JPWO2019004261A1 - Ethylene-vinyl alcohol copolymer composition, pellets and multilayer structure - Google Patents

Abstract

An ethylene-vinyl alcohol-based copolymer composition and a multilayer structure in which coloring after heating is suppressed, containing an ethylene-vinyl alcohol-based copolymer (A), a quinone compound (B) and an iron compound (C). An ethylene-vinyl alcohol-based copolymer composition, wherein the content of the iron compound (C) is 0.01 to 20 ppm in terms of metal, based on the weight of the ethylene-vinyl alcohol-based copolymer composition. -Providing a vinyl alcohol-based copolymer resin composition.

Description

  TECHNICAL FIELD The present invention relates to an EVOH resin composition containing an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as “EVOH resin”) as a main component, a pellet made of the EVOH resin composition, and a multilayer structure. More specifically, the present invention relates to an EVOH resin composition in which coloring after heating is suppressed, a pellet made of the EVOH resin composition, and a multilayer structure including a layer made of the EVOH resin composition.

  EVOH resin is excellent in transparency, gas barrier properties against oxygen, etc., aroma retention, solvent resistance, oil resistance, mechanical strength, etc., and is molded into films, sheets, bottles, etc., and used as food packaging materials, pharmaceutical packaging materials, It is widely used as various packaging materials such as industrial chemical packaging materials and agricultural chemical packaging materials.

  However, the EVOH resin has a relatively active hydroxyl group in the molecule and therefore tends to be deteriorated by heat. Therefore, coloring problems tend to occur during melt molding.

  On the other hand, since EVOH resin (a resin composition capable of suppressing defects such as fish eyes, gels, streaks and the like during melt molding) to form molded articles such as containers and films having excellent appearance, There is known a resin composition containing A) and an unsaturated aldehyde (B), and the content of the unsaturated aldehyde (B) in the EVOH resin composition is 0.01 ppm or more and 100 ppm or less (for example, Patent Document 1). 1). When such a resin composition further contains a conjugated polyene compound, oxidative deterioration during melt molding can be suppressed. As a result, it is described that the resin composition can further suppress the occurrence and coloring of defects such as fish eyes, improve the appearance of molded articles, and have excellent long-run properties.

International Publication No. 2013/146901

  However, an aldehyde compound such as the above unsaturated aldehyde may cause a bad odor even in a small amount, and it is particularly difficult to employ because it may be volatilized in the molding step exposed to high temperature and deteriorate the working environment. .. Therefore, there has been a demand for an EVOH resin that is less likely to be colored after heating and that provides a high-quality molded product.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problem can be solved when a small amount of an iron compound and a quinone compound are used in combination. Conventionally, it has not been known that the thermal stability of a molded EVOH resin is improved by using a quinone compound together with a small amount of an iron compound. However, in the present invention, unexpectedly, it was found that the coloring of the EVOH resin composition after heating was suppressed when a specific trace amount of the iron compound and the quinone compound were used in combination, and a high quality molded product was obtained. I found that I can be.

  That is, the present invention is an EVOH resin composition containing an EVOH resin (A), a quinone compound (B) and an iron compound (C), wherein the content of the iron compound (C) is the weight of the EVOH resin composition. Therefore, the first gist is an EVOH resin composition having a metal content of 0.01 to 20 ppm. The second aspect of the present invention is a pellet made of the EVOH resin composition. A third aspect of the present invention is a multilayer structure having a layer made of the above EVOH resin composition.

  The EVOH resin composition of the present invention is an EVOH resin composition containing an EVOH resin (A), a quinone compound (B) and an iron compound (C), wherein the content of the iron compound (C) is an EVOH resin composition. Since it is 0.01 to 20 ppm in terms of metal per weight of the product, coloring after heating can be suppressed.

  Moreover, especially in the present invention, when the content of the quinone compound (B) is 1 to 10000 ppm based on the weight of the EVOH resin composition, the coloring after heating can be further suppressed.

  Furthermore, in the present invention, in particular, when the weight ratio of the content of the quinone compound (B) to the metal-converted content of the iron compound (C) is 0.2 to 50,000, it is further heated. Can be suppressed.

  Further, since the pellets made of the EVOH resin composition of the present invention are suppressed from being colored after being heated, they can be suitably used as various molded products, for example, as packaging materials for foods, chemicals, agricultural chemicals and the like.

  Since the multilayer structure provided with the layer made of the EVOH resin composition of the present invention has good quality, it is particularly useful as a packaging material for foods, medicines, agricultural chemicals and the like.

  Hereinafter, the configuration of the present invention will be described in detail, but these show examples of preferred embodiments and are not limited to these contents.

The EVOH resin composition of the present invention contains an EVOH resin (A) as a main component, and contains a quinone compound (B) and an iron compound (C). In the EVOH resin composition of the present invention, the base resin is EVOH resin (A). That is, the content of the EVOH resin (A) in the EVOH resin composition is usually 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and particularly preferably 95% by weight. That is all.
Each component will be described below.

[EVOH resin (A)]
The EVOH resin (A) used in the present invention is usually a resin obtained by saponifying an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and a vinyl ester monomer, and is water-insoluble. It is a thermoplastic resin. From the economical viewpoint, vinyl acetate is generally used as the vinyl ester-based monomer.

  As a polymerization method of ethylene and a vinyl ester-based monomer, any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization or the like can be used. Generally, methanol is used as a solvent. Solution polymerization is used. Saponification of the obtained ethylene-vinyl ester copolymer can also be performed by a known method.

  The EVOH resin (A) thus produced is mainly composed of ethylene-derived structural units and vinyl alcohol structural units, and contains a small amount of vinyl ester structural units remaining without being saponified.

  As the vinyl ester-based monomer, vinyl acetate is typically used from the viewpoint of market availability and efficiency of treating impurities during production. Other vinyl ester-based monomers include, for example, vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, etc. Examples thereof include aromatic vinyl esters, aromatic vinyl esters such as vinyl benzoate, and the like. Use of an aliphatic vinyl ester having usually 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms. You can These are usually used alone, but if necessary, a plurality of types may be used simultaneously.

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-based monomer and ethylene, and is usually 20 to 60 mol%, preferably 25 to 50 mol. %, Particularly preferably 25 to 35 mol%. If the content is too low, the gas barrier property under high humidity and the melt moldability tend to be lowered, and conversely, if it is too high, the gas barrier property tends to be lowered.
The content of the ethylene structural unit can be measured based on ISO14663.

The degree of saponification of the vinyl ester component in the EVOH resin (A) depends on the amount and temperature of the saponification catalyst (usually an alkaline catalyst such as sodium hydroxide is used) when saponifying the ethylene-vinyl ester copolymer. The amount is usually 90 to 100 mol%, preferably 95 to 100 mol%, particularly preferably 99 to 100 mol%. If the degree of saponification is too low, the gas barrier properties, thermal stability, moisture resistance, etc. tend to deteriorate.
The degree of saponification of the EVOH resin (A) can be measured based on JIS K6726 (however, the EVOH resin is used as a solution uniformly dissolved in a water / methanol solvent).

The melt flow rate (MFR) (210 ° C., load 2160 g) of the EVOH resin (A) is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, particularly preferably 3 to. It is 35 g / 10 minutes. If the MFR is too large, the stability during film formation tends to be impaired, and if 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 the ethylene and the vinyl ester monomer are copolymerized.

  The EVOH resin (A) used in the present invention further contains structural units derived from the following comonomer within a range that does not impair the effects of the present invention (for example, 10 mol% or less of the EVOH resin (A)). It may be.

  Examples of the comonomer include olefins such as propylene, 1-butene and isobutene, 3-butene-1-ol, 3-butene-1,2-diol, 4-penten-1-ol, 5-hexene-1,2. -Hydroxy group-containing α-olefins such as diols and derivatives thereof such as esterified products and acylated products; hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; Hydroxyalkyl vinylidene diacetates such as 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane and 1,3-dibutyryloxy-2-methylenepropane; acrylic acid, methacrylic acid , Crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, etc. Saturated acids or salts thereof or mono- or dialkyl esters having 1 to 18 carbon atoms; acrylamide, N-alkyl acrylamide having 1 to 18 carbon atoms, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or salt thereof, acrylamidopropyl Acrylamides such as dimethylamine or acid salts thereof or quaternary salts thereof; methacrylamide, N-alkylmethacrylamides having 1 to 18 carbon atoms, N, N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or salts thereof, Methacrylamides such as methacrylamidopropyldimethylamine or its acid salts or quaternary salts thereof; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide; Vinyl cyanides such as tolyl and methacrylonitrile; vinyl ethers such as alkyl vinyl ethers having 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers and alkoxyalkyl vinyl ethers; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide, etc. Halogenated vinyl compounds; vinylsilanes such as trimethoxyvinylsilane; allyl halides such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; trimethyl- (3-acrylamido-3-dimethyl) Examples thereof include comonomers such as propyl) -ammonium chloride and acrylamido-2-methylpropanesulfonic acid. These may be used alone or in combination of two or more.

In particular, an EVOH resin having a primary hydroxyl group in the side chain is preferable in that the secondary moldability is improved while maintaining the gas barrier property, and among them, an EVOH resin in which a hydroxy group-containing α-olefin is copolymerized is preferable. Particularly, EVOH resin having a 1,2-diol structure in its side chain is preferable.
Particularly, in the case of an EVOH resin having a primary hydroxyl group in the side chain, the content of the structural unit derived from the monomer having a primary hydroxyl group is usually 0.1 to 20 mol% of the EVOH resin, further 0.5 to It is preferably 15 mol%, particularly preferably 1 to 10 mol%.

  Further, as the EVOH resin (A) used in the present invention, an EVOH-based resin which has been “post-modified” such as urethanated, acetalized, cyanoethylated or oxyalkylenated can also be used.

  Further, the EVOH resin (A) used in the present invention may be a mixture with other EVOH resins different from each other, and such other EVOH resins having different ethylene structural unit contents and different saponification degrees. Examples thereof include those having different degrees of polymerization, those having different copolymerization components, and the like.

[Quinone compound (B)]
The quinone compound (B) used in the present invention means a compound having a quinone skeleton or a derivative thereof having an ability to resonance-stabilize and trap radicals. The compound having a quinone skeleton is specifically a cyclic diketone compound having a ketone structure at the 1-position and 4-position or the 1-position and 2-position of the benzene ring as a carbon skeleton. Examples of the quinone compound (B) include quinones and hydroquinones.

  Examples of the quinones include o-benzoquinone, p-benzoquinone, diphenoquinone, 1,4-naphthoquinone, anthraquinone, and the like, and among them, p-benzoquinone is preferable. Examples of hydroquinones include hydroquinone, hydroquinone monomethyl ether, dipentylhydroquinone, p-methoxyphenol, p-butoxyphenol, p-pentoxyphenol, and monobenzone. Among them, hydroquinones are preferable in terms of productivity, and hydroquinone is particularly preferable. Moreover, these can be used individually or in combination of 2 or more types.

  The molecular weight of the above quinone compound (B) is usually 100 to 100,000, preferably 100 to 10,000, particularly preferably 100 to 1,000, and particularly preferably 100 to 300. When the molecular weight is in the above range, the effect of the present invention tends to be more effectively obtained.

The content of the quinone compound (B) is usually 1 to 10000 ppm, preferably 5 to 1000 ppm, particularly preferably 10 to 500 ppm, and particularly preferably 20 to 100 ppm, based on the weight of the EVOH resin composition of the present invention. is there. If the content of the quinone compound (B) is too large, the productivity tends to decrease, and if it is too small, the thermal stability tends to decrease.
When two or more quinone compounds (B) having different structures, compositions, molecular weights and the like are used together as the quinone compound (B), the total weight (total content) thereof may be in the above range.

  The content of the quinone compound (B) per weight of the EVOH resin composition can be measured as follows. First, 1 g of a sample obtained by freeze-grinding an EVOH resin composition is extracted with an extraction solvent, the volume of the extract is fixed, and the measurement is performed using a liquid chromatograph-ultraviolet spectroscopic detector. Separately, a calibration curve is prepared from a standard solution of the quinone compound (B), and the content of the quinone compound (B) can be quantified by the absolute calibration curve method.

[Iron compound (C)]
The present invention is characterized by containing an EVOH resin (A), a quinone compound (B), and an iron compound (C), and the content of the iron compound (C) is a specific trace amount. It has been found that by adopting such a constitution, the obtained resin composition is suppressed from being colored after heating.

Generally, EVOH resin is colored due to thermal deterioration. This is because the EVOH resin is deteriorated by heat and radicals are generated, the hydroxyl group of the EVOH resin is dehydrated, a double bond is generated in the main chain of the EVOH resin, and such a site serves as a reaction starting point to promote dehydration, and the conjugation It is considered to form a polyene structure.
On the other hand, it is presumed that the EVOH resin composition of the present invention has excellent deterioration resistance for the following reasons. Normally, iron can exist as divalent and trivalent ions. In the present invention, the quinone compound (B) is often used in combination with the specific trace amount of the iron compound (C), so that the quinone compound (B) often reduces the trivalent iron ion and the divalent iron ion. It is speculated that this divalent iron ion is generated and a cycle occurs in which the activity of the quinone compound (B) is restored by reducing the quinone compound (B) that has already trapped the radicals.

  Further, when the iron compound (C) is contained, it is considered that the product is colored by iron ions, and therefore, it is a common general technical knowledge for those skilled in the art to avoid using the above iron compound. However, in the present invention, contrary to such common general knowledge, an EVOH resin composition in which coloring after heating is suppressed is obtained when a specific trace amount of an iron compound (C) and a quinone compound (B) are used in combination. I found that I could be done.

  The iron compound (C) may be present in the EVOH resin composition as, for example, an oxide, a hydroxide, a chloride, or an iron salt, or in an ionized state, or may interact with a resin or another ligand. It may exist in the state of the complex that has acted. Examples of the oxide include ferric oxide, ferric tetroxide, iron suboxide, and the like. Examples of the chloride include ferrous chloride and ferric chloride. Examples of the hydroxide include ferrous hydroxide, ferric hydroxide and the like. Examples of the iron salt include inorganic salts such as iron phosphate and iron sulfate, and organic salts such as iron carboxylic acid (acetic acid, butyric acid, stearic acid, etc.). These may be used alone or in combination of two or more.

  From the viewpoint of dispersibility in the EVOH resin composition, the iron compound (C) is preferably water-soluble. From the viewpoint of dispersibility and productivity, the molecular weight is usually 100 to 10,000, preferably 100 to 1,000, and particularly preferably 100 to 500.

The EVOH resin composition of the present invention is characterized in that the content of the iron compound (C) is 0.01 to 20 ppm in terms of metal based on the weight of the EVOH resin composition. The content of such iron compound is preferably 0.03 to 15 ppm, more preferably 0.05 to 3 ppm, and particularly preferably 0.05 to 1.5 ppm.
If the content of the iron compound is too small, the anti-coloring effect tends to decrease, and if it is too large, the molded product tends to be colored.

  Here, the content of the iron compound (C) is determined by ashing 0.5 g of a measurement sample obtained by freeze-milling an EVOH resin composition in an infrared heating furnace (650 ° C. in an oxygen stream for 1 hour), and then removing the remaining ash content. Can be determined by measuring with ICP-MS (7500ce type; standard addition method, manufactured by Agilent Technologies) using a sample solution prepared by dissolving acid in acid and adjusting the volume with pure water.

  The weight ratio of the content of the quinone compound (B) to the metal equivalent content of the iron compound (C) in the EVOH resin composition of the present invention is usually 0.2 to 50,000, preferably 1 to 10000. , Particularly preferably 5 to 5,000, particularly preferably 50 to 1,000. If this value is too large, the suppression of coloration after heating tends to be hindered, and if it is too small, the molded product tends to be colored.

[Other thermoplastic resins]
The EVOH resin composition of the present invention contains a thermoplastic resin other than the EVOH resin (A) in a range that does not impair the effects of the present invention (for example, usually 30% by weight or less, preferably 20% by weight or less of the EVOH resin composition). , Particularly preferably 10% by weight or less).

  As the other thermoplastic resin, a known thermoplastic resin can be used. For example, specifically, polyolefin resin, polyester resin, polystyrene resin, polyvinyl chloride resin, polycarbonate resin, polyacrylic resin, ionomer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer Examples thereof include polymers, ethylene-methacrylic acid copolymers, ethylene-methacrylic acid ester copolymers, polyvinylidene chloride, vinyl ester resins, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, chlorinated polypropylene and the like. These may be used alone or in combination of two or more.

[Other compounding agents]
Further, the EVOH resin composition of the present invention may contain a compounding agent that is generally compounded with the EVOH resin within a range that does not impair the effects of the present invention. Examples of the compounding agent include inorganic double salts (eg, hydrotalcite), plasticizers (eg, aliphatic polyhydric alcohols such as ethylene glycol, glycerin, and hexanediol), oxygen absorbers [eg, aluminum powder. Inorganic oxygen absorbers such as potassium sulfite and photocatalytic titanium oxide; polyphenols such as ascorbic acid, its fatty acid esters and metal salts, gallic acid, hydroxyl group-containing phenol aldehyde resins, bis-salicylaldehyde-imine cobalt, Coordination bond between nitrogen-containing compounds such as tetraethylenepentaminecobalt, cobalt-Schiff base complex, porphyrins, macrocyclic polyamine complex, polyethyleneimine-cobalt complex and transition metals other than iron, terpene compounds, amino acids and hydroxyl Reactant of group-containing reducing substance, trif Organic compound-based oxygen absorbers such as nylmethyl compounds; coordination bonds of nitrogen-containing resins with transition metals other than iron (for example, a combination of methylxylylenediamine [MXD] nylon and cobalt), tertiary hydrogen-containing resins and iron Blends with transition metals other than (for example, a combination of polypropylene and cobalt), blends of carbon-carbon unsaturated bond-containing resin with transition metals other than iron (for example, a combination of polybutadiene and cobalt), photooxidative disintegration Resin (eg polyketone), anthraquinone polymer (eg polyvinyl anthraquinone), etc., and photoinitiators (benzophenone etc.) and antioxidants and deodorants (activated carbon etc.) other than the above to these compounds Polymeric oxygen absorbers such as those prepared, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants, antistatic agents, surfactants ( However, except for those used as lubricants), antimicrobial agents, antiblocking agents, fillers (e.g., may be blended inorganic fillers and the like) and the like. These compounds can be used alone or in combination of two or more.

[Method for producing EVOH resin composition]
Examples of the method for producing the EVOH resin composition of the present invention include known methods such as a dry blending method, a melt mixing method, a solution mixing method and an impregnation method, and these methods can be combined arbitrarily.

Examples of the dry blending method include a method of dry blending (i) EVOH resin (A) pellets with a quinone compound (B) and an iron compound (C) using a tumbler or the like.
Examples of the melt-mixing method include (ii) a method in which EVOH resin (A) pellets and a dry blend of a quinone compound (B) and an iron compound (C) are melt-kneaded to obtain pellets or a molded article, or (iii) ) A method in which a quinone compound (B) or an iron compound (C) is added to a molten EVOH resin (A) and the mixture is melt-kneaded to obtain pellets or a molded product can be used.

  As a solution mixing method, for example, (iv) a commercially available EVOH resin (A) pellet is used to prepare a solution, and at least one of a quinone compound (B) and an iron compound (C) is added to the solution and coagulated and molded. Pelletization, solid-liquid separation and drying, or (v) EVOH resin (A) production process, before the saponification ethylene-vinyl ester copolymer solution or EVOH resin homogeneous solution (water / alcohol). (Solution) and the like, at least one of the quinone compound (B) and the iron compound (C) is added, and then the mixture is solidified and molded into pellets, solid-liquid separated, and dried.

  As the impregnation method, for example, (vi) EVOH resin (A) pellets are contacted with an aqueous solution containing at least one of a quinone compound (B) and an iron compound (C), and the EVOH resin (A) pellet is filled with the quinone compound. A method of adding at least one of (B) and the iron compound (C) and then drying it may be mentioned.

  In the present invention, it is possible to combine the different methods described above. Among them, the melt mixing method is preferable, and the method (ii) is particularly preferable from the viewpoint that a resin composition having more remarkable productivity and effects of the present invention can be obtained.

  The shape of the EVOH resin composition pellets of the present invention obtained by each of the above methods and the EVOH resin (A) pellets used in each method are arbitrary. For example, there are a spherical shape, an oval shape, a cylindrical shape, a cubic shape, a rectangular parallelepiped shape, etc., but usually, an oval shape or a cylindrical shape, the size of which is convenient for later use as a molding material. In the case of the shape, the minor axis is usually 1 to 10 mm, preferably 2 to 6 mm, more preferably 2.5 to 5.5 mm, and the major axis is usually 1.5 to 30 mm, preferably 3 to 20 and more preferably. Is 3.5 to 10 mm. In the case of a cylindrical shape, the diameter of the bottom surface is usually 1 to 6 mm, preferably 2 to 5 mm, and the length is usually 1 to 6 mm, preferably 2 to 5 mm.

  Further, as the iron compound (C) used in each of the above-mentioned methods, as described above, a water-soluble iron compound is preferably used, and examples thereof include ferric oxide, ferric tetroxide, and iron suboxide. Oxides, 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 carboxylic acids (acetic acid, Butyric acid, stearic acid, etc.) Iron salts such as iron organic salts. As described above, the iron compound (C) is present in the EVOH resin composition as the above-mentioned salt, in the ionized state, or in the complex state using the resin or another compound as a ligand. May exist in.

Further, as the aqueous solution containing the iron compound (C) used in the method (vi), the iron compound is eluted by immersing the aqueous solution of the iron compound (C) or the steel material in water containing various chemicals. What was made to use can be used. In that case, the content of the iron compound (C) in the EVOH resin composition (as metal) is the concentration of the iron compound (C) in the aqueous solution in which the EVOH resin (A) pellets are immersed, the immersion temperature, and the immersion time. And the like. The immersion temperature and the immersion time are usually 0.5 to 48 hours, preferably 1 to 36 hours, and the immersion temperature is usually 10 to 40 ° C, preferably 20 to 35 ° C.
The EVOH resin composition pellets are solid-liquid separated by a known method, and dried by a known drying method. Various drying methods can be adopted as such a drying method, and either static drying or fluidized drying may be used. Moreover, it is also possible to combine these.

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

The water content of the EVOH resin composition pellets in the present invention is measured and calculated by the following method.
The weight (W1) of the EVOH resin composition pellet before drying was weighed with an electronic balance, dried in a hot air dryer at 150 ° C. for 5 hours, and allowed to cool in a desiccator for 30 minutes, then weighed (W2). , Calculated from the following formula.
Moisture content (% by weight) = [(W1-W2) / W1] × 100

  The pellets of the EVOH resin composition thus obtained can be directly subjected to melt molding, but in order to stabilize the feedability during melt molding, a known lubricant should be attached to the surface of the pellet. Is also preferable. Examples of the lubricant include higher fatty acids having 12 or more carbon atoms (for example, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, etc.), higher fatty acid esters (methyl ester of higher fatty acid, isopropyl ester, Butyl ester, octyl ester, etc.), higher fatty acid amides (eg, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, etc., saturated higher fatty acid amides; oleic acid amide, erucic acid amide, etc. Saturated higher fatty acid amides, bis higher fatty acid amides such as ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, and ethylene bis lauric acid amide), low molecular weight polyolefins (for example, a molecular weight of about 500 to 10,000) Molecular weight polyethylene or low molecular weight polypropylene, or an acid modified products), the number 6 or higher alcohol carbon, ester oligomers, such as ethylene fluoride resins. These compounds may be used alone or in combination of two 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 thus obtained is prepared as an EVOH resin composition in various forms such as pellets, powder or liquid, and provided as a molding material for various molded products. In particular, in the present invention, when provided as a material for melt molding, the effect of the present invention tends to be obtained more efficiently, which is preferable. The EVOH resin composition of the present invention also includes a resin composition obtained by mixing a resin other than the EVOH resin (A) used in the EVOH resin composition of the present invention.

  Then, as such a molded product, a multilayer structure having a layer molded using the EVOH resin composition of the present invention, including a single-layer film molded using the EVOH resin composition of the present invention, is practically used. Can be offered.

[Multilayer structure]
The multilayer structure of the present invention has a layer formed of the EVOH resin composition of the present invention. The layer containing the EVOH resin composition of the present invention (hereinafter, simply referred to as “EVOH resin composition layer”) is formed of another base material (hereinafter, referred to as a base) containing a thermoplastic resin as a main component other than the EVOH resin composition of the present invention. The resin used for the material may be abbreviated as “base resin”.) To provide more strength, protect the EVOH resin composition layer from the influence of moisture, etc. Can be given.

  Examples of the base resin include linear low density polyethylene, low density polyethylene, ultra low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-propylene (block and random) copolymer, ethylene-α-olefin. Polyethylene resin such as (C4-20 α-olefin) copolymer, polypropylene, polypropylene such as propylene-α-olefin (C4-20 α-olefin) copolymer, polybutene, polypentene , (Unmodified) polyolefin resins such as polycyclic olefin resins (polymers having a cyclic olefin structure having at least one of a main chain and side chains), and graft modification of these polyolefins with unsaturated carboxylic acids or their esters Unsaturated carboxylic acid modified polyolefin resin, etc. Broadly defined polyolefin resin including modified olefin resin, ionomer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic ester copolymer, polyester resin, polyamide resin (copolymerized polyamide (Including also), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, polystyrene elastomer, chlorinated polyethylene, halogenated polyolefin such as chlorinated polypropylene, Examples thereof include aromatic or aliphatic polyketones.

  Of these, hydrophobic resins such as polyamide-based resins, polyolefin-based resins, polyester-based resins, and polystyrene-based resins are preferred, and more preferably polyethylene-based resins, polypropylene-based resins, polycyclic olefin-based resins, and unsaturated resins thereof. A polyolefin resin such as a carboxylic acid-modified polyolefin resin.

  When the EVOH resin composition layer of the present invention is a (a1, a2, ...) And the base resin layer is b (b1, b2, ...), the layer structure of the multilayer structure is 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, etc., Any combination is possible. In addition, the EVOH resin composition of the present invention and a thermoplastic resin other than the EVOH resin composition of the present invention, which are obtained by remelt-molding edges and defective products generated in the process of manufacturing the multilayer structure, When the recycled layer containing the mixture is R, b / R / a, b / R / a / b, b / R / a / R / b, b / a / R / a / b, b / R / a It is also possible to use / R / a / R / b or the like. The total number of layers of the multilayer structure is usually 2 to 15, preferably 3 to 10. In the above layer structure, an adhesive resin layer containing an adhesive resin may be interposed between the respective layers, if necessary.

  As the above adhesive resin, a known adhesive resin can be used and may be appropriately selected depending on the type of the thermoplastic resin used for the base resin “b”. Typically, a modified polyolefin polymer containing a carboxyl group obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof to a polyolefin resin by an addition reaction or a graft reaction can be mentioned. Examples of the modified polyolefin polymer containing a carboxyl group include maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene (block and random) copolymers, maleic anhydride. Examples thereof include graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, maleic anhydride-modified polycyclic olefin-based resin, maleic anhydride graft-modified polyolefin-based resin, and the like. Then, one kind or a mixture of two or more kinds selected from these can be used.

  When an adhesive resin layer is used between the EVOH resin composition layer of the present invention and the base resin layer in a multilayer structure, the adhesive resin layer is located on both sides of the EVOH resin composition layer, and It is preferable to use an adhesive resin having excellent properties.

  The above-mentioned base resin and adhesive resin have plasticity as conventionally known within a range that does not impair the gist of the present invention (for example, 30% by weight or less, preferably 10% by weight or less based on the entire resin). Agents, fillers, clay (such as montmorillonite), colorants, antioxidants, antistatic agents, lubricants, core materials, antiblocking agents, and waxes may be included. These may be used alone or in combination of two or more.

  The EVOH resin composition layer of the present invention and the above-mentioned base resin layer may be laminated (including a case where an adhesive resin layer is interposed) by a known method. For example, 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, an EVOH resin composition and a base. Method of co-extruding a material resin, and EVOH resin composition (layer) and base resin (layer) are dry-laminated using a known adhesive such as an organic titanium compound, an isocyanate compound, a polyester compound or a polyurethane compound. Examples of the method include a method of applying a solution of the EVOH resin composition on the base resin and then removing the solvent. Among these, the coextrusion method is preferable from the viewpoints of cost and environment.

  The above-mentioned multilayer structure is then subjected to a (heating) stretching treatment, if necessary. The stretching treatment may be uniaxial stretching or biaxial stretching, and in the case of biaxial stretching, it may be simultaneous stretching or sequential stretching. As a stretching method, a roll stretching method, a tenter stretching method, a tubular stretching method, a stretching blow method, a vacuum pressure molding or the like having a high stretching ratio can be adopted. The stretching temperature is a temperature in the vicinity of the melting point of the multilayer structure and is usually selected from the range of 40 to 170 ° C, preferably about 60 to 160 ° C. If the stretching temperature is too low, the stretchability will be poor, and if it is too high, it will be difficult to maintain a stable stretched state.

  In addition, heat setting may be performed for the purpose of imparting dimensional stability after stretching. The heat setting can be carried out by a well-known means. For example, the stretched film is usually heat-treated at 80 to 180 ° C., preferably 100 to 165 ° C. for usually 2 to 600 seconds while maintaining a tension state. When the multilayer stretched film obtained from the EVOH resin composition of the present invention is used as a shrink film, the above heat setting is not performed in order to impart heat shrinkability, and for example, the stretched film is cooled with cold air. It suffices to apply a process such as applying heat to fix it.

  In some cases, it is possible to obtain a cup-shaped or tray-shaped multilayer container by using the multilayer structure of the present invention. In that case, the draw forming method is usually adopted, and specific examples thereof include a vacuum forming method, a pressure forming method, a vacuum pressure forming method, a plug assist type vacuum pressure forming method and the like. Further, when a tube or bottle-shaped multilayer container (laminate structure) is obtained from a multilayer parison (a hollow tubular preform before being blown), a blow molding method is adopted. Specifically, extrusion blow molding method (double head type, mold moving type, parison shift type, rotary type, accumulator type, horizontal parison type, etc.), cold parison type blow molding method, injection blow molding method, biaxial stretching. Blow molding methods (extrusion cold parison biaxial stretching blow molding method, injection cold parison biaxial stretching blow molding method, injection molding in-line biaxial stretching blow molding method, etc.) can be mentioned. If necessary, the resulting 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, tube processing, split processing, etc. You can

  The thickness of the multilayer structure (including stretched ones), and further the thickness of the EVOH resin composition layer, the base resin layer and the adhesive resin layer forming the multilayer structure are the layer structure, the type of base resin, and the adhesion. The thickness of the multilayer structure (including stretched ones) is usually 10 to 5000 μm, preferably 30 to 3000 μm, and particularly preferably, though it cannot be generally stated depending on the type of the resin, the application, the packaging form, the required physical properties and the like. It is 50 to 2000 μm. The EVOH resin composition layer is usually 1 to 500 μm, preferably 3 to 300 μm, particularly preferably 5 to 200 μm, and the base resin layer is usually 5 to 3000 μm, preferably 10 to 2000 μm, particularly preferably 20 to 1000 μm. The adhesive resin layer has a thickness of usually 0.5 to 250 μm, preferably 1 to 150 μm, and particularly preferably 3 to 100 μm.

  Furthermore, the thickness ratio of the EVOH resin composition layer to the base resin layer in the multilayer structure (EVOH resin composition layer / base resin layer) is the ratio of the thickest layers when there are multiple layers. , Usually 1/99 to 50/50, preferably 5/95 to 45/55, particularly preferably 10/90 to 40/60. Further, the thickness ratio of the EVOH resin composition layer to the adhesive resin layer in the multilayer structure (EVOH resin composition layer / adhesive resin layer) is the ratio between the thickest layers when there are a plurality of layers, It is usually 10/90 to 99/1, preferably 20/80 to 95/5, particularly preferably 50/50 to 90/10.

  The film and sheet obtained as described above, a bag and a cup made of a stretched film, a tray, a tube, a container made of a bottle or the like, a general food, mayonnaise, seasonings such as dressing, miso, etc. It is useful as a packaging material container for fermented foods, oil and fat foods such as salad oil, beverages, cosmetics, pharmaceuticals, and the like.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the description of the examples as long as the gist thereof is not exceeded.
In addition, "part" in the examples means weight basis unless otherwise specified.

Prior to the examples, the following EVOH resin (A) pellets were prepared, and the content of the iron compound (C) contained in the EVOH resin (A) was measured.
EVOH resin (A): ethylene structural unit content 29 mol%, saponification degree 99.6 mol%, MFR 3.9 g / 10 min (210 ° C., load 2160 g) ethylene-vinyl alcohol copolymer.

[Measurement of Content of Iron Compound (C)]
0.5g sample of crushed pellets of the EVOH resin (A) was ashed in an infrared heating furnace (650 ° C in an oxygen stream for 1 hour), and the ash was acid-dissolved to give a fixed volume with pure water. It was a solution. The solution was measured by the standard addition method using the following ICP-MS (ICP mass spectrometer 7500ce type manufactured by Agilent Technologies). As a result, the content of the iron compound (C) was 0 ppm in terms of metal.

[Example 1]
100 parts of the EVOH resin (A) pellets, 0.003 parts of hydroquinone as the quinone compound (B) (30 ppm based on the weight of the EVOH resin composition), and iron (III) phosphate n-hydrate as the iron compound (C) (sum Koujunyaku Kogyo Co., Ltd., 230 ° C dry weight loss 20.9% by weight) 0.000034 parts (0.1 ppm in terms of metal based on the weight of the EVOH resin composition) at 230 ° C with a plastograph (Bravender Co., Ltd.) After preheating for 5 minutes, the mixture was melt-kneaded for 5 minutes to obtain an EVOH resin composition. The obtained EVOH resin composition was pulverized with a pulverizer (Sometan Sangyo Co., Ltd. model: SKR16-240) at 650 rpm to obtain a pulverized product. The pulverized product was a small piece of 1 to 5 mm square.

[Example 2]
In the same manner as in Example 1 except that the amount of the iron (III) phosphate n-hydrate mixed was changed to 0.00034 parts (1 ppm in terms of metal per weight of the EVOH resin composition). An EVOH resin composition and a pulverized product thereof were obtained.

[Example 3]
In the same manner as in Example 1 except that the amount of the iron (III) phosphate n-hydrate blended was changed to 0.0034 parts (10 ppm in terms of metal per weight of the EVOH resin composition). An EVOH resin composition and a pulverized product thereof were obtained.

[Comparative Example 1]
In Example 1, iron (III) phosphate n-hydrate was not added. An EVOH resin composition and a pulverized product thereof were obtained in the same manner as in Example 1 except for the above.

  Next, the EVOH resin compositions obtained in Examples 1 to 3 and Comparative Example 1 were evaluated for coloring by the method described below. The results are shown in Table 1 below.

[Coloring evaluation]
The pulverized product of the above EVOH resin composition was used as a sample, and the YI value was measured by a spectral color difference meter SE6000 manufactured by Nippon Denshoku Industries Co., Ltd. At this time, the sample was filled in a cylinder having an inner diameter of 32 mm and a height of 30 mm, and the sample was rubbed and used for the measurement. Further, a sample obtained by heating the sample at 150 ° C. for 5 hours in an oven under an air atmosphere was similarly measured. The ratio of the YI value after heating to the YI value before heating was calculated. The larger the value, the more the resin composition is colored yellow after heating.

  As a result, in the product of Comparative Example 1 containing no iron compound (C) and containing only the quinone compound (B), the YI value ratio before and after heating was 1.9. On the other hand, in Examples 1 to 3 containing the quinone compound (B) and the specific trace amount of the iron compound (C), the ratio of YI values before and after heating was lower than that of the product of Comparative Example 1, and coloring after heating. It can be seen that is suppressed.

  Although specific embodiments of the present invention have been shown in the above embodiments, the above embodiments are merely examples and should not be construed as limiting. Various modifications apparent to those skilled in the art are intended to be within the scope of the present invention.

  Since the EVOH resin composition of the present invention suppresses coloring after heating, in addition to various foods, seasonings such as mayonnaise and dressings, fermented foods such as miso, oil and fat foods such as salad oil, beverages, cosmetics, and pharmaceuticals It is useful as various packaging materials such as.

Claims (5)

  An ethylene-vinyl alcohol-based copolymer composition containing an ethylene-vinyl alcohol-based copolymer (A), a quinone compound (B), and an iron compound (C), wherein the content of the iron compound (C) is The ethylene-vinyl alcohol-based copolymer composition is 0.01 to 20 ppm in terms of metal, based on the weight of the ethylene-vinyl alcohol-based copolymer composition.   The ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the content of the quinone compound (B) is 1 to 10000 ppm based on the weight of the ethylene-vinyl alcohol copolymer composition.   The ethylene-vinyl according to claim 1 or 2, wherein the weight ratio of the content of the quinone compound (B) to the metal-converted content of the iron compound (C) is 0.2 to 50000. Alcohol-based copolymer composition.   A pellet made of the ethylene-vinyl alcohol copolymer composition according to any one of claims 1 to 3.   A multi-layer structure comprising a layer comprising the ethylene-vinyl alcohol copolymer composition according to claim 1.