JP2024100967A - Resin composition and molding including the same, and film or sheet having layer composed of the resin composition - Google Patents

Abstract

To provide a resin composition containing an ethylene-vinyl alcohol copolymer and a polyamide resin which is excellent in transparency, and can suppress occurrence of poor appearance such as delamination even after heat treatment by hot water or steam of retort treatment.SOLUTION: A resin composition contains an ethylene-vinyl alcohol copolymer (A) having an ethylene unit content of 20 mol% or more and 60 mol% or less, a polyamide resin (B) and silicon oxide particles (C), in which a mass ratio (A/B) of the ethylene-vinyl alcohol copolymer (A) to the polyamide resin (B) is 55/45 to 99/1, and a content of the silicon oxide particles (C) to the total amount of the ethylene-vinyl alcohol copolymer (A) and the polyamide resin (B) is 5 ppm or more and 5,000 ppm or less.SELECTED DRAWING: None

Description

The present invention relates to a resin composition containing an ethylene-vinyl alcohol copolymer, a molded article containing the same, and a film or sheet having a layer made of the resin composition.

Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") is a resin that has excellent barrier properties against oxygen, odors, flavors, etc. Therefore, EVOH is suitable for use as a packaging material for food and the like. After filling such packaging materials with food or other contents, they are often subjected to a heat treatment with hot water or steam (retort treatment or boiling treatment). However, when packaging materials containing EVOH are heat-treated for a long period of time with hot water or steam, there are disadvantages in that whitening streaks, partial clouding (whitening, etc.), and delamination (hereinafter sometimes abbreviated as "delamination") occur, resulting in a deteriorated appearance, and various studies have been conducted to eliminate such disadvantages.

Patent Document 1 describes a resin composition pellet that contains a specific amount of EVOH, polyamide resin (hereinafter sometimes abbreviated as "PA"), and a fatty acid magnesium salt having 6 or less carbon atoms, with the fatty acid magnesium salt having 6 or less carbon atoms being dispersed in both the EVOH and the PA. It is said that a film using the resin composition pellet has excellent thermal stability during film formation and excellent appearance after heat treatment.

WO2015/174396

However, depending on the layer structure of the packaging material and the retort treatment conditions, poor appearance such as delamination may occur, and the technology described in Patent Document 1 may not be sufficient. Therefore, there is a demand for a resin composition containing EVOH and PA that has improved delamination resistance after retort treatment and has an excellent appearance.

The present invention has been made to solve the above problems, and aims to provide a resin composition containing EVOH and PA that has excellent transparency and can suppress the occurrence of appearance defects such as delamination even after heat treatment with hot water or steam such as retort treatment. It also aims to provide a molded article containing the resin composition, and a film or sheet having a layer made of the resin composition.

In order to solve the above problems, the present invention provides the following resin composition, a molded article containing the same, and a film or sheet having a layer made of the resin composition.

That is, the present invention provides
[1] A resin composition comprising an ethylene-vinyl alcohol copolymer (A) having an ethylene unit content of 20 mol% or more and 60 mol% or less (hereinafter may be abbreviated as "EVOH (A)"), a polyamide resin (B) (hereinafter may be abbreviated as "PA (B)"), and silicon oxide particles (C), in which the mass ratio (A/B) of EVOH (A) to PA (B) is 55/45 to 99/1, and the content of the silicon oxide particles (C) relative to the total amount of EVOH (A) and PA (B) is 5 ppm or more and 5,000 ppm or less;
[2] The resin composition according to [1], wherein the average particle size of the silicon oxide particles (C) is 1 μm or more and 30 μm or less;
[3] The resin composition according to [1] or [2], further comprising a divalent metal compound (D), the content of the divalent metal compound (D) being 10 ppm or more and 500 ppm or less in terms of divalent metal atom relative to the total amount of the EVOH (A) and the PA (B);
[4] A molded article comprising the resin composition according to any one of [1] to [3];
[5] A film or sheet having a layer made of the resin composition according to any one of [1] to [3];
This is achieved by providing:

The present invention provides a resin composition containing EVOH and PA that is excellent in transparency and can suppress the occurrence of appearance defects such as delamination even after heat treatment with hot water or steam such as retort treatment.

The resin composition of the present invention contains EVOH (A) having an ethylene unit content of 20 mol% or more and 60 mol% or less, PA (B) and silicon oxide particles (C), the mass ratio (A/B) of EVOH (A) to PA (B) is 55/45 to 99/1, and the content of silicon oxide particles (C) relative to the total amount of EVOH (A) and PA (B) is 5 ppm or more and 5000 ppm or less. By satisfying such a constitution, a resin composition is provided which is excellent in transparency and can suppress the occurrence of appearance defects such as delamination even after heat treatment with hot water or steam such as retort treatment.

[EVOH (A)]
The resin composition of the present invention tends to have excellent gas barrier properties by containing EVOH (A). EVOH (A) contained in the resin composition of the present invention is a copolymer mainly composed of ethylene units and vinyl alcohol units, and is obtained by saponifying the vinyl ester units in an ethylene-vinyl ester copolymer. The EVOH (A) used in the present invention is not particularly limited, and any known EVOH used in melt molding applications can be used. EVOH (A) can be used alone or in a mixture of two or more types.

The ethylene unit content of EVOH (A) is 20 mol% or more and 60 mol% or less. If the ethylene unit content is less than 20 mol%, the melt moldability of the resin composition may be reduced, so 24 mol% or more is preferable, and 26 mol% or more is more preferable. On the other hand, if the ethylene unit content exceeds 60 mol%, the gas barrier properties may be reduced, so 48 mol% or less is preferable, and 46 mol% or less is more preferable.

The degree of saponification of EVOH (A) is not particularly limited, but from the viewpoint of maintaining gas barrier properties and exhibiting long-run properties, it is preferably 95 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more. On the other hand, the upper limit of the degree of saponification of EVOH (A) is preferably 100 mol%, more preferably 99.99 mol%. The degree of saponification is a value measured in accordance with JIS K6726.

The melt flow rate of EVOH (A) (measured under conditions of a temperature of 210°C and a load of 2160 g according to the method described in ASTM D1238; hereinafter, "melt flow rate" may be referred to as "MFR") is preferably 0.5 g/10 min as a lower limit, more preferably 1.0 g/10 min, and even more preferably 2.0 g/10 min. On the other hand, the upper limit of MFR is preferably 100 g/10 min, more preferably 50 g/10 min, and even more preferably 25 g/10 min. When the MFR is in the above range, the moldability and processability of the resin composition are improved.

EVOH (A) may have units derived from other monomers other than ethylene, vinyl esters, and saponified products thereof. When EVOH (A) has the other monomer units, the content of the other monomer units relative to the total structural units of EVOH (A) is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. When EVOH (A) has units derived from the other monomers, the lower limit may be 0.05 mol% or 0.10 mol%. Examples of the other monomers include alkenes such as propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl 1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methyl Examples of the EVOH include alkenes having an ester group such as dimethylpropane or saponified products thereof; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, or the like, or the anhydrides, salts, or mono- or dialkyl esters thereof; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, or salts thereof; vinyl silane compounds such as vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tri(β-methoxy-ethoxy) silane, and γ-methacryloxypropyl methoxy silane; alkyl vinyl ethers, vinyl ketones, N-vinyl pyrrolidone, vinyl chloride, and vinylidene chloride. The EVOH (A) may be post-modified by a method such as urethanization, acetalization, cyanoethylation, or oxyalkylenation.

EVOH (A) can be produced, for example, by producing an ethylene-vinyl ester copolymer according to a known method, and then saponifying the copolymer to produce EVOH (A). The ethylene-vinyl ester copolymer can be obtained, for example, by polymerizing ethylene and a vinyl ester under pressure in an organic solvent such as methanol, t-butyl alcohol, or dimethyl sulfoxide, using a radical polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile. As the vinyl ester raw material, vinyl acetate, vinyl propionate, vinyl pivalate, etc. can be used, and among these, vinyl acetate is preferred. An acid catalyst or an alkali catalyst can be used to saponify the ethylene-vinyl ester copolymer. The saponification method can be either continuous or batchwise. As the alkali catalyst, sodium hydroxide, potassium hydroxide, alkali metal alcoholate, etc. can be used.

In this way, a solution containing EVOH (A) is obtained, and then the solvent is removed. The method for removing the solvent is not particularly limited as long as it can reduce the solvent content. The EVOH solution can be solidified by extruding it into a poor solvent such as water and solidifying it to reduce the solvent content. In an extruder or kneader, water may be mechanically squeezed out or water vapor may be evaporated from a vent. After the solvent is removed in this way, the EVOH (A) pellets are obtained by cutting. The method for obtaining EVOH (A) pellets by cutting is not particularly limited. The solidified strands in a water-containing state can be cut with a cutter, or the strands in a fluid state in which the water content has been reduced in an extruder or kneader can be cut with a hot cutter or underwater cutter.

Drying can also reduce the moisture content of the resin composition. In this case, the lower limit of the drying time is, for example, 3 hours. On the other hand, the upper limit is, for example, 100 hours. In this specification, the drying time of the pellets refers to the time required for the moisture content of the pellets to become less than 0.5% by mass.

The lower limit of the drying temperature (ambient temperature) during drying is preferably 100°C, more preferably 110°C, even more preferably 120°C, and particularly preferably 125°C. Meanwhile, the upper limit is preferably 150°C, and more preferably 140°C. By setting the drying temperature at or above the above lower limit, efficient and sufficient drying can be performed, and the drying time can be shortened. Meanwhile, by setting the drying temperature at or below the above upper limit, thermal degradation of the EVOH can be suppressed.

The drying may be performed in an air atmosphere, but is preferably performed in an inert gas atmosphere such as nitrogen gas. The drying may be performed under reduced pressure or while dehumidifying. There are no particular limitations on the drying method used in the drying step, and drying may be performed by hot air drying, ultraviolet light irradiation, or infrared light irradiation.

[PA(B)]
The resin composition of the present invention contains PA (B), and the mass ratio (A/B) of EVOH (A) to PA (B) is 55/45 to 99/1. By containing PA (B) at this mass ratio, the gas barrier property and long-run property are excellent, and the appearance after heat treatment with hot water or steam such as retort treatment tends to be excellent. If the mass ratio (A/B) is less than 55/45, the gas barrier property may deteriorate, and it is preferably 60/40 or more, more preferably 70/30 or more, and even more preferably 80/20 or more. On the other hand, if the mass ratio (A/B) exceeds 99/1, the appearance after heat treatment with hot water or steam such as retort treatment may become insufficient, and it is preferably 95/5 or less.

PA (B) includes polycaproamide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), polylauryl lactam (nylon 12), polyethylenediamineadipamide (nylon 26), polytetramethyleneadipamide (nylon 46), polyhexamethyleneadipamide (nylon 66), polyhexamethylenesebacamide (nylon 610), polyhexamethylenedodecamide (nylon 612), Polyoctamethylene adipamide (nylon 86), polydecamethylene adipamide (nylon 106), caprolactam/lauryl lactam copolymer (nylon 6/12), caprolactam/ω-aminononanoic acid copolymer (nylon 6/9), caprolactam/hexamethylenediammonium adipate copolymer (nylon 6/66), lauryl lactam/hexamethylenediammonium adipate copolymer (nylon 12/66), ethylenediammonium adipate/hexamethylenediammonium ammonium adipate copolymer (nylon 26/66), caprolactam/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer (nylon 6/66/610), ethylene diammonium adipate/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer (nylon 26/66/610), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalamide (nylon 6T), hexamethylene Examples of such polyamides include isophthalamide/hexamethylene terephthalamide copolymer (nylon 6I/6T), 11-aminoundecaneamide/hexamethylene terephthalamide copolymer, polynonamethylene terephthalamide (nylon 9T), polydecamethylene terephthalamide (nylon 10T), polyhexamethylene cyclohexylamide, polynonamethylene cyclohexylamide, or polyamides modified with aromatic amines such as methylenebenzylamine and metaxylylenediamine. Metaxylylenediammonium adipate is also included.

Among these, from the viewpoint of improving the appearance after heat treatment with hot water or steam such as retort treatment, a polyamide resin mainly composed of caproamide is preferred, and specifically, it is preferred that 75 mol % or more of the constituent units of PA (B) are caproamide units. Among these, from the viewpoint of compatibility with EVOH (A), it is preferred that PA (B) is nylon 6.

The polymerization method for PA(B) is not particularly limited, and any known method can be used, such as melt polymerization, interfacial polymerization, solution polymerization, bulk polymerization, solid-phase polymerization, or a combination of these.

The thermoplastic resin constituting the resin composition of the present invention may contain other thermoplastic resins other than EVOH (A) and PA (B) to the extent that the effect of the present invention is not impaired. Examples of such other thermoplastic resins include thermoplastic resins such as polyolefins, polyesters, polystyrenes, polyvinyl chlorides, acrylic resins, polyurethanes, polycarbonates, and polyvinyl acetates. The content of such other thermoplastic resins is preferably less than 5% by mass. From the viewpoint of further improving the appearance characteristics after retort treatment, the thermoplastic resin constituting the resin composition of the present invention is preferably 95% by mass or more of EVOH (A) and PA (B), more preferably 97% by mass or more of EVOH (A) and PA (B), even more preferably 99% by mass or more of EVOH (A) and PA (B), and particularly preferably substantially composed of only EVOH (A) and PA (B).

[Silicon oxide particles (C)]
The resin composition of the present invention contains silicon oxide particles (C), and the content of silicon oxide particles (C) relative to the total amount of EVOH (A) and PA (B) is 5 ppm or more and 5000 ppm or less. It has been revealed that by containing silicon oxide particles (C) at this content, the transparency is excellent and the occurrence of appearance defects such as delamination can be suppressed even after heat treatment with hot water or steam such as retort treatment. The content of silicon oxide particles (C) is preferably 20 ppm or more, more preferably 60 ppm or more, even more preferably 100 ppm or more, and particularly preferably 300 ppm or more. If the content of silicon oxide particles (C) is less than 5 ppm, the appearance after heat treatment with hot water or steam such as retort treatment tends to be insufficient. The content of the silicon oxide particles (C) is preferably 4500 ppm or less, more preferably 3500 ppm or less, further preferably 2300 ppm or less, and particularly preferably 1800 ppm or less. If the content of the silicon oxide particles (C) exceeds 5000 ppm, the transparency tends to deteriorate.

The silicon oxide particles (C) used in the present invention are silicon oxides composed of silicon and oxygen atoms, and examples thereof include silicon monoxide (SiO), silicon dioxide (SiO ₂ ), and silicon suboxide (SiOx, 1<x<2). These may be used alone or in combination. The silicon oxide particles (C) are preferably at least one selected from the group consisting of silicon monoxide (SiO), silicon dioxide (SiO ₂ ), and silicon suboxide (SiOx, 1<x<2), and among these, silicon dioxide (SiO ₂ ) is more preferable. The silicon oxide particles (C) may contain metals other than silicon. Examples of other metals include lithium, sodium, potassium, calcium, barium, aluminum, magnesium, zirconium, cerium, tungsten, molybdenum, titanium, chromium, manganese, iron, cobalt, nickel, copper, and zinc. The content of other metals is usually 20 mol% or less based on the total amount of the constituent metals and silicon constituting the silicon oxide particles (C). That is, the content of silicon is 80 mol% or more based on the total amount of the constituent metals and silicon constituting the silicon oxide particles (C). By using silicon oxide particles (C) containing silicon at this content, it has the advantage that the occurrence of appearance defects such as delamination can be suppressed even after heat treatment with hot water or steam such as retort treatment. The content of silicon is preferably 85 mol% or more based on the total amount of the constituent metals and silicon constituting the silicon oxide particles (C), more preferably 90 mol% or more, and even more preferably 95 mol% or more.

The average particle diameter of the silicon oxide particles (C) is not particularly limited, but is preferably 1 μm or more and 30 μm or less. The average particle diameter of the silicon oxide particles (C) is more preferably 1.5 μm or more, even more preferably 1.8 μm or more, and particularly preferably 2.2 μm or more. The average particle diameter of the silicon oxide particles (C) is more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 8 μm or less. By setting the average particle diameter of the silicon oxide particles (C) within the above range, a film with better transparency can be obtained. If the average particle diameter of the silicon oxide particles (C) is within the above range, the silicon oxide particles may be secondary particles formed by agglomeration of the silicon oxide particles. The average particle diameter of the silicon oxide particles (C) is determined by measurement using a laser diffraction type particle size distribution measuring device, and is specifically measured by the method described in the examples described later.

The specific surface area of the silicon oxide particles (C) is not particularly limited, but is preferably 100 m ² /g or more and 1000 m ² /g or less. The specific surface area of the silicon oxide particles (C) is more preferably 150 m ² /g or more, even more preferably 200 m ² /g or more, and particularly preferably 250 m ² /g or more. The specific surface area of the silicon oxide particles (C) is more preferably 900 m ² /g or less, even more preferably 800 m ² /g or less, and particularly preferably 750 m ² /g or less. The specific surface area of the silicon oxide particles (C) can be determined by the BET method.

The aspect ratio of the silicon oxide particles (C) is not particularly limited, but is preferably 1 or more and 10 or less. The aspect ratio of the silicon oxide particles (C) is more preferably 8 or less, even more preferably 5 or less, and particularly preferably 3 or less. The aspect ratio can be determined by the SEM method from the arithmetic average of the measured values of the primary particle width (long axis) and primary particle thickness (short axis) of any 100 crystals in an SEM photograph.

[Divalent metal compound (D)]
The resin composition of the present invention contains a divalent metal compound (D), and the content of the divalent metal compound (D) in terms of divalent metal atoms relative to the total amount of EVOH (A) and PA (B) is preferably 10 ppm or more and 500 ppm or less. The content of the divalent metal compound (D) in terms of divalent metal atoms in the above range tends to be excellent in long-run properties during melt molding. The content of the divalent metal compound (D) in terms of divalent metal atoms is more preferably 10 ppm or more, even more preferably 20 ppm or more, and particularly preferably 30 ppm or more. In addition, the content of the divalent metal compound (D) in terms of divalent metal atoms is more preferably 400 ppm or less, even more preferably 300 ppm or less, and particularly preferably 200 ppm or less.

The metal atom constituting the divalent metal compound (D) is not particularly limited, but preferably contains at least one selected from the group consisting of magnesium, calcium, iron, and zinc. In particular, from the viewpoint of long-run properties in melt molding, it is more preferable that the metal atom constituting the divalent metal compound (D) is at least one selected from the group consisting of magnesium, calcium, and zinc, even more preferable that it is at least one selected from the group consisting of magnesium and calcium, and particularly preferable that it is magnesium.

The divalent metal compound (D) may be a fatty acid salt or a divalent metal hydroxide containing the above metal atom. The fatty acid salt is preferably at least one selected from the group consisting of fatty acid magnesium, fatty acid calcium, fatty acid iron, and fatty acid zinc. Among them, from the viewpoint of long-running properties in melt molding, it is more preferable to use at least one selected from the group consisting of fatty acid magnesium, fatty acid calcium, and fatty acid zinc, and it is even more preferable to use at least one selected from the group consisting of fatty acid magnesium and fatty acid calcium, and it is particularly preferable to use fatty acid magnesium. The fatty acid may be a fatty acid having 1 to 30 carbon atoms, and among them, a fatty acid having 1 to 7 carbon atoms is preferable, a fatty acid having 1 to 3 carbon atoms is more preferable, and it is even more preferable to use acetic acid. The divalent metal hydroxide is preferably at least one selected from the group consisting of magnesium hydroxide, calcium hydroxide, iron hydroxide, and zinc hydroxide. Among them, from the viewpoint of long-running properties in melt molding, it is more preferable to use at least one selected from the group consisting of magnesium hydroxide, calcium hydroxide, and zinc hydroxide, and it is even more preferable to use at least one selected from the group consisting of magnesium hydroxide and calcium hydroxide, and it is particularly preferable to use magnesium hydroxide.

In a preferred embodiment, the ratio of magnesium atoms to all metal atoms constituting the divalent metal compound (D) is 80 mol% or more. This has the advantage of excellent long-run performance in long-term melt molding. The ratio is more preferably 90 mol% or more, and even more preferably 95 mol% or more, and it is particularly preferred that the divalent metal atoms of the divalent metal compound (D) are substantially magnesium atoms.

The resin composition of the present invention may contain various additives other than those described above, provided that the effects of the present invention are not impaired. Examples of such additives include carboxylic acid compounds, phosphoric acid compounds, boron compounds, alkali metal salts, antioxidants, plasticizers, heat stabilizers, UV absorbers, antistatic agents, lubricants, colorants, fillers, other resins, and the like, and specific examples include the following. The content of the additives is usually 10% by mass or less, preferably 5% by mass or less, and more preferably 1% by mass or less.

When the resin composition of the present invention contains a carboxylic acid compound, it tends to be less likely to discolor during melt molding. The carboxylic acid may be a monocarboxylic acid or a polycarboxylic acid, or a combination of these. The carboxylic acid may also be an ion, and such a carboxylic acid ion may form a salt with a metal ion. Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, acrylic acid, methacrylic acid, benzoic acid, and 2-naphthoic acid, and among these, acetic acid is preferred. Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, maleic acid, and fumaric acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; tricarboxylic acids such as aconitic acid; carboxylic acids having four or more carboxy groups such as 1,2,3,4-butanetetracarboxylic acid and ethylenediaminetetraacetic acid; hydroxycarboxylic acids such as tartaric acid, citric acid, isocitric acid, and malic acid; ketocarboxylic acids such as oxaloacetic acid, mesoxalic acid, and 2-ketoglutaric acid; and amino acids such as glutamic acid and aspartic acid. Among these, succinic acid, malic acid, tartaric acid, and citric acid are preferred because they are easily available. When the resin composition of the present invention contains a carboxylic acid compound, the content thereof is preferably 0.01 μmol/g or more and 20 μmol/g or less in terms of carboxylic acid radical.

When the resin composition of the present invention contains a phosphoric acid compound, it tends to be less likely to discolor during melt molding. The phosphoric acid compound is not particularly limited, and various acids such as phosphoric acid and phosphorous acid and their salts can be used. The phosphate may be contained in the form of any of primary phosphate, secondary phosphate, and tertiary phosphate, but primary phosphate is preferred. The cation species is also not particularly limited, but alkali metal salts are preferred. Among these, sodium dihydrogen phosphate and potassium dihydrogen phosphate are preferred. When the resin composition of the present invention contains a phosphoric acid compound, the content of the phosphoric acid compound is preferably 5 to 200 ppm in terms of phosphate radical. When the content of the phosphoric acid compound is 5 ppm or more, the discoloration resistance during melt molding tends to be good. On the other hand, when the content of the phosphoric acid compound is 200 ppm or less, the melt moldability tends to be good, and more preferably 160 ppm or less.

When the resin composition of the present invention contains a boron compound, the torque fluctuation during heat melting tends to be suppressed. The boron compound is not particularly limited, and examples thereof include boric acids, boric acid esters, borate salts, boron hydrides, etc. Specifically, examples of boric acids include orthoboric acid, metaboric acid, tetraboric acid, etc., examples of borate esters include triethyl borate, trimethyl borate, etc., and examples of borates include alkali metal salts, alkaline earth metal salts, borax, etc. of the various borates mentioned above. Among these compounds, orthoboric acid (hereinafter, sometimes simply referred to as boric acid) is preferred. When the resin composition of the present invention contains a boron compound, the content of the boron compound is preferably 20 to 2000 ppm in terms of boron element. When the content of the boron compound is 20 ppm or more, the torque fluctuation during heat melting tends to be suppressed, and more preferably 50 ppm or more. On the other hand, if the content of boron compounds is 2000 ppm or less, moldability tends to be good, and more preferably 1000 ppm or less.

When the resin composition of the present invention contains an alkali metal salt, the interlayer adhesion between the layer containing the resin composition of the present invention and other resin layers tends to be improved. The cation species of the alkali metal salt is not particularly limited, but sodium salt or potassium salt is preferable. The anion species of the alkali metal salt is also not particularly limited. It can be added as a carboxylate, carbonate, hydrogen carbonate, phosphate, hydrogen phosphate, borate, hydroxide, etc. When the resin composition of the present invention contains an alkali metal salt, the content of the alkali metal salt is preferably 10 to 500 ppm in terms of metal element. The content of the alkali metal salt is more preferably 50 ppm or more. On the other hand, when the content of the alkali metal salt is 500 ppm or less, the melt stability tends to be improved, and is more preferably 300 ppm or less.

Antioxidants: 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis-(6-t-butylphenol), 2,2'-methylene-bis-(4-methyl-6-t-butylphenol), octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, 4,4'-thiobis-(6-t-butylphenol), etc. Plasticizers: diethyl phthalate, dibutyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate ester, etc. UV absorbers: ethylene-2-cyano-3,3'-diphenylacrylate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, etc. Antistatic agents: pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, etc. Lubricants: ethylene bisstearamide, butyl stearate, etc.

The method for producing the resin composition of the present invention is not particularly limited, and it is preferable to prepare the resin composition by dry blending EVOH (A), PA (B) and silicon oxide particles (C), and then adding divalent metal compound (D) and various additives as necessary and melt-kneading the mixture. Specifically, the mixture can be prepared using a known mixing or kneading device such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer. The temperature during melt-kneading is usually 110 to 300°C. The silicon oxide particles (C), divalent metal compound (D) and various additives may be contained in EVOH (A) or PA (B) in advance. In addition, when the divalent metal compound (D) is a divalent metal hydroxide, a method of adding the divalent metal compound (D) to EVOH (A), PA (B) and silicon oxide particles (C) and dry-blending the mixture is preferably adopted. The resin composition of the present invention may be in any form such as pellets or powder, and pellets are preferred from the viewpoint of stable melt molding.

The resin composition of the present invention is preferably used as a molded product. Specific examples of the molded product include extrusion molded products, films or sheets (particularly oriented films or heat-shrinkable films), thermoformed products, wallpaper or decorative panels, pipes or hoses, profile molded products, extrusion blow molded products, injection molded products, flexible packaging materials, and containers (particularly retort containers). When the molded product is a multilayer structure, preferred examples include coextruded films or coextruded sheets, heat-shrinkable films, containers (particularly coextrusion blow molded containers, coinjection molded containers, and retort containers), pipes (particularly fuel pipes or hot water circulation pipes), and hoses (particularly fuel hoses).

When the molded article of the present invention is a multilayer structure including a layer made of the resin composition of the present invention, the multilayer structure is formed by laminating layers other than the layer made of the resin composition of the present invention. Examples of the layer configuration of the multilayer structure of the present invention include x/y, x/y/x, x/z/y, x/z/y/z/x, x/y/x/y/y/x, x/z/y/z/x/z/y/z/x, etc., where x is a layer made of a polymer other than the resin composition of the present invention, y is a layer made of the resin composition of the present invention, and z is an adhesive polymer layer. When multiple x layers are provided, the types of layers may be the same or different. In addition, a layer using a recovered polymer made of scrap such as trim generated during molding may be provided separately, or the recovered polymer may be blended with a layer made of another polymer. The thickness configuration of each layer of the multilayer structure is not particularly limited, but from the viewpoint of moldability and cost, the thickness ratio of the y layer to the total layer thickness is preferably 2 to 20%.

The polymer used for the x layer is preferably a thermoplastic polymer from the viewpoint of processability, etc. Examples of such a thermoplastic polymer include the following polymers.
polyethylene, polypropylene, ethylene-propylene copolymers, ethylene or propylene copolymers (copolymers of ethylene or propylene with at least one of the following monomers: α-olefins such as 1-butene, isobutene, 4-methyl-1-pentene, 1-hexene, 1-octene, etc.; unsaturated carboxylic acids such as itaconic acid, methacrylic acid, acrylic acid, maleic anhydride, etc., salts thereof, partial or complete esters thereof, nitriles thereof, amides thereof, anhydrides thereof; vinyl esters of carboxylic acids such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octanoate, vinyl dodecanoate, vinyl stearate, vinyl arachidonate, etc.; vinyl silane compounds such as vinyl trimethoxysilane, etc.; unsaturated sulfonic acids or salts thereof; alkylthiols; vinylpyrrolidones, etc.);
Polyolefins such as poly(4-methyl-1-pentene) and poly(1-butene);
Polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate;
Polyamides such as poly-ε-caprolactam, polyhexamethylene adipamide, and polymetaxylylene adipamide;
-Polyvinylidene chloride, polyvinyl chloride, polystyrene, polyacrylonitrile, polycarbonate, polyacrylate, etc.
Such a thermoplastic polymer layer may be unoriented, or may be uniaxially or biaxially oriented or rolled.

Of these thermoplastic polymers, polyolefins are preferred in terms of moisture resistance, mechanical properties, cost-effectiveness, heat sealability, etc., while polyamides and polyesters are preferred in terms of mechanical properties, heat resistance, etc.

On the other hand, the adhesive polymer used in the z-layer may be any polymer capable of bonding the layers together, and is preferably a polyurethane- or polyester-based one- or two-component curable adhesive, a carboxylic acid-modified polyolefin polymer, or the like. The carboxylic acid-modified polyolefin polymer is an olefin-based polymer or copolymer containing an unsaturated carboxylic acid or its anhydride (maleic anhydride, etc.) as a copolymerization component; or a graft copolymer obtained by grafting an unsaturated carboxylic acid or its anhydride to an olefin-based polymer or copolymer.

When the multilayer structure is manufactured by a co-injection molding method or a co-extrusion molding method, the adhesive polymer is preferably a carboxylic acid-modified polyolefin polymer. In particular, when the x layer is a polyolefin polymer, the adhesive polymer has good adhesion to the y layer. Examples of polyolefin polymers constituting such carboxylic acid-modified polyolefin polymers include polyethylenes such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE); polypropylene; copolymerized polypropylene; ethylene-vinyl acetate copolymer; ethylene-(meth)acrylic acid ester (methyl ester or ethyl ester) copolymer; and the like. On the other hand, when the multilayer structure is manufactured by a dry lamination method, a polyurethane-based two-liquid curable adhesive is more preferable. In this case, a variety of polymers can be used for the x layer, so that the functionality of the multilayer structure can be made more advanced.

Methods for obtaining the multilayer structure include, for example, extrusion lamination, dry lamination, co-injection molding, and co-extrusion molding. Examples of co-extrusion molding methods include co-extrusion lamination, co-extrusion sheet molding, co-extrusion pipe molding, co-extrusion tube molding, co-extrusion inflation molding, and co-extrusion blow molding.

The sheet, film, parison, etc. of the multilayer structure thus obtained can be reheated at a temperature below the melting point of the polymer contained therein, and uniaxially or biaxially stretched by a thermoforming method such as squeeze molding, a roll stretching method, a pantograph stretching method, an inflation stretching method, a blow molding method, etc. to obtain a stretched molded product.

The molded article containing the resin composition of the present invention obtained in this manner has excellent transparency and is able to suppress the occurrence of appearance defects such as delamination even after heat treatment with hot water or steam such as retort treatment, so it is suitable for use as packaging materials and containers, and is particularly suitable for retort packaging materials and retort containers.

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the examples shown below. The measurement, calculation, and evaluation methods were as follows.

<Ingredients used>
[EVOH (A)]
A-1: "EVAL (registered trademark) L171B" (manufactured by Kuraray Co., Ltd., EVOH pellets, ethylene unit content 27 mol%, MFR 4.0 g/10 min (210°C, 2160 g load), melting point 190°C)
[PA(B)]
B-1: "SF1018A" (manufactured by Ube Industries, Ltd., polyamide 6 pellets, melting point 220°C)
[Silicon oxide particles (C)]
C-1: "Sylysia (registered trademark) 310P" (manufactured by Fuji Silysia Chemical Ltd., average particle size 2.7 μm, specific surface area 300 m ² /g, proportion of silicon to the total amount of constituent metals and constituent silicon 96 mol %)
C-2: "Sylysia (registered trademark) 380" (manufactured by Fuji Silysia Chemical Ltd., average particle size 9.0 μm, specific surface area 300 m ² /g, ratio of silicon to the total amount of constituent metals and constituent silicon 96 mol %)
C-3: "Sylysia (registered trademark) 530" (manufactured by Fuji Silysia Chemical Ltd., average particle size 2.7 μm, specific surface area 500 m ² /g, ratio of silicon to the total amount of constituent metals and constituent silicon 96 mol %)
C-4: "Sylysia (registered trademark) 710" (manufactured by Fuji Silysia Chemical Ltd., average particle size 2.8 μm, specific surface area 700 m ² /g, ratio of silicon to the total amount of constituent metals and constituent silicon 96 mol %)
[Inorganic layered silicate (C')]
C'-5: "Kunipia-F" (manufactured by Kunimine Industries Co., Ltd., montmorillonite, average particle size 2.0 μm, specific surface area 25 m ² /g, proportion of silicon to the total amount of constituent metals and constituent silicon 63 mol%).

<Evaluation method>
(1) Delamination resistance after retort treatment The 20 μm thick monolayer film, biaxially oriented nylon 6 film (Unitika Ltd.'s "EMBLEM (registered trademark) ONBC", thickness 15 μm) and non-oriented polypropylene film (Mitsui Chemicals Tohcello's "RXC-22", thickness 50 μm) obtained in the examples and comparative examples were each cut to A4 size, and a dry lamination adhesive was applied to both sides of the monolayer film, and dry lamination was performed so that the outer layer was a nylon 6 film and the inner layer was a non-oriented polypropylene film, and the film was dried at 80 ° C. for 3 minutes to obtain a transparent laminate film consisting of three layers. The dry lamination adhesive used was Mitsui Chemicals Inc.'s "Takelac (registered trademark) A-520" as the main agent, Mitsui Chemicals Inc.'s "Takenate (registered trademark) A-50" as the hardener, and ethyl acetate as the diluent. The amount of the adhesive applied was 4.0 g/m ² , and after lamination, the laminate was left to cure at 40° C. for 3 days.

Two sheets of the obtained laminate film were used to overlap the non-oriented polypropylene film and produce a pouch with four sealed sides of outer dimensions of 12 cm x 12 cm. The content was water. This was subjected to retort treatment at 125°C for 30 minutes using a retort device (Hisaka Manufacturing Co., Ltd.'s high-temperature, high-pressure cooking sterilization tester "RCS-40RTGN"). After the retort treatment, the surface water was wiped off and the pouch was left for one day in a constant temperature and humidity room at 20°C and 65% RH, and then the appearance characteristics were evaluated as delamination resistance according to the following criteria. Of the following criteria, A, B, and C are usable levels.
Judgment: Criteria A: No delamination B: About 10% of the pouch surface is delaminated C: About 20% of the pouch surface is delaminated D: About 50% of the pouch surface is delaminated E: More than 70% of the pouch surface is delaminated

(2) Haze Value For the single-layer films having a thickness of 20 μm obtained in the Examples and Comparative Examples, the haze value was measured using a reflectance/transmittance meter "HR-100" (manufactured by Murakami Color Research Laboratory) in accordance with ASTM D1003-61.

(3) Oxygen transmission rate (OTR)
For the monolayer films having a thickness of 20 μm obtained in the examples and comparative examples, the oxygen transmission rate (cc·20 μm/(m ² ·day·atm)) was measured using an oxygen transmission rate measuring device "OX-TRAN2/20 type" (detection limit value 0.01 cc·20 μm/(m ² ·day·atm)) manufactured by MOCON INC. under conditions of a temperature of 20° C. and a humidity of 65% RH in accordance with the method described in JIS K 7126 (isobaric method).

(4) Quantitative Determination of the Metal Atom Equivalent of the Divalent Metal Compound (D) 0.5 g of the resin composition pellet obtained in the example was added to a Teflon (registered trademark) pressure-resistant container manufactured by Actac Co., Ltd., and 5 mL of nitric acid for precision analysis manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was added. After leaving it for 30 minutes, the container was covered with a cap lip with a rupture disk, and decomposition treatment was performed under conditions of 150 ° C. for 10 minutes and then 180 ° C. for 10 minutes using a microwave high-speed decomposition system "Speed Wave MWS-2" manufactured by Actac Co., Ltd. If the decomposition of the resin composition pellet was insufficient, the treatment conditions were appropriately adjusted. The contents after the decomposition treatment were diluted with 10 mL of ion-exchanged water, and all the liquid was transferred to a 50 mL measuring flask and the volume was adjusted with ion-exchanged water to obtain a decomposition solution. The above decomposition solution was measured using an ICP emission spectrometer "Optima 4300 DV" manufactured by PerkinElmer Japan Co., Ltd., and the metal atom equivalent amount of the divalent metal compound (D) was quantified.

(5) Evaluation of long-run properties Using the resin composition pellets obtained in the examples, a 20 μm monolayer film was continuously produced using a single-screw extruder (Toyo Seiki Seisakusho Co., Ltd., D2020, D (mm) = 20, L / D = 20, compression ratio = 3.5, screw: full flight). The extrusion conditions are as follows.
Extrusion temperature: 230°C
Dice width: 30cm
Take-up roll temperature: 80°C
Screw rotation speed: 40 rpm
Take-up roll speed: 3.0 m/min

Six hours after the start of film formation, the monolayer film obtained was sampled to a size of 10 cm x 10 cm, and the number of visually visible bumps (approximately 50 μm or larger) was visually counted and compared with the number of bumps found when a similar test was conducted using the resin composition pellets obtained in Example 2.

(6) Measurement of the average particle size of silicon oxide particles (C) The average particle size of silicon oxide particles (C) was measured using a laser diffraction particle size distribution analyzer SALD-2200 manufactured by Shimadzu Corporation. The evaluation sample was prepared by adding 50 cc of pure water and 5 g of silicon oxide particles (C) to be measured to a glass beaker, stirring with a spatula, and then dispersing for 10 minutes with an ultrasonic cleaner. Next, a liquid containing silicon oxide particles (C) that had been dispersed was added to the sampler section of the device, and measurements were performed when the absorbance became stable, and the particle size distribution (particle size and relative particle amount) was calculated from the light intensity distribution data of the diffracted/scattered light of the particles. The average particle size was obtained by multiplying the measured particle size and the relative particle amount and dividing by the sum of the relative particle amounts. The average particle size of silicon oxide particles (C) did not change substantially even in the resin composition. The average particle size is the average diameter of the particles.

Example 1
90 parts by mass of EVOH (A-1), 10 parts by mass of PA (B-1), and silicon oxide particles (C-1) were dry-blended to 600 ppm relative to the total of 100 parts by mass of EVOH (A-1) and PA (B-1), and then melt-extruded at a melt temperature of 230° C. and an extrusion rate of 20 kg/hr using a twin-screw extruder "TEX30α" (screw diameter 30 mm) manufactured by The Japan Steel Works, Ltd., and the extruded strand was cooled and solidified in a cooling tank and then cut to obtain resin composition pellets. Note that a forward kneading disk having L (screw length)/D (screw diameter)=3 was used as the screw of the twin-screw extruder.

Using the obtained resin composition pellets, a single-layer film having a thickness of 20 μm was produced using a single-screw extruder (Toyo Seiki Seisakusho Co., Ltd., D2020, D (mm) = 20, L / D = 20, compression ratio = 3.0, screw: full flight). The extrusion conditions are as follows.
Extrusion temperature: 230°C
Dice width: 30cm
Take-up roll temperature: 80°C
Screw rotation speed: 40 rpm
Take-up roll speed: 3.0 m/min

The delamination resistance, haze value, and oxygen permeability of the obtained monolayer film after retort treatment were measured according to the methods described in the above evaluation methods (1) to (3). The results are shown in Table 1.

<Examples 2 to 6, 9 to 11, Comparative Examples 1 to 5>
As shown in Table 1, the evaluation was performed in the same manner as in Example 1, except that the content of PA (B) and the type and content of silicon oxide particles (C) were changed.

Example 7
Resin composition pellets and a monolayer film were produced and evaluated in the same manner as in Example 2, except that an aqueous solution of magnesium acetate was added as the divalent metal compound (D) in the twin-screw extruder when producing the resin composition pellets, using a liquid addition pump, so that the magnesium concentration became the concentration shown in Table 1. The results are shown in Table 1.

The resin composition pellets obtained in Example 7 were subjected to quantification of the metal atom equivalent amount of the divalent metal compound (D) according to the method described in the evaluation method (4) above. The results are shown in Table 1. In addition, the resin composition pellets obtained in Example 7 were subjected to a long-run evaluation according to the method described in the evaluation method (5) above. As a result, it was confirmed that the number of bumps 6 hours after the start of film formation could be suppressed to one-quarter or less compared to the case where the resin composition pellets of Example 2 were used.

Example 8
90 parts by mass of EVOH (A-1), 10 parts by mass of PA (B-1), silicon oxide particles (C-1) were 1200 ppm relative to the total of 100 parts by mass of EVOH (A-1) and PA (B-1), and "KISUMA (registered trademark) 10A" (manufactured by Kyowa Chemical Industry Co., Ltd., magnesium hydroxide) as a divalent metal compound (D) was dry-blended and melt-extruded to 45 ppm (magnesium atom equivalent) relative to the total of 100 parts by mass of EVOH (A-1) and PA (B-1). Resin composition pellets and a single layer film were produced and evaluated in the same manner as in Example 2. The results are shown in Table 1.

The resin composition pellets obtained in Example 8 were subjected to quantitative analysis of the metal atom equivalent amount of the divalent metal compound (D) according to the method described in the above evaluation method (4). The results are shown in Table 1. Furthermore, the resin composition pellets obtained in Example 8 were subjected to a long-run evaluation according to the method described in the above evaluation method (5). As a result, it was confirmed that the number of bumps 6 hours after the start of film formation could be suppressed to less than one-quarter compared to the case where the resin composition pellets of Example 2 were used. Furthermore, when retort treatment was performed under severe retort conditions of 125°C for 45 minutes according to the method described in the above evaluation method (1), the results showed no appearance defects such as delamination or whitening.

<Comparative Example 6>
In Comparative Example 1, resin composition pellets and a single layer film were produced and evaluated in the same manner as in Comparative Example 1, except that an aqueous solution of magnesium acetate was prepared in the twin-screw extruder when preparing the resin composition pellets, and the aqueous solution was added by a liquid addition pump so that the magnesium concentration was the concentration shown in Table 1. For the resin composition pellets obtained in Comparative Example 6, the amount of divalent metal compound (D) converted into divalent metal atoms was quantified according to the method described in the above evaluation method (4). The results are shown in Table 1.

Claims (5)

A resin composition comprising an ethylene-vinyl alcohol copolymer (A) having an ethylene unit content of 20 mol% or more and 60 mol% or less, a polyamide resin (B) and silicon oxide particles (C), the mass ratio (A/B) of the ethylene-vinyl alcohol copolymer (A) to the polyamide resin (B) being 55/45 to 99/1, and the content of the silicon oxide particles (C) relative to the total amount of the ethylene-vinyl alcohol copolymer (A) and the polyamide resin (B) being 5 ppm or more and 5,000 ppm or less. The resin composition according to claim 1, wherein the average particle size of the silicon oxide particles (C) is 1 μm or more and 30 μm or less. The resin composition according to claim 1 or 2, further comprising a divalent metal compound (D), the content of the divalent metal compound (D) relative to the total amount of the ethylene-vinyl alcohol copolymer (A) and the polyamide resin (B) being 10 ppm or more and 500 ppm or less in terms of divalent metal atoms. A molded article comprising the resin composition according to any one of claims 1 to 3. A film or sheet having a layer made of the resin composition according to any one of claims 1 to 3.