JP3273631B2 - Terminal ion-modified ethylene-vinyl alcohol copolymer and aqueous dispersion thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene-vinyl alcohol copolymer having an ionic group at its terminal and an aqueous dispersion thereof, and more particularly to an aqueous emulsion of an ethylene-vinyl alcohol copolymer having excellent dispersibility. It relates to a dispersion.

[0002]

2. Description of the Related Art Ethylene-vinyl ester copolymers,
In particular, an ethylene-vinyl alcohol-based copolymer (hereinafter abbreviated as EVOH) obtained by saponifying an ethylene-vinyl acetate-based copolymer is excellent in gas barrier properties of oxygen and the like, oil resistance, and chemical resistance, and is therefore used in packaging materials and the like. 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, for which it is important to prevent the contents from being oxidized or to maintain the flavor. In addition, for PVC wallpaper, PVC leather, sheets and the like made of soft vinyl chloride, a coating material for preventing bleeding of a plasticizer is required. Therefore, it has been widely practiced to meet these required properties to a high degree by providing EVOH having excellent gas barrier properties, fragrance retention properties and oil / chemical resistance in the inner layer, the outer layer or the intermediate layer.

In general, as a method for forming an EVOH layer, a method by 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 emulsion dispersion is applied and dried. This method attracts 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 an organic solvent such as dimethyl sulfoxide or a mixed solvent of a large amount of alcohol and water. In the formation process, there are problems such as deterioration of the working environment due to volatilization of the organic solvent and the necessity of an apparatus for collecting the organic solvent, which is economically disadvantageous. On the other hand, the method of applying the EVOH aqueous dispersion is considered to be advantageous from the viewpoint of the above working environment and economy because the solvent is water-based, and is expected.

[0006] The aqueous emulsified dispersion of EVOH is obtained by emulsifying and dispersing ordinary EVOH in the presence of an ordinary surfactant or an ordinary polymer colloid, for example, polyethylene oxide, carboxymethylcellulose, hydroxyethylcellulose, polyvinyl alcohol and the like. Have been proposed in JP-A-54-101844 and JP-A-56-61430. However, according to the study of the present inventors, the aqueous emulsion 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 that a vinyl monomer such as acrylic acid or acrylamide is terpolymerized with ethylene and vinyl acetate and saponified.
So-called random copolymerized random copolymer E
It has been shown that VOH itself is dispersed with a conventional surfactant as a dispersion stabilizer.

However, according to the study by the present inventors, no improvement in emulsion dispersion stability was observed for EVOH obtained by simple ternary random copolymerization, and no practical emulsion dispersion was obtained. When acrylic acid having an ionic group is copolymerized in the emulsion, the emulsification dispersion stability is improved by the ionic group, but since the ionic group is contained at random, if the content is not increased, the emulsification is not improved. Dispersion stability cannot be sufficiently attained, and if this is the case, the structure of the EVOH becomes so disordered that crystallinity is reduced and gas barrier performance is significantly reduced, which is not practical.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a novel EVOH having an ionic group at the terminal, and a remarkably improved stability during storage or use using the same, and excellent dispersion stability. An object of the present invention is to provide an EVOH-based aqueous dispersion having excellent film properties, particularly an aqueous emulsion dispersion.

[0010]

The above object can be attained by self-emulsifying and dispersing a specific ion-modified EVOH-based copolymer having an ionic group at an end as an EVOH and being insoluble in water at ordinary temperature. .

The most important feature of the present invention is that the EVOH-based aqueous emulsified dispersion is remarkably improved in storage or use stability and is excellent in dispersion stability. Originally small particle size can be obtained and excellent dispersion stability,
Since the particle size is not significantly increased due to aggregation of the particles during storage or use, the small particle size is also a major feature. Due to this feature, the EVOH-based aqueous emulsified dispersion of the present invention has good film-forming properties and can be applied to a thinner uniform film,
The dried film has excellent gas barrier properties. Since an ionic group is bonded to the terminal of the EVOH molecule, EVOH
It is considered that the structure of the components is hardly disturbed, and high gas barrier performance can be maintained.

The EVOH of the present invention has a sulfonic acid
Group or its salt, carboxylic acid group or its salt, ammonium
At least one or more selected from the group consisting of
Intrinsic viscosity measured at 30 ° C. in a water / phenol-based mixed solvent (15/85 by weight) containing the above ionic groups and containing 1 mol / l ammonium thiocyanate was used.
A saponified ethylene-vinyl alcohol copolymer having 45 deciliters / g or more, an ethylene content of 15 to 65 mol% and a saponification degree of 90 mol% or more, and insoluble in water at ordinary temperature (hereinafter referred to as terminal ion-modified EVOH) to include abbreviated). Certification of having an ionic group at the terminal is based on NM
It can be performed by R (nuclear magnetic resonance) analysis. 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 insoluble content in water is preferably higher, more preferably 80% or more, more preferably 90% or more.

In the present invention, the ionic group is a group that exhibits ionicity in water, and includes a sulfonic acid group or a salt thereof,
It is a carboxylic acid group or a salt thereof, or an ammonium group . The ionic group may be one type or a mixture of two or more types.

The composition of the terminal ion-modified EVOH must have an ethylene content of 15 to 65 mol% and a degree of saponification (the degree of saponification in the present invention indicates the degree of saponification of vinyl ester units) of at least 90 mol%. If the ethylene content is less than 15 mol%, the stability of the aqueous emulsion dispersion becomes poor, and
If the amount exceeds mol%, the gas barrier property of the polymer becomes poor and the polymer is unsuitable. From the viewpoint of the stability and gas barrier properties of the aqueous emulsion dispersion, a more preferable range of the ethylene content is 20.
~ 55 mol%. If the degree of saponification is less than 90 mol%, the gas barrier property becomes insufficient. Therefore, the saponification degree needs to be 90 mol% or more, more preferably 95 mol% or more, and further preferably 97 mol% or more.

Further, a monomer component copolymerizable with ethylene and vinyl ester in EVOH, for example, propylene,
Α-olefins such as isobutene; silicon-containing monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; acrylamides such as acrylamide and N-methoxymethylacrylamide; acrylonitrile; N-vinyl-2-pyrrolidone; May be contained in such a small amount that the object of the invention is not hindered.

The intrinsic viscosity is selected according to the application. However, an extremely low viscosity is 0.45 deciliter / g or more, preferably 0.6 mm or less, because the strength of the resulting film is low and not practical.
0 deciliter / g or more. The higher the intrinsic viscosity, the more advantageous it is to apply and use as an aqueous emulsified dispersion, and it can usually be used up to about 3 deciliter / g.

[0017] The sulfonic acid group or a salt thereof at the end of the end, Cal
Selected from the group consisting of boronic acid groups or salts thereof and ammonium groups
At least one or two or more ionic groups are introduced
As a method for obtaining EVOH having excellent stability and the like as an aqueous emulsion dispersion, a sulfonic acid group or a salt thereof, a carboxylic acid group or a salt thereof, and a thiol containing an ammonium group are coexistent as a chain transfer agent. Te, and copolymerizing ethylene and vinyl ester, then there is a method of saponification.

The copolymerization of ethylene and vinyl ester is as follows:
In a known method, that is, in a batch system, a semi-batch system, or a continuous system, the polymerization is performed by solution polymerization, suspension polymerization, or emulsion polymerization in the presence of a polymerization initiator, but is performed by solution polymerization in the presence of an alcohol. Is industrially preferred.
In the case of solution polymerization, the solvent concentration is 0 to 50%, preferably 3 to 50%.
30%, and the polymerization rate is usually 20-80%, preferably 3
0 to 60%. The polymerization temperature is usually 20 to 100.
° C, preferably 40-80 ° C. 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-n-propylpropyl-oxycarbonate, bis-4-tert-phenyl
Butylhexyl par-oxydicarbonate, bis-2-
Known radical polymerization initiators such as carbonates such as ethylhexyl peroxycarbonyl carbonate and peroxides such as benzoyl peroxide, lauroyl peroxide and acetylcyclohexanesulfonyl peroxide can be used. As the alcohol, lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol are used, and methyl alcohol is preferable from the viewpoint of economy.

When ethylene and vinyl ester are copolymerized in the presence of a thiol containing a sulfonic acid group or a salt thereof, a carboxylic acid group or a salt thereof, an ammonium group, etc., the amount and method of addition of the thiol to the polymerization system Is appropriately selected. The thiol acts as a chain transfer agent, and the amount of the thiol added to the polymerization system and the method of addition affect the degree of polymerization and the degree of polymerization distribution of the resulting polymer. It is determined as appropriate from the viewpoint of the strength of the film, etc., but in order to efficiently introduce ionic groups at the terminals and obtain excellent quality, thiol is added according to the reaction rate of the polymerization vinyl ester and ethylene. By doing so, it is preferable that the amount of thiol in the reaction system does not change much with respect to vinyl ester and ethylene.

Various thiols containing a sulfonic acid group or a salt thereof, a carboxylic acid group or a salt thereof, and an ammonium group are used.

The thiol having a sulfonic acid group or a salt thereof includes those represented by the following general formula. Here, n respectively 1~4, R ¹ ~R ⁸ are a methyl group or a hydrogen atom, M is a hydrogen atom or an alkali metal.

[0022]

Embedded image

[0023]

Embedded image

[0024]

Embedded image

The thiol having a carboxylic acid group or a salt thereof includes those represented by the following general formula. Here, n represents 0 to 4, R ^{9 to} R ¹¹ represent a hydrogen atom or a lower alkyl group (which may have a substituent), and M represents a hydrogen atom, an alkali metal or an ammonium group.

[0026]

Embedded image

[0027]

Embedded image

As a thiol having an ammonium group,
Examples include those represented by the following general formula. Where n is 0
And m are 1 to 10, R ¹² , R ¹³ , R ¹⁶ , R ¹⁷ and R ¹⁸ are a hydrogen atom or a methyl group, R ¹⁴ and R ¹⁵ are a lower alkyl group (which may contain a substituent), A represents a group connecting an amine or ammonium nitrogen atom to a nitrogen atom of an amide group in the formula or an oxygen atom in the formula.

[0029]

Embedded image

[0030]

Embedded image

[0031]

Embedded image

[0032]

Embedded image

The vinyl ester can be copolymerized with ethylene such as vinyl formate, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl trifluoroacetate, vinyl pivalate, and the like. One or more of the convertible monomers can be used, but vinyl acetate is particularly preferred from an economic standpoint.

The ethylene-vinyl ester copolymer having an ionic group at the terminal obtained by polymerization is then subjected to a saponification reaction. The saponification reaction is advantageously carried out by a known method using an alkaline catalyst, that is, the reaction is usually carried out by alcoholysis using a copolymer as an alcohol solution. In particular, Japanese Patent Nos. 575889 and 61155
The most preferred method is to use the column reactor disclosed in No. 7 and remove methyl acetate by-produced during the saponification reaction from the top of the column by blowing alcohol vapor from the bottom of the column. 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 in view of economy. The saponification reaction temperature is appropriately selected from the range of 60 to 175 ° C. In particular, when the above-mentioned tower reactor is used, the temperature is preferably 100 ° C. or higher from the viewpoint of shortening the reaction time and solubility of EVOH in alcohols, although it depends on the composition of the copolymer.

For isolating the terminal ion-modified EVOH after the saponification reaction, a known method is applied, and a method of precipitating in the form of a strand disclosed in Japanese Patent No. 725520 is particularly preferable. The terminal ion-modified EVOH which has been isolated by precipitation is washed with water by a known method, and if necessary, subjected to a known heat stabilization treatment such as an acid treatment, and then dried.

The thus obtained EVOH of the present invention
Has an ionic group attached to the end of the molecule,
Since the structure of the VOH component is hardly disturbed, there is a feature that a decrease in melting point is small and high barrier performance can be maintained. Further, it is easily dispersed in water and is suitable for producing an aqueous emulsified dispersion, a thin homogeneous film can be applied, and a dried film has excellent gas barrier properties.

The method of emulsifying and dispersing the terminal ion-modified EVOH is not limited, and a known method can be used. For example, a solution of a terminal ion-modified EVOH is brought into contact with water, which is a non-solvent for the EVOH, with stirring to make the EVOH particles 3 μm.
The aqueous emulsified dispersion can be obtained by precipitating as fine particles having a particle size of 2 μm or less, optimally 1 μm or less, and then removing the solvent. Here, the diameter of the fine particles is a number average particle diameter.

The solid content concentration of the aqueous emulsion dispersion is appropriately determined depending on the production conditions, the intended use, and the like, and it is a feature of the present invention that a highly concentrated and stable dispersion can be obtained.
The solid content concentration is 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. 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. A particularly preferred solvent system is an alcohol-water mixed solvent such as water-
Methyl alcohol, water-normal propyl alcohol,
Water-isopropyl alcohol.

The solvent-based organic 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.

As another method, a terminal ion-modified EVO is dissolved in a solvent system which dissolves at a high temperature but becomes insoluble at a low temperature.
After H is dissolved by heating, the solution may be cooled to precipitate and disperse the fine particles. Thereafter, by replacing the solvent with water, an aqueous emulsified dispersion can be obtained. As the solvent system which dissolves at a high temperature but becomes insoluble at a low temperature, any of the above-mentioned solvents alone or a mixed solvent with water can be used.

As still another method, terminal ion-modified E
A method is also possible in which a VOH solution is brought into contact with a non-solvent or cooled, and the particles precipitated and dispersed by filtration are separated by filtration, and the particles are dispersed in water.

In some cases, the terminal ion-modified EVOH can be directly dispersed in water. For example, it is also possible to emulsify and disperse by mixing ion-modified EVOH with water and stirring with a stirrer or a ball mill.
However, there is a problem that dispersion takes time.

In the present invention, a suitable aqueous dispersion is prepared by adding a terminal ion-modified EVOH to a solvent such as water-
The mixture was dissolved in a mixed solvent of alcohol at a temperature of 50 to 75 ° C under stirring to form a solution, and then cooled (temperature of -10 to 30 ° C).
EVOH particles are precipitated and dispersed (emulsified),
Next, under reduced pressure (temperature of 10 to 30 ° C., pressure of 10 to 150 mm
A method of obtaining an aqueous dispersion having a desired solid content concentration by removing the alcohol in Hg) and further removing a desired amount of water. Sodium hydroxide, sodium chloride, sodium acetate, sodium sulfate, alkali metal compounds such as sodium nitrate, calcium hydroxide, calcium chloride, calcium acetate, calcium sulfate, calcium nitrate for the purpose of reducing the viscosity of the aqueous dispersion of the present invention Alkaline earth metal compounds such as
You may mix | blend 01-0.5 weight% (with respect to a polymer). The compounding may be performed before or after the terminal ion-modified EVOH of the dispersoid is formed into fine particles.

The terminal ion-modified EVOH of the present invention is particularly suitable for producing an aqueous dispersion,
Like H, it is also used as a melt molding material,
It can be molded by various methods such as injection molding.

The aqueous emulsion dispersion of the present invention is useful as a coating material for forming a film having excellent gas barrier properties.
Utilizing its excellent mechanical performance and chemical performance, it can be used in a wide range of applications such as spray-drying to fine particle powder, and binders and vehicles for paints and adhesives.

The aqueous emulsified dispersion of the present invention may be optionally added with a usual surfactant or protective colloid as long as the object of the present invention is not hindered. In addition, an aqueous dispersion of another resin, a stabilizer against light or heat, a pigment,
Lubricants, fungicides, film-forming auxiliaries and the like can also be added.

As described above, according to the present invention, an aqueous dispersion having a solid concentration 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 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.
It is.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. “Parts” or “%” in the examples are expressed on a weight basis unless otherwise specified. The solvent composition is also shown by weight ratio.

[0051]

【Example】

Example 1 1340 parts of vinyl acetate, 84 parts of methyl alcohol, 3-
0.23 parts of sodium mercaptopropanoate was charged into a high-pressure polymerization tank, and the inside thereof was sufficiently purged with nitrogen, and then ethylene gas was charged. Internal temperature 60 ° C, ethylene pressure 41Kg / cm ²
After adjusting to G, 1.07 parts of a polymerization initiator 2,2'-azobisisobutyronitrile was added, and 38.4 parts of a methyl alcohol solution of sodium 3-mercaptopropanoate (concentration 2.0%) was further added. Per hour for 3.8 hours to carry out polymerization. The conversion of vinyl acetate is 39.
%Met.

After cooling, ethylene gas was separated and removed, and unreacted vinyl acetate was driven out of the system while adding methyl alcohol under reduced pressure to obtain a methyl alcohol solution of an ethylene-vinyl acetate copolymer.

Next, this methyl alcohol solution was fed to a tower type saponification reactor, and sodium hydroxide was further added to the reactor such that the molar ratio to vinyl acetate units in the copolymer was 0.03. Saponification reaction was carried out at a temperature in the tower of 120 ° C. while methyl alcohol vapor was blown in from the bottom of the tower to remove by-product methyl acetate from the top of the tower. Then, steam is blown into the obtained EVOH methyl alcohol solution to change the solvent composition of the solution to a water / methyl alcohol mixed system, and then discharged into a 10% aqueous solution of methyl alcohol at 5 ° C. in the form of a strand, and solidified and precipitated. Cut. Next, it was sufficiently washed with distilled water, dried with hot air at 60 ° C. for 5 hours, and further dried in vacuum at 100 ° C. for 12 hours.

This EVOH was dissolved in a mixed solvent consisting of d ₆ -DMSO (deuterated dimethyl sulfoxide) and CD ₃ OD (deuterated methyl alcohol), and ¹ H-NM
When R was measured, the spectrum of FIG. 1 was obtained. This shows that the terminal ion-modified EVOH having an ethylene content of 32 mol% having a sodium carboxylate at the terminal of the molecule and a saponification degree of 99.9 mol%. This EVOH is mixed with a water / phenol-based mixed solvent containing ammonium thiocyanate at a concentration of 1 mol / l (weight ratio 15/85).
Was dissolved at 30 ° C. and the intrinsic viscosity (hereinafter, the intrinsic viscosity measured under these conditions is simply referred to as the intrinsic viscosity) was measured.
It was 62 deciliters / g. 30% at 1% concentration
Water-insoluble matter when dissolved in water for 1 day (hereinafter, the water-insoluble matter measured under these conditions is simply referred to as water-insoluble matter) is 99%
Met. The melting point measured by a DSC at a rate of temperature rise of 10 ° C./min (hereinafter, the melting point measured under these conditions is simply referred to as melting point) was 182 ° C.

50 parts of the terminal ion-modified EVOH was added to water /
65 in 600 parts of a mixed solvent of methyl alcohol 30/70
It melted by heating at ° C. Then, when the mixture was cooled to room temperature with stirring, particles were precipitated and a stable dispersion was obtained. The average particle size was 0.9 μm. The dispersion is then stirred for 2 hours.
Evaporation at 0 ° C. under reduced pressure removed methyl alcohol. Almost no aggregation of particles was observed in the process of distilling off methyl alcohol, and an aqueous emulsified dispersion having an average particle diameter of 0.9 μm and a solid content of 24% was obtained. The storage stability was also good, and almost no aggregation was observed even after being left at 40 ° C. for 10 days.

On the other hand, for comparison, an intrinsic viscosity of 0.63 deciliter / g, an ethylene content of 32 mol%, and a saponification degree of 9
When dispersed using unmodified ordinary EVOH having a melting point of 9.5 mol%, a melting point of 183 ° C., and a water-insoluble content of 99%, ethylene oxide of nonyl phenol ether, a nonionic surfactant known as a dispersant in this ordinary EVOH, An adduct, sodium dodecylbenzenesulfonate as an anionic surfactant, or partially saponified polyvinyl alcohol having a saponification degree of 80 mol% and an intrinsic viscosity of 0.76 deciliter / g was used as a polymer protective colloid. Attempts were made to disperse the particles under the same conditions.
It has been blocked.

An intrinsic viscosity obtained by copolymerizing and saponifying ethylene, vinyl acetate and acrylic acid is 0.62 deciliter / g, an acrylic acid content is 0.5 mol%, an ethylene content is 32 mol%, and a saponification degree is 99.5. Mol%, melting point 174
The dispersion was attempted under the same conditions as in Example 1 except that a ternary random copolymer EVOH having a water-insoluble content of 98% and a water insoluble content of 98% were used. A good aqueous emulsion dispersion was not obtained.

As described above, the terminal ion-modified EVO of the present invention
It can be seen that when H is used, the ionic group bonded to the molecular terminal has a remarkable effect on the emulsification and dispersion stabilization, and a stable aqueous emulsion dispersion can be obtained. Then, this aqueous emulsified dispersion is applied to the primer-treated surface of a biaxially stretched polypropylene film (thickness: 20 μm) and dried at 70 ° C. for 5 minutes to form a clean film, and a continuous coating film can be formed. It turned out to be excellent. Further, the obtained formed film was subjected to 150
Film heat treated at 30 ° C. for 30 seconds (EVOH layer thickness 5
μm), the oxygen permeability was 3.4 cc / m ² · day · atm (20 ° C., 0% R
H) showed good performance as a food packaging material. (Less than,
The measurement conditions and units for the amount of oxygen permeation are the same. )

Example 2 2-acrylamido-2-methylpropanesulfonic acid 9
1 part, sodium hydroxide 16 parts, benzoyl peroxide 0.1 part
06 parts are dissolved in 290 parts of methyl alcohol at room temperature,
Oxygen in the system was replaced with nitrogen. Then the internal temperature is 15-20
After continuously adding thioacetic acid at a rate of 2 parts / minute for 80 minutes while maintaining the temperature at ℃, the internal temperature was brought to 65 ° C and refluxed for 4 hours. Next, thioacetic acid and methyl alcohol were distilled off under reduced pressure at an internal temperature of 40 ° C. After dissolving 100 parts of the obtained white powder in 300 parts of methyl alcohol, 4 parts of sodium hydroxide was added, and the mixture was heated at 40 ° C. for 3 hours under a nitrogen stream. Then, after adding 6 parts of acetic acid to this solution, methyl alcohol was distilled off under reduced pressure at an internal temperature of 35 ° C. to obtain a thiolated product of 2-acrylamido-2-methylpropanesulfonic acid. It was confirmed that the thiolation was performed quantitatively by a redox titration method.

1090 parts of vinyl acetate, 105 parts of methyl alcohol, and 0.25 part of a sodium salt obtained by neutralizing a thiolated product of 2-acrylamido-2-methylpropanesulfonic acid with sodium hydroxide were charged into a high-pressure polymerization tank. After the inside was sufficiently purged with nitrogen, ethylene gas was charged. After adjusting the internal temperature to 60 ° C. and the ethylene pressure to 30 kg / cm ² G, 1.53 parts of a polymerization initiator 2,2′-azobisisobutyronitrile was added, and the above 2-acrylamido-2-methylpropanesulfonic acid was further added. 13. A solution of sodium thiol in methyl alcohol (18% concentration)
Polymerization was carried out by continuously adding at a rate of 4 parts / hour for 3.4 hours. The polymerization rate of vinyl acetate was 40%.

In the same manner as in Example 1, unreacted ethylene and vinyl acetate were removed, saponified, coagulated and precipitated, cut, washed with distilled water, and further washed with a 0.5 g / liter aqueous acetic acid solution.
Then, it is dried and modified with terminal ions having an intrinsic viscosity of 0.87 deciliter / g having a sulfonic acid group at the terminal of the molecule, an ethylene content of 25 mol%, a saponification degree of 99.3 mol%, a melting point of 193 ° C. and a water-insoluble content of 97%. EVOH was obtained.

The terminal ion-modified EVOH (50 parts) was mixed with water /
7 in 500 parts of a mixed solvent of methyl alcohol = 40/60
The mixture was heated and dissolved at 0 ° C. When this solution was cooled to room temperature with stirring, particles were precipitated and a stable dispersion was obtained. The average particle size was 0.8 μm. The dispersion was then evaporated under reduced pressure at 25 ° C. with stirring to distill off the methyl alcohol. Almost no particle aggregation was observed during the methyl alcohol distillation process, and an aqueous emulsified dispersion having an average particle size of 0.8 μm and a solid content of 26% was obtained. This aqueous emulsion dispersion was prepared in Example 1.
The oxygen permeation amount of the film (EVOH layer thickness 5 μm) coated, dried and heat-treated in the same manner as described above was 2.6, and the gas barrier property was very good.

For comparison, an aqueous dispersion was obtained in the same manner as in Example 2 by using the same terminal ion-modified EVOH (water-insoluble content: 95%) as in Example 2 except that the saponification degree was 87.6 mol%. However, the aggregation of particles was conspicuous, and the oxygen permeation amount of the coated (dried and heat-treated) film (film thickness 4 μm) was 100 μm.
At 0 or more, the gas barrier properties were extremely poor.

In the same manner as in Example 2, an intrinsic viscosity having a sulfonic acid group at the terminal of the molecule was 0.35 dL / g, an ethylene content was 25 mol%, a saponification degree was 99.4 mol%, a melting point was 193 ° C., and water was A terminal ion-modified EVOH having an insoluble content of 97% was synthesized, an aqueous dispersion was prepared, and this was applied and dried. When this was applied and cracked, cracks occurred and a film having sufficient strength could not be formed.

Example 3 In the same manner as in Example 2, trimethyl- (3-methacrylamido) ammonium chloride was subjected to an addition reaction with thioacetic acid in the presence of benzoyl peroxide, followed by saponification with sodium hydroxide to obtain ammonium chloride. A thiol containing groups was obtained.

990 parts of vinyl acetate, methyl alcohol 1
20 parts and 0.17 part of a thiolated product of trimethyl- (3-methacrylamide) ammonium chloride were charged into a high-pressure polymerization tank, and the inside thereof was sufficiently purged with nitrogen, and then ethylene gas was charged. Internal temperature 60 ° C, ethylene pressure 61Kg / cm ² G
After adjusting to 2, the polymerization initiator 2,2'-azobis- (2,
Then, 6.2 parts of 4-dimethylvaleronitrile) were added, and further, the above-mentioned ammonium chloride group-containing thiol methyl alcohol solution (concentration: 5%) was continuously added at a rate of 39.4 parts / hour for 3.3 hours to carry out polymerization. Was done. The conversion of vinyl acetate was 38%.

In the same manner as in Example 1, unreacted ethylene and vinyl acetate were removed, saponified, coagulated and precipitated, cut, washed with distilled water, and dried to obtain an intrinsic viscosity of 0.54 deciliter having an ammonium chloride group at the terminal of the molecule. / G, ethylene content 48 mol%, degree of saponification 99.2 mol%, melting point 1
There was obtained a terminal ion-modified EVOH having a water-insoluble content of 98% at 57 ° C.

The terminal ion-modified EVOH (50 parts) was mixed with water /
Isopropyl alcohol = 20/80 mixed solvent 100
In 0 part, the mixture was heated and dissolved at 65 ° C., and then the solution was cooled to room temperature with stirring to obtain a stable dispersion having an average particle diameter of 0.8 μm. Then, this dispersion was evaporated under reduced pressure at 30 ° C. under stirring to distill off isopropyl alcohol, thereby obtaining a stable aqueous dispersion having an average particle diameter of 0.8 μm and a solid content of 22%. A film obtained by applying, drying and heat-treating this aqueous emulsion dispersion in the same manner as in Example 1 (EVOH thickness: 5 μm)
Had an oxygen permeation of 8.0 and good gas barrier properties.

For comparison, in the same manner as in Example 3, the terminal having an intrinsic viscosity of 0.75 deciliter / g, an ethylene content of 13 mol%, a saponification degree of 98.1 mol%, a melting point of 212 ° C. and a water insoluble content of 30% was used. Having ammonium chloride group
OH was synthesized, and 50 parts of this EVOH was added to 1000 parts of a mixed solvent of water / isopropyl alcohol = 90/10 at 60 ° C.
The solution was heated and melted, then cooled, and isopropyl alcohol was distilled off.However, because the water-insoluble matter was too small, it was difficult to precipitate as fine particles, and a water dispersion having poor stability and practical use was not obtained. Was.

Further, in the same manner as in Example 3, the intrinsic viscosity was set to 0.1.
46 deciliter / g, ethylene content 68 mol%, degree of saponification 99.0 mol%, melting point 123 ° C., water insoluble content 99%
Was synthesized by heating 50 parts of this EVOH in 1000 parts of a mixed solvent of water / isopropyl alcohol = 10/90 at 65 ° C., followed by cooling and distilling off isopropyl alcohol to obtain a solid content. An aqueous dispersion having a concentration of 24% was obtained. However, a film (EVOH thickness: 5 μm) obtained by applying, drying and heat-treating this aqueous emulsified dispersion in the same manner as in Example 1 had an oxygen permeation of 1000 or more, and the gas barrier properties were extremely poor.

Example 4 1000 parts of vinyl pivalate, 300 parts of methyl alcohol
Parts and sodium 3-mercaptopropanoate (0.11 part) were charged into a high-pressure polymerization tank, and the inside thereof was sufficiently purged with nitrogen, and then ethylene gas was charged. Inner temperature 60 ° C, ethylene pressure 24Kg
/ Cm ² G, 0.65 parts of a polymerization initiator 2,2′-azobisisobutyronitrile was added, and a solution of sodium 3-mercaptopropanoate in methyl alcohol (concentration: 2.0%) was further added to the solution. Polymerization was carried out by continuously adding at a rate of 0.0 parts / hour for 5.0 hours. The polymerization rate of vinyl pivalate was 51%.

After cooling, ethylene gas was separated and removed, and unreacted vinyl acetate was driven out of the system while adding normal propyl alcohol under reduced pressure to obtain a normal propyl alcohol solution of an ethylene-vinyl pivalate copolymer. .

Next, to this normal propyl alcohol solution was added potassium hydroxide in a methyl alcohol solution such that the molar ratio of potassium hydroxide to vinyl pivalate units in the copolymer was 3.2, and the mixture was added under a nitrogen atmosphere. 90 ° C
For 1.5 hours. Then, add 20
After cooling to ℃ to precipitate a saponified substance, and after centrifugal elimination, it was repeatedly washed with distilled water, dried at 70 ° C. for 3 hours with hot air, and further dried at 105 ° C. for 12 hours under vacuum.

The saponified ethylene-vinyl pivalate copolymer had an intrinsic viscosity of 0.81 deciliter / g having sodium carboxylate at the terminal of the molecule, an ethylene content of 32 mol%, and a saponification degree of 99.2 mol%. Melting point 183
It was a terminal ion-modified EVOH having a water-insoluble content of 98% at ℃.

The terminal ion-modified EVOH was dissolved in a mixed solvent of water and methyl alcohol under the same conditions as in Example 1,
After cooling, the methyl alcohol was distilled off to obtain an aqueous dispersion having an average particle diameter of 1.0 μm and a solid concentration of 23%.
The oxygen permeation amount of the film (EVOH layer thickness: 5 μm) coated, dried and heat-treated in the same manner as in Example 1 was 2.5, and the gas barrier property was very good.

Example 5 50 parts of the terminal ion-modified EVOH described in Example 4 was added to and mixed with 500 parts of a mixed solvent of water / ethyl alcohol = 30/70, and dissolved by heating at 70 ° C. The solution was then added to a solution containing 0.5% sodium dodecylbenzenesulfonate.
When the mixture was added dropwise to 100 parts of water at 5 ° C. under high-speed stirring at 5000 rpm, a stable dispersion having an average particle diameter of 0.8 μm was obtained. Subsequently, this dispersion was evaporated under reduced pressure at 15 ° C. with stirring to remove ethyl alcohol, and the average particle diameter was 0.8 μm.
m, a stable aqueous dispersion having a solid content of 20% was obtained. A film (EVOH thickness 5 μm) obtained by applying, drying and heat-treating this aqueous emulsion dispersion in the same manner as in Example 1 had an oxygen permeation amount of 2.5 and an extremely good gas barrier property.

[0077]

The aqueous emulsion dispersion which is self-emulsified and dispersed using the terminal ion-modified EVOH of the present invention is an aqueous dispersion having a high solid content and excellent in stability during storage or use. It has high industrial value and can be used as a useful coating agent capable of forming a thin film showing excellent gas barrier properties, fragrance retention properties, and oil and chemical resistance by coating and drying.

[Brief description of the drawings]

FIG. 1 shows an ethylene content having sodium carboxylate at the end of the molecule described in Example 1, an ethylene content of 32 mol%, and a degree of saponification of 99.
9 mol% of the terminally ion-modified EVOH was converted to d ₆ -DMSO
^{1 is} a ¹ H-NMR spectrum measured by dissolving in a mixed solvent consisting of (deuterated dimethyl sulfoxide) and CD ₃ OD (deuterated methyl alcohol).

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 23/26 C08L 23/26 (72) Inventor Li Li Hiroto 1621 Sakurazu, Kurashiki-shi, Okayama Pref. Document JP-A-61-81403 (JP, A) JP-A-61-81405 (JP, A) JP-A-63-301206 (JP, A) JP-A-63-46202 (JP, A) 187003 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 8/00-8/50

Claims (7)

(57) [Claims] 1. A sulfonic acid group or a salt thereof, a carboxylic acid
Group or a salt thereof, or a small group selected from the group of ammonium groups.
Thiol groups containing at least one or more ionic groups
Copolymerization of ethylene and vinyl ester in the presence of all
Was then obtained by saponification, sulfone terminated Sanmotoma
Or its salt, carboxylic acid group or its salt, ammonium
Water / phenolic mixed solvent containing at least one or more ionic groups selected from the group of groups and containing 1 mol / l ammonium thiocyanate (weight ratio 15/85) Intrinsic viscosity 0.45 deciliter / g or more measured at 30 ° C., ethylene content 15 to 65 mol%,
An ethylene-vinyl alcohol copolymer having a saponification degree of 90 mol% or more and an insoluble content of 50% or more when dissolved in water at 30 ° C. for 1 day at a concentration of 1%. 2. An aqueous dispersion of the ethylene-vinyl alcohol copolymer according to claim 1 . 3. A laminate obtained by applying the aqueous dispersion according to claim 2 to a substrate. 4. A method for producing an aqueous dispersion, comprising: bringing a solution of the ethylene-vinyl alcohol copolymer according to claim 1 into contact with water to precipitate fine particles, and then removing the solvent. 5. The ethylene-vinyl alcohol copolymer according to claim 1 is dissolved by heating in a solvent which dissolves at a high temperature but becomes insoluble at a low temperature, cools the solution, and then replaces the solvent with water. A method for producing an aqueous dispersion, comprising: 6. An aqueous dispersion characterized by dispersing particles precipitated by bringing the solution of the ethylene-vinyl alcohol copolymer according to claim 1 into contact with a non-solvent or cooling the solution. Manufacturing method. 7. A water-alcohol mixed solution of the ethylene-vinyl alcohol copolymer according to claim 1 is cooled,
A method for producing an aqueous dispersion, comprising precipitating, then removing alcohol and, if necessary, removing water.