JPH0578404A - Production of ethylene-vinyl ester copolymer, ethylene-vinyl alcohol copolymer and molded product - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer, having a wide ethylene content and a high polymerization degree and alcoholysis rate by copolymerizing ethylene with a vinyl ester in the presence of a radical polymerization initiator using a dialkyl sulfoxide as a polymerization solvent. CONSTITUTION:Ethylene and a vinyl ester (e.g. vinyl acetate) are copolymerized in the presence of a radical polymerization initiator (e.g. azobisisobutyronitrile) using a dialkyl sulfoxide (e.g. dimethyl sulfoxide) as a polymerization solvent. The dialkyl sulfoxide is then added to the polymerization solution to distill away and remove the residual monomer from the polymerization system kept in a state of a liquid phase and <=500 P viscosity. The residual solution is introduced into pure water to precipitate the produced copolymer, which is then washed, separated and dried to afford an ethylene-vinyl ester copolymer. The resultant copolymer is then subjected to alcoholysis in the liquid form with methanol, etc., in the presence of an alkali by using the dialkyl sulfoxide as a solvent. Thereby, the objective ethylene-vinyl alcohol copolymer is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an ethylene-vinyl ester copolymer, a method for producing an ethylene-vinyl alcohol copolymer and a method for producing a molded article.

[0002]

(1) Ethylene-vinyl ester, especially ethylene-vinyl alcohol copolymer obtained by saponifying vinyl acetate copolymer has an ethylene content of 25-45.
The copolymer having a mol% and an intrinsic viscosity [η] ph of 0.099 to 0.110 liter / gram (hereinafter, liter / gram is referred to as 1 / g) has a high gas barrier property of the copolymer. Utilizing its characteristics, it is mainly used in food packaging containers, oil packaging containers, and parts that come into contact with oils, etc., and a significant increase in demand is recognized in conjunction with changes in eating habits.

An ethylene-vinyl alcohol copolymer having an ethylene content of less than 25 mol% is a product having improved water resistance, water absorption and swelling property of a polyvinyl alcohol polymer 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, ethylene content is 25 to 45
[Η] ph 0.099 to 0.110 l / g (1
An ethylene-vinyl alcohol copolymer having a content of 5 wt% water-containing phenol, measured at 30 ° C.) is expected to contribute to various performance improvements in various application fields as a product having improved durability and mechanical strength. As described above, an ethylene-vinyl alcohol copolymer having a lower ethylene content or a higher ethylene content than a conventionally known ethylene content, and an ethylene-vinyl alcohol copolymer having a higher polymerization degree than a conventionally known degree of polymerization are conventionally available. Since it has the possibility of exhibiting excellent performance that cannot be achieved with a copolymer having an ethylene content and a degree of polymerization, it is desired to develop an inexpensive and rational production method thereof.

It has been conventionally known that alcohol such as methanol and t-butanol is mainly used as a polymerization solvent in the case of solution polymerization when copolymerizing ethylene and vinyl ester. Heretofore, in the method for producing an ethylene-vinyl ester copolymer, there is no disclosure of using dimethyl sulfoxide as a polymerization solvent. In the conventional method,
When alcohol such as methanol is used as the polymerization solvent, 50
In the temperature range below ℃, the ethylene content of the polymer is 5
It has been confirmed that when the ethylene content is as high as 0 mol% or more, even if the solvent is present in the polymerization system in an amount of about 20% by weight, the polymer is precipitated in the system to form a non-uniform solution. When considering, it is inconvenient in operation. Further, in the case of solution polymerization, it is known that the higher the concentration of the solvent in the polymerization system, the lower the degree of polymerization of the polymer obtained. In order to obtain a polymer having a high degree of polymerization, conventionally known methanol, etc. In the case of the solvent (1), it is necessary to carry out unfavorable treatments such as lowering the polymerization temperature, suppressing the polymerization rate, and suppressing the amount of methanol added. Further, in the case of copolymerization at a high temperature of 60 ° C. or higher, the reaction heat becomes large, and it is difficult to maintain a uniform temperature in the system. Particularly, in a radical polymerization system, there is a large risk of a runaway reaction, and a suitable polymerization method is required. I can't say.

On the other hand, homopolymerization of vinyl acetate using dimethyl sulfoxide is known from Japanese Patent Publication No. 36-3999 (US Pat. No. 3,080,350) and the like.
There is no description of the copolymerization of ethylene and vinyl acetate, and what function dimethylsulfoxide plays in the radical copolymerization of ethylene and vinyl acetate, and what is the internal structure of the resulting copolymer. There is no description of the effect.

(Part 2) As a method for saponifying an ethylene-vinyl ester copolymer, an alcohol solvent such as methanol is used, a homogeneous saponification method using an alkaline catalyst, and a solvent such as an aqueous methanol system is used. Heterogeneous saponification methods using catalysts are known. However, in the saponification reaction using methanol as a solvent, the saponification reaction rate significantly decreases as the ethylene content increases. 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 or a mixture of methanol and a non-solvent in a methanol solution state. It is generally extruded in a mixed solvent, molded into a certain shape such as a strand shape or a chip shape, and then subjected to a primary step of drying to be commercialized. It is advantageous. The ethylene-vinyl alcohol copolymer is melted (dry-molded) or dissolved in a specific solvent (wet-molded) to give a desired shape such as fiber, hollow fiber, film or particle. The second product is formed into the final product. The known general manufacturing method includes various problems to be improved as described below.

1) The ethylene-vinyl acetate copolymer is
The solubility in methanol tends to decrease as the ethylene content increases, and unfavorable conditions such as high temperature and pressurization are necessary for carrying out a homogeneous methanolysis reaction.

2) The ethylene-vinyl alcohol copolymer produced by the methanolysis of the ethylene-vinyl acetate copolymer has an ethylene content of 25 to 45 mol% and has a solubility in methanol on both the low ethylene side and the high ethylene side. Decrease, especially on the low ethylene side
Even in the state of high temperature pressurization exceeding ° C, it is no longer possible to maintain a homogeneous state at a concentration industrially sufficient, and the methanolysis reaction in a homogeneous system cannot be carried out.

3) The methanolysis reaction of ethylene-vinyl acetate copolymer has a slower reaction rate than that of vinyl acetate polymer and requires a large amount of catalyst and methanol. In combination with 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, capital investment for reactors, etc. will increase, leading to an increase in manufacturing costs.

Further, according to the conventional research, ethylene-
The vinyl acetate copolymer is difficult to hydrolyze when the content of vinyl acetate is 40 mol% or less because of its extremely low solubility.
o 3344129) reports that the alcoholysis of these polymers in methanol or ethanol is very slow because the solubility of the polymers in the solvent is extremely small. Then, a heterogeneous substance containing both hydrolyzed molecules and non-degraded molecules in the same reaction product is obtained. According to Bestian, the Roland method (US Pat. No. 2,386,347), which uses a mixture of aromatic hydrocarbons and alcohols as 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 aromatic hydrocarbon required is extremely large, which is uneconomical and the reaction rate thereof is extremely slow. To overcome these problems, Bestian describes improved solubility by using an alcohol having 4 to 8 carbon atoms as a reaction solvent, but suggests the use of high temperature.

In US Pat. No. 3,080,350 to Imai et al. (Japanese Examined Patent Publication No. 36-4539), vinyl acetate is polymerized using dimethylsulfoxide, which is an aprotic solvent having a large polarity. Although a method of hydrolyzing or alcoholysis into alcohol is described, there is no description of copolymerizing ethylene and vinyl acetate, and further obtaining alcohol ethylene-vinyl alcohol by alcoholysis of the copolymer. Also, there is no description of what function dimethyl sulfoxide plays in alcoholysis of an ethylene-vinyl acetate copolymer, and how it affects the resulting ethylene-vinyl alcohol copolymer.

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

Further, US Pat. No. 378,000 to John et al.
4 (JP-A-49-71082) and the like, the alcoholysis reaction of an ethylene-vinyl ester copolymer is carried out in an aprotic reaction medium such as dimethylformamide and dimethylsulfoxide, and in some cases, a hydrocarbon-based reaction medium is used in combination. However, a method for carrying out an alcoholysis reaction in a solid phase is also disclosed, but the disclosure in a homogeneous liquid phase is not found.

(Part 3) Ethylene-produced by methanolysis reaction of ethylene-vinyl acetate copolymer in methanol solvent using sodium hydroxide as a catalyst
The vinyl alcohol copolymer is in the state of methanol solution,
It is extruded into a non-solvent of the copolymer centered on water or a mixed solvent of methanol and a non-solvent, molded into a strand shape, a chip shape, etc., and dried to obtain a product. The product is subjected to secondary molding in a desired shape such as fiber, hollow fiber, film, sheet, or particle in a molten (dry molding) or a solution (wet molding) dissolved in a specific solvent final Become a product. Such known general molding methods are described in 1), 2),
In addition to 3), it includes the following problems.

4) The ethylene-vinyl alcohol copolymer does not have sufficient thermal stability and is liable to be thermally deteriorated by drying for a long time after extrusion molding into an aqueous system, so-called gel at the time of secondary molding, It is easy to generate heat-deteriorated products that cause spots.

5) The degree of polymerization is [η] ph 0.099-0.
An ethylene-vinyl alcohol copolymer having a high degree of polymerization of more than 10 l / g has a high solution viscosity, tends to form a gel-like substance at the time of drying, etc., and tends to leave an undissolved part at the time of re-dissolution.

(Part 4) The ethylene-vinyl alcohol copolymer produced by the methanolysis reaction is extruded in a state of a methanol solution into a non-solvent of the copolymer represented by water or a mixed solvent of methanol and a non-solvent. It is then formed into a strand, a chip, etc., dried and then commercialized. The product is secondary molded into a desired shape such as fiber, hollow fiber, film, sheet or particle in the state of melting (dry molding) or a solution dissolved in a specific solvent (wet or dry-wet molding). Will be the final product. The known general manufacturing method includes the following problems in addition to the above 1) to 5).

6) In the ethylene-vinyl ester copolymer system containing methanol, the degree of polymerization of the ethylene-vinyl ester copolymer produced decreases with an increase in the coexisting amount of methanol. Therefore, in order to suppress the decrease in the degree of polymerization, it is necessary to carry out unfavorable treatments such as lowering the polymerization temperature, suppressing the polymerization rate, and suppressing the amount of methanol added.

7) Even if attempts are made to obtain EVOH having a wide range of ethylene content, it is extremely difficult to obtain EVOH having a high ethylene content because the upper limit of ethylene content is limited in polymerization using methanol.

[0020]

The first problem is to solve the above-mentioned problem (1) and to set the range of conventionally known production standards (ethylene content rate, degree of polymerization) of ethylene-vinyl ester copolymers. It is expanding and establishing a cheap and rational manufacturing method.

The second problem is to solve the above-mentioned problem (No. 2) and to establish a cheaper and more rational production method of a conventionally known ethylene-vinyl alcohol copolymer.

A third problem is to solve the above-mentioned problem (3), and is cheaper and more rational than a conventional method for producing an ethylene-vinyl alcohol copolymer molded article. Is to establish a manufacturing method.

The fourth problem is to solve the above-mentioned problem (No. 4), expand the range of conventionally known production standards (ethylene content, degree of polymerization) of ethylene-vinyl alcohol copolymer, and be inexpensive and rational. To establish a method for producing a specific ethylene-vinyl alcohol copolymer molded article.

[0024]

Means for Solving the Problem The means for solving the above-mentioned first problem is to use ethylene glycol by using dialkyl sulfoxide as a polymerization solvent when copolymerizing ethylene and vinyl ester in the presence of a radical initiator. It is a method for obtaining a vinyl ester copolymer.

That is, according to the present invention, an ethylene-vinyl ester copolymer having a small decrease in the degree of polymerization can be obtained, and the dialkyl sulfoxide is a good solvent for the produced ethylene-vinyl ester copolymer. Therefore, the ethylene-vinyl ester copolymer is capable of maintaining a uniform polymerization system over a wide range of ethylene content, and also adjusts the dialkyl sulfoxide concentration in the system in the subsequent unreacted vinyl ester removal step. By doing so, a uniform solution state can be maintained as it is, and stable continuous process can be realized.

According to the studies by the present inventors, methanol 20
When an ethylene-vinyl acetate polymer (EVA) having an ethylene content of 60 mol% is tried to be reacted in a system of 50 parts by weight of vinyl acetate and 80 parts by weight of vinyl acetate, the polymerization system is changed from a stage of low polymerization rate. While EVA was precipitated and the polymerization system became non-uniform, in the case of the dimethylsulfoxide system according to the above-mentioned set conditions, precipitation of the polymer into the polymerization system was not observed even at a polymerization rate of about 70%. Further, the reaction was carried out in a system of 10 parts by weight of methanol and 90 parts by weight of vinyl acetate at 40 ° C., and the polymer obtained at a polymerization rate of 20% was saponified. ] Ph is 0.
In comparison with 135 liter / g, in the reaction under the same conditions with dimethylsulfoxide solvent, EVOH [η] ph was 0.149 l / g when compared under the same conditions of polymerization rate, polymerization rate and ethylene content. there were. These experimental facts show that a copolymer having a higher intrinsic viscosity can be obtained when ethylene and vinyl ester are copolymerized with dimethylsulfoxide as a polymerization solvent, as compared with methanol. [Η] ph of EVOH obtained by saponifying the ethylene-vinyl ester copolymer obtained by the present invention is preferably 0.4 l / g or less, more preferably 0.35 l / g or less, further 0.3 l / g. g or less. Further, the lower limit is preferably 0.05 l / g or more, further 0.06 l / g or more, further 0.07 l
/ G or more.

The production of the copolymer by the copolymerization reaction of ethylene and vinyl ester in the present invention is carried out under pressure of ethylene with respect to a mixed solution of vinyl ester in which 1% by weight or more of dialkyl sulfoxide is present in the polymerization system. It is carried out by adding a radical initiator. The ethylene content and the intrinsic viscosity of the copolymer are variously changed depending on the ethylene pressure of the polymerization system, the polymerization temperature, the polymerization rate, the polymerization rate, the composition of the vinyl ester monomer and the solvent, etc., and the ethylene content and the intrinsic viscosity of the copolymer are desired. Strict adjustment of the above conditions is required for acquisition.

The ethylene content of the copolymer in the present invention is preferably 0.1 to 80 mol%. When the ethylene content of the copolymer is less than 0.1 mol%, the ethylene-vinyl alcohol copolymer obtained by saponification does not substantially exhibit the effect of improving performance such as water resistance as compared with polyvinyl alcohol. The preferred ethylene content is 1 mol% or more,
Further, it is 5 mol% or more, 10 mol% or more, and further 20 mol% or more. Further, when the ethylene content exceeds 80 mol%, the copolymer is difficult to dissolve in dimethylsulfoxide, which is not suitable. Judging from the solubility of the copolymer, a copolymer having an ethylene content of 70 mol% or less is more desirable.

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 also vinyl propionate. Further, in the present invention, an ethylenic unsaturated monomer copolymerizable with ethylene and vinyl ester other than ethylene and vinyl ester may be used within a range not impairing the object of the present invention. Here, as the ethylenically unsaturated monomer, for example, “Poval (revised new edition)” (Kobunshi Kogakukai, published April 1, 1981) 28
The monomers described on pages 1-285 and references cited therein can be exemplified as typical examples.

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

The dialkyl sulfoxide used in the present invention is composed of a lower alkyl group, and includes ethylene-
From the viewpoint of solubility in vinyl ester copolymers and ethylene-vinyl alcohol copolymers, the lower alkyl group preferably has 3 or less carbon atoms. Specific examples of the dialkyl sulfoxide include dimethyl sulfoxide, diethyl sulfoxide, di i-propyl sulfoxide, di n-propyl sulfoxide, methyl ethyl sulfoxide, methyl i-propyl sulfoxide, and the like. -Obtaining a vinyl ester copolymer, further thermal,
It is particularly preferable because it has excellent chemical safety and is easily available. The water content in the dialkyl sulfoxide is preferably 2% by weight or less, more preferably 1% by weight or less.

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

The content of the dialkyl sulfoxide in the polymerization system (content of the dialkyl sulfoxide with respect to the total amount of the dialkyl sulfoxide and the vinyl ester) is preferably 1% by weight or more, and the polymerization depends on the ethylene content of the desired EVA and the intrinsic viscosity. Considering the heat removal of the system, the stability considering the prevention of abnormal polymerization, the retention of a homogeneous solution state, the method of charging the radical initiator, etc., 3% by weight or more, and further 5
Weight% or more is suitable.

When the content of the dialkyl sulfoxide in the polymerization system is less than 1% by weight, it becomes substantially the same as in the case of bulk polymerization, it is difficult to prevent the occurrence of abnormal polymerization reaction, and the radical initiator is easily charged. Not preferable. The upper limit of the content of dialkyl sulfoxide is not particularly limited, but from the viewpoint of the production efficiency of the copolymer, it is preferably less than 80% by weight, and more preferably less than 70% by weight. A copolymer having an ethylene content of 0.1 to 80 mol% is produced by setting the ethylene pressure in consideration of the desired intrinsic viscosity of the polymer and the polymerization conditions, so that the ethylene pressure is uniquely determined. Although it cannot be done, a pressure from normal pressure to about 100 kg / cm ² is general. The polymerization temperature is closely related to the intrinsic viscosity and ethylene content of the copolymer, but it is about 0-8.
It is selected from the range of 0 ° C. When a copolymer having a normal intrinsic viscosity is obtained, it is selected from the range of 40 to 80 ° C, and when a copolymer having a higher intrinsic viscosity is obtained, it is selected from a lower temperature, for example, a polymerization temperature of 40 ° C or less. It

As the radical initiator used in the present copolymerization, 2,2'-azobisisobutyronitrile, which is conventionally known,
An azo compound such as 2,2′-azobis- (4-methoxy-2,4-dimethylvaleronitrile) and a peroxide such as benzoyl peroxide and isopropyl peroxydicarbonate can be used as they are. The amount of the initiator used is 0.001 to 1.0% by weight, preferably 0.01 to 0.5% by weight, based on the vinyl ester monomer. The removal of the heat of polymerization is controlled by adjusting the amount of the initiator charged, and the rate of polymerization related to the intrinsic viscosity of the copolymer is adjusted.

As the polymerization method in the present invention, any of batch reaction method, semi-batch reaction method and continuous reaction method can be adopted. From the viewpoint of stability, it is desirable to use the continuous method.

A homogeneous solution consisting of the copolymer produced by the main copolymerization, unreacted vinyl ester monomer, ethylene, dialkyl sulfoxide, and a trace amount of the initiator may be dissolved ethylene in the solution after deactivating the initiator, if necessary. Collect,
The vinyl ester monomer is sent to the unreacted vinyl ester monomer recovery step in the next step to recover the vinyl ester monomer. In this recovery system, it is possible to appropriately add a dialkyl sulfoxide in consideration of the viscosity of the recovery system and recover the vinyl ester monomer in a substantially uniform liquid phase while keeping the solution viscosity within a specific range. The solution viscosity of the polymerization system is preferably 500 poise or less, preferably 300 poise or less, and more preferably 100 or less. The lower limit is not particularly limited, but is about 1 poise. In this recovery operation, in consideration of the thermal stability of the vinyl ester monomer, the temperature of the can solution is generally kept at 100 ° C, preferably 80 ° C or lower, and the pressure is kept at normal pressure or reduced pressure (in any case, the boiling point of the vinyl ester or higher). It is preferable to carry out under the condition). A lower alcohol used as a reaction agent for alcoholysis in the subsequent saponification step is added to this recovery system, and the azeotropy of the vinyl ester monomer and the lower alcohol, particularly methanol, is used to recover the vinyl ester, for example, vinyl acetate monomer, at low temperature and at normal temperature. Carrying out under pressure is also one of the preferred embodiments. The present recovery system is carried out by using a stirring tank type, a tower type, the use of a thin film evaporator, and the like, but the tower type and the thin film evaporator are preferably used from the viewpoints of recovery efficiency, equipment investment, continuous processing, and the like. Since the residual vinyl ester monomer may also become a coloring factor in the subsequent alcoholysis step, it is preferable to reduce the residual amount in the solution subjected to the monomer recovery treatment to 0.5 wt% or less, further to 0.2 wt% or less.

An ethylene-vinyl alcohol copolymer (EVOH) can be obtained by saponifying an ethylene-vinyl ester copolymer such as EVA obtained according to the present invention. The saponification method is a usual method. Either alkali saponification or acid saponification can be adopted, but the saponification method using an alkali catalyst such as caustic soda or sodium methylate in a methanol solvent is most suitable. In the saponification reaction, the methanol solvent may contain a dialkyl sulfoxide such as dimethyl sulfoxide used in the polymerization.

Next, the means for solving the above-mentioned second problem is that in the alcoholysis of an ethylene-vinyl ester copolymer, a dialkyl sulfoxide is used as a solvent, and the alcoholysis in a liquid state is carried out to obtain an ethylene-vinyl alcohol copolymer. It is a way to get coalesced. Such a method realizes significantly accelerated alcoholysis as compared with the conventional method. By the implementation of the present invention, the above problem (2) in the conventional method is rationally solved,
An inexpensive 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 in conventionally known methanol, and shows a specific dissolution behavior of the solvent in an ethylene-vinyl ester copolymer and an ethylene-vinyl alcohol copolymer. By effectively utilizing it, even if the ethylene content and the intrinsic viscosity are increased from the conventional specifications, a reaction in a uniform state is always realized.

The present invention is carried out by uniformly dissolving the ethylene-vinyl ester copolymer in a mixed system of a dialkyl sulfoxide and a lower alcohol. According to the detailed study by the present inventors, the ethylene-vinyl ester in the present invention is examined. It was found that the alcoholysis reaction rate of the ester copolymer was increased as compared to the solvent system of lower alcohol alone. The ethylene-vinyl ester copolymer generally has a smaller reaction rate than the vinyl ester homopolymer, and is forced to adopt unfavorable conditions such as an increase in the reaction temperature and an increase in the amount of the alkaline catalyst used. By the completion of
It is possible to carry out the reaction under mild conditions.

In the conventional solvent system of lower alcohol alone, the solubility of ethylene-vinyl alcohol produced by alcoholysis in the lower alcohol is low. Therefore, in order to carry out the alcoholysis reaction in a homogeneous system, the reaction temperature should be raised. We could not take any measures other than to improve the solubility. Due to the solubility limitation, homogeneous alcoholysis of ethylene-vinyl acetate copolymers having an ethylene content of about 25 mol% or less and about 45 mol% or more is very difficult by a conventionally known method, and in some cases it is substantially impossible. Exists. The present invention also provides a solution to such a situation. Dialkyl sulfoxide is a good solvent for both ethylene-vinyl ester copolymers and ethylene-vinyl alcohol copolymers, can hold the reaction system uniformly without raising the temperature of the reaction system, and causes catalyst deactivation due to temperature rise. Undesirable phenomena such as increase and thermal deterioration of the copolymer can be avoided.

In the present invention, alcoholysis proceeds in a liquid phase, and the liquid phase here 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 it is necessary to bring the alcoholysis equilibrium to the production system side in order to increase the degree of saponification. Therefore, efficient distillation of the ester, for example, acetic acid ester, out of the system is desired. Detailed studies by the present inventors have revealed that the dialkyl sulfoxide coexisting in the present reaction system has an effect of improving the separation efficiency of the acetate ester and the lower alcohol. The distillative removal method of the mixture includes distillation removal under reduced pressure in a tank system, and in a tower system, ethylene dissolved in a dialkyl sulfoxide from the middle stage of the reaction tower.
A method in which a vinyl ester copolymer is introduced and a lower alcohol is blown into the alcohol vapor to carry out a saponification reaction, and a lower alcohol and a fatty acid alcohol ester are distilled from the upper step can be recommended as a preferred embodiment. If such an effect is utilized, the number of separation stages of the distillation column and the reflux ratio required for the separation of the mixture can be significantly reduced, and it contributes greatly to the reduction of equipment cost and utility cost.

The degree of saponification of the ethylene-vinyl alcohol copolymer can be variously changed depending on the final use, and is preferably 20% or more, and more preferably 50% or more. When used, the saponification degree is preferably 99.0% or more, more preferably 99.5% or more. The dialkyl sulfoxide used in this reaction system is composed of a lower alkyl group, and the carbon number of the lower alkyl group is generally preferably 3 or less from the viewpoint of solubility in the ethylene-vinyl ester copolymer and the ethylene-vinyl alcohol copolymer. Specific examples of the dialkyl sulfoxide include dimethyl sulfoxide, diethyl sulfoxide, di i-propyl sulfoxide, di n-propyl sulfoxide, methyl ethyl sulfoxide, methyl i-propyl sulfoxide, and the like. If you take into consideration the acquisition price,
Dimethylsulfoxide and diethylsulfoxide are preferable, and dimethylsulfoxide is particularly preferable from the comprehensive judgment of the above conditions. The amount of the dialkyl sulfoxide used is not particularly limited as long as it is an amount that uniformly dissolves the ethylene-vinyl ester copolymer and the ethylene-vinyl alcohol copolymer, but considering the solution viscosity and the like, the ethylene-vinyl ester copolymer is used. The concentration of the combined product as a dialkyl sulfoxide solution is preferably 0.1 to 70% by weight (based on the total amount of 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 agent for alcoholysis. Although a method for producing an ethylene-vinyl alcohol copolymer by an alcoholysis reaction of an ethylene-vinyl ester copolymer is known, as compared with polyvinyl acetate, which is a homopolymer of vinyl acetate, the reaction rate of the alcoholysis reaction by an alkaline catalyst is known. Is generally small, and the reaction rate tends to decrease with increasing ethylene content. Results of various studies on the alcoholysis reaction of ethylene-vinyl ester copolymer,
For the alcoholysis reaction, the use of lower alcohol is preferable, and it has been judged that the use of primary lower alcohol having 1 to 5 carbon atoms is preferable. Examples of primary lower alcohols 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 ethylene-vinyl ester, etc., the use of methanol or ethanol is preferable, and the use of methanol is particularly preferable 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. 1.0 to 50 times mol, 1.5 to 30 times mol is preferable, considering the reaction equilibrium of alcoholysis, post-treatment cost of charged lower alcohol, etc., with respect to the mol number calculated from 20 can be disclosed as a more preferable range.

The alcoholysis reaction of the present invention is carried out in the presence of an alkaline catalyst. As the alkaline catalyst, polyvinyl alcohol or an ethylene-vinyl ester copolymer conventionally used in alkaline alcoholy reaction is used. 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, sodium methylate, alkali metal alcoholates such as potassium t-butoxide, 1,8-diazabicyclo [5,4,0]. ] A strongly basic amine represented by undecene-7 (DBU),
Furthermore, although alkali metal carbonates, alkali metal hydrogencarbonates and the like can be disclosed, sodium hydroxide is preferably used because of its ease of handling and catalyst cost. The amount of the catalyst used varies depending on the required degree of saponification, the reaction temperature, etc., but is generally a molar ratio of 0.001 to 1.0 per mol calculated from the average molecular weight of the ethylene-vinyl ester copolymer.

The reaction temperature for the alcoholysis in the present invention may be any temperature from room temperature to about 150 ° C., if necessary, but in order to obtain a high reaction rate in a normal pressure reaction system, it is 40 to 120 ° C. 50 to 100 ° C. is recommended as a suitable temperature range. The alcoholysis reaction of the ethylene-vinyl ester copolymer may be a stirring tank type, a tower type or the like, but 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 acetic ester is withdrawn from the upper stage can be recommended as one of the preferred embodiments.

In the present invention, it is preferable to carry out the 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, because the degree of polymerization is less lowered. In order to keep the oxygen concentration in the reaction system below this level, there is a method of substituting with nitrogen gas having a purity of 99.9% or more, or after heating to 60 ° or more and then substituting with nitrogen or argon.

Next, means for solving the third problem are as follows.
Ethylene-vinyl ester copolymer (A) is used as a solvent, dialkyl sulfoxide is used, and alcoholysis is performed in a solution to obtain ethylene-vinyl alcohol copolymer (B).
Process for producing solution ... Process (I)

Step of contacting the solution of the copolymer (B) in the step (I) with a non-solvent of the copolymer (B) or a mixed solvent having a non-solvent content of at least 20% by weight or more ... A process for producing the above-mentioned copolymer (B) molded product, which comprises the combination of the step (II).

The present invention uniformly dissolves in a dialkyl sulfoxide and a lower alcohol coexisting system as a reaction reagent, and carries out an alcoholysis reaction with an alkaline catalyst.
The ethylene-vinyl alcohol copolymer (B) is obtained as a uniform solution. After the concentration of the homogeneous solution is adjusted as necessary, the solution state is not subjected to the first precipitation step of the copolymer (B) into a strand shape or a chip shape, which is conventionally performed by a known method. Secondary molding (wet or dry-wet molding) into an arbitrary shape (fibrous shape, hollow fiber shape, film shape, sheet shape, particle shape, etc.) as it is. By implementing the present invention, the above-mentioned problems pointed out in the conventional method can be rationally solved, and an inexpensive product cost can be realized. In the present invention, dialkyl sulfoxide is used as a solvent for the reaction system in conventionally known methanol, and the unique dissolution behavior of the solvent in the copolymers (A) and (B) is effectively used to obtain ethylene. Even if the content and degree of polymerization are increased from the conventional specifications, the reaction in a uniform state is always realized, the process is stabilized, and the copolymer (B) maintains a solution state without isolation during the process. By sending it to the final molding step, the deterioration of the reaction system and molding is suppressed as much as possible, which contributes to the stabilization of quality. The conditions for alcoholysis are the same as those described above.

The solution of the copolymer (B) thus obtained is neutralized and deactivated with an alkaline catalyst after confirming the degree of saponification of the copolymer (B), and if necessary, the concentration of the solution of the copolymer (B). Make adjustments. The boiling point of dialkyl sulfoxide is generally higher than the boiling points of lower alcohols and fatty acid lower alcohol esters, and it is possible to obtain copolymer (B) as a solution of copolymer (B) in dialkyl sulfoxide.
It is also possible to use a dialkyl sulfoxide solution containing a small amount of a lower alcohol or a fatty acid lower alcohol ester. The copolymer (B) -containing dialkyl sulfoxide solution that has been subjected to such treatment is sent to a molding step and contacted with a non-solvent of the copolymer (B) or a mixed solvent having a non-solvent content of at least 20% by weight or more. Fiber, hollow fiber, film, sheet, particle, strand,
It is wet-molded or dry-wet molded into a desired shape such as a spherical shape. When the content of the non-solvent is less than 20% by weight, the elution of the copolymer (B) into the non-solvent containing system is increased, and wet or dry-wet molding by coagulation is incomplete, which is not preferable. The content ratio of the non-solvent is preferably 40% by weight or more, and more preferably 50% by weight or more from the viewpoint of completely coagulating the copolymer (B). Although the solidification temperature depends on the shape at the time of molding, it is generally -20.
C. to 100.degree. C., and -10.degree. C. to 50.degree. C. can be recommended as a more suitable range. Furthermore, in the present invention, the solution of the dialkyl sulfoxide of the copolymer (B) is extruded onto, for example, a substrate, and then the non-solvent of the copolymer (B) or the content of the non-solvent is at least 20% by weight or more. It is also possible to obtain a molded product by contacting (for example, dipping) with a mixed solvent. Molded products obtained by the above-mentioned wet or dry-wet molding, in particular, particulates, spherical materials as they are, or strands as pellets cut into a desired size, and melt-molded, Can be formed into a fibrous shape, a hollow fiber shape, a film shape, a sheet shape, or a bottle shape by wet molding, dry molding, or dry wet molding.

As the non-solvent of the copolymer (B), although the effect varies depending on the ethylene content, water, lower alcohols such as methanol and ethanol, esters such as methyl acetate and ethyl acetate, acetone, diethyl ketone and the like. Examples thereof include ketones, ethers such as ethylene glycol dimethyl ether, and other solvents having compatibility with dialkyl sulfoxide, and mixtures thereof. In the case of the copolymer (B) having a low ethylene content, alcohols centering on methanol, ketones such as acetone, esters such as methyl acetate are generally effective, and copolymers having a high ethylene content ( In B), water and esters such as methyl acetate are effective. By adopting the present wet or dry-wet molding method, it is possible to prevent the formation of gels and lumps due to thermal deterioration mainly during the drying in the conventional method, and it is significant to improve the product performance. Typical examples of the solvent used in combination with the non-solvent include dialkyl sulfoxide, particularly dimethyl sulfoxide.

The molded product molded by the above method is a high-performance EVOH fiber with improved water resistance, an EVOH hollow fiber membrane having excellent permeation performance for artificial kidneys, a high-performance optical film such as a polarizing film, and industrial materials. It is possible to develop various applications such as film for film, barrier encapsulating material with good thermal stability, sealing material, biodegradable material that makes good use of compatibility with starch.

The above-mentioned copolymer (B) molded into various shapes is commercialized by extracting and washing a dialkyl sulfoxide as a solvent, a deactivating catalyst and the like and then drying.

Next, means for solving the fourth problem are as follows.
Step of producing ethylene-vinyl ester copolymer (A) solution by copolymerizing ethylene and vinyl ester in the presence of a radical initiator using dialkyl sulfoxide as a polymerization solvent ... Step (I) ′

From the solution of the copolymer (A) in step (I) ', the step of distilling off the remaining unreacted vinyl ester while the viscosity of the solution is kept at 500 poise or less. II) '

The copolymer (A) obtained in the step (II)
Step of producing ethylene-vinyl alcohol copolymer (B) solution by carrying out alcoholysis of the solution in a liquid state ... Step (III) ′

The solution of the copolymer (B) in the step (III) 'has a non-solvent content of the copolymer (B) of 20 or less.
The step of contacting with a mixed solvent of dialkyl sulfoxide / non-solvent in an amount of not less than wt.

The polymerization step of step (I) 'of the present invention, (I
The step of distilling off the residual monomer of I) ′, the alcoholysis step of (III) ′, and the step of contacting with the non-solvent of (IV) ′ are as described above.

The present invention uses a dialkyl sulfoxide as a reaction solvent for polymerization and saponification (methanolysis) with respect to conventionally known methanol, and effectively utilizes the peculiar behavior of the solvent in the polymerization system. It is possible to produce a copolymer with a small decrease in the degree of polymerization, and even if the ethylene content and the degree of polymerization are increased from the conventional specifications, a reaction in a uniform state is always realized and the process is stabilized and shortened. It is a thing. In addition, according to the present invention, the copolymer (B) can be allowed to undergo a reaction under mild conditions while maintaining a solution state without being isolated during the process, and can be directly used as a product for wet or dry wet molding. it can. In this case, since many molding steps are not performed, (thermal) deterioration of the copolymer resulting from the steps can be suppressed as much as possible, and the quality can be stabilized.

Further, according to the detailed study by the present inventors, the present invention has constructed an ethylene-vinyl ester copolymer system in which the degree of polymerization is smaller in a dialkyl sulfoxide solvent system than in a methanol solvent system [Step ( I) '].
In addition, since the dialkyl sulfoxide is generally a good solvent for the copolymer (A) to be produced, this copolymer system can maintain a uniform reaction system over a wide range of ethylene content. Also in the unreacted vinyl ester removing step [step (II) '], the viscosity of the solution is adjusted to 50 by adjusting the concentration with the dialkyl sulfoxide in the system.
Since it is 0 poise or less, a uniform solution state can be maintained as it is, and stable continuous process can be realized.

The step (III) ′ in the present invention is the step (I
Although the alcoholysis reaction is carried out in a homogeneous solution system in which a lower alcohol as a reaction reagent is added to the dialkyl sulfoxide solution of the copolymer (A) obtained in I) ′, according to the detailed study by the inventors, It was found that the alcoholysis reaction rate of the copolymer (A) in the present invention is increased as compared with the solvent system of lower alcohol alone. As described above, the copolymer (A) generally has a lower reaction rate than the vinyl ester homopolymer, and it is inevitable to set unfavorable conditions such as an increase in the reaction temperature and an increase in the amount of the alkaline catalyst used. The completion of the reaction allows the reaction to be carried out under mild conditions.

Since the solubility of the copolymer (B) produced by the alcoholysis in the lower alcohol is low in the solvent system of the conventionally known lower alcohol alone, the reaction temperature is increased in order to carry out the alcoholysis reaction in a homogeneous system. However, no measures could be taken other than to improve the solubility. Due to the limitation of the solubility, the ethylene content is 2 in the conventionally known method.
In some cases, homogeneous alcoholysis of the copolymer (A) in an amount of 5 mol% or less and 45 mol% or more is very difficult and substantially impossible in some cases. The present invention also provides a solution to such a situation. Dimethyl sulfoxide is a good solvent for both the copolymers (A) and (B) and can hold the reaction system uniformly without raising the temperature of the reaction system, increasing catalyst deactivation due to temperature increase, and Undesirable phenomena such as thermal deterioration can be avoided.

Further, in the reaction system of the present invention, a lower alcohol ester of a fatty acid is by-produced by the alcoholysis reaction, and it is necessary to bring the alcoholysis equilibrium to the production system side. Therefore, efficient distillation of the fatty acid ester out of the system is desired. Detailed studies by the present inventors have revealed that dimethyl sulfoxide coexisting in this reaction system has an effect of improving the separation efficiency of fatty acid ester and lower alcohol. If such an effect is utilized, the number of separation stages of the distillation column and the reflux ratio required for the separation of the mixture can be significantly reduced, and it contributes greatly to the reduction of equipment cost and utility cost.

The molded article molded according to the present invention is a high-performance EVOH fiber having improved water resistance, an EVOH hollow fiber membrane having superior permeation performance for artificial kidneys, a high-performance optical film such as a polarizing film, industrial Various applications are possible, such as material films, barrier-encapsulating materials with good thermal stability, sealing materials, and biodegradable materials that make good use of compatibility with starch.

The above-mentioned copolymer (B) molded into various shapes is commercialized by extracting and washing dimethylsulfoxide as a solvent, a deactivating catalyst, etc., and then drying.

Furthermore, the EVOH obtained by the present invention has a three-dimensional structure specificity derived from DMSO-based polymerization and / or a 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 degree of saponification, obtained by conventional polymerization and / or saponification in lower alcohol
It exhibits physical properties peculiar to the present invention such that the melting point tends to be lower than that of H. This is apparent from Example 7-1 described later. Utilizing this physical property, for example, in melt stretch molding of EVOH, suppression of gel and lump generation due to thermal deterioration, improvement of stretching speed and stretching ratio, reduction of voids and cracks, improvement of thickness unevenness, stable operation for a long time Is expected to contribute to the securing of

The fact that the distribution of residual ester groups of EVOH obtained by the present invention is more random (sharper) is indicated by the block character, and the larger the value of the block character, the more random (sharper) it is. . EVOH obtained by the present invention
Is preferably 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) means two chains {vinyl alcohol unit-vinyl alcohol unit two chains mole fraction (A
₁₎ + vinyl alcohol units - two chain molar fraction of vinyl ester units (A ₂₎ + vinyl ester units - two chain molar fraction of vinyl ester units (A _3)} Total mole fraction of (A ₁ + A + ₂ shows the ratio of the mole fraction (A ₂ ) of two chains of vinyl alcohol unit-vinyl ester unit to ₂ A ₃ ).

The molar fraction (A ₁ ) of the two chains of vinyl alcohol unit-vinyl alcohol unit is determined from the absorption intensity of the peak in the region of δ of 45.7 to 48 ppm by ¹³ C-NMR spectrum. -The molar fraction (A ₂ ) of vinyl ester units is 8 from 43.5 to
It is determined from the peak absorption intensity in the region of 45.5 ppm. The vinyl ester unit-vinyl ester unit two-chain mole fraction (A ₃ ) is the value obtained by subtracting A ₁ and A ₂ from the value obtained by squaring the mole fraction of the total amount of vinyl alcohol units and vinyl ester units in EVOH. Is required by doing. Further, in the above formula (OH) and (OAC),
The mole fractions of vinyl alcohol units and vinyl ester units in two and more chains, respectively, are shown.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples. In the examples, [η] ph of EVA means EV obtained by completely saponifying EVA (saponification degree of 99.4 mol% or more).
It represents the intrinsic viscosity of OH.

[0072]

【Example】

Example 1 Dimethyl sulfoxide (DMSO) (water content: 0.1% by weight) was added to a high-pressure autoclave equipped with a stirrer and having a volume of 3 L.
52 g, vinyl acetate (VAC) 1009 g (DMSO /
(VAc = 2/8, weight ratio), 0.040 wt% of azobisisobutyronitrile (AIBN) (vs vinyl acetate) was charged, and after sufficient ethylene substitution, a reaction temperature of 60 ° C. and an ethylene pressure of 43 kg / Polymerization was carried out for 5 hours at cm ² G. After the polymerization was completed, 1200 g of DMSO was added to the polymerization solution to evaporate and remove unreacted monomers (50 mmHg or less, 4
0 ° C). The viscosity of the solution immediately after the start of ejection was 12 poises, and the viscosity of the solution at the end of ejection was 21 poises. Further, the solution after the unreacted monomer was removed by evaporation was put into pure water to precipitate EVA. After washing with water, the polymer was further heated and boiled in water to remove unreacted monomers and the solvent for purification, and sufficiently dried to obtain EVA having a polymerization rate of 50% and an ethylene content of 32 mol%. 25 g of this EVA is added to methanol (MeOH) 100
g, and then 10% -caustic soda (N
aOH) methanol solution 29.5 g (NaOH / EVA
= 0.2, molar ratio), and the mixture was kept at 60 ° C. for 0.5 hours, and then 29.5 g of the NaOH solution was added and kept at 60 ° C. for 2 hours to carry out a saponification reaction. The polymer solution obtained here was poured into an aqueous acetic acid solution to cause precipitation and precipitation.
It was left for 5 hours. After draining, the solution was immersed in an acetic acid aqueous solution for 0.5 hours, and finally, immersed in tap water for 0.5 hours and allowed to stand.
The polymer obtained is then crushed, dried thoroughly and then EVO
H was obtained.

The degree of saponification of the EVOH obtained is 99.5.
The [η] ph was 0.119 l / g in mol%. On the other hand, as a control (Comparative Example 1), at 60 ° C., methanol 24
3 g, 972 g of vinyl acetate (MeOH / VAc = 2 /
8, weight ratio), azobisisobutyronitrile 0.104
% By weight (to vinyl acetate) was charged and ethylene substitution was sufficiently performed, and then the reaction temperature was 60 ° C. and the ethylene pressure was 41 kg /
cm ² G, polymerization was carried out for 5 hours, post-treatment was carried out in the same manner as in the case of dimethylsulfoxide system, EVA having a polymerization rate of 50% and ethylene content of 32 mol% was obtained, and saponification was carried out under the conditions similar to those of dimethylsulfoxide system. By carrying out the reaction, the degree of saponification is 99.5 mol%, [η] ph = 0.097 l
/ G of EVOH was obtained. In both polymerization systems, it was confirmed from the state of the sampled polymerization solution during the polymerization that the reaction always proceeded while being kept in a uniform liquid phase. From these results, it is suggested that in the case of solution polymerization using dimethyl sulfoxide as a solvent, a polymer having an intrinsic viscosity higher than that of EVOH obtained by polymerization in a methanol solvent system is obtained.

Examples 2 to 5 Polymerization was carried out under the conditions according to Example 1 while changing the amount of dimethyl sulfoxide used, and the obtained EVA was saponified under the conditions according to Example 1 to obtain EVOH
(Ethylene content 32 mol%, degree of saponification 99.4 to 99.
7 mol%) was measured. Also, as a control,
Bulk polymerization without using dimethyl sulfoxide and solution polymerization with a methanol system were carried out with the same composition as the system of dimethyl sulfoxide (Comparative Examples 2 to 6). The polymerization is
In order to see the influence of the decrease in the intrinsic viscosity, the polymerization rate and the polymerization rate were all the same, and the ethylene pressure was set so that the ethylene content was the same (Table 1, FIG. 1).

[0075]

[Table 1]

As can be seen from Table 1, in both dimethyl sulfoxide and methanol solvents, the higher the solvent composition, the higher the rate of decrease in intrinsic viscosity. In the case of, it is clear that a polymer having an intrinsic viscosity higher than that of a polymer (EVOH) obtained by using a methanol solvent having the same composition can be obtained. In the bulk polymerization of Comparative Example 2, the internal temperature of the polymerization system tended to rise, and careful cooling operation was required.

Examples 6 to 8 2,2'-azobis-2,4-dimethylvaleronitrile (AVN) was used as a polymerization initiator, and the polymerization temperature was 40.
Polymerization saponification was carried out in the same manner as in Example 1 except that the amount of dimethyl sulfoxide used was changed at 0 ° C. In this case as well, as a control, bulk polymerization without dimethyl sulfoxide, solution polymerization in methanol system were polymerized with the same composition as the system of dimethyl sulfoxide, and all were subjected to the same polymerization in order to see the influence of reduction in intrinsic viscosity. The ethylene pressure was set so that the speed and the polymerization rate were adjusted and the same ethylene content was obtained (Comparative Examples 7 to 10). The polymerization conditions and the results are shown in Table 2. As is clear from the comparison with Table 1, the influence of the dimethyl sulfoxide solvent composition on the decrease in the intrinsic viscosity of the obtained EVOH is clear even if the polymerization temperature is lowered. It is clear that the amount is much less than that of the methanol type.
In this case as well, it was confirmed that in both dimethyl sulfoxide-based and methanol-based polymerization systems as in Examples 1 to 5, the reaction proceeded while the system was always kept in a uniform liquid phase (Table 2).

[0078]

[Table 2]

Example 9 639 g of vinyl acetate and 160 g of dimethyl sulfoxide
(DMSO / VAc = 2/8, weight ratio), 2,2′-azobis-2,4-dimethylvaleronitrile (AVN)
Using 0.116% (vs. vinyl acetate), reaction temperature 50
Polymerization was carried out in the same manner as in Example 1 at 70 ° C. and ethylene pressure of 70 kg / cm ² G. During the polymerization, the polymerization solution is sampled at each time, and after the polymerization inhibitor is added, it is evaporated to dryness by an infrared dryer to follow the change with time of the solid content, and to ensure the uniformity of the polymerization system (uniformity of EVA concentration). And precipitation EV
The presence or absence of A) was examined. The homogeneity was also confirmed from the state of the sampling solution. Under the above conditions, EVA having a polymerization rate of 30% was obtained with a polymerization time of 6 hours. Further, the solution after polymerization was saponified according to the method of Example 1 (NaOH / EVA =
0.25, molar ratio x 2 times, other conditions are the same as in Example 1), post-treatment is carried out, ethylene content 60 mol%, saponification degree 99.5%, [η] ph = 0.088 l / g. EVO
H was obtained. The change with time of the solid content is shown in FIG. 2. From the fact that the straight line is obtained, it can be seen that the system always proceeds in a uniform state. Also, the state of the sampling solution was transparent and was uniform without precipitation of polymer.

As a control, a reaction using methanol in place of dimethyl sulfoxide was carried out using 624 g of vinyl acetate,
Using 156 g of methanol and 0.118% of AVN (vs. vinyl acetate), 50 ° C, ethylene pressure 62.5 kg / cm
Performed under ² G conditions. In the case of the methanol type, the polymerization rate is 30 hours and the polymerization rate is
% EVA was obtained. After the saponification reaction according to Example 9, ethylene content 60 mol%, saponification degree 99.5%, [η] ph
= 0.075 l / g of EVOH was obtained. Similar to the dimethylsulfoxide system, the homogeneity of the polymerization system was investigated by following the change with time of the solid content during the polymerization. The results are also shown in FIG. 2. However, the plots varied from a low polymerization rate, and a good linear relationship was not obtained. The state of the sampled solution was cloudy. From this, when dimethyl sulfoxide was used as a solvent during the polymerization of EVA having a high ethylene content,
As compared with the methanol system, it can be seen that the polymerization can proceed while keeping the system always in a uniform state.

It is also understood that the influence of the solvent composition of dimethylsulfoxide on the reduction of the intrinsic viscosity of the EVOH obtained is extremely small as compared with that of the methanol type, even during the polymerization of the high ethylene type polymer.

Examples 10 to 11 Polymerization and saponification were carried out in the same manner as in Example 9 except that the amount of dimethyl sulfoxide used was changed. As a control, solution polymerization and bulk polymerization in a methanol system were also performed (Comparative Examples 11 to 14). All the polymerization conditions were set so that the same polymerization rate, the same polymerization rate, and the same ethylene content would be obtained. Also, from the change with time of the solid content and the state of the solution,
The homogeneity in the system was investigated. The results are shown in Table 3.

[0083]

[Table 3]

As is clear from Table 3, in the case of the dimethylsulfoxide solvent, the reaction proceeds while keeping the polymerization system always in a homogeneous state as compared with the case of the methanol solvent, and a polymer having a reduced intrinsic viscosity is obtained. I understand.

Example 12 Vinyl acetate 1371 g, dimethyl sulfoxide 343
g, azobisisobutyronitrile 0.018% (vs vinyl acetate), reaction temperature 60 ° C., ethylene pressure 3.
Polymerization was carried out in the same manner as in Example 1 except that the amount was 5 kg / cm ² G, and a polymerization rate of 40% and an ethylene content of 5 mol% were obtained in a polymerization time of 4 hours. Saponification according to the method of Example 1 (NaOH / EVAc = 0.1, molar ratio, x
The EVOH [η] ph after twice, other conditions being the same as in Example 1, was 0.236 l / g. The state of the sampling solution during the polymerization was transparent and was uniform without precipitation of the polymer.

Example 13 In accordance with Example 1, the EVA solution after polymerization was purged with ethylene, transferred to a 3 L separable flask, and 1360 g of dimethyl sulfoxide was added to the solution, followed by 5
The residual monomer was distilled out of the system under reduced pressure (100 mmHg or less) at 0 ° C. The viscosity of the solution immediately after the start of ejection was 10 poises, and the viscosity of the solution at the end of ejection was 15 poises. The amount of vinyl acetate in the distillate was measured, and the distillate was stopped when the distillate was 100% dimethyl sulfoxide.
The state of the solution was uniform during and after the distillation.

Example 2-1 An ethylene-vinyl acetate copolymer (EVA) having an ethylene content of 5 mol% was placed in a 5 l separable flask equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet tube.
340 g of ([η] ph = 0.224 l / g), 660 g of methanol, and 1700 g of dimethyl sulfoxide were added, and heated and stirred at 70 ° C. to obtain a uniform solution. 3% sodium hydroxide-methanol solution 51.6 was added to this solution.
g was added and the reaction was carried out 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, then precipitated in methanol and washed repeatedly. After that, pulverization and drying are performed to obtain a saponification degree of 9
7.8% ethylene-vinyl alcohol copolymer (EV
OH) was obtained. Furthermore, in order to bring the equilibrium of alcoholysis toward the production system side of the solution reacted for 20 minutes, a mixed solution of methanol and methyl acetate was distilled out of the system by vacuum distillation. When the amount of distillate outside the system reached 780 g, the reaction was stopped by neutralization, and the same post-treatment as above was carried out to obtain EVOH with a saponification degree of 99.9%. The state of the solution at the time of stopping the reaction was uniform.

Example 2-2 E having an ethylene content of 32 mol% was prepared according to Example 2-1.
100 g of VA ([η] ph = 0.111 l / g), 170 g of methanol and 580 g of dimethyl sulfoxide were added, and the mixture was heated and stirred at 60 ° C. to obtain a uniform solution. A 3% sodium hydroxide-methanol solution 160 was added to this solution.
g was added and the reaction was carried out 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, 1 g / L acetic acid-
The polymer was precipitated in a 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, the solution was discarded, and then 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 saponification degree is shown in FIG. 3. The saponification degree 2 minutes after the start of the reaction was 75% and the final saponification degree was 98.
It was 3%. Regarding the solution reacted for 30 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 side according to Example 2-1. The amount of distillate outside the system is 260 g
The sample treated in 1) was post-treated in the same manner as above, and the saponification degree was measured to be 99.4%. Further, 190 g of methanol was added to the reaction system, and vacuum distillation was carried out in the same manner. When the amount of distillate out of the system reached 150 g, the reaction was stopped by neutralization and post-treatment was similarly carried out to give a saponification degree of 99. .8
% EVOH was obtained. The weight ratio of methanol to methyl acetate in the distillate after the start of direct distillation was 1: 9. The state of the solution during the reaction and at the time of stopping the reaction was a uniform liquid phase.

Comparative Example 2-1 In Example 2-2, methanol was used instead of dimethyl sulfoxide, and the same catalytic amount (vs. V in EVA) was used.
The reaction was performed at an AC molar ratio. The change with time in the degree of saponification up to the reaction time of 30 minutes was examined by performing the same post-treatment as in the above example. 2 minutes after the start of the reaction, the degree of saponification was 55% and was 3
The final degree of saponification after reacting for 0 minutes was 95%. The results are also shown in FIG. 3, and as is clear from FIG. 3, it can be seen that, by coexisting dimethyl sulfoxide in the reaction system, accelerated alcoholysis can be carried out as compared with the system containing only methanol. Further, with respect to the solution that had reacted for 30 minutes, a mixed solution of methanol and methyl acetate was distilled out of the system by vacuum distillation. The weight ratio of methanol to methyl acetate in the distillate immediately after the start of distillation was 2: 8. When the saponification degree was measured after post-treatment of a sampling sample whose amount of distillation outside the system was 260 g, it was 96.5%.

In order to bring the equilibrium of alcoholysis to the production side by comparing the weight ratio of methanol and methyl acetate in the distillate of Example 2-1 and Comparative Example 2-1, the by-product methyl acetate was distilled out of the system. When dimethylsulfoxide coexisted in the reaction system, it was found that the separation efficiency of methyl acetate and methanol was improved as compared with the system containing only methanol, and methyl acetate was efficiently distilled out of the system. The state of the solution during the reaction and at the time of stopping the reaction was uniform as in the dimethyl sulfoxide system.

Example 2-3 According to Example 2-1, E having an ethylene content of 27 mol% was used.
100 g of VA ([η] ph = 0.109 l / g), 170 g of methanol and 550 g of dimethyl sulfoxide were used, and after uniform dissolution at 60 ° C., 3% -sodium hydroxide-
150 g of a methanol solution was added and the reaction was carried out at the same temperature for 30 minutes. The state of the solution during and after the reaction was uniform. A portion of this reaction solution was sampled, and the saponification degree of the post-treated EVOH was 77% in a reaction time of 2 minutes and was 3%.
It was 98.6% at 0 minutes. For the solution reacted for 30 minutes, a mixed solution of methanol and methyl acetate was distilled out of the system by vacuum distillation in order to bring the equilibrium of alcoholysis to the production side, as in the above-mentioned Example. The amount of distillate outside the system is 25
After the post treatment, the saponification degree of the 0 g sampled sample was 99.5%. Furthermore, in the reaction system,
Add 190 g of methanol and perform vacuum distillation in the same manner.
When the amount of distillate out of the system reached 150 g, the reaction was stopped by neutralization and post-treatment was carried out to obtain an EVO with a saponification degree of 99.8%.
H was obtained. The state of the solution during the reaction and at the time of stopping the reaction was uniform.

Comparative Example 2-2 In Example 2-3, methanol was used instead of dimethyl sulfoxide, and the same catalytic amount (vs. VA in EVA) was used.
The reaction was carried out at a C molar ratio). The state of the solution was uniform at the start of the reaction, but 5 minutes after the addition of the catalyst, EV was added to the system.
OH started to precipitate and solidified 10 minutes later.
After 30 minutes, the solid was taken out, crushed with a mixer, and post-treated to obtain an EVOH having a saponification degree of 96.0%.
The degree of saponification 2 minutes after the start of the reaction was 58%.

Example 2-4 E with an ethylene content of 60 mol% was prepared according to Example 2-1.
Using 100 g of VA ([η] ph = 0.077 l / g), 180 g of methanol and 760 g of dimethylsulfoxide, after uniform dissolution at 60 ° C., 3% -sodium hydroxide-
260 g of a methanol solution was added, and the reaction was carried out at the same temperature for 40 minutes. The degree of saponification of EVOH after reacting for 40 minutes was 97.2%. A mixed solution of methanol and methyl acetate was distilled out under reduced pressure from the solution that had reacted for 40 minutes. The amount of distillate outside the system is 350 g
After the post-treatment, the saponification degree of the sample sampled in 1. was 99.0%. Furthermore, after adding 200 g of methanol to the reaction system, distillation under reduced pressure was performed to obtain a distillate amount of 16
The reaction was stopped when it reached 0 g. The final degree of saponification after the post-treatment was 99.4%. The state of the solution during the reaction and at the time of stopping the reaction was uniform.

Comparative Example 2-3 In Example 2-4, methanol was used in place of dimethyl sulfoxide, and the same catalytic amount (vs. V in EVA) was used.
The reaction was performed at an AC molar ratio. At 60 ° C., the polymer was not completely dissolved and was cloudy. After the catalyst was added, the system became homogeneous and the reaction was carried out for 40 minutes. The degree of saponification of EVOH after reacting for 40 minutes was 94.2%. Further, a mixed solution of methanol and methyl acetate was distilled out of the system by vacuum distillation. The degree of saponification of the sampling sample when the amount of distillate outside the system was 350 g was 95.6%. Further, after adding 200 g of methanol to the reaction system, distillation under reduced pressure was carried out. From the system coexisting with dimethylsulfoxide in Example 2-4,
Distilled a lot. When the amount of distillate was 200 g, the reaction was stopped, post-treatment was carried out, and the saponification degree was measured and found to be 97.4%.

Example 2-5 E with an ethylene content of 32 mol% was prepared according to Example 2-2.
VA ([η] ph = 0.111 l / g) 100 g, methanol 170 g, diethyl sulfoxide 780 g, 3%
-Using 160 g of sodium hydroxide-methanol solution, the reaction was carried out at 60 ° C for 30 minutes. The saponification degree of the sampling sample after reacting for 30 minutes was 98.0%. Further, 260 g of distillate gives a saponification degree of 99.3%, 190 g of methanol is added, and 150 g of distillate gives a saponification degree of 99.
6% EVOH was obtained. The weight ratio of methanol to methyl acetate in the distillate immediately after the start of distillation was 1: 9. The state of the solution during the reaction and at the time of stopping the reaction was uniform.

Example 2-6 According to Example 2-2, E having an ethylene content of 32 mol% was used.
VA ([η] ph = 0.111 l / g) 100 g, ethanol 320 g, dimethylsulfoxide 580 g, 3%
-Using 160 g of sodium hydroxide-ethanol solution,
The reaction was carried out at 60 ° C for 40 minutes. The saponification degree of the sampling sample after reacting for 40 minutes was 96.5%. Furthermore, a saponification degree of 98.5% was obtained with 380 g of distillate, and after adding 270 g of ethanol, a saponification degree of 99.5 with 220 g of distillate.
% EVOH was obtained. The state of the solution during the reaction and at the time of stopping the reaction was uniform.

Example 3-1 An ethylene-vinyl acetate copolymer (ethylene content 5 mol%, [η] ph) was placed in a separable flask having a content of 5 l equipped with a stirrer, a reflux condenser, a catalyst liquid inlet, and a sampling port. =
0.181 l / g) 328 g (3.95 mol), methanol 710 g (22.19 mol), and dimethyl sulfoxide 1700 g were charged, and the system was replaced with nitrogen gas.
Temperature rising was started in an oil bath with stirring, and the ethylene-vinyl acetate copolymer was dissolved at 60 ° C. Then, 1.58 g (0.0395 mol) of sodium hydroxide was added to methanol 5
The catalyst solution dissolved in 0 ml was added all at once under N ₂ atmosphere to start the reaction, and the reaction was continued at 60 ° C. for 30 minutes.
The saponification degree of the produced ethylene-vinyl alcohol copolymer obtained by sampling after the reaction for 30 minutes was 97.
It was 8%. A vacuum distillation apparatus was installed in the above reactor, and methyl acetate and methanol by-produced from the reaction solution obtained under the condition that the temperature of the can liquid was constant at 70 ° C. were distilled off under normal pressure or reduced pressure. Further saponification of the polymer was carried out. Immediately after the start of distillation of by-product methyl acetate and methanol, the weight ratio of methyl acetate / methanol in the distillate was 9/1, and the distillation exceeded the azeotropic distillation composition (8/2) of methyl acetate / methanol. The composition is shown. The distillation operation was carried out for 1.5 hours under the above conditions, 900 g of the distillate was distilled in a dry ice-acetone cooling bath, and the saponification degree of the ethylene-vinyl alcohol copolymer in the can was 99.8%. there were. Through the above reaction system and the additional saponification system, the reaction system always maintained a uniform state. 2.37 g (0.0395 mol) of acetic acid in the can solution after saponification.
Was added to deactivate the catalyst, the temperature of the bottom liquid was adjusted to 9 under reduced pressure.
While maintaining the temperature at 0 ° C. or lower, the concentration of the ethylene-vinyl alcohol copolymer in the can solution was adjusted to obtain a 17 wt% dimethylsulfoxide solution of the ethylene-vinyl alcohol copolymer. The ethylene-vinyl alcohol copolymer solution obtained by the above operation was charged into a dry-wet spinning device as a spinning stock solution, the spinning stock solution head temperature was 80 ° C., the coagulation bath composition was methanol / DMSO = 7/3 (weight ratio), and the coagulation was performed. The spinning operation was carried out under the condition that the bath temperature was 5 ° C. Ethylene-vinyl alcohol copolymer fibers were obtained by carrying out extraction removal of DMSO remaining in the yarn with methanol, wet heat drawing, drying and dry heat drawing in the subsequent steps. The strength and elongation of this fiber were 15.2 g / dr and 4.5%, and the WTb value showing hot water resistance was 130 ° C., which was measured by fusing under a constant load (200 mg / dr).

Example 3-2 Ethylene content of 10 as ethylene-vinyl acetate copolymer
Copolymer 31 with mol% and [η] ph = 0.271 / l
By the same method as in Example 3-1, except that 7 g (3.95 mol) was used, methanolysis of ethylene-vinyl acetate copolymer, additional saponification, catalyst deactivation treatment, and concentration adjustment were carried out to obtain a saponification degree of 99. A 7% by weight solution of a 7% ethylene-vinyl alcohol copolymer in dimethylsulfoxide was obtained. The reaction system maintained a uniform state throughout the above operations. The solution was cast on a polyethylene terephthalate film, immersed in a methanol coagulation bath at 10 ° C. to form a film, and then introduced into a methanol extraction bath to remove dimethyl sulfoxide by extraction. Then, it was naturally dried at room temperature, uniaxially stretched 6 times at 150 ° C., and further heat-fixed at 190 ° C. for 3 minutes in a nitrogen gas atmosphere under a fixed length to give a gel having a thickness of 24 μm where almost no gel or lumps were observed. An ethylene-vinyl alcohol copolymer film was obtained.

Example 3-3 Ethylene-vinyl acetate copolymer as ethylene content 32
Copolymer 26 with mol% of [η] ph = 0.106 l / g
Using 6 g (3.95 mol), sodium hydroxide 7.
By the same method as in Example 3-1, except that 9 g (0.198 mol) of the methanolysis catalyst was used, methanolysis of ethylene-vinyl acetate copolymer, additional saponification, catalyst deactivation treatment, and concentration adjustment were carried out, and saponification was carried out. A 25% by weight dimethylsulfoxide solution of an ethylene-vinyl alcohol copolymer having a degree of 99.5% was obtained. The reaction system maintained a uniform state throughout the above operations. The solution was heated to 70 ° C., extruded through a slit of a sheet molding machine into cooling water kept at 3 ° C. and coagulated to obtain a white opaque sheet-like wet gel having a thickness of 600 μm. This gel at 65 ° C in water for 3
After dipping for 60 minutes, the sheet was dried at 40 ° C. for 60 minutes to obtain a sheet having a thickness of 480μ.

Example 3-4 In Example 3-1, 1021 g (22.2 mol) of ethanol was used in place of methanol, 1700 g of diethyl sulfoxide was used in place of dimethyl sulfoxide, and potassium hydroxide was used in place of sodium hydroxide. 43 g
By the same method as in Example 3-1, except that (0.079 mol) was used, ethanolysis of ethylene-vinyl acetate copolymer, additional saponification, and catalyst deactivation treatment by addition of acetic acid equimolar to charged potassium hydroxide. Then, the concentration was adjusted to obtain a 15 wt% diethyl sulfoxide solution of an ethylene-vinyl alcohol copolymer having a saponification degree of 99.6 mol%. The reaction system maintained a uniform state throughout the above operations. The ethylene-vinyl alcohol copolymer solution obtained by the above operation was charged as a spinning stock solution into a spinning apparatus of the upflow wet method, the spinning stock solution head temperature was 60 ° C., coagulation bath composition ethanol / diethyl sulfoxide = 4/1 (weight ratio) The spinning operation was carried out under the condition that the coagulation bath temperature was 5 ° C. Ethylene-vinyl alcohol copolymer fibers were obtained by extraction and removal of diethyl sulfoxide remaining in the system with ethanol, wet heat drawing, drying and dry heat drawing in the subsequent steps. The strength and elongation of this fiber are 14.9 g each.
/ Dr was 4.8%.

Example 3-5 In Example 3-1, the ethylene-vinyl acetate copolymer had an ethylene content of 33 mol%, and [η] ph = 0.14.
Ethylene-acetic acid was prepared in the same manner as in Example 3-1, except that 261 g (3.90 mol) of the copolymer of Example 8 was used and 7.9 g (0.198 mol) of sodium hydroxide was used as the methanolysis catalyst. Vinylolysis methanolysis,
Addition of saponification, catalyst deactivation treatment by addition of equimolar acetic acid to the charged sodium hydroxide, concentration adjustment were carried out, and 1% of ethylene-vinyl alcohol copolymer having a saponification degree of 99.8% was obtained.
A 3 wt% dimethylsulfoxide solution was obtained. Throughout all the above operations, the reaction system maintained a uniform state, and no gel adhesion to the vessel wall was observed. A 30 wt% dimethylsulfoxide aqueous solution kept at −7 ° C. was used as a coagulation bath, nitrogen was used as an internal injection agent, and the solution was extruded as a spinning dope from a circular nozzle of a wet hollow fiber manufacturing apparatus at a nozzle draft of 1.5. Thus, a hollow fiber of ethylene-vinyl alcohol copolymer was prepared. After the subsequent heat treatment at 40 ° C. for 6 minutes, washing with water, washing with acetone, and drying, 6 ml /
A hollow fiber having a water permeability of mmHg · hr / m ² was obtained.

Example 3-6 In Example 3-1, the ethylene-vinyl acetate copolymer had an ethylene content of 70 mol% and [η] ph = 0.07.
81 l / g copolymer 174 g (4.0 mol), methanol 384 g (12.0 mol), dimethyl sulfoxide 1700 g were used, and sodium hydroxide 16 g (0.4
Mol) as a methanolysis catalyst, methyl acetate / methanol was further distilled off by additional saponification, and 256 g (8.0 mol) of methanol was added to carry out additional saponification again. , Ethylene-vinyl acetate copolymer methanolysis, additional saponification, catalyst deactivation treatment by addition of equimolar acetic acid with charged sodium hydroxide, concentration adjustment, saponification degree 99.5%
A 12% by weight dimethylsulfoxide solution of the ethylene-vinyl alcohol copolymer was obtained. The reaction system maintained a uniform state throughout the above operations. The ethylene-vinyl alcohol copolymer solution obtained by the operation had a diameter of 0.
Charge into a granulation device with a vibrating nozzle of 6 mm, 2
Particle formation was carried out under a vibration of 70 Hertz using water at 0 ° C. as a coagulation bath to obtain a spherical wet gel having an average particle size of 1.5 mm. The spherical gel was washed with water and dried to obtain a spherical copolymer having a sharp particle size distribution with an average particle size of 0.55 mm and a short axis / long axis average ratio of 0.9.

Comparative Example 3-1 In Example 3-1, instead of the ethylene-vinyl acetate copolymer, 344 g (4.0 mol) of vinyl acetate polymer having [η] ph = 0.186 l / g, 2400 g of methanol.
Was used, and the methanolysis reaction was carried out under the same conditions as in Example 3-1 except that dimethyl sulfoxide was not added. Immediately after the start of the methanolysis reaction, the reaction system became heterogeneous, and the reaction in a homogeneous system was impossible.

Comparative Example 3-2 In Example 3-1, the ethylene-vinyl acetate copolymer had an ethylene content of 90 mol%, and [η] ph = 0.06.
The methanolysis reaction was carried out under the same conditions as in Example 3-1 except that 135 g (4.0 mol) of the 78 l / g copolymer was used. The solubility of the above copolymer in the reaction system was insufficient and it was not completely dissolved. The methanolysis reaction was carried out for 2 hours as it was in a heterogeneous state, but the reaction system remained in a heterogeneous state. The degree of saponification after the reaction is 52
Remained at%.

Example 4-1 Vinyl acetate (VAc) 2.7 purified by distillation in an autoclave having a content of 5 l equipped with an electromagnetic stirrer and a sampling port.
4 kg (31.86 mol), dimethyl sulfoxide (D
MSO) 0.69 kg (VAc / DMSO = 4/1, weight ratio), azobisisobutyronitrile 0.159 g
(0.0058 wt% / VAc) was charged, the system was sufficiently replaced with ethylene gas, and the ethylene pressure was kept constant at 3 kg / cm ² by a pressure regulator, and the temperature was raised to 60 ° C.
The copolymerization reaction of ethylene and vinyl acetate was started under the constant condition of 0 ° C. The polymerization reaction was carried out for 5 hours while following the reaction process by sampling. The polymerization system was a uniform solution throughout the entire reaction process, and the polymerization rate after 5 hours was 30%. The ethylene content of the ethylene-vinyl acetate copolymer obtained by sampling the solution was 5 mol%, and [η] ph as EVOH after saponification was
It was 0.247 l / g. A polymerization inhibitor was added to the above polymerization solution, and the polymerization solution was introduced into a separable flask having a content of 10 l equipped with a stirrer, a reduced pressure distillation apparatus, a catalyst solution introduction port, and a sampling port under N ₂ atmosphere, and DMSO3700 g was added.
Was added. The temperature inside the system was raised to 60 ° C. under stirring in an oil bath, and the residual VAc was expelled while changing the degree of pressure reduction (50 mmHg to 5 mmHg) under the condition that the temperature of the can liquid was constant at 60 ° C. The viscosity of the solution immediately after the start of discharging was 11 poises, and the viscosity of the solution at the end of discharging was 19 poises. It was confirmed that the residual VAc in the can was 0.02% by collecting 2 kg of the distillate. This ejection operation could be carried out in the state of a homogeneous solution. Then, 6
1700 g of methanol (53.1
3 mol) and sodium hydroxide 3.82 under stirring.
A catalyst solution prepared by dissolving g (0.096 mol) in 100 ml of methanol was added all at once under N ₂ atmosphere to start the reaction.
The reaction was continued at 0 ° C for 30 minutes. The saponification degree of the produced ethylene-vinyl alcohol copolymer obtained by sampling after the reaction for 30 minutes was 97.8%.
A vacuum distillation apparatus was installed in the reactor, and methyl acetate and methanol by-produced from the reaction solution obtained under the condition that the temperature of the can liquid was constant at 70 ° C. were distilled off under normal pressure or reduced pressure, and ethylene-
The vinyl alcohol copolymer was subjected to additional saponification. The methyl acetate / MeOH weight ratio in the distillate immediately after the start of distillation of the by-product methyl acetate and methanol was 9/1, and the methyl acetate / methanol azeotropic distillation composition (8/2)
The distillate composition was above. Distillation was carried out for 1.5 hours under the above conditions, 2250 g of distillate was distilled in a dry ice-acetone cooling bath, and ethylene in the can-
The saponification degree of the vinyl alcohol copolymer was 99.8%. Through the above reaction system and the additional saponification system, the reaction system always maintained a uniform state. 5.76 g (0.096 mol) of acetic acid was added to the can liquid after the additional saponification to deactivate the catalyst, and then the can liquid temperature was kept under 90 ° C. under reduced pressure.
The concentration of the ethylene-vinyl alcohol copolymer in the can solution was adjusted to obtain the ethylene-vinyl alcohol copolymer 1
A 2 wt% dimethylsulfoxide solution was obtained. The ethylene-vinyl alcohol copolymer solution obtained by the above operation was charged as a spinning dope into a dry-wet spinning device, the spinning dope head temperature was 80 ° C, and the coagulation bath composition was methanol / D.
The spinning operation was carried out under the conditions of MSO = 7/3 (weight ratio) and coagulation bath temperature of 5 ° C. D remaining in the yarn in the subsequent process
Extraction removal of MSO with methanol, wet heat stretching, drying,
Ethylene-vinyl alcohol copolymer fibers were obtained by carrying out dry heat drawing. The strength and elongation of this fiber are
The values were 16.5 g / dr and 4.7%, respectively, and the WTb value showing the hot water resistance was 135 ° C., which was measured by melting under a constant load (200 mg / dr).

Example 4-2 In Example 4-1, the addition amount of azobisisobutyronitrile to the polymerization system was 0.225 g (0.0082 wt%).
/ VAc), the polymerization reaction was carried out under the same conditions as in Example 4-1 except that the ethylene pressure was 7 kg / cm ² , the polymerization rate was 31%, the ethylene content was 10 mol%, and [η] as EVOH was An ethylene-vinyl acetate copolymer having a pH of 0.210 1 / g was obtained. Removal of residual VAc from the solution was also performed under the same conditions as in Example 4-1, and it was confirmed that the amount of residual VAc was 0.02% or less. The viscosity of the solution immediately after the start of ejection was 9 poises, and the viscosity of the solution after the completion of ejection was 15 poises. The system always maintained a uniform state through the above steps. Methanolysis reaction, additional saponification,
The solution concentration was adjusted in the same manner as in Example 4-1 to obtain a 6 wt% EVOH dimethyl sulfoxide solution with a saponification degree of 99.7%. The reaction system maintained a uniform state throughout the above operations. The solution was cast on a polyethylene terephthalate film, immersed in a methanol coagulation bath at 10 ° C. to form a film, and then introduced into a methanol extraction bath to remove dimethyl sulfoxide by extraction. Then, naturally dried at room temperature, uniaxially stretched 6 times at 150 ° C., and further heat-fixed at 190 ° C. for 3 minutes in a nitrogen gas atmosphere under a fixed length,
An ethylene-vinyl alcohol copolymer film having a thickness of 20 μm in which almost no gel or lumps was observed was obtained.

Example 4-3 The amount of azobisisobutyronitrile added to the polymerization system in Example 4-1 was 1.10 g (0.04 wt% / VA).
c), the polymerization reaction was carried out under the same conditions as in Example 4-1, except that the ethylene pressure was 43 kg / cm ² , the polymerization rate was 30%, the ethylene content was 32 mol%, and [η] ph as EVOH was = 0.119 l / g of ethylene-vinyl acetate copolymer solution was obtained. Removal of residual VAc from the solution was also performed under the same conditions as in Example 4-1, and it was confirmed that the amount of residual VAc was 0.02% or less. The viscosity immediately after the start of ejection was 5 poise, and the viscosity at the end of ejection was 7 poise. The system always maintained a uniform state through the above steps. Sodium hydroxide as a methanolysis catalyst 19.
The methanolysis reaction using 1 g (0.48 mol), additional saponification, and adjustment of the solution concentration were carried out in the same manner as in Example 4-1, with a saponification degree of 99.5% and a DS of 21% by weight of EVOH.
The MO solution was obtained. The reaction system maintained a uniform state throughout the above operations. The solution was heated to 70 ° C., extruded through a slit of a sheet molding machine into cooling water kept at 3 ° C. and coagulated to obtain a white opaque sheet-like wet gel having a thickness of 600 μm. This gel is immersed in water at 65 ° C for 3 minutes and then dried at 40 ° C for 60 minutes to obtain a thickness of 4
A 50μ sheet was obtained.

Example 4-4 Copolymerization of ethylene and vinyl acetate, removal of residual VAc, methanolysis and additional saponification were carried out in the same manner as in Example 4-1, and the saponification degree was 99.8 by subsequent concentration adjustment. %,
A 10 wt% dimethylsulfoxide solution was obtained. The ethylene-vinyl alcohol copolymer solution obtained by the operation was charged as a spinning stock solution into a spinning apparatus of the upflow wet method, the spinning stock solution head temperature was 60 ° C., coagulation bath composition methanol / DMSO = 4/1 (weight ratio), The spinning operation was carried out under the condition that the coagulation bath temperature was 5 ° C. Extraction and removal of DMSO remaining in the yarn with methanol in a continuous process, wet heat drawing,
Ethylene-vinyl alcohol copolymer fibers were obtained by performing drying and dry heat drawing. The strength and the elongation of this fiber were 16.2 g / dr and 4.9%, respectively.

Example 4-5 In Example 4-1, the polymerization temperature was 40 ° C. and the amount of azobisisobutyronitrile added to the polymerization system was 2.33 g (0.30 g).
085wt% / VAc), ethylene pressure 32kg / c
Polymerization reaction was carried out under the same conditions as in Example 1 except that m ² was used, the polymerization rate was 20%, the ethylene content was 32 mol%, and E
A solution of ethylene-vinyl acetate copolymer having [η] ph as VOH of 0.143 l / g was obtained. Removal of residual VAc from the solution was also performed under the same conditions as in Example 4-1, and it was confirmed that the amount of residual VAc was 0.02% or less. The system always maintained a uniform state through the above steps. 26.9 g of sodium hydroxide as a methanolysis catalyst
A methanolysis reaction using (0.67 mol), additional saponification, and solution concentration adjustment were performed in the same manner as in Example 4-1, and a 12 wt% DSMO solution with a saponification degree of 99.6% was obtained. The reaction system maintained a uniform state throughout each process, and gel adhesion to the vessel wall was not confirmed. -7 ℃ as coagulation bath
Ethylene-vinyl alcohol by using a 30 wt% aqueous solution of dimethylsulfoxide kept at room temperature, nitrogen as an internal injecting agent, and extruding the solution as a spinning dope from a circular nozzle of a wet hollow fiber manufacturing apparatus at a nozzle draft of 1.5. A copolymer hollow fiber was prepared. After the subsequent wet heat treatment at 40 ° C. for 6 minutes, washing with water, washing with acetone, and drying, a hollow fiber having a water permeability of 6.3 ml / mmHg · hr / m ² was obtained.

Example 4-6 In Example 4-1, 1800 g of vinyl acetate (20.
93 mol, DMSO 1200 g (VAc / DMSO = 6
/ 4, weight ratio), azobisisobutyronitrile 2.36
g (0.131 wt% / VAc), ethylene pressure 65 k
g / cm ^2, except for using polymerization time 6 hours Example 4-1
Polymerization reaction is carried out by the same method as above, and the polymerization rate is 30%.
And ethylene content 60 mol%, [η] as EVOH
A solution of ethylene-vinyl acetate copolymer having a ph of 0.0854 l / g was obtained. The polymerization system always maintained a homogeneous system. In the operation of expelling the residual VAc, 4800 g of DMSO was added and the same operation as in Example 4-1 was carried out to maintain the system in a uniform state. Methanolysis reaction is methanol 150
0 g (47.1 mol), sodium hydroxide 31.4 g
(0.79 mol) was added, methyl acetate / methanol was distilled off by additional saponification, and then 973 g (30.4 mol) of methanol was added, and the additional saponification was carried out again. In the same way as
The ethylene-vinyl acetate copolymer was subjected to methanolysis, additional saponification, catalyst deactivation treatment by adding sodium hydroxide in an equimolar amount to the catalyst, and concentration adjustment.
1 of 9.6% ethylene-vinyl alcohol copolymer
A 1.5 wt% dimethylsulfoxide solution was obtained.
The reaction system maintained a uniform state throughout the above operations. The ethylene-vinyl alcohol copolymer solution obtained by the above operation was charged into a granulating device having a vibrating nozzle having a diameter of 0.6 mm, and the particles were granulated under a vibration of 65 Hertz using 20 ° C. water as a coagulating bath. A spherical wet gel having an average particle size of 1.5 mm was obtained. The spherical gel was washed with water and dried to obtain a spherical copolymer having a sharp particle size distribution with an average particle size of 0.55 mm and a short axis / long axis average ratio of 0.9.

Comparative Example 4-1 In Example 4-1, 0.69 kg of methanol (VAc / methanol = 4/1, weight ratio) instead of DMSO, 0.39 g of azobisisobutyronitrile (0.0
14 wt% / VAc) was charged, and homopolymerization of vinyl acetate was carried out for 5 hours under the same conditions except that ethylene was not allowed to coexist. The polymerization rate was 50%, and from the analysis of the polymer, [η] ph as polyvinyl alcohol was 0.210 l.
/ G. The removal of the residual VAc was carried out under the conditions of normal pressure by adding 3.5 kg of methanol instead of DMSO, and a methanol solution of polyvinyl acetate having a concentration of 35 wt% was obtained as a can solution. In the above operation, the system was in a homogeneous state. 6.4 in the methanol solution of polyvinyl acetate
g (0.16 mol) of sodium hydroxide was added, and the methanolysis reaction was carried out under the same conditions as in Example 4-1. Immediately after the start of the methanolysis reaction, the reaction system became heterogeneous, and the reaction in a homogeneous system was impossible.

Comparative Example 4-2 In Example 4-1, instead of DMSO, 0.69 kg of methanol (VAc / methanol = 4/1, weight ratio), 3.23 g of azobisisobutyronitrile (0.1
18 wt% / VAc) was charged and the ethylene pressure was adjusted to 62.
Example 4 except that the polymerization temperature was 5 kg / cm ² and the polymerization temperature was 50 ° C.
The polymerization reaction was carried out under the same conditions as for -1. The sample taken from the polymerization system was opaque and the system was found to be in a non-uniform state. The polymerization rate after 6 hours was 30%, the ethylene content was 60 mol%, and [η] ph as EVOH was 0.0749 l / g. Add 3.0% methanol to the opaque copolymer solution obtained by the above operation.
After adding kg, the residual VAc was expelled in accordance with Example 4-1 under conditions of normal pressure. The can liquid system became cloudy with the progress of VAc ejection, and precipitation of an ethylene-vinyl acetate copolymer was observed, and it was difficult to eject VAc in a uniform state.

Examples 5-1 to 5-4 In accordance with Example 2-1, ethylene content O (PVAc),
Under the conditions shown in Table 4, 20, 32, 47, and 60 mol% of EVA was reacted at 40 ° C for 60 minutes. As a solvent for precipitating the polymer after saponification, water, ethanol, or a mixed solvent of both of them was appropriately used depending on the ethylene content and the degree of saponification. The state of the solution after the reaction was uniform. Figure 4
Shows the change with time of saponification degree. As a control, in Example 5-1, methanol was used instead of dimethylsulfoxide, and the saponification reaction was performed under the same other conditions. The polymer solidified after the reaction was pulverized, neutralized and post-treated. (Comparative Examples 5-1 to 5-5) In the case of the methanol system, it was a solid or a slurry during and after the reaction, although it varied depending on the ethylene content. Figure 5
Shows the change with time in the degree of saponification in the case of methanol type.
As can be seen from the comparison between FIG. 4 and FIG. 5, when dimethyl sulfoxide is used as the solvent, the reaction is very fast as compared with the methanol system. From FIGS. 4 and 5, the reaction rate at each ethylene content was determined for each solvent system, and the ratio (DMSO-based saponification / MeOH-based saponification) was determined (FIG. 6). As can be seen from FIG. 6, the reaction rate ratio increases as the ethylene content increases, and thus it can be said that the saponification reaction using dimethyl sulfoxide is very specific.

[0115]

[Table 4]

Examples 6-1 to 6-5 Under the same conditions as in Example 1, dimethyl sulfoxide and vinyl acetate were charged in equal amounts (DMSO / VAc = 5/5, weight ratio), and the ethylene pressure was changed to be the same. The amount of the initiator was adjusted so that the polymerization rate and the polymerization rate were adjusted, and the polymerization was performed.
The saponification reaction of VA under the conditions according to Example 1 was performed on the EVA obtained under the conditions according to Example 1 to obtain EVOH having various ethylene contents (saponification degree: 9).
Intrinsic viscosity of 9.4-99.7 mol%) was measured. Further, as a control, solution polymerization in a methanol system without using dimethyl sulfoxide was carried out with the same composition as in the system of dimethyl sulfoxide (Comparative Examples 6-1 to 6-).
5). In the polymerization, in order to see the influence of the decrease in intrinsic viscosity, the polymerization rate and the polymerization rate were all the same, and the ethylene pressure was set so that the ethylene content was the same (Table 5, FIG. 7).
As can be seen from FIG. 7, even when the ethylene content is high, in the case of solution polymerization using dimethylsulfoxide as a solvent, a polymer having an intrinsic viscosity higher than that of EVOH obtained by polymerization in a methanol solvent system can be obtained.

[0117]

[Table 5]

Example 7-1 According to the method similar to that of Example 3-1, the ethylene content was 32 mol%.
EVA ([η] ph = 0.111 l / g) 100 g,
Using 96 g of methanol and 1788 g of dimethyl sulfoxide, 2.0 g of sodium hydroxide as a methanolysis catalyst, the reaction was carried out at a reaction temperature of 40 ° C. for 2 minutes, and the post-treatment was carried out in the same manner as in Example 3-1 to obtain a saponification degree of 76. 0.5 mol% of partially saponified EVOH was obtained. The obtained EVOH has a melting point of 116.4 ° C and a block character of 0.3.
It was 45. In addition, as a control (Comparative Example 7-1), a reaction temperature of 40 ° C. was used in the same manner except that methanol was used instead of dimethylsulfoxide of Example 7-1.
By reacting for 90 minutes and performing the same post-treatment,
A partially saponified product having a saponification degree of 76.5 mol% was obtained. The obtained EVOH had a melting point of 143.8 ° C. and a block character of 0.118. As described above, when saponified in a DMSO solvent system, the melting point is lower than that in a MeOH solvent system even at the same degree of saponification, and the distribution of residual acetyl groups in the obtained EVOH is more random. It turns out that it is (more sharp).

[0119]

EFFECT OF THE INVENTION Ethylene having a wide range of ethylene contents
A vinyl ester copolymer can be obtained, and since the polymerization system is maintained in a substantially uniform liquid phase, the quality of EVA obtained and the EVOH obtained by saponifying the same are also uniform, and Recovery of residual monomers is also easy. Furthermore, EVA having a higher degree of polymerization can be obtained as compared with solution polymerization using methanol. The reaction rate of alcoholysis is increased as compared with the solvent system of lower alcohol alone, and furthermore, since the alcohol reaction system is maintained in a substantially uniform liquid phase, the quality of the obtained EVOH copolymer is uniform. is there. Also, the decrease in the alcoholysis reaction rate with the increase in ethylene content is slight, and it is of interest that the reaction rate ratio (reaction rate / diamine sulfoxide used is less than that in the case of using a methanol solvent). The reaction rate when used) tends to increase as the ethylene content increases. Therefore, the present invention is extremely effective for the alcoholysis reaction of high ethylene EVA.

Since the steps from the EVOH manufacturing method to the molding method using EVOH can be directly connected and carried out,
Manufacturing cost is low.

From the process for producing EVA having a wide range of ethylene content, saponification of EVA to obtain EVOH and E
The manufacturing cost is low because the method of manufacturing a molded product using VOH can be directly connected.

[Brief description of drawings]

FIG. 1 shows the intrinsic viscosity (l / l) of EVOH in Examples 2 to 5 and Comparative Examples 2 to 6 with the amount of solvent (% by weight) as the abscissa.
3 is a graph having a vertical axis of g).

FIG. 2 shows the polymerization time (hr) (excluding the induction date) in Example 9 and Comparative Example 13, the polymerization solution was sampled, and the solid content of EVA obtained by evaporation to dryness (polymerization) (% By weight of liquid) is a graph having the vertical axis.

FIG. 3 is a saponification degree (%) of EVOH in Example 2-2 and Comparative Example 2-1, with the abscissa representing the saponification time (minutes).
Is a graph having a vertical axis. It is extremely effective for the alcoholysis reaction of Tiren EVA.

FIG. 4 is a graph showing the saponification time (minutes) on the horizontal axis and the saponification degree (%) of EVOH on the vertical axis in Examples 5-1 to 5-4.

FIG. 5 is a graph showing the saponification time (minutes) on the horizontal axis and the saponification degree (%) of EVOH on the vertical axis in Comparative Examples 5-1 to 5-5.

6] Examples 5-1 to 5-4 and Comparative examples 5-1 to 5
5 is a graph in which the ethylene content (mol%) in -5 is on the horizontal axis and the reaction rate ratio (DMSO-based saponification / MeOH saponification) is on the vertical axis.

FIG. 7 is a graph of Examples 6-1 to 6-5 and Comparative examples 6-1 to 6-6.
The ethylene content (mol%) at -5 is plotted on the horizontal axis, and E
It is a graph which makes the vertical axis the intrinsic viscosity (l / g) of VOH.

[Explanation of symbols]

1 Examples 2 to 5 (solution polymerization using dimethyl sulfoxide) 2 Comparative example 2 (bulk polymerization), Comparative examples 3 to 6 (solution polymerization using methanol) 3 Example 9 (solution polymerization using dimethyl sulfoxide) 4 Comparative Example 11 (Solution Polymerization Using Methanol) 5 Example 2-2 6 Comparative Example 2-1

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C08F 210/02 MJK 9053-4J 218/04 MLG 6904-4J (72) Inventor Katsumi Shimizu Okayama Kaigan Toru 1-2-1 Kuraray Co., Ltd. (72) Inventor Akimasa Aoyama 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. (72) Inventor Ken Moriya 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd.

Claims (6)

[Claims] 1. A process for producing an ethylene-vinyl ester copolymer, which comprises using a dialkyl sulfoxide as a polymerization solvent when copolymerizing ethylene and a vinyl ester in the presence of a radical initiator. 2. The method for producing an ethylene-vinyl ester copolymer according to claim 1, wherein the residual monomer is distilled off from the polymerization system while the polymerization system is in a liquid phase and the viscosity is kept at 500 poise or less. 3. An ethylene-vinyl alcohol copolymer, characterized in that when an ethylene-vinyl alcohol copolymer is produced by alcoholysis of an ethylene-vinyl ester copolymer, a dialkyl sulfoxide is used as a solvent and alcoholysis is performed in a liquid state. How to combine. 4. The method for producing an ethylene-vinyl alcohol copolymer according to claim 3, wherein alcoholysis is carried out while distilling and removing the by-produced ester out of the reaction system. 5. A dialkyl sulfoxide is used with the ethylene-vinyl ester copolymer (A) as a solvent,
A step of carrying out alcoholysis in a liquid phase to produce an ethylene-vinyl alcohol copolymer (B) solution ... Step (I) The copolymer (B) solution of Step (I) is added to the copolymer (B).
Of the non-solvent or the mixed solvent having a non-solvent content of at least 20% by weight or more ... the step (I
A process for producing the above-mentioned copolymer (B) molded product, which comprises the combination of I). 6. A step of producing an ethylene-vinyl ester copolymer (A) solution by copolymerizing ethylene and vinyl ester in the presence of a radical initiator using a dialkyl sulfoxide as a polymerization solvent ... ) ′ A step of distilling off the remaining unreacted vinyl ester from the solution of the copolymer (A) in the step (I) while keeping the viscosity of the solution at 500 poises or less ...
I) A step of producing an ethylene-vinyl alcohol copolymer (B) solution by performing alcoholysis in a liquid state on the copolymer (A) solution obtained in the'step (II) '... step (II
I) contacting the solution of the copolymer (B) in the step (III) 'with a non-solvent of the copolymer (B) or a mixed solvent of dialkyl sulfoxide / non-solvent having a non-solvent content of 20% by weight or more The step of producing ... The method for producing the above-mentioned copolymer (B) molded article, which comprises a combination of step (IV) '