JPH05331332A - Aqueous dispersion - Google Patents

Abstract

(57) [Summary] [Structure] Ion-modified EVO having ionic group at terminal
An aqueous dispersion containing H as a dispersion stabilizer and EVOH as a dispersoid, and a dispersion stabilizer used therefor. [Effect] A high solid content aqueous dispersion having excellent stability during storage or use can be obtained. In addition, the film obtained by coating, drying and heat treating this aqueous dispersion has excellent gas barrier properties.

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.

[0002]

2. Description of the Related Art Ethylene-vinyl ester copolymer, particularly ethylene-vinyl alcohol copolymer obtained by saponifying ethylene-vinyl acetate copolymer (abbreviated as EVOH).
Has excellent gas barrier properties against oxygen, etc., and has excellent oil / chemical resistance, and has thus attracted attention as a material for packaging materials and as a protective coating material for plastic moldings, metal surfaces, paper, wood, and the like.

In particular, films, sheets, laminates, hollow containers and the like for food packaging, which are required to prevent oxidation of contents or retain fragrance, are required to have a high gas barrier property. 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 that EVOH having excellent gas barrier property, aroma retaining property, and oil / chemical resistance is provided in the inner layer, 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 noted because it is possible to form a film having a relatively thin film thickness, and it is possible to easily form a film on a complicated shape such as a hollow container.

However, in the method of applying a solution of EVOH, it is basically difficult to use a solution having a high concentration due to its high viscosity, and the solvent is an organic solvent such as dimethyl sulfoxide or a mixed solvent of a large amount of alcohol and water. In the film formation process, there are problems such as economic disadvantages such as deterioration of the work environment due to volatilization of the organic solvent and a device for recovering the organic solvent. In contrast, EVOH
The method of applying the aqueous dispersion of is considered to be advantageous because it is considered to be advantageous in terms of the above-mentioned working environment and economical efficiency when the solvent is an aqueous system.

As an aqueous dispersion of EVOH, a conventional E
What was obtained by emulsifying and dispersing VOH in the presence of an ordinary surfactant or an ordinary polymer protective colloid, for example, polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol and the like is disclosed in JP-A-54-101844 and JP-A-56-. 61430 and the like. However, according to the studies by the present inventors, the aqueous dispersion of EVOH obtained by these known methods has insufficient dispersion stability and is difficult to practically use 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 itself is dispersed by using an ordinary surfactant as a dispersion stabilizer.

However, when the so-called random carboxyl anion-modified EVOH itself is dispersed, since the ionic groups are randomly contained in the entire EVOH, a large amount is copolymerized in order to achieve sufficient dispersion stability. It is necessary to do so, and there are drawbacks such that the crystallinity of EVOH is reduced, the disorder of the structure becomes large, and the barrier property of the formed film is lowered.

[0009]

The present invention was devised in order to solve the above-mentioned drawbacks of the prior art, and is excellent in the dispersion stability of EVOH, which is a dispersoid, and of a formed film. It is an object of the present invention to provide an EVOH-based aqueous dispersion having excellent barrier properties, particularly an EVOH-based aqueous emulsion dispersion.

[0010]

The above object is achieved by dispersing EVOH, which is a dispersoid, in water by using EVOH having an ionic group introduced at the terminal as a dispersion stabilizer.

The first feature of the present invention is that the EVOH-based aqueous dispersion is remarkably improved in stability during storage or use and is excellent in dispersion stability. The second feature of the present invention is that 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, so that a film-forming property is good and a thinner uniform film can be applied. The dried film has excellent barrier properties.

The dispersion stabilizer used in the present invention has an ionic group at the terminal and has an ethylene content of 10 to 70 mol%,
It includes a saponified product of an ethylene-vinyl ester copolymer having a saponification degree of 80 mol% or more (hereinafter abbreviated as ion-modified EVOH), and there is no limitation on its production method and the like.

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. From the viewpoint of the effect of stabilizing dispersion, an anionic group is preferred.

Examples of the anionic group include groups such as sulfonic acid, sulfonic acid salt, sulfuric acid ester, sulfuric acid ester salt, phosphoric acid, phosphoric acid salt, carboxylic acid and carboxylic acid salt, and these acids and salts are contained at the same time. It may be. A sulfonic acid, a carboxylic acid, or a salt thereof is preferable in terms of excellent dispersion stabilizing effect, and a sulfonic acid or a salt is particularly preferable.

Examples of the cationic group include groups such as amines and salts thereof, 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 composition of the EVOH component in the ion-modified EVOH must have an ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% (the saponification degree in the present invention indicates the saponification degree of vinyl ester units) or more. .. The preferable range of the ethylene content is 12 mol% or more, more preferably 15 mol% or more, and further 20 mol% or more. The upper limit is preferably 65 mol% or less, more preferably 60 mol% or less.
It is not more than mol%. The preferred degree of saponification is 90 mol%.
As described above, it is 95 mol% or more. EVO of dispersoids
The ethylene content and the degree of saponification of H will be described later, but those close to that are preferable in terms of the particle dispersion stabilizing effect. More preferably, almost the same ethylene content and degree of saponification are desired.

The intrinsic viscosity of the ion-modified EVOH is 0.1 deciliter / g or more (intrinsic viscosity measured at 30 ° C. in a water / phenol mixed solvent containing ammonium thiocyanate at 1 mol / liter (weight ratio 15/85)). Viscosity} is desirable. Preferably 0.15 deciliters /
g or more, and further 0.2 deciliter / g or more.

EVOH having an ionic group such as a sulfonic acid group or its salt, a carboxyl group or its salt, or an ammonium group at the terminal can be produced by various methods. For example, a sulfonic acid group or a salt thereof, a carboxyl group or a salt thereof, an alcohol having an ammonium group or the like, a compound containing an active group such as an aldehyde or a thiol is allowed to coexist as a chain transfer agent, and ethylene and a vinyl ester are copolymerized, Then, a method of saponifying the vinyl ester unit, or a method of introducing a compound having a sulfonic acid group or a salt thereof, a carboxyl group or a salt thereof, an ammonium group or the like into a terminal of a saponified product of ethylene and a vinyl ester by a chemical reaction. Etc. Among these methods, EVO which introduces an ionic group at the terminal economically and efficiently and exhibits excellent stability as an aqueous dispersion and the like.
As a method of obtaining H, a method of copolymerizing ethylene and a vinyl ester in the presence of a thiol having a sulfonic acid group or a salt thereof, a carboxyl group or a salt thereof, an ammonium group or the like, and then saponifying is preferable.

The copolymerization of ethylene and vinyl ester is
It is carried out by a known method, that is, a batch system, a semi-batch system, or a continuous system by solution polymerization, suspension polymerization, or emulsion polymerization in the presence of a polymerization initiator, but solution polymerization in the presence of alcohol. Is industrially preferable.
In the case of solution polymerization, the solvent concentration is 0 to 50%, preferably 3
-30%, and the polymerization rate is usually 20-80%, preferably 30-60%. The polymerization temperature is usually 20-100.
C., preferably 40 to 80.degree. As the polymerization initiator, 2,2′-azobisisobutyronitrile, 2,2 ′
-Azobis- (2,4-dimethylvaleronitrile),
Nitriles such as 2,2′-azobis- (4-methoxy-2,4-dimethylvaleronitrile), di-normal propyl peroxycarbonate, bis-4-tert-butylhexyl peroxydicarbonate, bis-2-
Known radical polymerization initiators such as carbonates such as ethylhexyl peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, peroxides such as acetylcyclohexane sulfonyl peroxide, and the like can be used. As the alcohol, lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol and butyl alcohol are used, but from the economical viewpoint, methyl alcohol is preferable.

Various thiols containing an ionic group such as a sulfonic acid group or a salt thereof, a carboxyl group or a salt thereof, and an ammonium group can be used.

Examples of the thiol having a sulfonic acid group or a salt thereof include those represented by the following general formula.

[0022]

[Chemical 1]

[0023]

[Chemical 2]

[0024]

[Chemical 3]

Examples of the thiol having a carboxyl group or a salt thereof include those represented by the following general formula.

[0026]

[Chemical 4]

[0027]

[Chemical 5]

As the thiol having an ammonium group,
The thing represented by the following general formula is mentioned.

[0029]

[Chemical 6]

[0030]

[Chemical 7]

[0031]

[Chemical 8]

[0032]

[Chemical 9]

The vinyl ester can be copolymerized with ethylene such as vinyl formate, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl trifluoroacetate and vinyl pivalate, and vinyl alcohol can be obtained by saponifying the copolymer. A monomer that can be converted into a vinyl acetate can be used, but vinyl acetate is particularly preferable.

The copolymer obtained by the polymerization is then subjected to a saponification reaction. It is advantageous to carry out the saponification reaction by a known method using an alkaline catalyst, that is, usually by alcoholysis using the copolymer as an alcohol solution. Especially Japanese Patent Nos. 575889 and 61155
The most preferable method is to use the tower reactor disclosed in No. 7 and remove methyl acetate produced as a by-product during the saponification reaction while blowing alcohol vapor into the bottom of the tower to remove it from the top of the tower. As the alkaline catalyst, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide and alcoholates such as sodium methylate and potassium methylate are used, and sodium hydroxide is particularly preferable from the economical viewpoint. The saponification reaction temperature is appropriately selected from the range of 60 to 175 ° C. In particular, when the tower reactor is used, it is preferably 100 ° C. or higher from the viewpoint of shortening the reaction time, etc., although it depends on the composition of the copolymer.

A known method is applied to the isolation of the ion-modified EVOH after the saponification reaction, and the method of depositing in strand form disclosed in Japanese Patent No. 725520 is particularly preferable. Ion-modified EVO isolated by precipitation
The H is washed with water by a known method, optionally subjected to a known heat stabilization treatment such as an acid treatment, and then dried.

EVOH, which is a dispersoid polymer, comprises ethylene and vinyl acetate, vinyl formate, vinyl propionate,
A vinyl ester such as vinyl benzoate, vinyl trifluoracetate, vinyl pivalate, etc., particularly an ethylene-vinyl alcohol copolymer obtained by copolymerizing with vinyl acetate and saponification, having an ethylene content of 15 to 65 mol%, The degree of saponification must be 90 mol% or more. If the ethylene content is less than 15 mol%, the stability of the aqueous dispersion will be poor, and if it exceeds 65 mol%, the gas barrier property will be poor, such being unsuitable. From the viewpoint of stability of the aqueous dispersion and gas barrier properties, the ethylene content is preferably 20 to 55 mol%. If the saponification degree is less than 90 mol%, the gas barrier property 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 gas barrier.
It has high properties, and is preferably 95 mol% or more, more preferably 97 mol% or more.

The degree of polymerization of EVOH as the dispersoid is selected according to the application, but an extremely low degree of EVOH is not preferred because the strength of the formed film is low and is not preferred. The higher the degree of polymerization, the more advantageous it is to apply and use as an aqueous dispersion, and usually up to about 5,000 can be used. Here, the degree of polymerization of the dispersoid is water /
30 ° C in phenol-based mixed solvent (weight ratio 15/85)
It is determined from the intrinsic viscosity measured in. If necessary, 5 mol% or less of a copolymerizable monomer other than ethylene and vinyl ester may be copolymerized.

The amount of ion-modified EVOH used as a dispersion stabilizer is appropriately selected in consideration of the type and content of ionic groups, but is 2 to 2 per 100 parts by weight of EVOH of the dispersoid.
00 parts by weight, preferably 3 to 100 parts by weight, more preferably 5 to 50 parts by weight. If the amount is too small, the dispersion stability will be poor, and if it is too large, the gas barrier properties of the formed film will be insufficient, which is unsuitable.

There is no limitation on the method of dispersing EVOH which is a dispersoid using the ion-modified EVOH as a dispersion stabilizer, and known methods can be used. For example, EVO which is dispersoid
The solution of H is brought into contact with water, which is a non-solvent of EVOH, in the coexistence of ion-modified EVOH which is a dispersion stabilizer, and E
An aqueous dispersion can be obtained by precipitating VOH particles as fine particles of 3 μm or less, preferably 2 μm or less, optimally 1 μm or less, and then removing the solvent. 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, intended use, etc., but the feature of the present invention is that a high concentration and stable dispersion can be obtained. The solid content concentration is 10% by weight or more, more preferably 15%.
It is at least 20% by weight, most preferably at least 20% by weight. The upper limit of the solid content concentration is not particularly limited, but 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. % 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. A particularly preferred solvent is a water-alcohol-based mixed solvent such as water-methyl alcohol, water-normal propyl alcohol, water-isopropyl alcohol and the like.

Ion-modified EVOH is a dispersoid EVO
It can be made to coexist in the H solution or in the non-solvent water, or both, but it is preferable to coexist in the EVOH solution.

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. A high degree of removal is desirable, but a small proportion of the organic solvent may be left in consideration of economy.

As another method, the EVOH of the dispersoid and the ion-modified EVOH of the dispersion stabilizer are 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 to obtain fine particles. A method of depositing and dispersing can also be adopted. Thereafter, the solvent is replaced with water to form an aqueous dispersion. As the solvent which dissolves at a high temperature and precipitates at a low temperature, alcohols alone among the above-mentioned solvents or a mixed solvent with water can be used.

As yet another method, ion-modified EVO
A method is also possible in which a solution of EVOH coexisting with H is brought into contact with a non-solvent or cooled to filter out particles that have been precipitated and dispersed, and the particles are dispersed in water in the coexistence of ion-modified EVOH.

A preferred method for producing an aqueous dispersion in the present invention is to disperse EVOH as a dispersoid and EVOH having an ionic group as a dispersion stabilizer in a common solvent thereof, for example, a mixed solvent of water-alcohol while stirring. , Melt at a temperature of 50 to 75 ° C. to form a solution, and then cool (temperature -10 to 30 ° C.),
VOH particles are precipitated and dispersed (emulsified), and then under reduced pressure (temperature 10 to 30 ° C., pressure 10 to 150 mmH).
A method of obtaining an aqueous dispersion having a desired solid content concentration by removing alcohol in g) and further removing a desired amount of water can be mentioned.

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
You may mix | blend 0.5 weight% (with respect to polymer). The composition is
It may be before or after atomizing the EVOH of the dispersoid.

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.

It is possible to add a usual surfactant or protective colloid to the aqueous dispersion of the present invention, if necessary, within a range not impairing 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 dispersion stabilizer of the present invention is most suitable as a dispersion stabilizer for EVOH described above, but other organic materials (resins)
It can also be used as a dispersion stabilizer for inorganic materials.

As described above, according to the present invention, an aqueous dispersion having a high solid content concentration having excellent stability during storage or use can be obtained, and since it is aqueous, there is no problem of 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 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) Various molded articles (films, sheets, cups, bottles, etc.), etc., and fiber aggregates (paper, non-woven fabric, woven cloth, fibrous casing, etc.), inorganic materials (cement, etc.) ), Metal, polyvinyl chloride wallpaper, photographic paper, etc.

The method of applying the aqueous dispersion of the present invention onto 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 / 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, most preferably 2 to 6 μm. is there.

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

[0054]

【Example】

Example 1 A thiolized product of sodium 2-acrylamido-2-methylpropanesulfonate was introduced at the end of the molecule, and contained 35 mol% of ethylene content, 99.6 mol% of saponification degree, and 1 mol / liter of ammonium thiocyanate. In water / phenol mixed solvent (weight ratio 15/85) at 30 ℃
50 parts of a mixed solvent solution of water / methyl alcohol = 50/50 containing 10% of ion-modified EVOH of 0.31 deciliter / g. Ethylene content 35 mol%, saponification degree 99.5 mol%, polymerization degree 1000
28 parts of ordinary EVOH, 100 parts of methyl alcohol and 100 parts of water were added and mixed, and heated and dissolved at 65 ° C.

When this solution was cooled to 5 ° C. with stirring, particles were precipitated and a stable dispersion liquid was obtained. The average particle size was 0.3 μm. This dispersion is then stirred 2
It was evaporated under reduced pressure at 0 ° C. to remove methyl alcohol. Even in the process of distilling off methyl alcohol, there is almost no aggregation of particles and it is stable. The average particle size is 0.3 μm and the solid content is 25%.
Aqueous emulsion dispersion of was obtained. It also has good storage stability, 4
In the 10-day storage test at 0 ° C, almost no aggregation was observed.

Then, this aqueous emulsion dispersion was applied to the primer-treated surface of a biaxially oriented polypropylene film (film thickness 20 μm) and dried and heat-treated at 110 ° C. for 5 minutes to obtain an oxygen barrier of the film (EVOH layer thickness 3 μm). -Gender 2
When measured at 0 ° C. and 0% RH, the oxygen transmission rate was
At 2.7 cc / m ² · day · atm, good barrier properties were exhibited as a food packaging material (hereinafter, the measurement conditions and units of oxygen permeation amount are the same).

Comparative Examples 1 to 5 In Example 1, when ion-modified EVOH was not used and dispersion was performed using only ordinary EVOH (Comparative Example 1), the ion-modified EVOH was replaced with a conventional nonionic surfactant. Nonylphenyl ether compound with ethylene oxide (Comparative Example 2), anionic surfactant sodium dodecylbenzenesulfonate (Comparative Example 3), or saponification degree of 80 mol% and polymerization degree of 600 as a polymer protective colloid.
Partially saponified polyvinyl alcohol (Comparative Example 4), 2-
Ion-modified polyvinyl alcohol with thiol derivative of sodium acrylamido-2-methylpropanesulfonate introduced at the terminal (saponification degree 80 mol%, polymerization degree 600)
(Comparative Example 5) was used as a dispersion stabilizer, and the dispersion was attempted under the same conditions as in Example 1 except that, in any case, the solution which was heated and dissolved was cooled under stirring to agglomerate at the stage where particles were precipitated. However, a stable dispersion was not obtained.

Thus, the ion-modified EVOH of the present invention
However, it has a remarkable effect on the dispersion stabilization of the ordinary EVOH, which is a dispersoid, and a stable aqueous emulsion dispersion can be obtained.

Example 2 A thiolized product of sodium 2-acrylamido-2-methylpropanesulfonate was introduced at the end of the molecule, ethylene content 22 mol%, saponification degree 99.1 mol%, intrinsic viscosity 0.23 deciliter / g of ion-modified EVOH2
1900 parts of water was added to 50 parts to prepare a dissolved solution. A high-speed stirrer was dipped in this solution and stirred at 5000 rpm while ethylene content was 25 mol% and saponification degree was 99.
5000 parts of a 10% concentration of a 7 mol% ordinary EVOH having a polymerization degree of 1100 dissolved in a mixed solvent of water / isopropyl alcohol = 30/70 was added dropwise to obtain a stable dispersion liquid. The average particle diameter was 0.8 μm.

Next, this dispersion was evaporated under reduced pressure at 20 ° C. with stirring to remove isopropyl alcohol, and an aqueous emulsion dispersion having a solid content concentration of 21% was obtained. The average particle size of this aqueous dispersion was 0.8 μm, and there was almost no particle enlargement during the vacuum evaporation process, and a stable aqueous dispersion was obtained. Example 1
A film (EVO coated, dried and heat treated in the same manner as
The amount of oxygen permeated through the H layer (thickness: 3 μm) was 3.6, indicating good barrier properties.

Example 3 Sodium 3-mercaptopropanoate was introduced at the end of the molecule, ethylene content 38 mol%, degree of saponification 99.5.
Water / ethyl alcohol = 4 containing 10% of ion-modified EVOH having a mol% and an intrinsic viscosity of 0.37 deciliter / g
50 parts of a 0/60 mixed solvent solution is a solution of a normal EVOH water / ethyl alcohol = 40/60 mixed solvent (concentration 10%) having an ethylene content of 40 mol%, a saponification degree of 99.5 mol% and a polymerization degree of 900. The mixture was mixed with 140 parts by heating at 75 ° C. with stirring.

Next, when this solution was cooled to 15 ° C. with stirring, particles were precipitated and a stable dispersion liquid was obtained. The average particle diameter was 0.6 μm. This dispersion was evaporated under reduced pressure at 25 ° C. with stirring to distill off ethyl alcohol to obtain an aqueous emulsion dispersion having an average particle diameter of 0.6 μm and a solid content concentration of 26%. A film (EVOH layer thickness 3 μm) coated, dried and heat-treated with this dispersion in the same manner as in Example 1 had an oxygen permeation amount of 2.5, indicating good barrier properties.

Example 4 A thiol compound of trimethyl- (3-methacrylamido) ammonium chloride was introduced at the end of the molecule, ethylene content 33 mol%, saponification degree 99.8 mol%, intrinsic viscosity 0.40 deciliter / g. Ion-modified EVOH42
Part of the dispersion stabilizer is a normal EVOH having an ethylene content of 32 mol%, a saponification degree of 99.8 mol% and a polymerization degree of 1200.
100 parts and 1000 parts of a mixed solvent of water / methyl alcohol = 50/50 were mixed and heated and mixed at 70 ° C.

Next, when this solution was cooled to 0 ° C. with stirring, particles were precipitated and a stable dispersion liquid was obtained. The average particle size was 0.5 μm. This dispersion is stirred for 3
By evaporating under reduced pressure at 0 ° C. and distilling off methyl alcohol, a stable aqueous emulsion dispersion was obtained. The average particle size is 0.
It was 5 μm and the solid content concentration was 23%. This dispersion was applied, dried and heat treated in the same manner as in Example 1 (E
The oxygen permeability of the VOH layer (thickness 3 μm) was 2.1, which showed good barrier properties.

Example 5 50 parts of the ion-modified EVOH described in Example 3 and 5 parts of sodium dodecylbenzenesulfonate were added to and mixed with 500 parts of a mixed solvent of water / methyl alcohol = 50/50 to prepare 70 parts.
Melted at ° C. Immerse a high speed stirrer in this solution and
Normal EVOH with ethylene content of 38 mol%, saponification degree of 99.7 mol% and polymerization degree of 1000 with stirring at 0 rpm.
When 5,000 parts of a 10% concentration solution of water was dissolved in a mixed solvent of water / methyl alcohol = 50/50, particles were precipitated to obtain a stable dispersion liquid. Average particle size is 0.9 μm
Met.

Next, this dispersion liquid was evaporated under reduced pressure at 20 ° C. with stirring to distill off methyl alcohol to obtain a solid content concentration of 20%.
Aqueous emulsion dispersion of was obtained. The average particle size of this aqueous dispersion was 0.9 μm, and there was almost no particle enlargement during the vacuum evaporation process, and a stable aqueous dispersion was obtained. A film (EVOH layer thickness 3 μm) coated, dried and heat-treated in the same manner as in Example 1 had an oxygen permeation amount of 3.8 and showed a good barrier property.

[0067]

As described above, when the ion-modified EVOH of the present invention is used as a dispersion stabilizer, it has excellent stability during storage or use, and has a high solid content in an aqueous dispersion, particularly an aqueous emulsion. Since the dispersion is obtained and it is aqueous, it has the advantage of not causing problems such as environmental pollution. By coating and drying, it is possible to form a thin film with excellent gas barrier properties, aroma retention and oil / chemical resistance. It has high industrial value and can be used as a coating agent.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ken Moriya, 1621 Sakazu, Kurashiki, Okayama Prefecture, Kuraray Co., Ltd.

Claims (1)

[Claims] 1. A dispersion stabilizer comprising a modified ethylene-vinyl ester copolymer saponified product having an ionic group at the end and having an ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% or more, and an ethylene content of 15 to 65 mol. % Ethylene-vinyl alcohol copolymer as the dispersoid.