JP5787630B2 - Co-injection molding and co-injection molding method - Google Patents

Description

  The present invention relates to a molded product obtained by co-injection molding of a resin composition of an ethylene-vinyl ester copolymer saponified product (hereinafter sometimes referred to as “EVOH resin”), and a method for producing the molded product.

  Laminated ethylene-vinyl ester copolymer saponified product (EVOH resin), which is a resin with high gas barrier property, to give a gas barrier property to films and containers made of thermoplastic resins such as polyester and polyolefin. In general, films and containers having a multilayer structure of thermoplastic resin and EVOH resin are obtained and used for various packaging applications.

However, since EVOH resin has abundant hydroxyl groups, it is more easily decomposed and crosslinked by heat than other thermoplastic resins. Therefore, depending on the molding method, the EVOH resin layer is thermally deteriorated and adversely affects the multilayer structure. Sometimes.
For example, according to the co-injection molding method, the temperature of the multi-layer manifold portion where the EVOH resin composition and other thermoplastic resin are merged is usually the high temperature of the resin that has been set as the injection molding temperature (cylinder temperature). It is set according to the molding temperature. Accordingly, the temperature of the multi-layer manifold portion where the EVOH resin composition and other thermoplastic resin join together is inevitably very high in accordance with the melt molding temperature of a polyolefin resin or a polyester resin. In such a molding method, the EVOH resin is thermally deteriorated and adversely affects the multilayer structure.

  In contrast, JP-A-2005-89482 (Patent Document 1) describes an alkali metal salt as an EVOH resin composition used for a multilayer structure by co-injection molding of PET / EVOH / PET of two types and three layers. Contains 0.1 to 20 μmol / g in terms of alkali metal, contains 0 to 2 μmol / g of carboxylic acid radical (C1) extracted by immersion treatment in 95 ° C. water for 10 hours, and 0.05 ° C. of 95 ° C. A blow molded container made of an EVOH resin composition containing 0 to 40 μmol / g of a carboxylic acid radical (C2) extracted by immersion in an aqueous sodium hydroxide solution for 10 hours is disclosed. Specifically, the EVOH resin composition pellets contain 3.40 μmol / g of potassium salt in terms of potassium, 1.2 μmol / g of phosphate compound in terms of phosphate radical, and further hot water at 95 ° C. for 10 hours. When the EVOH resin (Example 1) containing 0 ppm of the carboxylate radical (C1) that is free-extracted in (1) is used, even if the co-injection blow molding of two types and three layers is carried out continuously for 72 hours, ) Is not observed and no coloration is observed (paragraph numbers 0119, 0120, Table 2).

JP 2005-89482 A

In Patent Document 1, while adding an alkali metal salt for the purpose of imparting interlayer adhesion, hot water at 95 ° C. for 10 hours contained in EVOH resin for the purpose of improving melt stability and preventing the generation of odor and sourness The amount of free-extracted carboxylic acid radicals is minimized. Further, a phosphoric acid compound is blended for the purpose of imparting long run properties during melt molding, particularly coloring resistance. However, there is no mention of the molding stability of the molded product due to the heat resistance of the EVOH resin layer and the appearance such as foaming.

The present invention is excellent in appearance even in a molding method in which it is inevitable that the EVOH resin is exposed to a high temperature, such as a co-injection molding method using an EVOH resin and a thermoplastic resin having a melting point of 100 ° C. or higher. The purpose is to provide a molded product with good productivity.

  According to the present invention, it is possible to make a resin composition melted by polyvalent metal ions alkaline by adding (B) a completely dehydrated or partially dehydrated polyvalent metal sulfate hydrate to EVOH resin. For this reason, it has been found that a balance between the decomposition reaction and the crosslinking reaction of the EVOH resin by heat is maintained, and a co-injection molded article having excellent high-temperature thermal stability and excellent appearance can be obtained.

That is, the gist of the present invention is that a resin composition containing (A) a saponified ethylene-vinyl ester copolymer and (B) a fully dehydrated or partially dehydrated polyvalent metal sulfate hydrate , and a melting point is It exists in the molded object formed by co-injection molding with the thermoplastic resin of 100 degreeC or more . (Hereinafter, such a resin composition may be referred to as “EVOH resin composition” or “resin composition”.)

Since the resin composition used in the present invention is excellent in thermal stability at high temperature and further foaming is suppressed, a molded product having excellent appearance in the co-injection molding method can be obtained with high productivity.
In addition, the resin composition used in the present invention is included in the composition because a fully dehydrated or partially dehydrated polyvalent metal sulfate hydrate capable of stably presenting a complete hydrate at room temperature has water absorption ability. Water is absorbed to form a hydrate, and the EVOH resin phase in the resin composition can be kept dry. As a result, it is possible to prevent a decrease in the gas barrier property of the EVOH resin due to moisture, or to quickly recover from a decrease in the gas barrier property of the EVOH resin even if hot water treatment is performed.

The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.
First, the EVOH resin composition of the present invention will be described.

<EVOH resin composition>
The EVOH resin composition used in the present invention comprises (A) a saponified ethylene-vinyl ester copolymer (EVOH resin) as a matrix, and (B) a completely dehydrated or partially dehydrated polyvalent metal sulfate hydrate. contains.

[(A) EVOH resin]
The EVOH resin used in the present invention is a known resin obtained by copolymerization of ethylene and a vinyl ester monomer and then saponification, and is a water-insoluble thermoplastic resin excellent in gas barrier properties. Generally used as food packaging materials.

  For the polymerization of ethylene and vinyl ester monomer, any known polymerization method such as solution polymerization, suspension polymerization, emulsion polymerization and the like can be employed.

  Saponification of the obtained ethylene-vinyl ester copolymer is also performed by a known method, that is, using an alkali catalyst or an acid catalyst in a state where the ethylene-vinyl ester copolymer is dissolved in an alcohol or water / alcohol solvent. Can do. Examples of the alkali catalyst include alkali metal hydroxides and alcoholates such as potassium hydroxide, sodium hydroxide, sodium methylate, sodium ethylate, potassium methylate, and lithium methylate. As the acid catalyst, sulfuric acid, hydrochloric acid, nitric acid, metasulfonic acid and the like can be used. In addition, zeolite, cation exchange resin, etc. can also be used as a saponification catalyst.

  As the vinyl ester monomer, vinyl acetate is generally used. 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. These are usually used alone, but a plurality of them may be used simultaneously as necessary.

  Content of the ethylene structural unit in EVOH resin used by this invention is a value measured based on ISO14663, and is 20-60 mol% normally, Preferably it is 25-50 mol%, Most preferably, it is 25-40 mol%. If the content of the ethylene structural unit is too low, gas barrier properties at high humidity, water resistance, and melt moldability tend to decrease. On the other hand, if the content is too high, the hydroxyl group content is relatively reduced. Therefore, gas barrier properties tend 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 usually 90 to 100 mol%, preferably Is 95 to 100 mol%, particularly preferably 99 to 100 mol%. When the degree of saponification is too low, gas barrier properties, thermal stability, moisture resistance and the like tend to decrease.

  The melt flow rate (MFR) (210 ° C., load 2160 g) of the EVOH resin is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, particularly preferably 2 to 35 g / 10 minutes. is there. If the MFR is too large, the melt moldability tends to be unstable, and if it is too small, the viscosity is too high and poor flow tends to occur, resulting in appearance defects such as streaks and unevenness. Particularly in co-injection molding, there may be a problem in the uniform formation of the EVOH resin layer.

  The component (A) EVOH resin is obtained by copolymerizing, in addition to ethylene and vinyl ester monomers, an ethylenically unsaturated monomer copolymerizable within a range that does not impair the effects of the present invention, for example, at 5 mol% or less. It may be. Such monomers include olefins such as propylene, 1-butene and isobutene, and hydroxy group-containing α such as 3-buten-1-ol, 4-penten-1-ol and 5-hexene-1,2-diol. -Derivatives such as olefins, esterified products thereof, acylated products, acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid and other unsaturated acids or their salts or carbon Mono- or dialkyl esters having 1 to 18 carbon atoms, acrylamide, N-alkyl acrylamide having 1 to 18 carbon atoms, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or its salt, acrylamidopropyldimethylamine or its acid salt or Acrylamides such as quaternary salts, methacrylamide, Methacrylamides such as N-alkyl methacrylamide having a prime number of 1 to 18, N, N-dimethylmethacrylamide, 2-methacrylamide propanesulfonic acid or a salt thereof, methacrylamide amidopropylamine or an acid salt thereof or a quaternary salt thereof, N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, alkyl vinyl ethers having 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers, alkoxyalkyl vinyl ethers, etc. Vinyl ethers, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl halides such as vinyl bromide, vinyl silanes such as trimethoxyvinyl silane, allyl acetate, chloride Halogenated allyl compounds such as Lil, allyl alcohol, allyl alcohols such as dimethoxy allyl alcohol, trimethyl - (3-acrylamido-3-dimethylpropyl) - ammonium chloride, and the like acrylamido-2-methylpropanesulfonic acid. Furthermore, the EVOH resin used in the present invention may be “post-modified” such as urethanization, acetalization, cyanoethylation, and oxyalkyleneation by a known method.

  In particular, EVOH resins copolymerized with hydroxy group-containing α-olefins are preferable in that secondary moldability such as blow molding and vacuum molding is improved. Among them, EVOH resins having 1,2-diol in the side chain are preferable. preferable.

The EVOH resin having 1,2-diol in the side chain is specifically an EVOH resin having the following structural unit (1).

[In 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 bonded chain, and R ⁴ , R ⁵ , and R ⁶ represent Each independently represents a hydrogen atom or an organic group. ]

The organic group that can be used for R ^{1 to} R ⁶ is not particularly limited. For example, a saturated group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, or a tert-butyl group. Aromatic hydrocarbon groups such as hydrocarbon group, phenyl group, benzyl group, halogen atom, hydroxyl group, acyloxy group, alkoxycarbonyl group, carboxyl group, sulfonic acid group and the like can be mentioned.

R ^{1 to} R ⁶ are all 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. . Accordingly, it is most preferable that R ^{1 to} R ⁶ are all hydrogen.

Moreover, X in the structural unit represented by the general formula (1) is typically a single bond. Accordingly, in the most preferred structure of the 1,2-diol structural unit represented by the general formula (1), R ^{1 to} R ⁶ 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.

X in the general formula (1) may be a binding chain as long as it does not inhibit the effects of the present invention. Examples of the bonding chain include hydrocarbon chains such as alkylene, alkenylene, alkynylene, phenylene, and naphthylene (these hydrocarbons may be substituted with halogen such as fluorine, chlorine, and bromine), as well as —O—, — _{(CH 2 O) m -,} - (OCH 2) m -, - (CH 2 O) m CH 2 - structure containing an ether binding site, such as, -CO -, - COCO -, - CO (CH 2) m _{CO -, - 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 heteroatom such as structure containing a phosphorus atom, such as, -Si (OR) _{2 -, - OSi (OR)} 2 -, - OSi (OR) 2 O Structures containing a silicon atom and the _{like, -Ti (OR) 2 -,} - OTi (OR) 2 -, - OTi structure comprising (OR) ₂ O-such as titanium atom, -Al (OR) -, - OAl ( OR)-, -OAl (OR) O-, and the like include structures containing metal atoms such as structures containing aluminum atoms (R is independently an arbitrary substituent, preferably a hydrogen atom or an alkyl group). M is a natural number, usually 1 to 30, preferably 1 to 15, and more preferably 1 to 10). Of these bonding chains, from the viewpoint of stability during production or use, —CH ₂ OCH ₂ — and hydrocarbon chains having 1 to 10 carbon atoms are preferable, and hydrocarbons having 1 to 6 carbon atoms are more preferable. Chain, particularly preferably 1 carbon.

  In addition, the resin composition used by this invention is a composition whose base resin is EVOH resin (A). Therefore, the content of the EVOH resin (A) in the entire resin composition is usually 50 to 99% by weight, preferably 60 to 95% by weight, and particularly preferably 85 to 95% by weight. If the amount of EVOH resin is too small, gas barrier properties tend not to be sufficient.

[(B) Completely or partially dehydrated polyvalent metal sulfate]
The completely dehydrated or partially dehydrated polyvalent metal sulfate hydrate (B) used in the present invention means a compound obtained by drying and dehydrating a polyvalent metal sulfate hydrate. That is, any polyvalent metal sulfate having a property of taking water molecules as crystal water may be used. The completely dehydrated or partially dehydrated polyvalent metal sulfate hydrate is usually a solid at normal temperature and pressure.

The component (B) is specifically represented by Mm (SO ₄ ) n · xH ₂ O. The metal M is a polyvalent metal, preferably a divalent or trivalent metal, more preferably a divalent metal, still more preferably an alkaline earth metal, and most preferably magnesium. Therefore, in the formula, m is preferably 1 or 2, n = 1 when m = 1, and n = 3 when m = 2. x is a positive value smaller than the saturated hydrate of each compound, and varies depending on the type of the metal M. The case where x is 0 corresponds to an anhydride (completely dehydrated).

Specifically, the divalent metal M forming the metal salt includes beryllium (beryllium sulfate (BeSO ₄ .4H ₂ O)), magnesium (magnesium sulfate (MgSO ₄ .7H ₂ O)), calcium (sulfuric acid). In addition to alkaline earth metals such as calcium (CaSO ₄ · 2H ₂ O)), copper (copper sulfate (CuSO ₄ ) · 5H ₂ O)), zinc (zinc sulfate (ZnSO ₄ · 7H ₂ O)), iron ( Examples thereof include transition metals capable of forming divalent ions such as iron sulfate (FeSO ₄ .7H ₂ O). Examples of the trivalent metal M include aluminum (aluminum sulfate (Al ₂ (SO ₄ ) ₃ .16H ₂ O)), iron, and the like. The compounds shown in parentheses are chemical formulas of saturated hydrates of each metal.

  Specifically, for example, calcium sulfate is known as hemihydrate (x = 1/2), dihydrate (x = 2), etc., and hemihydrate absorbs water to dihydrate. It is easy to form things. Therefore, x is a number less than 2.

Ferrous sulfate is preferably a heptahydrate dehydrate, that is, x <7, because the heptahydrate is stable in a humid environment. Further, in ferric sulfate, hexahydrate, heptahydrate and the like can exist stably, and therefore, these dehydrates, that is, x <7 are preferable.
As for copper sulfate, pentahydrate is stably present, and it is hygroscopic when it is completely dehydrated (x = 0) or partially dehydrated (x <5). Therefore, x is a number less than 5.
In magnesium sulfate, hexahydrate and heptahydrate are stable at room temperature. Accordingly, x is preferably less than 7, more preferably less than 6, still more preferably less than 1, and most preferably an anhydride (x = 0).

  The partially dehydrated polyvalent metal sulfate hydrate used as the component (B) is not limited as long as part of the crystal water of the saturated hydrate shown above is dehydrated. When the amount of water of crystallization possessed by the saturated salt hydrate is 100% on a weight basis, the hydrate of polyvalent metal sulfate having water of crystallization of less than 90% is applicable. Since it is preferable to use a partially dehydrated product that allows a saturated hydrate to exist stably at room temperature, it is preferable to use a partially hydrated product that has been dehydrated to a water content of less than 70%. Is completely dehydrated.

  For example, in the case of a completely dehydrated or partially dehydrated product of magnesium sulfate, the water content of the partially dehydrated or completely dehydrated compound as the component (B) is a thermogravimetric measuring device (manufactured by Perkin Elmer, The value measured at 550 ° C. for 30 minutes using a weight measuring device “Pyris 1 TGA”) is usually 0 to 50% by weight, preferably 0 to 40% by weight, particularly preferably 0 to 10% by weight. It is. Here, the moisture content as a measured value is the ratio of the moisture content to the whole compound, and the weight change after holding for 30 minutes at 550 ° C. is measured as the moisture content, and calculated as the moisture content relative to the compound weight at the start of measurement. It is the value.

  In the case of a completely dehydrated product (corresponding to an anhydride), since the water content is theoretically 0, the water content is also 0% by weight. May be greater than 0% by weight. For example, in the case of complete dehydration (anhydride) of magnesium sulfate, the value measured by the thermogravimetric apparatus may be about 0 to 10% by weight. These are considered to be because the water content was lower than that of the monohydrate (theoretical water content: 13% by weight) and moisture was absorbed. Even in the case of moisture absorption, the value as measured with the thermogravimetric apparatus is preferably 0 to 5% by weight as a completely dehydrated product.

  As for the complete dehydration or partial dehydration of the polyvalent metal sulfate hydrate as described above, since the complete hydrate can exist stably at room temperature, it is contained in the resin composition as an anhydride or partial dehydration. In this case, it is possible to absorb water contained in the composition to form a hydrate and prevent water molecules from being taken into EVOH resin, or to capture water molecules once taken into EVOH resin. It is. Therefore, EVOH resin can suppress that gas barrier property falls by mixing of water. In addition, since crystal water can be taken in until it becomes a stable state as a saturated hydrate of polyvalent metal sulfate, the more the amount of crystal water that can be taken in until saturated hydrate is, the better the drying ability is.

  Furthermore, when the fully dehydrated or partially dehydrated polyvalent metal sulfate hydrate as the component (B) is blended in the EVOH resin and melt kneaded, the melt viscosity is stabilized. For example, specifically, 55 g of a resin composition pellet obtained by melt-kneading a completely dehydrated product or a partially dehydrated product of (A) EVOH resin and (B) polyvalent metal sulfate hydrate is brought to a temperature of 230 ° C. The torque value (Nm) when it is melted and kneaded at a rotational speed of 50 rpm over time after being put into a set torque detection type rheometer ("Placicoder-PLE331" manufactured by Brabender, roller mixer: W50E), preheated for 5 minutes The value after 120 minutes from the start of measurement / the value after 10 minutes in the value measured in (Nm) is usually 0.1 to 1.5, preferably 0.2 to 0.5.

When EVOH resin is melt-kneaded, the viscosity may decrease immediately after the start of kneading, but the melt viscosity tends to gradually increase thereafter.
However, such a phenomenon in the resin composition used in the present invention is in contrast to the general tendency of EVOH resin, and is a characteristic effect due to the inclusion of component (B). Regarding the mechanism, the stabilization or decrease in melt viscosity is thought to be due to the suppression of the crosslinking reaction of EVOH resin and the progress of decomposition. Therefore, an increase in metal ions that can make the molten resin composition alkaline contributes. It is thought that it is.

  The increase in viscosity when melt molding is carried out at an industrial level causes the resin to stay in the melt molding machine (for example, an extruder or an injection molding machine). When the resin staying in the melt molding machine is immediately discharged, it is not a big problem. However, when a resin that shows a tendency to increase in viscosity due to heating over time is melt-molded, the remaining resin is further discharged due to further thickening. It becomes hard to be done and is easy to generate a heat degradation thing. This is because heat-degraded products are mixed in the molded product, it becomes difficult to clean the resin flow path of the melt molding machine, and the resin flow path is clogged. It becomes the cause of. Therefore, when the component (B) is contained, not only the suppression of gas barrier property reduction due to moisture absorption but also the effect of stabilizing the viscosity at the time of melt molding and improving the melt moldability are obtained.

  In addition, it is known to add an alkali metal salt for the purpose of imparting interlayer adhesion when laminating another thermoplastic resin to a layer having an EVOH resin as a base resin, but adding an excessive alkali metal salt When the melt molding is performed, the viscosity decreases, and when the resin stays in the melt molding machine or when the melt molding is performed at a high temperature, the resin turns yellow or foaming occurs.

In addition, the content of the (B) polyhydric metal sulfate hydrate completely dehydrated or partially dehydrated is the mixing weight ratio (B / A) with the EVOH resin (A), and the EVOH resin only needs to be higher. . Specifically, the component (B) is usually in a weight as a completely dehydrated product, and (B / A) is usually less than 50 / more than 50/1/99, more preferably 30 / 70-1 / 99, The ratio is preferably 20/80 to 5/95, particularly preferably 15/85 to 5/95.
(A) When expressed per 100 parts by weight of EVOH resin, (B) the metal sulfate salt is preferably 1 part by weight or more and less than 100 parts by weight, more preferably 1 to 43 parts by weight, still more preferably 5 to 25 parts by weight. Parts, particularly preferably 5 to 15 parts by weight.

  When the content of the component (B) is too large, transparency tends to be impaired, or the screen mesh of the molding machine tends to be clogged at the time of molding due to aggregation, and when it is too small, the EVOH resin (A) There is a shortage of the effect of removing moisture that has entered, and gas barrier properties after hot water treatment such as boil treatment and retort treatment tend not to be sufficient.

  Moreover, when manufacturing the complete dehydration or partial dehydration of the said polyvalent metal sulfate hydrate, the compound whose dehydration temperature is 100 degreeC or more is preferable. When a metal salt that is easily dehydrated at 100 ° C. or lower is used in a state of having partially crystal water (partially dehydrated product), the crystal water evaporates by heating during melt kneading with the EVOH resin, thereby causing foaming. May occur.

[(C) Other thermoplastic resin]
The EVOH resin composition used in the present invention may contain (C) another thermoplastic resin in addition to the EVOH resin, usually 20% by weight or less, preferably 10% by weight or less based on the EVOH resin. .

  Examples of the “other thermoplastic resin” include linear low density polyethylene, low density polyethylene, ultra low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-propylene (block and random) copolymer, ethylene -Polyethylene resins such as α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polypropylene resins such as polypropylene and propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer (Unmodified) polyolefin resins such as polybutene, polypentene, polycyclic olefin resins (polymers having a cyclic olefin structure in the main chain and / or side chain), and unsaturated carboxylic acids or esters thereof. Unsaturated carboxylic acid modified polyolefin tree grafted with A wide range of polyolefin resins including modified olefin resins such as ionomers, vinyl ester resins such as ethylene-vinyl acetate copolymers, acrylic resins such as ethylene-acrylic acid copolymers and ethylene-acrylic acid ester copolymers Resins, polyester resins, polyamide resins (including copolyamides), chlorinated resins such as polyvinyl chloride and polyvinylidene chloride, aromatic hydrocarbon resins such as polystyrene, elastomers such as polyester elastomers and polyurethane elastomers, Examples thereof include halogenated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, and aromatic or aliphatic polyketones.

[Other additives]
In the resin composition used in 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 polyolefins (for example, low molecular weight polyethylene having a molecular weight of about 500 to 10,000, or low molecular weight polypropylene); antiblocking agents; antioxidants; coloring agents; antistatic agents; ultraviolet absorbers; (For example, hydrotalcite); filler (for example, inorganic filler); oxygen absorber; surface activity Agents, waxes; can be appropriately added known additives such as dispersing agents (stearic acid monoglyceride, etc.).

<Method for preparing resin composition>
The resin composition used in the present invention is obtained by blending the above components (A) and (B) and other components blended as desired. Specifically, it is a composition containing the component (A) and the component (B) (and the component (C) and other additives as required).

  Preparation of the resin composition used by this invention can be performed by mixing the said component by a normal melt kneading or a mechanical mixing method (pellet dry blend). Such a resin composition can be obtained by mixing each component by melt kneading to obtain a resin composition, which can be subjected to melt molding described later, and each component can be machined using a Banbury mixer or the like. It is also possible to perform mixing by a mechanical mixing method (pellet dry blend), and to use it as it is as a dry blend product in the melt molding described later. A method of mixing by a melt kneading method is preferable.

  The effect of stabilizing the viscosity at the time of melt kneading, which is recognized when magnesium sulfate is used, is the effect that a highly uniform resin composition can be stably produced in the production of the resin composition of any of the above embodiments. Can bring.

In the case of the melt-kneading method, examples of the mixing order include the following methods.
(1) A method in which (A) and (B) are simultaneously melt-kneaded, (2) A method in which (A), which is a resin, is previously melted, and (B) is blended and melt-kneaded, (3) A resin ( A high-concentration composition (generally also referred to as a master batch) in which (B) is added in an excessive amount to (A) is manufactured, and resin (A) is added to such a composition and blended. Method of diluting with resin (A); and when compounding component (C), (4) (B) is melt-kneaded into one of resins (A) or (C), and then the other resin is melt-kneaded (5) A high-concentration composition (generally referred to as a masterbatch) obtained by blending resin (A) (and / or resin (C)) with an excessive amount of (B) is produced in advance. Add resin (A) (and / or resin (C)) to the composition. Blended Te, a method of diluting the component (B). In addition, about the mixing | blending of another additive, it can carry out at arbitrary timings.

The machine used for the melt-kneading method is not particularly limited, and a known melt-kneader can be used. Examples thereof include a kneader ruder, a mixing roll, a Banbury mixer, a plast mill, and an extruder.
Especially, in the case of an extruder, a monoaxial or biaxial extruder etc. are mentioned, The method of extruding the resin composition obtained by melt-kneading in a strand form, cutting and pelletizing can be employ | adopted. It is also preferable to provide a vent suction device, a gear pump device, a screen device, etc. as necessary. The temperature in the melt kneading is usually 150 to 300 ° C, preferably 170 to 250 ° C.

In some cases, it is possible to employ a method in which the component (B) is contained by immersing the component (A) and / or the component (C) in the aqueous solution of the component (B) and dried. Since the metal salt of sulfuric acid as the component (B) needs to retain the hydrate-forming ability in the molded product obtained by molding the resin composition, for example, JP 2000-136281 A The preparation method disclosed in the publication, that is, the method of containing a metal salt of sulfuric acid by immersing an EVOH resin in an aqueous solution of the metal salt of sulfuric acid tends to reduce the hydrate forming ability of the metal salt of sulfuric acid. It is difficult to adopt because there are.
In some cases, the (A) component and / or the (C) component and the saturated hydrate of the (B) component are mixed and melted at such a high temperature that the (A) component and / or (C) component melts. A method of obtaining the resin composition of the present invention by evaporating the hydrated water of the saturated hydrate of component (B) by kneading can also be employed, but in this method, foaming occurs in the resin composition. It is difficult to adopt because there is a tendency.

  The EVOH resin composition having the above composition is excellent in thermal stability at high temperatures, and particularly has a stable viscosity behavior at high temperatures in the vicinity of 250 ° C., and foaming because the thermal decomposition of the EVOH resin is suppressed. Is suppressed. Specifically, the weight reduction rate when held at 240 ° C. in a nitrogen atmosphere for 1 hour is usually 1.5% by weight or less, and preferably the weight reduction rate when held at 250 ° C. in a nitrogen atmosphere for 1 hour. Is usually 1% by weight or less.

  In particular, in this invention, MFR (210 degreeC, 2160g load) of the said resin composition is 3-40 g / 10min normally, Preferably it is 6-30 g / 10min, Most preferably, it is 8-20 g / 10min. In performing co-injection molding, if such MFR is too high, there is a tendency that it becomes difficult to form a uniform EVOH layer due to viscosity mismatch with other thermoplastic resins, and if such MFR is too low, the EVOH There is a tendency that the fluidity is insufficient and it is difficult to form the EVOH layer up to the target location.

  When decomposition gas is generated from EVOH resin during melt molding, in the multi-layer structure in which other thermoplastic resin layers are provided on both sides, degassing of the generated gas is blocked by the thermoplastic resin layer, resulting in swelling due to the generated gas. Or pinholes may occur near the bulge. In this regard, in the resin composition used in the present invention, the amount of gas generated by high-temperature pyrolysis is suppressed to a small amount, so that the EVOH resin composition is used as an intermediate layer in a multilayer structure with another thermoplastic resin. Appearance defects can be suppressed.

  This means that it is possible to obtain a molded article having an excellent appearance even when melt-molded in a high temperature range of 200 to 350 ° C., for example. Accordingly, co-injection molding with a thermoplastic resin having a high melt molding temperature range such as a polyolefin-based resin or a polyester resin is possible, and a multilayer structure excellent in adhesiveness and appearance can be obtained.

<Co-injection molding method>
The resin composition used in the present invention can be used as a material for various molded products by performing co-injection molding. When the resin composition of the present invention is melt-kneaded, in the co-injection molding, the balance between the decomposition reaction and the crosslinking reaction of the EVOH resin is maintained, and an effect that a molded product with high homogeneity can be obtained with high productivity can be brought about. .

According to the present invention, in particular, a polyolefin resin or a polyester resin has a melting point of 100 ° C. or higher, preferably 130 to 260 ° C., particularly preferably 150 to 260 ° C., and a melt molding temperature region in a high temperature range. when subjected to co-injection molding of the thermoplastic resin, the effect of the present invention is Ru effectively obtained.

In general, at the time of co-injection molding, the molding temperature of the EVOH resin is appropriately set in the range of usually 150 to 300 ° C, and more preferably 160 to 260 ° C.
However, the thermoplastic resin to be co-injection molded is usually 200 to 350 ° C., preferably 230 to 350 ° C., more preferably 250 to 330 ° C., particularly preferably 270 to 310 ° C., like a polyolefin resin and a polyester resin. In the case of a resin to be melt-molded, the temperature of the die (multilayer manifold portion) where the EVOH resin and the thermoplastic resin merge is the same temperature, that is, usually 200 to 350 ° C., preferably 230 to 350 ° C., more preferably 250 to The temperature is set to 330 ° C, more preferably 270 to 310 ° C, higher than the normal extrusion temperature. Therefore, in the die (multilayer manifold portion) that merges with the thermoplastic resin, the EVOH resin is necessarily exposed to the same high temperature.
On the other hand, since the EVOH resin composition of the present invention is excellent in thermal stability at high temperatures, even if co-injection molding is performed such that it is exposed to the high temperature range as described above, coloring, foaming and pinning are performed. Since a problem in appearance such as a hole hardly occurs, a multilayer structure having an excellent appearance can be obtained.

  In the co-injection molding method, first, at least an EVOH resin composition layer is used as an intermediate layer, and other thermoplastic resin layers are arranged on both outer layers. Usually, it has two injection cylinders and a multilayer manifold system. It can be obtained by injecting molten EVOH resin composition and other thermoplastic resin into the single mold from the respective injection cylinders simultaneously or at different times using a injection molding machine.

  For example, the other thermoplastic resin for both outer layers is injected first, then the EVOH resin composition as the intermediate layer is injected, and after injection of a predetermined amount of the EVOH resin composition, another thermoplastic resin is injected. By continuing, it consists of three layers of other thermoplastic resin layer / EVOH thermoplastic resin layer / other thermoplastic resin layer, and the middle EVOH layer is completely enclosed in the other thermoplastic resin layers on both sides. Molded articles (wide-mouth containers such as cups and trays and preforms) are obtained.

  In addition, the other thermoplastic resin for the inner and outer layers is first injected, then the EVOH resin composition is injected, and at the same time or thereafter, the other thermoplastic resin that becomes the central layer is injected again, and the other thermoplastic resin A molded product having a five-layer structure of layer / EVOH resin composition layer / other thermoplastic resin layer / EVOH resin composition layer / other thermoplastic resin layer can be obtained.

  In the case of other thermoplastic resins, the molding temperature (cylinder temperature) of such a molded product is appropriately set in the range of usually 200 to 350 ° C. depending on the type of resin, the melting point, and the thermal decomposition point. In particular, in the case of polyolefin resin, it is usually 200 to 270 ° C, more preferably 205 to 260 ° C, and particularly preferably 210 to 250 ° C. Moreover, especially in the case of a polyester-type resin, it is 230-350 degreeC normally, More preferably, it is 250-330 degreeC, Most preferably, it is 270-310 degreeC. If the molding temperature is too low, the melting of other thermoplastic resins may be insufficient.

  The molding temperature (cylinder temperature) of the EVOH resin composition is usually from 150 to 300 ° C., more preferably from 160 to 270 ° C., particularly preferably from 170 to 260 ° C., and the temperature of the multilayer manifold part that joins with other thermoplastic resins. It is set appropriately according to

  The temperature of the multi-layer manifold part where the EVOH resin composition and other thermoplastic resin merge is set in accordance with the molding temperature of the resin that has been normally set as the high molding temperature (cylinder temperature). Therefore, the temperature of the multi-layer manifold part where the EVOH resin composition and other thermoplastic resin merge is usually 200 to 350 ° C, preferably 230 to 350 ° C, more preferably 250 to 330 ° C, and particularly preferably 270 to 310 ° C. It is. Since the EVOH resin composition of the present invention is excellent in heat decomposition resistance at high temperatures, it is possible to stably perform co-injection molding such that the manifold portion temperature is set in the high temperature range.

  Moreover, the temperature of the mold into which the EVOH resin composition and other thermoplastic resin flow is usually 0 to 80 ° C., more preferably 5 to 60 ° C., particularly preferably 10 to 30 ° C., and the temperature is too low. In such a case, the mold may be condensed and the appearance of the resulting molded product is deteriorated. If it is too high, the transparency of the obtained molded product may be decreased.

  As described above, a molded product having a multilayer structure can be obtained by co-injection molding.

The co-injection blow molding method is preferable when it is desired to obtain a multilayer structure of a hollow container such as a tank or a bottle. In the case of the co-injection blow molding method, a preform (container precursor) having a multilayer structure is prepared by co-injection molding in the same manner as described above, and this is directly or directly reheated and heated. The film is mechanically stretched in the longitudinal direction while maintaining a constant temperature (blow molding), and is blown in the circumferential direction by blowing pressurized air simultaneously or sequentially.
The volume of the hollow container can be arbitrarily selected, and is usually 50 mL to 10 L, preferably 50 mL to 5 L, and particularly preferably 50 mL to 2 L.

  The co-injection-molded preform is immediately sent to the reheating process in a warm state and blow-molded (hot parison method), and the injection-molded preform is stored at room temperature for a certain period of time before being reheated. There is a feed blow molding method (cold parison method), and both can be used depending on the purpose, but in general, the cold parison method is superior in the productivity of molded products filled with bottles. preferable.

  Reheating the preform can be performed using a heating element such as an infrared heater or a block heater. The temperature of the heated preform is usually 80 to 140 ° C. (more preferably 85 to 130 ° C., particularly preferably 90 to 120 ° C.). If this temperature is too low, the uniformity of stretching can be insufficient. The shape and thickness of the multilayer container may be non-uniform. On the other hand, when it is too high, crystallization is promoted in the case of a polyester resin, and the resulting multilayer container may be whitened, which is not preferable.

  The reheated preform is biaxially stretched to obtain a desired molded article such as a bottle. Generally, it is usually stretched about 1 to 7 times in the longitudinal direction and mechanically stretched by a plug or rod, etc., and then stretched in the lateral direction usually about 1 to 7 times to obtain the intended bottle. It is done. The stretching in the machine direction and the stretching in the transverse direction can be performed simultaneously or sequentially. It is also possible to use aerodynamic force in the longitudinal stretching.

[Multilayer structure]
The thickness of the multilayer structure (including stretched ones) obtained by co-injection molding as described above, and further, the EVOH resin composition layer constituting the multilayer structure, other thermoplastic resin layers, and as necessary The thickness of the adhesive resin layer can be selected depending on the layer configuration, the type of thermoplastic resin, the type of adhesive resin, the application and packaging form, the required physical properties, and the like.
The thickness of the multilayer structure (including the stretched structure) is usually 10 to 5000 μm, preferably 30 to 3000 μm, particularly preferably 50 to 2000 μm. The EVOH resin composition layer is usually 1 to 500 μm, preferably 3 to 300 μm, particularly preferably 5 to 200 μm, and the other thermoplastic resin layer is usually 5 to 3000 μm, preferably 10 to 2000 μm, particularly preferably 20 to 1000 μm. It is. When the adhesive resin layer is used, the adhesive resin layer is usually 0.5 to 250 μm, preferably 1 to 150 μm, particularly preferably 3 to 100 μm.

  Further, the thickness ratio (resin composition layer / other thermoplastic resin layer) between the EVOH resin composition layer and the other thermoplastic resin layer in the multilayer structure is the largest when there are a plurality of the same kind of layers. The ratio between the layers is usually 0.1 / 99.9 to 20/80, preferably 1/99 to 15/85, and particularly preferably 3/97 to 10/90. When an adhesive resin is used, the thickness ratio of the resin composition layer to the adhesive resin layer in the multilayer structure (resin composition layer / adhesive resin layer) is usually 10/90 to 99/1, preferably 20 / 80 to 95/5, particularly preferably 50/50 to 90/10.

  Examples of the thermoplastic resin constituting the “other thermoplastic resin layer” include linear low density polyethylene, low density polyethylene, ultra low density polyethylene, medium density polyethylene, high density polyethylene, and ethylene-propylene (block and random). Copolymers, polyethylene-based resins such as ethylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer Unsaturated (unmodified) polyolefin resins such as polypropylene resins such as polybutene, polypentene, polycyclic olefin resins (polymers having a cyclic olefin structure in the main chain and / or side chain), and these polyolefins Unsaturated carboxylic acid modified polymer graft modified with carboxylic acid or its ester Broadly defined polyolefin resins including modified olefin resins such as olefin resins, ionomers, vinyl ester resins such as ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, etc. Acrylic resins, polyester resins, polyamide resins (including copolyamides), chlorinated resins such as polyvinyl chloride and polyvinylidene chloride, aromatic hydrocarbon resins such as polystyrene, polyester elastomers, polyurethane elastomers, etc. Examples include elastomers, halogenated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, and aromatic or aliphatic polyketones.

These are appropriately selected depending on the purpose and use of the multilayer structure. In order to impart mechanical strength, inexpensive resins such as polyolefin resins and polystyrene resins are preferable from an economical point of view, and polycyclic olefin resins are preferable in order to improve hot water resistance. In particular, polycyclic olefin resins are preferably used as hydrophobic resins.
Particularly in the present invention, a thermoplastic resin having a melting point of 100 ° C. or higher, preferably 130 to 260 ° C., particularly preferably 150 to 260 ° C. is preferable, and a polypropylene resin is particularly preferable. is there.

  In addition, as said polycyclic olefin resin, well-known resin (For example, refer Unexamined-Japanese-Patent No. 2003-103718, Unexamined-Japanese-Patent No. 5-177777, special table 2003-504523, etc.) can be used. Polycyclic olefin-based resins have low moisture permeability compared to chain aliphatic polyolefins such as polyethylene and polypropylene. For this reason, in the multilayer structure of the sandwich structure using the resin composition layer of the present invention as an intermediate layer and other thermoplastic resin layers and adhesive resin layers used on both sides, the other thermoplastic resin layers and adhesive properties are used. By using a polycyclic olefin-based resin in the resin layer, the amount of external moisture mixed in due to moisture or hot water treatment can be reduced, and as a result, the drying effect of the component (B) in the resin composition layer is effectively exhibited. Moreover, the recovery of oxygen permeability after hot water treatment is quick.

The layer structure of the multilayer structure is such that when the resin composition layer is a (a1, a2,...) And the other thermoplastic resin layer is b (b1, b2,...), A / b, b / a / b, a / b / a, a1 / a2 / b, a / b1 / b2, b2 / b1 / a / b1 / b2, b2 / b1 / a / b1 / a / b1 / b2, etc. Combinations are possible. The number of layers of the multilayer structure is generally 2 to 15 layers, preferably 3 to 10 layers in total.
In the above layer configuration, an adhesive resin layer may be interposed between the respective layers as necessary.

  Among the multilayer structures as described above, in particular, a unit of a multilayer structure including the resin composition layer of the present invention as an intermediate layer, and providing other thermoplastic resin layers as both side layers of the intermediate layer (b / A multilayer structure comprising at least a / b) is preferred. In the sandwich-like multilayer structure sandwiching the resin composition layers of the present invention, moisture absorption from the outside can be prevented by using a hydrophobic resin in at least one layer located on both sides of the resin composition layer. It is speculated that the drying effect by the component (B) can be more effectively exhibited. Therefore, in the case of a multilayer structure for a packaging material used for an application to be subjected to hydrothermal treatment, a hydrophobic resin is used in at least one layer located on both sides of the resin composition layer in the unit of the multilayer structure. Thus, there is an effect that the oxygen permeability after the hot water treatment is quickly recovered.

In the multilayer structure obtained by the present invention, an adhesive resin layer may be interposed between the resin composition layer and another thermoplastic resin layer as necessary, and the other thermoplastic resin layer In order to impart adhesive ability, an adhesive resin may be blended.
However, the resin composition layer is excellent in thermal stability, particularly a polyolefin resin, a polyester resin or the like, such as a thermoplastic resin having a melting point of usually 100 ° C. or higher, preferably 130 to 260 ° C., particularly preferably 150 to 260 ° C. Thus, by co-injection molding with a thermoplastic resin that is melt-molded in a high temperature range, it is possible to produce a multilayer structure with good adhesion and good appearance without interposing an adhesive resin layer. it can.
Accordingly, in a multilayer structure with a thermoplastic resin having a melting point of usually 100 ° C. or higher, such as a polyolefin resin or a polyester resin, the thermoplastic resin layer / EVOH resin composition layer / the thermoplastic resin layer (b / It can be suitably used as a raw material to be provided for a multilayer structure having a layer structure with a / b).

  As the adhesive resin, known resins can be used, and may be appropriately selected according to the kind of the thermoplastic resin used for the other thermoplastic resin “b” as the base material. A typical example is a modified polyolefin polymer containing a carboxyl group obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof to a polyolefin resin by an addition reaction or a graft reaction. For example, maleic anhydride graft modified polyethylene, maleic anhydride graft modified polypropylene, maleic anhydride graft modified ethylene-propylene (block and random) copolymer, maleic anhydride graft modified ethylene-ethyl acrylate copolymer, maleic anhydride graft Modified ethylene-vinyl acetate copolymer, maleic anhydride-modified polycyclic olefin resin, maleic anhydride graft-modified polyolefin resin, and the like, and one or a mixture of two or more selected from these can be used.

  In the multilayer structure, when an adhesive resin layer is used between the resin composition layer of the present invention and the thermoplastic resin layer, the adhesive resin layer is at least one layer located on both sides of the resin composition layer. Therefore, it is preferable to use an adhesive resin excellent in hydrophobicity.

  The other thermoplastic resins and adhesive resins include plasticizers, fillers, and the like that have been conventionally known within a range that does not impair the gist of the present invention (for example, 30% by weight or less, preferably 10% by weight or less). It may contain clay (montmorillonite, etc.), colorant, antioxidant, antistatic agent, lubricant, core material, antiblocking agent, ultraviolet absorber, wax and the like.

The multilayer structure of the present invention thus obtained is used in various applications as a wide-mouthed container such as a cup or tray, or a hollow container such as a tank or bottle, and is preferably a hollow container.
Such uses include, in addition to general foods, seasonings such as soy sauce, sauce, ketchup, mayonnaise, dressing, fermented foods such as miso and vinegar, fats and oils such as salad oil, sake, beer, mirin, whiskey, shochu, Useful as various containers for wine and other alcoholic beverages, carbonated drinks, juices, sports drinks, milk, coffee drinks, oolong tea, tea, mineral water, etc., cosmetics, pharmaceuticals, detergents, cosmetics, industrial chemicals, agricultural chemicals, etc. In particular, it is useful for beverages such as beer, wine, carbonated beverages, juice, tea, milk, coffee beverages, and containers for seasonings such as sauces and dressings.
In particular, since the layer made of the resin composition of the present invention has excellent gas barrier properties after hot water treatment such as boil treatment and retort treatment, it is particularly useful as a packaging material for foods subjected to hot water treatment.

  In the EVOH resin composition after the hydrothermal treatment of the multilayer structure, the component (B) absorbed water in the (A) EVOH resin. As a result, the crystal water usually exceeds 70% by weight of the saturated crystal water amount. It exists as a sulfate hydrate with Specifically, when magnesium sulfate is used, it exists as heptahydrate (saturated hydrate) or hexahydrate (86% by weight of the amount of saturated crystallization water).

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to description of a following example.
In the examples, “part” means a weight basis unless otherwise specified.

<Measurement evaluation method>
(1) Melt moldability evaluation at 230 ° C. 55 g of resin composition pellets are put into a torque detection type rheometer (“Plasticcoder PLE331” manufactured by Brabender, roller mixer: W50E) set at a temperature of 230 ° C. for 5 minutes. After preheating, the torque value (Nm) when melt kneaded at a rotational speed of 50 rpm was measured over time (10 minutes, 50 minutes, 80 minutes, 100 minutes, 120 minutes after the start of melt kneading).

(2) Melt moldability evaluation at 250 ° C. 55 g of resin composition pellets are put into a torque detection type rheometer (“Plasticcoder PLE331” manufactured by Brabender, Roller mixer: W50E) set at a temperature of 250 ° C. for 5 minutes. After preheating, the torque value (Nm) when melt kneaded at a rotation speed of 50 rpm was measured over time (5 minutes, 10 minutes, 30 minutes, and 60 minutes after the start of melt kneading).

(3) Thermal decomposition resistance (weight reduction)
3 mg of the resin composition pellets were held for 1 hour in a nitrogen atmosphere at 210 ° C., 230 ° C., 240 ° C., and 250 ° C. using an aluminum pan having a diameter of 5 mm. The weight before and after holding each temperature was measured, and the degree of decrease (% by weight) relative to the weight before heating was calculated. For the evaluation, a thermogravimetric measuring device “Pyris1 TGA” (manufactured by PerkinElmer) was used.

Example 1
(A) An ethylene-vinyl acetate copolymer saponified product having an ethylene structural unit content of 29 mol%, a saponification degree of 99.7 mol%, and an MFR of 4 g / 10 min (210 ° C., load of 2160 g) was used as the EVOH resin. Further, magnesium sulfate anhydride was used as the complete dehydration of (B) polyvalent metal sulfate hydrate.

90 parts of the EVOH resin is supplied to a hopper of a twin screw extruder, and 10 parts of the above (B) is supplied to the hopper with a powder feeder, and a twin screw extruder having two mixing zones (φ30 mm, L / D = 43), after melt kneading (extruder set temperature: C1 / C2 / C3 / C4 / C5 / C6 / C7 / H / D = 200/210/230/230/230/230/230/230 ° C.) And extruded into strands and cut to obtain cylindrical pellets of the EVOH resin composition. That is, the weight ratio (B / A) of (A) EVOH resin and (B) complete dehydration of polyvalent metal sulfate hydrate is 10/90.
Using the pellets, (1) the melt formability evaluation at 230 ° C. was performed.

Example 2
In Example 1, the same evaluation was performed in the same manner except that sodium sulfate anhydride was used instead of magnesium sulfate anhydride.

Comparative Example 1
In Example 1, the same evaluation was performed in the same manner except that magnesium succinate anhydride was used instead of magnesium sulfate anhydride.

Comparative Example 2
In Example 1, the same evaluation was performed except that sodium pyrophosphate anhydride was used instead of magnesium sulfate anhydride.

Reference example 1
The same evaluation was carried out in the same manner as in Example 1, except that (B) the complete dehydrated polyvalent metal sulfate hydrate was not blended.

  As can be seen from Table 1, in Example 1 containing magnesium sulfate anhydride, the torque value decreases after 50 minutes of kneading, and then shows a substantially constant torque value, indicating that the viscosity behavior is stable. . The value of the torque value after 120 minutes of kneading (viscosity variation) with respect to the torque value after 10 minutes of kneading is 0.3, indicating that the viscosity shows a decreasing behavior compared to the initial stage of melt-kneading.

  On the other hand, in Example 2 containing sodium sulfate anhydride, the torque value decreased after 50 minutes of kneading. The value of the torque value after 120 minutes of kneading (viscosity variation) with respect to the torque value after 10 minutes of kneading was 1.3, and the viscosity decreased and slightly increased compared to the initial stage of melt kneading.

When magnesium succinate anhydride is contained (Comparative Example 1), when sodium pyrophosphate anhydride is contained (Comparative Example 2), the value of the torque value after 120 minutes of kneading relative to the torque value after 10 minutes of kneading, respectively. (Viscosity fluctuation degree) was 3.1 and 1.8, and the viscosity showed an increasing behavior from the initial stage of melt kneading.
From the above results, when (B) the complete dehydration of polyvalent metal sulfate hydrate is used, the viscosity stabilization effect is superior to the case of using the complete dehydration of other polyvalent metal salt hydrates. Recognize.

Example 3
(A) As an EVOH resin, an ethylene-vinyl acetate copolymer saponified pellet having an ethylene structural unit content of 32 mol%, a saponification degree of 99.7 mol%, and an MFR of 12 g / 10 min (210 ° C, load of 2160 g) was used. (B) An anhydrous magnesium sulfate was used as a complete dehydration of polyvalent metal sulfate hydrate.

90 parts of the EVOH resin pellets are supplied to a hopper of a twin screw extruder, and 10 parts of the (B) are supplied to the hopper with a powder feeder, and a twin screw extruder (φ30 mm, L / L) having two mixing zones. D = 43), melt kneading (extruder set temperature: C1 / C2 / C3 / C4 / C5 / C6 / C7 / H / D = 200/210/230/230/230/230/230/230 ° C.) Thereafter, it was extruded into a strand shape and cut to obtain cylindrical pellets of the EVOH resin composition. That is, the weight ratio (B / A) of (A) EVOH resin and (B) complete dehydration of polyvalent metal sulfate hydrate is 10/90.
It was 13 g / 10min when MFR of this pellet was measured by 210 degreeC and the load of 2160g.
Using these pellets, (2) evaluation of melt moldability at 250 ° C. and (3) evaluation of thermal decomposition resistance (weight reduction) were performed. These are shown in Table 2 and Table 3, respectively.

Reference example 2
In Example 3, the same evaluation was performed in the same manner except that (B) the completely dehydrated polyvalent metal sulfate hydrate was not blended. It was 11 g / 10min when MFR of this pellet was measured by 210 degreeC and the load of 2160g.

As can be seen from Table 2, in Example 3 containing magnesium sulfate anhydride, the value of the melt viscosity behavior from 5 minutes to 60 minutes after kneading is stable even under severe conditions of high temperature of 250 ° C. The increase / decrease was very excellent at -0.1 to +0.1 based on 5 minutes after kneading.
On the other hand, in Reference Example 2 in which no magnesium sulfate anhydride was used, the increase / decrease in the value of the melt viscosity behavior was as large as -1.2 to -0.3 on the basis of 5 minutes after kneading. As a result.
Therefore, it can be seen that in the co-injection molded article of the present invention, the viscosity of the EVOH resin composition is stable immediately after the start of kneading even under a severe condition of 250 ° C., and a molded article having a good appearance can be obtained with high productivity.

As can be seen from Table 3, in Reference Example 2 in which no magnesium sulfate anhydride was used, although the value was not a problem at 210 ° C., the weight reduction rate increased because the resin decomposed as the temperature rose. I understand that.
On the other hand, in Example 3 containing magnesium sulfate anhydride, the decomposition rate of the resin is suppressed even under severe conditions such as 240 ° C. and 250 ° C. The value was as small as -50%.
From the results in Tables 2 and 3, the EVOH resin composition used in the present invention is excellent in viscosity stability at high temperature and heat decomposability, so that foaming in the injection molding machine during co-injection molding is suppressed, and the flow of the resin Since it is smooth, resin burning inside the molding machine is prevented. As a result, a molded product having an excellent appearance can be obtained with high productivity.

Example 4 <Hot water treatment test>
Using the EVOH resin composition pellets obtained in Example 3 and using a coextrusion multilayer sheet molding apparatus, a multilayer structure of 3 types and 5 layers (polypropylene layer / adhesive resin layer / EVOH resin composition layer / adhesiveness) Resin layer / polypropylene layer).
In addition, polypropylene ("EA6A" manufactured by Japan Polypropylene Corporation) is used for the polypropylene layer, and maleic anhydride-modified polypropylene ("MODIC-AP P604V" manufactured by Mitsubishi Chemical Corporation) is used as the adhesive resin. )It was used.

(Co-extrusion conditions)
Intermediate layer extruder (EVOH resin composition layer): 40 mmφ single screw extruder (barrel temperature: 250 ° C.)
・ Upper and lower layer extruder (polypropylene layer): 40 mmφ single screw extruder (barrel temperature: 250 ° C.)
・ Middle upper and lower layer extruder (adhesive resin layer): 32 mmφ single screw extruder (barrel temperature: 250 ° C.)
-Die: 3 types, 5 layers feed block type T die (die temperature: 250 ° C)
・ Taking speed: 1.5 m / min ・ Roll temperature: 50 ℃

  Extrusion conditions were such that the die was 250 ° C. and the molded product was cooled by a chill roll in which cooling water circulated. The structure (thickness (μm)) of the three-kind five-layer multilayer structure is 285/15/30/15/285 for polypropylene layer / adhesive resin layer / EVOH resin composition layer / adhesive resin layer / polypropylene layer. is there.

A sample piece (10 cm × 10 cm) of the multilayer structure was subjected to a retort treatment at 121 ° C. for 30 minutes using a hot water immersion type retort apparatus (Hisaka Seisakusho). After the retort treatment, oxygen permeability was measured over time using an oxygen gas permeation measuring device (manufactured by Mocon, OX-TRAN 2/21) under conditions of temperature 23 ° C., humidity inside 90% RH, external 50% RH). It was measured.
In addition, when the EVOH resin composition used in the present invention is used as one layer of a multilayer structure, the speed of gas barrier recovery after the hot water treatment of the multilayer structure can be greatly improved.
The multilayer structure in this example is manufactured by coextrusion molding, but the barrel temperature and die temperature during melt molding of each layer are the same high temperature conditions as in the case of co-injection molding, so the resulting multilayer structure The oxygen permeability of is the same value as the molded product obtained by co-injection molding.
Similarly, the barrier recovery measurement value after the hydrothermal treatment of the multilayer structure also depends on the properties of the EVOH resin composition layer and the properties of other thermoplastic resin layers. If the temperature is the same as in the case of co-injection molding, the same value as that of a similar multilayer structure obtained by co-injection molding can be obtained.
In this example, maleic anhydride-modified polypropylene is used as the adhesive resin, but its properties are almost the same as the polypropylene used as the outermost layer, so that the adhesive resin is the oxygen of the molded product. The effect on transmission is negligible.

Reference example 4
In Example 4, a multilayer structure produced in the same manner was obtained using EVOH resin alone without blending the metal salt (B), and was similarly evaluated.
The results are also shown in Table 4.

In the multilayer structure (Reference Example 4) using the EVOH resin alone which does not contain the complete dehydrate or partial dehydrate of the polyvalent metal sulfate hydrate of the component (B), the gas barrier property is remarkably impaired by the hot water treatment. One day after the hot water treatment, the oxygen permeation amount was 121 cc / m ² · day · atm, which was a very high value. The gas barrier performance thus impaired gradually recovers as the multilayer structure is naturally dried, but the recovery speed is slow, and the oxygen transmission rate is 61 cc / m ² · day · atm even after 20 days. It was still big.

On the other hand, in the multilayer structure (Example 4) using the resin composition containing the magnesium sulfate anhydride corresponding to the complete dehydration or partial dehydration of (B) polyvalent metal sulfate hydrate, Only one day after the hot water treatment showed a very low level of oxygen permeability. This was the same level as the oxygen permeability after 60 days in Reference Example 4.
From the above results, (B) a molded product obtained by co-injection molding of a resin composition containing magnesium sulfate, which is a completely dehydrated or partially dehydrated polyvalent metal sulfate hydrate, is damaged by hot water treatment. It can be seen that the recovery speed of the gas barrier property is very fast and the level of the gas barrier performance after recovery is very excellent.

  The resin composition used in the present invention is stable in viscosity behavior even at high temperatures, and is resistant to thermal decomposition and foaming. For example, the resin composition is subjected to co-injection molding with a high-melting point thermoplastic resin such as polyolefin resin or polyester resin. However, a molded article having a good appearance can be obtained with high productivity.

Claims (10)

A resin composition containing (A) a saponified ethylene-vinyl ester copolymer and (B) a fully dehydrated or partially dehydrated polyvalent metal sulfate hydrate , and a thermoplastic resin having a melting point of 100 ° C. or higher; Molded product formed by co-injection molding. The molded article according to claim 1, wherein the component (B) is a completely dehydrated or partially dehydrated divalent metal sulfate hydrate. The content ratio (B / A) of the component (B) relative to the saponified ethylene-vinyl ester copolymer (A) is 50 / The molded product according to claim 1, which is 50 to 1/99. The molded product according to any one of claims 1 to 3, wherein the MFR of the resin composition is 3 to 40 g / 10 min at 210 ° C and a load of 2160 g.   The reduced weight ratio with respect to the weight before heating when the resin composition is held at 240 ° C. for 1 hour in a nitrogen atmosphere by a thermogravimetric apparatus is 1.5% by weight or less. Item 5. The molded product according to any one of Items 1 to 4.   The layer (a) including the resin composition containing (A) a saponified ethylene-vinyl ester copolymer and (B) a completely dehydrated or partially dehydrated polyvalent metal sulfate hydrate. The molded product according to any one of claims 1 to 5, which is a multilayer structure having at least one thermoplastic resin layer (b) having a melting point of 100 ° C or higher.   The molded article according to claim 6, wherein the layer (a) containing the resin composition is an intermediate layer, and a thermoplastic resin layer (b) having a melting point of 100 ° C or higher is provided on both sides of the intermediate layer. Moldings.   The molded article according to claim 6 or 7, wherein the thermoplastic resin (b) having a melting point of 100 ° C or higher is a polypropylene resin.   The molded product according to any one of claims 1 to 8, which has a thickness of 10 to 5000 µm. (A) a resin composition containing a saponified ethylene-vinyl ester copolymer and (B) a completely dehydrated or partially dehydrated polyvalent metal sulfate hydrate, and a thermoplastic resin having a melting point of 100 ° C. or higher A method for producing a molded product, characterized by co-injection molding.