Pellets made of a resin composition

Abstract

To provide a pellet made of a resin composition containing an EVOH capable of being stably melt-molded and capable of suppressing defects in a molding after the melt molding.SOLUTION: A pellet made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a lubricant (B), wherein the content of the lubricant (B) in the pellet is 5 ppm or more and 150 ppm or less, and the flow surface angle (C) of the pellet is 40 degrees or less and the rotational repose angle (D) of the pellet is 40 degrees or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to pellets made of a resin composition containing an ethylene-vinyl alcohol copolymer and a lubricant. [Background technology]

[0002] Ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as EVOH) is a thermoplastic resin that has excellent gas barrier properties, fuel barrier properties, chemical resistance, stain resistance, anti-static properties, mechanical strength, etc. Taking advantage of these characteristics, EVOH is molded into forms such as films, sheets, bottles, cups, tubes, and pipes, and is used in a variety of applications, including packaging containers.

[0003] It is known that the moldability of EVOH during melt molding depends on the melting behavior of the EVOH pellets in the molding machine. Therefore, there is a demand for EVOH pellets that can be melt molded stably and that can suppress defects in the molded products after melt molding.

[0004] Patent Document 1 describes saponified ethylene-vinyl ester copolymer pellets having 10 to 400 ppm by weight of higher fatty acid amide attached to the surface of the saponified ethylene-vinyl ester copolymer, in which when 100 g of the pellets are washed in a 500 ml beaker in 300 ml of ion-exchanged water at a water temperature of 23°C and a rotation speed of 250 rpm using a three-one motor with helical blades, the amount of higher fatty acid amide that falls off is less than 35 wt % of the amount attached to the surface before washing.

[0005] Patent Document 2 describes a method for producing pellets of saponified ethylene-vinyl acetate copolymer, which comprises extruding a solution of saponified ethylene-vinyl acetate copolymer in the form of strands into a coagulating liquid from a nozzle made of any one of an aluminum compound, a glass compound, and a thermosetting resin, and then cutting the strands.

[0006] Patent Document 3 describes a method for producing ethylene-vinyl alcohol copolymer resin pellets, which comprises feeding an ethylene-vinyl alcohol copolymer to an extruder, maintaining the resin melt temperature in the extruder in the range of 70 to 170°C, adjusting the water content in the extruder so that the copolymer has a water content of 5 to 40% by weight immediately after being discharged from the extruder, and cutting the copolymer after extrusion. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-92160 [Patent Document 2] Japanese Patent Application Publication No. 11-77672 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-96529 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the pellets described in Patent Document 1 and the pellets obtained by the manufacturing methods described in Patent Documents 2 and 3 are still not stable enough when melt-molded, and the suppression of defects in the molded product after melt-molding is also insufficient.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide pellets made of a resin composition containing EVOH, which can be stably melt-molded and can suppress defects in molded articles after melt-molding. [Means for solving the problem]

[0010] The above-mentioned problem is solved by providing pellets made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a lubricant (B), wherein the content of the lubricant (B) in the pellets is 5 ppm or more and 150 ppm or less, the flow surface angle (C) of the pellets is 40 degrees or less, and the rotational angle of repose (D) of the pellets is 40 degrees or less.

[0011] In this case, the half-value width of the particle size distribution of the equivalent circle diameter of the pellets is preferably 0.7 mm or less. Furthermore, the ratio (D / C) of the flow surface angle (C) to the rotational angle of repose (D) is preferably 0.8 or more. The shape of the pellets is also preferably cylindrical, spherical, or spheroidal. [Effects of the Invention]

[0012] The pellets of the present invention can be stably melt-molded and can suppress defects in the molded product after melt-molding. Therefore, pressure fluctuations in the extruder during melt-molding can be suppressed, and fluctuations in the motor torque of the extruder can be reduced. Furthermore, in the film obtained by forming the pellets into a film, it is possible to suppress the occurrence of bumps and streaks on the film surface, and it is also possible to suppress unevenness in the film thickness. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a twin-screw extruder used in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] The pellets of the present invention are pellets made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) (hereinafter sometimes referred to as EVOH (A)) and a lubricant (B), wherein the content of the lubricant (B) in the pellets is 5 ppm or more and 150 ppm or less, the flow surface angle (C) of the pellets is 40 degrees or less, and the rotational angle of repose (D) of the pellets is 40 degrees or less.

[0015] The EVOH (A) used in the present invention is obtained by saponifying an ethylene-vinyl ester copolymer, and preferably obtained by saponifying an ethylene-vinyl acetate copolymer. The ethylene unit content is preferably 20 to 60 mol%. If the ethylene unit content is less than 20 mol%, the melt moldability may be insufficient. On the other hand, if the ethylene unit content exceeds 60 mol%, the gas barrier properties may be insufficient. The ethylene unit content is more preferably 25 mol% or more, and even more preferably 30 mol% or more. Furthermore, the ethylene unit content is more preferably 55 mol% or less, and even more preferably 50 mol% or less.

[0016] The saponification degree of EVOH (A) is preferably 90 mol% or more. If the saponification degree is less than 90 mol%, the barrier properties and melt moldability may be insufficient. The saponification degree is more preferably 95 mol% or more, even more preferably 99 mol% or more, and particularly preferably 99.3 mol% or more. On the other hand, the saponification degree of EVOH (A) may be 99.9 mol% or less. The saponification degree is a value measured in accordance with JIS K6726.

[0017] The pellets of the present invention contain a lubricant (B) in an amount of 5 ppm to 150 ppm. The inclusion of the lubricant (B) in the pellets of the present invention in this range tends to suppress pressure fluctuations and motor torque fluctuations, particularly during melt molding. Examples of lubricants (B) include higher fatty acid esters (e.g., methyl esters, isopropyl esters, butyl esters, and octyl esters of lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and oleic acid); higher fatty acid amides (saturated fatty amides such as stearic acid amide, stearic acid bisamide, and behenic acid amide; unsaturated fatty acid amides such as oleic acid amide and erucic acid amide; and bisfatty acid amides such as ethylene bisstearic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, and ethylene bislauric acid amide); low-molecular-weight polyolefins (e.g., low-molecular-weight polyethylene or low-molecular-weight polypropylene having a number-average molecular weight of about 500 to 10,000, or acid-modified products thereof); higher alcohols; fluorinated ethylene resins; and inorganic substances such as silicon dioxide (synthetic silica particles), clay, talc, and mica. Among these, preferred are higher fatty acid esters, higher fatty acid amides, or inorganic substances, more preferred are higher fatty acid amides or inorganic substances, and even more preferred are higher fatty acid amides.

[0018] From the viewpoint of enabling more stable melt molding and further suppressing defects in the molded article after melt molding, the content of lubricant (B) is preferably 120 ppm or less, more preferably 100 ppm or less, even more preferably 80 ppm or less, and particularly preferably 60 ppm or less. From the same viewpoint, the content of lubricant (B) is preferably 8 ppm or more, more preferably 10 ppm or more, even more preferably 20 ppm or more, and particularly preferably 30 ppm or more.

[0019] The resin composition constituting the pellets of the present invention may contain, in addition to the EVOH (A) and the lubricant (B), at least one additive selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts, and alkaline earth metal salts, thereby improving qualities such as thermal stability.

[0020] Examples of carboxylic acids include oxalic acid, succinic acid, benzoic acid, citric acid, acetic acid, and lactic acid. Among these, acetic acid is preferred from the standpoints of cost and availability. The content of carboxylic acid in the dried EVOH resin pellets of the present invention is preferably 10 to 5000 ppm, since too little may cause discoloration during melt molding, and too much may result in insufficient interlayer adhesion. The content of carboxylic acid is preferably 30 ppm or more, more preferably 50 ppm or more. The content of carboxylic acid is also preferably 1000 ppm or less, more preferably 500 ppm or less.

[0021] Examples of boron compounds include, but are not limited to, boric acids, boric acid esters, borate salts, and boron hydrides. Specifically, 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 various boric acids listed above. Among these compounds, orthoboric acid (hereinafter simply referred to as boric acid) is preferred. The content of the boron compound in the dried EVOH resin pellets of the present invention is preferably 10 to 2000 ppm, more preferably 50 to 1000 ppm, of boron, since too little improves thermal stability and too much can lead to gelation and poor moldability.

[0022] Examples of phosphate compounds include various acids such as phosphoric acid and phosphorous acid, and their salts. The phosphate may be present in the form of monophosphate, diphosphate, or triphosphate. 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. The content of the phosphate compound in the dried EVOH resin pellets of the present invention is preferably 1 to 1,000 ppm, calculated as phosphate radicals. Addition within this range can suppress discoloration of molded products and the occurrence of gels and particles. If the content of the phosphate compound is less than 1 ppm, there is a risk of severe discoloration during melt molding. Furthermore, if it exceeds 1,000 ppm, there is a risk of gels and particles occurring more easily in molded products.

[0023] Examples of alkali metal salts include monovalent metal aliphatic carboxylates, aromatic carboxylates, phosphates, and metal complexes. Examples include sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, and the sodium salt of ethylenediaminetetraacetic acid. Among these, sodium acetate, potassium acetate, and sodium phosphate are preferred. The content of the alkali metal salt in the dried EVOH resin pellets of the present invention 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.

[0024] Examples of alkaline earth metal salts 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. The content of alkaline earth metal in the dried EVOH resin pellets of the present invention is preferably 10 to 1,000 ppm, more preferably 20 to 500 ppm, calculated as metal. If the alkaline earth metal content is less than 10 ppm, the effect of improving long-run properties may be insufficient. Furthermore, if it exceeds 1,000 ppm, the resin may become severely discolored when melted.

[0025] The resin composition of the present invention may contain components other than the EVOH (A) and the lubricant (B) as long as the effects of the present invention are not impaired. Examples of such components include heat stabilizers, UV absorbers, antioxidants, colorants, fillers, plasticizers, photoinitiators, deodorizers, antistatic agents, lubricants, desiccants, bulking agents, pigments, dyes, processing aids, flame retardants, and antifogging agents. The content of such components in the resin composition is preferably 0.001 to 1% by mass.

[0026] The proportion of EVOH (A) in the resin constituting the pellet of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 99% by mass or more, or may consist essentially of EVOH (A) alone. The proportions of EVOH (A) and lubricant (B) in the pellet of the present invention are preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 99% by mass or more.

[0027] The pellets of the present invention have a flow surface angle (C) of 40 degrees or less. If the flow surface angle (C) exceeds 40 degrees, problems such as the inability to suppress pressure fluctuations in the extruder during melt molding and increased fluctuations in the extruder motor torque occur, making stable melt molding impossible. Furthermore, problems such as the occurrence of bumps and streaks on the surface of molded products such as films and uneven thickness occur, making it impossible to suppress defects in the molded products after melt molding. The flow surface angle (C) is preferably 38 degrees or less, more preferably 36 degrees or less, and even more preferably 34 degrees or less. In some cases, 31 degrees or less or 30 degrees or less may be preferred. Meanwhile, the flow surface angle (C) may be 23 degrees or more or 26 degrees or more. Here, the flow surface angle (C) in this specification refers to the angle (°) measured by the measurement method described in the Examples. The flow surface angle (C) can be adjusted by the lubricant content, the type of lubricant, the pellet shape, and the half-value width of the particle size distribution of the pellet's equivalent circle diameter.

[0028] The rotational repose angle (D) of the pellets of the present invention is 40 degrees or less. If the rotational repose angle (D) exceeds 40 degrees, problems such as the inability to suppress pressure fluctuations in the extruder during melt molding and increased fluctuations in the extruder motor torque occur, making stable melt molding impossible. Furthermore, problems such as the occurrence of bumps and streaks on the surface of molded products such as films and uneven thickness occur, making it impossible to suppress defects in the molded products after melt molding. The rotational repose angle (D) is preferably 38 degrees or less, more preferably 35 degrees or less, and even more preferably 33 degrees or less. In some cases, 30 degrees or less, 29 degrees or less, 28 degrees or less, 27 degrees or less, or 25 degrees or less may be preferred. On the other hand, the rotational repose angle (D) may be 20 degrees or more or 22 degrees or more. Here, the rotational repose angle (D) in this specification refers to the angle (°) measured by the method described in the Examples. The rotational repose angle (D) can be adjusted by the lubricant content, the type of lubricant, the pellet shape, and the half-value width of the particle size distribution of the pellet's equivalent circle diameter.

[0029] The ratio (D / C) of the flow surface angle (C) to the rotational angle of repose (D) is preferably 0.8 or greater. If the ratio (D / C) is less than 0.8, it may be difficult to suppress pressure fluctuations in the extruder during melt molding. Furthermore, there is a risk of large fluctuations in the motor torque of the extruder. Furthermore, there is a risk of lumps or streaks appearing on the film surface or uneven thickness. The ratio (D / C) is more preferably 0.85 or greater. On the other hand, the ratio (D / C) is preferably 1 or less, more preferably 0.97 or less, and in some cases, 0.95 or less, 0.93 or less, or 0.90 or less is preferred. While the reason for this is unclear, it is believed that the flow surface angle (C) is related to the pellet bite in the extruder, and the rotational angle of repose (D) is related to the feed from the hopper to the screw. Therefore, if D / C is outside the above range, the balance between pellet feedability and pellet biteability is disrupted, resulting in reduced extrusion stability.

[0030] In the present invention, the half-value width in the particle size distribution of the equivalent circle diameter of the pellets is preferably 0.7 mm or less. By producing pellets with a small half-value width and uniform particle size, it is possible to further suppress the occurrence of bumps and streaks on the surface of a film or the like. From the viewpoint of suppressing pressure fluctuations in the extruder during melt molding and minimizing fluctuations in the extruder motor torque, the half-value width is more preferably 0.5 mm or less, and even more preferably 0.4 mm or less. On the other hand, the half-value width may be 0.1 mm or more. The half-value width of the particle size distribution can be determined from the distribution of diameter values ​​obtained as equivalent circle diameters from the area of ​​multiple pellet images observed two-dimensionally. Specifically, it can be measured using a dynamic image analyzer.

[0031] As described above, methods for obtaining pellets with a uniform particle size include a method of devising a cutting method and a sieving method. Among these, the sieving method is preferred because it can reliably and simply reduce the half-value width of the particle size distribution. When sieving, it is preferable to use sieves with at least two types of openings to remove pellets that are too large and pellets that are too small, and it is more preferable to use sieves with three types of openings. Specifically, sieving using sieves stacked in the order of 3.5 to 6.5 mesh / 7 mesh / 8 mesh is a preferred embodiment, sieving using sieves stacked in the order of 5 to 6.5 mesh / 7 mesh / 8 mesh is a more preferred embodiment, and sieving using sieves stacked in the order of 6.5 mesh / 7 mesh / 8 mesh is an even more preferred embodiment.

[0032] In the present invention, the shape of the pellets is not particularly limited, but is preferably cylindrical, spherical, or spheroidal. Here, "cylindrical" includes rectangular and cylindrical shapes. Furthermore, "spheroidal" refers to a shape in which the radii of two perpendicular axes are equal. Furthermore, the terms "cylindrical," "spheroidal," and "spheroidal" are not used in the strict sense, and slight distortions are acceptable. Furthermore, as long as the effects of the present invention are not impaired, some of the pellets of the present invention may contain pellets of shapes other than cylindrical, spherical, or spheroidal.

[0033] The length of the pellet in the longitudinal direction is not particularly limited, but is preferably 2.0 to 4.0 mm. The length of the pellet in the lateral direction is also not particularly limited, but is preferably 2.0 to 4.0 mm.

[0034] A method for producing the EVOH (A) used in the present invention will be described below. The method for producing the EVOH (A) used in the present invention is not particularly limited. A suitable production method includes the steps of adding an alkali catalyst to a methanol solution of an ethylene-vinyl ester copolymer to saponify the ethylene-vinyl ester copolymer, thereby obtaining a methanol solution of an ethylene-vinyl alcohol copolymer, and removing the solvent from the saponified solution.

[0035] First, the process for obtaining a methanol solution of an ethylene-vinyl alcohol copolymer will be described. Ethylene and a vinyl ester are copolymerized using a radical initiator as a catalyst to obtain an ethylene-vinyl ester copolymer. Preferably, vinyl acetate is used as the vinyl ester to obtain an ethylene-vinyl acetate polymer. In this case, solution polymerization is carried out using methanol as a solvent. Either a continuous or batch system may be used. The polymerization temperature is 20 to 90°C, preferably 40 to 70°C. The polymerization time (average residence time in the case of a continuous system) is 2 to 15 hours, preferably 3 to 11 hours. The polymerization rate is 10 to 90%, preferably 30 to 80%, based on the vinyl ester charged. The resin content in the solution after polymerization is 5 to 85%, preferably 20 to 70%.

[0036] Examples of the catalyst used include azonitrile initiators such as 2,2-azobisisobutyronitrile, 2,2-azobis-(2,4-dimethylvaleronitrile), 2,2-azobis-(4-methyl-2,4-dimethylvaleronitrile), 2,2-azobis-(4-methoxy-2,4-dimethylvaleronitrile), and 2,2-azobis-(2-cyclopropylpropionitrile), as well as isobutyryl peroxide, cumyl peroxyneodecanoate, diisopropyl peroxycarbonate, di-n-propyl peroxydicarbonate, t-butyl peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide.

[0037] Monomers copolymerizable with ethylene and vinyl esters, such as alkenes such as propylene, butylene, pentene, and hexene; 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 ... 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, 1,3-diacetoxy-2-methyl Copolymerization can also be carried out in the presence of small amounts of alkenes having an ester group such as olefin propane or their saponification products; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, and itaconic acid or their anhydrides, salts, or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid or their salts; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, and vinylidene chloride. In such cases, the amount of copolymerization is typically 5 mol % or less, and it is preferable that these compounds are substantially absent.

[0038] After a predetermined time of polymerization, when a predetermined polymerization rate is reached, a polymerization inhibitor is added as necessary, unreacted ethylene gas is removed by evaporation, and then unreacted vinyl ester is expelled. As a method for expelling unreacted vinyl ester from the ethylene-vinyl ester copolymer solution from which ethylene has been evaporated, for example, a method is employed in which the copolymer solution is continuously fed at a constant rate from the top of a tower packed with Raschig rings, methanol vapor is blown in from the bottom of the tower, a mixed vapor of methanol and unreacted vinyl ester is distilled from the top of the tower, and the ethylene-vinyl ester copolymer solution from which unreacted vinyl ester has been removed is taken out from the bottom of the tower.

[0039] An alkali catalyst is added to a methanol solution of an ethylene-vinyl ester copolymer from which unreacted vinyl ester has been removed, and the vinyl ester component in the copolymer is saponified to obtain a methanol solution of an ethylene-vinyl alcohol copolymer. 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. The saponification conditions are as follows: the ethylene-vinyl ester copolymer concentration is preferably 10 to 50% by mass. The saponification reaction temperature is preferably 30 to 150°C. The amount of alkali catalyst used is preferably 0.005 to 0.6 equivalents (per vinyl ester unit). The saponification time (average residence time in the case of a continuous reaction) is preferably 10 minutes to 6 hours.

[0040] In this way, a solution containing EVOH (A) is obtained, and then the solvent is removed. The method for removing the solvent is not particularly limited as long as it can reduce the solvent content. The EVOH solution can be solidified by extruding it into a poor solvent such as water and solidifying it to reduce the solvent content. Alternatively, water may be mechanically squeezed out of the extruder or kneader, or water vapor may be evaporated from a vent. After the solvent is removed in this way, the EVOH is cut. The method for obtaining pellets by cutting is not particularly limited. The solidified, water-containing strands can be cut with a cutter, or the material whose moisture content has been reduced in the extruder or kneader can be cut with a hot cutter or underwater cutter while still in a fluid state.

[0041] After cutting into pellets, the pellets are dried. The drying method is not particularly limited, and a hot air dryer or the like can be used. The dryer may be a fluidized type dryer or a static type dryer, or a combination of these may be used. Among these, a method in which the pellets are first dried by fluidized drying and then dried by static drying is preferred. The drying temperature is not particularly limited, but a temperature of about 70 to 120°C is usually used, and the temperature can be increased as the drying progresses. The moisture content after drying is usually 1% by mass or less, and preferably 0.5% by mass or less.

[0042] Although the method for incorporating the lubricant (B) into the EVOH (A) obtained above is not particularly limited, a method of dry-blending the EVOH (A) and the lubricant (B) to obtain a resin composition containing the EVOH (A) and the lubricant (B) is preferred. In this case, it is preferable to use EVOH (A) pellets that have been molded into pellets in advance. In this way, pellets consisting of a resin composition containing the EVOH (A) and the lubricant (B) can be easily obtained.

[0043] When the pellets of the present invention contain at least one additive selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts, and alkaline earth metal salts, the method of adding the additive is not particularly limited. Methods that can be used include immersing hydrous pellets in an aqueous solution containing the additive to impregnate them, or injecting an aqueous solution containing the additive into hydrous and fluidized EVOH in an extruder or the like, kneading the mixture, and then cutting the mixture to produce pellets.

[0044] The pellets of the present invention can be melt-molded to obtain various molded products such as films, sheets, containers, pipes, fibers, etc. Melt molding methods include extrusion molding, inflation extrusion, blow molding, melt spinning, injection molding, etc. The melting temperature varies depending on the melting point of EVOH (A), etc., but is preferably about 150 to 270°C. [Example]

[0045] The present invention will be explained in more detail below using examples.

[0046] [Manufacturing method 1] A saponification reactor was charged with 100 parts by weight of an ethylene-vinyl acetate copolymer with an ethylene content of 32 mol% and 400 parts by weight of methanol, followed by 0.16 parts by weight of a methanol solution of sodium hydroxide (80 g / L) (sodium hydroxide / vinyl acetate unit = 0.4 / 1, molar ratio). Nitrogen gas was blown into the reactor, and the reaction was carried out at 60°C for 4 hours while the by-product methyl acetate was removed from the system along with the methanol. The reaction was then terminated by neutralization with acetic acid, yielding a methanol solution of EVOH consisting of 57 parts by weight of EVOH and 75 parts by weight of methanol. The saponification degree of this EVOH was 99.95 mol%.

[0047] The EVOH solution was extruded into water through a gold plate with a circular opening, solidifying into strands, which were then cut into pellets approximately 3 mm in diameter and 5 mm in length. The pellets were dewatered using a centrifuge, and the dewatering process was repeated by adding a large amount of water.

[0048] The resulting pellets (EVOH, ethylene unit content 32 mol%, saponification degree 99.95 mol%, water content 26% by mass) were fed into the twin-screw extruder shown in Figure 1. The resin temperature at the discharge port was adjusted to 100°C, and a treatment solution consisting of an aqueous solution of acetic acid, boric acid, sodium acetate, magnesium acetate, and potassium dihydrogen phosphate was added through the trace ingredient addition section shown in Figure 1 at the tip of the discharge port. The EVOH was fed at a rate of 10 kg / hr (including the mass of water) and the treatment solution was fed at a rate of 0.65 L / hr. The treatment solution contained 4.3 g / L of acetic acid, 15 g / L of boric acid, 4.6 g / L of sodium acetate, 3.0 g / L of magnesium acetate, and 1.4 g / L of potassium dihydrogen phosphate. The specifications of the twin-screw extruder are shown below.

[0049] Type: Twin-screw extruder L / D: 45.5 Caliber: 30mmφ Screw: Same direction full intermeshing type Rotation speed: 300 rpm Motor capacity: DC22KW Heater: 13-split type Number of die holes: 6 holes (3mm diameter) Resin temperature inside the die: 105℃ Center hot cutter rotation speed: 600-2800 rpm

[0050] The EVOH resin composition discharged from the discharge port was extruded from a die with six 3 mm diameter holes. The temperature of the EVOH resin composition inside the die was 105°C. The extruded EVOH was cut in a fluid state with a center hot cutter. The rotation speed of the cutter blade was 2700 rpm.

[0051] The moisture content of the pellets after extrusion was 17% by mass. The resulting pellets were dried at 100°C for 15 hours using a fluidized bed dryer, and then dried at 100°C for 15 hours using a static dryer. As a result, the moisture content of the dried pellets was 0.3% by mass. The dried pellets contained 300 ppm of acetic acid, 270 ppm of boron compounds (calculated as boron), 100 ppm of phosphate compounds (calculated as phosphate radicals), 40 ppm of potassium and 130 ppm of sodium (calculated as metals), and 50 ppm of magnesium (calculated as metals). The MFR (190°C, 2160 g load) was 1.5 g / 10 min.

[0052] [Manufacturing method 2] A saponification reactor was charged with 100 parts by weight of an ethylene-vinyl acetate copolymer with an ethylene content of 32 mol% and 400 parts by weight of methanol, followed by 0.16 parts by weight of a methanol solution of sodium hydroxide (80 g / L) (sodium hydroxide / vinyl acetate unit = 0.4 / 1, molar ratio). Nitrogen gas was blown into the reactor, and the reaction was carried out at 60°C for 4 hours while the by-product methyl acetate was removed from the system along with the methanol. The reaction was then terminated by neutralization with acetic acid, yielding a methanol solution of EVOH consisting of 57 parts by weight of EVOH and 75 parts by weight of methanol. The saponification degree of this EVOH was 99.95 mol%.

[0053] The EVOH solution was extruded into water through a gold plate with a circular opening, solidifying into strands, which were then cut into pellets approximately 3 mm in diameter and 5 mm in length. The pellets were dewatered using a centrifuge, and the dewatering process was repeated by adding a large amount of water.

[0054] 3.5 kg of the pellets thus obtained (EVOH, ethylene unit content 32 mol%, saponification degree 99.5 mol%, water content 35% by mass) were immersed in 6 L of an aqueous solution containing 0.4 g / L of acetic acid, 0.4 g / L of sodium acetate, 0.3 g / L of magnesium acetate, 0.1 g / L of potassium dihydrogen phosphate, and 0.7 g / L of boric acid at 25°C for 6 hours. After immersion, the pellets (water content 55% by mass) made of the EVOH resin composition were drained and dried in a fluidized bed dryer at 80°C for 15 hours and then in a static dryer at 100°C for 24 hours to obtain dried pellets (water content 0.3% by mass).

[0055] The dried pellets contained 300 ppm of acetic acid, 270 ppm of boron compounds, 100 ppm of phosphate compounds, 40 ppm of potassium and 130 ppm of sodium salts, and 50 ppm of magnesium salts, respectively. The MFR (190°C, 2160g load) was 1.5g / 10min.

[0056] [Example 1] Stearic acid bisamide (lubricant) was added to the dried pellets obtained by the above-mentioned Production Method 1, and the mixture was dry-blended using a blender. The amount of lubricant added was adjusted so that the content of the lubricant relative to the pellets was 5 ppm.

[0057] The pellets were then sieved through sieves stacked in this order of 6.5 mesh, 7 mesh, and 8 mesh for 10 minutes, and the pellets remaining on the 8 mesh were collected to obtain pellets of Example 1. The obtained pellets were spheroidal, with a longitudinal length of 3.2 mm and a lateral length of 2.1 mm.

[0058] 175 g of the sieved pellets of Example 1 were filled into a cylindrical sample container and sealed. The container was then placed in a measuring instrument ("FSA-100S" manufactured by Tsutsui Scientific Instruments Co., Ltd.) and rotated at 23°C and 50% relative humidity. The rotation speed was adjusted so that the powder surface of the pellets in the container was nearly straight. When the powder surface of the rotating pellets became straight, the angle between the powder surface and the horizontal plane was measured using a goniometer attached to the measuring instrument to determine the flow surface angle (C). The results are shown in Table 1.

[0059] After determining the flow surface angle (C), the container was rotated at 1-2 rpm for 2-3 minutes, and the rotation was stopped at the highest angle just before the top of the pellets crumbled. In this state, the angle between the powder surface and the horizontal plane was measured with the goniometer attached to the measuring device to determine the rotational angle of repose (D). The results are shown in Table 1.

[0060] The pellets obtained were evaluated according to the evaluation methods described below. The evaluation results are shown in Table 1.

[0061] [Examples 2 to 10, Comparative Examples 1 to 3] Pellets were produced and evaluated in the same manner as in Example 1, except that the production method, type of lubricant, amount of lubricant added, and sieving conditions were changed as shown in Table 1. The evaluation results are shown in Table 1.

[0062] [Evaluation method] (1) Half-width The particle size distribution of the equivalent circle diameter (diameter) of the pellets was determined from the equivalent circle diameter (diameter) calculated for 500 g of pellets using Verder Scientific's "CAMSIZER XT" by dynamic image analysis in accordance with ISO 13322-2 (2006). The equivalent circle diameter is determined from the area of ​​a two-dimensionally observed pellet image. The half-width (mm) was calculated from the obtained particle size distribution.

[0063] (2) Bumps, streaks, and thickness variations on the film A single layer film formation test was carried out on the pellets obtained in the Examples and Comparative Examples using an extruder and a T-die having the following specifications. Extruder: "GT-40-A" manufactured by Plastics Engineering Research Institute Co., Ltd. Type: Single-screw extruder (non-vent type) L / D:26 CR:2.8 Caliber: 40mmφ Screw: Double flight type Rotation speed: 40 rpm Drive: Sumitomo Heavy Industries DC motor SCR-DC218B Motor capacity: DC 7.5KW (rated 45A) Extruder heater: 3-split type C1 / C2 / C3=190℃ / 240℃ / 260℃ Ten resin pressure gauges are installed at equal intervals on the cylinder. Die width: 550mm Resin temperature inside die: 260℃ Take-up speed: 10m / min

[0064] One hour after the start of film production, the number of particles (visible to the naked eye with a diameter of approximately 100 μm or more) in the film was counted and the number of particles was measured at 1.0 m. 2 This is converted to 1.0m 2 The appearance of the film was evaluated based on the number of lumps as follows: If the evaluation was A to D, it was determined that the occurrence of lumps was suppressed. A: Less than 20 pieces B: More than 20 and less than 50 C: More than 50 and less than 80 D: More than 80 and less than 100 E: More than 100

[0065] One hour after the start of film production, streaks (visible to the naked eye with a width of approximately 100 μm or more) in the film were counted and the number of streaks was set to 1.0 m. 2 This streak is converted to 1.0m 2 The appearance of the film was evaluated based on the number of streaks as follows: If the evaluation was A to C, it was determined that streaks were suppressed. A: Less than 2 B: 2 or more but less than 6 C: 6 or more but less than 10 D: 10 or more

[0066] One hour after the start of film production, a sample was taken in the MD direction, and the thickness over a 2 m length range was measured using a continuous thickness meter. Measurements were taken at 25 mm intervals, and the standard deviation (μm) of the values ​​obtained was calculated, and thickness unevenness was evaluated according to the following criteria. If the evaluation was A to D, it was determined that thickness unevenness had been suppressed. A: 1.0μm or less B: More than 1.0μm and less than 2.0μm C: More than 2.0μm and less than 4.0μm D: More than 4.0μm and less than 6.0μm E: More than 6.0μm

[0067] (3) Pressure fluctuation A single-layer film production test was conducted in the same manner as in (2) above. During the 6-hour continuous film production from 1 hour to 7 hours after the start of film production, the difference ΔP between the maximum pressure PMAX and the minimum pressure PMIN at the resin pressure P10 at the tip of the extruder (10th extruder) was evaluated according to the following criteria. If the evaluation was A to D, it was determined that pressure fluctuations were suppressed. A: ΔP≦0.3 B: 0.3<ΔP≦0.6 C: 0.6<ΔP≦1.0 D: 1.0<ΔP≦1.5 E:1.5<ΔP

[0068] (4) Torque stability During continuous film production from 1 hour to 6 hours after the start of film production (2) above, the fluctuation range of the motor torque of the extruder was evaluated according to the following criteria. If the rating was A to D, it was determined that torque fluctuation was suppressed. A: Fluctuation range 5N·m or less B: Fluctuation range: Over 5 N·m and up to 10 N·m C: Fluctuation range: over 10 N·m and up to 15 N·m D: Fluctuation range over 15 N m and below 20 N m E: Fluctuation range over 20 N·m

[0069] [Table 1] [Explanation of symbols]

[0070] 1 Raw material supply section 2, 4, 6 Full flight screw section 3, 5 Reverse flight screw section 7. Vent 8 Trace component addition section 9. Temperature Sensor 10 Cylinder barrel 11 Discharge port 20 Twin-screw extruder

Claims

1. A pellet made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a lubricant (B), the lubricant (B) is a higher fatty acid ester, a higher fatty acid amide, a low-molecular-weight polyolefin, a higher alcohol, a fluorinated ethylene resin, or an inorganic substance; The content of the lubricant (B) in the pellets is 5 ppm or more and 150 ppm or less, The flow surface angle (C) of the pellet is 40 degrees or less, The rotational angle of repose (D) of the pellet is 40 degrees or less, and Pellets having a ratio (D / C) of a flow surface angle (C) to a rotational angle of repose (D) of 0.8 or more and 0.97 or less.

2. 2. The pellet according to claim 1, wherein the half width of the particle size distribution of the equivalent circle diameter of the pellet is 0.7 mm or less.

3. 3. The pellet according to claim 1, wherein the pellet has a cylindrical, spherical or spheroidal shape.

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