pellets made from a resin composition

Abstract

To provide a pellet containing an EVOH having stable behavior during melt molding and capable of obtaining a molding with less defects.SOLUTION: A pellet (C) made of a resin composition containing an EVOH (A) and a lubricant (B), wherein the content of the lubricant (B) in the pellet (C) is 5 ppm or more and 150 ppm or less, and the ratio (q / p) of the bulk specific gravity (q) of a standard pellet (D) containing 2000 ppm of the lubricant (B) to the bulk specific gravity (p) of the pellet (C) is less than 0.97.SELECTED DRAWING: None

Description

【Technical Field】 【0001】 The present invention relates to pellets composed of a resin composition containing an ethylene-vinyl alcohol copolymer and a lubricant. 【Background Art】 【0002】 Ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as EVOH) is a thermoplastic resin excellent in gas barrier properties, fuel barrier properties, chemical resistance, stain resistance, non-chargeability, mechanical strength, etc. Taking advantage of such characteristics, EVOH is molded into forms such as films, sheets, bottles, cups, tubes, pipes, etc., and is used in various applications including packaging containers. 【0003】 It is known that the moldability of EVOH depends on the behavior of molten EVOH in an extruder. During extrusion molding, problems such as large fluctuations in the motor torque of the extruder and pressure fluctuations (fluctuations in resin pressure) occur. 【0004】 On the other hand, it is known that increasing the set temperature of the extruder reduces unmolten EVOH and stabilizes the behavior. However, if the set temperature is too high, thermal degradation of EVOH is promoted, and problems such as bumps occurring on the obtained film occur. 【0005】 For these reasons, there is a demand for EVOH pellets that have stable behavior during melt molding and can obtain molded products with few defects. 【0006】 Patent Document 1 describes an ethylene-vinyl ester copolymer saponified pellet in which 10 to 400 ppm by weight of higher fatty acid amide is attached to the surface of the ethylene-vinyl ester copolymer saponified pellet, wherein when 100 g of the pellet is washed in 300 ml of deionized water using a 500 ml beaker with a three-one motor having helical blades at a water temperature of 23 °C and a rotation speed of 250 rpm for 1 hour, the amount of higher fatty acid amide removed is less than 35% by weight of the amount attached to the surface before washing. 【0007】 Patent Document 2 describes a method for producing ethylene-vinyl acetate copolymer saponified pellets, which involves extruding a solution of ethylene-vinyl acetate copolymer saponified material into a solidifying liquid in strand form from a nozzle made of one of the following materials: an aluminum compound, a glass compound, or a thermosetting resin, and then cutting the strand. 【0008】 Patent Document 3 describes a method for producing ethylene vinyl alcohol copolymer resin pellets, which involves supplying an ethylene-vinyl alcohol copolymer to an extruder, maintaining the resin melting temperature in the extruder in the range of 70 to 170°C, adjusting the amount of moisture in the extruder so that the moisture content immediately after the copolymer is discharged from the extruder is 5 to 40% by weight, and cutting the copolymer after extrusion. [Prior art documents] [Patent Documents] 【0009】 [Patent Document 1] Japanese Patent Publication No. 2012-92160 [Patent Document 2] Japanese Patent Application Publication No. 11-77672 [Patent Document 3] Japanese Patent Publication No. 2001-96529 [Overview of the project] [Problems that the invention aims to solve] 【0010】 However, when melt-molding pellets obtained by the manufacturing methods described in Patent Document 1 or Patent Documents 2 and 3, the behavior of EVOH was still unstable, which sometimes caused problems. 【0011】 The present invention was made to solve the above problems, and aims to provide pellets containing EVOH that exhibit stable behavior during melt molding and produce molded products with few defects. [Means for solving the problem] 【0012】 The above problem is solved by providing a pellet (C) made of a resin composition containing EVOH (A) and a lubricant (B), wherein the content of lubricant (B) in the pellet (C) is 5 ppm or more and 150 ppm or less, and the ratio (q / p) of the bulk density (q) of a standard pellet (D) containing 2000 ppm of lubricant (B) to the bulk density (p) of the pellet (C) is less than 0.97. 【0013】 In this case, it is preferable that the half-width in the particle size distribution of the equivalent circular diameter of the pellet (C) is 0.7 mm or less. It is also preferable that the bulk density (p) is 71 g / 100 ml or more. Furthermore, it is preferable that the shape of the pellet (C) is columnar, spherical, or spheroidal. [Effects of the Invention] 【0014】 The pellets (C) of the present invention exhibit stable behavior during melt molding, with minimal fluctuations in the extruder motor torque and suppressed pressure fluctuations. By using such pellets, molded products such as films with fewer defects, including blemishes, flow irregularities, and thickness variations can be obtained. [Brief explanation of the drawing] 【0015】 [Figure 1] This is a schematic diagram of the twin-screw extruder used in the examples and comparative examples. [Modes for carrying out the invention] 【0016】 The pellet (C) of the present invention consists of a resin composition containing EVOH (A) and a lubricant (B), wherein the lubricant (B) content in pellet (C) is 5 ppm or more and 150 ppm or less, and the ratio (q / p) of the bulk density (p) of pellet (C) to the bulk density (q) of a standard pellet (D) containing 2000 ppm of lubricant (B) is less than 0.97. 【0017】 The EVOH(A) used in the present invention is obtained by saponifying an ethylene-vinyl ester copolymer, and among these, the EVOH(A) obtained by saponifying an ethylene-vinyl acetate copolymer is preferred. 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. 【0018】 Furthermore, the degree of saponification of EVOH(A) is preferably 90 mol% or higher. If the degree of saponification is less than 90 mol%, the barrier properties and melt moldability may be insufficient. More preferably, the degree of saponification is 95 mol% or higher, even more preferably 99 mol% or higher, and particularly preferably 99.3 mol% or higher. On the other hand, the degree of saponification of EVOH(A) may be 99.9 mol% or lower. The degree of saponification is a value measured in accordance with JIS K6726. 【0019】 The pellet (C) of the present invention contains 5 ppm or more and 150 ppm or less of the lubricant (B). By containing the lubricant (B) within the above range, the pellet (C) of the present invention tends to particularly suppress pressure fluctuations and motor torque fluctuations during melt molding. Examples of the lubricant (B) include higher fatty acid esters (such as methyl esters, isopropyl esters, butyl esters, octyl esters, etc. of lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, etc.); higher fatty acid amides (saturated aliphatic amides such as stearic acid amide, bis stearic acid amide, behenic acid amide, etc., unsaturated fatty acid amides such as oleic acid amide, erucic acid amide, etc., bis fatty acid amides such as ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, ethylene bis lauric acid amide, etc.); low molecular weight polyolefins (such as low molecular weight polyethylene or low molecular weight polypropylene having a number average molecular weight of about 500 to 10,000 or their acid-modified products); higher alcohols, fluorinated ethylene resins; inorganic substances such as silicon dioxide (synthetic silica particles), clay, talc, mica, etc. Among them, higher fatty acid esters, higher fatty acid amides or inorganic substances are preferably used, more preferably higher fatty acid amides or inorganic substances, and still more preferably higher fatty acid amides. 【0020】 From the viewpoint of being able to melt-mold more stably and further suppressing defects in the molded product after melt molding, the content of the lubricant (B) is preferably 120 ppm or less, more preferably 100 ppm or less, still more preferably 80 ppm or less, and particularly preferably 60 ppm or less. Also from the same viewpoint, the content of the lubricant (B) is preferably 8 ppm or more, more preferably 10 ppm or more, still more preferably 20 ppm or more, and particularly preferably 30 ppm or more. 【0021】 In addition to EVOH (A) and the lubricant (B), the resin composition constituting the pellet (C) of the present invention may further contain at least one additive selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts, and alkaline earth metal salts. Thereby, the quality such as thermal stability can be improved. 【0022】 Examples of the carboxylic acid include oxalic acid, succinic acid, benzoic acid, citric acid, acetic acid, lactic acid, etc. Among these, acetic acid is preferable from the viewpoints of cost, availability, etc. If the content of the carboxylic acid in the EVOH resin pellet after drying of the present invention is too small, coloring may occur during melt molding, and if it is too large, the interlayer adhesion may become insufficient. Therefore, 10 to 5000 ppm is preferable. The content of the carboxylic acid is preferably 30 ppm or more, more preferably 50 ppm or more. Also, the content of the carboxylic acid is preferably 1000 ppm or less, more preferably 500 ppm or less. 【0023】 Examples of the boron compound include, but are not limited to, boronic acids, boronic esters, borates, boron hydrides, etc. Specifically, examples of the boronic acids include orthoboric acid, metaboric acid, tetraboric acid, etc., examples of the boronic esters include triethyl borate, trimethyl borate, etc., and examples of the borates include alkali metal salts, alkaline earth metal salts, borax, etc. of the above various boronic acids. Among these compounds, orthoboric acid (hereinafter simply referred to as boric acid) is preferable. If the content of the boron compound in the EVOH resin pellet after drying of the present invention is too small, the effect of improving thermal stability is small, and if it is too large, it may gel and cause poor moldability. Therefore, 10 to 2000 ppm in terms of boron is preferable, and 50 to 1000 ppm is more preferable. 【0024】 Examples of phosphate compounds include various acids such as phosphoric acid and phosphorous acid, and their salts. The phosphate may be included in the form of monophosphate, diphosphate, or tertiary phosphate, and the cation species is not particularly limited, but alkali metal salts and alkaline earth metal salts are preferred. In particular, 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 1000 ppm in terms of phosphate root. By adding it within this range, it is possible to suppress discoloration of the molded product and the occurrence of gel and lumps. If the content of the phosphate compound is less than 1 ppm, discoloration during melt molding may become severe. Also, if it exceeds 1000 ppm, the occurrence of gel and lumps in the molded product may increase. 【0025】 Examples of alkali metal salts include monovalent metal aliphatic carboxylates, aromatic carboxylates, phosphates, and metal complexes. For example, sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, and sodium salts of ethylenediaminetetraacetic acid are used. Among these, sodium acetate, potassium acetate, and sodium phosphate are preferred. The alkali metal salt content in the dried EVOH resin pellets of the present invention is preferably 5 to 5000 ppm in terms of alkali metal elements. More preferably 20 to 1000 ppm, and even more preferably 30 to 750 ppm. 【0026】 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 anionic species of the alkaline earth metal salt is not particularly limited, but acetate salts and phosphate salts are preferred. The alkaline earth metal content in the dried EVOH resin pellets of the present invention is preferably 10 to 1000 ppm in terms of metal equivalent, and more preferably 20 to 500 ppm. If the alkaline earth metal content is less than 10 ppm, the improvement effect on long-run performance may be insufficient. Also, if it exceeds 1000 ppm, discoloration during resin melting may become severe. 【0027】 The resin composition constituting the pellet (C) of the present invention may contain other components besides EVOH (A) and lubricant (B), as long as they do not impair the effects of the present invention. Examples of other components include heat stabilizers, ultraviolet absorbers, antioxidants, colorants, fillers, plasticizers, photoinitiators, deodorizers, antistatic agents, lubricants, drying agents, fillers, pigments, dyes, processing aids, flame retardants, and antifogging agents. The content of other components in the resin composition is preferably 0.001 to 1% by mass. 【0028】 In the resin constituting the pellet (C), the proportion of EVOH(A) 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 substantially only of EVOH(A), or consist only of EVOH(A). Furthermore, the proportion of EVOH(A) and lubricant (B) in the pellet (C) 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. 【0029】 In the present invention, the ratio (q / p) of the bulk density (q) of a standard pellet (D) containing 2000 ppm of lubricant (B) to the bulk density (p) of pellet (C) must be less than 0.97. Here, the standard pellet (D) is obtained in the same manner as pellet (C), except that the amount of lubricant (B) added is adjusted so that the content is 2000 ppm. Because the ratio (q / p) is less than 0.97, that is, because the bulk density (p) of the pellet (C) of the present invention is higher than the bulk density (q) of the standard pellet (D), surprisingly, during melt molding, the motor torque fluctuation of the extruder is small, and pressure fluctuations are also suppressed, resulting in stable behavior of the pellet (C). By using such a pellet (C), a high-quality molded product can be obtained with fewer imperfections, flow variations, thickness variations, etc. The ratio (q / p) is preferably 0.95 or less, more preferably 0.93 or less, and even more preferably 0.90 or less. On the other hand, the ratio (q / p) is usually 0.8 or higher. The bulk density of the pellets can be measured by the method described in the examples. The ratio (q / p) can be adjusted by adjusting the amount of lubricant (B) added, the type of lubricant (B), the shape of the pellets (C), and the full width at half maximum in the particle size distribution of the equivalent circle diameter of the pellets. 【0030】 From the viewpoint of further stabilizing the behavior of the pellets (C) during melt molding, it is preferable that the bulk density (p) of the pellets (C) be 71 g / 100 ml or higher. It is more preferable that the bulk density (p) be 72 g / 100 ml or higher, and even more preferable that it be 73 g / 100 ml or higher. On the other hand, the bulk density (p) is usually 80 g / 100 ml or lower. The bulk density (p) can be adjusted by adjusting the amount of lubricant (B) added, the type of lubricant (B), the shape of the pellets (C), and the full width at half maximum in the particle size distribution of the equivalent circle diameter of the pellets. 【0031】 In the present invention, it is preferable that the half-width in the particle size distribution of the equivalent circle diameter of the pellet (C) is 0.7 mm or less. By using pellets with a small half-width and uniform particle size, it is possible to further suppress blemishes and streaks that occur on the surface of films and the like. From the viewpoint of suppressing pressure fluctuations in the extruder during melt molding and reducing fluctuations in the motor torque of the extruder, it is more preferable that the half-width is 0.5 mm or less, and even more preferable that it is 0.4 mm or less. On the other hand, the half-width is usually 1.0 mm or more. The half-width of the particle size distribution can be determined from the distribution of diameter values ​​obtained as the equivalent circle diameter from the area of ​​a large number of pellet images observed in two dimensions. Specifically, it can be measured using a dynamic image analysis device. 【0032】 Thus, methods for obtaining pellets (C) with uniform particle size include methods for devising cutting methods and methods for sieving. Among these, the sieving method is preferred because it can reliably and easily reduce the full width at half maximum of the particle size distribution. When sieving, it is preferable to use sieves with at least two different mesh sizes to remove pellets that are too large and pellets that are too small, and it is more preferable to use sieves with three different mesh sizes. Specifically, a preferred embodiment is to sieve using sieves stacked in the order of 3.5-6.5 mesh / 7 mesh / 8 mesh, a more preferred embodiment is to sieve using sieves stacked in the order of 5-6.5 mesh / 7 mesh / 8 mesh, and an even more preferred embodiment is to sieve using sieves stacked in the order of 6.5 mesh / 7 mesh / 8 mesh. 【0033】 In the present invention, the shape of the pellet (C) is not particularly limited, but it is preferably columnar, spherical, or ellipsoidal. Here, columnar includes prismatic and cylindrical shapes. An ellipsoidal shape is one in which the radii of two orthogonal axes are equal. Furthermore, the terms columnar, spherical, and ellipsoidal are not used in a strict sense, and a slight distortion is acceptable. In addition, as long as it does not hinder the effects of the present invention, some pellets of shapes other than columnar, spherical, or ellipsoidal may be included in the pellets of the present invention. 【0034】 The length of the pellet (C) in the longitudinal direction is not particularly limited, but is preferably 2.0 to 4.0 mm. Similarly, the length of the pellet (C) in the short direction is not particularly limited, but is preferably 2.0 to 4.0 mm. 【0035】 The following describes a method for producing EVOH(A) used in the present invention. The method for producing EVOH(A) used in the present invention is not particularly limited. A preferred method includes the steps of adding an alkaline catalyst to a methanol solution of an ethylene-vinyl ester copolymer, saponifying the ethylene-vinyl ester copolymer to obtain a methanol solution of an ethylene-vinyl alcohol copolymer, and removing the solvent from the solution after saponification. 【0036】 First, the process of obtaining a methanol solution of ethylene-vinyl alcohol copolymer will be described. Using a radical initiator as a catalyst, ethylene and vinyl ester are copolymerized 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, methanol is used as the solvent for solution polymerization. Either a continuous or batch process 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 process) is 2 to 15 hours, preferably 3 to 11 hours. The polymerization rate is 10 to 90%, preferably 30 to 80%, relative to the input vinyl ester. The resin content in the solution after polymerization is 5 to 85%, preferably 20 to 70%. 【0037】 The catalysts used include azonitrile-based 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. 【0038】 Monomers copolymerizable with ethylene and vinyl esters, such as alkenes like propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diasiloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy Roxy-3-methyl-1-butene, 3,4-diasiloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diasiloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diasiloxy-1-hexene, 1,3-diacetoxy-2-methyl Alkenes having ester groups such as lenpropane or their saponides; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, 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 vinylsulfonic acid, allylsulfonic acid, and methallylsulfonic acid, or their salts; vinylsilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane, and γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, etc. can also be copolymerized in small amounts. In this case, the copolymerization amount is usually 5 mol% or less, and it is preferable that they are substantially absent. 【0039】 After polymerization for a predetermined time and reaching a predetermined polymerization rate, a polymerization inhibitor is added as needed, and unreacted ethylene gas is evaporated and removed, followed by the removal of unreacted vinyl ester. As a method for removing unreacted vinyl ester from the ethylene-vinyl ester copolymer solution from which ethylene has been evaporated, for example, the copolymer solution is continuously supplied at a constant rate from the top of a column packed with Raschig rings, methanol vapor is blown in from the bottom of the column, a mixed vapor of methanol and unreacted vinyl ester is distilled from the top of the column, and the ethylene-vinyl ester copolymer solution from which the unreacted vinyl ester has been removed is taken out from the bottom of the column. 【0040】 An alkaline catalyst is added to a methanol solution of the 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 the ethylene-vinyl alcohol copolymer. Both continuous and batch saponification methods are possible. Sodium hydroxide, potassium hydroxide, alkali metal alcohols, etc., can be used as the alkaline catalyst. The saponification conditions are as follows: The concentration of the ethylene-vinyl ester copolymer is preferably 10 to 50% by mass. The saponification reaction temperature is preferably 30 to 150°C. The amount of alkaline catalyst used is preferably 0.005 to 0.6 equivalents (per vinyl ester unit). The saponification time (average residence time in the case of continuous saponification) is preferably 10 minutes to 6 hours. 【0041】 A solution containing EVOH(A) is obtained in this way, after which 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 allowing it to solidify, thereby reducing the solvent content. Alternatively, water may be mechanically squeezed out in an extruder or kneader, or water vapor may be evaporated from a vent. After the solvent has been removed in this way, the material is cut. The method for obtaining pellets by cutting is not particularly limited. The solidified, water-containing strand can be cut with a cutter, or the material, whose water content has been reduced in an extruder or kneader, can be cut in a fluid state using a hot cutter or underwater cutter. 【0042】 After cutting into pellets, the material is dried. The drying method is not particularly limited, and a hot air dryer can be used. The dryer can be a fluidized bed dryer or a static dryer, or a combination of both. Among these, a method in which the material is first dried by the fluidized bed drying method and then subsequently dried by the static drying method is preferred. The drying temperature is not particularly limited, but a temperature of around 70 to 120°C is usually used, and the temperature can be increased as drying progresses. The moisture content after drying is usually 1% by mass or less, preferably 0.5% by mass or less. 【0043】 The pellets (C) of the present invention consist of a resin composition containing EVOH (A) and a lubricant (B). The method for producing the resin composition used in the present invention is not particularly limited, but a method of obtaining a resin composition containing EVOH (A) and a lubricant (B) by dry blending EVOH (A) and a lubricant (B) is preferred. In this case, it is preferable to use EVOH (A) pellets that have been pre-formed into pellet shape. In this way, pellets consisting of a resin composition containing EVOH (A) and a lubricant (B) can be easily obtained. 【0044】 When the pellet (C) of the present invention contains 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 such as immersing a hydrated pellet in an aqueous solution containing the additive to impregnate it, or injecting an aqueous solution containing the additive into hydrated and fluid EVOH using an extruder or the like, kneading it, and then cutting it to produce pellets, can be employed. 【0045】 Various molded products such as films, sheets, containers, pipes, and fibers can be obtained by melt molding using the pellets (C) of the present invention. Possible melt molding methods include extrusion molding, inflation extrusion, blow molding, melt spinning, and injection molding. The melting temperature varies depending on the melting point of EVOH(A), but is preferably around 150 to 270°C. [Examples] 【0046】 The present invention will be described in more detail below using examples. 【0047】 [Manufacturing method 1] 100 parts by mass of ethylene-vinyl acetate copolymer with an ethylene content of 32 mol% and 400 parts by mass of methanol were charged into a saponification reactor. Furthermore, 0.16 parts by mass of a methanol solution of sodium hydroxide (80 g / L) (sodium hydroxide / vinyl acetate units = 0.4 / 1, molar ratio) were charged. Nitrogen gas was blown into the reactor, and the reaction was carried out at 60°C for 4 hours while removing the by-product methyl acetate along with the methanol. The reaction was then stopped by neutralization with acetic acid, yielding a methanol solution of EVOH consisting of 57 parts by mass of EVOH and 75 parts by mass of methanol. The degree of saponification of this EVOH was 99.95 mol%. 【0048】 An EVOH solution was extruded into water through a gold plate with a circular opening and solidified into strands. These strands were then cut to obtain pellets approximately 3 mm in diameter and 5 mm in length. The pellets were dehydrated using a centrifuge, and the dehydration process was repeated by adding a large amount of water. 【0049】 The resulting pellets (EVOH, ethylene unit content 32 mol%, degree of saponification 99.95 mol%, water content 26 mass) were fed into the twin-screw extruder shown in Figure 1. The resin temperature at the discharge port was set to 100°C, and a treatment solution consisting of an aqueous solution of acetic acid / boric acid / sodium acetate / magnesium acetate / potassium dihydrogen phosphate was added from the trace component addition section at the tip of the discharge port, as shown in Figure 1. The input rate of EVOH per unit time was 10 kg / hr (including the mass of contained water), and the input rate of the treatment solution per unit time was 0.65 L / hr. The composition of the treatment solution was an aqueous solution containing 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. 【0050】 Type: Twin-screw extruder L / D: 45.5 Caliber: 30mmφ Screw: Fully meshing in the same direction Rotation speed: 300 rpm Motor capacity: DC22KW Heater: 13-section type Number of die holes: 6 holes (3mm diameter) Die resin temperature: 105℃ Center hot cutter rotation speed: 600~2800rpm 【0051】 The EVOH resin composition discharged from the outlet was extruded through a die with six 3mm diameter holes. The temperature of the EVOH resin composition inside the die at this time was 105°C. The extruded EVOH was cut while still in a fluid state using a center hot cutter. The rotation speed of the cutter blade was 2700 rpm. 【0052】 The moisture content of the pellets after extrusion was 17% by mass. The obtained pellets were dried in a fluidized bed dryer at 100°C for 15 hours, and then in a static dryer at 100°C for another 15 hours. As a result, the moisture content of the dried pellets was 0.3% by mass. The acetic acid content in the dried pellets was 300 ppm, the boron compound content was 270 ppm (boron equivalent), the phosphate compound content was 100 ppm (phosphate equivalent), the alkali metal salt content was 40 ppm (potassium, metal equivalent) and 130 ppm (sodium, metal equivalent), and the alkaline earth metal salt content was 50 ppm (magnesium, metal equivalent). The MFR (190°C, 2160 g load) was 1.5 g / 10 min. 【0053】 [Manufacturing method 2] 100 parts by mass of ethylene-vinyl acetate copolymer with an ethylene content of 32 mol% and 400 parts by mass of methanol were charged into a saponification reactor. Furthermore, 0.16 parts by mass of a methanol solution of sodium hydroxide (80 g / L) (sodium hydroxide / vinyl acetate units = 0.4 / 1, molar ratio) were charged. Nitrogen gas was blown into the reactor, and the reaction was carried out at 60°C for 4 hours while removing the by-product methyl acetate along with the methanol. The reaction was then stopped by neutralization with acetic acid, yielding a methanol solution of EVOH consisting of 57 parts by mass of EVOH and 75 parts by mass of methanol. The degree of saponification of this EVOH was 99.95 mol%. 【0054】 An EVOH solution was extruded into water through a gold plate with a circular opening and solidified into strands. These strands were then cut to obtain pellets approximately 3 mm in diameter and 5 mm in length. The pellets were dehydrated using a centrifuge, and the dehydration process was repeated by adding a large amount of water. 【0055】 3.5 kg of the resulting pellets (EVOH, ethylene unit content 32 mol%, degree of saponification 99.95 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 were drained, and the resulting EVOH resin composition pellets (water content 35% by mass) were dried in a fluidized bed dryer at 80°C for 15 hours, followed by drying in a static dryer at 100°C for 24 hours to obtain dried pellets (water content 0.3% by mass). 【0056】 The dry pellets contained 300 ppm of acetic acid, 270 ppm of boron compounds (in boron equivalent), 100 ppm of phosphate compounds (in phosphate equivalent), 40 ppm of potassium and 130 ppm of sodium as alkali metal salts, and 50 ppm of magnesium as alkaline earth metal. The MFR (at 190°C and 2160 g load) was 1.5 g / 10 min. 【0057】 [Example 1] Stearic acid bisamide (lubricant) was added to the dried pellets obtained in the above manufacturing method 1, and the mixture was dry-blended using a blender. The amount of lubricant added was adjusted so that the lubricant content relative to the pellets was 5 ppm. 【0058】 Subsequently, the pellets were passed through a sieve consisting of 6.5 mesh, 7 mesh, and 8 mesh sieves in that order for 10 minutes, and the pellets remaining on the 8 mesh were collected to obtain pellet (C) of Example 1. The obtained pellet (C) was ellipsoidal in shape, with a longitudinal length of 3.2 mm and a transverse length of 2.1 mm. 【0059】 The bulk density (p) of the above pellet (C) was determined. The results are shown in Table 1. In addition, a standard pellet (D) was obtained in the same manner as above, except that the amount of lubricant added was adjusted so that the lubricant content relative to the pellet was 2000 ppm. The bulk density (q) of the standard pellet (D) was then determined. The bulk density (q) of the standard pellet (D) and the ratio of bulk density (q) to bulk density (p) (q / p) are shown in Table 1. 【0060】 The obtained pellets (C) were evaluated according to the evaluation method described later. The evaluation results are shown in Table 1. 【0061】 [Example 2~ 7 Comparative Example 1~ 6 ] As shown in Table 1, pellets (C) and standard pellets (D) were prepared and evaluated in the same manner as in Example 1, except that the manufacturing method, type of lubricant, amount of lubricant added, and sieving conditions were changed. The evaluation results are shown in Table 1. 【0062】 [Evaluation Method] (1) Blemishes, streaks, and thickness variations in the film-formed product Single-layer film formation tests were performed on pellets (C) obtained in the examples and comparative examples using an extruder and T-die with the following specifications. Extruder: "GT-40-A" manufactured by Plastics Engineering Laboratory Co., Ltd. Type: Single-screw extruder (non-vented type) L / D: 26 CR:2.8 Caliber: 40mmφ Screw: Double flight type Rotation speed: 40 rpm Drive unit: Sumitomo Heavy Industries, Ltd. DC motor SCR-DC218B Motor capacity: DC 7.5KW (rated 45A) Extruder heater: 3-part type C1 / C2 / C3 = 190℃ / 240℃ / 260℃ Ten resin pressure gauges are installed on the cylinder at equal intervals. Die width: 550mm Resin temperature inside die: 260℃ Pickup speed: 10m / min 【0063】 Count the number of particles (those with a diameter of approximately 100 μm or more that can be seen with the naked eye) in the film one hour after the start of film formation, and count 1.0 m 2 Converted to a unit per 1.0m of this item. 2 The appearance of the film was judged as follows based on the number of imperfections per unit area. A rating of A to D indicated that the imperfections were suppressed. A: Less than 20 pieces B: More than 20, and 50 or less. C: More than 50, and 80 or less. D: More than 80, and less than or equal to 100. E: More than 100 【0064】 One hour after the start of film formation, count the number of flow spots in the film (spots with a width of approximately 1 cm or more that can be seen with the naked eye by holding the film up to a fluorescent light and observing a change in refractive index), and count 1.0 m 2 This was converted to an average of 1.0m. 2 The appearance of the film was judged as follows based on the number of streaks per unit. If the evaluation was A to C, it was determined that the streaks were suppressed. A: Less than 2 B: 2 or more but less than 6 C: 6 to less than 10 bottles D: 10 or more 【0065】 In the continuous film deposition described in (1) above, a sample was taken in the MD direction one hour after the start of deposition, and the thickness over a 2m length range was measured using a continuous thickness gauge. The standard deviation (μm) of the values ​​obtained from measurements at 25mm intervals was calculated, and the thickness variation was evaluated according to the following criteria. If the evaluation was A to D, it was judged that the thickness variation was 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 【0066】 (2) Pressure fluctuations A single-layer film formation test was conducted in the same manner as described in (1) above. During continuous film formation for 6 hours, from 1 hour to 7 hours after the start of film formation, the difference ΔP between the maximum pressure PMAX and the minimum pressure PMIN at the resin pressure P10 at the extruder tip (10th position) 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 【0067】 (3) Torque stability During continuous film formation from 1 hour to 6 hours after the start of film formation as described in (1) above, the range of fluctuation in the extruder motor torque was evaluated according to the following criteria. A rating of A to D indicated that the torque fluctuation was suppressed. A: Fluctuation range 5 N·m or less B: Fluctuation range greater than 5 N·m and less than or equal to 10 N·m C: Fluctuation range greater than 10 N·m and less than or equal to 15 N·m D: Fluctuation range over 15 N m and below 20 N m E: Fluctuation range exceeding 20 N·m 【0068】 (4) Half-width The particle size distribution of the pellet's equivalent circle diameter (diameter) was determined for 500g of pellets using Verder Scientific's "CAMSIZER XT" and calculated from the equivalent circle diameter (diameter) according to ISO 13322-2 (2006). This equivalent circle diameter refers to the diameter obtained from the area of ​​the pellet image observed in two dimensions. The half-width (mm) was calculated from the obtained particle size distribution. 【0069】 (5) Bulk density (JIS K-7365) The pellets obtained in the examples and comparative examples were filled into a damped funnel (mouth diameter 33 mmφ) fixed at a height of 20 mm from a metal graduated cylinder. A metal graduated cylinder (volume 100 ml, diameter 45 mm, mass 162.2995 g) was placed below the funnel, and then the damper was removed to allow the pellets to fall naturally into the metal graduated cylinder. After that, the pellets that had risen on the surface of the graduated cylinder were leveled by moving a glass rod once along the rim of the metal cylinder. The mass of resin that entered the metal graduated cylinder was measured, and the bulk density (g / 100 ml) of the pellets was determined to three significant figures. 【0070】 [Table 1] [Explanation of Symbols] 【0071】 1 Raw material supply section 2, 4, 6 Full Flight Screw Section 3.5 Reverse Flight Screw Section 7 Bent 8 Trace component addition section 9. Temperature sensor 10 Cylinder Barrel 11 Discharge port 20 Twin-screw extruder

Claims

[Claim 1] A pellet (C) comprising a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a lubricant (B), The lubricant (B) content in the pellet (C) is 5 ppm or more and 120 ppm or less. Pellet (C) is a pellet in which the ratio (q / p) of the bulk density (q) of a standard pellet (D) containing 2000 ppm of lubricant (B) to the bulk density (p) of pellet (C) is 0.953 or less. [Claim 2] The pellet (C) according to claim 1, wherein the half-width in the particle size distribution of the equivalent circular diameter of the pellet (C) is 0.7 mm or less. [Claim 3] A pellet (C) according to claim 1 or 2, wherein the bulk density (p) is 71 g / 100 ml or more. [Claim 4] The pellet (C) according to any one of claims 1 to 3, wherein the shape of the pellet (C) is columnar, spherical, or ellipsoidal.

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