JP2023153000A - 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 thermal deterioration during heating such as melt molding.SOLUTION: An ethylene-vinyl alcohol copolymer composition contains an ethylene-vinyl alcohol copolymer (A), a styrene derivative with a substituent at α-position (B), and a titanium compound (C). The content of the titanium compound (C) 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 ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH resin") compositions, pellets, multilayer structures, methods for producing EVOH resin compositions, and methods for producing multilayer structures. .

EVOH resin has excellent transparency, gas barrier properties against oxygen and other gases, aroma retention, solvent resistance, oil resistance, mechanical strength, etc., and can be molded into films, sheets, bottles, etc., and is used as food packaging materials, pharmaceutical packaging materials, It is widely used as a variety of packaging materials such as industrial drug packaging materials and agricultural chemical 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.

To address the above-mentioned problem, for example, Patent Document 1 discloses that by containing an unsaturated aldehyde in EVOH resin, oxidative deterioration and coloring can be suppressed during melt molding of EVOH resin.

International Publication No. 2013/146961

However, even a trace amount of aldehyde compounds such as the unsaturated aldehyde may cause a bad odor, and there is a concern that the aldehyde compounds may volatilize in a molding process that is exposed to high temperatures, thereby worsening the working environment. In addition, it cannot be said that the effects of improving long-run moldability, such as suppressing oxidative deterioration during heating during melt kneading and melt molding, are still sufficient. Therefore, there is a strong demand for an EVOH resin composition that does not deteriorate the working environment and that is resistant to thermal deterioration during heating and can yield high-quality molded products.

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

However, in view of the above circumstances, the present inventors added a styrene derivative having a substituent at the α-position and a specific trace amount of a titanium compound to the EVOH resin, thereby suppressing the thermal deterioration of the EVOH resin during heating during melt molding and the like. It has been found that an EVOH resin composition can be obtained.

That is, the present invention has the following aspects.
[1] An EVOH resin composition containing an EVOH resin (A), a styrene derivative (B) having a substituent at the α-position, and a titanium compound (C),
An EVOH resin composition in which the metal equivalent content of the titanium compound (C) 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 content of the styrene derivative (B) having a substituent at the α-position is 1 to 10,000 ppm per mass of the EVOH resin composition.
[3] The mass ratio of the content of the styrene derivative (B) having a substituent at the α-position to the metal equivalent content of the titanium compound (C) is 0.2 to 10,000,000 [1] or [2] The EVOH resin composition described.
[4] The EVOH resin composition according to any one of [1] to [3], wherein the styrene derivative (B) having a substituent at the α-position is an α-methylstyrene derivative.
[5] A pellet made of the EVOH resin composition according to any one of [1] to [4].
[6] A multilayer structure comprising at least one layer made of the EVOH resin composition according to any one of [1] to [4].
[7] A method for producing the EVOH resin composition according to any one of [1] to [4], 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.
[8] A method for manufacturing the multilayer structure according to [6], comprising:
A method for producing a multilayer structure, comprising the step of melt-molding a layer made of the EVOH resin composition.

Since the EVOH resin composition of the present invention has excellent thermal stability, it is possible to suppress thermal deterioration of the EVOH resin during melt molding.

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 "this EVOH resin composition") has an EVOH resin (A) as a main component, and a styrene derivative (B) having a substituent at the α-position. It contains a specific trace amount of titanium compound (C).
That is, in the present EVOH resin composition, the base resin is EVOH resin (A), and the content of EVOH resin (A) in the present EVOH resin composition is usually 70% by mass or more, preferably 80% by mass or more, and more. The content is preferably 90% by mass or more, particularly preferably 95% by mass or more.
Each component will be explained 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 a water-insoluble resin. It is a thermoplastic resin.

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 (A) produced in this way mainly contains 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 (A) 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 (A) 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 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 35 g/10 minutes. It's 10 minutes. 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 (A), 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 (A) may further contain a structural unit derived from a comonomer shown below within a range that does not impede the effects of the present invention (for example, 10 mol% of the EVOH resin (A)). below).
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 (A) used in the present invention 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 of the EVOH resin (A). %, preferably 0.5 to 15 mol %, particularly preferably 1 to 10 mol %.

Further, as the EVOH resin (A), 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 used is too high, it tends to be easily thermally degraded and its long run properties tend to decrease.

Further, the EVOH resin (A) 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.

[Styrene derivative (B) having a substituent at α-position]
The styrene derivative having a substituent at the α-position (hereinafter sometimes referred to as "specific styrene derivative") (B) used in the present invention is an aromatic compound having the ability to resonance stabilize and capture radicals. , is a compound that has a styrene molecular structure as a molecular skeleton and has a substituent at the α position.

Examples of the specific styrene derivative (B) include α-methylstyrene derivatives, specifically α-methylstyrene, 4-t-butylstyrene, 4-methoxystyrene, 2-acetoxystyrene, 2,4 -diphenyl-4-methyl-1-pentene and the like. Among these, 2,4-diphenyl-4-methyl-1-pentene, whose radicals are resonance stabilized by having a benzyl position, is preferable from the viewpoint of suppressing thermal deterioration, which is an effect of the present invention.

The molecular weight of the specific styrene derivative (B) is usually 100 to 100,000, preferably 100 to 10,000, particularly preferably 100 to 1,000, particularly preferably 130 to 300. When the molecular weight is within the above range, the effects of the present invention tend to be more effectively obtained.

The content of the specific styrene derivative (B) is preferably 1 to 10,000 ppm, more preferably 100 to 8,000 ppm, particularly preferably 300 to 5,000 ppm, even more preferably 500 to 4,000 ppm, especially Preferably it is 1000 to 3000 ppm. If it is too large, productivity tends to decrease, and if it is too small, thermal stability tends to decrease.

The EVOH resin composition that serves as the standard for the content ratio of the specific styrene derivative (B) includes the EVOH resin (A), the specific styrene derivative (B), the titanium compound (C), and various compounds blended as necessary. This is an EVOH resin composition as a final product containing additives and the like.

The content of the specific styrene derivative (B) in the present EVOH resin composition is determined based on the following conditions using, for example, thermal extraction-cooling concentration introduction-gas chromatography mass spectrometry (TD-CI-GC/MS). can be measured.

<Method for measuring the content of styrene derivative (B)>

[TD-CI-GC/MS measurement conditions]
(TDS section conditions)
Equipment used: TDS-2 [manufactured by GERSTEL]
Sample mode: standby cooling
Flow mode: splitless
Standby temp: 20℃
Transfer temperature: 250℃
Initial temperature: 20℃
Initial time: 4min
1st rate: 60℃/min
1st final temp: 200℃
1st final time: 60min

(CIS section conditions)
Equipment used: CIS-4 [manufactured by GERSTEL]
Initial temp:-150℃
Initial time: 1min
1st rate: 12℃/sec
1st final temp: 250℃
1st final time: 5min
equilib. time: 0.5min
(split rate: 30:1)

(GC/MS section conditions)
Equipment used: 7890A (GC)-5977 (MS) quadrupole type [manufactured by Agilent Technologies]
Column: DB-WAX [manufactured by Agilent Technologies]
Length x inner diameter x film thickness = 30m x 0.25mm x 0.25μm
Temperature: OVEN40℃(5min hold)-Rate10℃/min-250℃(10min hold)
INJ250℃ AUX250℃
Carrier gas: He (Flow 1mL/min, constant flow)
Split ratio: 30:1
Measurement mode: SIM (m/z=91,119,236)
Solvent waiting time: 10min

[Titanium compound (C)]
Examples of the titanium compound (C) used in the present invention 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 salt of titanium include titanium carboxylates such as titanium acetate, titanium butyrate, and titanium stearate.

In addition, the titanium compound (C) may exist in the EVOH resin composition not only as a titanium compound but also in an ionized state or in a complex state that interacts with the EVOH resin or other ligands. It's okay.

The average particle size of the titanium compound (C) 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, thermal stability tends to be further improved.

The content of the titanium compound (C) 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 (C) within the above range, thermal deterioration during melt molding can be suppressed, resulting in excellent long-run properties. Further, if the content of the titanium compound (C) is too small, the effect of suppressing thermal deterioration 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 (C) is determined by weighing the present EVOH resin composition into a platinum crucible, sequentially incinerating it with a burner and an electric furnace, and heating and decomposing the ashed product with nitric acid and hydrofluoric acid. Titanium in a fixed volume solution obtained by treatment with a mixed acid of nitric acid and dilute hydrofluoric acid is measured by ICP mass spectrometry using an ICP mass spectrometer (manufactured by Agilent Technologies, Agilent 8800). It can be quantified by

The mass ratio of the content of the specific styrene derivative (B) to the metal equivalent content of the titanium compound (C) is preferably 0.2 to 1,000,000, more preferably 0.3 to 1,000,000, even more preferably 100 to 270,000, particularly preferably 600 to 100,000, particularly preferably 800 to 50,000, particularly preferably 1,000 to 30,000.
If this value is too large, the UV absorption ability of the EVOH resin composition tends to decrease, and if it is too small, the thermal stability tends to decrease.

Here, it is generally known that EVOH resin deteriorates due to heat. This can be considered as follows. That is, the EVOH resin is degraded by heat and radicals are generated, and the radicals cause a dehydration reaction in the hydroxyl groups of the EVOH resin, and a double bond structure is generated in the main chain of the EVOH resin. This is thought to be because this site becomes a reaction starting point and further causes a dehydration reaction, forming a polyene structure in the main chain of the EVOH resin.

Generally, 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, when a specific styrene derivative (B) and a specific trace amount of a titanium compound (C) are used in combination, an EVOH resin whose thermal deterioration is significantly suppressed is produced. They have found that a composition can be obtained.

That is, 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 EVOH resin and stabilizes it by forming a chelate. It is assumed that this suppresses the formation of It is presumed that the coexistence of the specific styrene derivative (B) with the titanium compound (C) allows the stabilizing effect of the titanium compound (C) to be more effectively exerted.
On the other hand, if the content of the titanium compound (C) is too large, it is thought that thermal decomposition of the EVOH resin will occur due to the titanium compound (C), so in the present invention, the content of the titanium compound (C) is reduced to a specific trace amount. Limited.

[Other thermoplastic resins]
The present EVOH resin composition contains a thermoplastic resin other than the EVOH resin (A) 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 20% by mass or less of the present EVOH resin composition). (preferably 10% by 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, and polyurethane elastomers. , chlorinated polyethylene, chlorinated polypropylene, etc. 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 compounding agents include inorganic double salts (such as hydrotalcite), plasticizers (such as aliphatic polyhydric alcohols such as ethylene glycol, glycerin, and hexanediol), and oxygen absorbers [such as aluminum powder and potassium sulfite]. 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), etc., and polymeric oxygen absorbers such as those containing photoinitiators (benzophenone, etc.), antioxidants and deodorants (activated carbon, etc.) other than those mentioned 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.). It's okay. These compounds can be used alone or in combination of two or more.

[Method for manufacturing EVOH resin composition]
The present EVOH resin composition is prepared by blending the EVOH resin (A), the specific styrene derivative (B), and the titanium compound (C) by a known method such as a dry blending method, a melt mixing method, a solution mixing method, an impregnation method, etc. It can be manufactured by mixing, and 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 a method in which (i) pelletized EVOH resin (A), a specific styrene derivative (B), and a titanium compound (C) are dry blended using a tumbler or the like.

As the melt mixing method, for example, (ii) a dry blend of pellet-shaped EVOH resin (A), a specific styrene derivative (B), and a titanium compound (C) is melt-kneaded to form pellets or molded products. and (iii) a method of adding a specific styrene derivative (B) and/or a titanium compound (C) to a molten EVOH resin (A) and melt-kneading the mixture to obtain pellets or molded products.

As the solution mixing method, for example, (iv) a solution is prepared using pelletized EVOH resin (A), a specific styrene derivative (B) and/or a titanium compound (C) is blended therein, and the solution is solidified and molded. (v) In the manufacturing process of EVOH resin (A), a homogeneous solution (water/alcohol solution, etc.) of EVOH resin before saponification is used. Examples include a method of containing the specific styrene derivative (B) and/or titanium compound (C), coagulating and forming into pellets, followed by solid-liquid separation and drying by known means.

As the impregnation method, for example, (vi) pellet-shaped EVOH resin (A) is brought into contact with an aqueous solution containing a specific styrene derivative (B) and/or a titanium compound (C), and the Examples include a method of containing the specific styrene derivative (B) and/or titanium compound (C) and then drying.
As the aqueous solution containing the titanium compound (C), an aqueous solution of the titanium compound (C) or a titanium compound (C) obtained by immersing the titanium compound (C) in water containing various chemicals to elute titanium ions can be used. can. The same applies to the aqueous solution containing the specific styrene derivative (B).

In addition, in the impregnation method, the content (metal equivalent) of the specific styrene derivative (B) and the titanium compound (C) is the content (metal equivalent) of the specific styrene derivative (B) and the titanium compound (C) in the aqueous solution in which the EVOH resin (A) is immersed. It is possible to control the concentration of C), immersion temperature, immersion time, etc.
The immersion time is 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.

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

As mentioned above, these various methods can be combined to obtain the present EVOH resin composition. 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.

The shape of the EVOH resin composition obtained in this way is arbitrary, but 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 ~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 (A) used in each of the above manufacturing methods are also the same.

In addition, when the present EVOH resin composition is in the form of pellets, it is 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 present EVOH resin composition obtained in this way can suppress thermal deterioration during heating, and the 5% weight loss temperature of the present EVOH resin composition is usually 330°C or higher, preferably The temperature is 331°C or higher. Further, the 10% weight loss temperature of the EVOH resin composition is usually 351°C or higher, preferably 352°C or higher, particularly preferably 353°C or higher.
The upper limits of the 5% weight loss temperature and 10% weight loss temperature are usually 450°C, although the higher the better.
The difference in weight loss temperature of 1° C. appears as a large difference in yield in actual production, so the difference is very large.

The above-mentioned "5% weight loss temperature" and "10% weight loss temperature" mean that 5 mg of the present EVOH resin composition was measured at an air flow rate under a nitrogen atmosphere using a thermogravimetric measuring device (manufactured by Perkin Elmer, Pyris 1 TGA). : 20 mL/min, heating rate: 10°C/min, temperature range: 30 to 550°C, temperature at which the weight decreases to 95% of the weight before measurement (5% weight loss temperature), and weight It means the temperature at which the weight decreases to 90% of the mass before measurement (10% weight loss temperature).

Further, the water 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. It is.

The water content of the present 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.
<Formula>
Moisture content (mass%) = [(W ₁ - W ₂ )/W ₁ ] x 100

The present EVOH resin composition is prepared in various forms such as pellets, powder, and liquid, and is 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 (A) 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. This EVOH resin composition layer is sometimes abbreviated as "base resin") to provide further strength, protect the EVOH resin composition layer from the effects of moisture, and provide other functions. can do.

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, and ethylene-α-olefin. Polyethylene resins such as (α-olefin having 4 to 20 carbon atoms) copolymers, polypropylene, polypropylene resins such as propylene-α-olefin (α-olefin 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 modification 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, Polyester resin, polyamide resin (including copolyamide polyamide), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, polystyrene elastomer, chlorinated Examples include halogenated polyolefins such as polyethylene and chlorinated polypropylene, aromatic or aliphatic polyketones, and the like.

Among these, hydrophobic resins such as polyamide resins, polyolefin resins, polyester resins, and polystyrene resins are preferable, and polyethylene resins, polypropylene resins, polycyclic olefin resins, and unsaturated resins thereof are more preferable. Polyolefin resins such as carboxylic acid-modified polyolefin resins, particularly polycyclic olefin resins, are preferably used as hydrophobic 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, recycled products containing a mixture of the present EVOH resin composition and a thermoplastic resin other than the present EVOH resin composition obtained by remelting and molding the edges and defective products generated in the process of manufacturing the 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-grafted modified polyethylene, maleic anhydride-grafted modified polypropylene, maleic anhydride-grafted modified ethylene-propylene (block and random) copolymers, and maleic anhydride. 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 base resin and the adhesive resin may contain a conventionally known plasticizer within a range that does not impede the spirit 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 consideration from the viewpoint of cost and environment, the present EVOH resin composition layer can be manufactured by including a step of melt molding. Specifically, a coextrusion method is preferred.

This multilayer structure may be subjected to (heating) stretching treatment as 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 the stretched multilayer structure is, for example, blown with cold air. 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 and containers and lids made of bags, cups, trays, tubes, bottles, etc. made of this multilayer structure can be used for general foods, as well as mayonnaise, dressings, etc. It is useful as a variety of packaging materials 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.

<Example 1>
As the EVOH resin (A), pellets of an 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.
In addition, 2,4-diphenyl-4-methyl-1-pentene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the specific styrene derivative (B), and titanium oxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was used as the titanium compound (C). Using.
For the pellets of the EVOH resin (A), the specific styrene derivative (B) is 2000 ppm per mass of the EVOH resin composition, and the titanium oxide is 0.1 ppm per mass of the EVOH resin composition as a metal equivalent content. A mixture was obtained by dry blending. Then, the mixture was preheated at 230° C. for 5 minutes using Plastograph (manufactured by Brabender), and then melt-kneaded for 5 minutes to obtain an EVOH resin composition. The obtained EVOH resin composition was pulverized at 650 rpm using a pulverizer (manufactured by Sometani Sangyo Co., Ltd., SKR16-240) to obtain a pulverized product.

<Example 2>
A pulverized EVOH resin composition was 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 metal terms.

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

<Comparative example 2>
A pulverized EVOH resin composition was obtained in the same manner as in Example 1, except that the amount of titanium oxide was changed to 5 ppm per mass of the EVOH resin composition in metal terms.

The following thermal stability evaluation was performed using the obtained crushed EVOH resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2. The results are shown in Table 1 below.

[Thermal stability evaluation]
Using 5 mg of the obtained pulverized EVOH resin composition, it was measured using a thermogravimetry device (manufactured by PerkinElmer, Pyris 1 TGA) in a nitrogen atmosphere at an air flow rate of 20 mL/min and a temperature range of 30 to 550°C. The temperature at which the weight decreased to 95% of the weight before measurement (5% weight reduction temperature) and the temperature at which the weight decreased to 90% of the weight before measurement (10% weight reduction temperature) were measured. The higher the temperature, the better the thermal stability.

From Table 1, the EVOH resin compositions of Examples 1 and 2 containing the specific styrene derivative (B) and a specific trace amount of the titanium compound (C) are different from the EVOH resin of Comparative Example 1 that does not contain the titanium compound (C). Compared to the EVOH resin composition of Comparative Example 2 containing titanium compound (C) in an amount larger than the specific range, both the 5% weight loss temperature and the 10% weight loss temperature are higher, and the composition has excellent thermal stability. I understand that.
Further, the multilayer structure including the layers made of the EVOH resin compositions of Examples 1 and 2 also has excellent thermal stability with suppressed thermal deterioration.

This EVOH resin composition suppresses thermal deterioration during heating during melt molding, etc., so it can be used in various foods, seasonings such as mayonnaise and dressing, fermented foods such as miso, oil and fat foods such as salad oil, beverages, etc. It is useful as a variety of packaging materials for cosmetics, pharmaceuticals, etc.

Claims (8)

An ethylene-vinyl alcohol copolymer composition containing an ethylene-vinyl alcohol copolymer (A), a styrene derivative (B) having a substituent at the α-position, and a titanium compound (C),
An ethylene-vinyl alcohol copolymer composition in which the content of the titanium compound (C) 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 content of the styrene derivative (B) having a substituent at the α-position is 1 to 10,000 ppm per mass of the ethylene-vinyl alcohol copolymer composition. thing. The ethylene-vinyl according to claim 1 or 2, wherein the mass ratio of the content of the styrene derivative (B) having a substituent at the α-position to the metal equivalent content of the titanium compound (C) is 0.2 to 10,000,000. Alcohol-based copolymer composition. The ethylene-vinyl alcohol copolymer composition according to claim 1 or 2, wherein the styrene derivative (B) having a substituent at the α-position is an α-methylstyrene derivative. 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 6, comprising:
A method for producing a multilayer structure, comprising the step of melt-molding a layer made of the ethylene-vinyl alcohol copolymer composition.