Pellet, method for producing same, and molded article using same

Abstract

These pellets contain EVOH and satisfy formulas (1) to (3) when subjected to an IR spectrum analysis where, in a range from 1120 cm-1 to 1150 cm-1, a surface and a cut surface of each of the pellets are subjected to measurement at 5°C interval in the temperature range from 30°C to 200°C. Such pellets allow stable melt molding, and suppress the occurrence of die buildup during melt molding. Therefore, the pellets are suitably used for producing a molded article such as a multilayer structure body.　Formula (1): 40 ≤ Tcmin ≤ 100; Formula (2): 10 ≤ Tcmin-Tsmin ≤ 70; Formula (3): -15 < Tcmax − Tsmax < 15, where: Tcmin (°C) is the lowest temperature at which the IR spectrum of the pellet cut surface has a maximum point; Tsmin (°C) is the lowest temperature at which the IR spectrum of the pellet surface has a maximum point; Tcmax (°C) is the maximum temperature at which the IR spectrum of the pellet cut surface has a maximum point, and Tsmax (°C) is the highest temperature at which the IR spectrum of the pellet surface has a maximum point.

Description

Pellets, their manufacturing method and molded products using them

[0001] The present invention relates to pellets containing an ethylene-vinyl alcohol copolymer, a method for producing the same, and molded articles using the same.

[0002] Ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH") is excellent in gas barrier properties, transparency, oil resistance, antistatic properties, mechanical strength, etc., and is widely used as a material for molded articles such as films, sheets, and containers. Molded articles of EVOH are usually molded by melt molding. Therefore, EVOH is required to have stability during melt molding and excellent appearance properties (no discoloration such as yellowing occurs, and transparent molded articles can be obtained), etc.

[0003] In order to improve the various properties required of EVOH, particularly appearance properties, various EVOH compositions containing acids such as carboxylic acids and phosphoric acids, and metal salts such as alkali metal salts and alkaline earth metal salts in appropriate contents have been proposed (Patent Document 1). These EVOH compositions are said to improve appearance properties and stability during melt molding, and to produce molded articles with excellent appearance.

[0004] Japanese Patent Application Laid-Open No. 2001-146539

[0005] However, the melt stability of the pellets described in Patent Document 1 during melt molding is still insufficient.

[0006] Furthermore, in recent years, with the diversification of layer configurations, there has been an increasing trend to produce multilayer structures by co-extruding an EVOH layer as the outermost layer, with the aim of obtaining a synergistic effect of improving barrier properties by laminating with an inorganic vapor-deposited layer. When EVOH is co-extruded as the outermost layer of a multilayer structure or when EVOH is extruded as a single-layer film, die buildup (i.e., deposits on the outer surface of the die lip) on the outer surface of the discharge port of the molten resin composition can easily cause bumps, streaks, and the like to appear on the film due to die buildup. Applying inorganic vapor deposition to a film with bumps, streaks, and the like is likely to cause defects and reduce the adhesion of the inorganic vapor-deposited layer, which is undesirable. It has been found that the EVOH composition described in Patent Document 1 is insufficient in terms of die buildup and leaves room for improvement.

[0007] The present invention has been made in light of the above circumstances, and provides pellets that can be stably melt-molded and that suppress the occurrence of die build-up during melt-molding, and molded articles such as multilayer structures using the pellets.

[0008] The present inventors have conducted extensive research to solve the above problems and have completed the present invention, which relates to the following [1] to

[15] .

[0009] [1] A pellet containing EVOH, the surface and cut surface of the pellet are measured at 5 ° C. intervals from 30 ° C. to 200 ° C., and the 1120 cm －１ ~1150cm －１ A pellet that satisfies formulas (1) to (3) in the IR spectrum at each temperature in the range: 40≦Tcmin≦100 (1) 10≦Tcmin−Tsmin≦70 (2) −15<Tcmax−Tsmax<15 (3) where, Tcmin (°C) is the lowest temperature at which the IR spectrum of the cut surface of the pellet has a maximum, Tsmin (°C) is the lowest temperature at which the IR spectrum of the pellet surface has a maximum, Tcmax (°C) is the highest temperature at which the IR spectrum of the pellet cut surface has a maximum, and Tsmax (°C) is the highest temperature at which the IR spectrum of the pellet surface has a maximum.

[0010] [2] The pellet according to [1], which satisfies formula (4): 0.95≦(Tsmax−Tsmin) / (Tcmax−Tcmin)<2.5 (4) [3] The pellet according to [1] or [2], which satisfies formula (5): 40≦Tcmax−Tcmin<130 (5) [4] The pellet according to any one of [1] to [3], wherein the EVOH has an ethylene unit content of 20 to 60 mol%. [5] The pellet according to any one of [1] to [4], wherein the EVOH has a degree of saponification of 99 mol% or more. [6] The pellet according to any one of [1] to [5], wherein the ethylene-vinyl alcohol copolymer comprises an ethylene-vinyl alcohol copolymer (A1) having an ethylene unit content of 20 mol% to 50 mol% and an ethylene-vinyl alcohol copolymer (A2) having an ethylene unit content of 30 mol% to 60 mol%, wherein the difference in ethylene unit content between the ethylene-vinyl alcohol copolymer (A2) and the ethylene-vinyl alcohol copolymer (A1) (A2-A1) is 4.5 mol% or more, and wherein the mass ratio of the ethylene-vinyl alcohol copolymer (A1) to the ethylene-vinyl alcohol copolymer (A2) (A1 / A2) is 60 / 40 to 95 / 5. [7] The pellet according to any one of [1] to [6], further comprising an antioxidant (B) in an amount of 0.01 mass% to 5 mass%. [8] The pellet according to any one of [1] to [7], further comprising a nonionic surfactant (C) in an amount of 0.1 ppm to 1,000 ppm. [9] A molded article obtained by extrusion molding the pellets according to any one of [1] to [8].

[10] A molded article obtained by injection molding the pellets according to any one of [1] to [8].

[11] A molded article obtained by blow molding the pellets according to any one of [1] to [8].

[12] A multilayer structure obtained by co-extrusion molding the pellets according to any one of [1] to [8] and pellets of another thermoplastic resin.

[13] The multilayer structure according to

[12] , wherein the layer obtained by extrusion molding the pellets is the outermost layer.

[14] A method for producing the pellets according to any one of [1] to [8], wherein the moisture content W ０ EVOH water-containing pellets having a water content of 25 to 50% by mass are introduced into a dryer, and the water content W of the water-containing pellets is １a first drying step (I) for reducing the moisture content W to 5 to 25% by mass; a melt-kneading step (II) for introducing the water-containing pellets obtained in the first drying step (I) into an extruder and melt-kneading the pellets; and a melt-kneading step (II) for cutting the molten resin discharged from the extruder to reduce the moisture content W ２ a cutting step (III) for obtaining water-containing pellets having a water content of 5 to 25% by mass; and drying the water-containing pellets obtained in the cutting step (III) to obtain water-containing pellets having a water content of 5 to 25% by mass. ３ a second drying step (IV) for obtaining the pellets having a moisture content of 0.5% by mass or less, ０ -W １

[15] A method for producing a multilayer structure by co-extrusion molding the pellets according to any one of [1] to [8] and other thermoplastic resin pellets.

[0011] The pellets of the present invention enable stable melt molding and suppress the occurrence of die build-up during melt molding. Therefore, the pellets are suitable for use in producing molded articles such as multilayer structures. The production method of the present invention is suitable for producing such pellets.

[0012] FIG. 1 is a diagram showing IR spectra at each temperature obtained by measuring the cut surface of the pellet of Example 1 at 5° C. intervals from 30° C. to 200° C.

[0013] The pellet of the present invention is a pellet containing EVOH, and the surface and cut surface of the pellet are measured at 5°C intervals from 30°C to 200°C using a 1120cm －１ ~1150cm －１The pellets satisfy the formulas (1) to (3) in the IR spectrum at each temperature in the range. By using such pellets, stable melt molding is possible and the occurrence of die build-up during melt molding is suppressed. 40≦Tcmin≦100 (1) 10≦Tcmin−Tsmin≦70 (2) −15<Tcmax−Tsmax<15 (3) where, Tcmin (°C) is the lowest temperature at which the IR spectrum of the cut surface of the pellet has a maximum, Tsmin (°C) is the lowest temperature at which the IR spectrum of the pellet surface has a maximum, Tcmax (°C) is the highest temperature at which the IR spectrum of the cut surface of the pellet has a maximum, and Tsmax (°C) is the highest temperature at which the IR spectrum of the pellet surface has a maximum.

[0014] The method for producing the pellets is not particularly limited. ０ EVOH water-containing pellets having a water content of 25 to 50% by mass are introduced into a dryer, and the water content W of the water-containing pellets is １ a first drying step (I) for reducing the moisture content W to 5 to 25% by mass; a melt-kneading step (II) for introducing the water-containing pellets obtained in the first drying step (I) into an extruder and melt-kneading the pellets; and a melt-kneading step (II) for cutting the molten resin discharged from the extruder to reduce the moisture content W ２ a cutting step (III) for obtaining water-containing pellets having a water content of 5 to 25% by mass, and drying the water-containing pellets obtained in the cutting step (III) to obtain water-containing pellets having a water content of W ３ a second drying step (IV) for obtaining the pellets with a moisture content of 0.5% by mass or less, and ０ -W １ In the cutting step (III), it is more preferable to adjust the cooling method after cutting (such as the temperature of the cooling water and the length of the line along which the cooling water is transported). By appropriately adjusting not only the moisture content in each step but also the cooling method in the cutting step (III), it becomes easier to produce pellets whose Tcmin (°C), Tsmin (°C), Tcmax (°C), and Tsmax (°C) satisfy the formulas (1) to (3).

[0015] First, the method for producing the EVOH used in the present invention will be described. EVOH is usually obtained by saponifying an ethylene-vinyl ester copolymer. The copolymerization of ethylene and vinyl ester may be any of solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization. Furthermore, it may be either a continuous system or a batch system. An example of the polymerization conditions for solution polymerization is shown below.

[0016] The solvent used is preferably an alcohol having a boiling point of 100°C or less, from the viewpoints of solubility of the ethylene-vinyl ester copolymer and EVOH, ease of handling, and ability to efficiently replace alcohol with water. The boiling point is more preferably 80°C or less, and even more preferably 70°C or less. Examples of alcohols having a boiling point of 100°C or less include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and t-butyl alcohol, with methanol being particularly preferred.

[0017] Examples of initiators that can be used in the polymerization include azonitrile initiators such as 2,2-azobisisobutyronitrile, 2,2-azobis-(2,4-dimethylvaleronitrile), 2,2-azobis-(4-methoxy-2,4-dimethylvaleronitrile), and 2,2-azobis-(2-cyclopropylpropionitrile), and organic peroxide initiators such as isobutyryl peroxide, cumyl peroxy neodecanoate, diisopropyl peroxycarbonate, di-n-propyl peroxydicarbonate, t-butyl peroxy neodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide.

[0018] Examples of vinyl esters include fatty acid vinyl esters such as vinyl acetate, vinyl propionate, and vinyl pivalate, with vinyl acetate being preferred. In addition to ethylene and vinyl esters, monomers copolymerizable therewith, for example, α-olefins such as propylene, butylene, isobutylene, pentene, hexene, α-octene, and α-dodecene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4- Acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene It is also possible to carry out polymerization in the presence of small amounts of alkenes having an ester group such as 1,3-diacetoxy-2-methylenepropane; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid, and their anhydrides, salts, and mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, or salts thereof; vinyl silanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers; vinyl ketones; N-vinylpyrrolidone; vinyl chloride; vinylidene chloride, etc. The content of other monomer units in the EVOH other than ethylene, vinyl ester, and vinyl alcohol is preferably 20 mol % or less, and in some cases, 10 mol % or less, 5 mol % or less, 3 mol % or less, 1 mol % or less, or 0.1 mol % or less is preferred. The EVOH may not contain the other monomer units.

[0019] The polymerization conditions are preferably as follows: (1) Temperature: preferably 20 to 90°C, more preferably 40 to 70°C. (2) Time (average residence time in the case of a continuous polymerization): preferably 2 to 15 hours, more preferably 3 to 11 hours. (3) Conversion rate: preferably 10 to 90%, more preferably 30 to 80%, based on the vinyl ester charged. (4) Resin content in the solution after polymerization: preferably 5 to 85% by mass, more preferably 20 to 70% by mass.

[0020] After polymerization for a predetermined time has reached a predetermined polymerization rate, a polymerization inhibitor is added as necessary, unreacted ethylene gas is evaporated and removed, and then unreacted vinyl ester is purged. For example, a method for purging the unreacted vinyl ester may be employed in which the polymerization solution from which ethylene has been removed is continuously fed at a constant rate from the top of a column packed with Raschig rings, vapor of an organic solvent, preferably an alcohol having a boiling point of 100°C or less, and most preferably methanol, is blown into the bottom of the column, a mixed vapor of the organic solvent and unreacted vinyl ester is distilled from the top of the column, and the copolymer solution from which unreacted vinyl ester has been removed is taken out from the bottom of the column.

[0021] An alkali catalyst is added to the copolymer solution from which the unreacted vinyl ester has been removed, and the vinyl ester component in the copolymer is saponified. The saponification method can be either continuous or batchwise. Examples of alkali catalysts that can be used include sodium hydroxide, potassium hydroxide, and alkali metal alcoholates. Methanol is preferred as the solvent used for saponification. For example, the saponification conditions are as follows: (1) Concentration of ethylene-vinyl ester copolymer in the solution: 10 to 50 mass % (2) Reaction temperature: 30 to 150°C (3) Amount of catalyst used: 0.005 to 0.6 equivalents (per vinyl ester component) (4) Time (average residence time in the case of a continuous method): 10 minutes to 6 hours

[0022] In general, continuous saponification allows for more efficient removal of methyl acetate produced by saponification, resulting in a resin with a higher degree of saponification with a smaller amount of catalyst than batch saponification. Furthermore, continuous saponification requires higher temperatures to prevent EVOH from precipitating. Therefore, continuous saponification preferably uses the following reaction temperature and catalyst amount: Reaction temperature: 70 to 150°C. Catalyst amount used: 0.005 to 0.1 equivalents (per vinyl ester component).

[0023] The saponification degree of the EVOH used in the present invention is preferably 95 mol% or more. A saponification degree of 95 mol% or more further improves the gas barrier properties and thermal stability of the resulting molded article. The saponification degree is more preferably 98 mol% or more, even more preferably 99 mol% or more, and even more preferably 99.5 mol% or more. On the other hand, the saponification degree may be 100 mol% or less, 99.97 mol% or less, or 99.94 mol% or less. Since the saponification degree does not substantially change in any of the first drying step (I), the melt-kneading step (II), the cutting step (III), and the second drying step (IV), the saponification degree of the EVOH may be considered to be the same in the hydrous EVOH pellets introduced in the first drying step (I) and in the pellets after the second drying step (IV).

[0024] The EVOH used in the present invention preferably has an ethylene unit content of 20 to 60 mol%. When the ethylene unit content is 20 mol% or more, the melt moldability of the resulting pellets is further improved. The ethylene unit content is more preferably 24 mol% or more, and even more preferably 28 mol% or more. On the other hand, an ethylene unit content of 60 mol% or less improves the gas barrier properties of the EVOH. The ethylene unit content is more preferably 50 mol% or less, and even more preferably 45 mol% or less. Since the ethylene unit content does not substantially change in any of the first drying step (I), the melt-kneading step (II), the cutting step (III), and the second drying step (IV), the ethylene unit content of the EVOH may be considered to be the same in the hydrous EVOH pellets introduced into the first drying step (I) and in the pellets after the second drying step (IV).

[0025] Furthermore, the EVOH used in the present invention may contain two or more types of EVOH that differ in the degree of saponification, ethylene unit content, etc., and in some cases it may be preferable to contain two or more types of EVOH that differ in the ethylene unit content. When two or more types of EVOH that differ in the ethylene unit content are contained, flexibility, secondary processability, heat stretchability, etc. tend to be improved while maintaining gas barrier properties.

[0026] When two or more EVOHs having different ethylene unit contents are used in combination, it is preferred that the EVOH contained in the pellets contains EVOH (A1) having an ethylene unit content of 20 mol% or more and 50 mol% or less and EVOH (A2) having an ethylene unit content of 30 mol% or more and 60 mol% or less, the difference in ethylene unit content between EVOH (A2) and EVOH (A1) (the value (A2-A1) obtained by subtracting the ethylene unit content of EVOH (A1) from the ethylene unit content of EVOH (A2)) is 4.5 mol% or more, and the mass ratio (A1 / A2) of EVOH (A1) to EVOH (A2) is 60 / 40 or more and 95 / 5 or less.

[0027] The lower limit of the ethylene content of EVOH (A1) is usually 20 mol%, preferably 23 mol%, and more preferably 25 mol%. On the other hand, the upper limit of the ethylene content of EVOH (A1) is usually 50 mol%, and preferably 47 mol%. By setting the ethylene content of EVOH (A1) to the above lower limit or more, the flexibility, secondary processability, heat stretchability, and other effects of the obtained pellets can be more fully exhibited. On the other hand, by setting the ethylene content of EVOH (A1) to the above upper limit or less, the gas barrier properties of the obtained pellets can be further improved.

[0028] The lower limit of the ethylene content of EVOH (A2) is usually 30 mol%, preferably 34 mol%, and more preferably 38 mol%. On the other hand, the upper limit of the ethylene content of EVOH (A2) is usually 60 mol%, preferably 55 mol%, and more preferably 52 mol%. By setting the ethylene content of EVOH (A2) to the above lower limit or more, the flexibility, secondary processability, heat stretchability, and other effects of the obtained pellets can be more fully exhibited. On the other hand, by setting the ethylene content of EVOH (A2) to the above upper limit or less, the gas barrier properties of the obtained pellets can be further improved.

[0029] The lower limit of the difference (A2-A1) in the ethylene unit content between EVOH (A2) and EVOH (A1) is preferably 5 mol%, more preferably 8 mol%, even more preferably 12 mol%, particularly preferably 15 mol%, and most preferably 16 mol%. The upper limit of the difference (A2-A1) is preferably 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%. By making the difference (A2-A1) equal to or greater than the lower limit, the heat stretchability of the resulting pellets can be improved. Conversely, by making the difference (A2-A1) equal to or less than the upper limit, the gas barrier properties of the resulting pellets can be further improved.

[0030] The lower limit of the mass ratio (A1 / A2) of EVOH (A1) to EVOH (A2) is preferably 60 / 40, more preferably 62 / 38, and in some cases, 65 / 35, 68 / 32, 70 / 30, or 85 / 15 is even more preferable. The upper limit of the mass ratio (A1 / A2) is preferably 95 / 5, more preferably 93 / 7, even more preferably 92 / 8, even more preferably 91 / 9, and even more preferably 85 / 15. When the mass ratio is within the above range, the flexibility, heat stretchability, and secondary processability of the resulting pellets are excellent while maintaining gas barrier properties against various gases. For example, by setting the mass ratio (A1 / A2) to the above lower limit or more, the gas barrier properties and oil resistance of the resulting pellets can be further improved. On the other hand, by setting the mass ratio (A1 / A2) to the above upper limit or less, the flexibility, heat stretchability, and secondary processability of the resulting pellets can be improved.

[0031] The lower limit of the difference between the melting points of EVOH (A1) and EVOH (A2) is preferably 12°C, more preferably 14°C, even more preferably 15°C, and particularly preferably 17°C. The upper limit of the melting point difference may be, for example, 100°C, but is preferably 80°C, more preferably 40°C, even more preferably 34°C, and particularly preferably 28°C. By making the melting point difference equal to or greater than the lower limit, the heat stretchability of the resulting pellets can be improved. Conversely, by making the melting point difference equal to or less than the upper limit, the effect of suppressing flow marks during long runs (long-term continuous operation) of the resulting pellets can be improved. It is also preferable that the melting point of EVOH (A1) is higher than that of EVOH (A2).

[0032] The lower limit of the total content of EVOH (A1) and EVOH (A2) in the pellets of the present invention is preferably 80% by mass, more preferably 90% by mass, still more preferably 95% by mass, and in some cases particularly preferably 99.9% by mass.

[0033] The lower limit of the content of EVOH (A2) in the resin component of the pellets of the present invention is preferably 4% by mass, more preferably 6% by mass, and even more preferably 7% by mass. On the other hand, the upper limit of the content of EVOH (A2) is preferably 40% by mass, more preferably 35% by mass, even more preferably 30% by mass, and particularly preferably 15% by mass. By setting the content of EVOH (A2) to the above lower limit or more, the flexibility, heat stretchability, and secondary processability of the obtained pellets can be improved. Conversely, by setting the content of EVOH (A2) to the above upper limit or less, the content of EVOH (A1) can be increased, and the gas barrier property and oil resistance of the obtained pellets can be improved.

[0034] Methods for incorporating two or more types of EVOH include: (i) a method in which each EVOH pellet is separately produced up to a stage prior to being subjected to the first drying step (I) described below, and then dry-blended and subjected to the first drying step (I); and (ii) a method in which each EVOH pellet is separately produced up to the first drying step (I), and then one of the EVOH pellets is fed from a side feeder and melt-kneaded in the melt-kneading step (II).

[0035] The saponification process yields a solution containing EVOH. Hereinafter, the EVOH-containing solution will be referred to simply as the EVOH solution. Hereinafter, the term "EVOH solution" also includes solutions that are not completely homogeneous but have a phase-separated paste-like structure. A post-treatment method for the EVOH solution after the saponification reaction involves supplying a mixed vapor of solvent and water to a tower vessel from the bottom of the vessel and supplying the EVOH solution from a position above the supply position of the mixed vapor. This replaces a portion of the solvent present in the supplied EVOH solution with water, thereby producing a highly concentrated EVOH solution. The EVOH concentration in the EVOH solution supplied to the tower vessel is preferably 15 to 50% by mass, more preferably 25 to 40% by mass. It is also preferable that the ratio of the supply rate of the EVOH solution to the supply rate of the mixed vapor (solution supply rate / steam supply rate) be 100 / 400 to 100 / 8 by mass. Furthermore, it is preferable that the water content in the mixed vapor be 20 to 70% by mass. The solvent used for the mixed vapor is preferably an alcohol having a boiling point of 130° C. or less, and examples of such alcohol include alcohols such as methanol, ethanol, propanol, butanol, etc. Alcohols having a boiling point of 100° C. or less are more preferred, and among these, methanol is preferred because it is easily available, inexpensive, has a low boiling point, and is easy to handle.

[0036] The high-concentration EVOH solution thus obtained typically contains 50 parts by mass or more of an alcohol having a boiling point of 100°C or less per 100 parts by mass of EVOH. The alcohol content is preferably 1,000 parts by mass or less, and more preferably 500 parts by mass or less. By setting the alcohol content within this range, the fluidity of the EVOH solution is ensured and efficient resin production becomes possible. The alcohol used here is preferably methanol. The EVOH solution may also contain water together with the alcohol, and preferably contains 10 to 500 parts by mass of water.

[0037] A suitable method for obtaining hydrous EVOH pellets to be subjected to the first drying step (I) is, for example, a method in which the highly concentrated EVOH aqueous solution obtained as described above is subjected to the following steps (A), (B), and (C) in this order. Specifically, the hydrous EVOH pellets used in the present invention are obtained by the following steps: (A) introducing an EVOH solution containing 50 parts by mass or more of an alcohol having a boiling point of 100° C. or less per 100 parts by mass of EVOH into a vessel, contacting the EVOH with steam in the vessel to remove the alcohol together with the steam, and removing the hydrous EVOH from the vessel; (B) feeding the hydrous EVOH into an extruder, melt-kneading the extruder, and then discharging the copolymer from the extruder; and (C) cutting the hydrous EVOH discharged from the extruder. This method not only efficiently replaces the alcohol in the EVOH solution with water, but also facilitates adjustment of the water content and temperature of the EVOH.

[0038] In step (A), the method for contacting the EVOH solution introduced into a vessel with steam within the vessel is not particularly limited, and may be either a continuous or batch method. The vessel shape is also not particularly limited, but a tower-type vessel is preferred for the continuous method, and a tank-type vessel is preferred for the batch method. Considering production efficiency, the continuous method is industrially preferable. Examples of tower-type vessels include plate towers such as perforated plate towers and bubble cap towers, and packed towers containing ring-type packings.

[0039] It is preferable that steam is supplied from the bottom of a tower vessel and an EVOH solution is supplied from a position above the steam supply position, thereby extracting the solvent (alcohol) present in the supplied EVOH solution together with the steam, and extracting a water-containing EVOH having a water content of 10 to 90% by mass from the vessel. The amount of steam introduced is preferably 0.3 to 30 times, in mass ratio, the amount of the EVOH solution introduced.

[0040] The alcohol vapor and water vapor discharged from the top of the column are condensed in a condenser and recovered as an aqueous alcohol solution, which can be purified and reused as necessary. The EVOH solution comes into direct contact with water vapor in the vessel, gradually reducing the solvent (alcohol) content. During this time, the EVOH remains in a swollen, paste-like state, allowing it to be discharged from the vessel while maintaining its fluidity and without gelation. EVOH dissolves in a methanol / water mixed solvent at atmospheric pressure, for example, at temperatures of approximately 60 to 70°C, but does not dissolve in water alone. However, in the presence of pressurized water vapor at temperatures of, for example, 90°C or higher, EVOH can maintain its fluidity even when it contains essentially only water. The temperature inside the vessel is preferably 100 to 150°C, and the pressure is preferably 0.1 to 0.6 MPa.

[0041] After the EVOH solution is brought into contact with water vapor as described above, the fluid water-containing EVOH is discharged from the vessel. In step (B), the water-containing EVOH discharged from the vessel is fed to an extruder and melt-kneaded, and the copolymer is then discharged from the extruder.

[0042] In step (B), the water-containing EVOH introduced into the extruder has a water content of 10 to 90% by mass. The content of alcohol having a boiling point of 100°C or less in the water-containing EVOH is preferably 10% by mass or less. The water-containing EVOH may also contain, for example, alkali metal salts, which correspond to residues of the catalyst used in the saponification step, in an amount of about 0.1 to 5% by mass, calculated as metal, and may also contain by-product salts, other impurities, and the like.

[0043] The extruder used in step (B) may be a single-screw extruder or a multi-screw extruder, but a twin-screw extruder is preferred. The L / D ratio of the extruder is preferably 8 to 30. The cylinder of the extruder is provided with an inlet for the water-containing EVOH, through which the water-containing EVOH is introduced. The screw disposed inside the cylinder rotates, causing the water-containing EVOH to be melt-kneaded and then discharged from the discharge port at the tip of the cylinder. At this time, it is preferred to provide a dewatering slit in the cylinder to remove moisture.

[0044] The water content of the water-containing EVOH discharged from the extruder is preferably 25 to 50% by mass. When the water content is 25% by mass or more, the melt viscosity of the water-containing EVOH decreases, and the water-containing EVOH tends to be easily discharged. The water content is more preferably 30% by mass or more. On the other hand, when the water content is 50% by mass or less, the melt viscosity of the water-containing EVOH increases, and leakage of the EVOH tends to be suppressed. The water content is more preferably 40% by mass or less.

[0045] Following step (B), in step (C), the hydrous EVOH discharged from the extruder is cut to obtain hydrous EVOH pellets. The method for this is not particularly limited, and examples include a method in which the hydrous EVOH (molten state) discharged from the extruder is directly cut, or a method in which the hydrous EVOH discharged from the extruder is extruded into a coagulation liquid to solidify and then cut. Of these, the method of directly cutting the hydrous EVOH is preferred. Methods for directly cutting the hydrous EVOH discharged from the extruder include hot cutting and underwater cutting. When the hydrous EVOH is extruded into a strand shape and then cut, cylindrical pellets are obtained, while when the hydrous EVOH is directly cut in a molten state, spherical (or nearly spherical) pellets are obtained. The size of the produced hydrous EVOH pellets can be, for example, 1 mm to 10 mm in diameter if spherical (or nearly spherical), or 1 mm to 10 mm in diameter and 1 mm to 10 mm in length if cylindrical. The hydrous EVOH pellets obtained as described above are subjected to the first drying step (I).

[0046] Another method for obtaining the hydrous EVOH pellets used in the present invention is to extrude the high-concentration EVOH aqueous solution from a nozzle into a coagulation liquid in the form of a strand, coagulate it in a water bath, and then cut it. Water is used as the coagulation liquid, but it may contain a small amount of alcohol. The coagulated strand is cut into pellets with a cutter. A strand cutter is preferably used as the cutter. The size of the obtained pellets can be, for example, 1 mm to 10 mm in diameter and 1 mm to 10 mm in length in the case of a cylindrical shape, or 1 mm to 10 mm in diameter in the case of a spherical shape. The hydrous EVOH pellets obtained in this manner can also be subjected to the first drying step (I).

[0047] The hydrous EVOH pellets obtained as described above contain an alkali catalyst, by-product salts such as sodium acetate and potassium acetate, and other impurities, which may be removed by neutralization and washing as necessary. In this case, some catalyst residues such as sodium acetate may remain in the hydrous EVOH pellets.

[0048] In the first drying step (I), the moisture content W obtained as described above is ０ EVOH water-containing pellets having a water content of 25 to 50% by mass are introduced into a dryer, and the water content W of the pellets is １ The EVOH water-containing pellets introduced into the dryer are porous and have a high drying rate, so they can be dried at a low drying temperature in a short time.

[0049] Moisture content W when introduced into the dryer ０ is 25 to 50 mass%. ０ When the moisture content W is 25% by mass or more, the color of the obtained pellets becomes good, and it is preferably 30% by mass or more. ０ When the water content W is less than 25% by mass, the average residence time can be shortened even if the mixture is subjected to the melt-kneading step (II) as is, so there is little point in adopting the first drying step (I). ０ If the moisture content W exceeds 50% by mass, the material may stick together in the dryer and the drying efficiency may decrease. ０is preferably 45 mass % or less.

[0050] The dryer used in the first drying step (I) is not particularly limited as long as it can dry the pellets while maintaining their shape. A hot air dryer or the like can be used. The drying method may be a fluidized drying method using a fluidized dryer or a static drying method using a static dryer, but fluidized drying is preferred to prevent the pellets from sticking together. A combination of these methods may also be used, or a method may be used in which the pellets are first dried by fluidized drying and then dried by static drying.

[0051] The drying temperature is not particularly limited, but drying at 40 to 150°C for 0.1 to 15 hours is preferred. The EVOH hydrous pellets introduced into the dryer can be dried quickly even at low temperatures, thereby suppressing thermal degradation. The drying temperature is more preferably 50°C or higher, and even more preferably 60°C or higher. The drying temperature is more preferably 120°C or lower, even more preferably 100°C or lower, and optimally 90°C or lower. The drying time varies depending on the drying temperature and the target moisture content, but is more preferably 0.2 hours or longer, even more preferably 0.5 hours or longer. It is also more preferably 5 hours or shorter, and even more preferably 3 hours or shorter. Drying may be performed in air or in an inert gas such as nitrogen. When drying in an inert gas, thermal degradation is less likely to occur even if the drying temperature is set higher.

[0052] The moisture content W of the EVOH hydrous pellets obtained by drying in the first drying step (I) １ is 5 to 25% by mass, and the reduction in water content (W ０ -W １ ) is 10 to 45 mass%. １ If the water content W is less than 5% by mass, the resin temperature in the extruder in the melt-kneading step (II) becomes too high, and the water-containing EVOH discharged from the extruder is likely to foam. １ is preferably 7% by mass or more, and more preferably 10% by mass or more. １If the water content W exceeds 25% by mass, the water content in the extruder in the melt-kneading step (II) will be too high, causing EVOH to leak from the dewatering slit or foaming of the discharged EVOH composition. １ is preferably 22% by mass or less, more preferably 18% by mass or less. ０ -W １ When the moisture content (W) is less than 10% by mass, there is little point in providing the first drying step (I). ０ -W １ ) is preferably 15% by mass or more, more preferably 20% by mass or more. ０ -W １ If the moisture content (W) exceeds 45% by mass, it is difficult to dry the pellets in a short time while maintaining their shape. ０ -W １ ) is preferably 35% by mass or less, more preferably 30% by mass or less. １ and the reduction in moisture content (W ０ -W １ ) is within the above range, the moisture content W of the EVOH hydrous pellets to be subjected to the second drying step (IV) is ２ It becomes easier to adjust the value to fall within a predetermined range, and it becomes easier to obtain pellets that satisfy the formulas (1) to (3).

[0053] In the melt-kneading step (II), the water-containing pellets obtained in the first drying step (I) are introduced into an extruder, and an aqueous solution or aqueous dispersion containing additives is added as needed, followed by melt-kneading. The additives may be dissolved in water in the form of an aqueous solution or a dispersion in water. Examples of such an aqueous solution include an aqueous solution containing at least one additive selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts, antioxidants (B), and nonionic surfactants (C).

[0054] The carboxylic acid contained in the aqueous solution is not particularly limited. Examples include acetic acid, lactic acid, oxalic acid, succinic acid, benzoic acid, and citric acid, with carboxylic acids having four or fewer carbon atoms being preferred. Among these, acetic acid is preferred from the standpoints of cost and availability. When the pellets of the present invention contain a carboxylic acid, the content is preferably 10 to 5,000 ppm. The carboxylic acid content is more preferably 30 ppm or more, and even more preferably 50 ppm or more. The carboxylic acid content is more preferably 1,000 ppm or less, and even more preferably 500 ppm or less. The content of components other than EVOH in the pellets of the present invention is preferably 30% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less. In this specification, "ppm" means "ppm by mass."

[0055] Examples of boron compounds contained in the aqueous solution include, but are not limited to, boric acids, boric acid esters, borate salts, and boron hydrides. Specific examples of boric acids include orthoboric acid, metaboric acid, and tetraboric acid. Examples of borate esters include triethyl borate and trimethyl borate. Examples of borates include alkali metal salts, alkaline earth metal salts, and borax of the above-mentioned various boric acids. Among these compounds, orthoboric acid (hereinafter simply referred to as boric acid) is preferred. When the pellets of the present invention contain a boron compound, the content thereof is preferably 10 to 2000 ppm, and more preferably 50 to 1000 ppm, in terms of boron.

[0056] Examples of the phosphate compound contained in the aqueous solution include various acids such as phosphoric acid and phosphorous acid, and salts thereof. The phosphate may be contained in the form of any of primary phosphate, secondary phosphate, and tertiary phosphate, and the cation species is not particularly limited, but alkali metal salts and alkaline earth metal salts are preferred. Among these, it is preferable to add the phosphate compound in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, or dipotassium hydrogen phosphate. When the pellets of the present invention contain a phosphate compound, the content thereof is preferably 1 to 1,000 ppm in terms of phosphate radical.

[0057] Examples of alkali metal salts contained in the aqueous solution include aliphatic carboxylates, aromatic carboxylates, and phosphates. Examples include sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, and the sodium salt of ethylenediaminetetraacetic acid. Of these, sodium acetate, potassium acetate, and sodium phosphate are preferred. When the pellets of the present invention contain an alkali metal salt, the content thereof is preferably 5 to 5,000 ppm, calculated as the alkali metal element, more preferably 20 to 1,000 ppm, and even more preferably 30 to 750 ppm.

[0058] Examples of alkaline earth metal salts contained in the aqueous solution include magnesium salts, calcium salts, barium salts, and beryllium salts, with magnesium salts and calcium salts being particularly preferred. The anion species of the alkaline earth metal salt is not particularly limited, but acetate and phosphate are preferred. When the pellets of the present invention contain an alkaline earth metal salt, the content thereof is preferably 10 to 1,000 ppm, more preferably 20 to 500 ppm, calculated as the metal.

[0059] On the other hand, the dispersion to be added to the hydrous EVOH may be a colloid of inorganic particles such as colloidal silica, colloidal titania, or colloidal zirconia, or a dispersion of inorganic particles having a larger particle size.

[0060] (Antioxidant (B)) The pellets of the present invention may further contain an antioxidant (B) to improve the oxidative degradation of the pellets, etc. When the pellets further contain an antioxidant, it is possible to suppress the occurrence of cracks in a molded product such as a pipe formed from the pellets.

[0061] The antioxidant (B) is a compound having antioxidant properties. The melting point of the antioxidant (B) is not necessarily limited, but is preferably 170°C or lower. When the melting point of the antioxidant (B) is 170°C or lower, it is easily melted in an extruder when producing pellets by melt mixing. This can prevent the antioxidant (B) from localizing in the pellets and causing discoloration of high-concentration portions. The melting point of the antioxidant (B) is preferably 50°C or higher, and more preferably 100°C or higher in some cases. When the melting point of the antioxidant (B) is 50°C or higher, it can prevent the antioxidant from bleeding out onto the surface of the obtained molded product (such as a pipe), resulting in poor appearance.

[0062] The molecular weight of the antioxidant (B) is preferably 300 or more. When the molecular weight of the antioxidant (B) is 300 or more, when a molded article is obtained from the pellets of the present invention, bleeding out of the antioxidant onto the surface, which would result in a poor appearance of the molded article, can be suppressed, and the thermal stability of the pellets is also improved. The molecular weight is more preferably 400 or more, and particularly preferably 500 or more. On the other hand, the upper limit of the molecular weight of the antioxidant (B) is not particularly limited, but from the viewpoint of dispersibility, it is preferably 8000 or less, more preferably 6000 or less, even more preferably 4000 or less, and particularly preferably 2000 or less.

[0063] A compound having a hindered phenol group is preferably used as the antioxidant (B). A compound having a hindered phenol group not only has excellent thermal stability itself but also has the ability to capture oxygen radicals, which are the cause of oxidative degradation, and when blended into pellets as an antioxidant, it has an excellent effect of preventing oxidative degradation.

[0064] As the compound having a hindered phenol group, commercially available compounds can be used, and examples thereof include the following products. (1) "IRGANOX 1010" manufactured by BASF: melting point 110-125°C, molecular weight 1178, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (2) "IRGANOX 1076" manufactured by BASF: melting point 50-55°C, molecular weight 531, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (3) "IRGANOX 1098" manufactured by BASF: melting point 156-161°C, molecular weight 637, N,N'-(hexane-1,6-diyl)bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide] (4) "IRGANOX" manufactured by BASF 245": melting point 76-79°C, molecular weight 587, triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (5) BASF "IRGANOX 259": melting point 104-108°C, molecular weight 639, 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (6) Sumitomo Chemical Co., Ltd. "Sumilizer MDP-s": melting point about 128°C, molecular weight 341, 2,2'-methylene-bis(4-methyl-6-tert-butylphenol) (7) Sumitomo Chemical Co., Ltd. "Sumilizer (8) "Sumilizer GA-80" manufactured by Sumitomo Chemical Co., Ltd.: melting point about 110°C, molecular weight 741, 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane

[0065] A compound having a hindered amine group is also preferably used as the antioxidant (B). When the compound having a hindered amine group is blended into the pellets as the antioxidant (B), it not only prevents thermal degradation of EVOH but also has the effect of capturing aldehydes generated by thermal decomposition of EVOH, thereby reducing the generation of decomposition gases and thereby suppressing the generation of voids or bubbles during molding. Furthermore, by capturing aldehydes, when the pellets of the present invention are used as food packaging containers, the problem of the odor caused by aldehydes impairing the taste of the contents is also alleviated.

[0066] The compound having a hindered amine group is preferably a piperidine derivative, and particularly preferably a 2,2,6,6-tetraalkylpiperidine derivative having a substituent at position 4. The substituent at position 4 may be a carboxyl group, an alkoxy group, or an alkylamino group.

[0067] The N-position of the hindered amine group may be substituted with an alkyl group, but it is preferable to use one having a hydrogen atom bonded thereto, as this provides excellent thermal stability.

[0068] As the compound having a hindered amine group, commercially available products can be used, for example, the following products. (9) BASF "TINUVIN 770": melting point 81-85°C, molecular weight 481, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (10) BASF "TINUVIN 765": liquid compound, molecular weight 509, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (mixture) (11) BASF "TINUVIN 622LD": melting point 55-70°C, molecular weight 3100-4000, dimethyl succinate / 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (12) BASF "CHIMASSORB" (119FL)": melting point 130-140°C, molecular weight 2000 or more, N,N'-bis(3-aminopropyl)ethylenediamine / 2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate. (13) BASF "CHIMASSORB 944LD": melting point 100-135°C, molecular weight 2000-3100, poly[[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl](2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene(2,2,6,6-tetramethyl-4-piperidyl)imino]] (14) BASF "TINUVIN 144": melting point 146-150°C, molecular weight 685, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate (15) BASF "UVINUL 4050H": melting point 157°C, molecular weight 450, N,N'-1,6-hexanediylbis{N-(2,2,6,6-tetramethyl-4-piperidinyl)-formamide} (16) BASF "UVINUL 5050H": melting point 104-112°C, molecular weight approximately 3500, compound having the following structural formula

[0069]

[0070] These compounds having a hindered phenol group or a hindered amine group may be used alone or in combination of two or more kinds.

[0071] The lower limit of the content of the antioxidant (B) in the pellets of the present invention is preferably 0.01% by mass, more preferably 0.1% by mass, and even more preferably 0.3% by mass. The upper limit of the content of the antioxidant (B) is preferably 5% by mass, more preferably 3% by mass, and even more preferably 1% by mass. When the content of the antioxidant (B) is within the above range, the antioxidant (B) is well dispersed, and when a molded article is obtained from the pellets of the present invention, the appearance tends to be excellent.

[0072] (Nonionic surfactant (C)) The pellets of the present invention can contain 0.1 ppm to 1,000 ppm of nonionic surfactant (C). By containing 0.1 ppm or more of nonionic surfactant (C), the resin output during melt molding can be increased and coloration of molded articles obtained from the pellets of the present invention can be suppressed. The content of the nonionic surfactant is preferably 0.5 ppm or more, more preferably 1 ppm or more. On the other hand, a content of 1,000 ppm or less is economically advantageous, and is less likely to cause problems such as insufficient resin supply to the extruder due to resin slippage, resulting in a decrease in the resin output. Furthermore, the residence time of the resin in the extruder is shortened, and the pellets of the present invention and molded articles obtained from the pellets tend to be less prone to yellowing. Furthermore, a content of 1,000 ppm or less tends to improve the interlayer adhesion of laminates obtained from the pellets of the present invention. The content is preferably 400 ppm or less, more preferably 300 ppm or less, and even more preferably 150 ppm or less.

[0073] The nonionic surfactant (C) is not particularly limited, but is preferably at least one selected from the group consisting of ether-type, aminoether-type, ester-type, ester-ether-type, and amide-type surfactants. These nonionic surfactants (C) may be used alone or in combination of two or more.

[0074] (Ether-Type Nonionic Surfactant) As the ether-type nonionic surfactant, polyoxyalkylene alkyl ether, polyoxyalkylene alkenyl ether, and polyoxyethylene styrenated phenyl ether are preferred.

[0075] The polyoxyalkylene alkyl ether and polyoxyalkylene alkenyl ether are preferably those represented by the following formula (i): R—O—(AO) ｎ H...(i)

[0076] In formula (i), R is a linear or branched alkyl group or alkenyl group having 6 to 22 carbon atoms, each A is independently an alkylene group having 2 to 4 carbon atoms, and n represents the degree of condensation of the polyoxyalkylene unit and is 1 to 30.

[0077] In formula (i), the number of carbon atoms in R is preferably 8 to 18, and more preferably 12 or more. The number of carbon atoms in A is preferably 2 or 3. n is preferably 2 to 25, and more preferably 3 to 20, and even more preferably 4 or more.

[0078] Specific examples of polyoxyalkylene alkyl ethers include polyoxyethylene alkyl ethers such as polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene tetradecyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether and polyoxyethylene eicosyl ether; polyoxypropylene alkyl ethers such as polyoxypropylene stearyl ether; and polyoxyethylene polyoxypropylene alkyl ethers.

[0079] Specific examples of polyoxyalkylene alkenyl ethers include polyoxyethylene alkenyl ethers such as polyoxyethylene oleyl ether.

[0080] Specific examples of polyoxyethylene styrenated phenyl ether include polyoxyethylene monostyrenated phenyl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene tristyrenated phenyl ether, etc. The number of ethylene oxide additions in the polyoxyethylene styrenated phenyl ether is preferably 5 to 30 moles.

[0081] (Amino ether type nonionic surfactant) As the amino ether type nonionic surfactant, polyoxyalkylene alkylamine, polyoxyalkylene alkenylamine, etc. are preferred. As the polyoxyalkylene alkylamine, cocoalkylamine-ethylene oxide adduct, polyoxyethylene stearylamine, polyoxyethylene laurylamine, polyoxyethylene polyoxypropylene laurylamine, polyoxyethylene stearylamine, etc. are suitable. As the polyoxyalkylene alkenylamine, polyoxyethylene oleylamine, etc. are suitable. The number of ethylene oxide additions to the polyoxyalkylene alkylamine is preferably 1 to 40 moles.

[0082] (Ester-Type Nonionic Surfactant) Suitable examples of the ester-type nonionic surfactant include polyoxyalkylene alkyl esters, polyoxyalkylene alkenyl esters, sorbitan alkyl esters, sorbitan alkenyl esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene sorbitan alkylene esters, glycerol alkyl esters, glycerol alkenyl esters, polyglycerin alkyl esters, and polyglycerin alkenyl esters.

[0083] The polyoxyalkylene alkyl ester and polyoxyalkylene alkenyl ester are preferably those represented by the following formula (ii): R—COO(AO) ｎ H... (ii)

[0084] In formula (ii), the definitions of R, A, and n are the same as in formula (i) above. In formula (ii), the number of carbon atoms in R is preferably 8 to 18, the number of carbon atoms in A is preferably 2 or 3, and n is preferably 7 to 14. When n is within the above range, both good discharge amount and good appearance can be achieved.

[0085] Specific examples of polyoxyalkylene alkyl esters include polyoxyethylene monolaurate, polyoxyethylene dilaurate, polyoxyethylene monopalmitate, polyoxyethylene monostearate, and polyoxyethylene distearate.

[0086] Specific examples of polyoxyalkylene alkenyl esters include polyoxyethylene oleate and polyethylene glycol dioleate.

[0087] Specific examples of suitable sorbitan alkyl esters include sorbitan monocaprylate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, and sorbitan monolaurate.

[0088] Specific examples of suitable sorbitan alkenyl esters include sorbitan monooleate, sorbitan trioleate, and sorbitan sesquioleate.

[0089] Specific examples of polyoxyethylene sorbitan alkyl esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, and polyoxyethylene sorbitan monolaurate.

[0090] Specific examples of polyoxyethylene sorbitan alkenyl esters include polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate.

[0091] Specific examples of glycerol alkyl esters include glycerol monostearate and glycerol monomyristate.

[0092] Specific examples of glycerol alkenyl esters include glycerol monooleate.

[0093] Specific examples of polyglycerin alkyl esters include diglycerin laurate, tetraglycerin stearate, polyglycerin laurate, and polyglycerin stearate.

[0094] Specific examples of polyglycerol alkenyl esters include polyglycerol oleate.

[0095] (Ester / Ether Type Nonionic Surfactant) Examples of the ester / ether type nonionic surfactant include polyoxyethylene sorbitan alkyl esters and polyoxyethylene sorbitan alkenyl esters.

[0096] (Amide-Type Surfactant) As the amide-type nonionic surfactant, higher fatty acid amides are preferred, and higher fatty acid alkanolamides are more preferred.

[0097] Examples of higher fatty acid alkanolamides include higher fatty acid mono- or dialkanolamides, and specific examples include caproic acid mono- or diethanolamide, caprylic acid mono- or diethanolamide, capric acid mono- or diethanolamide, lauric acid mono- or diethanolamide, palmitic acid mono- or diethanolamide, stearic acid mono- or diethanolamide, oleic acid mono- or diethanolamide, coconut oil fatty acid mono- or diethanolamide, and those in which the ethanolamide constituting these is replaced with propanolamide or butanolamide.

[0098] Examples of higher fatty acid amides other than higher fatty acid alkanolamides include caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, and oleic acid amide.

[0099] The nonionic surfactant (C) is more preferably at least one selected from the group consisting of polyoxyalkylene alkyl ethers, polyoxyalkylene alkenyl ethers, polyoxyethylene styrenated phenyl ethers, polyoxyalkylene alkylamines, polyoxyalkylene alkenylamines, polyoxyalkylene alkyl esters, polyoxyalkylene alkenyl esters, sorbitan alkyl esters, sorbitan alkenyl esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene sorbitan alkenyl esters, glycerol alkyl esters, glycerol alkenyl esters, polyglycerin alkyl esters, polyglycerin alkenyl esters, and higher fatty acid amides.

[0100] In particular, from the viewpoint of obtaining a molded product with reduced coloration, the nonionic surfactant (C) is preferably an ether type or an ester type, and among these, from the viewpoint of coloration, at least one selected from the group consisting of polyoxyalkylene alkyl ethers, polyoxyalkylene alkenyl ethers, polyoxyalkylene alkyl esters, polyoxyalkylene alkenyl esters, glycerol alkyl esters, polyglycerin alkyl esters, and polyglycerin alkenyl esters is more preferred. These may be used alone or in combination.

[0101] The extruder used in the melt-kneading step (II) may be a single-screw extruder or a multi-screw extruder, but a twin-screw extruder is preferred. The L / D ratio of the extruder is preferably 10 to 55, more preferably 20 to 47. The cylinder of the extruder is provided with an inlet for EVOH hydrous pellets, through which the EVOH hydrous pellets are introduced, and then melt-kneaded by the rotation of a screw disposed within the cylinder, and discharged from a discharge port at the tip of the cylinder. The screw configuration within the cylinder is not particularly limited, but it is preferable to provide a full-flight screw and a partial reverse-flight screw to thoroughly knead the molten resin.

[0102] The resin temperature inside the extruder is preferably 120 to 210°C. If the resin temperature is too low, the screw torque may become too large, so the temperature is more preferably 140°C or higher, and even more preferably 150°C or higher. On the other hand, if the resin temperature is too high, the resulting pellets tend to foam, and there is a risk of discoloration or gel formation when melt-kneaded for a long period of time. Therefore, the resin temperature is more preferably 200°C or lower, and even more preferably 190°C or lower.

[0103] The extruder used in the melt-kneading step (II) may be provided with an additive introduction section downstream of the pellet introduction port. From the additive introduction section, an aqueous solution or dispersion containing additives is injected into the molten, water-containing EVOH (molten resin) and melt-kneaded. When the aqueous solution or dispersion is added, the amount added is preferably 1 to 30 parts by mass per 100 parts by mass of the dry mass of EVOH. Addition of less than 1 part by mass may make uniform blending difficult; more preferably, it is 2 parts by mass or more, and even more preferably, it is 5 parts by mass or more. On the other hand, addition of more than 30 parts by mass increases the water content of the water-containing EVOH, making it prone to leaking from the dehydration slit and increasing the energy required for drying. Therefore, the amount added is more preferably 20 parts by mass or less, and even more preferably, it is 15 parts by mass or less.

[0104] In the melt-kneading step (II), it is preferable to discharge liquid water or water vapor from at least one location in the extruder. This can reduce the water content of the water-containing EVOH in the extruder. The method for discharging liquid water or water vapor is not particularly limited, and a dewatering slit or vacuum vent can be used. In the melt-kneading step of the present invention, the water content of the molten resin discharged from the extruder is not particularly low, so a vacuum vent is often unnecessary, and a dewatering slit is preferably used. Either water vapor or liquid water can be discharged from the dewatering slit, but discharging water vapor is preferred from the viewpoint of removing the latent heat of vaporization and removing heat. Furthermore, when an aqueous solution or aqueous dispersion is added in the melt-kneading step (II) of the present invention, it is preferable to discharge liquid water or water vapor from a position downstream of the position where the aqueous solution or aqueous dispersion is added. This can effectively reduce the water content of the discharged molten resin and suppress foaming.

[0105] In the cutting step (III), the molten resin discharged from the extruder is cut to reduce the water content W ２ The resulting hydrous EVOH pellets have a molecular weight of 5 to 25% by mass. The cutting method is not particularly limited, and examples include a method in which the molten hydrous EVOH (molten resin) discharged from the extruder is directly cut, and a method in which the hydrous EVOH discharged from the extruder is extruded into a coagulation liquid in the form of strands, solidified, and then cut. Of these, the method of directly cutting the hydrous EVOH is preferred. Methods for directly cutting the hydrous EVOH discharged from the extruder include a hot-cut method and an underwater cutting method. When the hydrous EVOH is extruded in the form of strands, solidified, and then cut, cylindrical pellets are obtained, while when the hydrous EVOH is directly cut in the molten state, spherical (or nearly spherical) pellets are obtained. The size of the produced hydrous EVOH pellets can be, for example, 1 mm to 10 mm in diameter if they are spherical (or nearly spherical), or 1 mm to 10 mm in diameter and 1 mm to 10 mm in length if they are cylindrical.

[0106] In addition to keeping the moisture content within a predetermined range in each step, adjusting the cooling method after cutting in the cutting step (III) (such as the temperature of the cooling water and the length of the line along which the cooling water is transported) makes it easier to obtain pellets that satisfy the above formulas (1) to (3). The temperature of the cooling water is preferably 0 to 50°C, more preferably 5 to 40°C, and even more preferably 10 to 30°C. The cut hydrous EVOH pellets are appropriately cooled by being transported along the line along with the cooling water. The length of the line is preferably 1 to 20 m, more preferably 2 to 10 m, and even more preferably 3 to 8 m. However, the cooling method is not limited to the above, as long as pellets that satisfy the above formulas (1) to (3) can be obtained.

[0107] The moisture content W of the EVOH water-containing pellets obtained in the cutting step (III) ２ is 5 to 25% by mass. ２ By making the water content W 5% by mass or more, the temperature of the molten resin in the melt-kneading step (II) can be lowered, and therefore, thermal deterioration of the EVOH during melt-kneading can be suppressed. ２ If the moisture content W is 5% by mass or more, it is not necessary to provide a vacuum vent in the extruder to reduce the moisture content, and the equipment can be simplified. ２ By setting the moisture content W to 25% by mass or less, it is possible to prevent EVOH from leaking from the dewatering slit even when the extruder is operated at high speed, thereby improving productivity. In addition, it is possible to prevent foaming of the obtained pellets and also to reduce energy consumption in the subsequent second drying step (IV). Furthermore, it is possible to prevent the moisture content W from leaking from the dewatering slit even when the extruder is operated at high speed, thereby improving productivity. ２ When is in the above range, pellets that satisfy the above formulas (1) to (3) can be easily obtained.

[0108] The EVOH hydrous pellets thus obtained in the cutting step (III) are subjected to the second drying step (IV). The dryer used in the second drying step (IV) is not particularly limited as long as it can dry the pellets while maintaining their shape. A hot air dryer or the like can be used. The drying method may be fluidized drying using a fluidized dryer or static drying using a static dryer, or a combination of these methods may be used. A method in which the pellets are first dried at a relatively low temperature using a fluidized dryer, and then dried at a high temperature using a static dryer is preferably used.

[0109] Since pellets satisfying the above formulas (1) to (3) can be more easily obtained, the drying temperature is preferably 50 to 150°C, and the drying time is preferably 1 hour to 7 days. When both fluidized drying and static drying are employed, the drying temperatures of both methods are included in the above temperature range, and the sum of the drying times of both methods is included in the above drying time. The drying temperature is more preferably 60°C or higher, even more preferably 70°C or higher, and particularly preferably 80°C or higher. The drying temperature is more preferably 140°C or lower, even more preferably 130°C or lower, and particularly preferably 120°C or lower. The drying time is more preferably 2 hours or longer, even more preferably 5 hours or longer. It is also more preferably 5 days or shorter, and even more preferably 3 days or shorter. When both fluidized drying and static drying are employed, the drying temperature of the latter method is preferably 5°C or higher, and even more preferably 10°C or higher, than the drying temperature of the former method. Drying may be performed in air or in an inert gas such as nitrogen. When drying is performed in an inert gas, thermal degradation is unlikely to occur even if the drying temperature is set high.

[0110] The moisture content W of the pellets of the present invention containing EVOH obtained by drying in the second drying step (IV) ３ The water content W is preferably 0.5% by mass or less. ３ When the water content W is 0.5% by mass or less, problems such as foaming do not occur even if the composition is subjected to melt molding without further drying. ３ is more preferably 0.4% by mass or less, and even more preferably 0.3% by mass or less.３ is usually 0.01% by mass or more, and the water content W ３ Lowering it will only increase energy consumption.

[0111] The pellets of the present invention thus obtained are measured on their surfaces and cut surfaces at 5°C intervals from 30°C to 200°C using a 1120cm －１ ~1150cm －１ The IR spectrum at each temperature in the range satisfies the following formulas (1) to (3): 40≦Tcmin≦100 (1) 10≦Tcmin−Tsmin≦70 (2) −15<Tcmax−Tsmax<15 (3) where, Tcmin (°C) is the lowest temperature at which the IR spectrum of the cut surface of the pellet has a maximum, Tsmin (°C) is the lowest temperature at which the IR spectrum of the cut surface of the pellet has a maximum, Tcmax (°C) is the highest temperature at which the IR spectrum of the cut surface of the pellet has a maximum, and Tsmax (°C) is the highest temperature at which the IR spectrum of the cut surface of the pellet has a maximum.

[0112] The IR spectrum of the pellet is measured as follows. In the present invention, the IR spectrum of each of the surface and cut surface of the pellet is measured by the ATR method (attenuated total reflection method). The wave number range for measurement is 1120 cm －１ ~1150cm －１ The range is set to include the above. Measurements are performed at 5°C intervals from 30°C to 200°C, and an IR spectrum is obtained at each temperature. Specific measurement conditions for the IR spectrum of the pellet and a method for determining whether or not there is a maximum point are those described in the Examples.

[0113] 1 shows the IR spectra at each temperature obtained by measuring the cut surface of a pellet of Example 1 described later from 30°C to 200°C at 5°C intervals. In the present invention, the IR spectrum of the cut surface of the pellet measured at each temperature has a peak at 1120 cm －１ ~1150cm －１The lowest temperature having a maximum point in the range is defined as Tcmin (°C), and the highest temperature is defined as Tcmax (°C). In FIG. 1, IR spectrum 1 is one measured at 65°C or less. Thus, the IR spectrum measured at 65°C or less has a wavenumber of 1120 cm －１ ~1150cm －１ IR spectrum 2 is an IR spectrum at 70 °C and has no maximum at 1120 cm －１ ~1150cm －１ In other words, 70°C is the lowest temperature Tcmin at which the IR spectrum of the pellet cut surface of Example 1 has a maximum. The IR spectrum of the pellet cut surface at 75 to 165°C also has a maximum at 1120 cm －１ ~1150cm －１ IR spectrum 3 is one of those measured at 170°C or higher. Thus, the IR spectrum of the cut surface of the pellet measured at 170°C or higher has a maximum point in the range of 1120cm －１ ~1150cm －１ That is, at 165°C, the IR spectrum of the cut surface of the pellet of Example 1 has a peak at 1120 cm －１ ~1150cm －１ is the maximum temperature Tcmax having a maximum point in the range.

[0114] The IR spectrum of the pellet surface at each temperature was measured at 1120 cm －１ ~1150cm －１ The minimum temperature Tsmin (°C) and maximum temperature Tsmax (°C) having a maximum point in the range are also determined in the same manner as the minimum temperatures Tcmin (°C) and Tcmax (°C) in the IR spectrum of the pellet cut surface.

[0115] In the present invention, the IR spectrum of the cut surface of the pellet at each temperature is 1120 cm －１ ~1150cm －１The minimum temperature Tcmin having a maximum point in the range must satisfy the above formula (1). When Tcmin is 40 to 100°C, the melting initiation temperature inside the pellet increases and the distribution of the melting temperature throughout the pellet becomes smaller, thereby reducing uneven melting in the extruder and stabilizing fluidity. The minimum temperature Tcmin is preferably 48°C or higher, more preferably 55°C or higher, and even more preferably 65°C or higher, and may be 75°C or higher, 85°C or higher, or 90°C or higher. The minimum temperature Tcmin may be 90°C or lower.

[0116] In the present invention, the lowest temperature Tcmin at which the IR spectrum of the cut surface of the pellet at each temperature has a maximum point and the lowest temperature Tsmin at which the IR spectrum of the pellet surface at each temperature has a maximum point must satisfy the above formula (2). When the difference (Tcmin - Tsmin) is 10 to 70°C, die buildup is less likely to occur when the resulting pellets are molded. The difference (Tcmin - Tsmin) is preferably 15°C or higher, more preferably 25°C or higher, and even more preferably 35°C or higher, and may be 45°C or higher, 50°C or higher, or 55°C or higher. On the other hand, the difference (Tcmin - Tsmin) is preferably 65°C or lower, and may be 55°C or lower.

[0117] In the present invention, the difference (Tcmax - Tsmax) between the highest temperature Tcmax at which the IR spectrum of the cut surface of the pellet at each temperature has a maximum and the highest temperature Tsmax at which the IR spectrum of the pellet surface at each temperature has a maximum must satisfy the above formula (3). When the difference (Tcmax - Tsmax) is more than -15°C and less than 15°C, die buildup is less likely to occur when the resulting pellets are molded. The difference (Tcmax - Tsmax) is preferably -10°C or more, more preferably -5°C or more, and even more preferably -1°C or more. On the other hand, the difference (Tcmax - Tsmax) is preferably 10°C or less, more preferably 7°C or less, even more preferably 4.5°C or less, and particularly preferably 3.5°C or less.

[0118] The present inventors have conducted extensive research to improve the melt stability of EVOH-containing pellets, and have surprisingly found that pellets satisfying the above formulas (1) to (3) have excellent melt stability. The reason for this is unclear, but the following is thought to be the case. －１ ~1150cm －１ The peak with a maximum at 1000 kJ / s is known as the crystalline band of EVOH and serves as an index of crystallinity. It has been known that the crystallinity at low temperatures differs between the interior and exterior of EVOH-containing pellets. However, the crystalline state upon heating and melting and its effect on melt-formability were unknown. Therefore, the inventors measured IR spectra of the cut surface and surface of the pellets at 30 to 200°C to confirm the relationship between the crystalline state of the interior and exterior of the pellets and melt-formability. As a result, it was found that the crystalline state of the interior and exterior of the pellets upon heating and melting differs depending on the pellet manufacturing method. The inventors discovered that pellets manufactured by a predetermined method and satisfying the above formulas (1) to (3) have a narrow melting temperature distribution and are less likely to experience uneven melting inside the extruder, resulting in stable fluidity. Furthermore, the exterior of the pellets is relatively less likely to melt, shortening the contact time with the extruder wall, thereby suppressing die buildup and enabling the production of molded products with good appearance and high barrier properties.

[0119] In the present invention, it is preferable that the minimum temperature Tcmin and maximum temperature Tcmax at which the IR spectrum of the cut surface of the pellet at each temperature has a maximum, and the minimum temperature Tsmin and maximum temperature Tsmax at which the IR spectrum of the pellet surface at each temperature has a maximum, satisfy the following formula (4). This further improves the appearance of molded articles obtained using the pellets. "(Tsmax-Tsmin) / (Tcmax-Tcmin)" is more preferably 1 or more, and even more preferably 1.05 or more. On the other hand, "(Tsmax-Tsmin) / (Tcmax-Tcmin)" is more preferably 2.3 or less. 0.95≦(Tsmax-Tsmin) / (Tcmax-Tcmin)<2.5 (4)

[0120] In the present invention, it is preferable that the minimum temperature Tcmin and maximum temperature Tcmax at which the IR spectrum of the cut surface of the pellet has a maximum point satisfy the following formula (5). This makes it even more difficult for die buildup to occur when the resulting pellets are melt-molded. The difference (Tcmax - Tcmin) is more preferably 50°C or higher, and even more preferably 55°C or higher. On the other hand, the difference (Tcmax - Tcmin) is more preferably 120°C or lower, even more preferably 115°C or lower, even more preferably 100°C or lower, particularly preferably 90°C or lower, and most preferably 80°C or lower. 40≦Tcmax - Tcmin<130 (5)

[0121] The pellet size may be, for example, a diameter of 0.8 mm to 9.8 mm if spherical (or approximately spherical), or a diameter of 0.8 mm to 9.8 mm and a length of 0.8 mm to 9.8 mm if cylindrical.

[0122] From the viewpoint of improving melt moldability, the melt flow rate (MFR) (210°C, under a load of 2160 g) of the pellets measured in accordance with the method described in JIS K7210 (2014) is preferably 0.1 to 30 g / 10 min, more preferably 0.3 to 25 g / 10 min, and even more preferably 0.5 to 20 g / 10 min.

[0123] A preferred embodiment of the present invention is a molded article obtained by melt-molding the pellets of the present invention. Examples of such molded articles include films, sheets, tubes, bags, bottles, packaging materials, and containers. When the pellets of the present invention are used, stable melt-molding is possible, and die buildup during melt-molding is suppressed. The resulting molded article has a good appearance and excellent gas barrier properties. The molded article may have a portion formed from the pellets of the present invention. That is, the molded article may be a molded article consisting solely of the pellets of the present invention, or a molded article consisting solely of the pellets of the present invention and other portions. Examples of methods for melt-molding the pellets include extrusion molding, cast molding, inflation extrusion molding, blow molding, melt spinning, injection molding, injection blow molding, and co-extrusion blow molding. Of these, extrusion molding, injection molding, and blow molding are preferred. A molded article obtained by molding the pellets by these methods is a more preferred embodiment of the present invention. The melt-molding temperature varies depending on the melting point of the pellets, but is preferably approximately 150 to 270°C. These molded articles can also be crushed and remolded for reuse. Furthermore, films, sheets, etc. can be uniaxially or biaxially stretched.

[0124] The molded article is preferably a multilayer structure having a barrier layer made of the pellets of the present invention and a layer made of a thermoplastic resin other than EVOH. The multilayer structure has excellent gas barrier properties. The multilayer structure may further have a layer made of a component other than resin, such as a layer made of paper, a metal layer, or an inorganic vapor deposition layer. Examples of the multilayer structure include a multilayer film, a multilayer sheet, a multilayer pipe, and a multilayer fiber, with a multilayer film being preferred.

[0125] The layer structure of the multilayer structure is not particularly limited, and examples thereof include structures such as T / E / T, E / Ad / T, T / Ad / E / Ad / T, E / Ad / T / Ad / E, E / Ad / T / Ad / E, E / Ad / T / Ad / E / Ad / T / Ad / E / Ad / E / Ad / E / Ad / E. Each of these layers may be a single layer or multiple layers.

[0126] From the viewpoint of improving the gas barrier property, the content of components other than EVOH in the barrier layer is preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

[0127] Examples of thermoplastic resins other than EVOH include linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene, polypentene, and other olefin homopolymers or copolymers thereof; polyethylene terephthalate, and other polyesters; polyester elastomers; polyamides such as nylon-6 and nylon-66; polystyrene; polyvinyl chloride, polyvinylidene chloride, acrylic resins, vinyl ester resins, polyurethane elastomers, polycarbonate, chlorinated polyethylene, chlorinated polypropylene, etc. Among these, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene, and polyester are preferably used.

[0128] The adhesive resin is not particularly limited as long as it has adhesive properties with the barrier layer and other thermoplastic resin layers, but an adhesive resin containing a carboxylic acid-modified polyolefin is preferred. The carboxylic acid-modified polyolefin is preferably a modified olefin polymer containing a carboxyl group formed by chemically bonding an ethylenically unsaturated carboxylic acid, its ester, or its anhydride to an olefin polymer. Here, the olefin polymer refers to polyolefins such as polyethylene, linear low-density polyethylene, polypropylene, and polybutene, as well as copolymers of olefins with other monomers. Among these, linear low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer are preferred, with linear low-density polyethylene and ethylene-vinyl acetate copolymer being particularly preferred.

[0129] The barrier layer is preferably the outermost layer of the multilayer structure. Conventionally, when EVOH is co-extruded as the outermost layer of a multilayer structure, the EVOH contacts a large area of ​​the die lip, which can lead to die buildup (a deposit on the outer surface of the die lip) on the outer surface of the die lip, resulting in the problem of lumps, streaks, and the like appearing in the film. In contrast, the pellets of the present invention make such die buildup less likely to occur. The outermost layer refers to a layer that is in contact with other layers of the multilayer structure on only one side. When a multilayer structure has an inner and outer surface, the outermost layer may be the layer on the outer surface (outermost layer) or the layer on the inner surface (innermost layer). The multilayer structure is preferably a multilayer film obtained by co-extrusion molding the pellets of the present invention and pellets of another thermoplastic resin. In this case, the outermost layer of the multilayer film is preferably a barrier layer made of the pellets of the present invention. The multilayer structure may also be a vapor-deposited multilayer film obtained by forming an inorganic vapor-deposited layer on the barrier layer of the multilayer film. In this case, an inorganic vapor deposition layer may be formed on the uniaxially or biaxially stretched multilayer film by the method described below. The multilayer structure may also be one in which a layer composed of another component is laminated on a barrier layer. EVOH has a high affinity with inorganic vapor deposition layers, particularly vapor deposition layers of aluminum or aluminum oxide, and therefore tends to provide good interlayer adhesion between the barrier layer and the inorganic vapor deposition layer. Examples of layer configurations in which a barrier layer is the outermost layer include E for the barrier layer, Ad for the layer composed of an adhesive resin, and T for the layer composed of a thermoplastic resin, with direct lamination represented by " / " such as E / Ad / T, E / Ad / T / Ad / E, and E / Ad / T / Ad / E / Ad / T / Ad / E. In the case of a multilayer structure in which a barrier layer is the outermost layer, T is preferably a polyolefin from the viewpoint of improving recyclability.

[0130] In the multilayer structure, the thickness of the barrier layer is preferably 0.2 μm or more and 20 μm or less, more preferably 0.4 μm or more and 16 μm or less, and even more preferably 0.6 μm or more and 12 μm or less, and the ratio of the thickness of the barrier layer to the total thickness of all layers of the multilayer structure is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less.

[0131] The method for producing the multilayer structure is not particularly limited, and examples thereof include a method of melt-extruding other components onto a molded article (film, sheet, etc.) made of the pellets, a method of co-extruding the pellets with other thermoplastic resin pellets, a method of coinjection molding the pellets with other thermoplastic resin pellets, and a method of laminating a barrier layer made of the pellets and a layer made of other components using a known adhesive such as an organic titanium compound, an isocyanate compound, or a polyester-based compound.

[0132] The method for co-extruding the pellets with other thermoplastic resin pellets is not particularly limited, and examples thereof include a multi-manifold confluence type T-die method, a feed block confluence type T-die method, and an inflation method.

[0133] The multilayer structure has excellent thermoformability and can therefore be suitably used as a material for thermoforming of thermoformed containers and the like.

[0134] The multilayer structure may be in the form of a film or a sheet, and may be molded into various shapes. Examples of methods for further molding a molded article using the film- or sheet-like multilayer structure include heat-stretch molding, vacuum molding, pressure molding, vacuum-pressure molding, and blow molding. The multilayer structure subjected to various secondary moldings may be a multilayer sheet. The multilayer structure can be used for packaging materials, containers, tubes, and the like. The multilayer structure may be a non-stretched multilayer sheet or a stretched multilayer sheet.

[0135] The multilayer structure may be stretched at least uniaxially by 2 times or more and 12 times or less. This stretching ratio may be 3 times or more and 10 times or less, or 4 times or more and 8 times or less. A multilayer structure uniaxially stretched in this manner has excellent gas barrier properties, break resistance, etc. Such a uniaxially stretched multilayer structure can be suitably used for packaging materials, etc. The uniaxial stretching of the multilayer structure can be carried out by a conventionally known method.

[0136] The multilayer structure may be biaxially stretched by 2 times or more and 12 times or less. This stretching ratio may be 10 times or less, 8 times or less, or 6 times or less. A multilayer structure biaxially stretched in this manner has excellent gas barrier properties, break resistance, etc. Such a biaxially stretched multilayer structure can be suitably used for packaging materials, etc. Biaxial stretching of the multilayer structure can be carried out by a conventionally known method.

[0137] The multilayer structure can be molded by vacuum pressure molding to obtain a container. Vacuum pressure molding is a method in which the multilayer structure is heated and molded using a combination of vacuum and pressure. Containers molded from the multilayer structure by vacuum pressure molding can be produced simply and reliably, and are excellent in appearance, gas barrier properties, etc.

[0138] In the vacuum / pressure molding method, for example, a multilayer structure is heated to soften it and then molded into the shape of a mold. Examples of molding methods include methods using vacuum or compressed air, and optionally a plug, to mold the structure into the shape of a mold (straight method, drape method, air slip method, snapback method, plug assist method, etc.), and press molding. Various molding conditions, such as molding temperature, degree of vacuum, compressed air pressure, and molding speed, are appropriately set depending on the plug shape, mold shape, and properties of the raw material film and multilayer structure.

[0139] The molding temperature is not particularly limited, and may be any temperature at which the resin is softened sufficiently for molding. For example, when thermoforming a multilayer structure, it is desirable not to use a temperature so high that the multilayer structure melts due to heating or that the unevenness of the metal surface of the heater plate is transferred to the multilayer sheet, but also not to use a temperature so low that the shaping is insufficient. Specifically, the temperature of the multilayer structure is 50°C to 180°C, preferably 60°C to 160°C.

[0140] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the examples and comparative examples described below, analyses and evaluations were carried out by the methods shown below.

[0141] (1) Measurement of Moisture Content of Pellets Using a halogen moisture analyzer, the moisture content of the pellets obtained in the examples and comparative examples was measured by a heated dry mass measurement method under the conditions of a drying temperature of 180°C, a drying time of 20 minutes, and a sample weight of 10 g. The moisture content of the pellets was calculated using the following formula: Moisture content (mass%) = [(mass before drying - mass after drying) / mass before drying] x 100

[0142] (2) Melt Flow Rate (MFR) The EVOH pellets obtained in the Examples and Comparative Examples were filled into a cylinder of a Melt Indexer L244 (manufactured by Takara Kogyo Co., Ltd.) with an inner diameter of 9.55 mm and a length of 162 mm, and melted at 210°C. A load was then applied uniformly to the molten resin composition using a plunger with a mass of 2,160 g and a diameter of 9.48 mm. The amount of resin composition extruded per unit time (g / 10 min) through an orifice with a diameter of 2.1 mm provided in the center of the cylinder was measured and used as the MFR.

[0143] (3) Measurement of IR Spectrum The surface of one EVOH pellet obtained in each of the Examples and Comparative Examples, or the central part of the cross section obtained by cutting an EVOH pellet into two equal parts with a slicer, was subjected to IR measurement by the ATR method (attenuated total reflection absorption spectroscopy) under the following conditions. When the EVOH pellet was spherical, it was cut into hemispheres; when it was spheroidal, it was cut at half the long side in a direction perpendicular to the long axis; and when it was cylindrical, it was cut at positions equidistant from the two bases so that the cut surface was parallel to the bases. The infrared absorption spectra obtained at each temperature were analyzed for the 1140 cm band, which is known as the crystallization band. －１ The presence or absence of a maximum point in the absorption band of 1120 cm －１ ~1150cm －１ The spectrum in this range was first differentiated, and the presence or absence of a maximum point was determined based on whether there was a wavenumber at which the positive and negative signs of the differential value were reversed, and Tcmin (°C), Tsmin (°C), Tcmax (°C), and Tsmax (°C) for each sample were determined. (Measurement conditions) Apparatus: Fourier transform infrared spectrophotometer FT-IR-6000 (manufactured by JASCO Corporation) Wavenumber resolution: 4 cm －１ Cell: Diamond Measurement mode: Heating single reflection ATR method Number of accumulations: 16 accumulations at each temperature Measurement area: 500 to 4000 cm －１ Temperature rise rate: 5°C / min from 30°C to 200°C Measurement temperature: Set temperature ±1°C Measurement interval: 5°C Measurement atmosphere: Air

[0144] (4) Preparation of Multilayer Film Using each of the EVOH pellets obtained in the Examples and Comparative Examples, a three-kind, three-layer multilayer structure (EVOH / Ad / PE = 10 μm / 10 μm / 100 μm) was produced under the following conditions using low-density polyethylene "INNATE (trademark) TF80" (PE) as the material for the other thermoplastic resin layer and maleic anhydride-modified polyethylene "ADMER (trademark) NF518" (Ad) as the adhesive layer. Extruder for EVOH: Single-screw extruder (Toyo Seiki Co., Ltd., Lab Machine ME Type CO-EXT), caliber 20 mm, L / D 20, full-flight screw, feed section / compression section / metering section / die = 175 / 220 / 220 / 220°C. Extruder for Ad: Single-screw extruder (Technovel Co., Ltd., SZW20GT-20MG-S TD), caliber 20 mm, L / D 20, full-flight screw, feed section / compression section / metering section / die = 175 / 220 / 220 / 220°C. Extruder for PE: Single-screw extruder (Plastics Technology Research Institute Co., Ltd., GT-32-A), caliber 32 mm, L / D 28, full-flight screw, feed section / compression section / metering section / die = 175 / 220 / 220 / 220°C. Die: 300mm wide, 3-type, 3-layer coat hanger die (manufactured by Plastics Engineering Research Institute)

[0145] (5) Die Build-up Evaluation The multilayer film production in (4) above was carried out continuously for 2 hours, and after 2 hours, die build-up around the die (die lip) on the EVOH layer side was visually inspected and evaluated according to the following criteria. In cases A to C, it was determined that die build-up was suppressed. (Evaluation: Criteria) A: No die build-up was observed over the entire width even after 2 hours of operation B: Very slight die build-up was observed after 2 hours of operation C: A small amount of die build-up was observed after 2 hours of operation D: Die build-up was observed after 1.5 hours of operation, and then an increase in die build-up was observed E: Die build-up was observed after 1 hour of operation, and then an increase in die build-up was observed

[0146] (6) Appearance Evaluation of Multilayer Film The multilayer film obtained in (4) above was stretched 5 times in the machine direction (MD) to obtain a multilayer film with an average thickness of EVOH / Ad1 / PE = 2 μm / 2 μm / 20 μm. The appearance characteristics of the uniaxially stretched co-extruded film were evaluated according to the following criteria. In the cases of A to C, the appearance was judged to be good. (Evaluation: Judgment Criteria) A: No streaks were observed B: Slight streaks were observed C: Some streaks were observed D: Many streaks were observed

[0147] (7) Measurement of Oxygen Transmission Rate (OTR) Aluminum was vacuum-deposited onto the surface of the EVOH of the uniaxially stretched co-extruded film obtained in (6) above using a vacuum deposition apparatus "EWA-105" manufactured by Nippon Vacuum Engineering Co., Ltd., to a mean thickness of 50 nm, to produce a vapor-deposited multilayer film (Al / EVOH / Ad1 / PE = 50 nm / 2 μm / 2 μm / 20 μm) having an aluminum vapor-deposited layer. The oxygen transmission rate was measured with the PE layer as the oxygen supply side. Specifically, the oxygen transmission rate (unit: cc / (m)) was measured using an oxygen transmission amount measuring apparatus ("MOCON OX-TRAN2 / 21" manufactured by Modern Control Co., Ltd.) under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 65% RH on the carrier gas side, an oxygen pressure of 1 atmosphere, and a carrier gas pressure of 1 atmosphere. ２ The gas barrier properties were evaluated based on the following criteria: Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. A rating of C was given, indicating poor gas barrier properties. (Evaluation: Evaluation criteria) A: 0.1 cc / (m ２ ・day・atm) B: 0.1cc / (m ２ ・day・atm) or more, 0.5cc / (m ２ ・day・atm) C: 0.5cc / (m ２ ・day・atm) or more

[0148] (8) Thermoformability Evaluation Test [Preparation of Thermoformable Multilayer Sheet] Using the EVOH pellets obtained in Examples 8 to 12, Reference Example 1, and Comparative Example 3 as the gas barrier layer, a layer made of polypropylene "Novatec (trademark) PP EA7AD" (PP solubility parameter = 8.0) as the thermoplastic resin layer, and adhesive polyolefin "Admer (trademark) QF500" (Ad1) as the adhesive layer, a three-kind, five-layer multilayer structure (PP / Ad1 / EVOH / Ad1 / PP = 368 μm / 16 μm / 32 μm / 16 μm / 368 μm) was obtained under the following conditions. The film-forming equipment had a temperature-controllable take-up roll after an extruder with a film-forming die, and the obtained multilayer sheet (multilayer body) was wound up on a winder. (Film production conditions) Extruder for EVOH: Single-screw extruder (laboratory machine ME type CO-EXT, manufactured by Toyo Seiki Co., Ltd.), caliber 20 mmφ, L / D=20, screw full-flight type, feed section / compression section / metering section / die=175 / 210 / 220 / 230°C Extruder for PP: Single-screw extruder (GT-32-A, manufactured by Plastics Technology Research Institute Co., Ltd.), caliber 32 mmφ, L / D=28, screw full-flight type, feed section / compression section / metering section / die=170 / 200 / 210 / 230°C Extruder for Ad1: Single-screw extruder (SZW20GT-20MG-STD, manufactured by Technovel Co., Ltd.), caliber 20 mmφ, L / D=20, screw full-flight type Supply section / compression section / metering section / die=150 / 200 / 220 / 220°C Die: 300mm wide coat hanger die (manufactured by Plastics Engineering Research Institute) Take-up roll temperature: 80°C

[0149] [Production and Evaluation of Thermoformed Containers] The obtained multilayer sheet was thermoformed (compressed air: 5 kg / cm) into a cup shape (mold shape: 70φ×70 mm, drawing ratio S=1.0) at a sheet temperature of 150° C. using a thermoforming machine (manufactured by Asano Seisakusho Co., Ltd.). ２, plug: 45φ×65mm, syntax form, mold temperature: 40°C) to produce thermoformed containers. The bottoms of the produced containers were visually evaluated according to the following criteria. Criterion D indicates poor appearance and is difficult to use for packaging purposes. The evaluation results are shown in Table 5. A: Uniform and no unevenness was observed B: Slight streak-like unevenness was observed C: Slight streak-like unevenness was observed D: Severe unevenness was observed

[0150] (9) Oxidation Degradation Resistance Evaluation Test [Preparation of Monolayer Film for Oxidation Degradation Resistance Evaluation] Using the EVOH pellets obtained in Examples 13 to 15 and Comparative Example 4, a monolayer film was formed under the following conditions using a 20 mm extruder "D2020" (D (mm) = 20, L / D = 20, compression ratio = 2.0, screw: full flight) manufactured by Toyo Seiki Seisaku-sho, Ltd. to obtain a monolayer film. Extrusion temperature: feeding section / compression section / metering section / die = 175 / 210 / 220 / 220°C Screw rotation speed: 90 rpm Discharge rate: 2.1 kg / hr Take-up roll temperature: 80°C Take-up roll speed: 0.9 m / min Film thickness: 100 μm

[0151] [Evaluation of oxidation degradation resistance] The change in tensile strength and elongation over time was evaluated for the obtained monolayer film by measuring multiple samples with different heat treatment times under the following evaluation conditions. The time until the breaking elongation became one-fourth of that of a sample that had not been heat treated was determined and used as an index of oxidation degradation resistance. The evaluation results are shown in Table 7. (Evaluation conditions) After treating for a predetermined time in a hot air dryer set at 140°C, the film was removed. Thereafter, the film was immersed in water at 20°C for 5 days, the surface water was wiped off, and the film was left to stand in a room at 20°C and 65% RH for 2 weeks, after which the tensile strength and elongation were measured under the following conditions. (Measurement conditions) Sample width 15 mm, chuck spacing 30 mm, pulling speed 50 mm / min, measurement atmosphere 20°C and 65% RH

[0152] In the above evaluation, when the breaking elongation falls to ¼ or less, the gas barrier property of the EVOH layer deteriorates significantly due to the generation of cracks caused by oxidative degradation, and therefore the time at which the breaking elongation reaches ¼ can be considered as one index of the lifespan of EVOH due to oxidative degradation at high temperatures. The time at which the breaking elongation reaches ¼ shows Arrhenius-type temperature dependency, and if the time at which the breaking elongation reaches ¼ at 80°C (lifespan) is to be 100 years or more, the time at which the breaking elongation reaches ¼ at 140°C needs to be 210 hours or more.

[0153] (10) Discharge Rate Evaluation Test Each of the resin composition pellets obtained in Examples 16 to 19 and Comparative Example 5 was formed into a film under the following conditions to obtain a monolayer film having a thickness of 20 μm. The production amount of the monolayer film per hour was evaluated as the discharge rate of the resin composition. A discharge rate of 0.5 kg / hr or more is considered practical. The results are shown in Table 9. - Apparatus: 20 mmφ single screw extruder (D2020, manufactured by Toyo Seiki Seisaku-sho, Ltd.) - L / D: 20 - Screw: full flight - Die width: 30 cm - Take-up roll temperature: 80°C - Screw rotation speed: 40 rpm - Set temperatures: C1 / C2 / C3 / D = 160°C / 180°C / 210°C / 210°C

[0154] (11) Evaluation of coloration (appearance) of monolayer film The monolayer film produced in the above-mentioned discharge amount evaluation test was wound around a paper tube, and the coloration of the film edge surface was evaluated with the naked eye according to the following criteria. The results are shown in Table 9. If the results were A to C, it was determined that a molded product with suppressed coloration had been obtained. A: No coloration was observed B: Slight yellowing was observed C: Yellowing was observed, but to an extent that was usable D: Severe yellowing was observed and the product was not usable

[0155] (12) Evaluation of Adhesion of Laminates Using each resin composition pellet obtained in Examples 16 to 19 and Comparative Example 5, linear low-density polyethylene (LLDPE: Ultzex ​​2022L manufactured by Mitsui Chemicals, Inc.) and adhesive resin (Bondine TX8030 manufactured by SUMICA. ATOCHEM Co. Ltd., hereinafter sometimes abbreviated as Ad), a three-kind, five-layer multilayer film (LLDPE / Ad / resin composition / Ad / LLDPE = 50 μm / 10 μm / 10 μm / 10 μm / 50 μm) was obtained as follows. The obtained multilayer film (laminate) was cut into 150 mm in the MD direction and 10 mm in the TD direction immediately after multilayer film formation, and then immediately measured the peel strength between the resin composition layer / Ad layer in T-peel mode using an autograph (Shimadzu Corporation DCS-50M), and evaluated according to the following criteria. The results are shown in Table 9. (Multilayer film production conditions) Extruder: For EVOH: 20 mm φ extruder, Lab machine ME type CO-EXT (manufactured by Toyo Seiki Co., Ltd.) For Ad: 25 mm φ extruder P25-18AC (manufactured by Osaka Seiki Co., Ltd.) For LLDPE: 32 mm φ extruder GF-32-A (manufactured by Plastics Technology Research Institute) EVOH set temperatures: C1 / C2 / C3 / D = 175°C / 210°C / 220°C / 220°C Ad set temperatures: C1 / C2 / C3 / D = 100°C / 160°C / 220°C / 220°C LLDPE set temperatures: C1 / C2 / C3 / D = 150°C / 200°C / 210°C / 220°C Die 300 mm wide coat hanger die (manufactured by Plastics Technology Research Institute) (Adhesion evaluation criteria) A : 600g / 15cm or more B: 450g / 15cm or more and less than 600g / 15cm C: 300g / 15cm or more and less than 450g / 15cm D: Less than 300g / 15cm

[0156] [Example 1] Water content W ０ EVOH hydrous pellets (ethylene unit content: 32 mol%, saponification degree: 99.9 mol%) having a water content of 40% by mass were placed in a fluidized bed dryer and dried at 80°C for 60 minutes. １EVOH hydrous pellets with a 13% by mass content were fed into a twin-screw extruder. The resin temperature was adjusted to 160°C, and an aqueous solution of acetic acid, boric acid, sodium acetate, magnesium acetate, and potassium dihydrogen phosphate was added through the additive introduction port. The input rate per unit time of the aqueous solution was 20.8 L / hr. The aqueous solution contained 3.5 g / L of acetic acid, 15 g / L of boric acid, 7.7 g / L of sodium acetate trihydrate, 3.1 g / L of magnesium acetate tetrahydrate, and 1.7 g / L of potassium dihydrogen phosphate.

[0157] The specifications of the twin-screw extruder are as follows: Type: twin-screw extruder L / D: 45.5 Diameter: 30 mmφ Screw: unidirectional fully intermeshing type Rotational speed: 300 rpm Die diameter: 3.0 mmφ

[0158] The molten water-containing EVOH discharged from the twin-screw extruder was cut with a hot cutter to obtain water-containing EVOH pellets. The temperature of the water circulating in the cutter (cooling water) was 15°C, and the rotation speed of the cutter blade was 3000 rpm. The obtained pellets were transported along a 5 m line together with the cooling water, and dewatered using a centrifuge. The water content W of the water-containing EVOH pellets immediately after the obtained pellets was 1000 rpm. ２ The water content of the EVOH pellets was 10% by mass, and the discharge rate of the EVOH from the twin-screw extruder was 208 kg / hour (excluding the amount of water contained therein). The obtained water-containing EVOH pellets were dried in a fluidized bed dryer at 90°C for 15 hours, and then in a static dryer at 105°C for 15 hours. ３ Spherical EVOH pellets having a diameter of 3 mm and a molecular weight of 0.2% by mass were obtained. The obtained EVOH pellets were evaluated according to the methods described in (2) to (7) above. The results are shown in Table 2.

[0159] [Example 2] Ethylene unit content and moisture content W of EVOH hydrous pellets ０ EVOH pellets were prepared in the same manner as in Example 1, except that the drying temperature in the first drying step and the amount of aqueous solution added in the melt-kneading step were changed as shown in Table 1, and the aqueous solution added was an aqueous solution of acetic acid / sodium acetate / magnesium acetate / potassium dihydrogen phosphate. The results are shown in Table 2.

[0160] [Examples 3 and 4] EVOH pellets were prepared in the same manner as in Example 1, except that the drying temperature in the first drying step, the resin temperature in the melt-kneading step, and the cooling water temperature and cooling length in the cutting step were changed as shown in Table 1, and then analyzed and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0161] Example 5 EVOH pellets were prepared in the same manner as in Example 1, except that the drying temperature in the first drying step, the resin temperature and the amount of aqueous solution added in the melt-kneading step, and the cooling water temperature in the cutting step were changed as shown in Table 1, and the aqueous solution containing additives was changed to an aqueous solution containing 1.8 g / L of acetic acid, 3.8 g / L of sodium acetate trihydrate, 1.5 g / L of magnesium acetate tetrahydrate, and 0.9 g / L of potassium dihydrogen phosphate. The results are shown in Table 2.

[0162] [Example 6] Ethylene unit content and moisture content W of EVOH hydrous pellets ０ EVOH pellets were prepared in the same manner as in Example 1, except that the temperature of the resin in the melt-kneading step and the amount of aqueous solution added were changed as shown in Table 1, and then analyzed and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0163] [Example 7] Ethylene unit content and moisture content W of EVOH hydrous pellets ０ EVOH pellets were prepared in the same manner as in Example 1, except that the drying temperature in the first drying step and the amount of aqueous solution added in the melt-kneading step were changed as shown in Table 1, and then analyzed and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0164] Comparative Example 1: A solution of EVOH having an ethylene unit content of 32 mol% and a saponification degree of 99.9 mol% in a methanol-water mixed solvent (methanol / water = 65 / 35, mass ratio) (EVOH concentration: 40% by mass) was extruded through a die with a 2 mm diameter hole into a coagulation bath of a 5°C aqueous methanol solution (methanol / water = 10 / 90, mass ratio) to coagulate into strands. The strands were cut with a cutter to obtain cylindrical hydrous EVOH pellets having a base diameter and height of 2.5 to 3.5 mm. The obtained hydrous pellets were washed in a water bath at 30°C for 1 hour, this process was repeated four times, and further washed in acetic acid water at 30°C for 1 hour. After that, the pellets were immersed in an aqueous solution containing acetic acid, boric acid, sodium acetate trihydrate, magnesium acetate tetrahydrate, and potassium dihydrogen phosphate to incorporate additives, and hydrous EVOH pellets having a water content of 57% by mass were obtained. The composition of the aqueous solution was adjusted so that the additive composition in the dried EVOH pellets would be the same as that in Example 1. The obtained hydrous EVOH pellets were dried using a fluidized bed dryer at 80°C for 15 hours, and then dried using a static dryer at 107°C for 24 hours to obtain cylindrical EVOH pellets with a moisture content of 0.2% by mass. The obtained EVOH pellets were evaluated according to the methods described in (2) to (7) above. The results are shown in Table 2.

[0165] Comparative Example 2 A solution (EVOH concentration: 41% by mass) of EVOH having an ethylene unit content of 32 mol% and a saponification degree of 99.9 mol% in a methanol-water mixed solvent (methanol / water = 65 / 35, mass ratio) was cut using a rotary knife by the underwater pelletizing method. The EVOH pellets were simultaneously cooled using circulating cooling water at 5°C to obtain oblong hydrous EVOH pellets with a long side of 3.0 mm and a short side of 2.4 mm. The obtained hydrous EVOH pellets were washed, additives were added, and dried in the same manner as in Comparative Example 1 to obtain EVOH pellets with a moisture content of 0.2% by mass. The obtained EVOH pellets were evaluated according to the methods described in (2) to (7) above. The results are shown in Table 2.

[0166]

[0167]

[0168] [Example 8] EVOH (A1) with water content W ０ EVOH hydrous pellets a-1 (ethylene unit content 32 mol%, saponification degree 99.9 mol%) having a water content of 40 mass%, EVOH (A2) having a water content of W ０ EVOH hydrous pellets a-2 (ethylene unit content 44 mol%, saponification degree 99.9 mol%) having a water content of 35% by mass were used, and charged into a fluidized bed dryer in a mass ratio (A1 / A2) of 80 / 20, and dried at 90°C for 60 minutes. The water content W １ EVOH hydrous pellets with a 6% by mass content were fed into a twin-screw extruder with the same specifications as in Example 1. The resin temperature was set to 160°C, and an aqueous solution of acetic acid, boric acid, sodium acetate, magnesium acetate, and potassium dihydrogen phosphate was added through the additive introduction port. The amount of the aqueous solution added per unit time was 20.8 L / hr. The aqueous solution contained 3.5 g / L of acetic acid, 15 g / L of boric acid, 7.7 g / L of sodium acetate trihydrate, 3.1 g / L of magnesium acetate tetrahydrate, and 1.7 g / L of potassium dihydrogen phosphate.

[0169] The molten, water-containing EVOH discharged from the twin-screw extruder was cut and dried in the same manner as in Example 1 to obtain EVOH pellets. The obtained EVOH pellets were evaluated according to the methods described in (2) to (8) above. The boric acid content in the EVOH pellets was also measured. The results are shown in Tables 4 and 5.

[0170] [Examples 9 to 12] Ethylene unit content and water content W of EVOH (A1) and EVOH (A2) ０ EVOH pellets were prepared in the same manner as in Example 8, except that the mass ratio (A1 / A2), drying temperature in the first drying step, cooling water temperature and cooling length in the cutting step, and drying temperature and drying time in the second drying step were changed as shown in Tables 3 and 4, and then analyzed and evaluated in the same manner as in Example 8. The results are shown in Tables 4 and 5.

[0171] Reference Example 1 EVOH pellets were prepared in the same manner as in Example 3, and analyzed and evaluated in the same manner as in Example 8. The results are shown in Tables 4 and 5.

[0172] Comparative Example 3 A solution (EVOH concentration: 41% by mass) of EVOH having an ethylene unit content of 32 mol% and a saponification degree of 99.9 mol% in a methanol-water mixed solvent (methanol / water = 65 / 35, mass ratio) was cut using a rotary knife by an underwater pelletizing method, and the EVOH pellets were simultaneously cooled using circulating cooling water at 5°C to obtain spheroidal 32 mol% hydrous EVOH pellets having a long side of 3.0 mm and a short side of 2.4 mm. Also, EVOH having an ethylene unit content of 44 mol% and a saponification degree of 99.9 mol% was treated in the same manner as above to obtain spheroidal 44 mol% hydrous EVOH pellets having a long side of 3.0 mm and a short side of 2.4 mm. The resulting pellets, which were 32 mol% water-containing EVOH pellets / 44 mol% water-containing EVOH pellets in a mass ratio of 80 / 20 (A1 / A2), were washed, additives were added, and dried in the same manner as in Comparative Example 1 to obtain EVOH pellets with a moisture content of 0.2 mass%. The EVOH pellets were evaluated according to the methods described in (2) to (8) above. The results are shown in Tables 4 and 5.

[0173]

[0174]

[0175]

[0176] [Example 13] Water content W ０ EVOH hydrous pellets (ethylene unit content: 32 mol%, saponification degree: 99.9 mol%) having a water content of 40% by mass were placed in a fluidized bed dryer and dried at 90°C for 60 minutes. The water content W １ The antioxidant (B) was dry-blended with EVOH hydrous pellets having a % by mass content of 6% by mass, and the mixture was then fed into a twin-screw extruder having the same specifications as in Example 1. The resin temperature was adjusted to 180°C, and an aqueous solution of acetic acid, boric acid, sodium acetate, magnesium acetate, and potassium dihydrogen phosphate was added through the additive introduction port. The input rate of the aqueous solution per unit time was 20.8 L / hr. The aqueous solution contained 3.5 g / L of acetic acid, 15 g / L of boric acid, 7.7 g / L of sodium acetate trihydrate, 3.1 g / L of magnesium acetate tetrahydrate, and 1.7 g / L of potassium dihydrogen phosphate.

[0177] The molten, water-containing EVOH discharged from the twin-screw extruder was cut and dried in the same manner as in Example 1, except that the temperature of the cutter circulating water (cooling water) was set to 40°C, to obtain EVOH pellets. The obtained EVOH pellets were evaluated according to the methods described in (2) to (7) and (9) above. The results are shown in Table 7. As the antioxidant (B), Irganox 1098 was used so that its content in the EVOH pellets was 0.5% by mass.

[0178] [Examples 14 and 15] Ethylene unit content and water content W of EVOH ０ EVOH pellets were prepared in the same manner as in Example 13, except that the content of the antioxidant, the drying temperature in the first drying step, the resin temperature and the amount of aqueous solution added in the melt-kneading step, and the cooling water temperature in the cutting step were changed as shown in Table 6, and then analyzed and evaluated in the same manner as in Example 13. The results are shown in Table 7.

[0179] [Comparative Example 4]

[0180] A solution (EVOH concentration: 41% by mass) of EVOH with an ethylene unit content of 32 mol% and a saponification degree of 99.9 mol% in a methanol-water mixed solvent (methanol / water = 65 / 35, mass ratio) was cut using a rotary knife by the underwater pelletization method. The EVOH pellets were simultaneously cooled using circulating cooling water at 5°C to obtain spheroidal 32 mol% hydrous EVOH pellets with a long side of 3.0 mm and a short side of 2.4 mm. The obtained hydrous EVOH pellets were washed, additives were added, and dried in the same manner as in Comparative Example 1 to obtain EVOH pellets with a moisture content of 0.2% by mass. A predetermined amount of antioxidant (B) was dry-blended with the obtained EVOH pellets to prepare a sample. The EVOH pellets were evaluated according to the methods described above in (2) to (7) and (9). The results are shown in Table 7.

[0181]

[0182]

[0183] [Example 16] Water content W ０EVOH hydrous pellets (ethylene unit content: 32 mol%, saponification degree: 99.9 mol%) having a water content of 40% by mass were placed in a fluidized bed dryer and dried at 90°C for 60 minutes. The water content W １ EVOH hydrous pellets with a molecular weight of 6% by mass were fed into a twin-screw extruder with the same specifications as in Example 1. The resin temperature was adjusted to 180°C, and an aqueous solution of acetic acid, boric acid, sodium acetate, magnesium acetate, potassium dihydrogen phosphate, and polyoxyethylene (7) stearyl ether was added through the additive introduction port. The input rate per unit time of the aqueous solution was 20.8 L / hr. The aqueous solution contained 3.5 g / L of acetic acid, 15 g / L of boric acid, 7.7 g / L of sodium acetate trihydrate, 3.1 g / L of magnesium acetate tetrahydrate, 1.7 g / L of potassium dihydrogen phosphate, and 0.1 g / L of polyoxyethylene (7) stearyl ether.

[0184] The molten, water-containing EVOH discharged from the twin-screw extruder was cut and dried in the same manner as in Example 1, except that the temperature of the cutter circulating water (cooling water) was set to 40°C, to obtain EVOH pellets. The obtained EVOH pellets were evaluated according to the methods described in (2) to (7) and (10) to (12) above. The results are shown in Table 9. The content of the nonionic surfactant (C) (polyoxyethylene (7) stearyl ether) in the EVOH pellets was 100 ppm.

[0185] [Examples 17 to 19] EVOH pellets were prepared in the same manner as in Example 16, except that the type of nonionic surfactant (C) was changed as shown in Table 8 and the concentration of polyoxyethylene (7) stearyl ether in the aqueous solution added through the additive introduction port was changed to 0.015 g / L in Example 17 and 0.4 g / L in Example 18, and then analyzed and evaluated in the same manner as in Example 16. The results are shown in Table 9.

[0186] Comparative Example 5 A solution (EVOH concentration: 41% by mass) of EVOH with an ethylene unit content of 32 mol% and a saponification degree of 99.9 mol% in a methanol-water mixed solvent (methanol / water = 65 / 35, mass ratio) was cut using a rotary knife by the underwater pelletization method. The EVOH pellets were simultaneously cooled using circulating cooling water at 5°C to obtain spheroidal hydrous EVOH pellets with a long side of 3.0 mm and a short side of 2.4 mm. The obtained hydrous EVOH pellets were washed in the same manner as in Comparative Example 1, except that polyoxyethylene (7) stearyl ether was added as an additive, and then the additives were added and the pellets were dried to obtain EVOH pellets with a water content of 0.2% by mass. The obtained EVOH pellets were evaluated according to the methods described above in (2) to (7) and (10) to (12). The results are shown in Table 9.

[0187]

[0188]

[0189] 1, 2, 3 IR spectrum

Claims

1. A pellet containing an ethylene-vinyl alcohol copolymer, the surface and cut surface of the pellet being measured at 5°C intervals from 30°C to 200°C, and the 1120 cm －１ ~1150cm －１ A pellet that satisfies formulas (1) to (3) in the IR spectrum at each temperature in the range: 40≦Tcmin≦100 (1) 10≦Tcmin−Tsmin≦70 (2) −15<Tcmax−Tsmax<15 (3) where, Tcmin (°C) is the lowest temperature at which the IR spectrum of the cut surface of the pellet has a maximum, Tsmin (°C) is the lowest temperature at which the IR spectrum of the pellet surface has a maximum, Tcmax (°C) is the highest temperature at which the IR spectrum of the pellet cut surface has a maximum, and Tsmax (°C) is the highest temperature at which the IR spectrum of the pellet surface has a maximum.

2. The pellet according to claim 1, which satisfies the formula (4): 0.95≦(Tsmax−Tsmin) / (Tcmax−Tcmin)<2.5 (4) 3. The pellet according to claim 1, which satisfies the formula (5): 40≦Tcmax−Tcmin<130 (5) 4. The pellet according to claim 1, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 20 to 60 mol %.

5. The pellet according to claim 1, wherein the ethylene-vinyl alcohol copolymer has a degree of saponification of 99 mol % or more.

6. The pellet according to claim 1, wherein the ethylene-vinyl alcohol copolymer comprises an ethylene-vinyl alcohol copolymer (A1) having an ethylene unit content of 20 mol% or more and 50 mol% or less and an ethylene-vinyl alcohol copolymer (A2) having an ethylene unit content of 30 mol% or more and 60 mol% or less, a difference in ethylene unit content (A2-A1) between the ethylene-vinyl alcohol copolymer (A2) and the ethylene-vinyl alcohol copolymer (A1) is 4.5 mol% or more, and a mass ratio (A1 / A2) of the ethylene-vinyl alcohol copolymer (A1) to the ethylene-vinyl alcohol copolymer (A2) is 60 / 40 or more and 95 / 5 or less.

7. The pellet according to claim 1, further comprising 0.01% by mass or more and 5% by mass or less of an antioxidant (B).

8. The pellet according to claim 1, further comprising a nonionic surfactant (C) in an amount of 0.1 ppm to 1,000 ppm.

9. A molded article obtained by extrusion molding the pellets according to any one of claims 1 to 8.

10. A molded article obtained by injection molding the pellets according to any one of claims 1 to 8.

11. A molded article obtained by blow molding the pellets according to any one of claims 1 to 8.

12. A multilayer structure obtained by co-extrusion molding the pellets according to any one of claims 1 to 8 and pellets of another thermoplastic resin.

13. The multilayer structure according to claim 12, wherein the layer formed by extrusion molding of the pellets is the outermost layer.

14. A method for producing pellets according to any one of claims 1 to 8, wherein the moisture content W ０ 25 to 50% by mass of ethylene-vinyl alcohol copolymer water-containing pellets are introduced into a dryer, and the water content W of the water-containing pellets is １ a first drying step (I) for reducing the moisture content W to 5 to 25% by mass; a melt-kneading step (II) for introducing the water-containing pellets obtained in the first drying step (I) into an extruder and melt-kneading the pellets; and a melt-kneading step (II) for cutting the molten resin discharged from the extruder to reduce the moisture content W ２ a cutting step (III) for obtaining water-containing pellets having a water content of 5 to 25% by mass; and drying the water-containing pellets obtained in the cutting step (III) to obtain water-containing pellets having a water content of 5 to 25% by mass. ３ a second drying step (IV) for obtaining the pellets having a moisture content of 0.5% by mass or less, ０ -W １ ) is 10 to 45 mass%.

15. A method for producing a multilayer structure by co-extrusion molding the pellets according to any one of claims 1 to 8 and pellets of another thermoplastic resin.

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