JP2009242644A - Ethylene-vinyl alcohol copolymer resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EVOH resin composition which is excellent in barrier properties, not discolored, beautiful and excellent in appearance characteristics. <P>SOLUTION: The ethylene-vinyl alcohol copolymer resin composition comprises a fluorescent whitening agent of 0.010 to 5.0 μmol/g and at least one metal salt of 0.10 to 20 μmol/g in terms of a metal element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ethylene-vinyl alcohol copolymer resin composition, and particularly relates to a novel ethylene-vinyl alcohol copolymer resin composition that is beautiful without coloration and has excellent appearance characteristics.

  An ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is a useful polymer material having excellent oxygen shielding properties, transparency, oil resistance, non-charging properties, mechanical strength, and the like. Although its uses are diverse, the beauty of appearance is particularly important in applications such as films, sheets, containers, and textile fibers, and the quality requirements for the appearance characteristics of EVOH resin compositions are increasing.

  The ethylene-vinyl ester copolymer saponified composition containing 1 to 5000 ppm of sulfite and / or hydrogen sulfite in terms of sulfite is said to be less colored and less likely to generate during melt molding ( For example, see Patent Document 1). A method for treating a saponified ethylene-vinyl ester copolymer, characterized in that an ethylene-vinyl ester copolymer having an ethylene content of 20 to 60 mol% is saponified and then treated with hydroxylamine and / or a salt thereof. It is said that an ethylene-vinyl ester copolymer saponified product with little coloration and less generation of molding during molding is obtained (for example, see Patent Document 2). In addition, as described in Patent Document 1, conventionally, an acid such as acetic acid and phosphoric acid and / or a salt thereof is added to the EVOH resin composition, and further dried to reduce coloring and shading. An EVOH resin composition is supposed to be obtained.

  The fluorescent whitening agent is widely used for preventing coloring of various resins and improving whiteness. For example, an ultraviolet absorber 5 made of a benzotriazole compound having a specific structure with respect to 100 parts by weight of a polycarbonate resin composition. Excellent weather resistance is obtained by containing ˜25 parts by weight and 0.1 to 10 parts by weight of a fluorescent whitening agent composed of one or two of a coumarin compound and a naphthalimide compound having a specific structure. And has yellowing resistance (see, for example, Patent Document 3). In addition, an optical brightener aqueous liquid composition comprising a fluorescent brightener represented by a specific structure or a salt thereof and a polyvinyl alcohol resin is useful for improving the whiteness of paper. (For example, refer to Patent Document 4).

Japanese Patent No. 36060277 Japanese Patent No. 3976809 Japanese Patent No. 2578573 JP 2007-224438 A

  As described in Patent Documents 1 and 2, various resin compositions and manufacturing methods have been proposed in order to suppress coloring of the EVOH resin composition and improve appearance characteristics. However, in the above-described invention, although coloring such as yellowing when the EVOH resin composition is melt-molded can be suppressed, the appearance of the resin composition such as whiteness and glossiness is sufficient. However, it is desired to make the resin composition more beautiful optically and chromatically.

Moreover, the beauty of various resin compositions can be added by using additives such as fluorescent whitening agents as in Patent Documents 3 and 4. However, when an additive such as a fluorescent brightening agent is blended in the EVOH resin composition, depending on the blending amount and type, fish eyes and streaks may occur during melt molding, resulting in poor appearance.

  The present invention has been made to solve the above-mentioned problems, and provides an EVOH resin composition that is not colored, has a beautiful appearance such as whiteness and gloss, and has no appearance defects such as fish eyes and streaks. It is intended to do.

  As a result of intensive studies aimed at achieving the above-mentioned problems, the inventors of the present invention contain 0.010 to 5.0 μmol / g of a fluorescent brightening agent, and at least one kind of metal salt is converted to a metal element equivalent of 0.000. It has been found that an ethylene-vinyl alcohol copolymer resin composition containing 10 to 20 μmol / g is excellent in appearance characteristics.

  According to the present invention, it is possible to provide an EVOH resin composition that is not colored and is beautiful and excellent in appearance characteristics. In addition, since EVOH resin has excellent gas barrier properties and processing characteristics, various molded products such as various films, sheets, pipes, containers, fibers and the like using the characteristics can be provided.

  Details of the present invention will be described below.

  The EVOH resin composition contains 0.010 to 5.0 μmol / g of a fluorescent brightening agent. When the content of the fluorescent brightening agent is 0.010 μmol / g or less, the beauty such as whiteness and glossiness of the resin composition is not sufficient. On the other hand, if it exceeds 5.0 μmol / g, there is a risk of appearance defects such as fish eyes and streaks occurring during melt molding, or coloring. The content of the optical brightener is more preferably 0.020 to 2.0 μmol / g, and further preferably 0.050 to 0.5 μmol / g.

  The type of fluorescent whitening agent used in the present invention is not particularly limited, and is selected from fluorescent whitening agents that absorb ultraviolet to visible light in the vicinity of 200 nm to 400 nm and emit fluorescence in the vicinity of 400 to 600 nm. It is. Specifically, 2,5-bis (5-t-butyl-2-benzoxazolyl) thiophene, 4,4′-bis (benzoxazol-2-yl) stilbene, 4,4′-bis (benzoxazole-2) Benzoxazoyl fluorescent whitening agents such as -yl) furan and 4,4-bis (benzoxazol-2-yl) naphthalene, 3-phenyl-7-aminocoumarin, 3-phenyl-7- (imino-1'3 '5'-triazine-2'-diethylamino-4'-chloro) coumarin, 3-phenyl-7- (imino-1'3'5'-triazine-2'-diethylamino-4'-methoxy) coumarin, 3- Phenyl-7- (2H-naphtho (1,2-d) -triazol-2-yl) coumarin, 4-methyl-7-hydroxycoumarin, 7-diethylamino-4-methylcouma And styrene biphenyl fluorescent brighteners such as 4,4-bis (2-distyryl styryl) biphenyl and 4,4-bis (2-methoxystyryl) biphenyl. It is done. In order to maintain good melt moldability and processing characteristics of the EVOH resin composition, a benzoxazoyl fluorescent whitening agent is particularly suitable.

  The content of the fluorescent brightener used in the present invention can be quantified by using various analytical techniques. For convenience, an EVOH resin composition containing a fluorescent brightening agent is dissolved in an organic solvent, and then quantified using an absorptiometer or a fluorometer. Various spectrum analysis such as nuclear magnetic resonance spectrum and infrared spectrum, separation analysis such as gas chromatography and liquid chromatography, etc. can be used, sulfur like 4,4-bis (styryl) diphenyl biphenyl, etc. The fluorescent brightening agent containing the specific element may be quantified by atomic absorption analysis, ICP emission analysis, ICP mass spectrometry, etc. after the EVOH resin composition is pretreated by ashing, wet decomposition, or the like. Is possible.

  Moreover, this EVOH resin composition contains 0.10-20 micromol / g of at least 1 or more types of metal salt in conversion of a metal element. If the content of the metal salt is 0.10 μmol / g or less in terms of metal element, fish eyes and streaks may occur during melt molding, resulting in poor appearance. When the content of the metal salt exceeds 20 μmol / g, the resin composition is likely to be colored. The content of the metal salt is more preferably 0.50 to 15 μmol / g, and further preferably 1.0 to 10 μmol / g.

  The kind of metal salt used for this invention is not specifically limited. The metal component is selected from lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, silver, cerium, etc. The acid component is sulfuric acid , Sulfonic acid, phosphoric acid, phosphorous acid, hypophosphorous acid, boric acid, carbonic acid and other inorganic acids, formic acid, acetic acid, propionic acid, butyric acid, lactic acid, glycolic acid, malic acid, oxalic acid, malonic acid, lauric acid It is selected from various organic acids such as acid, stearic acid and ethylenediaminetetraacetic acid.

  In order to obtain an EVOH resin composition that is not particularly colored and has excellent appearance characteristics, the metal salt is preferably a sodium salt, potassium salt, magnesium salt, or calcium salt. Specifically, various sodium borates such as sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, borax, sodium carbonate, sodium bicarbonate, sodium acetate, sodium propionate, sodium lactate, glycolic acid Sodium, sodium laurate, sodium stearate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium carbonate, potassium bicarbonate, potassium acetate, potassium propionate, potassium lactate, potassium glycolate, lauric acid Potassium, potassium stearate, magnesium acetate, magnesium lactate, magnesium stearate, calcium acetate, calcium lactate, calcium stearate, etc. are preferred, among which sodium acetate, sodium dihydrogen phosphate Disodium hydrogen phosphate, sodium carbonate, sodium bicarbonate, potassium acetate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium carbonate, potassium hydrogen carbonate, magnesium acetate, calcium acetate is particularly preferred. Only one kind of these metal salts may be used, and there is no problem even if a plurality of these metal salts are used simultaneously. By containing a metal salt, not only coloring properties and appearance characteristics can be obtained, but also an EVOH resin composition having good melt moldability and processing characteristics can be obtained.

  The content of the metal salt used in the present invention can be quantified by using various analytical techniques. Depending on the type of metal element contained, after pretreatment of the metal salt by hot water extraction, ashing, wet decomposition, etc., titration analysis, atomic absorption analysis, ion chromatography analysis, ICP issuance analysis, ICP Examples include, but are not limited to, a method for quantification by mass spectrometry and the like and a method for quantification by nondestructive analysis such as fluorescent X-ray analysis.

  The method for adding a metal salt or a fluorescent brightening agent to the EVOH resin composition is not particularly limited. A method of immersing the EVOH resin composition by adjusting a solution or emulsion of a metal salt or a fluorescent brightener, a method of melt-molding by blending an EVOH resin composition with a metal salt or a fluorescent brightener, a metal salt or a fluorescent A method of blending a masterbatch containing a brightener and an EVOH resin composition and melt molding, a method of adding a solution or emulsion of a metal salt or a fluorescent brightener when melt-molding the EVOH resin composition, EVOH Examples thereof include a method of preparing a solution comprising a resin, a metal salt, and a fluorescent brightening agent, but are not particularly limited thereto. It may be added in two or more different ways.

  When the optical brightener is a salt having an ionic structure, it is possible to obtain the effect as a metal salt described in the present invention, but it contains a different type of metal salt from the optical brightener. Is preferred. For example, when the EVOH resin composition of the present invention contains sodium salt of 4,4-bis (styryl 2-disulfonate) biphenyl, in addition to the effect as the fluorescent whitening agent of the present invention, the effect as a metal salt Can also be obtained. However, in order to optimize the content, it is preferable to blend a metal salt of a different type from 4,4-bis (styryl 2-disulfonate) biphenyl.

In order to achieve the good appearance characteristics that are the gist of the present invention, it is preferable that the EVOH resin composition of the present invention exhibits as little absorption in the visible light region as possible. In particular, when the resin composition has absorption in visible light around 400 nm, it is colored yellow, so it is important to minimize the absorption of light around 400 nm. Specifically, the extinction coefficient ε represented by the following formula (1) measured by dissolving the EVOH resin composition of the present invention in dimethyl sulfoxide is preferably 0.05 or less.
ε = A / (L × C) (1)
Here, A represents the absorbance of 400 nm light measured with an absorptiometer, L represents the optical path length (unit: cm), and C represents the concentration of the EVOH resin composition (unit: wt%).

To specifically describe the method for measuring the extinction coefficient ε, the EVOH resin composition of the present invention is dissolved in dimethyl sulfoxide, and the absorbance is measured with an ultraviolet-visible spectrophotometer or other absorptiometer. In order to accurately measure the absorbance A, it is preferable to measure under the condition that A is 1.0 or less. For example, when a dimethyl sulfoxide solution of a 5.0 wt% EVOH resin composition is prepared and the absorbance at 400 nm measured using a quartz cell having a 5.0 cm optical path length is 0.25, the following formula (2) As shown in FIG. 4, the extinction coefficient ε of the present invention is 0.01.
ε = 0.25 / (5.0 × 5.0) = 0.01 (2)

  Suitable melt flow rate (MFR) of the resin composition comprising EVOH obtained in the present invention (measured at 190 ° C. under a load of 2160 g; provided that the melting point is around 190 ° C. or exceeds 190 ° C. under a load of 2160 g, the melting point It is measured at the above plural temperatures, and in a semi-logarithmic graph, the reciprocal absolute temperature is plotted on the horizontal axis, the melt flow rate is plotted on the vertical axis (logarithm), and the value extrapolated to 190 ° C.) is preferably 0.1 200 g / 10 min. It is. The lower limit of MFR is more preferably 0.2 g / 10 min. More preferably, 0.5 g / 10 min. Above, optimally 1 g / 10 min. That's it. Further, the upper limit of MFR is more preferably 50 g / 10 min. Or more preferably 30 g / 10 min. And optimally 15 g / 10 min. It is as follows. When the melt flow rate is smaller than the above range, the inside of the extruder is in a high torque state at the time of molding, making extrusion difficult, and when larger than the range, the mechanical strength of the molded product is insufficient, which is preferable. Absent.

  The saponification degree of the EVOH resin composition of the present invention is preferably 99.0 to 100 mol%. When the saponification degree is 99.0 mol% or less, it is difficult to obtain a sufficient gas barrier property, and fish eyes may be generated during melt molding, which may deteriorate the appearance. Depending on the application, an EVOH resin composition having a saponification degree lower than 99.0 mol% can be obtained.

  It is also possible to blend and melt mold EVOH having different degrees of polymerization, ethylene content and saponification degree to the resin composition obtained in the present invention. Add appropriate amounts of other plasticizers, antioxidants, UV absorbers, slip agents, antistatic agents, plasticizers, cross-linking agents such as boric acid, inorganic fillers, inorganic desiccants, various fibers, etc. However, it is important for the purpose of the present invention that the appearance characteristics of the resin composition are not impaired.

  The obtained EVOH resin composition of the present invention is formed into various molded products such as films, sheets, containers, pipes, fibers and the like. Among them, applications that require a beautiful appearance such as containers and textile fibers are applications that are suitable for using the resin composition of the present invention.

  The EVOH molding method of the present invention is not particularly limited. Molding by extrusion molding, inflation extrusion, blow molding, melt spinning, wet spinning, injection molding or the like is common. The melting temperature varies depending on the melting point of the copolymer, but is preferably about 150 to 270 ° C.

  The EVOH of the present invention can be used as a molded product composed of only a single layer of the resin composition, but is preferably a multilayer structure including at least one layer of the EVOH. The layer structure of the multilayer structure is represented by E / T, T / E / T, E / Ad / T, where E is EVOH of the present invention, Ad is an adhesive, and T is another thermoplastic resin or substrate. , T / Ad / E / Ad / T and the like, but are not limited thereto. Each of the layers shown here may be a single layer or may be a multilayer according to circumstances.

  The method for producing the multilayer structure shown above is not particularly limited. The EVOH resin composition of the present invention is mixed with alcohols such as methanol, ethanol, 1-propanol, 2-propanol and water, dimethyl sulfoxide, halogens such as 1, 1, 1, 3, 3, 3-hexafluoroisopropanol. It is preferable to dissolve in a halogenated alcohol and apply on a base material in order to achieve the effects of the present invention. Since the molded product thus obtained can improve the appearance characteristics of the base material, whiteness and glossiness can be enhanced particularly when a white base material is used.

  The coating method on the surface of the substrate includes ejection from a casting head, roll coating, air knife coating, gravure roll coating, doctor roll coating, doctor knife coating, curtain flow coating, spray, wire bar, rod coating, dipping, brush coating Arbitrary means are illustrated. Examples of a method for drying and heat-treating the substrate thus coated include a dry heat treatment method such as an infrared irradiation method and a hot air drying method. These infrared irradiation, hot air drying and the like may be used alone or in combination. Moreover, it is preferable that the temperature of drying and heat processing is 30-180 degreeC, About 50 degreeC or more is preferable about a lower limit, and it is 80 degreeC or more optimally. The drying / heat treatment time is preferably 5 seconds to 10 minutes, more preferably 1 to 5 minutes. During drying and heat treatment, it is free to increase / decrease the conditions, for example, the temperature, for example, to initially treat at a low temperature and gradually increase the temperature.

  It is preferable to apply and dry an adhesive on the surface of the base material in advance by dry lamination or the like, that is, anchor coat. The adhesive for dry lamination is not particularly limited as long as the interlayer adhesion is sufficient. For example, polyurethane-based and polyester-based adhesives for dry lamination can be mentioned. Further, the surface of the base material may be subjected to corona discharge treatment, sputtering treatment, high frequency treatment, fire treatment, chromic acid treatment, solvent etching treatment, or a combination of these. The application may be performed once or a plurality of times.

  The following are mentioned as a base material. Thermoplastic resin film, for example, polypropylene resin, polyamide resin such as nylon-6, nylon-6, 6, polyester resin such as polyethylene terephthalate, polycarbonate resin, polyvinylidene chloride resin, polystyrene resin, linear low density polyethylene, Examples thereof include films made of polyethylene such as low density polyethylene, medium density polyethylene, and high density polyethylene.

  In addition, various molded products (sheets, cups, bottles, etc.) other than the above-mentioned films are also suitable, and fiber aggregates (paper, nonwoven fabrics, woven fabrics, fibrous casings, etc.), polyvinyl chloride resin wallpaper, Also includes photographic paper.

  Also, a method of melt-extruding another thermoplastic resin of the EVOH resin composition of the present invention, and conversely, a method of co-extruding the EVOH and another thermoplastic resin on a base material such as a thermoplastic resin, a thermoplastic resin A method of co-extrusion or co-injection of EVOH comprising EVOH and EVOH of the present invention, a film obtained from the EVOH of the present invention and a film or sheet of another substrate, and known adhesion of organic titanium compounds, isocyanate compounds, polyester compounds, etc. A multilayer structure can also be obtained by a method of laminating using an agent.

  The method of co-extrusion molding of the composition of the present invention and the thermoplastic resin is not particularly limited, and a multi-manifold merging method T-die method, a feed block merging method T-die method, an inflation method and the like are exemplified as suitable ones. Further, the method of co-injection molding is not particularly limited, and a general method can be used.

  The thermoplastic resin used for laminating with the EVOH of the present invention includes linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer. , Polypropylene, propylene-α-olefin copolymer (α-olefin having 4 to 20 carbon atoms), polybutene, polypentene and other olefins alone or copolymers thereof, polyester such as polyethylene terephthalate, polyester elastomer, nylon-6, Examples thereof include polyamide resins such as nylon-6, 6, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resins, vinyl ester resins, polyurethane elastomers, polycarbonates, chlorinated polyethylene, and chlorinated polypropylene. Among these, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene, and polyester are preferably used.

  When laminating the EVOH of the present invention and a thermoplastic resin, an adhesive resin may be used. In this case, an adhesive resin made of a carboxylic acid-modified polyolefin is preferable. Here, the carboxylic acid-modified polyolefin is a modified olefinic polymer containing a carboxyl group obtained by chemically (for example, by addition reaction or graft reaction) bonding an ethylenically unsaturated carboxylic acid or its anhydride to an olefin polymer. Refers to coalescence. In addition, the olefin polymer is a polyethylene (low pressure, medium pressure, high pressure), a polyolefin such as linear low density polyethylene, polypropylene, boribten, or the like, a comonomer (vinyl ester, non-polymer) capable of copolymerizing the olefin and the olefin. Means a copolymer with a saturated carboxylic acid ester and the like, for example, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ethyl ester copolymer, and the like. Of these, linear low density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content 5-55 wt%), ethylene-acrylic acid ethyl ester copolymer (acrylic acid ethyl ester content 8-35 wt. %), Linear low density polyethylene and ethylene-vinyl acetate copolymers are particularly preferred. Examples of the ethylenically unsaturated carboxylic acid or its anhydride include ethylenically unsaturated monocarboxylic acid, its ester, ethylenically unsaturated dicarboxylic acid, its mono or diester, and its anhydride. Among these, ethylenically unsaturated dicarboxylic acid Anhydrides are preferred. Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, and fumaric acid monomethyl ester. Acid is preferred.

  The addition amount or graft amount (degree of modification) of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer is 0.01 to 15% by weight, preferably 0.02 to 10% by weight, based on the olefin polymer. It is. The addition reaction and grafting reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be obtained, for example, by radical polymerization in the presence of a solvent (such as xylene) or a catalyst (such as a peroxide). The melt flow rate (MFR) measured at 190 ° C. under a load of 2160 g of the carboxylic acid-modified polyolefin thus obtained is preferably 0.2 to 30 g / 10 minutes, more preferably 0.5 to 10 g. / 10 minutes. These adhesive resins may be used alone or in combination of two or more.

By subjecting the coextruded multilayer structure or co-injection multilayer structure thus obtained to secondary processing, various molded articles (films, sheets, tubes, bottles, etc.) can be obtained. Examples include the following.
(1) A multilayer structure (sheet or film, etc.) is stretched uniaxially or biaxially, and a multilayer co-stretched sheet or film by heat treatment as required (2) A multilayer structure (sheet or film, etc.) is rolled Multi-layer rolled sheet or film by (3) Multi-layer structure (sheet or film, etc.) Multi-layer tray cup-shaped container by thermoforming such as vacuum forming, pressure forming, vacuum-pressure forming, etc. (4) Multi-layer structure (pipe) Etc.) bottles by stretch blow molding, etc., cup-like containers (5) bottle-like containers by biaxial stretch blow molding from multilayer structures (parison etc.)

  There is no restriction | limiting in particular in such a secondary processing method, The well-known secondary processing methods other than the above can also be employ | adopted. The coextruded multilayer structure or co-injection multilayer structure thus obtained is suitably used as a material for various food containers, such as packaging films, deep-drawn containers, cup-shaped containers, bottles, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this Example. Hereinafter, “%” and “parts” are based on weight unless otherwise specified.

(1) Quantification of fluorescent brightening agent 1.0 g of dried EVOH pellets was dissolved in a 1-propanol / water mixture (weight ratio: 1-propanol / water = 55/45) to make a total amount of 500 mL. The obtained EVOH solution was quantitatively analyzed by measuring fluorescence intensity at an excitation wavelength of 360 nm using a fluorometer RF-5300PC manufactured by Shimadzu Corporation. For the determination, a calibration curve prepared with a fluorescent brightener sample was used. When the fluorescence intensity was strong and self-quenching occurred, the adjusted EVOH solution was appropriately diluted with a 1-propanol / water mixture and measured.

(2) Quantitative determination of metal salt 5 mL of nitric acid was added to 0.5 g of EVOH resin composition powder pulverized by freeze pulverization, and wet-decomposed with Speedwave MWS-2 manufactured by BERGHOF. The liquid after wet decomposition was diluted with ion-exchanged water to make the total liquid volume 50 mL. Each element was quantitatively analyzed for the diluted solution using ICP emission spectrophotometer Optima 4300 DV manufactured by PerkinElmer Japan. From the amount of each metal element thus obtained, the amount of metal element was obtained in terms of metal element. In the determination, a calibration curve prepared using a commercially available metal element standard solution was used.

(3) Measurement of extinction coefficient ε 1.0 g of dried EVOH pellets were dissolved in 24 g of dimethyl sulfoxide to prepare a 4.0% EVOH solution. The obtained EVOH solution was put in a quartz cell having an optical path length of 1.0 cm, and the absorbance at 400 nm was measured with a spectrophotometer UV-2450 manufactured by Shimadzu Corporation. From the analysis result, the extinction coefficient ε was calculated according to the above-described equation (1). When the absorbance exceeded 1.0, the adjusted EVOH solution was appropriately diluted with dimethyl sulfoxide, and then the absorbance was measured.

Example 1
[Production of hydrous pellets]
EVOH resin (5.0 kg) having an ethylene content of 26 mol% and a saponification degree of 99.8 mol% was dissolved in a water / methanol = 48/52 (weight ratio) mixture at 80 ° C. for 12 hours with stirring to give 37 wt. % EVOH solution was obtained. Next, the stirring was stopped and the temperature of the dissolution tank was lowered to 65 ° C. and left for 5 hours to degas the EVOH water / methanol solution. And it extrudes from the metal plate which has a circular opening part with a diameter of 3.5 mm during mixing of water / methanol = 9/1 (weight ratio) at 5 ° C., precipitates in a strand shape, and is cut to have a diameter of about 3 A pellet having a length of about 0.5 mm and a length of about 3.5 mm was obtained. The moisture content of the obtained EVOH pellets was 60% by weight.

[Purification of hydrous pellets]
The operation of adding 80 L of pure water to 8.1 kg of the thus obtained hydrous EVOH pellets, washing with stirring at 25 ° C. for 2 hours, and then removing the liquid was repeated twice. Next, an operation of washing with 1 g / L aqueous acetic acid solution while stirring at 25 ° C. for 2 hours and then removing the liquid was repeated twice. Furthermore, the operation of washing the water-containing pellets with 100 L of ion-exchanged water while stirring at 25 ° C. for 2 hours and then draining was repeated 6 times.

[Addition of metal salt and optical brightener]
Next, 30 L of an aqueous solution containing 0.1 mmol / L of zinc acetate and 0.5 mg / L of disodium salt of fluorescent whitening agent 4,4-bis (styryl 2-disulfonate) biphenyl (hereinafter referred to as DSBP) Was charged with 3.0 kg of the above hydrous EVOH pellets, and immersed and stirred at 25 ° C. for 5 hours. The treated water-containing pellets were dried at 80 ° C. for 3 hours and then at 120 ° C. for 24 hours to obtain dry EVOH pellets.

  The obtained EVOH pellets were melt-kneaded with a twin screw extruder to obtain EVOH pellets having a diameter of about 3 mm and a length of about 3 mm. The melt kneading conditions are shown below.

Specifications of twin screw extruder (manufactured by Toyo Seiki Seisakusho) Model: Twin screw extruder L / D: 25
Diameter: 26mmφ
Screw: Fully meshed in the same direction Number of die holes: 2 holes (3mmφ)
Kneading conditions Rotation speed: 150rpm
Extrusion temperature: C1 / C2 / C3 / C4 / C5 / Die
= 180/200/220/240/240/240 ° C.
Discharge rate: 2.3 kg / hr

  The content of zinc acetate in the obtained EVOH pellets was 2.1 μmol / g in terms of zinc element. The content of the optical brightener DSBP was 1.5 μmol / g. In addition, the extinction coefficient ε of the EVOH pellet was 0.07. In addition, the MFR of the EVOH pellet is 5.5 g / 10 min. (Converted to 190 ° C., under a load of 2160 g).

  Subsequently, the obtained EVOH pellets were subjected to a single-layer film formation test and a white film application test described below to evaluate color resistance and appearance characteristics.

[Single layer film formation test]
Using EVOH pellets, 20 mm extruder D2020 (D (mm) = 20, L / D = 20, compression ratio = 2.0, screw: full flight) manufactured by Toyo Seiki Seisakusho Co., Ltd. A single layer film was obtained under the conditions.
Extrusion temperature: C1 / C2 / C3 / Die = 175/220/220/220 ° C.
Screw rotation speed: 40rpm
Discharge rate: 1.2 kg / hr
Take-up roll temperature: 80 ° C
Take-up roll speed: 2.0 m / min.
Film thickness: 30 μm

[Evaluation of coloring resistance of single layer film]
The single-layer film produced by the above method was wound around a paper tube, and the degree of coloring of the film end face was determined with the naked eye as follows.
Judgment: Criteria A: No coloring B: Slightly yellowing.
C: Yellowish.
D: Remarkably yellowed

[Appearance evaluation of single-layer film]
The fish eyes and streaks of the single-layer film produced by the above method were visually confirmed, and the appearance of the film was determined as follows.
A: The appearance is beautiful and there is almost no fish eye or streak.
B: There is no problem in appearance, but fish eyes and streaks are slightly noticeable.
C: There are many fish eyes and streaks, and there is a problem in appearance.
D: Fish eyes and streaks are remarkable, and the transparency of the film is also difficult.

  The EVOH resin composition film obtained was not colored, and the coloration resistance evaluation result of the single-layer film was A. Moreover, the external appearance evaluation result of the single layer film was A determination.

[Application test to white film]
The above EVOH pellets were added to and mixed with a mixed solution of water / 1-propanol (weight ratio: water / 1-propanol = 45/55), dissolved by heating at 70 ° C., and the concentration of the EVOH resin composition was 10%. Solution was obtained. This solution was coated on a white polyethylene terephthalate film (Merinex, Teijin DuPont Films, 50 μm) and dried at 110 ° C. for 5 minutes to obtain a multilayer film (EVOH layer thickness 3 μm).

[Appearance evaluation of white film]
The appearance of the white film produced by the above method was determined with the naked eye as follows.
Judgment: Criteria A: It is excellent in whiteness and glossiness than a base film, and is beautiful.
B: There are whiteness and glossiness equivalent to a base film.
C: Yellowing is more conspicuous than the base film.

  The appearance evaluation result of the white film obtained in this test was B.

Example 2
A purified hydrous EVOH pellet (3.0 kg) prepared in the same manner as in Example 1 was placed in 30 L of an aqueous solution containing 5.3 mmol / L sodium acetate and 10 mmol / L acetic acid, immersed at 25 ° C. for 5 hours, Stirring was performed. The treated water-containing pellets were dried at 80 ° C. for 3 hours and then at 120 ° C. for 24 hours to obtain dry EVOH pellets.

  100 parts of the obtained EVOH pellets were mixed with 0.010 part of a fluorescent brightener 4,4′-bis (benzoxazol-2-yl) stilbene (hereinafter referred to as BBOS), and the same procedure as in Example 1 was performed. The mixture was melt-kneaded with a twin screw extruder to produce pellets. The content of sodium acetate in the obtained EVOH pellets was 6.2 μmol / g in terms of sodium element, and the content of BBOS was 0.24 μmol / g. The EVOH pellet has an extinction coefficient ε of 0.18 and an MFR of 6.3 g / 10 min. (Converted to 190 ° C., under a load of 2160 g).

  When the single layer film formation test and evaluation were performed according to the method described in Example 1, the color resistance evaluation result of the single layer film of the EVOH resin composition was B, and the appearance evaluation result of the single layer film was A. It was a judgment. Moreover, the external appearance evaluation result of the white film was A determination.

Example 3
Except for adding 0.025 part of the optical brightener as 2,5-bis (5-t-butyl-2-benzoxazolyl) thiophene (hereinafter referred to as BBOT) to 100 parts of the EVOH resin composition. Were produced in the same manner as in Example 2 and evaluated. The content of sodium acetate in the obtained EVOH pellets was 6.3 μmol / g in terms of sodium element, and the content of the optical brightener BBOT was 0.58 μmol / g. Moreover, the extinction coefficient ε of the EVOH pellet is 0.13, and the MFR is 6.5 g / 10 min. (Converted to 190 ° C., under a load of 2160 g). Moreover, the coloring resistance evaluation result of the single layer film of this EVOH resin composition was B determination, and the external appearance evaluation result of the single layer film was A determination. Moreover, the external appearance evaluation result of the white film was A determination.

Example 4
EVOH pellets were produced and evaluated in the same manner as in Example 3 except that the amount of BBOT added was 0.0050 parts with respect to 100 parts of the EVOH resin composition. The content of sodium acetate in the obtained EVOH pellets was 6.2 μmol / g in terms of sodium element, and the content of the optical brightener BBOT was 0.12 μmol / g. Moreover, the extinction coefficient ε of the EVOH pellet is 0.02, and the MFR is 6.6 g / 10 min. (Converted to 190 ° C., under a load of 2160 g). Moreover, the coloring resistance evaluation result of the single layer film of this EVOH resin composition was A determination, and the external appearance evaluation result of the single layer film was A determination. Moreover, the external appearance evaluation result of the white film was A determination.

Comparative Example 1
When immersing the hydrous EVOH pellets in the aqueous solution, EVOH pellets were produced and evaluated in the same manner as in Example 1 except that DSBP was not added. The content of zinc acetate in the obtained EVOH pellets was 1.8 μmol / g in terms of zinc element. The extinction coefficient ε is 0.06, and the MFR is 5.5 g / 10 min. (Converted to 190 ° C., under a load of 2160 g). Moreover, the coloring resistance evaluation result of the single layer film was D determination, and the external appearance evaluation result was B determination. The appearance evaluation result of the white film was C determination.

Comparative Example 2
When immersing the hydrous EVOH pellets in the aqueous solution, EVOH pellets were produced and evaluated in the same manner as in Example 2 except that BBOS was not added. The content of sodium acetate in the obtained EVOH pellets was 6.4 μmol / g in terms of sodium element. The extinction coefficient ε is 0.01, and the MFR is 6.5 g / 10 min. (Converted to 190 ° C., under a load of 2160 g). Moreover, the coloring resistance evaluation result of the single layer film was C determination, and the appearance evaluation result was B determination. The appearance evaluation result of the white film was B determination.

Comparative Example 3
EVOH pellets were prepared and evaluated in the same manner as in Example 4 except that the immersion treatment in an aqueous solution containing sodium acetate and acetic acid was not performed. The content of the optical brightener BBOT in the obtained EVOH pellet was 0.12 μmol / g, and no sodium element was detected in EVOH. The extinction coefficient ε is 0.08, and the MFR is 3.8 g / 10 min. (Converted to 190 ° C., under a load of 2160 g). Moreover, the coloring-resistant evaluation result of a single layer film was D determination, and the external appearance evaluation result was D determination. The appearance evaluation result of the white film was C determination.

Example 5
[Production of hydrous pellets]
EVOH resin (5.0 kg) having an ethylene content of 32 mol% and a saponification degree of 99.7 mol% was dissolved in a mixture of water / methanol = 35/65 (weight ratio) at 80 ° C. for 12 hours with stirring, and was 35 wt%. Of EVOH was obtained. Subsequently, 0.25 g of a fluorescent brightening agent BBOT (0.0050 parts with respect to 100 parts of EVOH resin) was added to the EVOH solution, and the mixture was further stirred for 3 hours. Next, the stirring was stopped and the temperature of the dissolution tank was lowered to 65 ° C. and left for 5 hours to degas the EVOH water / methanol solution. And it extrudes in the liquid mixture of water / methanol = 9/1 (weight ratio) at 5 degreeC from the metal plate which has a circular opening part with a diameter of 3.5 mm, precipitates in strand shape, and cuts about diameter. A pellet having a length of 3.5 mm and a length of about 3.5 mm was obtained. The moisture content of the obtained EVOH pellets was 68% by weight.

[Purification of hydrous pellets]
The operation of adding 60 L of pure water to 6.0 kg of the water-containing pellets thus obtained, washing the mixture with stirring at 25 ° C. for 2 hours, and then removing the liquid was repeated twice. Next, an operation of washing with 1 g / L aqueous acetic acid solution while stirring at 25 ° C. for 2 hours and then removing the liquid was repeated twice. Furthermore, the operation of washing the water-containing pellets with 100 L of ion-exchanged water while stirring at 25 ° C. for 2 hours and then draining was repeated 6 times.

[Addition of metal salt]
Next, 2.0 kg of the above water-containing pellets was put into 20 L of an aqueous solution containing 5.3 mmol / L sodium acetate, 10 mmol / L acetic acid, and 1.6 mmol / L boric acid, and immersed at 25 ° C. for 5 hours. And stirring was performed. The treated water-containing pellets were dried at 80 ° C. for 3 hours and then at 120 ° C. for 30 hours with a dryer (oxygen concentration 200 ppm) in a nitrogen atmosphere to obtain EVOH pellets. The MFR of the dried EVOH pellet is 1.7 g / 10 min. The content of the fluorescent brightening agent BBOT was 0.14 μmol / g. The content of sodium acetate in the EVOH pellets was 6.2 μmol / g in terms of sodium element. In addition, the extinction coefficient ε of the EVOH pellet was 0.02.

  A single layer film and a white film were produced and evaluated according to the method described in Example 1 without melt-kneading the obtained EVOH pellets with a twin screw extruder. Both the coloration resistance evaluation result and the appearance evaluation result of the single layer film were A determinations. The appearance evaluation result of the white film was A.

Comparative Example 4
EVOH pellets were prepared in the same manner as in Example 5 except that the amount of the optical brightener BBOT added to the EVOH solution was 13 g (0.26 parts with respect to 100 parts of EVOH resin). Evaluation was performed according to the method described. The content of the optical brightener BBOT in the obtained EVOH pellets was 6.0 μmol / g, and the content of sodium acetate was 6.7 μmol / g in terms of sodium element. The extinction coefficient ε is 0.84, and the MFR is 1.8 g / 10 min. (Under 190 ° C. and 2160 g load). Moreover, the coloring resistance evaluation result of the single layer film was C determination, and the appearance evaluation result was B determination. The appearance evaluation result of the white film was B determination.

Examples 6-10 and Comparative Examples 5-6
Except for changing the composition of the metal salt-containing treatment liquid in which the hydrous EVOH pellets are immersed, as shown in Table 1, EVOH pellets are produced in the same manner as in Example 5, and the method described in Example 1 Evaluation was performed according to Table 2 shows the contents of the fluorescent whitening agent and the metal salt in the EVOH pellets, and Table 3 shows the evaluation results.

Example 11
Using the EVOH pellets obtained in Example 5 and polyethylene terephthalate (PET) “PET9921W” manufactured by VORIDIAN, co-injection molding was continuously performed for 24 hours using a KORTEC / HUSKY co-injection molding machine (four SL160 molds). Then, PET / resin composition / PET 2 types and 3 layers of bottomed parison were molded. At this time, the PET side injection machine temperature is 280 ° C., the resin composition side injection machine temperature is 210 ° C., the hot runner block part where the PET and the resin composition merge is 270 ° C., the injection mold core temperature is 10 ° C., the injection The mold cavity temperature was 10 ° C. Further, the injection speed and the injection amount were adjusted so that the thickness ratio of the PET layer and the EVOH resin composition layer in the container was 95/5. When this parison was visually observed, no coloring or streak was observed.

  Then, using a stretch blow molding machine made by CRUPP CORPLAST MASCHINENBAU (one LB01 type 530 mL), the surface temperature of the bottomed parison (immediately after 24 hours of continuous operation) is heated to 105 ° C., stretch blow molding is performed, A two-kind three-layer co-injection stretch blow molded container was obtained. The thickness constitution of the container was (inner) PET / resin composition / PET (outer) = 140/25/180 (μm). The appearance of the obtained container was visually observed, but no delamination, haze, or irregularities were observed, and the appearance was good.

As is clear from the above evaluation results, in Examples 1 to 10, EVOH resin compositions having excellent appearance characteristics when applied to a single layer film and a white film were obtained. In Example 11, a molded article having excellent appearance characteristics was obtained.

Claims (5)

An ethylene-vinyl alcohol copolymer resin composition containing 0.010 to 5.0 μmol / g of a fluorescent brightening agent and containing 0.10 to 20 μmol / g of at least one metal salt in terms of metal element. The ethylene-vinyl alcohol copolymer resin composition according to claim 1, wherein the optical brightener is a benzoxazoyl fluorescent brightener. The ethylene-vinyl alcohol copolymer resin composition according to claim 1 or 2, wherein the metal salt is a sodium salt, potassium salt, magnesium salt, or calcium salt. The extinction coefficient ε represented by the following formula (1) measured by dissolving an ethylene-vinyl alcohol copolymer resin composition in dimethyl sulfoxide is 0.05 or less. Vinyl alcohol copolymer resin composition.
ε = A / (L × C) (1)
Here, A represents the absorbance of light at 400 nm measured with an absorptiometer, L represents the optical path length (unit: cm), and C represents the concentration (unit: wt%) of the ethylene-vinyl alcohol copolymer resin composition. . The molded article formed by shape | molding the ethylene-vinyl alcohol copolymer resin composition of Claims 1-4.