JP2021138824A - Ethylene-vinyl alcohol copolymer-containing resin composition and molded article - Google Patents

Abstract

To provide an EVOH excellent in melt moldability and appearance characteristics and capable of improving water resistance of a molded article.SOLUTION: A resin composition contains: an ethylene-vinyl alcohol copolymer (A); and at least one boron compound (B) selected from the group consisting of diboronic acids or compounds capable of being converted into the diboronic acids in the presence of water. The ethylene-vinyl alcohol copolymer (A) has an ethylene unit content of 15-60 mol% and a degree of saponification of 85 mol% or more. The content of the boron compound (B) is 30-300 ppm in terms of boron element.SELECTED DRAWING: None

Description

The present invention relates to a resin composition containing an ethylene-vinyl alcohol copolymer as a main component, and a molded product using the resin composition.

Since ethylene-vinyl alcohol copolymer (hereinafter referred to as "EVOH") has excellent gas barrier properties and melt moldability, it can be molded into films, sheets, pipes, tubes, bottles, etc. by various melt molding methods. It is widely used as a packaging material in the food and industrial fields where gas barrier properties are required. Further, as a method of controlling physical properties related to melt moldability such as melt viscosity, melt tension, and extensional viscosity, or as a method of improving mechanical properties of molded products such as tensile strength and elongation, a method of adding a boric acid compound to EVOH. Is widely known. On the other hand, if the amount of boric acid-based compound added is too large or localized, appearance defects such as fish eyes may occur and the quality of the molded product may deteriorate. Studies have been made (Patent Documents 1 to 3).

Special Publication No. 62-3866 Japanese Unexamined Patent Publication No. 2000-44756 International Publication No. 2017/11676

However, the interaction between EVOH and the boric acid-based compound is reversible. For example, the interaction is weakened under high humidity conditions, and the boric acid-based compound flows out in water. In some cases, the expected effects such as the mechanical properties of the above were not sufficiently exhibited. This is likely to be a problem in applications where the EVOH layer is in direct contact with water, especially hot water, for long periods of time, such as water guide pipes where EVOH is used as the innermost layer and foods where EVOH is used as the outermost layer. An example is packaging. The interaction between EVOH and a boric acid-based compound may be 3-coordinated or 4-coordinated with the boron atom as the center. In such an interaction method, as described above in either case. It was difficult to improve the water resistance.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide EVOH which is excellent in melt moldability and appearance characteristics and can also improve the water resistance of a molded product.

［式中、Ｒ1、Ｒ２、Ｒ３及びＲ４は、それぞれ独立して水素原子又は炭素原子数１〜４のアルキル基を表し、Ｘは単結合、又は１つ以上の原子からなる結合鎖を表す。］
［３］Ｘが１つ以上の原子からなる結合鎖であり、ホウ素原子間の最短鎖の原子数が３〜６である、［２］の樹脂組成物；
［４］Ｘが１つ以上の原子からなる結合鎖であり、ホウ素原子間の最短鎖が炭素原子のみからなる、［２］又は［３］の樹脂組成物；
［５］Ｘが１つ以上の原子からなる結合鎖であり、ホウ素原子間の最短鎖が単結合のみを有する、［２］〜［４］のいずれかの樹脂組成物；
［６］さらにアルカリ金属イオン（Ｃ）を１００〜４００ｐｐｍ含有する、［１］〜［５］のいずれかの樹脂組成物；
［７］さらにカルボン酸（Ｄ）を５０〜４００ｐｐｍ含有する、［１］〜［６］のいずれかの樹脂組成物；
［８］［１］〜［７］のいずれかの樹脂組成物を含む成形体；
［９］［１］〜［７］のいずれかの樹脂組成物からなる層を少なくとも１層有する多層成形体；
を提供することで解決される。 As a result of diligent studies on the interaction between EVOH and a boron compound, the present inventors have excellent melt moldability and appearance characteristics by using a diboronic acid-based compound having two boron atoms in the molecule, and molding. We have found that the water resistance of the body can also be improved. On the other hand, even if the molecule has two boron atoms, the improvement in water resistance is limited in the polyboric acid-based compound produced by dehydration condensation of boric acid. Furthermore, they have found that the above-mentioned properties can be balanced at a higher level by using a diboronic acid-based compound having a specific structure, and have completed the invention. That is, the above problem is
[1] A resin composition containing an ethylene-vinyl alcohol copolymer (A) and at least one boron compound (B) selected from the group consisting of diboronic acid or a compound capable of converting to diboronic acid in the presence of water. The ethylene-vinyl alcohol copolymer (A) has an ethylene unit content of 15 to 60 mol%, a saponification degree of 85 mol% or more, and a boron compound (B) content in terms of boron element. Resin composition of 30-300 ppm;
[2] The resin composition of [1], wherein the boron compound (B) is represented by the following formula (I);

[In the formula, R1, R2, R3 and R4 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and X represents a single bond or a bond chain consisting of one or more atoms. ]
[3] The resin composition of [2], wherein X is a bonded chain composed of one or more atoms, and the number of atoms in the shortest chain between boron atoms is 3 to 6.
[4] The resin composition of [2] or [3], wherein X is a bond chain consisting of one or more atoms, and the shortest chain between boron atoms consists of only carbon atoms;
[5] The resin composition according to any one of [2] to [4], wherein X is a bond chain consisting of one or more atoms, and the shortest chain between boron atoms has only a single bond;
[6] The resin composition according to any one of [1] to [5], further containing 100 to 400 ppm of alkali metal ion (C);
[7] The resin composition according to any one of [1] to [6], which further contains 50 to 400 ppm of carboxylic acid (D);
[8] A molded product containing the resin composition according to any one of [1] to [7];
[9] A multilayer molded product having at least one layer made of the resin composition according to any one of [1] to [7];
Will be resolved by providing.

Since the resin composition of the present invention is excellent in melt moldability and appearance characteristics and can improve the water resistance of the molded product, it is also preferable for applications in which the EVOH layer is in direct contact with water, particularly hot water, for a long period of time. Can be used.

Hereinafter, embodiments of the present invention will be described. In the following description, specific materials (compounds and the like) may be exemplified as those exhibiting a specific function, but the present invention is not limited to the mode in which such a material is used. Further, unless otherwise specified, the exemplified materials may be used alone or in combination.

<EVOH (A)>
EVOH (A) is the main component of the resin composition of the present invention. EVOH (A) is a copolymer having an ethylene unit and a vinyl alcohol unit as a main structural unit. EVOH (A) is usually obtained by polymerizing ethylene and vinyl ester and saponifying the obtained ethylene-vinyl ester copolymer. The main component indicates that the content of EVOH (A) in the resin constituting the resin composition of the present invention is 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. , 95% by mass or more is particularly preferable, and 99% by mass or more may be used. By setting the content of EVOH (A) in this range, the melt moldability of the obtained pellets is improved, and the gas barrier property of the molded product obtained from the pellets is also excellent.

The ethylene unit content of EVOH (A), i.e. the ratio of the number of ethylene units to the total number of monomeric units in EVOH (A), should be in the range of 15-60 mol%. The lower limit of the ethylene unit content of EVOH (A) is preferably 20 mol%, more preferably 23 mol%. On the other hand, the upper limit of the ethylene unit content of EVOH (A) is preferably 55 mol%, more preferably 50 mol%. When the ethylene unit content of EVOH (A) is less than 15 mol%, the gas barrier property under high humidity may be lowered, and the melt moldability may also be deteriorated. If the ethylene unit content of EVOH (A) exceeds 60 mol%, sufficient gas barrier properties may not be obtained.

The saponification degree of EVOH (A), that is, the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH (A) needs to be 85 mol% or more. The lower limit of the saponification degree of EVOH (A) is preferably 95 mol%, more preferably 99 mol%. On the other hand, the upper limit of the saponification degree of EVOH (A) is preferably 100 mol%, more preferably 99.99 mol%. If the saponification degree of EVOH (A) is less than 85 mol%, sufficient gas barrier properties may not be obtained, and thermal stability may be insufficient.

EVOH (A) may be a mixture of two or more types of EVOH having different ethylene unit contents. In this case, the difference in ethylene unit content between EVOHs having the farthest ethylene unit contents is preferably 30 mol% or less, more preferably 20 mol% or less, still more preferably 15 mol% or less. Similarly, EVOH (A) may be a mixture of two or more types of EVOH having different saponification degrees. In this case, the difference in the degree of saponification between the farthest EVOHs is preferably 7% or less, more preferably 5% or less. If a resin composition having a higher level of thermoformability and gas barrier properties is desired, an EVOH having an ethylene unit content of 24 mol% or more and less than 34 mol% and a saponification degree of 99 mol% or more is desired. (A-1) and EVOH (A-2) having an ethylene unit content of 34 mol% or more and less than 50 mol% and a saponification degree of 99 mol% or more are blended in a mass ratio (A-1 / A-). It is preferable to mix 2) so that it becomes 60/40 to 90/10 and use it as EVOH (A). The ethylene unit content and saponification degree of EVOH (A) can be determined by a nuclear magnetic resonance (NMR) method.

The lower limit of the melt flow rate (hereinafter, may be simply abbreviated as "MFR") (temperature 210 ° C., load 2160 g) conforming to JIS K 7210: 2014 of EVOH (A) is preferably 0.1 g / 10 minutes. 0.5 g / 10 minutes is more preferable, and 1 g / 10 minutes is even more preferable. On the other hand, the upper limit of MFR of EVOH (A) is preferably 50 g / 10 minutes, more preferably 30 g / 10 minutes, and even more preferably 15 g / 10 minutes. By setting the MFR of EVOH (A) to a value in this range, the melt moldability of the obtained resin composition is improved.

EVOH (A) can contain monomer units other than ethylene units, vinyl alcohol units and vinyl ester units as copolymerization units as long as the object of the present invention is not impaired. Examples of the monomer include α-olefins such as propylene, 1-butene, isobutene, 4-methyl-1-pentene, 1-hexene and 1-octene; itaconic acid, methacrylic acid, acrylic acid and maleic acid. Unsaturated carboxylic acids such as, salts thereof, partial or complete esters thereof, nitriles thereof, amides thereof, anhydrides thereof; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxyethoxy) silane, γ-methacryloxypropyl. Examples thereof include vinylsilane compounds such as trimethoxysilane; unsaturated sulfonic acid or salts thereof; unsaturated thiols; and vinylpyrrolidones. The content of the monomer unit other than the ethylene unit, vinyl alcohol unit and vinyl ester unit in EVOH (A) is usually 5 mol% or less, preferably 2 mol% or less, and more preferably 1 mol% or less.

［式中、Ｒ¹、Ｒ^２、Ｒ^３及びＲ^４は、それぞれ独立して水素原子又は炭素原子数１〜４のアルキル基を表し、Ｘは単結合、又は１つ以上の原子からなる結合鎖を表す。］ <Boron compound (B)>
The resin composition of the present invention needs to contain at least one boron compound (B) selected from the group consisting of compounds that can be converted to diboronic acid in the presence of diboronic acid or water in an amount of 30 to 300 ppm in terms of boron element. There is. The boron compound (B) can be represented by the following formula (I).

[In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and X is a single bond or a bond consisting of one or more atoms. Represents a chain. ]

In the formula (I), it is preferable that X is a bonded chain composed of one or more atoms and the number of atoms in the shortest chain between boron atoms is 3 to 6. When the number of atoms in the shortest chain between boron atoms is in this range, the film-forming property and water resistance of the obtained resin composition can be balanced at a high level. Further, in the formula (I), it is also preferable that X is a bonded chain composed of one or more atoms and the shortest chain between boron atoms is composed of only carbon atoms. Since the shortest chain between boron atoms consists only of carbon atoms, the water resistance of the obtained resin composition can be improved. Further, in the formula (I), it is also preferable that X is a bond chain consisting of one or more atoms and the shortest chain between boron atoms has only a single bond. Since the shortest chain between the boron atoms has only a single bond, the coloring of the obtained resin composition can be reduced. In the present application, the shortest chain between boron atoms refers to the shortest atomic chain among a plurality of atomic chains connecting boron atoms.

Examples of the boron compound (B) include methanediboronic acid, ethanediboronic acid, propandiboronic acid, butanediboronic acid, pentandiboronic acid, hexanediboronic acid, and isomers thereof, and 1,4-benzenediboronic acid, 1. , 3-benzenediboronic acid and the like.

The lower limit of the content of the boron compound (B) is 30 ppm in terms of boron element, and 50 ppm is preferable. On the other hand, the upper limit of the content of the boron compound (B) is 300 ppm in terms of boron element, preferably 250 ppm. If the content of the boron compound (B) is less than 30 ppm, neck-in becomes severe during film formation, and melt moldability may be insufficient. On the other hand, when the content of the boron compound (B) exceeds 300 ppm, the fish eye may increase during film formation and the appearance characteristics of the molded product may deteriorate.

<Alkali metal ion (C)>
The resin composition of the present invention preferably contains an alkali metal ion (C). The lower limit of the content of the alkali metal ion (C) is preferably 100 ppm, more preferably 150 ppm. On the other hand, the upper limit of the content of the alkali metal ion (C) is preferably 400 ppm, more preferably 350 ppm. When the content of the alkali metal ion (C) is less than 100 ppm, the interlayer adhesiveness of the multilayer molded product containing the layer obtained by molding the resin composition of the present invention may be insufficient. On the other hand, when the content of the alkali metal ion (C) exceeds 400 ppm, coloring due to thermal deterioration may become a problem. The reason why the interlayer adhesion is improved by the alkali metal ion (C) is not clear, but when the layer adjacent to EVOH (A) has a molecule having a functional group capable of reacting with the hydroxy group of EVOH (A), It is considered that this bond formation reaction is accelerated by the alkali metal ion (C). Further, by controlling the content ratio of the alkali metal ion (C) and the carboxylic acid (D) described later, the melt moldability and coloring resistance of the obtained resin composition can be further improved.

Examples of the alkali metal ion (C) include lithium, sodium, potassium, rubidium, and cesium ions, but sodium or potassium ions are preferable from the viewpoint of industrial availability. In particular, by using potassium ions, the hue of the resin composition of the present invention and the interlayer adhesiveness of the multilayer molded product including the layer obtained by molding the resin composition of the present invention may be compatible at a high level. be. One of these may be used alone, or two or more thereof may be used in combination.

Examples of the alkali metal salt that gives the alkali metal ion (C) include aliphatic carboxylates of alkali metals such as lithium, sodium, and potassium, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, and phosphoric acids. Examples include salts and metal complexes. Of these, sodium acetate, potassium acetate, sodium phosphate, and potassium phosphate are more preferable because they are easily available.

<Carboxylic acid (D)>
The resin composition of the present invention preferably contains a carboxylic acid (D). The lower limit of the content of the carboxylic acid (D) is preferably 50 ppm, more preferably 100 ppm. On the other hand, the upper limit of the content of the carboxylic acid (D) is preferably 400 ppm, more preferably 350 ppm. If the content of the carboxylic acid (D) is less than 50 ppm, the coloring resistance may be insufficient. On the other hand, when the content of the carboxylic acid (D) exceeds 400 ppm, the interlayer adhesiveness of the multilayer molded product containing the layer obtained by molding the resin composition of the present invention becomes insufficient, and odor becomes a problem. It may happen. The content of the carboxylic acid (D) is determined by extracting 10 g of pellets with 50 ml of pure water at 95 ° C. for 8 hours, and then titrating the obtained extract. As the content of the carboxylic acid (D) in the pellet, the carboxylic acid present as a salt in the extract is not taken into consideration. When the resin composition of the present invention contains an acidic compound other than the carboxylic acid (D), the carboxylic acid in the resin composition can be obtained by subtracting the contribution of the acidic compound from the measured value by titration. The content of D) can be determined.

The pKa of the carboxylic acid (D) is preferably 3.5 to 5.5. When the pKa of the carboxylic acid (D) is in the above range, the pH buffering capacity of the obtained resin composition is enhanced, the melt moldability can be further improved, and the coloring by an acidic substance or a basic substance can be further improved.

The carboxylic acid (D) may be a monovalent carboxylic acid. One of these may be used alone, or two or more thereof may be used in combination. The monovalent carboxylic acid is a compound having one carboxyl group in the molecule. The monovalent carboxylic acid having a boiling point of less than 150 ° C. having a pKa in the range of 3.5 to 5.5 is not particularly limited, and is, for example, formic acid (pKa = 3.77), acetic acid (pKa = 4.76), and propion. Acids (pKa = 4.85), acrylic acid (pKa = 4.25) and the like can be mentioned. These carboxylic acids may further have substituents such as hydroxyl groups, amino groups and halogen atoms as long as the boiling point is less than 150 ° C. Of these, acetic acid is preferable because it is highly safe and easy to obtain and handle.

The carboxylic acid (D) may be a polyvalent carboxylic acid. When the carboxylic acid (D) is a polyvalent carboxylic acid, the coloring resistance of the resin composition at a high temperature and the coloring resistance of the obtained melt-molded product may be further improved. It is also preferable that the polyvalent carboxylic acid compound has three or more carboxyl groups. In this case, the coloring resistance may be improved more effectively.

A polyvalent carboxylic acid is a compound having two or more carboxyl groups in the molecule. In this case, the pKa of at least one carboxyl group is preferably in the range of 3.5 to 5.5, for example, oxalic acid (pKa2 = 4.27), succinic acid (pKa1 = 4.20), phthalic acid. (PKa2 = 4.44), succinic acid (pKa2 = 5.13), glutaric acid (pKa1 = 4.30, pKa2 = 5.40), adipic acid (pKa1 = 4.43, pKa2 = 5.41), Pimelic acid (pKa1 = 4.71), phthalic acid (pKa2 = 5.41), isophthalic acid (pKa2 = 4.46), terephthalic acid (pKa1 = 3.51, pKa2 = 4.82), succinic acid (pKa2) = 4.75), tartaric acid (pKa2 = 4.40), glutamic acid (pKa2 = 4.07), aspartic acid (pKa = 3.90) and the like.

<Other ingredients>
The resin composition of the present invention may contain other components as long as the effects of the present invention are not impaired. Other components include, for example, a divalent metal ion (E), a phosphoric acid compound (F), a boron compound (G) other than the boron compound (B), a thermoplastic resin other than EVOH (A), a cross-linking agent, and a desiccant. , Antioxidants, Antioxidants, Oxygen Absorbents, Plasticizers, Phosphoric Acids, Heat Stabilizers (Melting Stabilizers), Processing Aids, Surface Activators, Deodorants, Antistatic Agents, UV Absorbents, Antifogging Agents, Examples thereof include flame retardants, pigments, dyes, fillers, fillers, and reinforcing agents for various fibers.

<Divalent metal ion (E)>
The resin composition of the present invention may further contain a divalent metal ion (E). The lower limit of the content of the divalent metal ion (E) is preferably 10 ppm. On the other hand, the upper limit of the content of the divalent metal ion (E) is preferably 100 ppm. By setting the content of the divalent metal ion (E) in this range, the resin composition of the present invention suppresses coloring due to thermal deterioration of EVOH (A), and is molded even when melt molding is performed for a long period of time. The generation of gels and lumps on the body may be suppressed.

Examples of the divalent metal ion (E) include ions of beryllium, magnesium, calcium, strontium, barium, iron, copper, and zinc, but magnesium is not affected by coloring and is easily available industrially. , Calcium or zinc ions are preferred. Magnesium ions are particularly preferable from the viewpoint of effectively suppressing the generation of gels and lumps with a small amount of content, but calcium ions and zinc ions, particularly zinc ions, are preferable from the viewpoint of balance with hue. One of these may be used alone, or two or more thereof may be used in combination.

Examples of the divalent metal salt that gives the divalent metal ion (E) include aliphatic carboxylates such as magnesium, calcium and zinc, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates and phosphates. , Metal complexes. Of these, magnesium acetate, calcium acetate and zinc acetate are more preferable because they are easily available.

<Phosphoric acid compound (F)>
The resin composition of the present invention may further contain the phosphoric acid compound (F). The lower limit of the content of the phosphoric acid compound (F) is preferably 5 ppm in terms of phosphoric acid root. On the other hand, the upper limit of the content of the phosphoric acid compound (F) is preferably 100 ppm in terms of phosphoric acid root. By containing the phosphoric acid compound (F) in this range, coloring of the obtained resin composition and the obtained melt-molded product may be suppressed, and thermal stability may be improved.

As the phosphoric acid compound (F), for example, various acids such as phosphoric acid and phosphite and salts thereof are used. The phosphate may be any of a first phosphate, a second phosphate, and a third phosphate. The cation species of the phosphate is not particularly limited, but the cation species is preferably an alkali metal or an alkaline earth metal. Among them, as the phosphoric acid compound (F), sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate are preferable.

<Boron compound (G)>
The resin composition of the present invention may further contain a boron compound (G) other than the boron compound (B). The lower limit of the content of the boron compound (G) is preferably 15 ppm in terms of boron element. On the other hand, the upper limit of the content of the boron compound (G) is preferably 150 ppm in terms of boron element. In the present invention, the resin composition can be produced more economically by using the boron compound (B) and the boron compound (G) in combination.

Examples of the boron compound (G) include boric acid, borate ester, borate, and boron hydride. Specifically, boric acid such as orthoboric acid (H ₃ BO ₃ ), metaboric acid, tetraboric acid; borate ester such as trimethyl borate, triethyl borate; alkali metal salt or alkaline earth metal of the boric acid. Examples thereof include borates such as salt and boric acid. Of these, orthoboric acid is preferable.

The resin composition of the present invention may further contain a thermoplastic resin other than EVOH (A). Examples of thermoplastic resins other than EVOH (A) include various polyolefins (polyethylene, polypropylene, poly1-butene, poly4-methyl-1-pentene, ethylene-propylene copolymer, ethylene and α- with 4 or more carbon atoms. Copolymers with olefins, copolymers of polyolefins and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylic acid ester copolymers, or modifications obtained by graft-modifying these with unsaturated carboxylic acids or derivatives thereof. Polyethylene, etc.), various polyamides (nylon 6, nylon 6.6, nylon 6/66 copolymer, nylon 11, nylon 12, polymethoxylylen adipamide, etc.), various polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene na) Phthalates, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, modified polyvinyl alcohol resin, and the like. The content of the thermoplastic resin in the resin composition of the present invention is less than 30% by mass, preferably less than 20% by mass, more preferably less than 10% by mass, further preferably 5% by mass or less, and 1% by mass or less. It may be.

<Pellet manufacturing method>
The method for producing the resin composition of the present invention is not limited as long as EVOH (A) and the boron compound (B) are finally contained in the above range, but the production method of the present invention described later is used. It is preferable to manufacture.

The method for incorporating the boron compound (B) into the resin composition of the present invention is not particularly limited. For example, (1) a method for immersing a water-containing pellet containing EVOH (A) in a solution in which the boron compound (B) is dissolved. , (2) A method of melting EVOH (A) and mixing the boron compound (B), (3) a method of dissolving EVOH (A) in an appropriate solvent and mixing the boron compound (B), etc. are applicable. Is.

Above all, the method (1) above is preferable in order to exert the effect of the present invention more remarkably. This process can be performed by either a batch method or a continuous method. At that time, the shape of the EVOH (A) may be any shape such as powder, granular, spherical, and cylindrical pellets. The concentration of the boron compound (B) in the above solution is not particularly limited. The solvent of the solution is not particularly limited, but an aqueous solution is preferable because of its ease of handling and its influence on the environment. The immersion time varies depending on the form of EVOH (A), but in the case of pellets of about 1 to 10 mm, it is preferably 1 hour or more, preferably 2 hours or more. When the treatment is carried out by immersing in a solution as described above, a resin composition having a volatile content of less than 0.3% can be obtained by finally drying.

EVOH is usually synthesized by saponification of an ethylene-vinyl ester copolymer, and vinyl acetate is generally used as the vinyl ester. Further, when copolymerizing ethylene and vinyl acetate, other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can also be used in combination.

The polymerization of ethylene and vinyl ester may be any of solution polymerization, suspension polymerization, emulsion polymerization and bulk polymerization, and may be continuous type or batch type, for example, batch type solution polymerization. The polymerization conditions in this case are as follows.

Solvent: Alcohols are preferable, but other organic solvents (dimethyl sulfoxide and the like) capable of dissolving ethylene, vinyl ester and ethylene-vinyl ester copolymers can be used. As the alcohols, methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, t-butyl alcohol and the like can be used, and methyl alcohol is particularly preferable.
Catalyst: 2,2'-azobisisobutyronitrile, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis- (4-methyl-2,4-dimethylvaleronitrile) ), 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis- (2-cyclopropylpropionitrile) and other azonitrile-based initiators and isobutyryl peroxide. , Cumylperoxyneodecanoate, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, t-butylperoxyneodecanoate, lauroyl peroxide, benzoyl peroxide, t-butyl hydroperoxide, etc. Organic peroxide-based initiators and the like are used.
Temperature: 20-90 ° C, preferably 40 ° C-70 ° C.
Time: 2 to 15 hours, preferably 3 to 11 hours.
Polymerization rate: 10 to 90%, preferably 30 to 80% with respect to the charged vinyl ester.
Resin content in the solution after polymerization: 5 to 85%, preferably 20 to 70%.

In addition to ethylene and vinyl ester, it is also possible to allow a small amount of monomers copolymerizable with them to coexist. Examples of the monomer that can be copolymerized include α-olefins such as propylene, isobutylene, α-octene, and α-dodecene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid, or anhydrides thereof. Substances, salts, mono- or dialkyl esters, etc .; vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tri (β-methoxy-ethoxy) silane, γ-methacryloxypropyl methoxysilane; acrylonitrile, methacrylonitrile, etc. Nitriles; amides such as acrylamide and methacrylicamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride and the like. Can be mentioned.

After polymerization for a predetermined time and reaching a predetermined polymerization rate, a polymerization inhibitor is added as necessary to evaporate and remove unreacted ethylene gas, and then unreacted vinyl acetate is expelled. As a method of expelling unreacted vinyl acetate from the ethylene-vinyl acetate copolymer from which ethylene has been evaporated and removed, for example, the copolymer solution is continuously supplied at a constant rate from the upper part of a column filled with Raschichling, and the lower part of the column. A method in which an organic solvent vapor such as methanol is blown in, a mixed vapor of an organic solvent such as methanol and unreacted vinyl acetate is distilled off from the top of the column, and the copolymer solution from which the unreacted vinyl acetate is removed is taken out from the bottom of the column. Will be adopted.

An alkali catalyst is added to the copolymer solution from which unreacted vinyl acetate has been removed to saponify the vinyl acetate component in the copolymer. The saponification method can be either continuous or batch. As the alkali catalyst, sodium hydroxide, potassium hydroxide, alkali metal alcoholate and the like are used. For example, the saponification conditions in the case of the batch type are as follows.
The copolymer solution concentration: 10 to 50%.
Reaction temperature: 30-60 ° C.
Amount of catalyst used: 0.02 to 0.6 equivalent (per vinyl acetate component).
Time: 1-6 hours.
Further, after the saponification step, an acid such as acetic acid is generally added to neutralize the remaining alkaline catalyst.

Granulation operations include, for example, (1) a method of extruding a solution containing EVOH into a low-temperature poor solvent to precipitate it, or a method of coagulating it and cutting it immediately after it or after further cooling and solidifying it, and (2) a solution of EVOH. A method of cutting the hydrous resin composition after obtaining an EVOH hydrous resin composition in advance by contacting the water with water vapor can be mentioned. The water content of EVOH obtained by these methods in the water-containing pellets is preferably 50 to 200 parts by mass, more preferably 70 to 150 parts by mass with respect to 100 parts by mass of EVOH.

The resin composition of the present invention can be obtained, for example, by drying the hydrous pellets of EVOH obtained in the above granulation step. The volatile content of the resin composition of the present invention is preferably less than 0.5% by mass, more preferably less than 0.3% by mass. Examples of the method for drying the water-containing pellets include static drying and fluid drying. These drying methods may be used alone or in combination of two or more. The drying treatment may be carried out 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. From the viewpoint of reducing deterioration of pellets due to oxygen during drying, it is also preferable to perform drying in a low oxygen concentration or anoxic state. The drying temperature is usually less than 150 ° C.

<Molded body>
The resin composition of the present invention can be processed into various molded bodies by various melt molding methods. The molded product thus obtained is also an aspect of the present invention. Examples of the molded body of the present invention include a molded body having a single-layer structure and a multilayer molded body having a layer made of the resin composition of the present invention and another layer. Examples of the molding method include extrusion molding, thermoforming, malformed molding, hollow molding, rotary molding, and injection molding. Suitable uses of the molded product of the present invention include films, sheets, containers, bottles, tanks, pipes, hoses and the like.

The following methods are exemplified as specific molding methods. Films, sheets, pipes, hoses, etc. can be obtained by extrusion molding. If it is in the shape of a container, it can be obtained by injection molding. Hollow containers such as bottles and tanks are obtained by hollow molding or rotary molding. Examples of the hollow molding include extrusion hollow molding in which a parison is obtained by extrusion molding and then blown to perform molding, and injection hollow molding in which a preform is molded by injection molding and then blown to perform molding. .. As a method for molding a flexible packaging material or a container, a method for obtaining a packaging material such as a multilayer film by extrusion molding and a method for thermoforming a multilayer sheet obtained by extrusion molding into a container-shaped packaging material are preferably used. ..

<Multi-layer molded body>
A multilayer molded product having at least one layer made of the resin composition of the present invention is also a preferred embodiment of the present invention. The multilayer molded product is formed by laminating a layer made of the resin composition of the present invention and another layer. As the layer other than the resin composition layer, a layer made of a resin other than EVOH (A) is preferable. Further, the multilayer molded product may further have a layer made of an adhesive resin. As the layer structure of the multilayer molded body, if the layer made of a resin other than EVOH (A) is the x layer, the layer made of the resin composition of the present invention is the y layer, and the adhesive resin layer is the z layer, for example, x / y, x / y / x, x / z / y, x / z / y / z / x, x / y / x / y / x, x / z / y / z / x / z / y / z / Examples include x and the like. When a plurality of x-layers, y-layers, and z-layers are provided, the types may be the same or different. Further, a layer using a recovery resin made of scrap such as trim generated during molding may be separately provided, or the recovery resin may be blended with any of the layers. The thickness and composition of each layer of the multilayer molded product are not particularly limited, but the thickness ratio of the y layer to the total layer thickness is usually preferably 2 to 20% from the viewpoint of moldability and cost.

As the resin used for the x-layer, a thermoplastic resin is preferable from the viewpoint of processability and the like. Examples of the thermoplastic resin include various polyolefins (polyethylene, polypropylene, poly1-butene, poly4-methyl-1-pentene, ethylene-propylene copolymer, and a copolymer of ethylene and α-olefin having 4 or more carbon atoms. , Polypolymer of polyolefin and maleic anhydride, ethylene-vinyl ester copolymer, ethylene-acrylic acid ester copolymer, or modified polyolefin obtained by graft-modifying these with unsaturated carboxylic acid or a derivative thereof), various polyamides (Nylon 6, Nylon 6.6, Nylon 6/66 copolymer, Nylon 11, Nylon 12, Polymethoxylylene adipamide, etc.), Various polyesters (Polyethylene terephthalate, Polybutylene terephthalate, Polyethylene naphthalate, etc.), Polychloride Examples thereof include vinyl, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate and modified polyvinyl alcohol resin. The thermoplastic resin layer may be unstretched, or may be uniaxially or biaxially stretched or rolled. Among them, polyolefin is preferable from the viewpoint of excellent moisture resistance, mechanical properties, economy, heat sealability and the like, and polyamide and polyester are preferable from the viewpoint of excellent mechanical properties, heat resistance and the like.

The adhesive resin used for the z-layer is not particularly limited as long as each layer can be bonded, and polyurethane-based or polyester-based one-component or two-component curable adhesives, carboxylic acid-modified polyolefins, and the like can be used. It is preferably used. As the carboxylic acid-modified polyolefin, for example, a polyolefin-based copolymer containing an unsaturated carboxylic acid or an anhydride thereof (maleic anhydride or the like) as a copolymerization component; or an unsaturated carboxylic acid or an anhydride thereof is grafted onto a polyolefin. Examples thereof include graft copolymers and the like.

Examples of the method for obtaining a multi-layer molded product containing a layer made of the resin composition of the present invention include co-extrusion molding, co-extrusion hollow molding, co-injection molding, extrusion laminating, co-extrusion laminating, dry laminating, solution coating and the like. .. The multilayer molded product obtained by such a method is secondarily heated after being reheated in a range below the melting point of EVOH (A) by a method such as vacuum or pressure-pneumatic deep drawing, blow molding, or press molding. It may be processed and molded to obtain a desired molded product. Further, the multilayer molded product is stretched by a roll stretching method, a pantograph stretching method, an inflation stretching method, or the like after reheating in a range below the melting point of EVOH (A) and then uniaxially or biaxially stretched. A molded product can also be obtained.

Since the resin composition of the present invention is excellent in melt moldability and appearance characteristics and can improve the water resistance of the molded product, an application in which the EVOH layer is in direct contact with water, particularly hot water, for a long period of time, for example, It can be preferably used for a water guide pipe in which EVOH is used as the innermost layer, food packaging in which EVOH is used as the outermost layer, and the like.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. In addition, each analysis and evaluation in this Example was performed by the following method.

(1) Ethylene unit content and saponification degree of EVOH (A) Tetramethylsilane (TMS) was used as an internal standard substance, and trifluoroacetic acid (TFA) was used as an additive using the pellets of the resin composition obtained in each Example and Comparative Example. ) Is dissolved in deuterated dimethylsulfoxide (DMSO-d ₆ ^{) and measured at 80 ° C. using 1} H-NMR (Nippon Denshi Co., Ltd. “GX-500”) at 500 MHz, ethylene unit, vinyl alcohol unit, vinyl. The ethylene unit content and saponification degree were determined from the peak intensity ratio of the ester units.

(2) Content of Boron Compound (B) and Metal Ion (C) 0.5 g of pellets of the resin composition obtained in each Example and Comparative Example was placed in a pressure vessel made of Teflon (registered trademark), and concentrated therein. 5 mL of nitrate was added and the mixture was decomposed at room temperature for 30 minutes. After the decomposition, the container was covered, and then further decomposed 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 measured with pure water. The content of boron compounds and metal ions in the dried pellets was quantified by measuring this solution with an ICP emission spectrophotometer "Avio500" manufactured by PerkinElmer. The content of the phosphoric acid compound can also be quantified by the same method.

(3) Content of carboxylic acid (D) 10 g of pellets of the resin composition obtained in each Example and Comparative Example and 50 mL of pure water were put into a 100 mL Erlenmeyer flask with a stopper, a cooling condenser was attached, and the temperature was 95 ° C. The mixture was stirred for 8 hours. After cooling the obtained extract to 20 ° C., the content of carboxylic acid (D) was quantified by titrating with a 0.02 mol / L sodium hydroxide aqueous solution using phenolphthalein as an indicator. When the resin composition contains an acid compound other than the carboxylic acid (D), the carboxylic acid (D) can be quantified by separately quantifying the amount and subtracting it from the quantified value by the above titration.

(4) Hue Evaluation Using a spectrophotometer "LabScan XE Sensor" manufactured by HunterLab, the YI (yellow index) value of the pellets of the resin composition obtained in each Example and Comparative Example was measured, and the following determination was made. Evaluated by criteria. The YI value is an index indicating the yellowness (yellowness) of the object, and the higher the YI value, the stronger the yellowness, while the lower the YI value, the weaker the yellowness and less coloring.
Judgment: Criteria A: YI is less than 15 B: YI is 15 or more and less than 25 C: YI is 25 or more

(5) Evaluation of film-forming property (neck-in) A single-layer film having a thickness of 20 μm was formed by using the pellets of the resin compositions obtained in each Example and Comparative Example under the extrusion conditions shown below. A layered film was obtained. The thickness of the monolayer film was adjusted by changing the take-up roll speed.
Extruder: Toyo Seiki Seisakusho Co., Ltd. Single-screw extruder Screw diameter: 20 mmφ (L / D = 20, compression ratio = 3.5, full flight type)
Dice width: 30 cm
Air gap: 1 cm
Screw rotation speed: 40 rpm
Pick-up roll speed: Approximately 3 m / min Extrusion temperature: C1 / C2 / C3 / D = 190/220/220/220 ° C.
Pick-up roll temperature: 80 ° C
The difference between the die width and the obtained single-layer film width was used as an index of film-forming property (neck-in), and was evaluated according to the following criteria. The smaller the value, the better the film-forming property, that is, the melt-molding property.
Judgment: Criteria A: Neck-in is less than 4 cm B: Neck-in is 4 cm or more and less than 6 cm C: Neck-in is 6 cm or more

(6) Evaluation of Appearance Characteristics (Fish Eyes) The result of visually confirming the single-layer film obtained in (5) above was defined as appearance characteristics (fish eyes) and evaluated according to the following criteria.
Judgment: Criteria A: Slightly small fish eyes are seen B: Slightly many fine fish eyes are seen on the entire surface of the film C: Many large and small fish eyes are seen on the entire surface of the film

(7) Evaluation of Water Resistance A single-layer film having a thickness of 100 μm was obtained in the same manner as in (5) above except that the screw rotation speed and the take-up roll speed were changed. The obtained single-layer film was immersed in pure water at 60 ° C. for 6 hours and then dried at 60 ° C. for 12 hours (hot water treatment). After adjusting the humidity of the hot water-treated film and the non-hot water-treated film at 23 ° C. and 50% RH for 24 hours or more, a sample having a length of 150 mm and a width of 15 mm was cut out along the extrusion direction. The tensile elongation of the sample was measured at a tensile speed of 500 mm / min using an Autograph DCS-50M type tensile tester manufactured by Shimadzu Corporation. The ratio of the tensile elongation of the hot water-treated film to the tensile elongation of the non-hot water-treated film was used as an index of water resistance and evaluated according to the following criteria.
Judgment: Criteria A: (tensile elongation of hot water treated film / tensile elongation of non-hot water treated film) is 0.85 or more B: (tensile elongation of hot water treated film / hot water treated) (Tensile elongation of untreated film) is 0.65 or more and less than 0.85 C: (Tensile elongation of hot water treated film / Tensile elongation of non-hot water treated film) is less than 0.65

(8) Adhesiveness between layers The pellets of the resin composition obtained in each Example and Comparative Example, linear low density polyethylene (Novatec LL-UF943 manufactured by Nippon Polyethylene Co., Ltd., hereinafter abbreviated as LLDPE) and adhesive resin (Dupont). Using the above-mentioned LLDPE-diluted 7% of Binel CXA417E10, hereinafter abbreviated as Ad), 3 types and 5 layers of multilayer film (LLDPE / Ad / EVOH / Ad / LLDPE = 50 μm) under the extrusion conditions shown below. / 10 μm / 10 μm / 10 μm / 50 μm) was formed into a film. The extruder, extrusion conditions, and die used were as follows.
Extruder:
EVOH: Single-screw extruder (Toyo Seiki Seisakusho Co., Ltd. ME type CO-EXT)
Diameter 20 mmφ, L / D20, full flight screw Supply part / compression part / measuring part / die = 175/210/220/220 ° C
LLDPE: Single-screw extruder (Plastic Engineering Laboratory Co., Ltd. GT-32-A)
Diameter 32 mmφ, L / D28, full flight screw Supply part / compression part / measuring part / die = 150/200/210/220 ° C
Ad: Single-screw extruder (Technobel Co., Ltd. SZW20GT-20MG-STD)
Diameter 20 mmφ, L / D20, full flight screw Supply part / compression part / measuring part / die = 150/200/220/220 ℃
Die: Coat hanger die for 300 mm width 3 types 5 layers (Plastic Engineering Research Institute)

The multilayer film obtained 15 minutes after the start of the film formation was adjusted to a humidity of 23 ° C. and a relative humidity of 50% RH for 24 hours or more, and then 150 mm in length along the extrusion direction. A sample having a width of 15 mm was cut out. The peel strength of the sample was measured in a T-type peeling mode at a tensile speed of 250 mm / min using an Autograph DCS-50M type tensile tester manufactured by Shimadzu Corporation, and evaluated according to the following criteria.
Judgment: Criteria A: 500 g / 15 mm or more B: 300 g / 15 mm or more, less than 500 g / 15 mm C: 300 g / less than 15 mm

[Example 1]
A water-containing EVOH pellet having an ethylene content of 32 mol%, a saponification degree of 99.95 mol%, a melting point of 182 ° C., and a volatile content of 110% by mass was added to an aqueous solution containing 1,4-butandiboronic acid (B1), sodium acetate, and acetic acid 25. It was immersed at ° C. for 6 hours and stirred. The concentrations of 1,4-butaniboronic acid, sodium acetate, and acetic acid in the aqueous solution in the dipping treatment were adjusted so that the contents in the obtained pellets were as shown in Table 1, respectively. 1,4-Butanjiboronic acid had a large adsorption ratio from the aqueous solution to the pellets, and the concentration of the aqueous solution could be reduced to about 1/10 of the usual concentration. After the immersion treatment, the aqueous solution and the hydrous pellet are separated by centrifugal dehydration to remove the liquid, and then placed in a hot air dryer and dried at 80 ° C. for 3 hours and then at 110 ° C. for 35 hours to obtain a volatile content of 0.3. The weight was reduced to% by mass or less, and the dried pellets of the present invention were obtained. The volatile content of the hydrous EVOH pellets and the dried pellets is measured by a halogen moisture content analyzer (“HX204” manufactured by METTLER TOLEDO) under the conditions of a drying temperature of 180 ° C., a drying time of 20 minutes, and a sample amount of 10 g. Measured by. The obtained pellets were subjected to the above-mentioned various analyzes and evaluations. The results are shown in Table 1.

[Examples 2 to 4, Comparative Examples 2 and 3]
Pellets were obtained in the same manner as in Example 1 except that the amount of 1,4-butandiboronic acid (B1) added was changed as shown in Table 1, and various analyzes and evaluations were performed. The results are shown in Table 1.

[Examples 5 and 6]
Pellets were obtained in the same manner as in Example 1 except that the amount of sodium acetate added was changed as shown in Table 1, and various analyzes and evaluations were performed. The results are shown in Table 1.

[Examples 7 and 8]
Pellets were obtained in the same manner as in Example 1 except that the amount of acetic acid added was changed as shown in Table 1, and various analyzes and evaluations were performed. The results are shown in Table 1.

[Example 9]
Pellets were obtained in the same manner as in Example 1 except that potassium acetate was used instead of sodium acetate and the addition amount was changed as shown in Table 1, and various analyzes and evaluations were performed. The results are shown in Table 1.

[Example 10]
Ethandiboronic acid (B2) was used instead of 1,4-butandiboronic acid (B1), and pellets were obtained in the same manner as in Example 1 except that the addition amount was changed as shown in Table 1, and various analyzes and evaluations were performed. rice field. The results are shown in Table 1.
[Example 11]
Pellets were prepared in the same manner as in Example 1 except that the boron compound (B3) represented by the following formula (II) was used instead of 1,4-butanediboronic acid (B1) and the addition amount was changed as shown in Table 1. Obtained, various analyzes and evaluations were performed. The results are shown in Table 1.

[Example 12]
Pellets were obtained in the same manner as in Example 1 except that 1,4-benzenediboronic acid (B4) was used instead of 1,4-butanediboronic acid (B1) and the amount added was changed as shown in Table 1. Various analyzes and evaluations were performed. The results are shown in Table 1.

[Example 13]
Pellets were obtained in the same manner as in Example 1 except that water-containing EVOH pellets having an ethylene content of 44 mol%, a saponification degree of 99.95 mol%, and a melting point of 165 ° C. were used, and various analyzes and evaluations were performed. The results are shown in Table 1. Compared with Example 1, the obtained monolayer film had a slightly higher oxygen permeability, but the coloring and fish eyes were particularly improved, and the appearance characteristics were good.

[Comparative Example 1]
Pellets were obtained in the same manner as in Example 1 except that 1,4-butandiboronic acid (B1) was not used, and various analyzes and evaluations were performed. The results are shown in Table 1.

[Comparative Example 4]
Boric acid was used instead of 1,4-butandiboronic acid (B1), and pellets were obtained in the same manner as in Example 1 except that the addition amount was changed as shown in Table 1, and various analyzes and evaluations were performed. The results are shown in Table 1.

Table 1 shows the composition and evaluation results of each resin composition of Examples and Comparative Examples.

Claims (9)

A resin composition containing an ethylene-vinyl alcohol copolymer (A) and at least one boron compound (B) selected from the group consisting of diboronic acid or a compound capable of converting to diboronic acid in the presence of water. ,
The ethylene-vinyl alcohol copolymer (A) has an ethylene unit content of 15 to 60 mol% and a saponification degree of 85 mol% or more.
A resin composition in which the content of the boron compound (B) is 30 to 300 ppm in terms of boron element. The resin composition according to claim 1, wherein the boron compound (B) is represented by the following formula (I).

[In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and X is a single bond or a bond consisting of one or more atoms. Represents a chain. ] The resin composition according to claim 2, wherein X is a bonded chain composed of one or more atoms, and the number of atoms in the shortest chain between boron atoms is 3 to 6. The resin composition according to claim 2 or 3, wherein X is a bonded chain composed of one or more atoms, and the shortest chain between boron atoms is composed of only carbon atoms. The resin composition according to any one of claims 2 to 4, wherein X is a bond chain consisting of one or more atoms, and the shortest chain between boron atoms has only a single bond. The resin composition according to any one of claims 1 to 5, further containing 100 to 400 ppm of an alkali metal ion (C). The resin composition according to any one of claims 1 to 6, further containing 50 to 400 ppm of carboxylic acid (D). A molded product containing the resin composition according to any one of claims 1 to 7. A multilayer molded product having at least one layer made of the resin composition according to any one of claims 1 to 7.