JP6915530B2 - Method for producing ethylene-vinyl alcohol-based copolymer pellets and ethylene-vinyl alcohol-based copolymer pellets - Google Patents

Description

The present invention relates to pellets of an ethylene-vinyl alcohol-based copolymer (hereinafter, may be referred to as "EVOH") capable of providing a film in which fish eyes are less likely to occur when the film is molded. The present invention relates to EVOH pellets in which the content of the boron compound present in the film is adjusted and a predetermined amount of lubricant is contained, and a method for producing the same.

In EVOH, the hydroxyl groups contained in the molecular chain are strongly hydrogen-bonded to form a crystal portion, and the crystal portion prevents the invasion of gas such as oxygen from the outside. Therefore, EVOH has excellent gas barrier properties including oxygen barrier properties. Can show sex. Taking advantage of these characteristics, EVOH is used by being molded into films and sheets such as food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, agricultural chemical packaging materials, and packaging containers such as bottles.

EVOH is usually formed and processed into a film shape, a sheet shape, a bottle shape, a cup shape, a tube shape, a pipe shape, or the like by melt molding, and is put into practical use. Therefore, the moldability and workability of EVOH are important.

Therefore, in order to improve the melt moldability, Patent Document 1 describes boric acid or a salt thereof from the viewpoint of film moldability of a melt moldable vinyl alcohol copolymer such as EVOH, particularly from the viewpoint of preventing surging during film formation. It is disclosed that it is effective to melt-mold a composition having an increased melt viscosity as the blended composition.

Further, in Patent Document 2, EVOH treated with a boron compound is co-extruded with polyolefin to obtain a laminate having excellent adhesiveness between the EVOH layer and the polyolefin layer, which is suitable in a field requiring gas barrier performance. It is disclosed that various packaging materials can be provided.
The boron compound treatment of Patent Document 2 is performed by adding a boron compound to an EVOH solution or a dispersion, and EVOH pellets containing a boron component are used as an extrusion molding raw material.

By the way, due to the recent increase in demand for the appearance of EVOH film or multilayer structure as a packaging material, improvement is required even for small fish eyes of less than 0.1 mm.
In Patent Document 3, it has been found that the boron-containing EVOH pellets obtained by treating EVOH with a boron compound are related to the generation of fish eyes having a water content of less than 0.1 mm, and the water content is 0. It is disclosed that the generation of fish eyes of less than 0.1 mm can be suppressed by contacting with water after drying to 0001 to 2% by weight.

In the examples of Patent Document 3, EVOH pellets to which a boron compound has been added are immersed in water and then dried to adjust the content and water content of the boron compound [moisture content 0.13 to 0]. .4% by weight, boron content per 100 parts by weight of EVOH 0.015 to 0.039 parts by weight (150 to 390 ppm)] was produced, and the EVOH pellets were supplied to a multi-layer extruder to supply 3 types and 5 layers of multi-layers. Laminates are manufactured (Examples 1, 3 and 4). Then, the fish eyes of the obtained multilayer structure are evaluated by visually observing and counting the number of fish eyes having a diameter of 0.01 to 0.1 mm (paragraphs [0038]-[0041]. ]).

Special Publication No. 62-3866 Tokusei No. 3-11270 Japanese Unexamined Patent Publication No. 2000-44756

In recent years, the demand for the appearance of packaging materials has become more and more strict, and further improvement of fish eyes is desired while ensuring melt moldability such as prevention of surging during molding. In particular, when EVOH is formed into a single layer, large fish eyes are more likely to be generated and the number of EVOHs is likely to be larger than in the case of a multilayer structure. Therefore, even with a single layer film of EVOH, fish eyes are generated. Suppressed EVOH pellets have been required, and the techniques disclosed in Patent Documents 1 to 3 have not yet been satisfactory.

The present invention has been made in view of the above circumstances, and an object of the present invention is to produce an EVOH pellet containing a boron compound and a lubricant capable of suppressing the generation of fish eyes even in an EVOH monolayer film and its production. To provide a method.

The present inventors investigated the relationship between the generation of fish eyes and EVOH pellets containing a boron compound. As a result of various studies, it is considered that fish eyes are generated by agglomerates of boron compounds causing local thickening of EVOH. Then, in the case of single-layer film formation, it was thought that the boron compound existing in the surface layer portion of the pellet, which would come into contact with the metal of the molding machine, would easily aggregate, and as a result, fish eyes would easily occur and would be conspicuous.

Generally, when EVOH pellets are supplied to an extruder, the frictional force on the surface of the pellets is high, so that the EVOH pellets are poorly bitten into the screw and are difficult to be supplied to the extruder. The present inventors considered that EVOH pellets are constantly exposed to high temperatures while they are not supplied, so that they are susceptible to thermal deterioration, resulting in an increase in fish eyes.

Comprehensively examining the above two types of fisheye generation mechanisms, the surface portion where the boron compound is present is preferentially heated while the EVOH pellet is not bitten into the screw, so that the boron compound is likely to aggregate. Therefore, it is presumed that the occurrence of fish eyes will become more prominent.

Based on this recognition, as a result of diligent studies, the present inventors focused on the content of the boron compound in the surface layer of the pellet and the content of the lubricant, and reduced the content of the boron compound in the surface layer of the pellet to be lower than before. In addition, by setting the content of the lubricant in EVOH within a predetermined range, it becomes easier to supply EVOH to the extruder, and fish eyes generated when a large amount of boron compound is present on the pellet surface are synergistically reduced. We found what we could do and completed the present invention.
The film (including the layer and the film) obtained by using the boron compound and the lubricant-containing EVOH pellet of the present invention is excellent in moldability and appearance even if it is a single-layer film, and therefore has excellent water resistance and strength. From the above viewpoints, it can be naturally applied to a multilayer structure in which other resin layers are laminated.

That is, the present invention is an EVOH pellet containing a boron compound and a lubricant (hereinafter, may be referred to as "boron compound and a lubricant-containing EVOH pellet"), and the boron compound content in the surface layer of the pellet is converted to boron. The first gist is an EVOH pellet having an amount of 1.7 ppm or less per weight of the pellet and a lubricant content of 0.001 to 0.15% by weight of the pellet.

Further, the present invention is a step of adding a boron compound by contacting an EVOH pellet with a boron compound, washing the pellet obtained by the above step, and adjusting the boron compound content of the pellet surface layer to ethylene- in terms of boron. A method for producing an EVOH pellet containing a boron compound and a lubricant, which comprises a step of reducing the weight of the vinyl alcohol-based copolymer pellet to 1.7 ppm or less and a step of adding a lubricant. The step of adding the lubricant is to bring the dried pellets into contact with a water / alcohol mixture or alcohol having a weight ratio (water / alcohol) of 80/20 to 0/100 to alcohol. The second gist is a method for producing an EVOH pellet containing 0.001 to 0.15% by weight of the pellet.

In the boron compound and lubricant-containing EVOH pellet of the present invention, the boron compound content of the surface layer of the pellet is 1.7 ppm or less per the weight of the pellet in terms of boron, and the content of the lubricant is 0.001 of the pellet. ~ 0.15% by weight. Therefore, the boron compound and lubricant-containing EVOH pellets of the present invention are excellent in the effect of suppressing the generation of fish eyes while ensuring melt moldability.

Further, among the present inventions, in particular, when the total content of the boron compound in the entire EVOH pellet containing a boron compound and a lubricant is 10 to 1000 ppm per the weight of the pellet in terms of boron, the viscosity becomes suitable for film formation, and the film is formed. The performance can be improved, and the effect of suppressing the occurrence of fish eyes can be excellent.

Further, among the present inventions, in particular, the weight ratio of the boron compound content (boron equivalent) of the pellet surface layer portion to the total boron compound content (boron equivalent) of the entire boron compound and lubricant-containing EVOH pellet (boron content in the surface layer portion). When the amount / total boron content) is 1.38 × ^10-2 or less, the effect of further suppressing the generation of fish eyes can be further improved, and the appearance of the film can be improved. can.

Further, among the present inventions, in particular, when the water content of the boron compound and the lubricant-containing EVOH pellet is 0.01 to 1% by weight, the effect of further suppressing the generation of fisheye can be made excellent. It can also improve the appearance of the film.

Further, a step of bringing the EVOH pellets into contact with a boron compound to contain the boron compound, and washing the pellets obtained by the above step to change the boron compound content of the pellet surface layer portion in terms of ethylene and vinyl alcohol. A method for producing EVOH pellets containing a boron compound and a lubricant, which comprises a step of reducing the weight of the polymer pellet to 1.7 ppm or less and a step of containing a lubricant. , The weight ratio (water / alcohol) of water to alcohol is 80/20 to 0/100 of contact with a water / alcohol mixture or alcohol, and the step of containing the lubricant is to bring the lubricant to 0 of the pellet. According to the method for producing EVOH pellets of the present invention, which is contained so as to be .001 to 0.15% by weight, the boron content of the surface layer portion can be reduced, and EVOH pellets containing a lubricant can be obtained. The melt-molded product using pellets has good melt-moldability and reduces the occurrence of fish eyes.

Hereinafter, the present invention will be described in detail, but these are examples of desirable embodiments and are not specified in their contents.

In the present specification, the content measured as the boron content in the EVOH pellet containing the boron compound and the lubricant is referred to as "boron compound content (boron equivalent)" or simply "boron content".

In the boron compound and lubricant-containing EVOH pellet of the present invention, the boron content of the surface layer of the pellet is 1.7 ppm or less per the weight of the pellet in terms of boron, and the content of the lubricant is 0.001 of the pellet. ~ 0.15% by weight.

Here, the "boron compound content of the pellet surface layer portion" means the amount of the boron compound present near the surface among the boron compounds contained in the boron compound and the lubricant-containing EVOH pellet. Specifically, 4 g of EVOH pellets containing a boron compound and a lubricant was immersed in 20 mL of methanol at 30 ° C. for 6 hours, and then the inductively coupled plasma mass spectrometer (ICP-MS) was used to determine the boron content in the obtained methanol solution. It was measured using and divided by the weight (4 g) of the above EVOH pellets. The "boron compound on the surface layer of the pellet" includes a boron compound that is only attached to the surface of the pellet, a boron compound that has bleeded on the surface, and the like.
The "boron compound content in the surface layer of the pellet" is distinguished from the boron compound content in the boron compound and the lubricant-containing EVOH pellet ("total boron compound content in the pellet"). ..

Hereinafter, prior to the description of the EVOH pellet containing the boron compound and the lubricant of the present invention, each component and a method for producing the EVOH pellet before containing the boron compound and the lubricant will be described.

<EVOH>
The EVOH constituting the boron compound and the lubricant-containing EVOH pellet of the present invention is usually a resin obtained by saponifying a copolymer (ethylene-vinyl ester-based copolymer) of ethylene and a vinyl ester-based monomer. , A water-insoluble thermoplastic resin generally called an ethylene-vinyl alcohol-based copolymer or an ethylene-vinyl ester-based copolymer saponified product. The polymerization method can also be carried out by using any known polymerization method, for example, solution polymerization, suspension polymerization or emulsion polymerization, but in general, solution polymerization using a lower alcohol such as methanol, particularly preferably methanol as a solvent. Is used. The obtained ethylene-vinyl ester copolymer can also be saponified by a known method.
The EVOH produced in this manner is mainly composed of ethylene-derived structural units and vinyl alcohol structural units, and usually contains a small amount of vinyl ester structural units remaining without saponification, if necessary.

As the vinyl ester-based monomer, vinyl acetate is typically used because it is easily available on the market and the processing efficiency of impurities during production is good. Examples of other vinyl ester-based monomers include vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versaticate and the like. Examples thereof include aliphatic vinyl esters and aromatic vinyl esters such as vinyl benzoate. Usually, an aliphatic vinyl ester having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms is used. Can be done. These are usually used alone, but if necessary, a plurality of types may be used at the same time.

The ethylene and vinyl ester-based monomers usually use petroleum-derived raw materials such as naphtha, but natural gas-derived raw materials such as shale gas, sugars and starches contained in sugar cane, tensai, corn, potatoes and the like. Etc., or monomers from plant-derived raw materials purified from components such as cellulose contained in rice, wheat, millet, grass plants and the like may be used.

The content of ethylene structural units in EVOH is a value measured based on ISO14663 and is usually 20 to 60 mol%, preferably 25 to 50 mol%, particularly preferably 27 to 48 mol%. If the content is too low, the gas barrier property and melt moldability under high humidity tend to decrease, and if the content is too high, the gas barrier property tends to decrease.

The saponification degree of the vinyl ester component in EVOH is a value measured based on JIS K6726 (however, water / methanol is used as a solvent), and is usually 90 to 100 mol%, preferably 95 to 100 mol%, particularly preferably. It is 99 to 100 mol%. If the saponification degree is too low, the gas barrier property, thermal stability, moisture resistance and the like tend to decrease.

The melt flow rate (MFR) (210 ° C., load 2160 g) of the EVOH is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, and particularly preferably 2 to 35 g / 10 minutes. Is. If the MFR is too large, the film forming property tends to be unstable, and if it is too small, the viscosity tends to be too high and melt extrusion tends to be difficult.

The EVOH used in the present invention may further contain structural units derived from the commonomers shown below as long as the effects of the present invention are not impaired (for example, 10 mol% or less).

Examples of the comonomer include olefins such as propylene, 1-butene and isobutene, 3-butene-1-ol, 3-butene-1,2-diol, 4-pentene-1-ol and 5-hexene-1,2. Hydroxyl-containing α-olefins such as −diol and derivatives such as esterified products and allyl groups thereof; hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; 1 , 3-Diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, 1,3-dibutyronyloxy-2-methylenepropane and other hydroxyalkyl vinylidene diacetates, acryloacid, methacrylic acid , Crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid and other unsaturated acids or salts thereof or mono- or dialkyl esters having 1 to 18 carbon atoms; acrylamide, having 1 to 18 carbon atoms. Acrylamides such as N-alkylacrylamide, N, N-dimethylacrylamide, 2-acrylamide propanesulfonic acid or a salt thereof, acrylamidepropyldimethylamine or an ester thereof or a quaternary salt thereof; metaacrylamide, N having 1 to 18 carbon atoms. Methylamides such as -alkylmetharylamide, N, N-dimethylmethacrylate, 2-methallylamide propanesulfonic acid or a salt thereof, methallylamide propyldimethylamine or an ester thereof or a quaternary salt thereof; N-vinylpyrrolidone, N. -N-vinylamides such as vinylformamide and N-vinylacetamide; vinyl cyanide such as acrylonitrile and methacrylnitrile; vinyl ethers such as alkylvinyl ethers having 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers and alkoxyalkyl vinyl ethers; vinyl chloride , Vinyl halide compounds such as vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide; vinylsilanes such as trimethoxyvinylsilane; allyl halides such as allyl acetate and allyl chloride; allyl alcohol, dimethoxyallyl alcohol Allyl alcohols such as trimethyl- (3-acrylamide-3-dimethylpropyl) -ammonium chloride, comonomers such as acrylamide-2-methylpropanesulfonic acid can be mentioned. These can be used alone or in combination of two or more.

In particular, EVOH obtained by copolymerizing a hydroxyl group-containing α-olefin is preferable in that the secondary moldability is improved. Among them, EVOH having a primary hydroxyl group in the side chain, particularly 1,2-diol structure in the side chain. EVOH having is preferable.

An EVOH having such a 1,2-diol structure in a side chain contains a 1,2-diol structural unit in the side chain. The 1,2-diol structural unit is specifically a structural unit represented by the following general formula (1).

In the above general formula (1), R ^{1 to} R ⁶ independently represent a hydrogen atom or an organic group, and X represents a single bond or a bond chain.

Examples of the organic group in the 1,2-diol structural unit represented by the general formula (1) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group and a tert-butyl group. Examples thereof include saturated hydrocarbon groups such as, aromatic hydrocarbon groups such as phenyl group and benzyl group, halogen atoms, hydroxyl groups, acyloxy groups, alkoxycarbonyl groups, carboxyl groups and sulfonic acid groups.
R ^{1 to} R ³ are usually preferably saturated hydrocarbon groups or hydrogen atoms having 1 to 30 carbon atoms, particularly 1 to 15 carbon atoms, and further preferably 1 to 4 carbon atoms, and hydrogen atoms are most preferable. R ^{4 to} R ⁶ usually have 1 to 30 carbon atoms, particularly preferably 1 to 15 carbon atoms, more preferably an alkyl group or a hydrogen atom having 1 to 4 carbon atoms, and most preferably a hydrogen atom. In particular, it is most preferable that ^{R 1 to} R ^{6 are all hydrogen atoms.}

Further, X in the structural unit represented by the general formula (1) is typically a single bond.
In addition, X may be a binding chain as long as it does not hinder the effect of the present invention. The bonding chain is not particularly limited, but for example, a hydrocarbon chain such as alkylene, alkenylene, alkynylene, phenylene, naphthylene (these hydrocarbons may be substituted with halogens such as fluorine, chlorine and bromine). Other structures containing ether binding sites such as −O−, − (CH ₂ O) m−, − (OCH ₂ ) m−, − (CH ₂ O) mCH _{2 −; −CO−, −COCO−, −} Structure containing carbonyl groups such as CO (CH ₂ ) mCO-, -CO (C ₆ H ₄ ) CO-; Structure containing sulfur atoms such as _{-S-, -CS-, -SO-, -SO 2-;} -NR -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - structure containing a nitrogen atom such as NRNR-; -HPO ₄ - structure containing a heteroatom structure such as that containing a phosphorus atom and the like; _{-Si (OR) 2 -, -} OSi (OR) 2 -, - OSi (OR) structure containing ₂ O- such as silicon _{atoms; -Ti (OR) 2 -,} - OTi (OR) 2 -, - OTi (OR) ₂ Structure containing titanium atom such as O−; Structure containing metal atom such as structure containing aluminum atom such as −Al (OR) −, −OAl (OR) −, −OAl (OR) O− Can be given.
Further, m is a natural number, and is usually 1 to 30, preferably 1 to 15, and more preferably 1 to 10. _{Among them, −CH 2} OCH ₂ − and a hydrocarbon chain having 1 to 10 carbon atoms are preferable in terms of stability during production or use, and a hydrocarbon chain having 1 to 6 carbon atoms, particularly 1 carbon atom. Is preferable.

The most preferable structure in the 1,2-diol structural unit represented by the general formula (1) is that R ^{1 to} R ⁶ are all hydrogen atoms and X is a single bond. That is, the structural unit represented by the following general formula (1a) is most preferable.

When the 1,2-diol structural unit represented by the general formula (1a) is contained, the content thereof is usually 0.1 to 20 mol%, further 0.1 to 15 mol%, particularly 0.1. 10 mol% is preferable.

Further, as the EVOH used in the present invention, "post-modified" EVOH such as urethanization, acetalization, cyanoethylation, and oxyalkyleneization can also be used.

<Boron compound>
The boron compound used in the present invention includes boric acid or a metal salt thereof, for example, sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, sodium octaborate). Etc.), potassium borate (potassium metaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, potassium octaborate, etc.), lithium borate (lithium metaborate, lithium tetraborate, lithium pentaborate, etc.) Etc.); Calcium borate, barium borate (barium orthoborate, barium metaborate, barium diborate, barium tetraborate, etc.), magnesium borate (magnesium orthoborate, magnesium diborate, magnesium metaborate, tetraborate, etc.) Trimagnesium acid, pentamagnesium tetraborate, etc.); Manganese borate (primary borate, manganese metaborate, manganese tetraborate, etc.), cobalt borate, zinc borate (zinc tetraborate, zinc metaborate, etc.) ), Cadmium borate (cadmium orthoborate, cadmium tetraborate, etc.), silver borate (silver metaborate, silver tetraborate, etc.), copper borate (second copper borate, copper metaborate, copper tetraborate, etc.) Etc.), Nickel borate (nickel orthoborate, nickel diborate, nickel tetraborate, nickel octaborate, etc.), aluminum / potassium borate, ammonium borate (ammonium metaborate, ammonium tetraborate, pentaboric acid, etc.) Ammonium, ammonium octaborate, etc.), lead borate (lead metaborate, lead hexaborate, etc.), bismuth borate, etc. Examples thereof include borate minerals, and preferably boric acid and boric acid. These can be used alone or in combination of two or more.

<Glidant>
Examples of the lubricant used in the present invention include higher fatty acids, for example, higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and oleic acid; aluminum salts, calcium salts, and zinc of these higher fatty acids. Metal salts of higher fatty acids such as salts, magnesium salts and barium salts; esters of higher fatty acids such as methyl ester, isopropyl ester, butyl ester and octyl ester of the higher fatty acids; saturated higher fatty acid amides such as stearate amide and behenic acid amide. Of higher fatty acids such as unsaturated higher fatty acid amides such as oleic acid amide and erucic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, ethylene bis-erucic acid amide and bis higher fatty acid amide such as ethylene bislauric acid amide. Amid can be mentioned. Examples thereof include low molecular weight polyethylene having a molecular weight of about 500 to 10000, low molecular weight polypropylene, and low molecular weight polyolefins such as acid-modified products thereof; higher alcohols, ester oligomers, ethylene fluoride resins and the like. These can be used alone or in combination of two or more. In the compound used for the lubricant, higher fatty acids are preferable from the viewpoint of extrusion stability and market availability, and the number of carbon atoms in one molecule of the above higher fatty acids is usually 12 to 25, preferably 12 carbon atoms. It is ~ 23, and particularly preferably 15 to 20 carbon atoms. Further, in the compound used for the lubricant, the valence of the higher fatty acids is usually 1 to 5 valences, preferably 1 to 3 valences, and particularly preferably 1 to 2 valences from the viewpoint of extrusion stability and market availability. It is a value. At this time, such a valence means the number of structures derived from higher fatty acids contained in one molecule of the compound used for the lubricant. For example, when bisstearic acid amide is used as the lubricant, it is derived from a higher fatty acid molecule having 18 carbon atoms. Since it has two structures in one molecule, it is an amide of a higher fatty acid having 18 carbon atoms, and the valence of the higher fatty acid is divalent. Among these, a higher fatty acid, a metal salt of a higher fatty acid, an ester of a higher fatty acid, and an amide of a higher fatty acid are preferable, and a metal salt of a higher fatty acid and an amide of a higher fatty acid are particularly preferable, and extrusion stability is more preferable. From a sexual point of view, it is a higher fatty acid amide.

As the lubricant, any property such as solid (powder, fine powder, flakes, etc.), semi-solid, liquid, paste, solution, emulsion (aqueous dispersion), etc. can be used. Of these, powder is preferable. The particle size of the powdered lubricant is usually 0.1 to 100 μm, preferably 1 to 75 μm, and particularly preferably 5 to 50 μm.

<Manufacturing of EVOH pellets>
As a method for producing pellets from EVOH, a conventionally known method can be adopted, for example,
a) A hot-cut method in which EVOH in a molten state is extruded from the discharge port of an extruder, cut in a molten state, and then cooled and solidified to produce pellets.
b) A strand cut method in which the molten EVOH is extruded into a coagulation bath and the EVOH strands obtained by cooling and solidifying are cut.

In both of the above a) hot-cut method and b) strand-cut method, the EVOH used as a pellet raw material is obtained by saponifying a solution of an ethylene-vinyl ester copolymer in the production of (α) EVOH. The obtained EVOH solution or slurry, or EVOH hydrous composition (hereinafter, may be referred to as "EVOH solution / hydrous composition"); or (β) EVOH (dry EVOH) pellets are melted, and such a molten state is obtained. EVOH can be used.

The EVOH water-containing composition is obtained by appropriately adjusting the water content of the EVOH solution or slurry using a solvent, and the concentration of EVOH in the EVOH water-containing composition is usually 20 to 60% by weight.

As the above solvent, alcohol, water / alcohol mixed solvent and the like can be used. Of these, a water / alcohol mixed solvent is preferable. As the alcohol, for example, an aliphatic alcohol having 1 to 10 carbon atoms such as methanol, ethanol, propanol, n-butanol, and tert-butanol can be used, and methanol is particularly preferable. The water / alcohol mixed weight ratio is preferably 80/20 to 5/95.

The EVOH water-containing composition usually contains 0 to 10 parts by weight of alcohol and 10 to 500 parts by weight of water with respect to 100 parts by weight of EVOH.

The method for adjusting the water content of the EVOH water-containing composition is not particularly limited, but in order to increase the water content, a method of spraying the above solvent on the EVOH solution or slurry, the EVOH solution or slurry and the above solvent A method of mixing with, a method of bringing an EVOH solution or a slurry into contact with the vapor of the above solvent, or the like can be adopted. In order to reduce the water content, the EVOH solution or slurry may be appropriately dried, and can be dried using, for example, a fluid hot air dryer or a static hot air dryer.

Next, a) hot-cut method and b) strand-cut method will be described.

a) Hot-cut method When the EVOH solution / water-containing composition is put into an extruder as a pellet raw material to be produced by the hot-cut method, the temperature of the EVOH solution / water-containing composition in the extruder is preferably 70 to 170 ° C. It is preferably 80 to 170 ° C, more preferably 90 to 170 ° C. If the temperature of the EVOH solution / water-containing composition is too low, the EVOH tends not to melt completely, and if it is too high, the EVOH tends to be susceptible to thermal deterioration.
When dry EVOH is used as a pellet raw material, the temperature of EVOH in the extruder is preferably 150 to 300 ° C, more preferably 160 to 280 ° C, and even more preferably 170 to 250 ° C.
The temperature of the EVOH solution / water-containing composition and the dried EVOH refers to the temperature detected in the vicinity of the ejection port at the tip of the extruder by the temperature sensor installed in the extruder cylinder.

The EVOH solution / water-containing composition extruded from the die of the extruder, that is, the EVOH in the molten state is cut before cooling and solidifying. The cutting method may be either a hot cutting method of cutting in the air (air hot cutting method) or an underwater cutting method of extruding into a cutter installation container filled with cooling water and cutting in cooling water.

The temperature of the cooling water in the above-mentioned underwater cutting method is such that the EVOH extruded in the molten state does not instantly solidify (solidify), and the temperature of the cooling water when the EVOH solution / water-containing composition is used as a raw material is-. The temperature is preferably 20 to 50 ° C, more preferably −5 to 30 ° C.
Further, when dry EVOH is used as a raw material, it is easier to solidify than when an EVOH solution / water-containing composition is used as a raw material. Therefore, the temperature of the cooling water in the underwater cutting method is higher than that when the EVOH water-containing composition is used as a raw material. It is high, usually 0 to 90 ° C, preferably 20 to 70 ° C.

The cooling water is not limited to water, but is a water / alcohol mixed solution; aromatic hydrocarbons such as benzene; ketones such as acetone and methyl ethyl ketone; ethers such as dipropyl ether; methyl acetate, ethyl acetate and propionic acid. Organic esters such as methyl can also be used. Of these, water or a water / alcohol mixed solution is used because it is easy to handle. In the water / alcohol mixed solution, the water / alcohol (weight ratio) is usually 90/10 to 99/1. As the alcohol, lower alcohols such as methanol, ethanol and propanol can be used, and methanol is preferably used industrially.

b) Strand-cut method When the EVOH solution / water-containing composition is put into an extruder as a pellet raw material produced by the strand-cut method, the temperature of EVOH extruded into the coagulation bath is usually 10 to 100 ° C., and the temperature of the coagulation bath is , The temperature at which the extruded EVOH can be cooled and solidified, usually −10 to 40 ° C., and the residence time is usually about 10 to 400 seconds.
When dry EVOH is put into an extruder as a pellet raw material, the temperature at which EVOH is extruded into the coagulation bath is usually 150 to 300 ° C., the temperature of the coagulation bath is usually 0 to 90 ° C., and the residence time is It takes about 2 to 400 seconds.

As the coagulation liquid used in the coagulation bath, a solution similar to the above-mentioned a) hot-cut type cooling water can be adopted.

In this way, EVOH pellets are obtained.

Among the above EVOH pellets, it is preferable to use a porous pellet having a plurality of pores inside the pellet from the viewpoint of the treatment containing a boron compound described later. By infiltrating the boron compound into the pores, the boron compound can be easily retained in the pellet, and the boron compound can be efficiently taken into the pellet. The size of the pores of the porous pellets is not particularly limited as long as the boron compound can penetrate into the pores.

Such a porous pellet usually uses the above-mentioned EVOH resin water-containing composition as a pellet raw material, and the EVOH concentration in the EVOH water-containing composition, the type of solvent, the temperature at the time of extrusion, the temperature of the coagulation bath, and the residence time. It can be obtained by adjusting the above.

The water content of the porous pellets is preferably 20 to 80% by weight. The porous pellets having a water content can uniformly and rapidly contain the boron compound in the step of containing the boron compound, which will be described later.

The shape of the EVOH pellet usually depends on the method for producing the pellet, and various shapes can be used, and the shape of the EVOH pellet obtained by each of the above methods and the EVOH composition pellet of the present invention is arbitrary. The shape of the pellet includes, for example, spherical, oval, cylindrical, cubic, rectangular parallelepiped, amorphous, etc., but is usually oval or cylindrical, and the size thereof will be used later as a molding material. From the viewpoint of convenience in the case, the major axis is usually 1 to 10 mm, preferably 2 to 7 mm in the case of the oval type, the minor axis is usually 1 to 6 mm, preferably 2 to 5 mm in the case of the cylindrical type, and the bottom surface in the case of the cylindrical type. The diameter of the cylinder is usually 1 to 10 mm, preferably 2 to 7 mm, and the length is usually 1 to 10 mm, preferably 3 to 8 mm.

Further, the EVOH pellet used in the present invention may be a mixture with other EVOH pellets different from each other, and the other EVOH pellets mentioned above include those having a different content of ethylene structural units, those having a different degree of saponification, and melts. Examples thereof include those having different flow rates (MFR) and those having different other copolymerization components, for example, those having different contents of 1,2-diol structural units represented by the general formula (1). ..

The boron compound and lubricant-containing EVOH pellet of the present invention can be obtained by adding a specific amount of boron compound and lubricant to the EVOH pellet. The method for producing the boron compound and lubricant-containing EVOH pellets of the present invention is not particularly limited, but typical production will be described below.

<Manufacture of EVOH pellets containing boron compounds and lubricants>
The boron compound and lubricant-containing EVOH pellet of the present invention is a step of adding a boron compound by contacting the EVOH pellet with the boron compound, and the EVOH pellet containing the boron compound is washed to contain the boron compound in the surface layer of the pellet. Can be obtained by going through a step of reducing the amount of boron to 1.7 ppm or less per the weight of the pellet and a step of adding a lubricant. Either of these steps may be performed first, or may be performed at the same time. When the above steps are performed at the same time, for example, a solution containing a boron compound and a lubricant can be used.

<Step of adding boron compound>
The step of containing the boron compound is performed by bringing the EVOH pellet into contact with the boron compound.

As a method of bringing the EVOH pellet into contact with the boron compound, for example,
i) A method of contacting EVOH with a boron compound in the EVOH pellet manufacturing stage,
ii) A method of contacting a previously prepared EVOH pellet with a boron compound,
It can be done by such as.

As a method of contacting EVOH with a boron compound in the EVOH pellet production step of i), for example, a boron compound is added to a pellet raw material (EVOH solution / water-containing composition, dried EVOH), or a solution containing the boron compound is added. , The method used for the coagulating liquid in the production of pellets and the like.
When an EVOH solution / water-containing composition is used as the pellet raw material, a boron compound may be added to the EVOH solution / water-containing composition. When the dried EVOH pellets are melted and the melted EVOH is used as a raw material, the dried EVOH may contain a boron compound in advance.
Preferably, the EVOH water-containing composition to which the boron compound is added is extruded into a coagulating liquid in the form of strands, and the obtained strands are cleaved.

As a method of contacting the EVOH pellet prepared in advance of ii) with the boron compound, a method of spraying a solution containing the boron compound onto the EVOH pellet; a method of immersing the EVOH pellet in the solution containing the boron compound; Examples thereof include a method of adding EVOH pellets while stirring the solution containing the above. Of these, a method in which the EVOH pellet is charged while stirring the solution containing the boron compound is preferably used because the boron compound can be efficiently contained inside the pellet.

As the solvent of the solution containing the boron compound, for example, water; lower alcohol such as methanol, ethanol, propanol; water / alcohol mixing solution and the like can be used. In the water / alcohol mixed solution, the water / alcohol (weight ratio) is usually 90/10 to 99/1.

The concentration of the solution of the boron compound used for the contact treatment between the EVOH pellet and the boron compound is usually 0.001 to 1% by weight, preferably 0.003 to 0.5% by weight. If the concentration is too low, it tends to be difficult to contain a predetermined amount of the boron compound, and if it is too high, the appearance of the finally obtained molded product tends to be deteriorated.

The amount of the boron compound in the EVOH pellet (total content of the boron compound in the EVOH pellet) is determined by the concentration of the boron compound in the solution containing the boron compound, the contact treatment time, the contact treatment temperature, the stirring speed at the time of the contact treatment, and the treatment. It can be controlled by the water content of the EVOH pellets.

Among the methods for contacting the EVOH pellet with the boron compound as described above, the method for contacting the EVOH pellet prepared in advance in ii) with the boron compound in that it can be applied to various pellets and has excellent versatility. Is preferable. More preferably, it is a method of contacting the porous EVOH pellet with a solution of a boron compound.

An EVOH pellet containing a boron compound obtained by such a boron compound contact treatment [the content of the boron compound in the surface layer of the pellet has not been adjusted, and the pellet is hereinafter referred to as "EVOH pellet before boron adjustment in the surface layer"]. The amount of the boron compound contained (total content of the boron compound in the EVOH pellet) is usually 10 to 10000 ppm, preferably 20 to 5000 ppm, and more preferably 30 to 3000 ppm in terms of boron. If the content is too small, the effect of adding the boron compound tends to decrease, and if it is too large, the appearance of the finally obtained molded product tends to deteriorate.

The amount of boron compound [total boron compound content (boron equivalent)] contained in the above-mentioned surface layer portion boron-adjusted EVOH pellet is determined by adding a solution obtained by treating the pellet with concentrated nitrate by a microwave decomposition method. The amount is measured by an inductively coupled plasma emission spectrometer (ICP-AES) using pure water as a test solution.

The surface layer portion of the EVOH pellet before boron adjustment obtained by the above step may be used as it is in the next step, but it is usually preferable to dry the pellet. A known method can be adopted for such drying, for example, a cylindrical / groove type stirring dryer, a cylindrical dryer, a rotary dryer, a fluidized bed dryer, a vibrating fluidized bed dryer, a conical rotary dryer, or the like. It may be dried by the fluidized bed used or a static drying using a batch box type dryer, a band dryer, a tunnel dryer, a vertical silo dryer or the like. By passing a gas such as nitrogen gas at 80 to 150 ° C. through the dryer, the surface layer portion of the EVOH pellet before boron adjustment can be efficiently dried without affecting the EVOH pellets.

<Process of cleaning EVOH pellets>
Next, the step of washing the EVOH pellets will be described.
The above-mentioned EVOH pellet before adjusting boron in the surface layer portion has a boron compound content in the pellet surface layer portion by a washing treatment, although it depends on the total content of the boron compound contained in the pellet and the content of the boron compound in the pellet surface layer portion. Can be adjusted.

The cleaning treatment is performed by bringing the cleaning treatment liquid into contact with the EVOH pellets before adjusting the surface layer boron. Examples of the contact method include a method of immersing the surface layer portion boron-adjusted EVOH pellets in a cleaning treatment liquid and stirring them, a method of circulating the surface layer portion boron-adjusted EVOH pellets in the cleaning treatment liquid, and a surface layer portion. This can be done by spraying a cleaning treatment liquid onto the EVOH pellets before boron adjustment. Further, in the above dipping method, it is also effective to apply vibration such as ultrasonic waves during dipping. Among the above methods, industrially, preferably, a method of immersing the EVOH pellets before boron adjustment in the surface layer in the cleaning treatment liquid and stirring the EVOH pellets, and a method of circulating the EVOH pellets in the surface layer before boron adjustment in the cleaning treatment liquid are preferable. Used.

The cleaning treatment solution is preferably a water / alcohol mixed solution or alcohol, and more preferably a water / alcohol mixed solution.

Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, 2-methyl-2-propanol and the like having 1 to 8 carbon atoms. In particular, it is preferable to use 1 to 5 alcohols and further 1 to 3 alcohols, and among these, methanol is particularly preferably used in terms of easy availability and low cost.

When a water / alcohol mixed solution or alcohol is used as the cleaning treatment solution, the water / alcohol (weight ratio) is 80/20 to 0/100, preferably 65/35 to 15/85, and particularly preferably 50 /. It is 50 to 20/80. Even if the amount of water is too large or the alcohol concentration is too high, the effect of reducing the boron compound content in the surface layer tends to decrease. Therefore, a water / alcohol mixed solution in the above range is preferable.

In general, the solubility of a boron compound is higher in alcohol than in water. Therefore, alcohol is usually used as a cleaning treatment liquid for adjusting the content of the boron compound. However, in the present invention, surprisingly, by using a water / alcohol mixed solution as the cleaning treatment solution rather than alcohol alone, the boron compound can be more efficiently eluted from the surface layer portion of the EVOH pellet before boron adjustment. I found. The solubility of the boron compound in 10 g of water at 23 ° C. is about 0.1 to 10% by weight, and the solubility of the boron compound in 10 g of methanol at 23 ° C. is about 15 to 30% by weight.

The contact time between the surface layer portion of the EVOH pellet before boron adjustment and the cleaning treatment liquid is not particularly limited as long as the boron compound content reaches a predetermined concentration, but is usually 5 minutes to 48 hours, and further 10 minutes to. 24 hours is preferable, and the temperature of the cleaning treatment liquid is usually 10 to 80 ° C., more preferably 20 to 60 ° C.

The boron compound-containing EVOH pellets after the cleaning treatment may be dried if necessary. Specifically, it is preferable to dry to a moisture content of about 0.01 to 1% by weight, preferably about 0.05 to 0.5% by weight. As the drying method, the same method as the method for drying the EVOH pellets before adjusting the surface layer boron can be adopted.

By the above cleaning treatment, the content of the boron compound in the surface layer of the pellet can be reduced, and the content of the boron compound in the surface layer of the pellet, which is the first feature of the present invention, is reduced to 1.7 ppm or less in terms of boron. EVOH pellets containing a boron compound are obtained.

Next, a step of incorporating the lubricant into the EVOH pellet, which is the second feature of the present invention, will be described.

<Step of adding lubricant>
The EVOH pellet containing the lubricant can be produced by bringing the EVOH pellet into contact with the lubricant.

As a method of incorporating a lubricant in the EVOH pellet, for example,
iii) Method of contacting with lubricant at the EVOH pellet manufacturing stage,
iv) A method of contacting a prefabricated EVOH pellet with a lubricant,
It can be done by such as.

As the method of contacting with the lubricant in the above-mentioned iii) EVOH pellet production stage, for example, a method of adding the lubricant to the pellet raw material (EVOH solution / water-containing composition, dried EVOH), a method of using the solution containing the lubricant in the coagulation liquid. And so on.
When an EVOH solution / water-containing composition is used as the pellet raw material, for example, the lubricant may be dispersed in the EVOH solution / water-containing composition. When dry EVOH is used, the dried EVOH pellets may be melted, and the melted EVOH and the lubricant may be melt-kneaded by an extruder.

As a method of contacting the EVOH pellet prepared in advance of iv) with the lubricant, a method of spraying the solution or dispersion containing the lubricant on the EVOH pellet; a method of immersing the EVOH pellet in the solution or dispersion containing the lubricant. The EVOH pellets are added while stirring the solution or dispersion containing the lubricant; the lubricant powder is directly added to the EVOH pellets and mixed. Of these, a method in which the lubricant powder is directly added to the EVOH pellets and mixed is preferably used because the lubricant can be efficiently contained.

The concentration of the lubricant in the solution or dispersion containing the lubricant is usually 1 to 80% by weight, preferably 20 to 70% by weight. If the concentration is too low, it tends to be difficult to contain a predetermined amount of lubricant, and if it is too high, the appearance of the finally obtained molded product tends to be deteriorated. When a solution containing a lubricant or a dispersion is used, the same solvent as that used for the solution containing the boron compound can be used.

Further, in the method using the solution or dispersion containing the lubricant, in the contact treatment with the solution or dispersion containing the lubricant, the amount added, the concentration of the lubricant, the contact treatment time, the contact treatment temperature, and the contact treatment The lubricant content can be controlled by the stirring speed, the water content of the EVOH pellets to be treated, and the like.

When the above-mentioned lubricant powder is directly added to the EVOH pellet, the addition amount can be the content of the lubricant, and the amount of the lubricant to be added is usually 0.001 to 0.15 weight with respect to the EVOH pellet. %, Preferably 0.003 to 0.12% by weight, more preferably 0.005 to 0.10% by weight. If the amount is too small, the friction between the screw surface of the extruder and the EVOH pellets becomes strong, which tends to cause an increase in fish eyes due to the inability to supply stable pellets. On the contrary, this tends to cause an increase in fish eyes, or a decrease in friction between the EVOH pellets and the screw surface, which makes it impossible to stably supply pellets, which tends to cause an increase in fish eyes.

Among the methods of contacting the EVOH pellet lubricant as described above, the method of contacting the EVOH pellet prepared in advance in iv) with the lubricant is preferable in that it can be applied to various pellets and has excellent versatility. Particularly preferred is a method in which the lubricant powder is directly added to the EVOH pellet and mixed.

The lubricant-containing EVOH pellets may be dried, if necessary. Specifically, the water content is usually 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight. As the drying method, the same method as the drying method of the EVOH pellets before adjusting the surface layer boron can be adopted.

By the above steps, lubricant-containing EVOH pellets are obtained.

The boron compound and lubricant-containing EVOH pellets of the present invention can be obtained through the steps of adding the boron compound, washing the EVOH pellets, and adding the lubricant.

Among them, from the viewpoint of work efficiency, it is preferable to carry out a step of containing a boron compound, then a step of washing the EVOH pellets, and finally a step of adding a lubricant, and among them, a step of containing a boron compound is step ii. ), The step of containing the lubricant is particularly preferably performed in step iv).

<EVOH pellets containing boron compounds and lubricants>
The total content of the boron compound in the boron compound and lubricant-containing EVOH pellets is preferably 10 to 1000 ppm, more preferably 20 to 500 ppm, still more preferably 30 in terms of boron relative to the weight of the boron compound and lubricant-containing EVOH pellets. ~ 300 ppm. The total content of the boron compound in the above-mentioned boron compound and the lubricant-containing EVOH pellet can be measured by the same method as the amount of the boron compound contained in the surface layer portion boron-adjusted EVOH pellet.

If the content of the boron compound contained in the boron compound and the lubricant-containing EVOH pellet is too small, the melt viscosity tends to be low, the film forming performance tends to be lowered, and inflationary filming tends to be particularly difficult. Therefore, it is preferable to contain the boron compound so that the content of the boron compound is at least about 10 ppm.

Further, in the boron compound and lubricant-containing EVOH pellets, the boron compound content in the surface layer of the pellet is 1.7 ppm or less, preferably 1.6 ppm or less, and more preferably 1.5 ppm or less per weight of the pellet in terms of boron. Is. The lower limit is not particularly limited, but when the total content of the boron compound in the boron compound and the lubricant-containing EVOH pellet is within the above range, it is usually 1 ppb or more, preferably 50 ppb or more, and more preferably 100 ppb or more.
If the content of the boron compound in the surface layer of the pellet is too large, fish eyes and the like are likely to occur, the appearance of the film is deteriorated, and the film forming property is also deteriorated.

The boron compound content in the surface layer of the pellet was determined by inductively coupled plasma mass spectrometry of the boron compound content in the obtained methanol solution after 4 g of EVOH pellets containing a boron compound and a lubricant were immersed in 20 mL of methanol at 30 ° C. for 6 hours. It was measured using (ICP-MS) and divided by the weight (4 g) of the above EVOH pellets.

The boron compound and lubricant-containing EVOH pellets are the weight ratio of the boron compound content (boron equivalent) of the pellet surface layer portion to the total boron compound content (boron equivalent) in the boron compound and lubricant-containing EVOH pellets (boron content of the surface layer portion). The amount / total boron content) ^{is preferably 1.38 × 10 −2} or less, more preferably 1.35 × 10 ⁻² or less, and further preferably 1.30 × 10 ⁻² or less. If the ratio is too high, fish eyes are likely to occur and the appearance of the film tends to deteriorate. The lower limit is usually 1 × 10 ^-7 .

The lubricant content of the boron compound and lubricant-containing EVOH pellets is 0.001 to 0.15% by weight, preferably 0.003 to 0.12% by weight, more preferably 0.003 to 0.12% by weight of the boron compound and lubricant-containing EVOH pellets. It is 0.005 to 0.10% by weight. If the content is too small, the friction between the screw surface of the extruder and the EVOH pellets is strong, which tends to cause an increase in fish eyes due to the inability to supply stable pellets. If the content is too large, the lubricant is poorly dispersed. On the contrary, the agglomeration of the sol tends to cause an increase in fish eyes, and the friction between the EVOH pellets and the screw surface is reduced, so that a stable pellet supply cannot be performed, which tends to cause an increase in fish eyes.

As for the content of the lubricant, for example, when the lubricant is adhered to the surface of the EVOH pellet, the amount of the lubricant added can be regarded as the content. When the lubricant is contained in the EVOH pellet, if the lubricant is, for example, a higher fatty acid amine, the total nitrogen content in the boron compound and the lubricant-containing EVOH pellet is measured using a trace total nitrogen analyzer and converted to the lubricant content. By doing so, the content of the lubricant in the boron compound and the lubricant-containing EVOH pellet can be measured.

The water content of the boron compound and lubricant-containing EVOH pellets of the present invention is usually 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight. If the water content is too low, the EVOH will not be plasticized by water molecules, and the EVOH pellets will be difficult to melt during extrusion molding, and defects of unmelted matter will tend to occur. If it is too high, a foaming phenomenon will occur during extrusion molding. Tends to occur and the appearance of the molded product tends to deteriorate.

[Other ingredients]
The boron compound and lubricant-containing EVOH pellets of the present invention include resins other than EVOH generally used in EVOH compositions within a range that does not impair the effects of the present invention (for example, 20% by weight or less, preferably 10% by weight or less). The resin composition obtained by mixing the above can also be included.

The boron compound and lubricant-containing EVOH pellets of the present invention are generally blended with EVOH as long as the effects of the present invention are not impaired, such as heat stabilizers, antioxidants, antistatic agents, colorants, and ultraviolet absorption. Agents, plasticizers, light stabilizers, surfactants, antibacterial agents, desiccants, antiblocking agents, flame retardants, cross-linking agents, hardeners, foaming agents, crystal nucleating agents, antifogging agents, biodegradation additives, silanes A coupling agent, an oxygen absorber, or the like may be contained. These can be used alone or in combination of two or more.

The heat stabilizer includes inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, and phosphoric acid, or alkali metal salts (sodium, potassium, etc.) of these, for the purpose of improving various physical properties such as thermal stability during melt molding. Additives such as alkaline earth metal salts (calcium and the like), salts such as zinc salts; and the like may be added. These can be used alone or in combination of two or more.

When these components are blended, the blending may be usually carried out at any stage before the contact treatment of the boron compound or lubricant and the EVOH pellet, with the contact treatment, or after the contact treatment. It is preferably carried out together with the contact treatment in that it has little effect on the content of boron or lubricant.

The method of blending the other components is not particularly limited, but it can usually be carried out by contacting the EVOH pellet with the solution containing these blending agents. Therefore, before the contact treatment with the boron compound or the lubricant, the EVOH pellet is immersed in the solution containing the above-mentioned compounding agent, or the solution containing at least one of the boron compound and the lubricant is further added to the above-mentioned compounding agent. By containing it, it can be blended.

The melt-molded product of the boron compound and the lubricant-containing EVOH pellet of the present invention is excellent in moldability and appearance even if it is a single-layer film. A multi-layer structure in which the resin layers of the above are laminated may be used.

Hereinafter, such a multilayer structure will be described.
In producing the above-mentioned multilayer structure, another base material (thermoplastic resin or the like) is laminated on one side or both sides of a layer formed by using the boron compound and the lubricant-containing EVOH pellet of the present invention. As a laminating method, for example, a method of melt-extruding and laminating another base material on a film, a sheet or the like formed by using the boron compound of the present invention and an EVOH pellet containing a lubricant, or conversely, the present invention on another base material. A method of melt-extruding and laminating a boron compound and a lubricant-containing EVOH pellet, etc. A method of dry laminating a film, sheet, etc. (layer) made of Be done. The melt molding temperature at the time of melt extrusion is often selected from the range of 150 to 300 ° C.

As such other base materials, thermoplastic resins are useful, and specifically, various polyethylenes such as linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, and high-density polyethylene, ethylene- Vinyl acetate copolymer, ionomer, ethylene-propylene (block or random) copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-α-olefin (4 to 20 carbon atoms) Α-Olefin) Copolymers, olefins such as polybutene and polypentene alone or copolymers, or olefins alone or copolymers of these olefins graft-modified with unsaturated carboxylic acids or esters thereof. Based resin, polyester resin, polyamide resin (including copolymerized polyamide), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene, chlorine Examples thereof include copolymerized polypropylene, aromatic or aliphatic polyketones, polyalcohols obtained by reducing them, and EVOH other than EVOH used in the present invention. From the viewpoint of practicality such as physical properties (particularly strength) of the multilayer structure, polypropylene, ethylene-propylene (block or random) copolymer, polyamide resin, polyethylene, ethylene-vinyl acetate copolymer, polystyrene resin, polyethylene Terephthalate (PET) and polyethylene naphthalate (PEN) are preferably used.

Further, another base material is extruded and coated on a molded product such as a film or a sheet formed by using the boron compound of the present invention and a lubricant-containing EVOH pellet or the like, or a film, a sheet or the like of another base material is adhered to the molded product. In the case of laminating with an agent, such a base material may be any base material (paper, metal foil, uniaxial or biaxially stretched plastic film or sheet and its inorganic vapor deposition, woven, etc., in addition to the above-mentioned thermoplastic resin. Cloth, non-woven fabric, metal cotton strip, wood, etc.) can also be used.

In the layer structure of the multilayer structure, a layer formed by using the boron compound and the lubricant-containing EVOH pellet of the present invention is a (a1, a2, ...), And another base material, for example, a thermoplastic resin layer is b. In the case of (b1, b2, ...), In the configuration in which the a layer is the innermost layer, not only the two-layer structure of [inside] a / b [outside] (the same applies hereinafter), but also, for example, a / b. Any combination such as / a, a1 / a2 / b, a / b1 / b2, a1 / b1 / a2 / b2, a1 / b1 / b2 / a2 / b2 / b1 is possible, and at least of the present invention. When the regrind layer composed of a mixture of a boron compound, a lubricant-containing EVOH pellet, or the like and a thermoplastic resin is R, for example, a / R / b, a / R / a / b, a / b / R / a / R. It is also possible to use / b, a / b / a / R / a / b, a / b / R / a / R / a / R / b, and the like.

In the above layer structure, an adhesive resin layer can be provided between the layers as needed. Various adhesive resins can be used, but in terms of obtaining a multilayer structure having excellent stretchability, for example, an unsaturated carboxylic acid or an anhydride thereof is used as an olefin polymer (in the broad sense described above). A modified olefin polymer containing a carboxyl group, which is obtained by chemically bonding to the polyolefin resin) by an addition reaction, a graft reaction, or the like.

Specifically, maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene (block and random) copolymer, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, anhydrous. One or a mixture of two or more selected from a maleic anhydride graft-modified ethylene-vinyl acetate copolymer and the like can be mentioned as suitable. At this time, the amount of the unsaturated carboxylic acid or its anhydride contained in the thermoplastic resin is preferably 0.001 to 3% by weight, more preferably 0.01 to 1% by weight, and particularly preferably 0.03. ~ 0.5% by weight. If the amount of modification in the modified product is too small, the adhesiveness tends to decrease, and conversely, if it is too large, a cross-linking reaction occurs and the moldability tends to decrease.

In addition, these adhesive resins include EVOH derived from the boron compound and lubricant-containing EVOH pellets of the present invention, other rubber / elastomer components such as EVOH, polyisobutylene, ethylene-propylene rubber, and b-layer resin. It is also possible to blend. In particular, blending a polyolefin-based resin different from the polyolefin-based resin that is the base of the adhesive resin is useful because the adhesiveness may be improved.

The thickness of each layer of the multilayer structure cannot be unequivocally determined depending on the layer structure, the type of layer b, the application, the form of the molded product, the required physical properties, etc., but usually, the a layer is 5 to 500 μm, preferably 10 to 10 μm. The 200 μm, the b layer is selected from the range of 10 to 5000 μm, preferably 30 to 1000 μm, and the adhesive resin layer is selected from the range of 5 to 400 μm, preferably about 10 to 150 μm.

The multilayer structure is used as it is for various shapes, but it is also preferable to perform a heat stretching treatment in order to improve the physical properties of the multilayer structure. Here, the "heat-stretching treatment" refers to a film, a sheet, or a parison-shaped laminate that has been uniformly heated by a chuck, a plug, a vacuum force, a compressed air force, a blow, or the like, by means of a forming means such as a chuck, a plug, a vacuum force, a compressed air force, or a blow. It means the operation of uniformly molding into a tube or film. The stretching may be either uniaxial stretching or biaxial stretching, and it is better to perform stretching at the highest possible magnification in terms of physical properties. A stretched molded product having excellent gas barrier properties, which does not cause delamination (delamination) or the like, can be obtained.

As the stretching method of the multilayer structure, a roll stretching method, a tenter stretching method, a tubular stretching method, a stretching blow method, vacuum compressed air forming, or the like, which has a high stretching ratio, can also be adopted. In the case of biaxial stretching, either the simultaneous biaxial stretching method or the sequential biaxial stretching method can be adopted. The stretching temperature is selected from the range of 60 to 170 ° C., preferably about 80 to 160 ° C. It is also preferable to perform heat fixation after the stretching is completed. The heat fixing can be carried out by a well-known means, and the heat fixing can be performed by heat-treating the stretched film at 80 to 170 ° C., preferably 100 to 160 ° C. for about 2 to 600 seconds while maintaining a tense state. can.

When used for heat-shrink packaging of raw meat, processed meat, cheese, etc., it is used as a product film without heat fixing after stretching, and after storing the above-mentioned raw meat, processed meat, cheese, etc. in the film, The film is heat-shrinked at 50 to 130 ° C., preferably 70 to 120 ° C. for about 2 to 300 seconds, and then tightly packaged.

The shape of the multilayer structure thus obtained may be any shape, and examples thereof include films, sheets, tapes, and extruded cross-sections. In addition, the above-mentioned multilayer structure may be heat-treated, cooled, rolled, printed, dry-laminated, solution or melt-coated, bag-made, deep-drawn, boxed, tube-processed, split-processed, if necessary. Etc. can be performed.

Bags and cups, trays, tubes, bottles, etc. made of films, sheets, stretched films, etc. obtained as described above can be used for general foods, seasonings such as mayonnaise, dressings, miso, etc. It is useful as a container for various packaging materials such as fermented foods, oil and fat foods such as salad oil, beverages, cosmetics, and pharmaceuticals.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the description of the examples as long as the gist of the present invention is not exceeded.
In the example, "part" and "%" mean the weight standard.

First, a method for measuring and evaluating pellets used in Examples and Comparative Examples will be described.

[Measurement evaluation method]
(1) Total content of boron compounds in pellets (boron equivalent)
A solution obtained by treating 0.1 g of EVOH pellets with concentrated nitric acid by the microwave decomposition method in pure water (0.75 mg / mL) was used as the test solution, and an inductively coupled plasma emission spectrometer (ICP) was used. -AES) (720-ES type manufactured by Agilent Technologies). The measured boron content corresponds to the amount of boron derived from the boron compound. The measurement and evaluation method is applied to the surface layer portion of the EVOH pellets before boron adjustment, the boron compound-containing EVOH pellets, and the boron compound and lubricant-containing EVOH pellets.

(2) Boron compound content in the surface layer of the pellet (boron equivalent)
4 g of EVOH pellets containing a boron compound (and lubricant) was immersed in 20 mL of methanol (30 ° C.) for 6 hours, and the obtained methanol solution was used as a measurement sample. The amount of boron in this measurement sample was measured using an inductively coupled plasma mass spectrometer (ICP-MS) (ELAN DRCII, manufactured by PerkinElmer), and divided by the EVOH pellet weight (4 g) to divide the pellet surface layer. The boron content was determined. The measured boron content corresponds to the amount of boron derived from the boron compound.

(3) Moisture content of pellets (%)
The volatile content was determined from the weight of the EVOH pellet before drying and the weight of the EVOH pellet after drying at a temperature of 150 ° C. for 5 hours, and this was taken as the water content of the EVOH pellet. Specifically, the water content is expressed by the following formula. The measurement and evaluation method is applied to EVOH pellets, EVOH pellets having a surface layer before boron adjustment, EVOH pellets containing a boron compound, and EVOH pellets containing a boron compound and a lubricant.
Moisture content (%) = (EVOH pellet weight before drying-EVOH pellet weight after drying) / EVOH pellet weight before drying x 100

(4) Using EVOH pellets containing a fisheye boron compound (and lubricant), a single-layer film having a thickness of 30 μm was formed under the following conditions.
(Film formation conditions)
Extruder: Diameter (D) 40 mm, L / D = 28
Screw: Full flight type compression ratio = 2.5
Screen pack: 60/90/60 mesh Die: Width 450 mm, coat hanger type Set temperature: C1 / C2 / C3 / C4 / A / D = 190/200/210/210/210/210 ° C
Screw rotation speed: 20 rpm
Roll temperature: 80 ° C

The fish eyes of the obtained single-layer film having a thickness of 30 μm were measured using a digital defect inspection device (GX-70LT manufactured by Mamiya-OP Co., Ltd.).
^{The fish eye is measured around 100 cm 2} (size: 10 cm x 10 cm) by shining light from the lower surface of the single-layer film and treating the part that did not transmit light (diameter 0.1 to 0.2 mm) as one fish eye. This was done by counting the number of fish eyes. The reading speed at the time of measurement is 3 m / min.

[Manufacture of EVOH pellets containing boron compounds and lubricants]
<Example 1>
EVOH [ethylene content: 44 mol%, saponification degree: 99.6 mol%, MFR: 3.8 g / 10 minutes (210 ° C., load 2160 g)] with water / methanol mixed solvent [water / methanol = 20/80] (By weight ratio)], the solution (60 ° C., EVOH concentration 40%) was extruded into a strand shape in a water tank containing water maintained at 5 ° C. to solidify it, and then cut with a cutter to form a columnar shape. Pellets (diameter 4 mm, length 4 mm) were obtained. Next, the EVOH pellets were put into warm water at 30 ° C. and stirred for about 4 hours to obtain porous EVOH pellets having a water content of 50%.

100 parts of the porous EVOH pellet was put into 200 parts of a 0.0054% boric acid aqueous solution, and the mixture was stirred at 30 ° C. for 5 hours. After stirring, the porous EVOH pellets before boron adjustment in the surface layer were recovered.
The surface layer portion of the EVOH pellets before boron adjustment was dried to a moisture content of 20% by passing nitrogen gas at 75 ° C. for 3 hours in a batch type column-type fluidized bed dryer.
Then, using a batch box type ventilation dryer, nitrogen gas at 125 ° C. was passed for 18 hours to dry to a moisture content of 0.3%. The pre-treatment boron compound-containing EVOH pellet after drying was measured by the above-mentioned measurement and evaluation method and found to be 130 ppm.

The dried EVOH pellets before boron adjustment (moisture content: 0.3%, total boron content: 130 ppm) were subjected to the following cleaning treatment.

5 parts of EVOH pellets before boron adjustment on the surface layer after drying and 10 parts of water / methanol mixed solvent (water / methanol = 1/1 (weight ratio)) as a cleaning treatment liquid were placed in a stainless steel container at 35 ° C. Was stirred for 1 hour. Then, the pellet was taken out and dried at 120 ° C. for 16 hours under a nitrogen stream. As described above, an EVOH pellet containing a boron compound was obtained.

Subsequently, a lubricant (ethylene bisstearic acid amide: manufactured by NOF Corporation, Alflo H-50T) was added to the above-mentioned EVOH pellet containing a boron compound so as to be 0.0054%, and shaken so as to be uniform. mixed.

The obtained boron compound and lubricant-containing EVOH pellets were measured for the total boron content and the boron content of the surface layer by the above measurement and evaluation method. The total boron content was 128.8 ppm, and the boron content of the surface layer was 1.1 ppm (moisture content 0.10%).

The obtained boron compound and lubricant-containing EVOH pellets were formed into a film using a single-layer T-die extruder at a maximum temperature of 210 ° C. and a screw rotation speed of 20 rpm to produce a single-layer film having a thickness of 30 μm. For this single-layer film, the number of fish eyes generated was examined by the above measurement and evaluation method. The results are shown in Table 1 below.

<Examples 2 and 3>
A boron compound and lubricant-containing EVOH pellets were obtained in the same manner as in Example 1 except that the lubricant content in the boron compound and lubricant-containing EVOH pellets was adjusted to the content shown in Table 1 below (moisture content). Is 0.10%).
Then, using these pellets, a single-layer film was prepared in the same manner as in Example 1, and the occurrence of fish eyes was evaluated. The results are shown in Table 1 below.

<Example 4>
In Example 1, calcium stearate was used as a lubricant, and the total content of the boron compound, the content of the boron compound on the surface layer and the content of the lubricant were adjusted to the contents shown in Table 1 below to obtain EVOH pellets containing the boron compound and the lubricant. rice field. Moreover, the total content of the boron compound and the content of the boron compound on the surface layer of the obtained boron compound and the lubricant-containing EVOH pellet were measured (moisture content 0.15%).
Then, using these pellets, a single-layer film was prepared in the same manner as in Example 1, and the occurrence of fish eyes was evaluated. The results are shown in Table 1 below.

<Example 5>
Magnesium stearate was used as a lubricant in Example 1, and the total content of the boron compound, the content of the boron compound on the surface layer and the content of the lubricant were adjusted to the contents shown in Table 1 below, and the boron compound and the lubricant-containing EVOH pellet were prepared. Obtained. Moreover, the total content of the boron compound and the content of the boron compound on the surface layer of the obtained boron compound and the lubricant-containing EVOH pellet were measured (moisture content 0.15%).
Then, using these pellets, a single-layer film was prepared in the same manner as in Example 1, and the occurrence of fish eyes was evaluated. The results are shown in Table 1 below.

<Comparative example 1>
The washing treatment liquid was changed to water, and the lubricant content was adjusted to the content shown in Table 1 below to obtain a boron compound and a lubricant-containing EVOH pellet. The total boron content of the obtained boron compound and the lubricant-containing EVOH pellet and the boron content of the surface layer were measured (moisture content 0.13%).
Then, using these pellets, a single-layer film was prepared in the same manner as in Example 1, and the occurrence of fish eyes was evaluated. The results are shown in Table 1 below.

<Comparative example 2>
A boron compound-containing EVOH pellet was obtained in the same manner as in Example 1 except that the cleaning with the cleaning treatment solution was not performed and no lubricant was added. In addition, the total boron compound content of the obtained boron compound-containing EVOH pellet and the boron compound content of the surface layer were measured (moisture content 0.09%).
Then, using these pellets, a single-layer film was prepared in the same manner as in Example 1, and the occurrence of fish eyes was evaluated. The results are shown in Table 1 below.

<Comparative Examples 3 and 4>
EVOH pellets were obtained in the same manner as in Example 1 except that the lubricant content was adjusted to the content shown in Table 1 below. The total boron content of the obtained boron compound and the lubricant EVOH pellets and the boron content of the surface layer were measured (both water content was 0.10%).
Then, using these pellets, a single-layer film was prepared in the same manner as in Example 1, and the occurrence of fish eyes was evaluated. The results are shown in Table 1 below.

The EVOH pellets of Examples 1 to 5 having a surface layer having a boron content of 1.7 ppm or less and containing 0.001 to 0.15% by weight of a lubricant of the pellets generated fish eyes as compared with Comparative Examples. Was able to be significantly suppressed. That is, when Example 2 and Comparative Example 1 were compared, the boron compound content in the surface layer of the pellet was reduced even if the boron compound content of the entire pellet was the same level and the lubricant content was the same. It can be seen that the pellets of Example 2 generate significantly less fish eyes when the film is produced.

The boron compound and lubricant-containing EVOH pellets of the present invention improve the appearance without impairing moldability by reducing the content of the boron compound on the surface layer of the pellet and setting the content of the lubricant within a predetermined range. Therefore, it can be suitably used in a field where the appearance requirement as a packaging material is stricter than that of the conventional EVOH pellets.

Claims (5)

Ethylene-vinyl alcohol-based copolymer pellets containing a boron compound and a lubricant.
The boron compound content of the surface layer of the pellet is 1.7 ppm or less per the weight of the pellet in terms of boron, and the content of the lubricant is 0.001 to 0.15% by weight of the pellet. Ethylene-vinyl alcohol-based copolymer pellets. The ethylene according to claim 1, wherein the total content of the boron compound in the whole ethylene-vinyl alcohol copolymer pellet containing the boron compound and the lubricant is 10 to 1000 ppm per the weight of the pellet in terms of boron. -Vinyl alcohol-based copolymer pellets. Weight ratio of boron compound content (boron equivalent) in the surface layer of the pellet to the total boron compound content (boron equivalent) of the entire ethylene-vinyl alcohol copolymer pellet containing the boron compound and lubricant (boron content in the surface layer) The ethylene-vinyl alcohol-based copolymer pellet according to claim 1 or 2, wherein (amount / total boron content) is 1.38 × ^{10-2 or less.} The ethylene-ethylene according to any one of claims 1 to 3, wherein the ethylene-vinyl alcohol-based copolymer pellet containing the boron compound and the lubricant has a water content of 0.01 to 1% by weight. Vinyl alcohol-based copolymer pellets. A step of bringing an ethylene-vinyl alcohol-based copolymer pellet into contact with a boron compound to contain a boron compound, and washing the pellet obtained by the above step to change the boron compound content of the surface layer of the pellet to ethylene in terms of boron. A method for producing an ethylene-vinyl alcohol-based copolymer pellet containing a boron compound and a lubricant, which comprises a step of reducing the weight to 1.7 ppm or less per vinyl alcohol-based copolymer pellet weight and a step of adding a lubricant.
The washing in the washing step is to bring the pellets after drying into contact with a water / alcohol mixed solution or alcohol having a weight ratio (water / alcohol) of water to alcohol of 80/20 to 0/100.
A method for producing an ethylene-vinyl alcohol-based copolymer pellet, wherein the step of containing the lubricant is such that the lubricant is contained in an amount of 0.001 to 0.15% by weight of the pellet.