JPH0360732B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a stretched multilayer plastic container, and more specifically, it has excellent gas barrier properties,
Stretched multilayer plastic containers having a combination of delamination resistance and mechanical properties. (Conventional technology) Polyethylene terephthalate has excellent moldability and is capable of biaxial molecular orientation, making it a lightweight product with excellent impact resistance, rigidity, gas barrier properties, light weight, and transparency. plastic container,
It has come to be widely used as a beverage bottle. However, the gas permeability of polyester bottles is still not negligible compared to glass bottles, and the shelf life of bottles filled with carbonated drinks such as cola is said to be about 3 months at most. In order to improve the gas barrier properties of such stretched polyester containers, resins with excellent gas barrier properties such as ethylene vinyl alcohol copolymer or polyamide are laminated onto polyester. Containers using composite laminates in which a resin is used as an intermediate layer and polyester is laminated as a surface layer on both sides have been proposed (for example, Japanese Patent Application Laid-open No. 136253/1983, Japanese Patent Application Laid-Open No. 1983-1999)
-60436). (Problem to be solved by the invention) However, there is almost no thermal adhesion between the ethylene vinyl alcohol copolymer layer or polyamide layer and the polyester layer, and even if they are bonded using an adhesive, Even if the laminate exhibits good adhesion in an unstretched state, it has the disadvantage that it easily peels off at the adhesive interface when the laminate is stretched to impart a molecular blend. For example, copolyester adhesives and copolyamide adhesives that have been conventionally proposed for bonding polyester layers and polyamide layers both have the above-mentioned tendency, and are still sufficiently satisfactory as adhesives for stretched multilayer plastic containers. It's not possible. Additionally, amide group-containing thermoplastic resin adhesives have been proposed for bonding the polyester layer and the ethylene vinyl alcohol copolymer layer, but these are not necessarily fully satisfactory. Therefore, it is formed from a multilayer laminate of a polyester layer and a resin layer with excellent gas barrier properties, and even after stretching, it has excellent delamination resistance, especially blister resistance, and has gas barrier properties, impact resistance, and rigidity. Furthermore, there was a need to provide a stretched multilayer plastic container with excellent transparency. (Structure of the Invention) According to the present invention, the present invention comprises an inner and outer surface layer made of polyester, an intermediate layer made of an ethylene-vinyl alcohol copolymer, and an adhesive layer interposed between the inner and outer surface layers and the intermediate layer. A multilayer plastic container is provided in which the adhesive layer comprises a sulfonic acid group-containing copolyester layer on the polyester side and a polyamide layer on the ethylene-vinyl alcohol copolymer side. Further, according to the present invention, the adhesive layer comprises an inner and outer surface layer made of polyester, an intermediate layer made of an ethylene-vinyl alcohol copolymer, and an adhesive layer interposed between the inner and outer surface layers and the intermediate layer. Stretched multilayer plastic characterized in that a sheet or preform with a multilayer structure consisting of a sulfonic acid group-containing copolyester layer on the polyester side and a polyamide layer on the ethylene-vinyl alcohol copolymer side is formed into a container shape under stretching conditions. A method of manufacturing a container is provided. (Operations and Effects of the Invention) The present invention combines a polyester layer and an ethylene-vinyl alcohol copolymer layer with an adhesive layer consisting of a sulfonic acid group-containing copolyester layer on the polyester side and a polyamide layer on the ethylene-vinyl alcohol copolymer side. This is based on the unexpected finding that a structure formed by laminating the above materials maintains excellent adhesive strength without causing delamination even when subjected to stretch molding. Table 1 below shows how unstretched polyethylene terephthalate film (thickness: 400 μm) and unstretched nylon 6/nylon 66 copolymer were bonded using various conventionally known adhesives and the sulfonic acid group-containing copolyester adhesive used in the present invention. Combined film (thickness 100μ)
m), and the adhesive strength of this laminated film and the adhesive strength of a biaxially stretched film obtained by biaxially stretching this laminated film twice in the longitudinal direction and twice in the transverse direction are shown.

【table】

[Table] According to the results in Table 1 above, although the adhesives of Samples 1 to 4 exhibit considerably high adhesive strength in the unstretched state, they all show a significant decrease in adhesive strength after stretching and forming. , in the sulfonic acid group-containing copolyester (sample 5) of the present invention,
It is clear that the degree of decrease in adhesive strength after stretch molding is significantly small, and exhibits greater adhesive strength than Samples 1 to 4 even after stretch molding. The sulfonic acid group-containing copolyester used in the present invention has a chemical structural feature in that the main chain consists of repeating ester units, and the sulfonic acid group is bonded to this main chain. Therefore, it is presumed that this adhesive not only bonds extremely strongly to polyethylene terephthalate, but also forms a strong chemical bond between the sulfonate and polyamide. Further, polyamide and ethylene-vinyl alcohol copolymer can be easily and extremely firmly thermally bonded. Therefore, the multilayered plastic of the present invention maintains strong adhesive strength between each layer of the polyester layer, the sulfonic acid group-containing copolyester layer, the polyamide layer, and the vinyl-ethylene copolymer layer even after stretching. As a result, even when this container is subjected to a drop impact, delamination is prevented from occurring, and furthermore, even when filled with contents such as carbonated drinks or beer, the polyester layer and ethylene-
This effectively eliminates the problem of blisters, etc. occurring at the joint with the vinyl alcohol copolymer layer. Furthermore, the excellent gas barrier properties of the ethylene-vinyl alcohol copolymer provided in the intermediate layer can be sufficiently effective, and since the polyester layer has been molecularly oriented by stretching, it has excellent gas barrier properties. Barrier properties, delamination resistance, impact resistance,
A multilayer plastic container with excellent rigidity or even transparency is provided. (Description of preferred embodiments of the invention) Adhesive layer The adhesive layer in the present invention is formed of two layers: a sulfonic acid group-containing copolyester layer and a polyamide layer. As described above, the sulfonic acid group-containing copolyester layer is bonded to the polyester layer;
The polyamide layer is used in conjunction with the ethylene-vinyl alcohol copolymer layer. This sulfonic acid group-containing copolyester is
As already mentioned, it refers to a copolyester consisting of a main chain skeleton consisting of repeating ester units and a sulfonate group bonded to this main chain skeleton. Of course,
The adhesive may consist of the above-mentioned copolyester alone or may be a blend of the above-mentioned copolyester and a conventional polyester containing no sulfonic acid groups. In the present invention, copolyester is used in the above-mentioned meaning. The concentration of sulfonate groups in the copolyester used in the present invention ranges from 1 to 1 per 100 g of adhesive.
Preferably it is present in an amount of 520 mmol, especially in the range 5 to 300 mmol. If this concentration is lower than the above range, adhesion with polyamide will be insufficient, while if it is higher than the above range, stretchability will be reduced, or adhesion with polyester will be insufficient. There is a tendency for defects to occur in the thermal stability of the copolyester itself. As the sulfonate, alkali metal salts such as sodium salts, potassium salts, and lithium salts are suitable, but alkaline earth metal salts such as calcium salts and magnesium salts, and zinc salts are not particularly prohibited. In order to incorporate a unit having a sulfonate group into the polyester skeleton, a component containing a sulfonate group may be used as part of the dibasic acid component and/or diol component for forming the polyester. Generally, it is preferable to use a dibasic acid component containing a sulfonic acid group. A suitable example of such a component is sodium 3,5-di(carboxy)benzenesulfonate.
Examples include potassium di(carboxy)benzenesulfonate, magnesium 3,5-di(carboxy)benzenesulfonate, and functional derivatives thereof, such as esters with methyl alcohol, ethyl alcohol, ethylene glycol, and the like. Other examples include sodium sulfosuccinic acid, sodium sulfoterephthalic acid, 4-sodium sulfonaphthalene-2,7-dicarboxylic acid, and lower alcohol esters thereof. The dibasic acids constituting this copolyester include benzene dicarboxylic acids such as terephthalic acid and isophthalic acid, other aromatic dicarboxylic acids such as naphthalene dicarboxylic acid; succinic acid, adipic acid, azelaic acid, sebacic acid, dodecane acid, etc. Examples include aliphatic dicarboxylic acids such as dicarboxylic acid; or alicyclic dicarboxylic acids such as hexahydroterephthalic acid; diol components include ethylene glycol, propylene glycol, butanediol, diethylene glycol, neopentyl glycol, and hexane. Aliphatic diols such as diol; cyclic glycols such as cyclohexane diol, xylylene glycol, bisphenol A, and bisphenol F; and the like. In the copolyester used in the present invention, terephthalic acid accounts for 50 mol% or more, particularly 85 mol% or more of the total dibasic acid component, excluding those introduced as sulfonic acid metal base-containing units, and Preferably, 50 mol% or more, especially 85 mol% or more of ethylene glycol. The copolyester used should have sufficient molecular weight to form a film. In addition, polyamides include aliphatic, aromatic,
Polyamides or copolyamides made from aromatic aliphatic diamines and aliphatic, aromatic dicarboxylic acids, or aliphatic, aromatic, araliphatic aminocarboxylic acids or lactams thereof, or mixtures thereof can be used. Such polyamides are known per se, and from the viewpoint of gas barrier properties against oxygen, carbon dioxide, etc., the number of amide groups per 100 carbon atoms in the polyamide is 3 to 30, particularly 4 to 25. It is preferable to use homopolyamides, copolyamides, or blends thereof within the range of . Examples of suitable homopolyamides are: polycapramide (nylon 6) poly-ω-aminoheptanoic acid (nylon 7) poly-ω-aminononanoic acid (nylon 9) polyundecaneamide (nylon 11) polylaurinlactam (nylon 12) polyethylene diamine Adipamide (nylon 2,
6) Polytetramethylene adipamide (nylon 4,
6) Polyhexamethylene adipamide (nylon 6,
6) Polyhexamethylene sebamide (nylon 6,
10) Polyhexamethylene dodecamide (nylon 6,
12) Polyoctamethylene adipamide (nylon 8,
6) Polydecamethylene adipamide (nylon 10, 6) Polydodecamethylene sebacamide (nylon 10,
8) etc. Examples of suitable copolyamides include caprolactam/laurinlactam copolymer, caprolactam/hexamethylene diammonium adipate copolymer, lauryl lactam/hexamethylene diammonium adipate copolymer, hexamethylene diammonium adipate/hexamethylene diammonium Sebacate copolymer, ethylene diammonium adipate/hexamethylene diammonium adipate copolymer, caprolactam/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer, and the like. These homopolyamides and copolyamides are
It can also be used in the form of a so-called blend; for example, a blend of polycaprolactam and polyhexamethylene adipamide, a blend of polycaprolactam and a caprolactam/hexamethylene diammonium adipate copolymer, etc. can all be used for the purpose of the present invention. It is possible. In addition, it is slightly inferior in moldability compared to the above-mentioned aliphatic polyamide, but it is disclosed in, for example, Japanese Patent Publication No. 1156/1983, Japanese Patent Publication No. 5751/1982, Japanese Patent Publication No. 5753/1982, and Japanese Patent Publication No. 10196/1982. , Japanese Patent Publication No. 50-29697
Meta-xylylene diamine, or mixed xylylene diamine containing 30% or less of para-xylylene diamine in the meta-xylylene diamine and the diamine, as described in the above publication, and α having 6 to 10 carbon atoms. , ω-aliphatic dicarboxylic acid and at least 70 structural units in the molecular chain.
Aromatic polyamides containing mole % can also be used. Furthermore, an aromatic dicarboxylic acid containing metaxylylene diamine or mixed xylylene diamine containing not more than 30% of waxylylene diamine in the metaxylylene diamine and the diamine and isophthalic acid in an amount of 30 mol% or more, preferably 40 mol% or more. It is also possible to use aromatic polyamides containing at least 70 mol % of structural units produced from and in the molecular chain. Furthermore, metaphenylene diamine and/or
or paraphenylenediamine and isophthalic acid
Aromatic polyamides containing 30 mol % or more, preferably 40 mol % or more can also be used. Generally speaking, the molecular weight of these polyamides can be used without any particular restriction as long as they are within the range that allows film forming. It is generally desirable that the relative viscosity (ηrel) is from 0.2 to 3.5, particularly from 0.3 to 3.0. If the relative viscosity is greater than 3.5, the moldability of the polyamide will be poor, and if the relative viscosity is less than 0.2, the adhesive strength will be poor. Polyester The polyester used in the present invention usually contains 50 mol% or more, preferably 70 mol% or more of ethylene terephthalate structural units. Carbon number 2 to 4
It is a polyester obtained from an alkylene glycol and an aromatic dicarboxylic acid. As the alkylene glycol, ethylene glycol is mainly used, but in addition to ethylene glycol,
For example, 1,3-propanediol and 1,4-butanediol can be used in an amount that satisfies the content of the above-mentioned ethylene terephthalate structural units. Further, as the aromatic dicarboxylic acid, terephthalic acid is mainly used, but in addition to terephthalic acid, for example, isophthalic acid, phthalic acid, taffeline dicarboxylic acid, etc. Can be used in limited quantities. Among these, polyethylene terephthalate is particularly preferred for practical purposes. Intrinsic viscosity [η] of the polyester (in phenol-tetrachloroethane mixed solvent (weight ratio 1/
1) measured at 25℃) is usually 0.5 to 1.5 dl/
g, preferably 0.6 to 1.2 dl/g, the melting point is usually 210 to 265°C, preferably 220 to 260°C, and the glass transition temperature is usually 50 to 120°C, preferably 60 to 100°C. The polyester may contain appropriate amounts of various additives such as a nucleating agent, an inorganic filler, a lubricant, a slip agent, an anti-blocking agent, a stabilizer, an antistatic agent, an antifogging agent, and a pigment, as necessary. It may be blended. Ethylene-vinyl alcohol copolymer The ethylene-vinyl alcohol copolymer used in the present invention is preferably a copolymer containing 50 mol% or less of ethylene in order to improve gas barrier properties. As is already known, polyvinyl alcohol is not thermoformable unless special processing methods are used, but ethylene-vinyl alcohol copolymers show a decrease in melting point and an increase in thermoplasticity as the ethylene content increases. bring. Since the ethylene-vinyl alcohol copolymer is stretch-molded together with the polyester resin as described below, it is normally assumed that the melting point is as low as possible and the temperature at which it can be stretched is as low as possible, but here, the melting point and stretching temperature are A high-quality ethylene-vinyl alcohol copolymer is selected. The first reason is that when the ethylene component exceeds 50 mol%, the melting point is low.
The temperature at which it can be stretched is low, which is convenient for co-stretching with the polyester resin layer, but if the ethylene component increases, the gas barrier properties will drop sharply, so there is no point in creating multiple layers of polyester resin. The second reason is that even if the ethylene-vinyl alcohol copolymer has a low ethylene content and a high vinyl alcohol content, according to the present invention, as will be described in detail later, it is possible to form a multilayer structure with a polyester resin. It was discovered that the ethylene-vinyl alcohol copolymer layer can be stretched even at the appropriate stretching temperature for polyester resin. In other words, those with a high vinyl alcohol content were selected. In the present invention, as the ethylene-vinyl alcohol copolymer, a copolymer obtained by saponifying a copolymer with a vinyl ester such as ethylene-vinyl acetate is used. Considering molding workability and barrier properties, Ethylene content is 15 to 50 mol%,
In particular, those with a saponification degree of 25 to 45 mol% and a saponification degree of 96% or more are advantageously used. The molecular weight of this copolymer may be any as long as it has film-forming ability. Multilayer Plastic Container In the container of the present invention, the main melting portion is made of plastic having a multilayer structure. This multilayer structure includes: polyester layer/sulfonic acid group-containing copolyester layer (adhesive layer)/polyamide layer (adhesive layer)/ethylene-vinyl alcohol copolymer layer/
It has a seven-layer structure consisting of a polyamide layer (adhesive layer)/sulfonic acid group-containing copolyester layer (adhesive layer)/polyester layer. The thickness of the polyester layer is usually 3 to 4000μ
m, preferably 5 to 1500 μm, and the thickness of the ethylene-vinyl alcohol copolymer layer is usually 1
350 μm to 350 μm, preferably 2 to 200 μm,
The thickness of both the sulfonic acid group-containing copolyester layer and the polyamide layer is typically 0.5 to 200μ.
m, preferably 1 to 50 μm. The total thickness of the plastic with multilayer structure is between 0.1 and 4
mm, preferably 0.15 to 1 mm. The ratio between the total thickness of the polyester layer and the thickness of the blend layer is between 2:1 and 100:1, especially between 4:1 and 50:1.
Preferably, it is within the range of 1. At least one of the plastics having a multilayer structure
The polyester layers of the layer, preferably all the polyester layers, more preferably all the polyester layers and the blend layer, are oriented. The stretching is carried out in at least one axial direction, preferably in two axial directions perpendicular to each other. From the viewpoint of strength and gas barrier properties, it is preferable that the film be stretched in two axial directions. The stretching ratio is usually 1.1 to 10 times, preferably 1.2 to 8 times, and more preferably 1.5 to 7 times. Furthermore, the multilayer plastic can also be heat set depending on its intended use. In the multilayer plastic of the present invention, a sulfonic acid group-containing copolyester layer and a polyamide layer are bonded together to form an adhesive layer, and the sulfonic acid group-containing copolyester layer of the adhesive layer is bonded to the polyester layer, and the adhesive layer The polyamide layer is ethylene-
It adheres to the vinyl alcohol copolymer layer, forming the above-mentioned multilayer structure centered on the ethylene-vinyl alcohol copolymer layer, and the sulfonic acid group-containing copolyester layer, polyamide layer, and polyester layer. The affinity adhesive strength is high, and the affinity adhesive strength between the polyamide layer and the ethylene-vinyl alcohol copolymer layer is also high, so even if the multilayer plastic is stretched uniaxially or biaxially, it will not cause delamination and can be stretched to the required degree. It can be stretched sufficiently according to the requirements. Method for manufacturing a container The stretched multilayer plastic container of the present invention having the above-mentioned excellent features is based on the second invention of the present application, namely, an inner and outer surface layer made of polyester, an intermediate layer made of an ethylene-vinyl alcohol copolymer, and the inner and outer surfaces. A multilayer sheet consisting of an adhesive layer interposed between a layer and an intermediate layer, the adhesive layer comprising a sulfonic acid group-containing copolyester layer on the polyester side and a polyamide layer on the ethylene-vinyl alcohol copolymer side; or The preform can be produced by a method for producing stretched multilayer plastic containers characterized in that the preform is formed into the shape of the container under stretching conditions. In the manufacturing method of the present invention, when manufacturing a container from a multilayered sheet having the above structure, the container is manufactured by a sheet stretch molding method known per se, except that the multilayered sheet having the above structure is formed. can be manufactured. For example, a sheet of the above-mentioned multilayer plastic of the present invention is formed using an extruder equipped with a multilayer die, and the sheet is uniaxially or biaxially stretched;
Alternatively, without stretching, a container of a desired shape can be produced by stretch forming by a method such as a vacuum forming method, a pressure forming method, a sheet blow molding method, a drawing method, a drawing/ironing method, or a compression molding method. I can do it. In addition, the multilayer plastic sheet can be prepared by separately molding polyester, polyamide, and sulfonate-containing copolyester into a sheet or film, and then uniaxially or biaxially stretching or not stretching. It can also be manufactured by laminating layers to form a structure and then heat-pressing them. In the manufacturing method of the present invention, when manufacturing a container from a multilayer preform having the above structure,
The container can be manufactured by blow molding methods known per se, except that the multilayer structure of the preform and the material of construction are specified according to the invention. For example, a multilayer parison can be produced by using four or more extruders to extrude the four types of molten resins used in the present invention in a laminated form as described above in a multilayer die. Molding and closing one end of the parison to make a bottomed parison (preform),
After heating at a predetermined temperature for a predetermined time in a mold that fits the desired container shape, the preform is stretched in the axial (longitudinal) direction of the preform using a stretching rod.
There is a method of horizontally stretch blow molding in a mold using compressed air. The preform may be molded by injection molding. The stretching conditions when manufacturing containers by stretch-molding sheets or preforms vary depending on the resin used, but stretching should be carried out at a temperature that is above the glass transition temperature and below the crystallization initiation temperature of the resin used. is preferably stretched in at least one axial direction, preferably in two axial directions, and the stretching ratio is usually 1.1 to 1.1.
The resin layer of the resulting container is stretched by 10 times, preferably 1.2 to 8 times, more preferably 1.5 to 7 times, so that the resin layer has molecular orientation. Applications The multilayer plastic container of the present invention is suitable for liquid or pasty foods and beverages, such as beer and other low-malt beer, alcoholic beverages including fruit liquors such as alcohol, whisky, shochu and grape wine, and various cocktails such as Jinfu's; Various carbonated drinks including cola, cider, plain soda, etc.; Fruit juice drinks including straight juices such as lemon juice, orange juice, plum juice, budo juice, strawberry juice, and processed fruit juice drinks such as nectar; tomato juice and various vegetable juices. vegetable juice drinks containing; synthetic drinks and vitamin-enriched drinks containing synthetic fruit juices made with sugars such as sugar or fructose, citric acid, coloring agents, flavorings, etc., or vitamins added as necessary; lactic acid bacteria drinks; For example, rice oil, sauce, vinegar, mirin, dressing, mayonnaise, ketchup, cooking oil, miso, lard,
Seasonings such as ketchup; condiments such as tofu, jam, butter, and margarine; liquid medicines,
Pesticides, cosmetics, cosmetics, detergents; Also, ketones such as acetone and methyl ethyl ketone; aliphatic hydrocarbons such as normal hexane and normal heptane; alicyclic hydrocarbons such as cyclohexane;
Aromatic hydrocarbons such as benzene, toluene, and xylene; chlorine-containing compounds such as carbon tetrachloride, ethane tetrachloride, and ethylene tetrachloride; or various higher fatty acids;
Gasoline, kerosene, petroleum benzene, heavy oil, thinner, grease, silicone oil, light oil, machine oil; Useful as a container. Example 1 Polyethylene terephthalate (PET) with an intrinsic viscosity of 1.06 at 30°C was used as the inner and outer polyester layers,
The intermediate layer is an ethylene-vinyl alcohol copolymer (EVOH-1) with a vinyl alcohol content of 69.0 mol%, an ethylene content of 30.6 mol%, and a vinyl acetate residue of 0.4 mol%, and a sodium sulfonate group is used as a polymer. Copolyester (S-1) containing 250 mmol per 100 g was used as the adhesive layer on the polyester side, and caprolactam/hexamethylene diammonium adipate copolymer (nylon 6/6,6 copolymer, N-
1) is the adhesive layer on the ethylene-vinyl alcohol copolymer side, and an extruder with a built-in screw with a diameter of 65 mm and an effective length of 1820 mm is used as an extruder for the PET layer, and an extruder with a built-in screw with a diameter of 50 mm and an effective length of 1400 mm is used. The extruder for S-1 layer is 38mm in diameter and 950mm in effective length.
An extruder with a built-in screw is used as an extruder for the N-1 layer, and an extruder with a built-in screw with a diameter of 38 mm and an effective length of 912 mm is used as an extruder for the EVOH-1 layer.
Using a 7-layer feedblock, a single manifold T-type die, a 3-roll sheet forming machine with a diameter of 40 mm, and a traveling cutter,
PET layer/S-1 layer/N-1 layer/EVOH-1 layer/
The total thickness of the symmetrical four-type seven-layer structure consisting of N-1 layer/S-1 layer/PET layer is 3.2 mm (PET/S-1/N-
1/EVOH-1=88/3/3/6 thickness ratio), width
A 350mm sheet was molded. The density of PET, which is the inner and outer surface layer of the obtained sheet, at 20℃ is 1.339
g/ ^cm3 . Next, this sheet is punched into a disc-shaped blank with a diameter of 75 mm, and this blank is heated using an infrared heater.
After heating to 110℃, press molding into inner diameter 65mm and height 100mm.
It was molded into a can-shaped container with a mm flange. Oxygen gas permeability of this can-shaped container (permeation permeated into the container during storage at 28℃ and 60% relative humidity for one month after heat-sealing the can-shaped container with aluminum foil/copolyester multilayer film in a nitrogen gas atmosphere) The amount of oxygen was measured using a gas chromatograph), and a rectangle (diameter in the height direction of the container) was cut out from the container body wall to measure the delamination strength. Comparative Example 1 Polyethylene terephthalate (PET) and ethylene-vinyl alcohol copolymer (EVOH-1) used in Example 1 were used, and the sodium sulfonate group-containing copolyester (S- 1), the 65 mm extruder used in Example 1 was used as the PET layer extruder, the 50 mm extruder was used as the S-1 layer extruder, and the 38 mm extruder was used as the EVOH-1 extruder.
As a layer extruder, a 5-layer feedblock, a single manifold T-type die, a 3-roll sheet molding machine with a diameter of 40 mm, and a traveling cutter are used to form PET layer/S-1 layer/EVOH-layer/S
-The total thickness of the symmetrical 5-layer structure of 3 types consisting of 1 layer/PET layer is 3.2 mm (PET/S-1/EVOH=88/6/
6 thickness ratio) and a width of 350 mm. The density of the PET on both the inner and outer surfaces of the obtained sheet at 20°C was 1.339 g/cm ³ . Next, in the same manner as in Example 1, this sheet was punched into a blank and press-molded to form a can-shaped container having the same shape as in Example 1. Example 1 The oxygen gas permeability of this container and the delamination strength of the container body wall were measured
It was measured in the same manner. Comparative Example 2 The nylon 6/6,6 copolymer (N-1) used in Example 1 is used as an adhesive instead of the sulfonate sodium group-containing copolyester (S-1) used in Comparative Example 1. Other than that, PET/N-1/EVOH-1/N-1/PET was prepared in the same manner as Comparative Example 1.
Three types of five-layer can-shaped containers were molded, and the oxygen gas permeability and interlayer peel strength of the containers were measured. The evaluation results of the can-shaped containers of Example 1, Comparative Example 1, and Comparative Example 2 are summarized in Table 2.

【table】

Claims (1)

[Claims] 1 Consists of an inner and outer surface layer made of polyester, an intermediate layer made of an ethylene-vinyl alcohol copolymer, and an adhesive layer interposed between the inner and outer surface layers and the intermediate layer, the adhesive layer being A stretched multilayer plastic container comprising a sulfonic acid group-containing copolyester layer on the polyester side and a polyamide layer on the ethylene-vinyl alcohol copolymer side. 2. Claim 1, wherein at least the polyester layer is stretched in at least one axis direction and has molecular orientation.
Containers listed in section. 3 The content of sulfonic acid groups in the sulfonic acid group-containing copolyester is
A container according to claim 1, characterized in that the amount is 1 to 520 mmol per portion. 4 Consisting of an inner and outer surface layer made of polyester, an intermediate layer made of an ethylene-vinyl alcohol copolymer, and an adhesive layer interposed between the inner and outer surface layers and the intermediate layer, the adhesive layer being a sulfonic acid base on the polyester side. 1. A method for producing a stretched multilayer plastic container, which comprises forming a multilayered sheet or preform comprising a copolyester containing layer and a polyamide layer on the ethylene-vinyl alcohol copolymer side into a container shape under stretching conditions.