JP4746290B2 - Process for producing modified ethylene-vinyl alcohol copolymer - Google Patents

Description

The present invention relates to a method for producing a modified ethylene-vinyl alcohol copolymer which can be acetalized or ketalized easily and with high efficiency even with an ethylene-vinyl alcohol copolymer having a high ethylene content.

Sheets made of an ethylene-vinyl alcohol copolymer are excellent in gas barrier properties against oxygen and the like, and thus are widely used as packaging materials for packaging products having severe storage conditions such as food. Since various performances of the ethylene-vinyl alcohol copolymer sheet are determined by the blending ratio of the ethylene component and the vinyl alcohol component, the blending ratio has been determined so as to exhibit optimum performance depending on the application.

Generally, an ethylene-vinyl alcohol copolymer is produced by a method of hydrolyzing (saponifying) a vinyl ester copolymer such as an ethylene-vinyl acetate copolymer in a solution. Examples of the saponification method of the ethylene-vinyl acetate copolymer include a uniform saponification method using an alkaline catalyst; a heterogeneous saponification method using an alkaline catalyst using a solvent such as a methanol-water system, and the like. However, for example, in the ethylene-vinyl acetate copolymer, the solvability is markedly deteriorated with the increase in the ethylene content, and even if hydrolysis is performed in the solution, the ethylene content of the resulting ethylene-vinyl alcohol copolymer is reduced. There was a limit to the degree of saponification.

On the other hand, Patent Document 1 discloses a method in which dialkyl sulfoxide is used as a solvent excellent in solubility of an ethylene-vinyl acetate copolymer in order to perform hydrolysis or alcoholysis of an ethylene-vinyl acetate copolymer. Is disclosed. However, dialkyl sulfoxide is produced because it has a higher boiling point than ordinary solvents such as low molecular weight alcohols, esters and water, and has a high affinity with the hydroxyl groups in the resulting ethylene-vinyl alcohol copolymer. There is a problem that it is impossible to completely remove the ethylene-vinyl alcohol copolymer. When dimethyl sulfoxide remains in the resin in this way, there is a concern that the deterioration of the resin is promoted.
In addition, a method of using dimethyl sulfoxide as a solvent for hydrolysis or alcoholysis of an ethylene-vinyl acetate copolymer has been proposed. However, when dimethyl sulfoxide is used as a solvent, only a yellowish ethylene-vinyl alcohol copolymer is obtained, and there is a problem that its use is extremely limited.
Furthermore, Patent Document 2 discloses a method for synthesizing an ethylene-vinyl alcohol copolymer from a monomer. However, even in this case, when the ethylene content of the obtained ethylene-vinyl alcohol copolymer is increased, there is a problem that there is no solvent that can be dissolved, and the ethylene content of the obtained ethylene-vinyl alcohol copolymer is 2-19. About mol% was the limit.

Ethylene-vinyl alcohol copolymers are frequently used as food packaging materials because they have high gas barrier properties and good solvent resistance. However, it is known that the hygroscopic property is high due to the remaining hydroxyl group, and the physical properties are remarkably lowered by moisture absorption.
As a method for preventing such deterioration of physical properties of the ethylene-vinyl alcohol copolymer due to moisture absorption, a method of acetalizing, ketalizing or esterifying the ethylene-vinyl alcohol copolymer is known. The acetalized, ketalized or esterified modified ethylene-vinyl alcohol copolymer has high optical properties such as transparency because of low crystallinity. Further, if a modified ethylene-vinyl alcohol copolymer that has been acetalized, ketalized or esterified is used as a starting material, development of a film imparted with new performance can be expected.

However, in the acetalization, ketalization or esterification methods of ethylene-vinyl alcohol copolymers known at present, the achievable degree of acetalization, ketalization or esterification is at most about 30 mol%, It was difficult to carry out significant modification because the hydroxyl groups of the silane remained as they were. Also, in the case of an ethylene-vinyl alcohol copolymer, the solvation property is remarkably deteriorated as the ethylene content increases, and an appropriate solvent is not present. Therefore, in the acetal-modified ethylene-vinyl alcohol copolymer that can be produced The ethylene content was also limited.

Japanese Patent No. 3066167 JP 2001-261745 A

In view of the above situation, the present invention provides a method for producing a modified ethylene-vinyl alcohol copolymer that can be acetalized or ketalized easily and with high efficiency even with an ethylene-vinyl alcohol copolymer having a high ethylene content. The purpose is to provide.

The present invention relates to a method for producing a modified ethylene-vinyl alcohol copolymer, which comprises mixing an ethylene-vinyl alcohol copolymer with an aldehyde or a ketone and reacting them in a fluid in a supercritical state or a subcritical state. It is.
The present invention is described in detail below.

In the method for producing an ethylene-vinyl alcohol copolymer of the reference invention, an ethylene-vinyl acetate copolymer and water and / or alcohol are mixed and reacted in a fluid in a supercritical state or a subcritical state.
As a result of intensive studies, the present inventors have surprisingly found that when they are reacted in a fluid in a supercritical state or a subcritical state, it is extremely high even under a solvent-free system or a condition close to a solvent-free system. The inventors have found that the ethylene-vinyl acetate copolymer is efficiently hydrolyzed or alkoxide decomposed to obtain an ethylene-vinyl alcohol copolymer, and the present invention has been completed.

The ethylene-vinyl acetate copolymer used as the raw material is not particularly limited, but when an ethylene-vinyl acetate copolymer having an ethylene content of 10 mol% or more is used, it is difficult to obtain by the conventional method. An ethylene-vinyl alcohol copolymer having an ethylene content of 10 mol% or more can be easily obtained. Further, when an ethylene-vinyl acetate copolymer having an ethylene content of 50 mol% or more is used, an ethylene-vinyl alcohol having an ethylene content of 50 mol% or more which cannot be obtained by a conventional method. A copolymer can also be obtained.

Although it does not specifically limit as said alcohol, For the purpose of performing alcoholysis, primary alcohol is used suitably. Moreover, in order to make the removal after reaction easy, the C1-C9 alcohol is suitable. When the number of carbon atoms exceeds 9, the boiling point becomes high, and it becomes difficult to remove by a normal method. Moreover, since secondary alcohols, such as 2-propanol, and tertiary alcohols, such as isopropanol, can also play the role as a dispersion stabilizer, you may use together with water or a primary alcohol.
The said water and alcohol may be used independently and may use 2 or more types together.

The mixing ratio of the ethylene-vinyl acetate copolymer and water and / or alcohol is not particularly limited, but the preferred lower limit of the mixing amount of water and / or alcohol with respect to 100 parts by weight of the ethylene-vinyl acetate copolymer is 5 weights. Part. If it is less than 5 parts by weight, the efficiency of hydrolysis or alkoxide decomposition may deteriorate. A more preferred lower limit is 10 parts by weight. The upper limit is not particularly limited, but if the supercritical extruder described later is used if it is excessive, the stirring efficiency may be lowered, so the preferable upper limit is 500 parts by weight, and the more preferable upper limit is 300 parts by weight. .

In the method for producing an ethylene-vinyl alcohol copolymer of the reference invention , the obtained mixture of ethylene-vinyl acetate copolymer and water and / or alcohol is reacted in a fluid in a supercritical state or a subcritical state.
In the present specification, the supercritical fluid means a fluid having a critical pressure (hereinafter also referred to as Pc) and a critical temperature (hereinafter also referred to as Tc). The subcritical fluid is in a state other than the supercritical state, and when the pressure and temperature during the reaction are P and T, respectively, 0.5 <P / Pc <1.0 and 0.5 < T / Tc, or a fluid having a condition of 0.5 <P / Pc and 0.5 <T / Tc <1.0. A preferable pressure and temperature range of the subcritical fluid is 0.6 <P / Pc <1.0 and 0.6 <T / Tc, or 0.6 <P / Pc and 0.6 <T / Tc. <1.0. However, when the fluid is water, the temperature and pressure ranges for the subcritical fluid are 0.5 <P / Pc <1.0 and 0.5 <T / Tc, or 0.5 <P / Pc and 0.5 <T / Tc <1.0. In addition, although temperature represents a Celsius here, when either Tc or T is minus in Celsius, the formula showing the said subcritical state is not this limitation.

The fluid is not particularly limited, but may be a liquid at room temperature and normal pressure such as an organic medium such as water or alcohol, or room temperature and normal pressure such as carbon dioxide, nitrogen, oxygen, helium, argon, air. It may be a gas or a mixed fluid thereof. In particular, carbon dioxide can be brought into a supercritical state or subcritical state relatively easily, and in the supercritical state or subcritical state, it is almost liquid and suitable for kneading of the above mixture, and is easily vaporized by decompression. Can be removed.
In addition, a conventionally known acid-base catalyst may be added to the fluid.

The method of the reaction is not particularly limited, and a fluid in a supercritical state or a subcritical state may be allowed to flow into the pressure vessel containing the mixture, but the extrusion is performed using a supercritical extruder, etc. The continuous production method is preferred. Also, the reaction is carried out by preliminarily swelling the ethylene-vinyl acetate copolymer, which is the raw material, with water or alcohol, and then bringing the water / or alcohol into a supercritical or subcritical state by performing a normal extrusion kneading process May be.

The supercritical extruder has at least means for kneading the mixture, means for supplying a fluid in a supercritical state or a subcritical state, and means for extruding the kneaded mixture into a certain shape. If such a supercritical extruder is used, a molded body (for example, a sheet or the like) of an ethylene-vinyl alcohol copolymer can be obtained directly from the kneaded product by an extrusion molding method. In addition, if there exists a means to knead | mix and a means to extrude, it will not specifically limit to extrusion molding, Well-known molding methods, such as injection molding and blow molding, can be used.
When carbon dioxide is used as the fluid, carbon dioxide or the like is vaporized by extruding the molded body into the atmosphere, and quickly removed from the molded body. Further, water and / or alcohol contained in the mixture and acetic acid produced by the reaction are also released into the atmosphere at the time of extrusion and do not remain in the molded body. In order to increase the efficiency of this release, it is preferable to introduce a deaeration means after the kneading means. Examples of the devolatilizing means include a method in which a part of the kneaded resin is once opened so as to be at normal pressure, and a method in which the pressure is reduced with a vacuum pump.
A method for producing an ethylene-vinyl alcohol copolymer molded product, characterized by reacting a mixture of an ethylene-vinyl acetate copolymer with water and / or alcohol using a supercritical extruder, is also provided by the present invention. It is one of.

According to the method for producing an ethylene-vinyl alcohol copolymer of the reference invention , the selection range of the ratio of the ethylene component to the vinyl alcohol component is extremely wide compared to the conventional method, and it can be obtained at all by the conventional method. Even an ethylene-vinyl alcohol copolymer having an ethylene content of 50 mol% or more that was not present can be easily produced. If an ethylene-vinyl alcohol copolymer having an ethylene content of 50 mol% or more is used, various properties can be obtained by absorbing moisture while maintaining the excellent properties of conventional ethylene-vinyl alcohol copolymer films such as gas barrier properties against oxygen and the like. Can be obtained.
An ethylene-vinyl alcohol copolymer having an ethylene content of 50 mol% or more is also one aspect of the present invention.
In addition, although the upper limit of the ethylene content of the ethylene-vinyl alcohol copolymer of the present invention is not particularly limited, the preferable upper limit is about 99 mol% depending on the method for producing the ethylene-vinyl alcohol copolymer of the present invention.

The ethylene-vinyl alcohol copolymer of the present invention preferably has a saponification degree of 60 mol% or more. If it is less than 60 mol%, a crystal structure due to a hydroxyl group cannot be obtained, and the heat resistance and gas barrier properties that are manifested by the presence of the hydroxyl group are greatly deteriorated.

The ethylene-vinyl alcohol copolymer of the present invention preferably has a degree of polymerization of 500 or more. When it is less than 500, the strength of the molded body may be inferior when processed into a molded body such as a film. More preferably, it is 1000 or more.

According to the method for producing an ethylene-vinyl alcohol copolymer of the reference invention, even an ethylene-vinyl alcohol copolymer having an ethylene content of 10 mol% or more can be produced without using dimethyl sulfoxide or the like. . Thus, if the ethylene-vinyl alcohol copolymer manufactured without using dimethyl sulfoxide or the like is used, it is possible to obtain a molded article with extremely high transparency without yellowing.
An ethylene-vinyl alcohol copolymer molded article using an ethylene-vinyl alcohol copolymer having an ethylene content of 10 mol% or more, and having a yellowness measured by a method according to JIS K 7103 at a thickness of 300 μm. An ethylene-vinyl alcohol copolymer molded body having 2 or less is also one aspect of the present invention.

The ethylene-vinyl alcohol copolymer molded product of the present invention is extremely high in transparency and hardly yellows. Therefore, the ethylene-vinyl alcohol copolymer film of the present invention can be suitably used for optical applications.

The ethylene-vinyl alcohol copolymer molded article of the present invention has a thickness of 300 μm and a yellowness measured by a method according to JIS K 7103 of 2 or less. If it exceeds 2, it cannot be used for optical applications.
Moreover, it is preferable that the haze value measured by the method based on JISK7105 is 2 or less as for the ethylene-vinyl alcohol copolymer molded object of this invention in thickness 300micrometer. If it exceeds 2, it may not be used for optical applications.
In measuring the yellowness and haze value, it is preferable to actually measure a sample having a thickness of 300 μm. The yellowing degree and haze value can be obtained by measuring a sample having a thickness of 300 μm or less and extrapolating the result. Degrees and haze values may not be accurate.

In the method for producing a modified ethylene-vinyl alcohol copolymer of the present invention , an ethylene-vinyl alcohol copolymer and a carbonyl group-containing compound are mixed and reacted in a fluid in a supercritical state or a subcritical state.
As a result of intensive studies, the present inventors have surprisingly found that when they are reacted in a fluid in a supercritical state or a subcritical state, the conventional method can be used even under a solventless system or a condition close to a solventless system. The inventors found that an ethylene-vinyl acetate copolymer can be acetalized, ketalized or esterified with extremely high efficiency that could not be achieved by the method, and the present invention was completed.

The ethylene-vinyl alcohol copolymer used as the raw material is not particularly limited. However, since the method for producing the modified ethylene-vinyl alcohol copolymer of the present invention is a solvent-free system, the ethylene-vinyl alcohol copolymer of the reference invention is used. An ethylene-vinyl alcohol copolymer having an ethylene content of 10 mol% or more obtained by a method for producing a coal can be used as a raw material, and an ethylene content that cannot be obtained by a conventional method is 50 mol% or more. A certain modified ethylene-vinyl alcohol copolymer can be easily obtained.

Although it does not specifically limit as said carbonyl group containing compound, For example, at least 1 sort (s) selected from the group which consists of an aldehyde, a ketone, carboxylic acid, and a carboxylic acid derivative is suitable.
The aldehyde is not particularly limited, and may be any of linear, branched, cyclic, and aromatic aspects. Examples of linear aldehydes include formaldehyde, acetaldehyde, propylene aldehyde, butyraldehyde, isobutyraldehyde, glutaraldehyde, paraformaldehyde, phthalic acid dicarboxaldehyde, salicylaldehyde, hydroxybenzaldehyde, isovaleric aldehyde, valeric aldehyde, phenylacetaldehyde. Etc.
The ketone is not particularly limited, and may be linear, branched, cyclic, or aromatic. Specific examples include acetone, ethyl methyl ketone, methyl propyl ketone, isopropyl methyl ketone, acetophenone, cyclohexanone, cyclopentanone, and cyclobutanone.
It does not specifically limit as said carboxylic acid, A linear, branched, cyclic | annular, and aromatic aspect may be sufficient. Specific examples include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, isovaleric acid, salicylic acid, oleic acid, linoleic acid, acrylic acid, methacrylic acid, benzoic acid and the like.
The carboxylic acid derivative is not particularly limited, and examples thereof include esterified products and halides of the carboxylic acid.

In the method for producing a modified ethylene-vinyl alcohol copolymer of the present invention , the mixing ratio of the ethylene-vinyl alcohol copolymer and the carbonyl group-containing compound is not particularly limited, but the hydroxyl group of the ethylene-vinyl alcohol copolymer is not limited. A preferred upper limit of the amount of the carbonyl group-containing compound relative to the amount is 20 equivalents. If it exceeds 20 equivalents, it may be difficult to remove the carbonyl group-containing compound from the product, and the mixing efficiency may be reduced when kneading using a supercritical extruder. The lower limit is not particularly limited, and may be appropriately determined depending on the target degree of acetalization.
The above equivalent means the ratio of the number of moles of hydroxyl group in the ethylene-vinyl alcohol copolymer to the number of moles required for acetalization to be obtained.

In the method for producing a modified ethylene-vinyl alcohol copolymer of the present invention , a mixture of an ethylene-vinyl alcohol copolymer and a carbonyl group-containing compound is reacted in a fluid in a supercritical state or a subcritical state.
As the fluid in the supercritical state or subcritical state, the same fluid as that used in the reference invention can be used.

The method of the reaction is not particularly limited, and a fluid in a supercritical state or a subcritical state may be allowed to flow into a pressure vessel containing the mixture, but extrusion using a supercritical extruder, etc. A continuous production method is preferred. In addition, the ethylene-vinyl alcohol copolymer is swollen in water and / or alcohol in advance, and the reaction is performed by bringing water and / or alcohol into a supercritical or subcritical state by performing a normal extrusion kneading process. May be. Furthermore, the carbonyl group-containing compound may be kneaded with an ethylene-vinyl alcohol copolymer to make a supercritical or subcritical state and directly react. In this case, water / and / or alcohol may be added for dehydration or as a catalyst.

The supercritical extruder has at least means for kneading the mixture, means for supplying a fluid in a supercritical state or a subcritical state, and means for extruding the kneaded mixture into a certain shape. If such a supercritical extruder is used, a molded body (for example, a sheet or the like) of a modified ethylene-vinyl alcohol copolymer that is acetalized and / or ketalized and / or esterified from the kneaded product by an extrusion molding method. Is obtained. If there are means for kneading and means for extruding, it is not particularly limited to extrusion molding, and known molding methods such as injection molding and blow molding can also be used.
Furthermore, when carbon dioxide is used as the fluid, carbon dioxide and the like are vaporized by extruding the molded body into the atmosphere and quickly removed from the molded body. In addition, water and / or alcohol contained in the mixture, acetic acid and acetate produced by the reaction, etc. are released into the atmosphere at the time of extrusion and do not remain in the molded body. In order to increase the efficiency of this release, it is preferable to introduce a deaeration means after the kneading means. Examples of the degassing means include a method in which a part of the kneaded resin is once opened so as to be at normal pressure, and a method in which the pressure is reduced with a vacuum pump. Further, in the case of performing a dehydration reaction such as acetalization, the deaeration means is effective for tilting the equilibrium reaction toward the product.
A method for producing a modified ethylene-vinyl alcohol copolymer molded product in which a mixture of an ethylene-vinyl alcohol copolymer and a carbonyl group-containing compound is reacted using a supercritical extruder is also one aspect of the present invention. .

According to the method for producing a modified ethylene-vinyl alcohol copolymer of the present invention , the total of the degree of acetalization and / or the degree of ketalization and / or the degree of esterification, which has been difficult to achieve by the conventional method, is 10 A modified ethylene-vinyl alcohol copolymer having a mol% or more can be easily obtained.
In the present specification, the acetal group or ketal group of the obtained modified ethylene-vinyl alcohol copolymer is formed by acetalizing or ketalizing two hydroxyl groups of the ethylene-vinyl alcohol copolymer as a raw material. Therefore, the degree of acetalization or the degree of ketalization is calculated by a method of counting two acetalized or ketalized hydroxyl groups.

Further, if the ethylene-vinyl alcohol copolymer obtained by the method for producing the ethylene-vinyl alcohol copolymer of the reference invention is used as a raw material, the ethylene-vinyl acetate copolymer is modified from the modified ethylene-vinyl alcohol copolymer. Up to the production of the polymer can be performed in a lump.

If the modified ethylene-vinyl alcohol copolymer obtained in the present invention is used , a sheet imparted with water resistance can be obtained while maintaining the excellent gas barrier properties of the ethylene-vinyl alcohol copolymer sheet. Further, the modified ethylene-vinyl alcohol copolymer obtained in the present invention is excellent in reactivity, and is therefore suitable as a raw material for further chemically modifying to impart various properties.

ADVANTAGE OF THE INVENTION According to this invention, even if it is a high ethylene content ethylene-vinyl alcohol copolymer, the manufacturing method of the modified ethylene-vinyl alcohol copolymer which can be acetalized or ketalized easily and highly efficiently can be provided.

( Reference Example 1 )
An ethylene-vinyl acetate copolymer having an ethylene content of 81 mol% (Evaflex EV460; manufactured by Mitsui DuPont Polychemical Co., Ltd.) and 200 parts by weight of distilled water were charged into a supercritical extruder, After kneading while feeding 15 MPa of carbon dioxide, it was formed into a sheet having a thickness of 300 μm and extruded into the atmosphere. When the copolymer of ethylene-vinyl alcohol constituting the obtained sheet was analyzed by 1H-NMR method, almost all vinyl acetate components were hydrolyzed, and the ethylene content was the same as that of the raw material. It was 81 mol%.

( Reference Example 2 )
An ethylene-vinyl acetate copolymer having an ethylene content of 81 mol% (Evaflex EV460; manufactured by Mitsui DuPont Polychemical Co., Ltd.) and 10 parts by weight of distilled water were charged into a supercritical extruder. After kneading while feeding 15 MPa of carbon dioxide, it was formed into a sheet having a thickness of 300 μm and extruded into the atmosphere. When the copolymer of ethylene-vinyl alcohol constituting the obtained sheet was analyzed by 1H-NMR method, almost all vinyl acetate components were hydrolyzed, and the ethylene content was the same as that of the raw material. It was 81 mol%.

( Reference Example 3 )
An ethylene-vinyl acetate copolymer having an ethylene content of 81 mol% (Evaflex EV460; manufactured by Mitsui DuPont Polychemical Co., Ltd.) and 10 parts by weight of distilled water were charged into a supercritical extruder. After kneading while feeding 8 MPa of carbon dioxide, it was made into a sheet having a thickness of 300 μm and extruded into the atmosphere. When the copolymer of ethylene-vinyl alcohol constituting the obtained sheet was analyzed by 1H-NMR method, almost all vinyl acetate components were hydrolyzed, and the ethylene content was the same as that of the raw material. It was 81 mol%.

( Reference Example 4 )
An ethylene-vinyl acetate copolymer having an ethylene content of 81 mol% (Evaflex EV460; manufactured by Mitsui DuPont Polychemical Co., Ltd.) and 10 parts by weight of ethyl alcohol were charged into a supercritical extruder, After kneading while feeding 15 MPa of carbon dioxide, it was formed into a sheet having a thickness of 300 μm and extruded into the atmosphere. When the copolymer of ethylene-vinyl alcohol constituting the obtained sheet was analyzed by 1H-NMR method, almost all vinyl acetate components were hydrolyzed, and the ethylene content was the same as that of the raw material. It was 81 mol%.

( Reference Example 5 )
100 parts by weight of an ethylene-vinyl acetate copolymer (Evaflex EV460; manufactured by Mitsui DuPont Polychemical Co., Ltd.) having an ethylene content of 81 mol% and 10 parts by weight of 50% by weight ethyl alcohol aqueous solution are charged into a supercritical extruder. After kneading while feeding carbon dioxide at 200 ° C. and 15 MPa, the sheet was formed into a 300 μm thick sheet and extruded into the atmosphere. When the copolymer of ethylene-vinyl alcohol constituting the obtained sheet was analyzed by 1H-NMR method, almost all vinyl acetate components were hydrolyzed, and the ethylene content was the same as that of the raw material. It was 81 mol%.

(Example 6)
100 parts by weight of a powder obtained by pulverizing the ethylene-vinyl alcohol copolymer sheet obtained in Reference Example 1 and 50 parts by weight of butyraldehyde were charged into a supercritical extruder, and carbon dioxide at 200 ° C. and 15 MPa was added. After kneading while feeding, it was formed into a sheet having a thickness of 300 μm and extruded into the atmosphere.
When the modified ethylene-vinyl alcohol copolymer constituting the obtained sheet was analyzed by 1H-NMR method, the degree of butyralization was 15 mol%, and the ethylene content was 81 mol%, which was the same as that of the raw material. .

( Reference Example 7 )
100 parts by weight of powder obtained by pulverizing the ethylene-vinyl alcohol copolymer sheet obtained in Reference Example 1 and 10 parts by weight of orthophthalic acid were charged into a supercritical extruder, and carbon dioxide at 200 ° C. and 15 MPa was added. After kneading while feeding, it was formed into a sheet having a thickness of 300 μm and extruded into the atmosphere.
When the modified ethylene-vinyl alcohol copolymer constituting the obtained sheet was analyzed by 1H-NMR method, the degree of esterification was 15 mol%, and the ethylene content was 81 mol%, which was the same as the raw material. .

( Reference Example 8 )
An ethylene-vinyl acetate copolymer having an ethylene content of 81 mol% (Evaflex 460, manufactured by Mitsui DuPont) was kneaded while feeding a methanol solution of 1 wt% sodium hydroxide at 250 ° C. and 9 MPa, and then the thickness was increased. A 300 μm sheet was extruded into the atmosphere.
When the modified ethylene-vinyl alcohol copolymer constituting the obtained sheet was analyzed by 1H-NMR method, 100% of the vinyl acetate component was hydrolyzed and the degree of saponification was 100 mol%. The ethylene content was 81 mol%, the same as the raw material.

(Comparative Example 1)
A commercially available ethylene-vinyl alcohol copolymer (F101A, manufactured by Kuraray Co., Ltd.) having an ethylene content of 32 mol% was extruded into a film having a thickness of 300 μm using an extruder.

(Comparative Example 2)
100 parts by weight of an ethylene-vinyl acetate copolymer (Evaflex 460, manufactured by Mitsui DuPont) having an ethylene content of 81 mol%, 1000 parts by weight of dimethyl sulfoxide and 10 parts by weight of a 10% by weight aqueous sodium hydroxide solution were mixed to add water. A decomposition reaction was performed. The treated resin was formed into a film having a thickness of 300 μm and extruded into the atmosphere. When the obtained resin was analyzed by ¹ H-NMR method, the vinyl acetate component was not hydrolyzed at all and the saponification degree was 0 mol%.

(Evaluation)
The films produced in Example 6, Reference Examples 1 to 5, 7, 8 and Comparative Examples 1 and 2 were evaluated by the following methods.
The results are shown in Table 1.

(1) Measurement of total light transmittance and haze value Using a haze meter (TC-HIIIDKP, manufactured by Tokyo Denshoku Co., Ltd.), the haze value and total light transmittance were determined according to JIS K 7105.

(2) Measurement of yellowness Yellowness in a 2 ° C. field of view using a C / 2 light source on a film sample having a thickness of 300 μm using a color difference meter (Automatic Color Analyzer; manufactured by Tokyo Denshoku Co., Ltd.) Was measured.

(3) Evaluation of solvent resistance The obtained film was immersed in a tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), toluene, and water-isopropyl alcohol (IPA) mixed solution at 25 ° C. and 65 ° C., The case where it did not melt | dissolve evaluated as (circle) and the case where it melt | dissolved as x.

ADVANTAGE OF THE INVENTION According to this invention, even if it is a high ethylene content ethylene-vinyl alcohol copolymer, the manufacturing method of the modified ethylene-vinyl alcohol copolymer which can be acetalized or ketalized easily and highly efficiently can be provided.

Claims (3)

A method for producing a modified ethylene-vinyl alcohol copolymer, comprising mixing an ethylene-vinyl alcohol copolymer with an aldehyde or a ketone and reacting them in a fluid in a supercritical state or a subcritical state. The method for producing a modified ethylene-vinyl alcohol copolymer according to claim 1 , wherein the ethylene-vinyl alcohol copolymer has an ethylene content of 10 mol% or more. A method for producing a modified ethylene-vinyl alcohol copolymer molded article, wherein a mixture of an ethylene-vinyl alcohol copolymer and an aldehyde or a ketone is reacted using a supercritical extruder.