JP6403560B2 - Method for producing saponified ethylene-vinyl ester copolymer composition - Google Patents

Description

  The present invention relates to an EVOH resin composition containing a saponified ethylene-vinyl ester copolymer (hereinafter sometimes referred to as “EVOH resin”) and a polyamide resin, and more specifically, coloring with time during storage. The present invention relates to a method for producing an EVOH resin composition that is not recognized.

  EVOH resin is excellent in transparency, gas barrier properties, fragrance retention, solvent resistance, oil resistance, etc., taking advantage of such properties, food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, agricultural chemical packaging materials, etc. It is used after being molded into a container such as a film, a sheet, or a bottle.

In such molding, EVOH resin pellets are usually put into an extruder or the like and formed into a film or sheet by melt molding. Depending on the properties of such EVOH resin pellets, the extruder being molded Torque fluctuations and discharge fluctuations are large, and the resulting molded product may not have good dimensional stability accuracy.
For example, the accuracy of the shape and thickness of the molded product may be lowered, and the properties of the pellets are becoming very important.

  As a method for producing such EVOH resin pellets having excellent pellet properties, for example, Patent Document 1 describes the relationship between the shear rate (γ) at the die nozzle and the surface temperature (T) of the EVOH resin or EVOH resin composition at the time of cutting. It is proposed that EVOH resin pellets with excellent pellet properties can be obtained when a specific relational expression is satisfied.

  EVOH resin films are used for retort applications by taking advantage of their excellent gas barrier properties. However, when the hot water treatment is performed for a long time as in the retort treatment, there are disadvantages that the gas barrier property immediately after the hot water treatment is deteriorated, the film is whitened, and the shape cannot be maintained.

  As a resin composition capable of obtaining a packaging film having an excellent form even after hot water treatment, a resin composition in which a polyamide-based resin is blended with an EVOH resin is known.

JP 2001-105428 A

  In Patent Document 1, when the EVOH resin composition is melt-kneaded, extruded and cut into strands to produce pellets, those having a relatively low or high pellet surface temperature at the time of cutting are exemplified. The surface temperature of the pellet at the time of cutting is not particularly limited.

Here, the pellet having a relatively low surface temperature at the time of cutting can be obtained by a method in which the EVOH resin composition after melt-kneading is sufficiently cooled by water cooling and then cut, but in such a method, it is included in the EVOH resin pellet. As a result, the moisture content is increased, and a drying process for removing the moisture is required. Therefore, a pellet having a relatively low surface temperature at the time of cutting is not preferable from the viewpoint of production efficiency because a post-drying step is required.
That is, from the viewpoint of shortening the process, it is desirable that the post-drying process is not necessary after the strand cutting, and that the cutting is performed at a high temperature within a range in which the pellets do not melt.

In the manufacturing process of the conventional EVOH resin composition, the EVOH resin composition is melt-kneaded and extruded into a strand shape. When producing pellets by cutting at a relatively high temperature, there is no special cooling step after cutting. Usually it was naturally cooled.
Actually, if only the EVOH resin is used, there is no particular problem even if the surface temperature of the pellet after strand cutting is relatively high.

  However, the EVOH resin composition in which the polyamide resin is blended with the EVOH resin has a problem that the pellet is yellowed when the surface temperature of the pellet after strand cutting is relatively high.

  As a result of intensive studies in view of the above circumstances, the present inventor has melt-kneaded EVOH resin (A) and polyamide-based resin (B), extruded into a strand shape, cooled by water cooling, and then cut the strand at a surface temperature of 100 to 130 ° C. The pellets obtained by doing so were found to be able to suppress yellowing of the EVOH resin composition pellets by cooling to a surface temperature of 60 ° C. or less within 30 minutes, thereby completing the present invention.

  According to the method for producing an EVOH resin composition pellet containing the EVOH resin (A) and the polyamide resin (B) of the present invention, yellowing of the pellet can be suppressed.

In addition, since the EVOH resin composition which mix | blended the polyamide-type resin with EVOH resin is not yellowing immediately after melt-kneading, it was thought that heat was unrelated as a factor of a yellowing problem.
However, unexpectedly, yellowing could be suppressed by cooling the obtained pellets to a surface temperature of 60 ° C. or less within 30 minutes.

  Hereinafter, although it demonstrates in detail about the structure of this invention, these show an example of a desirable embodiment and are not specified by these content.

  The manufacturing method of the EVOH resin composition of this invention is a resin composition containing EVOH resin (A) and a polyamide-type resin (B).

First, the EVOH resin used in the present invention will be described.
<EVOH resin>
The EVOH resin (A) used in the present invention is a resin obtained by saponifying a copolymer of ethylene and a vinyl ester monomer (ethylene-vinyl ester copolymer). It is a thermoplastic resin. The polymerization can also be carried out using any known polymerization method such as solution polymerization, suspension polymerization, and emulsion polymerization. Generally, solution polymerization using methanol as a solvent is used. Saponification of the obtained ethylene-vinyl ester copolymer can also be performed by a known method.
The EVOH resin produced in this way is mainly composed of ethylene-derived structural units and vinyl alcohol structural units, and contains a slight amount of vinyl ester structural units remaining without saponification.

  As the vinyl ester monomer, vinyl acetate is typically used from the viewpoint of market availability and good impurity treatment efficiency during production. Examples of other vinyl ester monomers include, for example, fats such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl versatate. Aromatic vinyl esters such as aromatic vinyl esters and vinyl benzoates, and the like. Usually, aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms are used. it can. These are usually used alone, but a plurality of them may be used simultaneously as necessary.

  The content of the ethylene structural unit in the EVOH resin is a value measured based on ISO14663, and is usually 20 to 60 mol%, preferably 25 to 55 mol%, particularly preferably 29 to 48 mol%. When the content is too low, the gas barrier property and melt moldability under high humidity tend to be lowered, and when it is too high, the gas barrier property tends to be insufficient.

  The saponification degree of the vinyl ester component in the EVOH resin is a value measured based on JIS K6726 (however, the EVOH resin is a solution uniformly dissolved in water / methanol solvent) and is usually 90 to 100 mol%, preferably It is 95-100 mol%, Most preferably, it is 99-100 mol%. When the degree of saponification is too low, gas barrier properties, thermal stability, moisture resistance and the like tend to decrease.

  Further, the melt flow rate (MFR) (210 ° C., load 2,160 g) of the EVOH resin is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, particularly preferably 3 to 35 g. / 10 minutes. When the MFR is too large, the film forming property tends to be unstable, and when it is too small, the viscosity becomes too high and melt extrusion tends to be difficult.

  The EVOH resin used in the present invention may contain an ethylene structural unit, a vinyl alcohol structural unit (including an unsaponified vinyl ester structural unit), and a structural unit derived from a comonomer shown below. Good. Examples of the comonomer include α-olefins such as propylene, isobutene, α-octene, α-dodecene, α-octadecene; 3-buten-1-ol, 4-penten-1-ol, 3-butene-1, 2- Hydroxy group-containing α-olefins such as diols and hydroxy-containing α-olefin derivatives such as esterified products and acylated products thereof; unsaturated carboxylic acids or salts thereof, partial alkyl esters, fully alkyl esters, nitriles, amides or anhydrides; Examples thereof include unsaturated sulfonic acid or a salt thereof; vinyl silane compound; vinyl chloride; styrene.

  Furthermore, “post-modified” EVOH-based resins such as urethanization, acetalization, cyanoethylation, oxyalkyleneation, and the like can also be used.

In particular, an EVOH resin obtained by copolymerizing a hydroxy group-containing α-olefin is preferable in terms of good secondary moldability, and among them, an EVOH resin having a 1,2-diol in the side chain is preferable.
Such EVOH resin having 1,2-diol in the side chain contains 1,2-diol structural units in the side chain. The 1,2-diol structural unit is specifically a structural unit represented by the following structural unit (1).

[In the general formula (1), R 1, R 2 and R 3 each independently represent a hydrogen atom or an organic group, X represents a single bond or a bond chain, and R 4, R 5 and R 6 each independently represent a hydrogen atom. Or an organic group is shown. ]

The organic group in the 1,2-diol structural unit represented by the general formula (1) is not particularly limited, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. And saturated hydrocarbon groups such as tert-butyl group, aromatic hydrocarbon groups such as phenyl group and benzyl group, halogen atom, hydroxyl group, acyloxy group, alkoxycarbonyl group, carboxyl group and sulfonic acid group.
R1 to R3 are preferably a saturated hydrocarbon group or a hydrogen atom having 1 to 30 carbon atoms, particularly 1 to 15 carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably a hydrogen atom. R4 to R6 are preferably an alkyl group having 1 to 30 carbon atoms, particularly 1 to 15 carbon atoms, more preferably 1 to 4 carbon atoms, or a hydrogen atom, and most preferably a hydrogen atom. In particular, it is most preferable that R1 to R6 are all hydrogen.

Moreover, X in the structural unit represented by the general formula (1) is typically a single bond.
In addition, a bond chain may be used as long as the effect of the present invention is not inhibited. Such a bonding chain is not particularly limited, but other than hydrocarbon chains such as alkylene, alkenylene, alkynylene, phenylene, naphthylene (these hydrocarbons may be substituted with halogen such as fluorine, chlorine, bromine, etc.), _{-O -, - (CH 2 O} ) m -, - (OCH 2) m -, - (CH 2 O) mCH 2 - structure containing an ether binding site, such as, -CO -, - COCO -, - CO ( _{CH 2) mCO -, - CO} (C 6 H 4) CO- structure containing a carbonyl group such as, -S -, - CS -, - SO -, - SO 2 - structure containing a sulfur atom, such as, -NR -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - structure comprising NRNR- such as nitrogen atoms, -HPO ₄ - structure containing a hetero atom such as structure containing a phosphorus atom, such as, -Si (OR) _2- , -OSi (OR) _2- , -OSi (OR) 2O- structure containing silicon atoms such _{as, -Ti (OR) 2 -,} - OTi (OR) 2 -, - OTi (OR) 2 O- and the like structure containing titanium atoms, -Al ( OR)-, -OAl (OR)-, -OAl (OR) O-, and the like include structures containing metal atoms such as structures containing aluminum atoms. In addition, R is an arbitrary substituent each independently, a hydrogen atom and an alkyl group are preferable, and m is a natural number, and is 1-30 normally, Preferably it is 1-15, More preferably, it is 1-10. Among them, —CH 2 OCH 2 — and a hydrocarbon chain having 1 to 10 carbon atoms are preferable from the viewpoint of stability during production or use, and further, a hydrocarbon chain having 1 to 6 carbon atoms, particularly 1 carbon atom. Is preferred.

  The most preferable structure in the 1,2-diol structural unit represented by the general formula (1) is one in which R1 to R6 are all hydrogen atoms and X is a single bond. That is, the structural unit represented by the following structural formula (1a) is most preferable.

  In particular, when the 1,2-diol structural unit represented by the general formula (1) is contained, the content thereof is usually 0.1 to 20 mol%, further 0.1 to 15 mol%, and particularly preferably 0.1. The thing of 1-10 mol% is preferable.

  In addition, the EVOH resin used in the present invention may be a mixture with other different EVOH resins. Examples of such other EVOH resins include 1,2-diol structural units represented by the general formula (1). Examples thereof include those having different contents, those having different saponification degrees, those having different polymerization degrees, and those having different other copolymerization components.

<Polyamide resin>
Specific examples of the polyamide resin (B) used in the present invention include polycapramide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecanamide ( Nylon 11), polylauryl lactam (nylon 12), polyethylenediamine adipamide (nylon 26), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (Nylon 610), polyhexamethylene dodecamide (nylon 612), polyoctamethylene adipamide (nylon 86), polydecamethylene adipamide (nylon 108), caprolactam / lauryl lactam copolymer (nylon 6/12) , Capro Tam / ω-aminononanoic acid copolymer (nylon 6/9), caprolactam / hexamethylene diammonium adipate copolymer (nylon 6/66), lauryl lactam / hexamethylene diammonium adipate copolymer (nylon 12/66) , Ethylenediamine adipamide / hexamethylene diammonium adipate copolymer (nylon 26/66), caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon 66/610), ethylene ammonium adipate / hexa Methylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon 6/66/610), polyhexamethylene isophthalamide, polyhexamethyle Examples include terephthalamide, hexamethylene isophthalamide copolymer / terephthalamide copolymer or those polyamide resins modified with aromatic amines such as methylenebenzylamine and metaxylenediamine, and metaxylylenediamine adipate. Then, a polyamide-based resin whose terminal is adjusted with a carboxyl group or an amino group is preferably used.

  As such a polyamide resin having a terminal adjusted, caproamide is the main structural unit, and the terminal carboxyl group content [X] and terminal amino group content [Y] are {{1 0 × [Y]) / ([X] + [Y])} ≧ 5 (where [X], [Y] units are μ eq / g polymer) It is done.

  As a terminal regulator in the above, a C2-C23 carboxylic acid and a C2-C20 diamine are used. Here, as monocarboxylic acid having 2 to 23 carbon atoms, aliphatic monocarboxylic acid (acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, capric acid, pelargonic acid, undecanoic acid, lauric acid , Tridecanoic acid, myristic acid, myroleic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, arachidic acid, behenic acid, etc.), alicyclic monocarboxylic acids (cyclohexanecarboxylic acid, methylcyclohexanecarboxylic acid, etc.), aromatic Group monocarboxylic acids (benzoic acid, toluic acid, ethylbenzoic acid, phenylacetic acid, etc.).

  Examples of the diamine having 2 to 20 carbon atoms include aliphatic diamines (ethylene diamine, trimethylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, octamethylene diamine, decamethylene diamine, dodecamethylene diamine, hexadecamethylene diamine, 2 , 2,4- (or 2,4,4-) trimethylhexamethylenediamine)), cycloaliphatic diamine (cyclohexanediamine, bis- (4,4'-aminocyclohexyl) methane, etc.), aromatic diamine (xylyl). Range amine etc.).

  In addition to the above monocarboxylic acids, aliphatic dicarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedione Acid, hexadecenedioic acid, octadecanedioic acid, octadecenedioic acid, eicosadioic acid, eicosenedioic acid, docosandioic acid, 2,2,4-trimethyladipic acid, etc.), alicyclic dicarboxylic acid (1,4-cyclohexanedicarboxylic acid) Acid) and aromatic dicarboxylic acids (terephthalic acid, isophthalic acid, phthalic acid, xylylene dicarboxylic acid, etc.) can be used or used in combination.

  The degree of polymerization of the polyamide is not particularly limited, but is preferably 1.7 to 5.0, particularly preferably 2.0 to 5.0, in terms of relative viscosity measured according to JISK6810.

  As a method for polymerizing polyamide, melt polymerization, interfacial polymerization, solution polymerization, bulk polymerization, solid phase polymerization, or a combination of these can be employed. Further, as the polyamide raw material, ε-caprolactam is particularly preferable from the viewpoint that better boil resistance and retort resistance can be obtained.

  The content ratio of the EVOH resin (A) and the polyamide resin (B) is not particularly limited, but the polyamide resin (B) is added in an amount of 1 to 40 parts by weight (more preferably 5 parts per 100 parts by weight of the EVOH resin (A)). ~ 30 parts by weight, particularly 10 to 20 parts by weight) is preferably included, and when the content of the polyamide-based resin (B) is too small, the appearance and delamination resistance after retort treatment tend to decrease, Conversely, when the content of the polyamide-based resin (B) is too large, the long run processability tends to decrease, which is not preferable.

  In the present invention, EVOH resin (A) and polyamide resin (B) are melt-kneaded, extruded into a strand shape, and then pellets obtained by strand cutting at a surface temperature of 100 to 130 ° C. are produced within 30 minutes. The method for producing such EVOH resin composition pellets will be described below.

  When the EVOH resin composition is melt-kneaded and extruded into a strand shape, the EVOH resin composition is supplied to a melt extruder such as a single-screw extruder or a twin-screw extruder provided with a die nozzle, and the EVOH resin composition is discharged from the die nozzle. What is necessary is just to extrude a resin composition.

  The resin temperature of the EVOH resin composition when extruded from the die nozzle is preferably 150 to 300 ° C. (more preferably 180 to 290 ° C., particularly 200 to 280 ° C.). On the contrary, if the gel is generated frequently and is too high, the EVOH resin is undesirably deteriorated by heat and colored.

  Moreover, it is preferable that L / D which is a ratio of the screw length L (mm) of the extruder and the diameter D (mm) of the screw satisfies the relationship of 10 <(L / D) <100. Preferably, 15 <(L / D) <70. In particular, 40 <(L / D) <60. If the ratio is too low, unmelted gel is frequently generated. On the other hand, if the ratio is too high, the EVOH resin is thermally deteriorated and colored, which is not preferable.

  The shape of the die nozzle is not particularly limited, but is preferably a circular nozzle having a diameter of 1 to 10 mm, and more preferably a circular nozzle having a diameter of 2 to 7 mm in terms of the shape of the pellet.

The EVOH resin composition extruded into a strand form from a die nozzle and water-cooled is then cut into pellets, and the water-cooling temperature is usually 0 to 40 ° C. If the temperature is too high, a sufficient cooling effect cannot be obtained, and conversely, if the temperature is too low, water becomes ice and normal cooling cannot be performed, and excessive moisture absorption tends to occur.
In addition, what is necessary is just to cool through a strand in the water tank which put the water of predetermined temperature in cooling with water.

  Further, after the strand water cooling, the surface moisture may be removed by blowing air or sucking the strand before cutting the pellet.

  The surface temperature of the EVOH resin composition at the time of strand cutting is preferably adjusted to about 100 to 130 ° C, preferably 105 to 125 ° C, and particularly preferably about 110 to 120 ° C. If the temperature is too low, the strands will become too hard and cracking of the pellets will occur in the cutting process, which tends to impair the appearance of fine particles and pellets, making them unsuitable for the product. Produces defects and makes manufacturing difficult.

  Thus, the pellets are cut into pellets. From the viewpoint of ease of handling of the pellets, the pellets have a diameter of 1 to 6 mm and a length of 1 to 6 mm in the case of a column (more each 2 ˜5 mm) is preferred.

  The present invention is characterized in that the EVOH resin composition pellets obtained by cutting the strands at a relatively high temperature are cooled, and the surface temperature of the pellets is set to 60 ° C. or less within 30 minutes.

  The pellet surface temperature after cooling in the present invention is 60 ° C. or less, preferably 45 ° C. or less, particularly preferably 30 ° C. or less. If this temperature is too high, yellowing tends to occur due to heat storage.

  The pellet cooling time is within 30 minutes, preferably within 20 minutes, particularly preferably within 10 minutes, and particularly preferably within 5 minutes. If this time is too long, yellowing tends to occur due to heat storage. Furthermore, if this time is too long, there is a problem that the production efficiency is lowered because the cooling efficiency is poor.

  The cooling method of the pellet in the present invention is not particularly limited, and examples thereof include an air cooling method, a water cooling method, a method using a heat exchanger, and the like.

  Although it does not specifically limit as an air-cooling system, For example, the system of spraying air and performing uniform cooling, the system of applying a cold wind locally, etc. are mentioned. Specific examples of the former include Tanaka Co., Ltd. “Mistral ASC 40-1500”, SOLEX THERMAL SCIENCE “Air-cooled pellet cooling device”, Seiwa Iron Works “PCS-500” and the like. Specific examples of the latter include Hitachi Appliances Co., Ltd. “COOL SHOT SR-P60YLTE1”, Daikin Industries, Ltd. “Crisp SUAS3MBU”, Suiden Co., Ltd. “Cool Suifan SS-25EC-1H”, Nakatomi Co., Ltd. “Spot Cooler N407-” R ”, Denso Sales Co., Ltd.“ INSPAC 15HF-NKF ”, Haier Japan Sales Co., Ltd.“ Floor Spot Air Conditioner JA-SP25J ”, Trusco Nakayama Co., Ltd.“ TS-25DP-1 ”and the like.

  Although it does not specifically limit as a water cooling system, For example, the system of performing a water bath, the system of spraying water, etc. are mentioned, A well-known technique can be used.

  The method using the heat exchanger is not particularly limited, and examples thereof include a method using a cooling fin, a method using a discharge medium through which a coolant has passed, and the like. Specifically, a known technique can be used. As an example, SOLEX THERMAL SCIENCE “heat exchanger cooled pellet cooling device” can be cited.

The water-cooling method is excellent in cooling efficiency, but requires a post-process such as centrifugation or drying after cooling, resulting in poor production efficiency and is not preferable for production.
The method using a heat exchanger is excellent in production efficiency, but because the pellets are cooled while touching the heat exchanger, the cracking of the pellets occurs and the generation of fine powder and the appearance of the pellets are impaired, thereby maintaining product quality. Is not suitable.
Therefore, from the viewpoint of cooling efficiency, production efficiency, and product quality, the air cooling method is desirable as the cooling method.

  The moisture content of the obtained pellets is usually 0.5% by weight or less, preferably 0.4% by weight or less, particularly preferably 0.3% by weight or less. When the water content is too high, foaming tends to occur in the molded product when it is molded, and the molded product tends to have poor appearance.

<Other resins>
The EVOH resin pellet used in the present invention may be a composition in which the base resin is an EVOH resin.
Therefore, in the EVOH resin composition of the present invention, in addition to the EVOH resin (A) and the polyamide resin (B), other thermoplastic resins are usually contained in an amount of 30% by weight or less based on the EVOH resin. Also good.

  Specific examples of the other thermoplastic resins include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ionomer, and ethylene-propylene copolymer. , Ethylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer Polyolefin resins in a broad sense such as polymers, polybutenes, polypentenes or other olefins alone or copolymers, polycyclic olefins, or those olefins alone or copolymers grafted with unsaturated carboxylic acids or esters thereof, Polystyrene resin, polyester, polyamide, copolymer polyamid , Polyvinyl chloride, polyvinylidene chloride, acrylic resin, vinyl ester resin, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, a thermoplastic resin such as chlorinated polypropylene.

  Thermoplastic resins are usually made from petroleum-derived raw materials such as naphtha, but are derived from natural gas-derived raw materials such as shale gas, sugar, starch, sugar and other ingredients contained in sugarcane, sugar beet, corn, potato, etc. Plant-derived raw materials purified from components such as cellulose contained in rice, wheat, millet, grass plants and the like may be used.

  In particular, when the resin composition of the present invention is used as a food packaging material as a multilayer structure, after the hot water treatment of the packaging material, the EVOH resin layer is prevented from being eluted at the end of the packaging material. It is preferable to blend a polyamide resin.

  Moreover, in the EVOH resin pellet of the present invention, in addition to the above components, ethylene glycol, glycerin, if necessary, as long as the effects of the present invention are not impaired (for example, less than 5% by weight of the entire resin composition). Plasticizers such as aliphatic polyhydric alcohols such as hexanediol; saturated aliphatic amides (such as stearic acid amide), unsaturated fatty acid amides (such as oleic acid amide), bis fatty acid amides (such as ethylene bisstearic acid amide) , Lubricants such as low molecular weight polyolefin (for example, low molecular weight polyethylene having a molecular weight of about 500 to 10,000, or low molecular weight polypropylene), heat stabilizer, antiblocking agent, antioxidant, coloring agent, antistatic agent, ultraviolet absorber, antibacterial agent Insoluble inorganic salt (for example, hydrotalcite); filler (for example, inorganic filler) Crystal nucleating agents (eg, talc, kaolin, etc.); surfactants, waxes; dispersants (eg, calcium stearate, stearic acid monoglyceride, etc.); conjugated polyene compounds, aldehyde compounds (eg, unsaturated aldehydes such as crotonaldehyde, etc.), etc. A well-known additive can be mix | blended suitably.

  The heat stabilizer is an organic acid such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid, or an alkali thereof for the purpose of improving various physical properties such as heat stability during melt molding. Metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), salts such as zinc; or inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, phosphoric acid, boric acid, or alkali metal salts thereof Additives such as salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc, etc. may be added. Of these, it is particularly preferable to add boron compounds, acetates and phosphates including acetic acid, boric acid and salts thereof.

  Such pellets are formed into films, sheets, containers, fibers, rods, tubes, various molded products, etc. by melt molding, etc., and melted again using these pulverized products (for example, when the recovered products are reused). An extrusion molding method and an injection molding method are mainly employed as the melt molding method. The melt molding temperature is often selected from the range of 150 to 300 ° C. In addition, the pellet can be used as a single layer, or it is also useful to laminate a thermoplastic resin layer or the like on at least one side of the layer made of the pellet and use it as a multilayer laminate.

  In producing the laminate, another substrate is laminated on one side or both sides of the layer made of pellets. For example, a thermoplastic resin is melt-extruded into a film or sheet made of the pellets. On the contrary, a method of melt-extruding the pellets on a substrate such as a thermoplastic resin, a method of co-extrusion of the pellets and another thermoplastic resin, and a film or sheet comprising the pellets obtained in the present invention And a method of dry-laminating films and sheets of other substrates with known adhesives such as organic titanium compounds, isocyanate compounds, polyester compounds, polyurethane compounds, and the like.

  The other resin in the case of coextrusion is linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene-acrylic acid. Ester copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene, polypentene and other olefins alone or copolymers, or these olefins alone or copolymers Polyolefin resins such as those obtained by graft modification with unsaturated carboxylic acids or esters thereof, polyesters, polyamides, copolymerized polyamides, polyvinyl chloride, polyvinylidene chloride, acrylic resins, polystyrene, vinyl ester resins, polyester elastomers , Poly Examples include urethane elastomer, chlorinated polyethylene, chlorinated polypropylene, polyketone, polyalcohol and the like. Other EVOHs can be coextruded. Among these, polypropylene, polyamide, polyethylene, ethylene-vinyl acetate copolymer, polystyrene, PET, and PEN are preferably used from the viewpoint of ease of coextrusion film formation and practicality of film physical properties (particularly strength).

  Further, a molded product such as a film or a sheet is once obtained from the pellet obtained in the present invention, and another substrate is extrusion coated thereon, or a film or sheet of another substrate is laminated using an adhesive. In this case, any base material (paper, metal foil, uniaxial or biaxially stretched plastic film or sheet, woven fabric, non-woven fabric, metallic cotton, wood, etc.) can be used in addition to the thermoplastic resin.

  The layer structure of the laminate is a (a1, a2,...) For the layer made of pellets obtained in the present invention, and b (b1, b2,...) For another substrate, for example, a thermoplastic resin layer. If it is a film, sheet or bottle, not only a / b two-layer structure but also b / a / b, a / b / a, a1 / a2 / b, a / b1 / b2, b2 Any combination such as / b1 / a / b1 / b2 is possible, and in the filament form, a and b are bimetal type, core (a) -sheath (b) type, core (b) -sheath (a) type, or Arbitrary combinations such as an eccentric core-sheath type are possible.

  The shape of the laminate thus obtained may be any shape, and examples thereof include films, sheets, tapes, bottles, pipes, filaments, profile cross-section extrudates, and the like. In addition, the obtained laminate can be subjected to heat treatment, cooling treatment, rolling treatment, printing treatment, dry lamination treatment, solution or melt coating treatment, bag making processing, deep drawing processing, box processing, tube processing, split processing, etc. It can be carried out. The film, sheet or container obtained as described above is useful as various packaging materials such as foods, pharmaceuticals, industrial chemicals and agricultural chemicals.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the description of the examples unless it exceeds the gist.
In the examples, “part” means a weight basis unless otherwise specified.

[Example 1]
11. Ethylene content 29 mol%, saponification degree 99.7 mol%, MFR 3.8 g / 10 min (210 ° C., load 2160 g) EVOH resin 87.5 parts and nylon 6 (DSM “NOVAmid 1028EN”) Five parts were dry blended. The obtained mixture was supplied to a twin screw extruder and extruded in the form of a strand under the following conditions.
[Biaxial extrusion conditions]
Screw inner diameter 48mm
L / D 48
Resin temperature 270 ° C

  Next, the extruded strand is water-cooled with 26 ° C. water, and the EVOH resin composition (strand) at the time of cutting is adjusted to a surface temperature of 115 ° C., and then cut using a pelletizer. Pellets (columnar shape, length 3.0 mm, diameter 2.3 mm) were obtained.

The obtained EVOH resin composition pellets were cooled with an air-cooled pellet cooler (“Mistral ASC 40-1500” manufactured by Tanaka Co., Ltd.), and the surface temperature of the EVOH resin composition pellets was cooled to 44 ° C. within 1 minute. EVOH resin composition pellets having a water content of 0.21% by weight were obtained.
Such EVOH resin composition pellets were charged into a tank (material: SUS) and then filled into a flexible container (material: aluminum).

  Evaluation was performed in the following manner using the obtained EVOH resin composition pellets.

[Evaluation of yellowing of pellets]
YI was measured for an extracted sample 1 minute after pelletization and an extracted sample in the center of the flexible container 10 days after pelletization using a “spectral color difference meter SE 6000” manufactured by Nippon Denshoku Industries Co., Ltd.

[Comparative Example 1]
In Example 1, a VOH resin composition was produced in the same manner as in Example 1 except that an air-cooled pellet cooler was not used, and was similarly evaluated. In this EVOH resin composition pellet, the surface temperature of the pellet after 1 minute from pelletization was 80 ° C.

  The evaluation results of Examples and Comparative Examples are summarized in Table 1.

  From the above results, EVOH resin and polyamide-based resin are melt-kneaded, and in the step of producing EVOH resin composition pellets, cooling is performed after pelletization, and the pellet surface temperature is reduced to 60 ° C. or less within a specific time, thereby producing pellets. It was possible to suppress yellowing.

  The EVOH resin composition obtained by the production method of the present invention is useful as a production raw material for retort use.

Claims (2)

  Obtained by melt-kneading the ethylene-vinyl ester copolymer saponified product (A) and the polyamide resin (B), extruding into a strand shape, cooling with water cooling, and then cutting the strand at a surface temperature of 100 to 130 ° C. A method for producing an ethylene-vinyl ester copolymer saponified composition pellet, wherein the pellet is cooled to a surface temperature of 60 ° C. or less within 30 minutes.   The method for producing pellets according to claim 1, wherein cooling is performed using an air-cooled pellet cooler.