TWI725055B - Resin composition, its manufacturing method and multilayer structure - Google Patents

Abstract

The present invention is a resin composition containing EVOH (A), a component (B) composed of at least one of nitric acid and nitrate ions, and a metal ion (C), and a substance containing the aforementioned component (B) The amount Bm is 0.5 μmol/g or more and 100 μmol/g or less, the content Cm of the aforementioned metal ion (C) is 2 μmol/g or more and 120 μmol/g or less, and the content Bm of the aforementioned component (B) is the same as the aforementioned metal ion (C) The content Cm and the average valence Cv satisfy the following formula (1), and when it contains a component (D) composed of at least one of a carboxylic acid and a carboxylic acid ion, the aforementioned Bm and the aforementioned The content of Cm, the aforementioned Cv, and the aforementioned component (D) Dm and its average valence Dv satisfy the following formula (2), (Cv×Cm)/Bm≧1.0‧‧‧(1)

((Cv×Cm)-Bm)/(Dv×Dm)≧0.2‧‧‧(2).

Description

Resin composition, its manufacturing method and multilayer structure

The present invention relates to a resin composition, its manufacturing method, and a multilayer structure having a layer obtained from the resin composition.

Ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) is widely used as various packaging materials for films, sheets, containers, etc. due to its excellent oxygen barrier properties. Since these packaging materials are usually formed by a melt forming method, EVOH seeks appearance characteristics (excellent transparency and low coloration such as yellowing, or no gel and particle generation), or long-term relationship (Longrun) ( Even in long-term molding, the physical properties such as viscosity will not change drastically, and there are no fish eyes or stripes, etc.). In addition, many packaging materials are used as multilayer structures. Here, in order to improve the layer adhesion of this multilayer structure, metal ions may be contained in the EVOH composition. However, when metal ions are contained in the EVOH composition, coloration is likely to occur, which reduces the appearance characteristics of the molded body. In addition, when reclaimed and molded into a sheet, and the cut and removed sheet edge (Trim) is reused, the EVOH is thermally deteriorated, gels and particles are generated, and the appearance characteristics of the molded body are deteriorated. Furthermore, after a long period of time under high temperature conditions In the case of time use, the appearance characteristics are reduced due to the coloration such as yellowing.

In order to improve the above-mentioned characteristics required for EVOH, Patent Document 1 and Patent Document 2 describe EVOH compositions containing acids such as carboxylic acids and metal ions. In addition, Patent Document 3 describes an EVOH composition containing a polyvalent carboxylic acid and metal ions. These EVOH compositions are excellent in appearance characteristics and long-term relationship. Patent Document 4 describes a method for producing an EVOH composition that is characterized by adding a specific acid such as nitric acid to an EVOH composition containing sodium acetate and having less thermal deterioration.

[Prior technical literature] 〔Patent Literature〕

[Patent Document 1] Japanese Patent Application Laid-Open No. 64-66262

[Patent Document 2] Japanese Patent Application Publication No. 2001-146539

[Patent Document 3] International Publication No. 2011/118648

[Patent Document 4] Japanese Patent Application Laid-Open No. 51-49294

However, some of the characteristics such as appearance characteristics, long-term relationship, layer indirectness, etc., partly represent a trade-off relationship with each other, and it is difficult to express all the characteristics at a higher level. For example, by adding metal ions, although the indirect focus of the layer is increased, the appearance characteristics and long-term relationship are reduced. Although the reduced properties can be improved by adding acid, the net property improvement becomes very limited due to the indirect effort of the reduced layer. On the other hand, on The market has requested to further improve these characteristics, even in the case of long-term use under higher temperature conditions than in the past, these characteristics are strongly sought, especially the appearance characteristics are expressed at a higher level. In addition, the technique of Patent Document 4 mentioned above is not sufficient in terms of appearance characteristics, long-term relationship, and layer adhesion.

The present invention was completed based on the above-mentioned matters, and it is to provide a resin composition that has excellent appearance characteristics, long-term relationship and layer adhesion, and is used as a packaging material to maintain a good appearance even after long-term use under high temperature conditions. Object, and its manufacturing method as the purpose. In addition, the present invention aims to provide a multilayer structure obtained from such a resin composition and excellent in layer adhesion.

That is, the present invention is as follows.

(1) A resin composition containing 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), the aforementioned components ( The content Bm of B) is 0.5 μmol/g or more and 100 μmol/g or less, the content Cm of the aforementioned metal ion (C) is 2 μmol/g or more and 120 μmol/g or less, and the content Bm of the aforementioned component (B) is the same as the aforementioned metal ion ( The content Cm of C) and its average valence Cv satisfy the relationship of (Cv×Cm)/Bm≧1.0, and when it contains a component (D) composed of at least one of carboxylic acid and carboxylic acid ion, the aforementioned Bm , The content Dm of the aforementioned Cm, the aforementioned Cv, and the aforementioned component (D) and its average valence Dv satisfy the criterion of ((Cv×Cm)-Bm)/(Dv×Dm)≧0.2 System; (2) The resin composition of (1) above, wherein the aforementioned Bm is 5 μmol/g or more and 25 μmol/g or less; (3) The resin composition of (1) or (2) above, wherein the aforementioned Bm The metal ion (C) is composed of only the alkali metal ion (C1); (4) The resin composition according to the above (1) or the above (2), wherein the metal ion (C) contains the alkali metal ion (C1) ) The content of alkaline earth metal ion (C2), the content of alkali metal ion (C1) C1m, and the content of alkaline earth metal ion (C2) C2m satisfy the relationship of C1m/(C1m+2×C2m)≧0.5; (5) The resin composition of any one of (1) to (4) above, which contains the aforementioned component (D), and the aforementioned component (D) contains at least one of a monovalent carboxylic acid and a monovalent carboxylic acid ion At least one of the component (D1) consisting of a polyvalent carboxylic acid and a polyvalent carboxylic acid ion (D2), the aforementioned Bm, the aforementioned Cm, the aforementioned Cv, and the aforementioned component The content Dm of (D) and its average valence Dv satisfy the relationship of 0.3≦((Cv×Cm)-Bm)/(Dv×Dm)≦1.0; (6) The resin composition of (5) above, wherein , The aforementioned component (D) includes both the aforementioned component (D1) and the aforementioned component (D2), and the aforementioned component (D2) has 3 or more carboxyl groups; (7) is any of the aforementioned (1) to (6) The resin composition of item 1, which further contains a phosphoric acid compound (E), the content Ew of which is 5 ppm or more and 500 ppm or less in terms of phosphate; (8) The resin composition of any one of (1) to (7) above, which further contains a boron compound (F), and its content Fw is 5 ppm or more and 2,000 ppm or less in terms of boron element; (9) The resin composition of any one of (1) to (8) above, which is used for coextrusion molding; (10) The manufacture of a resin composition of any one of (1) to (9) above The method includes a copolymerization step of copolymerizing ethylene and vinyl ester to obtain an ethylene-vinyl ester copolymer, and a saponification step of saponifying the aforementioned ethylene-vinyl ester copolymer to obtain an ethylene-vinyl alcohol copolymer (A), by After the aforementioned copolymerization step, the aforementioned ethylene-vinyl ester copolymer or ethylene-vinyl alcohol copolymer (A), the aforementioned component (B), and the aforementioned metal ion (C) are mixed together; (11) as in the aforementioned (10) A method for producing a resin composition of ), which comprises granulating a solution containing the ethylene-vinyl alcohol copolymer (A) obtained in the aforementioned saponification step to obtain a water-containing solution of the ethylene-vinyl alcohol copolymer (A) The granulation step of the particles, and the drying step of drying the aforementioned water-containing granules, the aforementioned mixing step is performed after the aforementioned granulation step; (12) The method for producing a resin composition as described in the aforementioned (11), wherein, as the aforementioned mixing step, Between the aforementioned granulation step and the aforementioned drying step, the aforementioned water-containing particles are immersed in a solution containing the aforementioned component (B) and metal ions (C); (13) A multilayer structure having at least one layer as described in (1) ) ~ A layer obtained from the resin composition of any one of (9) above.

The resin composition of the present invention is excellent in appearance characteristics or long-term relationship, and at the same time as a packaging material, it can maintain good appearance characteristics even after long-term use under high temperature conditions. In addition, by manufacturing the resin composition by the manufacturing method of the present invention, the above-mentioned effects can be easily obtained. Furthermore, by using the resin composition of the present invention, a multilayer structure having excellent layer adhesion can be obtained.

<EVOH(A)>

The resin composition of the present invention has EVOH (A) as the main component. Still, the so-called main component refers to the component with the largest content on a quality basis in a dry state. The lower limit of the content of EVOH (A) in the resin composition is, for example, preferably 90% by mass, and more preferably 99% by mass. Note that the content of each component in the resin composition refers to the resin composition in a dry state (hereinafter also referred to as "dry resin composition"), and is synonymous with the content in terms of solid content (hereinafter the same).

Although EVOH (A) is a copolymer having ethylene units and vinyl alcohol units, it 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%, may be 1 mol%, or may be 0.1 mol% relative to the total structural units constituting EVOH (A). EVOH(A) is usually obtained by polymerizing ethylene and vinyl ester and then saponifying the ethylene-vinyl ester copolymer To.

The lower limit of the ethylene unit content of EVOH (A) is preferably 20 mol%, more preferably 22 mol%, and still more preferably 25 mol%. On the other hand, as the upper limit of the ethylene unit content of EVOH (A), it is preferably 60 mol%, more preferably 55 mol%, and still more preferably 50 mol%. By setting the ethylene unit content of EVOH (A) in the above range, yellowing after melt molding is suppressed, and a resin composition with excellent long-term relationship is obtained. The ethylene unit content of EVOH(A) is smaller than the above lower limit, which may reduce the long-term relationship of the resin composition, or the water resistance, hot water resistance and gas barrier properties of the multilayer structure under high humidity. On the contrary, when the ethylene unit content of EVOH (A) exceeds the above upper limit, the gas barrier properties of the multilayer structure may be reduced.

The lower limit of the degree of saponification of EVOH (A) is preferably 80 mol%, more preferably 95 mol%, and still more preferably 99 mol%. The saponification degree of EVOH (A) is smaller than the above lower limit, which may reduce the gas barrier properties or appearance characteristics of the obtained multilayer structure.

The lower limit of the melt flow rate of EVOH (A) (measured at a temperature of 210°C and a load of 2160 g in accordance with JIS K7210, hereinafter referred to as MFR) is preferably 0.1 g/10 min, more preferably 0.5 g/10 Minutes, still more preferably 1g/10 minutes, particularly preferably 3g/10 minutes. On the other hand, as the upper limit of the MFR of EVOH (A), it is preferably 200 g/10 minutes, more preferably 50 g/10 minutes, still more preferably 30 g/10 minutes, particularly preferably 15 g/10 minutes, and most preferably 10g/10 minutes. By setting the MFR of EVOH(A) to the value in the above range, it becomes the appearance characteristics and Those who have excellent long-term relationships.

<Component (B) consisting 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 containing the component (B), the resin composition of the present invention is not affected by other components constituting the resin composition, and can suppress coloration such as yellowing after melt molding and long-term use.

The component (B) essentially needs to be nitrate ions, which is achieved by adjusting the relative ratio with the metal ions (C) described later. This stabilizes the viscosity characteristics of the resin composition during melt molding, and can suppress coloration such as yellowing or the occurrence of gels and particles. In other words, with the trade-off relationship in the past, it is possible to become an excellent one with high-level and difficult characteristics. Although the reason for this effect has not yet been determined, it is speculated that the component (B) competes with the metal ion (C) that promotes the decomposition or coloring of EVOH (A) and inhibits its catalytic action.

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 at least the above lower limit, it becomes a coloring agent that suppresses yellowing after melt forming and after long-term use. On the other hand, when Bm is below the above upper limit, transparency can be maintained at a high level, the generation of gels and particles can be suppressed, and the economical efficiency is also excellent. In addition, the viscosity characteristics of the stable resin composition during melt molding are Those who have excellent long-term relationships.

Component (B) can be mixed in the state of nitric acid. Although it can be used as a counter cation to form metal ions and the like and a salt nitrate, it is preferably used as a counter cation to form metal ions and the like in the resin composition. The presence of nitrate with salt. Examples of the nitrate include lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, and the like. In addition, by mixing in the state of nitrous acid or nitrite, and oxidizing after mixing, nitric acid or nitrate ions can also be formed. In addition, when the counter cation forming a metal ion or the like is mixed with the nitrate of the salt, the metal ion is expressed as the metal ion (C) described later.

<Metal ion (C)>

The resin composition of the present invention contains metal ions (C). By containing the metal ion (C) in the resin composition of the present invention, the layer adhesion of the obtained multilayer structure becomes excellent. Although the reason for the indirect adhesion of the metal ion (C)-enhancing layer is not yet clear, it is believed that the affinity between the hydroxyl groups of EVOH (A) between the layers is increased by the presence of metal ions. In addition, when one of the adjacent layers has a functional group capable of reacting with the hydroxyl group of EVOH (A) in the molecule, it is considered that this bonding formation reaction is accelerated by the presence of the metal ion (C).

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 120μmol/g, which is more It is preferably 60 μmol/g, more preferably 30 μmol/g. When Cm is not less than the above lower limit, the layer indirect adhesion of the multilayer structure becomes excellent. On the other hand, when Cm is less than or equal to the above upper limit, discoloration such as yellowing after melt forming and after long-term use can be suppressed, and economical efficiency is also excellent.

In the resin composition of the present invention, the average valence Cv of Bm, Cm, and metal ion (C) must satisfy the following formula (1). Here, Cv refers to the value obtained by multiplying the valence of the element constituting the metal ion (C) by its existence ratio. Furthermore, 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, component (B) can substantially exist as nitrate ions, which can suppress coloration such as yellowing or the occurrence of gels and particles, and is excellent in long-term relationship. At the same time, it has excellent layer adhesion when used as a multilayer structure. Although the upper limit of (Cv×Cm)/Bm is not particularly limited, it is, for example, 20, preferably 10, more preferably 5, and still more preferably 2.5.

(Cv×Cm)/Bm≧1.0‧‧‧(1)

Examples of metal ions (C) include alkali metal ions (C1), alkaline earth metal ions (C2), other transition metal ions, and the like, and these may be one type or a plurality of types of metal species. Among them, the alkali metal ion (C1) is preferably contained, and the metal ion (C) may be composed of only the alkali metal ion (C1). Since the metal ion (C) is composed only of the alkali metal ion (C1), not only the manufacturing method can be simplified, but also the layer adhesion of the multilayer structure can be further improved.

As the alkali metal ion (C1), for example, lithium, The ions of sodium, potassium, rubidium, and cesium are preferably sodium and potassium ions from the viewpoint of industrial acquisition.

Examples of the alkali metal salts that give alkali metal ions (C1) include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, and phosphates of lithium, sodium, and potassium. , And metal complexes. Among these, from the viewpoint of easy acquisition, more preferred are sodium acetate, potassium acetate, sodium phosphate, and potassium phosphate. In the case of using nitrate, the nitrate ion system appears as the component (B). Similarly, the phosphate system is expressed as the 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 still more preferably 4.0 μmol/g. On the other hand, as the upper limit of C1m, it is preferably 120 μmol/g, more preferably 60 μmol/g, and still more preferably 30 μmol/g. When C1m is not less than the above lower limit, the layer adhesion when used as a multilayer structure is improved. On the other hand, when C1m is equal to or lower than the above upper limit, it is possible to suppress coloration such as yellowing or the occurrence of gels and particles.

It is also preferable that the metal ion (C) contains alkaline earth metal ion (C2). Since the metal ion (C) contains the alkaline earth metal ion (C2), the thermal degradation of EVOH (A) during reutilization and trimming is suppressed, and the formation of gels and particles in the molded body is suppressed.

Examples of alkaline earth metal ions (C2) include ions of beryllium, magnesium, calcium, strontium, and barium, but from the viewpoint of industrial acquisition, ions of magnesium and calcium are preferred.

As an alkaline earth gold that gives alkaline earth metal ions (C2) Examples of the genus salt include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes of magnesium or calcium. When a nitrate is used, in the resin composition, the nitrate ion system appears as the component (B). Similarly, the phosphate system appears as a phosphoric acid compound (E).

The lower limit of the content C2m of the alkaline earth metal ion (C2) in the dry resin composition is not particularly limited. For example, it may be 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, still more preferably 15 μmol/g, and may also be 5 μmol/g. When C2m is equal to or less than the above upper limit, excessive decomposition does not occur during melt molding of the resin composition, and the resin composition has an excellent long-term relationship. Furthermore, C2m preferably satisfies the following formula (3) at the same time as the above-mentioned C1m. By doing so, the long-term relationship and the layer indirectness when used as a multilayer structure become excellent at the same time. Furthermore, 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 carboxylic acid ion>

The resin composition of the present invention may not contain the component (D) composed of at least one of a carboxylic acid and a carboxylic acid ion (hereinafter abbreviated as the component (D)), or may also contain it.

When the resin composition of the present invention contains the component (D), the content Dm of the component (D) in the dry resin composition meets the following requirements together with Bm, Cm, Cv, Dm and the average valence Dv of the component (D) The formula (2). By this, it is possible to suppress coloration such as yellowing after melt forming and long-term use, and at the same time improve long-term relationship and interlayer adhesion. This presumption is because, 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 not good, that is, the relative component (D) More metal ions (C) that are effective are reduced, so that each characteristic cannot be fully exerted. Here, Dm is the total amount of component (D1) and component (D2) described later. Of the total number (number of molecules) divided by the total number of the component (D) of ^- Dv lines constituting the component (D) of a carboxyl group and a carboxylic acid ester group (-COO). That is, Dv is an average value of the number of carboxyl groups and carboxylate groups in 1 molecule of component (D).

((Cv×Cm)-Bm)/(Dv×Dm)≧0.2‧‧‧(2)

Still, the lower limit of ((Cv×Cm)-Bm)/(Dv×Dm) is preferably 0.3. In addition, the upper limit of ((Cv×Cm)-Bm)/(Dv×Dm) may be 1.5, preferably 1.0.

Component (D) is composed of at least one of monovalent carboxylic acid and monovalent carboxylic acid ion (D1) (hereinafter referred to as component (D1)), and at least one of polyvalent carboxylic acid and polyvalent carboxylic acid ion (D2) (hereinafter referred to 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 coloration such as yellowing.

In the component (D1), the so-called monovalent carboxylic acid refers to a compound having one carboxyl group in the molecule. Also, monovalent carboxylic acid ion is one of monovalent carboxylic acid The hydrogen ion of the carboxyl group is a detached one.

The content D1m of the component (D1) in the dry resin composition is preferably less than 2 μmol/g, more preferably less than 1.5 μmol/g, and still more from the viewpoint of reducing odors relative to the entire resin composition It is preferably less than 1.2 μmol/g, and particularly preferably less than 1.0 μmol/g. When D1m is in the above range, in addition to reducing the odor of the resin composition itself, the odor generated when the resin composition is melted is reduced, and the working environment is also improved. In addition, since the odor of the molded body after melt molding is reduced, the multilayer structure of the resin composition is preferably used as a package even for contents such as rice or drinking water that have a particularly odor that may damage the value of the product. 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 still more preferably 3 μmol/g or more with respect to the entire resin composition. When the content of the monovalent carboxylic acid and the monovalent carboxylic acid ion is in the above-mentioned range, the control of the content of the metal ion (C) during the production of the resin composition becomes easier, and at the same time, it becomes the one having excellent long-term relationship. Furthermore, as the upper limit of D1m, it is, for example, 50 μmol/g, and preferably 20 μmol/g.

Examples of monovalent carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, acrylic acid, methacrylic acid, benzoic acid, and 2-naphthoic acid (Naphthoic acid). These monovalent carboxylic acids may have a hydroxyl group or a halogen atom. Moreover, as a monovalent carboxylic acid ion, the hydrogen ion of the carboxyl group of each said monovalent carboxylic acid is desorbed. As the monovalent carboxylic acid, acetic acid is preferred among these.

In component (D2), the so-called polyvalent carboxylic acid system has Compounds with more than 2 carboxyl groups. Here, the polyvalent carboxylic acid does not include a polymer. In addition, at least one of the hydrogen ions of the carboxyl group of the polyvalent carboxylic acid ion is a polyvalent carboxylic acid ion. When the resin composition contains the above-mentioned component (D2), the pH in the resin composition can be adjusted, and in addition to inhibiting the generation of gels and particles, it is also possible to inhibit coloration such as yellowing derived from metal ions.

Although the reason why the component (D2) can inhibit yellowing and other coloring is not yet clear, it is speculated that it is due to the stable coordination of the component (D2) relative to the metal ion (C) that causes yellowing and the like, and it can be incorporated into the metal ion (C). ). In this way, relative to the metal ion (C), by stably existing in the state of coordinated polyvalent carboxylic acid, etc., the catalytic function of the reaction such as yellowing of the EVOH (A) of the metal ion (C) can be suppressed. As a result It is considered that even during high-temperature melt molding, the occurrence of coloration such as yellowing is suppressed. Furthermore, since the pentametal ion (C) and the polyvalent carboxylic acid are relatively weakly interacting bonds, the resin composition of the present invention can exhibit excellent interlayer adhesion even when forming a multilayer structure. Still, from the viewpoint of productivity or economy, the component (D2) is preferably used in combination with the above-mentioned component (D1).

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 particularly preferably 0.5 μmol/g. 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 at least the above lower limit, coloration such as yellowing can be suppressed. On the other hand, with D2m as the upper The above-mentioned upper limit or less becomes an excellent long-term relationship.

As the multivalent carboxylic acid of component (D2), if it has two or more carboxyl groups in the molecule, for example, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, malic acid, and glutaric acid are listed. Aliphatic dicarboxylic acids such as, adipic acid and pimelic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; tricarboxylic acids such as citric acid, isocitric acid and aconitic acid Acid; 1,2,3,4-butane tetracarboxylic acid, ethylene diamine tetraacetic acid and other carboxylic acids with more than 4 carboxyl groups; citric acid, isocitric acid, tartaric acid, malic acid, mucic acid Hydroxy carboxylic acids such as oxalic acid, mesoxalic acid, 2-ketoglutaric acid, 3-ketoglutaric acid, etc.; glutamic acid, aspartic acid, etc. Amino acids such as 2-amino adipic acid.

As the polyvalent carboxylic acid, among these, citric acid and tartaric acid are preferred. Moreover, as the polyvalent carboxylic acid ion of the component (D2), these anions can be cited.

The component (D2) is also preferably a polyvalent carboxylic acid having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, and a ketone group, or an anion thereof. In the case of having such functional groups, the stability of the state coordinated to the metal ion (C) is improved, and the coloration at the time of high-temperature melt molding can be suppressed more effectively. Among them, for the metal ion (C) As a result of moderate adjustment of the coordination strength, discoloration such as yellowing can be suppressed, and it is more preferable to have a hydroxyl group because it has excellent layer indirect adhesion when used as a multilayer structure.

As the multivalent carboxylic acid of component (D2), it is also preferable to have 3 or more carboxyl groups. By using such a polyvalent carboxylic acid, since the component (D2) can be electrically and sterically stable and efficiently coordinated to the metal ion (C), the yellowing of the resin composition of the present invention can be suppressed more effectively Wait for the coloring.

<Phosphoric Acid Compound (E)>

The resin composition of the present invention may contain a phosphoric acid compound (E). As a result, the thermal stability of the resin composition during melt molding can be improved, and as a result, the generation of gels and particles can be suppressed when the resin composition is used as a molded body.

Examples of the phosphoric acid compound (E) include various phosphorus oxyacids such as phosphoric acid and phosphorous acid or their salts. As the phosphate, for example, it can be contained in any form of the first phosphate, the second phosphate, and the third phosphate. Although the relative cation is not particularly limited, it is preferably an alkali metal salt or alkaline earth metal salt, more preferably It is an alkali metal salt. Specifically, by using sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, or dipotassium hydrogen phosphate by repeating the melt molding and trimming recovery of the resin composition, the effect of improving thermal stability during melt molding The higher point is better. Here, in the case of mixing the phosphate compound (E) which forms a relatively cation metal ion and a salt, the metal ion is expressed as the above-mentioned metal ion (C).

As the phosphoric acid compound (E) in the dry resin composition The lower limit of the content Ew in terms of phosphate radical is preferably 5 ppm, more preferably 8 ppm. On the other hand, the upper limit of Ew is preferably 500 ppm, more preferably 200 ppm, and still more preferably 50 ppm. When Ew is in the above range, the formation of gels and particles in the molded body can be suppressed.

<Boron Compound (F)>

The resin composition of the present invention may contain a boron compound (F). As a result, the thermal stability of the resin composition during melt molding can be improved, and as a result, the generation of gels and particles can be suppressed when the resin composition is used as a molded body. In detail, it is believed that when the resin composition is blended with a boron compound (F), a chelate compound is formed between EVOH (A) and the boron compound (F) to improve the thermal stability and mechanical properties of the resin composition. nature.

Examples of the boron compound (F) include boric acid, boric acid ester, borate, and boron hydride. 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 boric acid salts include The above-mentioned various boric acid alkali metal salts, alkaline earth metal salts, borax, etc. Among these, orthoboric acid is preferred. Here, in the case of mixing the boron compound (F) which forms the metal ion and the salt of the opposite cation, the metal ion is expressed as the above-mentioned metal ion (C).

The lower limit of the content Fw in terms of boron element of the boron compound (F) in the dry resin composition is preferably 5 ppm, more preferably 10 ppm. On the other hand, as the upper limit of Fw, it is preferably 2,000 ppm, more preferably 1,000 ppm, and still more preferably 500 ppm. With Fw as the above The range can suppress the formation of gels and particles when used as a molded body.

<Other additives, etc.>

The resin composition of the present invention may contain appropriate amounts of plasticizers, stabilizers, surfactants, colorants, ultraviolet absorbers, oxygen absorbers, slip agents, and antistatic agents within a range that does not impair the effects of the present invention. , Desiccant, cross-linking agent, filler, reinforcing agent for various fibers. However, the upper limit of the content of components other than the above-mentioned (A) to (F) components in the resin composition may be 10% by mass, 1% by mass, or 0.1% by mass.

In addition, other thermoplastic resins other than EVOH (A) may be blended in an appropriate amount within a range that does not impair the effects of the present invention. As the above-mentioned other thermoplastic resins, for example, various polyolefins (polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene and carbon number 4 or more) α-olefin copolymer, copolymer of olefin and maleic anhydride, ethylene-vinyl ester copolymer, ethylene-acrylate copolymer, or modified by grafting these with unsaturated carboxylic acid or its derivatives Polyolefin, etc.), 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 thermoplastic resins other than EVOH (A), the content of the other thermoplastic resins in the dry resin composition is preferably less than 50% by mass, more preferably less than 30% by mass, and further More preferably, it is less than 10% by mass, and may be less than 1% by mass.

<Resin composition>

The preferable range of the MFR of the resin composition of the present invention is the same as the above-mentioned MFR of EVOH (A), and the effect obtained by being in this range is also the same as in the case of EVOH (A).

The resin composition of the present invention can be melt-molded into various molded bodies such as films, sheets, containers, tubes, fibers, and the like. These shaped bodies can also be pulverized and reshaped for the purpose of reuse. In addition, films, sheets, fibers, etc. may be uniaxially or biaxially stretched. Examples of melt molding methods include extrusion molding, inflation extrusion, blow molding, melt spinning, and injection molding. Among them, the resin composition of the present invention can be used with other resins to easily form a multilayer structure. Can be suitably used in co-extrusion molding.

The melting temperature during melt molding is preferably about 150 to 300°C, and usually a melting temperature of about 200 to 250°C is used. The molding system obtained in this way has excellent transparency after melt molding and long-term use, and inhibits coloration such as yellowing, and at the same time inhibits the generation of gels and particles, and is also an excellent long-term relationship.

<Manufacturing method of resin composition>

The resin composition of the present invention can be obtained by, for example, a copolymerization step (step 1) comprising copolymerizing ethylene and vinyl ester to obtain an ethylene-vinyl ester copolymer, and saponifying the aforementioned ethylene-vinyl ester copolymer to obtain EVOH (A) The saponification step (step 2) is further included after the aforementioned copolymerization step The production method including the step of mixing the above-mentioned ethylene-vinyl ester copolymer or EVOH (A), the component (B), and the metal ion (C) (step α) is effectively obtained. Here, by performing the mixing step after the copolymerization step, the coloration such as yellowing of the resin composition caused during melt molding can be suppressed. Hereinafter, each step will be described in detail.

(Step 1: Copolymerization step)

In addition to the copolymerization step of ethylene and vinyl ester, the copolymerization step also includes a step of adding a polymerization inhibitor if necessary, followed by removing unreacted ethylene and unreacted vinyl ester to obtain an ethylene-vinyl ester copolymer solution. When the component (B) and the metal ion (C) are added before the copolymerization step, not only the coloration of the resin composition cannot be suppressed, but coloration may occur instead. As a copolymerization method of ethylene and vinyl ester, well-known methods, such as solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, etc. are mentioned, for example.

As a representative vinyl ester used for polymerization, although vinyl acetate can be cited, other aliphatic vinyl esters such as vinyl propionate or vinyl pivalate can also be used. Other small amounts of copolymerizable monomers can also be copolymerized.

The polymerization temperature is preferably 20 to 90°C, more preferably 40 to 70°C. 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% relative to the vinyl ester placed. The resin content in the solution after polymerization is preferably 5 to 85% by mass, more preferably 20 to 70% by mass.

(Step 2: Saponification step)

Secondly, an alkali catalyst is added to the ethylene-vinyl ester copolymer solution to saponify the copolymer in the solution. The saponification method is both continuous and reciprocating. As this alkali catalyst, sodium hydroxide, potassium hydroxide, and alkali metal alcoholate are mentioned, for example.

(Step α(1): mixing step)

In the mixing step, the ethylene-vinyl ester copolymer obtained in the copolymerization step or the EVOH (A) obtained in the saponification step, the component (B), and the metal ion (C) are mixed. In this mixing, for example, (1) a method of pre-adding component (B) and metal ion (C) to a solution containing an ethylene-vinyl ester copolymer for the saponification step, (2) in the saponification step, in the ethylene-vinyl ester copolymer The method of adding component (B) and metal ion (C) in the saponification reaction of vinyl ester copolymer, and (3) the method of mixing component (B) and metal ion (C) after obtaining EVOH (A) in the saponification step.

Furthermore, by performing the mixing step in the saponification step, the thermal degradation of EVOH (A) in the manufacturing steps after the saponification step is suppressed, and the resulting resin composition is suppressed from yellowing and other coloring.

Furthermore, after the saponification step, although the remaining alkali catalyst is often neutralized, as the acid used for the neutralization, component (B) or component (D) can be used.

(Step 3: Granulation step)

In order to obtain the resin composition of the present invention in the shape of particles, 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 even by this method, the coloration of the resin composition during melt molding can be suppressed. EVOH(A) is obtained in the form of a solution containing the solvent used in the saponification reaction, and is washed in order to remove residual catalysts such as alkali or by-products such as sodium acetate 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 as the water-containing particles of EVOH (A).

As a granulation operation, for example, (I) extruding the solution containing EVOH (A) in a coagulation bath, cooling and solidifying it or cutting immediately, (II) making EVOH (A) solution and steam Contact, as a method of cutting the aqueous resin composition of EVOH (A) in advance. The moisture content in the water-containing pellets of EVOH (A) obtained by this method is preferably 40 to 200% by mass based on the dry weight of EVOH (A), more preferably 45 to 180% by mass, and more Preferably, it is 50 to 150% by mass.

(Step 4: Drying step)

The water-containing particles of EVOH obtained in the granulation step are preferably dried to become dry particles of EVOH (A). The moisture content in the dry pellets is for the purpose of preventing molding problems such as voids during molding. Therefore, relative to the entire dry pellets, it is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and still more preferably 0.5% by mass or less.

As a drying method of water-containing particles, for example, standing still Dry or flow dry. These drying methods can be used alone or in combination. The drying process can be performed by either continuous method or batch method. When multiple drying methods are combined, the continuous method and batch method can be freely selected for each drying method. Even if the drying is performed in a low oxygen concentration or an oxygen-free state, the deterioration of the resin composition due to the oxygen in the drying can be reduced.

(Step α(2): mixing step)

As a method of performing the mixing step after the granulation step, for example, (1) a method of contacting the aqueous particles of EVOH (A) with a solution containing the component (B) and metal ions (C), and (2) the EVOH ( A) The method of melting and kneading the water-containing particles, components (B) and metal ions (C) in the extruder

. At this time, component (D), component (E), component (F), etc. can be mixed with EVOH (A) at the same time. Among these, the method of (1) is preferred. Specifically, the method of immersing water-containing particles in a solution containing component (B) and metal ion (C) between the granulation step and the drying step is preferred. . According to this method, the component (B) and the metal ion (C) can be efficiently mixed in the resin composition, and the resin composition of the present invention has excellent properties.

In the case of such impregnation, the shape of the water-containing particles is arbitrary, and the operation can be either a batch method or a continuous method. Although the immersion can separate the components contained in the resin composition in a dissolved plural solution separately, it can be treated once with a liquid that dissolves the plural components, but It is preferable to process a solution containing all components other than EVOH (A) from the viewpoint of simplification of the steps. To obtain a solution containing components other than EVOH (A), the components may form salts with each other. Although the solvent of the solution is not particularly limited, it is preferably water for operational reasons.

In the manufacturing method of 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 (1) of granulation, the component (B) or metal ion (C) can be contained in the coagulation bath in advance. Thereby, the components (B) and metal ions (C) can be uniformly contained in the water-containing particles of EVOH (A).

<Multilayer structure>

The multilayer structure system of the present invention includes a multilayer structure having at least one layer derived from the above-mentioned resin composition. Since the multilayer structure of the present invention has a layer obtained from a resin composition with excellent appearance characteristics or long-term relationship, it already has excellent appearance characteristics, and it can maintain good appearance characteristics even when used for a long time at high temperature. .

In addition, the so-called multi-layer structure system refers to a structure having two or more layers. The lower limit of the number of layers of the multilayer structure may be three or five. 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, a layer obtained from the resin composition of the present invention is represented by E, a layer obtained from an adhesive resin is represented by Ad, and a layer obtained from a thermoplastic resin is represented by T. The situation becomes the structure of T/E/T, E/Ad/T, T/Ad/E/Ad/T. Each of these layers may be a single layer or multiple layers. In addition, other layers other than the above may be included.

As said adhesive resin, the adhesive resin containing a carboxylic acid modified polyolefin is mentioned, for example. As a carboxylic acid-modified polyolefin, it can be suitable for olefin polymers using ethylenically unsaturated carboxylic acids, containing carboxyl groups obtained by chemically (for example, addition reaction, grafting reaction, etc.) bonded to its ester or its anhydride. Modified olefin-based polymer. Examples of ethylenically unsaturated carboxylic acids, their esters or their anhydrides include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleate, monoethyl maleate, Diethyl maleate, monomethyl fumarate, etc., more preferably maleic anhydride. These adhesive resins can be used alone, or two or more of them can be mixed for use.

As the thermoplastic resin, for example, 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, polybutene, polypentene and other olefins alone or their copolymers; polyesters such as polyethylene terephthalate; polyester elastomers; polyamides such as nylon 6, nylon 66, etc.; Polystyrene; polyvinyl chloride; polyvinylidene chloride; acrylic resin; vinyl ester resin; polyurethane elastomer; polycarbonate; chlorinated polyethylene; chlorinated polypropylene. Among these, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene, and polyester are preferably used.

<Manufacturing method of multilayer structure>

As a method of manufacturing the multilayer structure of the present invention, for example, (1) A method of melt-extruding a thermoplastic resin on a molded body obtained from the resin composition of the present invention, (2) A method of co-extruding the resin composition of the present invention and other thermoplastic resins, (3) Co-injecting the present invention The method of the resin composition and the thermoplastic resin, and (4) the method of laminating the molded body obtained from the resin composition of the present invention and other substrates using an adhesive.

Among these methods, the method (2) can be preferably used. This is because the resin composition of the present invention has excellent long-term relationship even if it is melted under high temperature conditions, and also suppresses subsequent coloration. Even if it is co-extruded with other thermoplastic resins with a high melting point, the coloration and appearance can be suppressed Multi-layer structure with excellent characteristics. As a method of co-extrusion, for example, a multi-branch merging method T die method, a feed block merging method T die method, and an expansion method can be cited.

By secondary processing the multilayer structure obtained by the above-mentioned co-extrusion, for example, the following molded body is obtained.

(1) A multilayer stretched sheet or film obtained by stretching a multilayer structure (sheet or film, etc.) in a uniaxial or biaxial direction and heat-treating it; (2) By making a multilayer structure (sheet or film, etc.) ) Multi-layer laminated sheets or films obtained by calendering, (3) Multi-layer discs and cups obtained by thermoforming of multilayer structures (sheets or films, etc.) by vacuum forming, pressure forming, vacuum pressure forming, etc. container, (4) Bottles, cup-shaped containers, etc. obtained by stretch blow molding from multilayer structures (tubes, etc.).

Still, secondary processing methods other than the above can be used. The molded body obtained by such secondary processing methods can be preferably used as food containers such as deep-drawn containers, cup-shaped containers, bottles, etc., for example.

[Example]

Hereinafter, the present invention will be described in further detail with examples. In the following Examples and Comparative Examples, analysis and evaluation were performed in the methods shown below.

(1) Determination of the moisture content of water-containing EVOH pellets

Using a halogen moisture content analyzer, the moisture content of the water-containing EVOH pellets was measured by the heat-drying gravimetric method under the conditions of a drying temperature of 180°C, a drying time of 20 minutes, and a sample size of 10 g. The moisture content of hydrated EVOH shown below is determined as the mass% based on dry EVOH.

(2) Ethylene unit content and saponification degree of EVOH(A)

The dry EVOH particles are used as the internal standard material, dissolved in tetramethylsilane, and dimethylsulfoxide (DMSO)-d ₆ containing trifluoroacetic acid (TFA) as an additive. This uses 500MHz ¹ H-NMR at 80°C The measurement is carried out, and the ethylene unit content and the saponification degree are obtained from the peak intensity ratio of the ethylene unit, the vinyl alcohol unit, and the vinyl ester unit.

(3) Quantification of component (B) and component (D)

Put 10 g of EVOH powder obtained by freeze-grinding and drying EVOH particles and 50 mL of ion-exchange water into a 100 mL Erlenmeyer flask with a stopper, attach a cooling condenser, and stir at 95°C for 10 hours to obtain an extract. 2 mL of the obtained extract was diluted with 8 mL of ion-exchanged water for quantitative analysis using ion chromatography, and the amounts of nitrate ions and carboxylic ions were quantified to calculate the individual amounts of component (B) and component (D).

(4) Quantification of metal ions (C)

Put 0.5 g of dry EVOH pellets into a pressure vessel made of Teflon (registered trademark), and add 5 mL of concentrated nitric acid here to decompose at room temperature for 30 minutes. After decomposing, cover the lid, heat it at 150°C for 10 minutes by a wet decomposition device, and then heat it at 180°C for 5 minutes to further decompose, and then cool to room temperature. Transfer this treatment solution to a 50 mL measuring flask to make up the volume with pure water. For this solution, the amount of each metal ion was quantified by an ICP emission spectrometer.

(5) Quantification of phosphoric acid compound (E)

Put 0.5 g of dry EVOH pellets into a pressure vessel made of Teflon (registered trademark), and add 5 mL of concentrated nitric acid here to decompose at room temperature for 30 minutes. After decomposing, cover the lid, heat it at 150°C for 10 minutes by a wet decomposition device, and then heat it at 180°C for 5 minutes to further decompose, and then cool to room temperature. Transfer this treatment solution to a 50 mL measuring flask to make up the volume with pure water. For this solution, the phosphorous element is quantified by ICP emission spectrophotometer Calculate the amount of phosphoric acid compound (E) in terms of phosphate radical.

(6) Quantification of boron compound (F)

Put 0.5 g of dry EVOH pellets into a pressure vessel made of Teflon (registered trademark), and add 5 mL of concentrated nitric acid here to decompose at room temperature for 30 minutes. After decomposing, cover the lid, heat it at 150°C for 10 minutes by a wet decomposition device, and then heat it at 180°C for 5 minutes to further decompose, and then cool to room temperature. Transfer this treatment solution to a 50 mL measuring flask to make up the volume with pure water. For this solution, the amount of the boron compound (F) was quantified in terms of boron element by an ICP emission spectrometer.

(7) Appearance characteristics (transparency and coloring)

Using 8 g of dried EVOH pellets, it was heated and melted at 240°C for 5 minutes in a heating compression press device to produce a disc-shaped sample with a thickness of 1 mm. The transparency and coloration of the obtained disc-shaped sample were visually confirmed, and evaluated by the following criteria A to E as an indicator of the appearance characteristics (transparency and coloration) after melt molding. Standards A to C are sufficient for actual use.

A: Excellent transparency and almost no coloring

B: Transparency is slightly low, or only slightly colored

C: Transparency is slightly low, or slightly colored (light yellow)

D: Transparency is quite low, or quite colored (yellow)

E: Opaque or intensely colored (brown)

Secondly, the aforementioned disc-shaped sample was statically placed in the air at 120°C. Leave it for 50 hours, visually confirm the transparency and coloration, and evaluate the appearance characteristics (transparency and coloration) after long-term use using the following A~E standards. Standards A to C are sufficient for actual use.

A: Excellent transparency and almost no coloring

B: Transparency is slightly low, or only slightly colored

C: Transparency is slightly low, or slightly colored (light yellow)

D: Transparency is quite low, or quite colored (yellow)

E: Opaque or intensely colored (brown)

(8) Appearance characteristics (generation of gel and particles)

、L/D 20、Screw full flight type)之單層製膜，而得到EVOH之單層薄膜(20μm)。擠出條件定為供給部/壓縮部/計量部/模具=175/215/225/220℃。將從製膜開始2小時後所得之單層薄膜的凝膠及質點的發生量以目視確認，藉由用下述之A~E的基準進行評估，作為初次製膜後之外觀特性(凝膠及質點的發生)的指標。基準A~C為實質使用上有充分水準。 Using dry EVOH pellets, it was carried out on a single-screw extruder (D2020 Toyo Seiki Co., Ltd.. Caliber 20mm

, L/D 20, Screw full flight type) single-layer film formation, and obtain a single-layer film (20μm) of EVOH. The extrusion conditions were set as supply section/compression section/metering section/die=175/215/225/220°C. The amount of gel and particle generation of the monolayer film obtained 2 hours after the film formation was confirmed visually, and evaluated by the following criteria A to E as the appearance characteristics after the first film formation (gel And the occurrence of mass points). Standards A to C are sufficient for actual use.

A: Almost no gel or particles are observed

B: Only some micro gels or particles are observed

C: A little gel or particles are observed

D: A lot of gels or particles are observed

E: A lot of gels or particles are observed

Next, the EVOH powder obtained by pulverizing the aforementioned single-layer film is used to form a single-layer film using the same extruder and extrusion conditions as described above to obtain a single-layer film (20 μm) of EVOH. The amount of gel and particle generation of the single-layer film obtained by repeating this operation again was visually confirmed, and the appearance characteristics of the reproduced film (gel and particle Occurs) indicators. Standards A to C are sufficient for actual use.

A: Almost no gel or particles are observed

B: Only some micro gels or particles are observed

C: A little gel or particles are observed

D: A lot of gels or particles are observed

E: A lot of gels or particles are observed

(9) Long-term relationship

60 g of dry EVOH pellets were measured using a Laboplastomill (biaxially different direction) to measure the torque change when kneaded at 100 rpm and 240°C. Calculate the average value of torque (TI) from 20 minutes to 30 minutes after the start of mixing, and the average value of torque (TF) from 170 minutes to 180 minutes after the start of mixing, and then use the ratio of TF/TI. The following benchmark assessments of A~E are used as indicators of long-term relationship. Standards A to C are sufficient for actual use.

A: 75/100 or more but less than 125/100

B: More than 125/100 but less than 150/100

C: 150/100 or more but less than 200/100

D: More than 200/100 but less than 300/100

E: 300/100 or more, or less than 75/100

(10) Hierarchical indirectness

Dry EVOH pellets, linear low-density polyethylene (Nippon Polyethylene Corporation Novatec LL-UF943, hereafter referred to as LLDPE) and adhesive resin (Bynel CXA417E 10 manufactured by DuPont Co., Ltd. diluted to 6% with the above LLDPE, below (Referred to as Ad) using the following extruder and extrusion conditions, and a 300mm width three kinds of 5-layer hanger-type molds (manufactured by the Institute of Plastics Technology) to form 3 kinds of 5-layer multilayer films (LLDPE/ Ad/EVOH/Ad/LLDPE=50μm/10μm/10μm/10μm/50μm).

Extruder:

EVOH: Single-screw extruder (Toyo Seiki Co., Ltd. laboratory machine ME type CO-EXT)

、L/D 20、Screw full flight type Caliber 20mm

, L/D 20, Screw full flight type

LLDPE: Single-screw extruder (GT-32-A, Institute of Plastic Engineering, Co., Ltd.)

、L/D 28、Screw full flight type Caliber 32mm

, L/D 28, Screw full flight type

Ad: Single shaft extruder (TECHNOVEL SZW20GT-20MG-STD Co., Ltd.)

、L/D 20、Screw full flight type Caliber 20mm

, L/D 20, Screw full flight type

Extrusion conditions:

EVOH: supply department/compression department/measurement department/mold=175/210/220/ 220°C

LLDPE: supply department/compression department/measurement department/mold=150/200/210/220℃

Ad: supply department/compression department/measurement department/mold=150/200/220/220℃

Cut out the aforementioned multilayer film 150mm in the MD direction and 15mm in the TD direction. The peel strength between the EVOH layer and the Ad layer was measured in the T-type peeling mode of the universal testing machine, and the peel strength was measured by Use the following benchmark assessments from A to E as indicators of indirect effort. Standards A to C are sufficient for actual use.

A: 500g/15mm or more

B: above 400g/15mm but less than 500g/15mm

C: 300g/15mm or more but less than 400g/15mm

D: 200g/15mm or more but less than 300g/15mm

E: Less than 200g/15mm

<Synthesis Example 1> Synthesis of aqueous EVOH pellets (w-EVOH-1)

(Copolymerization step)

Place 83.0 kg of vinyl acetate and 26.6 kg of methanol in a 250L pressurized reaction tank equipped with a casing, agitator, nitrogen inlet, ethylene inlet and initiator addition port. After the temperature is raised to 60°C, it is heated by nitrogen bubbling for 30 minutes. Nitrogen substitution in the system. Next, ethylene was introduced so that the pressure in the reaction tank became 3.6 MPa. As a starter, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMV) was dissolved in methanol to prepare a starter solution with a concentration of 2.5g/L, Perform nitrogen substitution by bubbling nitrogen gas. The above polymerization tank After the internal temperature was adjusted to 60°C, 362 mL of the above-mentioned initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced, the pressure in the reaction tank was maintained at 3.6 MPa, and the polymerization temperature was maintained at 60°C. The above-mentioned initiator solution was used to continuously add AMV at 1120 mL/hr to perform polymerization. After 5 hours, when the polymerization rate reached 40%, cooling was performed to stop the polymerization. After opening the reaction tank for deethylene, bubbling nitrogen gas to complete deethylene. Secondly, the unreacted vinyl acetate monomer is removed under reduced pressure to obtain a methanol solution containing ethylene-vinyl acetate copolymer (EVAc).

(Saponification step)

Methanol was further added to the methanol solution containing EVAc obtained above to obtain a diluted solution of EVAc with a concentration of 15% by mass. Place 100 kg of the EVAc diluted solution obtained above in a 400L reaction tank equipped with a casing, a mixer, a nitrogen inlet, a steam cooler, and a solution addition port. The solution was heated to 60°C while blowing nitrogen into it, and 30.2L of a 10% by mass methanol solution of NaOH was added over 2 hours, followed by stirring at 60°C for 2 hours to advance the saponification reaction of EVAc. Then, the saponification reaction was stopped by adding 3.6 kg of acetic acid and 24 L of water for neutralization to obtain an EVOH suspension. The aforementioned EVOH suspension was deliquored by a centrifugal deliquoring machine, and the contents were transferred to a drum tank. Here, 160 kg of pure water is added and stirred, and this is again transferred to a centrifugal deliquor for deliquoring. The pure water was repeatedly added 5 times, and the operation of deliquoring was performed to wash, and then dried at 60°C for 24 hours to obtain a crudely dried product of EVOH.

(Granulation step)

Put 4.2 kg of EVOH crude dried product and 9.0 kg of water/methanol mixed solution (mass ratio: water/methanol=40/60) obtained above into a stirring tank equipped with a casing, agitator and reflux cooler, while stirring at 85°C Let it dissolve. Next, stop stirring and lower the temperature of the dissolution tank to 65°C and leave it for 5 hours to degas the EVOH water/methanol solution described above. And extrude the water/methanol solution of EVOH after degassing from a mold with a circular opening with a diameter of 3.5mm in a water/methanol mixed solution at 5°C (mass ratio: water/methanol=90/10) It is deposited into strips and cut into pellets with a wire cutter to obtain water-containing EVOH pellets with a diameter of about 4 mm and a length of about 5 mm.

Repeat 2 times to put 30 kg of the obtained aqueous EVOH pellets and 150 L of ion exchange water into a drum tank, stir at 25°C for 2 hours, and then perform the operation of deliquoring. Next, repeat the operation of adding 150L of 1g/L acetic acid aqueous solution to 30kg of water-containing EVOH pellets, stirring at 25°C for 2 hours, and then deliquoring. Furthermore, by adding 150L of ion-exchanged water to 30kg of water-containing EVOH particles 6 times, stirring at 25°C for 2 hours, and then performing the operation of deliquoring, the water-containing EVOH particles (w -EVOH-1). The moisture content of the obtained hydrous EVOH pellets was 110% by mass. In addition, the water-containing EVOH pellets were dried in a hot air dryer at 80°C for 3 hours, and then dried at 120°C for 24 hours to obtain dried EVOH pellets. According to the above analysis of the ethylene unit content and the degree of saponification, the ethylene unit content was 32 mol%. The degree of saponification is more than 99.98 mol%.

<Synthesis example 2> Synthesis of aqueous EVOH pellets (w-EVOH-2)

Except that in Synthesis Example 1, the amounts of vinyl acetate and methanol during the polymerization of EVAc were changed to 85.2kg and 32.3kg, respectively, the pressure of the reaction tank was changed to 2.9MPa, and the initiator solution (2.5g of AMV) /L concentration of methanol solution) at the start of polymerization was changed to 310 mL, and the continuous addition of the starter solution was changed to 950 mL/hr. The other procedures were the same as in Synthesis Example 1 to obtain the EVAc. Methanol solution. The reaction time during the polymerization reaction is 5 hours, and the polymerization rate is 40%.

Next, except that the addition amount of the alkaline solution was changed to 31.1L and the addition amount of acetic acid during neutralization was changed to 3.7kg, the other saponification and washing were performed in the same manner as in Synthesis Example 1 to obtain EVOH rough drying. Things.

Furthermore, except that the water/methanol mass ratio of the water/methanol mixed solution used when dissolving EVOH was changed to 50/50, the same operations as in Synthesis Example 1 were carried out to perform precipitation and washing to obtain water-containing EVOH pellets ( w-EVOH-2). The moisture content of the obtained hydrous EVOH pellets was 110% by mass. In addition, the water-containing EVOH pellets were dried in a hot air dryer at 80°C for 3 hours, and then dried at 120°C for 24 hours to obtain dried EVOH pellets. According to the above analysis of the ethylene unit content and the degree of saponification, the ethylene unit content was 27 mol%. The degree of saponification is more than 99.98 mol%.

<Synthesis example 3> Synthesis of aqueous EVOH pellets (w-EVOH-3)

Except that in Synthesis Example 1, the amount of vinyl acetate and methanol added during the polymerization of EVAc was changed to 76.7 kg and 11.0 kg, respectively, and the reaction tank was pressed Change the force to 5.5MPa, change the injection volume at the start of polymerization of the initiator solution (2.5g/L methanol solution of AMV) to 510mL, and change the continuous addition volume of the initiator solution to 1570mL/hr. , Others, by the same operation as in Synthesis Example 1, a methanol solution of EVAc was obtained. The reaction time during the polymerization reaction is 5 hours, and the polymerization rate is 40%.

Next, except that the amount of alkali solution added was changed to 27.7L, and the amount of acetic acid added during neutralization was changed to 3.3kg, the other saponification and washing were performed in the same manner as in Synthesis Example 1 to obtain EVOH rough drying. Things.

Furthermore, except that the water/methanol mass ratio of the water/methanol mixed solution used when dissolving EVOH was changed to 25/75, the same operations as in Synthesis Example 1 were carried out to perform precipitation and washing to obtain water-containing EVOH pellets ( w-EVOH-3). The moisture content of the obtained hydrous EVOH pellets was 110% by mass. In addition, the water-containing EVOH pellets were dried in a hot air dryer at 80°C for 3 hours, and then dried at 120°C for 24 hours to obtain dried EVOH pellets. According to the above analysis of the ethylene unit content and the degree of saponification, the ethylene unit content was 44 mol%. The degree of saponification is more than 99.98 mol%.

<Synthesis Example 4> Synthesis of aqueous EVOH pellets (w-EVOH-4)

Except that in Synthesis Example 1, the amounts of vinyl acetate and methanol during the polymerization of EVAc were changed to 102.0kg and 17.7kg, respectively, the pressure of the reaction tank was changed to 2.9MPa, and the initiator solution (2.5g of AMV) /L concentration of methanol solution) at the start of polymerization was changed to 280 mL, and the continuous addition of the initiator solution was changed to 850 mL/hr. The other operations were the same as in Synthesis Example 1 to obtain the EVAc. Methanol solution. polymerization The reaction time during the reaction was 5 hours, and the polymerization rate was 40%.

Next, except that the addition amount of the alkaline solution was changed to 31.6L and the addition amount of acetic acid during neutralization was changed to 3.8kg, the other saponification and washing were performed in the same manner as in Synthesis Example 1 to obtain EVOH rough drying. Things.

Furthermore, except that the water/methanol mass ratio of the water/methanol mixed solution used when dissolving EVOH was changed to 55/45, the same operations as in Synthesis Example 1 were carried out to perform precipitation and washing to obtain water-containing EVOH pellets ( w-EVOH-4). The moisture content of the obtained hydrous EVOH pellets was 110% by mass. In addition, the water-containing EVOH pellets were dried in a hot air dryer at 80°C for 3 hours, and then dried at 120°C for 24 hours to obtain dried EVOH pellets. According to the above analysis of the ethylene unit content and the degree of saponification, the ethylene unit content was 24 mol%. The degree of saponification is more than 99.98 mol%.

<Synthesis Example 5> Synthesis of aqueous EVOH pellets (w-EVOH-5)

According to the method described in Example 2 of JP 51-49294 A (Patent Document 4), water-containing EVOH pellets (w-EVOH-5) were obtained. This water-containing pellet (w-EVOH-5) corresponds to the "resin" before acid treatment in Example 2 of Patent Document 4 above.

<Example 1>

As shown in Table 1, 90.0 L of an aqueous solution of potassium nitrate dissolved in water was added to 10.0 kg of w-EVOH-1 so that potassium nitrate became 1.95 g/L, and immersion was performed while stirring at 25°C for 6 hours. After centrifugal dewatering the impregnated pellets, dry them in a hot air dryer at 80°C for 3 hours, and then at 120°C Dry for 24 hours to obtain dry EVOH pellets. For the obtained particles, the results of the analysis and evaluation as described above are shown in Table 2.

<Examples 2 to 16 and Comparative Examples 1 to 8>

Except that the components and concentrations blended in the aqueous solution were changed as shown in Table 1, the other operations were performed in the same manner as in Example 1 to obtain dry EVOH pellets. For the obtained particles, the results of the analysis and evaluation as described above are shown in Table 2.

<Examples 17-19>

Except that the type of aqueous EVOH particles used and the components and concentrations blended in the aqueous solution were changed as shown in Table 1, the other operations were the same as in Example 1 to obtain dry EVOH particles. For the obtained particles, the results of the analysis and evaluation as described above are shown in Table 2.

<Example 20>

By drying w-EVOH-1 in a hot air dryer at 80°C for 1 hour, water-containing EVOH pellets with a moisture content of 50% by mass were obtained. The obtained water-containing EVOH pellets were put into a twin-screw extruder at 10kg/hr, the resin temperature of the discharge nozzle was set to 100°C, and the solution addition part at the tip of the discharge nozzle was used to make potassium nitrate 22.5g/L The solution of potassium nitrate dissolved in water was added at 0.6L/hr. The strip-shaped molten EVOH spit out from the crystal grains was cut with a wire cutter to obtain water-containing EVOH pellets with a water content of 25% by mass. The obtained water-containing EVOH pellets were dried in a hot air dryer at 80°C for 1 hour, and then dried at 120°C for 24 hours to obtain dried EVOH pellets. For the obtained dry EVOH pellets, the results of the above analysis and evaluation are shown in Table 2.

<Comparative Example 9>

Using w-EVOH-5, acid treatment (impregnation in an aqueous solution) and drying were performed in accordance with the method described in Example 2 of JP Sho 51-49294 A (Patent Document 4) to obtain dry EVOH pellets. That is, Comparative Example 9 reproduces Example 2 of Patent Document 4 described above. For the obtained dry EVOH pellets, the results of the above analysis and evaluation are shown in Table 2.

<Comparative Example 10>

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

As shown in Table 2, EVOH contains at least one of nitric acid and nitrate ions and metal ions in a predetermined and ratio. It does not contain carboxylic acid and carboxylic ions, or contains carboxylic acid and carboxylic ions in a predetermined ratio. When at least one of them is used, a resin composition having excellent appearance characteristics and long-term relationship can be obtained. In addition, by using the aforementioned resin composition, a multilayer structure with excellent layer adhesion can be obtained. Furthermore, by containing at least one of acid and carboxylic acid ion in a predetermined amount and ratio, the above-mentioned characteristics can be further improved.

Also, as in Example 8 and Example 9, as the metal ion, In the case of containing alkaline earth metal ions, as in Example 3, as compared with the case of not containing alkaline earth metal ions, repeated procedures can further suppress the formation of gels and particles after film formation. In particular, as compared with Example 9, Example 8 is also excellent in the balance of long-term relationship and layer-to-layer adhesion.

Furthermore, as in Example 10, Example 11, and Example 16, at least one of a polyvalent carboxylic acid and a polyvalent carboxylic acid ion and at least one of a monovalent carboxylic acid and a monovalent carboxylic acid ion are set as predetermined When the amount and ratio are used in combination, as in Example 3, the transparency and coloration can be suppressed as compared with the case where the combination is not used. In particular, when Examples 10 and 16 are compared with Example 11, by using a trivalent carboxylic acid, transparency and coloration after long-term use can be suppressed.

In addition, as in Example 14, Example 15, and Example 16, when a predetermined amount of a phosphoric acid compound or a boron compound is contained, as in Example 3, compared with the case where the phosphoric acid compound and the boron compound are not contained, repeating the process can further suppress the production. The occurrence of gel and particles behind the membrane. In particular, compared with Example 14 and Example 15, Example 16 can suppress the transparency and coloration after melt forming and after long-term use.

Claims (12)

A resin composition containing 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 composition composed of carboxylic acid and carboxylic acid A component (D) composed of at least one of acid ions, the aforementioned component (D) includes a component (D1) composed of at least one of a monovalent carboxylic acid and a monovalent carboxylic acid ion, and a component (D1) composed of a polyvalent At least one of the components (D2) composed of at least one of carboxylic acid and polyvalent carboxylic acid ion, the content Bm of the aforementioned component (B) relative to the total amount of the resin composition in a dry state is 0.5 μmol/g Above 100 μmol/g, the content Cm of the aforementioned metal ion (C) is 2 μmol/g or more and 120 μmol/g or less relative to the total amount of the resin composition in the dry state, and the content Bm of the aforementioned component (B) is the same as the aforementioned metal ion (C) The content Cm and its average valence Cv satisfy the following formula (1), the content Dm of the aforementioned Bm, the aforementioned Cm, the aforementioned Cv, and the aforementioned component (D) relative to the total amount of the resin composition in the dry state, and Its average valence Dv satisfies the following formula (2), (Cv×Cm)/Bm≧1.0‧‧‧(1) ((Cv×Cm)-Bm)/(Dv×Dm)≧0.2‧‧‧(2 ). Such as the resin composition of claim 1, wherein the aforementioned Bm is Above 5μmol/g and below 25μmol/g. The resin composition of claim 1 or claim 2, wherein the aforementioned metal ion (C) is composed only of alkali metal ion (C1). For example, the resin composition of claim 1 or claim 2, wherein the aforementioned metal ion (C) contains alkali metal ion (C1) and alkaline earth metal ion (C2), the ratio of alkali metal ion (C1) relative to the dry state The content C1m of the total resin composition and the content C2m of the alkaline earth metal ion (C2) relative to the total amount of the resin composition in the dry state satisfies the following formula (3), C1m/(C1m+2×C2m )≧0.5‧‧‧(3). The resin composition of claim 1, wherein the component (D) includes both the component (D1) and the component (D2), and the component (D2) has 3 or more carboxyl groups. Such as the resin composition of claim 1, which further contains a phosphoric acid compound (E), and its content Ew is 5 ppm or more and 500 ppm or less in terms of phosphate based on the total amount of the resin composition in a dry state. Such as the resin composition of claim 1, which further contains a boron compound (F), and its content Fw is 5 ppm or more and 2,000 ppm or less in terms of boron element relative to the total amount of the resin composition in a dry state. Such as the resin composition of claim 1, which is used for co-extrusion molding. A method for producing a resin composition according to any one of claims 1 to 8, which includes a copolymerization step of copolymerizing ethylene and vinyl ester to obtain an ethylene-vinyl ester copolymer, and The saponification step of saponifying the aforementioned ethylene-vinyl ester copolymer to obtain an ethylene-vinyl alcohol copolymer (A). After the aforementioned copolymerization step, the aforementioned ethylene-vinyl ester copolymer or ethylene-vinyl alcohol copolymer (A) is mixed, The mixing step with the aforementioned component (B) and the aforementioned metal ion (C). The method for producing a resin composition according to claim 9, which comprises granulating a solution containing the ethylene-vinyl alcohol copolymer (A) obtained in the aforementioned saponification step to obtain an ethylene-vinyl alcohol copolymer (A) The step of granulating the water-containing particles of ), and the step of drying the aforementioned water-containing granules, the mixing step is performed after the aforementioned granulating step. The method for producing a resin composition according to claim 10, wherein, as the mixing step, between the granulation step and the drying step, the water-containing particles are immersed in the material containing the component (B) and the metal ion (C) Solution. A multilayer structure having at least one layer made of the resin composition of any one of claims 1 to 8.