JPWO2017047806A1 - Resin composition, method for producing the same, and multilayer structure - Google Patents

Abstract

The present invention contains EVOH (A), a component (B) composed of at least one of nitric acid and nitrate ions, and a metal ion (C), and the content Bm of the component (B) is 0.00. 5 μmol / g or more and 100 μmol / g or less, the content amount Cm of the metal ion (C) is 2 μmol / g or more and 120 μmol / g or less, and the content amount Bm of the component (B) and the metal ion When the content amount Cm of (C) and its average valence Cv satisfy the following formula (1) and contain the component (D) consisting of at least one of carboxylic acid and carboxylate ion, Bm, the Cm, the Cv, the content amount Dm of the component (D) and the average valence Dv are resin compositions that satisfy the following formula (2).
(Cv × Cm) /Bm≧1.0 (1)
((Cv × Cm) −Bm) / (Dv × Dm) ≧ 0.2 (2)

Description

  The present invention relates to a resin composition, a method for producing the same, and a multilayer structure having a layer obtained from the resin composition.

  An ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH) is widely used as various packaging materials for films, sheets, containers and the like because of its excellent properties such as oxygen barrier properties. Since these packaging materials are usually molded by a melt molding method, the appearance characteristics of EVOH (excellence in transparency, little coloration such as yellowing, and no occurrence of gels and blisters) In addition, long run properties (physical properties such as viscosity do not change drastically even during long-time molding, and there are no fish eyes or streaks) are required. In addition, the packaging material is often used as a multilayer structure. Therefore, in order to improve the interlayer adhesion of the multilayer structure, metal ions may be contained in the EVOH composition. However, when a metal ion is contained in the EVOH composition, coloring tends to occur, and the appearance characteristics of the molded article are deteriorated. Further, when the sheet end portion (trim) to be cut and removed is collected and reused in sheet forming, EVOH is thermally deteriorated, gels and blisters are generated, and the appearance characteristics of the formed body are deteriorated. Furthermore, when used over a long period of time under high temperature conditions, appearance characteristics deteriorate due to coloring such as yellowing.

  In order to improve the above-mentioned various properties required for EVOH, Patent Document 1 and Patent Document 2 describe an EVOH composition containing an acid such as a carboxylic acid and a metal ion. Patent Document 3 describes an EVOH composition containing a polyvalent carboxylic acid and a metal ion. These EVOH compositions are excellent in appearance characteristics and long run properties. Patent Document 4 describes a method for producing an EVOH composition with low thermal degradation, characterized by adding a specific acid such as nitric acid to an EVOH composition containing sodium acetate.

JP-A 64-66262 JP 2001-146539 A International Publication No. 2011/118648 JP 51-49294 A

  However, since some of the characteristics such as appearance characteristics, long run properties, interlayer adhesion properties and the like show a trade-off relationship with each other, it is difficult to express all the properties at a high level. For example, the addition of metal ions increases the interlayer adhesion, but the appearance characteristics and long run properties are reduced. The reduced properties can be improved by adding acid, but this reduces the interlaminar adhesion, making the net property improvement very limited. On the other hand, in the market, it is required to further improve these characteristics, and even when used for a long time under higher temperature conditions than before, these characteristics, especially the appearance characteristics, are expressed at a high level. There is a strong demand for it. In addition, the technique of the above-mentioned Patent Document 4 cannot achieve sufficient appearance characteristics, long run properties and interlayer adhesion.

  The present invention has been made based on the circumstances as described above, and is excellent in appearance characteristics, long run properties and interlayer adhesion, and can maintain a good appearance even after long-term use as a packaging material under high temperature conditions. It aims at providing a composition and its manufacturing method. Another object of the present invention is to provide a multilayer structure obtained from such a resin composition and having excellent interlayer adhesion.

That is, the present invention is as follows.
(1) An ethylene-vinyl alcohol copolymer (A), a component (B) composed of at least one of nitric acid and nitrate ions, and a metal ion (C), and a substance contained in the component (B) The amount Bm is 0.5 μmol / g or more and 100 μmol / g or less, the content amount Cm of the metal ion (C) is 2 μmol / g or more and 120 μmol / g or less, and the content amount Bm of the component (B) And the content amount Cm of the metal ion (C) and the average valence Cv satisfy the relationship of (Cv × Cm) /Bm≧1.0, and from at least one of carboxylic acid and carboxylate ion When the component (D) is contained, the Bm, the Cm, the Cv, the contained substance amount Dm of the component (D) and the average valence Dv thereof are ((Cv × Cm) −Bm) / ( Dv x Dm Resin composition satisfies the relationship ≧ 0.2;
(2) The resin composition according to (1), wherein the Bm is 5 μmol / g or more and 25 μmol / g or less;
(3) The resin composition according to the above (1) or (2), wherein the metal ion (C) consists only of an alkali metal ion (C1);
(4) The metal ion (C) includes an alkali metal ion (C1) and an alkaline earth metal ion (C2), the content amount C1m of the alkali metal ion (C1), and the alkaline earth metal ion (C2) The resin composition according to (1) or (2) above, wherein the content amount of C2m satisfies a relationship of C1m / (C1m + 2 × C2m) ≧ 0.5;
(5) The component (D), wherein the component (D) comprises at least one of a monovalent carboxylic acid and a monovalent carboxylic acid ion, and a polyvalent carboxylic acid and a polyvalent carboxylic acid. It contains at least one of the components (D2) composed of at least one of acid ions, and the Bm, the Cm, the Cv, the content Dm of the component (D) and the average valence Dv thereof are 0. The resin composition according to any one of (1) to (4) above, which satisfies a relationship of 3 ≦ ((Cv × Cm) −Bm) / (Dv × Dm) ≦ 1.0;
(6) The resin composition according to (5), wherein the component (D) includes both the component (D1) and the component (D2), and the component (D2) has three or more carboxyl groups. ;
(7) The resin composition according to any one of (1) to (6), further including a phosphate compound (E), the content Ew of which is 5 ppm or more and 500 ppm or less in terms of phosphate radical. ;
(8) The resin composition according to any one of (1) to (7), further including a boron compound (F), the content Fw of which is 5 ppm or more and 2,000 ppm or less in terms of boron element. object;
(9) The resin composition according to any one of (1) to (8) above, which is for coextrusion molding;
(10) A copolymerization step of copolymerizing ethylene and vinyl ester to obtain an ethylene-vinyl ester copolymer, and saponifying the ethylene-vinyl ester copolymer to obtain an ethylene-vinyl alcohol copolymer (A). A saponification step to be obtained, and after the copolymerization step, the ethylene-vinyl ester copolymer or ethylene vinyl alcohol copolymer (A), the component (B), and the metal ion (C) are mixed. The method for producing a resin composition according to any one of (1) to (9), including a mixing step;
(11) A granulation step of obtaining a water-containing pellet of the ethylene-vinyl alcohol copolymer (A) by a granulation operation from the solution containing the ethylene-vinyl alcohol copolymer (A) obtained in the saponification step, and the water content The method for producing a resin composition according to the above (10), which includes a drying step of drying pellets, and the mixing step is performed after the granulation step;
(12) As the mixing step, the water-containing pellet is immersed in a solution containing the component (B) and the metal ion (C) between the granulation step and the drying step. A method for producing a resin composition;
(13) A multilayer structure having at least one layer obtained from the resin composition according to any one of (1) to (9) above.

  The resin composition of the present invention is excellent in appearance characteristics and long run properties, and can maintain good appearance characteristics even after long-term use as a packaging material under high temperature conditions. Moreover, said effect can be acquired easily by manufacturing a resin composition with the manufacturing method of this invention. Furthermore, a multilayer structure excellent in interlayer adhesion can be obtained by using the resin composition of the present invention.

<EVOH (A)>
The resin composition of the present invention contains EVOH (A) as a main component. In addition, a main component means the component with most content on a mass basis in a dry state. As a minimum of content of EVOH (A) in the said resin composition, 90 mass% is preferable, for example, and 99 mass% may be more preferable. In addition, content of each component in the said resin composition says the resin composition (henceforth "dry resin composition") of a dry state, and is synonymous with content of solid content conversion (hereinafter the same). .

  EVOH (A) is a copolymer having an ethylene unit and a vinyl alcohol unit, but may contain one or more other structural units. The upper limit of the content of structural units other than ethylene units, vinyl alcohol units, and vinyl ester units is preferably 10 mol% with respect to all structural units constituting EVOH (A) and may be 1 mol%. It may be 1 mol%. EVOH (A) is usually obtained by saponifying an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and a vinyl ester.

  As a minimum of ethylene unit content of EVOH (A), 20 mol% is preferred, 22 mol% is more preferred, and 25 mol% is still more preferred. On the other hand, the upper limit of the ethylene unit content of EVOH (A) is preferably 60 mol%, more preferably 55 mol%, and even more preferably 50 mol%. By setting the ethylene unit content of EVOH (A) within the above range, a yellowing after melt molding is suppressed, and a resin composition excellent in long run properties is obtained. When the ethylene unit content of EVOH (A) is smaller than the above lower limit, the long run property of the resin composition, the water resistance of the multilayer structure, the hot water resistance, and the gas barrier property under high humidity may be deteriorated. Conversely, if the ethylene unit content of EVOH (A) exceeds the above upper limit, the gas barrier properties of the multilayer structure may be reduced.

  As a minimum of the saponification degree of EVOH (A), 80 mol% is preferable, 95 mol% is more preferable, 99 mol% is further more preferable. If the saponification degree of EVOH (A) is smaller than the above lower limit, the gas barrier properties and appearance characteristics of the resulting multilayer structure may be deteriorated.

  The lower limit of the EVOH (A) melt flow rate (according to JIS K7210, measured at a temperature of 210 ° C. and a load of 2160 g, hereinafter abbreviated as MFR) is preferably 0.1 g / 10 min, 0.5 g / 10 min is more preferable, 1 g / 10 min is further preferable, and 3 g / 10 min is particularly preferable. On the other hand, the upper limit of the MFR of EVOH (A) is preferably 200 g / 10 minutes, more preferably 50 g / 10 minutes, further preferably 30 g / 10 minutes, particularly preferably 15 g / 10 minutes, and most preferably 10 g / 10 minutes. preferable. By setting the MFR of EVOH (A) within the above range, the appearance characteristics after melt molding and the long run property are excellent.

<Component (B) composed of at least one of nitric acid and nitrate ion>
The resin composition of the present invention contains a component (B) composed of at least one of nitric acid and nitrate ions (hereinafter abbreviated as component (B)). By including the component (B), the resin composition of the present invention suppresses coloring such as yellowing after melt molding and after long-term use without being affected by other components constituting the resin composition. be able to.

  The component (B) needs to be substantially nitrate ions, which is achieved by controlling the relative ratio with the metal ions (C) described later. Thereby, the viscosity behavior at the time of melt molding of the resin composition is stabilized, and the occurrence of coloring such as yellowing and gels and blisters can be suppressed. That is, it is possible to improve various characteristics that are conventionally in a trade-off relationship and difficult to achieve at a high level. The reason for such an effect is not clear, but component (B) competitively interacts with metal ion (C) that catalytically promotes the decomposition and coloring of EVOH (A), and its catalytic action is reduced. Presumed to be suppressed.

  The lower limit of the content Bm of the component (B) in the dry resin composition is 0.5 μmol / g, preferably 1 μmol / g, and more preferably 5 μmol / g. On the other hand, the upper limit of Bm is 100 μmol / g, preferably 50 μmol / g, and more preferably 25 μmol / g. When Bm is equal to or more than the above lower limit, coloring such as yellowing after melt molding and long-term use is suppressed. On the other hand, when Bm is equal to or less than the above upper limit, transparency can be maintained at a high level, generation of gels and blisters can be suppressed, and economic efficiency can be improved. Moreover, the viscosity behavior at the time of melt molding of the resin composition is stable, and the long run property is excellent.

  The component (B) may be mixed in the form of nitric acid, or may be mixed as a nitrate that forms a salt with a counter cation such as a metal ion. In the resin composition, the component (B) may be mixed with a counter cation such as a metal ion. It is preferably present as a nitrate that forms a salt. Examples of the nitrate include lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate. It is also possible to form nitric acid and nitrate ions by mixing in the state of nitrous acid or nitrite and oxidizing after mixing. When a counter cation such as a metal ion is mixed with a nitrate that forms a salt, the metal ion behaves as a metal ion (C) described later.

<Metal ion (C)>
The resin composition of the present invention contains a metal ion (C). When the resin composition of the present invention contains a metal ion (C), the resulting multilayer structure has excellent interlayer adhesion. The reason why the metal ion (C) improves the interlayer adhesion is not clear, but it is considered that the affinity between the hydroxy groups of EVOH (A) between layers is higher due to the presence of the metal ion. In addition, when one of the adjacent layers has a functional group capable of reacting with the hydroxy group of EVOH (A) in the molecule, this bond formation reaction may be accelerated by the presence of the metal ion (C). It is done.

  The lower limit of the content Cm of the metal ion (C) in the dry resin composition is 2.0 μmol / g, preferably 3.0 μmol / g, and more preferably 5.0 μmol / g. On the other hand, the upper limit of Cm is 120 μmol / g, preferably 60 μmol / g, and more preferably 30 μmol / g. When Cm is at least the above lower limit, the interlayer adhesion of the multilayer structure is excellent. On the other hand, when Cm is equal to or less than the above upper limit, coloring such as yellowing after melt molding and long-term use can be suppressed, and at the same time, the economy is excellent.

  In the resin composition of the present invention, the average valence Cv of Bm, Cm and metal ion (C) needs to satisfy the following formula (1). Here, Cv is a value obtained by multiplying the valence of the element constituting the metal ion (C) by the presence ratio and adding it. In addition, the valence of alkali metal ions is 1, and the valence of alkaline earth metal ions is 2. When (Cv × Cm) / Bm is 1.0 or more, the component (B) can be substantially present as nitrate ions, coloring such as yellowing and generation of gels and blisters can be suppressed, and long-running properties can be achieved. It will be excellent. At the same time, the interlayer adhesion when the multilayer structure is formed is excellent. The upper limit of (Cv × Cm) / Bm is not particularly limited, but is, for example, 20, 10 is preferable, 5 is more preferable, and 2.5 is more preferable.

    (Cv × Cm) /Bm≧1.0 (1)

  Examples of the metal ions (C) include alkali metal ions (C1), alkaline earth metal ions (C2), other transition metal ions, and the like, which are composed of one or more kinds of metal species. May be. Especially, it is preferable that an alkali metal ion (C1) is included, and a metal ion (C) may consist only of an alkali metal ion (C1). When the metal ion (C) is composed only of the alkali metal ion (C1), not only the production method can be simplified, but also the interlayer adhesion of the multilayer structure can be further improved.

  Examples of the alkali metal ion (C1) include lithium, sodium, potassium, rubidium and cesium ions, but sodium and potassium ions are preferred from the viewpoint of industrial availability.

  Examples of alkali metal salts that give alkali metal ions (C1) include lithium, sodium, and potassium aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and A metal complex is mentioned. Among these, sodium acetate, potassium acetate, sodium phosphate, and potassium phosphate are more preferable because they are easily available. When nitrate is used, the nitrate ion behaves as component (B). Similarly, the phosphate behaves as a phosphoric acid compound (E) described later.

  The lower limit of the content C1m of the alkali metal ion (C1) in the dry resin composition is preferably 2.0 μmol / g, more preferably 3.0 μmol / g, and even more preferably 4.0 μmol / g. On the other hand, the upper limit of C1m is preferably 120 μmol / g, more preferably 60 μmol / g, and even more preferably 30 μmol / g. When C1m is equal to or more than the above lower limit, interlayer adhesion when a multilayer structure is formed is increased. On the other hand, when C1m is less than or equal to the above upper limit, coloring such as yellowing and generation of gels and blisters can be suppressed.

  It is also preferred that the metal ion (C) contains an alkaline earth metal ion (C2). When the metal ion (C) contains the alkaline earth metal ion (C2), thermal degradation of the EVOH (A) when the trim is reused is suppressed, and the formation of gels and blisters in the molded body is suppressed.

  Examples of the alkaline earth metal ion (C2) include beryllium, magnesium, calcium, strontium, and barium ions. Magnesium and calcium ions are preferable from the viewpoint of industrial availability.

  Examples of alkaline earth metal salts that give alkaline earth metal ions (C2) include magnesium and calcium aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, And metal complexes. When nitrate is used, the nitrate ion behaves as the component (B) in the resin composition. Similarly, phosphate behaves as phosphate compound (E).

  The lower limit of the content C2m of the alkaline earth metal ion (C2) contained in the dry resin composition is not particularly limited, and may be, for example, 0.1 μmol / g or 1 μmol / g. On the other hand, the upper limit of C2m is preferably 60 μmol / g, more preferably 30 μmol / g, further preferably 15 μmol / g, and may be 5 μmol / g. When C2m is equal to or less than the above upper limit, the long run property is excellent without causing excessive decomposition during melt molding of the resin composition. Furthermore, it is preferable that C2m satisfies the following formula (3) together with the above-described C1m. By doing so, the long-run property and the interlaminar adhesion when the multilayer structure is formed are simultaneously excellent. The upper limit of C1m / (C1m + 2 × C2m) may be 1.

    C1m / (C1m + 2 × C2m) ≧ 0.5 (3)

<Component (D) consisting of at least one of carboxylic acid and carboxylate ion>
The resin composition of the present invention may or may not contain component (D) (hereinafter abbreviated as component (D)) consisting of at least one of carboxylic acid and carboxylate ion. May be.

When the resin composition of the present invention contains the component (D), the content Dm of the component (D) in the dry resin composition is Bm, Cm, Cv, Dm and the average valence Dv of the component (D). And the following formula (2) is satisfied. Thereby, while being able to suppress coloring, such as yellowing after melt molding and long-term use, long run property and interlayer adhesiveness can be improved. For example, when ((Cv × Cm) −Bm) / (Dv × Dm) is less than 0.2, the balance between the metal ion (C) and the component (D) is poor, that is, the component ( It is presumed that D) is large and the metal ions (C) that work effectively are reduced, which makes it impossible to fully exhibit each characteristic. Here, Dm is the total amount of the component (D1) and the component (D2) described later. Dv is a value obtained by dividing the total number of carboxyl groups and carboxylate groups (—COO ⁻ ) constituting the component (D) by the total number (number of molecules) of the component (D). That is, Dv is the average value of the number of carboxyl groups and carboxylate groups that one molecule of component (D) has.

    ((Cv × Cm) −Bm) / (Dv × Dm) ≧ 0.2 (2)

  The lower limit of ((Cv × Cm) −Bm) / (Dv × Dm) is preferably 0.3. Moreover, the upper limit of ((Cv × Cm) −Bm) / (Dv × Dm) may be 1.5, for example, and preferably 1.0.

  Component (D) is at least one of monovalent carboxylic acid and monovalent carboxylic acid ion (D1) (hereinafter abbreviated as component (D1)), and at least polyvalent carboxylic acid and polyvalent carboxylic acid ion. It consists of at least one of either one (D2) (hereinafter abbreviated as component (D2)). Here, as the component (D), it is also preferable to include both the component (D1) and the component (D2) from the viewpoint of suppressing coloring such as yellowing.

  In the component (D1), the monovalent carboxylic acid is a compound having one carboxyl group in the molecule. Further, the monovalent carboxylate ion is obtained by eliminating the hydrogen ion of the carboxyl group of the monovalent carboxylic acid.

  The content D1m of the component (D1) in the dry resin composition is preferably less than 2 μmol / g and less than 1.5 μmol / g with respect to the entire resin composition from the viewpoint of reducing odor. Is more preferably less than 1.2 μmol / g, and particularly preferably less than 1.0 μmol / g. When D1m is in the above range, the odor of the resin composition itself is reduced, and the odor generated when the resin composition is melt-molded is reduced, so that the working environment is improved. In addition, since the odor of the molded article after melt molding is reduced, the multilayer structure using the resin composition is particularly suitable for contents such as cooked rice and drinking water where the generation of odor impairs the commercial value. However, it is preferably used as a packaging material.

  On the other hand, from the viewpoint of quality stability, D1m is preferably 2 μmol / g or more, more preferably 2.5 μmol / g or more, and more preferably 3 μmol / g or more based on the entire resin composition. Is more preferable. The content of the monovalent carboxylic acid and the monovalent carboxylic acid ion is in the above range, so that the content of the metal ion (C) can be easily controlled during the production of the resin composition, and the long run property is excellent. It becomes. In addition, as an upper limit of D1m, it is 50 micromol / g, for example, and 20 micromol / g is preferable.

  Examples of the monovalent carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, acrylic acid, methacrylic acid, benzoic acid, and 2-naphthoic acid. These monovalent carboxylic acids may have a hydroxyl group or a halogen atom. Examples of the monovalent carboxylate ion include those from which the hydrogen ion of the carboxyl group of each monovalent carboxylic acid is eliminated. Among these, acetic acid is preferable as the monovalent carboxylic acid.

  In the component (D2), the polyvalent carboxylic acid is a compound having two or more carboxyl groups in the molecule. The polyvalent carboxylic acid does not include a polymer. In addition, the polyvalent carboxylate ion is one in which at least one hydrogen ion of the carboxyl group of the polyvalent carboxylate ion is eliminated. The resin composition contains the component (D2), thereby controlling the pH in the resin composition and suppressing the generation of gels and blisters, as well as suppressing coloring such as yellowing derived from metal ions. can do.

  The reason why the component (D2) can suppress coloring such as yellowing is not clear, but the component (D2) is stably coordinated with the metal ion (C) causing yellowing and the like, and the metal ion It is estimated that (C) can be captured. Thus, the presence of a polyvalent carboxylic acid or the like in a coordinated state with respect to the metal ion (C) provides a catalytic function for reactions such as yellowing of EVOH (A) of the metal ion (C). As a result, it is considered that the occurrence of coloring such as yellowing is suppressed even during melt molding at high temperatures. In addition, since this metal ion (C) and polyvalent carboxylic acid are bonds of relatively weak interaction, the resin composition of the present invention has excellent interlayer adhesion even when a multilayer structure is formed. It can be demonstrated. In view of productivity and economy, the component (D2) is preferably used in combination with the component (D1) described above.

  The lower limit of the content D2m of the component (D2) in the dry resin composition is preferably 0.01 μmol / g, more preferably 0.05 μmol / g, still more preferably 0.1 μmol / g, and 0.5 μmol / g. Is particularly preferred. On the other hand, the upper limit of D2m is preferably 20 μmol / g, more preferably 15 μmol / g, still more preferably 10 μmol / g, and particularly preferably 6 μmol / g. When D2m is not less than the above lower limit, coloring such as yellowing can be suppressed. On the other hand, when D2m is not more than the above upper limit, the long run property is excellent.

The polyvalent carboxylic acid of component (D2) only needs to have two or more carboxyl groups in the molecule. For example, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, malic acid, glutaric acid , Aliphatic dicarboxylic acids such as adipic acid and pimelic acid;
Aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid;
Tricarboxylic acids such as citric acid, isocitric acid, aconitic acid;
Carboxylic acids having four or more carboxyl groups such as 1,2,3,4-butanetetracarboxylic acid, ethylenediaminetetraacetic acid;
Hydroxycarboxylic acids such as citric acid, isocitric acid, tartaric acid, malic acid, mucinic acid, tartronic acid, citramalic acid;
Examples include ketocarboxylic acids such as oxaloacetic acid, mesooxalic acid, 2-ketoglutaric acid, and 3-ketoglutaric acid, and amino acids such as glutamic acid, aspartic acid, and 2-aminoadipic acid. Among these, citric acid and tartaric acid are preferable as the polyvalent carboxylic acid. In addition, these anions can be mentioned as a polyvalent carboxylate ion of a component (D2).

  It is also preferable that the component (D2) is a polyvalent carboxylic acid having at least one functional group selected from the group consisting of a hydroxy group, an amino group, and a ketone group, or an anion thereof. When these functional groups are included, the stability of the state coordinated to the metal ion (C) is increased, so that coloring during melt molding at high temperatures can be more effectively suppressed. Among them, as a result of appropriately adjusting the coordination strength with respect to the metal ion (C), it is possible to suppress coloring such as yellowing and to obtain an excellent interlayer adhesion when a multilayer structure is obtained. Therefore, it is more preferable to have a hydroxy group.

  The component (D2) polyvalent carboxylic acid preferably has three or more carboxyl groups. By using such a polyvalent carboxylic acid, the component (D2) can be coordinated electrically and sterically stably and efficiently to the metal ion (C), so that the yellowing of the resin composition of the present invention And the like can be more effectively suppressed.

<Phosphate compound (E)>
The resin composition of the present invention may contain a phosphoric acid compound (E). Thereby, the thermal stability at the time of melt molding of the resin composition can be improved, and as a result, generation of gels and blisters when formed into a molded body can be suppressed.

  Examples of the phosphoric acid compound (E) include various phosphoric oxygen acids such as phosphoric acid and phosphorous acid and salts thereof. As the phosphate, for example, it may be contained in any form of a first phosphate, a second phosphate, and a third phosphate, and the counter cation is not particularly limited, but an alkali metal salt or an alkali Earth metal salts are preferred, and alkali metal salts are more preferred. Specifically, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate is the thermal stability during the melt molding of the resin composition and repeated melt molding by trim recovery, etc. It is preferable in that the improvement effect is high. Here, when mixing the metal ion of a counter cation and the phosphate compound (E) which formed the salt, the said metal ion behaves also as the above-mentioned metal ion (C).

  The lower limit of the phosphate radical content Ew of the phosphate compound (E) in the dry resin composition is preferably 5 ppm, and more preferably 8 ppm. On the other hand, the upper limit of Ew is preferably 500 ppm, more preferably 200 ppm, and even more preferably 50 ppm. When Ew is in the above range, it is possible to suppress the formation of gels and bumps in the molded body.

<Boron compound (F)>
The resin composition of the present invention may contain a boron compound (F). Thereby, the thermal stability at the time of melt molding of the resin composition can be improved, and as a result, generation of gels and blisters when formed into a molded body can be suppressed. Specifically, when a boron compound (F) is blended in the resin composition, a chelate compound is generated between EVOH (A) and the boron compound (F), thereby improving the thermal stability of the resin composition. The mechanical properties are thought to improve.

Examples of the boron compound (F) include boric acid, boric acid ester, borate, and borohydride. Specifically, examples of boric acid include orthoboric acid (H ₃ BO ₃ ), metaboric acid, and tetraboric acid. Examples of boric acid esters include triethyl borate and trimethyl borate. Examples of the acid salt include alkali metal salts, alkaline earth metal salts, and borax of the various boric acids described above. Of these, orthoboric acid is preferred. Here, when the metal ion of the counter cation and the boron compound (F) that forms a salt are mixed, the metal ion also behaves as the above-described metal ion (C).

  As a minimum of content Fw of the boron compound conversion of boron compound (F) in a dry resin composition, 5 ppm is preferred and 10 ppm is more preferred. On the other hand, the upper limit of Fw is preferably 2,000 ppm, more preferably 1,000 ppm, and even more preferably 500 ppm. When Fw is in the above range, it is possible to suppress the generation of gels and blisters when formed into a molded body.

<Other additives>
The resin composition of the present invention is, for example, a plasticizer, a stabilizer, a surfactant, a colorant, an ultraviolet absorbent, an oxygen absorbent, a slip agent, an antistatic agent, a desiccant, as long as the effects of the present invention are not impaired. An appropriate amount of a reinforcing agent such as a crosslinking agent, a filler, and various fibers may be included. However, the upper limit of the content of components other than the components (A) to (F) in the resin composition may be 10% by mass, 1% by mass, or 0.1% by mass. %.

  Further, an appropriate amount of a thermoplastic resin other than EVOH (A) can be blended within a range that does not impair the effects of the present invention. Examples of the other thermoplastic resin include various polyolefins (polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene and α-olefin having 4 or more carbon atoms). Copolymer, copolymer of olefin and maleic anhydride, ethylene-vinyl ester copolymer, ethylene-acrylic ester copolymer, or modified polyolefin obtained by graft-modifying these with unsaturated carboxylic acid or derivatives thereof) , Various nylons (nylon 6, nylon 66, nylon 6/66 copolymer, etc.), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, and modified polyvinyl alcohol resin. When the resin composition contains a thermoplastic resin other than EVOH (A), the content of the other thermoplastic resin in the dry resin composition is preferably less than 50% by mass, and less than 30% by mass. More preferably, it is less than 10% by mass, and may be less than 1% by mass.

<Resin composition>
The preferable range of MFR of the resin composition of the present invention is the same as that of the above-mentioned MFR of EVOH (A), and the effect obtained by setting the range is the same as that of EVOH (A).

  The resin composition of the present invention can be formed into various molded articles such as films, sheets, containers, pipes, fibers, etc. by melt molding. These molded bodies can be pulverized and molded again for the purpose of reuse. It is also possible to uniaxially or biaxially stretch films, sheets, fibers, and the like. As the melt molding method, for example, extrusion molding, inflation extrusion, blow molding, melt spinning, and injection molding are possible. Among them, the resin composition of the present invention can be easily used together with other resins to easily form a multilayer structure. Therefore, it can be suitably used for coextrusion molding.

  The melting temperature at the time of melt molding is preferably about 150 to 300 ° C, and usually a melting temperature of about 200 to 250 ° C is employed. The molded body thus obtained is excellent in transparency after melt molding and long-term use, and is suppressed in coloration such as yellowing, is suppressed in the generation of gels and blisters, and is excellent in long run properties. Become.

<Method for producing resin composition>
The resin composition of the present invention includes, for example, a copolymerization step (step 1) in which ethylene and vinyl ester are copolymerized to obtain an ethylene-vinyl ester copolymer, and the ethylene-vinyl ester copolymer is saponified to produce EVOH. A saponification step (step 2) for obtaining (A) is performed, and the ethylene-vinyl ester copolymer or EVOH (A), component (B), and metal ion (C) are mixed after the copolymerization step. It can obtain effectively by the manufacturing method which further includes a mixing process (process (alpha)). Here, by performing the mixing step after the copolymerization step, coloring such as yellowing of the resin composition occurring during melt molding is suppressed. Hereinafter, each step will be described in detail.

(Step 1: Copolymerization step)
In the copolymerization process, in addition to the copolymerization process of ethylene and vinyl ester, a polymerization inhibitor is added if necessary, and then unreacted ethylene and unreacted vinyl ester are removed to remove ethylene-vinyl ester copolymer. Obtaining a coalesced solution. When the component (B) and the metal ion (C) are added before the copolymerization step, not only the coloring of the resin composition is not suppressed, but also the coloring may be performed. Examples of the copolymerization method of ethylene and vinyl ester include known methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization.

  Typical vinyl esters used for polymerization include vinyl acetate, but other aliphatic vinyl esters such as vinyl propionate and vinyl pivalate can also be used. In addition, a small amount of a copolymerizable monomer can be copolymerized.

  As polymerization temperature, 20-90 degreeC is preferable and 40-70 degreeC is preferable. The polymerization time is preferably 2 to 15 hours, more preferably 3 to 11 hours. The polymerization rate is preferably 10 to 90%, more preferably 30 to 80% with respect to the vinyl ester charged. The resin content in the solution after polymerization is preferably 5 to 85% by mass, and more preferably 20 to 70% by mass.

(Process 2: Saponification process)
Next, an alkali catalyst is added to the ethylene-vinyl ester copolymer solution to saponify the copolymer in the solution. The saponification method can be either a continuous type or a batch type. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, and alkali metal alcoholate.

(Process α (1): Mixing process)
In the mixing step, the ethylene-vinyl ester copolymer obtained in the copolymerization step or EVOH (A) obtained in the saponification step, component (B), and metal ion (C) are mixed. For this mixing, for example, (1) a method in which the component (B) and the metal ion (C) are added in advance to a solution containing an ethylene-vinyl ester copolymer used in the saponification step,
(2) A method in which component (B) and metal ion (C) are added during the saponification reaction of the ethylene-vinyl ester copolymer in the saponification step, and (3) component (after obtaining EVOH (A) in the saponification step) A method of mixing B) and the metal ion (C) can be used.

  In addition, by performing a mixing process in a saponification process, the thermal deterioration which EVOH (A) receives during the manufacturing process after a saponification process is suppressed, and coloring, such as yellowing, of the resin composition obtained is suppressed.

  Further, the remaining alkali catalyst is often neutralized after the saponification step, but component (B) or component (D) may be used as an acid used for neutralization.

(Process 3: Granulation process)
In order to obtain the resin composition of the present invention in the form of pellets, a granulation step may be provided after the copolymerization step and the saponification step. As described later, it is also preferable to perform the mixing step after the granulation step, and the coloring of the resin composition at the time of melt molding is also suppressed by this method. Since EVOH (A) is obtained in the form of a solution containing the solvent used in the saponification reaction, washing is performed to remove by-products such as alkali and sodium acetate remaining in the solution. In order to facilitate this washing operation, it is preferable to granulate the EVOH (A) -containing solution obtained in the saponification step to obtain EVOH (A) hydrous pellets.

  As granulation operations, for example, (I) a method in which an EVOH (A) -containing solution is extruded into a coagulation bath and cooled or solidified and then cut immediately or (II) an EVOH (A) solution is brought into contact with water vapor And a method of cutting in advance as a water-containing resin composition of EVOH (A). The moisture content in the hydrous pellets of EVOH (A) obtained by these methods is preferably 40 to 200% by mass, more preferably 45 to 180% by mass, based on the dry weight of EVOH (A). Preferably, it is 50-150 mass%.

(Process 4: Drying process)
The EVOH hydrous pellets obtained in the granulation step are preferably dried to form EVOH (A) dry pellets. The moisture content in the dry pellets is preferably 1.0% by mass or less and 0.8% by mass or less with respect to the entire dry pellets for the purpose of preventing molding troubles such as generation of voids during molding. Is more preferably 0.5% by mass or less.

  Examples of the method for drying the water-containing pellet include stationary drying and fluidized drying. These drying methods may be used alone or in combination. The drying treatment may be performed by either a continuous method or a batch method. When a plurality of drying methods are combined, a continuous method or a batch method can be freely selected for each drying method. It is also preferable to perform drying at a low oxygen concentration or in an oxygen-free state from the viewpoint that the deterioration of the resin composition due to oxygen during drying can be reduced.

(Process α (2): Mixing process)
As a method of performing the mixing step after the granulation step, for example, (1) a method of contacting the water-containing pellets of EVOH (A) with a solution containing the component (B) and the metal ion (C), and (2) EVOH ( Examples thereof include a method of melt-kneading the water-containing pellets of A), the component (B) and the metal ion (C) in an extruder. At this time, the component (D), the component (E), the component (F) and the like can be mixed with the EVOH (A) at the same time. Among these, the method (1) is preferable, and specifically, a method in which the hydrous pellets are immersed in a solution containing the component (B) and the metal ion (C) between the granulation step and the drying step is preferable. . According to the said method, a component (B) and a metal ion (C) can be mixed in a resin composition efficiently, and the various characteristics of the resin composition of this invention will be excellent.

  When soaking, the shape of the water-containing pellet is arbitrary, and the operation may be either a batch method or a continuous method. Immersion may be divided into a plurality of solutions in which each component to be contained in the resin composition is individually dissolved, or may be treated at once using a solution in which a plurality of components are dissolved, but other than EVOH (A) It is preferable from the point of simplification of a process to process with the solution containing all of these components. In obtaining a solution containing each component other than EVOH (A), a solution in which each component forms a salt may be used. The solvent of the solution is not particularly limited, but water is preferable for handling reasons.

  In the method for producing the resin composition of the present invention, it is also preferable to perform the mixing step simultaneously with the granulation step. That is, in the operation of granulation (1), the coagulation bath may contain the component (B) and the metal ion (C) in advance. Thereby, a component (B) and a metal ion (C) can be uniformly contained in the water-containing pellet of EVOH (A).

<Multilayer structure>
The multilayer structure of the present invention is a multilayer structure including at least one layer obtained from the resin composition. The multilayer structure of the present invention has excellent appearance characteristics because it has a layer obtained from a resin composition having excellent appearance characteristics and long run properties, and even when used for a long time at high temperatures. , Good appearance characteristics can be maintained.

  Note that a multilayer structure refers to a structure having two or more layers. The lower limit of the number of layers of the multilayer structure may be 3 or 5. On the other hand, the upper limit of the number of layers of the multilayer structure may be 100 or 50, for example.

  As the layer structure of the multilayer structure, for example, the layer obtained from the resin composition of the present invention is represented by E, the layer obtained from the adhesive resin is represented by Ad, and the layer obtained from the thermoplastic resin is represented by T. Examples of the structure include / E / T, E / Ad / T, and T / Ad / E / Ad / T. Each of these layers may be a single layer or a multilayer. Moreover, you may include other layers other than the above.

  Examples of the adhesive resin include an adhesive resin containing a carboxylic acid-modified polyolefin. As the carboxylic acid-modified polyolefin, a modified olefin containing a carboxyl group obtained by chemically bonding an ethylenically unsaturated carboxylic acid, its ester or its anhydride to an olefin polymer (for example, addition reaction, graft reaction, etc.) A polymer can be preferably used. Examples of the ethylenically unsaturated carboxylic acid, its ester or its anhydride include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid Acid monomethyl ester and the like, and maleic anhydride is more preferable. These adhesive resins may be used alone or in admixture of two or more.

  Examples of the thermoplastic resin include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene-α-olefin copolymer. Polyolefins such as polymers, polybutenes, polypentenes, or copolymers thereof; polyesters such as polyethylene terephthalate; polyester elastomers; polyamides such as nylon 6 and nylon 66; polystyrenes; polyvinyl chloride; polyvinylidene chloride; Resin, polyurethane elastomer, polycarbonate, chlorinated polyethylene, and chlorinated polypropylene. Among these, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene, and polyester are preferably used.

<Method for producing multilayer structure>
As a method for producing the multilayer structure of the present invention, for example, (1) a method of melt-extruding a thermoplastic resin on a molded product obtained from the resin composition of the present invention,
(2) A method of co-extrusion of the resin composition of the present invention and another thermoplastic resin,
(3) A method of co-injecting the resin composition of the present invention and a thermoplastic resin, and (4) A method of laminating a molded product obtained from the resin composition of the present invention and another substrate using an adhesive. Is mentioned. Among these methods, the method (2) can be preferably used. This is because the resin composition of the present invention is excellent in long run properties even when melted under high temperature conditions, and subsequent coloring is also suppressed, so even if it is co-extruded with other thermoplastic resins having a high melting point, It is because coloring can be suppressed and a multilayer structure excellent in appearance characteristics can be obtained. Examples of the coextrusion method include a multi-manifold merging method T-die method, a feed block merging method T-die method, and an inflation method.

By subjecting the multilayer structure obtained by the above-described coextrusion to secondary processing, for example, the following molded body is obtained.
(1) A multilayer stretched sheet or film obtained by stretching and heat-treating a multilayer structure (sheet or film, etc.) in a uniaxial or biaxial direction,
(2) A multilayer rolled sheet or film obtained by rolling a multilayer structure (sheet or film, etc.),
(3) A multilayer tray, cup-shaped container obtained by thermoforming a multilayer structure (sheet or film, etc.) such as vacuum forming, pressure forming, vacuum pressure forming,
(4) Bottles, cup-shaped containers, etc. obtained by stretch blow molding from multilayer structures (pipe, etc.).

  A secondary processing method other than the above may be used. The molded body obtained by these secondary processing methods can be preferably used as food containers such as deep-drawn containers, cup-shaped containers, and bottles.

  Hereinafter, the present invention will be described in more detail with reference to examples. In Examples and Comparative Examples described later, analysis and evaluation were performed by the following methods.

(1) Measurement of water content of water-containing EVOH pellets Using a halogen water content analyzer, the water content of water-containing EVOH pellets was measured by a thermodry weight measurement method under the conditions of a drying temperature of 180 ° C., a drying time of 20 minutes, and a sample amount of 10 g. did. The water content of the water-containing EVOH shown below is set to mass% based on the dry EVOH.

(2) Ethylene unit content and saponification degree of EVOH (A) Dissolve dry EVOH pellets in dimethyl sulfoxide (DMSO) -d ₆ containing tetramethylsilane as an internal standard substance and trifluoroacetic acid (TFA) as an additive, It measured at 80 degreeC using ¹ H-NMR of 500 MHz, and ethylene unit content and saponification degree were calculated | required from the peak intensity ratio of an ethylene unit, a vinyl alcohol unit, and a vinyl ester unit.

(3) Quantification of component (B) and component (D) 10 g of EVOH powder obtained by freeze-grinding dry EVOH pellets and 50 mL of ion-exchanged water are put into an Erlenmeyer flask equipped with a 100 mL stopper, and a cooling condenser is attached. The mixture was stirred at 95 ° C. for 10 hours to obtain an extract. An extract obtained by diluting 2 mL of the obtained extract with 8 mL of ion-exchanged water is quantitatively analyzed using ion chromatography, and the amounts of nitrate ion and carboxylate ion are respectively determined, whereby component (B) and component ( The amount of each of D) was calculated.

(4) Determination of metal ion (C) 0.5 g of dry EVOH pellets was placed in a pressure vessel made of Teflon (registered trademark), and 5 mL of concentrated nitric acid was added thereto and decomposed at room temperature for 30 minutes. After decomposition, the lid was covered, and further decomposition was performed by heating at 150 ° C. for 10 minutes and then at 180 ° C. for 5 minutes by a wet decomposition apparatus, and then cooled to room temperature. This treatment liquid was transferred to a 50 mL volumetric flask and diluted with pure water. About this solution, the quantity of each metal ion was quantified with the ICP emission-spectral-analysis apparatus.

(5) Quantitative determination of phosphoric acid compound (E) 0.5 g of dried EVOH pellets was placed in a pressure vessel made of Teflon (registered trademark), and 5 mL of concentrated nitric acid was added thereto to decompose at room temperature for 30 minutes. After decomposition, the lid was covered, and further decomposition was performed by heating at 150 ° C. for 10 minutes and then at 180 ° C. for 5 minutes by a wet decomposition apparatus, and then cooled to room temperature. This treatment liquid was transferred to a 50 mL volumetric flask and diluted with pure water. About this solution, the quantity of the phosphorus element was quantified with the ICP emission-spectral-analysis apparatus, and the quantity of the phosphoric acid compound (E) was computed by the phosphate radical conversion value.

(6) Quantitative determination of boron compound (F) 0.5 g of dry EVOH pellets was placed in a pressure vessel made of Teflon (registered trademark), and 5 mL of concentrated nitric acid was added thereto and decomposed at room temperature for 30 minutes. After decomposition, the lid was covered, and further decomposition was performed by heating at 150 ° C. for 10 minutes and then at 180 ° C. for 5 minutes by a wet decomposition apparatus, and then cooled to room temperature. This treatment liquid was transferred to a 50 mL volumetric flask and diluted with pure water. With respect to this solution, the amount of the boron compound (F) was quantified in terms of boron element using an ICP emission spectroscopic analyzer.

(7) Appearance characteristics (transparency and coloring)
A disk-shaped sample having a thickness of 1 mm was prepared by using 8 g of dried EVOH pellets and heating and melting at 240 ° C. for 5 minutes in a heat compression press apparatus. The transparency and coloring state of the obtained disk-shaped sample were confirmed visually, and evaluated according to the following criteria A to E as an index of appearance characteristics (transparency and coloring) after melt molding. Criteria A to C are sufficient for actual use.
A: Excellent transparency and hardly colored B: Transparency slightly low or slightly colored C: Transparency slightly low or slightly colored (light yellow) D: Transparent Equally low or very colored (yellow) E: Opaque or intensely colored (brown)

Next, the disk-like sample is allowed to stand in air at 120 ° C. for 50 hours, and the transparency and coloring are visually confirmed. The appearance characteristics (transparency and coloring) after long-term use are as shown in A to E below. Evaluated by criteria. Criteria A to C are sufficient for actual use.
A: Excellent transparency and hardly colored B: Transparency slightly low or slightly colored C: Transparency slightly low or slightly colored (light yellow) D: Transparent Equally low or very colored (yellow) E: Opaque or intensely colored (brown)

(8) Appearance characteristics (Generation of gel and scum)
Using the dried EVOH pellets, a single-layer film was formed with a single-screw extruder (Toyo Seiki Co., Ltd. D2020, caliber 20 mmφ, L / D 20, screw full flight type), and an EVOH single-layer film (20 μm) was formed. Obtained. The extrusion conditions were set to supply part / compression part / metering part / die = 175/215/225/220 ° C. Visually confirm the amount of gel and gel generated in the single-layer film obtained 2 hours after the start of film formation, and evaluate it according to the following criteria A to E. Occurrence). Criteria A to C are sufficient for actual use.
A: Almost no gel or stuff is seen B: Slight gel or stuff is seen C: Some gel or stuff is seen D: Pretty much gel or stuff is seen E: Vigorous gel or stuff is seen

Next, the EVOH powder obtained by pulverizing the single layer film was used to form a single layer using the same extruder and extrusion conditions as described above, to obtain an EVOH single layer film (20 μm). . Visually confirm the amount of the gel and blister generation of the single-layer film obtained by repeating this operation again, and evaluate it according to the criteria of A to E below. Occurrence). Criteria A to C are sufficient for actual use.
A: Almost no gel or stuff is seen B: Slight gel or stuff is seen C: Some gel or stuff is seen D: Pretty much gel or stuff is seen E: Vigorous gel or stuff is seen

(9) Long-run property The torque change when 60 g of dry EVOH pellets were kneaded at 100 rpm and 240 ° C. using a lab plast mill (biaxially different direction) was measured. The average value (TI) of torque from 20 minutes to 30 minutes after the start of kneading and the average value (TF) of torque from 170 minutes to 180 minutes after the start of kneading were calculated, respectively, and the following A to By evaluating with E criteria, it was used as an index of long run performance. Criteria A to C are sufficient for actual use.
A: 75/100 or more and less than 125/100 B: 125/100 or more and less than 150/100 C: 150/100 or more and less than 200/100 D: 200/100 or more and less than 300/100 E: 300/100 or more, or 75 / Less than 100

(10) Interlayer adhesion Dry EVOH pellets, linear low density polyethylene (Novatec LL-UF943 manufactured by Nippon Polyethylene Co., Ltd., hereinafter abbreviated as LLDPE) and adhesive resin (Bunel CXA417E 10 manufactured by DuPont, 6% of the above LLDPE) (Hereinafter abbreviated as Ad)) using the following extruder and extrusion conditions, and a coat hanger die for 300 mm width 3 types and 5 layers (manufactured by Plastic Engineering Laboratory Co., Ltd.) A multilayer film (LLDPE / Ad / EVOH / Ad / LLDPE = 50 μm / 10 μm / 10 μm / 10 μm / 50 μm) was formed.
Extruder:
EVOH: Single-screw extruder (Toyo Seiki Co., Ltd., laboratory machine ME type CO-EXT)
Diameter 20mmφ, L / D 20, Screw Full flight type LLDPE: Single screw extruder (Plastic Engineering Laboratory Co., Ltd. GT-32-A)
Diameter 32mmφ, L / D 28, screw Full flight type Ad: Single screw extruder (Technobel Co., Ltd. SZW20GT-20MG-STD)
Diameter 20mmφ, L / D 20, Screw Full flight type Extrusion conditions:
EVOH: supply unit / compression unit / metering unit / die = 175/210/220/220 ° C.
LLDPE: supply unit / compression unit / metering unit / die = 150/200/210/220 ° C.
Ad: Supply unit / compression unit / metering unit / die = 150/200/220/220 ° C.

After cutting out the multilayer film immediately after multilayer formation to 150 mm in the MD direction and 15 mm in the TD direction, the peel strength between the EVOH layer / Ad layer is measured in a T-type peel mode of a universal testing machine to determine the strength of the peel strength. By evaluating according to the following criteria A to E, an index of interlayer adhesion was obtained. Criteria A to C are sufficient for actual use.
A: 500 g / 15 mm or more B: 400 g / 15 mm or more and less than 500 g / 15 mm C: 300 g / 15 mm or more and less than 400 g / 15 mm D: 200 g / 15 mm or more and less than 300 g / 15 mm E: Less than 200 g / 15 mm

<Synthesis Example 1> Synthesis of hydrous EVOH pellets (w-EVOH-1) (copolymerization step)
A 250 L pressure reactor equipped with a jacket, a stirrer, a nitrogen inlet, an ethylene inlet and an initiator addition port was charged with 83.0 kg of vinyl acetate and 26.6 kg of methanol, heated to 60 ° C., and then nitrogen for 30 minutes. The system was purged with nitrogen by bubbling. Next, ethylene was charged so that the reaction vessel pressure was 3.6 MPa. As an initiator, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (AMV) is dissolved in methanol to prepare an initiator solution having a concentration of 2.5 g / L, and bubbling with nitrogen gas is performed. To replace the nitrogen. After adjusting the polymerization tank internal temperature to 60 ° C., 362 mL of the initiator solution was injected to initiate polymerization. During the polymerization, ethylene was introduced to maintain the reactor pressure at 3.6 MPa, the polymerization temperature at 60 ° C., and AMV was continuously added at 1120 mL / hr using the above initiator solution to carry out the polymerization. After 5 hours, when the polymerization rate reached 40%, the polymerization was stopped by cooling. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled to completely remove ethylene. Next, unreacted vinyl acetate monomer was removed under reduced pressure to obtain an ethylene-vinyl acetate copolymer (EVAc) -containing methanol solution.

(Saponification process)
Methanol was further added to the EVAc-containing methanol solution obtained above to obtain an EVAc diluted solution with an EVAc concentration of 15% by mass. 100 kg of the EVAc diluted solution obtained above was charged into a 400 L reaction vessel equipped with a jacket, a stirrer, a nitrogen inlet, a steam cooler, and a solution addition port. The temperature was raised to 60 ° C. while blowing nitrogen into this solution, 30.2 L of a 10% by mass methanol solution of NaOH was added over 2 hours, and the mixture was further stirred for 2 hours at 60 ° C., thereby proceeding with the saponification reaction of EVAc. I let you. Thereafter, 3.6 kg of acetic acid and 24 L of water were added to neutralize the saponification reaction to obtain an EVOH suspension. The EVOH suspension was drained with a centrifugal drainer, and the contents were transferred to a drum. Here, 160 kg of pure water was added and stirred, and this was again transferred to a centrifugal drainer to drain the liquid. Washing was carried out by repeating the operation of adding this deionized water and removing the liquid 5 times, and then drying at 60 ° C. for 24 hours to obtain a crude EVOH dried product.

(Granulation process)
4.2 kg of the EVOH crude dry product obtained above and 9.0 kg of water / methanol mixed solution (mass ratio: water / methanol = 40/60) were charged into a stirring tank equipped with a jacket, a stirrer and a reflux condenser, and 85 ° C. And dissolved with stirring. 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 described above. Then, from a mold having a circular opening having a diameter of 3.5 mm, a water / methanol solution of EVOH after defoaming in a water / methanol mixed solution (mass ratio: water / methanol = 90/10) at 5 ° C. Was extruded into a strand shape and cut into a pellet shape with a strand cutter to obtain a hydrous EVOH pellet having a diameter of about 4 mm and a length of about 5 mm.

  The operation of putting 30 kg of the hydrous EVOH pellets and 150 L of ion-exchanged water thus obtained into a drum can, stirring for 2 hours at 25 ° C., and then removing the liquid was repeated twice. Next, 150 L of 1 g / L acetic acid aqueous solution was added to 30 kg of hydrous EVOH pellets, and the mixture was stirred at 25 ° C. for 2 hours and then drained twice. Further, 150 L of ion-exchanged water was added to 30 kg of hydrous EVOH pellets, and the operation of stirring at 25 ° C. for 2 hours and then draining was repeated 6 times to remove impurities such as by-products in the saponification process. A hydrous EVOH pellet (w-EVOH-1) was obtained. The water content of the obtained hydrous EVOH pellets was 110% by mass. Further, the water-containing EVOH pellets were dried in a hot air dryer at 80 ° C. for 3 hours and subsequently at 120 ° C. for 24 hours to obtain dry EVOH pellets, and then analyzed for ethylene unit content and saponification degree according to the above. The ethylene unit content was 32 mol%, and the saponification degree was 99.98 mol% or more.

<Synthesis Example 2> Synthesis of Hydrous EVOH Pellet (w-EVOH-2) In Synthesis Example 1, the amounts of vinyl acetate and methanol charged during polymerization of EVAc were 85.2 kg and 32.3 kg, respectively, and the reactor pressure was 2 Synthesis Example 1 except that the injection amount at the start of the polymerization of the initiator solution (AMV 2.5 g / L concentration methanol solution) was changed to 310 mL and the continuous addition amount of the initiator solution was changed to 950 mL / hr. A methanol solution of EVAc was obtained by the same operation as above. The reaction time during the polymerization reaction was 5 hours, and the polymerization rate was 40%.
Next, saponification and washing were performed in the same manner as in Synthesis Example 1 except that the addition amount of the alkaline solution was changed to 31.1 L and the addition amount of acetic acid at the time of neutralization was changed to 3.7 kg to obtain a crude EVOH dried product. .
Furthermore, water-containing methanol-containing EVOH pellets (w-EVOH-2) were deposited and washed in the same manner as in Synthesis Example 1 except that the water / methanol mass ratio of the water / methanol mixed solution used for EVOH dissolution was changed to 50/50. Got. The water content of the obtained hydrous EVOH pellets was 110% by mass. Further, the water-containing EVOH pellets were dried in a hot air dryer at 80 ° C. for 3 hours and subsequently at 120 ° C. for 24 hours to obtain dry EVOH pellets, and then analyzed for ethylene unit content and saponification degree according to the above. The ethylene unit content was 27 mol% and the saponification degree was 99.98 mol% or more.

<Synthesis Example 3> Synthesis of hydrous EVOH pellets (w-EVOH-3) In Synthesis Example 1, the charge amounts of vinyl acetate and methanol during polymerization of EVAc were 76.7 kg and 11.0 kg, respectively, and the reactor pressure was 5 Synthesis Example 1 except that the injection amount at the start of polymerization of the initiator solution (2.5 g / L methanol solution of AMV) was changed to 510 mL and the continuous addition amount of the initiator solution was changed to 1570 mL / hr at 5 MPa. A methanol solution of EVAc was obtained by the same operation as above. The reaction time during the polymerization reaction was 5 hours, and the polymerization rate was 40%.
Subsequently, saponification and washing were performed in the same manner as in Synthesis Example 1 except that the addition amount of the alkaline solution was changed to 27.7 L and the addition amount of acetic acid at the time of neutralization was changed to 3.3 kg to obtain a crude EVOH dried product. .
Furthermore, water-containing methanol-containing EVOH pellets (w-EVOH-3) were deposited and washed in the same manner as in Synthesis Example 1 except that the water / methanol mass ratio of the water / methanol mixed solution used for EVOH dissolution was changed to 25/75. Got. The water content of the obtained hydrous EVOH pellets was 110% by mass. Further, the water-containing EVOH pellets were dried in a hot air dryer at 80 ° C. for 3 hours and subsequently at 120 ° C. for 24 hours to obtain dry EVOH pellets, and then analyzed for ethylene unit content and saponification degree according to the above. The ethylene unit content was 44 mol%, and the degree of saponification was 99.98 mol% or more.

<Synthesis Example 4> Synthesis of hydrous EVOH pellets (w-EVOH-4) In Synthesis Example 1, the charged amounts of vinyl acetate and methanol during polymerization of EVAc were 102.0 kg and 17.7 kg, respectively, and the reactor pressure was 2 Synthesis Example 1 except that the injection amount at the start of polymerization of the initiator solution (2.5 g / L concentration methanol solution of AMV) was changed to 280 mL and the continuous addition amount of the initiator solution was changed to 850 mL / hr. A methanol solution of EVAc was obtained by the same operation as above. The reaction time during the polymerization reaction was 5 hours, and the polymerization rate was 40%.
Next, saponification and washing were performed in the same manner as in Synthesis Example 1 except that the addition amount of the alkaline solution was changed to 31.6 L and the addition amount of acetic acid at the time of neutralization was changed to 3.8 kg to obtain a crude EVOH dried product. .
Further, the water-containing methanol mixture solution used for EVOH dissolution was precipitated and washed in the same manner as in Synthesis Example 1 except that the water / methanol mass ratio was changed to 55/45, and the hydrous EVOH pellets (w-EVOH-4) Got. The water content of the obtained hydrous EVOH pellets was 110% by mass. Further, the water-containing EVOH pellets were dried in a hot air dryer at 80 ° C. for 3 hours and subsequently at 120 ° C. for 24 hours to obtain dry EVOH pellets, and then analyzed for ethylene unit content and saponification degree according to the above. The ethylene unit content was 24 mol%, and the saponification degree was 99.98 mol% or more.

<Synthesis Example 5> Synthesis of hydrous EVOH pellets (w-EVOH-5) According to the method described in Example 2 of JP-A-51-49294 (Patent Document 4), hydrous EVOH pellets (w-EVOH-5) Got. This water-containing pellet (w-EVOH-5) corresponds to “resin” before acid treatment in Example 2 of Patent Document 4 above.

<Example 1>
As shown in Table 1, 10.0 kg of w-EVOH-1 was added to 90.0 L of an aqueous solution in which potassium nitrate was dissolved in water so that the potassium nitrate would be 1.95 g / L, and stirred occasionally at 25 ° C. for 6 hours. Soaking was performed. The pellet after the immersion was subjected to centrifugal dehydration, and then dried in a hot air dryer at 80 ° C. for 3 hours and then at 120 ° C. for 24 hours to obtain a dried EVOH pellet. The results of analysis and evaluation of the obtained pellets according to the above are shown in Table 2.

<Examples 2 to 16 and Comparative Examples 1 to 8>
Dry EVOH pellets were obtained by operating in the same manner as in Example 1 except that the components and concentrations blended in the aqueous solution were changed as shown in Table 1. Table 2 shows the results of analysis and evaluation of the obtained pellets according to the above.

<Examples 17 to 19>
Dry EVOH pellets were obtained by operating in the same manner as in Example 1 except that the types of hydrous EVOH pellets used and the components and concentrations blended in the aqueous solution were changed as shown in Table 1. Table 2 shows the results of analysis and evaluation of the obtained pellets according to the above.

<Example 20>
By drying w-EVOH-1 in a hot air dryer at 80 ° C. for 1 hour, water-containing EVOH pellets having a water content of 50% by mass were obtained. The obtained hydrous EVOH pellets are charged into a twin-screw extruder at 10 kg / hr, the resin temperature of the discharge port is set to 100 ° C., and the potassium nitrate is 22.5 g / L from the solution addition portion at the discharge port side tip. An aqueous solution in which potassium nitrate was dissolved in water was added at 0.6 L / hr. The strand-like water-containing EVOH discharged from the die was cut with a strand cutter to obtain water-containing EVOH pellets having a water content of 25% by mass. The obtained hydrous EVOH pellets were dried in a hot air dryer at 80 ° C. for 1 hour and then at 120 ° C. for 24 hours to obtain dry EVOH pellets. Table 2 shows the results of analysis and evaluation of the obtained dry EVOH pellets according to the above.

<Comparative Example 9>
Using w-EVOH-5, acid treatment (immersion in an aqueous solution) and drying were performed according to the method described in Example 2 of JP-A-51-49294 (Patent Document 4) to obtain dry EVOH pellets. That is, Comparative Example 9 is a reproduction of Example 2 of Patent Document 4. Table 2 shows the results of analysis and evaluation of the obtained dry EVOH pellets according to the above.

<Comparative Example 10>
Using w-EVOH-5, acid treatment (immersion in an aqueous solution) and drying were performed according to the method described in Comparative Example 9 of JP-A-51-49294 (Patent Document 4) to obtain dry EVOH pellets. That is, Comparative Example 10 is a reproduction of Control Example 9 of Patent Document 4 above. Table 2 shows the results of analysis and evaluation of the obtained dry EVOH pellets according to the above.

  As shown in Table 2, EVOH contains at least one of nitric acid and nitric acid ions and metal ions in a predetermined amount and ratio, and does not contain carboxylic acid and carboxylic acid ions, or carboxylic acid and carboxylic acid. When at least one of the ions was contained in a predetermined ratio, a resin composition having excellent appearance characteristics and long run properties could be obtained. Moreover, the multilayer structure excellent in interlayer adhesiveness was able to be obtained by using the said resin composition. Furthermore, the said characteristic was further improved by containing at least any one of carboxylic acid and carboxylate ion by a predetermined quantity and ratio.

  Further, as in Example 8 and Example 9, when alkaline earth metal ions were contained as metal ions, it was repeatedly produced as compared with the case where alkaline earth metal ions were not contained as in Example 3. Generation | occurrence | production of the gel and scum after a film | membrane could be further suppressed. In particular, Example 8 was superior to Example 9 in terms of a balance between long run properties and interlayer adhesion.

  Furthermore, as in Example 10, Example 11, and Example 16, at least one of polyvalent carboxylic acid and polyvalent carboxylic acid ion is determined as at least one of monovalent carboxylic acid and monovalent carboxylic acid ion. When used together in the amount and ratio, transparency and coloring could be suppressed as compared to the case where the combination was not used as in Example 3. In particular, Examples 10 and 16 were able to suppress the transparency and coloring after long-term use by using a trivalent carboxylic acid as compared with Example 11.

  In addition, as in Example 14, Example 15 and Example 16, when a predetermined amount of phosphoric acid compound or boron compound was contained, no phosphoric acid compound or boron compound was contained as in Example 3. Compared to the case, it was possible to further suppress the generation of gels and blisters after repeated film formation. In particular, Example 16 was able to suppress transparency and coloration after melt molding and after long-term use, as compared with Example 14 and Example 15.

Claims (13)

An ethylene-vinyl alcohol copolymer (A);
A component (B) comprising at least one of nitric acid and nitrate ions;
Containing metal ions (C) and
The content Bm of the component (B) is 0.5 μmol / g or more and 100 μmol / g or less,
The content amount Cm of the metal ion (C) is 2 μmol / g or more and 120 μmol / g or less, and the content amount Bm of the component (B), the content amount Cm of the metal ion (C) and the average thereof The valence Cv satisfies the following formula (1),
When the component (D) composed of at least one of carboxylic acid and carboxylate ion is contained, the Bm, the Cm, the Cv, the content Dm of the component (D) and the average valence Dv thereof, Is a resin composition satisfying the following formula (2).
(Cv × Cm) /Bm≧1.0 (1)
((Cv × Cm) −Bm) / (Dv × Dm) ≧ 0.2 (2)   The resin composition according to claim 1, wherein the Bm is 5 μmol / g or more and 25 μmol / g or less.   The resin composition according to claim 1 or 2, wherein the metal ion (C) consists only of an alkali metal ion (C1). The metal ion (C) includes an alkali metal ion (C1) and an alkaline earth metal ion (C2),
The resin composition according to claim 1 or 2, wherein the content C1m of the alkali metal ion (C1) and the content C2m of the alkaline earth metal ion (C2) satisfy the following formula (3).
C1m / (C1m + 2 × C2m) ≧ 0.5 (3) Containing the component (D),
The component (D) is a component (D1) comprising at least one of a monovalent carboxylic acid and a monovalent carboxylate ion, and a component (D2) comprising at least one of a polyvalent carboxylic acid and a polyvalent carboxylate ion. The resin composition according to any one of claims 1 to 4, comprising at least one of the following.   The resin composition according to claim 5, wherein the component (D) includes both the component (D1) and the component (D2), and the component (D2) has three or more carboxyl groups.   Furthermore, the phosphoric acid compound (E) is contained, The content Ew is 5 ppm or more and 500 ppm or less in conversion of phosphate radical, The resin composition of any one of Claims 1-6.   Furthermore, the boron compound (F) is contained, The content Fw is 5 ppm or more and 2,000 ppm or less in conversion of a boron element, The resin composition of any one of Claims 1-7.   The resin composition according to any one of claims 1 to 8, which is used for coextrusion molding. A copolymerization step of copolymerizing ethylene and vinyl ester to obtain an ethylene-vinyl ester copolymer, and a saponification step of saponifying said ethylene-vinyl ester copolymer to obtain an ethylene-vinyl alcohol copolymer (A) Including
After the copolymerization step,
Any of the Claims 1-9 including the mixing process which mixes the said ethylene-vinyl ester copolymer or ethylene vinyl alcohol copolymer (A), the said component (B), and the said metal ion (C). A method for producing the resin composition according to claim 1. A granulating step of obtaining a water-containing pellet of the ethylene-vinyl alcohol copolymer (A) by a granulating operation from the solution containing the ethylene-vinyl alcohol copolymer (A) obtained in the saponification step; and drying the water-containing pellet Including the drying process
The manufacturing method of the resin composition of Claim 10 which performs the said mixing process after the said granulation process.   The resin composition according to claim 11, wherein the water-containing pellet is immersed in a solution containing the component (B) and the metal ion (C) between the granulation step and the drying step as the mixing step. Production method. A multilayer structure having at least one layer obtained from the resin composition according to any one of claims 1 to 9.