TW201934641A - Resin composition containing ethylene-vinyl alcohol copolymer, shaped article and packaging material - Google Patents

Abstract

A resin composition which comprises an ethylene/vinyl alcohol copolymer (A) and a compound (B) represented by formula (X), wherein the ethylene/vinyl alcohol copolymer (A) has an ethylene unit content of 15-60 mol% and a degree of saponification of 85 mol% or higher and the compound (B) is contained in an amount of 5-100 ppm. The resin composition is inhibited from scorching even in repetitions of a melt-molding process and is highly inhibited from coloring under basic conditions. (In formula (X), Z1 and Z2 are each independently a hydrogen atom or a methyl group).

Description

Resin composition, formed body and packaging material containing ethylene-vinyl alcohol copolymer

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

Ethylene-vinyl alcohol copolymer (hereinafter referred to as "EVOH") has excellent gas barrier properties and melt moldability, and is formed into films, sheets, pipes, and tubes (by various melt forming methods). Tubes, bottles, etc. are widely used as packaging materials in the food and industrial fields where gas barrier properties are required. However, when the melt molding of EVOH is performed continuously for a long time, there is a problem in that the scorch occurs in the barrel, screw, and die of the extruder. The occurrence of such scorch causes not only instability of the melt molding process, but also deterioration in the appearance, mechanical properties, and other qualities of the obtained molded body. Therefore, it is necessary to periodically stop the operation and perform disassembly and cleaning of the extruder. Therefore, an increase in manufacturing costs or material loss caused by the stop and restart of the extruder also occurs. Based on this, improvement of the scorch problem is required.

In order to improve the above problems, various resin compositions containing EVOH have been developed. For example, Patent Document 1 describes a resin composition containing EVOH, a boron compound, sodium acetate, and magnesium acetate. In addition, it is described that the resin composition improves long-term operability during melt molding. Patent Document 2 describes a resin composition containing EVOH and a conjugated polyene compound. In addition, it is described that the occurrence of gels or pits caused by melt molding is suppressed by the resin composition. Patent Document 3 describes a resin composition containing EVOH, a specific carboxylic acid metal salt, and a hindered phenol-based antioxidant. Furthermore, it is described that this resin composition is excellent in thermal stability and suppresses the formation of oxidative gels at high temperatures. Patent Document 4 describes a resin composition containing EVOH and a specific unsaturated aldehyde. In addition, it is described that the resin composition suppresses the occurrence of defects such as fish eyes and gels caused by melt molding, and improves long-term operability during melt molding.
[Prior technical literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 11-60874
[Patent Document 2] Japanese Unexamined Patent Publication No. 9-71620
[Patent Document 3] Japanese Patent Laid-Open No. 4-227744
[Patent Document 4] International Publication No. 2013/146961

[Problems to be Solved by the Invention]

On the other hand, the trimming or burrs that occur during the manufacture of a melt-molded article are widely recovered, and then pulverized and melted for use. The inventors have found that the above-mentioned EVOH-containing resin composition has been subjected to thermal history many times Sometimes, the problem of scorching occurs. In addition, in recent years, the contents of packages packed with packaging materials have become more and more diverse. As for packaging materials, stability to acidic substances or alkaline substances is particularly required. However, the present inventors have found that the above-mentioned EVOH-containing resin composition has a problem of being easily colored under alkaline conditions, especially under high temperature conditions.

The present invention was completed based on the above-mentioned circumstances, and an object thereof is to obtain an EVOH which suppresses the occurrence of scorch even in a repeated melt molding process and is excellent in color resistance under alkaline conditions.

[Means for solving problems]

The present inventors conducted an intensive review in order to solve the above problems, and as a result, it was found that by including a compound having a specific structure in a resin composition mainly composed of EVOH, the occurrence of scorch can be suppressed even in a repeated melt molding process . In addition, by controlling the content of the compound in an appropriate range, the occurrence of scorch is suppressed, and the coloring resistance under alkaline conditions is also improved, which has reached the present invention. The above-mentioned problems are solved by the following inventions.

(1) A resin composition comprising a resin composition comprising an ethylene-vinyl alcohol copolymer (A) and a compound (B) represented by the following formula (X), an ethylene-vinyl alcohol copolymer (A) The content of the ethylene unit is 15 to 60 mol%, the degree of saponification is 85 mol% or more, and the content of the compound (B) is 5 to 100 ppm.

(In formula (X), Z ¹ and Z ² are each independently a hydrogen atom or a methyl group).
(2) The resin composition according to (1), wherein the pH of the extract obtained by extracting 10 g of the resin composition with 50 ml of pure water at 95 ° C for 8 hours is in the range of 4.0 to 5.5 at 20 ° C.
(3) The resin composition according to (1) or (2), further containing 100 to 400 ppm of metal ions (C).
(4) The resin composition according to any one of (1) to (3), which further contains 50 to 400 ppm of a carboxylic acid (D) having a pKa in the range of 3.5 to 5.5.
However, the content of the carboxylic acid (D) was obtained by extracting 10 g of the resin composition with 50 ml of pure water, 95 ° C., and 8 hours, and then titrating the obtained extract to determine the content.
(5) A molded article comprising the resin composition according to any one of (1) to (4).
(6) The molded article according to (5), which is a multilayer structure including a layer formed of the resin composition.
(7) A packaging material having a molded body according to (5) or (6).

[Effect of the invention]

The resin composition of the present invention suppresses the occurrence of scorch even in repeated melt molding processes, and is excellent in color resistance under alkaline conditions. In addition, since the resin composition of the present invention can be provided economically, it can be applied to various packaging materials.

[Mode for Carrying Out the Invention]

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto. In addition, the exemplified materials may be used alone or in combination of two or more.

＜ Resin composition ＞
The resin composition of the present invention contains EVOH (A) and the compound (B) represented by the following formula (X), and may contain other additives as necessary.

(In formula (X), Z ¹ and Z ² are each independently a hydrogen atom or a methyl group).

The pH of the extract solution obtained by extracting 10 g of the resin composition of the present invention with 50 ml of pure water at 95 ° C. for 8 hours is preferably in the range of 4.0 to 5.5. Since the pH of the extraction liquid is in this range, the pH buffering ability of the resin composition is increased, and the melt formability or the coloring caused by an acidic substance or an alkaline substance is further improved. The pH of the extraction liquid can be controlled by changing the type or content of a metal ion (C), a carboxylic acid (D), or the like described later. Hereinafter, each component is demonstrated.

＜ EVOH (A) ＞
EVOH (A) is the main component of the resin composition of the present invention. EVOH (A) is a copolymer having ethylene units and vinyl alcohol units as main structural units. EVOH (A) is usually obtained by polymerizing ethylene and vinyl ester and saponifying the obtained ethylene-vinyl ester copolymer.

The content of ethylene units (that is, the ratio of the number of ethylene units to the total number of monomer units in EVOH (A)) of EVOH (A) must be in the range of 15 to 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%, and more preferably 50 mol%. When the ethylene unit content of EVOH (A) is less than 15 mol%, the gas barrier properties under high humidity are reduced, and the melt formability is also deteriorated. On the contrary, if the content of ethylene units of EVOH (A) exceeds 60 mol%, sufficient gas barrier properties cannot be obtained.

The degree of saponification 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)) must be 85 mol% or more. The lower limit of the degree of saponification of EVOH (A) is preferably 95 mol%, more preferably 99 mol%. On the other hand, the upper limit of the degree of saponification of EVOH (A) is preferably 100 mol%, and more preferably 99.99 mol%. When the degree of saponification of EVOH (A) is less than 85 mol%, sufficient gas barrier properties may not be obtained, and further, thermal stability may become insufficient.

When EVOH (A) is composed of a mixture of two or more types of EVOH having different ethylene unit contents, the average value calculated from the mixing mass ratio is taken as the ethylene unit content. At this time, the difference between the ethylene unit contents of the EVOH whose ethylene unit content is farthest away is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less. Similarly, when EVOH (A) is a mixture of two or more types of EVOH having different saponification degrees, the average value calculated from the mixing mass ratio is taken as the saponification degree of the mixture. At this time, the difference between the saponification degree of the EVOH farthest away is preferably 7% or less, and more preferably 5% or less. When it is desired to obtain a resin composition having a balance between thermoformability and gas barrier properties at a higher level, it is preferred that the blending mass ratio (A-1 / A-2) be 60/40 to 90/10. EVOH (A-1) with a mixed ethylene unit content of 24 mol% or more and less than 34 mol%, a saponification degree of 99 mol% or more, and an ethylene unit content of 34 mol% or more and less than 50 mol EVOH (A-2) with a saponification degree of 99 mol% or more is used as EVOH (A). The ethylene unit content and saponification degree of EVOH (A) can be obtained by a nuclear magnetic resonance (NMR) method.

The lower limit of the melt flow rate of EVOH (A) in accordance with JIS K 7210: 2014 (hereinafter also referred to as "MFR"; temperature 210 ° C, load 2160g) is usually 0.1g / 10 minutes, and the upper limit is usually 50g / 10 minutes. .

The EVOH (A) may contain, as a copolymerization unit, a monomer unit other than an ethylene unit, a vinyl alcohol unit, and a vinyl ester unit, so long as the object of the present invention is not hindered. Examples of the monomers include α-olefins such as propylene, 1-butene, isobutylene, 4-methyl-1-pentene, 1-hexene, and 1-octene; Unsaturated carboxylic acids such as acrylic acid, acrylic acid, maleic acid, etc., their salts, their partial or complete esters, their nitriles, their amides, their anhydrides; vinyltrimethoxysilane, vinyltriethoxysilane, ethylene Vinylsilane compounds such as tris (β-methoxyethoxy) silane, g-methacryloxypropyltrimethoxysilane, etc .; unsaturated sulfonic acids or salts thereof; unsaturated thiols; Vinyl pyrrolidones. The content of monomer units other than ethylene units, vinyl alcohol units and vinyl ester units in EVOH (A) is usually 5 mol% or less, preferably 2 mol% or less, and more preferably 1 mol% or less.

The content of EVOH (A) in the resin composition of the present invention is generally 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. By setting the content of EVOH (A) within this range, the melt-moldability of the obtained resin composition is improved, and the molded body obtained therefrom is also excellent in gas barrier properties, oil resistance, and the like.

<Compound (B)>
The resin composition of the present invention contains a compound (B) represented by the following formula (X). The resin composition of the present invention contains a specified amount of the compound (B) and suppresses the occurrence of scorch even in a repeated melt molding process. Although the reason for the suppression of the scorch is not clear, it is judged that the compound (B) acts as a lubricant. When the resin composition of the present invention is melt-molded, the friction between the resin composition and the surface of the screw or the die is reduced, and deterioration Resin adhesion and local shear heating. In addition, the resin composition of the present invention also improves color resistance under alkaline conditions. Although the reason for improving the coloring resistance is not clear, it is judged that the adjacent nitrile group in the compound (B) interacts with the alkali component.

(In formula (X), Z ¹ and Z ² are each independently a hydrogen atom or a methyl group).

The content of the compound (B) in the resin composition must be in a range of 5 to 100 ppm. The lower limit of the content of the compound (B) is preferably 10 ppm. On the other hand, the upper limit of the content of the compound (B) is preferably 60 ppm. When the content of the compound (B) is less than 5 ppm, the occurrence of scorch is not sufficiently suppressed in the repeated melt molding process, and the long-term operability becomes insufficient. On the other hand, when the content of the compound (B) exceeds 100 ppm, the coloring resistance under alkaline conditions becomes insufficient, which may cause a problem. The content of the compound (B) in the resin composition can be determined by a nuclear magnetic resonance (NMR) method.

＜ Metal ion (C) ＞
The resin composition of the present invention preferably further contains a metal ion (C). Since the resin composition of the present invention contains a metal ion (C), it has excellent layer indirect adhesion when it is formed into a multilayer structure. Although the reason why the layer indirect contact is increased by the metal ion (C) is unknown, one reason is judged that when the layer adjacent to EVOH (A) has a molecule having a functional group capable of reacting with the hydroxyl group of EVOH (A) This bond formation reaction is accelerated by the metal ion (C). In addition, by controlling the content ratio of the metal ion (C) and the carboxylic acid (D) to be described later, it is possible to further improve the melt moldability or color resistance of the obtained resin composition.

The lower limit of the content of the metal ion (C) in the resin composition is preferably 100 ppm, and more preferably 150 ppm. On the other hand, the upper limit of the content of the metal ion (C) in the resin composition is preferably 400 ppm, and more preferably 350 ppm. When the content of the metal ion (C) in the resin composition is less than 100 ppm, the indirect adhesion of the obtained multilayer structure may be insufficient. On the other hand, when the content of the metal ion (C) in the resin composition exceeds 400 ppm, the coloring resistance may be insufficient.

Examples of the metal ion (C) include alkali metal ions, alkaline earth metal ions, and other transition metal ions. These systems may be used alone or in combination of two or more. Among them, the metal ion (C) preferably contains an alkali metal ion, and more preferably consists of only an alkali metal ion. Since the metal ion (C) is composed of only alkali metal ions, not only the simplification of the manufacturing method becomes possible, but also the layer indirect adhesion of the multilayer structure can be further improved.

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

Examples of the alkali metal salt that imparts an alkali metal ion include aliphatic carboxylic acid salts, aromatic carboxylic acid salts, carbonates, hydrochlorides, nitrates, sulfates, and phosphoric acids of alkali metals such as lithium, sodium, and potassium. Salt and metal complexes. Among them, sodium acetate, potassium acetate, sodium phosphate, and potassium phosphate are more preferable from the viewpoint of easy availability.

It is sometimes preferable that the metal ion (C) contains an alkaline-earth metal ion. Since the metal ion (C) contains alkaline earth metal ions, the thermal degradation of EVOH (A) at the time of reutilization trimming is suppressed, and the occurrence of gelling and pitting of the molded body may be suppressed.

Examples of the alkaline earth metal ion include ions of beryllium, magnesium, calcium, strontium, and barium. From the viewpoint of industrial availability, ions of magnesium or calcium are preferred.

Examples of the alkaline earth metal salt that imparts alkaline earth metal ions include aliphatic carboxylic acid salts, aromatic carboxylic acid salts, carbonates, hydrochlorides, nitrates, sulfates of alkaline earth metals such as magnesium and calcium, Phosphate, metal complex.

<Carboxylic acid (D)>
The resin composition of the present invention preferably further contains a carboxylic acid (D) having a pKa in the range of 3.5 to 5.5. By containing the carboxylic acid (D), the resin composition of the present invention can further improve the melt moldability of the resin composition or the color resistance at high temperatures. In particular, since the pKa of the carboxylic acid (D) is in the range of 3.5 to 5.5, the pH buffering ability of the obtained resin composition is increased, and the coloring caused by an acidic substance or an alkaline substance may be further improved.

The lower limit of the content of the carboxylic acid (D) in the resin composition is preferably 50 ppm, and more preferably 100 ppm. On the other hand, the upper limit of the content of the carboxylic acid (D) in the resin composition is preferably 400 ppm, and more preferably 350 ppm. When the content of the carboxylic acid (D) in the resin composition is less than 50 ppm, the coloring resistance at high temperatures may be insufficient. On the other hand, when the content of the carboxylic acid (D) in the resin composition exceeds 400 ppm, melt moldability may become insufficient, or odor may become a problem. The content of the carboxylic acid (D) was obtained by extracting 10 g of the resin composition with 50 ml of pure water at 95 ° C. for 8 hours, and then titrating the obtained extract solution and measuring it. Here, as the content of the carboxylic acid (D) in the resin composition, the carboxylic acid existing as a salt in the extraction solution is not considered.

Examples of the carboxylic acid (D) include a monocarboxylic acid and a polycarboxylic acid, and these systems may be used alone or in combination of two or more. When the said resin composition contains both a monocarboxylic acid and a polycarboxylic acid as a carboxylic acid (D), melt-formability or the coloring resistance at high temperature may be improved significantly. The polycarboxylic acid may have three or more carboxyl groups. In this case, the coloring resistance of the resin composition of the present invention may be more effectively improved.

The so-called monocarboxylic acid is a compound having one carboxyl group in the molecule. The monocarboxylic acid having a pKa in the range of 3.5 to 5.5 is not particularly limited, and examples thereof include formic acid (pKa = 3.77), acetic acid (pKa = 4.76), propionic acid (pKa = 4.85), and butyric acid (pKa = 4.82), hexanoic acid (pKa = 4.88), capric acid (pKa = 4.90), lactic acid (pKa = 3.86), acrylic acid (pKa = 4.25), methacrylic acid (pKa = 4.65), benzoic acid (pKa = 4.20), 2-naphthoic acid (pKa = 4.17) and the like. These carboxylic acids may further have a substituent of a hydroxyl group, an amine group, or a halogen atom as long as the pKa is in the range of 3.5 to 5.5. Among these, acetic acid is preferred from the viewpoints of high safety and easy handling.

The so-called polycarboxylic acid is a compound having two or more carboxyl groups in the molecule. In this case, the pKa of at least one carboxyl group may be in the range of 3.5 to 5.5. Examples thereof include oxalic acid (pKa ₂ = 4.27), succinic acid (pKa ₁ = 4.20), fumaric acid (pKa ₂ = 4.44), Malic acid (pKa ₂ = 5.13), glutaric acid (pKa ₁ = 4.30, pKa ₂ = 5.40), adipic acid (pKa ₁ = 4.43, pKa ₂ = 5.41), pimelic acid (pKa ₁ = 4.71), Phthalic acid (pKa ₂ = 5.41), isophthalic acid (pKa ₂ = 4.46), terephthalic acid (pKa ₁ = 3.51, pKa ₂ = 4.82), citric acid (pKa ₂ = 4.75), tartaric acid (pKa ₂ = 4.40), glutamic acid (pKa ₂ = 4.07), aspartic acid (pKa = 3.90), and the like.

＜ Other ingredients ＞
As long as the effect of the present invention is not impaired, the resin composition of the present invention may contain other components. Examples of other components include phosphoric acid compounds, boron compounds, thermoplastic resins other than EVOH (A), crosslinking agents, desiccants, oxidation accelerators, antioxidants, oxygen absorbers, plasticizers, lubricants, and thermal stabilizers. (Melting stabilizer), processing aids, surfactants, deodorants, antistatic agents, ultraviolet absorbers, anti-fog agents, flame retardants, pigments, dyes, fillers, fillers, reinforcing agents for various fibers, etc. .

<Phosphate compound>
When a phosphoric acid compound is contained, the lower limit of the content in the resin composition is preferably 1 ppm in terms of phosphate radical conversion, and more preferably 10 ppm. On the other hand, the upper limit of the content of the phosphoric acid compound in the resin composition is preferably 200 ppm in terms of phosphate radical conversion, and more preferably 100 ppm. By containing a phosphoric acid compound in this range, the thermal stability of the said resin composition can be improved. In particular, it is possible to suppress the occurrence of gel-like pits or coloring when melt molding is performed for a long time.

Examples of the phosphoric acid compound include various acids such as phosphoric acid and phosphorous acid, or salts thereof. The phosphate may be any of the first phosphate, the second phosphate, and the third phosphate. The cationic species of the phosphate are not particularly limited, but the cationic species are preferably alkali metals and alkaline earth metals. Among these, as said phosphate compound, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate are preferable.

<Boron compound>
When a boron compound is contained, the lower limit of its content in the resin composition is preferably 5 ppm in terms of boron, and more preferably 10 ppm. On the other hand, the upper limit of the content in the resin composition is preferably 1000 ppm in terms of boron conversion, and more preferably 500 ppm. When the boron compound is contained within this range, the thermal stability at the time of melt molding of the resin composition is increased, and the occurrence of gel-like pits may be suppressed. In addition, the mechanical properties of the obtained formed body may be increased. It is speculated that these effects are due to the chelation interaction between EVOH (A) and the boron compound.

Examples of the boron compound include boric acid, borate, borate, and boron hydride. Specifically, examples of the boric acid include orthoboric acid (H ₃ BO ₃ ), metaboric acid, and tetraboric acid. Examples of the borate include trimethyl borate and triethyl borate. Examples of the borate include: Examples thereof include alkali metal salts or alkaline earth metal salts of boric acid, and borax. Among these, orthoboric acid is preferred.

Examples of the thermoplastic resin other than EVOH (A) include various polyolefins (polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, ethylene-propylene copolymer, ethylene and carbon Copolymers of a-olefins of 4 or more, copolymers of polyolefins and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylate copolymers, or these are grafted with unsaturated carboxylic acids or their derivatives Modified polyolefins, etc.), various polyamides (nylon 6, nylon 6,6, nylon 6/66 copolymer, nylon 11, nylon 12, polym-xylylene adipamide, etc.), various polyesters (Polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyamine Formates, polycarbonates, polyacetals, polyacrylates, and modified polyvinyl alcohol resins. The content of the thermoplastic resin in the resin composition is usually less than 30% by mass, preferably less than 20% by mass, and more preferably less than 10% by mass.

＜ Manufacturing method of resin composition ＞
As the method for producing the resin composition of the present invention, there is no method as long as the compound (B) can be uniformly mixed in the EVOH (A) so that the resin composition finally obtained contains 5 to 100 ppm of the compound (B). Special limitation. As a preferable manufacturing method, a method including the following steps: copolymerization step (I) of copolymerizing ethylene and a vinyl ester to obtain an ethylene-vinyl ester copolymer, and saponifying the ethylene-vinyl ester copolymer to Saponification step (II) to obtain EVOH (A), granulation step (III) to obtain aqueous particles of EVOH (A) by a granulation operation, and drying of the aqueous particles to obtain a resin composition containing EVOH (A) The drying step (IV), after the copolymerization step (I), includes a mixing step of mixing the ethylene-vinyl ester copolymer or EVOH (A) and the compound (B). At this time, by adjusting the amount of the compound (B) added in the mixing step, the content of the compound (B) in the finally obtained resin composition can be easily controlled. Further, if necessary, a washing operation for removing the compound (B) may be performed. The adjustment of the content of the compound (B) caused by the washing operation can be performed by adjusting the paste concentration and temperature when the paste of EVOH (A) is precipitated in the granulation step (III), the composition and temperature of the coagulation bath, or It is appropriate to adjust the type, temperature, immersion time and number of times of the solution in which the EVOH (A) aqueous particles are impregnated in the subsequent steps. In addition, by adding a weak solvent little by little to a solution in which the dried resin composition is dissolved in a good solvent, the resin composition is precipitated, precipitated, and recovered to recover the compound (B) in the resin composition. Reducing the content to a necessary amount is also an effective method for adjusting the content of the compound (B).

As a mixing step of adding the compound (B) to the EVOH (A) after the copolymerization step (I), for example, a method of adding the compound (B) during or after the saponification reaction, and making the EVOH (A) The method of impregnating the compound (B) in the strands precipitated in the step of paste precipitation, the method of cutting the precipitated strands and impregnating the compound (B), and drying the dried EVOH (A) The method of adding the compound (B) to the re-dissolved raw materials, the method of melt-kneading the two components blended with EVOH (A) and the compound (B), and compound (B) from the middle of the extruder. ) Feed the molten material of EVOH (A) as a powder, solution or dispersion, and melt-knead it. Compound (B) is blended into a part of EVOH (A) at a high concentration to make a granulated product. Masterbatch, a method of dry-blending the masterbatch with EVOH (A), and melt-kneading.

Among these, from the viewpoint of being able to uniformly disperse a small amount of the compound (B) in the EVOH (A), as a mixing step of adding the compound (B) to the EVOH (A), it is preferable to perform saponification. A method of adding compound (B) to EVOH (A) after the reaction. Specifically, a solution of EVOH (A) obtained in the saponification step is dissolved in a good solvent such as a water / methanol mixed solvent, compound (B) is added, and the mixed solution is extruded from a nozzle or the like into a weak solvent. After the precipitated strands are cut to obtain water-containing particles, the particles are washed, if necessary, and then dried to obtain particles of a resin composition in which EVOH (A) is uniformly mixed with the compound (B).

As a method for making the resin composition of the present invention contain components other than the compound (B), for example, particles of the resin composition in which the compound (B) is mixed with EVOH (A) are mixed with each component. The method of melt-kneading is a method of mixing the components with the EVOH (A) and the compound (B) while preparing the particles of the resin composition, and immersing the particles of the resin composition in a solution containing the components Methods, etc. In this case, as the particles of the resin composition, both water-containing particles and dry particles can be used.

<Copolymerization step (I)>
The copolymerization step is a step of adding a polymerization inhibitor, if necessary, and then removing unreacted ethylene and unreacted vinyl ester to obtain an ethylene-vinyl ester copolymer solution, in addition to the copolymerization step of ethylene and vinyl ester. Examples of the copolymerization method of ethylene and vinyl ester include well-known methods such as solution polymerization, suspension polymerization, emulsion polymerization, and overall polymerization. As a representative vinyl ester used in the polymerization, vinyl acetate may be mentioned, but other aliphatic vinyl esters such as vinyl propionate or trimethyl vinyl acetate may be used. In addition, a small amount of copolymerizable monomers can be copolymerized. The polymerization temperature is preferably 20 to 90 ° C, and more preferably 40 to 70 ° C. The polymerization time is preferably 2 to 15 hours, and more preferably 3 to 11 hours. The polymerization rate is preferably 10 to 90%, and more preferably 30 to 80%, relative to the vinyl ester added. The content of the resin in the solution after the polymerization is preferably 5 to 85% by mass, and more preferably 20 to 70% by mass.

The initiator used in the copolymerization step (I) is not particularly limited, but an azonitrile-based polymerization initiator is preferably used. The molecular skeleton of the azonitrile-based polymerization initiator can be used to control the rate of radical generation or solubility in solvents. In addition, azonitrile-based polymerization initiators are less prone to decomposition due to metal contact and the like, and are less susceptible to the influence of solvents during decomposition. Therefore, by using an azonitrile-based polymerization initiator, the polymerization step can be performed safely and stably. Examples of the azonitrile-based polymerization initiator include 4,4'-azobis (4-cyanovaleric acid), 1,1'-azobis (cyclohexane-1-carbonitrile), and 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile) , 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile). Among these, 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-coupling can be more suitably used in view of rapid polymerization at relatively low temperatures. Nitrobis (4-methoxy-2,4-dimethylvaleronitrile).

<Saponification step (II)>
Next, an alkali catalyst was added to the ethylene-vinyl ester copolymer solution, and the copolymer in the solution was saponified to obtain EVOH (A). As the saponification method, either a continuous method or a batch method can be used. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, and an alkali metal alkoxide. After the saponification step, an acid such as acetic acid is generally added to neutralize the remaining alkali catalyst.

<Granulation step (III)>
Examples of the granulation operation include (1) extruding a solution of EVOH (A) into a low-temperature weak solvent to precipitate or solidify it, and then cutting it immediately after it is cooled or solidified. Method (2) A method of contacting a solution of EVOH (A) with water vapor to obtain an aqueous resin composition of EVOH (A) in advance, and then cutting the aqueous resin composition. The water content of the water-containing particles of EVOH (A) obtained by such methods 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 (A).

<Drying step (IV)>
It is preferred that the water-containing particles of EVOH (A) obtained in the granulation step be dried to be dried particles of EVOH (A). The moisture content in the dried particles is to prevent troubles during molding, such as generation of voids, and is preferably 1.0 part by mass or less, more preferably 0.5 part by mass or less, and even more preferably 0.3 part by mass relative to 100 parts by mass of EVOH (A). Mass parts or less. Examples of the method for drying the water-containing particles include stationary drying or flow drying. These drying methods can be used alone or in combination. The drying process can be performed by either a continuous method or a batch method. When a plurality of drying methods are combined, the continuous method and the batch method can be freely selected for each drying method. Drying at a low oxygen concentration or an anaerobic state is also preferable in that the deterioration of the resin composition due to oxygen during drying can be reduced.

<Formed body>
A molding system comprising the resin composition of the present invention is a suitable embodiment of the present invention. The resin composition of the present invention may be a molded body having a single-layer structure, or a molded body having a multilayer structure of a layer formed of the resin composition and other layers, that is, a multilayer structure. Examples of the molding method include extrusion molding, thermoforming, heteroforming, hollow molding, rotary molding, and injection molding. The use of the formed article of the present invention is various, and examples thereof include films, sheets, containers, bottles, buckets, pipes, hoses, and the like.

As a specific molding method, the following methods can be exemplified. If it is a film, sheet, tube, hose, etc., it can be obtained by extrusion. If it is a container shape, it can be obtained by injection molding. If it is a hollow container such as a bottle or bucket, it can be obtained by hollow forming or rotary forming. Examples of the hollow molding include extrusion hollow molding in which a parison is obtained by extrusion molding, and then blow molding, and injection molding to form a preform, and blow molding and injection molding. Hollow forming. As a method for forming a flexible packaging material or a container, a method of obtaining a packaging material such as a multilayer film by extrusion molding is preferably used. The multilayer sheet obtained by extrusion molding is thermoformed into a container-like packaging material. method.

＜ Multilayer Structures ＞
A layer structure system including a layer made of the resin composition of the present invention is a more suitable embodiment of the present invention. In this multilayer structure system, a layer made of the resin composition of the present invention is laminated with other layers. As a layer other than the said resin composition layer, the layer which consists of resin other than EVOH (A) is preferable. The multilayer structure may further include a layer made of an adhesive resin. As the layer structure of this multilayer structure, if a layer made of a resin other than EVOH (A) is taken as the x layer, the resin composition layer of the present invention is taken as the y layer, and the adhesive resin layer is taken as 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 / x and so on. When plural x-layers, y-layers, and z-layers are provided, the types may be the same or different. Further, a layer made of a recycled resin made of waste such as trimming that occurs during molding may be separately provided, or the recycled resin may be blended in a layer made of a resin other than EVOH (A). The thickness or structure of each layer of the multilayer structure is not particularly limited, but from the viewpoints of moldability and cost, the thickness ratio of the y layer to the thickness of the entire layer is usually 2 to 20%.

As the resin used for the x-layer, a thermoplastic resin is preferred from the viewpoint of processability and the like. Examples of the thermoplastic resin include various polyolefins (polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, an ethylene-propylene copolymer, ethylene, and a- Copolymers of olefins, copolymers of polyolefins and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylate copolymers, or these modified polymers grafted with unsaturated carboxylic acids or their derivatives Olefins, etc.), various polyamides (nylon 6, nylon 6,6, nylon 6/66 copolymer, nylon 11, nylon 12, polym-xylylene diamine, etc.), various polyesters (poly terephthalic acid (Ethylene glycol, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate Ester, polyacetal, polyacrylate and modified polyvinyl alcohol resin. Such a thermoplastic resin layer may be unstretched, or may be uniaxially or biaxially stretched or calendered. Among these thermoplastic resins, polyolefins are preferred in terms of moisture resistance, mechanical properties, economy, heat sealability, etc. Polyamide or polyester are preferred in terms of mechanical properties, heat resistance, etc. More appropriate.

The adhesive resin used for the z layer is not particularly limited as long as it is capable of adhering the respective layers. Polyurethane-based or polyester-based one- or two-liquid type curable adhesives, Carboxylic acid modified polyolefins, etc. The carboxylic acid modified polyolefin is a polyolefin copolymer containing an unsaturated carboxylic acid or an anhydride (maleic anhydride, etc.) as a copolymerization component; or a copolymer obtained by grafting an unsaturated carboxylic acid or an anhydride thereof to a polyolefin Graft copolymer.

Examples of a method for obtaining the multilayer structure of the present invention include coextrusion molding, coextrusion hollow molding, co-injection molding, extrusion lamination, coextrusion lamination, dry lamination, and solution coating. Furthermore, the multilayer structure obtained by such a method is further heated in a range below the melting point of EVOH (A) by a method such as further vacuum or pressure deep drawing, blow molding, and pressure molding. It can be used as a shaped body by secondary processing. In addition, for multilayer structures, uniaxial or biaxial stretching may be performed after reheating in a range below the melting point of EVOH (A) by methods such as roll stretching, scaling stretching, and inflation stretching. An extended multilayer structure was obtained.

The resin composition of the present invention suppresses the occurrence of scorch even in repeated melt molding processes, and is excellent in color resistance under alkaline conditions. The resin composition of the present invention can be provided economically. Therefore, the resin composition of the present invention can be formed into a film, a sheet, a container, or the like, and is suitable as various packaging materials. A packaging material having a molded article containing the resin composition of the present invention is a suitable embodiment of the present invention.

[Example]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited at all by 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) Dissolve the dried granules in heavy dimethylsulfinium (DMSO-d) containing tetramethylsilane (TMS) as an internal standard substance and trifluoroacetic acid (TFA) as an additive. ₆ ) using ¹ H-NMR at 500 MHz (manufactured by Japan Electronics Co., Ltd .: "GX-500"), measured at 80 ° C, and determined from the peak intensity ratios of ethylene units, vinyl alcohol units, and vinyl ester units. Ethylene unit content and saponification degree.

(2) Content of compound (B) The dried particles were dissolved in DMSO-d ₆ containing TMS as an internal standard substance, and ¹ H-NMR (manufactured by Japan Electronics Co., Ltd .: "GX-500") was used at 500 MHz. Measured at 45 ° C, from the ratio of the peak intensities of the ethylene units, vinyl alcohol units, and vinyl ester units to the peak intensities of the methoxymethyl hydrogen or ethoxy methylene hydrogen of the compound (B). The content of the compound (B) is shown. The peaks of the methoxymethyl hydrogen or ethoxy methylene hydrogen contained in the compound (B) were detected in the vicinity of 3.13 ppm.

(3) Content of metal ion (C) 0.5 g of dry granules were placed in a pressure vessel made of Teflon (registered trademark), 5 mL of concentrated nitric acid was added thereto, and the mixture was decomposed at room temperature for 30 minutes. After decomposition, the lid was placed in the aforementioned container, and then heated at 150 ° C. for 10 minutes by a wet decomposition device, and then heated at 180 ° C. for 5 minutes to further decompose, and then cooled to room temperature. Into a 50mL volumetric flask, adjust the volume with pure water. This solution was measured by an ICP emission spectrophotometer, and the content of each metal ion in the dried particles was quantified. The content of the phosphoric acid compound and the boron compound can also be quantified in the same manner.

(4) Content of carboxylic acid (D) Put 10 g of dry granules and 50 mL of pure water into a 100 mL Erlenmeyer flask with a stopper, install a cooling condenser, and stir at 95 ° C. for 8 hours. After the obtained extract was cooled to 20 ° C, phenolphthalein was used as an indicator, and titration was performed with an aqueous sodium hydroxide solution of 0.02 mol / L to quantify the content of carboxylic acid (D).

(5) pH of the extract
10 g of dry particles and 50 mL of pure water were put into a 100 mL Erlenmeyer flask with a stopper, a cooling condenser was installed, and the mixture was stirred at 95 ° C. for 8 hours. The obtained extract was cooled to 20 ° C, and the pH was measured.

(6) Evaluation of coke black Using 2 kg of dry granules, granulation was performed with a uniaxial extruder (Toyo Seiki Co., Ltd. D2020, caliber 20 mmφ, L / D 20, fully threaded screw) to obtain pellets which were melt-formed once. The temperature conditions are: supply section / compression section / metering section / die = 175/215/225/220 ° C, and the number of screw rotations is 50 rpm. The obtained melt-formed pellets were granulated again under the same conditions to obtain pellets which were melt-formed twice. Similarly, the pellets were recompounded five times, and then washed with 500 g of high-density polyethylene in a uniaxial extruder (washing). Next, the screw was pulled out, and after visually confirming the adhesion state of the charcoal on the screw, it was collected and weighed, and evaluated on the basis of the following A to D as an evaluation index of the charcoal black.
A: The color of scorched black is light yellow, and the amount is less than 0.1g
B: The color of scorched black is yellow or brown, and the amount is less than 0.1g
C: The color of charred is yellow or brown, and the amount is 0.1 g or more and less than 0.3 g
D: The color of charred is yellow or brown, and the amount is 0.3 g or more

(7) Coloring resistance 100 g of the dried granules were immersed in 1000 g of a 0.1 mol / liter sodium hydroxide aqueous solution, the lid of the container containing the aforementioned granules was covered, and the granules were allowed to stand at 80 ° C. for 1 week. "LabScan XE Sensor" manufactured by HunterLab was used to measure the YI (yellow index) value of the particles before and after immersion, and the amount of increase in YI due to immersion was determined. Evaluation was performed on the following A to D standards. This evaluation result is used as an index of the color resistance of the resin composition under alkaline conditions. The YI value is an index of the yellowness (yellow value) of the object. The higher the YI value, the stronger the yellowness. On the other hand, the lower the YI value, the weaker the yellowness, indicating less coloration.
A: The increase of YI has not reached 2
B: The increase of YI is 2 or more and less than 4
C: The increase of YI is 4 or more and less than 6
D: The increase of YI is 6 or more

(8) Appearance characteristics after melt-molding Using 10 g of dried granules, a heating compression compression device was heated and melted at 220 ° C. for 6 minutes to prepare a disc-shaped sample having a thickness of 3 mm. The "LabScan XE Sensor" manufactured by HunterLab was used to measure the YI value of the obtained disk-shaped sample, and evaluated based on the following A to D standards. This evaluation result was used as an index of the external appearance characteristics after melt-forming.
A: YI is less than 8
B: YI is 8 or more and less than 13
C: YI is 13 or more and less than 20
D: YI is 20 or more

(9) Indirect adhesion: Dry granules, linear low-density polyethylene (Novatec LL-UF943 manufactured by Japan Polyethylene Corporation, hereinafter referred to as LLDPE) and adhesive resin (Bynel CXA417E10 manufactured by DuPont, diluted to 7% with the above LLDPE) , Hereinafter referred to as Ad), and produced three kinds of five-layer multilayer films (LLDPE / Ad / EVOH / Ad / LLDPE = 50 μm / 10 μm / 10 μm / 10 μm / 50 μm). The extruder, extrusion conditions, and die used are as follows.
Extruder:
EVOH: Single-shaft Extruder (TOYO Seiki Co., Ltd. Experimental Model ME CO-EXT)
Caliber 20mmφ, L / D20, full-screw screw supply section / compression section / metering section / die = 175/210/220/220 ° C
LLDPE: Uniaxial Extruder (PLASTIC Engineering Research Institute GT-32-A)
Caliber 32mmφ, L / D28, full-screw screw supply section / compression section / metering section / die = 150/200/210/220 ° C
Ad: Uniaxial Extruder (TECHNOVEL SZW20GT-20MG-STD)
Caliber 20mmφ, L / D20, Full Threaded Screw Supply Section / Compression Section / Measuring Section / Die Head = 150/200/220/220 ℃
Die: 300mm width three types of five-layer hanger type die (made by PLASTI Engineering Research Institute)

After the above-mentioned film formation was started, the multilayer film obtained at the elapse of 15 minutes was humidity-conditioned at a temperature of 23 ° C. and a relative humidity of 50% RH, and then a sample having a length of 150 mm and a width of 15 mm was cut along the extrusion direction. Using an Autograph DCS-50M tensile tester manufactured by Shimadzu Corporation, the peel strength of the sample was measured (at an environment of 23 ° C and 50% RH, a tensile speed of 250 mm / min, and a T-type peeling mode). Evaluation was performed on the basis of -C. Use this evaluation result as an indicator of layer indirect effort.
A: 500g / 15mm or more
B: 300g / 15mm or more and less than 500g / 15mm
C: less than 300g / 15mm

[Synthesis example 1]
Using a 250-liter pressurized reaction tank, the ethylene-vinyl acetate copolymer was polymerized under the following raw materials and conditions.
・ Vinyl acetate: 105.0kg
・ Methanol: 38.3kg
・ Starter: 2,2'-azobis (2,4-dimethylvaleronitrile) (10.0g / L methanol solution), initial supply: 2440mL, continuous supply: none ・ Polymerization temperature: 60 ° C
・ Polyethylene pressure in polymerization tank: 3.7MPa

When the polymerization rate of vinyl acetate was about 40%, sorbic acid was added, and the polymerization was stopped by cooling. Next, the reaction tank was opened for deethylene, and then it was supplied to the ejection tower. Unreacted vinyl acetate was removed from the top of the tower by introducing methanol vapor from the lower part of the tower to obtain a methanol solution of ethylene-vinyl acetate copolymer. . This solution was added to a saponification reactor so that the molar ratio of sodium hydroxide to the vinyl ester unit in the copolymer became 0.7. Sodium hydroxide / methanol solution (80 g / L) was added, and methanol was added to increase the concentration of the copolymer. Adjusted to 15%. This solution was heated to 60 ° C, and saponification was performed for about 4 hours while blowing nitrogen into the reactor. Then, acetic acid and water were added to the reaction solution to stop the saponification reaction. After obtaining the EVOH suspension, the solution was deliquored by a centrifugal dehydrator. In the obtained EVOH, the molar ratio of acetonitrile to all monomer units in the EVOH was set to 2, and after adding acetonitrile, the deliquoring operation was repeated twice. Furthermore, a large amount of water was added to the EVOH, and the deliquoring operation was repeated. Next, by drying at 60 ° C. for 24 hours, a crude dried product of EVOH having an ethylene unit content of 32 mol% and a degree of saponification of 99.9 mol% was obtained.

[Synthesis example 2]
A crude EVOH having an ethylene unit content of 32 mol% and a saponification degree of 99.9 mol% was obtained in the same manner as in Synthesis Example 1 except that the conditions during the polymerization of the ethylene-vinyl acetate copolymer were changed to the following. Dry things.
・ Vinyl acetate: 83.0kg
・ Methanol: 26.6kg
・ Starter: 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (2.5g / L methanol solution), initial supply: 362mL, continuous supply: 1120mL / hr
・ Polymerization temperature: 60 ° C
・ Polyethylene pressure in polymerization tank: 3.6MPa

[Synthesis example 3]
A crude EVOH having an ethylene unit content of 44 mol% and a saponification degree of 99.9 mol% was obtained in the same manner as in Synthesis Example 1 except that the conditions during the polymerization of the ethylene-vinyl acetate copolymer were changed to the following. Dry things.
・ Vinyl acetate: 76.7kg
・ Methanol: 11.0kg
・ Starter: 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) (2.5g / L methanol solution), initial supply: 510mL, continuous supply: 1570mL / hr
・ Polymerization temperature: 60 ° C
・ Polyethylene pressure in polymerization tank: 5.5MPa

[Examples 1 to 9 and Comparative Examples 1 to 5]
The crude dried EVOH obtained in the above Synthesis Example 1 was placed in a mixed solvent of water / methanol = 40/60 (mass ratio) so that the solid content was 40%, and stirred at 60 ° C. for 6 hours to dissolve it. . To the obtained solution, the compound (B) in which Z ¹ and Z ² are hydrogen atoms in the above formula (X) was added, and after stirring for 1 hour, it was continuously extruded from a nozzle with a diameter of 4 mm to water adjusted to 0 ° C. / Methanol = 90/10 (mass ratio) in a precipitation bath, which was precipitated into strands. This strand was introduced into a granulator to obtain porous water-containing granules. The aqueous particles were washed with an acetic acid aqueous solution and ion-exchanged water, and then subjected to an immersion treatment with an aqueous solution containing sodium acetate and acetic acid. This aqueous solution and the water-containing particles were separated and deliquored, and then placed in a hot-air dryer, dried at 80 ° C for 3 hours, and then dried at 110 ° C for 35 hours to obtain dried particles. Using the dried granules, the above analysis and evaluation were performed. In addition, a resin composition having a composition described in Table 1 was produced by adjusting the amount of the compound (B) added and the concentration of each component of the aqueous solution for immersion treatment.

[Example 10]
Except that potassium acetate was used instead of sodium acetate, dry granules were produced in the same manner as in Example 1 and analyzed and evaluated.

[Example 11]
Except that sodium lactate was used instead of sodium acetate, and lactic acid was used instead of acetic acid, dry granules were produced in the same manner as in Example 1, and analyzed and evaluated.

[Example 12]
Except that sodium trifluoroacetate was used instead of sodium acetate, and trifluoroacetic acid was used instead of acetic acid, dry granules were produced in the same manner as in Example 1, and analyzed and evaluated.

[Example 13]
A dry pellet was produced in the same manner as in Example 1 except that the crude dried product of EVOH obtained in Synthesis Example 2 was used, and then analyzed and evaluated.

[Example 14]
A dry pellet was prepared and analyzed in the same manner as in Example 1 except that the crude dry product of EVOH obtained in Synthesis Example 3 was used above, and a mixed solvent of water / methanol = 25/75 (mass ratio) was used for dissolution. And evaluation.

Table 1 shows the composition and evaluation results of each resin composition in the examples and comparative examples.

Claims (7)

A resin composition comprising a resin composition comprising an ethylene-vinyl alcohol copolymer (A) and a compound (B) represented by the following formula (X), and an ethylene-vinyl alcohol copolymer (A) being an ethylene unit The content is 15 to 60 mole%, the saponification degree is more than 85 mole%, and the content of the compound (B) is 5 to 100 ppm; (In formula (X), Z ¹ and Z ² are each independently a hydrogen atom or a methyl group). For example, the resin composition of claim 1, wherein the pH of the extraction solution obtained by extracting 10 g of the resin composition with 50 ml of pure water at 95 ° C for 8 hours is in the range of 4.0 to 5.5 at 20 ° C. The resin composition according to claim 1 or 2, further comprising 100 to 400 ppm of metal ions (C). The resin composition according to claim 1 or 2, further comprising 50 to 400 ppm of a carboxylic acid (D) having a pKa in the range of 3.5 to 5.5. A molded article comprising the resin composition according to any one of claims 1 to 4. The formed article according to claim 5 is a multilayer structure including a layer formed of the resin composition. A packaging material having a shaped body as claimed in claim 5 or 6.