JP3066167B2 - Method for producing 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 a method for producing an ethylene-vinyl alcohol copolymer obtained by saponifying an ethylene-vinyl ester copolymer, and more particularly to a method for producing an ethylene-vinyl ester copolymer by alcoholysis. The present invention also relates to a process for producing a liquid alcoholic ethylene-vinyl alcohol copolymer using a dialkyl sulfoxide as a solvent.

[0002]

2. Description of the Related Art An ethylene-vinyl alcohol copolymer has an ethylene content of 25 to 45 mol%, an intrinsic viscosity,
[Η] ph = 0.099 to 0.110 liter / gram (hereinafter liter / gram is referred to as 1 / g) (15% by weight)
(Hydrogen-containing phenol, measured at 30 ° C) is used to make food packaging containers, oil packaging containers, and parts that come into contact with oils, taking advantage of the high gas barrier properties of the copolymers. It is mainly used, and the demand has been greatly increased in conjunction with changes in eating habits. An ethylene-vinyl alcohol copolymer having an ethylene content of less than 25 mol% is an improved product of the polyvinyl alcohol copolymer such as water resistance, water absorption and swelling property, and has an ethylene content of 45 mol% or more. The ethylene-vinyl alcohol copolymer is expected to be developed as an ethylene-vinyl alcohol resin having good flexibility and excellent moldability. Furthermore, when the ethylene content is 25 to 45 mol%, [η] ph0.
An ethylene-vinyl alcohol copolymer exceeding 099 to 0.110 l / g is expected to contribute to performance improvement in various application fields as a product having improved durability and mechanical strength. As described above, from the conventionally known ethylene content, an ethylene-vinyl alcohol copolymer having a low ethylene content or a high ethylene content, and an ethylene-vinyl alcohol copolymer having a higher polymerization degree than the conventionally known polymerization degree, A copolymer having a conventional ethylene content and a degree of polymerization has a possibility of exhibiting excellent performance that cannot be achieved, and it is desired to develop an inexpensive and rational production method.

[0003] As a method for saponifying an ethylene-vinyl acetate copolymer, an alcoholic solvent such as methanol is used, a homogeneous saponification method using an alkaline catalyst, and a solvent such as a methanol-water system is used. Known heterogeneous saponification methods are known. However, in a saponification reaction using methanol as a solvent, the rate of the saponification reaction is greatly reduced with an increase in the ethylene content. Furthermore, in the case of the homogeneous saponification method, conventionally, an ethylene-vinyl alcohol copolymer produced by a methanolysis reaction is a non-solvent of the copolymer centered on water in the state of a methanol solvent, or methanol and a non-solvent. Extruded into a mixed solvent, formed into a certain shape such as a strand or chip, and subjected to a primary step of drying, which is generally commercialized. Is advantageous.
The ethylene-vinyl alcohol copolymer may be melted (dry molding) or a solution (wet molding) dissolved in a specific solvent into a desired shape such as fibrous, hollow fiber, film, or particulate. It is subjected to secondary molding and becomes the final product. Such known general production methods include various problems to be improved as described below.

[0004] 1) Ethylene-vinyl acetate copolymers show a tendency to decrease their solubility in methanol with an increase in ethylene content. To perform a homogeneous methanolysis reaction, unfavorable conditions such as high temperature and pressure are required. Required.

2) The ethylene-vinyl alcohol copolymer produced by the methanolysis of the ethylene-vinyl acetate copolymer has a solubility in methanol of 25 to 45 mol% in both low ethylene and high ethylene. Decrease, especially on the low ethylene side
Even under the condition of high temperature and pressure exceeding ℃, it is no longer possible to maintain a homogeneous state at an industrially sufficient concentration, and it is no longer possible to carry out a methanolysis reaction in a homogeneous system.

3) The methanolysis reaction of the ethylene-vinyl acetate copolymer has a slower reaction rate than the methanolysis of the vinyl acetate polymer and requires a large amount of catalyst and methanol. Along with the solubility, a high temperature and pressure reaction system is required. For that reason,
Raw material costs such as the amount of catalyst used, utilities centering on steam, and capital investment for reactors increase, which causes production costs to rise.

Further, according to previous studies, it has been found that ethylene-
When the vinyl acetate content is less than 40 mol%, the vinyl acetate copolymer has a very low solubility and is therefore difficult to hydrolyze. Therefore, Bestian (US Pat.
o3344129) reports that the rate of alcoholysis of these polymers in methanol or ethanol is extremely low due to the extremely low solubility of the polymers in solvents. Thus, a heterogeneous substance containing both hydrolyzed and non-degraded molecules in the same reaction product is obtained. According to Bestian, Roland's method (US Pat. No. 2,386,347) using a mixture of aromatic hydrocarbon and alcohol as the reaction solvent is effective only when the vinyl ester / ethylene molar ratio is 1/5 or less. When the vinyl acetate content in the polymer is low, the amount of the aromatic hydrocarbon required is extremely large, which is uneconomical, and the reaction rate is extremely slow. To overcome these problems, Bestian describes improving the solubility by using alcohols having 4 to 8 carbon atoms as the reaction solvent, but also suggests the use of higher temperatures.

[0008] US Pat. No. 3,080,350 to Imai et al. (JP-B-36-4439) discloses a method of polymerizing vinyl acetate using a highly polar aprotic solvent, dimethyl sulfoxide, and further converting the obtained polyvinyl acetate to polyvinyl. Although a method of hydrolysis or alcoholysis to alcohol is described, there is no description that an ethylene-vinyl alcohol copolymer is obtained by copolymerizing ethylene and vinyl acetate, and further by alcoholysis of the copolymer. In addition, there is no description of what function dimethyl sulfoxide plays in alcoholysis of an ethylene-vinyl acetate copolymer and what effect it has on the obtained ethylene-vinyl alcohol copolymer.

It has been reported that the use of dimethyl sulfoxide as a reaction solvent increases the rate of saponination of vinyl acetate. (Vinson, J. Chem. E.
d. , 46 , 877 (1969)). But Vinso
The saponination of n occurs in the presence of a considerable amount of water, and in the case of an ethylene-vinyl acetate copolymer, a heterogeneous reaction occurs because the ethylene-vinyl alcohol copolymer formed is insoluble in water. Will be.

In addition, John et al., US Pat.
4 (JP-A-49-71082), the alcoholysis reaction of an ethylene-vinyl ester copolymer is carried out in an aprotic reaction medium such as dimethylformamide or dimethylsulfoxide, and in some cases, a hydrocarbon-based reaction medium. There is also disclosed a method for performing an alcoholysis reaction in a solid phase, but there is no disclosure in a homogeneous liquid phase.

[0011]

SUMMARY OF THE INVENTION The problems involved in the above-mentioned known production methods are solved, and the production standards (ethylene content, degree of polymerization) of the conventionally known ethylene-vinyl alcohol copolymer are varied. In addition, the present inventors have diligently studied a low-cost and rational manufacturing method and completed the present invention.

[0012]

DISCLOSURE OF THE INVENTION The present invention provides an alcoholysis of an ethylene-vinyl ester copolymer by using a dialkyl sulfoxide as a solvent and performing an alcoholysis in a liquid phase, and remarkably accelerated in comparison with the conventional method. This realizes the improved alcoholysis. By implementing the present invention, the above-mentioned problems in the conventional method can be rationally solved, and a low product cost can be realized. The present invention uses a dialkyl sulfoxide composed of a lower alkyl group as a solvent for a reaction system with respect to conventionally known methanol,
By effectively utilizing the specific dissolution behavior of the solvent for ethylene-vinyl ester copolymer and ethylene-vinyl alcohol copolymer, even if the ethylene content and intrinsic viscosity are expanded from the conventional specifications, a uniform state is maintained. To realize the reaction at

The present invention is practiced by uniformly dissolving an ethylene-vinyl acetate copolymer in a mixed system of a dialkyl sulfoxide and a lower alcohol. According to a detailed study by the present inventors, the ethylene-acetic acid copolymer of the present invention is examined. It has been found that the reaction rate of alcoholysis of the vinyl copolymer is increased as compared with the solvent system of lower alcohol alone. Ethylene-vinyl acetate copolymers generally have lower reaction rates than vinyl acetate homopolymers, and are forced to employ undesirable conditions such as an increase in reaction temperature and an increase in the amount of alkaline catalyst used. Is completed, the reaction can be performed under mild conditions.

In a conventionally known solvent system of a lower alcohol alone, since the solubility of ethylene-vinyl alcohol formed by the alcoholysis in the lower alcohol is low, the reaction temperature must be increased in order to carry out the alcoholysis reaction in a homogeneous system. No measures could be taken other than to improve the solubility. Due to the solubility limitation, it is very difficult to obtain a homogeneous alcoholysis of an ethylene-vinyl acetate copolymer having an ethylene content of about 25 mol% or less and about 45 mol% or more by a conventionally known method. Exists. The present invention provides a solution to such a situation. Dialkyl sulfoxide is a good solvent for both ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer, can maintain the reaction system uniformly without increasing the temperature of the reaction system, and can deactivate the catalyst due to the temperature increase. Unwanted phenomena such as increase and thermal degradation of the copolymer can be avoided.

In the present invention, alcoholysis proceeds in a liquid phase. Here, the liquid phase means a substantially uniform liquid phase.

Next, in the reaction system of the present invention, a lower alcohol ester of a fatty acid such as acetic acid is by-produced by the alcoholysis reaction, and in order to further increase the degree of saponification, it is necessary to bring the alcoholysis equilibrium to the production system side. Therefore, efficient removal of an ester, for example, an acetic ester, out of the system is desired. Detailed studies by the present inventors have revealed that dialkyl sulfoxide coexisting in the present reaction system has an effect of improving the separation efficiency of acetate and lower alcohol. As a method for removing the mixture by distillation, distillation-removal under reduced pressure in a tank type, and in a tower type, ethylene-dissolved in dialkyl sulfoxide from the middle stage of the reaction tower was used.
As a preferred embodiment, a method in which a vinyl ester copolymer is introduced, and a lower alcohol and a fatty acid alcohol ester are distilled out from an upper stage while performing a saponification reaction by blowing an alcohol vapor from a lower stage can be recommended. If such an effect is utilized, the number of separation stages and the reflux ratio of the distillation column required for separating the mixture can be greatly reduced, and the contribution to the reduction of equipment costs and utility costs is large. The ethylene-vinyl ester polymer used in the present invention is generally synthesized by a copolymerization reaction of ethylene and vinyl ester.

The ethylene content of the ethylene-vinyl ester copolymer is preferably from 0.1 to 80 mol%. When the ethylene content of the copolymer is less than 0.1 mol%, the above-described effect of improving the performance of polyvinyl alcohol is not substantially exhibited. Suitable ethylene contents are at least 1 mol%, more preferably at least 5 mol%, at least 10 mol%, even at least 20 mol%. The ethylene content is 80 mol%
In a region exceeding the above range, the ethylene-vinyl ester copolymer is not suitable because it is difficult to completely dissolve in the reaction solution system mainly containing dialkyl sulfoxide. Judging from the solubility of the ethylene-vinyl ester copolymer, a copolymer having an ethylene content of 70 mol% or less is more preferable.

In the present invention, examples of the vinyl ester include vinyl esters of lower fatty acids having 5 or less carbon atoms, typically vinyl acetate, and vinyl propionate. In the present invention, other than ethylene and vinyl ester, an ethylenically unsaturated monomer copolymerizable therewith can be used in a range that does not hinder the practice of the present invention. Here, examples of the ethylenically unsaturated monomer include “Poval (revised new edition)” (Polymer Publishing Association, issued on April 1, 1981) 28
Monomers described on pages 1-285 and references cited therein can be exemplified as typical examples.

Representative monomers include, for example, olefins (such as olefins having 3 to 18 carbon atoms), vinyl carboxylates (such as vinyl versatate and vinyl stearate), alkyl vinyl ethers (such as lauryl vinyl ether and methyl vinyl ether), and ) Acrylates {eg, methyl (meth) acrylate), acrylamides (acrylamide, methacrylamide, N, N
-Dimethyl acrylamide, etc.), unsaturated carboxylic acids (esters) or (anhydrides) (acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, esters, anhydrides thereof, etc.), sulfonic acid monomers (vinyl sulfonic acid) Acryl sulfonic acid), cationic monomers (dimethylaminoethyl methacrylate, vinyl imidazole, vinyl pyridine, vinyl succinimide, etc.) and others (vinylene carbonate, allyl alcohol, allyl acetate, etc.).

The degree of saponification of the ethylene-vinyl alcohol copolymer can be varied depending on the final use, and is preferably at least 20%, more preferably at least 50%. When used, the degree of saponification is preferably at least 99.0%, more preferably at least 99.5%. The dialkyl sulfoxide used in this reaction system is composed of a lower alkyl group, and the number of carbon atoms of the lower alkyl group is generally preferably 3 or less from the viewpoint of solubility in an ethylene-vinyl ester copolymer and an ethylene-vinyl alcohol copolymer. Specific examples of the dialkyl sulfoxide include dimethyl sulfoxide, diethyl sulfoxide, di-propyl sulfoxide, di-n-propyl sulfoxide, methyl ethyl sulfoxide, methyl i-propyl sulfoxide, and the like. In consideration of the price and the like, dimethyl sulfoxide and diethyl sulfoxide are preferable, and dimethyl sulfoxide is particularly preferable from the comprehensive judgment on the above conditions. The amount of the dialkyl sulfoxide used is not particularly limited as long as the ethylene-vinyl ester copolymer and the ethylene-vinyl alcohol copolymer are uniformly dissolved.However, in consideration of the solution viscosity and the like, the ethylene-vinyl ester copolymer is used. The concentration of the combined dialkyl sulfoxide solution is 0.1 to 70% by weight (based on the total amount of the ethylene-vinyl ester copolymer and dialkyl sulfoxide), and more preferably 1 to 50% by weight.

In the present invention, a lower alcohol is used as a reaction reagent for alcoholysis. Although a method for producing an ethylene-vinyl alcohol copolymer by the alcoholysis reaction of an ethylene-vinyl ester copolymer is known, the reaction rate of the alcoholysis reaction with an alkaline catalyst is higher than that of polyvinyl acetate which is a homopolymer of vinyl acetate. Is generally small, and the reaction rate tends to decrease as the ethylene content increases. As a result of various studies on the alcoholysis reaction of the ethylene-vinyl ester copolymer,
The use of lower alcohols is preferred for the alcoholysis reaction, and the use of primary lower alcohols having 1 to 5 carbon atoms has been judged to be suitable. Examples of the primary lower alcohol having 1 to 5 carbon atoms include methanol, ethanol, n-propanol, n-butanol, i-butanol, n-amyl alcohol, i-amyl alcohol and the like. Considering the reaction rate of the reaction, the solubility in the ethylene-vinyl ester copolymer, and the like, the use of methanol and ethanol is preferred, and the use of methanol is particularly preferred from the viewpoint of the reaction rate. The amount of the lower alcohol used is not particularly limited as long as it is an amount sufficient to produce ethylene-vinyl alcohol by the alcoholysis reaction of the ethylene-vinyl ester copolymer, but the average molecular weight of the ethylene-vinyl ester copolymer is not limited. The molar number is preferably from 1.0 to 50 times, preferably from 1.5 to 30 times the molar number in consideration of the reaction equilibrium of alcoholysis, the post-treatment cost of the charged lower alcohol, and the like. 20 can be disclosed as a more suitable range.

The alcoholysis reaction of the present invention is carried out in the presence of an alkaline catalyst. Examples of the alkaline catalyst include those used in an alcoholysis reaction of polyvinyl acetate or an ethylene-vinyl ester copolymer with an alkaline catalyst. A known catalyst can be used as it is. Specific examples thereof include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkali metal alcoholates such as sodium methylate and potassium t-butoxy, and 1,8-diazabicyclo [5,4,10 ]
Strongly basic amines represented by undecene-7 (DBU), as well as alkali metal carbonates and alkali metal hydrogencarbonates can be disclosed, but use of sodium hydroxide is preferred from the viewpoint of easy handling and catalyst cost. The amount of the catalyst used varies depending on the required degree of saponification, the reaction temperature and the like, but is generally 0.001 to 1.0 mol ratio per mol calculated from the average molecular weight of the ethylene-vinyl ester copolymer.

The reaction temperature for alcoholysis in the present invention may be any temperature from room temperature to about 150 ° C., if necessary. However, in order to obtain a high reaction rate in a normal pressure reaction system, the reaction temperature is preferably from 40 to 120 ° C. Is recommended as a suitable temperature range of 50 to 100 ° C. The alcoholysis reaction of the ethylene-vinyl ester copolymer may be a stirred tank type, a tower type, or the like.A dialkyl sulfoxide solution in which the copolymer is dissolved is introduced from the middle stage of the reaction tower, and alcohol vapor is blown from the lower stage. A tower type in which the by-produced acetate is removed from the upper stage can be recommended as one of the preferred embodiments.

In the present invention, it is preferable to conduct alcoholysis in a state where oxygen is substantially removed, for example, in a state where the oxygen concentration is 5 × 10 ⁻⁴ mol / l or less, since the degree of polymerization is hardly reduced. In order to keep the oxygen concentration of the reaction system below this level, there is a method of replacing with a nitrogen gas having a purity of 99.9% or more, or a method of heating to 60 ° or more and then replacing with nitrogen or argon.

Further, the EVOH obtained by the present invention is characterized by the specificity of the steric structure derived from DMSO polymerization and / or the distribution behavior of residual ester groups due to DMSO-based saponification (the distribution of residual ester groups is more random). EVO having the same degree of polymerization and saponification obtained by polymerization and / or saponification in a conventional lower alcohol
It shows physical properties peculiar to the present invention, such as a tendency of the melting point to be lower than that of H. This is apparent from Example 11 described later. If the physical properties are used, for example, in the melt-stretch molding of EVOH, suppression of gel and lumps caused by thermal deterioration, improvement of stretching speed and stretching ratio, reduction of voids and cracks, improvement of thickness unevenness, stable operation for a long time It is expected to contribute to the securing of security.

The more random (sharper) distribution of the residual ester groups of the EVOH obtained by the present invention is indicated by the block character, and the larger the value of the block character, the more random (sharper) the character is. .

The EVOH obtained according to the present invention preferably exhibits a block character of 0.2 or more, more preferably 0.25 or more, and even more preferably 0.3 or more. Here, the block character is calculated by the following equation. Block character = (OH-OAC) / 2 (OH)
(OAC) Here, (OH-OAC) refers to the molar fraction (A) of two chains of two chains ｛vinyl alcohol unit-vinyl alcohol unit.
₁ ) + Mole fraction of two chains of vinyl alcohol units-vinyl ester units (A ₂ ) + Mole fraction of two chains of vinyl ester units-vinyl ester units (A ₃ )} (A ₁ + A + _It shows the ratio of the molar ratio of two chains of vinyl alcohol units-vinyl ester units (A ₂ ) to ₂ A ₃ ).

The molar fraction (A ₁ ) of a two-chain vinyl alcohol unit-vinyl alcohol unit is determined from the absorption intensity of the peak in the region where δ is from 45.7 to 48 ppm by ¹³ C-NMR spectrum. - mole fraction of vinyl ester units (a ₂₎ is δ is 43.5～
It is determined from the absorption intensity of the peak in the region of 45.5 ppm. The vinyl ester units - two chain molar fraction of vinyl ester units (A ₃₎ is the total amount mole fraction of vinyl alcohol units and vinyl ester units in the EVOH from the square values A ₁ and A ₂ It is determined by subtraction. In the above formula, (OH) and (OAC)
Represents the mole fraction of vinyl alcohol units and vinyl ester units in two chains and more chains, respectively.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited by the Examples. In the examples, [η] ph of EVA refers to EV obtained by completely saponifying EVA (degree of saponification of 99.4 mol% or more).
Represents the intrinsic viscosity of OH.

[0030]

【Example】

Example 1 An ethylene-vinyl acetate copolymer (EVA) having an ethylene content of 5 mol% was placed in a 5-liter separable flask equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet tube.
([Η] ph = 0.224 l / g) 340 g, methanol 660 g, and dimethyl sulfoxide 1700 g were added, and the mixture was heated and stirred at 70 ° C. to form a uniform solution. A 3% sodium hydroxide-methanol solution 51.6 was added to this solution.
g was added and reacted at 70 ° C. for 20 minutes. The state of the solution after the reaction was uniform. At this time, a part of the reaction solution was sampled, neutralized, and then precipitated and washed in methanol repeatedly. After that, it is pulverized and dried to obtain a saponification degree of 9
7.8% ethylene-vinyl alcohol copolymer (EV
OH). Further, with respect to the solution reacted for 20 minutes, a mixed solution of methanol and methyl acetate was distilled out of the system by distillation under reduced pressure in order to bring the equilibrium of alcoholysis to the production system side. The reaction was stopped by neutralization when the amount of distilling out of the system became 780 g, and the same post-treatment as above was carried out to obtain EVOH having a saponification degree of 99.9%. The state of the solution when the reaction was stopped was uniform.

Example 2 According to Example 1, EVA having an ethylene content of 32 mol% was used.
([Η] ph = 0.111 l / g) 100 g, methanol 170 g, and dimethyl sulfoxide 580 g were added, and 6
The mixture was heated and stirred at 0 ° C. to obtain a uniform solution. 160 g of a 3% sodium hydroxide-methanol solution was added to this solution, and a reaction was performed at 60 ° C. for 30 minutes. The state of the solution after the reaction was uniform. During the reaction time, the reaction solution was sampled at each time, and after neutralization, the polymer was precipitated in a 1 g / L acetic acid-pure aqueous solution and then immersed for 30 minutes. The acetic acid aqueous solution was replaced, an acid treatment was further performed for 30 minutes, and after the liquid was discarded, it was immersed in tap water for 30 minutes.

Then, it was pulverized and dried to obtain EVOH.
The relationship between the saponification reaction time and the degree of saponification is shown in FIG. 1. The degree of saponification two minutes after the start of the reaction was 75% and the final degree of saponification was 98.
3%. According to Example 1, a mixed solution of methanol and methyl acetate was distilled out of the solution by distillation under reduced pressure in order to shift the equilibrium of alcoholysis to the production side in the same manner as in Example 1 for the solution reacted for 30 minutes. The sample after the amount of distilling out of the system of 260 g was subjected to the same post-treatment as above, and the degree of saponification was measured to be 99.4%. Further, 190 g of methanol was added to the reaction system, and vacuum distillation was performed in the same manner.
When the amount of distilling out of the system became 150 g, the reaction was stopped by neutralization, and post-treatment was carried out in the same manner to obtain EVOH having a saponification degree of 99.8%. The weight ratio of methanol to methyl acetate in the distillate immediately after the start of distilling was 1: 9. The state of the solution during and after the reaction was a homogeneous liquid phase.

Comparative Example 1 In Example 2, methanol was used in place of dimethyl sulfoxide, and the reaction was carried out with the same amount of catalyst (the molar ratio of vinyl acetate in EVA). The change over time in the degree of saponification up to a reaction time of 30 minutes was examined by performing the same post-treatment as in the above example. The degree of saponification 2 minutes after the start of the reaction was 55% and 3
The final degree of saponification after reaction for 0 minutes was 95%. The results are also shown in FIG. 1, and as is clear from FIG. 1, it is found that accelerated alcoholysis can be performed by coexisting dimethyl sulfoxide in the reaction system, as compared with methanol alone. Further, a mixed solution of methanol and methyl acetate was distilled out of the system by vacuum distillation with respect to the solution after the reaction for 30 minutes. The weight ratio of methanol to methyl acetate in the distillate immediately after the start of distillation was 2: 8. After the post-processing, the degree of saponification of the sampled sample with the amount of distilling out of the system of 260 g was 96.5%.

By comparing the weight ratio of methanol and methyl acetate in the distillate of Example 1 and Comparative Example 1, the alcoholysis equilibrium was brought closer to the production side. When dimethyl sulfoxide coexists in the system,
It can be seen that the separation efficiency of methyl acetate and methanol is improved as compared with a system using only methanol, and that efficient distillation of methyl acetate out of the system can be achieved. The state of the solution during the reaction and at the time of stopping the reaction were uniform as in the case of the dimethyl sulfoxide system.

Example 3 According to Example 1, EVA having an ethylene content of 27 mol% was used.
([Η] ph = 0.109 l / g) Using 100 g, methanol 170 g, and dimethyl sulfoxide 550 g,
After uniform dissolution at 60 ° C., 150 g of a 3% sodium hydroxide-methanol solution was added, and the reaction was carried out at the same temperature for 30 minutes. During and after the reaction, the state of the solution was uniform. A part of this reaction solution was sampled, and the degree of saponification of the post-treated EVOH was 77% for 2 minutes and 98.6% for 30 minutes. For the solution reacted for 30 minutes, the mixed solution of methanol and methyl acetate was depressurized in order to bring the equilibrium of alcoholysis to the production side, as in the above example.
Distilled out of the system by distillation. Distillation amount outside the system is 250
After the post-treatment, the degree of saponification of the sampled sample in g was 99.5%. Furthermore, 190 g of methanol was added to the reaction system, and distillation under reduced pressure was carried out in the same manner. When the amount of distilling out of the system reached 150 g, the reaction was stopped by neutralization, post-treatment was carried out, and the saponification degree was 99. 8% EVOH
I got During and after the reaction, the state of the solution was uniform.

Comparative Example 2 In Example 3, methanol was used in place of dimethyl sulfoxide, and the reaction was carried out with the same amount of catalyst (the molar ratio of vinyl acetate in EVA). The state of the solution at the start of the reaction was uniform, but after 5 minutes from the addition of the catalyst, EV was introduced into the system.
OH began to precipitate and solidified after 10 minutes.
After 30 minutes, the solid was taken out, the mixture was crushed, and the post-treated EVOH obtained had a degree of saponification of 96.0%.
The saponification degree 2 minutes after the start of the reaction was 58%.

Example 4 According to Example 1, EVA having an ethylene content of 60 mol% was used.
([Η] ph = 0.077 l / g) Using 100 g, methanol 180 g, dimethyl sulfoxide 760 g,
After uniform dissolution at 60 ° C., 260 g of a 3% sodium hydroxide-methanol solution was added, and the reaction was carried out at the same temperature for 40 minutes. The degree of saponification of EVOH after reaction for 40 minutes is 9
7.2%. With respect to the solution reacted for 40 minutes, a mixed solution of methanol and methyl acetate was distilled out of the system by distillation under reduced pressure. The amount of distilling out of the system was 99.0% when the degree of saponification of the sample sampled at 350 g was measured after the post-treatment. Further, after adding 200 g of methanol to the reaction system, distillation under reduced pressure was performed, and the amount of distillate was 160 g.
The reaction was stopped where it became. The final degree of saponification after the post-treatment was 99.4%. During and after the reaction, the state of the solution was uniform.

Comparative Example 3 In Example 4, methanol was used in place of dimethyl sulfoxide, and the reaction was carried out with the same catalytic amount (molar ratio of vinyl acetate in EVA). At 60 ° C., the polymer did not completely dissolve and was in a cloudy state. After the addition of the catalyst, the system became homogeneous and reacted for 40 minutes. After the reaction for 40 minutes, the degree of saponification of EVOH was 94.2%. Further, a mixed solution of methanol and methyl acetate was distilled out of the system by distillation under reduced pressure. The saponification degree of the sampled sample when the amount of distilling out of the system was 350 g was 95.6%. Further, 200 g of methanol was added to the reaction system, followed by distillation under reduced pressure. The reaction was stopped at a distillation amount of 200 g, post-treatment was performed, and the degree of saponification was measured to be 97.4%.

Example 5 According to Example 2, EVA having an ethylene content of 32 mol% was used.
([Η] ph = 0.111 l / g) 100 g, methanol 170 g, diethylsulfoxide 780 g, 3% -sodium hydroxide-methanol solution 160 g, 6 g
The reaction was performed at 0 ° C. for 30 minutes. The saponification degree of the sample sample after the reaction for 30 minutes was 98.0%. Furthermore, a saponification degree of 99.3% was obtained with 260 g of distillate, and methanol 1
After the addition of 90 g, EVOH having a degree of saponification of 99.6% was obtained from 150 g of the distillate. The weight ratio of methanol to methyl acetate in the distillate immediately after the distillation was 1: 9. During and after the reaction, the state of the solution was uniform.

Example 6 According to Example 2, EVA having an ethylene content of 32 mol% was used.
([Η] ph = 0.111 l / g) 60 g using 100 g, ethanol 320 g, dimethyl sulfoxide 580 g, and 3% sodium hydroxide-ethanol solution 160 g.
Reaction was performed at 40 ° C. for 40 minutes. The saponification degree of the sampled sample after the reaction for 40 minutes was 96.5%. Furthermore, a saponification degree of 98.5% was obtained with 380 g of distillate, and ethanol 27
After the addition of 0 g, EVOH having a saponification degree of 99.5% was obtained from 220 g of the distillate. During and after the reaction, the state of the solution was uniform.

Examples 7 to 10 According to Example 1, ethylene content 0 (PVAc), 2
EVA of 0, 32, 47, and 60 mol% was reacted at 40 ° C. for 60 minutes under the conditions shown in Table 1. As a solvent for precipitating the polymer after saponification, water, ethanol, or a mixed solvent of both was appropriately used according to the ethylene content and the degree of saponification. The state of the solution after the reaction was all uniform. In FIG.
The change over time in the degree of saponification is shown. As a control, in Examples 7 to 10, the saponification reaction was performed using methanol instead of dimethyl sulfoxide under the same other conditions. The polymer solidified after the reaction was subjected to neutralization and post-treatment after pulverization (Comparative Examples 4 to 8). In the case of the methanol system, it was solid or slurry during or after the reaction, depending on the ethylene content. FIG. 3 shows the change over time in the degree of saponification in the case of the methanol system. As can be seen from a comparison between FIG. 2 and FIG. 3, when dimethyl sulfoxide is used as the solvent, the reaction is much faster than when using methanol.

From FIGS. 2 and 3, the reaction rate at each ethylene content was determined for each solvent system, and the ratio (DMS
O-based saponification / MeOH-based saponification) was determined (FIG. 4). As can be seen from FIG. 4, the reaction rate ratio increases as the ethylene content increases, indicating that the saponification reaction using dimethyl sulfoxide is very specific.

Example 11 According to a method similar to that of Example 1, E having an ethylene content of 32 mol%
Using 100 g of VA ([η] ph = 0.111 l / g), 96 g of methanol and 1788 g of dimethyl sulfoxide, the reaction was carried out at a reaction temperature of 40 ° C. for 2 minutes using 2.0 g of sodium hydroxide as a methanolysis catalyst. The same post-treatment as in Example 1 was carried out to obtain a partially saponified EVOH having a saponification degree of 76.5 mol%. The melting point of the obtained EVOH is
The block character was 116.4 ° C. and the block character was 0.345. As a control (Comparative Example 9), the reaction was carried out at a reaction temperature of 40 ° C. for 90 minutes in the same manner except that methanol was used instead of dimethyl sulfoxide of Example 11, and the same post-treatment was performed. , Saponification degree 76.5
A mole percent of partially saponified product was obtained. The melting point of the obtained EVOH is 143.8 ° C., and the block character is 0.118.
Met. As described above, when saponified with a DMSO solvent system, the melting point is lowered even with the same degree of saponification as compared with saponification with a MeOH solvent system.
It can be seen that the distribution of residual acetyl groups in H is more random (sharper).

[0044]

[Table 1]

[0045]

According to the present invention, the reaction rate of alcoholysis is increased as compared with the solvent system of lower alcohol alone, and the alcoholysis reaction system is maintained in a substantially uniform liquid phase. The quality of the resulting ethylene-vinyl alcohol copolymer is also uniform. Also, the decrease in the rate of alcoholysis reaction with the increase in ethylene content was slight,
Interestingly, the reaction rate ratio (reaction rate when dialkyl sulfoxide is used / reaction rate when methanol is used) is higher than when methanol solvent is used.
Shows an increasing tendency with an increase in ethylene content. Therefore, the present invention is extremely effective for the alcoholysis reaction of high ethylene EVA.

[Brief description of the drawings]

FIG. 1 is a graph in Example 2 and Comparative Example 1, in which the abscissa represents the saponification time (minutes) and the ordinate represents the saponification degree (%) of EVOH.

FIG. 2 is a graph in Examples 7 to 10 in which the abscissa is the saponification time (minutes) and the ordinate is the degree of saponification (%) of EVOH.

FIG. 3 is a graph in Comparative Examples 4 to 8, in which the abscissa represents the saponification time (minutes) and the ordinate represents the saponification degree (%) of EVOH.

FIG. 4 shows the results obtained in Examples 7 to 10 and Comparative Examples 4 to 8.
It is a graph with the ethylene content (mol%) of EVOH on the horizontal axis and the reaction rate ratio (DMSO-based saponification / MeOH saponification) on the vertical axis.

[Explanation of symbols]

 1 Curve of Example 2 2 Curve of Comparative Example 1

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akimasa Aoyama 1621 Sazu, Kurashiki City, Okayama Prefecture Inside Kuraray Co., Ltd. (72) Inventor Ken Moriya 1621 Sazu, Kurashiki City, Okayama Prefecture Kuraray Co. 56) References JP-A-49-71082 (JP, A) JP-A-5-78404 (JP, A) JP-A-59-80446 (JP, A) JP-A-3-287630 (JP, A) Sho-36-4539 (JP, B1) JP-B-43-5893 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 8/12

Claims (2)

(57) [Claims] 1. A process for producing an ethylene-vinyl alcohol copolymer by alcoholysis of an ethylene-vinyl ester copolymer, using dialkyl sulfoxide as a solvent and distilling off by-produced esters out of the reaction system.
One, ethylene characterized by alcoholysis in the liquid phase - method for producing vinyl alcohol copolymer. 2. An air having an ethylene content of 0.1 to 70 mol%.
By alcoholysis of the Tylene-vinyl ester copolymer
When producing ethylene-vinyl alcohol copolymer
And use dialkyl sulfoxide as the solvent
Ethylene-vinyl, characterized by alcoholysis with
A method for producing an alcohol copolymer.