JP4046245B2 - Process for producing saponified ethylene-vinyl acetate copolymer - Google Patents

Description

【００５０】
▲１▼フィッシュアイ
フィルム１００ｃｍ^２当たりのフィッシュアイの数を測定した。
◎・・・１個以下
○・・・２〜５個以下
△・・・６〜９個以下
×・・・１０以上
【００５１】
▲３▼押出機の負荷変動
５ｈｒ連続製膜中の押出機のモーター負荷（スクリュー回転数６０ｒｐｍでのスクリュートルクＡ（アンペア））の変動により求めた。
○・・・５％以下
△・・・５〜１０％未満
×・・・１０％以上
結果を表１〜３に示した。
【００５５】
比較例１
実施例１の再ケン化工程において、塔底からメタノール１００部のみを共沸点下に供給する様変更し、実施例１と同様に評価した。
【００５６】
実施例２
実施例１において、棚段塔（ケン化塔）の塔上部にエチレン含量３１モル％の エチレン−酢酸ビニル共重合体を実施例１に準じて仕込む以外は同様に実験を行い、実施例１と同様に評価した。
【００５７】
比較例２
実施例１のエチレン−酢酸ビニル共重合体のエチレン含量を１３モル％に替えた以外は実施例１に準じて実験を行い、実施例１と同様に評価した。
【００５８】
比較例３
実施例１のエチレン−酢酸ビニル共重合体のエチレン含量を６５モル％に替えた以外は実施例１に準じて実験を行い、実施例１と同様に評価した。
【００５９】
比較例４
実施例１の工程（１）で塔上部に０．２５ｋｇ／時で水を加えながら、酢酸ビニル成分のケン化度が６０.０モル％のエチレン−酢酸ビニル共重合体部分ケン化物を得、以下工程（２）、（３）は実施例１に準じて実験を行い、実施例１と同様に評価した。
【００６０】
比較例５
実施例１の工程（２）で水酸化ナトリウムの添加をせずに、酢酸ビニル成分のケン化度が９０.０モル％のエチレン−酢酸ビニル共重合体ケン化物を得た以外は実施例１に準じて実験を行い、実施例１と同様に評価した。
【００６１】
比較例６
実施例１の工程（１）で使用する水酸化ナトリウムを０．０２当量に変更した以外は実施例１に準じて実験を行い、ケン化度９９．５モル％のエチレン−酢酸ビニル共重合体部分ケン化物を得た以外は実施例１に準じて実験を行い、実施例１と同様に評価した。
【００６２】
【表１】
エチレン含量 ケン化度（モル％）
（モル％） 部分ケン化物 ケン化物
実施例１ ３５ ８８.０ ９９.８
実施例２ ３１ ９７ . ８ ９９ . ９
比較例１ ３５ ８８.０ ９９.９
比較例２ １３ ９７.０ ９９.９
比較例３ ６５ ７８.０ ９９.５
比較例４ ３５ ６０.０ ９０.０
比較例５ ３５ ８８.０ ９０.０
比較例６ ３５ ＊ ９９ . ５
＊工程（１）でケン化度が９９.５％となり、部分ケン化物に相当するものは得られなかった。
【００６３】
【表２】
ストランド 凝固液
硬化時間 切れ ペレット 汚れ 樹脂損失
サイズ精度 （％）
実施例１ ○ ０ ◎ 透明 ０．５
実施例２ ○ ０ ◎ 透明 ０．８
比較例１ ○ ０ ◎ 透明 ０．６
比較例２ × ５ ◎ 白濁 １５．０
比較例３ （測 定 不 可）＊1
比較例４ （測 定 不 可）＊2
比較例５ ○ ８ × やや白濁 ８．４
比較例６ （測 定 不 可）＊ 1
＊1：工程（１）で既にエチレン−酢酸ビニル共重合体ケン化物が析出し、工 程（３）に入る前で反応液が溶液とならずノズルより押出すことができない。
＊2：ストランドが硬化しない。
【００６４】
【表３】
フィルム
フィッシュ 押出機の
アイ 負荷変動
実施例１ ◎ ○
実施例２ ◎ ○
比較例１ ○ ×
比較例２ △ ×
比較例３ ＊ ＊
比較例４ ＊ ＊
比較例５ × ○
比較例６ ＊ ＊
＊上記の如くペレットが得られず、測定不可。
実施例１において、棚段塔（ケン化塔）の塔上部にエチレン含量３１モル％の エチレン−酢酸ビニル共重合体を実施例１に準じて仕込む以外は同様に実験を行い、実施例１と同様に評価した。
【００６５】
【発明の効果】
本発明では、特定の方法によりエチレン−酢酸ビニル共重合体ケン化物を製造しているので、均一で、尚且つ溶融成型性の優れたエチレン−酢酸ビニル共重合体ケン化物のペレットが得られ、有機溶剤用容器、特にＨＤＰＥとの組み合わせにより農薬ボトル、燃料用タンク容器等に有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a saponified ethylene-vinyl acetate copolymer having a uniform shape and excellent melt moldability.
[0002]
[Prior art]
Saponified ethylene-vinyl acetate copolymer is widely used in various applications such as films, sheets, containers and fibers because of its excellent properties such as oxygen barrier properties and mechanical strength.
Among them, when a sheet or film is produced by melt molding, the copolymer saponified product is preferably in the form of pellets from the handling surface and molding surface, and as a method for producing the pellet, for example, JP-B-47- No. 38634 discloses a method of producing pellets by extruding water and / or methanol mixed solution of ethylene-vinyl acetate copolymer saponified product into water or a methanol-containing aqueous coagulation liquid and cutting the resulting strands. In addition, Japanese Patent Application Laid-Open No. 62-116614 discloses a method of using, as a coagulating liquid, an organic solvent which is compatible with methanol as a coagulating liquid for the strand but does not dissolve the saponified copolymer. Furthermore, in JP-A-62-106904, in order to improve the melt moldability of pellets, Extruded from the dry blend into strands, a process for preparing the pellets is disclosed the agent.
[0003]
[Problems to be solved by the invention]
However, in the technique disclosed in Japanese Patent Publication No. 47-38634, the hardness of the solidified strands is not necessarily sufficient, and there is a drawback that the shape becomes non-uniform or deforms when cut and pelletized. In the technique disclosed in JP-A-116614, since an organic solvent such as methyl acetate is used, there is a disadvantage that equipment for improving the working environment is required and the cost is increased, and further, JP-A-62-106904 is disclosed. In the technology, when a film or sheet is produced by melt-molding the obtained pellets, it is difficult to say that the moldability is always good, and the layer thickness accuracy of the formed film or sheet is still insufficient. In recent years, the layer thickness accuracy of films and sheets is particularly required in the market, but when pellets with poor shape or non-uniform diameter are used for extrusion molding, fluctuations in feeding to the extruder, fluctuations in the load on the extruder, etc. As a result, it is difficult to stably obtain a uniform molded product. Therefore, a saponified ethylene-vinyl acetate copolymer excellent in melt moldability having a uniform shape and a low heat history is desired. ing.
[0004]
[Means for Solving the Problems]
  As a result of intensive studies to solve the above problems, the present inventors have (1)Using a tower reactor, methanolSaponification of an ethylene-vinyl acetate copolymer having an ethylene content of 15 to 60 mol% in a solvent with an alkali catalyst and a partially saponified ethylene-vinyl acetate copolymer having a saponification degree of the vinyl acetate component of 70 to 98 mol% A step of obtaining a solution; (2) using a tower reactor, the ethylene-vinyl acetate copolymer partially saponified product solution is mixed with water or water /methanolForming a mixed solution to which is added, re-saponifying in the presence of an alkali catalyst, and obtaining a saponified solution of a high saponification degree ethylene-vinyl acetate copolymer having a saponification degree of 99.4 mol% or more, ( 3) The above-mentioned three steps (1) to (3) in the step of subjecting the ethylene-vinyl acetate copolymer saponified product solution to extrusion treatment in the form of a strand in a coagulation bath, followed by cutting and pelletizing, and then acid treatment. It was found that the desired saponified ethylene-vinyl acetate copolymer can be obtained by combining the above, and the present invention has been completed.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail for each step.
Process (1)
The ethylene-vinyl acetate copolymer used in the present invention is required to have an ethylene content of 15 to 60 mol%, preferably 20 to 55 mol%, and more preferably 25 to 50 mol%.
[0006]
When the ethylene content is less than 15 mol%, when the product after re-saponification in the subsequent step (2) is precipitated with water, the precipitation is incomplete and emulsified, which is not preferable in operation. The ethylene-vinyl acetate copolymer In order to keep the methanol solution in a uniform solution state, it is necessary to pressurize it and heat it to a considerably high temperature. Further, depending on the residence time, there is a disadvantage that quality deterioration occurs, and when a film or sheet is produced by melt molding, it is easy to generate scorching or gel, which is not preferable.
[0007]
  On the other hand, when it exceeds 60 mol%, it is in the step (2).methanol/ Since it does not dissolve in a mixed solvent, it becomes difficult to carry out re-saponification uniformly, and even when using a method in which the saponification reaction is difficult to proceed when molding after re-saponification, a considerable amount of catalyst is required. For this reason, when the saponified product produced is melt-molded, it is not preferable because it tends to cause fish eyes and hardly improves the mechanical strength.
[0008]
In addition to ethylene and vinyl acetate, the ethylene-vinyl acetate copolymer of the present invention may contain an ethylenically unsaturated monomer copolymerizable therewith as a copolymerization component. Examples of the monomer include olefins such as propylene, isobutylene, α-octene, α-dodecene, α-octadecene, and unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid. Acids or salts thereof or mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or salts thereof, Alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (Meth) allyl ether, polyoxyalkylene (meth) allyl ether such as polyoxypropylene (meth) allyl ether, polyoxyalkylene (meth) acrylate such as polyoxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate , Polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether , Polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, etc. It is below.
[0009]
  In step (1)methanolThe ethylene-vinyl acetate copolymer is saponified with an alkali catalyst in a solvent.. MaThemethanolIt is also preferable to use together with aliphatic polyhydric alcohols such as glycerin, ethylene glycol and hexanediol.
[0010]
The saponification reaction in the step (1) is carried out in the presence of an alkali catalyst, and the alkali catalyst is a conventional saponification reaction using an alkali catalyst of polyvinyl acetate or ethylene-vinyl acetate copolymer. A known 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 t-butoxy potassium, 1,8-diazabicyclo [5,4,10] Cobasic amines represented by undecene-7 (DBU), alkali metal carbonates, alkali metal hydrogen carbonates, and the like can be mentioned. From the viewpoint of ease of handling and catalyst cost, use of sodium hydroxide is preferable.
[0011]
The amount of the catalyst used varies depending on the required degree of saponification, reaction temperature, etc., but 0.03 equivalent or less is used with respect to the remaining acetate groups in the ethylene-vinyl acetate copolymer, and preferably 0.02 equivalent or less. . Moreover, it is also possible to use acid catalysts, such as hydrochloric acid and a sulfuric acid, instead of an alkali catalyst.
[0012]
  In the saponification, the ethylene-vinyl acetate copolymer ismethanolOrmethanolIt melt | dissolves so that it may become a density | concentration of about 20-60 weight% normally in a containing medium, an alkali catalyst or an acid catalyst is added, and it is made to react at the temperature of 40-140 degreeC. The concentration of the partial saponification product is not particularly limited as long as the ethylene-vinyl acetate copolymer partial saponification product (hereinafter abbreviated as “partial saponification product”) is not precipitated at the solution temperature. May be 10 to 50% by weight, preferably 15 to 45% by weight.
[0013]
The saponification degree of the vinyl acetate component of the partially saponified product obtained by such saponification is required to be 70 to 98 mol%, preferably 80 to 98 mol%. When the degree of saponification exceeds 98 mol%, the partially saponified product produced becomes insoluble and precipitates in the reaction medium, resulting in a heterogeneous system, and it is generally difficult to further increase the degree of saponification in the next step. On the other hand, when the degree of saponification is less than 70 mol%, the amount of the alkali catalyst used in the step (2) is increased, and the thermal stability of the product is deteriorated.
[0014]
The obtained partially saponified solution is preferably used as it is for the next step (2) because it is easier to produce and is preferable. However, if necessary, an acetic acid ester by-produced by a saponification reaction, for example, methyl acetate, is used as a reaction solution. Can be removed to the extent that the solution state can be maintained, and is suitable for the re-saponification reaction in the next step (2), in which the partially saponified product is separated from the reaction medium by means of steam distillation, centrifugation, pressing, drying, etc. It may be prepared so as to have a solution composition and subjected to re-saponification reaction. If necessary, ethylene glycol or the like may be added and subjected to re-saponification reaction.
[0015]
  Step (2)
  In this step, in the step of re-saponifying the partially saponified solution obtained in step (1), water or water / water /methanolPlusmethanolReaction is performed in a water / solvent mixture. To dissolve the above partially saponified productmethanolThe reaction is performed in a mixed solvent in which both are mixed at a ratio of 15 to 150 volumes of water with respect to 100 volumes.. or,A small amount of other solvent may be mixed as long as the saponification reaction is not hindered and the coloring property of the product is not impaired.
[0016]
  The above partial saponification product has a specific proportion of the abovemethanolThe saponification reaction can be carried out in a homogeneous system since it can be uniformly dissolved in the / water mixture.
[0017]
  methanolWater and / or so as to have a ratio of 15 to 150 volumes, preferably 15 to 120 volumes of water to 100 volumes.methanolWhen the molded article is made from the saponified ethylene-vinyl acetate copolymer obtained by re-saponification reaction in a mixed solvent, it is preferable from the point that the formation of fish eyes can be prevented, and the amount of water is as described above. The saponified solution becomes unstable even if it is more or less than the range, which may cause precipitation of the saponified product, and is not practical. When the saponified product is molded, it is difficult to avoid the formation of fish eyes.
[0018]
  In such re-saponification, the partially saponified product is removed.methanolThe solution dissolved in the / water mixed solvent is re-saponified by adding an alkali catalyst or an acid catalyst at a temperature of 50 to 145 ° C. The amount of the catalyst used is suitably 0.001 to 0.5 equivalent in the case of alkali with respect to the vinyl acetate group, and 0.005 to 0.5 equivalent in the case of acid. However, the conditions for re-saponification are not limited by the above numerical range.
[0019]
In such re-saponification, the saponification degree of the vinyl acetate component of the saponified high saponification ethylene-vinyl acetate copolymer obtained is required to be 99.4 mol% or more, and 99.5 mol% or more. It is preferable that If the degree of saponification is less than 99.4 mol%, an acetic acid odor occurs during melt molding and fish eyes frequently occur, which is not preferable.
[0020]
Step (3)
In this step, water is first added directly to the saponified ethylene-vinyl acetate copolymer saponified solution obtained in the above step (2), or water is added after concentrating or diluting the saponified solution as appropriate. Thus, a solution for producing a strand is prepared. At this point, lubricants such as saturated aliphatic amides (such as stearic acid amide), unsaturated fatty acid amides (such as olefinic acid amides), bis fatty acid amides (such as ethylene bisstearic acid amide), fatty acid metal salts (such as calcium stearate) Etc.), low molecular weight polyolefin (for example, low molecular weight polyethylene having a molecular weight of about 500 to 10,000, or low molecular weight polypropylene), inorganic salt (for example, hydrotalcite), plasticizer (for example, ethylene glycol, glycerin, hexanediol, etc.) Aliphatic polyhydric alcohol and the like) may be blended.
[0021]
Next, the saponified solution of the high saponification ethylene-vinyl acetate copolymer is extruded in a strand form in the coagulation liquid, and the saponification solution in the saponification solution of the high saponification ethylene-vinyl acetate copolymer is precipitated. The concentration of the compound is preferably 15 to 55% by weight, more preferably 20 to 50% by weight. If it is less than 15% by weight, it is difficult to solidify in the coagulation liquid. Conversely, if it exceeds 55% by weight, the void ratio of the pellet is lowered, which adversely affects the thermal stability during molding.
Further, it is desirable to adjust the weight mixing ratio of water and alcohol in the saponified solution so as to be 1/9 to 7/3, preferably 2/8 to 6/4.
If the ratio of water to alcohol is less than 1/9, the solution becomes slightly unstable, and the porosity during strand deposition slightly decreases. On the other hand, if the ratio exceeds 7/3, the solution becomes unstable and saponification may be precipitated. is there.
[0022]
As the coagulation liquid, water or a water / alcohol mixed solvent is used, and the alcohol concentration when using the alcohol is preferably equal to or lower than the alcohol content of the alcohol / water mixture in the copolymer saponified solution. Exceeding this is not preferable because the polymer loss during strand precipitation in the coagulation liquid increases.
[0023]
Further, it is possible to use an organic solvent having a boiling point of 100 ° C. or less as the coagulation liquid and having compatibility with alcohol, but not dissolving the saponified ethylene-vinyl acetate copolymer having a high saponification degree. Examples of the organic solvent include aromatic hydrocarbons such as benzene, ketones such as acetone and methyl ethyl ketone, ethers such as dipropyl ether, and organic acid esters such as methyl acetate, ethyl acetate, and methyl propionate. The temperature at which the saponified ethylene-vinyl acetate copolymer saponified solution is brought into contact with the coagulation liquid is −10 to 40 ° C., preferably 0 to 20 ° C. Since the above organic solvent is a non-solvent for the saponified product, there is little concern that the saponified product will dissolve in the coagulation liquid and cause resin loss, but operation at as low a temperature as possible is safe.
[0024]
The saponified ethylene-vinyl acetate copolymer solution having a high saponification degree is extruded into a coagulating liquid in a strand form from a nozzle or a die having an arbitrary shape, usually a circular hole. The cross-sectional shape of the pore is usually circular, but depending on the case, it may be oval, square, diamond, star or the like, and the pore diameter is suitably about 1 to 5 mm. Moreover, the strand does not necessarily need to be one, and can be extruded in any number between several to several hundred.
[0025]
The strands are extruded and solidified sufficiently, and then the strands are cut and pelletized.
[0026]
As washing conditions, the pellets are washed in a water bath at a bath ratio (indicating a weight ratio of the saponified ethylene-vinyl acetate copolymer to the weight of the bath coagulation liquid) of 1 to 10 and a temperature of 10 to 60 ° C. By washing with water, oligomers and impurities in EVOH are removed, and particularly sodium acetate is removed to 0.5% by weight or less.
[0027]
In the case of a columnar shape from the viewpoint of workability and handling during molding, those having a diameter of 2 to 5 mm and a length of 2 to 5 mm are practical, and in the case of a spherical shape, those having a diameter of about 2 to 5 mm are practical.
The pellet washed with water needs to be acid-treated, and examples thereof include acetoacetic acid, formic acid, acetic acid, adipic acid, phosphoric acid, boric acid and the like, and more preferably acetic acid is used.
As conditions for the acid treatment, for example, washing is performed in an acetic acid aqueous solution of 3% by weight or less, and the treatment is performed so that the pH of the washing solution becomes 3 to 8.
[0028]
In the present invention, the method is not particularly limited as long as the steps (1) to (3) are sequentially performed. However, for industrial production, the steps (1) and (2) are performed using a known tower reactor ( It is also effective to carry out the saponification reaction continuously using two or more saponification towers. In the present invention, the partial saponification product obtained by performing the operation of the above step (1) in the first tower reactor. The solution is continuously supplied to the second column reactor and the operation of the above step (2) is performed to obtain a saponified solution of a high saponification degree ethylene-vinyl acetate copolymer.
[0029]
  Usable as the first column type reactor is a plate column such as a perforated plate column and a bubble bell column, and a normal distillation column such as a packed column. In general, a plate column with a large residence time is used. Is preferred.
  In the first column reactor, ethylene-vinyl acetate copolymermethanolA method is used in which a solution and an alkali catalyst are supplied, and water-soluble lower alcohol vapor is blown from the bottom or bottom of the column to form a uniform liquid phase in the column to obtain a partially saponified product.
[0030]
  The ethylene-vinyl acetate copolymer ismethanolAs described above, the solution is supplied to the upper part of the column reactor. In this case, the concentration of the copolymer is not particularly limited, but in the case of an extremely high value of 60% by weight or more,methanolThis is not preferable because the viscosity of the solution is increased and the operation is difficult. Of the copolymermethanolThe concentration of the solution is generally preferably 25 to 60% by weight although it depends on the degree of polymerization of the copolymer and the reaction temperature.
[0031]
  As water-soluble lower alcohol blown into the tower, methanolLeUsed. The operation of step (1) using methanol is described below.The
  The temperature of the methanol vapor blown into the tower is usually the boiling point of methanol under the pressure in the tower reactor, but it can be overheated and is preferably 100 to 140 ° C.
[0032]
The pressure in the tower during the reaction is 1 to 15 kg / cm.²The range of G is suitable, and the temperature in the tower is below the boiling point determined from the pressure and composition in the tower, and is in the range of 60 to 150 ° C. The position where the methanol vapor is blown is preferably directly below the bottom stage of the tower and above the liquid level at the bottom of the tower.
[0033]
The partially saponified solution after completion of the reaction in the first column reactor is preferably 20 to 45% by weight of the partially saponified product in order to improve the supply to the second column reactor. Moreover, the saponification degree of the vinyl acetate unit of the partially saponified product is preferably 70 to 98 mol%, more preferably 80 to 97 mol% in order to improve the re-saponification reaction in the second column reactor. .
[0034]
The partially saponified solution obtained by such an operation is then continuously supplied to the second column reactor to perform re-saponification. In this case, a porous reactor can be used as a porous reactor. It is a usual distillation tower such as a plate tower such as a plate tower or bubble tower, or a packed tower, but it is preferable to use a plate tower such as bubble tower.
Alkaline catalyst is fed to the top of the reactor.
[0035]
Thus, an ethylene-vinyl acetate copolymer saponified solution having a saponification degree of the vinyl acetate component of 99.5 mol% or more as described above can be obtained. Thereafter, it is pelletized by the step (3) as described above.
[0036]
The pellets obtained by the production method of the present invention are melt-molded and formed into the desired molded product, and it is desirable that the temperature condition during melt-molding is about 160 to 260 ° C. In molding, a known additive such as a reinforcing material such as glass fiber or carbon fiber, a stabilizer such as a filler, a colorant, or hydrotalcite, a foaming agent, or a desiccant may be appropriately blended. Further, an appropriate amount of a thermoplastic resin for modification can be blended in the saponified ethylene-vinyl acetate copolymer.
[0037]
As the melt molding method, any molding method such as an injection molding method, a compression molding method, and an extrusion molding method can be employed. Among these, the extrusion molding method includes a T-die method, a hollow molding method, a pipe extrusion method, a filament extrusion method, a modified die extrusion method, an inflation method, and the like, but molding of an ethylene-vinyl acetate copolymer saponified product alone. Coextrusion molding of not only products (films, sheets, tapes, bottles, pipes, filaments, profile cross-section extrudates, etc.) but also ethylene-vinyl acetate copolymer saponified layers and other thermoplastic resin layers is possible. .
[0038]
In the case of co-extrusion molding, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-α-olefin (α-olefin having 3 to 20 carbon atoms) Polymers, ethylene-acrylic acid ester copolymers, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene, polypentene, or other olefins alone or copolymers, or these Polyolefin resins such as those obtained by graft-modifying olefin homo- or copolymers with unsaturated carboxylic acids or esters thereof, polyesters, polyamides, copolymerized polyamides, polyvinyl chloride, polyvinylidene chloride, acrylic resins, styrene resins , Vinyl ester resin, polyester error Tomah, polyurethane elastomers, chlorinated polyethylene, and chlorinated polypropylene. Coextrusion with a saponified ethylene-vinyl acetate copolymer having a composition different from that of the present application is also possible.
[0039]
Further, a molded product such as a film or a sheet is once obtained from a saponified ethylene-vinyl acetate copolymer, and this is subjected to extrusion coating with other thermoplastic resin such as polyolefin, or an adhesive for film or sheet of other thermoplastic resin. When laminating, any substrate (paper, metal foil, stretched or unstretched plastics film or sheet, woven fabric, non-woven fabric, metal foil, wood surface, etc.) is saponified with ethylene-vinyl acetate copolymer. It is also possible to coat by extrusion coating (in some cases, other resin, for example, heat sealable resin may be extrusion coated).
[0040]
Molded, co-extruded, and melt-coated products after melt molding are heat treated, cooled, rolled, uniaxial or biaxially stretched, printed, dry laminated, solution or melt coated, Bag processing, deep drawing processing, box processing, tube processing, split processing, etc. can be performed.
[0041]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples. In the examples, “parts” and “%” are based on weight unless otherwise specified.
[0042]
Example 1
Process (1)
A methanol solution containing an ethylene content of 35 mol% and an ethylene-vinyl acetate copolymer at a rate of 10 kg / hr was supplied to the upper portion of the plate tower (saponification tower), and at the same time, residual acetate groups in the polymer. In contrast, a methanol solution containing 0.002 equivalents of sodium hydroxide was supplied from the top of the tower. On the other hand, methanol vapor was supplied from the bottom of the column at a rate of 15 kg / hr. The tower temperature is 128 ° C and the tower pressure is 5 kg / cm.²G. From 10 minutes after the start of charging, the ethylene-vinyl acetate copolymer partially saponified solution was taken out. The ethylene-vinyl acetate copolymer partially saponified solution obtained from the bottom of the column is a completely transparent homogeneous solution, the composition of which is 35% ethylene-vinyl acetate copolymer partially saponified, 65% methanol, and ethylene-acetic acid. The saponification degree of the vinyl acetate component of the partially saponified vinyl copolymer was 88.0 mol%.
[0043]
  Step (2)
  Subsequently, the partially saponified solution is supplied to the upper part of another plate tower (saponification tower), and at the same time, a methanol solution containing 0.015 equivalents of sodium hydroxide with respect to acetic acid groups in the copolymer is prepared. It was supplied from the top of the tower. On the other hand, both were mixed at a ratio of 30 parts water to 100 parts methanol from the bottom.The boilingSupplied below the spot. The temperature inside the tower was 140 ° C. at the bottom, 128 ° C. at the top, and the pressure was 5 kg / cm 2 G. The saponified ethylene-vinyl acetate copolymer saponified solution obtained from the bottom of the column is a completely transparent homogeneous solution, and the saponification degree of the vinyl acetate component of the saponified ethylene-vinyl acetate copolymer is 99.8 mol. %Met.
[0044]
Step (3)
Subsequently, the ethylene-vinyl acetate copolymer saponified product solution was extruded in a strand form from a nozzle having a pore diameter of 4 mm into a coagulating liquid tank maintained at 5 ° C. composed of 5% methanol and 95% water. The time required for the strands to cure was 30 seconds. After completion of the solidification, the strand was cut with a cutter to obtain white and porous pellets having a diameter of 3.8 mm and a length of 4 mm. The obtained pellets were uniform in shape and had no deformation. The coagulation liquid was not turbid at all and the resin loss was 1% or less. The porous pellet was washed with water in a water bath at a temperature of 30 ° C. for 1 hour, and this was repeated four times. After removing sodium acetate, the product washed for 1 hour in acetic water at a temperature of 30 ° C. was dried and dried. Turned into.
[0045]
(1) Strand evaluation
(1) Curing time
The strand hardness was measured in accordance with JIS K 6301 with a spring-type hardness tester (Shimadzu Corporation) until the hardness reached 30 degrees or more, and evaluated as follows.
○ ・ ・ ・ 80 seconds or less
× ・ ・ ・ 81 seconds or more
[0046]
▲ 2 ▼ Cut of strand
The number of strand breaks during the 36-hour operation was measured and expressed as the number of breaks per 10 strands.
[0047]
(3) Accuracy of pellet size
The diameter and length of 100 pellets were measured with a vernier caliper, and the ratio of the pellets whose diameter and length were within the range of ± 0.2 mm was measured and evaluated as follows.
◎ ... 95% or more
○ ... 80-95%
△ ... Less than 60-80%
× ... less than 60%
[0048]
(4) Coagulation stain and resin loss
The contamination of the coagulation liquid was visually observed, and the resin loss into the coagulation liquid was calculated by the following equation.
Resin loss (% by weight) = ((A−B) / A) × 100
A: Weight of high saponification ethylene-vinyl acetate copolymer saponification solution in saponification solution of high saponification ethylene-vinyl acetate copolymer before entering the coagulation liquid
B: Weight of saponified ethylene-vinyl acetate copolymer having high saponification degree in the obtained strand pellets
[0049]
(2) Film performance
The obtained product pellets were formed under the following conditions, and the appearance of the obtained film was observed.

[0050]
▲ 1 Fisheye
100cm film²The number of fish eyes per was measured.
◎ ... 1 piece or less
○ 2-5 or less
△ ... 6-9 or less
× ・ ・ ・ 10 or more
[0051]
(3) Extruder load fluctuation
It was determined by fluctuations in the motor load of the extruder (screw torque A (ampere) at a screw speed of 60 rpm) during continuous film formation for 5 hours.
○ ・ ・ ・ 5% or less
Δ: Less than 5-10%
× ... 10% or more
The results are shown in Tables 1-3.
[0055]
Comparative Example 1
In the re-saponification process of Example 1, it changed so that only 100 parts of methanol might be supplied under an azeotropic point from the tower bottom, and evaluated similarly to Example 1. FIG.
[0056]
Example2
  In Example 1, an experiment was conducted in the same manner as in Example 1 except that an ethylene-vinyl acetate copolymer having an ethylene content of 31 mol% was charged in the upper part of the plate tower (saponification tower) according to Example 1. Evaluation was performed in the same manner.
[0057]
Comparative Example 2
An experiment was performed according to Example 1 except that the ethylene content of the ethylene-vinyl acetate copolymer of Example 1 was changed to 13 mol%, and evaluation was performed in the same manner as in Example 1.
[0058]
Comparative Example 3
An experiment was performed according to Example 1 except that the ethylene content of the ethylene-vinyl acetate copolymer of Example 1 was changed to 65 mol%, and evaluation was performed in the same manner as in Example 1.
[0059]
Comparative Example 4
While adding water at 0.25 kg / hour to the top of the column in step (1) of Example 1, an ethylene-vinyl acetate copolymer partially saponified product having a vinyl acetate component saponification degree of 60.0 mol% was obtained, The following steps (2) and (3) were conducted according to Example 1 and evaluated in the same manner as in Example 1.
[0060]
Comparative Example 5
Example 1 except that a saponified ethylene-vinyl acetate copolymer having a saponification degree of the vinyl acetate component of 90.0 mol% was obtained without adding sodium hydroxide in the step (2) of Example 1. An experiment was conducted according to the above and evaluated in the same manner as in Example 1.
[0061]
Comparative Example 6
An experiment was conducted according to Example 1 except that the sodium hydroxide used in step (1) of Example 1 was changed to 0.02 equivalent, and an ethylene-vinyl acetate copolymer having a saponification degree of 99.5 mol% was obtained. An experiment was performed according to Example 1 except that a partially saponified product was obtained, and evaluation was performed in the same manner as in Example 1.
[0062]
[Table 1]
            Ethylene contentSaponification degree (mol%)
(Mol%) Partial saponification product Saponification product
Example 1 35 88.0 99.8
Example 2 31 97 . 8 99 . 9
Comparative Example 1 35 88.0 99.9
Comparative Example 2 13 97.0 99.9
Comparative Example 3 65 78.0 99.5
Comparative Example 4 35 60.0 90.0
Comparative Example 5 35 88.0 90.0
Comparative Example 6 35 * 99 . 5
  * In step (1), the saponification degree was 99.5%, and a product corresponding to a partially saponified product was not obtained.
[0063]
[Table 2]
          Strand      Coagulation liquid
          Curing time expired Pellet Dirt Resin loss
Size accuracy (%)
Example 1 ○ 0 ◎ Transparent 0.5
Example 2 ○ 0 ◎ Transparent 0.8
Comparative Example 1 ○ 0 ◎ Transparent 0.6
Comparative Example 2 × 5 ◎ Cloudiness 15.0
Comparative Example 3 (Measurement not possible) * 1
Comparative Example 4 (Measurement not possible) * 2
Comparative Example 5 ○ 8 × Slightly cloudy 8.4
Comparative Example 6 (Measurement not possible) * 1
  * 1: The saponified ethylene-vinyl acetate copolymer has already precipitated in step (1), and the reaction solution does not become a solution and cannot be extruded from the nozzle before entering step (3).
  * 2: Strand does not harden.
[0064]
[Table 3]
          the film
            Fish extruder
Eye load fluctuation
Example 1 ◎ ○
Example 2 ◎ ○
Comparative Example 1 ○ ×
Comparative Example 2
Comparative Example 3 **
Comparative Example 4 **
Comparative Example 5 × ○
Comparative Example 6 **
  * As above, pellets cannot be obtained and measurement is not possible.
  In Example 1, an experiment was conducted in the same manner as in Example 1 except that an ethylene-vinyl acetate copolymer having an ethylene content of 31 mol% was charged in the upper part of the plate tower (saponification tower) according to Example 1. Evaluation was performed in the same manner.
[0065]
【The invention's effect】
In the present invention, since a saponified ethylene-vinyl acetate copolymer is produced by a specific method, a pellet of a saponified ethylene-vinyl acetate copolymer that is uniform and excellent in melt moldability is obtained. It is useful for agrochemical bottles, fuel tank containers, etc. in combination with organic solvent containers, particularly HDPE.

Claims (2)

(1) Using a tower reactor, an ethylene-vinyl acetate copolymer having an ethylene content of 15 to 60 mol% in a methanol solvent is converted to a saponification degree of a vinyl acetate component of 70 to 98 mol% with an alkali catalyst. Saponifying to obtain an ethylene-vinyl acetate copolymer partially saponified solution,
(2) Using a tower reactor, water or water / methanol is added to the ethylene-vinyl acetate copolymer partially saponified solution at a boiling point to form a mixed solution, and then re-saponified in the presence of an alkali catalyst. Performing a high saponification degree ethylene-vinyl acetate copolymer saponified solution having a saponification degree of the vinyl acetate component of 99.4 mol% or more,
(3) The above saponification degree ethylene-vinyl acetate copolymer saponified product solution is formed by a combination of the above three steps (1) to (3) in the step of extruding and precipitating the saponified solution in a coagulation bath and acid treatment. A process for producing a saponified ethylene-vinyl acetate copolymer . The step (2) of obtaining a saponified ethylene-vinyl acetate copolymer saponification solution having a saponification degree of 99.4 mol% or more is formed using a tower reactor to form a uniform liquid phase in the tower. preparation of vinyl acetate copolymer saponification product - claim 1 Symbol placement of ethylene and performing saponification reaction.