JPH0427097B2 - - 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,
In particular, they have come to be widely used as beverage bottles. 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. A container using a composite laminate in which a resin is used as an intermediate layer and polyester is laminated as a surface layer on both sides of the intermediate layer has been proposed. (For example, JP-A-59-136253, JP-A-Sho
61-60436). (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 molecular orientation. For example, copolyester adhesives and copolyamide adhesives that have been conventionally proposed for joining polyester layers and polyamide layers both have the above-mentioned tendency, and are still insufficient as adhesives for stretched multilayer plastic containers. It's not something I can be satisfied with. 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 inner and outer surface layers are made of polyester, the intermediate layer is made of a blend of ethylene-vinyl alcohol copolymer and polyamide, and the sulfone layer is provided between the surface layer and the intermediate layer. A stretched multilayer plastic container comprising an acid-base containing copolyester layer is provided. Further, according to the present invention, the inner and outer surface layers are made of polyester, the intermediate layer is made of a blend of ethylene-vinyl alcohol copolymer and polyamide, and the sulfonic acid group-containing copolymer is provided between the surface layer and the intermediate layer. A method for producing a stretched multilayer plastic container is provided, which comprises forming a multilayered sheet or preform of polyester layers into a container shape under stretching conditions. (Operations and Effects of the Invention) The present invention uses a sulfonic acid group-containing copolyester as an adhesive to bond a polyester layer and an ethylene-
It was unexpected that a structure made by laminating layers of a blend of vinyl alcohol copolymer and polyamide maintains excellent adhesive strength without delamination even when subjected to stretch molding. This is based on the knowledge of With the present invention, an ethylene-vinyl alcohol copolymer, which has extremely excellent gas barrier properties but has been difficult to use due to its poor adhesion with polyester, can be used to provide a gas barrier for polyester stretch-molded containers. It became possible to put it to practical use as a material. Table 1 below shows how unstretched polyethylene terethalate film (thickness: 400 μm) and ethylene-vinyl alcohol copolymer were bonded via various conventionally known adhesives and the sulfonic acid group-containing copolyester adhesive used in the present invention. (EVOH) (ethylene content 31 mol%) and nylon 6/nylon 66 copolymer blend (blend ratio EVOH:nylon = 6:4).
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 adhesive strength is greater than that of 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. For this reason, this adhesive not only bonds extremely strongly with polyethylene terephthalate, but also forms a strong chemical bond with the polyamide in the blend of sulfonate, ethylene-vinyl alcohol copolymer, and polyamide. It is estimated to be. Furthermore, although a blend of ethylene-vinyl alcohol copolymer and polyamide is a polymer that requires stricter stretching conditions than polyester, in the present invention, this blend is sandwiched between inner and outer surface layers of polyethylene terephthalate. Furthermore, by strongly bonding the two with a copolyester having a sulfonate group, stretch molding becomes possible, and it is thought that strong adhesive strength is maintained even after stretch molding. According to the present invention, strong adhesive strength is maintained between the polyester layer and the blend layer of ethylene-vinyl alcohol copolymer and polyamide even after stretching, and as a result, the container is subjected to drop impact. This prevents delamination even when the material is filled with carbonated beverages, beer, etc., and also prevents blisters from forming at the joint between the polyester layer and the blend layer. This problem is effectively solved. Furthermore, a blend of ethylene-vinyl alcohol copolymer and polyamide with excellent gas barrier properties is provided in the intermediate layer, and the polyester layer is molecularly oriented by stretching, resulting in excellent gas barrier properties and resistance to delamination. A multilayer plastic container with excellent durability, impact resistance, rigidity, and even transparency is provided. (Description of preferred embodiments of the invention) Adhesive As mentioned above, the sulfonic acid group-containing copolyester used in the present invention has a main chain skeleton composed of repeating ester units and sulfonate groups bonded to this main chain skeleton. means a copolyester consisting of Of course, this adhesive may consist of the above-mentioned copolyester alone, or may be a blend of the above-mentioned copolyester and a normal 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 the blend is insufficient,
On the other hand, if it is higher than the above range, adhesion to the polyester tends to be insufficient or the copolyester itself tends to have defects in its thermal stability. 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. Suitable examples of such components include sodium 3,5-di(carboxy)benzenesulfonate, 3,
Examples include potassium 5-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, especially 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. Polyester The polyester used in the present invention usually contains 50 mol% or more, preferably 70 mol% or more of ethylene terephthalate structural units, and has 2 to 4 carbon atoms.
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 unit. In addition, terephthalic acid is mainly used as the aromatic dicarboxylic acid, but in addition to terephthalic acid, for example, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, etc. may be used as long as the content of the ethylene terephthalate structural unit is satisfied. can be used in amounts of In particular,
Polyethylene terephthalate is practically preferred.
Intrinsic viscosity [η] of the polyester (phenol-
In tetrachloroethane mixed solvent (weight ratio 1/1)
(value measured at 25℃) is usually 0.5 to 1.5 dl/g,
Preferably 0.6 to 1.2 dl/g, and the melting point is usually
210 to 265°C, preferably 220 to 260°C,
Glass transition temperature is usually 50 to 120℃, preferably
The temperature is 60 to 100°C. The polyester may contain appropriate amounts of various additives such as nucleating agents, inorganic fillers, lubricants, slip agents, antiblocking agents, stabilizers, antistatic agents, antifogging agents, and pigments, as necessary. It may be blended. Blend of ethylene-vinyl alcohol copolymer and polyamide The resin used as the intermediate layer in the present invention is a blend of ethylene-vinyl alcohol copolymer and polyamide. As the ethylene-vinyl alcohol copolymer, a copolymer containing 50 mol% or less of ethylene component is preferable in order to improve gas barrier properties. As is already known, polyvinyl alcohol is not thermoformable unless special processing methods are used.
In ethylene-vinyl alcohol copolymers, as the ethylene content increases, the melting point decreases and thermoplasticity increases. 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 and the temperature at which it can be stretched is also low, which is convenient for co-stretching with the polyester resin layer, but as the ethylene component increases, the There is no point in multilayering the polyester resin because the gas barrier properties will deteriorate.The second reason is that even if the ethylene-vinyl alcohol copolymer is low in ethylene content and high in vinyl alcohol content, According to the present invention, as will be described in detail later, in the form of a multilayer structure with polyester resin, even at the appropriate stretching temperature of polyester resin, ethylene-
Since it has been discovered that it is possible to stretch a vinyl alcohol copolymer layer, the ethylene-vinyl alcohol copolymer used for multilayering of the present invention is selected to have an ethylene content of 50 mol% or less, that is, a high vinyl alcohol content. That's what I did. In the present invention, the ethylene-vinyl alcohol copolymer used is a copolymer obtained by saponifying a copolymer of ethylene and a vinyl ester such as vinyl acetate. , with an ethylene content of 15 to 50 mol%, especially 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. In addition, polyamides include aliphatic, aromatic,
Polyamides or copolyamides made from araliphatic 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 seba Examples include cate copolymer, ethylene diammonium adipate/hexamethylene ammonium 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. Although they are slightly inferior in moldability compared to the above-mentioned aliphatic polyamides, for example, JP-A-50-1156, JP-A-50-5751, JP-A-50-5753, JP-A-Sho 50 -10196 Publication, JP-A-50-29697
Meta-xylylene diamine, or mixed xylylene diamine containing 30% or less of para-xylylene diamine in the diamine and carbon number 6, as described in the above publication.
It is also possible to use an aromatic polyamide containing at least 70 mol % of structural units formed from α,ω-aliphatic dicarboxylic acids in the molecular chain. Furthermore, an aromatic dicarboxylic acid containing metaxylylene diamine or a mixed xylylene diamine containing not more than 30% of paraxylylene 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. The molecular weight of these polyamides can be used without any particular restriction as long as it is generally within a range that allows film forming ability. The blend ratio of ethylene-vinyl alcohol copolymer (EVOH) and polyamide is preferably EVOH:polyamide=7:3 to 2:8 by weight. As a method for blending the ethylene-vinyl alcohol copolymer and polyamide, methods applicable to blending two or more types of polymers that are known per se, for example, a method in which powders of each polymer are blended in a Banbury mixer. Various methods can be employed, such as blending powders or chips of the respective polymers in an extruder and extruding them to form blended chips or films. Blends of ethylene-vinyl alcohol copolymers and polyamides may contain nucleating agents, inorganic fillers, lubricants, slip agents, and anti-slip agents that are blended in conventional ethylene-vinyl alcohol copolymers or polyamides. Appropriate amounts of various additives such as blocking agents, stabilizers, antistatic agents, antifogging agents, and pigments may be blended. Multilayer Plastic Container The main part of the container of the present invention is made of plastic having a multilayer structure. This multilayer structure includes: polyester layer/sulfonic acid group-containing copolyester layer (adhesive layer)/blend layer of ethylene-vinyl alcohol copolymer and polyamide/sulfonic acid group-containing copolyester layer (adhesive layer)/ It has a five-layer structure consisting of polyester layers. Furthermore, as necessary, the polyester layer/the adhesive layer/the blend layer/the adhesive layer/the polyester layer/the adhesive layer/
It may have a nine-layer structure consisting of the blend layer/the adhesive layer/the polyester layer. The thickness of the polyester layer is usually 3 to 4000μ
m, preferably 5 to 1500 μm, the thickness of the blend layer is usually 1 to 350 μm, preferably 2 to 200 μm, and the thickness of the sulfonic acid group-containing copolyester layer is usually 0.5 to 350 μm,
Preferably it is 2 to 200 μm. The total thickness of the plastic with multilayer structure is 0.1 to 4 mm,
Preferably it is 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.
It is preferable that it is within the range of . 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, the polyester layer and the blend layer of ethylene-vinyl alcohol copolymer and polyamide are bonded together by the sulfonic acid group-containing copolyester layer, and the sulfonic acid group-containing copolyester layer itself At the same time as it has stretchability, it also has high affinity adhesive strength with polyester and with the blend layer, so even if the multilayer plastic is stretched uniaxially or biaxially, it can be stretched without causing delamination. It can be stretched sufficiently depending on the degree of stretching. Container Manufacturing Method The stretched multilayer plastic container of the present invention having the excellent features described above is based on the second invention of the present application, namely, the inner and outer surface layers are made of polyester and are made of a blend of ethylene-vinyl alcohol copolymer and polyamide. A stretched multilayer plastic characterized in that a sheet or preform with a multilayer structure comprising an intermediate layer and a sulfonic acid group-containing copolyester layer provided between the surface layer and the intermediate layer is formed into a container shape under stretching conditions. It can be manufactured by a container manufacturing method. In the manufacturing method of the present invention, when manufacturing a container from a multilayered sheet having the above structure, a sheet stretch molding method known per se is used, except that the multilayered sheet having the above structure is formed. Containers 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. The multilayer plastic sheet may be prepared by forming the polyester, the blend and the sulfonate-containing copolyester separately into a sheet or film, and then uniaxially or biaxially stretching them.
Alternatively, it may be manufactured by laminating layers to form the structure of the present invention without stretching and then heat-pressing the layers. In the manufacturing method of the present invention, when manufacturing a container from a multilayered opreform having the above-mentioned structure, blow molding, which is known per se, is used, except that the multilayered structure and structural material of the preform are specified in the present invention. Containers can be manufactured by the method. For example, a multilayer parison can be produced by using three or more extruders to extrude the three 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 producing containers by stretch-molding a sheet or preform vary depending on the resin used, but the stretching temperature is within the range of the glass transition temperature or higher and the crystallization initiation temperature of the resin used. It is preferably stretched in at least one axial direction, preferably in two axial directions, and the stretching ratio is usually 1.1 to 10 times, preferably 1.2 to 8 times, more preferably 1.5 to 7 times, The purpose is to ensure that the resin layer of the resulting container 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 beverages 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 drink containing;
Synthetic drinks and vitamin-enriched drinks containing synthetic fruit juices using sugars such as sugar or fructose, citric acid, coloring agents, flavorings, etc., or adding vitamins as necessary; Lactic acid bacteria drinks; for example, mustard oil,
Seasonings such as sauce, vinegar, mirin, dressing, mayonnaise, ketchup, edible oil, miso, lard, ketchup; tofu, diyam, butter, margarine, etc.; liquid medicines, pesticides, cosmetics, and perfumes; Detergents; and ketones such as acetone and methyl ethyl ketone; aliphatic hydrocarbons such as normal hexane and normal peptane;
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 benzine, heavy oil, thinner, grease, silicone oil, light oil, machine oil; or liquefied Freon (DuPont, USA) It is useful as a container for storing each of the above-mentioned contents, as it has little deterioration or weight loss. Example 1 Polyethylene terephthalate (PET) with an intrinsic viscosity of 1.06 at 30°C was used as the inner and outer aliphatic polyester layers, and the vinyl alcohol content was 69.0 mol%.
Ethylene-vinyl alcohol copolymer (EVOH) with an ethylene content of 30.6 mol% and vinyl acetate residues of 0.4 mol% and caprolactam/hexamethylene diammonium adipate copolymer (nylon 6/6) with a caprolactam concentration of 91 mol%. ,6
Copolyester (S) containing 250 mmol of sodium sulfonate group per 100 g of polymer is adhered to the middle layer, which is a blend (EVPA) mixed with copolymer (PA) at a ratio of 70/30 (weight ratio). As an agent, 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 PET, an extruder with a built-in screw with a diameter of 50 mm and an effective length of 1400 mm is used as an extruder for intermediate layer (blend), An extruder with a built-in screw with a diameter of 38 mm and an effective length of 950 mm is used as an extruder for the adhesive (sodium sulfonate-containing copolyester) layer, and pipe forming consists of a die for 3 types and 5 layers, a sizing unit, a cooling tank, and a cutter. With the equipment, PET (outer layer)/S/EVPA/S/PET
A multilayer pipe having a thickness ratio of (inner layer) = 10/0.2/1/0.2/5 was molded. Both ends of this open-end pipe were heated and a neck and bottom were formed by compression molding to obtain a preform.
This preform was heated to 105° C. and then stretch-blow molded to obtain a bottle with an internal volume of 1500 ml and a weight of 59 g. The oxygen gas permeability of this bottle (the amount of oxygen that permeated into the bottle during storage for one month at 37°C and 60% RH after heat-sealing the bottle opening with aluminum foil/copolyester multilayer film in a nitrogen gas atmosphere) was measured using a gas chromatograph. A rectangle (with the major axis in the bottle height direction) was cut out from the bottle body wall and the interlayer peel strength was measured. Comparative Example 1 Instead of the ethylene-vinyl alcohol copolymer and nylon 6/6,6 copolymer blend of Example 1, the vinyl alcohol content was 69.0 mol%, the ethylene content was 30.6 mol%, and vinyl acetate residue was used. but
A stretched blow bottle was molded having the same materials, layer composition ratio, content capacity, and weight as in Example 1, except that 0.4 mol% ethylene-vinyl alcohol copolymer was used as the intermediate layer. The oxygen gas permeability and delamination strength of the body wall of this bottle were measured. Comparative Example 2 The same materials and layer composition ratio as in Example 1 except that nylon 6/6,6 copolymer with a caprolactam concentration of 91 mol% was used as an adhesive instead of the sodium sulfonate group-containing copolyester of Example 1. A stretched blow bottle having the following contents and weight was molded. The oxygen gas permeability and delamination strength of the body wall of this bottle were measured. The evaluation results of the bottles of Example 1 and Comparative Examples 1 and 2 are summarized in Table 2.

[Table] *2; Peel strength between adhesive layer and intermediate layer *3; Peel strength between PET layer and adhesive layer

Claims (1)

[Claims] 1. Inner and outer surface layers made of polyester, an intermediate layer made of a blend of ethylene-vinyl alcohol copolymer and polyamide, and a sulfonic acid group-containing copolymer provided between the surface layer and the intermediate layer. Stretched multilayer plastic container consisting of polyester layers. 2. Claim 1, wherein at least the polyester layer is stretched in at least one axis direction and has molecular orientation.
Multilayer plastic containers as described in Section 1. 3 The content of sulfonic acid groups in the sulfonic acid group-containing copolyester is
Stretched multilayer plastic container according to claim 1, characterized in that the amount thereof is 1 to 520 mmol/ml. 4. Multilayer structure consisting of inner and outer surface layers made of polyester, an intermediate layer made of a blend of ethylene-vinyl alcohol copolymer and polyamide, and a sulfonic acid group-containing copolyester layer provided between the surface layer and the intermediate layer. A method for producing a stretched multilayer plastic container, comprising forming a sheet or preform into a container shape under stretching conditions.