阅读说明：本技术 乙烯-乙烯醇系共聚物组合物、粒料及多层结构体 (Ethylene-vinyl alcohol copolymer composition, pellet, and multilayer structure ) 是由 碓氷真太郎 西村大知 池下美奈子 于 2018-06-27 设计创作，主要内容包括：作为着色得以抑制的乙烯-乙烯醇系共聚物组合物,提供如下乙烯-乙烯醇系共聚物组合物,其含有乙烯-乙烯醇系共聚物(A)、聚酰胺系树脂(B)及铁化合物(C),上述铁化合物(C)的含量相对于乙烯-乙烯醇系共聚物组合物的单位重量以金属换算为0.01～20ppm。(Disclosed is an ethylene-vinyl alcohol copolymer composition wherein coloration is suppressed, which contains an ethylene-vinyl alcohol copolymer (A), a polyamide resin (B), and an iron compound (C), wherein the content of the iron compound (C) is 0.01-20 ppm in terms of metal relative to the unit weight of the ethylene-vinyl alcohol copolymer composition.)

1. An ethylene-vinyl alcohol copolymer composition comprising an ethylene-vinyl alcohol copolymer (A), a polyamide resin (B), and an iron compound (C), wherein the iron compound (C) is contained in an amount of 0.01 to 20ppm in terms of metal relative to the unit weight of the ethylene-vinyl alcohol copolymer composition.

2. The ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the weight content ratio of the ethylene-vinyl alcohol copolymer (A) to the polyamide resin (B) is 99/1 to 10/90.

3. A pellet comprising the ethylene-vinyl alcohol copolymer composition according to claim 1 or 2.

4. A multilayer structure comprising a layer formed from the ethylene-vinyl alcohol copolymer composition according to claim 1 or 2.

Technical Field

The present invention relates to an EVOH resin composition containing an ethylene-vinyl alcohol copolymer (hereinafter referred to as "EVOH resin"), a pellet, and a multilayer structure, and more particularly, to an EVOH resin composition in which coloring and an increase in viscosity with time are suppressed, a pellet formed from the EVOH resin composition, and a multilayer structure having a layer formed from the EVOH resin composition.

Background

EVOH resins are excellent in transparency, gas barrier properties such as oxygen gas, aroma retention, solvent resistance, oil resistance, mechanical strength and the like, and are widely used as various packaging materials such as food packaging materials, pharmaceutical packaging materials, industrial pharmaceutical packaging materials, and pharmaceutical packaging materials by being formed into films, sheets, bottles and the like. However, when a packaging material containing an EVOH resin layer is subjected to hot water sterilization treatment such as retort (retorting) and boiling (boil), the EVOH resin layer tends to be eluted out, and the gas barrier property of the EVOH resin layer tends to be lowered. In contrast, a technique of using a polyamide resin in combination is known (for example, see patent documents 1 and 2).

Disclosure of Invention

Problems to be solved by the invention

On the other hand, a resin composition containing an EVOH resin and a polyamide resin tends to be colored after heating such as melt kneading and melt molding, and tends to increase in viscosity with time, and improvement is required.

Means for solving the problems

The present inventors have intensively studied in view of the above circumstances and, as a result, have found that the above problems can be solved when a resin composition containing an EVOH resin and a polyamide resin is blended with a small amount of an iron compound.

That is, the invention 1 is the EVOH resin composition containing an EVOH resin (A), a polyamide resin (B), and an iron compound (C), wherein the content of the iron compound (C) is 0.01 to 20ppm in terms of metal relative to the unit weight of the EVOH resin composition. The invention also provides a pellet formed from the EVOH resin composition as described above in the 2 nd aspect, and a multilayer structure having a layer formed from the EVOH resin composition as described above in the 3 rd aspect.

ADVANTAGEOUS EFFECTS OF INVENTION

The EVOH resin composition of the present invention contains an EVOH resin (A), a polyamide resin (B), and an iron compound (C), and the content of the iron compound (C) is 0.01 to 20ppm in terms of metal relative to the unit weight of the EVOH resin composition, so that coloring is suppressed and dynamic viscosity behavior is excellent.

In addition, when the weight ratio of the EVOH resin (a) to the polyamide resin (B) is 99/1 to 10/90, coloration can be further suppressed.

The pellets of the EVOH resin composition of the present invention are inhibited from coloring, and therefore can be formed into various molded articles suitable for use as packaging materials for foods, medicines, agricultural chemicals, etc., particularly packaging materials for hot water sterilization.

The multilayer structure having a layer comprising the EVOH resin composition of the present invention is suppressed in coloration, and therefore can be formed into various molded articles and suitably used as packaging materials for foods, medicines, agricultural chemicals, and the like, particularly packaging materials for hot water sterilization.

Detailed Description

The configuration of the present invention will be described in detail below, but these embodiments are merely examples of preferred embodiments and are not limited to these.

< EVOH resin composition >

The EVOH resin composition of the present invention contains an EVOH resin (A), a polyamide resin (B), and an iron compound (C). The EVOH resin composition of the present invention contains the EVOH resin (a) and the polyamide resin (B) as main components. That is, the total content of the EVOH resin (a) and the polyamide resin (B) in the EVOH resin composition is usually 70 wt% or more, preferably 80 wt% or more, more preferably 90 wt% or more, and particularly preferably 95 wt% or more. Hereinafter, the respective components of the EVOH resin composition of the present invention will be described in order.

[ EVOH resin (A) ]

The EVOH resin (a) used in the present invention is generally a resin obtained by saponifying an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and a vinyl ester monomer, and is a water-insoluble thermoplastic resin. As the vinyl ester monomer, vinyl acetate is generally used from the economical viewpoint.

The polymerization method of ethylene and vinyl ester monomers may be any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, etc., and usually solution polymerization using methanol as a solvent is used. The saponification of the ethylene-vinyl ester copolymer obtained can also be carried out by a known method.

The EVOH resin (a) thus produced contains, mainly, ethylene-derived structural units and vinyl alcohol structural units, and a few vinyl ester structural units remaining without saponification.

Vinyl acetate is typically used as the vinyl ester monomer in view of its availability in the market and its high efficiency in impurity treatment during production. Examples of the other vinyl ester monomer include aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl versatate, and aromatic vinyl esters such as vinyl benzoate, and aliphatic vinyl esters having usually 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms can be used. These may be used alone or in combination as necessary.

The content of the ethylene structural unit in the EVOH resin (a) can be controlled by the pressure of ethylene at the time of copolymerizing the vinyl ester monomer and ethylene, and is usually 20 to 60 mol%, preferably 25 to 50 mol%, and particularly preferably 25 to 35 mol%. If the content is too low, the gas barrier property and the stretchability under high humidity tend to be reduced, whereas if the content is too high, the gas barrier property tends to be reduced. The content of the ethylene structural unit may be determined based on ISO 14663.

The saponification degree of the vinyl ester component in the EVOH resin (a) can be controlled by the amount, temperature, time, and the like of a saponification catalyst (usually, an alkaline catalyst such as sodium hydroxide is used) in saponifying the ethylene-vinyl ester copolymer, and is usually 90 to 100 mol%, preferably 95 to 100 mol%, and particularly preferably 98 to 100 mol%. If the degree of saponification is too low, gas barrier properties, thermal stability, moisture resistance, and the like tend to be reduced. The degree of saponification of the EVOH resin can be measured in accordance with JIS K6726 (in which the EVOH resin is used in the form of a solution in which the EVOH resin is uniformly dissolved in a water/methanol solvent).

The Melt Flow Rate (MFR) (210 ℃ C., load 2160g) of the EVOH resin (A) is usually 0.5 to 100g/10 min, preferably 1 to 50g/10 min, and particularly preferably 3 to 35g/10 min. When the MFR is too large, the stability during film formation tends to be impaired, and when it is too small, the viscosity tends to be too high, and melt extrusion tends to be difficult. The MFR is an index of the degree of polymerization of the EVOH resin, and can be adjusted by the amount of the polymerization initiator and the amount of the solvent when copolymerizing ethylene and the vinyl ester monomer.

The EVOH resin (a) used in the present invention may further contain a structural unit derived from a comonomer shown below within a range not hindering the effect of the present invention (for example, 20 mol% or less of the EVOH resin (a)).

Examples of the comonomer include olefins such as propylene, 1-butene and isobutylene, hydroxyl-containing α -olefins such as 3-butene-1-ol, 3-butene-1, 2-diol, 4-pentene-1-ol and 5-hexene-1, 2-diol, and derivatives such as esters and acylates thereof; hydroxyalkyl vinylene compounds (such as 2-methylenepropane-1, 3-diol and 3-methylenepentane-1, 5-diol); hydroxyalkyl vinylidene diacetates such as 1, 3-diacetoxy-2-methylene propane, 1, 3-dipropoyloxy-2-methylene propane and 1, 3-dibutyryloxy-2-methylene propane; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, phthalic acid (anhydride), maleic acid (anhydride), and itaconic acid (anhydride), salts thereof, and mono-or dialkyl esters of these unsaturated acids having 1 to 18 carbon atoms in the alkyl group; acrylamides such as acrylamide, N-alkylacrylamide in which the number of carbon atoms in the alkyl group is 1 to 18, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof; methacrylamides such as methacrylamide, N-alkylmethacrylamides having 1 to 18 carbon atoms in the alkyl group, N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof; n-vinylamides such as N-vinylpyrrolidone, N-vinylformamide and N-vinylacetamide; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl ethers having 1 to 18 carbon atoms in the alkyl group such as alkyl vinyl ether, hydroxyalkyl vinyl ether and alkoxyalkyl vinyl ether; halogenated vinyl compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and vinyl bromide; vinylsilanes such as trimethoxyvinylsilane; allyl acetate; halogenated allyl compounds such as allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; trimethyl- (3-acrylamide-3-dimethylpropyl) -ammonium chloride, acrylamide-2-methylpropanesulfonic acid and the like. These may be used alone or in combination of 2 or more.

In particular, EVOH resins having a primary hydroxyl group in the side chain are preferable because they maintain gas barrier properties and are excellent in secondary moldability, among them, EVOH resins obtained by copolymerizing α -olefins containing a hydroxyl group are preferable, and EVOH resins having a1, 2-diol structure in the side chain are particularly preferable. In particular, when the side chain has a primary hydroxyl group, the content thereof is usually 0.1 to 20 mol%, further 0.5 to 15 mol%, and particularly preferably 1 to 10 mol% of the EVOH resin.

The EVOH resin (a) used in the present invention may be one that has been "post-modified" such as urethanization, acetalization, cyanoethylation, or oxyalkylene.

The EVOH resin (a) used in the present invention may be a mixture with another EVOH resin different from the EVOH resin (a), and examples of the other EVOH resin include those having different ethylene structural unit contents, different degrees of saponification, different degrees of polymerization, different copolymerization components, and the like. Among them, from the viewpoint of maintaining the gas barrier property and improving the secondary moldability, it is preferable to use 2 or more kinds of EVOH resins having different ethylene structural unit contents.

[ Polyamide resin (B) ]

The polyamide resin (B) used in the present invention is a known resin, and is a water-insoluble thermoplastic resin.

Examples of the polyamide resin (B) include homopolymers such as polycaprolactam (nylon 6), poly- ω -aminoheptanoic acid (nylon 7), poly- ω -aminononanoic acid (nylon 9), polyundecanamide (nylon 11), and polylaurolactam (nylon 12). Further, as the copolymerized polyamide resin, there may be mentioned polyethylene adipamide (nylon 26), polybutylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecanoamide (nylon 612), polyhexamethylene adipamide (nylon 86), polyhexamethylene adipamide (nylon 108), caprolactam/laurolactam copolymer (nylon 6/12), caprolactam/ω -aminononanoic acid copolymer (nylon 6/9), caprolactam/diammonium hexamethyleneadipate copolymer (nylon 6/66), laurolactam/diammonium hexamethyleneadipate copolymer (nylon 12/66), ethylene adipamide/diammonium hexamethyleneadipate copolymer (nylon 26/66), and the like, Aliphatic polyamides such as caprolactam/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymers (nylon 66/610) and ethylenediammonium adipate/hexamethylenediammonium sebacate copolymers (nylon 6/66/610), aromatic polyamides such as polyhexamethyleneisophthalamide, polyhexamethyleneterephthalamide, poly-m-xylylene adipamide, hexamethyleneisophthalamide/terephthalamide copolymers, poly-p-phenylene terephthalamide and poly-p-phenylene-3, 4' -diphenyletherterephthalamide, amorphous polyamides, polyamides obtained by modifying these polyamide resins with aromatic amines such as methylenebenzylamine and m-xylylenediamine, diammonium isophthalate, and the like. Or may be a terminal-modified polyamide resin thereof, preferably a terminal-modified polyamide resin. These polyamide resins (B) may be used in 1 kind or in combination of 2 or more kinds.

The polyamide resin (B) tends to have a high bonding force with a polar group-containing resin such as EVOH resin.

The ratio of amide bonds in the amide monomer units constituting the polyamide resin (B) is determined by the ratio of the molecular weight to the amide monomer units (for example, [ -C in the case of nylon 6)₆H₅-CONH-]The amide bond (-CONH-)) in (A) is preferably 20 to 60%, more preferably 30 to 50%, and particularly preferably 35 to 45%. If the ratio of the amide bond is too low, the bonding force to the interface of the polar resin such as EVOH resin (a) tends to be reduced, whereas if it is too high, the reactivity with the polar resin such as EVOH resin (a) during melt molding tends to be too strong, and appearance defects due to roughness of the bonding interface tend to occur during coextrusion.

The melting point of the polyamide resin (B) is preferably 160 to 270 ℃, more preferably 175 to 250 ℃, and particularly preferably 190 to 230 ℃. When the melting point of the polyamide resin (B) is too low, the heat resistance of a multilayer structure produced using the EVOH resin composition tends to decrease. On the other hand, when the melting point of the polyamide resin (B) is too high, the multilayer structure including other resin layers tends to be as follows: the difference in melting point between the resin used in the other layer and the EVOH resin composition becomes large, and when the other resin and the EVOH resin composition are co-extruded, layer disorder occurs at the time of confluence, resulting in a decrease in the appearance of the multilayer structure. Further, when the EVOH resin (a) and the polyamide resin (B) are co-extruded, the die temperature may be too high to promote coloring of the multilayer structure due to thermal deterioration of the EVOH resin (a).

From the above viewpoints, the polyamide resin (B) is preferably a polyamide having a melting point of 160 to 270 ℃, more preferably 175 to 250 ℃, particularly preferably 190 to 230 ℃, and an amide bond ratio of 20 to 60%, more preferably 30 to 50%, and particularly preferably 35 to 45%. Specifically, for example, nylon 6 (melting point: about 220 ℃ C., amide bond ratio: 38%) and nylon 6/66 (melting point: about 200 ℃ C., amide bond ratio: 38%) are preferable.

The polymerization degree of the polyamide resin (B) is preferably 1.5 to 6, more preferably 2.0 to 6, and still more preferably 2.5 to 5, as measured by JIS K6810. When the relative viscosity is too low, the extruder tends to be in a high torque state during molding and extrusion processing tends to be difficult, and when it is too high, the thickness accuracy of the obtained film or sheet tends to be lowered. The relative viscosity can be measured by completely dissolving 1g of the polyamide resin (B) in 100mL of 96% concentrated sulfuric acid in accordance with JIS K6810 and measuring the relative viscosity at 25 ℃ using a capillary viscometer.

The content of the terminal carboxyl group in the polyamide resin (B) is usually 10 to 40. mu. eq/g, preferably 15 to 30. mu. eq/g, and particularly preferably 15 to 25. mu. eq/g. When the content of the terminal carboxyl group is outside the above range, thermal stability tends to be poor. The content of the terminal carboxyl group can be measured as follows.

< content of terminal carboxyl group >

0.2g of polyamide resin (B) was added to 15mL of o-cresol and dissolved by heating to 110 ℃. After cooling to about room temperature (23 ℃ C.), 10mL of benzyl alcohol, 50mL of o-cresol, and 50. mu.L of formaldehyde were added. A content of terminal carboxyl group ([ COOH ], unit: μ eq/g) was measured using a potentiometric titrator using 0.05mol/L alcoholic potassium hydroxide as a titration solution.

In the EVOH resin composition of the present invention, the weight content ratio of the EVOH resin (A) to the polyamide resin (B) (ethylene-vinyl alcohol copolymer (A)/polyamide resin (B)) is usually 99/1 to 10/90, preferably 95/5 to 40/60, and particularly preferably 90/10 to 60/40. If the weight content ratio of the polyamide resin (B) is too small, the effect of blending the polyamide resin (for example, hot water sterilization performance) tends to be reduced, whereas if it is too large, the gas barrier property tends to be reduced.

[ iron Compound (C) ]

The EVOH resin composition of the present invention is characterized by containing an iron compound (C) in addition to the EVOH resin (a) and the polyamide resin (B), and by the amount of the iron compound (C) being a specific trace amount. The EVOH resin composition of the present invention has the above-described structure, and therefore can suppress coloring and has excellent dynamic viscosity behavior.

The coloring of the EVOH resin composition containing the EVOH resin (a) and the polyamide resin (B) is considered to be caused by a reaction such as condensation and decomposition of a hydroxyl group of the EVOH resin (a), a carboxyl group at a polymerization terminal, and a highly reactive site such as an amide bond, an amino group, and a carboxyl group of the polyamide resin (B) due to heat.

Further, it is considered that the EVOH resin composition containing the iron compound (C) may color the product due to iron ions, and therefore, those skilled in the art will generally avoid the use thereof. However, the present inventors have unexpectedly found that an EVOH resin composition in which coloring after heating is suppressed can be obtained by adding a trace amount of the iron compound (C) to the EVOH resin composition.

The reason why the above-described effects are obtained is presumed to be that since iron is stable as a 3-valent ion, even a trace amount of iron forms an ionic bond or a chelate with a plurality of functional groups such as a hydroxyl group, a carboxyl group, an amide bond, and an amino group as described above to stabilize the iron, and thereby the above-described condensation and decomposition are suppressed, and coloring is suppressed.

The iron compound (C) may be present in the EVOH resin composition in an ionized state or in a complex state in which it interacts with a resin or other ligands, in addition to being present in the form of an oxide, hydroxide, chloride, or iron salt, for example. Examples of the oxide include iron oxide, ferroferric oxide, and ferrous oxide (ferrous oxide). Examples of the chloride include ferrous chloride and ferric chloride. Examples of the hydroxide include ferrous hydroxide and ferric hydroxide. Examples of the iron salt include inorganic salts such as iron phosphate and iron sulfate, and organic salts such as iron carboxylate (e.g., acetic acid, butyric acid, and stearic acid). These may be used alone or in combination of 2 or more.

The iron compound (C) is preferably water-soluble from the viewpoint of dispersibility in the EVOH resin composition. From the viewpoint of dispersibility and productivity, the molecular weight is usually 100 to 10000, preferably 100 to 1000, and particularly preferably 100 to 500.

The EVOH resin composition of the present invention contains an iron compound (C) in an amount of 0.01 to 20ppm in terms of metal relative to the unit weight of the EVOH resin composition. The content of the iron compound is preferably 0.03 to 8ppm, particularly preferably 0.05 to 3ppm, and particularly preferably 0.05 to 0.8 ppm. If the content of the iron compound (C) is too small, the coloring-suppressing effect becomes insufficient, whereas if it is too large, the viscosity increase tendency with time becomes remarkable.

The content of the iron compound (C) can be determined by subjecting 0.5g of the EVOH resin composition to ashing treatment in an infrared heating furnace (650 ℃ C., 1 hour in an oxygen gas flow), then dissolving the remaining ash with an acid, making a constant volume with pure water, and measuring the obtained solution as a sample solution by ICP-MS (Standard additive method, 7500ce, manufactured by Agilent Technologies).

[ other thermoplastic resins ]

The EVOH resin composition of the present invention may contain a thermoplastic resin other than the EVOH resin (a) and the polyamide resin (B) within a range not to impair the effects of the present invention (for example, generally 30 wt% or less, preferably 20 wt% or less, and particularly preferably 10 wt% or less of the EVOH resin composition).

As the other thermoplastic resin, a known thermoplastic resin can be used. Specific examples thereof include polyolefin resins, polyester resins, polystyrene resins, polyvinyl chloride resins, polycarbonate resins, polyacrylic resins, ionomers, ethylene-acrylic acid copolymers, ethylene-acrylic ester copolymers, ethylene-methacrylic acid copolymers, ethylene-methacrylic ester copolymers, polyvinylidene chloride, vinyl ester resins, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, and chlorinated polypropylene. These may be used alone or in combination of 2 or more.

[ other compounding agents ]

The EVOH resin composition of the present invention may contain a compounding agent usually compounded in an EVOH resin within a range not to impair the effects of the present invention. For example, an inorganic double salt (e.g., hydrotalcite), a plasticizer (e.g., an aliphatic polyhydric alcohol such as ethylene glycol, glycerin, or hexanediol), an oxygen absorbent [ e.g., an inorganic oxygen absorbent such as aluminum powder, potassium sulfite, or photocatalytic titanium oxide; ascorbic acid, further fatty acid esters and metal salts thereof, polyhydric phenols such as hydroquinone, gallic acid and hydroxyl group-containing phenol resins, disalicyliminocobalt, tetraethylenepentaminocobalt, cobalt-schiff base complexes, porphyrins, macrocyclic polyamine complexes, coordination complexes of nitrogen-containing compounds such as polyethyleneimine-cobalt complexes with transition metals other than iron, terpene compounds, reaction products of amino acids and hydroxyl group-containing reducing substances, and organic compound-based oxygen absorbents such as triphenylmethyl compounds; a coordination complex of a nitrogen-containing resin and a transition metal other than iron (for example, a combination of m-xylylenediamine (MXD) nylon and cobalt), a blend of a tertiary hydrogen-containing resin and a transition metal other than iron (for example, a combination of polypropylene and cobalt), a blend of a resin having a carbon-carbon unsaturated bond and a transition metal other than iron (for example, a combination of polybutadiene and cobalt), a photooxidatively degradable resin (for example, polyketone), an anthraquinone polymer (for example, polyvinyl anthraquinone), and the like, and further a polymeric oxygen absorber, such as one obtained by adding a photoinitiator (benzophenone, and the like), a peroxide scavenger (commercially available antioxidant, and the like), a deodorant (activated carbon, and the like), a heat stabilizer, a light stabilizer, an ultraviolet absorber, a colorant, an antistatic agent, a surfactant (except for a lubricant user), a surfactant, and the like, Antibacterial agents, antiblocking agents, filler materials (e.g., inorganic fillers, etc.), and the like. Among them, from the viewpoint of suppressing coloring, an oxygen absorber is preferable, and a terpene compound is particularly preferably used. These compounds may be used alone or in combination of 2 or more.

[ method for producing EVOH resin composition ]

The method for producing the EVOH resin composition of the present invention using the above components includes known methods such as a dry blending method, a melt blending method, a solution blending method, and an impregnation method, and any combination thereof may be used.

The dry blending method includes, for example, (i) a method of dry blending pellets containing the EVOH resin (a) and the polyamide resin (B) with the iron compound (C) using a roll or the like.

Examples of the above melt mixing method include: (ii) a method in which pellets containing the EVOH resin (A) and the polyamide resin (B) are melt-kneaded with a dry blend of the iron compound (C) to obtain pellets and a molded article; (iii) a method in which an iron compound (C) is added to a mixture of the EVOH resin (A) and the polyamide resin (B) in a molten state, and the mixture is melt-kneaded to obtain pellets or a molded article.

Examples of the solution mixing method include: (iv) a method comprising preparing a solution from commercially available pellets containing the EVOH resin (A) and the polyamide resin (B), adding the iron compound (C) to the solution, solidifying the mixture to form pellets, separating the solid from the liquid, and drying the pellets; (v) in the production process of the EVOH resin (a), a solution of the polyamide resin (B) and the iron compound (C) are added to a homogeneous solution (water/alcohol solution or the like) of the EVOH resin, followed by solidification molding to form pellets, solid-liquid separation, and drying.

Examples of the impregnation method include: (vi) a method comprising bringing pellets containing the EVOH resin (A) and the polyamide resin (B) into contact with an aqueous solution containing an iron compound (C), allowing the pellets to contain the iron compound (C), and then drying the pellets.

In the present invention, the above-described different methods may be combined. Among them, the melt-mixing method is preferable, and the method (ii) is particularly preferable, from the viewpoint of obtaining a resin composition having more remarkable productivity and the effect of the present invention.

The shapes of the EVOH resin composition pellets obtained by the above methods and the pellets containing the EVOH resin (a) and the polyamide resin (B) used in the above methods are arbitrary. For example, the shape is a sphere, an ellipse, a cylinder, a cube, a rectangular parallelepiped, or the like, and is usually an ellipse or a cylinder, and in the case of the ellipse, from the viewpoint of convenience in the case of using the ellipse as a molding material in the future, the minor diameter is usually 1 to 10mm, preferably 2 to 6mm, and more preferably 2.5 to 5.5mm, and the major diameter is usually 1.5 to 30mm, preferably 3 to 20mm, and more preferably 3.5 to 10 mm. In addition, in the case of a cylindrical shape, the bottom surface has a diameter of usually 1 to 6mm, preferably 2 to 5mm, and a length of usually 1 to 6mm, preferably 2 to 5 mm.

As the iron compound (C) used in each of the above methods, as described above, a water-soluble iron compound is preferably used, and examples thereof include iron salts such as oxides such as iron oxide, ferroferric oxide, and ferrous oxide, chlorides such as ferrous chloride and ferric chloride, hydroxides such as ferrous hydroxide and ferric hydroxide, inorganic salts such as iron phosphate and iron sulfate, and organic salts such as iron carboxylate (such as acetic acid, butyric acid, and stearic acid). As described above, the iron compound (C) may be present in the EVOH resin composition in the form of a salt, in an ionized state, or in a complex state in which it interacts with a resin or another ligand.

As the aqueous solution containing the iron compound (C) used in the method (vi), an aqueous solution in which iron ions are eluted by immersing the iron compound aqueous solution or the ferrous material in water containing various chemical agents can be used. In this case, the content (in terms of metal) of the iron compound (C) in the EVOH resin composition may be controlled by the concentration of the iron compound (C) in the aqueous solution in which the pellet is immersed, the immersion temperature, the immersion time, and the like. The dipping temperature and the dipping time are usually 0.5 to 48 hours, preferably 1 to 36 hours, and the dipping temperature is usually 10 to 40 ℃, preferably 20 to 35 ℃. The impregnated pellets are subjected to solid-liquid separation by a known method and dried by a known drying method. As the drying method, various drying methods can be employed, and either of static drying and fluidized drying can be used. Further, they may be combined.

The water content of the EVOH resin composition pellet of the present invention is usually 0.01 to 0.5 wt%, preferably 0.05 to 0.35 wt%, and particularly preferably 0.1 to 0.3 wt%.

The water content of the EVOH resin composition pellet in the present invention can be measured and calculated by the following method.

The weight of EVOH resin composition pellets before drying (W1) was weighed using an electronic balance, dried in a hot air dryer at 150 ℃ for 5 hours, and the weight of EVOH resin composition pellets after cooling in the dryer for 30 minutes (W2) was weighed and calculated by the following formula.

Water content (% by weight) of [ (W1-W2)/W1] x 100

The pellets of the EVOH resin composition obtained in this way can be directly subjected to melt molding, and it is preferable that a known lubricant is attached to the surface of the pellets from the viewpoint of stabilizing the feeding property at the time of melt molding. Examples of the type of the lubricant include higher fatty acids having 12 or more carbon atoms (e.g., lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, etc.), higher fatty acid esters (e.g., methyl ester, isopropyl ester, butyl ester, octyl ester, etc. of higher fatty acids), higher fatty acid amides (e.g., saturated higher fatty acid amides such as lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, etc., unsaturated higher fatty acid amides such as oleic acid amide, erucic acid amide, etc., vinyl bisstearic acid amide, vinyl bisoleic acid amide, vinyl biserucic acid amide, vinyl bislauric acid amide, etc.), low molecular weight polyolefins (e.g., low molecular weight polyethylene having a molecular weight of about 500 to 10,000, or low molecular weight polypropylene, etc., or acid-modified products thereof), higher alcohols having 6 or more carbon atoms, Ester oligomers, vinyl fluoride resins, and the like. These compounds may be used alone or in combination of 2 or more. The content of the lubricant is usually 5% by weight or less, preferably 1% by weight or less of the EVOH resin composition.

The EVOH resin composition of the present invention is prepared into various forms such as pellets, powder, liquid, and the like, and is provided as a molding material for various molded articles. In particular, when the thermoplastic resin composition is provided as a material for melt molding in the present invention, the effects of the present invention tend to be more effectively obtained, and the thermoplastic resin composition is preferable. The EVOH resin composition of the present invention also includes a resin composition obtained by mixing resins other than the EVOH resin (a) and the polyamide resin (B) used in the EVOH resin composition of the present invention.

The molded article may be a single-layer film molded using the EVOH resin composition of the present invention, or a multi-layer structure having a layer molded using the EVOH resin composition of the present invention.

[ multilayer Structure ]

The multilayer structure of the present invention includes a layer formed of the EVOH resin composition of the present invention. The layer formed of the EVOH resin composition of the present invention (hereinafter referred to as "EVOH resin composition layer") may be laminated with another substrate (hereinafter referred to as "substrate resin") containing a thermoplastic resin other than the EVOH resin composition of the present invention as a main component, and further may be provided with strength, or may be provided with another function by protecting the EVOH resin composition layer from moisture or the like.

Examples of the base resin include polyethylene resins such as linear low density polyethylene, ultra-low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-propylene (block and random) copolymers, and ethylene- α -olefin (α -olefin having 4 to 20 carbon atoms) copolymers, polypropylene resins such as polypropylene and propylene- α -olefin (α -olefin having 4 to 20 carbon atoms) copolymers, non-modified polyolefin resins such as polybutene, polypentene, and polycycloolefin resins (polymers having a cyclic olefin structure in at least one of the main chain and the side chain), modified polyolefin resins such as unsaturated carboxylic acid-modified polyolefin resins obtained by graft-modifying these polyolefins with an unsaturated carboxylic acid or an ester thereof, broad-sense polyolefin resins including modified olefin resins such as unsaturated carboxylic acid-modified polyolefin resins, and the like, Ionomer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polyester resin, polyamide resin (including copolyamide), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, polystyrene elastomer, chlorinated polyethylene, chlorinated polypropylene and other halogenated polyolefin, aromatic or aliphatic polyketone, and the like.

Among these, the hydrophobic resins are preferably polyamide resins, polyolefin resins, polyester resins, polystyrene resins, and more preferably polyolefin resins such as polyethylene resins, polypropylene resins, polycycloolefin resins, and unsaturated carboxylic acid-modified polyolefin resins thereof.

In the layer structure of the multilayer structure, when the EVOH resin composition layer of the present invention is a (a1, a2, …) and the base resin layer is b (b1, b2, …), the EVOH resin composition layer may be any combination of a/b, b/a/b, a/b/a, a1/a2/b, a/b1/b2, b2/b1/a/b1/b2, b2/b1/a/b1/a/b1/b2, and the like. When R is used as a recycled layer of a mixture comprising the EVOH resin composition of the present invention and a base resin, which is obtained by remelting end parts, defective parts, and the like produced during the production of the multilayer structure, b/R/a/b, b/R/a/R/b, b/a/R/a/b, b/R/a/R/b, and the like can be used. The number of layers of the multilayer structure is usually 2 to 15, preferably 3 to 10 in total. In the above layer structure, an adhesive resin layer containing an adhesive resin may be interposed between the respective layers as necessary.

As the adhesive resin, a known resin can be used, and it may be selected as appropriate depending on the kind of the thermoplastic resin used for the base resin layer "b". Typical examples thereof include modified polyolefin-based polymers containing carboxyl groups, which are obtained by chemically bonding unsaturated carboxylic acids or anhydrides thereof to polyolefin-based resins by addition reaction, graft reaction, or the like. Examples of the modified polyolefin-based polymer having a carboxyl group include maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene (block and random) copolymer, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, maleic anhydride modified polyolefin-based resin, and maleic anhydride graft-modified polyolefin-based resin. Further, a mixture of 1 or 2 or more selected from these may be used.

In the multilayer structure, when an adhesive resin layer is used between the EVOH resin composition layer of the present invention and the base resin layer, the adhesive resin layer is located on both sides of the EVOH resin composition layer, and therefore, an adhesive resin having excellent hydrophobicity is preferably used.

The base resin and the adhesive resin may contain conventionally known plasticizers, fillers, clay (montmorillonite or the like), colorants, antioxidants, antistatic agents, lubricants, nucleating agents, antiblocking agents, waxes, and the like, within a range that does not inhibit the gist of the present invention (for example, 30 wt% or less, preferably 10 wt% or less with respect to the entire resin). These may be used alone or in combination of 2 or more.

The lamination of the EVOH resin composition of the present invention with the above-mentioned base resin (including the case of interposing an adhesive resin layer) may be performed by a known method. Examples thereof include: a method of melt extrusion-laminating a base resin on a film, sheet or the like of the EVOH resin composition of the present invention; a method of melt extrusion laminating the EVOH resin composition of the present invention on a base resin layer; a method of coextruding the EVOH resin composition and the substrate resin; a method of dry laminating the EVOH resin composition layer and the base resin layer using a known adhesive such as an organotitanium compound, an isocyanate compound, a polyester compound, or a polyurethane compound; a method of coating a solution of the EVOH resin composition on a base resin and then removing the solvent. Among these, the coextrusion method is preferable from the viewpoint of cost and environment.

As described above, the multilayer structure is then subjected to (heat) stretching treatment as necessary. The stretching treatment may be either uniaxial stretching or biaxial stretching, and in the case of biaxial stretching, simultaneous stretching may be used or sequential stretching may be used. As the stretching method, those having a high stretching ratio in a roll stretching method, a tenter stretching method, a tube stretching method, a stretch blow molding method, a vacuum pressure forming method, or the like can be used. The stretching temperature is selected from the range of about 40 to 170 ℃, preferably about 60 to 160 ℃ in terms of a thermometer around the melting point of the multilayer structure. When the stretching temperature is too low, the stretchability tends to be poor, and when it is too high, it tends to be difficult to maintain a stable stretched state.

After stretching, heat fixation may be performed subsequently for the purpose of imparting dimensional stability. The heat-fixing can be carried out by a known method, and for example, the stretched film can be heat-treated at a temperature of usually 80 to 180 ℃ and preferably 100 to 165 ℃ for usually 2 to 600 seconds while being kept in a stretched state. When a multilayer stretched film obtained from the EVOH resin composition of the present invention is used as a film for shrinkage, for example, a treatment such as blowing cold air to the stretched film and cooling and fixing may be performed without performing the above-described heat fixing in order to impart heat shrinkability.

In addition, a cup-or tray-shaped multilayer container can be obtained by using the multilayer structure of the present invention, as the case may be. In this case, a deep drawing method is generally used, and specific examples thereof include a vacuum forming method, a pressure-air forming method, a vacuum pressure-air forming method, a plunger-assisted vacuum pressure-air forming method (plug-assisted vacuum pressure forming), and the like. When a tube-or bottle-shaped multilayer container (laminate structure) is obtained from a multilayer parison (hollow tube-shaped preform before blow molding), a blow molding method is employed. Specifically, there may be mentioned extrusion blow molding (twin-head type, die-moving type, parison-moving type, rotary type, accumulator type, horizontal type, etc.), cold parison blow molding, injection blow molding, biaxial stretch blow molding (extrusion cold parison biaxial stretch blow molding, injection molding in-line biaxial stretch blow molding method, etc.), and the like. The obtained laminate may be subjected to heat treatment, cooling treatment, rolling treatment, printing treatment, dry lamination treatment, solution or melt coating treatment, bag making processing, deep drawing processing, box processing, pipe processing, slit processing, and the like as required.

The thickness of the multilayer structure (including those subjected to stretching), and further the thickness of the EVOH resin composition layer, the base resin layer and the adhesive resin layer constituting the multilayer structure vary depending on the layer constitution, the kind of the base resin, the kind of the adhesive resin, the use, the packaging method, the required physical properties, and the like, but in general, the thickness of the multilayer structure (including those subjected to stretching) is usually 10 to 5000 μm, preferably 30 to 3000 μm, and particularly preferably 50 to 2000 μm. The EVOH resin composition layer is usually 1 to 500 μm, preferably 3 to 300 μm, and particularly preferably 5 to 200 μm, the base resin layer is usually 5 to 3000 μm, preferably 10 to 2000 μm, and particularly preferably 20 to 1000 μm, and the adhesive resin layer is usually 0.5 to 250 μm, preferably 1 to 150 μm, and particularly preferably 3 to 100 μm.

Further, when the multilayer structure has a plurality of layers, the ratio of the thickness of the EVOH resin composition layer to the thickness of the base resin layer (EVOH resin composition layer/base resin layer) is usually 1/99 to 50/50, preferably 5/95 to 45/55, and particularly preferably 10/90 to 40/60. When the multilayer structure has a plurality of layers, the ratio of the thickness of the EVOH resin composition layer to the thickness of the adhesive resin layer (EVOH resin composition layer/adhesive resin layer) is usually 10/90 to 99/1, preferably 20/80 to 95/5, and particularly preferably 50/50 to 90/10.

Containers and lid materials including bags, cups, trays, tubes, bottles and the like formed from the films, sheets and stretched films obtained as described above are useful as containers for packaging materials for various kinds of foods, seasonings such as mayonnaise and salad dressing, fermented foods such as miso, fat and oil foods such as salad oil, beverages, cosmetics, pharmaceuticals and the like. In particular, the layer formed of the EVOH resin composition of the present invention suppresses coloring, and is therefore particularly useful as a packaging material for hot water sterilization treatment of foods, medicines, agricultural chemicals, and the like.