JP2000239316A - Production of saponified product of ethylene-vinyl acetate copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject compound hardly causing the loss of a resin and the whitening of the surfaces of pellets, excellent in formability and useful for a film for packing a food, a medicine or the like, or the like by carrying out the addition of water after saponification, and the precipitation of an ethylene-vinyl acetate copolymer in a coagulating liquid under a specific condition. SOLUTION: An ethylene-vinyl acetate copolymer is saponified to provide an alcohol solution, and water is added to the obtained alcohol solution so as to satisfy the formula: 0.0933×(50-X)2+26>=Y>=0.0933×(50-X)2+6 [X is an ethylene content (mol%); Y is the content (wt.%) of the water in the solvent of the mixed solution] to provide a water-alcohol mixed solution of the saponified product (EVOH) of the ethylene-vinyl acetate copolymer. The mixed solution of the EVOH is provided to an alcohol-containing water-based coagulation liquid satisfying the condition represented by the inequality: M<100-(Y+Z) [M is the alcohol content (wt.%) in the coagulation liquid; Z is the content (wt.%) of the EVOH in the mixed solution] to precipitate the EVOH and to provide the objective compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH). EVO with excellent properties (no fish eyes and no streaks during molding)
H.

[0002]

2. Description of the Related Art In general, EVOH is excellent in transparency, gas barrier property, fragrance retention, solvent resistance, oil resistance and the like. It is used after being formed into materials, films and sheets of packaging materials for agricultural chemicals, containers such as bottles, and the like. In such molding, usually, melt molding is performed, and by such molding, it is processed into a shape such as a film shape, a sheet shape, a bottle shape, a cup shape, a tube shape, a pipe shape, and is provided for practical use. (Moldability) is very important, and various studies have been made to improve such moldability. For example, in the step of depositing EVOH, Japanese Patent Publication No. Hei 5-79086 by the present applicant discloses that a methanol or water / methanol solution of EVOH containing a lubricant is extruded into a coagulating liquid to precipitate the EVO.
H are obtained, and
Japanese Patent Publication No. 5-58448 describes the use of an organic solvent having a boiling point of 100 ° C. or lower, such as methyl acetate, as the organic solvent of the coagulation liquid.

[0003]

However, in the former method, when a methanol or water / methanol solution of EVOH having a small ethylene content is extruded and precipitated in a coagulation liquid, the loss of EVOH increases, and In the latter method, the organic solvent remains in the final product, leaving problems such as foaming and safety during melt molding, and new improvements are desired.

[0004]

In view of the above situation, the present inventor has conducted intensive studies on the process from the saponification to the precipitation during the EVOH production process, and as a result, has found that ethylene-
Saponify the vinyl acetate copolymer, and then precipitate it to form EV
In obtaining OH, the alcoholic solution of EVOH after saponification is mixed with water so as to satisfy the condition of the following formula (1) to form a mixed solution of EVOH with water and alcohol, and then the mixed solution is mixed with the following (2) The inventors have found that, by precipitating EVOH in an alcohol-containing aqueous coagulating solution satisfying the formula, it is possible to obtain EVOH excellent in moldability with less resin loss of EVOH and whitening of the pellet surface, and completed the present invention. Was. 0.0933 × (50−X) ² + 26 ≧ Y ≧ 0.0933 × (50−X) ² +6 (1) (X is ethylene content (mol%), Y is water content in the solvent of the mixed solution) (% By weight)) M <100− (Y + Z) (2) (M is the alcohol content (% by weight) in the coagulation liquid, Y is the same as above, and Z is the EVOH content (% by weight) in the mixed solution. ))

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The EVOH obtained by the method of the present invention is obtained by saponifying an ethylene-vinyl acetate copolymer, and the ethylene-vinyl acetate copolymer as a raw material is not particularly limited. In consideration of this, the ethylene content is preferably 20 to 50 mol% (more preferably 25 to 50 mol%, particularly 27 to 48 mol%), and when the ethylene content is less than 20 mol%, the EVOH obtained at high humidity The gas barrier property and melt moldability of
If it exceeds 0 mol%, the obtained EVOH cannot obtain sufficient gas barrier properties, which is not preferable.

The ethylene-vinyl acetate copolymer may contain, as a copolymerizable component, an ethylenically unsaturated monomer copolymerizable therewith, in addition to ethylene and vinyl acetate. As the monomer, for example, propylene,
Olefins such as isobutylene, α-octene, α-dodecene, and α-octadecene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid; salts thereof; and mono- or dialkyl esters , Nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, olefinsulfonic acids such as ethylenesulfonic acid, allylsulfonic acid and methallylsulfonic acid or salts thereof, alkyl vinyl ethers and N-acrylamidomethyltrimethylammonium Chloride, allyltrimethylammonium chloride, dimethylallylvinylketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxy Polyoxyalkylene (meth) allyl ether such as propylene (meth) allyl ether, polyoxyethylene (meth) acrylate, polyoxyalkylene (meth) acrylate such as polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, Polyoxyalkylene (meth) such as polyoxypropylene (meth) acrylamide
Acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester,
Examples thereof include polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

[0007] The EVOH obtained in the present invention is obtained by saponifying the above-mentioned ethylene-vinyl acetate copolymer. The saponification reaction is carried out in the presence of an alkali catalyst. A conventionally known catalyst used for a saponification reaction of polyvinyl acetate or an ethylene-vinyl acetate copolymer with an alkali catalyst can be used as it is. Specifically, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkali metal alcoholates such as sodium methylate and potassium t-butoxy, and 1,8-diazabicyclo [5,
4,10] undecene-7 (DBU), such as strong basic amines, furthermore, alkali metal carbonates and alkali metal hydrogencarbonates. Use is preferred.

The amount of the catalyst used depends on the required degree of saponification, the reaction temperature and the like, but it is used in an amount of 0.05 equivalent or less, preferably 0.03 equivalent, based on the residual acetic acid groups in the ethylene-vinyl acetate copolymer. It is as follows. Further, instead of the alkali catalyst, an acid catalyst such as hydrochloric acid and sulfuric acid can be used.

In the saponification, the ethylene-vinyl acetate copolymer is dissolved in an alcohol or an alcohol-containing medium to a concentration of usually about 20 to 60% by weight, and an alkali catalyst or an acid catalyst is added. 40-1
React at a temperature of 40 ° C. EV at the solution temperature
The concentration of the EVOH is not particularly limited as long as OH is not precipitated.
The content may be 5% by weight, preferably 15 to 50% by weight. As the alcohol, alcohols such as methanol, ethanol, and propanol are used, and preferably, methanol is used.

[0010] The saponification degree of the vinyl acetate component of EVOH obtained by such saponification is preferably 70 to 100 mol%, and more preferably 80 to 100 mol%. When the saponification degree is less than 70 mol%, the thermal stability when the EVOH is melt-molded is unfavorably deteriorated.

Next, water is added to the EVOH alcohol solution obtained above. In the present invention, water is added at this time so as to satisfy the condition of the following formula (1), and water of EVOH is added. The first is to obtain an alcohol mixed solution
When such conditions are not satisfied, it is difficult to obtain the effects of the present invention.

In other words, it is necessary to add water so as to satisfy the following equation (1) depending on the ethylene content in the EVOH. 0.0933 × (50−X) ² + 26 ≧ Y ≧ 0.0933 × (50−X) ² +6 (1) where X is the ethylene content (mol%), and Y is the water-alcohol mixed solution of EVOH. Water content in solvent (% by weight)
Respectively.

Under the conditions of the above equation (1), when water is contained such that the value of Y is smaller than the calculated value on the right side, EVOH is difficult to precipitate and the resin loss of EVOH increases, and conversely, When water is contained so as to be larger than the calculated value on the left side, the viscosity of the water-alcohol mixed solution of EVOH becomes unstable, and EVOH precipitates before precipitation in the coagulation liquid, and the object of the present invention is not solved. It is difficult to achieve. The water-alcohol mixed solution of EVOH thus obtained is then supplied to a coagulation liquid, where EVOH is precipitated (coagulated). In the present invention, the condition of the following formula (2) is satisfied at this time. The second feature is that such EVOH is precipitated in an alcohol-containing aqueous coagulation liquid. Even when such conditions are not satisfied, it is difficult to obtain the effects of the present invention.

In other words, it is necessary to adjust the amount of alcohol contained in the coagulating liquid so as to satisfy the following equation (2). Such an adjustment is based on the EVO adjusted above.
It may be carried out before the water-alcohol mixed solution of H is added to the coagulation liquid. However, if the condition of the following formula (2) is deviated when the EVOH is precipitated in the coagulation liquid, the adjustment may be made each time. May be. In the present invention, even if the condition of the following formula (2) is deviated during the precipitation step, if the condition of the following formula (2) is satisfied during the step, Is to obtain the function and effect of the present invention. M <100− (Y + Z) (2) where M is the alcohol content (% by weight) in the coagulation liquid, Y
Represents the same as above, and Z represents the content (% by weight) of EVOH in the mixed solution.

When the alcohol content (M) in the coagulation liquid is larger than the calculated value on the right-hand side under the conditions of the above formula (2), the precipitation rate becomes slow, and the resin loss increases, so that it is industrially stable. It is difficult to achieve the object of the present invention.

As the alcohol in the coagulation liquid, alcohol such as methanol, ethanol, propanol or the like is used. Preferably, methanol is used, and the same alcohol as the above-mentioned alcohol in the EVOH alcohol solution is preferable. In such a coagulation liquid, if the above conditions are satisfied, saturated aliphatic amides (e.g., stearic acid amide, etc.), unsaturated fatty acid amides (e.g., olefin acid amides, etc.), bis fatty acid amides (e.g., ethylene bis stearic acid, etc.) Lubricants such as amides and fatty acid metal salts (such as calcium stearate); low molecular weight polyolefins (such as low molecular weight polyethylene having a molecular weight of about 500 to 10,000 or low molecular weight polypropylene); and inorganic salts (such as hydrotalcite and the like). ), A plasticizer (for example, an aliphatic polyhydric alcohol such as ethylene glycol, glycerin, and hexanediol). The temperature at which the mixed solution is brought into contact with the coagulating liquid is preferably from -10 to 40C, more preferably from 0 to 20C.

Thus, the EVOH solution is precipitated in the coagulating liquid to form EVOH by the method of the present invention. In the case of such a precipitation, usually, the EVOH solution is extruded into a coagulating liquid by a nozzle having an arbitrary shape into a strand. It is precipitated and then cut to produce a pellet.

The steps will be described below. The shape of the nozzle is not particularly limited, but is preferably a cylindrical shape, and the inner diameter is 0.1 to 10 cm, preferably 0.2 to 5.0 cm. The number of strands extruded from the nozzle is not necessarily one, and any number between several and several hundreds can be extruded. The EVOH extruded in the form of a strand is cut after the coagulation has sufficiently proceeded, pelletized, and then washed with water.

The washing conditions are as follows.
Rinse in a 60 ° C. water bath. By such water washing, EVO
The oligomers and impurities in H are removed, and in particular, sodium acetate is removed to 0.5% by weight or less. The washed pellets are preferably subjected to an acid treatment, for example, acetoacetic acid, formic acid, acetic acid, adipic acid, phosphoric acid, boric acid, etc., and more preferably acetic acid. As the conditions for the acid treatment, for example, washing is performed in an aqueous acetic acid solution of 3% by weight or less, and the treatment is performed so that the pH of the washing solution becomes 3 to 8.

Thus, EVOH pellets can be obtained. The shape of such pellets is 2-5 mm in diameter and 2-5 m in length in the case of a cylindrical shape from the viewpoint of workability during molding and handling.
m, and in the case of a spherical shape, those having a diameter of about 2 to 5 mm are practical.

According to the method of the present invention as described above, EVO having no resin loss or whitening of the pellet surface and excellent in moldability.
H (pellet) is obtained, but such EVO
In the H pellet, if necessary, a plasticizer, a lubricant,
It is also possible to use additives such as coloring agents, antibacterial agents, fillers and other resins. In particular, a hydrotalcite-based compound or a metal salt of a higher aliphatic carboxylic acid can be added as a gel generation inhibitor.

As the EVOH, two or more different EVOHs can be used. In this case, the ethylene content differs by 5 mol% or more and / or the saponification degree is 1%.
It is useful to use a blend of EVOH different in mole% since the stretchability at the time of high stretching and the secondary workability such as vacuum pressure forming and deep drawing can be improved while maintaining gas barrier properties.

Such EVOH pellets are formed into films, sheets, containers, fibers, rods, tubes, various molded products, etc. by melt molding or the like, and these pulverized products (for example, when reusing recovered products) are used. It can be used again for melt molding, and as such a melt molding method, an extrusion molding method and an injection molding method are mainly adopted. Melt molding temperature is 150 ~
It is often selected from the range of 300 ° C. Further, the EVOH obtained in the present invention can be used as a single layer,
It is also useful to laminate a thermoplastic resin layer or the like on at least one side of the EVOH layer and use it as a multilayer laminate.

In producing the laminate, the EV
The other substrate is laminated on one side or both sides of the layer made of OH. As a lamination method, for example, a method of melt-extruding a thermoplastic resin on a film or sheet made of the EVOH, and conversely, a method of laminating a thermoplastic resin or the like A method of melt-extruding the EVOH to a substrate, a method of co-extrusion of the EVOH and another thermoplastic resin, and a film or sheet of the EVOH and a film of another substrate, an organic titanium compound, A dry lamination method using a known adhesive such as an isocyanate compound, a polyester-based compound, or a polyurethane compound may, for example, be mentioned.

In the case of coextrusion, the mating resin may be a linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene -Acrylate copolymer, polypropylene, propylene-α-olefin (having 4 to 20 carbon atoms)
Α-olefins) copolymers, polyolefins such as polybutene and polypentene, and polyolefins in a broad sense such as homo- or copolymers of these olefins or graft-modified homo- or copolymers of these olefins with unsaturated carboxylic acids or esters thereof Resin, polyester, polyamide, copolymerized polyamide, polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene, vinyl ester resin,
Examples thereof include polyester elastomer, polyurethane elastomer, chlorinated polyethylene, and chlorinated polypropylene. Other EVOHs can be coextruded. Among the above, from the viewpoint of ease of coextrusion film formation and practicality of film physical properties (particularly strength), polypropylene, polyamide,
Polyethylene, ethylene-vinyl acetate copolymer, polystyrene, PET, and PEN are preferably used.

Further, a molded product such as a film or a sheet is once obtained from the EVOH obtained in the present invention, and another substrate is extrusion-coated thereon, or the film or sheet of the other substrate is applied using an adhesive. When laminating, any substrate (paper, metal foil, uniaxially or biaxially stretched plastic film or sheet, woven fabric, nonwoven fabric, metallic cotton,
Wood, etc.) can be used.

The layer structure of the laminate is such that the layer composed of the EVOH is a (a ₁ , a ₂ ,...), And the other base material, for example, the thermoplastic resin layer is b (b ₁ , b ₂ ,...). ·) that when a film, a sheet, if a bottle shape, not only the double layer structure of a / b, b / a / b, a / b / a, a 1 / a 2 / b, a /
Any combination such as b ₁ / b ₂ , b ₂ / b ₁ / a / b ₁ / b ₂ is possible. In the filament form, a and b are bimetal type, core (a) -sheath (b) type, core Any combination such as (b) -sheath (a) type or eccentric core-sheath type is possible.

The shape of the laminate thus obtained may be arbitrary, and examples thereof include a film, a sheet, a tape, a bottle, a pipe, a filament, and an extruded product having a modified cross section. Further, the obtained laminate is heat-treated, cooled, rolled, printed, dry-laminated,
Solution or melt coating processing, bag making processing, deep drawing processing, box processing, tube processing, split processing, and the like can be performed. The films, sheets, containers and the like obtained as described above are useful as various packaging materials for foods, pharmaceuticals, industrial chemicals, agricultural chemicals and the like.

[0029]

The present invention will be specifically described below with reference to examples. In the Examples, “parts” and “%” are based on weight unless otherwise specified.

Example 1 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 28 mol% was added 0.017 equivalent of water with respect to an acetic acid group in the copolymer. Methanol solution containing sodium oxide and methanol 150
The saponification reaction was carried out at 130 ° C. under a pressure of 0.76 MPa for 60 minutes, and methyl acetate generated during the reaction was distilled off together with a part of methanol to obtain a saponification degree of 99.2 mol. % EVOH in alcohol (methanol) containing 28% EVOH.

Next, steam was supplied to the obtained alcohol solution to concentrate the solution, thereby obtaining a water-alcohol mixed solution of EVOH having an EVOH content (Z) of 32%. Incidentally, the water content (Y) in the solvent of the mixed solution is 60%, and when the above ethylene content (X = 28 mol%) is substituted into the expression (1) in the text, 71 ≧ Y ≧ 51 The water content (Y) satisfied the expression (1).

Next, the obtained EVOH water-alcohol mixed solution was coagulated at 5 ° C. consisting of 5% methanol and 95% water [alcohol content (M) in the coagulated liquid at this time was 5% Then, when the content of water (Y = 60%) in the solvent of the mixed solution and the content of EVOH (Z = 32%) of the mixed solution are substituted into the expression (2) in the text, M <
100− (60 + 32) = 8, and the alcohol content (M) in the coagulation solution satisfies the expression (2), and the precipitation was performed for about 5 minutes. None] was extruded into a tank from a nozzle (inner diameter 4 mm) in the form of a strand and precipitated (coagulated).

After the coagulation was completed, the strand was cut with a cutter, washed in a water bath at a temperature of 30 ° C. for 1 hour, and washed with water for 4 hours.
After repeated removal of sodium acetate, the temperature was further increased to 30.
Wash in acetic acid water at ℃ for 1 hour, dry and
Pellets (diameter 3.8 mm, length 4 mm) were obtained. The resin loss (loss), the whitening of the pellet surface, and the moldability were evaluated in the following manner.

(Resin Loss) In the above precipitation step, the amount of EVOH charged into the coagulation tank and the EVO eluted in the coagulation solution
From the weight ratio to the H amount, the loss (%) of the EVOH resin was calculated as follows. Resin loss (%) = (eluted EVOH amount / charged EVOH amount)
× 100

(Whitening of pellet surface) EVOH obtained
From the pellets, 200 pieces were taken, and the number of those having a whitened surface on half or more of the surface was visually examined and evaluated as follows. ○ −−− 50 or less △ −−− 50 to less than 100 × −−− 100 or more

(Moldability) The obtained EVOH pellets were
It was supplied to a single-screw extruder equipped with a die, and a 100 μm-thick EVOH film was formed under the following conditions, and evaluated as follows.

[Film forming conditions by single screw extruder] Screw inner diameter 40 mm L / D 28 Screw compression ratio 3.2 T die coat hanger type Die width 450 mm Extrusion temperature C1: 180 ° C, H: 210 ° C C2: 200 ° C, D: 210 ° C C3: 220 ° C, C4: 220 ° C

The film immediately after molding (10 cm × 1
0 cm), gel (foreign matter having a diameter larger than 0.4 mm), fish eye (having a diameter of 0.1 to 0.1 mm).
The occurrence of streaks (foreign matter of 4 mm) and streaks (the number of streaks of 1 μm or more in the film TD direction) was visually observed and evaluated as follows.

Gel ○ −−− 0 to 1 Δ −−− 2 to 4 × −−− 5 or more Fisheye ○ −−− 0 to 10 Δ −−− 11 to 20 × −−− 21 Or more streaks ○ −−− 5 or less △ −−− 6 to 20 × −−− 21 or more

Example 2 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 38 mol% was added 0.017 equivalent of water to the acetic acid group in the copolymer. Methanol solution containing sodium oxide and methanol 150
And a saponification reaction was carried out at 105 ° C. under a pressure of 0.26 MPa for 60 minutes. Methyl acetate generated during the reaction was distilled off together with a part of methanol to give a saponification degree of 99.4 mol. Thus, an alcohol (methanol) solution of EVOH containing 32% of EVOH was obtained.

Next, water and methanol vapors are supplied to the obtained alcohol solution to distill off water and methanol, and the EVOH content (Z) of EVOH water-
An alcohol mixed solution was obtained. Incidentally, the water content (Y) in the solvent of the mixed solution is 30%, and the above ethylene content (X = 38 mol%) is substituted into the expression (1) in the main text.
39 ≧ Y ≧ 19, and the water content (Y) satisfied the expression (1).

Then, the obtained EVOH water-alcohol mixed solution was mixed with 5% methanol and 95% water and maintained at 5 ° C. in a coagulation solution [alcohol content (M) in the coagulation solution was 5% By substituting the content of water (Y = 30%) in the solvent of the mixed solution and the content of EVOH (Z = 40%) of the mixed solution into the equation (2) in the text, M <
100− (30 + 40) = 30, and the alcohol content (M) in the coagulation solution satisfies the formula (2). Precipitation was performed for about 5 minutes. None] was extruded into a tank from a nozzle (inner diameter 4 mm) in the form of a strand and precipitated (coagulated). After the solidification was completed, EVOH pellets were obtained in the same manner as in Example 1, and the evaluation was performed in the same manner.

Example 3 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 45 mol% was added 0.017 equivalent of water with respect to acetic acid groups in the copolymer. Methanol solution containing sodium oxide and methanol 150
And a saponification reaction was carried out at 105 ° C. under a pressure of 0.26 MPa for 60 minutes. Methyl acetate generated during the reaction was distilled off together with a part of methanol to give a saponification degree of 99.4 mol. % EVOH in alcohol (methanol) containing 28% EVOH.

Next, water and methanol vapors are supplied to the obtained alcohol solution to distill water and methanol, and the EVOH content (Z) is 32%.
An alcohol mixed solution was obtained. Incidentally, the water content (Y) in the solvent of the mixed solution was 20%, and the above ethylene content (X = 45 mol%) was substituted into the expression (1) in the text to give:
28 ≧ Y ≧ 8, and the water content (Y) is (1)
The expression was satisfied.

Next, the obtained EVOH water-alcohol mixed solution was coagulated with 8% methanol and 95% water and maintained at 5 ° C. [The alcohol content (M) in the coagulated liquid at this time was 8% Then, when the content of water (Y = 20%) in the solvent of the mixed solution and the content of EVOH (Z = 32%) of the mixed solution are substituted into the expression (2) in the text, M <
100− (20 + 32) = 48, and the alcohol content (M) in the coagulation solution satisfies the expression (2), and the precipitation was performed for about 5 minutes. None] was extruded into a tank from a nozzle (inner diameter 4 mm) in the form of a strand and precipitated (coagulated). After the solidification was completed, EVOH pellets were obtained in the same manner as in Example 1, and the evaluation was performed in the same manner.

Example 4 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 28 mol% was added 0.017 equivalent of water with respect to acetic acid groups in the copolymer. Methanol solution containing sodium oxide and methanol 150
And a saponification reaction was carried out at 120 ° C. under a pressure of 0.70 MPa for 90 minutes, and methyl acetate produced during the reaction was distilled off together with a part of methanol to obtain a saponification degree of 99.4 mol. % EVOH in alcohol (methanol) solution containing 30% EVOH.

Next, steam was supplied to the obtained alcohol solution to obtain a water-alcohol mixed solution of EVOH having an EVOH content (Z) of 40%. The water content (Y) in the solvent of the mixed solution was 55%, and when the above ethylene content (X = 28 mol%) was substituted into the expression (1) in the text, 71 ≧ Y ≧ 51 The water content (Y) satisfied the expression (1).

Then, the obtained EVOH water-alcohol mixed solution was coagulated with 3% methanol and 97% water and maintained at 5 ° C. [The alcohol content (M) in the coagulated liquid at this time was 3% Then, when the content of water (Y = 55%) in the solvent of the mixed solution and the content of EVOH (Z = 40%) of the mixed solution are substituted into the expression (2) in the text, M <
100− (55 + 40) = 5, and the alcohol content (M) in the coagulation solution satisfies the expression (2), and the alcohol content (M) is about 45 hours after the start of precipitation.
Was close to the upper limit, water was added to the coagulation liquid to adjust the alcohol content to 3%.]
m) was extruded into a strand shape and precipitated (solidified). After the solidification was completed, EVOH pellets were obtained in the same manner as in Example 1, and the evaluation was performed in the same manner.

Example 5 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 28 mol% was added 0.017 equivalent of water to an acetic acid group in the copolymer. Methanol solution containing sodium oxide and methanol 150
And a saponification reaction was carried out at 120 ° C. under a pressure of 0.7 MPa for 90 minutes. Methyl acetate generated during the reaction was distilled off together with a part of methanol to give a saponification degree of 9
An alcohol (methanol) solution of EVOH containing 30% of 9.4 mol% EVOH was obtained.

Next, water vapor is supplied to the obtained alcohol solution so that the EVOH content (Z) is 38%.
To obtain a mixed solution of water and alcohol. The water content (Y) in the solvent of the mixed solution was 52%, and when the above ethylene content (X = 28 mol%) was substituted into the expression (1) in the text, 71 ≧ Y ≧ 51 The water content (Y) satisfied the expression (1).

Next, the obtained EVOH water-alcohol mixed solution was treated with a coagulation liquid consisting of 7% methanol and 93% water maintained at 5 ° C. [The alcohol content (M) in the coagulation liquid at this time was 7% Then, when the content of water (Y = 52%) in the solvent of the mixed solution and the content of EVOH (Z = 38%) of the mixed solution are substituted into the expression (2) in the text, M <
100− (52 + 38) = 10, and the alcohol content (M) in the coagulation solution satisfies the expression (2). Since the alcohol content (M) became close to the upper limit about 60 hours after the start of precipitation. Water was added to the coagulation liquid to adjust the alcohol content to 5%]. Extruded into a tank from a nozzle (4 mm inside diameter) in the form of a strand, and precipitated (coagulated).
I let it. After the solidification was completed, EVOH pellets were obtained in the same manner as in Example 1, and the evaluation was performed in the same manner.

Comparative Example 1 To 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 38 mol% was added 0.017 equivalent of water with respect to the acetic acid group in the copolymer. Methanol solution containing sodium oxide and methanol 150
And a saponification reaction was carried out at 105 ° C. under a pressure of 0.26 MPa for 60 minutes. Methyl acetate generated during the reaction was distilled off together with a part of methanol to give a saponification degree of 99.4 mol. Thus, an alcohol (methanol) solution of EVOH containing 32% of EVOH was obtained.

Next, steam of the obtained alcohol solution water and methanol was supplied to distill off water and methanol, and the EVOH content (Z) of the EVOH water-
An alcohol mixed solution was obtained. Incidentally, the water content (Y) in the solvent of the mixed solution was 43%, and the above ethylene content (X = 38 mol%) was substituted into the expression (1) in the text.
39 ≧ Y ≧ 19, and the water content (Y) did not satisfy the expression (1).

Then, the obtained EVOH water-alcohol mixed solution was coagulated with 5% methanol and 95% water and maintained at 5 ° C. [The alcohol content (M) in the coagulated liquid was 5% By substituting the content of water (Y = 40%) in the solvent of the mixed solution and the content of EVOH (Z = 37%) of the mixed solution into the expression (2) in the text, M <
100− (43 + 44) = 13, and the alcohol content (M) in the coagulation liquid satisfies the expression (2).] The resin is extruded into a tank from a nozzle (inner diameter 4 mm) in the form of a strand and precipitated (coagulated). Was. After the solidification was completed, EVOH pellets were obtained in the same manner as in Example 1, and the evaluation was performed in the same manner.

COMPARATIVE EXAMPLE 2 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 38 mol% was added with 0.017 equivalent of water relative to the acetic acid group in the copolymer. Methanol solution containing sodium oxide and methanol 150
And a saponification reaction was carried out at a temperature of 105 ° C. and a pressure of 0.26 MPa for 60 minutes. Methyl acetate generated during the reaction was distilled off together with a part of methanol to obtain a saponification degree of 99.4 mol. % EVOH containing 32% EVOH
(Methanol) solution was obtained.

Next, steam of the obtained alcohol solution water and methanol was supplied to distill off water and methanol to obtain a mixed solution of EVOH containing 35% EVOH in a water-alcohol mixture. The water content (Y) in the solvent of the mixed solution was 15%, and the ethylene content (X = 38
Mol%) into the expression (1) in the text, 39 ≧ Y ≧
As a result, the water content (Y) did not satisfy the expression (1).

Then, the obtained EVOH water-alcohol mixed solution was coagulated with 5% methanol and 95% water and maintained at 5 ° C. [The alcohol content (M) in the coagulated liquid was 5% Then, when the content of water (Y = 15%) in the solvent of the mixed solution and the content of EVOH (Z = 35%) of the mixed solution are substituted into the expression (2) in the text, M <
100− (15 + 35) = 50, and the alcohol content (M) in the coagulation solution satisfies the expression (2).] The resin is extruded into a tank from a nozzle (inner diameter 4 mm) in the form of a strand, and precipitated (coagulated). Was. After the solidification was completed, EVOH pellets were obtained in the same manner as in Example 1, and the evaluation was performed in the same manner.

COMPARATIVE EXAMPLE 3 100 parts of a methanol solution containing 50% of an ethylene-vinyl acetate copolymer having an ethylene content (X) of 28 mol% was added with 0.017 equivalent of water based on acetic acid groups in the copolymer. Methanol solution containing sodium oxide and methanol 150
The saponification reaction was carried out at 130 ° C. under a pressure of 0.76 MPa for 60 minutes, and methyl acetate generated during the reaction was distilled off together with a part of methanol to obtain a saponification degree of 99.2 mol. % EVOH in alcohol (methanol) containing 28% EVOH.

Next, water vapor was supplied to the obtained alcohol solution and concentrated, thereby obtaining a water-alcohol mixed solution of EVOH having an EVOH content (Z) of 32%. Incidentally, the water content (Y) in the solvent of the mixed solution is 60%, and when the above ethylene content (X = 28 mol%) is substituted into the expression (1) in the text, 71 ≧ Y ≧ 51 The water content (Y) satisfied the expression (1).

Next, the obtained EVOH water-alcohol mixed solution was mixed with 10% methanol and 90% water at 5 ° C.
[The alcohol content (M) in the coagulation liquid at this time is 10%, the water content (Y = 60%) in the solvent of the mixed solution and the EVOH of the mixed solution Is substituted into the expression (2) in the text,
M> 100− (60 + 32) = 8, and the alcohol content (M) in the coagulation liquid does not satisfy the formula (2)]. ). After the solidification was completed, EVOH pellets were obtained in the same manner as in Example 1, and the evaluation was performed in the same manner. Table 1 summarizes the evaluation results of the above Examples and Comparative Examples.

[0061]

[Table 1] Resin loss Whitening moldability (%) of pellet surface Example 1 0.18 ○ ○ ○ ○ ○ 2 0.10 ○ ○ ○ ○ ○ 3 0.06 ○ ○ ○ ○ ○ 4 0.15 ○ ○ ○ ○ ５ 5 0.16 ○ ○ ○ ○ Comparative Example 1 0.22 × × △ × 〃 2 0.95 ○ ○ △ × 〃 32.13 ○ △ △ △

[0062]

The EVOH (pellet) of the present invention performs water addition after saponification and precipitation in a coagulation solution so as to satisfy specific conditions, so that resin loss of EVOH and whitening of the pellet surface occur. The EVOH obtained is excellent in moldability and can be made into various laminates, and is very suitable for applications such as films, sheets, tubes, bags, containers and the like for packaging foods, pharmaceuticals, agricultural chemicals, and industrial chemicals. Useful.

Claims (1)

[Claims] 1. Saponifying an ethylene-vinyl acetate copolymer and then depositing the saponified ethylene-vinyl acetate copolymer to obtain a saponified ethylene-vinyl acetate copolymer alcohol solution. A water-alcohol mixed solution of a saponified ethylene-vinyl acetate copolymer is added to water so as to satisfy the condition of the following formula (1), and the mixed solution is then mixed with an alcohol-containing solution satisfying the following formula (2). A method for producing a saponified ethylene-vinyl acetate copolymer, comprising precipitating a saponified ethylene-vinyl acetate copolymer in an aqueous coagulation liquid. 0.0933 × (50−X) ² + 26 ≧ Y ≧ 0.0933 × (50−X) ² +6 (1) (X is ethylene content (mol%), Y is water content in the solvent of the mixed solution) (Weight%)) M <100− (Y + Z) (2) (M is the alcohol content (% by weight) in the coagulation liquid, Y is the same as above, and Z is the ethylene-vinyl acetate copolymer in the mixed solution. Saponified substance content (% by weight)