JP2010042687A - Method of producing ethylene-vinyl alcohol copolymer pellet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EVOH (ethylene-vinyl alcohol copolymer) pellet, without worsening work environment or ambient environment, with stable production and high washing speed. <P>SOLUTION: In the method of producing the ethylene-vinyl alcohol copolymer pellet, an ethylene-vinyl alcohol copolymer hydrous composition containing 0-10 pts.wt. alcohol with a boiling point of ≤100°C and 10-500 pts.wt. water based on 100 pts.wt. ethylene-vinyl alcohol copolymer, is cut in a molten state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing ethylene-vinyl alcohol copolymer pellets, and more particularly, to a method for producing ethylene-vinyl alcohol copolymer pellets in which a water-containing composition of ethylene-vinyl alcohol copolymer is cut in a molten state.

  An ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is a useful polymer material excellent in oxygen barrier properties, aroma retention properties, oil resistance properties, non-charging properties, mechanical strength, and the like. It is widely used by being molded into sheets, containers and the like. As a method for producing EVOH, there is a method in which an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and a fatty acid vinyl ester such as vinyl acetate is saponified in an organic solvent containing an alcohol in the presence of a saponification catalyst. It is common.

  As a post-treatment method of the alcohol solution of EVOH obtained by saponification, after concentrating the methanol solution of EVOH as required in Patent Document 1, water is added in such an amount that EVOH does not precipitate. A methanol-water mixed solution of EVOH containing 15 to 45% by weight is extruded, and this is extruded into water at 50 ° C. or lower or a methanol-water mixed solution having a lower methanol concentration than the above solution to precipitate in a strand shape. Describes a method for producing EVOH pellets cut from At this time, the methanol-water mixed solution in the coagulation bath preferably contains 10 to 50% by weight of methanol. It is described that the pellets thus obtained are porous, and the saponification catalyst residue can be easily removed by washing with water, and can be easily handled in the subsequent washing and drying process.

As a method for adding water to a methanol solution of EVOH after saponification, for example, in Example 1 of Patent Document 2, a methanol content of EVOH having a resin concentration of 30% by weight has a water content of 62.5% by weight. An aqueous methanol solution was supplied under azeotropic conditions of 100 to 110 ° C. and a pressure of 3 kg / cm ² G, and methanol was distilled off until the resin concentration was 40% by weight. Is described.

Japanese Patent Publication No. 47-38634 JP-A-11-90927

  However, when EVOH pellets are produced by a method in which an EVOH solution containing a large amount of methanol is precipitated in a coagulation bath as described above, alcohol may be volatilized during the precipitation operation. The volatilization of alcohol not only deteriorates the work environment and impairs the health of workers, but also adversely affects the surrounding environment, and there has been a need for improvement.

  Further, among EVOH, when EVOH having an ethylene content of less than 20 mol% and / or EVOH having a saponification degree of less than 95% is employed, the solidification rate in the coagulation liquid is slow because of the slow coagulation rate. Therefore, it is difficult to precipitate, so that cut mistakes and fine powders are likely to be mixed, and it is difficult to stably produce. Moreover, even if EVOH has an ethylene content of 20 mol% or more and a saponification degree of 95% or more, in order to improve production efficiency, if precipitation of strands is performed at a high speed or by increasing the number of nozzles, solidification may occur. Insufficient or difficult to handle, it was difficult to produce stably due to frequent cut mistakes.

  Furthermore, since the pellet obtained by the conventional method contains alcohol and an alkali metal salt which is a catalyst residue at the time of saponification, a washing step is required to remove these. In order to increase the cleaning speed, it is effective to increase the temperature of the cleaning solution. However, if the temperature is increased too much, alcohol is contained in the pellets, so the pellets are fused together and the cleaning speed is sufficiently increased. There was a problem that it was not possible.

  That is, an object of the present invention is to provide an EVOH pellet that can be stably produced without deteriorating the working environment and the surrounding environment and has a high cleaning speed.

  The inventors of the present invention have made extensive studies, and ethylene-vinyl alcohol copolymer pellets that cut a molten ethylene-vinyl alcohol copolymer water-containing composition in which the alcohol and water contents are in a certain range, respectively. It has been found that the above-mentioned problems can be solved by providing the manufacturing method.

  That is, the present invention relates to a water-containing composition of ethylene-vinyl alcohol copolymer containing 0 to 10 parts by weight of alcohol having a boiling point of 100 ° C. or less and 10 to 500 parts by weight of water with respect to 100 parts by weight of ethylene-vinyl alcohol copolymer. This is a method for producing ethylene-vinyl alcohol copolymer pellets, wherein the product is cut in a molten state.

At this time, it is preferable that the cutting method is a hot cut method or an underwater cut method.
The ethylene-vinyl alcohol copolymer preferably has an ethylene content of 3 to 70 mol% and a saponification degree of 80 mol% or more.

  In the production method, an ethylene-vinyl alcohol copolymer solution containing 50 parts by weight or more of an alcohol having a boiling point of 100 ° C. or less with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer is introduced into the container. A preferred embodiment includes a production method in which the water-containing composition of ethylene-vinyl alcohol copolymer obtained by bringing the alcohol into contact with water vapor and cutting out the water together with water vapor is cut in a molten state. At this time, the ethylene-vinyl alcohol copolymer water-containing composition obtained by bringing the alcohol into contact with water vapor in the vessel and deriving the alcohol together with water vapor and further reducing the water content with a kneader is cut in a molten state. Is preferred.

  Further, the content of the alkali metal salt in the molten ethylene-vinyl alcohol copolymer water-containing composition before cutting is 0.1 to 5 parts by weight in terms of metal with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. It is preferable that Then, the pellets obtained by cutting in a molten state are washed, and the content of the alkali metal salt is preferably 0.05 parts by weight or less in terms of metal with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. is there. The temperature of the cleaning liquid at the time of cleaning is preferably 0 to 95 ° C.

In a preferred embodiment, at least one selected from the group consisting of a carboxylic acid, a boron compound, a phosphate compound, an alkali metal salt and an alkaline earth metal salt is added to the pellet obtained by cutting in a molten state. is there.
Further, a method for producing ethylene-vinyl alcohol copolymer pellets in which pellets obtained by cutting in a molten state are dried so that the moisture content is 1% by weight or less is also a preferred embodiment.

  According to the present invention, EVOH pellets that can be stably produced and have a high cleaning speed can be provided without deteriorating the working environment and the surrounding environment.

It is a figure which shows the example of a structure of the hot cutter used by this invention.

  EVOH used in the present invention is usually obtained by saponifying an ethylene-vinyl ester copolymer. The ethylene content is usually 3 to 70 mol%, and from the viewpoint of obtaining a molded article excellent in gas barrier properties and melt moldability, preferably 10 to 60 mol%, more preferably 20 to 55 mol%, Optimally, it is preferably 25 to 55 mol%. Furthermore, the saponification degree of the vinyl ester component is usually 80 mol% or more, and preferably 95 mol% or more, particularly preferably 99 mol% or more, from the viewpoint of obtaining a molded article having excellent gas barrier properties.

  On the other hand, EVOH having an ethylene content of 3 to 20 mol% is suitably used as EVOH having water solubility, and such an EVOH aqueous solution is excellent in barrier properties and film formability and is used as an excellent coating material.

  In addition, EVOH having a saponification degree of 80 to 95 mol% may be used to improve molding processability. Such EVOH can be used alone, but an embodiment in which EVOH is blended with EVOH having a saponification degree exceeding 99 mol% is also suitable.

  However, from the viewpoint of the production process, EVOH having an ethylene content of 3 to 20 mol% and EVOH having a saponification degree of 80 to 95 mol% are both formed into a strand form of a methanol solution of EVOH in a coagulation bath. It was difficult to extrude and precipitate. The present invention is also significant from the viewpoint that it is possible to easily coagulate against such EVOH and the pellets can be stably produced.

  When the ethylene content of EVOH is less than 3 mol%, melt moldability is generally poor, and water resistance, hot water resistance, and gas barrier properties under high humidity may be reduced. On the other hand, when it exceeds 70 mol%, barrier properties and printability are often insufficient. On the other hand, when the degree of saponification is less than 80 mol%, the barrier properties, coloring resistance and moisture resistance are often unsatisfactory.

  The EVOH production method will be specifically described below. Polymerization of ethylene and vinyl ester is not limited to solution polymerization, and may be any of solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization. Moreover, any of a continuous type and a batch type may be sufficient. An example of polymerization conditions for batch solution polymerization is shown below.

Solvent; alcohol having a boiling point of 100 ° C. or lower is used. Alcohol is used from the viewpoint of solubility of ethylene-vinyl ester copolymer or EVOH and handling. The reason why the boiling point is required to be 100 ° C. or less is that when alcohol is replaced with water, alcohol having a boiling point lower than that of water is more efficiently replaced. The boiling point is preferably 80 ° C. or lower, and more preferably 70 ° C. or lower.
Examples of the alcohol having a boiling point of 100 ° C. or lower include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, t-butyl alcohol and the like, and methyl alcohol is particularly preferable.

  Catalyst: 2,2-azobisisobutyronitrile, 2,2-azobis- (2,4-dimethylvaleronitrile), 2,2-azobis- (4-methoxy-2,4-dimethylvaleronitrile), 2 , 2-azobis- (2-cyclopropylpropionitrile) and other azonitrile initiators and isobutyryl peroxide, cumylperoxyneodecanoate, diisopropylperoxycarbonate, di-n-propylperoxydicarbonate, t Organic peroxide initiators such as butyl peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide can be used.

  Vinyl ester; vinyl acetate, fatty acid vinyl ester (vinyl propionate, vinyl pivalate, etc.) can be used, but vinyl acetate is preferred. Moreover, EVOH can contain 0.0002-0.2 mol% of vinyl silane compounds as a copolymerization component. Here, examples of the vinylsilane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane, and γ-methacryloxypropylmethoxysilane. Of these, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used.

The polymerization conditions are as follows.
(1) Temperature; 20 to 90 ° C, preferably 40 to 70 ° C.
(2) Time: 2 to 15 hours, preferably 3 to 11 hours.
(3) Polymerization rate: 10 to 90%, preferably 30 to 80%, relative to the charged vinyl ester.
(4) Resin content in the solution after polymerization; 5 to 85%, preferably 20 to 70%.
(5) Ethylene content in the copolymer; 3-70 mol%. Preferably 10-60 mol%, more preferably 20-55 mol%, optimally 25-55 mol%.

  In addition to ethylene and vinyl esters, monomers that can be copolymerized with these, for example, α-olefins such as propylene, isobutylene, α-octene, α-dodecene; acrylic acid, methacrylic acid, crotonic acid, maleic acid, itacone Unsaturated acids such as acids or their anhydrides, salts, mono- or dialkyl esters, etc .; Nitriles such as acrylonitrile and methacrylonitrile; Amides such as acrylamide and methacrylamide; Ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfone An olefin sulfonic acid such as an acid or a salt thereof; alkyl vinyl ethers, vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride and the like may be present in a small amount.

  After polymerization for a predetermined time, after reaching a predetermined polymerization rate, a polymerization inhibitor is added if necessary, and unreacted ethylene gas is removed by evaporation, and then unreacted vinyl ester is driven out. As a method for driving off the unreacted vinyl ester from the ethylene-vinyl ester copolymer from which ethylene has been removed by evaporation, for example, the copolymer solution is continuously fed at a constant rate from the upper part of the column filled with Raschig rings, An organic solvent, preferably an alcohol having a boiling point of 100 ° C. or less, is optimally blown from the bottom, and a vapor mixture of the organic solvent and the unreacted vinyl ester is distilled from the top of the column, and the unreacted vinyl ester from the bottom of the column. For example, a method of taking out the copolymer solution from which is removed is adopted.

An alkali catalyst is added to the copolymer solution from which unreacted vinyl ester has been removed to saponify the vinyl ester component in the copolymer. The saponification method can be either continuous or batch. As the alkali catalyst, sodium hydroxide, potassium hydroxide, alkali metal alcoholate or the like is used. For example, the saponification conditions in the case of a batch type are as follows.
(1) Concentration of the copolymer solution: 10 to 50%
(2) Reaction temperature: 30 to 65 ° C
(3) Amount of catalyst used: 0.02 to 1.0 equivalent (per vinyl ester component)
(4) Time: 1-6 hours

The EVOH solution after the reaction usually contains 50 parts by weight or more of alcohol having a boiling point of 100 ° C. or less with respect to 100 parts by weight of EVOH. The content of the alcohol is preferably 70 parts by weight or more, and more preferably 80 parts by weight or more. The alcohol content is preferably 1000 parts by weight or less, and more preferably 500 parts by weight or less. By setting it as such alcohol content, the fluidity | liquidity of EVOH solution is ensured and efficient resin manufacture is possible. The alcohol is preferably methanol.
The EVOH solution after saponification may be not only an alcohol solution but also a mixed solvent solution to which other solvent such as water is added as required. Examples of the method for adding water include the methods described in the prior art.

The present invention relates to a water-containing composition of ethylene-vinyl alcohol copolymer containing 0 to 10 parts by weight of alcohol having a boiling point of 100 ° C. or less and 10 to 500 parts by weight of water with respect to 100 parts by weight of ethylene-vinyl alcohol copolymer. Is a method for producing ethylene-vinyl alcohol copolymer pellets, characterized by cutting in a molten state.
In order to obtain a water-containing composition having such a composition, it is necessary to remove alcohol from the EVOH solution after saponification and to replenish water as necessary. The method for this is not particularly limited, but an ethylene-vinyl alcohol copolymer solution containing 50 parts by weight or more of an alcohol having a boiling point of 100 ° C. or less with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer is used as a container. The alcohol is brought into contact with water vapor in the container to bring out the alcohol together with the water vapor, and 0 to 10 parts by weight of the alcohol and 10 to 500 parts by weight of water with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. A suitable method is a method of deriving the water-containing ethylene-vinyl alcohol copolymer composition from the container.

  That is, as described above, the EVOH solution after saponification is usually obtained as a solution containing a large amount of alcohol. By introducing such an EVOH solution into a reaction vessel and bringing it into contact with water vapor in the vessel, the alcohol is dissolved. An EVOH water-containing composition having a low alcohol content can be derived from the container together with water vapor.

  The method of bringing the EVOH solution introduced into the container into contact with water vapor in the container is not particularly limited, and any of a continuous method and a batch method may be used. Further, the form of the container is not particularly limited, but a tower type container is suitable for the continuous type, and a tank type container is suitable for the batch type. In view of production efficiency, the continuous type is desirable industrially. Examples of the tower-type container include a plate tower such as a perforated plate tower and a bubble bell tower, and a packed tower containing a ring-type packing.

  The EVOH solution introduced into the processing vessel and the water vapor are preferably contacted in countercurrent from the viewpoint of alcohol removal efficiency. For example, in a tower-type container, an EVOH solution is introduced from the upper part of the tower, steam is introduced from the lower part of the tower and brought into countercurrent contact with the solution, an EVOH hydrous composition is led out from the lower part of the tower, and alcohol is introduced together with water vapor from the upper part of the tower. The method of deriving can be cited as a preferred embodiment. The alcohol vapor and water vapor derived from the top of the column are condensed by a condenser, taken out as an aqueous alcohol solution, and can be purified and reused as necessary.

  If the amount of water vapor introduced is too small, the alcohol removal efficiency is poor, and conversely if too large, it is disadvantageous in terms of cost. Weight ratio), preferably 0.5 to 10 times, more preferably 0.7 to 5 times. The water vapor that is brought into contact with the EVOH solution may contain 10 parts by weight or less of alcohol with respect to 100 parts by weight of water vapor. However, in order to remove the alcohol efficiently, it is preferable that the water vapor does not contain alcohol. .

It is preferable that the temperature in a processing container is 100-150 degreeC. When the temperature in the container is lower than 100 ° C., the fluidity of the EVOH water-containing composition becomes insufficient, which may cause gelation or clogging in the processing container. More preferably, it is 110 degreeC or more, More preferably, it is 120 degreeC or more. On the other hand, when the temperature in the container exceeds 150 ° C., the EVOH resin may deteriorate. More preferably, it is 140 ° C. or lower.
Further, if the pressure in the processing container is too low, the alcohol removal efficiency is poor, and if it is too high, the temperature of the EVOH solution in the processing container rises and the EVOH tends to be thermally deteriorated. 6 kg / cm ^2, preferably, 1.5~5kg / cm ^2, more preferably preferably carried out at 2-4 kg / cm ^2.

In the above method, the EVOH solution is in direct contact with water vapor in the container, and the alcohol content gradually decreases. Meanwhile, the EVOH is in the form of a swollen paste and does not gel while maintaining fluidity. It is possible to derive from
EVOH is dissolved in a water / methanol mixed solvent having a temperature of about 60 to 70 ° C. under normal pressure, but cannot be dissolved under normal pressure when the solvent is water alone. However, for example, in the presence of pressurized steam at a temperature of 100 ° C. or higher, fluidity can be maintained even when EVOH is substantially in a state containing only water. As a result, it is also easy to carry out continuous processing using, for example, a tower-shaped container.

  The EVOH water-containing composition derived from the container by the above method contains 0 to 10 parts by weight of the alcohol and 10 to 500 parts by weight of water with respect to 100 parts by weight of EVOH, and is derived from the container in a fluid state. The

The present invention relates to a water-containing composition of ethylene-vinyl alcohol copolymer containing 0 to 10 parts by weight of alcohol having a boiling point of 100 ° C. or less and 10 to 500 parts by weight of water with respect to 100 parts by weight of ethylene-vinyl alcohol copolymer. Is cut in a molten state.
Here, the content of the alcohol in the molten EVOH hydrous composition is 0 to 10 parts by weight, preferably 0 to 5 parts by weight, more preferably 0 to 1 part by weight, and even more preferably 0. -0.1 parts by weight. Since the alcohol content is small, it is possible to prevent the alcohol from being volatilized in a later process, and it is possible to maintain the work environment or the surrounding environment. Further, when washing the saponification catalyst residue or the like, the pellets are less likely to stick together even if the washing water temperature is raised, so that the washing water temperature can be raised, and as a result, the washing speed can be raised.

The water content in the molten EVOH hydrous composition is 10 to 500 parts by weight. When the water content is less than 10 parts by weight, for example, when the water-containing composition is produced by the above-described method, the fluidity in the processing container is insufficient, and the fluidity at the time of cutting is also insufficient. The amount is preferably 30 parts by weight or more, and more preferably 50 parts by weight or more. On the other hand, when the content of water exceeds 500 parts by weight, there arises a problem that when cutting in a molten state, the pellets after cutting are fused to each other or the shape is not uniform. The amount is preferably 300 parts by weight or less, and more preferably 200 parts by weight or less.
The EVOH water-containing composition thus obtained usually contains from 0.1 to 5% by weight of alkali metal salt in terms of metal, by-product salts, other impurities, and the like.

  This invention manufactures a pellet by cut | disconnecting the said EVOH hydrous composition. Specifically, the EVOH water-containing composition is cut in a molten state.

  As a method of directly cutting the EVOH hydrous composition in a molten state, a hot cut method or an underwater cut method is exemplified as a suitable method. From the viewpoint of easy handling of the pellets, the nozzle diameter is preferably 2 to 5 mmφ (φ is the diameter, the same applies hereinafter). An example of a hot cutter used in the hot cut method is shown in FIG. 1 is an EVOH water-containing composition supply port, 2 is a die, 3 is a rotary blade, 4 is a rotary shaft, 5 is a cutter box, 6 is a cooling water supply port, 7 is cooling water, 8 is a water film, and 9 is pellet discharge. Outlet 10 is cooling water and pellets.

  When the water content in the EVOH water-containing composition is high, water may be separated from the EVOH water-containing composition, and the separated water is discharged from the nozzle, so that stable cutting may be difficult. Therefore, it is preferable that the water content in the EVOH hydrous composition is reduced in advance with a kneader or the like and then discharged from the nozzle and cut.

  The pellets thus obtained usually contain an alkali metal salt that is a residue of the catalyst used during saponification, and if it is contained in a large amount, quality problems such as coloring occur, and therefore, it is preferable to remove it by washing. The cleaning method is not particularly limited, and examples include a method of cleaning by immersing in water or an aqueous solution of an acid such as acetic acid. The cleaning method is not particularly limited, and examples include a method of cleaning by immersing in water or an aqueous solution of an acid such as acetic acid.

  The washing temperature can be employed in the range of 0 to 95 ° C. From the viewpoint of improving the cleaning efficiency, a higher cleaning temperature is preferable, but if the temperature is too high, fusion between the pellets is not preferable. The lower limit of the washing temperature is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, and most preferably 40 ° C. or higher. The conventional cleaning temperature is generally about 25 to 30 ° C., and it is one of the features of the present invention that the cleaning temperature can be made higher than that. Moreover, the upper limit of the washing temperature is preferably 80 ° C. or less, and more preferably 70 ° C. or less. The alkali metal salt content after washing is 0.05 parts by weight or less, more preferably 0.03 parts by weight or less in terms of metal with respect to 100 parts by weight of EVOH.

  In order to improve the quality such as thermal stability, it is preferable to add at least one selected from the group consisting of carboxylic acid, boron compound, phosphoric acid compound, alkali metal salt and alkaline earth metal salt to the pellet. . The addition method is not particularly limited and a known method can be adopted. For example, there is a method in which pellets are immersed in an aqueous solution containing at least one selected from the group consisting of carboxylic acid, boron compound, phosphoric acid compound, alkali metal salt and alkaline earth metal salt, and these are adsorbed.

Examples of the carboxylic acid include oxalic acid, succinic acid, benzoic acid, citric acid, acetic acid, lactic acid, and the like, but it is preferable to use acetic acid from the viewpoint of cost and availability. If the content of the carboxylic acid in the dry resin composition pellets of the EVOH of the present invention is too small, coloring may occur during melt molding, and if it is too large, interlayer adhesion will be insufficient. Therefore, it is preferable to carry out at 10 to 5000 ppm. The lower limit of the carboxylic acid content is preferably 30 ppm or more, and more preferably 50 ppm or more. The upper limit of the carboxylic acid content is preferably 1000 ppm or less, and more preferably 500 ppm or less.

Examples of the phosphoric acid compound include various acids such as phosphoric acid and phosphorous acid, and salts thereof. The phosphate may be contained in any form of primary phosphate, secondary phosphate, and tertiary phosphate, and the cation species is not particularly limited, but alkali metal salts An alkaline earth metal salt is preferred. Among these, it is preferable to add the phosphoric acid compound in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, or dipotassium hydrogen phosphate. The content of the phosphoric acid compound in the dry resin composition pellet made of EVOH of the present invention is preferably 1 to 1000 ppm in terms of phosphate radical, and coloring of the molded product by adding the phosphoric acid compound in an appropriate range And it is possible to suppress the occurrence of gels and blisters. When the content of the phosphoric acid compound is less than 1 ppm, there is a possibility that coloring during melt molding becomes intense. Moreover, when it exceeds 1000 ppm, there exists a possibility that the gel of a molded product may occur easily.

Examples of boron compounds include, but are not limited to, boric acids, boric acid esters, borates, borohydrides, and the like. Specific examples of boric acids include orthoboric acid, metaboric acid, and tetraboric acid. Examples of boric acid esters include triethyl borate and trimethyl borate. Examples include alkali metal salts of acids, alkaline earth metal salts, and borax. Of these compounds, orthoboric acid (simply expressed as boric acid) is preferable. If the content of the boron compound in the dry resin composition pellet made of EVOH of the present invention is too small, the effect of improving the thermal stability is small, and if it is too large, gelation is likely to occur, resulting in poor moldability. Since it exists, it is preferable to implement at 10-2000 ppm in conversion of boron, and it is more preferable to implement at 50-1000 ppm.

Examples of the alkali metal salt include an aliphatic carboxylate, an aromatic carboxylate, a phosphate and a metal complex of a monovalent metal. Examples thereof include sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, sodium salt of ethylenediaminetetraacetic acid, and the like. Of these, sodium acetate, potassium acetate, and sodium phosphate are preferred. As for the addition amount of the alkali metal salt in the dry resin composition pellet which consists of EVOH of this invention, 5-5000 ppm is preferable in conversion of an alkali metal element. More preferably, it is 20-1000 ppm, More preferably, it is 30-750 ppm.

  Examples of alkaline earth metal salts include magnesium salts, calcium salts, barium salts, beryllium salts, and the like, and magnesium salts and calcium salts are particularly preferable. The anionic species of the alkaline earth metal salt is not particularly limited, but an acetate anion and a phosphate anion are preferable. The content of the alkaline earth metal in the dry resin composition pellet made of EVOH of the present invention is preferably 10 to 1000 ppm, more preferably 20 to 500 ppm in terms of metal. If the content of alkaline earth metal is less than 10 ppm, the effect of improving the long run property may be insufficient, and if it exceeds 1000 ppm, coloring during resin melting may be severe.

The obtained pellets are usually subjected to a drying process. The moisture content of the resin composition pellets comprising EVOH after drying is generally 1% by weight or less, and preferably 0.5% by weight or less.
Such a drying method is not particularly limited, and preferred examples include a stationary drying method and a fluidized drying method. It is also possible to employ a multistage drying process in which several drying methods are combined, such as a method of drying by a fluidized drying method and then a method of drying by a stationary drying method. .
When drying the water-containing composition pellets of the present invention, it may be possible to efficiently dry with only one drying method, even if it could not be efficiently dried without combining a plurality of conventional drying methods. One of the useful points is not only the reduction of time but also the large degree of freedom in adopting the drying process.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Example 1
An EVOH solution containing 100 parts by weight of methanol, 50 parts by weight of water, and 2 parts by weight of sodium acetate in terms of sodium with respect to 100 parts by weight of EVOH having an ethylene content of 32 mol% and a saponification degree of 90.5 mol% was obtained. The plate was continuously supplied at 52 kg / hr from the uppermost stage of a 3 m, 10-stage tray tower, and steam was blown from the lowermost stage at 86 kg / hr to bring the EVOH solution and water vapor into contact with each other in countercurrent. The temperature in the tower was 130 ° C., and the pressure in the tower was 3 kg / cm ² . Methanol vapor and water vapor were distilled off from the top of the column, and these were condensed by a condenser and recovered as an aqueous methanol solution. The EVOH water-containing composition was extracted from the bottom of the column. This EVOH hydrous composition contained 0.05 parts by weight of methanol, 105 parts by weight of water and 2 parts by weight of sodium acetate in terms of sodium with respect to 100 parts by weight of EVOH.

  Next, this EVOH hydrous composition was supplied at 41 kg / hr to a kneader having a diameter of 50 mm and a length of 660 mm (L / D = 13.2) having a liquid discharge port. The screw rotation speed at this time was 100 rpm. The EVOH hydrous composition obtained from the discharge port contains 0.03 parts by weight of methanol, 63 parts by weight of water and 1.2 parts by weight of sodium acetate in terms of sodium with respect to 100 parts by weight of EVOH. ° C. Subsequently, the EVOH hydrous composition was extruded from a die having a hole diameter of 3 mm and 6 holes, and cut with a hot cutter having four blades when the distance from the die was 0.05 mm. The rotation speed of the cutter blade was 1200 rpm.

  The obtained pellets were washed with water at 50 ° C. until sodium acetate became 0.002% by weight in terms of sodium. The pellets were not fused during washing with water. The pellet after washing with water was immersed in an aqueous solution of 0.09% acetic acid and 0.022% sodium dihydrogen phosphate at 50 ° C. for 4 hours to remove the liquid. Then, it was dried with a hot air dryer to a moisture content of 0.2% by weight. The dried pellets contained 400 ppm acetic acid, 35 ppm sodium metal, and 88 ppm phosphate radical. This pellet could be used for various moldings.

Example 2
In Example 1, an EVOH solution containing 85 parts by weight of methanol, 85 parts by weight of water, and 3 parts by weight of sodium acetate in terms of sodium with respect to 100 parts by weight of EVOH having an ethylene content of 17 mol% and a saponification degree of 99.1 mol% Was operated in the same manner as in Example 1 except that was supplied to the plate tower. Even during washing with water at 50 ° C., there was no fusion between the pellets. The dried pellets contained 450 ppm acetic acid, 40 ppm sodium metal and 94 ppm phosphate radicals. This pellet could be used for various moldings.

Example 3
Except that ethanol was used instead of methanol, the same operation as in Example 1 was carried out. As a result, 0.4 parts by weight of ethanol, 107 parts by weight of water and sodium acetate were converted into sodium with respect to 100 parts by weight of EVOH from the bottom of the plate tower. An EVOH water-containing composition containing 2 parts by weight was obtained. Subsequently, in the same manner as in Example 1, after passing through a kneader, it was cut with a hot cutter, washed with water, immersed in an aqueous solution of acetic acid and sodium dihydrogen phosphate, and drained. The dried pellets contained 410 ppm acetic acid, 44 ppm sodium metal and 90 ppm phosphate radicals. This pellet could be used for various moldings.

Comparative Example 1
An EVOH solution containing 100 parts by weight of methanol, 50 parts by weight of water and 2 parts by weight of sodium acetate in terms of sodium with respect to 100 parts by weight of EVOH having an ethylene content of 32 mol% and a saponification degree of 99.5 mol% is 10 wt. The solution was extruded from four nozzles (diameter 6 mm) into a coagulating liquid at 10 ° C. consisting of 90% by weight and 90% by weight of water, and solidified into a strand shape. After taking out from the coagulating liquid, it was cut into pellets with a strand cutter. When the obtained pellets were washed with water at 50 ° C. until the sodium acetate became 0.002% by weight in terms of sodium, the pellets were strongly fused during the washing. The pellets after washing with water were immersed in an aqueous solution of 0.09% acetic acid and 0.022% sodium dihydrogen phosphate for 2 hours to remove the liquid. Thereafter, the drying time for obtaining the same water content of Example 1 as 0.2% by weight was 35 hours at 100 ° C. The dried pellets contained 510 ppm acetic acid, 53 ppm sodium metal, and 104 ppm phosphate radical.

Comparative Example 2
EVOH having the same composition as in Example 1, 100 parts by weight of methanol, 50 parts by weight of water and sodium acetate in terms of sodium is 100 parts by weight of EVOH having an ethylene content of 32 mol% and a saponification degree of 90.5 mol%. The EVOH solution containing parts by weight was extruded from 6 nozzles (diameter 3 mm) into a 10 ° C. coagulating liquid consisting of 10% by weight of methanol and 90% by weight of water, and coagulated into a strand. At this time, there were many strand breaks and the operation was unstable. After taking out from the coagulating liquid, it was cut into pellets with a strand cutter. When the obtained pellets were washed with water at 50 ° C., the pellets were strongly fused, and it was impossible to obtain pellets that could be used for various molding applications.

Comparative Example 3
EVOH having the same composition as that of Example 2, with 100 parts by weight of EVOH having an ethylene content of 17 mol% and a saponification degree of 99.1 mol%, 85 parts by weight of methanol, 85 parts by weight of water and sodium acetate were 3 in terms of sodium. The EVOH solution containing parts by weight was extruded from 4 nozzles (diameter 6 mm) into a 10 ° C. coagulating liquid consisting of 5 wt% methanol and 95 wt% water. I couldn't continue to operate any more.

DESCRIPTION OF SYMBOLS 1 EVOH hydrous composition supply port 2 Die 3 Rotating blade 4 Rotating shaft 5 Cutter box 6 Cooling water supply port 7 Cooling water 8 Water film 9 Pellet discharge port 10 Cooling water and pellet

Claims (10)

  An ethylene-vinyl alcohol copolymer water-containing composition containing 0 to 10 parts by weight of an alcohol having a boiling point of 100 ° C. or less and 10 to 500 parts by weight of water in a molten state with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. A method for producing ethylene-vinyl alcohol copolymer pellets, comprising cutting.   The method for producing ethylene-vinyl alcohol copolymer pellets according to claim 1, wherein the cutting method is a hot cut method or an underwater cut method.   The method for producing ethylene-vinyl alcohol copolymer pellets according to claim 1 or 2, wherein the ethylene-vinyl alcohol copolymer has an ethylene content of 3 to 70 mol% and a saponification degree of 80 mol% or more.   2. The alkali metal salt content in the molten ethylene-vinyl alcohol copolymer water-containing composition is 0.1 to 5 parts by weight in terms of metal with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. The manufacturing method of the ethylene-vinyl alcohol copolymer pellet in any one of -3.   An ethylene-vinyl alcohol copolymer solution containing 50 parts by weight or more of an alcohol having a boiling point of 100 ° C. or less with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer is introduced into a container and brought into contact with water vapor in the container. The method for producing ethylene-vinyl alcohol copolymer pellets according to any one of claims 1 to 4, wherein the water-containing composition of ethylene-vinyl alcohol copolymer obtained by deriving the alcohol together with water vapor is cut in a molten state. .   6. The ethylene-vinyl alcohol copolymer water-containing composition obtained by bringing the alcohol into contact with water vapor in the vessel and deriving the alcohol together with water vapor, and further reducing the water content with a kneader, is cut in a molten state. The manufacturing method of the ethylene-vinyl alcohol copolymer pellet of description.   The pellet obtained by cutting in a molten state is washed, and the content of the alkali metal salt is 0.05 parts by weight or less in terms of metal with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. The manufacturing method of the ethylene-vinyl alcohol copolymer pellet in any one.   The temperature of the washing | cleaning liquid at the time of wash | cleaning is 0-95 degreeC, The manufacturing method of the ethylene-vinyl alcohol copolymer pellet in any one of Claims 1-7.   Any one of Claims 1-8 which add at least 1 sort (s) chosen from the group which consists of a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt, and an alkaline-earth metal salt to the pellet obtained by cut | disconnecting in a molten state. A method for producing the ethylene-vinyl alcohol copolymer pellets according to claim 1.   The manufacturing method of the ethylene-vinyl alcohol copolymer pellet in any one of Claims 1-9 which dry the pellet obtained by cut | disconnecting in a molten state so that a moisture content may be 1 weight% or less.

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