JP2023152984A - Ethylene-vinyl alcohol copolymer composition, pellet, multilayer structure, method for producing ethylene-vinyl alcohol copolymer composition, and method for producing multilayer structure - Google Patents

Abstract

To provide an ethylene-vinyl alcohol copolymer composition which is suppressed in coloring change due to thermal deterioration during melt molding.SOLUTION: An ethylene-vinyl alcohol copolymer composition contains an ethylene-vinyl alcohol copolymer, an alkaline earth metal compound, and a titanium compound. The content of the titanium compound in terms of metal is 0.001 ppm or more and less than 5 ppm per mass of the ethylene-vinyl alcohol copolymer composition.SELECTED DRAWING: None

Description

The present invention relates to an ethylene-vinyl alcohol copolymer composition, pellets, and a multilayer structure, a method for producing an ethylene-vinyl alcohol copolymer composition, and a method for producing a layer structure.

Ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH resin") has excellent transparency, gas barrier properties against oxygen and other gases, fragrance retention, solvent resistance, oil resistance, mechanical strength, etc. It is formed into films, sheets, bottles, etc., and is widely used as various packaging materials such as food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, and pesticide packaging materials.

However, since EVOH resin has a relatively active hydroxyl group in its molecule, it tends to be easily deteriorated by heat, and coloring problems are likely to occur during melt molding.

In response to the above-mentioned problems, for example, Patent Document 1 discloses that the EVOH resin (A), acetic acid (B), magnesium acetate and/or calcium acetate (C) is contained, and the content of (B) is that of (A). A resin composition characterized in that the content of (C) is 0.05 parts by weight or less per 100 parts by weight, and the content of (C) is 0.001 to 0.02 parts by weight per 100 parts by weight of (A) in terms of metal. things are disclosed. By using this resin composition, a molded product with excellent long-run properties during melt molding, less fish eyes, streaks, and coloring, and excellent appearance can be obtained, and furthermore, when the molded product is made into a laminate. It is also disclosed that the odor is reduced, and the interlayer adhesion of the laminate is also excellent even after secondary processing such as stretching and deep drawing.

Japanese Patent Application Publication No. 11-106592

The technique disclosed in Patent Document 1 provides a molded product that has excellent long-run properties during melt molding, has few fish eyes, streaks, and coloring, and has excellent appearance. However, in recent years, there has been a tendency for molding equipment to become more sophisticated due to the diversification of feedblock and die shapes in molding equipment, as well as demands for higher functionality such as thinner multilayer structures and increased number of layers in final products. be. As a result, resins tend to thermally deteriorate in molding equipment that has become more complex due to higher functionality, causing coloring and the like, resulting in a decrease in product productivity (long-run performance), and further improvements are required.

An object of the present invention is to provide an EVOH resin composition in which color change of the EVOH resin during heating during melt molding or the like is suppressed.

However, in view of such circumstances, the present inventor has created an EVOH resin composition in which the color change of the EVOH resin during heating such as melt molding is suppressed by adding an alkaline earth metal compound and a specific trace amount of a titanium compound to the EVOH resin. was found to be obtained.

That is, the present invention has the following aspects.
[1] An EVOH resin composition containing an EVOH resin, an alkaline earth metal compound, and a titanium compound,
An EVOH resin composition in which the metal equivalent content of the titanium compound is 0.001 ppm or more and less than 5 ppm per mass of the EVOH resin composition.
[2] The EVOH resin composition according to [1], wherein the alkaline earth metal compound has a metal equivalent content of 0.1 to 500 ppm based on the mass of the EVOH resin composition.
[3] The EVOH resin composition according to [1] or [2], wherein the mass ratio of the metal equivalent content of the alkaline earth metal compound to the metal equivalent content of the titanium compound is 0.02 to 500,000.
[4] A pellet made of the EVOH resin composition according to any one of [1] to [3].
[5] A multilayer structure comprising at least one layer made of the EVOH resin composition according to any one of [1] to [3].
[6] A method for producing the EVOH resin composition according to any one of [1] to [3], comprising:
A method for producing an EVOH resin composition, comprising a step of melt-mixing composition raw materials containing the EVOH resin and a titanium compound.
[7] A method for manufacturing the multilayer structure according to [5], comprising:
A method for producing a multilayer structure, comprising the step of melt-molding a layer made of the EVOH resin composition.

The EVOH resin composition of the present invention can suppress color change of EVOH resin during melt molding, and has excellent long-run properties.

Hereinafter, the present invention will be described in more detail based on embodiments of the present invention, but the present invention is not limited to these embodiments.
In addition, in the present invention, when expressed as "X to Y" (X, Y are arbitrary numbers), unless otherwise specified, it means "more than or equal to X and less than or equal to Y", and also means "preferably greater than X" or "preferably It also includes the meaning of "less than Y".
In addition, when expressed as "more than or equal to X" (X is any number) or "less than or equal to Y" (Y is any number), it is also possible to indicate that "it is preferably greater than X" or "it is preferably less than Y". It also includes meaning.
In the present invention, "x and/or y (x, y are arbitrary structures or components)" means three combinations: x only, y only, and x and y.

<EVOH resin composition>
The EVOH resin composition according to one embodiment of the present invention (hereinafter referred to as the "present EVOH resin composition") has an EVOH resin as a main component, and contains an alkaline earth metal compound and a specific trace amount of a titanium compound. be.
That is, in the present EVOH resin composition, the base resin is an EVOH resin, and the content of EVOH resin in the present EVOH resin composition is usually 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. , particularly preferably 95% by mass or more.
Each component will be explained below.

[EVOH resin]
The EVOH resin used in the present invention is 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. It is.

As the vinyl ester monomer, vinyl acetate is typically used because of its market availability and good efficiency in treating impurities during production. Examples of vinyl ester monomers other than vinyl acetate include vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and versatic acid. Examples include aliphatic vinyl esters such as vinyl, aromatic vinyl esters such as vinyl benzoate, and aliphatic vinyls having usually 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms. Esters are used. These are usually used alone, but multiple types may be used simultaneously if necessary.

The copolymerization method for copolymerizing ethylene and the vinyl ester monomer can be carried out using any known polymerization method, such as solution polymerization, suspension polymerization, emulsion polymerization, etc., but generally methanol is used. Solution polymerization using a solvent is used. Furthermore, the obtained ethylene-vinyl ester copolymer may be saponified by a known method.
The EVOH resin produced in this manner is mainly composed of structural units derived from ethylene and vinyl alcohol structural units, and contains a small amount of vinyl ester structural units that remain without being saponified.

The content of ethylene structural units in the EVOH resin is usually 20 to 60 mol%, preferably 25 to 50 mol%, particularly preferably 25 to 35 mol%. The content of the ethylene structural unit can be controlled by the pressure of ethylene when copolymerizing the vinyl ester monomer and ethylene, and if this content is too low, the gas barrier property under high humidity, melt molding On the other hand, if it is too high, gas barrier properties tend to decrease.
Note that the content of such ethylene structural units can be measured based on ISO14663.

The saponification degree of the EVOH resin is usually 90 to 100 mol%, preferably 95 to 100 mol%, particularly preferably 99 to 100 mol%. The degree of saponification can be controlled by the amount, temperature, time, etc. of the saponification catalyst (usually an alkaline catalyst such as sodium hydroxide is used) when saponifying the ethylene-vinyl ester copolymer. If the degree of oxidation is too low, gas barrier properties, thermal stability, moisture resistance, etc. tend to deteriorate.
The degree of saponification of such EVOH resin 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 is usually 0.5 to 100 g/10 minutes, preferably 1 to 50 g/10 minutes, particularly preferably 3 to 35 g/10 minutes. be. If the MFR is too large, stability during film formation tends to be impaired, and if it is too small, the viscosity tends to become too high, making melt extrusion difficult.
The MFR is an index of the degree of polymerization of the EVOH resin, and can be adjusted by adjusting the amount of polymerization initiator and the amount of solvent when copolymerizing ethylene and vinyl ester monomer.

Further, the EVOH resin may further contain a structural unit derived from a comonomer shown below (eg, 10 mol% or less of the EVOH resin) within a range that does not impede the effects of the present invention.
Examples of the comonomer include olefins such as propylene, 1-butene, and isobutene, 3-buten-1-ol, 3-buten-1,2-diol, 4-penten-1-ol, 5-hexene-1, Hydroxy group-containing α-olefins such as 2-diol, and derivatives thereof such as esters 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, 1,3-dibutyryloxy-2-methylenepropane; Acrylic acid, methacrylic Acid, unsaturated acids such as crotonic acid, phthalic acid (anhydride), maleic acid (anhydride), and itaconic acid (anhydride), or their salts, or mono- or dialkyl esters with an alkyl group having 1 to 18 carbon atoms; acrylamide, alkyl Acrylamides such as N-alkylacrylamide, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or its salt, acrylamidepropyldimethylamine, its acid salt, or its quaternary salt; meth Acrylamide, N-alkylmethacrylamide whose alkyl group has 1 to 18 carbon atoms, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or its salt, methacrylamidepropyldimethylamine or its acid salt, or its quaternary Methacrylamides such as salts; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, and N-vinylacetamide; vinylcyanides such as acrylonitrile and methacrylnitrile; Vinyl ethers such as alkyl vinyl ether, hydroxyalkyl vinyl ether, and alkoxyalkyl vinyl ether; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and vinyl bromide; Vinyl silanes such as trimethoxyvinylsilane; Allyl acetate , allyl halides such as allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; comonomers such as trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride and acrylamide-2-methylpropanesulfonic acid. can be given. These can be used alone or in combination of two or more.

Among these, hydroxy group-containing α-olefins are preferred, with 3-butene-1,2-diol and 5-hexene-1,2-diol being particularly preferred. When the hydroxy group-containing α-olefins are copolymerized, the resulting EVOH resin will have a primary hydroxyl group in the side chain. Such an EVOH resin having a primary hydroxyl group in the side chain, particularly an EVOH resin having a 1,2-diol structure in the side chain, is preferable because it maintains gas barrier properties and has good secondary moldability.

When the EVOH resin has a primary hydroxyl group in the side chain, the content of the structural unit derived from the monomer having the primary hydroxyl group is usually 0.1 to 20 mol%, preferably 0.5 to 15% by mole of the EVOH resin. mol %, particularly preferably 1 to 10 mol %.

Further, as the EVOH resin, it is also possible to use an EVOH resin that has been "post-modified" such as esterification, urethanization, acetalization, cyanoethylation, or oxyalkylenation.

When using the post-modified EVOH resin, the modification rate is usually 10 mol% or less, preferably 4 mol% or less. If the modification rate of the EVOH resin is too high, it tends to be easily thermally degraded and its long run properties tend to decrease.

Further, the EVOH resin may be a mixture of EVOH resins having different contents of ethylene structural units, degrees of saponification, degrees of polymerization, copolymerization components, and the like.

[Alkaline earth metal compounds]
Examples of the alkaline earth metal compound include salts, oxides, and hydroxides of alkaline earth metals. These may be used alone or in combination of two or more. Among these, alkaline earth metal salts and alkaline earth metal oxides are preferred from the viewpoint of economy and dispersibility, and alkaline earth metal oxides are particularly preferred.

Examples of the alkaline earth metal salts include inorganic alkaline earth metal salts and alkaline earth metal carboxylates.

Examples of the inorganic salts of alkaline earth metals include carbonates, hydrogen carbonates, phosphates, borates, sulfates, and chlorides of alkaline earth metals.
Examples of the alkaline earth metal carboxylates include saturated or unsaturated carboxylates having 2 to 25 carbon atoms, preferably 2 to 22 carbon atoms, particularly preferably 6 to 20 carbon atoms, and specifically, acetates. , monovalent carboxylates such as butyrate, propionate, enanthate, caprate, laurate, palmitate, stearate, 12-hydroxystearate, behenate, montanate, shu Examples include divalent carboxylates such as acid salts, malonates, succinates, adipates, suberates, and sebatates. Among these, linear saturated carboxylic acid salts are preferred from the viewpoint of market availability, and monovalent carboxylic acid salts are more preferred.

Examples of the alkaline earth metal species of the alkaline earth metal compound include beryllium, magnesium, calcium, strontium, barium, and radium. Among these, magnesium and calcium are preferred in terms of market availability and economic efficiency, and magnesium is particularly preferred.

Among these, magnesium oxide is preferred as the alkaline earth metal compound. Further, from the viewpoint of economy and dispersibility, it is preferable to exclude layered inorganic compounds such as montmorillonite and double salts such as hydrotalcite from the alkaline earth metal compound.

The alkaline earth metal compound may be in any form such as solid (powder, fine powder, flakes, etc.), semi-solid, liquid, paste, solution, emulsion (aqueous dispersion), etc. It is possible to use materials with different properties. Among these, a powder form is preferable.

The content of the alkaline earth metal compound is usually 0.1 to 1000 ppm, preferably 1 to 800 ppm, more preferably 5 to 500 ppm, particularly preferably 10 to 200 ppm, based on the mass of the EVOH resin composition.
If the content of the alkaline earth metal compound is too high, the thermal stability tends to decrease, and if it is too low, the moldability of the EVOH resin composition tends to decrease.

The content of the alkaline earth metal compound in terms of metal is preferably 0.1 to 500 ppm, more preferably 0.5 to 300 ppm, still more preferably 1 to 200 ppm, particularly preferably is from 2 to 150 ppm, particularly preferably from 3 to 80 ppm, most preferably from 5 to 40 ppm.
If the metal equivalent content of the alkaline earth metal compound is too large, the thermal stability tends to decrease, and if it is too small, the moldability of the EVOH resin composition tends to decrease.
The metal equivalent content of the alkaline earth metal compound is determined by, for example, adding pure water to a solution obtained by heating and incinerating the present EVOH resin composition and acid-treating it with hydrochloric acid or the like. It can be measured using an atomic absorption spectrophotometer using a sample as a test solution.

[Titanium compound]
Examples of the titanium compound include inorganic titanium compounds and organic titanium compounds. Note that the titanium compounds may be used alone or in combination of two or more. Among them, inorganic titanium compounds are preferred.

Examples of the inorganic titanium compound include titanium oxide, titanium hydroxide, titanium chloride, and inorganic salts of titanium.
Examples of the titanium oxide include titanium (II) oxide, titanium (III) oxide, titanium (IV) oxide, and titanium suboxide.
Examples of the titanium hydroxide include titanous titanium hydroxide, titanium dihydroxide, and the like.
Examples of the titanium chloride include titanous titanium chloride and titanium chloride. Examples of the inorganic salt of titanium include titanium phosphate and titanium sulfate.
Among these, titanium oxide is preferred, titanium (IV) oxide is more preferred, and rutile type titanium (IV) oxide is particularly preferred.

Examples of the organic titanium compound include titanium carboxylates such as titanium acetate, titanium butyrate, and titanium stearate.

In addition, the titanium compound may exist in the EVOH resin composition as a titanium compound, or may exist in an ionized state or in a complex state that interacts with the EVOH resin or other ligands. .

The average particle size of the titanium compound is usually 0.001 to 100 μm, preferably 0.01 to 50 μm, and more preferably 0.015 to 20 μm. When the average particle size of the titanium compound is within the above range, the effect of suppressing coloring tends to be excellent.

The content of the titanium compound in terms of metal is 0.001 ppm or more and less than 5 ppm per mass of the EVOH resin composition. It is preferably 0.01 to 3 ppm, more preferably 0.03 to 1 ppm, particularly preferably 0.05 to 0.5 ppm. By setting the content of the titanium compound within the above range, color change due to thermal deterioration during melt molding can be suppressed, resulting in excellent long-run properties. Moreover, if the content of the titanium compound is too small, the effect of suppressing color change will be reduced, and if the content is too large, thermal decomposition of the EVOH resin will easily occur and coloration will occur.

The metal equivalent content of the titanium compound is determined by weighing the present EVOH resin composition in a platinum crucible, incinerating it sequentially with a burner and electric furnace, heating the ashed product with nitric acid and hydrofluoric acid, and decomposing it with dilute nitric acid and diluted diluted nitric acid. Titanium in a fixed volume solution obtained by treatment with a mixed acid of hydrofluoric acid was determined by ICP mass spectrometry using an ICP mass spectrometer (manufactured by Agilent Technologies, Agilent 8800). can do.

The mass ratio of the content of the alkaline earth metal compound to the metal equivalent content of the titanium compound is usually 0.06 to 180,000, preferably 2 to 36,000, particularly preferably 7 to 15,000, especially Preferably it is 15-1500, most preferably 100-800.
When the mass ratio is within the range, there is a tendency that color change due to thermal deterioration can be further suppressed.

The mass ratio of the metal equivalent content of the alkaline earth metal compound to the metal equivalent content of the titanium compound is preferably 0.02 to 500,000, more preferably 0.03 to 50,000, and more It is preferably from 0.5 to 10,000, particularly preferably from 2 to 4,000, particularly preferably from 9 to 1,000, and most preferably from 50 to 500.
When the mass ratio is within the range, there is a tendency that color change due to thermal deterioration can be further suppressed. Furthermore, if the mass ratio is too large, thermal stability tends to decrease, and if it is too small, the molded product tends to be colored.

Generally, it is known that by blending an alkaline earth metal compound into an EVOH resin, the resin exhibits a tendency to decrease in viscosity over time during heating. The mechanism is not clear, but by blending an alkaline earth metal compound, the EVOH resin composition becomes basic, and some anions become nucleophiles, pulling out hydrogen bonded to the main chain carbon of the EVOH resin, etc. It is presumed that this is because a chain decomposition reaction is caused and the main chain of the EVOH resin is cut. The color change of EVOH resin after heating is due to the formation of a double bond structure in the main chain of EVOH resin during the above reaction, and this structure becomes a reaction starting point again and causes a dehydration reaction, etc., and a polyene structure is formed in the main chain of EVOH resin. It is assumed that this is due to the formation of
In contrast, the present EVOH resin composition contains an alkaline earth metal compound and a specific trace amount of a titanium compound, thereby suppressing the color change due to thermal deterioration of the EVOH resin.
Normally, when a titanium compound is contained in an EVOH resin composition, it is thought that the EVOH resin composition is colored by titanium ions, so it is common general knowledge for those skilled in the art to avoid the use of titanium compounds. However, in the present invention, contrary to such common technical knowledge, it has been found that when a specific trace amount of a titanium compound is used, an EVOH resin composition in which color change due to thermal deterioration is suppressed can be obtained.
In other words, titanium is stable as a tetravalent ion, and even if it is in a small amount, it coordinates with the double bond in the main chain of the EVOH resin as described above, stabilizes it by forming a chelate, etc., and forms a polyene structure. It is assumed that this suppresses the
On the other hand, if the amount of the titanium compound is too large, it is thought that titanium causes thermal decomposition of the EVOH resin, resulting in coloration.

[Other thermoplastic resins]
The present EVOH resin composition contains a thermoplastic resin other than the EVOH resin within a range that does not impede the effects of the present invention (for example, usually 30% by mass or less, preferably 20% by mass or less, particularly preferably 10% by mass or less of the present EVOH resin composition). mass% or less).
As other thermoplastic resins, known thermoplastic resins can be used, such as polyester resins, polystyrene resins, polyvinyl chloride resins, polycarbonate resins, ionomers, polyvinylidene chloride, polyester elastomers, polyurethane elastomers, Examples include chlorinated polyethylene and chlorinated polypropylene. These can be used alone or in combination of two or more.

[Other combination agents]
Further, the present EVOH resin composition may contain additives that are generally blended into EVOH resins within a range that does not impede the effects of the present invention. Examples of the above compounding agents include inorganic double salts (e.g. hydrotalcite, etc.), plasticizers (e.g. aliphatic polyhydric alcohols such as ethylene glycol, glycerin, hexanediol, etc.), oxygen absorbers [e.g. aluminum powder, potassium sulfite, etc. Inorganic oxygen absorbers such as ascorbic acid, its fatty acid esters and metal salts, gallic acid, polyhydric phenols such as hydroxyl group-containing phenol aldehyde resin, terpene compounds, blends of tertiary hydrogen-containing resins and transition metals. (e.g., a combination of polypropylene and cobalt), blends of carbon-carbon unsaturated bond-containing resins and transition metals (e.g., a combination of polybutadiene and cobalt), photooxidatively degradable resins (e.g., polyketones), anthraquinone polymers (e.g., polyvinyl anthraquinone), and polymeric oxygen absorbers such as those containing photoinitiators (benzophenone, etc.), antioxidants and deodorants (activated carbon, etc.) other than those listed above], thermally stable Contains additives, light stabilizers, ultraviolet absorbers, colorants, antistatic agents, surfactants (excluding those used as lubricants), antibacterial agents, anti-blocking agents, fillers (e.g. inorganic fillers, etc.). You can. These compounds can be used alone or in combination of two or more.

[Method for manufacturing EVOH resin composition]
The present EVOH resin composition can be produced by mixing the EVOH resin, alkaline earth metal compound, and titanium compound by a known method, such as a dry blending method, a melt mixing method, a solution mixing method, an impregnation method, etc. Among these, it is preferable to manufacture by including a step of melt-mixing composition raw materials containing the EVOH resin and a titanium compound. Moreover, these manufacturing methods can also be combined arbitrarily.

Examples of the dry blending method include (i) a method in which pelletized EVOH resin and an alkaline earth metal compound and/or a titanium compound are dry blended using a tumbler or the like.

Examples of the melt mixing method include (ii) a method of melt-kneading a dry blend of pelletized EVOH resin and an alkaline earth metal compound and/or a titanium compound; Examples include a method of adding an alkaline earth metal compound and/or a titanium compound to a resin and melt-kneading the mixture.

As the solution mixing method, for example, (iv) a solution is prepared using a commercially available EVOH resin, an alkaline earth metal compound and/or a titanium compound is mixed therein, solidified and formed, and then solidified by known means. (v) In the EVOH resin manufacturing process, alkaline earth metals are added to the ethylene-vinyl ester copolymer solution before saponification or the homogeneous solution of EVOH resin (water/alcohol solution, etc.). Examples include a method of containing a compound and/or a titanium compound, coagulating and molding the material, followed by solid-liquid separation and drying by known means.

The impregnation method includes, for example, (vi) bringing the EVOH resin in the form of pellets into contact with an aqueous solution containing an alkaline earth metal compound and/or a titanium compound, and injecting the alkaline earth metal compound and/or titanium compound into the EVOH resin. Examples include a method of containing the material and then drying it. As the aqueous solution containing the titanium compound, an aqueous solution of a titanium compound or a titanium compound obtained by immersing the titanium compound in water containing various chemicals to elute titanium ions can be used.
In the above impregnation method, the content of the alkaline earth metal compound and titanium compound (metal equivalent) depends on the concentration of the alkaline earth metal compound and titanium compound in the aqueous solution in which the EVOH resin is immersed, the immersion temperature, the immersion time, etc. It is possible to control by
The immersion temperature and 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.

As the drying method in each of the above manufacturing methods, various drying methods can be employed, and either stationary drying or fluidized drying may be used. Moreover, these can also be performed in combination.

As mentioned above, in the present invention, it is possible to combine the different methods described above. Among these, the melt-mixing method is preferred, and the method (ii) is particularly preferred, since a resin composition with more remarkable productivity and the effects of the present invention can be obtained. Further, when using the other thermoplastic resins and other compounding agents, they may be compounded by a conventional method according to the above-mentioned manufacturing method.

Although the shape of the present EVOH resin composition obtained by each of the above-mentioned manufacturing methods is arbitrary, pellets are preferable.
The pellets include, for example, a spherical shape, an oval shape, a cylinder shape, a cubic shape, a rectangular parallelepiped shape, etc., but they are usually oval or cylindrical, and the size of the pellets depends on the convenience when later used as a molding material. From this point of view, in the case of an oval shape, the short axis is usually 1 to 10 mm, preferably 2 to 6 mm, more preferably 2.5 to 5.5 mm, and the long axis is usually 1.5 to 30 mm, preferably 3 mm. ~20mm, more preferably 3.5~10mm. Further, 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, it is preferable that the shape and size of the pellet-shaped EVOH resin used in each of the above manufacturing methods are also the same.

This EVOH resin composition suppresses color change even when heated during melt molding and has excellent long-run properties, and the ratio of the YI value after heating to the YI value (yellow index) before heating. (YI value after heating/YI value before heating) is usually less than 3.2, preferably 3.1 or less, particularly preferably 2.7 or less. When the ratio of the YI value after heating to the YI value before heating is within the above range, color change tends to be more suppressed. Further, the lower limit of the ratio of the YI value after heating to the YI value before heating is usually 1.
Note that a difference of 0.1 in the ratio of the YI values appears as a large difference in yield in actual production, so the difference is very large.

The YI value before heating is determined by filling a cylinder with an inner diameter of 32 mm and a height of 30 mm with the EVOH resin composition crushed into 1 to 5 mm squares, and measuring with a spectrocolorimeter SE6000 (Nippon Electric Power Co., Ltd.). (manufactured by Iroki Kogyo Co., Ltd.).
In addition, the YI value after heating is measured by the same method after heating the present EVOH resin composition crushed into 1 to 5 mm square pieces at 150° C. for 5 hours in an oven under an air atmosphere. It is obtained by

The moisture content of the EVOH resin composition is usually 0.01 to 0.5% by mass, preferably 0.05 to 0.35% by mass, particularly preferably 0.1 to 0.3% by mass. .

The water content of the EVOH resin composition is measured and calculated by the following method.
Weigh the mass (W ₁ ) of the EVOH resin composition before drying using an electronic balance, dry it in a hot air dryer at 150°C for 5 hours, and weigh the mass (W ₂ ) after leaving it to cool in a desiccator for 30 minutes. It is calculated using the formula below.
Moisture content (mass%) = [(W ₁ - W ₂ )/W ₁ ] x 100

Further, when the present EVOH resin composition is in the form of pellets, it is also preferable to attach a known lubricant to the surface of the pellets in order to stabilize the feedability during melt molding. Types of lubricants include, for example, 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 (higher fatty acid methyl esters, isopropyl esters, butyl ester, octyl ester, etc.), higher fatty acid amides (for example, saturated higher fatty acid amides such as lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, etc.); Saturated higher fatty acid amide, ethylene bis stearamide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, bis higher fatty acid amide such as ethylene bis lauric acid amide, etc.), low molecular weight polyolefin (for example, low molecular weight of about 500 to 10,000) Examples include polyethylene, low molecular weight polypropylene, etc., or acid-modified products thereof), higher alcohols having 6 or more carbon atoms, ester oligomers, fluorinated ethylene resins, and the like. These compounds can be used alone or in combination of two or more. Further, the content of such a lubricant is usually 5% by mass or less, preferably 1% by mass or less of the EVOH resin composition. Note that the lower limit is usually 0% by mass.

The EVOH resin composition thus obtained is prepared in various forms such as pellets, powder, and liquid, and provided as a molding material for various molded products. In particular, in the present invention, it is preferable to provide the material as a material for melt molding, since the effects of the present invention tend to be more efficiently obtained.
Note that the present EVOH resin composition also includes a resin composition obtained by mixing resins other than the EVOH resin used in the present EVOH resin composition.

Examples of the molded product include a single layer film molded from the present EVOH resin composition, and a multilayer structure having layers made of the present EVOH resin composition.

[Multilayer structure]
A multilayer structure according to an embodiment of the present invention (hereinafter referred to as "this multilayer structure") includes a layer made of the present EVOH resin composition. A layer made of the present EVOH resin composition (hereinafter simply referred to as "the present EVOH resin composition layer") may be formed by using another base material (hereinafter referred to as a base material) containing a thermoplastic resin as a main component other than the present EVOH resin composition. (sometimes abbreviated as "base material resin"), the EVOH resin composition layer can be further strengthened, protected from the effects of moisture, etc., and provided with other functions. be able to.

Examples of the base resin include linear low density polyethylene, low density polyethylene, very low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-propylene (block and random) copolymers, ethylene-α-olefin ( Polyethylene resins such as copolymers (α-olefins having 4 to 20 carbon atoms), polypropylene, polypropylene resins such as propylene-α-olefin (α-olefins having 4 to 20 carbon atoms) copolymers, polybutene, polypentene, (Unmodified) polyolefin resins such as polycyclic olefin resins (polymers with a cyclic olefin structure having at least one of a main chain and a side chain), and graft-modified polyolefins of these polyolefins with unsaturated carboxylic acids or their esters. Broadly defined polyolefin resins including modified olefin resins such as unsaturated carboxylic acid modified polyolefin resins, ionomers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, polyesters resin, polyamide resin (including copolyamide polyamide), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, polystyrene elastomer, chlorinated polyethylene , halogenated polyolefins such as chlorinated polypropylene, aromatic or aliphatic polyketones, and the like. These can be used alone or in combination of two or more.

Among these, hydrophobic resins such as polyamide resins, polyolefin resins, polyester resins, and polystyrene resins are preferred, and polyethylene resins, polypropylene resins, polycyclic olefin resins, and unsaturated resins thereof are more preferred. These are polyolefin resins such as carboxylic acid-modified polyolefin resins.

The layer structure of the present multilayer structure is a/b, where the present EVOH resin composition layer is a (a1, a2, ...) and the base resin layer is b (b1, b2, ...). 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., arbitrary A combination of these is possible. In addition, recycling includes a mixture of the present EVOH resin composition and a thermoplastic resin other than the present EVOH resin composition, which is obtained by remelting and molding the edges and defective products generated in the process of manufacturing the present multilayer structure. When the layer is R, b/R/a, b/R/a/b, b/R/a/R/b, b/a/R/a/b, b/R/a/R/a /R/b etc. is also possible. The total number of layers in the present multilayer structure is usually 2 to 15, preferably 3 to 10. In the above layered structure, an adhesive resin layer containing an adhesive resin may be interposed between each layer, if necessary.

As the adhesive resin, any known adhesive resin can be used, and may be appropriately selected depending on the type of thermoplastic resin used for the base resin layer "b". A typical example is a modified polyolefin polymer containing a carboxyl group obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to a polyolefin resin by an addition reaction, a graft reaction, or the like. 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, and maleic anhydride graft-modified polypropylene (block and random) copolymers. Examples include graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, maleic anhydride-modified polycyclic olefin resin, maleic anhydride graft-modified polyolefin resin, and the like. These may be used alone or in combination of two or more.

In this multilayer structure, when an adhesive resin layer is used between the present EVOH resin composition layer and the base resin layer, since the adhesive resin layer is located on both sides of the present EVOH resin composition layer, the hydrophobic It is preferable to use an adhesive resin with excellent properties.

The above-mentioned base resin and adhesive resin may contain conventionally known plasticizers within a range that does not impede the purpose of the present invention (for example, 30% by mass or less, preferably 10% by mass or less based on the entire resin). , fillers, clays (such as montmorillonite), colorants, antioxidants, antistatic agents, lubricants, core materials, antiblocking agents, waxes, and the like. These can be used alone or in combination of two or more.

Lamination of the present EVOH resin composition layer and the base resin layer (including the case where an adhesive resin layer is interposed) can be performed by a known method. For example, a method of melt extrusion laminating a base resin on a film, sheet, etc. of the present EVOH resin composition, a method of melt extrusion laminating the present EVOH resin composition on a base resin layer, a method of melt extrusion laminating the present EVOH resin composition and a base resin, A method of dry laminating the present EVOH resin composition (layer) and a base resin (layer) using a known adhesive such as an organic titanium compound, an isocyanate compound, a polyester compound, or a polyurethane compound. Examples include a method in which a solution of the present EVOH resin composition is applied onto the base resin and then the solvent is removed. Among these, in view of cost and environment, it is preferable to manufacture the present EVOH resin composition layer by including a step of melt-molding it, and specifically, a coextrusion method is preferable.

This multilayer structure may be subjected to (heating) stretching treatment if necessary. The stretching treatment may be either uniaxial stretching or biaxial stretching, and in the case of biaxial stretching, simultaneous stretching or sequential stretching may be performed. Further, as the stretching method, a method with a high stretching ratio among roll stretching methods, tenter stretching methods, tubular stretching methods, stretch blowing methods, vacuum-pressure forming, etc. can be adopted. The stretching temperature is selected from the range of usually 40 to 170°C, preferably about 60 to 160°C, near the melting point of the multilayer structure. 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.

Further, the present multilayer structure after the stretching treatment may be heat-set for the purpose of imparting dimensional stability. Heat fixation can be carried out by well-known means. For example, the stretched multilayer structure is heat-treated at a temperature of usually 80 to 180°C, preferably 100 to 165°C, for about 2 to 600 seconds while maintaining a tensioned state. conduct.

When the stretched multilayer structure is used as a shrink film, in order to impart heat shrinkability, the above heat setting is not performed, and for example, cold air is applied to the stretched multilayer structure. Processing such as cooling and fixing may be performed.

The thickness of the present multilayer structure (including the stretched one) and the thickness of the present EVOH resin composition layer, base resin layer, and adhesive resin layer that constitute the multilayer structure are determined by the layer structure and the type of base resin. The thickness of the present multilayer structure (including the stretched one) is usually 10 to 5000 μm, preferably 30 to 3000 μm, although it cannot be definitively stated depending on the type of adhesive resin, application, packaging form, required physical properties, etc. Particularly preferred 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, particularly preferably 3 to 100 μm.

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

Moreover, it is also possible to obtain a multilayer container in the form of a cup or a tray using the present multilayer structure. In that case, a draw forming method is usually employed, and specific examples thereof include a vacuum forming method, a pressure forming method, a vacuum pressure forming method, a plug-assisted vacuum pressure forming method, and the like. Furthermore, when obtaining a tube- or bottle-shaped multilayer container (laminate structure) from a multilayer parison (a hollow tubular preform before blowing), a blow molding method is employed. Specifically, extrusion blow molding methods (double-head type, moving mold type, parison shift type, rotary type, accumulator type, horizontal parison type, etc.), cold parison blow molding, injection blow molding, biaxial stretching Examples include blow molding methods (extrusion type cold parison biaxial stretch blow molding method, injection type cold parison biaxial stretch blow molding method, injection molding inline type biaxial stretch blow molding method, etc.). 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, tube processing, split processing, etc. as necessary. I can do it.

Single-layer films molded from this EVOH resin composition, bags made from this multilayer structure, and containers and lids such as cups, trays, tubes, and bottles can be used for general foods, as well as mayonnaise, dressings, etc. It is useful as a variety of packaging material containers for seasonings, fermented foods such as miso, oil and fat foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc.

Hereinafter, the present invention will be specifically explained with reference to Examples. However, the present invention is not limited in any way by the following examples.
In addition, "part" in the examples means a mass standard unless otherwise specified.

<Example 1>
As the EVOH resin, pellets of EVOH resin having an ethylene structural unit content of 29 mol %, a degree of saponification of 99.6 mol %, and an MFR of 4 g/10 minutes (210° C., load 2160 g) were used.
Moreover, magnesium oxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was used as the alkaline earth metal compound, and titanium oxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was used as the titanium compound.
The pellets of the EVOH resin are dried so that the magnesium oxide content is 10 ppm per mass of the EVOH resin composition in terms of metal, and the titanium oxide is 0.1 ppm per mass of the EVOH resin composition in terms of metal content. Blend to obtain a mixture.
The mixture was supplied to a twin-screw extruder (20 mmφ) equipped with a two-hole die, extruded under the following extrusion conditions, and the discharged strand was air-cooled and solidified on a belt conveyor. Next, the solidified strands were cut to obtain pellets of the EVOH resin composition.
[Extrusion conditions]
Extruder setting temperature (℃): C1/C2/C3/C4/C5/C6
=150/200/210/210/210/210

<Example 2>
Pellets of an EVOH resin composition were obtained in the same manner as in Example 1, except that the amount of titanium oxide was changed to 1 ppm per mass of the EVOH resin composition in terms of metal.

<Comparative example 1>
Pellets of an EVOH resin composition were obtained in the same manner as in Example 1, except that titanium oxide was not used.

<Comparative example 2>
Pellets of an EVOH resin composition were obtained in the same manner as in Example 1, except that the amount of titanium oxide was changed to 10 ppm per mass of the EVOH resin composition in metal terms.

Using the obtained pellets of the EVOH resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2, the following long-run performance evaluation was performed. The results are shown in Table 1 below.

[Long run performance evaluation]
The obtained pellets of the EVOH resin composition were crushed at 650 rpm using a crusher (manufactured by Sometani Sangyo Co., Ltd., SKR16-240) to obtain a crushed product of 1 to 5 mm square.
The obtained pulverized material was filled into a cylinder with an inner diameter of 32 mm and a height of 30 mm, and the YI value was measured using a spectrophotometer SE6000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) in a rubbed state.
Further, the YI value was similarly measured for the pulverized product that had been heat-treated in an oven at 150° C. for 5 hours.
Thereafter, the ratio of the YI value after heating to the YI value before heating was calculated.
The larger the ratio of the YI value after heating to the YI value before heating, the more the EVOH resin composition is colored yellow after heating.

From Table 1 above, the EVOH resin compositions of Examples 1 and 2 that contain a specific trace amount of a titanium compound, the EVOH resin composition of Comparative Example 1 that does not contain a titanium compound, and the EVOH resin composition that contains a titanium compound beyond a specific range. Compared to the EVOH resin composition of Comparative Example 2, the YI value ratio was smaller and coloring due to heating was suppressed, so it had excellent long-run properties.
Note that the ratio of YI values between Example 2 and Comparative Example 1 differs by only 0.1, but in actual manufacturing sites, the yield changes significantly and the difference becomes a very large difference. . Further, the multilayer structure including the layers made of the EVOH resin compositions of Examples 1 and 2 also has the effect that color change is suppressed and excellent long-run properties are obtained.

This EVOH resin composition suppresses color change due to heat deterioration during melt molding and has excellent long-run properties, so it can be used in various foods, seasonings such as mayonnaise and dressing, fermented foods such as miso, oils and fats such as salad oil, etc. It is useful as a variety of packaging materials for foods, beverages, cosmetics, pharmaceuticals, etc.

Claims (7)

An ethylene-vinyl alcohol copolymer composition containing an ethylene-vinyl alcohol copolymer, an alkaline earth metal compound, and a titanium compound,
An ethylene-vinyl alcohol copolymer composition in which the content of the titanium compound in terms of metal is 0.001 ppm or more and less than 5 ppm per mass of the ethylene-vinyl alcohol copolymer composition. The ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the alkaline earth metal compound has a metal equivalent content of 0.1 to 500 ppm per mass of the ethylene-vinyl alcohol copolymer composition. The ethylene-vinyl alcohol copolymer composition according to claim 1 or 2, wherein the mass ratio of the metal equivalent content of the alkaline earth metal compound to the metal equivalent content of the titanium compound is 0.02 to 500,000. A pellet comprising the ethylene-vinyl alcohol copolymer composition according to claim 1 or 2. A multilayer structure comprising at least one layer made of the ethylene-vinyl alcohol copolymer composition according to claim 1 or 2. A method for producing the ethylene-vinyl alcohol copolymer composition according to claim 1 or 2, comprising:
A method for producing an ethylene-vinyl alcohol copolymer composition, comprising the step of melt-mixing composition raw materials containing the ethylene-vinyl alcohol copolymer and a titanium compound. A method for manufacturing the multilayer structure according to claim 5, comprising:
A method for producing a multilayer structure, comprising the step of melt-molding a layer made of the ethylene-vinyl alcohol copolymer composition.