JP2023093163A - Pellet made of resin composition - Google Patents

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 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) is 5 ppm or more and 150 ppm or less. A recess of a first metal plate is filled with 21 g of the pellet, the recess having a circular recess with a diameter of 8 cm and a depth of 3 mm, carbon paper and copy paper are stuck in this order so as to cover the recess after the filling, a second metal plate with a thickness of 1 mm having the same size as the first metal plate is stuck on the copy paper and pressed at a strength of 20 kg/cm2 to transfer a pellet shape distribution on the copy paper. In a transferred image, a square area of 391 pixels vertically and 406 pixels horizontally that does not contact a disc having a diameter of 8 cm is selected, and the total area of a black portion in the square area calculated by binarization with a threshold value set to a brightness of 180 is 8500 pixels or less.SELECTED DRAWING: None

Description

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

Ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as EVOH) is a thermoplastic resin that is excellent in gas barrier properties, fuel barrier properties, chemical resistance, stain resistance, antistatic properties, mechanical strength, and the like. Taking advantage of such characteristics, EVOH is formed into forms such as films, sheets, bottles, cups, tubes, pipes, etc., and is used for various purposes including packaging containers.

Furthermore, it is known that moldability in melt molding EVOH depends on the melting behavior of EVOH pellets in the molding machine. Therefore, EVOH pellets that can be stably melt-molded and that can suppress defects in molded articles after melt-molding are desired.

Patent Document 1 discloses a saponified ethylene-vinyl ester copolymer pellet having 10 to 400 ppm by weight of a higher fatty acid amide attached to the surface of the saponified ethylene-vinyl ester copolymer. 100 g of pellets were washed in 300 ml of ion-exchanged water using a 500 ml beaker at a water temperature of 23° C. with a three-one motor having a helical blade for 1 hour at a rotation speed of 250 rpm. Ethylene-vinyl ester copolymer saponified pellets are described that are less than 35% by weight.

In Patent Document 2, a solution of a saponified ethylene-vinyl acetate copolymer is extruded into a coagulating liquid from a nozzle made of any one of an aluminum compound, a glass compound, and a thermosetting resin in the form of strands, and then the strands are extruded. A process for producing ethylene-vinyl acetate copolymer saponified pellets that cuts is described.

In Patent Document 3, ethylene-vinyl alcohol copolymer is supplied to an extruder, the resin melting temperature in the extruder is kept in the range of 70 to 170 ° C., and the moisture content immediately after the copolymer is discharged from the extruder describes a method for producing ethylene-vinyl alcohol copolymer resin pellets in which the moisture content in the extruder is adjusted so that the content is 5 to 40% by weight, and the copolymer is cut after extrusion.

Japanese Unexamined Patent Application Publication No. 2012-92160 JP-A-11-77672 JP-A-2001-96529

However, the stability of melt-molding the pellets described in Patent Document 1 and the pellets obtained by the production methods described in Patent Documents 2 and 3 is still insufficient. In addition, suppression of defects in molded articles after melt molding was not sufficient.

The present invention has been made to solve the above problems, and comprises a resin composition containing EVOH that can be stably melt-molded and can suppress defects in molded articles after melt-molding. The purpose is to provide pellets.

The above problem is a pellet made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a lubricant (B), the content of the lubricant (B) being 5 ppm or more and 150 ppm or less, and having a diameter of 8 cm and a depth of 8 cm. The recess of the first metal plate having a circular recess of 3 mm is filled with the pellets 21g, and carbon paper and copy paper are stacked in this order so as to cover the recess after filling, and the size is the same as that of the first metal plate. ^A second metal plate having a thickness of 1 mm having Select a non-contact square area of 391 pixels long and 406 pixels wide, and provide a pellet with a total area of 8500 pixels or less of black parts in the square area calculated by binarization with a threshold value of 180. Solved by providing be done.

At this time, it is preferable that the half width in the particle size distribution of the equivalent circle diameter of the pellets is 0.7 mm or less. Further, it is preferable that the longitudinal length of the pellet is 2.0 to 4.0 mm and the transverse length is 2.0 to 4.0 mm. It is also preferable that the shape of the pellet is columnar, spherical, or spheroidal.

According to the pellet of the present invention, melt molding can be stably performed, and defects in the molded product after melt molding can be suppressed. Therefore, pressure fluctuations in the extruder can be suppressed during melt molding, and fluctuations in motor torque of the extruder can be reduced. In addition, in the film obtained by forming the pellet into a film, it is possible to suppress the generation of pimples and streaks on the film surface, and it is also possible to suppress unevenness in the thickness of the film.

1 is a schematic diagram of a twin-screw extruder used in Examples and Comparative Examples. FIG.

The pellet of the present invention is a pellet made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a lubricant (B), the content of the lubricant (B) is 5 ppm or more and 150 ppm or less, and the diameter The recess of the first metal plate having a circular recess of 8 cm depth of 3 mm is filled with the pellet 21g, and carbon paper and copy paper are stacked in this order so as to cover the recess after filling, the same as the first metal plate. A second metal plate having a thickness of 1 mm having a size is placed on the copy paper and pressed at a strength of 20 kg/cm ² to transfer the pellet shape distribution to the copy paper. A square area of 391 pixels in length and 406 pixels in width that does not come into contact with a circle is selected, and the total area of the black part in the square area calculated by binarization with a threshold of brightness of 180 (hereinafter abbreviated as "plate contact area" ) is 8500 pixels or less.

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

Moreover, the degree of saponification of EVOH (A) is preferably 90 mol % or more. If the degree of saponification is less than 90 mol %, barrier properties and melt moldability may be insufficient. The degree of saponification is more preferably 95 mol% or more, still more preferably 99 mol% or more, and particularly preferably 99.3 mol% or more. On the other hand, the degree of saponification of EVOH (A) may be 99.9 mol% or less. The degree of saponification is a value measured according to JIS K6726.

The pellets of the present invention contain 5 ppm or more and 150 ppm or less of the lubricant (B). When the pellets of the present invention contain the lubricant (B) within the above range, it tends to be possible to suppress pressure fluctuations and motor torque fluctuations particularly during melt molding. Lubricants (B) include higher fatty acid esters (e.g., methyl esters such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and oleic acid, isopropyl esters, butyl esters, octyl esters, etc.); higher fatty acid amides (stearic Saturated fatty amides such as acid amides, stearic acid bisamides and behenic acid amides, unsaturated fatty acid amides such as oleic acid amides and erucic acid amides, ethylene bis stearic acid amides, ethylene bis oleic acid amides, ethylene bis erucic acid amides, ethylene Bis fatty acid amide such as bislauric acid amide, etc.); Low molecular weight polyolefin (for example, low molecular weight polyethylene or low molecular weight polypropylene having a number average molecular weight of about 500 to 10000 or acid-modified product thereof); Higher alcohol, fluoroethylene resin; Silicon dioxide ( synthetic silica particles), clay, talc, and inorganic substances such as mica. Among them, higher fatty acid esters, higher fatty acid amides and inorganic substances are preferred, higher fatty acid amides and inorganic substances are more preferred, and higher fatty acid amides are further preferred.

The content of the lubricant (B) is preferably 120 ppm or less, more preferably 100 ppm or less, from the viewpoint of more stable melt molding and further suppression of defects in the molded product after melt molding. , is more preferably 80 ppm or less, and particularly preferably 60 ppm or less. 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.

The resin composition constituting the pellets of the present invention contains, in addition to EVOH (A) and lubricant (B), at least one selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts. It may contain seed additives. Thereby, qualities such as thermal stability can be improved.

Examples of carboxylic acids include oxalic acid, succinic acid, benzoic acid, citric acid, acetic acid, and lactic acid. Among these, acetic acid is preferred in terms of cost, availability, and the like. If the carboxylic acid content in the dried EVOH resin pellets of the present invention is too low, coloration may occur during melt molding. 10 to 5000 ppm is preferred. The carboxylic acid content is preferably 30 ppm or more, more preferably 50 ppm or more. Also, the content of carboxylic acid is preferably 1000 ppm or less, more preferably 500 ppm or less.

Boron compounds include, but are not limited to, boric acids, borate esters, borates, borohydrides, and the like. Specifically, examples of boric acids include orthoboric acid, metaboric acid, and tetraboric acid. Examples of boric acid esters include triethyl borate and trimethyl borate. Examples include alkali metal salts of acids, alkaline earth metal salts, borax, and the like. Among these compounds, orthoboric acid (hereinafter simply referred to as boric acid) is preferred. If the content of the boron compound in the dried EVOH resin pellets 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. is preferably 10 to 2000 ppm, more preferably 50 to 1000 ppm.

Examples of phosphoric acid compounds include various acids such as phosphoric acid and phosphorous acid, and salts thereof. The phosphate may be contained in any form of primary phosphate, secondary phosphate, and tertiary phosphate, and the cationic species thereof is not particularly limited, but alkali metal salts , alkaline earth metal salts. Among them, it is preferable to add the phosphoric acid compound in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, or dipotassium hydrogen phosphate. The content of the phosphoric acid compound in the dried EVOH resin pellets of the present invention is preferably 1 to 1000 ppm in terms of phosphate radical. By adding in such a range, it is possible to suppress the coloration of the molding and the occurrence of gels and spots. If the content of the phosphoric acid compound is less than 1 ppm, there is a possibility that the coloration during melt molding may become severe. On the other hand, if it exceeds 1000 ppm, there is a possibility that gels and pimples are likely to occur in the molding.

Alkali metal salts include monovalent metal aliphatic carboxylates, aromatic carboxylates, phosphates, metal complexes, and the like. Examples thereof include sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, and sodium salts of ethylenediaminetetraacetic acid. Among them, 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 element. More preferably 20 to 1000 ppm, still more preferably 30 to 750 ppm.

Alkaline earth metal salts include magnesium salts, calcium salts, barium salts, beryllium salts, etc. Magnesium salts and calcium salts are particularly preferred. The anion species of the alkaline earth metal salt is not particularly limited, but acetates and phosphates are suitable. The alkaline earth metal content in the dried EVOH resin pellets of the present invention is preferably 10 to 1000 ppm, more preferably 20 to 500 ppm in terms of metal. If the alkaline earth metal content is less than 10 ppm, the effect of improving long-run properties may be insufficient. On the other hand, if it exceeds 1000 ppm, there is a possibility that the coloration during melting of the resin becomes severe.

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

The ratio of EVOH (A) in the resin constituting the pellets of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and even if it is 99% by mass or more, substantially Basically, it may consist of EVOH (A) only, or may consist of EVOH (A) only. In addition, the ratio of EVOH (A) and lubricant (B) in the pellets of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and 99% by mass or more. good too.

The pellets of the present invention have a planar contact area of 8500 pixels or less. If the flat plate contact area of the pellets of the present invention exceeds 8500 pixels, the pressure fluctuation in the extruder cannot be suppressed during melt molding, and the problem that the fluctuation of the motor torque of the extruder increases occurs, resulting in stability. cannot be melt molded. In addition, problems such as formation of bumps, streaks, and uneven thickness on the film surface of a molded product such as a film occur, and defects in the molded product after melt-molding cannot be suppressed. The plate contact area of the pellet of the present invention is preferably 8300 pixels or less, more preferably 8150 pixels or less, even more preferably 7950 pixels or less, and may be 7850 pixels or less, 7750 pixels or less, or 7650 pixels or less. The plate contact area of the pellets of the present invention may be 7000 pixels or more. The plate contact area of the pellets of the present invention can be adjusted by adjusting the content of the lubricant, the type of the lubricant, the shape of the pellet, and the half width in the particle size distribution of the equivalent circle diameter of the pellet.

In the present invention, the half width in the particle size distribution of the equivalent circle diameter of the pellets is preferably 0.7 mm or less. By using pellets with a small half-value width and a 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 reducing fluctuations in motor torque of the extruder, the half width is more preferably 0.5 mm or less, and 0.4 mm or less. is more preferred. On the other hand, the half width is usually 0.1 mm or more. The half width of the particle size distribution can be obtained from the distribution of diameter values obtained as equivalent circle diameters from the areas of a large number of two-dimensionally observed pellet images. Specifically, it can be measured using a dynamic image analyzer.

Methods for obtaining pellets having a uniform particle size include a method of devising a cutting method and a method of sieving. Among them, the method of sieving is preferable because the half width of the particle size distribution can be reliably and easily reduced. At the time of sieving, at least two types of sieves are used to remove pellets that are too large and too small, and it is more preferable to use three types of sieves. Specifically, it is a preferred embodiment to sieve using sieves stacked in the order of 3.5 to 6.5 mesh/7 mesh/8 mesh. It is a more preferred embodiment to sieve using sieves stacked in order of mesh, and a more preferred embodiment is sieving using sieves stacked in order of 6.5 mesh/7 mesh/8 mesh. is.

In the present invention, the shape of the pellet is not particularly limited, but it is preferably columnar, spherical, or spheroidal. The columnar shape as used herein includes a prismatic shape and a columnar shape. A spheroidal shape means that two orthogonal axes have the same radius. Also, the terms columnar, spherical, or spheroidal are not used in a strict sense, and may be slightly distorted. A part of the pellets of the present invention may include pellets having a shape other than columnar, spherical, or spheroidal as long as the effects of the present invention are not impaired.

Although the longitudinal length of the pellet is not particularly limited, it is preferably 2.0 to 4.0 mm. Also, the length of the pellet in the transverse direction is not particularly limited, but it is preferably 2.0 to 4.0 mm. The longitudinal length of the pellet may be the same length as the transverse length. That is, the length in the longitudinal direction of the pellet is at least equal to or longer than the length in the transverse direction. More preferably, the longitudinal length of the pellet is 2.5 to 3.8 mm. On the other hand, the length of the pellet in the transverse direction is more preferably 2.0 to 2.5 mm.

The method for producing EVOH (A) used in the present invention will be described below. The method for producing EVOH (A) used in the present invention is not particularly limited. A preferred production method includes a step of adding an alkali catalyst to a methanol solution of an ethylene-vinyl ester copolymer to saponify the ethylene-vinyl ester copolymer to obtain a methanol solution of an ethylene-vinyl alcohol copolymer; There is a subsequent step of removing the solvent from the solution.

First, the process of obtaining a methanol solution of ethylene-vinyl alcohol copolymer will be described. Ethylene and 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 the ethylene-vinyl acetate polymer. At this time, solution polymerization is performed using methanol as a solvent. Either a continuous system or a batch system may be used. The polymerization temperature is 20-90°C, preferably 40-70°C. The polymerization time (average residence time in the case of 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 charged vinyl ester. The resin content in the solution after polymerization is 5-85%, preferably 20-70%.

Catalysts used are 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), 2,2-azobis-(2-cyclopropylpropionitrile) and other azonitrile initiators and isobutyryl peroxide, kumi Ruperoxyneodecanoate, diisopropylperoxycarbonate, di-n-propylperoxydicarbonate, t-butylperoxyneodecanoate, lauroyl peroxide, benzoyl peroxide, t-butylhydroperoxide and the like. .

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-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, 1,3-diacetoxy-2-methylenepropane and other alkenes having an ester group or saponified products thereof; acrylic acid, methacrylic acid , crotonic acid, unsaturated acids such as itaconic acid or their anhydrides, salts, or mono- or dialkyl esters; acrylonitrile, nitriles such as methacrylonitrile; amides such as acrylamide, methacrylamide; vinylsulfonic acid, allylsulfonic acid, Olefinsulfonic acids such as methallylsulfonic acid or salts thereof; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane, γ-methacryloxypropylmethoxysilane and other vinylsilane compounds; alkyl vinyl ethers, vinyl ketones, It is also possible to co-polymerize a small amount of N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, or the like. The amount of copolymerization in that case is usually 5 mol % or less, and it is preferred that it is substantially absent.

After polymerization for a predetermined time and reaching a predetermined rate of polymerization, a polymerization inhibitor is added as necessary, unreacted ethylene gas is removed by evaporation, and 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 off, for example, the copolymer solution is continuously supplied at a constant rate from the top of a tower packed with Raschig rings, A method of blowing methanol vapor from the bottom of the column, distilling off a mixed vapor of methanol and unreacted vinyl ester from the top of the column, and taking out an ethylene-vinyl ester copolymer solution from which the unreacted vinyl ester has been removed from the bottom of the column is adopted. .

An alkaline catalyst is added to a methanol solution of an ethylene-vinyl ester copolymer from which unreacted vinyl ester has been removed to saponify the vinyl ester component in the copolymer to obtain a methanol solution of an ethylene-vinyl alcohol copolymer. . The saponification method can be either continuous or batchwise. Sodium hydroxide, potassium hydroxide, alkali metal alcoholate and the like are used as the alkali catalyst. 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 system) is preferably 10 minutes to 6 hours.

A solution containing EVOH (A) is thus obtained, after which the solvent is removed. The method for removing the solvent is not particularly limited as long as it can reduce the content of the solvent. By extruding the EVOH solution into a poor solvent such as water and allowing it to solidify, the solvent content can be reduced and solidified. Alternatively, water may be mechanically squeezed out or water vapor may be evaporated from a vent in the extruder or kneader. After removal of the solvent in this manner, cutting is performed. The method of cutting to obtain pellets is not particularly limited. The coagulated strand in a water-containing state can be cut with a cutter, or the strand whose water content has been reduced in an extruder or kneader can be cut in a fluid state with a hot cutter or an underwater cutter.

After cutting into pellet shape, it is dried. A drying method is not particularly limited, and a hot air dryer or the like can be used. The dryer may be a fluidized dryer, a stationary dryer, or a combination thereof. Among these, a method of first drying by a fluidized drying method and then drying by a stationary drying method is preferable. Although the drying temperature is not particularly limited, a temperature of about 70 to 120° C. is usually adopted, and the temperature can be raised as the drying progresses. The moisture content after drying is usually 1% by mass or less, preferably 0.5% by mass or less.

The method for incorporating the lubricant (B) into the EVOH (A) obtained above is not particularly limited. A method of obtaining a resin composition containing At this time, it is preferable to use EVOH (A) pellets that have been formed into pellets in advance. In this way, pellets made of the resin composition containing EVOH (A) and lubricant (B) can be easily obtained.

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. . A method of impregnating the pellets in a hydrated state by immersing them in an aqueous solution containing the additive, or an extruder or the like is used to inject and knead an aqueous solution containing the additive into EVOH in a hydrated and fluid state, and then cut. A method of producing pellets, etc., is employed.

Various moldings such as films, sheets, containers, pipes and fibers can be obtained by melt molding the pellets of the present invention. Extrusion molding, inflation extrusion, blow molding, melt spinning, injection molding and the like can be used as the melt molding method. The melting temperature varies depending on the melting point of EVOH (A) and the like, but is preferably about 150 to 270°C.

EXAMPLES Hereinafter, the present invention will be described more specifically using examples.

[Manufacturing method 1]
100 parts by mass of an ethylene-vinyl acetate copolymer having an ethylene content of 32 mol% and 400 parts by mass of methanol were charged into a saponification reactor, and 0.16 parts by mass of a methanol solution of sodium hydroxide (80 g/L) (hydroxylation sodium/vinyl acetate unit=0.4/1, molar ratio) was charged. Nitrogen gas was blown into the reactor, and the reaction was carried out at 60° C. for 4 hours while removing by-product methyl acetate out of the system together with methanol. Thereafter, the reaction was stopped by neutralization with acetic acid to obtain an EVOH methanol solution containing 57 parts by mass of EVOH and 75 parts by mass of methanol. The degree of saponification of this EVOH was 99.95 mol%.

The EVOH solution was extruded into water through a metal plate with circular openings, solidified into strands, and cut into pellets with a diameter of about 3 mm and a length of about 5 mm. The pellet was deliquored with a centrifuge, and the operation of adding a large amount of water and deliquoring was repeated.

The pellets thus obtained (EVOH, ethylene unit content 32 mol%, degree of saponification 99.95 mol%, water content 26% by mass) were charged into the twin-screw extruder shown in FIG. was set to 100° C., and a treatment liquid consisting of an aqueous solution of acetic acid/boric acid/sodium acetate/magnesium acetate/potassium dihydrogen phosphate was added from the trace component addition portion shown in FIG. The input amount of EVOH per unit time was 10 kg/hr (including the mass of water contained), and the input amount of the treatment liquid per unit time was 0.65 L/hr. It was an aqueous solution containing 3 g/L, 15 g/L boric acid, 4.6 g/L sodium acetate, 3.0 g/L magnesium acetate, and 1.4 g/L potassium dihydrogen phosphate. Specifications of the twin-screw extruder are shown below.

Type: twin screw extruder L/D: 45.5
Diameter: 30mmφ
Screw: Same direction full mesh type Rotation speed: 300 rpm
Motor capacity: DC22KW
Heater: 13 division type Number of die holes: 6 holes (3mmφ)
Resin temperature in die: 105°C
Rotation speed of center hot cutter: 600-2800rpm

The EVOH resin composition drawn out from the ejection port was ejected from a die having six holes of 3 mmφ. At this time, the temperature of the EVOH resin composition in the die was 105°C. The discharged EVOH was cut with a center hot cutter in a fluid state. The rotation speed of the cutter blade was 2700 rpm.

The moisture content of the extruded pellets was 17% by mass. The obtained 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. rice field. The content of acetic acid in the dried pellets is 300 ppm, the content of boron compounds is 270 ppm in terms of boron, the content of phosphoric acid compounds is 100 ppm in terms of phosphate radicals, and the content of alkali metal salts is 40 ppm in terms of potassium. , sodium was 130 ppm in terms of metal, and the content of the alkaline earth metal salt was 50 ppm in terms of magnesium. Also, MFR (190° C., 2160 g load) was 1.5 g/10 min.

[Manufacturing method 2]
100 parts by mass of an ethylene-vinyl acetate copolymer having an ethylene content of 32 mol% and 400 parts by mass of methanol were charged into a saponification reactor, and 0.16 parts by mass of a methanol solution of sodium hydroxide (80 g/L) (hydroxylation sodium/vinyl acetate unit=0.4/1, molar ratio) was charged. Nitrogen gas was blown into the reactor, and the reaction was carried out at 60° C. for 4 hours while removing by-product methyl acetate out of the system together with methanol. Thereafter, the reaction was stopped by neutralization with acetic acid to obtain an EVOH methanol solution containing 57 parts by mass of EVOH and 75 parts by mass of methanol. The degree of saponification of this EVOH was 99.95 mol%.

The EVOH solution was extruded into water through a metal plate with circular openings, solidified into strands, and cut into pellets with a diameter of about 3 mm and a length of about 5 mm. The pellet was deliquored with a centrifuge, and the operation of adding a large amount of water and deliquoring was repeated.

3.5 kg of the pellets thus obtained (EVOH, ethylene unit content 32 mol%, degree of saponification 99.5 mol%, water content 35% by mass), acetic acid 0.4 g / L, sodium acetate 0.4 g / L , magnesium acetate 0.3 g/L, potassium dihydrogen phosphate 0.1 g/L, and boric acid 0.7 g/L. After immersion, the liquid was removed, and the obtained EVOH resin composition pellets (water content: 55% by mass) were dried at 80°C for 15 hours using a fluidized bed dryer and then dried at 100°C for 24 hours using a static dryer. Time drying was performed to obtain dry pellets (water content: 0.3% by mass).

The content of acetic acid in the dry pellets is 300 ppm, the content of boron compounds is 270 ppm in terms of boron, the content of phosphoric acid compounds is 100 ppm in terms of phosphate radicals, the content of alkali metal salts is 40 ppm in terms of potassium as metal, The content of sodium was 130 ppm in terms of metal, and the content of alkaline earth metals was 50 ppm in terms of magnesium. Also, MFR (190° C., 2160 g load) was 1.5 g/10 min.

[Example 1]
Bisamide stearate (lubricant) was added to the dried pellets obtained in the production method 1, and dry blended using a blender. The amount added was adjusted so that the content of the lubricant with respect to the pellets was 5 ppm.

Then, the pellets of Example 1 were obtained by passing the pellets through sieves stacked in order of 6.5 mesh, 7 mesh and 8 mesh for 10 minutes and collecting the pellets remaining on the 8 mesh. The obtained pellet had a spheroidal shape with a length of 3.2 mm in the longitudinal direction and a length of 2.1 mm in the transverse direction.

[Examples 2 to 10, Comparative Examples 1 to 3]
As described in Table 1, pellets were produced in the same manner as in Example 1, except that the manufacturing method, the type of lubricant, the amount of lubricant added, and the sieving conditions were changed, and evaluated according to the evaluation method described later. . Table 1 shows the evaluation results.

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

(2) Flat plate contact area On a SUS304 metal plate with a thickness of 1 mm, a SUS304 metal plate with a thickness of 3 mm cut into a circular shape with a diameter of 8 cm is superimposed, and the circular cut portion obtained in Examples and Comparative Examples. 21 g of the obtained pellets are filled, a carbon sheet is superimposed so as to cover the circular cut part after filling the pellets, a copy paper is superimposed on the carbon sheet, and a SUS304 metal plate with a thickness of 1 mm is placed on the copy paper. and pressed at a strength of 20 kg/cm ² using a press to transfer the pellet shape distribution onto the copy paper. The copy paper was removed from the press, and the carbon-transferred image on the copy paper was captured in an electronic file. The distribution of the particle shape was analyzed by the image processing described later, and the flat plate contact area was obtained.

The flat plate contact area was calculated by image analysis. Image-Pro Plus manufactured by Nippon Roper Co., Ltd. was used as image analysis software. In the image analysis, first, based on the carbon-transferred copying paper, the outline of the carbon-transferred black portion was traced (traced) to calculate the distribution area of the particle shape. The particle shape distribution area was measured for the carbon-transferred black portion for which the contrast was adjusted. This contrast adjustment can be automatically performed by using the "contrast optimum adjustment" command of the image analysis software. Also, by using the binarization “Segmentation (color extraction)” command, the black portion can be separated and extracted from the background (LSCF area) with high accuracy. Specifically, for example, in binarization, the contrast-adjusted image is converted into a black-and-white image. Here, binarization can be performed automatically (for example, binarization after shading correction). A threshold condition for binarization may be set. Here, the total area of the black portion was calculated by setting the threshold value to 180 in brightness. In the image analysis, the circular area with a diameter of 8 cm is 567 pixels, and a square area of 391 pixels in length and 406 pixels in width that does not contact the circle with a diameter of 8 cm was selected, and the total area of the black part in that area was analyzed. .

(3) Blisters, streaks, and uneven thickness of film-formed products A single-layer film-formation test of the pellets obtained in Examples and Comparative Examples was performed using an extruder and a T-die having the following specifications.
Extruder: “GT-40-A” manufactured by Plastic Engineering Laboratory Co., Ltd. Format: Single-screw extruder (non-vented type)
L/D: 26
CR: 2.8
Diameter: 40mmφ
Screw: Double flight type Rotation speed: 40 rpm
Drive machine: DC motor SCR-DC218B manufactured by Sumitomo Heavy Industries, Ltd.
Motor capacity: DC7.5KW (rated 45A)
Extruder heater: 3-split type C1/C2/C3 = 190°C/240°C/260°C
10 resin pressure gauges are installed on the cylinder at equal intervals Die width: 550 mm
Resin temperature in die: 260°C
Take-up speed: 10m/min

One hour after the start of film formation, the number of lumps (those with a diameter of about 100 μm or more that can be seen with the naked eye) in the film was counted and converted to per 1.0 m ² . The appearance of the film was judged as follows based on the number of the particles per 1.0 m ² . If the evaluation was A to D, it was judged that the lump was suppressed.
A: 20 or less B: More than 20 and 50 or less C: More than 50 and 80 or less D: More than 80 and 100 or less E: More than 100

Streaks (those with a width of about 100 μm or more that can be visually confirmed) in the film 1 hour after the start of film formation were counted and converted to per 1.0 m ² . Based on the number of streaks per 1.0 m ² , the appearance of the film was determined as follows. If the evaluation was A to C, it was judged that the streak was suppressed.
A: Less than 2 B: 2 or more and less than 6 C: 6 or more and less than 10 D: 10 or more

After 1 hour from the start of film formation, samples were taken in the MD direction, and the thickness in a length range of 2 m was measured with a continuous thickness meter. The standard deviation (μm) of the values obtained by measuring at intervals of 25 mm was obtained, and the thickness unevenness was evaluated according to the following criteria. If the evaluation was A to D, it was judged that unevenness in thickness could be suppressed.
A: 1.0 µm or less B: 1.0 µm or more and 2.0 µm or less C: 2.0 µm or more and 4.0 µm or less D: 4.0 µm or more and 6.0 µm or less E: 6.0 µm or less

(4) Pressure fluctuation A single layer film formation test was performed in the same manner as in (3) above, and in continuous film formation for 6 hours from 1 hour to 7 hours after the start of film formation, the resin at the tip of the extruder (10th) At the pressure P10, the difference ΔP between the maximum pressure PMAX and the minimum pressure PMIN was evaluated according to the following criteria. If the evaluation was A to D, it was judged that the pressure fluctuation was 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

(5) Torque stability In the continuous film formation for 6 hours from 1 hour after the start of film formation in (3) above, the fluctuation range of the motor torque of the extruder was evaluated according to the following criteria. It was judged that the torque fluctuation was suppressed in the evaluation of A to D.
A: Fluctuation width 5N・m or less B: Fluctuation width 5N・m or more and 10N・m or less C: Fluctuation width 10N・m or less 15N・m or less D: Fluctuation width 15N・m or less 20N・m or less E: Fluctuation width 20N・m or less more than m

1 raw material supply unit 2, 4, 6 full flight screw unit 3, 5 reverse flight screw unit 7 vent 8 trace ingredient addition unit 9 temperature sensor 10 cylinder barrel 11 discharge port 20 twin screw extruder

Claims (4)

A pellet made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a lubricant (B),
The content of the lubricant (B) is 5 ppm or more and 150 ppm or less,
The first metal plate having a circular recess with a diameter of 8 cm and a depth of 3 mm is filled with the pellets 21g, and carbon paper and copy paper are stacked in this order so as to cover the recess after filling, and the first metal plate and A second metal plate having the same size and a thickness of 1 mm was placed on the copy paper and pressed at a strength of 20 kg/cm ² to transfer the pellet shape distribution to the copy paper. A square area of 391 pixels in length and 406 pixels in width that does not touch the circle is selected, and the total area of the black part in the square area calculated by binarization with a threshold value of 180 is 8500 pixels or less. 2. The pellet according to claim 1, wherein the particle size distribution of the equivalent circle diameter of the pellet has a half width of 0.7 mm or less. 3. The pellet according to claim 1, wherein the pellet has a longitudinal length of 2.0 to 4.0 mm and a transverse length of 2.0 to 4.0 mm. The pellet according to any one of claims 1 to 3, wherein the shape of said pellet is columnar, spherical or spheroidal.

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