CN108473744B

CN108473744B - Resin composition and molded article

Info

Publication number: CN108473744B
Application number: CN201680075588.4A
Authority: CN
Inventors: 山崎义和; 米谷英里子
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2015-12-25
Filing date: 2016-12-12
Publication date: 2020-08-04
Anticipated expiration: 2036-12-12
Also published as: JPWO2017110568A1; WO2017110568A1; TWI622614B; TW201734110A; CN108473744A; JP6704415B2

Abstract

Provided are a resin composition which has excellent appearance characteristics and durability in melt molding, and which can suppress the occurrence of yellowing particularly even after repeated reuse, and a molded article obtained using such a composition. The resin composition of the present invention is a resin composition containing EVOH as a main component, and is characterized by containing a phosphorus compound and a metal salt, wherein the phosphorus compound is condensed phosphoric acid, a compound having 2 or more phosphonic acid groups, or a combination thereof, the content of the phosphorus compound is 0.1ppm or more and less than 50ppm, and the content of the metal salt is 5ppm or more and 500ppm or less in terms of metal elements. The metal salt is preferably an alkali metal salt, an alkaline earth metal salt, or a combination thereof. The molded article of the present invention is a molded article having a portion formed of the resin composition.

Description

Resin composition and molded article

Technical Field

The present invention relates to a resin composition and a molded article.

Background

Ethylene-vinyl alcohol copolymers (hereinafter abbreviated as EVOH) are widely used as various packaging materials such as films, sheets and containers because of their excellent oxygen-shielding properties. These packaging materials are generally molded by a melt molding method, and excellent appearance characteristics (less coloring such as yellowing) and excellent durability during melt molding are required for EVOH.

Packaging materials are often configured as multilayer structures, and EVOH resin compositions containing metal ions in EVOH are sometimes produced in order to improve interlayer adhesiveness and the like of the multilayer structures. However, if EVOH contains metal ions, it is liable to be colored, resulting in a defect that the appearance of the molded article is deteriorated.

In addition, in general, when a molded product is produced, an operation of cutting an excess sheet end portion (cut edge) is performed, and the cut edge is recovered and reused in order to effectively utilize the cut edge. However, in this case, EVOH suffers from a drawback that it undergoes thermal deterioration due to repeated heat history, and coloring such as yellowing occurs, thereby deteriorating the appearance characteristics of the molded article. Therefore, EVOH resin compositions that do not deteriorate in appearance even after repeated heat history during recycling have been demanded.

Further, EVOH has a large number of highly reactive hydroxyl groups in its molecular structure. Therefore, when EVOH is melt-molded by continuous operation for a long time, there is a problem concerning durability that defective spots such as gels and foreign matter increase with time or appearance defects in the form of stripes increase with time, and the commercial value as a molded article is lowered. In addition, there are two problems that may occur in the durability problem such as the increase of gel, foreign matter, or the like and the occurrence of the stripe-like appearance defect, unlike the case where either problem occurs or not depending on the equipment used in the molding process and the operating conditions. In any case, an EVOH resin composition having excellent durability with little change with time even in the case of continuous operation for a long time is desired.

In order to improve the above-mentioned various properties required of EVOH, JP-A-64-66262 discloses an EVOH resin composition containing an acid such as a carboxylic acid and a metal ion. Further, japanese patent No. 5619874 discloses an EVOH resin composition containing a polycarboxylic acid and a metal ion. These EVOH resin compositions are believed to be excellent in appearance characteristics and durability.

However, the demand for the quality of molded articles such as hue and appearance characteristics has been increasing in recent years, and it is a real situation that the above-mentioned EVOH resin composition of the related art cannot sufficiently meet the quality required for hue and appearance characteristics (gel, foreign matter, streaks, etc.) which has been increasing in recent years. Further, the importance of reusing the cut edge is increasing from the viewpoint of environmental considerations, but in reality, there is no effective measure against deterioration of appearance characteristics due to occurrence of yellowing or the like caused by the repeated heat history.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. Sho 64-66262

Patent document 2: japanese patent No. 5619874.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a resin composition having excellent appearance characteristics and durability in melt molding, and particularly being capable of suppressing the occurrence of yellowing even after repeated reuse, and a molded article obtained using such a composition.

Means for solving the problems

The invention obtained in order to solve the above problems is a resin composition containing EVOH as a main component, characterized by containing a phosphorus compound and a metal salt, wherein the phosphorus compound is condensed phosphoric acid, a compound having 2 or more phosphonic acid groups, or a combination thereof, the content of the phosphorus compound is 0.1ppm or more and less than 50ppm, and the content of the metal salt is 5ppm or more and 500ppm or less in terms of metal elements.

It is considered that, in the resin composition, when the content of the specific phosphorus compound which is a condensed phosphoric acid, a compound having 2 or more phosphonic acid groups, or a combination thereof is in the above range, the phosphoric acid group or the phosphonic acid group stably coordinates to a metal ion which is considered to be a cause of yellowing or the like, and thereby the metal ion can be trapped. That is, by stably existing the metal ions in a coordinated state as described above, it is possible to suppress the catalytic function of the EVOH having the metal ions against the reaction such as yellowing, and as a result, it is possible to suppress the occurrence of coloring such as yellowing even when repeatedly reused. Further, since the resin composition contains the metal salt in the above range, the defective spots such as gel and foreign matter do not increase with time even in long-term molding, or the appearance defect in the form of stripes does not increase with time even in long-term molding, and thus such excellent durability can be exhibited.

The metal salt is preferably an alkali metal salt, an alkaline earth metal salt, or a combination thereof. The metal salt is preferably an alkali metal salt. The alkali metal salt can suitably exhibit durability such that a defective spot such as a gel or a foreign matter does not increase with time even in molding for a long time. Preferably, the metal salt is an alkaline earth metal salt, and the content of the alkaline earth metal salt is 5ppm or more and 100ppm or less in terms of metal element. The alkaline earth metal salt can suitably exhibit durability such that the appearance of the bar-like product is not deteriorated with time even in molding for a long time.

The resin composition preferably further contains a monocarboxylic acid, and the content of the monocarboxylic acid is 5ppm to 500 ppm. The resin composition preferably further contains a boron compound in an amount of 5ppm or more and 2,000ppm or less in terms of boron element.

The molded article of the present invention is a molded article having a portion formed of the resin composition. The molded article has a portion obtained from the resin composition having excellent appearance characteristics and durability as described above, and therefore has an excellent appearance in which coloring such as yellowing, and occurrence of gels, foreign matter, fish eyes, streaks, and the like are suppressed.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a resin composition having excellent appearance characteristics and durability in melt molding, and particularly being capable of suppressing the occurrence of yellowing even after repeated reuse, and a molded article obtained using such a composition can be provided.

Detailed Description

Hereinafter, the embodiment of the present invention will be described in detail in the order of the resin composition and the molded article.

[ resin composition ]

The resin composition of the present invention contains EVOH as a main component, and contains a phosphorus compound and a metal salt. The main component is a component having the largest content on a mass basis.

(EVOH)

EVOH is a copolymer having ethylene units and vinyl alcohol units. However, the EVOH may also contain one or more other structural units.

EVOH can be produced by a known method. The lower limit of the ethylene unit content of the EVOH is preferably 15mol%, more preferably 20mol%, and still more preferably 25 mol%. On the other hand, the upper limit of the ethylene unit content of the EVOH is preferably 60mol%, more preferably 55mol%, and still more preferably 50 mol%. When the ethylene unit content of the EVOH is in the above range, a resin composition having more excellent durability can be obtained while suppressing yellowing after melt molding. If the ethylene unit content of the EVOH is less than the above lower limit, there is a risk of deterioration in durability of the resin composition, water resistance of the resulting molded article, hot water resistance, gas barrier property under high humidity, and the like. Conversely, if the ethylene unit content of EVOH is greater than the above upper limit, there is a risk that the gas barrier property and the like of the obtained molded article are reduced.

The lower limit of the saponification degree of EVOH is preferably 80mol%, more preferably 95mol%, and still more preferably 99 mol%. If the saponification degree of EVOH is less than the lower limit, the gas barrier property and the appearance of the molded article obtained may be deteriorated.

The method for producing EVOH is specifically described below. EVOH is generally obtained by saponifying an ethylene-vinyl ester copolymer obtained by copolymerizing ethylene and a vinyl ester. The polymerization of ethylene and vinyl ester may be carried out by any known method such as solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, etc., and may be either continuous or batch-wise. For example, the polymerization conditions in the solution polymerization are as follows.

Solvent: alcohols are preferred, but other organic solvents (dimethyl sulfoxide, etc.) that can dissolve ethylene, vinyl esters, and ethylene-vinyl ester copolymers may be used. As the alcohol, methanol, ethanol, propanol, n-butanol, tert-butanol, etc. can be used, and methanol is particularly preferable.

Polymerization initiator: azonitrile initiators such as 2,2 '-azobisisobutyronitrile, 2' -azobis- (2, 4-dimethylvaleronitrile), 2 '-azobis- (4-methoxy-2, 4-dimethylvaleronitrile), and 2,2' -azobis- (2-cyclopropylpropionitrile) can be used; and organic peroxide initiators such as isobutyryl peroxide, cumyl peroxyneodecanoate, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, tert-butyl peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide, tert-butyl hydroperoxide and diacetyl peroxide.

Temperature: 20 ℃ to 90 ℃, preferably 40 ℃ to 70 ℃.

Time: 2 to 15 hours, preferably 3 to 11 hours.

Polymerization rate: the amount of the vinyl ester to be charged is 10% to 90%, preferably 30% to 80%.

Resin component in solution after polymerization: 5% to 85%, preferably 20% to 70%.

Vinyl acetate may be mentioned as a representative vinyl ester used in polymerization, but other aliphatic vinyl esters, for example, vinyl formate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, and vinyl caproate may be mentioned.

In addition to this, other ethylenically unsaturated monomers copolymerizable therewith may be copolymerized in a small amount within a range not to impair the effects of the present invention. Examples of such ethylenically unsaturated monomers include:

α -olefins such as propylene, n-butene, isobutylene and 1-hexene;

unsaturated monomers having a 1, 2-diester group such as 3, 4-diacetoxy-1-butene;

unsaturated monomers having a 1, 3-diester group such as 2-methylene-1, 3-propanediol diacetate (1, 3-diacetoxy-2-methylenepropane), 2-methylene-1, 3-propanediol dipropionate, and 2-methylene-1, 3-propanediol dibutyrate;

acrylic acid and salts thereof;

an unsaturated monomer having an acrylate group;

methacrylic acid and salts thereof;

an unsaturated monomer having a methacrylate group;

acrylamide, N-methacrylamide, N-ethylacrylamide, N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and salts thereof, acrylamidopropyldimethylamine and salts thereof (e.g., quaternary salts);

methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and salts thereof, methacrylamidopropyldimethylamine and salts thereof (e.g., quaternary salts);

vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, and 2, 3-diacetoxy-1-vinyloxypropane;

cyanoethylenes such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride;

vinylidene halides such as vinylidene chloride and vinylidene fluoride;

allyl compounds such as allyl acetate, 2, 3-diacetoxy-1-allyloxypropane, and allyl chloride;

unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and salts or esters thereof;

vinylsilane compounds such as vinyltrimethoxysilane;

isopropenyl acetate, and the like.

After the polymerization is carried out for a predetermined time to reach a predetermined polymerization rate, a polymerization inhibitor is added as necessary, unreacted ethylene gas is evaporated and removed, and then unreacted vinyl ester is removed. As a method for removing unreacted vinyl ester from an ethylene-vinyl ester copolymer from which ethylene is removed by evaporation, for example, the following method and the like are employed: the copolymer solution was continuously supplied from the upper part of the column filled with Raschig rings at a constant rate, vapor of an organic solvent such as methanol was blown from the lower part of the column, mixed vapor of the organic solvent such as methanol and unreacted vinyl ester was distilled off from the top of the column, and the ethylene-vinyl ester copolymer solution from which the unreacted vinyl ester was removed from the bottom of the column.

Saponification of the ethylene-vinyl ester copolymer is performed by a known method such as acid saponification or alkali saponification. For example, in the case of alkali saponification, an alkali catalyst is added to the copolymer solution obtained in the above-mentioned manner from which unreacted ethylene and unreacted vinyl ester have been removed, and the vinyl ester portion of the copolymer is saponified. The saponification method may be either a continuous method or a batch method. As the alkali catalyst, sodium hydroxide, potassium hydroxide, alkali metal alkoxide, or the like is used, and the following conditions are suitably used.

Copolymer solution concentration: 10% or more and 50% or less.

Reaction temperature: 30 ℃ or higher and 60 ℃ or lower.

The usage amount of the catalyst is as follows: 0.02 equivalent to 0.6 equivalent (relative to the vinyl ester component).

Time: 1 hour to 6 hours or less.

The EVOH after the saponification reaction obtained in this way contains residues of a catalyst used in the saponification reaction, salts formed by a side reaction, other impurities, and the like, and therefore, it is preferably neutralized and washed as necessary to remove them.

The lower limit of the melt flow rate (measured at 210 ℃ C. under a load of 2160 g; hereinafter abbreviated as MFR) of EVOH is preferably 0.1g/10 min, more preferably 0.5g/10 min, still more preferably 1g/10 min, particularly preferably 3g/10 min, in accordance with JIS K7210. On the other hand, the upper limit of the MFR of the EVOH is preferably 200g/10 min, more preferably 50g/10 min, still more preferably 30g/10 min, yet more preferably 15g/10 min, and particularly preferably 10g/10 min. When the MFR of the EVOH is in the above range, the appearance characteristics and durability after melt molding are excellent.

The lower limit of the content of EVOH in the resin composition is, for example, preferably 80% by mass, and more preferably 90% by mass. Further, the lower limit of the content of EVOH may be 99 mass%, or may be 99.9 mass%. When the content of EVOH is not less than the lower limit, the resulting molded article can more effectively exhibit various properties of EVOH. The content of each component in the resin composition is a ratio to the whole dried resin composition (the same applies hereinafter).

(phosphorus Compound)

The resin composition contains a specific phosphorus compound. The phosphorus compound is condensed phosphoric acid and has more than 2 phosphonic acid groups (-P (O) (OH)₂) Or a combination thereof. That is, as the phosphorus compound, only 1 kind of condensed phosphoric acid or a compound having 2 or more phosphonic acid groups may be used, or a plurality of kinds may be used in combination.

By containing such a phosphorus compound, the resin composition can be inhibited from yellowing even after melt molding and after repeated reuse without being affected by other components constituting the resin composition. It is considered that the condensed phosphoric acid or the phosphorus compound having 2 or more phosphonic acid groups stably coordinates metal ions considered to be a cause of yellowing or the like, and can trap the metal ions. It is presumed that the phosphorus compound stably exists in a state of being coordinated to the metal ion, and thereby the action of catalyzing the metal ion which accelerates the decomposition and coloring of EVOH is suppressed.

Examples of the condensed phosphoric acid include pyrophosphoric acid (also referred to as diphosphoric acid), tripolyphosphoric acid, tetraphosphoric acid, etc., and pyrophosphoric acid is preferred. Examples of the compound having 2 or more phosphonic acid groups include etidronic acid (also referred to as 1-hydroxyethane-1, 1-diphosphonic acid), alendronic acid, nitrilotris (methylenephosphonic acid), ethylenediamine tetra (methylenephosphonic acid), and the like, and of these, etidronic acid and alendronic acid are preferable. The condensed phosphoric acid may have 2 or more phosphonic acid groups, or may not have 2 or more phosphonic acid groups. In addition, the compound having 2 or more phosphonic acid groups may include condensed phosphoric acids having 2 or more phosphonic acid groups. On the other hand, the compound having 2 or more phosphonic acid groups may be a compound other than condensed phosphoric acid having 2 or more phosphonic acid groups.

These phosphorus compounds may be present in the form of an oxyacid, or may be present in the form of a phosphate or phosphonate obtained by forming a salt with a counter cation such as a metal ion. Further, it may be a hydrate. The resin composition may or may not be dissociated into ions. The phosphate may be in the form of any of dihydrogen phosphate, hydrogen phosphate and phosphate, and the phosphonate may be in the form of any of hydrogen phosphonate and phosphonate. The counter cation species is not particularly limited. When a phosphorus compound obtained by forming a salt with a metal ion having a counter cation is mixed, the metal ion also functions as a metal ion in a metal salt described later.

The molecular weight of the phosphorus compound is not particularly limited, but the upper limit is, for example, preferably 1,000, and more preferably 600. On the other hand, the lower limit is, for example, 170. The compound having a molecular weight within the above range can coordinate metal ions more stably, and the ability to inhibit yellowing is improved.

The phosphorus compound has a phosphoric acid group (-O-P) (O) (OH)₂) And the number of phosphonic acid groups is 2 or more, and the upper limit thereof is, for example, 6, preferably 4, more preferably 3, and still more preferably 2. When the number of phosphoric acid groups and phosphonic acid groups in the phosphorus compound is in the above range, the metal ions can be more stably coordinated, and the ability to inhibit yellowing is improved.

The lower limit of the content of the phosphorus compound is 0.1ppm, preferably 0.5ppm, more preferably 3ppm, still more preferably 10ppm, and particularly preferably 20 ppm. When the content of the phosphorus compound is not less than the lower limit, the resin composition itself can be inhibited from coloring such as yellowing, and the occurrence of yellowing can be inhibited even in a molded article after repeated reuse. On the other hand, the content of the phosphorus compound is less than 50ppm, preferably less than 45ppm, more preferably less than 35 ppm. When the content of the phosphorus compound is less than the upper limit, a resin composition having excellent durability can be obtained.

(Metal salt)

The resin composition contains a metal salt. The metal salt may be an alkali metal salt, an alkaline earth metal salt, another transition metal salt, or the like, and may be a single metal species or may include a plurality of metal species. The metal salt is preferably an alkali metal salt, an alkaline earth metal salt, or a combination thereof. However, the metal salt does not include the metal salt of the specific phosphorus compound (condensed phosphoric acid and a compound having 2 or more phosphonic acid groups).

The lower limit of the metal salt in terms of metal element is 5ppm, preferably 30ppm, more preferably 50ppm, and may be 100ppm with respect to the entire resin composition. On the other hand, the upper limit of the metal salt in terms of metal element is 500ppm, preferably 400ppm, more preferably 300ppm, and may be 200 ppm. By containing the metal salt in the above range, a resin composition having excellent durability in which defective spots such as gels and foreign matter do not increase with time even in long-term molding or in which appearance defects such as streaky form do not increase with time even in long-term molding, and excellent appearance characteristics in which coloring such as yellowing is suppressed can be obtained in a balanced manner.

The resin composition in which the metal salt is an alkali metal salt is preferable in that the generation of defective spots such as gels and foreign matter is suppressed from increasing with time even in molding for a long time. Examples of the alkali metal forming the alkali metal salt include lithium, sodium, potassium, and the like, and sodium and potassium are preferable. Examples of the alkali metal salt include aliphatic carboxylates such as lithium, sodium, and potassium, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, and metal complexes. Among these, sodium acetate, potassium acetate, sodium carbonate, potassium carbonate, sodium phosphate and potassium phosphate are more preferable from the viewpoint of easy acquisition and the like.

The lower limit of the content of the alkali metal salt in terms of metal element is preferably 5ppm, more preferably 50ppm, and still more preferably 100ppm, based on the whole resin composition. On the other hand, the upper limit of the content of the alkali metal salt in terms of metal element is 500ppm, preferably 400ppm, and more preferably 300 ppm. When the content of the alkali metal salt is not less than the lower limit, crosslinking of EVOH is suppressed, and the occurrence of gels and seeds can be suppressed even in long-term molding. On the other hand, when the content of the alkali metal salt is not more than the upper limit, coloring such as yellowing can be suppressed.

The resin composition containing an alkaline earth metal salt as a metal salt is preferable in that the increase with time of the appearance defect in the form of a stripe is suppressed even in molding for a long time. Examples of the alkaline earth metal salt include salts of beryllium, magnesium, calcium, strontium, and barium. From the viewpoint of industrial availability, salts of magnesium and calcium are preferable, and examples thereof include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, metal complexes, and the like.

The lower limit of the content of the alkaline earth metal salt in terms of metal element is preferably 5ppm, more preferably 30ppm, with respect to the entire resin composition. On the other hand, the upper limit of the content of the alkaline earth metal salt in terms of metal element may be 150ppm, preferably 100ppm, and more preferably 80 ppm. When the content of the alkaline earth metal salt is not less than the lower limit, the increase of the appearance defect in the form of a stripe with time is effectively suppressed. On the other hand, when the content of the alkaline earth metal salt is not more than the upper limit, the deterioration of appearance characteristics due to coloring such as yellowing is effectively suppressed.

The lower limit of the ratio (phosphorus compound/metal salt) of the content of the phosphorus compound to the content of the metal salt (in terms of metal element) in the resin composition is preferably 0.001, more preferably 0.005, further preferably 0.01, particularly preferably 0.05, and further particularly preferably 0.1. Further, in the case where the metal salt is an alkaline earth metal salt, the lower limit of the ratio is more preferably 0.3. On the other hand, the upper limit of the ratio is preferably, for example, 5, and more preferably 1. Further, in the case where the metal salt is an alkali metal salt, the upper limit of the ratio is more preferably 0.5, and still more preferably 0.3. When the content ratio of the metal salt to the phosphorus compound is in the above range, the effect of the present invention can be more effectively exerted.

(monocarboxylic acid)

The resin composition may contain monocarboxylic acid. The monocarboxylic acid refers to a compound having 1 carboxyl group in the molecule.

The content of the monocarboxylic acid is preferably 500ppm or less, more preferably 300ppm or less, based on the entire resin composition, from the viewpoint of reducing odor. By setting the monocarboxylic acid content to the upper limit or less, the odor of the resin composition itself is reduced, and in addition, the odor generated when the resin composition is melt-molded is reduced, thereby improving the working environment. In addition, the molded article obtained using the resin composition can be preferably used as a packaging material for contents, such as cooked rice and drinking water, in which the generation of odor, in particular, impairs the value of the product, from the viewpoint of reducing odor possessed by the molded article after melt molding.

On the other hand, the content of the monocarboxylic acid is preferably 5ppm or more, more preferably 50ppm or more, with respect to the entire resin composition, from the viewpoint of quality stability. When the content of the monocarboxylic acid is not less than the lower limit, the pH of the aqueous solution can be easily controlled during the production of the resin composition, and a product having stable quality can be easily obtained.

Examples of the monocarboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, acrylic acid, methacrylic acid, benzoic acid, and 2-naphthoic acid. Among these, acetic acid is preferable. These monocarboxylic acids may have a hydroxyl group or a halogen atom.

(boron compound)

The resin composition may contain a boron compound. Examples of the boron compound include boric acid, boric acid esters, boric acid salts, and boron hydrides. Specifically, the boric acid includes, for example, orthoboric acid (H)₃BO₃) Examples of the boric acid salt include alkali metal salts, alkaline earth metal salts, and borax of the above-mentioned various boric acids. Among these, orthoboric acid is preferable.

The lower limit of the boron compound content in terms of boron element is preferably 5ppm, more preferably 10ppm, with respect to the entire resin composition. On the other hand, the upper limit of the boron compound content in terms of boron element is preferably 2,000ppm, more preferably 1,000ppm, and still more preferably 500 ppm. When the content of the boron compound in terms of boron element is in the above range, the thermal stability of the resin composition during melt molding can be improved, and as a result, the durability during molding can be further improved. In detail, when a boron compound is blended in the resin composition, a chelate compound is generated between the EVOH and the boron compound, and it is considered that the thermal stability and the mechanical properties of the resin composition are improved.

(other additives, etc.)

The resin composition may contain other components than the EVOH, the phosphorus compound, the metal salt, the monocarboxylic acid, and the boron compound in appropriate amounts within a range not impairing the effects of the present invention. Examples of such other components include additives such as plasticizers, stabilizers, surfactants, colorants, ultraviolet absorbers, lubricants, antistatic agents, drying agents, crosslinking agents, fillers, oxygen absorbers, and various fibers. However, the content of these additives (components other than EVOH, the phosphorus compound, the metal salt, the monocarboxylic acid, and the boron compound) in the resin composition may be less than 10 mass%, less than 1 mass%, and further less than 0.1 mass%.

Examples of the thermoplastic resin include various polyolefins (polyethylene, polypropylene, poly (1-butene), poly (4-methyl-1-pentene), ethylene-propylene copolymers, copolymers of ethylene and α -olefin having 4 or more carbon atoms, copolymers of olefin and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylic ester copolymers, modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acid or a derivative thereof, and the like), various nylons (nylon 6, nylon 66, nylon 6/66 copolymers, and the like), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, modified polyvinyl alcohol resins, and the like, and when the resin composition contains a thermoplastic resin other than EVOH, the amount of the thermoplastic resin is preferably less than 50 mass%, more preferably less than 30 mass%, further preferably less than 10 mass%, still further preferably less than 1 mass%, and may be less than 0.1 mass%.

The preferable range of MFR of the resin composition is the same as the above MFR of EVOH, and by setting this range, the same effects as those of EVOH can be obtained.

The resin composition can be formed into various molded articles such as pellets, films, sheets, containers, pipes, fibers, and the like by melt molding.

(method for producing resin composition)

The resin composition can be efficiently obtained by a production method comprising, for example, a copolymerization step (step 1) of copolymerizing ethylene and a vinyl ester to obtain an ethylene-vinyl ester copolymer, and a saponification step (step 2) of saponifying the ethylene-vinyl ester copolymer to obtain EVOH, and further comprising, after the copolymerization step, a mixing step (step α) of mixing the ethylene-vinyl ester copolymer or EVOH with the phosphorus compound and the metal salt.

(step 1: copolymerization step)

The copolymerization step includes, in addition to the step of copolymerizing ethylene and vinyl ester, a step of adding a polymerization inhibitor, followed by removing unreacted ethylene and unreacted vinyl ester to obtain an ethylene-vinyl ester copolymer solution, as required. Examples of the method for copolymerizing ethylene and a vinyl ester include known methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization. Specific polymerization conditions and the like are as described above as a method for producing EVOH.

(step 2: saponification step)

Next, an alkali catalyst or the like is added to the ethylene-vinyl ester copolymer solution, and the copolymer in the solution is saponified. Specific conditions and the like in the saponification are as described above as a method for producing EVOH.

(step α (1): mixing step)

In the present mixing step, the ethylene-vinyl ester copolymer obtained in the copolymerization step or the EVOH obtained in the saponification step is mixed with the above-mentioned phosphorus compound and the like, however, as described later, the mixing step may be performed after the pelletization of EVOH, and as the mixing step (step α (1)), for example:

(1) a method of previously adding the above-mentioned phosphorus compound to a solution containing an ethylene-vinyl ester copolymer supplied to a saponification step;

(2) a method of adding the above-mentioned phosphorus compound to the saponification reaction of an ethylene-vinyl ester copolymer in the saponification step; and

(3) a method of mixing the above-mentioned phosphorus compound after EVOH is obtained in the saponification step.

(step 3: granulation step)

In order to obtain the resin composition in the form of pellets, a granulating step may be provided after the copolymerization step and the saponification step. Since EVOH is obtained as a solution containing a solvent used in the saponification reaction, it is washed to remove a catalyst such as an alkali and a side reaction product such as sodium acetate remaining in the solution. In order to facilitate the washing operation, it is preferable to granulate the EVOH-containing solution obtained in the saponification step to obtain hydrous pellets of EVOH.

Examples of the granulation operation include: a method of extruding (I) a solution containing EVOH into a coagulation bath and cutting after or immediately after cooling solidification; (II) a method of contacting a solution of EVOH with water vapor to prepare an aqueous resin composition of EVOH in advance and cutting it. The water content of the hydrous pellets of EVOH obtained by these methods is preferably 40 mass% or more and 200 mass% or less based on the dry mass of EVOH.

(step 4: drying step)

The hydrous pellets of EVOH obtained in the pelletizing step are preferably dried to prepare dry pellets of EVOH. The water content in the dried pellets is preferably 1.0 mass% or less, more preferably 0.8 mass% or less, and still more preferably 0.5 mass% or less, based on the total amount of the dried pellets, in order to prevent molding failure such as generation of voids during molding.

Examples of the method for drying the water-containing pellets include standing drying and fluidized drying. These drying methods may be used alone or in combination of two or more. The drying treatment may be carried out by any of a continuous method and a batch method. In addition, when a plurality of drying methods are combined, a continuous method and a batch method can be freely selected for each drying method. Drying at a low oxygen concentration or in an oxygen-free state is also preferable from the viewpoint of reducing deterioration of the resin composition due to oxygen during drying.

(step α (2): mixing step)

The mixing step may be performed after granulation. Examples of the method of mixing the phosphorus compound and the like after the granulation step include:

(1) a method of bringing water-containing pellets of EVOH into contact with a solution containing the above-mentioned phosphorus compound and the like; and

(2) a method of melt-kneading hydrous pellets of EVOH with the above-mentioned phosphorus compound and the like in an extruder.

In this case, monocarboxylic acid, alkali metal salt, alkaline earth metal salt, boron compound, etc. may be mixed with EVOH at the same time.

In the case of impregnation as in (1) above, the shape of the hydrous pellets is arbitrary, and the operation may be either a batch system or a continuous system. In the impregnation, each component contained in the resin composition may be divided into a plurality of solutions each of which is dissolved independently, or may be treated at a time with a liquid obtained by dissolving a plurality of components.

In the method for producing the resin composition, the mixing step may be performed simultaneously with the granulating step. That is, for example, in the granulation operation, the phosphorus compound and the metal salt may be contained in advance in the coagulation bath.

[ molded article ]

The molded article is a molded article having a portion formed of the resin composition. The molded article may be formed of only the resin composition, or may be, for example, a laminate partially including a portion formed of the EVOH resin.

Examples of the molded article include pellets, films, sheets, containers, pipes, fibers, and the like. The molded article is generally molded by melt molding of the resin composition. These molded articles may be pulverized and then molded again for reuse. Further, the film, sheet, fiber, etc. may be uniaxially or biaxially stretched. As the melt molding method, any known molding method such as extrusion molding, inflation extrusion, blow molding, melt spinning, injection molding, or the like can be applied.

The melting temperature at the time of melt molding is preferably about 150 ℃ to 300 ℃, and a melting temperature of about 200 ℃ to 250 ℃ is usually employed. The molded article thus obtained has excellent appearance characteristics in which coloring such as yellowing after melt molding is suppressed, and gels, foreign materials, fish eyes, streaks, and the like are suppressed.

The molded article may be a multilayer structure having at least one layer obtained from the resin composition. The multilayer structure has a layer obtained from the resin composition having excellent appearance characteristics and durability, and thus has excellent appearance characteristics in which coloring such as yellowing, occurrence of gels and foreign matter, fish eyes, stripes, and the like are suppressed.

Examples of the layer structure of the multilayer structure include T/E/T, E/Ad/T, T/Ad/E/Ad/T, in which a layer obtained from the resin composition is denoted by E, a layer obtained from an adhesive resin is denoted by Ad, and a layer obtained from a thermoplastic resin is denoted by T. These layers may be a single layer or a plurality of layers. In addition, other layers than those described above may also be included.

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

Examples of the thermoplastic resin include homopolymers or copolymers of olefins such as linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene- α -olefin copolymer, polybutene, and polypentene, polyesters such as polyethylene terephthalate, polyester elastomers, polyamides such as nylon 6 and nylon 66, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resins, vinyl ester resins, polyurethane elastomers, polycarbonates, chlorinated polyethylene, and chlorinated polypropylene, and among these, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamides, polystyrene, and polyesters are preferably used.

Examples of the method for producing the multilayer structure include the following methods.

(1) A method of melt-extruding a thermoplastic resin onto a molded article obtained from the resin composition;

(2) a method of coextruding the resin composition with other thermoplastic resin;

(3) a method of co-injecting the resin composition with a thermoplastic resin;

(4) a method of laminating a molded article obtained from the resin composition and another base material with an adhesive.

Among these methods, the method (2) can be preferably used. The reason for this is that the resin composition of the present invention is melted at a high temperature, has excellent durability, and is inhibited from being colored thereafter, and therefore, even when coextruded with another thermoplastic resin having a high melting point, coloring is inhibited, and a multilayer structure having excellent appearance characteristics can be obtained. Examples of the method of coextrusion include a manifold (multi-manifold) confluence type T die method, a diverter (feedblock) confluence type T die method, and an inflation method.

The multilayer structure obtained by the above coextrusion is subjected to secondary processing, whereby, for example, the following molded article can be obtained.

(1) A multilayer stretched sheet or film obtained by stretching a multilayer structure (sheet, film, or the like) in a uniaxial or biaxial direction and performing heat treatment;

(2) a multilayer rolled sheet or film obtained by rolling a multilayer structure (sheet, film, or the like);

(3) multilayer trays or cup-shaped containers obtained by subjecting a multilayer structure (sheet, film, or the like) to thermoforming such as vacuum forming, compressed air forming, vacuum compressed air forming, or the like;

(4) bottles, cup-shaped containers, and the like obtained by stretch blow molding or the like of a multilayer structure (such as a tube).

Note that secondary processing methods other than the above may be used. The molded article obtained by these secondary processing methods can be preferably used as a food container such as a deep-drawing container, a cup-like container, and a bottle.

Examples

The present invention will be described in further detail below with reference to examples. In examples and comparative examples described below, analysis and evaluation were performed by the methods shown below.

(1) Measurement of Water content of Water-containing EVOH pellets

The water content of the hydrous EVOH pellets was measured by a heat drying gravimetric method using a halogen water fraction analyzer under conditions of a drying temperature of 180 ℃, a drying time of 20 minutes and a sample amount of 10 g. The water content of the hydrous EVOH shown below is mass% based on the dry EVOH.

(2) Quantification of phosphorus Compounds

0.5g of the resin composition pellets were put into a pressure vessel made of Teflon (registered trademark), concentrated nitric acid 5m L was added thereto, the mixture was decomposed at room temperature for 30 minutes, the decomposition was capped, the mixture was heated at 150 ℃ for 10 minutes by a wet decomposition apparatus ("MWS-2" manufactured by アクタック Co.), then heated at 180 ℃ for 5 minutes to further decompose the resin composition, and thereafter the decomposition was cooled to room temperature, the treated solution was transferred to a 50m L volumetric flask (manufactured by TPX), and a volume was determined by pure water to prepare a sample solution for measurement.

(3) Quantification of metal salts

0.5g of the resin composition pellets were put into a pressure vessel made of Teflon (registered trademark), concentrated nitric acid 5m L was added thereto, the mixture was decomposed at room temperature for 30 minutes, the decomposition was capped, the mixture was heated at 150 ℃ for 10 minutes by a wet decomposition apparatus ("MWS-2" manufactured by アクタック Co., Ltd.), then heated at 180 ℃ for 5 minutes to further decompose the resin, and thereafter the decomposition was cooled to room temperature, the treated solution was transferred to a 50m L volumetric flask (manufactured by TPX Co., Ltd.), and a volume was determined by pure water to prepare a sample solution for measurement, and the content of a metal element was determined by an ICP emission spectrophotometer ("OPTIMA 0 430 4300 DV" manufactured by パーキンエルマー Co., Ltd.) with respect to the sample solution, and the amount of the metal salt was quantified by metal element conversion.

(4) Quantification of monocarboxylic acids

10g of EVOH powder obtained by freezing and pulverizing resin composition pellets and 50m L of ion-exchanged water were put into a 100m L conical flask with a stopper, a cooling condenser was attached, and the mixture was stirred at 95 ℃ for 10 hours to obtain an extract, 2 drops of phenolphthalein as an indicator for titration were added to the obtained extract 25m L, and neutralization titration was performed with 0.01 mol/L of a sodium hydroxide solution to calculate the acid amount, the acid amount derived from the phosphorus compound quantified by subtracting the above-mentioned quantified acid amount from the acid amount, and the acid amount is referred to as the equivalent of the monocarboxylic acid amount, and the amount of the monocarboxylic acid contained in the resin composition was quantified from the molecular weight of the monocarboxylic acid used.

(5) Quantification of boron Compound

0.5g of the resin composition pellets were put into a pressure vessel made of Teflon (registered trademark), concentrated nitric acid 5m L was added thereto, the mixture was decomposed at room temperature for 30 minutes, the decomposition was capped, the mixture was heated at 150 ℃ for 10 minutes by a wet decomposition apparatus ("MWS-2" manufactured by アクタック Co., Ltd.), then heated at 180 ℃ for 5 minutes to further decompose the resin, and thereafter the decomposition was cooled to room temperature, the treated solution was transferred to a 50m L volumetric flask (manufactured by TPX Co., Ltd.), and the volume was determined with pure water to prepare a sample solution for measurement, and the amount of a boron compound was determined in terms of boron element by an ICP emission spectrometer ("OPTIMA 0 430 4300 DV" manufactured by パーキンエルマー Co., Ltd.).

(6) Production of Single-layer film Using resin composition

Using a 20mm extruder "D2020" (D (mm) =20, L/D =20, compression ratio =2.0, screw: full flight) of toyoyo seiki corporation, pellets of the resin composition were subjected to monolayer film formation under the following conditions, and the draw roll speed was adjusted for each of examples and comparative examples, thereby obtaining a 20 μm monolayer film.

Extrusion temperature: supply part/compression part/metering part/mold

=170/210/210/210℃

Screw rotation speed: 40rpm

Drawing roller temperature: 80 ℃.

(7) Appearance characteristics (occurrence of yellowing of film end face)

The single-layer film produced by the above method was wound on a paper tube, and the degree of coloration at the film end face was determined visually in the following manner. The reference C is a boundary level that can withstand actual use.

And (3) judging: datum

A: without coloring

B: slightly yellow

C: slight yellowing

D: yellowing.

(8) Evaluation of coloring Property in repeated Recycling

For 2kg of the resin composition pellets, a 20mm extruder "D2020" (D (mm) =20, L/D =20, compression ratio =2.0, screw: full screw) from Toyo Seiki Seisaku-Sho Ltd was used to pelletize the resin composition pellets under the following conditions, the resulting EVOH pellets were repeatedly pelletized 5 times under the same conditions again, and the coloring properties when the resulting pellets were reused were evaluated by visual evaluation of the coloring degree of the final pellets and the following criteria for evaluation.

Condition of granulation

Extrusion temperature supply part/compression part/metering part/die

=180/210/210/210℃

Screw speed 40rpm

Number of die holes 2

The temperature of the cooling water in the coagulation bath was 30 ℃.

Standard for determining coloring degree after repeated reuse

And (3) judging: datum

A: hardly colored

B: slightly colored

C: slight coloration

D: severe staining.

(9) Persistence (increase of sundries over time)

Using 200g of resin composition pellets, heat-treating at 210 ℃ for 30 minutes by a hot air dryer, coarsely pulverizing (to the same extent as the pellets) by a pulverizer, 2kg of EVOH pellets that were not heat-treated were prepared, and pelletized using a material blended with 5 mass% of the heat-treated and seeded EVOH, using a 20mm extruder "D2020" (D (mm) =20, L/D =20, compression ratio =2.0, screw: full flight) of the company manufactured by toyoyo sperm machine, the obtained pellets were used at a supply section/compression section/metering section/die =170/210/210/210 ℃, the film was formed using the obtained pellets, using a 20mm extruder "D2020" (D) =20, L/D =20, compression ratio =2.0, screw: full flight) of the company manufactured by toyoyo sperm machine, the film formation was performed under the same conditions as those of the above (6), the single-layer film formation was performed 30 minutes after the start of film formation, the number of the single-layer film was determined to be equal to or more than the standard level of the use of the gel-like.

And (3) judging: datum

A: the number of impurities is less than 10/0.1 m²

B: the number of the sundries is more than 11 and less than 50Per 0.1m²

C: the number of the sundries is more than 50 and less than 300 per 0.1m²

D: the number of the sundries is more than 300/0.1 m²。

(10) Permanence (strip appearance badness increasing with time)

For 5kg of the resin composition pellets, a 20mm extruder "D2020" (D (mm) =20, L/D =20, compression ratio =2.0, screw: full flight) manufactured by toyoyo seiki kogaku koku corporation was used to perform monolayer film formation under extrusion conditions of feed part/compression part/metering part/die =190/210/210/210 ℃. after a 20-minute film forming operation was performed at a screw rotation speed of 100rpm, the rotation of the screw was stopped, the temperature of the extruder was set to feed part/compression part/metering part/die =150/150/150/150 ℃. after 3 hours from the stop of the screw rotation, the extrusion temperature was again set to feed part/compression part/metering part/die =190/210/210/210 ℃, monolayer film formation was performed at a screw rotation speed of 100rpm, the monolayer film obtained after the rotation of the restart screw was sampled, gel-like impurities (impurities of about 150 μm or more visually recognizable) were counted, and the number of the impurities was 10 or less/0.1 m or more²The time of (a) was evaluated as an index of the increase with time corresponding to the streak-like appearance defect by the following criteria. The reference C is a boundary level that can withstand actual use.

And (3) judging: datum

A: the number of the impurities is less than 10/0.1 m²In a period of less than 10 minutes

B: the number of the impurities is less than 10/0.1 m²Is 10 minutes or more and less than 30 minutes

C: the number of the impurities is less than 10/0.1 m²Is 30 minutes or more and less than 60 minutes

D: the number of the impurities is less than 10/0.1 m²The time of (2) is 60 minutes or more.

< example 1 >

To a solution of each component in water in such a manner that 1-hydroxyethane-1, 1-diphosphonic acid (HEDP) became 0.08 g/L, sodium acetate became 0.84 g/L, acetic acid became 0.38 g/L, and boric acid became 0.25 g/LAn aqueous solution 92.4L was charged with 10.0kg of hydrous EVOH pellets having a water content of 105 mass% (ethylene unit content (Et) 32mol%, Degree of Saponification (DS) 99.98mol%), and immersed with stirring at 25 ℃ for 6 hours at intervals, the immersed pellets were centrifuged and dehydrated, and then dried at 80 ℃ for 3 hours and at 120 ℃ for 24 hours to obtain pellets of a resin composition, and as a result of the above analysis, the pellets obtained contained 30ppm of 1-hydroxyethane-1, 1-diphosphonic acid, 200ppm of sodium acetate as a metal salt, 200ppm of acetic acid as a monocarboxylic acid, and 175ppm of boric acid as a boron compound, and the above (7) appearance characteristics (presence or absence of yellowing at the film end faces) were evaluated, and as a, almost no coloration was found in the film end faces and as a, the evaluation of colorability when (8) was repeatedly reused was evaluated, and as a, the durability (9) was evaluated, the number of impurities was increased, and as a number of impurities was 0.10 m or less as needed²But is a decision.

< examples 2 to 17 and comparative examples 1 to 9 >

Pellets of a resin composition were obtained in the same manner as in example 1 except that the components to be blended in the aqueous solution and the concentrations thereof were changed as shown in table 1. The results of the analysis and evaluation of each of the obtained pellets as described above are shown in table 2. Note that HEDP in each table is 1-hydroxyethane-1, 1-diphosphonic acid, NTMP is nitrilotris (methylenephosphonic acid), and EDTMP is ethylenediaminetetra (methylenephosphonic acid) hydrate.

< comparative example 19 >

10.0kg of hydrous EVOH pellets (containing 55mol% of ethylene units (Et) and 97mol% of saponification Degree (DS)) having a water content of 105 mass% and containing 0.2% of sodium acetate (10.8 17.8L) were put into an aqueous solution obtained by dissolving the respective components in water so that pyrophosphoric acid became 0.89 g/L and acetic acid became 1.4 g/L, and the pellets were immersed with stirring at intervals at 25 ℃ for 4 hours, and after the immersed pellets were centrifuged and dehydrated, the pellets were dried at 80 ℃ for 3 hours and then at 120 ℃ for 24 hours in a hot air dryer to obtain pellets of a resin composition, and the results of the analyses and evaluations performed on the pellets are shown in Table 2.

< examples 18 to 20 >

Pellets of a resin composition were obtained in the same manner as in example 1 except that the kind of the hydrous EVOH pellets (Et of EVOH) used, and the components blended in the aqueous solution and the concentrations thereof were changed as shown in Table 1. The results of the analysis and evaluation of each of the obtained pellets as described above are shown in table 2.

[ Table 1]

HEDP 1-hydroxyethane-1, 1-diphosphonic acid

NTMP nitrilotris (methylenephosphonic acid)

EDTMP ethylenediaminetetra (methylenephosphonic acid) hydrate.

[ Table 2]

。

As shown in table 2, when the resin composition contains the specific phosphorus compound and the metal salt in the specific amounts, the judgment of C or more in all the evaluation items can provide a resin composition having excellent durability such that the coloring resistance and the increase of impurities with time are suppressed. Further, the above properties can be further improved by containing the monocarboxylic acid and the boric acid in predetermined amounts.

< example 21 >

Pellets of a resin composition were obtained in the same manner as in example 1 except that the components to be blended in the aqueous solution and the concentrations thereof were changed as shown in table 3. The results of the analysis of the obtained pellets as described above are shown in Table 4. As a result of the evaluation of the appearance characteristics (presence or absence of yellowing of the film end face) in (7), no coloration was observed in the film end face and the film was evaluated as "a", whereas almost no coloration was observed in the evaluation of the coloring property when (8) was repeatedly reused and the film was evaluated as "a". In addition, the number of the foreign matters reached 10 or less/0.1 m for (10) the durability (the increase with time of the stripe-like appearance failure) was²Is less than 10 minutes and is judged as AAnd (4) determining.

< examples 22 to 31 and comparative examples 10 to 18 >

Pellets of a resin composition were obtained in the same manner as in example 21 except that the components to be blended in the aqueous solution and the concentrations thereof were changed as shown in table 3. The results of the analysis and evaluation of each of the obtained pellets as described above are shown in Table 4.

< examples 32 to 34 >

Pellets of a resin composition were obtained in the same manner as in example 21 except that the kind of the hydrous EVOH pellets (Et of EVOH) used, and the components blended in the aqueous solution and the concentrations thereof were changed as shown in Table 3. The results of the analysis and evaluation of each of the obtained pellets as described above are shown in Table 4.

[ Table 3]

HEDP 1-hydroxyethane-1, 1-diphosphonic acid

NTMP nitrilotris (methylenephosphonic acid)

EDTMP ethylenediaminetetra (methylenephosphonic acid) hydrate.

[ Table 4]

。

As shown in Table 4, when the resin composition contains the specific phosphorus compound and the metal salt in the predetermined amounts, the judgment of C or more in all the evaluation items can provide a resin composition having excellent resistance to coloration and durability such that fish eyes, streaks, and the like do not occur even in molding for a long period of time. Further, the above properties can be further improved by containing the monocarboxylic acid and the boric acid in predetermined amounts.

Claims

1. A resin composition comprising an ethylene-vinyl alcohol copolymer as a main component, characterized in that,

contains a phosphorus compound and a metal salt,

the phosphorus compound is condensed phosphoric acid, a compound having 2 or more phosphonic acid groups, or a combination thereof,

the content of the phosphorus compound is 0.1ppm or more and less than 50ppm,

the content of the metal salt is 5ppm to 500ppm in terms of metal element.

2. The resin composition according to claim 1, wherein the metal salt is an alkali metal salt, an alkaline earth metal salt, or a combination thereof.

3. The resin composition according to claim 2, wherein the metal salt is an alkali metal salt.

4. The resin composition according to claim 2, wherein the metal salt is an alkaline earth metal salt,

the content of the alkaline earth metal salt is 5ppm to 100ppm in terms of metal element.

5. The resin composition according to any one of claims 1 to 4, further comprising a monocarboxylic acid,

the content of the monocarboxylic acid is 5ppm to 500 ppm.

6. The resin composition according to any one of claims 1 to 4, further comprising a boron compound,

the content of the boron compound is 5ppm or more and 2,000ppm or less in terms of boron element.

7. A molded article having a portion formed of the resin composition according to any one of claims 1 to 6.