TWI793152B - melt forming material - Google Patents

Abstract

The present invention provides a melt forming material which can suppress the generation of sudden pitting during continuous melt forming. The present invention is a molten molding material, which is a columnar, flat or spherical molten molding material containing ethylene-vinyl alcohol copolymer, and the maximum height roughness (Rz) of the side surface is 300 μm or less. It is preferable that the arithmetic average roughness (Ra) of the said side surface is 50 micrometers or less. It is preferable that the full width at half maximum of the particle size distribution of the circle-equivalent diameter of the melt-molded material is 1 mm or less. The ethylene unit content of the aforementioned ethylene-vinyl alcohol copolymer is preferably not less than 20 mol % and not more than 60 mol %.

Description

melt forming material

This invention relates to melt-formed materials.

Ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH") is excellent in gas barrier properties, transparency, oil resistance, non-electricity, mechanical strength, etc., and is used as various packaging materials such as films, sheets, containers, etc. widely used.

These various packaging materials are usually formed by melt molding. Therefore, melt molding materials containing EVOH are generally required to have excellent appearance properties, long-term usability, and the like in melt molding. The appearance characteristic generally refers to the characteristic that a molded article having an excellent appearance can be obtained without coloring such as gel, pitting, or yellowing. In addition, the so-called long-term usability means that even after long-term molding, the physical properties such as viscosity do not change, and a molded article without streaks or the like can be obtained.

As the main cause of deterioration of appearance characteristics and long-term usability, there is thermal deterioration of EVOH. Therefore, these various characteristics are required in the molten molding material containing EVOH, especially, in order to improve the appearance characteristics, in Patent Documents 1 and 2, acid such as carboxylic acid, phosphoric acid or alkali metal salt, alkaline earth Various proposals have been made on EVOH compositions including metal salts such as metal salts in EVOH at an appropriate content rate. With such EVOH composition, thermal deterioration can be suppressed, appearance characteristics and long-term usability can be improved, and molded articles with excellent appearance can be obtained even after long-term continuous molding. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Application Laid-Open No. 64-66262 [Patent Document 2] Japanese Patent Application Publication No. 2001-146539

[Problem to be Solved by the Invention]

In addition to the appearance characteristics and long-term usability characteristics caused by the above-mentioned thermal deterioration, it is required to suppress pitting (sudden pitting) that occurs suddenly during continuous melt molding in melt-molding materials containing EVOH. In addition, the inventors of the present invention confirmed the presence or absence of carbonyl generation by infrared spectroscopy, and confirmed that thermal deterioration hardly occurred. That is, according to the knowledge of the inventors of the present invention, the sudden pitting is caused by the above-mentioned thermal deterioration as the main reason, such as gel, pitting and coloring, etc. The addition of additives such as metal salts or metal salts cannot fully solve the problem.

The present invention was made based on the above matters, and an object of the present invention is to provide a melt-molded material capable of suppressing occurrence of sudden pitting during continuous melt-molding. [Means to solve the problem]

The invention made to solve the above-mentioned problems is a columnar, flat or spherical melt molding material comprising ethylene-vinyl alcohol copolymer (EVOH), which is a melt molding material with a maximum height roughness (Rz) of the side surface of 300 μm or less. Forming material.

The inventors of the present invention have known that the sudden pitting is caused by the following reasons. When the molten molding material (EVOH) is conveyed by the air flow through the piping and conveyed to the hopper of the melting molding machine during continuous melting molding, the following phenomenon occurs. In air conveying, a part of the molten molding material is chipped and pulverized due to the collision of the molten molding material to the inner surface of the pipe or the collision of the molten molding materials. In stagnant parts such as curved parts of piping, such micronized EVOH is melted by the frictional heat generated during air conveyance, and becomes band-shaped foreign matter. This foreign matter flows out discontinuously from the stagnation part during continuous melt molding, and is supplied to the melt molding machine together with the melt molding material. However, since this foreign matter is in the shape of a ribbon, it is difficult to shear and it is difficult to be melted in a melting molding machine. Therefore, the foreign matter remains in the obtained molten molded body, that is, pits derived from the foreign matter suddenly occur. In particular, EVOH-based resins are hard resins with a high glass transition temperature and hydroxyl groups, so they tend to be pulverized during air transfer, and sudden pitting is likely to occur. On the other hand, with the melt-molded material of the present invention, the maximum height roughness (Rz) of the side surface is set to be 300 μm or less, and it is difficult to chip off when it collides with the inner surface of the pipe during air conveyance. Therefore, by using the melt-molded material, the generation of fine powder during air-flow conveyance is suppressed, and as a result, the generation of sudden pitting can be suppressed.

The arithmetic mean roughness (Ra) of the aforementioned side surface is preferably 50 μm or less. By setting the arithmetic average roughness (Ra) of the side surface to be less than 50 μm, the generation of fine powder during air transfer is more suppressed, and the occurrence of sudden pitting can be further reduced. In addition, in this way, since the generation of fine powder is reduced and the generation of band-shaped foreign matter is also reduced, it is also possible to suppress the thickness unevenness of the obtained melt-molded article.

It is preferable that the full width at half maximum of the particle size distribution of the circle-equivalent diameter of the melt-molded material is 1 mm or less. By making the particle size of the melt-molded material more consistent in this way, the biting from the hopper to the extruder during melt-molding is stabilized, and thickness unevenness of the resulting melt-molded product can be suppressed.

The ethylene unit content of the aforementioned ethylene-vinyl alcohol copolymer is preferably not less than 20 mol % and not more than 60 mol %. By setting the ethylene unit content within the aforementioned range, melt formability, gas barrier properties, and the like can be exhibited in a well-balanced manner.

When the molten molding material is cylindrical, the height is 1 to 20 mm, and the diameter is 1 to 20 mm, so that the biting property at the time of fusion molding can be improved.

When the melt-molded material is flat or spherical, the length in the long-side direction is 1-20 mm, and the length in the short-side direction is 1-20 mm, so that the biting property during melt molding can be improved. [Effect of the invention]

The melt-molding material of the present invention can suppress the generation of sudden pitting during continuous melt-molding.

Hereinafter, a melt-molded material according to an embodiment of the present invention will be described in detail with reference to appropriate drawings.

(Shape, etc.) The melt-molded material 1 in Fig. 1(a) is a columnar melt-molded material containing EVOH. The molten molding material 1 series may also be a granular material called a pellet. Here, the term "columnar" refers to a shape that has substantially parallel upper and lower surfaces. The so-called substantially parallel means that the angle between the top and the bottom is within ±10°. In addition, although the upper surface and the lower surface are substantially flat, they may be curved. The so-called top and bottom are usually substantially the same shape, but may be different. In addition, although the upper surface and the lower surface have substantially the same size, they may be different. The melt-molded material 1 can also be a straight column, and can also be a slanted column, but a straight column is preferred.

Specifically, the molten molding material 1 in Fig. 1(a) is cylindrical. The term "cylindrical shape" refers to a columnar shape in which the cross section in the direction perpendicular to the central axis (axis direction) X is circular. Furthermore, the so-called circular shape is not limited to a true circle, and may be an ellipse, or a circle having a concave or protruding part. Furthermore, the melt-molded material may be in the shape of a square column, a hexagonal column, or the like in addition to a columnar shape. However, from the viewpoint of further suppressing micronization at the time of air conveyance, a cylindrical shape is preferable.

The cylindrical molten molding material 1 has an upper surface 3a, a lower surface 3b and a side surface 2. The top 3a and the bottom 3b are circular with the same size. The edges where the top 3a or the bottom 3b meet the side 2 can also have rounded corners.

The size of the molten molding material 1 is not particularly limited, but the lower limit of the height A is preferably 1 mm, more preferably 2 mm. On the other hand, the upper limit of the height A is preferably 20 mm, more preferably 10 mm, and still more preferably 5 mm. Also, the lower limit of the diameter B of the molten molding material 1 is preferably 1 mm, more preferably 2 mm. On the other hand, the upper limit of the diameter B is preferably 20 mm, more preferably 10 mm, and still more preferably 5 mm. When the melt-molded material 1 has such a size, the handleability, the conveyability by air flow, the biteability to the extruder, and the like can be improved.

The upper limit of the maximum height roughness (Rz) on the side surface 2 of the melt-molded material 1 is 300 μm, preferably 200 μm, more preferably 150 μm, still more preferably 120 μm, particularly preferably 100 μm. By setting the maximum height roughness (Rz) to 300 μm or less, the occurrence of band-shaped foreign matter can be suppressed by reducing the generation of fine powder during air transfer in the piping, and as a result, it is possible to suppress the sudden occurrence of continuous melt molding The occurrence of pitting or the uneven thickness of the obtained molten molded body.

On the other hand, the lower limit of the maximum height roughness (Rz) of the side surface 2 is preferably 10 μm, more preferably 30 μm, and even more preferably 50 μm. By setting the maximum height roughness (Rz) of the side surface 2 of the molten molding material 1 to 10 μm or more, for example, the biting of the molten molding material from the hopper to the extruder is stabilized, and the torque fluctuation of the melting molding machine or Discharge variation is suppressed, and thickness unevenness of the resulting melt-molded product can be reduced. Conversely, if the smoothness of the surface of the melt-molded material 1 is too high, it tends to become slippery, and biting into the extruder may become unstable. In addition, by setting the maximum height roughness (Rz) of the side surface of the melt-molded material 1 to be 10 μm or more, an increase in the cost of producing the melt-molded material 1 itself can be suppressed.

The upper limit of the arithmetic mean roughness (Ra) on the side surface 2 of the fusion-molded material 1 is preferably 50 μm, more preferably 40 μm, still more preferably 30 μm, still more preferably 25 μm, still more preferably 20 μm, and most preferably 10 μm . By setting the arithmetic average roughness (Ra) below 50 μm, the generation of fine powder during air transfer is more suppressed, and the occurrence of sudden pitting can be further reduced. In addition, since the amount of fine powder generated is reduced, the generation of band-shaped foreign matter is also reduced, so the thickness unevenness of the obtained melt-molded product can also be suppressed.

On the other hand, the lower limit of the arithmetic average roughness (Ra) of the side surface 2 is preferably 1 μm, more preferably 3 μm, even more preferably 3.5 μm, and still more preferably 5 μm. By setting the arithmetic average roughness (Ra) of the side surface 2 of the molten molding material 1 to 1 μm or more, the biting into the extruder is stabilized, and the thickness unevenness of the obtained molten molding product can be reduced. In addition, by setting the arithmetic average roughness (Ra) of the side surface 2 of the molten molding material 1 to 1 μm or more, an increase in the cost of producing the molten molding material 10 itself can be suppressed.

Here, in this specification, the maximum height roughness (Rz) and the arithmetic average roughness (Ra) of the melt-molded material are the average values of the measured values of 100 melt-molded materials selected arbitrarily. In addition, the measured values of the maximum height roughness (Rz) and the arithmetic mean roughness (Ra) of the melt-molded material are values measured with a cut-off value (λc) of 2.5 mm in accordance with JIS B 0601 (2001). In this specification, it means that the evaluation surface is measured in a non-contact manner, and the evaluation area has a maximum width of 1414 μm and a height of 1060 μm. In the case of a small melt-molded material, it is sufficient to adjust the evaluation area appropriately.

The melt-molded material 11 in Fig. 1(b) is a flat melt-molded material containing EVOH. The melt-molded material 11 may also be a granular material called pellets. Here, "flat shape" refers to an elliptical shape in which the cross section of the plane including the rotation axis (central axis) Y is defined as a cut plane. The flat molten molding material 11 can also be a spheroid. Also, when the flat molten molding material 11 is placed on a horizontal plane, the direction of the part having the longest linear distance along the horizontal direction is defined as the longitudinal direction d (in the first (b) figure, the horizontal direction parallel), let the direction perpendicular to the horizontal plane be the short side direction c. The short-side direction c is the same as the direction of the rotation axis Y. Generally, in the flat melt-molded material 11 , the length C in the short-side direction c is shorter than the length D in the long-side direction d. Furthermore, the melt-molding material system may be a spherical melt-molding material containing EVOH. The term "spherical" refers to a shape in which the cross-section of the plane including the rotation axis Y is a circular cross-section. In FIG. 1(b), when the length C in the short-side direction c and the length D in the long-side direction d are the same length, the melt-molded material 11 becomes spherical.

The maximum height roughness (Rz) of the side surface 12 of the flat or spherical melt-molded material 11 is 300 μm or less. Here, in the flat or spherical molten molding material 11, the so-called side surface 12 refers to the surface of the molten molding material 11, and the normal line is the curved surface portion substantially perpendicular to the rotation axis Y (short side direction c). The side 12 includes the so-called equator, which is a curved surface along the circumferential direction. In Fig. 1(b), the side 12 is an area surrounded by a dotted line along the longitudinal direction d (the area that should be on the back side of the paper of Fig. 1(b) is also the same.). Furthermore, in the case where the melt-molded material is spherical, any part of the surface is a side surface.

The size of the melt-molded material 11 is not particularly limited, but the lower limit of the length C in the short-side direction of the melt-molded material 11 is preferably 1 mm, more preferably 1.5 mm. On the other hand, the upper limit of the length C in the short side direction is preferably 20 mm, more preferably 10 mm, and still more preferably 5 mm. Also, the lower limit of the length D in the longitudinal direction is preferably 1 mm, more preferably 1.5 mm. On the other hand, the upper limit of the length D in the longitudinal direction is preferably 20 mm, more preferably 10 mm, and still more preferably 5 mm. When the melt-molded material 11 has such a size, the handleability, the conveyability by the air flow, the biteability to the extruder, and the like can be relatively improved.

The upper limit of the maximum height roughness (Rz) on the side surface 12 of the molten molding material 11 is 300 μm, preferably 200 μm, more preferably 150 μm, still more preferably 120 μm, and particularly preferably 100 μm. By setting the maximum height roughness (Rz) to 300 μm or less, the occurrence of band-shaped foreign matter can be suppressed by reducing the generation of fine powder during air transfer in the piping, and as a result, it is possible to suppress the sudden occurrence of continuous melt molding Generation of pitting, or uneven thickness of the obtained molten molded body.

On the other hand, the lower limit of the maximum height roughness (Rz) of the side surface 12 is preferably 10 μm, more preferably 30 μm, and even more preferably 50 μm. Set the maximum height roughness (Rz) of the side surface 12 of the molten molding material 11 to 10 μm or more, for example, the biting of the molten molding material from the hopper to the extruder is stabilized, and the torque fluctuation or discharge of the molten molding machine Fluctuation is suppressed, and thickness unevenness of the resulting melt-molded product can be reduced. Conversely, if the smoothness of the surface of the molten molding material 11 is too high, it tends to become slippery, and the biting into the extruder may become unstable. In addition, by setting the maximum height roughness (Rz) of the side surface of the molten molding material 11 to be 10 μm or more, an increase in the cost of producing the molten molding material 11 itself can be suppressed.

The upper limit of the arithmetic mean roughness (Ra) of the side surface 12 of the fusion-molded material 11 is preferably 50 μm, more preferably 40 μm, more preferably 30 μm, more preferably 25 μm, more preferably 20 μm, and most preferably 10 μm . By setting the arithmetic average roughness (Ra) below 50 μm, the generation of fine powder during air transfer is more suppressed, and the generation of sudden pitting can be further reduced. In addition, since the amount of fine powder generated is reduced, the generation of band-shaped foreign matter is also reduced, so the thickness unevenness of the obtained melt-molded product can also be suppressed.

On the other hand, the lower limit of the arithmetic average roughness (Ra) of the side surface 12 is preferably 1 μm, more preferably 3 μm, even more preferably 3.5 μm, and still more preferably 5 μm. By setting the arithmetic average roughness (Ra) of the side surface 12 of the molten molding material 11 to 1 μm or more, the biting into the extruder is stabilized, and the thickness unevenness of the obtained molten molding product can be reduced. In addition, by setting the arithmetic average roughness (Ra) of the side surface 12 of the molten molding material 11 to be 1 μm or more, an increase in cost for producing the molten molding material 11 itself can be suppressed.

Furthermore, the maximum height roughness (Rz) or the arithmetic average roughness (Ra) of the side surface 2 of the molten molding material 1 or the side surface 12 of the molten molding material 11 is as described later, by controlling the inner surface of the mold when molding the molten molding material It can be adjusted by the surface roughness, or the drying conditions of the molten molding material.

Full width at half maximum (FWHM) of the particle size distribution of the circle-equivalent diameter (diameter) of melt-molded materials (hereinafter, combined columnar, flat, and spherical melt-molded materials may be referred to only as melt-molded materials.) ) is preferably 1 mm, more preferably 0.6 mm, still more preferably 0.5 mm, and particularly preferably 0.4 mm. By making the half-value width of the particle size distribution in the melt-molded material 1mm or less, the size of the melt-molded material can be made uniform, and the biting into the extruder can be stabilized, so that the obtained melt-molded product can be suppressed. Uneven thickness. On the other hand, the lower limit of the full amplitude at half maximum of the particle size distribution may be 0.1 mm, 0.2 mm, or 0.3 mm.

In this specification, the particle size distribution of the circle-equivalent diameter (radius) of the melt-molded material is the circle-equivalent diameter calculated by the dynamic image analysis method based on ISO 13322-2 (2006) using 500 g of the melt-molded material The particle size distribution.

Furthermore, the particle size distribution of the melt-molded material can be adjusted by, for example, screening the produced melt-molded material.

(EVOH) Next, EVOH contained in this melt-molded material will be described. The EVOH system is a copolymer having ethylene units and vinyl alcohol units as the main structural unit. Furthermore, the EVOH system may contain one or more other structural units in addition to the ethylene unit and the vinyl alcohol unit. EVOH is generally obtained by polymerizing ethylene and vinyl ester and saponifying the resulting ethylene-vinyl ester copolymer. The polymerization and saponification can be carried out by conventionally known methods.

The lower limit of the ethylene unit content of EVOH (that is, the ratio of the number of ethylene units to the total number of monomer units in EVOH) is preferably 20 mol%, 22 mol% is better, and 24 mol% % is even better. On the other hand, the upper limit of the ethylene unit content of EVOH is preferably 60 mol%, more preferably 55 mol%, and still more preferably 50 mol%. When the ethylene unit content of EVOH is within the aforementioned range, sufficient melt moldability, gas barrier properties, and the like can be exhibited. More specifically, by setting the ethylene unit content of EVOH to 20 mol % or more, for example, the water resistance, hot water resistance, gas barrier property or melt moldability at high humidity of the obtained melt-molded article can be improved. On the other hand, by setting the ethylene unit content of EVOH to 60 mol% or less, the gas barrier properties of the molded article obtained can be improved.

The lower limit of the degree of saponification of EVOH (that is, the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH) is preferably 80 mole %, more preferably 95 mole % , 99 mol% is even better. On the other hand, the upper limit of the degree of saponification of EVOH is preferably 100 mol%, more preferably 99.99 mol%. By setting the saponification degree of EVOH to 80 mol% or more, the gas barrier property and coloring resistance of the molten molded product can be improved.

The lower limit of the melt flow rate of EVOH (according to JIS K 7210, measured at a temperature of 210°C and a load of 2160g) is preferably 0.1g/10 minutes, 0.5g/10 minutes is better, and 1g/10 minutes is further Good, 3g/10 is particularly good. On the other hand, the upper limit of the melt flow rate of EVOH is 200g/10 points is better, 50g/10 points is better, 30g/10 points is even better, 15g/10 points is particularly good, 10g/10 points optimal. When the melt flow rate of EVOH is set to a value within the aforementioned range, the melt formability of the melt molded material is relatively improved.

The lower limit of the content of EVOH in the melt-molded material is preferably 50% by mass, more preferably 90% by mass, still more preferably 99% by mass, and particularly preferably 99.9% by mass. When the content of EVOH in the melt-molded material is 50% by mass or more, various properties based on EVOH, such as gas barrier properties and transparency, of the resulting melt-molded product can be improved. Furthermore, the content of EVOH may be 100% by mass.

(Other Components) The melt-molding material may contain components other than EVOH. Examples of other components include carboxylic acids, carboxylate salts, phosphoric acid compounds, boron compounds, and the like. If these components are contained, the appearance characteristics and long-term usability can be improved.

The aforementioned carboxylic acid system may be monocarboxylic acid or polycarboxylic acid.

Examples of the monocarboxylic acid system include formic acid, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, acrylic acid, methacrylic acid, benzoic acid, and 2-naphthoic acid. These monocarboxylic acids may also have a hydroxyl group or a halogen atom. Moreover, as a monocarboxylic acid ion system, the hydrogen ion of the carboxyl group of each said monocarboxylic acid is detached.

As the polycarboxylic acid, it is only necessary to have two or more carboxyl groups in the molecule, for example, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, malic acid, glutaric acid, adipic acid, heptanedioic acid, etc. Aliphatic dicarboxylic acids such as diacids; Aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; Tricarboxylic acids such as citric acid, isocitric acid and aconitic acid;1,2 ,3,4-butanetetracarboxylic acid, ethylenediaminetetraacetic acid and other carboxylic acids with more than 4 carboxyl groups; citric acid, isocitric acid, tartaric acid, malic acid, mucus acid, hydroxymalonic acid, citric malic acid Isohydroxycarboxylic acids; Ketocarboxylic acids such as oxalic acid, mesooxalic acid, 2-ketoglutaric acid, 3-ketoglutaric acid, etc.; Amino groups of glutamic acid, aspartic acid, 2-aminoadipic acid, etc. Acid etc.

Examples of the phosphoric acid compound include various phosphorus oxyacids such as phosphoric acid and phosphorous acid, or their salts. As the phosphate, for example, it may be contained in any form of the first phosphate, the second phosphate, and the third phosphate, and the pair of cation species is not particularly limited, but alkali metal salts and alkaline earth metal salts are preferred. .

Examples of the boron compound system include boric acids, boric acid esters, borate salts, boron hydrides, and the like. Specifically, examples of the boric acid system include orthoboric acid (H ₃ BO ₃ ), metaboric acid, tetraboric acid, and the like. Examples of borate esters include triethyl borate, trimethyl borate, and the like. Examples of borates include alkali metal salts, alkaline earth metal salts, borax, and the like of the aforementioned various boric acids.

Additives such as lubricants, plasticizers, stabilizers, surfactants, colorants, ultraviolet absorbers, antistatic agents, desiccants, crosslinking agents, fillers, and various fibers may also be contained in appropriate amounts in the melt-molded material system. In addition, lubricants and the like may be attached to the surface of the molten molding material. Furthermore, the melt molding material may contain thermoplastic resins other than EVOH.

Examples of thermoplastic resins other than EVOH include polyolefin, nylon, polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, modified Quality polyvinyl alcohol, etc. Examples of the aforementioned polyolefins include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers, ethylene, and α-olefins having 4 or more carbon atoms. Copolymers of polyolefins, copolymers of polyolefin and maleic anhydride, ethylene-vinyl ester copolymers, ethylene-acrylic acid ester copolymers, modified polyolefins grafted with unsaturated carboxylic acids or their derivatives wait. Examples of the aforementioned nylon series include nylon-6, nylon-66, nylon-6/66 copolymer, and the like. When the melt molding material contains other thermoplastic resins than EVOH, the content of the other thermoplastic resins is preferably 50% by mass or less, more preferably 10% by mass or less, and even more preferably 1% by mass or less.

These other ingredients can be mixed with EVOH by generally known methods. For example, EVOH can be mixed by a method of melting and kneading other components, or a method of immersing EVOH in a solution containing other components.

(Method for producing melt-molded material) The melt-molded material can be obtained, for example, by a granulation step (step 1(a), step 1(b) of hydrated granules of EVOH obtained by a granulation operation from a solution containing EVOH. or step 1(c)), and the drying step (step 2) of drying the aforementioned water-containing particles.

In addition, after the aforementioned step 2, a screening step (step 3) may also be provided. In addition, the EVOH used in the step 1 can be obtained through the polymerization step and the saponification step of the generally known method as described above.

(Step 1(a)) In the production of melt-molded materials, EVOH is usually obtained as a solution dissolved in a solvent or the like used in the saponification reaction. In step 1(a) this solution is granulated to obtain aqueous granules comprising EVOH. The granulation operation for obtaining such water-containing granules is not particularly limited. For example, there is a method of extruding a solution of EVOH into strands in a coagulation bath containing a cooled poor solvent using a die, and cooling and solidifying it. Afterwards, the strand-shaped cured product is cut by a strand cutter to obtain columnar EVOH water-containing particles. As the coagulation bath system, for example, a mixed solvent of water and methanol or the like can be used. Furthermore, the water content of the obtained water-containing granules can be adjusted by the mass ratio of the mixed solvent to EVOH and the like.

(Step 1(b)) In addition, as a granulation step, the solution of the ethylene-vinyl alcohol copolymer can be extruded into a coagulation bath, and then cut with a rotating blade or the like to obtain a flat shape (go-piece shape) ~Generally known methods such as the method of spherical EVOH water-containing particles.

(Step 1(c)) Furthermore, as the granulation step, the method described in Japanese Patent Laid-Open No. 2002-121290, etc., can also be suitably used to contact the solution of ethylene-vinyl alcohol copolymer with water vapor and prepare EVOH in advance. After the water-containing resin composition is extruded into a coagulation bath, the method of cutting it to obtain water-containing particles of EVOH, etc.

Here, regarding the granulation step (step 1(a), step 1(b) and step 1(c)), by controlling the inner surface of the mold used to extrude the solution of EVOH, especially the outlet part ( The surface roughness of the inner surface of the die head) can adjust the surface roughness (maximum height roughness (Rz) and arithmetic mean roughness (Ra )). The surface shape of the inner surface of the die outlet part is transferred to the extruded EVOH solution (water-containing particles). Therefore, in order to improve the smoothness of the inner surface of the exit portion of the die, the surface roughness of the resulting melt-molded material can be reduced.

The upper limit of the maximum height roughness (Rz) of the inner surface of the die outlet portion is preferably 15 μm, more preferably 5 μm, still more preferably 3 μm, and particularly preferably 1 μm. On the other hand, the lower limit of the maximum height roughness (Rz) may be 0.1 μm or 0.3 μm. In addition, the upper limit of the arithmetic average roughness (Ra) of the inner surface of the die outlet portion is preferably 1.2 μm, more preferably 1 μm, still more preferably 0.5 μm, particularly preferably 0.2 μm, most preferably 0.1 μm. On the other hand, the lower limit of the arithmetic mean roughness (Ra) may be 0.01 μm or 0.03 μm.

Here, the maximum height roughness (Rz) and the arithmetic average roughness (Ra) of the inner surface of the die outlet portion are the average values of the measured values at 10 places arbitrarily selected respectively. Also, in this specification, the measured values of the maximum height roughness (Rz) and the arithmetic mean roughness (Ra) of the inner surface of the mold outlet are based on JIS B 0601 (1994), with the cut-off value (λc) 2.5mm, Evaluation length (1) 7.5mm, the value measured by the contact method.

The aqueous granule system obtained in this manner can also be washed as necessary. By washing, for example, by-products generated during saponification can be removed. In addition, the water-containing particle system may be immersed in a solution containing additives such as carboxylic acid, phosphoric acid compound, and boron compound. By such treatment, additives such as carboxylic acid can be contained in the obtained melt-molded material.

(Step 2) The water-containing granules of EVOH obtained through the above-mentioned steps are obtained through a drying step to be melt-molded materials (granules) containing EVOH.

The upper limit of the moisture content in the water-containing particles of EVOH used in the drying step is based on the dry mass of EVOH, preferably 200% by mass, more preferably 150% by mass, even more preferably 120% by mass, and especially 80% by mass good. By setting the water content of the hydrated pellets to 200% by mass or less, drying can be carried out under moderate conditions, and the surface roughness of the resulting melt-molded material can be reduced. On the other hand, the lower limit of the water content is, for example, 30% by mass, and may be 50% by mass. The drying efficiency can be improved by setting the moisture content to 30% by mass or more.

There is no particular limitation on the drying method of the water-containing granules, and various generally known methods can be used, and suitable ones such as static drying and flow drying can be mentioned. These drying methods may be used alone, or may be used in combination, for example, performing fluidized drying first and then static drying. The drying treatment may be performed by either continuous method or batch method, and when performing a combination of plural drying methods, the continuous method and the batch method can be freely selected for each drying method. Drying can also be carried out in an air environment, but it is preferable to carry out in a low-oxygen concentration or anaerobic state because it can reduce deterioration due to oxygen during drying.

For example, in the case of using a hot air dryer, especially by controlling the ambient temperature (the temperature of the blown gas), the dew point temperature of the blown gas, and the drying speed during the initial stage of drying, the temperature of the obtained molten molding material can be controlled. The surface roughness becomes smaller. Also, the so-called initial stage of drying means, for example, the stage where the water content of the water-containing particles reaches 10% by mass.

The upper limit of the ambient temperature (the temperature of the blown air) in the initial stage of drying is preferably 90°C, more preferably 75°C, and even more preferably 65°C. By keeping the ambient temperature below 90°C, volatilization of moisture occurs gently, and the roughening of the surface of the resulting melt-molded material can be suppressed. On the other hand, the lower limit of the ambient temperature is preferably 40°C, more preferably 50°C. The drying efficiency can be improved by setting the ambient temperature above 40°C.

The lower limit of the dew point temperature of the dry gas (air, etc.) used in the initial stage of drying is preferably -35°C, more preferably -25°C, and even more preferably -15°C. By setting the aforementioned dew point temperature at -35°C or higher, volatilization of moisture occurs gently, and roughening of the surface of the resulting melt-molded material can be suppressed. On the other hand, the upper limit of the dew point temperature is preferably 10°C, more preferably 0°C, and even more preferably -5°C. By setting the dew point temperature below 10°C, the drying efficiency can be improved.

The upper limit of the drying speed in the initial stage of drying is 50g/hr・100g-dry base is better, 30g/hr・100g-dry base is more preferable, and 20g/hr・100g-dry base is even better. By setting the drying rate below 50 g/hr·100 g-dry base, volatilization of moisture occurs gently, and the roughening of the surface of the obtained melt-molded material 10 can be suppressed. On the other hand, the lower limit of drying speed is preferably 5g/hr・100g-dry base, and 10g/hr・100g-dry base is more preferable. Setting the drying speed above 5g/hr・100g-dry base can improve the drying efficiency. For example, the so-called drying rate of 50g/hr·100g-dry base means that 50g of water is volatilized per hour per 100g of dry mass basis EVOH.

Also, after the initial stage, that is, when the moisture content of the particles becomes less than 10% by mass, for example, the amount of volatilized water decreases, and because the influence on the surface roughness becomes smaller, it can also be dried under the condition of increasing the drying speed. to dry. That is, drying can also be performed at a high temperature and a low dew point temperature. In this way, the drying efficiency can be improved.

The upper limit of the moisture content in the pellets (melt-molded material) obtained through the drying step is preferably 1% by mass, more preferably 0.8% by mass, and still more preferably 0.5% by mass, based on the entire pellets. By setting the moisture content to 1% by mass or less, molding problems such as generation of voids due to foaming during melt molding can be suppressed.

(Step 3) The particles (melt-molded material) obtained through the drying step can be further screened to adjust the particle size distribution. The mesh size of the sieve to be used is appropriately set in accordance with the size of the melt-molded resin, but may be, for example, 4 mesh or more and 10 mesh or less. In addition, the particle size can be adjusted by passing through plural kinds of sieves having different meshes (number of meshes).

The lower limit of the sieving time is preferably 1 minute, more preferably 5 minutes. On the other hand, the upper limit may be, for example, 1 hour, but is preferably 20 minutes, more preferably 15 minutes. When sieving for a long time, the particle size distribution becomes narrower, but the surface of the molten molding resin tends to be scratched, and the surface roughness may become larger. In addition, fine powder may be easily generated by sieving for a long time.

(Method of use) The melt-molded material is molded into various molded objects such as films, sheets, containers, tubes, and fibers by melt-molding. These shaped systems can also be crushed and reshaped for reuse purposes. In addition, a film, sheet, fiber, etc. may be stretched monoaxially or biaxially. As the melt molding method, extrusion molding, expansion extrusion, blow molding, melt spinning, injection molding, and the like can be used.

In addition, during continuous melt molding, the melt-molding material is usually conveyed continuously to an inlet of a melt-molding machine, such as a hopper, by air conveyance. The air flow system used for air conveyance is not particularly limited, but usually, air can be used, and inert gases such as nitrogen gas can also be used.

The lower limit of the temperature of the circulating gas is, for example, 0°C, and may be 10°C. In addition, the upper limit is, for example, 100°C, may be 80°C, or may be 60°C. Also, the flow rate of the circulating gas depends on the size of the molten molding material, the pipe diameter, etc., but is usually 10 m/sec or more and 100 m/sec or less. [Example]

Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited by these Examples.

In the following examples and comparative examples, measurement and evaluation were performed by the methods shown below.

(1) The measurement of the surface roughness of the melt-molded material (pellet) uses the shape measurement laser microscope "VK-X200" (non-contact type) of KEYENCE, according to JIS B 0601 (2001), as the cut-off value (λc) 2.5mm, evaluation area is 1414μm in width and 1060μm in height, measure the maximum height roughness (Rz) and arithmetic mean roughness (Ra) of the side surface of the melt-molded material, each set as the average value of 100 values.

(2) Measurement of particle size distribution and half-maximum full-amplitude of melt-molded material The particle size distribution of the circle-equivalent diameter (radius) of melt-molded material is about 500 g of melt-molded material, using "CAMSIZER XT" of Verder Scientific Company, by Calculated from the circle equivalent diameter calculated by the dynamic image analysis method of ISO 13322-2 (2006). From the obtained particle size distribution, the full width at half maximum (mm) was calculated|required.

(3) Determination of the moisture content of the molten molding material The moisture content of the molten molding material was measured using the halogen moisture content analyzer "HR73" manufactured by Mettler Toledo at a drying temperature of 180°C, a drying time of 20 minutes, and a sample size of about 10 g. Rate. The moisture content of the melt-molded material is set as mass% on a dry basis.

(4) The number of sudden pitting occurrences Using the obtained molten molding material, a single-layer film was produced with a single-screw extruder, and the pitting on the film was calculated. The pitting generation amount of the film was measured every 10 minutes. Usually, it is 10 or less per 1 m ² , but when it becomes 100 or more per 1 m ² , it is considered that sudden pitting occurs, and the number of times is continuously filmed for 48 hours for investigation. For the number of occurrences of sudden pitting, use the following criteria to evaluate. Also, in this continuous film production, the molten molding material is continuously supplied by air conveyance to the hopper provided in the single-screw extruder. A: 0 times B: 1-2 times C: 3-4 times D: more than 5 times

(5) Thickness unevenness In the continuous film production of the aforementioned (3), samples were taken in the MD direction 1 hour after the film production started, and the thickness in the length range of 2m was investigated by continuous thickness. Points were collected at intervals of 25 mm, the standard deviation (μm) was obtained, and thickness unevenness was evaluated using the following criteria. A: 2μm or less B: More than 2μm, 4μm or less C: More than 4μm, 6μm or less D: More than 6μm, 8μm or less E: More than 8μm

(6) Amount of fine powder In 50m of pipes with an inner diameter of 100mm, 5 L-shaped pipes are installed every 10m. By means of this L-shaped piping, 5 t of molten molding materials are air-transported by an air conveying facility equipped with a hopper having a cyclone. At this time, the fine powder is collected by the filter with the air recovered from the upper part of the cyclone. The captured fine powder is measured with a scale. Find the ratio (ppm) of the amount of captured fine powder to the transported amount, and use the following criteria to evaluate. In addition, the wind speed in the air transport is carried out so as to be 20m/sec. In addition, the molten molding materials used in the test were those whose fine powder was removed to 10 ppm or less with a fine powder remover. A: less than 100ppm B: more than 100ppm, less than 200ppm C: more than 200ppm, less than 300ppm D: more than 300ppm

(7) The surface roughness of the mold is measured using Mitutoyo's small surface roughness measuring machine surftest "SJ-400" (contact type), according to JIS B 0601 (1994), with a cut-off value (λc) of 2.5mm and an evaluation length ( 1) Measured at 7.5 mm.

<Synthesis Example 1> Synthesis of EVOH (Polymerization of Ethylene-Vinyl Acetate Copolymer) In a 250L pressurized reaction equipped with a stirrer, a nitrogen inlet, an ethylene inlet, an initiator addition port, and a delayed (sequential addition) solution addition port The tank was filled with 83.0 kg of vinyl acetate and 26.6 kg of methanol, and after the temperature was raised to 60° C., the system was replaced with nitrogen by bubbling with nitrogen for 30 minutes. Next, ethylene was charged so that the pressure of the reaction vessel became 3.6 MPa. As an initiator, dissolve 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMV) in methanol to prepare an initiator solution with a concentration of 2.5g/L. Nitrogen substitution was performed by bubbling by nitrogen gas. After adjusting the internal temperature of the polymerization tank to 60° C., 362 mL of the initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to maintain the reaction tank pressure at 3.6 MPa, the polymerization temperature was maintained at 60° C., and the polymerization was carried out by continuously adding AMV at 1120 mL/hr using the aforementioned initiator solution. When the polymerization ratio reached 40% after 5.0 hours, cooling was performed to stop the polymerization. After the reaction tank was opened and vinyl removal was performed, nitrogen gas was bubbled to complete vinyl removal. Next, the obtained copolymer solution is continuously supplied from the upper part of the tower filled with Raschig rings, methanol is blown into the lower part of the tower, and the mixed vapor of methanol and unreacted vinyl acetate monomer flows out from the top of the tower, and is obtained from the bottom of the tower. A methanol solution of ethylene-vinyl acetate copolymer (EVAc) after removal of unreacted vinyl acetate monomer.

(Saponification) 253.4 kg of methanol solution of EVAc (38 kg of EVAc in the solution) adjusted so that the concentration of EVAc was adjusted to be 15% by mass by adding methanol to the obtained EVAc was added by adding 76.6 L (for the vinyl acetate unit in EVAc) And the molar ratio (MR) 0.4) alkali solution (10 mass % methanol solution of NaOH) was stirred at 60° C. for 4 hours to perform saponification of EVAc. After 6 hours from the start of the reaction, 9.2 kg of acetic acid and 60 L of water were added to neutralize the aforementioned reaction solution to stop the reaction.

(Cleaning and drying) The neutralized reaction solution was moved from the reactor to a barrel and left at room temperature for 16 hours, allowing it to cool and solidify into a cake shape. After that, the cake-shaped resin was dehydrated using a centrifuge ("H-130" from a domestic centrifuge company with a rotation speed of 1200 rpm). Next, in the central part of the centrifugal separator, ion-exchanged water was continuously supplied from above while washing, and a step of washing the resin with water was performed for 10 hours. The conductivity of the cleaning solution from the beginning of cleaning to 10 hours later is 30 μS/cm (measured with "CM-30ET" of Donga Denpa Kogyo Co., Ltd.). The powdery EVOH thus obtained was dried at 60° C. for 48 hours using a drier to obtain dried powdery EVOH. Furthermore, the ethylene unit content of the obtained EVOH was 32 mol%.

<Example 1> Dissolve 20kg of the aforementioned dried powdered EVOH in 32L of water/methanol mixed solution (mass ratio: water/methanol=4/6) at 80°C for 12 hours while stirring. Next, the stirring was stopped, and the temperature of the dissolution tank was lowered to 65° C. and left for 5 hours to degas the above-mentioned water/methanol solution of EVOH. Then, extrude the aforementioned EVOH solution into a water/methanol mixed solution (mass ratio: water/methanol=9/1) at 5°C from a die with a circular opening with a diameter of 3.5mm to precipitate into strands shape, and cut to obtain water-containing EVOH particles with a diameter of about 4 mm and a length of about 5 mm. In addition, as the aforementioned die, a die with hard chromium plating, a maximum height roughness (Rz) of 0.6 μm and an arithmetic average roughness (Ra) of 0.05 μm on the inner surface of the die head (outlet portion) was used.

Put 40kg of water-containing EVOH particles obtained in this way and 150L of ion-exchanged water into a metal tank with a height of 900mm and an opening diameter of 600mm, and repeat twice at 25°C for 2 hours while washing and dehydrating. . Next, 150 L of 1 g/L acetic acid aqueous solution was added to 40 kg of water-containing EVOH pellets, and the operation of washing and dehydrating while stirring at 25° C. for 2 hours was repeated twice. Furthermore, 150 L of ion-exchanged water was added to 40 kg of water-containing EVOH particles, and the operation of washing and dehydrating while stirring at 25° C. for 2 hours was repeated six times to obtain water-containing EVOH particles (w-EVOH-1) from which impurities were removed. The conductivity of the cleaning solution after the sixth cleaning was measured with the "CM-30ET" of Toa Denpa Kogyo Co., Ltd. The conductivity of the cleaning solution was 3 μS/cm.

In such a way that 0.6g/L of acetic acid, 0.55g/L of sodium acetate, 0.015g/L of phosphoric acid, and 0.20g/L of boric acid are obtained, 94.5L of an aqueous solution in which each component is dissolved in water is put into water-containing EVOH particles (w-EVOH-1 ) 10.5kg, impregnated at 25°C for 6 hours, stirring frequently. The water-containing EVOH particles (w-EVOH-1) after impregnation were dehydrated by centrifugal dehydration. The water content of the obtained water-containing EVOH particles (w-EVOH-1) was 60% by mass.

The obtained water-containing EVOH particles (w-EVOH-1) were dried by the following operation. First, it dried at 60 degreeC for 5 hours in the hot-air drier using the air of -10 degreeC of dew point temperature, and made the moisture content into 10 mass %. Next, it was dried at 120° C. for 24 hours in a hot air dryer using air with a dew point temperature of -20° C.

Afterwards, the dried particles were sieved in the order of 6.5 mesh, 7 mesh and 8 mesh for 10 minutes to collect the particles remaining on the 8 mesh to obtain the dry EVOH particles (melt molding material) of Example 1. The obtained melt-molded material had a cylindrical shape with a height of 3.2 mm and a diameter of 2.8 mm.

<Example 2> Except that 20kg of the above-mentioned dried powdery EVOH was dissolved in 43L of water/methanol mixed solution (mass ratio: water/methanol=4/6) at 80°C for 12 hours while being dissolved. In the same manner as in Example 1, water-containing particles (w-EVOH-2) having a water content of 100% by mass were obtained. The water-containing granules (w-EVOH-2) were dried by the following operation. First, it dried at 70 degreeC for 4 hours in the hot-air drier using the air of -20 degreeC of dew point temperature, and made the moisture content into 10 mass %. Next, it was dried at 120° C. for 24 hours in a hot air dryer using air with a dew point temperature of -20° C. Thereafter, the same screening as in Example 1 was carried out to obtain dry EVOH pellets (melt molding material).

<Example 3> Except that 20kg of the above-mentioned dried powdered EVOH was dissolved in 55L of water/methanol mixed solution (mass ratio: water/methanol=4/6) at 80°C for 12 hours while being dissolved. In the same manner as in Example 1, water-containing particles (w-EVOH-3) having a water content of 140% by mass were obtained. The water-containing granules (w-EVOH-3) were dried by the following operation. First, it dried at 80 degreeC for 4 hours with the hot-air drier using the air of -30 degreeC of dew point temperature, and made the moisture content into 10 mass %. Then, it was dried at 120° C. for 24 hours using air having a dew point temperature of -20° C. Thereafter, the same screening as in Example 1 was carried out to obtain dry EVOH pellets (melt molding material).

<Example 4> In addition to being used as a die for extruding EVOH solution, hard chromium plating was used. The maximum height roughness (Rz) of the inner surface of the die (exit part) was 1.5 μm, and the arithmetic average roughness (Ra) was 0.43 Except for the mold of μm, the same operation as in Example 2 was carried out to obtain dry EVOH pellets (melt molding material).

<Example 5> Except that the dried particles were sieved in the order of 5 mesh, 7 mesh and 8 mesh for 10 minutes to collect the particles remaining on the 8 mesh, the same operation was carried out as in Example 4 to obtain dried Granules of EVOH (melt molding material).

<Example 6> Except that the dried particles were sieved in the order of 5 mesh, 7 mesh and 9 mesh for 10 minutes to collect the particles remaining on the 9 mesh, the same operation was carried out as in Example 4 to obtain dried Granules of EVOH (melt molding material).

<Example 7> Except that the dried particles were sieved in the order of 4 mesh, 7 mesh and 9 mesh for 10 minutes to collect the particles remaining on the 9 mesh, the same operation was carried out as in Example 4 to obtain dried Granules of EVOH (melt molding material).

<Example 8> In addition to being used as a die for extruding EVOH solution, hard chromium plating was used. The maximum height roughness (Rz) of the inner surface of the die (exit part) was 14.5 μm, and the arithmetic average roughness (Ra) was 0.99. Except for the mold of μm, the same operation as in Example 2 was carried out to obtain dry EVOH pellets (melt molding material).

<Example 9> Except that the dried granules were sieved for 30 minutes, the same operation as in Example 8 was carried out to obtain dried EVOH granules (melt molding material).

<Example 10> In addition to dissolving 20kg of dried powdered EVOH in 26L of water/methanol mixed solution (mass ratio: water/methanol=4/6) at 80°C for 12 hours while dissolving it, and then using The maximum height roughness (Rz) of the inner surface of the die head (exit part) that is precipitated into a strand shape is 0.5 μm, and the arithmetic average roughness (Ra) is 0.05 μm. The same method as in Example 1 This was carried out to obtain water-containing granules (w-EVOH-4) with a water content of 45% by mass. The water-containing granules (w-EVOH-4) were dried by the following operation. First, it dried at 60 degreeC for 4 hours in the hot-air drier using the air of -10 degreeC of dew point temperature, and made the moisture content into 10 mass %. Next, it was dried at 100° C. for 36 hours in a hot air dryer using air with a dew point temperature of -20° C. Thereafter, the same screening as in Example 1 was carried out to obtain dry EVOH pellets (melt molding material).

<Comparative Example 1> In addition to being used as a die for extruding EVOH solution, hard chromium plating was used. The maximum height roughness (Rz) of the inner surface of the die (exit part) was 18.2 μm, and the arithmetic average roughness (Ra) was 1.34 Sieve the dried particles in the order of 4 mesh, 7 mesh and 9 mesh for 10 minutes to collect the particles remaining on the 9 mesh, and perform the same operation as Example 2 to obtain dry EVOH. Pellets (melt-formed material).

<Example 11> The water-containing EVOH particles w-EVOH-1 obtained in Example 1 were dried in a hot air dryer at 80°C for 1 hour using air with a dew point temperature of -30°C to obtain a water content of 50% by mass. % of aqueous EVOH particles. Put the obtained water-containing EVOH pellets into a two-screw extruder at 10kg/hr (details are shown below), set the resin temperature at the discharge port to 100°C, as shown in Figure 1 at the front end of the discharge port In the solution addition section, an aqueous solution containing 10.0 g/L of acetic acid, 7.1 g/L of sodium acetate, 0.11 g/L of phosphoric acid, and 9.8 g/L of boric acid was added at 0.6 L/hr. As the die for extruding EVOH solution, hard chrome plating is used. The maximum height roughness (Rz) of the inner surface of the die head (outlet part) is 1.5 μm, and the arithmetic average roughness (Ra) is 0.43 μm. After the solution of ethylene-vinyl alcohol copolymer was extruded into the coagulation bath, it was cut with a rotating blade to obtain flat water-containing EVOH particles (moisture content: 25% by mass).

＜Specification details of two-screw extruder＞ Diameter 30mmφ L/D 45.5 Screws fully meshed in the same direction Screw rotation speed 300rpm Die mouth 3mmφ, 5-hole strand die head Traction speed: 5m/min.

The obtained water-containing EVOH particles were dried in a hot air dryer at 60° C. for 102 minutes using air having a dew point temperature of −10° C. to set the water content to 10% by mass. Next, it was dried at 120° C. for 24 hours in a hot air dryer using air with a dew point temperature of -20° C. Afterwards, the dried particles were sieved in the order of 6.5 mesh, 7 mesh and 8 mesh for 10 minutes to collect the particles remaining on the 8 mesh to obtain dry EVOH particles (melt molding material). The obtained melt-molded material was flat and had a length of 3.2 mm in the long-side direction and 2.1 mm in the short-side direction.

<Comparative Example 2> The water-containing EVOH particles w-EVOH-1 obtained in Example 1 were dried in a hot air dryer at 80°C for 1 hour using air with a dew point temperature of -30°C to obtain a water content of 50% by mass. % of aqueous EVOH particles. Put the obtained water-containing EVOH pellets into a two-screw extruder at 8 kg/hr (details are shown below), set the resin temperature at the discharge port to 100°C, as shown in Figure 1 at the front end of the discharge port In the solution adding section, an aqueous solution containing 5.0 g/L of acetic acid, 3.6 g/L of sodium acetate, 0.06 g/L of phosphoric acid, and 4.9 g/L of boric acid was added at 1.2 L/hr. As the die for extruding the solution of EVOH, hard chromium plating was used. The maximum height roughness (Rz) of the inner surface of the die head (outlet part) was 19.2 μm, and the arithmetic average roughness (Ra) was 1.45 μm. After the solution of ethylene-vinyl alcohol copolymer was extruded into the coagulation bath, it was cut with a rotating blade to obtain flat water-containing EVOH particles (water content: 42% by mass). The obtained water-containing EVOH particles were dried in a hot air dryer at 80°C for 48 minutes using air with a dew point temperature of -40°C to set the moisture content to 10% by mass. Next, it was dried at 120° C. for 24 hours in a hot air dryer using air with a dew point temperature of -20° C. Afterwards, the dried particles were sieved in the order of 4 mesh, 7 mesh and 9 mesh for 10 minutes to collect the particles remaining on the 9 mesh to obtain dry EVOH particles (melt molding material).

<Example 12> In addition to the water-containing pellets (w-EVOH-3), first, using air with a dew point temperature of -35°C, dried in a hot air dryer at 60°C for 3.7 hours to set the moisture content to 10% by mass, and then , using air with a dew point temperature of -20°C, and drying at 120°C for 24 hours in a hot air drier in the same manner as in Example 3 to obtain dry EVOH pellets (melt molding materials).

<Example 13> In addition to the water-containing pellets (w-EVOH-3), first, using air with a dew point temperature of -30°C, dried in a hot air dryer at 60°C for 13 hours to set the moisture content to 10% by mass, and then , using air with a dew point temperature of -20°C, and drying at 120°C for 24 hours in a hot air drier in the same manner as in Example 3 to obtain dry EVOH pellets (melt molding materials).

<Example 14> In addition to the water-containing pellets (w-EVOH-4), first, using air with a dew point temperature of -10°C, dried in a hot air dryer at 55°C for 5 hours to set the moisture content to 10% by mass, and then , using air with a dew point temperature of -20°C, and drying at 100°C for 36 hours in a hot air dryer in the same manner as in Example 10 to obtain dry EVOH pellets (melt molding materials).

<Comparative Example 3> In addition to dissolving 20kg of dried powdered EVOH in 28L of water/methanol mixed solution (mass ratio: water/methanol=4/6) at 80°C for 12 hours while dissolving it, and then using it The maximum height roughness (Rz) of the inner surface of the die head (exit part) that is precipitated into a strand shape is 18.2 μm, and the arithmetic average roughness (Ra) is 1.34 μm. The same method as in Example 1 This was carried out to obtain water-containing particles (w-EVOH-5) with a water content of 50% by mass. The water-containing granules (w-EVOH-5) were dried by the following operation. First, it dried at 75 degreeC for 3 hours in nitrogen atmosphere using the air of -10 degreeC of dew point temperature, and made the moisture content into 20 mass %. Next, it was dried at 120° C. for 12 hours in a nitrogen atmosphere using nitrogen gas having a dew point temperature of −20° C. Thereafter, the same screening as in Example 1 was carried out to obtain dry EVOH pellets (melt molding material).

<Evaluation> For each melt-molded material obtained, the surface roughness (maximum height roughness (Rz) and arithmetic mean roughness (Ra) and the full width at half maximum of the particle size distribution were measured by the aforementioned method. The measured The results are shown in Table 1. In Table 1, the drying conditions in the initial stage of drying when the above-mentioned respective melt-molded materials are combined are shown. In addition, each melt-molded material obtained was subjected to sudden anesthesia by the aforementioned method. Evaluation of the number of dots, uneven thickness and amount of fine powder. The evaluation results are shown in Table 1.

As shown in Table 1, the melt-molded materials of Examples 1 to 14 in which the maximum height roughness (Rz) of the side surface is 300 μm or less suppressed the occurrence of sudden pitting during continuous melt-molding. In order to reduce the maximum height roughness (Rz) and the arithmetic average roughness (Ra) of the side surface of the molten molding material, or to reduce the full width at half maximum of the molten molding material, and further reduce the Uneven thickness. In addition, the arithmetic average roughness (Ra) of the side surface of the melt-molded material is reduced to reduce the generation of fine powder.

In addition, Fig. 2(a) shows a photograph of a band-shaped foreign matter taken from a hopper when a single-layer film is formed from the molten molding material obtained in Comparative Example 1. Fix both ends of the foreign matter with adhesive tape, and take a picture together with the measuring ruler (displaying cm). Also, Fig. 2(b) shows an enlarged photograph of this band-shaped foreign body. Such foreign matter was confirmed to be the cause of sudden pitting. [Industrial availability]

The melt-molding material of the present invention is suitably used as a material for continuous melt-molding of films, sheets, containers, and the like.

1. 11‧‧‧melt molding material 2, 12‧‧‧side 3a‧‧‧top 3b‧‧‧bottom

[FIG. 1] (a) is a perspective view of a columnar melt-molded material according to an embodiment of the present invention. (b) is a front view of a flat melt-molded material according to an embodiment of the present invention. [Fig. 2] (a) It is a photograph of a band-shaped foreign matter taken from a hopper when a single-layer film is formed from the molten molding material obtained in Comparative Example 1. Fix both ends of the foreign matter with adhesive tape, and take a picture together with the measuring ruler (displaying cm). (b) is an enlarged photograph of the aforementioned band-shaped foreign matter obtained in Comparative Example 1.

Claims (6)

A melt-molded material, which is a columnar, flat or spherical melt-molded material comprising ethylene-vinyl alcohol copolymer, characterized in that the maximum height roughness (Rz) of the side surface is 200 μm or less. The melt-molded material according to claim 1, wherein the arithmetic mean roughness (Ra) of the side surface is 50 μm or less. The melt-molded material according to claim 1 or 2, wherein the full width at half maximum of the particle size distribution of the circle-equivalent diameter is 1 mm or less. The melt-molded material according to claim 1 or 2, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is not less than 20 mol % and not more than 60 mol %. The molten molding material as claimed in item 1 or 2, wherein it is cylindrical with a height of 1~20mm and a diameter of 1~20mm. The melt-molded material as claimed in claim 1 or 2, wherein it is flat or spherical with a length of 1 to 20 mm in the long side direction and 1 to 20 mm in the short side direction.

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