JP2836934B2 - Resin composition and multilayer structure using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of the Invention The present invention relates to a heat-stretching method, particularly a high-speed heat-stretching operation, in particular, a gas-barrier property, in which pinholes, cracks, local wall thickness unevenness, etc. do not occur, under high humidity conditions. TECHNICAL FIELD The present invention relates to an ethylene-vinyl alcohol copolymer composition having excellent gas barrier properties and a multilayer structure using the same, particularly to a high-speed heating multilayer structure.

B. Conventional technology Ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) is usually obtained by copolymerizing and saponifying ethylene and vinyl acetate, and has gas barrier properties, oil resistance, solvent resistance, and fragrance retention. Because of its excellent properties, it is widely used as a gas barrier material in the field of food packaging. At that time, since the EVOH single film lacks toughness and does not have sufficient barrier properties against water and water vapor, it is used in the form of a multilayer structure laminated with a layer of a low moisture permeable thermoplastic resin such as polyethylene and polypropylene. Is often done.

By the way, when a multi-layer structure (film, sheet, parison, etc.) is processed into a container or the like, especially when stretch-molded below the melting point of EVOH, small pinholes, cracks, local unevenness, etc. frequently occur in the EVOH layer. However, as a result, the gas barrier properties of the molded container and the like are significantly deteriorated. In addition, it is poor in appearance and cannot be used for food packaging.

As a countermeasure, the addition of various plasticizers to EVOH (Japanese Unexamined Patent Publication No.
88067, JP-A-59-20345), blends of polyamide resins (JP-A-52-141785, JP-A-58-154755, JP-A-58-154755)
36412, etc.) are considered, but in the former case, the gas barrier property is reduced and the contact strength between the EVOH layer and the other resin layer is considered to be caused by plastic bleeding. On the other hand, in the latter case, It is not practical due to the problem of gelation during melt molding. In addition, blends of EVOH with low saponification degree EVOH (JP-A-52-101182 and JP-A-63-230757) have been studied, but since low saponification degree EVOH easily gels during melt molding, Is difficult to form, and the gas barrier property under high humidity is poor.

C. Problems to be Solved by the Invention While EVOH has excellent properties as described above, when secondary processing of a laminate with a thermoplastic resin into containers and the like, pinholes and cracks are formed in the EVOH layer. In addition, local uneven thickness and the like occur, and the gas barrier property is greatly deteriorated. In addition, they are poor in appearance and cannot be used as food packaging containers. The present invention prevents the occurrence of pinholes, cracks, localized thickness deviation, etc., when secondary processing of the laminate into a container or the like,
An object of the present invention is to provide an EVOH composition for a multilayer container having excellent gas barrier properties, particularly excellent gas barrier properties under high humidity conditions, and a multilayer structure using the same.

C. Means for Solving the Problems As a result of diligent research, the present inventors have found that 90 to 10 parts by weight of an ethylene-vinyl alcohol-copolymer (A) having an ethylene content of 20 to 65 mol% and ethylene-containing Amount 20-65 mol%,
Syndiotacticity is 55 mol% in diat display
The resin composition comprising 10 to 90 parts by weight of the ethylene-vinyl alcohol-based copolymer (B) is a composition part having excellent gas barrier properties, particularly under high humidity conditions. The heat-stretched multilayer structure of the resin composition layer and the other thermoplastic resin layer was found to be a molded article having a good external appearance even when the stretching ratio and the stretching speed were extremely large, and completed the present invention. It has been reached.

In the present invention, the ethylene-vinyl alcohol copolymer (A) is ordinary EVOH obtained by saponifying an ethylene-vinyl acetate copolymer, and has an ethylene content of 20 to 65.
Mol%, preferably 25-55 mol%. If the ethylene content is less than 20 mol%, pin poles and cracks are liable to be generated during molding of the container, while if it exceeds 65 mol%, the gas barrier property is lowered, and in either case, it is not preferable. Further, the degree of saponification is desirably 80 mol% or more, preferably 90 mol% or more, more preferably.
96 mol% or more. If the degree of saponification is less than 80 mol%, the gas barrier properties are insufficient, and the thermal stability is poor, so that there is a disadvantage that a gel is easily generated during melt molding. The EVOH
(A) is as long as the object of the present invention is not impaired.
Propylene, α-olefins such as isobutene, olefinic unsaturated monomers containing silicon, acrylic acid, methacrylic acid, unsaturated carboxylic acids such as maleic acid or salts thereof,
Alternatively, it may contain an ester thereof.

Next, in the present invention, the ethylene-vinyl alcohol copolymer (B) is a specific EVOH obtained by a method described below.
It is particularly important that the resin is a synthetic resin and has a syndiotacticity of 55 mol% or more in diat. In the case of normal EVOH, ie, a saponified ethylene-vinyl acetate copolymer, the syndiotacticity is less than 55 mol%, but if it is less than 55 mol%, the gas barrier property under high humidity conditions is insufficient, Not preferred. The upper limit of the syndiotacticity is not particularly limited, but from the viewpoint of production, is 65 mol% or more, and furthermore, 70 mol%.
It is. Here, the syndiotacticity is based on a diatomic display, and is calculated from the integrated intensity ratio of the hydroxyl hydrogen peak present at 4.0 to 4.7 ppm in ¹ H-NMR. Further, the ethylene content needs to be 20 to 65 mol%, preferably 25 to 55 mol%. If the ethylene content is less than 20 mol%, pinholes and cracks are liable to be generated during molding of the container, while if it exceeds 65 mol%, the gas barrier property is lowered, and in either case, it is not preferable. The saponification degree is desirably 80 mol% or more, and is preferably
It is at least 90 mol%, more preferably at least 96 mol%. If the saponification degree is less than 80 mol%, the gas barrier property is insufficient.

In the present invention, the melt index (measured at a temperature of 210 ° C .; hereinafter, referred to as MI) of EVOH (A) and EVOH (B) is not particularly limited, but is preferably 0.4 to 150 g / 10 minutes, more preferably. It is 1.0-100g / 10min.

Here, the EVOH (B) having a large syndiotacticity according to the present invention is produced, for example, by the following method.

That is, it is a method of copolymerizing ethylene and a vinyl ester represented by the formula (I), and saponifying the obtained copolymer.

Here, R ¹ and R ² represent hydrogen or a hydrocarbon group, and R ³
Represents a hydrocarbon group, and examples of the hydrocarbon group include methyl,
A lower alkyl group such as ethyl, propyl, butyl and t-butyl; an aryl group such as phenyl; a C1-C18 hydrocarbon group such as a cycloalkyl group such as a cyclohexyl group. Among them, R ¹ , R ² , and R ³ are each preferably a lower alkyl group, particularly preferably a methyl group. That is, the vinyl ester component is most preferably vinyl pivalate in which R ¹ , R ² , and R ³ are all methyl groups.

Copolymerization of ethylene-vinyl ester includes bulk polymerization,
It is carried out by solution polymerization, suspension polymerization, or emulsion polymerization, but may be carried out under the conditions of 0 ° C to 100 ° C, preferably 30 ° C to 60 ° C, by solution polymerization in the presence of a bulk or a solvent. preferable. Polymerization rate is 20-80
%, Preferably 30 to 60%. In the case of solution polymerization, the solvent concentration is 50% or less, preferably 30% or less.

The solvent used in the solution polymerization is preferably an alcohol, and is usually methanol, ethanol, propanol,
Lower alcohols such as t-butanol are preferred. These solvents can be used alone or in combination of two or more. As the copolymerization operation, any of a batch system and a continuous system can be used, but a flow system operation using a stirring and mixing type polymerization tank is preferable.

The ethylene content of the ethylene-vinyl ester copolymer is determined by the vinyl ester present in the system and the amount of dissolved ethylene in the solution, and the latter depends on the ethylene pressure and temperature in the system. It is well known that when performing polymerization in a batch system, the copolymer composition fluctuates with the degree of polymerization in accordance with the copolymerization reactivity ratio, but one or both monomers are used so that the monomer composition is constant. In order to obtain a copolymer having a uniform copolymer composition, it is more preferable to employ a semi-batch method in which a polymer is added. An example of a method for calculating the amount of addition at this time is RJHanna (Industrial and Engineering Chemistry).
stry vol.49,208 (1957)). In the case of the continuous method, a one-stage flow-type reaction system of a complete mixing type in which a stirring and mixing tank is used as a copolymerization reaction tank is preferable. For this reason, it is more preferable to carry out the reaction while adding the monomers to the second and subsequent tanks so that the monomer composition in the copolymerization tank at each stage becomes constant.

In the copolymerization reaction, a radical polymerization initiator is used, for example, 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile), 2,4,4-trimethylvaleronitrile, 2,2 Nitriles such as' -azobis-isobutyronitrile, carbonates such as di-n-propylperoxycarbonyl, bis-4-tert-butylcyclohexylperoxydicarbonate, bis-2-ethyl-hexylperoxydicarbonate And peroxides such as acetylcyclohexanesulfonyl peroxide, benzoyl peroxide and lauroyl peroxide. The copolymer thus obtained is then subjected to a saponification reaction.

Generally, vinyl esters having a bulky group in the side chain as represented by the formula (I), for example, vinyl pivalate, are not easily hydrolyzed due to their steric hindrance, and are usually used in copolymers with ethylene. An alkyl saponification method under conditions such as those performed for ethylene-vinyl acetate copolymers does not provide sufficient saponification. Therefore, it is preferable to saponify under the following conditions.

First, it is important to perform saponification in the absence of oxygen or in the presence of an antioxidant, and furthermore, the molar ratio of the amount of basic substance / the content of vinyl ester unit is 0.1%.
It is important that the saponification temperature is 60 ° C. or higher.

Here, the absence of oxygen is typically represented by a method of substituting with an inert gas (such as nitrogen). The antioxidant is not particularly limited as long as it does not adversely affect the saponification reaction and does not lose the antioxidant effect in the saponification system. Compound represented by <IRGANOX 1010 (manufactured by Ciba-Geigy Japan)> Hindered phenolic antioxidants such as the compound represented by <IRGANOX 1098 (manufactured by Nippon Ciba Geigy)>, phenolic antioxidants such as hydroquinone, SANOL L
Hindered amine-based antioxidants such as S-770 (manufactured by Nippon Ciba Geigy) are typical examples.

The saponification reaction is performed in the presence of a basic substance, and any of a transesterification reaction and a direct saponification reaction can be selected according to the type, concentration, and solvent type of the basic substance.
Examples of the basic substance include strong bases such as sodium hydroxide, calcium hydroxide, and alkali hydroxide; metal alkoxides such as sodium methoxide, sodium ethoxide, potassium methoxide, calcium ethoxide, and potassium-t-butoxide. Is mentioned. The molar ratio of the amount of the basic substance used / the content of the vinyl ester unit is represented by a molar ratio to the vinyl ester unit contained in the copolymer, and is 0.1 to 10, preferably 0.5 to 3. This value varies depending on the target degree of saponification, degree of polymerization, solvent, type of basic substance, etc.In general, if the value is less than 0.1, the degree of saponification does not increase, and if it is more than 10, the degree of polymerization decreases during the saponification reaction. Occurs remarkably. The amount of the basic substance to be used may be different from those in the case where the monomer unit other than the copolymer contains a group that reacts with the basic substance (for example, a carboxyl group) or when the antioxidant reacts with the basic substance. Is set by compensating for the amount consumed.

The saponification temperature is 60 ° C or higher, preferably 60 to 140 ° C,
More preferably, it is 80 to 120 ° C.

The saponification reaction time is appropriately set depending on the target degree of saponification, polymer concentration, solvent, basic substance, temperature and the like. After completion of the saponification, it is preferable to immediately neutralize the basic substance remaining in the reaction system with an acid. Acids include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and carbonic acid,
Organic acids such as formic acid, acetic acid, benzoic acid and the like can be mentioned. Organic acids are preferred, and acetic acid is most preferred. If the basic substances remaining in the reaction system are not neutralized after completion of saponification,
The degree of polymerization of the copolymer decreases.

The solvent used at the time of saponification is a solvent capable of dissolving or swelling the ethylene-vinyl ester copolymer, and desirably a solvent capable of dissolving the basic substance and the polymer after saponification. Solvents having these properties include cyclic ethers such as tetrahydrofuran and dioxane; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; sulfoxides such as dimethyl sulfoxide; amides such as dimethyl formamide: toluene, benzene and the like. Aromatic hydrocarbons; alcohols such as methanol, ethanol, t-butanol, n-propanol, iso-propanol, sec-butanol, and cyclohexanol;
Particularly, tetrahydrofuran, methyl ethyl ketone, t-butanol, and the like are preferable. These can be used alone or in combination of two or more.

The concentration of the ethylene-vinyl ester copolymer in the solvent solution in the saponification system is appropriately determined according to the degree of polymerization of the copolymer, and is usually between 3 and 70% by weight.

Further, the ethylene-vinyl alcohol-based copolymer,
Propylene as long as the object of the present invention is not impaired,
Α-olefins such as isobutene, olefinic unsaturated monomers containing silicon, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic acid or salts thereof, or esters thereof, and ethylene such as vinyl acetate and the above ( I) A comonomer other than the formula may be contained as a copolymer component.

Next, when the composition of the present invention is used particularly as a deep drawing material, the ethylene content of EVOH (A) and EVOH
It is desirable that the ethylene content of (B) differs by 10 mol% or more. When the difference between the two ethylene contents is 10 mol% or more, uneven stretching, cracks, etc. are unlikely to occur, the appearance is good, and the gas barrier properties are excellent. The difference in ethylene content is more preferably at least 15 mol%, even more preferably at least 20 mol%. Either EVOH (A) or (B) may have a higher ethylene content.

Furthermore, in the present invention, the blend ratio of EVOH (A) and EVOH (B) needs to be A: B = 90: 10 to 10:90. If the blending ratio is out of this range, as in the case where the difference between the two ethylene contents is less than 10 mol%, stretching unevenness, cracks, etc. are generated, and the appearance defect and the gas barrier property are significantly reduced. I do not endure.

About EVOH (A) and EVOH (B) and blending method,
Although not particularly limited, EVOH (A) and EVOH
(B) is dry-blended and kneaded with a Banbury mixer, a single-screw or twin-screw extruder, or the like. If the mixing state is not uniform, or if gel or foreign matter is generated or mixed during the blending operation,
Since the EVOH blend layer often breaks and melts, it is preferable to use an extruder having a high degree of kneading, and perform nitrogen sealing at the hopper opening and low-temperature extrusion in the heating blending by the extruder. When blending EVOH (A) and EVOH (B), other additives (various resins, antioxidants, plasticizers, coloring agents, etc.) are used within a range that does not impair the effects of the present invention. It is free, especially, for the purpose of increasing the thermal stability of the resin and preventing the generation of gel, hydrotalcite compounds, hindered phenol compounds,
It is effective to add a hindered amine compound or the like in an amount of 0.01 to 1% by weight.

The resin composition of the present invention can be formed into any molded product such as a film, a sheet, a tube, and a bottle by a known melt molding method and a compression molding method, and a solution to a molded product such as the molded product can be obtained. Although it can be used as a coating material, as described above, when the resin composition is used as a multilayer structure and a single layer, remarkable features are exhibited. Therefore, this point will be described below.

First, examples of the thermoplastic resin used in the present invention include a polypropylene resin, a polystyrene resin, a polyester resin, a polyamide resin, and a polyvinyl chloride resin. Among them, polypropylene resins (homopolypropylene, ethylene-propylene block copolymer,
Random copolymerized polypropylene and the like), polystyrene resins and polyester resins are preferably used.

Next, as a method of obtaining a multilayer structure, the EVOH resin composition and the thermoplastic resin are contacted with each other via an extruded laminating method, a dry laminating method, a coextrusion laminating method, a coextruded sheet forming method (feed Block or multi-manifold method),
A laminate is obtained by a co-extrusion pipe molding method, a co-injection method, a solution coating method, and the like, and then reheated at a temperature equal to or lower than the melting point of the thermoplastic resin by a vacuum pressure deep drawing molding machine, a biaxial stretch blow molding machine, or the like, A stretching method (SPPF molding method), a melt molding method performed at a temperature equal to or higher than the melting point of the thermoplastic resin, or the laminate (sheet or film) is subjected to a biaxial stretching machine,
A method of heating and stretching, a method of co-injection biaxial stretching of an EVOH resin composition and a thermoplastic resin, and the like can be given.

The layer structure of the multilayer structure includes thermoplastic resin layer / resin composition layer of the present invention / thermoplastic resin layer, resin composition layer of the present invention / contact resin layer / thermoplastic resin layer, thermoplastic resin Typical examples include a layer, a contact resin layer / a resin composition layer of the present invention / a contact resin layer / a thermoplastic resin layer, but are not limited thereto. When a thermoplastic resin layer is provided on both outer layers, the resins may be different or the same. Here, the contact resin is EVOH
It is not particularly limited as long as it can be stretch-molded at a melting point of not more than and is capable of contacting the EVOH resin composition layer with the thermoplastic resin layer, but is preferably an ethylenically unsaturated carboxylic acid or an anhydride thereof ( Polyolefins (eg, polyethylene,
Polypropylene), an ethylene-vinyl acetate copolymer, an ethylene-acrylate ester (eg, methyl ester, ethyl ester) copolymer, and the like.

In the present invention, the heat-stretched multilayer structure is a container such as a cup, a bottle, or a sheet or a film-like material obtained by heat-stretching as described above, and the heating is necessary for heat-stretching the multilayer structure. At a predetermined temperature for a predetermined period of time so that the multilayer structure is thermally substantially uniform. The heating operation may be performed simultaneously with the stretching or before the stretching. Heating temperature is 110 ~ 230
° C, preferably 120-210 ° C. Stretching refers to the operation of uniformly forming a multilayered structure that has been thermally uniformly heated into a container, cup, sheet, or film in the form of a chuck, plug, vacuum air, blow, or the like.
Any of biaxial stretching (simultaneous or sequential) may be used. The stretching speed can be appropriately selected depending on the purpose. In the present invention, the high-speed stretching means that the stretching speed is 5 × 10 ⁵ % / min or more in area ratio at a rate of not less than 5 × 10 ⁵ % / min to form a container or a film. It is not necessary that the molded article be oriented. The stretching ratio is preferably 70 times or less in terms of area ratio, more preferably 3 times.
~ 60 times. If it exceeds 70 times, it is difficult to stretch a thermoplastic resin layer such as polypropylene, and it is difficult to obtain a good stretched multilayer structure.

In addition, in the present invention, in heating and stretching, the water content of the EVOH resin composition layer, which is one component of the multilayer structure, is not particularly limited, but is preferably in the range of 0.01 to 10%.

The thus obtained heat-stretched, particularly high-speed heat-stretched multilayer structure of the present invention shows no pinholes, cracks, uneven stretching or uneven thickness in the EVOH resin composition layer, and has a gas barrier property, particularly high humidity. It has excellent gas barrier properties under conditions, and is extremely useful as a food packaging container or the like.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by these examples.

E. Examples Example 1 As EVOH (A), ethylene content is 27 mol%, saponification degree is 99.5 mol%, syndiotacticity (diadetic display; the same applies hereinafter) 51 mol%, MI (temperature 210 ° C., load 2160 g)
Melt index measured under the following conditions; the same applies below) 3.
A saponified ethylene-vinyl acetate copolymer of 5 g / 10 min, ethylene content of 44 mol%, saponification degree of 99.1 mol%, syndiotacticity of 60 mol%, MI2 produced under the following conditions as EVOH (B) Using an ethylene-vinyl alcohol copolymer of 0.5 g / 10 min, production of a resin composition, production of a multilayer structure, and evaluation of gas barrier properties were performed.

(1) Production of EVOH (B) 100 parts by weight of vinyl pivalate, 12 parts by weight of methanol, 3 parts by weight of ethanol and 0.065 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator were placed in a pressure-resistant polymerization tank. After charging and replacing oxygen in the tank with ethylene, the ethylene pressure was maintained at 45 kg / cm ² , polymerization was carried out at 60 ° C. with stirring for 6 hours, and then a polymerization inhibitor was added. The conversion of vinyl pivalate was 35%. Next, unreacted ethylene was purged out of the tank, and unreacted vinyl pivalate was distilled off at 60 ° C. under reduced pressure. Next, 30 parts by weight of ethylene-vinyl pivalate copolymer together with 450 parts by weight of tetrahydrofuran,
It was charged into a pressure-resistant saponification tank and dissolved at 60 ° C. while blowing nitrogen. Then 78 parts by weight of potassium hydroxide and 22 parts of methanol
A solution consisting of 5 parts by weight was prepared, and after removing oxygen, it was charged into a pressure-resistant saponification tank, and was blown with nitrogen at 95 ° C.
The saponification reaction was performed under stirring for 75 minutes. Next, the saponified product is thoroughly washed with methanol and pure water, and is heated at 80 ° C. for 5 hours.
Further drying at 105 ° C. for 15 hours in nitrogen. The analytical values of EVOH thus obtained are as described above. The measurement of ethylene content, saponified product, and syndiotacticity was performed using ¹ H-NMR using d ₆ -dimethylsulfoxide (DMSO) as a solvent. The syndiotacticity was calculated from the integrated intensity ratio of the hydrogen peak of the hydroxyl group existing at 4.0 to 4.7 ppm.

(2) Production of resin composition and multilayer structure A dry blend of 60 parts by weight of EVOH (A) and 40 parts by weight of EVOH (B) is supplied to a twin-screw type vent type 40φ extruder, and a nitrogen stream is supplied. Pelletize at 210 ° C below, then 80
After drying at 1 ° C. for 1 hour, a sheet composed of a polypropylene layer / a contact resin layer / the resin composition layer / a contact resin layer / a polypropylene layer was fed block type 3
It was manufactured using a layer co-extrusion apparatus. The polypropylene used was Mitsubishi Noblen MA-6, and the contact resin was Mitsubishi Yuka Modic P-300F (maleic anhydride-modified polypropylene). The thickness configuration of the sheet is 800μ / 50μ / 50μ /
It was 50μ / 800μ. Next, the sheet was subjected to thermoforming (SPPF molding) at 150 ° C. under the conditions of a stretching speed of 3 × 10 ⁷ % / min, a drawing ratio of 2, and a stretching area magnification of 12 times using a vacuum pressure air molding machine. . The obtained cup-shaped container had a good appearance without cracks or uneven thickness.

(3) Evaluation of gas barrier properties Using OX-TRAN 10-50A manufactured by Modern Control Co., Ltd., the oxygen permeation amount of the cup-shaped container was set to 20 ° C., 65% RH and
It was measured under the condition of 100% RH. The results are shown in Table 1. Both the appearance of the container and the gas barrier properties were very good.

Example 2 A pellet-shaped resin was prepared in the same manner as in Example 1 except that EVOH (A) and EVOH (B) described in Example 1 were used and the mixing ratio was (A) :( B) = 40: 60. The composition was produced, then sheet-formed, and then thermoformed, and the gas barrier properties of the obtained cup-shaped container were measured. The results are shown in Table 1. There were no cracks or uneven thickness and good gas barrier properties.

Example 3 As EVOH (A), ethylene content 27 mol%, degree of saponification 99.5 mol%, sidiotacticity-51 mol%, MI3.
A saponified ethylene-vinyl acetate copolymer of 5 g / 10 min, and an ethylene content of 57 mol%, a saponification degree of 97.1 mol%, a syndiotacticity of 58 mol%, and a MI of 25 g produced as the EVOH (B) under the conditions described below. Production of a resin composition, production of a multilayer structure, and evaluation of gas barrier properties were performed using an ethylene-vinyl alcohol-based copolymer of / 10 minutes.

(1) Production of EVOH (B) 100 parts by weight of vinyl pivalate, 40 parts by weight of methanol, and 0.12 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator are charged into a pressure-resistant polymerization tank. After the oxygen in the tank was replaced with ethylene, the ethylene pressure was maintained at 45 kg / cm ² , polymerization was carried out at 60 ° C. with stirring for 4 hours, and then a polymerization inhibitor was added. The conversion of vinyl pivalate was 30%. Next, in the same manner as in Example 1, unreacted ethylene and vinyl pivalate were removed, and then saponification, washing and drying were performed.

(2) Production of resin composition and multilayer structure A pellet-shaped resin composition was produced in the same manner as in Example 1 except that 85 parts by weight of EVOH (A) and 15 parts by weight of EVOH (B) were used. Sheet molding and thermoforming were performed. The obtained cup-shaped container had a good appearance without cracks, uneven thickness and the like.

(3) Evaluation of gas barrier property The measurement results of gas barrier property of the cup-shaped container were good as shown in Table 1.

Comparative Example 1 Example 1 was repeated except that EVOH was a saponified ethylene-vinyl acetate copolymer alone having an ethylene content of 27 mol%, a degree of saponification of 99.5 mol%, a syndiotacticity of 51 mol%, and a MI of 3.5 g / 10 min. In the same manner as in the above, a pellet-shaped resin composition was produced, and then sheet molding and thermoforming were performed, and the gas barrier properties of the obtained cup-shaped container were measured. First result
It is shown in the table. Cracks and uneven thickness were extremely large, and gas barrier properties were poor.

Comparative Example 2 As EVOH (B), ethylene content 44 mol%, saponification degree 99.3 mol%, syndiotacticity 51 mol%, MI
A pellet-shaped resin composition was produced in the same manner as in Example 1 except that a saponified ethylene-vinyl acetate copolymer of 11 g / 10 min was used, and then sheet molding and thermoforming were performed. When the gas barrier properties of the container were measured, as shown in Table 1, the appearance was relatively good with some cracks and uneven wall thickness, but the gas barrier properties, especially under high humidity conditions, were good. The barrier properties were much worse than in Example 1.

Comparative Example 3 A pellet-shaped resin composition was prepared in the same manner as in Example 1 except that EVOH (A) and EVOH (B) described in Example 1 were used and the mixing ratio was (A) :( B) 95: 5. The product was manufactured, and then subjected to sheet molding and further thermoforming, and the gas barrier properties of the obtained cup-shaped container were measured. The results are shown in Table 1. Both appearance and gas barrier properties were poor.

Comparative Example 4 A pellet-shaped resin composition was produced in the same manner as in Example 1 except that the type of EVOH (A) was changed as shown in Table 1, and then sheet molding and further thermoforming were carried out. The gas barrier properties of the cup-shaped container thus obtained were measured. First result
It is shown in the table. In each case, both appearance and gas barrier properties were poor, but in Comparative Example 4, there was also a problem that gel was frequently generated during sheet molding.

Example 4 As EVOH (A), ethylene content 50 mol%, saponification degree 90.2 mol%, syndiotacticity 52 mol%, MI
13 g / 10 min saponified ethylene-vinyl acetate copolymer. Also, ethylene content 32 mol%, saponification degree 99.7 mol%, syndiotacticity 61 mol%, MI4 produced as EVOH (B) under the conditions described below. Using an ethylene-vinyl alcohol copolymer of 0.1 g / 10 minutes, production of a resin composition, production of a multilayer structure, and evaluation of gas barrier properties were performed.

(1) Production of EVOH (B) 100 parts by weight of vinyl pivalate, 23 parts by weight of methanol, 7.5 parts by weight of ethanol and 0.065 parts by weight of azobisisobutyronitrile are charged into a pressure-resistant polymerization tank, and oxygen in the tank is replaced with ethylene. After the replacement, the ethylene pressure was kept at 25 kg / cm ² , polymerization was carried out at 60 ° C. with stirring for 5 hours, and then a polymerization inhibitor was added. The conversion of vinyl pivalate was 50%.
Next, in the same manner as in Example 1, unreacted ethylene and vinyl pivalate were removed, and then saponification, washing and drying were performed.

(2) Production of resin composition and multilayer structure A pellet-shaped resin composition was produced in the same manner as in Example 1, except that EVOH (A) was 20 parts by weight and EVOH (B) was 80 parts by weight. Next, a sheet composed of a polystyrene layer / a contact resin layer, the resin composition layer / a contact resin layer / a polystyrene layer was produced using a feed block type three-type five-layer co-extrusion apparatus. The polystyrene used was Idemitsu Styrol ET-
61. The adhesive resin is Mersen M5420 manufactured by Tosoh. The thickness configuration of the sheet was 800 μ / 50 μ / 50 μ / 50 μ / 800 μ. Next, the sheet was subjected to 13
Thermoforming (SPPF molding) was performed at 0 ° C. under the conditions of a stretching speed of 9 × 10 ⁵ % / min, a drawing ratio of 1, and a stretching area magnification of 7 times. The obtained cup-shaped container had a good appearance without cracks, uneven thickness and the like.

(3) Evaluation of Gas Barrier Property In the same manner as in Example 1, the oxygen permeation amount of the cup-shaped container was measured at 20 ° C., 65% RH and 100% RH. The results are shown in Table 1. Both the appearance of the container and the gas barrier properties were very good.

Comparative Example 5 As EVOH (A), ethylene content 70 mol%, degree of saponification 98.8 mol%, syndiotacticity 52 mol%, MI
A pellet-shaped resin composition was prepared in the same manner as in Example 4 except that a saponified ethylene-vinyl acetate copolymer of 15 g / 10 min was used, and then sheet molding and thermoforming were performed. The gas barrier property of the container was measured. The results are shown in Table 1. Many cracks, uneven thickness, poor appearance,
The gas barrier properties were also poor.

Example 5 A pellet-shaped resin composition comprising EVOH (A) and EVOH (B) used in Example 4 and an intrinsic viscosity [η] = 0.70
Using dl / g polyethylene terephthalate (PET), a PET layer / co-injection / co-stretch blow molding machine manufactured by Nissei ASB
A two-layered three-layer bottle-shaped container of the resin layer composition layer / PET layer was formed. The stretching temperature was 100 ° C. and the stretching speed was 5 × 1
0 ^6% / min, and the areal draw ratio 10 times. The bottle-shaped container had no vertical stripe-like thickness unevenness, cracks, etc., and had good gas barrier properties as shown in Table 1.

Comparative Example 6 As EVOH (B), ethylene content 32 mol%, degree of saponification 75.6 mol%, syndiotacticity 61 mol%, MI
A pellet-shaped resin composition was produced in the same manner as in Example 5 except that a saponified ethylene-vinyl pivalate copolymer of 6.0 g / 10 minutes was used. The container was molded. The bottle-shaped container had many vertical streak-like thickness unevenness, and the gas barrier property was extremely poor as shown in Table 1.

F. Effects of the InventionThe resin composition of the present invention and the multilayer structure using the same have excellent heat stretchability and gas barrier properties, particularly excellent gas barrier properties under high humidity conditions, and are extremely useful in the food packaging field and the like. Useful.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08L 23/00-23/36 C08L 29/00-29/04

Claims (3)

(57) [Claims] 1. Ethylene having an ethylene content of 20 to 65 mol%.
90 to 10 parts by weight of a vinyl alcohol copolymer (A), an ethylene content of 20 to 65 mol%, and an ethylene-vinyl alcohol copolymer (B) 10 having a diotacticity of 55 mol% or more in diat representation A resin composition comprising up to 90 parts by weight. 2. The resin composition according to claim 1, wherein the ethylene content of (A) differs from the ethylene content of (B) by at least 10 mol%. 3. A multilayer structure having a thermoplastic resin layer on at least one surface of a layer comprising the resin composition according to claim 1.