JPH05140239A - Dispersion stabilizer, aqueous dispersion and their production - Google Patents

Abstract

PURPOSE:To obtain a dispersion stabilizer which can give an aqueous dispersion of an ethylene/vinyl alcohol copolymer excellent in stability by using a copolymer prepared by boding a specified saponified ethylene/vinyl ester copolymer component to a PVA component in a specified manner. CONSTITUTION:The objective stabilizer comprises a copolymer prepared by bonding a saponified ethylene/vinyl ester copolymer component (ethylene/vinyl alcohol copolymer) of an ethylene content of 10-70mol% and a degree of saponification of 80mol% or above to a PVA component to form a block or graft copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersion stabilizer, an aqueous dispersion and a method for producing an aqueous dispersion of an ethylene-vinyl alcohol copolymer, and particularly to a dispersion stability and a film-forming property with a small particle size. It relates to an excellent method for producing an aqueous dispersion.

[0002]

2. Description of the Related Art Ethylene-vinyl ester copolymers, particularly ethylene-vinyl alcohol copolymers (abbreviated as EVOH) obtained by saponifying vinyl acetate copolymers have excellent gas barrier properties against oxygen and the like, and oil and chemical resistance. Therefore, it has been attracting attention as a material for packaging materials and a material for protecting and coating plastic moldings, metal surfaces, paper, wood and the like.

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

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

However, in the method of applying an EVOH solution, it is basically difficult to use a solution having a high concentration due to the viscosity, and the solvent is an organic solvent such as dimethylsulfoxide or a mixed solvent of a large amount of alcohol and water. In the formation process, there is a problem in that the work environment is deteriorated due to volatilization of the organic solvent and an apparatus for recovering the organic solvent is required, which is economically disadvantageous. On the other hand, the method of applying the EVOH aqueous dispersion is expected to be considered to be advantageous from the viewpoint of the above-mentioned working environment and economy because the solvent is an aqueous system.

As an aqueous dispersion of EVOH, an ordinary EV is used.
A dispersion of OH in the presence of an ordinary surfactant or an ordinary polymer protective colloid such as polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, etc. is disclosed in JP-A-54-1.
01844, JP-A-56-61430 and the like. However, according to the study by the present inventors, the aqueous dispersion of EVOH obtained by these known methods has insufficient dispersion stability and poor film-forming property, and is difficult to be practically used for coating.

Further, in JP-A-54-101844, a so-called randomly copolymerized random copolymer obtained by terpolymerizing a vinyl monomer such as acrylic acid or acrylic acid amide with ethylene-vinyl acetate and saponifying the same. Combined EVO
It has been shown that H can be dispersed using a normal surfactant as an emulsion dispersion stabilizer.

However, according to the study by the present inventors, no improvement in dispersion stability was observed with a simple ternary random copolymer EVOH, and a practical dispersion was not obtained. Among them, when acrylic acid containing an ionic group is copolymerized, the dispersion stability is improved by the ionic group, but since the ionic group is randomly contained, it will be dispersed unless the content is increased. Stability cannot be fully achieved and EV
It is not practical because of the drawbacks that the disorder of the structure of OH becomes large, the gas barrier performance is greatly lowered, and the barrier property of the formed film is lowered.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a dispersant having excellent dispersion stability, which is remarkably improved in stability during storage or use, and EVOH having excellent film-forming property.
An object of the present invention is to provide a system aqueous dispersion, particularly an aqueous emulsion dispersion, and a method for producing the same.

[0010]

DISCLOSURE OF THE INVENTION The above object is to provide a specific EVOH system in which a dispersion stabilizer for EVOH, particularly a polyvinyl alcohol component (hereinafter abbreviated as PVA component) as a dispersion stabilizer, is bonded in a block or graft form. This is achieved by using block or graft copolymers.

The greatest feature of the present invention is that the stability of the EVOH-based aqueous dispersion during storage or use is remarkably improved, the dispersion stability is excellent, and the film-forming property is also excellent. A small particle size is also a major feature because it has a small particle size and has excellent dispersion stability, and there is almost no significant increase in the particle size due to agglomeration of particles during storage or use. In addition to this feature, by using a specific polymer in which the PVA component is blocked or grafted with the EVOH component as a dispersion stabilizer, the EVOH-based aqueous dispersion of the present invention has good film-forming properties and a thinner film can be applied and dried. The formed film has excellent barrier properties. Therefore, there is an advantage that it can be dried at a lower temperature. I'm not sure why, but that PV
It is considered that the component A acts on fusion of dispersed particles during film formation.

The dispersion stabilizer used in the present invention is an ethylene-vinyl ester copolymer soap in which the PVA component (B) has a block or graft form and an ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% or more. Compounds (A) -bonded ethylene-vinyl alcohol-based block or graft copolymers (hereinafter collectively referred to as P-modified EVOH, which will be divided into blocks and grafts later), and their production methods, etc. There is no limit to.

The composition of the EVOH component (A) of the P-modified EVOH must have an ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% (the saponification degree in the present invention indicates the saponification degree of vinyl ester units) or more. There is. The ethylene content and the degree of saponification of EVOH to be dispersed in particles will be described later, but it is preferable that the ethylene content and the degree of saponification are close to those in terms of the effect of stabilizing dispersion of particles. More preferably, almost 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 effect of stabilizing dispersion. If the degree of polymerization is too high, the efficiency of grafting and block is deteriorated, which is not preferable, but a polymer having a degree of polymerization of about 2000 can be used.

The PVA component (B) is a polymer component obtained by polymerizing a vinyl ester, particularly a vinyl acetate monomer, and saponifying it, and includes those having a saponification degree of 50 mol% or more. The saponification degree is preferably 80 mol%, more preferably 90 mol% or more. If the degree of saponification is less than 50%, the dispersion stabilizing effect is low and it is unsuitable. The content of the component (B) is appropriately determined depending on the dispersing effect of P modification, the addition amount, etc., but is preferably 5 to 20 relative to 100 parts by weight of the component (A).
0 part, preferably 10 to 150 parts, more preferably 3 parts
0 to 100 parts is preferable. If the content of the component (B) is too low, the dispersion stabilizing effect is low, and if it is too large, the wet performance of the formed film, particularly the gas barrier property, is unfavorable.

The PVA component may contain an ionic group component. From the viewpoint of dispersion stability, ionic P-modified EVOH having an ionic group component introduced by copolymerization or the like is preferable. By introducing an ionic group, the amount of PVA component can be reduced, and thereby the gas barrier property can be further improved. The content of the ionic group component in the PVA component is preferably 50 mol% or less, desirably 20 mol% or less, and further preferably 10 mol% or less. Also, the lower limit is preferably 0.5 mol%, and further 1
Mol% is desirable. The ionic group includes a group which dissociates in water and exhibits ionicity, that is, an anionic group, a cationic group and an amphoteric group. Among them, anionic groups are preferable, and sulfonic acid anion groups are particularly preferable.

The structure of the P-modified EVOH is not particularly limited as long as it is a so-called block or graft copolymer, and a diblock body, a triblock body or a multiblock body of more than that shown schematically below, or EV.
Examples thereof include a graft body obtained by grafting the PVA component (B) on the OH component (A), a graft body obtained by grafting the EVOH component (A) on the PVA component (B), and the like. It may also be a so-called star-shaped one.

(A) P-modified EVOH block

[0018]

[Chemical 1]

[0019]

[Chemical 2]

[0020]

[Chemical 3]

(B) P-modified EVOH graft product A product obtained by grafting the PVA component (B) on the oEVOH component (A).

[0022]

[Chemical 4] A product obtained by grafting the EVOH component (A) onto the oPVA component (B).

[0023]

[Chemical 5]

There is no limitation on the method for producing the P-modified EVOH, but examples thereof include the following.

(A) P-modified EVOH block (i) In the presence of PVA having a thiol group at the terminal, radical copolymerization of ethylene-vinyl ester, particularly vinyl acetate, is carried out to obtain a PVA polymer and an ethylene-vinyl ester copolymer. A block copolymer having PVA and EVOH bonded via S can be obtained by obtaining the block copolymer of (1) and then saponifying the vinyl ester unit into a vinyl alcohol unit.

For PVA having a thiol group at the terminal, a vinyl ester monomer, particularly vinyl acetate is polymerized in the presence of a thiocarboxylic acid such as thioacetic acid to synthesize the vinyl ester polymer having a thioester group at the terminal, and then the terminal thioester group is It can be synthesized by decomposing and converting into a thiol group, and saponifying a vinyl ester unit.

(Ii) On the contrary, by radical copolymerizing ethylene-vinyl ester in the presence of thiocarboxylic acid such as thioacetic acid, and then saponifying the resulting vinyl ester monomer in the presence of EVOH having a thiol group at the terminal. By polymerizing, a block copolymer in which the vinyl ester polymer and EVOH are bonded via S can be obtained.

(Iii) The ester polymer having a thioacetic acid ester group at the terminal, which is obtained by polymerizing a vinyl ester in the presence of a thiocarboxylic acid such as thioacetic acid, is saponified with a weak base such as ammonia to give a terminal thiol. The acetic acid ester group is preferentially saponified and decomposed to obtain the vinyl ester polymer having a thiol group at the terminal. Next, ethylene-vinyl ester is copolymerized in the presence of this polymer, and the resulting block copolymer in which the vinyl ester polymer and the ethylene-vinyl ester copolymer are bound via S is saponified to give a PVA component and EVO.
A block copolymer in which the H component is bound via S is obtained. It is also possible to reverse the order of polymerization of the vinyl ester and the ethylene-vinyl ester.

(Iv) Polyperoxide, for example, polyphthaloperoxide is used as a polymerization initiator to radically copolymerize ethylene and vinyl ester. Next, the resulting ethylene-vinyl ester copolymer containing a peroxide group in the molecule is brought into contact with a vinyl ester monomer as a polymer initiator to perform radical polymerization under heating, thereby performing block copolymerization of the ethylene-vinyl ester copolymer and the vinyl ester polymer. A polymer is obtained. A P-modified EVOH block can be obtained by saponifying a vinyl ester unit of this block copolymer by a conventional method to convert it into a vinyl alcohol unit.

(V) An organic disulfide, particularly tetraethylthiuram disulfide, is used as an initiator or a chain transfer agent to polymerize a vinyl ester monomer, and R ₂ NC (S) S- group (R is a hydrocarbon group having 1 to 20 carbon atoms) A vinyl ester polymer having Next, a block copolymer of a vinyl ester polymer and an ethylene-vinyl ester is obtained by copolymerizing ethylene and a vinyl ester by light irradiation polymerization using this polymer as a polymerization initiator. A P-modified EVOH block can be obtained by saponifying this block copolymer by a conventional method to convert the vinyl ester unit into a vinyl alcohol unit.

(B) P-modified EVOH graft product (a) By polymerizing a vinyl ester monomer to EVOH by a conventional method, that is, a method by radiation or ultraviolet irradiation, a method in which a peroxide coexists, and then saponifying it. , A P-modified EVOH graft body obtained by grafting a PVA polymer on EVOH is obtained.

(B) A method of radically copolymerizing a macromonomer containing EVOH and a vinyl ester monomer, or a radical monomer of a macromonomer containing an ethylene-vinyl ester copolymer and a vinyl monomer having an ionic group, Then, by saponification and converting the vinyl ester unit into vinyl alcohol, a P-modified EVOH graft product obtained by grafting EVOH onto the PVA polymer is obtained.

As described above, P-modified EVO can be prepared by various methods.
Although H can be produced, the production efficiency (block or graft efficiency) of block- or graft-type P-modified EVOH is not 100% theoretically, and PVA polymer and EVOH, which are homopolymers of each, are by-produced.

It is preferable that the efficiency is high, but it is usually difficult to strictly separate and distinguish the by-produced homopolymer, and EVOH can be used as the main polymer, and the PVA polymer must be in a large amount. It is not necessary to remove that homopolymer, so
A substance containing a homopolymer can be used as it is as a dispersion stabilizer.

Therefore, the P-modified EVOH of the present invention includes the PVA component by-produced during the production thereof and the entire block or graft reaction product including the homopolymer of EVOH. The content of means the weight% of the apparent block or graft component including the homopolymer with respect to the EVOH unit.

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

As the vinyl ester monomer forming the PVA component, those which can be converted into vinyl alcohol by polymerization and saponification can be used. Examples thereof include vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate and vinyl trifluoracetate.

A component containing an ionic group can be introduced into the PVA component by various methods such as copolymerization (random, graft, block) or post reaction. Although the method of copolymerization is simple and preferable, as the vinyl monomer forming the ionic component, a radical homopolymerizable or copolymerizable radical having an ionic functional group or a group convertible to ionicity can be used. An example will be given below.

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

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

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

These monomers can be used alone or in combination. It is also possible to copolymerize another monomer not containing an ionic group in a small proportion without impairing the effects of the present invention.

The EVOH of the dispersoid is obtained by copolymerizing and saponifying ethylene with a vinyl ester such as vinyl acetate, vinyl formate, vinyl propionate, vinyl benzoate, vinyl trifluoroacetate and vinyl pivalate, particularly vinyl acetate. Ethylene-vinyl alcohol copolymer,
It is necessary that the ethylene content is 15 to 65 mol% and the saponification degree of the vinyl ester unit is 90 mol% or more.
If it 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 poor, such being unsuitable.

From the viewpoint of stability of the aqueous dispersion and gas barrier performance, the ethylene content is preferably 20 to 50 mol%.
If the degree of saponification is less than 90 mol%, the gas barrier property of the polymer will be insufficient, so it is necessary to use a polymer having a saponification degree of 90 mol% or more. The higher the degree of saponification, the higher the barrier performance. Desirably, 95 mol% or more, and further 97 mol%.
The above is preferable.

The degree of polymerization of the EVOH of the dispersoid is selected according to the application, but an extremely low degree of EVOH is not preferable because the strength of the formed film is low and is not preferable. It is advantageous to use an aqueous dispersion having a high degree of polymerization, and the degree of polymerization is usually 5000
It can be used up to a certain degree. If necessary, 5 mol% or less of a copolymerizable monomer other than ethylene and vinyl ester may be copolymerized.

The amount of the P-modified EVOH used is appropriately selected in consideration of the type and amount of the PVA component and the efficiency of graft or block, but is 1 to 200 parts by weight, preferably 3 parts by weight based on 100 parts by weight of the EVOH of the dispersoid. ˜50, more preferably 5 to 30 parts by weight is desirable. If the amount is too small, the dispersion stability will be poor, and if it is too large, the gas barrier property when the formed film will be wet will be poor, which is unsuitable.

EPO as a dispersion stabilizer using P-modified EVOH
There is no limitation on the method of dispersing H, and a known method can be used.

For example, a solution of EVOH is brought into contact with an aqueous medium which is a non-solvent of EVOH in the presence of P-modified EVOH under stirring, so that EVOH particles are preferably 3 μm or less, more preferably 2 μm or less, most preferably 1 μm or less. An aqueous dispersion can be obtained by depositing as fine particles and then removing the solvent.

The solid content concentration of the aqueous dispersion is appropriately determined according to the production conditions, intended use, etc., but the feature of the present invention is that a stable dispersion having a high concentration can be obtained. The solid content concentration is preferably 10% or more, more preferably 15% or more, most preferably 20% or more. The upper limit of the solid content concentration is not particularly limited, but if the concentration is too high, the stability of the aqueous emulsion dispersion may be slightly poor. Therefore, it is preferably 60% by weight or less, more preferably 50% by weight or less. It is not more than 40% by weight, most preferably not more than 40% by weight.

Examples of the solvent include monohydric alcohols such as methanol, ethanol, propenol and butyl alcohol, dihydric alcohols such as ethylene glycol and propylene glycol, trihydric alcohols such as glycerin, phenols such as phenol and cresol, ethylenediamine, and the like. Amines such as trimethylenediamine, dimethylsulfoxide, dimethylacetamide, N-methylpyrrolidone, and the like, and hydrates thereof may be used alone or in combination of two or more. Particularly preferred solvent systems are alcohol-water mixed solvents such as water-methanol, water-normal propanol, water-isopropanol and the like.

The P-modified EVOH can be made to coexist in a solution of the main polymer EVOH to be dispersed, in non-solvent water, or both, but preferably EV.
It is desirable to coexist in a solution of OH. Further, it is also possible to add it as a post-additive to the dispersion liquid to further improve the dispersion stability.

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

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

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

As yet another method, a solution of EVOH in the presence of P-modified EVOH is brought into contact with a non-solvent or cooled to precipitate and disperse the particles,
A method of dispersing the particles in water in the presence of P-modified EVOH is also possible.

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

The aqueous dispersion of the present invention contains electrolytes (alkali metal compounds such as sodium hydroxide, sodium chloride, sodium acetate, sodium sulfate and sodium nitrate, calcium hydroxide, calcium chloride and acetic acid) for the purpose of decreasing the viscosity. Alkaline earth metal compounds such as calcium, calcium sulfate, calcium nitrate and other electrolytes)
May be blended in an amount of 0.01 to 0.5% by weight (based on the polymer). The compounding may be performed before or after atomizing the EVOH of the dispersoid. In addition to the P-modified EVOH, usual surfactants and protective colloids can be added to the aqueous dispersion of the present invention, if necessary, within the range not hindering the achievement of the object of the present invention. It is also possible to add an aqueous dispersion of another resin, a stabilizer such as light or heat, a pigment, a lubricant, a fungicide or a film-forming aid. Further, the dispersion stabilizer of the present invention is most suitable as a dispersion stabilizer for EVOH described above, but it can also be used as a dispersion stabilizer for other organic materials (resins) and inorganic materials.

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

[0059]

【Example】

Example 1 By the method of production method example (b)-(a), ethylene content 33 mol%, saponification degree 99.6 mol%, polymerization degree 1000.
To 100 parts of EVOH of (1), vinyl acetate was graft-polymerized using potassium persulfate as a catalyst, and then 55 parts of a polyvinyl alcohol component having a saponification degree of 98 mol% was obtained. 40 parts of ordinary EVOH having a content of 33 mol%, a saponification degree of 99.6 mol% and a polymerization degree of 1000 was added to a mixed solvent of 200 parts of methanol and 200 parts of water and dissolved by heating at 65 ° C.

When this solution was cooled to room temperature with stirring, it was stably dispersed and a uniform dispersion was obtained. The average particle size was 0.9μ. Next, this dispersion was evaporated under reduced pressure with stirring to distill off methanol. Even in the process of distilling off methanol, particles were hardly aggregated and stable, and an aqueous dispersion having an average particle diameter of 0.9 μ and a solid content concentration of 23% was obtained. Further, the storage stability was good, and almost no aggregation was observed in the storage test at 40 ° C. for 30 days.

On the other hand, for comparison, a conventional EV without the P-modified EVOH graft body grafted with the PVA component was used.
When dispersed only with OH, or in place of the P-modified EVOH graft body, an ethylene oxide adduct of a nonionic phenyl ether which is a conventional nonionic surfactant, sodium dodecylbenzenesulfonate as an anionic surfactant, or a saponification as a polymer protective colloid Dispersion was attempted under the same conditions as in Example 1, using polyvinyl alcohol having a degree of polymerization of 98 mol% and a degree of polymerization of 500 as a dispersion stabilizer. However, in any case, the solution dissolved by heating was cooled under stirring and agglomerated at the stage where particles were precipitated, and a dispersion was not obtained.

As described above, it can be seen that the P-modified EVOH graft product of the present invention has a remarkable effect in stabilizing the dispersion of ordinary EVOH, and a stable aqueous dispersion can be obtained. Then, it was found that when this aqueous dispersion was applied to the primer-treated surface of a biaxially oriented polypropylene film and dried at room temperature, a film was formed neatly and a continuous coating film could be formed, and the film forming property was excellent. Further, the formed film thus obtained was heated at 105 ° C. and sufficiently dried, and the oxygen barrier performance was measured. As a result, the oxygen permeation amount was ^2.5 cc / m ² . 24 hr ・ atm (film thickness 4
μ) (20 ° C., 0% RH), showing excellent performance as a food packaging material. (The unit of oxygen permeation amount is shown below in the same unit.)

Example 2 According to the production method example (b)-(a), using ammonium persulfate as a catalyst, the ethylene content was 44 mol% and the saponification degree was 9
10 parts of a P-modified EVOH graft body in which 90 parts of a PVA component having a saponification degree of 99 mol% was grafted to 100 parts of EVOH having a polymerization degree of 900 and 9.6 mol%, an ethylene content of 44 mol% and a saponification degree of 99.6 mol. %, Degree of polymerization 900
With 40 parts of EVOH, water / isopropanol = 4
Mix with 600 parts of a 0/60 mixed solvent solution and mix with stirring.
It melt | dissolved by heating at 0 degreeC.

Then, the solution was cooled to room temperature with stirring to obtain a stable dispersion liquid having a particle size of 0.7 μm. This dispersion was evaporated under reduced pressure at 25 ° C. to remove isopropanol to obtain a solid content concentration of 20% and an average particle size of 0.7.
A stable aqueous dispersion of μ was obtained. When coating and drying were carried out in the same manner as in Example 1, the film forming property was good, and the formed film (film thickness 4 μ) had an oxygen permeation amount of 5 and showed excellent oxygen gas barrier performance.

Example 3 Synthesis method example (b)-(b), ethylene content 50 mol%, saponification degree 98 mol%, polymerization degree 1
EVOH of 00 is a PVA component 40 with a saponification degree of 98 mol%
P-modified EVOH graft body 3 of the type grafted on the part
To 0 part, 140 parts of water was added and dissolved by heating, and then the solution was cooled to 20 ° C. to prepare a solution. An EVOH having an ethylene content of 48 mol%, a saponification degree of 99.4 mol% and a polymerization degree of 800 is immersed in a high speed stirrer in this solution while stirring at 5000 rpm.
When 70 parts of a solution prepared by dissolving 850 parts of a mixed solvent of isopropanol / water = 70/30 was dropped, the solution was uniformly dispersed to obtain a stable dispersion liquid. The average particle size was 0.7μ.

Next, this emulsified dispersion was evaporated under reduced pressure at 20 ° C. to remove the isopropanol by evaporation to obtain an aqueous emulsified dispersion having a solid content concentration of 22%. The average particle diameter of this aqueous emulsion dispersion was 0.7 μm, and the particles were not enlarged by the vacuum evaporation treatment, and a stable aqueous emulsion dispersion was obtained. When this aqueous emulsion dispersion was applied and dried in the same manner as in Example 1, a clean film (film thickness 4 μm) was obtained, and the oxygen permeation amount was 6, which was excellent.

Example 4 According to the production method examples (a)-(i), 90 parts of saponification degree 99.90 to 100 parts of EVOH having an ethylene content of 25 mol%, a saponification degree of 99.5 mol% and a polymerization degree of 500. P-modified EVO in which 5 mol% of PVA component is block-copolymerized
10 parts of H block, ordinary EVOH with ethylene content of 25 mol%, saponification degree of 99.5 mol% and polymerization degree of 1200
90 parts and mixed solvent of methanol / water = 50/50 8
It was mixed with 00 parts and dissolved by heating at 70 ° C.

Then, when the mixture was cooled to room temperature with stirring, the particles were deposited and dispersed. The average particle size was 0.8μ. By evaporating this dispersion under reduced pressure, methanol was distilled off to obtain a stable aqueous emulsion dispersion. The solid content concentration was 22%, and the average particle size was 0.8μ. This aqueous dispersion is 40
Even when it was left at 30 ° C. for 30 days, neither sedimentation nor enlargement of particles was observed, and the stability was good. The coated and dried film (film thickness 4 μm) had an oxygen transmission rate of 2.3, which was excellent, as in Example 1.

Example 5 PVA having a saponification degree of 89 mol% with respect to 100 parts of EVOH having an ethylene content of 25 mol%, a saponification degree of 99.5 mol% and a polymerization degree of 300 was prepared by the production method examples (a)-(ii).
15 parts of P-modified EVOH block obtained by block-copolymerizing 90 parts of component, ethylene content 28 mol%, saponification degree 9
9.2 mol% and 85 parts of EVOH having a polymerization degree of 1000,
The mixture was mixed with 800 parts of a mixed solvent of water / methanol = 50/50, and dissolved by heating at 70 ° C.

Then, when the mixture was cooled to room temperature with stirring, the particles were deposited and dispersed. The average particle size was 0.8μ. By evaporating this dispersion under reduced pressure, methanol was distilled off to obtain a stable aqueous dispersion. The solid content concentration was 25%, and the average particle size was 0.8μ. This aqueous emulsion dispersion is 40
Even when left at 30 ° C. for 30 days, almost no sedimentation and no enlargement of particles were observed, and the stability was good. This aqueous dispersion was applied and dried in the same manner as in Example 1, and the oxygen permeation amount of the film (film thickness 4 μm) was 2.2, which was excellent.

Example 6 An EV having an ethylene content of 30 mol%, a saponification degree of 99 mol%, and a polymerization degree of 400 was prepared by the production method examples (a)-(i).
Using 10 parts of a P-modified EVOH block obtained by block-copolymerizing 70 parts of a PVA component having a saponification degree of 99 mol% obtained by copolymerizing 5 mol% of sodium 2-acrylamido-2-methylpropanesulfonate with 100 parts of OH, ethylene was used. Content 30 mol%, saponification degree 99.5 mol%, degree of polymerization 1
Methanol / water = 5 with 90 parts EVOH of 000
It was heated and dissolved at 70 ° C. in 800 parts of a 0/50 mixed solvent.

Next, this solution was cooled to room temperature with stirring to obtain a stable dispersion liquid. This dispersion was evaporated under reduced pressure at room temperature to remove methanol to obtain an aqueous dispersion having a solid content concentration of 23% and an average particle size of 0.6μ.
A coating film (film thickness 4 μm) obtained by applying and drying this aqueous dispersion liquid in the same manner as in Example 1 had an excellent oxygen transmission amount of 2.0.

Example 7 S synthesized by the method of manufacturing method example (a)-(i)
Ethylene content 35 mol%, saponification degree 99.5 mol%, polymerization degree 400 to 100 parts of EVOH, trimethyl acrylamidopropyl ammonium chloride was copolymerized with 8 mol%, and a PVA component with a saponification degree of 98 mol% was 90%. Part block copolymerized P-modified EVOH block body was used as a dispersion stabilizer except that 10 parts were dispersed under the same conditions as in Example 6, and methanol was distilled off to obtain a solid content concentration of 22% and an average particle diameter of 0.7 μm. A stable aqueous dispersion of was obtained. This aqueous dispersion was applied and dried in the same manner as in Example 1 and the oxygen permeation amount of the film (film thickness 4 μm) was 2.1, which was good.

[0074]

As described above, by using the P-modified EVOH graft or block product of the present invention as an emulsion dispersion stabilizer, a high solid content concentration having a small particle size and excellent stability during storage or use can be obtained. To obtain an aqueous dispersion of
And since it has excellent film-forming properties, it has the advantage that coating and film formation can be performed at lower temperatures.
It has a high industrial value and can be used as a useful coating agent capable of forming a thin film showing aroma retention and oil / chemical resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Sato 1 Kuraray Co., Ltd., 2045 Sakazu, Kurashiki City, Okayama Prefecture (72) Inventor Hiroto Fujito 1621 Sakazu, Kurashiki City, Okayama Prefecture (72) Invention Person Tanaka feat 1-1239, Umeda, Kita-ku, Osaka Kuraray Co., Ltd.

Claims (3)

[Claims] 1. An ethylene-vinyl ester copolymer saponified component (A) having an ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% or more and a polyvinyl alcohol component (B) are bound in a block or graft form. Dispersion stabilizer consisting of the prepared copolymer. 2. An ethylene-vinyl ester copolymer saponification component (A) having an ethylene content of 10 to 70 mol% and a saponification degree of 80 mol% or more and a polyvinyl alcohol component (B) are bound in a block or graft form. Ethylene content containing the prepared copolymer as a dispersion stabilizer 15
~ 65 mol% ethylene-vinyl alcohol copolymer aqueous dispersion. 3. When an aqueous dispersion of an ethylene-vinyl alcohol copolymer having an ethylene content of 15 to 65 mol% is produced, the ethylene content is 10 to 70 mol% and the degree of saponification is 8.
It is characterized in that 0 mol% or more of an ethylene-vinyl ester copolymer saponified component (A) and a polyvinyl alcohol component (B) are used as a dispersion stabilizer in a block or graft form. And a method for producing an aqueous dispersion of an ethylene-vinyl alcohol copolymer.