or more.

The ionic group includes a group that 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, sulfate, sulfate, phosphoric acid, phosphate, carboxylic acid, and carboxylate, 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 because the dispersion stabilizing effect is excellent, and sulfonic acid or the base is particularly preferable.

Examples of the cationic group include groups such as an amine salt, a quaternary ammonium salt, a phosphonium salt and a sulfonium salt. In particular, quaternary ammonium salts are preferred because of their high dispersion stabilizing effect. Examples of the amphoteric group include aminocarboxylates (betaine type), aminosulfonates (sulfobetaine type), and aminosulfate salts (sulfate betaine type).

The content of the component (B) containing an ionic group is in the range of 0.1 to 5 mol% based on the units of the ethylene-vinyl alcohol copolymer component (A), and is insoluble in water at ordinary 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 resulting film becomes extremely poor and is unsuitable. Preferably 0.
5 to 4 mol% is desirable. A higher content of the ionic group-containing unit in the component containing an ionic group is preferable from the viewpoint of the dispersion stabilizing effect, but other units not containing an ionic group within a range not significantly impairing 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 in the present invention indicates the degree of saponification of a vinyl ester unit).

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

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

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

There are no particular restrictions on the structure of the ionic EVOH as long as it is a so-called block or graft copolymer, and diblocks, triblocks or higher multiblocks, and EVs, which are schematically shown below.
Examples include a graft in which the ionic component (B) is grafted on the OH component (A), and a graft in which the EVOH component (A) is grafted on the ionic component (B). Star-shaped ones can also be used.

(A) Ionic EVOH block

[0022]

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[0023]

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[0024]

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(B) Ionized EVOH graft oEVOH grafted with an ionic component.

[0026]

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O An EVOH grafted to an ionic component.

[0028]

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The method for producing the ionic EVOH is not limited, but examples thereof include the following.

(A) Ionic EVOH block (i) Radical copolymerization of ethylene and a vinyl ester, especially vinyl acetate, in the presence of an ionic group-containing polymer having a thiol group at the terminal, thereby having an ionic group By obtaining a block copolymer of a polymer and an ethylene-vinyl ester copolymer, and then saponifying the vinyl ester unit into a vinyl alcohol unit, the block copolymer in which the polymer having an ionic group and EVOH are bonded via S is obtained. 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 a thiocarboxylic acid such as thioacetic acid to synthesize an ionic group-containing polymer having a thioester group at a terminal. Then, it can be synthesized by decomposing the terminal thioester group and converting it to a thiol group. In addition, a condensed polymer having an ionic group-containing component obtained by condensing an ionic group-containing component with a hydroxyl group-terminated polymer and obtaining the thiol-terminated thiol group with hydrogen sulfide. Can also be used.

(Ii) Conversely, radical copolymerization of ethylene and vinyl ester in the presence of a thiocarboxylic acid such as thioacetic acid, followed by saponification contains an ionic group in the presence of EVOH having a terminal thiol group. By subjecting a vinyl monomer to be subjected to radical polymerization, a block copolymer in which a polymer having an ionic group and EVOH are bonded via S can be obtained.

(Iii) Ethyl-vinyl ester is radically copolymerized using a polyperoxide such as polyphthalopoxide as a polymerization initiator. Then, the obtained 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 heat radical polymerization to thereby 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 into a vinyl alcohol unit by a conventional method.

(Iv) An ionic vinyl monomer is polymerized using an organic disulfide such as tetraethylthiuram disulfide as an initiator or a chain transfer agent, and R ₂ NC is added to the terminal.
The (S) S-group ｛R represents a hydrocarbon group having 1 to 20 carbon atoms (eg, an alkyl group). A vinyl polymer containing an ionic group having｝ is synthesized. Next, by copolymerizing ethylene and vinyl ester by light irradiation polymerization using this polymer as a polymerization initiator, the ionic polymer and ethylene-
A block copolymer with a vinyl ester is obtained. An ionic EVOH block can be obtained by saponifying a vinyl ester unit into a vinyl alcohol unit by a conventional method.

(B) Ionic EVOH grafted product (a) Polymerization of a vinyl monomer containing an ionic group into EVOH by a usual method, that is, a method by radiation or ultraviolet irradiation, a method of coexisting a peroxide, or the like. As a result, an ionic EVOH graft obtained by grafting a polymer having an ionic group to EVOH is obtained.

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

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

Although the efficiency is preferably higher, it is usually difficult to strictly separate by-product homopolymers in many cases, and EVOH may be present in a mixed state. Otherwise, it is not necessary to remove the homopolymer,
A product containing a homopolymer can be used as it is.

Accordingly, the ionic EVOH of the present invention includes the entire block or graft reaction product including the homopolymer of the ionic component and the EVOH by-produced during the production thereof. The content of the sexual group component means the mole% of the apparent block or graft component including the homopolymer relative to the EVOH unit.

However, it is preferable that the content of the homopolymer, especially the homopolymer of the ionic component, is small, and the content of the homopolymer may be removed as required. From the viewpoint, preferable production methods with high efficiency include (i), (ii) and (b).

As the vinyl monomer forming the ionic component, a monomer having an ionic functional group or a radical capable of being converted to ionic, which can be used alone or copolymerizable, can be used. An example is shown below.

O Monomer forming anionic component Acrylamide type sulfonate monomer such as sodium 2-acrylamido-2-methylpropanesulfonate, styrene type sulfonate monomer such as potassium styrene sulfonate, and sodium allylate sulfonate Allyl sulfonate monomers and vinyl sulfonate monomers such as sodium vinyl sulfonate, as well as acid monomers thereof and the like. Esters of these sulfonic acids can also be used by converting the ester into its salt or its acid after polymerization.

Examples of the carboxylate anion monomers include acrylic acid, methacrylic acid, maleic anhydride, itaconic acid,
Mono-, di-, and polycarboxylic acid-based vinyl monomers such as fumaric acid, and alkali metal salts and ammonium salts thereof. These esters can also be used since the ester group can be converted to the acid or base after polymerization.

O Monomers that form cationic components Amino group-containing (meth) acrylamide monomers such as aminopropyl acrylamide or methacrylamide, amino group-containing (meth) acrylates such as aminoethyl acrylate or methacrylate or salts thereof are also polymerizable. Good and preferred. Particularly, the quaternary salt is preferable because the coloring of the polymer is small. Examples include acrylamidopropyltrimethylammonium chloride and methacryloylethyltriethylammonium bromide.

These monomers can be used alone or in combination. Copolymerization with a monomer containing no other ionic group is also possible.

The degree of polymerization of the EVOH of the present invention is selected according to the application. However, an extremely low degree is usually 500 or more, preferably 700 or more, because the strength of the resulting film is low and is not preferable. The higher the degree of polymerization, the more advantageous it is to apply and use as an aqueous dispersion, and usually about 5,000 can be used. If necessary, a copolymerizable monomer other than ethylene and vinyl ester may be copolymerized in an amount of 5 mol% or less.

The method for dispersing the ionic EVOH is not limited, and a known method can be used. For example, contacting a solution of ionic EVOH with water, which is a non-solvent for the EVOH, under 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 removing the solvent. Thus, an aqueous dispersion can be obtained. Here, the diameter of the fine particles is a number average particle diameter.

The solid content concentration of the aqueous dispersion is appropriately determined depending on the production conditions and applications, and the feature of the present invention is that a high concentration and stable dispersion can be obtained. The solid concentration is preferably at least 10% by weight, more preferably at least 15% by weight, and most preferably at least 20% by weight.
The upper limit of the solid content concentration is not particularly limited. However, if the concentration is too high, the storage stability of the aqueous dispersion may be slightly poor. Therefore, it is usually preferably 60% by weight or less, more preferably 50% by weight. %, Optimally up to 40% by weight.

As the solvent, for example, methyl alcohol,
Monohydric alcohols such as ethyl alcohol, propyl alcohol and butyl alcohol, dihydric alcohols such as ethylene glycol and propylene glycol, and trihydric alcohols such as glycerin
Polyhydric alcohols, phenols, phenols such as cresol, ethylenediamine, amines such as trimethylenediamine, dimethylsulfoxide, dimethylacetamide,
N-methylpyrrolidone or the like, or a hydrate thereof may be used alone or in combination 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 be high, but it is possible to leave a small proportion of the organic solvent in view of economy.

Another method is to heat and dissolve ionic EVOH in a solvent that dissolves at a high temperature but becomes insoluble at a low temperature, and then cools the solution in the presence of the ionic EVOH to precipitate and emulsify fine particles. A method of dispersing can also be adopted. Thereafter, by replacing the solvent with water, an aqueous dispersion can be obtained.

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

As still another method, ionic EVOH
The solution obtained by contacting the solution with a non-solvent or cooling may be used to filter the particles dispersed and emulsified and dispersed, and then disperse the particles in water.

Also, 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 be adopted.

In the present invention, a suitable aqueous dispersion is prepared by adding a dispersoid, ionic EVOH, to a common solvent, for example, a mixed solvent of water and alcohol at a temperature of 5 ° C.
Dissolve at 0-75 ° C to form a solution, then cool (temperature -1
0-30 ° C.) to precipitate and disperse (emulsify) the EVOH particles, and then reduce the pressure (at a temperature of 10-30 ° C. and a pressure of 1).
A method of obtaining an aqueous dispersion having a desired solid content concentration by removing the alcohol to 0 to 150 mmHg) and removing a desired amount of water.

The aqueous dispersion of the present invention may contain an alkali metal compound such as sodium hydroxide, sodium chloride, sodium acetate, sodium sulfate, sodium nitrate, calcium hydroxide, calcium chloride, calcium acetate, calcium sulfate for the purpose of decreasing the viscosity. , An alkaline earth metal compound such as calcium nitrate, and other electrolytes from 0.01 to
0.5% by weight (based on polymer) may be blended.
It may be before or after dispersing the EVOH into fine particles.

It is possible to add an ordinary surfactant or a protective colloid to the aqueous dispersion of the present invention, if necessary, in addition to the ionic EVOH as long as the object of the present invention is not hindered. Further, an aqueous dispersion of another resin, a stabilizer against light or heat, a pigment, a lubricant, a fungicide, a film-forming aid, and the like can be added.

Although the aqueous dispersion obtained by the method of the present invention is useful as a coating material for forming a film having excellent gas barrier properties, it can be used for other applications by taking advantage of its excellent mechanical performance and chemical performance. For example, by fine powder drying by atomization,
It can also be used in a wide range 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 such as environmental pollution. It has an advantage and can be applied to various substrate surfaces as a useful coating agent capable of forming a thin film having excellent gas barrier properties, fragrance retention properties, and oil and chemical resistance by coating and drying.
Here, the base material is, in particular, a 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. (films, sheets, cups, bottles, etc.) are suitable, and fiber aggregates (paper, nonwoven fabric, woven fabric, fibrous casing, etc.), inorganic substances (cement, etc.), Metal, polyvinyl chloride resin wallpaper, photographic paper and the like are also included.

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 brushing are exemplified. Examples of the method of drying and heat treating the substrate coated in this way include a dry heat treatment method, for example, an infrared irradiation method, a hot air drying method, and the like. These infrared irradiation, hot air drying and the like 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 ° C.
° C or higher. The drying and heat treatment time is preferably from 5 seconds to 10 minutes, more preferably from 1 to 5 minutes. During the drying and heat treatment, conditions such as increasing and decreasing the temperature, for example, treating at a low temperature at first and gradually increasing the temperature are free. By performing such drying and heat treatment, a film having excellent gas barrier properties is formed on the substrate surface. Further, 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, examples of the synthesis of ionic EVOH grafts and blocks are shown. Parts indicate parts by weight unless otherwise specified.

1. Carboxyl anionic EVOH graft product Ethylene and vinyl acetate are copolymerized and further saponified, ethylene content 33 mol%, saponification degree 99.6 mol%,
10 parts of EVOH having a polymerization degree 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 then heated in a water bath at 80 ° C. to dissolve EVOH.

Then, 0.5 parts of acrylic acid monomer substituted with nitrogen and 0.1% of ammonium persulfate as a polymerization initiator were added.
Five parts were added, and the mixture was subjected to heat graft polymerization at 80 ° C. for 4.5 hours under a nitrogen atmosphere. The unreacted acrylic acid monomer was analyzed by a double bond determination method by a bromine method. As a result, the polymerization rate of acrylic acid was 99%.

The obtained acrylic acid-grafted EVOH solution was added to 10% sodium hydroxide water / methyl alcohol = 5.
2.8 parts of a 0/50 (weight ratio) mixed solvent solution (sodium hydroxide in an equimolar amount with respect to acrylic acid) was added for neutralization, and apparently anionic sodium acrylate was grafted to EVOH at 2.6 mol%. 11% EVOH graft
A solution containing a concentration was obtained.

2. Sulfonate anionic EVOH graft product Ethylene and vinyl acetate are copolymerized and further saponified, ethylene content 44 mol%, saponification degree 99.5 mol%,
10 parts of EVOH having a polymerization degree 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 purged with nitrogen, followed by heating and dissolving in a 70 ° C water bath.

Next, 0.5 part of potassium styrenesulfonate substituted with nitrogen was used as a polymerization initiator, and 0.8 part of cerium ammonium nitrate was added. The mixture was heated and graft-polymerized at 70 ° C. for 6 hours in a nitrogen atmosphere. When the unreacted potassium styrenesulfonate monomer was analyzed by double bond determination by the bromine method, the polymerization rate was 97%. That is, potassium styrene sulfonate is 0.8 mol% based on apparent EVOH.
A grafted anionic EVOH graft was obtained.

3. Carboxyl anionic EVOH grafted product The amino group of aminoethanethiol was added to di-tert. Tert. Protected with butyl dicarbonate. Radical copolymerization of ethylene and vinyl acetate using butoxycarbonylaminoethanethiol as a chain transfer agent, obtained by reacting formic acid with the obtained copolymer and converting it to amino formate, followed by reaction with methacrylic acid chloride, Ethylene content 5
Methacrylamide type macromonomer of ethylene-vinyl acetate copolymer having 0 mol% and a polymerization degree of 500 ｛Average structural formula CH ₂ C (CH ₃ ) CONHCH ₂ CH ₂ S (-CH ₂ CH ₂
−) ₂₅₀ (−CH ₂ C (OCOCH ₃ ) H−) ₂₅₀ ０００3000
Parts, methacrylic acid 86 parts and methyl alcohol 700
0 parts into a polymerization reactor and after replacing with nitrogen, the temperature is raised to 65 ° C.
12 parts of azobisisobutyronitrile as a polymerization initiator was added, and polymerization was carried out for 3.5 hours. The unreacted monomer after the completion of the polymerization was analyzed by a gas chromatography method, and the polymerization rate was determined. The polymerization rate of methacrylic acid was almost 100%.

10% of sodium hydroxide was added to the solution after polymerization.
400 parts of a 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 powdery polymer. When this polymer was analyzed by nuclear magnetic resonance spectroscopy, it was found that the content of sodium methacrylate was 2 mol% with respect to EVOH.
In this case, the degree of saponification of EVOH was 98 mol%, and it was an anionic EVOH graft of a type in which EVOH was grafted on a sodium methacrylate polymer.

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

Then, saponification was performed to obtain an ethylene content of 25 mol%, a degree of saponification of 99.3 mol%, and a degree of polymerization of 100.
1.5 mol% 2-acrylamide-2 in EVOH 0
-A sulfonate anionic EVOH block obtained by block copolymerization of sodium methylpropanesulfonate via S was obtained.

5. Sulfonate anionic EVOH block body 2-Acrylamido-2-methylpropanesulfone in the same manner as 4 except that the degree of polymerization of the sodium 2-acrylamido-2-methylpropanesulfonate 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, 3.5 mol% with respect to EVOH and block copolymerized.

6. Carboxyl anionic EVOH blocker 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 form a thiol at the terminal. A methyl acrylate polymer having a polymerization degree of 20 having a group was synthesized.

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

7. Cationic EVOH block The same radical polymerization is carried out using a cationic vinyl monomer, for example, methacrylamidopropyltrimethylammonium chloride instead of the sodium 2-acrylamido-2-methylpropanesulfonate of the above item 5, to form EVOH via S via S. A cationic EVOH block obtained by block copolymerization of a cationic polymer was synthesized.

Hereinafter, the present invention will be described more specifically with reference to Examples, but it should not be construed that the invention is limited thereto. Parts in Examples are parts by weight unless otherwise specified.

Example 1 Synthesized according to Synthesis Example 1,
To an EVOH having an ethylene content of 33 mol%, a degree of saponification of 99.6 mol%, and a polymerization degree of 1,000, 2.6 mol% of sodium acrylate was grafted.
% Of an anionic EVOH graft was dissolved in a mixed solvent of water / methyl alcohol = 50/50 (indicating a weight ratio, the same applies hereinafter) containing 65% at 65 ° C.

When this solution was cooled to room temperature with stirring, it was emulsified and dispersed stably to obtain a uniform emulsified dispersion. The average particle size was 0.8 μm. Next, this emulsified dispersion was evaporated under reduced pressure with stirring to distill off methyl alcohol.
Even in the process of distilling off methyl alcohol, particles were hardly aggregated, and an aqueous emulsified dispersion having an average particle diameter of 0.8 μm was obtained. The storage stability was also 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 nonylphenyl ether as a normal nonionic surfactant, sodium dodecylbenzenesulfonate as an anionic surfactant, or polymer protection Emulsification dispersion was attempted under the same conditions as in Example 1 by using a partially saponified polyvinyl alcohol having a saponification degree of 80 mol% and a polymerization degree of 600 as a colloid as an emulsification dispersion stabilizer (5% by weight based on EVOH). In each case, the solution that had been heated and dissolved was cooled under stirring, and aggregation blocking occurred at the stage where the particles precipitated, and a stable emulsified dispersion could not be obtained.

Thus, it can be seen that the anionic group component grafted to the EVOH of the present invention has a remarkable effect on the stabilization of the emulsified dispersion of the EVOH, and a stable aqueous emulsified dispersion can be obtained. Then, this aqueous emulsified dispersion is applied to a primer-treated surface of a biaxially oriented polypropylene film, and
After drying at ℃, the resulting formed film was measured for oxygen gas barrier properties. The oxygen permeation amount was 4 cc / m ² · 24 hr ·
Atm (film thickness 5 μm, 20 ° C., 0% RH) 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% solution of an anionic EVOH graft in a water / ethyl alcohol = 40/60 mixed solvent (concentration: 11%) was heated to 70 ° C. with stirring.

Next, the solution was cooled to room temperature with stirring to obtain a stable emulsified dispersion having a particle diameter of 0.7 μm.
The emulsified dispersion was evaporated at 25 ° C. under reduced pressure to remove ethyl alcohol, thereby obtaining a stable aqueous emulsified dispersion having a solid content of 24% and an average particle diameter of 0.7 μm.

Example 3 Synthesized according to Synthesis Example 3,
An EVOH having an ethylene content of 50 mol%, a saponification degree of 98 mol% and a polymerization degree of 500 was grafted to a 2 mol% sodium methacrylate polymer.
150 parts of a 3% anionic EVOH graft was added to water 1
Then, 00 parts and 250 parts of isopropyl alcohol were added and dissolved by heating. This solution was 5,000 rpm by a high-speed
When the mixture was added dropwise to 500 parts of water maintained at 20 ° C. while stirring at m, it was uniformly emulsified to obtain a stable dispersion. The average particle size was 0.7 μm.

Next, this emulsified dispersion was evaporated under reduced pressure at 20 ° C., and isopropyl alcohol was distilled off by evaporation to obtain a solid content of 2%.
A 2% aqueous emulsion was obtained. The average particle size of the aqueous emulsion dispersion was 0.7 μm, and the particles were hardly enlarged by the evaporation under reduced pressure, and a stable aqueous emulsion dispersion was obtained.

Example 4 Synthesized according to Synthesis Example 4,
With respect to EVOH having an ethylene content of 25 mol%, a degree of saponification of 99.3 mol%, and a degree of polymerization of 1,000, 2-acrylamide-
Water / methyl alcohol of an anionic EVOH block having a solubility of 96% in water in which 1.5 mol% of sodium 2-methylpropanesulfonate was block-copolymerized,
A 50/50 mixed solvent solution (concentration: 12%) was heated and dissolved at 70 ° C.

After cooling to room temperature with stirring, the particles were precipitated and emulsified and dispersed. The average particle size was 0.7 μm.
By evaporating the dispersion under reduced pressure, methyl alcohol was distilled off to obtain a stable aqueous emulsion dispersion. The solid concentration was 23% and the average particle size was 0.8 μm. This aqueous emulsified dispersion had good stability with almost no sedimentation and no enlargement of particles observed even when left at 40 ° C. for 30 days.

[Examples 5 to 7] With respect to EVOH having an ethylene content of 25 mol%, a degree of saponification of 99.5 mol%, and a degree of polymerization of 1,000, synthesized according to Synthesis Example 5, 2-acrylamido-2-methylpropanesulfonic acid was used. Sodium is 0.
The anionic EVOH block copolymer block-copolymerized with 5, 1, 3.5 mol% 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 emulsified dispersion were good as shown in Table 1 below.

[0087]

[Table 1]

Example 8: Synthesized according to Synthesis Example 6,
Ethylene content of 35 mol% of saponified ethylene-vinyl pivalate copolymer, degree of saponification of 99 mol%, degree of polymerization of 90
Potassium acrylate-methyl acrylate copolymer having a degree of polymerization of 20 in EVOH of 0 (potassium acrylate content: 80)
Mol%, the block content of potassium acrylate is EVO
(1.8 mol% based on H) block copolymerized anionic EVOH block 50 having an insoluble content in water of 96%.
Parts are water / methyl alcohol = 50/50 mixed solvent 40
0 parts were heated and dissolved at 70 ° C. Then, the emulsion was cooled to room temperature with stirring to obtain an emulsified dispersion. The emulsified dispersion was evaporated under reduced pressure to remove methyl alcohol, whereby an aqueous emulsified dispersion having a solid content of 21% and an average particle diameter of 0.8 μm was obtained.

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

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

Example 10 Using methacryloyloxyethyltrimethylammonium chloride in place of acrylamidopropyldiltylbenzylammonium chloride of Example 9, insoluble in water which was 2 mol% block copolymerized to EVOH. Cationic E with a content of 93%
Except for using the VOH block, emulsification and dispersion were performed under the same conditions as in Example 9, and methanol was distilled off to obtain a stable aqueous emulsified dispersion having a solid content of 22% and an average particle diameter of 1.2 μm.

[0092]

As described above, by dispersing the anionic EVOH graft or block according to the present invention, particularly by dispersing it in an aqueous solution, a high solid content having a small particle size and excellent stability during storage or use. Aqueous dispersion liquid is obtained, and since it is water-based, there is an advantage that there is no problem such as environmental pollution. It has high industrial value and can be used as a coating agent and the like.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Li, Hiroto 1621 Sazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd. Examiner Takahiro Harada (56) References JP-A-3-205428 (JP, A) JP-A-3 -250005 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 51/06 B32B 27/00 C08L 51/00 C08F 255/02 C08F 261/04

Claims (1)

(57) [Claims] 1. An ethylene-vinyl alcohol copolymer component having an ethylene content of 15 to 65 mol% and a saponification degree of 90 mol% or more, and an ionic group of 0.1 to 5 mol% based on the copolymer component. A laminate obtained by applying an aqueous dispersion of a copolymer insoluble in water at ordinary temperature to a substrate, wherein the components are combined in a block or graft form.