JP2000248131A - Cap for container having excellent gas barrier properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cap for a container with good gas barrier properties, mechanical strength and recyclability. SOLUTION: A cap for a container is molded from a resin compsn. obtd. by compounding 5-60 wt.% of an ethylene-vinyl alcohol copolymer (A) with an ethylene content of 20-60 mol% and a saponification degree of 90% or more, 1-30 wt.% of a polyamide resin (B), 5-89 wt.% of an olefin-unsatd. carboxylic acid copolymer (C), and optionally, 5-89 wt.% of a polyolefin (D) other than the above resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a container cap having good gas barrier properties, mechanical strength, appearance and recyclability.

[0002]

2. Description of the Related Art In many cases, the body of a container such as a bottle for packaging foods such as sauces and ketchup, pharmaceuticals, industrial goods, etc. is used to protect the contents from oxidative deterioration or prevent the contents from evaporating active ingredients. For this reason, a method is known in which the container body has a multilayer structure including a gas barrier material such as a gas barrier resin or aluminum foil. As for the caps of these containers, metal caps have been mainly used until now, but in recent years, plastic caps have come to be used from the viewpoint of safety and disposal problems. However, since plastic caps generally do not have gas barrier properties, the deterioration of the contents becomes a problem.

On the other hand, it is not practical to use a gas barrier material such as an ethylene-vinyl alcohol copolymer alone as a cap itself, because there are problems in strength and moldability.

On the other hand, Japanese Utility Model Laid-Open Nos. 2-117384 and 2-117349 describe that a gas barrier layer is provided on the inner surface of a plastic cap so that the plastic cap has gas barrier properties. .

In Japanese Patent Publication No. 7-112865,
Resin composition comprising 0 to 50% by weight of polyethylene, 10 to 50% by weight of saponified ethylene-vinyl alcohol copolymer or ethylene-vinyl acetate copolymer, and 10 to 90% by weight of carboxylic acid-modified polyethylene adhesive resin There is a description of a container cap characterized by being molded from.

However, in the former, a gas barrier layer needs to be attached separately from the cap body, and the process becomes complicated. In the latter, the base material is limited to polyethylene, and there is no description about other base materials such as polypropylene. Even if only a carboxylic acid-modified polyethylene adhesive resin is used as a compatibilizer, sufficient mechanical strength cannot be obtained due to insufficient compatibility.

[0007] Further, in the case of molding by an injection molding method, burrs derived from runners are inevitably generated due to the problem of shape. Since this burr sometimes reaches more than half of the resin used, recyclability is indispensable.

As described above, there has been no example in which a container cap having sufficient mechanical strength and recyclability has been formed into a single layer using a gas barrier resin.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a container cap having excellent gas barrier properties and mechanical strength, appearance and recyclability.

[0010]

The above objects are achieved by the present invention. That is, the present invention provides an ethylene content of 20 to
60% by mole, 5 to 60% by weight of an ethylene-vinyl alcohol copolymer (A) having a saponification degree of 90% or more, 1 to 30% by weight of a polyamide resin (B), and an olefin-unsaturated carboxylic acid copolymer (C) A) A container cap formed by molding a resin composition comprising 10 to 94% by weight.

Further, the present invention provides an ethylene content of 20 to 6;
0 mol%, ethylene-vinyl alcohol copolymer (A) having a saponification degree of 90% or more, 5 to 60% by weight, polyamide resin (B), 1 to 30% by weight, olefin-unsaturated carboxylic acid copolymer (C) The present invention also relates to a container cap formed by molding a resin composition comprising 5 to 89% by weight of a polyolefin (D) other than the resin and 5 to 89% by weight.

In a preferred embodiment, the container cap comprises a continuous phase of an olefin-unsaturated carboxylic acid copolymer (C) and / or a polyolefin (D), and an ethylene-vinyl alcohol copolymer (A). It is molded from a resin composition forming a dispersed phase.

Furthermore, in a preferred embodiment, the olefin-unsaturated carboxylic acid copolymer (C) of the resin composition used for the container cap is an ethylene-unsaturated carboxylic acid random copolymer or a salt thereof.

Further, in a preferred embodiment, the polyolefin (D) of the resin composition used for the container cap is polypropylene.

In a preferred embodiment, the container cap of the present invention is formed by injection molding.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The ethylene-vinyl alcohol copolymer (A) (hereinafter referred to as EVOH) used in the present invention is obtained by saponifying a copolymer comprising ethylene and vinyl ester using an alkali catalyst or the like. Obtained. A typical example of the vinyl ester is vinyl acetate, but other fatty acid vinyl esters (such as vinyl propionate and vinyl pivalate) can also be used. EVOH can contain 0.0002 to 0.2 mol% of a vinylsilane compound as a copolymerization component.
Here, as the vinylsilane-based compound, for example, vinyltrimethoxysilane, vinyltriethoxysilane,
Vinyl tri (β-methoxy-ethoxy) silane and γ-methacryloxypropylmethoxysilane.
Among them, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used. Further, other comonomer such as propylene, butylene, or unsaturated carboxylic acid such as (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate and the like, as long as the object of the present invention is not hindered. Acids or esters thereof and vinylpyrrolidone such as N-vinylpyrrolidone can also be copolymerized.

In the present invention, the EVOH has an ethylene content of 20 to 60 mol%, preferably 25 to 55 mol%.
More preferably, it is 25 to 50 mol%. If the ethylene content is less than 20 mol%, the gas barrier property under high humidity is reduced, and the melt moldability is also deteriorated. If it exceeds 60 mol%, sufficient gas barrier properties cannot be obtained.

The degree of saponification of the vinyl ester component of the EVOH of the present invention is 90% or more, preferably 95% or more, more preferably 98% or more. 90% saponification degree
If it is less than 7, not only the gas barrier property at the time of high humidity is reduced, but also the thermal stability of EVOH is deteriorated, and a gel is easily generated in a molded product.

Suitable melt flow rate (MFR) of EVOH used in the present invention (at 190 ° C. under a load of 2160 g)
Is 0.1 to 50 g / 10 min. , Optimally 0.5-3
0 g / 10 min. It is. However, those having a melting point of around 190 ° C. or exceeding 190 ° C. are measured under a load of 2160 g at a plurality of temperatures equal to or higher than the melting point, and the reciprocal of the absolute temperature is plotted on the abscissa and the logarithm of MFR is plotted on the ordinate in a semilogarithmic graph. 19
Expressed as a value extrapolated to 0 ° C. These EVOH resins can be used alone or in combination of two or more.

The polyamide resin (B) used in the present invention
Is a polymer having an amide bond, for example, polycaproamide (nylon-6), polyundecaneamide (nylon-11), polylauryl lactam (nylon-12), polyhexamethylene adipamide (nylon-
6,6), polyhexamethylene sebacamide (nylon-
6,12), caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / aminoundecanoic acid polymer (nylon-6 / 1)
1), a caprolactam / ω-aminononanoic acid polymer (nylon-6, 9), a caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,
6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6,6 / 6,12), polymer of adipic acid and meta-xylylenediamine, or hexamethylenediamine And aromatic nylon which is a polymer of m, p-phthalic acid and the like. Each of these polyamide resins can be used alone,
Two or more kinds may be used as a mixture.

From the viewpoint of compatibility with EVOH, of these polyamide resins (B), polyamide resins containing nylon 6 components (for example, nylon-6, nylon-6,1)
2, nylon-6 / 12, nylon-6 / 6,6 etc.) are preferred. Since the EVOH and the polyamide resin react and gel during the melting process at a high temperature, the melting point of the polyamide resin (B) is preferably 240 ° C. or lower, more preferably 230 ° C., from the viewpoint of suppressing the thermal deterioration of the blend composition. It is as follows.

The polyamide resin (B) used in the present invention
Suitable melt flow rate (MFR) (210 ° C., 2
(Under a load of 160 g) is 0.1 to 50 g / 10 min. , Optimally 0.5 to 30 g / 10 min. It is. However, those having a melting point of around 210 ° C. or exceeding 210 ° C.
Measured at a plurality of temperatures above the melting point under a load of 60 g, the reciprocal of the absolute temperature is plotted on the horizontal axis and the logarithm of MFR is plotted on the vertical axis in a semilogarithmic graph.

The olefin-unsaturated carboxylic acid copolymer (C) used in the present invention refers to a copolymer comprising an olefin, in particular, an α-olefin and an unsaturated carboxylic acid. And those in which all or part of the carboxyl groups contained in the polyolefin are present in the form of a metal salt. Examples of the polyolefin serving as the base of the olefin-unsaturated carboxylic acid copolymer (C) include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLD).
PE) and various polyolefins such as polyethylene, polypropylene, copolymerized polypropylene, ethylene-vinyl acetate copolymer, and ethylene- (meth) acrylate copolymer.

Among the olefin-unsaturated carboxylic acid copolymers (C) used in the present invention, a polymer obtained by random copolymerization of a polyolefin and an unsaturated carboxylic acid or an anhydride thereof or a metal salt thereof is preferable. More preferably, ethylene and the unsaturated carboxylic acid or anhydride thereof are randomly copolymerized. The reason that the random copolymer or its metal salt is superior to the graft compound is that it is difficult to obtain a high acid content necessary for exhibiting compatibility with the graft compound. further,
In the case of a graft compound of an unsaturated carboxylic acid, for example, maleic anhydride, a hydroxyl group in EVOH and a carboxyl group in the graft copolymer react with each other to cause gels and butters, which is not preferable in some cases. In particular, when melt molding is performed for a long time, the occurrence of gel and lumps tends to be remarkable. Further, in the present resin composition, it is better to use the metal salt thereof than the ethylene-unsaturated carboxylic acid copolymer. Although the reason is not clear, it is considered that the polarity of the metal salt is higher and the compatibility with the polyamide resin is increased.

The content of unsaturated carboxylic acid or its anhydride is preferably 2 to 15 mol%, more preferably 3 to 15 mol%.
１２12 mol%. Examples of the unsaturated carboxylic acid or its anhydride include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, monomethyl maleate, monoethyl maleate, itaconic acid, itaconic anhydride, and maleic anhydride, and in particular, acrylic acid. Acids or methacrylic acid are preferred. Other monomers that may be included in the copolymer include vinyl acetate, vinyl esters such as vinyl propionate, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, and n-acrylate. -Butyl, 2-ethylhexyl acrylate, methyl methacrylate, isobutyl methacrylate, unsaturated maleic esters such as diethyl maleate, carbon monoxide and the like.

Examples of the metal ion in the metal salt of the olefin-unsaturated carboxylic acid copolymer include alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium and calcium, and transition metals such as zinc. Particularly, the case where zinc is used is preferable in view of compatibility with the polyamide resin. The degree of neutralization of the metal salt of the olefin-unsaturated carboxylic acid copolymer is preferably 100% or less, particularly preferably 90% or less, and more preferably 70% or less. The lower limit of the degree of neutralization is usually 5% or more, especially 1%.
0% or more, more preferably 30% or more.

Suitable melt flow rate (MF) of the olefin-unsaturated carboxylic acid copolymer (C) used in the present invention
R) (at 190 ° C. under a load of 2160 g) is preferably 0.05 to 50 g / 10 min. , More preferably 0.5 to 30 g / 10 min. It is. These olefin-unsaturated carboxylic acid copolymers (C) can be used alone or in combination of two or more.

Polyolefin (D) used in the present invention
Is not particularly limited, α is selected from high- or low-density polyethylene, polypropylene, α-olefin homopolymer such as polybutene-1, ethylene, propylene, butene-1, hexene-1 and the like. -Copolymers of olefins are exemplified. In addition, ethylene has the following components: diolefins, vinyl compounds such as vinyl chloride and vinyl acetate, and unsaturated carboxylic esters such as acrylates and methacrylates;
And those obtained by copolymerizing the above. In the present invention, it is preferable to use polyethylene or polypropylene from the viewpoint of mechanical strength, and it is more preferable to use polypropylene.

The preferred melt flow rate (MFR) of the polyolefin (D) used in the present invention (190 ° C., 216
0 g load) is preferably 0.05 to 100 g / 10
min. , More preferably 0.05 to 50 g / 10 m
in. , Optimally 0.5 to 30 g / 10 min. It is. However, those having a melting point of around 190 ° C. or exceeding 190 ° C. are measured under a load of 2160 g at a plurality of temperatures equal to or higher than the melting point. Expressed as a value extrapolated to 190 ° C.

In order to achieve the object of the present invention, 5 to 60% by weight of an ethylene-vinyl alcohol copolymer (A) having an ethylene content of 20 to 60 mol% and a saponification degree of 90% or more, and a polyamide resin (B) ) 1-30%, and 10-94% by weight of olefin-unsaturated carboxylic acid copolymer (C)
It is necessary to use a resin composition consisting of The content of EVOH (A) in the resin composition is preferably from 10 to
It is 50% by weight, more preferably 15 to 40% by weight.
If the content of EVOH (A) in the resin composition is less than 5% by weight, the gas barrier properties of the composition will be insufficient, and EVO
When the content of H (A) exceeds 60% by weight, the effect of improving the strength and adhesiveness of the composition is insufficient.

The content of the polyamide resin (B) in the resin composition is 1 to 30% by weight, preferably 1.5 to 20% by weight, more preferably 2 to 10% by weight. When the weight ratio of the polyamide resin (B) in the resin composition exceeds 30% by weight, the ratio of the polyamide resin (B) to the EVOH (A) increases, so that a gel is easily generated by the reaction between the two. If less than 1% by weight, EVO
The compatibility between H (A) and the olefin-unsaturated carboxylic acid copolymer (C) decreases, and the effect of improving the strength and adhesiveness of the composition becomes insufficient.

The content of the olefin-unsaturated carboxylic acid copolymer (C) in the resin composition is 10 to 94% by weight, preferably 20 to 85% by weight, more preferably 30 to 80% by weight. . When the content of the olefin-unsaturated carboxylic acid copolymer (C) in the resin composition is less than 10% by weight, the effect of improving the strength and adhesion of the composition is insufficient, and the olefin-unsaturated carboxylic acid When the content of the acid copolymer (C) is 9
If it exceeds 4% by weight, the gas barrier properties of the composition will be insufficient.

The content of the polyamide resin (B) relative to the total amount of the polyamide resin (B) and the olefin-unsaturated carboxylic acid copolymer (C) is 2 to the total amount of both resins.
It is preferably from about 98% by weight to about 98% by weight, and more preferably from 5 to 40% by weight. When the content of the polyamide resin (B) is less than 2% by weight, the compatibility between the EVOH (A) and the polyamide resin (B) decreases, and the polyamide resin (B)
When the content exceeds 98% by weight, the compatibility between the olefin-unsaturated carboxylic acid copolymer (C) and the polyolefin (D) decreases. When the content of the polyamide resin (B) is in such a range with respect to the total amount of both resins, the melt stability of the resin composition is improved, and a molded article having a good appearance even in melt molding for a long time is obtained. It is possible,
Productivity is improved. The reason for this is not clear, but EV
It is considered that the reaction between the OH (A) and the polyamide resin (B) adversely affected the melt stability. A decrease in compatibility between the components leads to a decrease in mechanical strength of the resin composition itself or a decrease in barrier properties and recyclability.

Further, by using a resin composition obtained by adding a polyolefin (D) to an ethylene-vinyl alcohol copolymer (A), a polyamide resin (B), and an olefin-unsaturated carboxylic acid copolymer (C), The effects of the present invention become more remarkable. At this time, the content of the olefin-unsaturated carboxylic acid copolymer (C) in the composition is 5 to 89% by weight, preferably 10 to 75% by weight, and more preferably 15 to 70% by weight. When the content of the olefin-unsaturated carboxylic acid copolymer (C) in the resin composition is less than 5% by weight, the effect of improving the strength and adhesion of the composition is insufficient, and the olefin-unsaturated carboxylic acid is insufficient. When the content of the acid copolymer (C) is 8
If it exceeds 9% by weight, the gas barrier properties of the composition will be insufficient. The content of the polyolefin (D) in the composition is 5 to 89% by weight, preferably 10 to 75% by weight, and more preferably 15 to 70% by weight. When the content of the polyolefin (D) in the resin composition is less than 5% by weight, the effect of improving the strength and adhesiveness of the composition is insufficient, and the content of the olefin-unsaturated carboxylic acid copolymer (C) is insufficient. Content is 89
If the content is more than 10% by weight, the gas barrier properties of the composition will be insufficient.

In the present invention, the resin composition in which the olefin-unsaturated carboxylic acid copolymer (C) and / or the polyolefin (D) is a continuous phase and the EVOH (A) is a dispersed phase is characterized by the characteristics of polyolefin as a whole. Is useful in that EVOH can be imparted with its properties by blending with EVOH. That is, the barrier property can be improved while maintaining the thermal adhesiveness and the mechanical strength. Such a dispersion form may be such that the melt viscosity of EVOH (A) is higher than the melt viscosity of the olefin-unsaturated carboxylic acid copolymer (C) and / or polyolefin (D), or EVOH ( EVOH based on the total weight of A) and polyolefin (D)
It can be obtained by reducing the weight value of (A). That is, the weight of EVOH (A) in the resin composition is W (A), and the total weight of EVOH (A) and the olefin-unsaturated carboxylic acid copolymer (C) and / or polyolefin (D) is W (A + D), W
(A) / W (A + D) is preferably at most 0.65, more preferably at most 0.6. W
When the value of (A) / W (A + D) exceeds 0.65, it becomes difficult for polyolefin (D) to form a continuous phase.

From the viewpoint of preventing thermal degradation of EVOH due to reaction between EVOH (A) and polyamide resin (B),
The resin composition used in the present invention preferably contains at least one of a metal salt of a higher aliphatic carboxylic acid and a hydrotalcite compound.

[0037] Here, in particular, as a hydrotalcite compound _{M x Al y (OH) 2x} + 3 y-2z (A) z ·
A hydrotalcite compound which is a double salt represented by aH ₂ O (M is Mg, Ca or Zn, A is CO ₃ or HPO ₄ , x, y, z, and a is a positive number) can be exemplified.
Particularly preferred examples include the following hydrotalcite compounds.

[0038] _{Mg 6 Al 2 (OH) 16} CO 3 · 4H 2 O Mg 8 Al 2 (OH) 20 CO 3 · 5H 2 O Mg 5 Al 2 (OH) 14 CO 3 · 4H 2 O Mg 10 Al 2 ( _{OH) 22 (CO 3) 2} · 4H 2 O Mg 6 Al 2 (OH) 16 HPO 4 · 4H 2 O Ca 6 Al 2 (OH) 16 CO 3 · 4H 2 O Zn 6 Al 6 (OH) 16 CO 3 .4H ₂ O Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O

Further, as the hydrotalcite compound,
JP-A-1-308439 (US Pat. No. 4,954,557)
The hydrotalcite-based solid solution described,
[Mg _0.75Zn_0.25]_0.67Al
_0.33(OH)₂(CO₃)_0.167・ 0.45H
₂Something like O can also be used.

The metal salt of a higher aliphatic carboxylic acid is a metal salt of a higher fatty acid having 8 to 22 carbon atoms.
Examples of higher fatty acids include lauric acid, stearic acid, and myristic acid, and examples of metals include sodium, potassium, magnesium, calcium, zinc, barium, and aluminum. Of these, alkaline earth metals such as magnesium, calcium and barium are preferred.

The content of the metal salt of these higher aliphatic carboxylic acids and the hydrotalcite compound is preferably 0.01 to 3 parts by weight, more preferably 0.05 to 3 parts by weight, based on the total weight of the resin composition. 2.5 parts by weight.

The resin composition used in the present invention may contain, in addition to the above resin components, appropriate additives (for example, heat stabilizer, plasticizer, ultraviolet absorber, antioxidant, colorant, filler, It is free to use other resins and the like as long as the object of the present invention is not hindered.

It is important that the container cap maintain the sealing property until the consumer opens it, maintain the simple sealing property after opening, and also exhibit the barrier property during storage after opening. FIG. 1 shows, as an example, a cross-sectional view of the container cap of the present invention. The container cap 1 is cylindrical, has a flat bottom surface, and has a screw groove 2. Although such a container cap can provide adhesion even as it is, it can be used together with a sealing liner (cap liner).
More preferred. The material of the sealing liner is not particularly limited, but ethylene-vinyl acetate copolymer or ethylene-poly-1
-Butene copolymer and the like are used.

The resin composition for molding the container cap of the present invention can be easily obtained by melt-kneading the components using an appropriate melt-kneading apparatus. The method of blending is not particularly limited,
EVOH (A), polyamide resin (B), olefin-
Examples include a method in which the unsaturated carboxylic acid copolymer (C) and / or the polyolefin (D) are pelletized and dried simultaneously or in an appropriate order using a single-screw or twin-screw extruder.

In particular, as shown in Examples described later, first, a polyamide resin (B) and an olefin-unsaturated carboxylic acid copolymer (C) are melt-mixed,
After granulation and drying, EVOH (A) alone or dry blended with EVOH and polyolefin (D)
A method of granulating and drying with a single screw or twin screw extruder or the like is preferable. The reason for this is that when components are simultaneously melt-kneaded, components having good compatibility (for example, E
Since mixing of the VOH (A) and the polyamide resin (B)) may proceed with priority, it may be difficult to stably control the morphology of the resin composition comprising three or four components. However, the polyamide resin (B) and the olefin-unsaturated carboxylic acid copolymer (C)
By preparing a blend with the above in advance, a resin composition composed of three or four components having a stable morphology can be obtained without being greatly affected by the conditions during melt mixing. In particular, this effect is achieved with polyolefin (D)
Is remarkable in a resin composition composed of four components blended with each other, and a stable compatibilizing effect between EVOH (A) and polyolefin (D) can be obtained. In addition,
In the melt compounding operation, there is a possibility that the blend becomes non-uniform, and gels and lumps are generated and mixed.Therefore, in the case of blend pelletization, use an extruder with a high degree of kneading as much as possible, and use a nitrogen gas It is desirable to extrude at a low temperature.

A container cap is prepared using the obtained resin composition. Examples of the method for producing the container cap include injection molding, a compression molding method, and a method of thermoforming a previously prepared sheet.In consideration of the shape of the screw groove and the like, the melt-kneaded composition is injection-molded. Is the most suitable method.

The form of the container body to which the obtained container cap is attached is not particularly limited. Containers such as glass bottles and PET (polyethylene terephthalate) bottles, and containers made using a laminated packaging material in which a gas barrier material such as aluminum foil or ethylene-vinyl alcohol copolymer and polyolefin or PET are laminated via an adhesive layer are used. Can be

The packaging container thus obtained is excellent in gas barrier properties, strength, and recyclability, and is a container for food, especially liquid foods (eg, alcohols such as wine and sake, soy sauce, etc.). It is suitable as a cap for use.

[0049]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. Resins (A) used in the following Examples and Comparative Examples,
(B), (C) and (D) are shown in Table 1, Table 2, Table 3 and Table 4 below, respectively.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

Example 1 Ethylene-vinyl alcohol copolymer resin (A-1) 3
0 parts by weight, 10 parts by weight of a mixture of nylon 6-12 (B-1) and a metal salt of ethylene-methacrylic acid random copolymer (C-1) having a weight ratio of 3/7, and polypropylene (D
-1) After premixing 60 parts by weight using a tumbler, the cylinder temperature was measured using a 30 mmφ twin screw extruder (TEX30, manufactured by Nippon Steel Works: L / D = 30) having a kneading disk, The kneading section and the vicinity of the nozzle were set at 210 ° C.
10rpm, feeder motor rotation speed 250rpm
To obtain a pellet.

Next, the above-mentioned pellets were supplied to an injection molding machine equipped with a mold for producing the container cap shown in FIG. 1, and the container cap was produced by the injection molding method. At this time, the cylinder temperature of the injection molding machine was 230 ° C, and the nozzle temperature was 220 ° C.

A part of the thus formed container cap was cut off to obtain a small piece. EVOH of cut surface of small piece
(A) was stained with iodine, and the cut surface of the small piece was observed with an optical microscope to determine whether EVOH (A) was a continuous phase or a dispersed phase.

The evaluation of the molded container cap was performed as follows. (1) Barrier Property (Oxygen Permeability Coefficient) The resin composition was charged into an extruder having a T stage and a screw diameter of 20 mmφ, and a single-layer film having a thickness of 100 μm was formed at an extrusion temperature of 210 ° C. 70 ° C.
Vacuum dried for at least 24 hours to make it completely dry, using a modern control company (U.S.A.) Ox-Tran 10/50 type oxygen permeability measuring apparatus at a temperature of 20 ° C. and 0% RH according to JIS K7126. And the oxygen permeability coefficient (cc
.20 μ / m ² · day · atm). Example 1
Is 200 cc · 20 μ / m ² · da
y · atm.

(2) Mechanical Strength The molded container cap was cooled sufficiently by holding it at -50 ° C. for 12 hours, and then dropped from a height of 5 m to check for damage, and judged according to the following criteria. . In Example 1, no damage due to the drop test was observed. ◎: No change ×: Crack or damage (fail)

(3) Appearance The degree of discoloration or scorching of the surface of the molded container cap was visually observed, and judged according to the following criteria. In Example 1, no change in appearance was observed. ：: Good appearance, no discoloration, no sticking of burn (pass) ○: Some discoloration but no burn (pass) ×: Large discoloration and / or sticking of burn (fail) )

(4) Recyclability After burrs such as a runner portion generated during the injection molding of the container cap were pulverized, they were charged into an injection molding machine again, and the container cap was molded again under the same conditions. The molded articles were evaluated for mechanical strength and appearance according to the above criteria (2) and (3), respectively. In Example 1, deterioration of the resin due to recycling was not recognized.

Examples 2 to 6 and Comparative Examples 1 to 6 Container caps were prepared in the same manner as in Example 1 at the composition ratios shown in Table 6, and evaluated in the same manner as in Example 1. Table 5 shows the results including the results of Example 1.

[0062]

[Table 5]

Examples 1 to 6 all had good evaluation items, but Comparative Example 1, in which EVOH had a composition outside the range of the present invention, was inferior in oxygen gas barrier properties. Comparative Example 2 containing no polyamide resin (B) was inferior in mechanical strength. Comparative Examples 4 and 5, which did not contain the polyamide resin (B) and the olefin-unsaturated carboxylic acid copolymer (C), had poor mechanical strength and poor recyclability. E
Comparative Example 6, in which the ethylene content of VOH (A) exceeds the predetermined range, had good mechanical strength and recyclability, but was inferior in oxygen barrier properties.

[0064]

EFFECT OF THE INVENTION A container cap formed by molding a resin composition comprising an ethylene-vinyl alcohol copolymer (A), a polyamide resin (B) and an olefin-unsaturated carboxylic acid copolymer (C), or A container formed by molding a resin composition comprising ethylene-vinyl alcohol copolymer (A), polyamide resin (B), olefin-unsaturated carboxylic acid copolymer (C), and polyolefin (D) other than the above resins. The cap for use is excellent in gas barrier properties, mechanical strength, appearance and recyclability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a container cap.

[Description of Signs] 1 Container Cap 2 Screw Groove

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E084 AB06 BA01 CA01 CC03 CC05 CC08 DA01 DB12 DC03 DC05 DC08 GA04 GB04 HA02 HB03 HC03 HD01 4J002 BB00Z BB06Y BB07Y BB08Y BB09Y BB12Z BB20Y BB21Y BB22X BB00X03X03X03X

Claims (5)

[Claims] 1. An ethylene-vinyl alcohol copolymer (A) having an ethylene content of 20 to 60 mol% and a saponification degree of 90% or more, 5 to 60% by weight, and a polyamide resin (B) 1 to 30
A container cap formed by molding a resin composition comprising 10% to 94% by weight of an olefin-unsaturated carboxylic acid copolymer (C). 2. An ethylene-vinyl alcohol copolymer (A) having an ethylene content of 20 to 60 mol% and a saponification degree of 90% or more, 5 to 60% by weight, and a polyamide resin (B) 1 to 30.
% By weight, olefin-unsaturated carboxylic acid copolymer (C)
A container cap formed by molding a resin composition comprising 5 to 89% by weight and 5 to 89% by weight of a polyolefin (D) other than the resin. 3. The container cap according to claim 1, wherein the olefin-unsaturated carboxylic acid copolymer (C) is an ethylene-unsaturated carboxylic acid random copolymer or a metal salt thereof. 4. The container cap according to claim 1, wherein the polyolefin (D) is polypropylene. 5. The container cap according to claim 1, which is formed by injection molding.