JP2007063428A - Ethylene-vinyl alcohol copolymer resin composition and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition excellent in a barrier property and excellent in meltability and moldability and local resistance to deterioration and to provide a method for producing a new ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) resin composition in which an acidic component can be reduced without always requiring immersion treatment of water-containing EVOH resin composition under acidic conditions. <P>SOLUTION: The EVOH resin composition comprises at least one kind of metal ion (A), and in the EVOH resin composition, a metal ion (A1) extracted by treatment for immersing into hot water is ≤1.0 μmol/g expressed in terms of metal element and a metal ion (A2) extracted by treatment for immersing into 0.01 N hydrochloric acid aqueous solution is 0.5-10 μmol/g expressed in terms of metal element. The method for producing the EVOH resin composition comprises bringing EVOH resin composition having 10-80 wt.% water content into contact with a water (E1) containing the metal ion (A) and then, bringing the resin composition into contact with pure water (E2). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ethylene-vinyl alcohol copolymer resin composition, and more particularly to a novel ethylene-vinyl alcohol copolymer resin composition having improved thermal stability. The present invention also relates to a method for producing an ethylene-vinyl alcohol copolymer resin composition.

  An ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is a useful polymer material excellent in oxygen shielding properties, oil resistance, non-charging properties, mechanical strength, etc. Widely used as packaging material. There are various methods for forming EVOH pellets into various molded products, but they are often melt-molded like extrusion molding or injection molding. However, since the melting temperature usually has to be 200 ° C. or higher when molding an EVOH resin composition, EVOH that does not contain additives such as metal ions is liable to deteriorate during melt molding, resulting in fish eyes and bumps in the product. It may cause the quality to deteriorate.

  When the resin composition is heated and melted as an EVOH resin composition, the MFR exhibits a specific behavior, carboxylic acid is 50 to 500 ppm, alkali metal salt is 50 to 500 ppm in terms of metal element, alkaline earth Resin compositions containing 10 to 120 ppm in terms of metal elements, 10 to 200 ppm in terms of phosphate radicals in terms of phosphate groups, and 50 to 2000 ppm in terms of boron elements in terms of boron compounds are known. This resin composition is said to be an EVOH resin composition that is excellent in appearance and long run property during melt molding, has little coloration during collection, and has excellent interlayer adhesion when formed into a laminate (patent) Reference 1).

  Moreover, as a method for producing a dry EVOH resin composition pellet containing a metal salt, a method of drying the EVOH hydrous pellet after bringing it into contact with an aqueous solution containing an additive is representative (see Patent Document 2). ). Further, if the immersion liquid remains alkaline, the stability at the time of melt molding often decreases, and an acid, particularly acetic acid, is separately contained in order to solve this problem. However, since the EVOH resin composition often generates a carboxylic acid odor when the content of carboxylic acid radicals derived from carboxylic acid or carboxylate salt is large, the metal salt is included and the content of carboxylic acid radicals is reduced. Minimizing is preferred.

  In order to solve the above problems, the ethylene-vinyl alcohol copolymer resin is brought into contact with an aqueous solution containing at least one additive selected from the group consisting of alkali metal salts and boron compounds and containing carbon dioxide gas. EVOH resin composition An ethylene-vinyl alcohol copolymer resin composition and a method for producing the resin composition have been proposed. According to this production method, an environment-friendly EVOH resin composition that does not discharge carboxylic acid such as acetic acid to the surrounding environment can be produced, odor generation is small, and long-running property at the time of melt molding is excellent. The EVOH resin composition can be provided (see Patent Document 3).

JP 2001-164059 A International Publication No. 99/05213 Pamphlet International Publication No. 03/068847

  As described above, in order to improve the melt moldability of the EVOH resin composition, various metal salts have been added, typically as alkali metal acetates / phosphates / carbonates. It has been added. That is, in the conventional technology, the EVOH resin composition includes an acid component (anion) such as acetate ion, phosphate ion, and carbonate ion that is a counter anion in addition to the metal ion. For this reason, since the metal ion in the conventional EVOH resin composition exists as a free metal salt, the metal salt may be dispersed unevenly in the EVOH. Such metal salt dispersion spots cause local deterioration of the EVOH resin composition, causing partial discoloration of the molded product of the EVOH resin composition, fish eyes, etc. There was a case that quality was impaired.

  Furthermore, acidic components such as acetate ions and phosphate ions added in conventional EVOH resin compositions have the property of promoting gelation of the EVOH resin composition during melt molding, and fish eyes during long run molding. It may be a cause of rashes. Further, as described above, when the content of carboxylic acid radicals derived from carboxylic acid or carboxylate salt is large, the odor of carboxylic acid has been a problem. Under such circumstances, it is desired to reduce the content of the acidic component (anion) contained in the EVOH resin composition as much as possible, and this must be solved in order to further improve the quality of the EVOH resin composition. It was an issue.

  Moreover, as a method for producing an EVOH resin composition containing metal ions as described above, an aqueous solution containing a metal salt is generally impregnated with a hydrous EVOH resin. Conventionally, acetic acid or It was necessary to acidify the aqueous solution using an acidic compound such as carbonic acid. However, from the viewpoint of the quality of the EVOH resin composition described above, it has been desired not to treat the EVOH resin under acidic conditions or to use an acidic compound in an aqueous solution even in the production stage.

  The present invention has been made to solve the above-mentioned problems, and is excellent in resistance to melt moldability and local deterioration by reducing free metal salts and acidic components contained in the EVOH resin composition. An object of the present invention is to provide a novel EVOH resin composition that can reduce the acidic component without necessarily impregnating the hydrous EVOH resin composition under acidic conditions. To do.

  As a result of intensive studies aimed at achieving the above-mentioned problems, the inventors of the present invention are ethylene-vinyl alcohol copolymer resin compositions containing at least one or more types of metal ions (A), which are immersed in hot water. The metal ion (A1) extracted in this manner is 1.0 μmol / g or less in terms of metal element, and the metal ion (A2) extracted by immersion treatment in a 0.01 N hydrochloric acid aqueous solution is 0.00 in terms of metal element. It has been found that an ethylene-vinyl alcohol copolymer resin composition of 5 to 10 μmol / g is excellent in melt moldability and resistance to local deterioration.

  The present inventors have also intensively studied a method for producing an EVOH resin composition that does not require impregnation of a hydrous EVOH resin under acidic conditions, which is another problem of the present invention. After the ethylene-vinyl alcohol copolymer resin composition of the weight% is brought into contact with water (E1) containing metal ions (A), the problem is achieved by contacting with pure water (E2). The headline and the present invention have been completed.

  The resin composition of the present invention has excellent barrier properties, melt moldability, resistance to local deterioration, and low odor. Moreover, the manufacturing method of the resin composition of this invention is a novel manufacturing method which does not necessarily need to immerse a hydrous EVOH resin composition on acidic conditions, and can reduce an acidic component.

  First, a novel ethylene-vinyl alcohol copolymer resin composition which is the first invention of the present application and is excellent in melt moldability and resistance to local deterioration and further has low odor during melt molding will be described. .

  The EVOH resin composition of the present invention contains at least one kind of alkali metal salt (A), and the metal ion (A1) extracted by immersion treatment in hot water is 1.0 μmol / g or less in terms of metal element. It is essential that the metal ions (A2) extracted by immersion treatment in a 0.01 N hydrochloric acid aqueous solution be 0.5 to 10 μmol / g in terms of metal element.

  Specifically, the metal ion (A1) extracted by being immersed in hot water is a metal ion extracted by immersing the EVOH resin composition in pure water at 90 ° C. or higher for 4 hours or longer. As pure water, it is necessary to use water with a low content of metal ions, specifically, sufficiently purified water such as ion-exchanged water or distilled water. Preferably, pure water having a conductivity of 4.0 μS / cm or less is used, and more preferably, 2.5 μS / cm or less is used. When the temperature at the time of extraction is 90 ° C. or lower, the metal ion (A1) in the EVOH resin composition may not be completely extracted. Further, even when the immersion treatment time is 4 hours or less, the metal ions (A1) may not be completely extracted. The method for quantitative analysis of metal ions (A1) is not particularly limited, but various instrumental analyzes such as atomic absorption analysis, ion chromatography, ICP emission analysis, ICP mass spectrometry, which can analyze trace amounts of metal ions. Are preferably used.

  Specifically, the metal ion (A2) extracted by being immersed in a 0.01 N hydrochloric acid aqueous solution is a metal extracted by being immersed in a 0.01 N hydrochloric acid aqueous solution at 90 ° C. or higher for 10 hours. It means ion (A2). Similar to the pure water described above, it is necessary to use a 0.01N aqueous hydrochloric acid solution having a low metal ion content. Specifically, a commercially available 0.01 N hydrochloric acid aqueous solution or a solution obtained by diluting concentrated hydrochloric acid with sufficiently purified water such as ion-exchanged water or distilled water is used. When the temperature at the time of extraction is 90 ° C. or lower, the metal ion (A2) in the EVOH resin composition may not be completely extracted. Further, even when the immersion treatment time is 10 hours or less, the metal ions (A2) may not be completely extracted. The method for quantitative analysis of metal ions (A2) is not particularly limited, but various instrumental analyzes such as atomic absorption analysis, ion chromatography, ICP emission analysis, and ICP mass spectrometry are possible. Preferably used.

  When the content of the metal ions (A1) extracted by immersion in hot water is 1.0 μmol / g or more, fish eyes and colored spots are likely to occur during melt molding. The content of the metal ion (A1) extracted by being immersed in hot water is more preferably 0.7 μmol / g or less, and further preferably 0.3 μmol / g or less.

  The content of metal ions (A2) extracted by immersion treatment in 0.01 N hydrochloric acid aqueous solution indicates the total content of metal ions (A) contained in the EVOH resin composition. If it is less than 1 μmol / g, both the coloration resistance and long run resistance at the time of melting are insufficient, and if it exceeds 10 μmol / g, the coloration resistance at the time of melting may be poor or the melt viscosity may be significantly reduced. The lower limit of the content of metal ions (A2) extracted by immersion treatment in 0.01 N hydrochloric acid aqueous solution is more preferably 0.5 μmol / g or more, and more preferably 1.0 μmol / g or more. is there. The upper limit of the content of metal ions (A2) extracted by immersing in a 0.01 N hydrochloric acid aqueous solution is preferably 8 μmol / g or less, and more preferably 5 μmol / g or less.

At this time, the content of metal ions (A1) extracted by immersion in hot water and the content of metal ions (A2) extracted by immersion in 0.01 N hydrochloric acid aqueous solution are as follows: It is preferable to satisfy Formula (1).
0 ≦ a1 / (a2−a1) <0.40 (1)
here,
a1 is the content (μmol / g) of metal ions (A1) extracted by immersion in hot water.
a2 is the content (μmol / g) of metal ions (A2) extracted by immersion treatment in 0.01 N hydrochloric acid aqueous solution
It is.

When the left side of the above equation (1) is larger than 0.40, fish eyes and stuff may increase.
It is more preferable to satisfy the following formula (1 ′), and it is more preferable to satisfy the following formula (1 ″).
0 ≦ a1 / (a2-a1) <0.20 (1 ')
0 ≦ a1 / (a2-a1) <0.10 (1 ")

  The kind of metal ion (A) in the EVOH resin composition of the present invention is not particularly limited. Lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion, magnesium ion, magnesium ion, barium ion, manganese ion, iron ion, cobalt ion, nickel ion, copper ion, zinc ion, aluminum ion, silver ion, cerium ion In order to obtain an EVOH resin composition excellent in melt moldability and coloring resistance, sodium ion, potassium ion, magnesium ion, and calcium ion are preferable, and among these, sodium ion and potassium ion Is particularly preferred. Only one kind of these metal ions may be used, and there is no problem even if a plurality of these metal ions are used simultaneously. By containing metal ions, an EVOH resin composition having not only excellent melt moldability and color resistance but also good interlayer adhesion can be obtained.

  In the EVOH resin composition of the present invention, the content of the phosphoric acid compound (B) is preferably 0.5 μmol / g or less in terms of phosphorus element. The content of the phosphoric acid compound (B) is more preferably 0.3 μmol / g or less, and further preferably 0.1 μmol / g or less, and the phosphoric acid compound (B) is not substantially contained. Is particularly preferred. If the content of the phosphoric acid compound (B) exceeds 0.5 μmol / g in terms of phosphorus element, fish eyes and stuff may increase.

  The method for quantifying the phosphoric acid compound (B) is not particularly limited. Examples of the pretreatment method include extraction with hot water, wet decomposition with strong acid, dry ashing (combustion) at high temperature, and the analysis method includes determination of P element by ICP emission analysis, ICP mass spectrometry, etc. Examples include ion chromatography and a colorimetric method (phosphomolybdic acid method).

  In the EVOH resin composition of the present invention, the content of carboxylic acid (C) is preferably 1.0 μmol / g or less in terms of carboxylic acid root. For reasons of production, as the carboxylic acid (C), a carboxylic acid (C) having a molecular weight of less than 75, such as formic acid, acetic acid and propionic acid, is preferably used. Since these carboxylic acids (C) have a low molecular weight and exhibit sufficient water solubility, they are easy to use when contacting an aqueous solution containing the metal ion (A) in the method for producing an EVOH resin composition described later. . However, these carboxylic acids may not only cause fish eyes and blisters during the melt molding of EVOH resin compositions, but also have a low boiling point, so they tend to volatilize when heated, and the odor during melt molding becomes a problem. There is. The content of carboxylic acid (C) is more preferably 0.8 μmol / g or less, further preferably 0.5 μmol / g or less, and even more preferably 0.2 μmol / g or less. It is particularly preferable that the carboxylic acid (C) is not substantially contained. If the content of the carboxylic acid (C) exceeds 1.0 μmol / g in terms of carboxylic acid radicals, not only will fish eyes and buoyancy increase, but odor during melt molding may become a problem.

  The method for quantifying the carboxylic acid (C) is not particularly limited, but specific examples include a method for quantifying the extract or solution of the EVOH resin composition by various chromatographies including ion chromatography and gas chromatography. Take as an example.

  The type of the phosphoric acid compound (B) or carboxylic acid (C) in the EVOH resin composition of the present invention is not particularly limited. In view of the gist of the present invention, it is desirable that the anion species is not substantially contained. However, as shown below, phosphoric acid, phosphorous acid, hypophosphorous acid, acetic acid, etc. from the viewpoint of production of the EVOH resin composition of the present invention Is preferably used.

  Generally, it is considered that the existence state of the metal ion (A) contained in the EVOH resin composition in EVOH is classified into two. The first existence state is when the metal ion (A) is ion-bonded with a free acidic component (anion) in the resin composition to form a free salt. In many cases, such a salt is soluble in water, and is easily flowed and eluted by moisture in the EVOH resin composition. Many conventional EVOH resin compositions contain the metal ion (A) in such a form.

  The second state exists when the metal ion (A) is ionically bonded to the anion component of EVOH. Examples of the anion component of EVOH include a carboxyl group present in a minute amount in a polymer chain, an alkoxide group generated by deprotonation of a hydroxyl group, and an enolate anion by deprotonation at the α-position of a carbonyl group. In this case, since the metal ion (A) is directly adsorbed on the EVOH, the metal ion (A) is in contact with the water in the EVOH resin composition unless an ion exchange reaction is performed with a strong acidic aqueous solution such as HCl. It is stable and difficult to elute.

  Moreover, in the 1st presence state of the said metal ion (A), a free anion component will necessarily be contained in EVOH resin composition. At the time of melt-molding the EVOH resin composition, the temperature is usually 200 ° C. or higher, and many chemical reactions can proceed at that temperature. It is considered that the anion component contained in the EVOH resin composition may undergo an ester exchange reaction with a carboxylic acid ester of an unsaponified portion of EVOH, or the anion component may react with a hydroxyl group of EVOH to generate an ester group. It is done. That is, in melt molding, the chemical reaction in the molten resin at the time of heating and melting cannot be ignored.

  On the other hand, in the second presence state, the metal ion (A) is bound to the anion component present in EVOH, and thus it is considered that such chemical reaction does not occur.

  The EVOH resin composition of the present invention focuses on these points, reduces the free metal salt in the resin composition, and converts the majority of metal ions (A) into anionic components in the polymer structure of EVOH. By adsorbing, the resin is intended to improve the melt moldability and the resistance to local deterioration. That is, the metal ion (A1) extracted by immersion treatment in hot water is made to be below a certain amount, and the metal ion (A2) extracted by immersion treatment in 0.01N hydrochloric acid aqueous solution is kept within a certain amount. By containing, a resin composition excellent in melt moldability and resistance to local deterioration can be provided. Moreover, in order to provide a resin composition having particularly excellent melt moldability and less odor, it is preferable to reduce the content of anionic components such as the phosphoric acid compound (B) and the carboxylic acid (C).

  In addition, the EVOH resin composition of the present invention preferably contains 1 to 200 μmol / g of the boron compound (D) in terms of boron element in terms of long run properties during melt molding. The content of the boron compound (D) is more preferably 2 μmol / g or more, and further preferably 3 μmol / g or more. Moreover, it is more preferable that it is 150 micromol / g or less, and it is further more preferable that it is 100 micromol / g or less.

  Examples of the boron compound (D) include, but are not limited to, boric acids, boric acid esters, borohydrides, and the like. Specifically, examples of boric acids include orthoboric acid, metaboric acid, and tetraboric acid, and examples of boric acid esters include triethyl borate and trimethyl borate. Among these compounds, orthoboric acid (hereinafter sometimes simply referred to as boric acid) is preferable.

  The method for quantifying the boron compound (D) is not particularly limited, and a method for quantifying the extract of the EVOH resin composition by the mannitol method or the curcumin method, wet lysis with a strong acid, or dry ashing at a high temperature (combustion) And the like, and a method of quantifying by ICP emission analysis or ICP mass spectrometry after the sample is prepared by the above method.

  Hereinafter, the use of the EVOH resin composition of the present invention will be described.

  The obtained EVOH resin composition of the present invention is molded into various molded products such as films, sheets, containers, pipes, fibers and the like by melt molding. Of these films, the film is often molded for a long time, and the gels and blisters that are likely to cause problems in long-run molding are easily manifested as problems in appearance, making it suitable for using the EVOH resin composition of the present invention. Application.

  These molded products can be pulverized and molded again for reuse. It is also possible to uniaxially or biaxially stretch films, sheets, fibers, and the like. As the melt molding method, extrusion molding, inflation extrusion, blow molding, melt spinning, injection molding and the like are possible. The melting temperature varies depending on the melting point of the copolymer, but is preferably about 150 to 270 ° C.

  The EVOH resin composition of the present invention can be used as a molded article composed of only a single layer of the resin composition, but has a multilayer structure including at least one layer of the resin composition because of excellent interlayer adhesion. It is preferable to use a body. The layer structure of the multilayer structure is represented by E / T, T / E / T, E / Ad / T, T, where E is the resin composition of the present invention, Ad is the adhesive resin, and T is the thermoplastic resin. Although / Ad / E / Ad / T etc. are mentioned, it is not limited to this. Each of the layers shown here may be a single layer or may be a multilayer according to circumstances.

  The method for producing the multilayer structure shown above is not particularly limited. For example, a method of melt-extruding a thermoplastic resin on a molded article (film, sheet, etc.) comprising the EVOH resin composition of the present invention, and conversely, the resin composition and other thermoplastics on a substrate such as a thermoplastic resin A method of co-extrusion of a resin, a method of co-extrusion or co-injection of a resin composition comprising a thermoplastic resin and EVOH, and a molded product obtained from the EVOH resin composition of the present invention and a film of another substrate, The method of laminating | stacking a sheet | seat using well-known adhesive agents, such as an organic titanium compound, an isocyanate compound, and a polyester-type compound, etc. are mentioned. Of these, the method of co-extrusion or co-injection is preferred.

  The method of co-extrusion molding of the EVOH composition of the present invention and a thermoplastic resin is not particularly limited, and a multi-manifold merging method T-die method, a feed block merging method T-die method, an inflation method and the like are exemplified as suitable ones. . Further, the method of co-injection molding is not particularly limited, and a general method can be used.

  The thermoplastic resin used for laminating with the EVOH resin composition of the present invention includes linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene. Copolymers, polypropylene, propylene-α-olefin copolymers (α-olefins having 4 to 20 carbon atoms), olefins such as polybutene and polypentene alone or copolymers thereof, polyesters such as polyethylene terephthalate, polyester elastomers, nylons Polyamide resin such as -6, nylon-6, 6 and the like, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resin, vinyl ester resin, polyurethane elastomer, polycarbonate, chlorinated polyethylene, chlorinated polypropylene, etc. It is done. Among these, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene, and polyester are preferably used.

  When laminating the EVOH resin composition of the present invention and the thermoplastic resin, an adhesive resin may be used, and the adhesive resin in this case is preferably an adhesive resin made of a carboxylic acid-modified polyolefin. Here, the carboxylic acid-modified polyolefin is a modified olefinic polymer containing a carboxyl group obtained by chemically (for example, by addition reaction or graft reaction) bonding an ethylenically unsaturated carboxylic acid or its anhydride to an olefin polymer. Refers to coalescence. In addition, the olefin polymer is a polyethylene (low pressure, medium pressure, high pressure), a polyolefin such as linear low density polyethylene, polypropylene, boribten, or the like, a comonomer (vinyl ester, non-polymer) capable of copolymerizing the olefin and the olefin. Means a copolymer with a saturated carboxylic acid ester and the like, for example, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ethyl ester copolymer, and the like. Of these, linear low density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content 5-55 wt%), ethylene-acrylic acid ethyl ester copolymer (acrylic acid ethyl ester content 8-35 wt. %), Linear low density polyethylene and ethylene-vinyl acetate copolymers are particularly preferred. Examples of the ethylenically unsaturated carboxylic acid or its anhydride include ethylenically unsaturated monocarboxylic acid, its ester, ethylenically unsaturated dicarboxylic acid, its mono or diester, and its anhydride. Among these, ethylenically unsaturated dicarboxylic acid Anhydrides are preferred. Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, and fumaric acid monomethyl ester. Acid is preferred.

  The addition amount or graft amount (degree of modification) of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer is 0.01 to 15% by weight, preferably 0.02 to 10% by weight, based on the olefin polymer. It is. The addition reaction and grafting reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be obtained, for example, by radical polymerization in the presence of a solvent (such as xylene) or a catalyst (such as a peroxide). The melt flow rate (MFR) measured at 190 ° C. under a load of 2160 g of the carboxylic acid-modified polyolefin thus obtained is preferably 0.2 to 30 g / 10 minutes, more preferably 0.5 to 10 g. / 10 minutes. These adhesive resins may be used alone or in combination of two or more.

By subjecting the coextruded multilayer structure or co-injection multilayer structure thus obtained to secondary processing, various molded articles (films, sheets, tubes, bottles, etc.) can be obtained. Examples include the following.
(1) A multilayer structure (sheet or film, etc.) is stretched uniaxially or biaxially, and a multilayer co-stretched sheet or film by heat treatment as required (2) A multilayer structure (sheet or film, etc.) is rolled Multi-layer rolled sheet or film by (3) Multi-layer structure (sheet or film, etc.) Multi-layer tray cup-shaped container by thermoforming such as vacuum forming, pressure forming, vacuum-pressure forming, etc. (4) Multi-layer structure (pipe) Etc.) bottles by stretch blow molding, etc., cup-like containers (5) bottle-like containers by biaxial stretch blow molding from multilayer structures (parison etc.)

  There is no restriction | limiting in particular in such a secondary processing method, The well-known secondary processing methods other than the above can also be employ | adopted. The coextruded multilayer structure or co-injection multilayer structure obtained in this way has excellent interlayer adhesion, good appearance, and odor generation is suppressed, so various food container materials such as packaging films It is preferably used as a material for deep-drawn containers, cup-shaped containers, bottles and the like.

In addition, although it does not specifically limit about the manufacturing method of the EVOH resin composition of this invention, 2nd embodiment of this invention described below is utilized suitably.

  Next, a method for producing a novel EVOH resin composition capable of reducing acidic components without necessarily impregnating the hydrous EVOH resin composition according to the second invention of the present application under an acidic condition will be described.

  In the method for producing an ethylene-vinyl alcohol copolymer resin composition of the present invention, an ethylene-vinyl alcohol copolymer resin composition having a moisture content of 10 to 80% by weight is converted into an aqueous solution (E1) containing a metal ion (A). ) And then contact with pure water (E2).

  Conventionally, in order to contain the metal ion (A) in the EVOH resin, a method of bringing EVOH into contact with an acidic aqueous solution containing these additives has been performed. In the present invention, the EVOH resin composition is brought into contact with an aqueous solution containing an additive and then brought into contact with pure water. However, the aqueous solution containing the additive may be alkaline to neutral. Furthermore, it is a main feature of the present invention that pure water treatment is performed after contact with an aqueous solution containing an additive.

  When the water-containing EVOH resin is brought into contact with the aqueous solution (E1) containing the metal ion (A), not only the free metal salt is retained in the moisture of the EVOH, but also the metal ion (A) is combined with the anion component of the EVOH polymer chain. As described above, it is adsorbed by ionic bonding. The tendency of ionic bonding with the anionic component of EVOH increases as the alkalinity of the aqueous solution increases. The present invention positively utilizes this tendency. Furthermore, the free metal salt held in the moisture of EVOH can be removed by bringing the hydrous EVOH subjected to the treatment into contact with pure water (E2). As described in the first invention, it is important to reduce the amount of the free metal salt as much as possible in order to improve the quality of the EVOH resin composition.

  The aqueous solution (E1) containing the metal ion (A) in the present invention is an aqueous solution containing at least one kind of metal ion (A) as an additive.

  A suitable range of the content of the metal ion (A) in the aqueous solution (E1) containing the metal ion (A) is generally 0.05 to 40 mmol / L.

  Moreover, the kind of metal ion (A) is not specifically limited. As described above, in order to obtain an EVOH resin composition excellent in melt moldability and color resistance, sodium ion, potassium ion, magnesium ion, and calcium ion are preferable. Among these, sodium ion and potassium ion are preferable. Is particularly preferred.

  The anion species of the metal ion (A) as an additive is not particularly limited. It is important to have sufficient water solubility, such as hydroxide, carbonate, bicarbonate, acetate, phosphate, hydrogen phosphate, phosphite, hypophosphite, carboxylate, etc. Among them, it is preferable to add them as hydroxides, carbonates, hydrogen carbonates, acetates, and hydrogen phosphates.

  The composition of pure water (E2) is not particularly limited, but it is preferable that the content of cation species and anion species is as small as possible in view of the purpose of the present invention to remove free metal salts.

  As a method for evaluating the purity of water, a method of measuring the conductivity is simply used. In the present invention, pure water having a conductivity of 5.0 μS / cm or less is preferably used, and more preferably 2.5 μS / cm or less. A method of directly evaluating the content of cation species or anion species by atomic absorption analysis, ion chromatography, ICP emission analysis, ICP mass spectrometry, or the like is also suitable. In this case, in particular, pure water with a total content of metal ions of 0.1 μmol / g or less is preferably used, and more preferably 0.05 μmol / g or less of pure water is used.

  Moreover, it is preferable to contact with pure water (E2) until the content of metal ions (A1) extracted by immersion treatment in hot water is 1.0 μmol / g or less in terms of metal elements. As described above, the quality of the EVOH resin composition of the present invention is such that the content of metal ions (A1) extracted by immersion treatment in hot water is 1.0 μmol / g or less in terms of metal elements. It is important to improve.

  Moreover, the method of introduce | transducing a carbon dioxide gas into the water (E1) containing said metal ion (A) is also used suitably. By introducing the carbon dioxide gas, the adsorption of the metal ions (A) to EVOH can be easily controlled, and the free metal salt can be easily removed even when contacting the pure water (E2) described later.

  The amount of the carbonic acid is not particularly limited and can be appropriately adjusted. However, it is necessary to dissolve an amount larger than an amount such that carbon dioxide gas existing in the air naturally dissolves. The concentration of carbon dioxide gas in the aqueous solution (total of free carbon dioxide and carbonic acid) is preferably 0.5 mmol / L or more, more preferably 2 mmol / L or more, and further preferably 10 mmol / L or more. Moreover, in order to raise the solubility of a carbon dioxide gas, you may process on pressurization conditions of about 1.5-10 atmospheres.

  As EVOH used in the present invention, those obtained by saponifying an ethylene-vinyl ester copolymer are preferable, and those obtained by saponifying an ethylene-vinyl acetate copolymer are particularly preferable. From the viewpoint of obtaining a molded article excellent in gas barrier properties and melt moldability, the ethylene content is preferably 20 to 60 mol%. When the ethylene content is less than 20 mol%, the melt moldability may be deteriorated, and when the ethylene content exceeds 60 mol%, the gas barrier property may be insufficient. The lower limit of the ethylene content is more preferably 22 mol% or more, and even more preferably 24 mol% or more. On the other hand, the upper limit of the ethylene content is more preferably 55 mol% or less, and even more preferably 50 mol% or less.

  Further, when ethylene and vinyl acetate are copolymerized, other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can be used in combination.

  The EVOH production method will be specifically described below. The polymerization of ethylene and vinyl acetate is not limited to solution polymerization, and may be any of solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, and may be either continuous or batch-type. The polymerization conditions in the case of polymerization are as follows.

Solvent: Alcohols are preferred, but other organic solvents (such as dimethyl sulfoxide) that can dissolve ethylene, vinyl acetate, and ethylene-vinyl acetate copolymer can be used. As alcohols, methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, t-butyl alcohol and the like can be used, and methyl alcohol is particularly preferable.
Catalyst: 2,2′-azobis (isobutyronitrile), 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobis- (4-methyl-2,4-dimethylvalero) Nitrile), 2,2′-azobis- (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis- (2-cyclopropylpropionitrile) and the like, and isobutyryl per Oxide, cumylperoxyneodecanoate, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, t-butylperoxyneodecanoate, lauroyl peroxide, benzoyl peroxide, t-butyl hydroperoxide An organic peroxide initiator such as can be used.
Temperature; 20-90 ° C, preferably 40 ° C-70 ° C.
Time (average residence time in case of continuous type); 2 to 15 hours, preferably 3 to 11 hours.
Polymerization rate: 10 to 90%, preferably 30 to 80%, relative to the charged vinyl ester.
Resin content in the solution after polymerization; 5 to 85%, preferably 20 to 70%.
Ethylene content in the copolymer; preferably 20 to 60 mol%, more preferably 22 to 55 mol%, still more preferably 24 to 50 mol%.

  In addition to ethylene and vinyl acetate, 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 Olefin sulfonic acids such as acids or salts thereof; alkyl vinyl ethers, vinyl ketones, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride; vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tris (β-methoxy-ethoxy) silane, γ-methacryl Oxy A small amount of vinylsilane compounds such as propylmethoxysilane can be present.

  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 acetate is driven off. As a method of driving off unreacted vinyl acetate from the ethylene-vinyl acetate copolymer solution from which ethylene has been removed by evaporation, for example, the copolymer solution is continuously supplied at a constant rate from the upper part of a tower packed with Raschig rings, A method in which an organic solvent vapor such as methanol is blown from the bottom of the tower, a mixed vapor of an organic solvent such as methanol and unreacted vinyl acetate is distilled from the top of the tower, and the copolymer solution from which the unreacted vinyl acetate has been removed is removed from the bottom of the tower Etc. are adopted.

An alkali catalyst is added to the copolymer solution from which unreacted vinyl acetate has been removed to saponify the vinyl acetate 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. Moreover, as a solvent used for saponification, methanol is preferable. For example, the saponification conditions are as follows.
The copolymer solution concentration: 10 to 50%.
Reaction temperature: 30-150 ° C.
Amount of catalyst used: 0.005 to 0.6 equivalent (per vinyl acetate component).
Time (in the case of continuous type, average residence time); 10 minutes to 6 hours.

In general, when saponification is performed continuously, methyl acetate produced by saponification can be removed more efficiently, so that a resin having a high saponification degree can be obtained with a smaller amount of catalyst than in the case of batch-wise. In the case of a continuous type, it is necessary to saponify at a higher temperature in order to prevent precipitation of EVOH produced by saponification. Therefore, it is preferable to set the reaction temperature and the catalyst amount within the following ranges in the continuous method.
Reaction temperature: 70-150 ° C.
Amount of catalyst used: 0.005 to 0.1 equivalent (per vinyl acetate component).

  The degree of saponification after the saponification reaction varies depending on the purpose, but is preferably 80 mol% or more, more preferably 95 mol% or more, still more preferably 98 mol% or more, particularly preferably 99 mol% or more of the vinyl acetate component. The degree of saponification can be arbitrarily adjusted according to the conditions.

  As described above, in the case of producing an EVOH composition having excellent melt stability and long run property, the saponification degree of EVOH is preferably 99.7 mol% or more, and 99.8 mol%. More preferably, it is more preferably 99.9 mol% or more, and particularly preferably 99.95 mol% or more.

  The method for producing EVOH pellets from the obtained alcohol solution of EVOH after saponification is not particularly limited. Preferably, an alcohol solution of EVOH is precipitated in a strand form in a coagulation bath, and then the strands are cut to obtain water-containing pellets. In the precipitation, the alcohol solution may be concentrated to increase the EVOH concentration as compared with the saponification, or a part or all of methanol may be replaced with water, and the EVOH water / alcohol mixed solution or A water-containing composition of EVOH may be used. A water-containing pellet is obtained by extruding this into water or an alcohol aqueous solution containing a small amount of alcohol, and precipitating it into a strand shape, followed by cutting. Moreover, it can cut | disconnect with a fluid state, without making it precipitate in a strand form, and can also solidify in water and can manufacture a pellet.

  The water-containing pellets obtained as described above are porous, and the saponification catalyst residue can be easily removed by washing with water, and the subsequent addition of additives, pure water treatment, and drying operation are also easy. It is preferable that the moisture content of such a water-containing pellet is 10 to 80% by weight because of the above operational advantages. The water content is more preferably 20% by weight or more, and further preferably 30% by weight or more. Moreover, it is 70 weight% or less more suitably, More preferably, it is 60 weight% or less.

  The water-containing pellets thus obtained usually contain an alkali metal salt that is a saponification catalyst residue, for example, sodium acetate, which causes problems such as coloring, and thus is preferably removed by washing. Usually, the alkali metal salt content of the water-containing pellets before washing is about 100 to 10,000 μmol / g (per EVOH weight) in terms of alkali metal. The cleaning method is not particularly limited, but a method of cleaning with water is preferable. The water used as the cleaning liquid at this time may be an aqueous solution of an acid such as acetic acid in order to efficiently remove alkali metal ions. Moreover, it is also preferable to reduce the content of the saponification catalyst residue efficiently by using water washing and acid washing together.

  It is preferable to reduce the alkali metal content of the water-containing pellets after washing to 0-50 μmol / g (per EVOH weight) in terms of alkali metal. The upper limit of the alkali metal content is more preferably 40 μmol / g, still more preferably 30 μmol / g, and particularly preferably 20 μmol / g. Since the saponification catalyst residue is usually contained in the form of an alkali metal salt of acetic acid, the content of carboxylic acid radicals was reduced by sufficiently reducing the alkali metal content of the water-containing pellets after washing. It becomes easy to obtain an EVOH composition.

  The method for washing the water-containing pellets is not particularly limited, and either a batch type processing container or a continuous type processing container can be used. Especially, the method of supplying and processing a pellet continuously in a tower type container is suitable from a viewpoint of productivity.

  After washing, the water-containing pellets are immersed in an aqueous solution (E1) containing metal ions (A). Moreover, when making a EVOH resin composition contain a boron compound (D), it is also immersed in the aqueous solution containing a boron compound (D). Further, it is also preferable to add carbonic acid to the aqueous solution (E1) containing the metal ion (A).

  The method for immersing the EVOH resin in the aqueous solution (E1) containing the metal ion (A) or the aqueous solution containing the boron compound (D) is not particularly limited. The shape of the EVOH resin when immersing the EVOH resin in the aqueous solution may be any shape such as powder, granular, spherical, cylindrical pellet, etc. For example, the water-containing EVOH pellet obtained as described above may be used. The contact with the aqueous solution is preferable because the metal ion (A) and the boron compound (D) can be efficiently and uniformly contained in the EVOH resin composition pellets. The water content of the water-containing pellets before being immersed in the aqueous solution is preferably 10 to 80% by weight. The water content is more preferably 20% by weight or more, and further preferably 30% by weight or more. Moreover, it is 75 weight% or less more suitably, More preferably, it is 70 weight% or less.

  The temperature of the aqueous solution brought into contact with the EVOH resin is not particularly limited, but is preferably 10 to 90 ° C. If it is less than 10 degreeC, there exists a possibility that it may take time to make a metal ion (A) contain uniformly in EVOH resin pellet, and if it exceeds 90 degreeC, there exists a possibility that pellets may fuse | melt. The temperature of the aqueous solution is more preferably 20 ° C. or higher, and further preferably 30 ° C. or higher. Moreover, it is 85 degreeC or less more suitably, More preferably, it is 80 degreeC or less. When carbonic acid is contained in the treatment liquid, the solubility of carbonic acid is reduced at a high temperature of 70 ° C. or higher, and therefore, it is preferable to make contact under a pressure of about 0.15-1.0 MPa.

  The preferred range of time for contacting the EVOH resin with the aqueous solution varies depending on the form of the EVOH resin, but in the case of pellets of about 1 to 10 mm, it is preferably 1 hour or more, more preferably 2 hours or more. preferable.

In order to uniformly adsorb the metal ions (A), the amount of the aqueous solution is preferably 5 parts by weight or more with respect to 1 part by weight of the EVOH resin. When the amount of the aqueous solution is 5 parts by weight or less, the content of the metal ion (A) in the aqueous solution is insufficient, and the adsorption of the metal ion (A) may be uneven. The amount of the aqueous solution is more preferably 10 parts by weight or more, and particularly preferably 20 parts by weight or more.

  A method for bringing the EVOH resin into contact with the aqueous solution is not particularly limited. The EVOH resin can be brought into contact with water in advance, and the additive and carbonic acid can be dissolved in water later. However, the method of bringing the prepared aqueous solution into contact with the EVOH resin in a uniform manner makes the additive uniform. Since the EVOH resin composition of the stable quality contained in is obtained, it is preferable.

  As a method of bringing the EVOH resin into contact with the aqueous solution, either a batch method or a continuous method can be adopted. In the continuous method, for example, a method in which the EVOH resin is brought into contact with the continuously supplied aqueous solution while gradually moving the EVOH resin downward in a tower-shaped container is preferable.

  Also, a plurality of aqueous solutions may be prepared and contacted in a plurality of times. For example, it is possible to employ a method in which contact is first made with an aqueous solution containing only the metal ion (A) and then contacted with an aqueous solution containing the metal ion (A) and the boron compound (D).

  Further, the metal ion (A) contained in the aqueous solution is not necessarily one type, and a plurality of metal ions (A) may be contained.

  After making it contact with the aqueous solution (E1) containing a metal ion (A), a water-containing pellet is contacted with a pure water (E2) continuously. As stated above, the purpose of the pure water treatment is to remove free metal salts.

  The higher the temperature of pure water (E2) that is brought into contact with the EVOH resin composition, the easier it is to remove free metal salts. However, if the temperature is too high, the pellets may be fused. The temperature of the pure water (E2) is preferably 20 ° C. or higher and lower than 90 ° C.

  The preferred range of the time when the EVOH resin composition is brought into contact with the aqueous solution varies depending on the form of the EVOH resin composition, but in the case of pellets of about 1 to 10 mm, it is preferably 1 hour or more, and 2 hours or more. More preferably.

  Moreover, in order to remove a free metal salt efficiently, it is suitable that the quantity of the said pure water (E2) is 10 weight part or more with respect to 1 weight part of EVOH resin composition. More preferably, it is 20 parts by weight or more, and the larger the amount of pure water (E2), the easier it is to remove the metal salt.

  The method for bringing the EVOH resin composition into contact with the pure water (E2) is not particularly limited. A method of continuously supplying pure water (E2) to the water-containing EVOH resin composition is preferably used, but a method of repeating immersion treatment while repeatedly updating the pure water (E2) in a batch manner is also suitable. Used for.

  In addition, the pure water (E2) used here is not specifically limited, The pure water adjusted with the general purification method is used. Specific purification methods include distillation, activated carbon adsorption, ion exchange, reverse osmosis, and filtration. It is also suitable to use various purification methods in combination such as purification by reverse osmosis and further purification by ion exchange.

  The EVOH resin composition, preferably the EVOH resin composition pellets, is immersed in the pure water (E2), drained, and then subjected to a drying step. The drying method is not particularly limited, and a hot air dryer or the like can be used. The dryer may be a fluid dryer or a stationary dryer, and may be used in combination. Among these, a method of drying by a fluidized drying method first and then drying by a stationary drying method is preferable. The drying temperature is not particularly limited, but usually a temperature of about 70 to 125 ° C. is adopted, and the temperature can be increased as the drying proceeds. The water content after drying is usually 1% by weight or less, preferably 0.5% by weight or less. The dried pellets thus obtained are used for the subsequent molding process.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this Example. Hereinafter, “%” and “parts” are based on weight unless otherwise specified. In addition, all the water used ion-exchange water (conductivity: 1.0-2.0 microsiemens / cm). The conductivity was measured with CM-30ET manufactured by Toa Denpa Kogyo.
(1) Quantification of metal ions (A1) extracted by immersion in hot water The pellets of the dry EVOH resin composition were pulverized by freeze pulverization. 10 g of the EVOH resin composition powder was put into 50 mL of water and extracted by heating at 95 ° C. for 10 hours. 2 mL of the obtained extract was diluted with 8 mL of ion exchange water. The diluted extract was quantitatively analyzed at the following observation wavelengths using an ICP emission spectroscopic analyzer Optima 4300 DV manufactured by PerkinElmer Japan. From the amount of each metal element thus obtained, the amount of metal ion (A1) extracted by immersion treatment in hot water was obtained in terms of metal element.

Observation wavelength: Sodium 589.592nm
Potassium 766.490nm
Magnesium 285.213nm
Calcium 317.933nm

(2) Quantification of alkali metal ions (A2) extracted by immersion treatment in 0.01 N hydrochloric acid aqueous solution The pellets of the dry EVOH resin composition were pulverized by freeze pulverization. 10 g of the EVOH resin composition powder was put into 50 mL of 0.01 N hydrochloric acid aqueous solution, stirred at 95 ° C. for 10 hours, and extracted by heating. 2 mL of the obtained extract was diluted with 8 mL of ion exchange water. The diluted extract was quantitatively analyzed using an ICP emission spectrophotometer Optima 4300 DV manufactured by PerkinElmer Japan Co., Ltd. in the same manner as (1) above. From the amount of each metal element thus obtained, the amount of alkali metal salt (A2) contained in the dry EVOH pellet was obtained in terms of metal element.

(3) Quantification of phosphoric acid compound (B) The pellets of the dry EVOH resin composition were pulverized by freeze pulverization. 1.0 g of the powder of the pulverized EVOH resin composition obtained was put into an Erlenmeyer flask equipped with a stopper, 15 ml of concentrated nitric acid and 4 ml of concentrated sulfuric acid were added, a cooling condenser was attached, and the solution was thermally decomposed at 200 to 230 ° C. Measure up to a 50 ml volumetric flask. The solution was quantitatively analyzed at an observation wavelength of 214.914 nm using an ICP emission spectrophotometer Optima 4300 DV manufactured by PerkinElmer Japan. From the amount of phosphorus element thus obtained, the amount of phosphoric acid compound (C) was obtained in terms of phosphorus element.

(4) Determination of carboxylic acid (C) Dry EVOH pellets were pulverized by freeze pulverization. 10 g of the above EVOH powder was put into 50 mL of ion-exchanged water, followed by stirring and extraction at 95 ° C. for 10 hours. 2 mL of the obtained extract was diluted with 8 mL of ion exchange water. Quantitative analysis of the diluted extract using ion chromatography IC7000 (column: Yokogawa SCS5-252, eluent: 0.1% phosphoric acid aqueous solution) manufactured by Yokogawa Electric Corporation Then, the amount of carboxylic acid (acetic acid) ions was quantified, and carboxylic acid (C) was quantified. Note that a calibration curve prepared using an aqueous acetic acid solution was used for quantification.

(5) Quantification of boron compound (D) 50 mg of dry EVOH pellets as a sample were completely burned by an oxygen flask combustion method, and the resulting combustion ash was dissolved in 10 mL of 1 mol / L nitric acid aqueous solution. The solution was quantitatively analyzed at an observation wavelength of 249.667 nm using an ICP emission spectroscopic analyzer Optima 4300 DV manufactured by PerkinElmer Japan. The boron compound (D) content was obtained in terms of boron element.

(6) Single-layer film formation test The obtained dry EVOH pellets were manufactured by Toyo Seiki Seisakusho, Ltd. 20 mm extruder D2020 (D (mm) = 20, L / D = 20, compression ratio = 2.0, screw: full A single-layer film was formed under the following conditions using a flight) to obtain a single-layer film.
Extrusion temperature: C1 / C2 / C3 / Die = 175/230/230/235 ° C.
Screw rotation speed: 20rpm
Discharge rate: 0.63 kg / hr
Take-up roll temperature: 80 ° C
Take-up roll speed: 1.0 m / min.
Film thickness: 30 μm

(6-a) Coloring resistance The monolayer film produced by the above method was wound around a paper tube, and the degree of coloring of the film end face was determined with the naked eye as follows.
Judgment: Standard A: No coloring B: Slightly yellow C: Yellowing

(6-b) Fish eye / colored color evaluation Sample the film 2 hours after the start of monolayer film formation, classify the gel-like color that can be confirmed with the naked eye in the film as follows, Counted the number. The number of bumps was converted to the number per 1.0 m 2 and judged as follows. Further, 10 gel-like particles having a size of 100 μm or more were arbitrarily selected and observed with a microscope, and the number of colored particles (yellow to brown) was examined.

Fish eye:
Big size: 100μm or more Small size: Less than 100μm

Judgment: Criteria A: Less than 10 B: 10 or more and less than 20 C: 20 or more and less than 100 D: 100 or more and less than 500 E: 500 or more

Coloring:

Judgment: Criteria A: No colored spots
B: 1 to 3 colored spots C: 4 or more colored spots

(6-c) 60-hour long run evaluation The film was sampled 60 hours after the start of single-layer film formation, and the number of gel-like particles of 100 μm or more that could be confirmed with the naked eye in the film was counted. The number of bumps was converted to the number per 1.0 m 2 and judged as follows.

Judgment: Criteria A: Less than 10 B: 10 or more and less than 20 C: 20 or more and less than 100 D: 100 or more and less than 500 E: 500 or more

(6-d) 120-hour long run evaluation 120 hours after the start of monolayer film formation, the film was sampled, and the number of gel-like particles having a size of 100 μm or more that could be confirmed with the naked eye in the film was counted. The number of bumps was converted to the number per 1.0 m 2 and judged as follows.

Judgment: Criteria A: Less than 10 B: 10 or more and less than 20 C: 20 or more and less than 100 D: 100 or more and less than 500 E: 500 or more

(7) Odor test 10 g of the obtained dry EVOH pellets and 10 mL of ion-exchanged water were put into a 100 mL glass screw tube, which was covered and sealed. Then, after putting in 90 degreeC safe vent dryer (dryer) and heat-extracting for 15 hours, it stood at room temperature for 30 minutes and cooled the said screw pipe | tube. After cooling, the lid of the screw tube was opened, and the odor of the resulting extract was evaluated as follows by using five monitors.
Judgment: Criteria A: No odor is felt.
B: A slight odor is felt.
C: Odor is felt.

(8) Measurement of moisture content of water-containing EVOH pellets Using a HR73 halogen moisture content analyzer manufactured by METLER, the moisture content of EVOH pellets was measured under the conditions of a drying temperature of 180 ° C, a drying time of 20 minutes, and a sample amount of about 10 g.

[Production of hydrous pellets]
20 kg of saponified EVOH resin (ethylene content 31 mol%, saponification degree 99.9 mol%) was dissolved in a mixture of water / methanol = 4/6 (weight ratio) at 80 ° C. for 12 hours with stirring. A 40% by weight EVOH solution was obtained. Next, the stirring was stopped and the temperature of the dissolution tank was lowered to 65 ° C. and left for 5 hours to degas the EVOH water / methanol solution. Then, from a metal plate having a circular opening having a diameter of 3.5 mm, it is extruded during mixing of water / methanol = 9/1 (weight ratio) at 5 ° C., precipitated into a strand shape, and cut to have a diameter of about 4 mm. A pellet having a length of about 5 mm was obtained. The moisture content of the obtained EVOH pellets was 50% by weight.

[Purification of hydrous pellets]
The operation of adding 50 L of pure water to 5.1 kg of the water-containing pellets thus obtained, washing the mixture with stirring at 25 ° C. for 2 hours, and then removing the liquid was repeated twice. Next, an operation of washing with 1 g / L aqueous acetic acid solution while stirring at 25 ° C. for 2 hours and then removing the liquid was repeated twice. Furthermore, the operation of washing the water-containing pellets with 50 L of ion-exchanged water while stirring at 25 ° C. for 2 hours and then draining was repeated 6 times. As a result of measuring the conductivity of the cleaning solution after the sixth cleaning with CM-30ET manufactured by Toa Denpa Kogyo, the conductivity of the cleaning solution was 1.5 μS / cm.

[Addition and drying of metal ions]
Next, 3000 g of the above water-containing pellets was put into 30 L of 0.5 mmol / L sodium hydroxide aqueous solution, and immersed and stirred at 25 ° C. for 5 hours. After stirring for 5 hours, the obtained pellets were immediately drained, and subsequently, 30 L of pure water was added and the operation of soaking for 2 hours while stirring was repeated twice. The conductivity of the treatment liquid after the second pure water treatment was 3.1 μS / cm. After washing, the obtained pellets were immediately drained, allowed to stand at 40 ° C. for 24 hours, and then dried with hot air at 80 ° C. for 3 hours and then at 120 ° C. for 30 hours to obtain dry EVOH pellets. The MFR of the dried EVOH pellet is 1.6 g / 10 min. (Under 190 ° C. and 2160 g load).

[Analysis / Evaluation]
The metal ion (A1) extracted by immersing in hot water in the obtained dry EVOH pellet was only sodium ion, and was 0.8 μmol / g in terms of sodium element. The metal ion (A2) extracted by immersing in a 0.01 N hydrochloric acid aqueous solution at 95 ° C. was only sodium ion, and was 5.0 μmol / g in terms of sodium element. In addition, neither the phosphoric acid compound (B) nor the carboxylic acid (C) in the dry EVOH pellet was detected and was 0 μmol / g.

  Using the obtained dried EVOH pellets, a single layer film was produced according to the above-described method, and various evaluations were performed. The evaluation result of the color resistance of EVOH in this example was B. The fisheye evaluation result was A for both large and small. The number of colored spots was one and it was B determination. The 60-hour long run evaluation result was A, and the 120-hour long run evaluation result was B. Moreover, when the odor test was done according to the above-mentioned method using the obtained dry EVOH pellet, all five monitors did not feel odor, and evaluation was A determination. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

  After impregnating with 0.5 mmol / L sodium hydroxide solution, the dry EVOH pellets were prepared in the same manner as in Example 1 except that the number of times that the hydrous EVOH pellets were treated with pure water was increased to four times. Evaluation was performed in the same manner as in Example 1. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

  A dry EVOH pellet was prepared in the same manner as in Example 1 except that the number of times that the hydrous EVOH pellet was treated with pure water was increased to 6 after impregnation in a 0.5 mmol / L sodium hydroxide solution, Evaluation was performed in the same manner as in Example 1. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

  The washed EVOH pellets obtained in the same manner as in Example 1 were charged into 10 L of a 0.5 mmol / L aqueous sodium bicarbonate solution, and the blowing rate was 1 L / min. Then, immersion and stirring were performed at 25 ° C. for 6 hours while blowing carbon dioxide gas. After stirring for 6 hours, the obtained pellets were immediately drained, and subsequently, 15 L of pure water was added, and the operation of soaking for 2 hours with stirring was repeated twice. The conductivity of the treatment liquid after the second pure water treatment was 1.3 μS / cm, and the conductivity could be reduced more efficiently than in Example 1. After washing, the obtained pellets were immediately drained, allowed to stand at 40 ° C. for 24 hours, and then dried with hot air at 80 ° C. for 3 hours and then at 120 ° C. for 30 hours to obtain dry EVOH pellets. The obtained dry pellets were evaluated in the same manner as in Example 1. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

[Production of hydrous pellets]
20 kg of saponified EVOH resin (ethylene content 31 mol%, saponification degree 99.9 mol%) was dissolved in a mixture of water / methanol = 4/6 (weight ratio) at 80 ° C. for 12 hours with stirring. A 40 wt% EVOH solution was obtained. Next, the stirring was stopped and the temperature of the dissolution tank was lowered to 65 ° C. and left for 5 hours to degas the EVOH water / methanol solution. And it extrudes in the mixed solvent of water / methanol = 9/1 (weight ratio) of 5 degreeC from the metal plate which has a circular opening part with a diameter of 3.5 mm, precipitates in a strand shape, and cuts about a diameter. A pellet having a length of 4 mm and a length of about 5 mm was obtained. The moisture content of the obtained EVOH pellets was 53% by weight.

[Purification of hydrous pellets]
The operation of adding 24 L of pure water to 2.4 kg of the water-containing pellets thus obtained, washing the mixture with stirring at 25 ° C. for 2 hours, and then removing the liquid was repeated twice. Next, an operation of adding 24 L of 1 g / L acetic acid aqueous solution to 2.4 kg of water-containing pellets, washing the mixture with stirring at 25 ° C. for 2 hours, and then removing the liquid was repeated twice. Further, 24 L of ion exchange water was added to 2.4 kg of the water-containing pellets, and the operation of washing with stirring at 25 ° C. for 2 hours and then draining was repeated 6 times. As a result of measuring the conductivity of the cleaning liquid after the sixth cleaning with CM-30ET manufactured by Toa Denpa Kogyo, the conductivity of the cleaning liquid was 1.4 μS / cm.

[Boric acid addition treatment]
It put in the boric-acid aqueous solution of 2.4 kg of hydrous EVOH pellets obtained in this way, and a density | concentration of 0.36 g / L, and it immersed for 10 hours at 25 degreeC, and dehydrated after immersion.

[Metal ion addition treatment / drying]
The water-containing pellets thus obtained were blown into a 0.5 mmol / L sodium bicarbonate aqueous solution in the same manner as in Example 4 at a rate of 1 L / min. The carbon dioxide gas was blown in, and after immersion treatment and pure water treatment, drying was performed to produce dry EVOH pellets. The MFR of the dried EVOH pellet is 1.8 g / 10 min. (Under 190 ° C. and 2160 g load).

[Analysis / Evaluation]
Various analyzes and evaluations were carried out in the same manner as in Example 1 using the obtained dried pellets. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

  The liquid in which the hydrous EVOH pellets after washing are immersed is 1.0 mmol / L potassium bicarbonate and 2.2 mmol / L potassium dihydrogen phosphate, and the blowing rate is 1 L / min. A dry EVOH pellet was prepared in the same manner as in Example 5 except that carbon dioxide gas was blown in and evaluated in the same manner as in Example 1. At the time of evaluation, the phosphate compound (B) was not detected and was 0 μmol / g. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

Example 7
The dried EVOH pellets were treated in the same manner as in Example 1 except that the liquid in which the washed water-containing EVOH pellets were immersed in an aqueous solution of 2.5 mmol / L magnesium acetate and 1.0 mmol / L sodium bicarbonate. This was prepared and evaluated in the same manner as in Example 1. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

Example 8
Dry EVOH pellets were produced in the same manner as in Example 1 except that the solution for immersing the hydrous EVOH pellets after washing was a calcium hypophosphite 2.0 mmol / L aqueous solution. And evaluated. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

Comparative Example 1
3000 g of the washed hydrous pellets obtained in the same manner as in Example 1 was immersed in 30 L of an aqueous solution containing 8.0 mmol / L acetic acid and 4.0 mmol / L sodium acetate at 25 ° C. for 6 hours and stirred. Then, it drained without performing a pure water process, and left still at 40 degreeC for 24 hours, Then, it dried by hot air at 80 degreeC for 3 hours, and then at 120 degreeC for 30 hours, and obtained the dried EVOH pellet. Various evaluations were performed in the same manner as in Example 1 using the obtained dried pellets. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

Comparative Example 2
The water-containing pellets were treated in the same manner as in Example 1 until immersed in a 0.5 mmol / L sodium hydroxide aqueous solution, and then immediately under the same conditions as in Example 1 without any pure water treatment. The hydrous pellets were dried. Various evaluations were performed in the same manner as in Example 1 using the obtained dried pellets. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

Comparative Example 3
Except that the concentration of potassium hydrogen carbonate was 0.1 mmol / L and the concentration of potassium dihydrogen phosphate was 2.2 mmol / L, the water-containing pellet was treated in the same manner as in Example 6, and then once The water-containing pellets were immediately dried under the same conditions as in Example 1 without performing pure water treatment. Various evaluations were performed in the same manner as in Example 1 using the obtained dried pellets. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

Comparative Example 4
The water-containing pellets were treated in the same manner as in Example 8 until immersed in a 2.0 mmol / L calcium hypophosphite aqueous solution, and then immediately under the same conditions as in Example 1 without any pure water treatment. The hydrous pellets were dried. Various evaluations were performed in the same manner as in Example 1 using the obtained dried pellets. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

Comparative Example 5
The water-containing pellets were treated in the same manner as in Comparative Example 1 until immersed in an aqueous solution containing acetic acid 8.0 mmol / L and sodium acetate 4.0 mmol / L. After the liquid removal, 15 L of pure water was added to the water-containing pellets, and the operation of immersion and stirring for 2 hours was repeated 6 times. The conductivity of the treatment liquid after the sixth pure water treatment was 1.2 μS / cm. The obtained pellets were immediately drained and allowed to stand at 40 ° C. for 24 hours, followed by hot-air drying at 80 ° C. for 3 hours and then at 120 ° C. for 30 hours to obtain dry EVOH pellets. Various evaluations were performed in the same manner as in Example 1 using the obtained dried pellets. Table 2 shows the composition of the dry EVOH resin composition, and Table 3 shows the evaluation results.

As is apparent from the above evaluation results, in Examples 1 to 8, EVOH resin compositions having less fish eyes and colored spots and excellent in melt moldability and local deterioration resistance were obtained. In particular, for Examples 3 to 6 in which the amount of metal ion (A) extracted by immersion in hot water is small and the content of phosphate compound (B) or carboxylic acid (C) is small, particularly excellent melting Has moldability and local degradation resistance. Furthermore, Examples 4 and 5 containing boric acid are excellent in long run property in addition to melt moldability and local deterioration resistance.

Claims (8)

It is an ethylene-vinyl alcohol copolymer resin composition containing at least one kind of metal ion (A), and the metal ion (A1) extracted by immersion treatment in hot water is 1.0 μmol / in terms of metal element. An ethylene-vinyl alcohol copolymer resin composition having a metal ion (A2) of 0.5 to 10 μmol / g in terms of a metal element, which is not more than g and is extracted by immersion in a 0.01 N hydrochloric acid aqueous solution. In the relationship between the metal ion (A1) extracted by immersion treatment in the hot water and the metal ion (A2) extracted by immersion treatment in a 0.01 N hydrochloric acid aqueous solution, the following expression (1) is satisfied. The ethylene-vinyl alcohol copolymer resin composition according to claim 1.

0 ≦ a1 / (a2−a1) <0.40 (1)
here,
a1 is the content (μmol / g) of metal ions (A1) extracted by immersion in hot water,
a2 is the content (μmol / g) of metal ions (A2) extracted by immersion treatment in a 0.01 N hydrochloric acid aqueous solution. The ethylene-vinyl alcohol copolymer resin according to claim 1 or 2, wherein the content of the phosphoric acid compound (B) in the ethylene-vinyl alcohol copolymer resin composition is 0.5 µmol / g or less in terms of phosphorus element. Composition. The ethylene-vinyl alcohol copolymer according to any one of claims 1 to 3, wherein the content of the carboxylic acid (C) in the ethylene-vinyl alcohol copolymer resin composition is 1.0 µmol / g or less in terms of carboxylic acid radical. Resin composition. The ethylene-vinyl alcohol copolymer resin composition further contains a boron compound (D), and the content of (D) is 1 to 200 µmol / g in terms of boron element. Vinyl alcohol copolymer resin composition. An ethylene-vinyl alcohol copolymer resin composition having a moisture content of 10 to 80% by weight is brought into contact with water (E1) containing a metal ion (A) and then brought into contact with pure water (E2). A process for producing an ethylene-vinyl alcohol copolymer resin composition. In the manufacturing method of the ethylene-vinyl alcohol copolymer resin composition of Claim 5, content of the metal ion (A1) extracted by being immersed in hot water is 1.0 μmol / g or less in terms of metal element. It is made to contact with pure water (E2) until it becomes, The manufacturing method of the ethylene-vinyl alcohol copolymer resin composition of Claim 6 characterized by the above-mentioned. The method for producing an ethylene-vinyl alcohol copolymer resin composition according to claim 6 or 7, wherein the water (E1) containing the metal ion (A) contains carbonic acid.