JP5781648B2 - Resin composition and pellet made of ethylene-vinyl alcohol copolymer having excellent long-running property - Google Patents

Description

  The present invention is particularly excellent in long run properties during melt molding, has less appearance of gels and blisters, has excellent appearance, has good recoverability, has little coloration during recovery, and has excellent interlayer adhesion when made into a laminate. Further, the present invention relates to a resin composition comprising an ethylene-vinyl alcohol copolymer and a laminate using the same.

  An ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) is a useful polymer material excellent in oxygen shielding properties, oil resistance, non-charging properties, mechanical strength, etc. Widely used as packaging material. Such a packaging material is usually manufactured by melt molding, and has a long run property at the time of melt molding (a molded product free of fish eyes and streaks can be obtained even when molding for a long time), appearance of the molded product (less coloring) , A molded product in which the generation of fish eyes is not observed) is required. In recent years, recyclability has also become an important issue. Even when an EVOH molded product is recovered, melt molded again, and heat history is repeated, the recoverability (moldability of recovered EVOH) is good. There is a need for EVOH that is less colored during recovery.

  EVOH is usually formed by melt molding. In order to improve productivity, it is preferable to operate the molding machine continuously for a long time, but depending on the shape in the molding machine, a part of EVOH may stay in the resin flow path for a long time. Appearance due to adhesion of heat-degraded resin to the molding machine die, mixing of gels and irregularities in the product, or expression of uneven thickness, streaks, etc. when EVOH in the part is gelated by prolonged heating It may cause defects. Further, when EVOH in the staying portion is severely decomposed by heating for a long time, coloring or foaming occurs, and the appearance of the molded product is deteriorated. Also, when a molded product made of EVOH was collected, the heat history was similarly accumulated, and thus gelation or decomposition of EVOH occurred, causing a problem in the appearance of the molded product. For this reason, EVOH with little occurrence of gelation or decomposition even during long-time heating has been desired.

  Furthermore, in general, in order to impart mechanical strength, moisture resistance, heat sealability, etc., a laminate is coextruded through a base material such as a polyolefin-based resin and an adhesive layer. Body interlayer adhesion is also important. That is, it is necessary to sufficiently satisfy the appearance of the molded product, the long run property during melt molding, the recoverability, and the interlayer adhesion of the laminate.

  Therefore, conventionally, as such countermeasures, the following proposals have been made for producing an excellent molded article by treating an ethylene-vinyl alcohol copolymer with various acids and metal salts.

  For example, (1) In order to improve the appearance represented by the above long-run property, gel and gel, the metal salt of Group II of the Periodic Table is added in an amount of 0.0005 to 0.05% by weight (metal conversion), pKa3. 5% or more of an acid having a boiling point of 180 ° C. or more and 0.002 to 0.2% by weight and an acid having a pKa of 3.5 or more and a boiling point of 120 ° C. or less of 0.01 to 0.2% by weight, and a specific flow An EVOH composition exhibiting characteristics has been disclosed (Japanese Patent Laid-Open No. 64-66262). (2) 0.001 to 1% by weight of boron compound (in terms of boron), 0.05% by weight or less of acetic acid, and 0.001 of acetate to improve appearance, long-run properties, stretching unevenness, and interlayer adhesion An EVOH composition containing ˜0.05% by weight (in terms of metal) and / or 0.0005 to 0.05% by weight (in terms of phosphate radical) is disclosed (International Publication No. 99/05213) . (3) 0-1% by weight (in terms of boron) of boron compound, 0-0.05% by weight of acetic acid, 0-0.1% by weight of sodium acetate in order to improve the appearance, long-run property, and interlayer adhesion An EVOH composition containing 0.001 to 0.02% by weight (in terms of metal) of magnesium acetate and / or calcium acetate (in metal conversion) is disclosed (European Patent Application Publication No. 906924). (4) 0.05-0.3 wt% boron compound (in terms of boron) and 0% sodium acetate in order to improve long run properties during melt molding, fish eyes, transparency, streaks, etc. An EVOH composition containing 0.001 to 0.02% by weight (converted to metal) and 0.001 to 0.02% by weight (converted to metal) of magnesium acetate is disclosed (Japanese Patent Laid-Open No. 11-60874). (5) An EVOH composition containing hydroxycarboxylic acid and / or a salt thereof, an alkali metal salt, an alkaline earth metal salt, a phosphate, or a boron compound is disclosed in order to improve coloring, appearance, and interlayer adhesion. (JP-A-10-67898). Further, in this publication, as Comparative Example 7, with respect to 100 parts by weight of EVOH, acetic acid 1230 ppm (as acetic acid root), sodium acetate 350 ppm (metal conversion), magnesium acetate 50 ppm (metal conversion), potassium dihydrogen phosphate 30 ppm (phosphorus conversion) ), A resin composition containing 40 ppm of boric acid (in terms of boron) has been disclosed, but a film formed by molding such a composition is excellent in interlayer adhesion, but has a film appearance such as coloring or shading. It states that there is a problem.

JP-A 64-66262 International Publication No. 99/05213 European Patent Application No. 906924 Japanese Patent Laid-Open No. 11-60874 Japanese Patent Laid-Open No. 10-67898

  However, in the above prior arts (1) to (5), the long run property at the time of melt molding, the appearance of the molded product, the recoverability, the coloration resistance at the time of recovery, and the interlaminar adhesion when formed into a laminate. In the present situation where moldings having high functions and quality are required, no satisfactory level has been reached.

The problem shown above is a resin composition comprising an ethylene-vinyl alcohol copolymer, and when the resin composition is heated at 220 ° C. in a nitrogen atmosphere, the MFR (230 ° C., 10.9 kg load) shows a minimum value within 10 hours from the start of heating, and shows a maximum value (MFRmax) within 100 hours after showing the minimum value. A carboxylic acid (A) having a molecular weight of less than 75 is 50 to 500 ppm, alkali metal salt (B) in terms of metal element 50 to 500 ppm, alkaline earth metal salt (C) in terms of metal element 10 to 120 ppm, and phosphate compound (D) in terms of phosphate radical 10 to 200 ppm This is solved by a resin composition characterized in that it contains 50 to 2000 ppm of boron compound (E) in terms of boron element and satisfies the following formula (1).
0.5 ≦ MFRmax / MFR0 ≦ 45 (1)
However,
MFRmax: Maximum value of MFR (230 ° C., 10.9 kg load) of the resin composition when the resin composition is heated at 220 ° C. in a nitrogen atmosphere MFR0: MFR of the resin composition not subjected to heat treatment (230 ° C, 10.9kg load)

That is, the present invention is a resin composition comprising an ethylene-vinyl alcohol copolymer, and when the resin composition is heated at 220 ° C. in a nitrogen atmosphere, the MFR (230 ° C., 10. 9 kg load) shows a minimum value within 10 hours from the start of heating, and shows a maximum value (MFRmax) within 100 hours after showing the minimum value. 50 to 50% of carboxylic acid (A) having a molecular weight of less than 75 500 ppm, alkali metal salt (B) 50 to 500 ppm in terms of metal element, alkaline earth metal salt (C) 10 to 120 ppm in terms of metal element, phosphate compound (D) 10 to 200 ppm in terms of phosphate radical, boron It is related with the resin composition characterized by including 50-2000 ppm of compounds (E) in conversion of a boron element, and satisfying following formula (1).
0.5 ≦ MFRmax / MFR0 ≦ 45 (1)
However,
MFRmax: Maximum value of MFR (230 ° C., 10.9 kg load) of the resin composition when the resin composition is heated at 220 ° C. in a nitrogen atmosphere MFR0: MFR of the resin composition not subjected to heat treatment (230 ° C, 10.9kg load)

  In a preferred embodiment, the carboxylic acid (A) having a molecular weight of less than 75 is acetic acid.

  In a preferred embodiment, in the resin composition of the present invention, the alkaline earth metal salt (C) is a magnesium salt and / or a calcium salt, and the magnesium salt is 10 to 60 ppm in terms of metal and / or 20 to 120 ppm in terms of metal. Containing a calcium salt.

In a preferred embodiment, the resin composition of the present invention satisfies the following formula (2).
[B (μmol / g) + C (μmol / g)] / [A (μmol / g) + D (μmol / g)] = 1-15 (2)
However, A: Content of carboxylic acid (A) having a molecular weight of less than 75 per unit weight of the resin composition (μmol / g)
B: Content of alkali metal salt (B) per unit weight of the resin composition (μmol / g)
C: Content of alkaline earth metal salt (C) per unit weight of the resin composition (μmol / g)
D: Content of the phosphoric acid compound (C) per unit weight of the resin composition (μmol / g)

  Furthermore, in a preferred embodiment, the resin composition of the present invention contains 0.005 to 1 part by weight of a lubricant with respect to 100 parts by weight of EVOH.

  In a preferred embodiment, the pellet made of the resin composition of the present invention is formed by adhering 0.005 to 0.5 part by weight of a lubricant to the outer surface of the pellet with respect to 100 parts by weight of the resin composition.

  The present invention also relates to a multilayer structure obtained by laminating a thermoplastic resin on at least one side of the layer made of the resin composition.

  Ethylene which has excellent coloring and fish eyes (gels and blisters), streaks, etc., excellent appearance, excellent long-run properties during melt molding, little coloring during recovery, and excellent interlayer adhesion when made into a laminate A resin composition comprising a vinyl alcohol copolymer and a multilayer structure using the same can be provided.

It is a figure which shows the relationship between the heating time in 220 degreeC of the resin composition which consists of EVOH, and MFR (230 degreeC, 10.9 kg load).

  As EVOH used for this invention, what is obtained by saponifying an ethylene-vinyl acetate copolymer is preferable, Among these, ethylene content is 3-70 mol% suitably. From the viewpoint of obtaining a molded article excellent in gas barrier properties and melt moldability, the ethylene content is preferably 10 to 65 mol%, more preferably 20 to 65 mol%, and most preferably 25 to 60 mol%. Some are preferred. Furthermore, the saponification degree of the vinyl ester component is preferably 80% or more, and more preferably 95% or more, and still more preferably 99% or more from the viewpoint of obtaining a molded article having excellent gas barrier properties. When ethylene content exceeds 70 mol%, there exists a possibility that barrier property, printability, etc. may be insufficient. On the other hand, if the degree of saponification is less than 80%, the barrier property, thermal stability and moisture resistance may be deteriorated.

  On the other hand, EVOH having an ethylene content of 3 to 20 mol% is suitably used as EVOH imparted with water solubility, and such an EVOH aqueous solution is excellent in barrier properties and coating film stability and is used as an excellent coating material.

  Further, when ethylene and vinyl acetate are copolymerized, other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can be used in combination. Moreover, EVOH can contain 0.0002-0.2 mol% of vinyl silane compounds as a copolymerization component. Here, examples of the vinylsilane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane, and γ-methacryloxypropylmethoxysilane. Of these, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used.

  The EVOH production method will be specifically described below. The polymerization of ethylene and vinyl acetate is not limited to solution polymerization, and may be any of solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, and may be either continuous or batch-type. For example, polymerization conditions in the case of batch solution polymerization are as follows.

Solvent: Alcohols are preferred, but other organic solvents (such as dimethyl sulfoxide) that can dissolve ethylene, vinyl acetate, and ethylene-vinyl acetate copolymer can be used. As alcohols, methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, t-butyl alcohol and the like can be used, and methyl alcohol is particularly preferable.
Catalyst: 2,2-azobisisobutyronitrile, 2,2-azobis- (2,4-dimethylvaleronitrile), 2,2-azobis- (4-methyl-2,4-dimethylvaleronitrile), 2 , 2-azobis- (4-methoxy-2,4-dimethylvaleronitrile), 2,2-azobis- (2-cyclopropylpropionitrile) and other azonitrile initiators, isobutyryl peroxide, cumylperoxyneo Organic peroxides such as decanoate, diisopropyl peroxycarbonate, di-n-propyl peroxydicarbonate, t-butyl peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide, t-butyl hydroperoxide An initiator or the like can be used.
Temperature; 20-90 ° C, preferably 40 ° C-70 ° C.
Time; 2-15 hours, preferably 3-11 hours.
Polymerization rate: 10 to 90%, preferably 30 to 80%, relative to the charged vinyl ester.
Resin content in the solution after polymerization; 5 to 85%, preferably 20 to 70%.
Ethylene content in the copolymer; preferably 3 to 70 mol%, more preferably 25 to 60 mol%.

  In addition to ethylene and vinyl acetate, monomers that can be copolymerized with these, for example, α-olefins such as propylene, isobutylene, α-octene, α-dodecene; acrylic acid, methacrylic acid, crotonic acid, maleic acid, itacone Unsaturated acids such as acids or their anhydrides, salts, mono- or dialkyl esters, etc .; Nitriles such as acrylonitrile and methacrylonitrile; Amides such as acrylamide and methacrylamide; Ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfone An olefin sulfonic acid such as an acid or a salt thereof; alkyl vinyl ethers, vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride and the like may be present in a small amount.

  After polymerization for a predetermined time, after reaching a predetermined polymerization rate, a polymerization inhibitor is added if necessary, and unreacted ethylene gas is removed by evaporation, and then unreacted vinyl acetate is driven off. As a method for driving off unreacted vinyl acetate from the ethylene-vinyl acetate copolymer from which ethylene has been removed by evaporation, for example, the copolymer solution is continuously fed at a constant rate from the upper part of the tower packed with Raschig rings, A method in which an organic solvent vapor such as methanol is blown from the bottom, a mixed vapor of an organic solvent such as methanol and unreacted vinyl acetate is distilled from the top of the tower, and the copolymer solution from which the unreacted vinyl acetate has been removed is removed from the bottom of the tower. Is adopted.

An alkali catalyst is added to the copolymer solution from which unreacted vinyl acetate has been removed to saponify the vinyl acetate component in the copolymer. The saponification method can be either continuous or batch. As the alkali catalyst, sodium hydroxide, potassium hydroxide, alkali metal alcoholate or the like is used. For example, the saponification conditions in the case of a batch type are as follows.
The copolymer solution concentration: 10 to 50%.
Reaction temperature: 30-60 ° C.
Amount of catalyst used: 0.02 to 0.6 equivalent (per vinyl acetate component).
Time; 1-6 hours.
Although the degree of saponification after the saponification reaction varies depending on the purpose, it is preferably 80% or more of the vinyl acetate component, more preferably 95% or more, and still more preferably 99% or more. The degree of saponification can be arbitrarily adjusted according to the conditions.

  Since the ethylene-vinyl alcohol copolymer after the reaction contains an alkali catalyst, by-product salts, other impurities, etc., it is preferable to remove these by neutralization and washing as necessary.

When the resin composition comprising EVOH of the present invention is heated at 220 ° C. in a nitrogen atmosphere, the MFR (230 ° C., 10.9 kg load) of the resin composition shows a minimum value within 10 hours from the start of heating. It is very important to exhibit the maximum value (MFRmax) within 100 hours after the minimum value is satisfied and to satisfy the following formula (1).
0.5 ≦ MFRmax / MFR0 ≦ 45 (1)
However,
MFRmax: Maximum value of MFR (230 ° C., 10.9 kg load) of the resin composition when the resin composition is heated at 220 ° C. in a nitrogen atmosphere MFR0: MFR of the resin composition not subjected to heat treatment (230 ° C, 10.9kg load)
The resin composition comprising EVOH of the present invention showing such melting behavior has a small amount of resin die attached during melt molding. Further, even during extremely long melt molding, it is possible to suppress gels and blisters of a molded product (film, etc.). That is, the resin composition comprising EVOH of the present invention is extremely excellent in long run properties.
On the other hand, when the resin composition composed of EVOH does not have the above-described configuration (Comparative Example 3: see FIG. 1), not only the effect of reducing the die adhesion amount is obtained, but also a long-term continuous operation is performed. In this case, it is clear that the number of gels and gels increases.

Further, as a result of detailed studies by the present inventors, it has been clarified that the resin composition comprising EVOH not having the above-described structure may rapidly increase the occurrence frequency of gels and blisters during long-term operation. . This sudden increase in the frequency of gel and buoyancy is not permanent, and usually after several minutes to several tens of minutes have passed since the frequency of the occurrence of gel and rashes, the normal level of gel and butsu Returning to the occurrence frequency, the appearance of the molded product when the occurrence frequency of gels and blisters rapidly increases is poor in appearance, and usually a product that can withstand practical use cannot be obtained.
However, by using the resin composition of the present invention developed by the present inventors, it has become possible to effectively suppress a sudden increase in the occurrence frequency of gels and blisters even during long melt molding. As described above, by using the resin composition of the present invention, long-time molding can be performed without problems even in applications that require an extremely high appearance such as a film, and productivity can be improved. From this viewpoint, the significance of the present invention is great.

As described above, the resin composition comprising EVOH of the present invention satisfies the following formula (1).
0.5 ≦ MFRmax / MFR0 ≦ 45 (1)
However,
MFRmax: Maximum value of MFR (230 ° C., 10.9 kg load) of the resin composition when the resin composition is heated at 220 ° C. in a nitrogen atmosphere MFR0: MFR of the resin composition not subjected to heat treatment (230 ° C, 10.9kg load)
The lower limit of MFRmax / MFR0 is more preferably 0.7, and even more preferably 1. The upper limit of MFRmax / MFR0 is more preferably 35, more preferably 25, still more preferably 20, and optimally 10. When the value of MFRmax / MFR0 is within such a range, the amount of the heat-degraded resin adhering to the molding machine die and the occurrence of gels and blisters of the molded product during the melt molding of the resin composition are small, and the gels and blisters are generated. It is possible to obtain a resin composition composed of EVOH with excellent frequency resistance, in which frequency fluctuations are suppressed.

  If the value of MFRmax / MFR0 is less than 0.5, the amount of resin adhesion to the molding machine die increases and the long run property deteriorates, and the effect of suppressing fluctuations in the occurrence frequency of gels and blisters is insufficient. Become. Further, it is clear from Comparative Example 4 that when the value of MFRmax / MFR0 exceeds 45, coloring due to the decomposition of EVOH becomes remarkable and the appearance becomes poor.

  The pKa at 25 ° C. of the carboxylic acid (A) having a molecular weight of less than 75 used in the present invention is preferably 3.5 or more. If the pKa at 25 ° C. is less than 3.5, it may be difficult to control the pH of the resin composition comprising EVOH, and the coloring resistance and interlayer adhesion may be unsatisfactory. Examples of the carboxylic acid (A) having a molecular weight of less than 75 include formic acid, acetic acid, propionic acid and the like, but in addition to cost merit, the acidity is appropriate and the pH of the resin composition is easily controlled. Acetic acid is particularly preferable.

  Moreover, content of the carboxylic acid (A) of molecular weight less than 75 in the resin composition of this invention is 50-500 ppm. The lower limit of the content of the carboxylic acid (A) having a molecular weight of less than 75 is more preferably 75 ppm or more, and further preferably 100 ppm or more. Moreover, the upper limit of the content of the carboxylic acid (A) having a molecular weight of less than 75 is preferably 400 ppm or less, and more preferably 300 ppm or less. When the content of the carboxylic acid (A) having a molecular weight of less than 75 is less than 50 ppm, coloring during melting is remarkable. When it exceeds 500 ppm, the interlayer adhesion deteriorates.

  Content of the alkali metal salt (B) in the resin composition of this invention is 50-500 ppm in metal conversion, Preferably it is 100-300 ppm. If it is less than 50 ppm, the adhesion to other resins is poor, and there is a problem with interlaminar adhesion particularly during coextrusion molding. On the other hand, if it exceeds 500 ppm, the coloring at the time of melting is remarkable. The alkali metal salt (B) is not particularly limited, and examples thereof include a sodium salt and a potassium salt. The anion species of the alkali metal salt is not particularly limited, but an acetate anion and a phosphate anion are preferable.

  Content of alkaline-earth metal salt (C) in the resin composition of this invention is 10-120 ppm in metal conversion, Preferably it is 20-100 ppm. It is very important that the content of the alkaline earth metal salt (C) is in such a range in order to control the MFR variation with time of the ethylene-vinyl alcohol copolymer composition. If it is less than 10 ppm, the long-run property is inferior, and if it exceeds 120 ppm, coloring at the time of melting is remarkable.

  The alkaline earth metal salt (C) is not particularly limited, and examples thereof include magnesium salts, calcium salts, barium salts, beryllium salts, etc. Magnesium salts and calcium salts are particularly preferable. The anionic species of the alkaline earth metal salt is not particularly limited, but an acetate anion and a phosphate anion are preferable. When the alkaline earth metal salt (C) in the resin composition of the present invention is a magnesium salt, the preferred content is 10 to 60 ppm in terms of metal, more preferably 20 to 50 ppm. Moreover, suitable content in case the alkaline-earth metal salt (C) in a resin composition is a calcium salt is 20-120 ppm in metal conversion, More preferably, it is 40-100 ppm.

  The content of the phosphoric acid compound (D) in the resin composition of the present invention is 10 to 500 ppm in terms of phosphate radical. The lower limit of the content of the phosphoric acid compound (D) is preferably 20 ppm or more, more preferably 30 ppm or more, and most preferably 50 ppm or more. Moreover, the upper limit of the content of the phosphoric acid compound (D) is preferably 250 ppm or less, and more preferably 150 ppm or less. By containing the phosphoric acid compound in such a range, it is possible to obtain a resin composition that gives a good appearance of a molded product with less coloring and excellent long-run properties. When the content of the phosphoric acid compound (D) is less than 10 ppm, coloring during melt molding is remarkably reduced in appearance. In particular, since the tendency is remarkable when the heat history is repeated, the resin composition has poor recoverability. If it exceeds 500 ppm, the formation of gels and blisters in the molded product becomes remarkable, and the appearance deteriorates. Examples of the phosphoric acid compound (D) include, but are not limited to, various acids such as phosphoric acid and phosphorous acid and salts thereof. The phosphate may be contained in any form of primary phosphate, secondary phosphate, and tertiary phosphate, and its cationic species is not particularly limited, but as described above. Preferred are alkali metal salts and alkaline earth metal salts. Among these, it is preferable to add the phosphoric acid compound (D) in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, or dipotassium hydrogen phosphate.

  Examples of the boron compound (E) used in the present invention include, but are not limited to, boric acids, boric acid esters, borates, borohydrides, and the like. Specific examples of boric acids include orthoboric acid, metaboric acid, and tetraboric acid. Examples of boric acid esters include triethyl borate and trimethyl borate. Examples include alkali metal salts of acids, alkaline earth metal salts, and borax. Among these compounds, orthoboric acid (hereinafter sometimes simply referred to as boric acid) is preferable. When a boron compound is added to a resin composition comprising EVOH, it is possible to increase the melt viscosity even when EVOH having a low polymerization degree is used. In addition, it is possible to suppress the generation of gels and blisters and improve the long run property.

  The content of the boron compound (E) in the resin composition of the present invention is 50 to 2000 ppm in terms of boron. The lower limit of the content of the boron compound (E) is more preferably 100 ppm or more, and further preferably 150 ppm or more. Moreover, it is preferable that the upper limit of content of a boron compound (E) is 1500 ppm or less in conversion of boron, More preferably, it is 1000 ppm or less. If it is less than 50 ppm, the effect of improving the long run property by adding the boron compound (E) cannot be obtained, and if it exceeds 2000 ppm, gelation tends to occur and the moldability becomes poor, and the appearance of the molded product deteriorates.

  The resin composition comprising EVOH of the present invention comprises a carboxylic acid (A) having a molecular weight of less than 75, an alkali metal salt (B), an alkaline earth metal salt (C), a phosphoric acid compound (D), and a boron compound (E). The effects of the present invention can be obtained for the first time by including all of the essential components and the specific amounts of them as described above. As will be apparent from the examples and comparative examples described later in the present specification, in the second resin composition of the present invention, the above components (A), (B), (C), (D) and Even if any one of (E) is missing, sufficient performance cannot be obtained.

In the present invention, when the following formula (2) is satisfied, it is preferable that the effects of the present invention can be obtained more remarkably.
[B (μmol / g) + C (μmol / g)] / [A (μmol / g) + D (μmol / g)] = 1-15 (2)
However, A: Content of carboxylic acid (A) having a molecular weight of less than 75 per unit weight of the resin composition (μmol / g)
B: Content of alkali metal salt (B) per unit weight of the resin composition (μmol / g)
C: Content of alkaline earth metal salt (C) per unit weight of the resin composition (μmol / g)
D: Content of the phosphoric acid compound (C) per unit weight of the resin composition (μmol / g)

  By increasing the content of alkali metal salt (B) and alkaline earth metal (C) in the resin composition comprising EVOH, the adhesiveness of the resin composition and the effect of reducing the amount of die adhesion are improved, and MFRmax / MFR0 generally increases. However, addition of an excessive amount of alkali metal salt (B) and alkaline earth metal salt (C) not only deteriorates the color resistance but also adversely affects low odor due to decomposition of the resin composition.

  On the other hand, the coloring resistance of the molded product can be improved by increasing the content of the carboxylic acid (A) having a molecular weight of less than 75 and the content of the phosphoric acid compound (D) in the resin composition comprising EVOH. / MFR0 generally decreases. It is also possible to improve long run properties by adding appropriate amounts of carboxylic acid (A) and phosphoric acid compound (D) having a molecular weight of less than 75. However, addition of an excessive amount of the carboxylic acid (A) having a molecular weight of less than 75 and the phosphoric acid compound (D) causes an increase in gels and blisters, and further decreases the adhesiveness of the resin composition. As described above, the influences of the carboxylic acid (A), alkali metal salt (B), alkaline earth metal salt (C), and phosphoric acid compound (D) having a molecular weight of less than 75 on the properties of the resin composition are mutually different. A resin composition composed of EVOH that exhibits high performance in all aspects of long run properties, appearance properties, recoverability, coloring resistance, and interlayer adhesion during melt molding. It is possible to obtain things.

  Here, when the resin composition of the present invention satisfies the above-mentioned formula (2), it is possible to obtain a resin composition that is highly balanced particularly in the interlayer adhesive strength and the appearance of the molded product. When [B (μmol / g) + C (μmol / g)] / [A (μmol / g) + D (μmol / g)] is less than 1, the interlayer adhesive strength may decrease. There is a possibility that coloring will be remarkable and appearance of the molded product will be deteriorated. The upper limit of [B (μmol / g) + C (μmol / g)] / [A (μmol / g) + D (μmol / g)] is more preferably 10 and even more preferably 7, optimally Is 5.

  Moreover, it is also suitable to add 0.005-1 weight part of lubricant with respect to 100 weight part of EVOH to the EVOH resin composition of this invention. By adding a lubricant, it is possible not only to reduce the amount of attached die, but also to obtain a resin composition made of EVOH which is difficult to be colored at the time of recovery and has good long run properties. Since the resin composition of the present invention contains a boron compound (E), the effect of suppressing fluctuations in the occurrence frequency of gels and blisters may be slightly reduced when continuously performing melt molding for an extremely long time. . However, as a result of detailed investigations by the present inventors, surprisingly, by adding 0.005 to 1 part by weight of a lubricant to 100 parts by weight of EVOH of the resin composition comprising such EVOH, a gel is obtained. -It has been found that the effect of suppressing fluctuations in the frequency of occurrence of irregularities can be maintained over an extremely long period of time.

  The preferred lubricant content is 0.005 to 1 part by weight of lubricant with respect to 100 parts by weight of EVOH. When the lubricant content is less than 0.005 parts by weight with respect to 100 parts by weight of EVOH, the effect of adding the lubricant as described above may be insufficient, and when it exceeds 1 part by weight, surging is likely to occur and the extrusion stability. May deteriorate. The lower limit of the content of the lubricant is more preferably 0.01 parts by weight or more with respect to 100 parts by weight of EVOH. Further, the upper limit of the content of the lubricant is more preferably 0.8 parts by weight or less, more preferably 0.7 parts by weight or less, and most preferably 0.5 parts by weight or less with respect to 100 parts by weight of EVOH. It is.

  The lubricant that can be used in the present invention is not particularly limited, and examples thereof include higher fatty acid amides, higher fatty acid metal salts (for example, calcium stearate), low molecular weight polyolefins (for example, low molecular weight polyethylene having a molecular weight of about 500 to 10,000, or low molecular weight polypropylene). However, it is not limited to this. Among these, higher fatty acid amides are preferably used. Specifically, higher saturated fatty acid amides (for example, stearic acid amide, palmitic acid amide, lauric acid amide, etc.), higher unsaturated fatty acid amides (for example, oleic acid amide, erucic acid) Amides), higher bis fatty acid amides (for example, ethylene bis stearamide, methylene bis stearamide, etc.) and the like. Here, the higher fatty acid means a fatty acid having 6 or more carbon atoms, and more preferably 10 or more carbon atoms.

  The form of the lubricant may be any of powder, solution, and dispersion liquid, and is not particularly limited. Also, the form of the lubricant is not particularly limited, and a method of melt-mixing the resin composition and the lubricant, a method of extruding the solution after the saponification reaction to which the lubricant has been added, into a coagulating liquid, and a method of combining these Etc.

  In addition, a resin composition pellet obtained by adhering 0.005 to 0.5 part by weight of a lubricant with respect to 100 parts by weight of the resin composition on the outer surface of the pellet made of the resin composition of the present invention is also an embodiment of the present invention. It is suitable as. The lower limit of the amount of lubricant adhered to the pellet is more preferably 0.01 parts by weight or more with respect to 100 parts by weight of EVOH. The upper limit of the amount of lubricant adhered to the pellet is more preferably 0.3 parts by weight or less, more preferably 0.2 parts by weight or less, and most preferably 0.1 parts by weight or less with respect to 100 parts by weight of EVOH. Less than parts by weight. When the amount of the lubricant adhering to the outer surface of the pellet made of the resin composition exceeds 0.5 parts by weight with respect to 100 parts by weight of the resin composition, the pellet feed to the extruder may be difficult to stabilize. is there. Although the manufacturing method of this resin composition pellet is not specifically limited, The method of dry-blending EVOH resin composition pellet and a lubricant is illustrated as a suitable thing.

  Suitable melt flow rate (MFR) of the resin composition comprising EVOH obtained in the present invention (measured at 190 ° C. under a load of 2160 g; provided that the melting point is around 190 ° C. or exceeds 190 ° C. under a load of 2160 g, the melting point It is measured at the above plural temperatures, and in a semi-logarithmic graph, the reciprocal absolute temperature is plotted on the horizontal axis, the melt flow rate is plotted on the vertical axis (logarithm), and the value extrapolated to 190 ° C.) is preferably 0.1 200 g / 10 min. It is. The lower limit of MFR is more preferably 0.2 g / 10 min. More preferably, 0.5 g / 10 min. Above, optimally 1 g / 10 min. That's it. Further, the upper limit of MFR is more preferably 50 g / 10 min. Or more preferably 10 g / 10 min. And optimally 7 g / 10 min. It is as follows. When the melt flow rate is smaller than the above range, the inside of the extruder is in a high torque state at the time of molding, making extrusion difficult, and when larger than the range, the mechanical strength of the molded product is insufficient, which is preferable. Absent.

  Further, ethylene-vinyl alcohol copolymers having different polymerization degrees, ethylene contents and saponification degrees can be blended and melt-molded in the resin composition of the present invention as long as the object of the present invention is not impaired. In addition, within the range that does not impair the object of the present invention, the resin composition may include other various plasticizers, stabilizers, surfactants, colorants, ultraviolet absorbers, slip agents, antistatic agents, drying agents, crosslinking agents, It is also possible to add appropriate amounts of reinforcing agents such as metal salts, fillers and various fibers.

  In addition, an appropriate amount of a thermoplastic resin other than the resin composition can be blended within a range that does not impair the object of the present invention. Examples of thermoplastic resins include various polyolefins (polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, ethylene-propylene copolymers, copolymers of ethylene and α-olefins having 4 or more carbon atoms, polyolefins. And maleic anhydride copolymers, ethylene-vinyl ester copolymers, ethylene-acrylic ester copolymers, or modified polyolefins obtained by graft-modifying them with unsaturated carboxylic acids or their derivatives), various nylons (nylon -6, nylon-6,6, nylon-6 / 6,6 copolymer, etc.), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, and modified polyvinyl alcohol resin.

  Method of incorporating ethylene-vinyl alcohol copolymer with carboxylic acid (A) having molecular weight of less than 75, alkali metal salt (B), alkaline earth metal salt (C), phosphoric acid compound (D) and boron compound (E) Is not particularly limited. For example, there are a method of immersing the EVOH in a solution in which the compound is dissolved, a method of melting the EVOH and mixing the compound, a method of dissolving the EVOH in an appropriate solvent and mixing the compound. .

  Especially, in order to exhibit the effect of this invention more notably, the method of immersing EVOH in the solution of the said compound is desirable. This process can be performed by either a batch method or a continuous method. In this case, the shape of the EVOH may be any shape such as powder, granular, spherical, or cylindrical pellet.

  When EVOH is immersed in a solution containing a carboxylic acid (A) having a molecular weight of less than 75, an alkali metal salt (B), an alkaline earth metal salt (C), a phosphoric acid compound (D) and a boron compound (E), the above solution Each concentration of carboxylic acid (A), alkali metal salt (B), alkaline earth metal salt (C), phosphoric acid compound (D) and boron compound (E) having a molecular weight of less than 75 is particularly limited. It is not a thing. The solvent of the solution is not particularly limited, but is preferably an aqueous solution for reasons of handling. The preferred range of immersion time varies depending on the form of EVOH, but in the case of pellets of about 1 to 10 mm, it is 1 hour or longer, preferably 2 hours or longer.

  The immersion treatment of the various compounds in the solution may be divided into a plurality of solutions or may be performed at a time. In particular, the treatment is performed with a solution containing all of the carboxylic acid (A), alkali metal salt (B), alkaline earth metal salt (C), phosphoric acid compound (D) and boron compound (E) having a molecular weight of less than 75. It is preferable from the point of simplification of the process. When the treatment is performed by immersing in the solution as described above, the final EVOH composition is obtained by drying.

  The obtained resin composition of the present invention is molded into various molded products such as films, sheets, containers, pipes, fibers and the like by melt molding. These molded products can be pulverized and molded again for reuse. It is also possible to uniaxially or biaxially stretch films, sheets, fibers, and the like. As the melt molding method, extrusion molding, inflation extrusion, blow molding, melt spinning, injection molding and the like are possible. The melting temperature varies depending on the melting point of the copolymer, but is preferably about 150 to 270 ° C.

  The resin composition of the present invention is a multilayer structure having at least one layer of a molded product such as the composition film or sheet of the present invention in addition to the production of a resin molded product having only the resin composition as a single layer as described above. Often used for practical use. As the layer structure of the multilayer structure, E / Ad / T, T / Ad / E / Ad / T, etc., when the resin composition of the present invention is represented by E, the adhesive resin is represented by Ad, and the thermoplastic resin is represented by T. However, it is not limited to this. Each layer may be a single layer or may be a multilayer according to circumstances.

  The method for producing the multilayer structure shown above is not particularly limited. For example, a method of melt-extruding a thermoplastic resin into a molded article (film, sheet, etc.) comprising the resin composition of the present invention, a method of co-extruding the resin composition of the present invention and another thermoplastic resin, a thermoplastic resin And a resin composition comprising EVOH and a molded product obtained from the EVOH resin composition of the present invention and a film and sheet of another substrate are combined with an organic titanium compound, an isocyanate compound, and a polyester system. Examples include a method of laminating using a known adhesive such as a compound, and among them, a method of co-extrusion with other thermoplastic resins is preferably used.

  The thermoplastic resin used is linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene-α-olefin copolymer. Polymers (α-olefins having 4 to 20 carbon atoms), homopolymers of olefins such as polybutene and polypentene or copolymers thereof, polyesters such as polyethylene terephthalate, polyester elastomers, polyamide resins such as nylon-6 and nylon-6,6 , Polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resin, vinyl ester resin, polyurethane elastomer, polycarbonate, chlorinated polyethylene, chlorinated polypropylene, and the like. Among these, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene, and polyester are preferably used.

  When laminating the resin composition of the present invention and the thermoplastic resin, an adhesive resin may be used, and the adhesive resin in this case is preferably an adhesive resin made of a carboxylic acid-modified polyolefin. Here, the carboxylic acid-modified polyolefin is a modified olefinic polymer containing a carboxyl group obtained by chemically (for example, addition reaction or graft reaction) bonding an ethylenically unsaturated carboxylic acid or its anhydride to an olefin polymer. Refers to coalescence. In addition, the olefin polymer is a polyethylene (low pressure, medium pressure, high pressure), a polyolefin such as linear low density polyethylene, polypropylene, boribten, or the like, a comonomer (vinyl ester, non-polymer) capable of copolymerizing the olefin and the olefin. Means a copolymer with a saturated carboxylic acid ester and the like, for example, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ethyl ester copolymer, and the like. Of these, linear low density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content 5-55 wt%), ethylene-acrylic acid ethyl ester copolymer (acrylic acid ethyl ester content 8-35 wt. %), Linear low density polyethylene and ethylene-vinyl acetate copolymers are particularly preferred. Examples of the ethylenically unsaturated carboxylic acid or its anhydride include an ethylenically unsaturated monocarboxylic acid, its ester, an ethylenically unsaturated dicarboxylic acid, its mono or diester, and its anhydride. Among them, the ethylenically unsaturated dicarboxylic acid Anhydrides are preferred. Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, and fumaric acid monomethyl ester. Acid is preferred.

  The addition amount or graft amount (modification degree) of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer is 0.0001 to 15% by weight, preferably 0.001 to 10% by weight, based on the olefin polymer. It is. The addition reaction and grafting reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be obtained, for example, by radical polymerization in the presence of a solvent (such as xylene) or a catalyst (such as a peroxide). The melt flow rate (MFR) measured at 190 ° C. of the carboxylic acid-modified polyolefin thus obtained is preferably 0.2 to 30 g / 10 minutes, more preferably 0.5 to 10 g / 10 minutes. is there. These adhesive resins may be used alone or as a mixture of two or more layers.

  The method of co-extrusion of the resin composition of the present invention and the thermoplastic resin is not particularly limited, and any of a multi-manifold merging method T-die method, a feed block merging method T-die method, and an inflation method may be used.

By subjecting the co-extruded multilayer structure thus obtained to secondary processing, various molded articles (films, sheets, tubes, bottles, etc.) can be obtained. Examples thereof include the following.
(1) Multilayer co-stretched sheet or film obtained by stretching a multilayer structure (sheet or film, etc.) in a uniaxial or biaxial direction, or stretching and heat treatment in a biaxial direction (2) Multilayer structure (sheet, film, etc.) Multi-layer rolled sheet or film by rolling (3) Multi-layer structure (sheet or film, etc.) Multi-layer tray cup-shaped container (4) Multi-layer structure by vacuum forming, pressure forming, vacuum-pressure forming, etc. Bottles and cup-like containers by stretch blow molding from (pipe, etc.) There are no particular limitations on such secondary processing methods, and other known secondary processing methods (blow molding, etc.) other than the above can also be employed.

  The multilayer structure thus obtained is excellent in low odor, has few fish eyes, is transparent and has few streaks, and is therefore suitable as a material for food containers such as deep-drawn containers, cup-shaped containers, bottles, etc. Used for.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this Example. Hereinafter, “%” and “parts” are based on weight unless otherwise specified. In addition, all the water used ion-exchange water.

(1) Quantitative determination of carboxylic acid (A) having a molecular weight of less than 75 A sample of 20 g of dried pellets was put into 100 ml of ion-exchanged water and extracted by heating at 95 ° C. for 6 hours. The extract was neutralized with 1/50 N NaOH using phenolphthalein as an indicator, and the content of carboxylic acid (A) having a molecular weight of less than 75 was quantified.

(2) Determination of alkali metal salt (B) and alkaline earth metal salt (C) (quantification of Na ion, K ion, Mg ion, and Ca ion)
10 g of dried pellets as a sample were put into 50 ml of 0.01 N hydrochloric acid aqueous solution and stirred at 95 ° C. for 6 hours. The aqueous solution after stirring was quantitatively analyzed using ion chromatography, and the amounts of Na ions, K ions, Mg ions, and Ca ions were quantified. The column used was ICS-C25 manufactured by Yokogawa Electric Corporation, and the eluent was an aqueous solution containing 5.0 mM tartaric acid and 1.0 mM 2,6-pyridinedicarboxylic acid. For the determination, calibration curves prepared with a sodium chloride aqueous solution, a potassium chloride aqueous solution, a magnesium chloride aqueous solution and a calcium chloride aqueous solution were used. From the amounts of Na ions, K ions, Mg ions, and Ca ions thus obtained, the amounts of alkali metal salt (B) and alkaline earth metal salt (C) in the dried pellets were obtained in terms of metal elements. .

(3) Quantification of phosphate compound (D) (quantification of phosphate ion)
10 g of dried pellets as a sample were put into 50 ml of 0.01 N hydrochloric acid aqueous solution and stirred at 95 ° C. for 6 hours. The aqueous solution after stirring was quantitatively analyzed using ion chromatography to determine the amount of phosphate ions. The column used was ICS-A23 manufactured by Yokogawa Electric Corporation, and the eluent was an aqueous solution containing 2.5 mM sodium carbonate and 1.0 mM sodium bicarbonate. A calibration curve prepared with an aqueous sodium dihydrogen phosphate solution was used for the determination. From the amount of phosphate ions thus obtained, the content of the phosphate compound (D) was obtained in terms of phosphate radical.

(4) Quantification of content of boron compound (E) 100 g of dried pellets as a sample was placed in a magnetic crucible and ashed in an electric furnace. The obtained ash was dissolved in 200 mL of 0.01 N nitric acid aqueous solution and quantified by atomic absorption analysis to obtain the content of boron compound (E) in an amount in terms of boron.

(5) Relationship between heating time and MFR 3-4 g of dried pellets as a sample were placed in a stainless steel pipe (inner diameter 2.2 cm, length 12.5 cm, inner volume 50 cm ³ ) in a nitrogen atmosphere, and inside the stainless steel pipe Was sufficiently replaced with nitrogen gas, followed by heat treatment at 220 ° C. After heat treatment, the resin MFR was changed to a melt indexer {Treasure Industry Co., Ltd. melt indexer L203 (cylinder hole diameter φ9.48 mm, piston diameter φ9.48 mm, die diameter φ2.09 mm, die length 8.01 mm) )}, The resin was heated at 230 ° C. for 6 minutes, then loaded with 10.9 kg and measured.

(6) Heat Melt Coloring Test 8 g of dried pellets used as a sample were sandwiched between hot plates heated to 230 ° C. (Sindo tabletop test press YS-5), and heated for 10 minutes while maintaining a gap of 5 mm between the hot plates. The degree of coloring was determined with the naked eye and determined as follows.
A: No coloring B: Slightly yellow C: Yellowing D: Intense coloring

(7) Single layer film formation test The single layer film was produced with the following method, and the external appearance of the molded product, die adhesion amount, and long run property were evaluated.
Type Single-screw extruder (non-vent type)
L / D 20
Diameter 20mmφ
Screw single-flight full flight type, surface nitrided steel Screw rotation speed 40rpm
Die 300mm width coat hanger die
Lip gap 0.3mm
Cylinder, die temperature setting
C1 / C2 / C3 / die = 195/230/230/220 (° C.)

(7-a) Variation in the number of occurrences of gelled blisters and the frequency of occurrence of gelled blisters The above-mentioned film formation was continued for 8 days, and the film was sampled every hour to obtain gelled blisters (about 150 μm that can be confirmed with the naked eye). The above were counted and converted per 1.0 m ² , and the average value per day of the number of gelled beads was obtained from the obtained data. In addition, during the film-forming test, the state of streaks and gel-like irregularities is continuously observed visually, and the number of streaks and gel-like irregularities increases rapidly (100 / m ² or more) per day. did.
(7-b) Die adhesion amount After the EVOH single layer film formation was carried out for 8 hours using the sample resin composition, the EVOH resin in the extruder was replaced with LDPE (low density polyethylene) of MFR = 1 over 1 hour. Thereafter, the weight of the EVOH thermally deteriorated resin adhering to the inside of the die was measured. The weight was determined as follows.
A; less than 1.5 g B; 1.5 to 5 g C; 5 to 10 g D; 10 g or more

(8) Interlaminar adhesive strength T-type peel strength between an ethylene-vinyl alcohol copolymer / adhesive resin immediately after film formation of a three-kind five-layer film obtained by the following coextrusion molding is 20 ° C.-65% RH condition Below, it measured using the autograph (tensile speed of 250 mm / min). The determination was made as follows according to the peel strength value.
A: 500 g / 15 mm or more B; 300 to less than 500 g / 15 mm C; less than 300 g / 15 mm (co-extrusion molding conditions)
Layer structure: LLDPE / adhesive resin / EVOH resin composition / adhesive resin / LLDPE (thickness 50/10/10/10/50: unit is μm)
LLDPE: Mitsui Chemicals' Ultra Zex 3523L
Adhesive resin: Bondin TX8030 manufactured by Sumitomo Chemical
Extrusion temperature of each resin: C1 / C2 / C3 / die = 170/170/220/220 ° C.
Extruder for each resin, T-die specifications:
LLDPE: 32φ extruder GT-32-A type (Plastic Engineering Laboratory)
Adhesive resin: 25φ extruder P25-18AC (Osaka Seiki)
EVOH; 20φ Extruder Lab Machine ME Type CO-EXT (Toyo Seiki)
T-die: 300mm width, 3 types, 5 layers (Plastic Engineering Laboratory)
Cooling roll temperature: 50 ° C
Take-off speed: 4m / min

(9) Recoverability The formed EVOH monolayer film (film-formed product up to 2 hours after the start of film formation) is pulverized, melted and pelletized again (the pelletization temperature is 220 ° C.), and the pellet is used. Then, single-layer film formation was performed again.
(9-a) Color resistance The film was wound around a paper tube, and the degree of coloration of the film end face was determined with the naked eye and determined as follows.
A: No coloration B: Slightly yellowing C; Yellowing D: Severe coloring (9-b) generation of gel 1 hour after film formation (single-layered film having a thickness of about 150 μm or more that can be confirmed with the naked eye) ) Was counted and converted per 1.0 m ² . Judgment was made as follows according to the number of items.
A; Less than 20 B; 20 to 40 C; 40 to 60 D; 60 or more

(10) Intrinsic viscosity 0.20 g of a sample pellet of a resin composition comprising EVOH is precisely weighed, and this is heated and dissolved in 40 ml of hydrous phenol (water / phenol = 15/85 wt%) at 60 ° C. for 3 to 4 hours. The viscosity was measured with an Ostwald viscometer at a temperature of 30 ° C. (t0 = 90 seconds), and the intrinsic (extreme) viscosity [η] was determined by the following equation.
[Η] = (2 × (ηsp−lnηrel)) ^1/2 / C (l / g)
ηsp = t / t0-1 (specific viscosity)
ηrel = t / t0 (relative viscosity)
C: EVOH concentration (g / l)
T0: Time for blank (hydrous phenol) to pass through viscometer t: Time for hydrous phenol solution in which sample is dissolved to pass viscometer

Example 1
A 45% methanol solution of an ethylene-vinyl acetate copolymer having an ethylene content of 38 mol% was charged into a saponification reactor, and a caustic soda / methanol solution (80 g / L) was added to the vinyl acetate component in the copolymer in an amount of 0. It added so that it might become 4 equivalent, and methanol was added and it adjusted so that a copolymer concentration might be 20%. The temperature was raised to 60 ° C., and the reaction was carried out for about 4 hours while blowing nitrogen gas into the reactor. Four hours later, the reaction was stopped by neutralization with acetic acid, extruded from a metal plate having a circular opening into water, precipitated, and cut to obtain pellets having a diameter of about 3 mm and a length of about 5 mm. The obtained pellets were drained with a centrifuge, and a large amount of water was further added to drain the pellets.

  100 parts by weight of the thus obtained water-containing pellets of ethylene-vinyl alcohol copolymer (ethylene content 38 mol%, saponification degree 99.4%, water content 55% by weight), boric acid 0.32 g / L, acetic acid It was immersed in 370 parts by weight of an aqueous solution containing sodium 0.4 g / L, magnesium acetate 0.24 g / L, potassium dihydrogen phosphate 0.17 g / L and acetic acid 0.5 g / L at 25 ° C. for 6 hours. After immersion, the solution was drained and dried at 80 ° C. for 3 hours and subsequently at 107 ° C. for 24 hours using a hot air dryer to obtain dried pellets. To 100 parts by weight of the dried pellets, 0.02 part by weight of lubricant Alflow H-50T (manufactured by NOF Corporation; ethylene bisstearic acid amide) was dry blended and mixed thoroughly to obtain EVOH resin composition pellets.

  The content of the carboxylic acid (A) having a molecular weight of less than 75 in the obtained dried pellet is 250 ppm, the content of the alkali metal salt (B) is 220 ppm in terms of metal, and the content of the alkaline earth metal salt (C) is metal. 35 ppm in terms of conversion, the content of the phosphate compound (D) was 100 ppm in terms of phosphate radical, and the content of the boron compound (E) was 240 ppm in terms of boron. Further, the MFR (measured under a load of 2160 g at 190 ° C.) of the obtained EVOH resin composition pellets was 2.0 g / 10 min.

  Using the obtained EVOH resin composition pellets, the relationship between the heating time and MFR was examined according to the above-described method (see FIG. 1), and a heating melt coloring test was conducted. MFRmax / MFR0 was 1.6, and the result of the heat-melt coloring test was A. Moreover, said resin composition showed the minimum value (MFRmax) within 100 hours after MFR showed the minimum value within 10 hours from the start of heating.

Using the obtained EVOH resin composition pellets, a single-layer film-forming test was performed according to the above-described method, and the number of generated gelled particles, the variation in the frequency of generated gelled particles, and the amount of attached die were examined. Occurrence of gelled spots is as small as 4 to 5 pieces / m ^{2 on} an average for 8 days, no steep and rapid increase of streaks or gelled spots is observed, and a molded article with a good appearance is obtained, which is good Long run characteristics were shown. The test result of the die adhesion amount was also A.

  Using the obtained EVOH resin composition pellets, interlayer adhesion was measured by the method described above. The T-type peel strength between the resin composition / adhesive resin composed of EVOH immediately after film formation was A.

  Using the film obtained by the single-layer film formation test (film-formation product up to 2 hours after the start of film formation), the test for recoverability ((a) coloration resistance and (b) generation of blisters) is performed by the above method. went. As a result of the test, the recoverability was determined as A in any of the evaluation items of (a) anti-coloring property and (b) occurrence of bumps.

Examples 2-6, Comparative Examples 1-8
Table 1 summarizes the composition of the liquid in which EVOH having the intrinsic viscosity shown in Table 2 is immersed in EVOH having an ethylene content of 38 mol% and a saponification degree of 99.4% after saponification, washing and liquid removal. Dry pellets were produced in the same manner as in Example 1 except for the change as shown and the presence or absence of addition of a lubricant, and a film was produced. Table 2 summarizes the composition of the pellets used in each example and comparative example, and Table 3 summarizes the evaluation results of various tests.

  The resin compositions of Examples 2 to 6, Comparative Examples 1 to 2, and Comparative Examples 4 to 8 had a minimum value within 10 hours from the start of heating, and a maximum value within 100 hours after the minimum value was exhibited. (MFRmax) was shown. However, in the resin composition of Comparative Example 4, MFR showed neither a minimum value nor a maximum value.

  The resin compositions composed of EVOH of Examples 1 to 6 having the structure of the present invention are excellent in appearance with little coloration, fish eyes (gels and blisters), streaks, etc., and excellent in long run properties during melt molding. In addition, there was little coloring at the time of collection, and the interlayer adhesion was excellent when a laminate was obtained. In Example 6, which does not contain a lubricant, the effect of improving coloring resistance and the effect of reducing the amount of attached die are slightly reduced when compared with Example 1, and the effect of suppressing gel / bucks and the generation of gel-like blisters are reduced. Although the effect of suppressing the rapid increase in the number was somewhat reduced, it could be put to practical use.

  However, Comparative Example 1 containing no boron compound (E) has an insufficient effect of suppressing the formation of gels and blisters, and Comparative Example 2 containing no phosphoric acid compound (D) is unsatisfactory in coloration resistance during film recovery. It was something.

  In addition, regarding the relationship between the heating time at 220 ° C. in a nitrogen atmosphere of the resin composition and MFR (230 ° C., 10.9 kg load), MFR showed a minimum value within 10 hours from the start of heating and showed a minimum value. In Comparative Example 3 that does not have the configuration of the present invention that shows the maximum value (MFRmax) within 100 hours after that, the effect of reducing the amount of die adhesion cannot be obtained, and the frequency of occurrence of gels and blisters multiple times a day Increased rapidly and productivity was inferior.

  In Comparative Example 4 in which MFRmax / MFR0 exceeds 45 and Comparative Example 5 in which the content of carboxylic acid (A) having a molecular weight of less than 75 is less than 50 ppm, sufficient color resistance was not obtained. In Comparative Example 6 in which the alkali metal salt (B) was less than 50 ppm, sufficient adhesion was not obtained.

In Comparative Example 7 of the present application having the same structure as Comparative Example 7 of the above-mentioned JP-A-10-67898, since MFRmax / MFR0 exceeds 45, the coloring resistance is poor, and the content of the boron compound (E) Is less than 50 ppm, and the generation of gels and blisters increased as the operation was continued for a long time. Moreover, in Comparative Example 8 in which the content of the carboxylic acid (A) having a molecular weight of less than 75 exceeds 500 ppm, the adhesiveness is poor and the effect of suppressing the generation of gels and blisters is also unsatisfactory.

Claims (2)

A resin composition comprising an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 65 mol% and a saponification degree of 95% or more, when the resin composition is heated at 220 ° C under a nitrogen atmosphere, The MFR (230 ° C., 10.9 kg load) of the resin composition shows a minimum value within 10 hours from the start of heating, and shows a maximum value (MFRmax) within 100 hours after showing the minimum value. Less than 75 carboxylic acid (A) 50-500 ppm, alkali metal salt (B) 50-500 ppm in terms of metal element, alkaline earth metal salt (C) 10-120 ppm in terms of metal element, phosphate compound (D ) In an amount of 10 to 200 ppm in terms of phosphate radicals, and a boron compound (E) in an amount of 50 to 2000 ppm in terms of boron element, and 100 weights of an ethylene-vinyl alcohol copolymer. A lubricant containing 0.005 parts by weight per part, the molecular weight less than 75 of the carboxylic acid (A) is acetic acid, the lubricant is a higher fatty acid amide, and the following formula (1) and (2) A resin composition characterized by satisfying
0.5 ≦ MFRmax / MFR0 ≦ 45 (1)
However,
MFRmax: Maximum value of MFR (230 ° C., 10.9 kg load) of the resin composition when the resin composition is heated at 220 ° C. in a nitrogen atmosphere MFR0: MFR of the resin composition not subjected to heat treatment (230 ° C, 10.9kg load)
1 ≦ [B (μmol / g) + C (μmol / g)] / [D (μmol / g) + A (μmol / g)] ≦ 10 (2)
However,
A: Content of carboxylic acid (A) having a molecular weight of less than 75 per unit weight of the resin composition (μmol / g)
B: Content of alkali metal salt (B) per unit weight of the resin composition (metal element conversion: μmol / g)
C: Content of alkaline earth metal salt (C) per unit weight of the resin composition (metal element conversion: μmol / g)
D: Content of the phosphoric acid compound (D) per unit weight of the resin composition (phosphate conversion: μmol / g) A pellet of a resin composition obtained by adhering 0.005 to 0.5 parts by weight of a lubricant to 100 parts by weight of a resin composition on the outer surface of a pellet made of the resin composition according to claim 1 .

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