JP3216908B2 - Aqueous dispersion of ethylene-vinyl alcohol copolymer - 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 aqueous emulsion having a small particle size and excellent dispersion stability.

[0002]

2. Description of the Related Art Ethylene-vinyl ester copolymers, in particular, ethylene-vinyl alcohol copolymers obtained by saponifying ethylene-vinyl acetate copolymers (abbreviated as EVOH)
Because of its excellent gas barrier properties against oxygen and the like and resistance to oils and chemicals, it has been attracting attention as a material for protective coatings for packaging materials, 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 emulsion 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 due to viscosity, and the solvent is a mixed solvent with an organic solvent such as dimethyl sulfoxide or water containing a large amount of alcohol. In addition, there is a problem that the working environment is deteriorated due to the volatilization of the organic solvent in the film forming process, and an apparatus for recovering the organic solvent is required. On the other hand, the method of applying the EVOH aqueous emulsified dispersion 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] 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 protective colloid, for example, polyethylene oxide, carboxymethylcellulose, hydroxyethylcellulose, polyvinyl alcohol and the like. It is known in JP-A-54-101844 and JP-A-56-61430. However, according to the study of the present inventors, the aqueous emulsion dispersion 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 gas barrier performance is greatly reduced, and the barrier properties of the formed film are reduced.

[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 specific ionic EVOH having EVOH as a dispersoid and having a component containing an ionic group bonded in a block or graft form.
This can be achieved by using a system block or a graft copolymer as a dispersion stabilizer.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The most important feature of the present invention is EVO.
The stability of the H-based 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 a product having a small particle size, the dispersion stability is excellent and the particle size does not significantly increase due to aggregation of the 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. The dispersion stabilizer used also has an ionic group component bonded to the EVOH component in a block or graft form, so that the crystallinity of the EVOH component is not significantly disturbed and the barrier property is excellent, contributing to the high barrier property. It is thought that there is.

In the dispersion stabilizer used in the present invention, the component (B) containing an ionic group has a block-like or graft-like ethylene content of 10 to 70 mol% and a saponification degree of 80.
Includes an ethylene-vinyl alcohol-based block or a graft copolymer (hereinafter abbreviated as ionic EVOH) bonded to a saponified ethylene-vinyl ester-based copolymer in an amount of at least mol%, and is limited to the production method and the like. There is no.

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, sulfonic acid salt, sulfate ester, sulfate ester salt, phosphoric acid, phosphate salt, carboxylic acid, and carboxylate salt, and even when these acids and bases are simultaneously contained. good. Sulfonic acid or carboxylic acid or its base is preferable in terms of excellent dispersion stabilizing effect, and sulfonic acid or its 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 appropriately selected within a range having a dispersion stabilizing effect. From the viewpoint of the dispersion stabilizing effect, a unit of the EVOH component (A) in the ionic EVOH is used. Is preferably 0.05 to 50 mol%.
More preferably, 0.1 to 30 mol%, especially 0.2 to 1 mol%.
5 mol%, more preferably 0.2 to 10 mol% is desirable.
If it is less than 0.1 mol%, the effect of stabilizing the dispersion is small, and if it exceeds 50 mol%, the water resistance of the film from the dispersion becomes poor, which is not preferable. 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 (A) of the ionic EVOH has an ethylene content of 10 to 70 mol% and a degree of saponification of 80.
It must be at least mol% (the degree of saponification in the present invention indicates the degree of saponification of the vinyl ester unit). A preferred range of the ethylene content is at least 12 mol%, more preferably 15 mol%.
Mol% or more, and more preferably 20 mol% or more. The upper limit is preferably not more than 65 mol%, more preferably 6 mol%.
0 mol% or less. This is because EVOH, which is a main polymer for dispersing particles, having a content close to the ethylene content and the degree of saponification is desirable from the viewpoint of the particle dispersion stabilizing effect. More preferably, substantially the same ethylene content and degree of saponification are desired. The degree of polymerization is not particularly limited, but is preferably 20 or more from the viewpoint of the dispersion stabilizing effect.

The structure of the ionic EVOH is not particularly limited as long as it is a so-called block or graft copolymer, and the diblock, triblock or higher multiblock, schematically shown below, or the EV, is 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). Moreover, what is called a star shape may be used.

(A) Ionic EVOH block

[0019]

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[0020]

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[0021]

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(B) Ionic EVOH Graft The oEVOH component (A) is grafted with the ionic component (B).

[0023]

Embedded image o An ionic component (B) grafted with an EVOH component (A).

[0024]

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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) Ethylene-vinyl ester, especially vinyl acetate, is subjected to radical copolymerization in the presence of an ionic group-containing polymer having a thiol group at the terminal to form 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 the 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) Radical copolymerization of ethylene-vinyl ester 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, particularly tetraethylthiuram disulfide as an initiator or a chain transfer agent, and R ₂ NC (S) is added to the terminal.
The 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, ethylene and vinyl ester are copolymerized by light irradiation polymerization using this polymer as a polymerization initiator to obtain a block copolymer of an ionic polymer and ethylene-vinyl ester. This block copolymer is saponified by a conventional method to convert the vinyl ester unit to a vinyl alcohol unit, thereby obtaining an ionic E
A VOH block can be obtained.

(B) Ionic EVOH graft (a) Polymerization of a vinyl monomer having an ionic group into EVOH by a usual method, that is, a method by irradiation with radiation or ultraviolet rays, 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. Ionic EVOH obtained by grafting EVOH to an ionic polymer by a method of polymerizing and then saponifying to convert vinyl ester units to vinyl alcohol.
A graft 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.

The efficiency is preferably higher, but it is usually difficult to strictly separate the by-produced homopolymer, and EVOH can be used as the main polymer, and the ionic polymer is too large. If not, it is not always necessary to remove the homopolymer, and the product containing the homopolymer can be used as it is as a dispersion stabilizer.

Therefore, the ionic EVOH of the present invention includes the entire block or graft reaction product including the homopolymer of the ionic component and EVOH which are 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, preferred 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 into an ionic group can be used alone or copolymerizable. 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 styrenesulfonate, sodium salt allyl sulfonate Allylic sulfonate monomers, vinyl sulfonate monomers such as sodium vinyl sulfonate,
Furthermore, these acid monomers etc. are mentioned. Esters of these sulfonic acids can also be used by converting the ester into its salt or its acid after polymerization.

The carboxylic acid 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 after the polymerization since the ester group can be converted into a base.

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. For example, acrylamidopropyltrimethylammonium chloride and diethyl methacryloylethyltriethylammonium bromide.

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

EVOH, the main polymer, copolymerizes ethylene with vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl benzoate, vinyl trifluoracetate and vinyl pivalate, especially vinyl acetate, and then saponifies. It is necessary that the ethylene-vinyl alcohol copolymer obtained by this process has an ethylene content of 15 to 65 mol% and a degree of saponification of vinyl ester units of 90 mol% or more. If the amount is less than 15 mol%, the stability of the aqueous dispersion will be poor, and if it exceeds 65 mol%, the gas barrier performance of the polymer will be unsatisfactory.

The ethylene content is preferably from 20 to 50 mol% from the viewpoint of the stability of the aqueous dispersion and the gas barrier performance.
If the degree of saponification is less than 90 mol%, the gas barrier properties of the polymer become 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, and more preferably 97 mol%.
The above is preferred.

The degree of polymerization of the dispersoid EVOH is selected according to the application, but an extremely low one 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 it is usually possible to use up to about 5,000. If necessary, a copolymerizable monomer other than ethylene and vinyl ester may be copolymerized in an amount of 5 mol% or less.

The amount of the ionic EVOH to be used is appropriately selected in consideration of the type and amount of the ionic component and the efficiency of grafting or blocking, etc., but is preferably 1 to 200 parts by weight, preferably 100 to 100 parts by weight of the dispersoid EVOH. 3-100, more preferably 5-50 parts by weight. If the amount is too small, the emulsification / dispersion stability becomes poor. If the amount is too large, the gas barrier property of the formed film when wet becomes poor, which is inappropriate.

The method for dispersing EVOH as a dispersoid using ionic EVOH as a dispersion stabilizer, in particular, emulsifying and dispersing, is not limited, and known methods can be used.

For example, a solution of EVOH, which is a dispersoid, is brought into contact with water, which is a non-solvent of EVOH, in the presence of ionic EVOH, which is a dispersion stabilizer, with stirring to reduce EVOH particles to 3 μm.
An aqueous dispersion can be obtained by precipitating as fine particles of m or less, preferably 2 μm or less, optimally 1 μm or less, and then removing the solvent.

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 ionic EVOH is a dispersoid, EVOH
, Or non-solvent water, or both, but it is preferable to coexist in an 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. 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 dissolve EVOH, which is a dispersoid, 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 ionic EVOH to remove fine particles. A method of precipitation emulsification and dispersion 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, any of the above-mentioned solvents alone or a mixed solvent with water can be used.

As still another method, ionic EVOH
Alternatively, a method of contacting or cooling the solution of EVOH in which the compound is coexisted with a non-solvent, filtering out the particles emulsified and dispersed by filtration, and dispersing the particles in water in the coexistence of the ionic EVOH is also possible.

In the present invention, a suitable method for preparing an aqueous dispersion includes EVOH as a dispersoid and ionic EV as a dispersion stabilizer.
OH is dissolved in a common solvent such as a mixed solvent of water and alcohol at a temperature of 50 to 75 ° C. with stirring to form a solution, and then cooled (temperature of -10 to 30 ° C.) to precipitate EVOH particles. To obtain an aqueous dispersion having a desired solid content concentration by removing alcohol under reduced pressure (temperature of 10 to 30 ° C., pressure of 10 to 150 mmHg) and removing a desired amount of water. There is a method of obtaining.

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.

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.

The aqueous dispersion of the present invention may contain, if necessary, a usual surfactant or protective colloid 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.

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, as the base material, in particular, thermoplastic resin ｛polyolefin (polyethylene, polypropylene, etc.), polyester, polyamide, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polystyrene, polyvinyl alcohol, vinyl acetate resin (ethylene-vinyl acetate copolymer, etc.) ), Etc. (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 printing 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. As a method for drying and heat-treating the substrate coated in this way, a dry heat treatment method, for example, an infrared irradiation method, a hot air drying method, or the like is exemplified. 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%,
20 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 the EVOH.

Next, 2 parts of an acrylic acid monomer substituted with nitrogen and 0.2 parts of ammonium persulfate as a polymerization initiator were added, and the mixture was heated and graft-polymerized at 80 ° C. for 5 hours in a nitrogen atmosphere. The unreacted acrylic acid monomer was analyzed by the double bond determination method by the bromine method. As a result, the conversion of acrylic acid was 98.
%Met.

The obtained acrylic acid-grafted EVOH solution was added to 10% sodium hydroxide water / methyl alcohol = 5.
A solution of a mixed solvent of 0/50 (weight ratio) 11.1 parts (equimolar sodium hydroxide with respect to acrylic acid) was added for neutralization,
An anionic EVOH graft obtained by grafting 5.3 mol% of apparent sodium acrylate to EVOH
% Solution was obtained.

2. Sulfonate anionic EVOH graft product Ethylene and vinyl acetate are copolymerized and further saponified, ethylene content 44 mol%, saponification degree 99.6 mol%,
20 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.

Then, 3 parts of potassium styrenesulfonate substituted with nitrogen and 1.5 parts of cerium ammonium nitrate as a polymerization initiator were added, and the mixture was subjected to heating graft polymerization at 70 ° C. for 6 hours in a nitrogen atmosphere. When the unreacted potassium styrenesulfonate monomer was analyzed by the double bond determination by the bromine method, the polymerization rate was 95%. That is, an anionic EVOH graft was obtained in which potassium styrene sulfonate was grafted to apparent EVOH by 2.5 mol%.

3. Carboxyl anionic EVOH grafted product The amino group of aminoethanethiol was added to di-tert. Tert. Protected with butyl dicarbonate. Ethylene obtained by radical copolymerization of ethylene and vinyl acetate using butoxycarbonylaminoethanethiol as a chain transfer agent, reacting the resulting copolymer with formic acid to convert it to aminoformate, and then reacting with methacrylic acid chloride. -Content 5
0 mol%, methacrylamide type macromonomer of ethylene-vinyl acetate copolymer having a degree of polymerization of 50 ｛Average structural formula C
_{H 2 = C (CH 3)} CONHCH 2 CH 2 S (-CH 2 CH 2 -)
₂₅ (-CH ₂ C (OCOCH ₃ ) H-) ₂₅ 3000 parts, methacrylic acid 520 parts and methyl alcohol 8000 parts were put into a polymerization reactor, and after nitrogen substitution, the temperature was raised to 65 ° C., and the polymerization initiator azobis 12 parts of isobutyronitrile was added and polymerized 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.
3500 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 3050 parts of a powder polymer.
When this polymer was analyzed by nuclear magnetic resonance spectroscopy, it was found that the content of sodium methacrylate component was 12 mol% with respect to EVOH, the saponification degree of EVOH was 98 mol%, and an anionic EVOH graft of a type in which EVOH was grafted on sodium methacrylate polymer. Met.

4. Carboxyl anionic EVOH block body Ethylene having a thiol group at the terminal is 25 mol% and saponification degree is 99.5 mol% synthesized by copolymerizing ethylene and vinyl acetate using thioacetic acid as a chain transfer agent and further saponifying. And 100 parts of EVOH having a polymerization degree of 155 were dissolved in 400 parts of a mixed solvent of methyl alcohol / water = 50/50. This solution was continuously dropped into a mixed solvent of 20 parts of acrylic acid, 0.5 part of potassium persulfate and 180 parts of a mixed solvent of methyl alcohol / water = 50/50 at 65 ° C. for 2 hours under a nitrogen atmosphere to carry out polymerization. After the completion of the dropwise addition, heating was further continued for one hour to drive the polymerization.

The unreacted acrylic acid after the completion of the reaction was determined by a double bond analysis by a bromine method. To this solution, 61 parts of a 10% solution of sodium hydroxide in methyl alcohol / water = 50/50 was added to neutralize the acrylic acid component. The sodium acrylate thus obtained is added to EVOH in a proportion of 1
A 1 mol% block copolymerized ionic EVOH block solution (21.7% concentration) was obtained.

5. Sulfonate anionic EVOH block body 2-acrylamide-2 in place of the acrylic acid of 4 above
-By changing the amount of sodium 2-acrylamido-2-methylpropanesulfonate in the same manner as 4 except that sodium methylpropanesulfonate is used,
An ionic EVOH block obtained by block copolymerization of 0.3, 5, 10, 30, and 50 mol% with respect to VOH was synthesized.

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 60 having a group was synthesized.

The radical copolymerization of ethylene and vinyl pivalate in a tetrahydrofuran solvent in the presence of this polymer gives methyl acrylate polymer and ethylene-
A block copolymer of a vinyl pivalate copolymer was synthesized, and then saponified with 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 a potassium acrylate-methyl acrylate copolymer (potassium acrylate content: 80 mol%) having a polymerization degree of 60 with EVOH having a polymerization degree of 200 via S.

7. Cationic EVOH block The same radical polymerization is carried out by using a cationic vinyl monomer, acrylamidopropyldimethylbenzylammonium chloride or methacryloyloxytrimethylammonium chloride, in place of the sodium 5-acrylamido-2-methylpropanesulfonate of 5 above. Thus, a cationic EVOH block was prepared by block copolymerizing each cationic polymer with EVOH via S.

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,
Water / methyl alcohol containing 20% of an anionic EVOH graft obtained by grafting 5.3 mol% of sodium acrylate to EVOH having an ethylene content of 33 mol%, a saponification degree of 99.6 mol% and a polymerization degree of 1000 /
50 (indicating weight ratio, the same applies hereinafter) mixed solvent solution 50
Parts were added and mixed with 20 parts of ordinary EVOH having an ethylene content of 33 mol%, a saponification degree of 99.6 mol%, and a polymerization degree of 1000, 90 parts of methyl alcohol and 90 parts of water, and dissolved by heating 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 0.6 μm. Next, this emulsified dispersion was evaporated under reduced pressure with stirring to distill off methyl alcohol.
In the process of distilling off methyl alcohol, particles are hardly aggregated and stable, with an average particle diameter of 0.6 μm and a solid concentration of 2 μm.
A 5% aqueous emulsified dispersion 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 ordinary EVOH without using an anionic EVOH graft grafted with sodium acrylate, or with a conventional nonionic surfactant instead of the above anionic EVOH graft, Examples of using an ethylene oxide adduct of nonylphenyl ether, sodium dodecylbenzenesulfonate as an anionic surfactant, or partially saponified polyvinyl alcohol having a saponification degree of 80 mol% and a polymerization degree of 600 as a polymer protective colloid as an emulsion dispersion stabilizer. 1
The emulsification and dispersion were attempted under the same conditions as in Example 1. However, in each case, the heat-dissolved solution was cooled with stirring to form aggregation blocking at the stage where particles were precipitated, and a stable emulsified dispersion could not be obtained.

Thus, it can be seen that the anionic EVOH-grafted product of the present invention has a remarkable effect on the emulsification and dispersion stabilization of ordinary EVOH as the main polymer, and a stable aqueous emulsion dispersion can be obtained. Then, this aqueous emulsified dispersion was applied to the primer-treated surface of a biaxially oriented polypropylene film, dried at 110 ° C., and the oxygen barrier property of the obtained formed film was measured. The oxygen permeation amount was 3 cc / m ² · 24 h.
At r.atm (film thickness 5 μm, 20 ° C., 0% RH), it exhibited excellent performance as a food packaging material.

Example 2 Synthesized according to Synthesis Example 2,
Water / ethyl alcohol = 40/60 mixed solvent of an anionic EVOH graft obtained by grafting 2.5 mol% of potassium styrenesulfonate to EVOH having an ethylene content of 44 mol%, a saponification degree of 99.6 mol% and a polymerization degree of 900 30 parts of the solution (concentration: 21%) were mixed with a 10% concentration of ethylene content of 44 mol%, a saponification degree of 99.6 mol%, and a polymerization degree of 900.
Was mixed with 175 parts of a solution of a mixed solvent of EVOH in water / ethyl alcohol = 40/60 and heated to 70 ° C. with stirring.

Next, the solution was cooled to room temperature with stirring to obtain a stable emulsified dispersion having an average particle diameter of 0.8 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 26% and an average particle diameter of 0.8 μm.

Example 3 Synthesized according to Synthesis Example 3,
A solution is prepared by dissolving 1900 parts of water in 150 parts of anionic EVOH grafted product of a type in which an ethylene content of 50 mol%, a saponification degree of 98 mol% and a polymerization degree of 50 are grafted on a sodium methacrylate polymer having 12 mol% of EVOH. did. A high-speed stirrer is immersed in this solution for 5000
While stirring at rpm, 5000 parts of a 15% solution of EVOH having an ethylene content of 48 mol%, a saponification degree of 99.4 mol%, and a polymerization degree of 800 dissolved in a mixed solvent of isopropyl alcohol / water = 70/30 were added dropwise. Uniform emulsification resulted in a stable dispersion. Average particle size is 0.7 μm
Met.

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 3% aqueous emulsion dispersion 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,
Water / methyl alcohol = 50/50 mixed solvent of an anionic EVOH block obtained by block copolymerization of 11 mol% of sodium acrylate with EVOH having an ethylene content of 25 mol%, a saponification degree of 99.5 mol%, and a polymerization degree of 155 280 parts of the solution were mixed with an ethylene content of 25 mol% and a saponification degree of 9
Ordinary EVOH100 with 9.5 mol% and polymerization degree of 1500
0 part and 6800 parts of a mixed solvent of methyl alcohol / water = 50/50, and dissolved by heating at 70 ° C.

After cooling to room temperature with stirring, the particles were precipitated and emulsified and dispersed. The average particle size was 0.8 μm.
By evaporating the dispersion under reduced pressure, methyl alcohol was distilled off to obtain a stable aqueous emulsion dispersion. The solid concentration was 25% 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 9] 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 155, synthesized according to Synthesis Example 5, 2-acrylamido-2-methylpropanesulfonic acid was used. Sodium is 0.
Using an anionic EVOH block obtained by block copolymerization of 3, 5, 10, 30, and 50 mol% as an emulsifying dispersion stabilizer, emulsifying and dispersing and distilling off methyl alcohol were carried out in the same manner as in Example 4. An aqueous dispersion was obtained. Table 1 below shows the conditions at the time of emulsification and dispersion and the properties of the aqueous emulsion dispersion.

[0087]

[Table 1]

Example 10 Anionic EV of Example 5
Instead of the OH block, anionic E having a block content of 0.1 mol% of sodium 2-acrylamido-2-methylpropanesulfonate synthesized according to Synthesis Example 5 was used.
Emulsification and dispersion and distillation of methyl alcohol were carried out under the same conditions as in Example 5 except that a VOH block was used. Although some aggregation was observed, the solid content concentration was 20%, and the average particle size was 1.
An aqueous emulsified dispersion of 9 μm was obtained.

Example 11 The saponified ethylene-vinyl pivalate copolymer synthesized according to Synthesis Example 6 had an ethylene content of 35 mol%, a degree of saponification of 97 mol%, and a degree of polymerization of 20.
Potassium acrylate-methyl acrylate copolymer having a degree of polymerization of 60 in EVOH of 0 (potassium acrylate content of 80)
Mol%, the block content of potassium acrylate is EVO
(4.8 mol% with respect to H), 3.3 parts of an anionic EVOH block obtained by block copolymerization with ethylene-vinyl pivalate, saponified ethylene content 30 mol%, saponification degree 99 mol%, polymerization EVOH1 with a degree of 1000
00 parts were heated and dissolved at 800C in 800 parts of a mixed solvent of water / methyl alcohol = 50/50. 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 22% and an average particle diameter of 0.8 μm was obtained.

Example 12 Synthesized according to Synthesis Example 7, ethylene content 25 mol% via S, saponification degree 9
Cationic EV in which acrylamidopropyldimethylbenzylammonium chloride is 11 mol% block copolymerized with 9.5 mol% EVOH having a degree of polymerization of 155
Using an OH block as an emulsification dispersion stabilizer, an ethylene content of 30 mol% obtained by copolymerizing and saponifying ethylene and vinyl acetate, a saponification degree of 99.6 mol%, and 15% of a normal EVOH having a degree of polymerization of 1020 are used. Parts / 100 parts, and dissolved by heating at 70 ° C. in a mixed solvent of water / methyl alcohol = 50/50 so that the solid concentration became 10%.

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

Example 13 A cationic EVOH block obtained by block copolymerizing 11 mol% with respect to EVOH using methacryloyloxyethyltrimethylammonium chloride instead of acrylamidopropyldimethylbenzylammonium chloride of Example 12 was used. Except for use, emulsification and dispersion were performed under the same conditions as in the example, and methyl alcohol was distilled off to obtain a stable aqueous emulsion having a solid content of 23% and an average particle diameter of 1.2 μm.

[0093]

As described above, by using the ionic EVOH graft or block according to the present invention as a dispersion stabilizer, a high solid content having a small particle diameter and excellent stability during storage or use can be obtained. An aqueous dispersion of
And because it is water-based, it has the advantage of not causing problems such as environmental pollution, and can be used as a useful coating agent that can form a thin film showing excellent gas barrier properties, fragrance retention properties, and oil and chemical resistance by coating and drying. It has high industrial value.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 29/04 C08L 29/04 // C08J 7/04 C08J 7/04 PC09D 123/26 : 00 C08L 101: 00 (72) Inventor Li Hiroto 1621 Sazu, Kurashiki-shi, Okayama Pref. Kuraray Co., Ltd. Examiner Satoshi Morikawa (56) References JP-A-56-61430 (JP, A) JP-A-54- 101844 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 3/07 C08L 23/26 C08L 29/04

Claims (7)

(57) [Claims] An ethylene content of 15 to 65 mol% , saponification
A saponified ethylene-vinyl ester copolymer component (A) having an ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% or more, using an ethylene-vinyl alcohol copolymer having a degree of 90 mol% or more as a dispersoid. An aqueous dispersion comprising a copolymer in which a component (B) having a functional group is bonded in a block or graft form as a dispersion stabilizer. 2. An aqueous dispersion according to claim 1 applied to a substrate.
Laminated body. 3. Saponification with an ethylene content of 10 to 70 mol%.
Ethylene-vinyl ester copolymer with a degree of 80 mol% or more
Body saponified component (A) and component containing ionic group
(B) is bonded in a block or graft form
A dispersion stabilizer composed of a copolymer. 4. Saponification with an ethylene content of 15 to 65 mol%.
Ethylene-vinyl alcohol copolymer having a degree of 90 mol% or more
The combined solution was prepared with an ethylene content of 10 to 70 mol% and a degree of saponification.
80 mol% or more of ethylene-vinyl ester copolymer
Saponified component (A) and component containing ionic group (B)
Is a block- or graft-bonded copolymer
Contact with water in the coexistence of the body to precipitate fine particles, then
Production of an aqueous dispersion characterized by removing the solvent by
Law. 5. Saponification, ethylene content 15-65 mol%
Ethylene-vinyl alcohol copolymer having a degree of 90 mol% or more
Solvent that dissolves at high temperature but becomes insoluble at low temperature
After heating and dissolving the solution, the ethylene content was 10-70.
Mol%, a saponification degree of 80 mol% or more
It contains a saponified stellate copolymer component (A) and an ionic group.
Component (B) has a block-like or graft-like
Cool in the presence of the bound copolymer to precipitate fines
And then replacing the solvent with water.
The method of manufacturing the liquid. 6. Saponification with an ethylene content of 10 to 70 mol%.
Ethylene-vinyl ester copolymer with a degree of 80 mol% or more
Body saponified component (A) and component containing ionic group
(B) is bonded in a block or graft form
An ethylene content of 15 to 65 mol% in the presence of a copolymer,
Ethylene-vinyl alcohol having a saponification degree of 90 mol% or more
Contact the solution of the copolymer with a non-solvent or cool
That dispersing the particles precipitated Ri by the Rukoto in water
A method for producing an aqueous dispersion characterized by the following. 7. Saponification with an ethylene content of 15 to 65 mol%.
Ethylene-vinyl alcohol copolymer having a degree of 90 mol% or more
Merged with ethylene content 10-70 mol%, saponification degree 80
% Or more of saponified ethylene-vinyl ester copolymer
Component (A) and component (B) containing an ionic group
Locked or Grafted Copolymer Water
-Cooling the alcohol mixture to precipitate it,
To remove alcohol and, if necessary, water.
A method for producing an aqueous dispersion as a feature.