JP3466284B2 - How to clean and reuse used plastic containers - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for cleaning and reusing used plastic containers.

[0002]

2. Description of the Related Art Various contents are filled and distributed in plastic containers made of polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, etc., but most containers are one-way. Except for glass bottles, the method of refilling the contents in a container returned by the consumer and distributing the contents is rarely performed. The reason why the plastic container is not used repeatedly is that once the contents are filled, the components in the contents will sorb to the plastic container, and the sorbent can be easily removed even if the plastic container is washed with warm water before refilling. This is because the flavor of the newly filled contents may change.

JP-A-54-94985 discloses that an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) is formed on the surface.
(Hereinafter abbreviated) solution-coated gas barrier tube. However, there is no description in the publication regarding collecting used containers, washing them with warm water, and filling the contents again. Further, this publication relates to improvement of gas barrier property, and as can be seen from the drawings attached to the specification, the coated surface is the outermost layer, and there is no description about reusability of the container and easy removal of sorbed material. It is known that the gas barrier property of the ethylene-vinyl alcohol copolymer is deteriorated in a high humidity region, and it is generally used for the intermediate layer or the outermost layer without directly contacting the contents.

In Japanese Unexamined Patent Publication (Kokai) No. 59-231731, there is ethylene-based resin on at least the outer surface of the body wall of a thermoplastic polyester container having a biaxially stretched container body.
It describes a method of treating a thermoplastic polyester container, which comprises coating a coating agent consisting of a solvent solution containing a vinyl alcohol copolymer as a film-forming component and drying it to form a coated synthetic resin layer. However, there is no description in the publication that the used container is recovered, washed with warm water, and refilled with the contents.

Japanese Unexamined Patent Publication (Kokai) No. 63-3950 describes a liquid container containing a paperboard substrate and an ethylene-vinyl alcohol copolymer layer. However, since the paper board is used, which has a different structure from that of the present invention, the paper absorbs water during washing with warm water, which causes a problem such as a decrease in strength. In addition, there is no description in the publication that the used container is recovered, washed with warm water, and refilled with the contents.

Japanese Unexamined Patent Publication (Kokai) No. 54-11028 describes a multilayer packaging material in which the innermost layer is a film or sheet made of a saponified ethylene-vinyl acetate copolymer. However, the used container is also collected in the publication,
There is no description about washing with warm water and filling the contents again.

In Japanese Patent Laid-Open No. 2-90980, in a method of spray cleaning a plastic bottle using a heated cleaning liquid, the bottle to be cleaned is heated in advance to a temperature equal to or higher than the temperature of the cleaning liquid. The method for cleaning a bottle is described. But,
The publication is intended to shorten the spray cleaning time by heating the bottle to be cleaned in advance, and there is no description about collecting the used container, cleaning with warm water, and filling the contents again.

Japanese Unexamined Patent Publication (Kokai) No. 5-116207 discloses a polyethylene naphthalate, 70 ° C., 3% NaOH.
Refillable bottles with good transparency in aqueous solution are described. However, this publication relates to polyethylene naphthalate and does not describe EVOH. Further, polyethylene naphthalate is an expensive resin, and it is required to be improved in terms of economical efficiency.

[0009]

[Problems to be Solved by the Invention] A plastic container that can be repeatedly used by removing the sorbed material by washing the plastic container with warm water before refilling is better than the industry because of environmental problems due to waste and resource saving measures. Coveted.

The present invention was devised in order to solve the above-mentioned drawbacks of the prior art. The sorption is small, and even if the sorption amount is large, the sorbed material can be easily washed by warm water washing. The purpose is to obtain a plastic container that can be removed and recovered and reused.

[0011]

The above object is to provide an EVOH layer having a body portion thickness of 1 to 30 μm, an ethylene content of 20 to 65 mol%, and a saponification degree of a vinyl ester component of 90 mol% or more as an innermost layer. Hot water in a used plastic container
It is achieved by washing .

The present invention will be described in more detail below. In the present invention, the plastic container is one in which an EVOH layer is provided as the innermost layer of a container using a thermoplastic resin as a substrate.
Here, as the thermoplastic resin used for the substrate of the container,
Polymers containing ethylene terephthalate as the main component, polymers containing butylene terephthalate as the main component, polymers containing ethylene naphthalate as the main component, polyesters such as aromatic polyesters, polymers containing carbonate as the main component, and propylene as the main component. Examples thereof include polymers, polymers containing ethylene as a main component, polymers containing methylpentene as a main component, and polymers containing acrylonitrile as a main component. Of these, polyesters, especially polyethylene terephthalate, polyethylene naphthalate and acrylonitrile-styrene copolymers are preferable from the viewpoints of transparency, mechanical strength, oxygen barrier property, carbon dioxide gas barrier property and non-sorbing property.

The substrate may be a single layer of the above-mentioned thermoplastic resin alone or a blend thereof, and EVOH, vinylidene chloride, nylon MXD for imparting gas barrier properties.
It may be a multi-layer body having an intermediate layer of a polymer containing 6, acrylonitrile, ethylene naphthalate or the like as a main component.

As the polyester, ethylene glycol, diethylene glycol, trimethylene glycol,
Propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, glycerin, Polyhydric alcohol components such as trimethylolpropane and pentaerythritol, and hydroxycarboxylic acid components such as parahydroxybenzoic acid, δ-valerolactone, ε-caprolactone and tartaric acid, terephthalic acid, isophthalic acid and 2,6-naphthalene dicarboxylic acid. , Azelaic acid, sebacic acid, pimelic acid, adipic acid, glutaric acid, succinic acid, trimellitic acid, and other polyvalent carboxylic acids, and polyesters obtained from the ester component thereof as a raw material.

As the polymer containing carbonic acid ester as a main component, a dialkyl ester of phosgene or carbonic acid, a monofunctional aromatic or aliphatic dihydroxy compound such as bisphenol A, or its bisalkyl carbonate, bisallyl carbonate or bischlorocarbonic acid. Examples thereof include polycarbonate obtained using an ester or the like as a raw material.

Further, as the polymer containing propylene as a main component, a homopolymer of propylene and ethylene, butene-1, pentene-1,4-methylpentene-1, hexene-1, octene containing propylene as a main component. -1,5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 1,4-hexadiene, copolymers with styrene and the like, and those graft-modified with carboxylic acid such as maleic anhydride Can be mentioned.

Further, as the polymer containing ethylene as a main component, high density polyethylene, medium density polyethylene, low density polyethylene which are homopolymers of ethylene,
And ethylene as a main component, propylene, butene-
1,4-methylpentene-1,1-hexene, 1-octene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, styrene, vinyl acetate, methyl acrylate, ethyl acrylate, acrylic acid, methacryl Examples thereof include copolymers with methyl acid, ethyl methacrylate, methacrylic acid, glycidyl methacrylate and the like.
Among the copolymers, the copolymer with acrylic acid or methacrylic acid may be crosslinked with sodium, zinc, aluminum or the like, and the copolymer with vinyl acetate may be a part of the vinyl acetate component or All may be saponified. The polyethylene may be graft-modified with a carboxylic acid such as maleic anhydride.

Further, as the polymer containing acrylonitrile as a main component, nitriles such as acrylonitrile, methacrylonitrile, fumaronitrile and maleonitrile are contained as main components, and styrene, methylstyrene, ethylstyrene, divinylbenzene, halogen-substituted styrene,
Sulfonic acid substituted styrene, methacryl sulfonic acid, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, methacrylic acid, acrylic acid, methyl fumarate, methyl itaconate, methyl maleate, ethyl fumarate, ethyl itaconate , A maleic acid, fumaric acid, itaconic acid, a copolymer with a maleic acid as a hard phase, butadiene, styrene, acrylonitrile, ethylene, isoprene, divinylbenzene, methyl methacrylate, methyl acrylate, ethyl methacrylate, Examples thereof include those obtained by using a copolymer such as ethyl acrylate or 1,3-butylene glycol dimethacrylate as an elastic phase, and acrylonitrile-styrene copolymer.

In the present invention, EVOH means a polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile under pressure in a solvent such as methanol, t-butanol or dimethylsulfoxide. It is a product obtained by polymerization by a known method, followed by saponification with an acid or alkali catalyst. Examples of the fatty acid vinyl ester include vinyl acetate, propionic acid vinyl ester, versatic acid vinyl ester, pivalic acid vinyl ester and the like, and aromatic carboxylic acid vinyl ester can also be used, but from the viewpoint of price, vinyl acetate ester Is preferred. The ethylene content of EVOH is 20 to 65 mol%, preferably 25 to 50 mol%, and the saponification degree of the vinyl ester component is 90 mol% or more.
It is preferably 95 mol% or more. Ethylene content is 2
If it is less than 0 mol%, the hot water resistance is lowered, and if it exceeds 65 mol%, sufficient non-sorption and easy removal of the sorbed material cannot be obtained.
On the other hand, even if the degree of saponification is less than 90 mol%, sufficient non-sorption and easy removal of the sorbate cannot be obtained.

Further, EVOH contains a smaller amount of propylene, isobutene, 4-methylpentene-1, hexene,
Α-Olefins such as octene, unsaturated carboxylic acids such as itaconic acid, methacrylic acid, acrylic acid, maleic anhydride, salts thereof, partial or complete esters thereof, nitriles thereof, amides thereof, anhydrides thereof, vinyltrimethoxysilane, etc. The vinyl silane compound, the unsaturated sulfonic acid such as 2- (meth) acrylamido-2-methylpropanesulfonic acid, a salt thereof, an alkylthiol, and a copolymerization component such as N-vinylpyrrolidone may be contained.

Furthermore, EVOH may be a mixture of two or more kinds of EVOH having different ethylene contents,
Also, two or more types of EVOH with different degrees of polymerization and saponification
It may be a mixture of. Further, the ethylene content and the degree of polymerization or the degree of saponification may be different.

Furthermore, EVOH contains, as far as it does not hinder the present invention, an antioxidant, a colorant, an ultraviolet absorber, a slip agent, an antistatic agent, a plasticizer, a cross-linking agent such as boric acid, an inorganic filler, Various additives such as inorganic desiccant, polyamide,
Various resins such as polyolefin and super absorbent resin may be blended.

Since the thermoplastic resin generally has a small polarity,
It is easy to sorb low-polarity components such as d-limonene, and difficult to sorb high-polarity components such as water and lower alcohols. On the other hand, EVOH has a large polarity, so that a component having a large polarity such as water or a lower alcohol is easily sorbed, and a component having a small polarity is difficult to be sorbed, as opposed to a general thermoplastic resin.

In the present invention, it is important that the innermost layer of the plastic container is the EVOH layer. By providing the EVOH layer in the innermost layer, the sorption of components having a small polarity in the contents can be reduced, while the sorption amount of the components having a large polarity is often increased by providing the EVOH in the innermost layer. The present invention has solved this point, and even if the sorption amount of a component having a large polarity is increased, EVOH swells by washing with warm water or alkaline warm water, and a polar sorbent such as a lower alcohol is easily swelled. As a result, the sorption amount of both the components having a small polarity and the components having a large polarity can be reduced. Therefore, after washing, the contents can be filled in a plastic container and reused.

On the other hand, if EVOH is the outermost layer, EV
Since OH has a good barrier property, carbon dioxide gas accumulates between the substrate and EVOH when filling and storing beer or carbonated drinks, and appearance defects such as delamination are likely to occur. Furthermore, EVOH is likely to be blocked during washing with warm water, and troubles are likely to occur in the washing step, which is not preferable. EV
If OH is the innermost layer, even if the adhesion between the substrate and the EVOH layer is low, there is no fear of delamination, and there is no concern of blocking during washing with warm water.

The longer the washing with warm water, the more preferable it is, but the productivity is lowered, so that it is 3 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, further preferably 10 seconds to 10 minutes. Normal hot water may be used for washing with warm water, but from the viewpoint of sterilization, 0.1 to 3 normal, more preferably 0.2 to 2 normal, and further preferably 0.3 to 2 normal caustic soda and caustic potassium. It is preferable to use an alkaline substance, or an acidic substance such as sulfuric acid or nitric acid, and particularly to use alkaline hot water. When washing with alkali or acid, cold water or warm water washing is necessary to remove the alkali or acid. Washing with warm water has a higher washing effect at higher temperatures, but heat loss and container deformation are more likely to occur at higher temperatures, so the temperature of warm water is 30 to 100 ° C, especially 50 to 80 ° C.
Is preferred. As a cleaning method, a known method such as dipping or shower can be adopted. If oil or oil is attached to the collected plastic container, remove hydrocarbons such as hexane, heptane or benzene before alkali or acid cleaning or warm water cleaning to remove oil or oil. It is desirable to wash with ethers such as methyl cellosolve. Further, when washing with ordinary hot water, acidic or alkaline hot water, hydrocarbons or ethers, 20 to 100 kHz, more preferably 25 to 50 kHz
Irradiation with ultrasonic waves of Hz facilitates removal of solid or oily deposits.

In the present invention, it is important that the thickness of the barrel portion of the innermost EVOH is 1 to 30 μm, preferably 1 to 20 μm, more preferably 2 to 10 μm. If the thickness of the body portion of the innermost layer EVOH is less than 1 μm,
A component having a small polarity permeates EVOH and is sorbed on the substrate, and cannot be removed by washing with warm water. Meanwhile, 30 μm
If it exceeds, it becomes difficult to remove the sorbate of a component having large polarity in EVOH.

In the present invention, a known method can be applied to the method for laminating the EVOH and the substrate. That is, EVOH is used as a preform for the substrate (adhesive or adhesive resin may be present, surface treatment such as corona treatment, flame treatment, etc. may be applied, or they may be used in combination).
Stretch blow after injection or coating and drying, thermoplastic resin and EVOH (adhesive resin may be present in the intermediate layer of both resins) stretch blow after multi-stage injection, thermoplastic resin and EVOH (adhesive Co-extruded sheet from a thermoplastic resin and EVOH (adhesive resin may be present in the intermediate layer of both resins) After heat molding, the plastic container (adhesive or adhesive resin may be present, surface treatment such as corona treatment, flame treatment may be applied, or they may be used together) Examples include a method of coating and drying EVOH. Among these, a method of coating and drying an EVOH emulsion or solution on a plastic container is preferable, and a method of coating and drying an EVOH emulsion is more preferable. Examples of the coating method include dipping and spraying methods. Further, as the layer structure of the plastic container of the present invention,
EVOH may be provided in an intermediate layer (two or more layers) in addition to the innermost layer so that the EVOH layer has two or more layers, and the thermoplastic resin as a substrate may have two or more layers.

In the present invention, the method for producing the EVOH emulsion is not particularly limited, but for example, sodium 2-acrylamido-2-methylpropanesulfonate or the like is randomly introduced into the ionic group in an amount of 0.2 to 10 mol%. 2 to 200 parts by weight of EVOH having an ethylene content of 20 to 65 mol%, a saponification degree of the vinyl ester component of 90 mol% or more and a polymerization degree of 100 to 2000 is used as a dispersion stabilizer, and an ethylene content of 20 to 65 mol% and a vinyl ester component. EVOH having a degree of saponification of 90 mol% or more and a degree of polymerization of 400 to 3000
100 parts by weight of the dispersoid was dissolved in a water / alcohol mixed solvent by heating at 50 to 90 ° C, and then cooled to -10 to 30 ° C.
EVOH particles are precipitated and dispersed (emulsified),
Then, under reduced pressure at a temperature of 10 to 30 ° C. (pressure 10 to 150 m
It is obtained by removing the mHg) alcohol and further removing the desired amount of water. As alcohol here,
Lower alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol are preferable because they are easy to remove alcohol under reduced pressure.

In the present invention, the method for producing the EVOH solution is not particularly limited, but for example, the ethylene content is 20 to 65.
It is obtained by heating and dissolving EVOH having a mol% and a saponification degree of the vinyl ester component of 90 mol% or more and a polymerization degree of 400 to 3000 in a water / alcohol mixed solvent at 50 to 100 ° C. In addition, water / alcohol mixed solvent phenol,
Dimethylsulfoxide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine, formic acid, etc. may be added or they may be directly dissolved. From the viewpoint of easy drying, it is preferable to use a mixed solvent of only water / alcohol,
As the alcohol, lower alcohols such as methanol, ethanol, 1-propanol, 2-propanol and 1-butanol are preferable, and water / 1-propanol or water / 2-propanol mixed solvent is more preferable.

In the present invention, examples of the form of the plastic container include bottles, tubes, cups and trays. In order to facilitate the sealing at the time of reuse, it is desirable that the mouth area such as bottles and tubes is narrower than the cross-sectional area of the center of the body, and the sealing method is preferably the screw cap method rather than heat sealing or winding. .

The plastic containers thus obtained can be used for various beverages such as beer, juice, carbonated drinks, milk, tea, mineral water and other beverages, soy sauce, sauces, edible oils, ketchup, mayonnaise and other seasonings. Contents such as food and industrial products such as motor oil can be filled and reused.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. All parts and% are based on weight unless otherwise specified.

[0034]

【Example】

Example 1 Polyethylene terephthalate (hereinafter abbreviated as PET)
Injection molding a preform with an intrinsic viscosity of 0.7
After heating to a temperature of ° C, stretch blow molding was performed to obtain a bottle having an average thickness of 300 µm and an internal volume of 1.5 l. After flame-treating the inner surface of the bottle, Toyo Morton Co., Ltd.
0.8 g / m 2 of an ethyl acetate solution of adhesive AD-503 / CAT-10 manufactured as a solid component was applied and dried. EVOH having an ethylene content of 32 mol% and a saponification degree of the vinyl ester component of 99.5 mol% dissolved in a water / 1-propanol mixed solvent was 6 g / m 2 (EVOH thickness about 5 μm) as a solid content on the adhesive-coated surface. A container was obtained by applying and drying by dipping.

Methanol having a large polarity and p-xylene (23% by weight of methanol) having a small polarity were filled in the container for 4 hours, and the surface-adhered methanol / p-xylene was removed with n-hexane. A portion was cut out, and the headspace gas at 125 ° C. was subjected to gas chromatographic analysis using toluene as an internal standard. Sorption amount is methanol 35
μg and 100 μg of p-xylene.

In another container, methanol having a large polarity and p-xylene (23 wt% methanol) having a small polarity were filled for 4 hours, and methanol / p-xylene adhering to the surface was removed with n-hexane. 60 more
After filling with warm water at ℃ for 5 minutes and washing with running water, the body was cut out and the headspace gas at 125 ℃ was subjected to gas chromatographic analysis using toluene as an internal standard. Sorption amount is methanol 0.
It was 4 μg and 20 μg of p-xylene, and the sorption amount of the component with large polarity was significantly lower than that before washing with warm water, and the sorption amount of the component with small polarity was also small. There was no p-xylene odor when water was placed in this container and drunk one day later.

Comparative Example 1 In Example 1, P before applying the adhesive and EVOH
Sorption and hot water washing tests were performed under the same conditions as in Example 1 except that the ET single layer container was used.

At the time of sorption, 25 μg of methanol and 150 μg of p-xylene, the sorption amount of methanol was better than in Example 1, but the sorption amount after washing with warm water was 20 μm of methanol.
g and p-xylene were 100 μg, which were both inferior. Water was placed in this container and drunk one day later, but a slight p-xylene odor was felt.

Comparative Example 2 EVOH having an ethylene content of 47 mol% and a saponification degree of a vinyl ester component of 99.5 mol% was melt extruded to 200 μm.
m EVOH film was obtained. The adhesive used in Example 1 as a solid content was applied to the film at 5 g / m 2 and dried,
A sorption and hot water washing test was conducted under the same conditions as in Example 1 except that a PET sheet having a thickness of 1 mm was laminated and then thermoformed to obtain a cup having an EVOH thickness of 50 μm.

90 μg of methanol and 70 μg of p-xylene at the time of sorption, the sorption amount after washing with warm water was 5 μg of methanol,
It was inferior to 35 μg of p-xylene, and the removal rate of components having large polarity was small.

Example 2 Sodium 2-acrylamido-2-methylpropanesulfonate units were randomly introduced into the EVOH component at 1.2 mol%, the ethylene content was 27 mol%, and the saponification degree of the vinyl ester component was 99. 5 mol%, degree of polymerization 800
50 parts by weight of sodium sulfonate-modified EVOH of
50 mol of EVOH with ethylene content of 27 mol%, saponification degree of vinyl ester component of 99.5 mol% and polymerization degree of 1000
Parts by weight were dissolved in a mixed solvent of water / methanol = 50/50 by heating at 65 ° C. to obtain a 10% solution. The solution was cooled at 10 ° C. under stirring to obtain a water / methanol emulsion. Then, with stirring, methanol was distilled off under reduced pressure at 20 ° C. to obtain an aqueous emulsion having a concentration of 20%.

After subjecting the inner surface of the PET bottle used in Example 1 to flame treatment, 2.4 g / m 2 (EVOH thickness about 2 μm) of the EVOH emulsion as a solid content was applied to the treated surface.
It was applied by spraying and dried to obtain a container.

Methanol having a large polarity and p-xylene (23% by weight of methanol) having a small polarity were filled in the container for 4 hours, and the surface-adhered methanol / p-xylene was removed with n-hexane. A portion was cut out, and the headspace gas at 125 ° C. was subjected to gas chromatographic analysis using toluene as an internal standard. Sorption amount is methanol 30
μg and p-xylene 80 μg.

Another container was charged with methanol as a component having a large polarity and p-xylene (23 wt% methanol) as a component having a small polarity for 4 hours, and the surface-adhered methanol / p-xylene was removed with n-hexane. 60 more
After filling and washing with 0.75N caustic soda aqueous solution for 7 minutes, wash the remaining caustic soda with warm water at 60 ° C.
Washed for minutes. The body of the bottle was cut out, and the headspace gas at 125 ° C. was subjected to gas chromatographic analysis using toluene as an internal standard. The sorption amounts were good, with 0.3 μg of methanol and 5 μg of p-xylene.

Example 3 The container obtained in Example 1 was filled with isooctane, the main component of gasoline, for 24 hours, isooctane adhering to the surface was removed with n-hexane, and a 0.75N caustic soda aqueous solution at 60 ° C. was further added. Was spray-washed for 7 minutes, and then the remaining caustic soda was washed with warm water at 60 ° C. for 1 minute. Cut out the body of the bottle and use toluene as an internal standard.
The headspace gas at 0 ° C was analyzed by gas chromatography. The sorbed amount was as good as 13 μg of isooctane.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

As described above, after the plastic container filled with the content has consumed the content under the consumer's sate, the used plastic container is recovered and the sorbent can be easily removed by washing with warm water. Therefore, it is an excellent plastic container that can be repeatedly collected and reused. It includes beer, juice, carbonated drinks, milk, tea, beverages such as mineral water, soy sauce, sauces, edible oil, seasonings such as ketchup and mayonnaise. It can be suitably applied to various foods and industrial products such as motor oils.

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Claims (5)

(57) [Claims] 1. The innermost layer has a container body thickness of 1 to 30.
Use, characterized in that a used plastic container having an ethylene-vinyl ester copolymer saponification layer having a μm, an ethylene content of 20 to 65 mol% and a saponification degree of a vinyl ester component of 90 mol% or more is washed with warm water. How to clean a used plastic container. 2. The method of cleaning a used plastic container according to claim 1, wherein the plastic container includes a layer of polyester. 3. A method for reusing a used plastic container by filling the contents into the plastic container obtained by the method according to claim 1 or 2. 4. The innermost layer has a container body thickness of 1 to 30.
A plastic container obtained by washing a used plastic container with warm water, which has an ethylene-vinyl ester copolymer saponification layer having a μm, an ethylene content of 20 to 65 mol%, and a saponification degree of a vinyl ester component of 90 mol% or more. 5. The plastic container according to claim 4, wherein the plastic container is obtained by coating a polyester container with a saponified product of an ethylene-vinyl ester copolymer and drying.