JPH1179156A - Multi-layer plastic container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multilayer plastic container with improved high-impact ply separation and hot fill filling ply separation characteristics, and furthermore superior in transparency. SOLUTION: This multilayer plastic container is made of thermoplastic polyester A outside and inside layers and a resin B intermediate layer. The resin B is made of ethylene-vinyl alcohol copolymer resin C with ethylene content 15-70 mole percentage, polyamide resin D and ethylene/unsaturated carvone copolymer resin E, and also satisfies equations: 0.5<=Wc/(Wc+Wd+We)<=0.99 and 0.02 <=Wd/(Wd+We)<=0.7. Here, Wc represents the weight of ethylene-vinyl alcohol copolymer C, Wd the weight of polyamide resin D and We the weight of ethylene/unsaturated carvone copolymer E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic container used for containers such as beverages, foods, cosmetics, etc., which has good gas barrier properties such as oxygen or carbon dioxide gas, moisture proofness, flavor barrier properties and good appearance, especially thermoplastic polyester ( (Hereinafter abbreviated as PES) as inner and outer layers, and a saponified ethylene-vinyl ester copolymer (hereinafter abbreviated as EVOH) -based composition as an intermediate layer. (Abbreviated as "delami"), and more particularly to a co-injection stretched multi-layer plastic container.

[0002]

2. Description of the Related Art Stretch blow molding PES containers are used in many fields due to their excellent transparency and rigidity, but their gas barrier properties are not always sufficient, so that foods can be stored only for a short period of time. I was In order to remedy this drawback, various methods for forming a multilayer structure by combining PES with EVOH having good gas barrier properties have been proposed. That is, prior to stretching blow, there are a co-injection molding method, a multi-stage injection molding method, a co-injection molding method, and the like as methods for manufacturing a preform, but each has advantages and disadvantages. Among them, the co-injection molding method has a simple apparatus and a structure in which the EVOH is entirely covered with PES. Therefore, even if there is no adhesive resin between the EVOH and the PES, the cohesion effect due to the atmospheric pressure causes an apparent appearance. It has features such as a good multilayer container, and is a method that is currently attracting attention. However, when the container is filled with food and subjected to impact such as dropping, PES and EV
Delamination occurred with OH, which was a serious problem in appearance. Therefore, a substrate / Ad / EVOH / Ad / substrate including an adhesive layer (hereinafter abbreviated as Ad) (JP-A-56-501)
040) or substrate / Ad / EVOH / Ad /
Substrate / Ad / EVOH / Ad / substrate (JP-A-50-13
5169, 61-152411, 61-15241
Although the co-injection molding method having a configuration such as that described in JP-A-61-259944) has been studied, the equipment becomes very complicated and it is often difficult to control the thickness of each layer. In this situation, it is lower than other methods, for example, a co-extrusion (pipe) method. As a further serious problem, it is often observed that even in the case of a multilayer co-injection stretch blow container containing the above-mentioned adhesive resin layer, impact delamination is not completely improved. That is, the PES and E of the container body
Adhesive strength with VOH (T-peel strength) is 400-600
g / 10mm width even for containers showing relatively high values,
On the other hand, impact delamination may occur very easily, but conversely, even in a container having the above-mentioned adhesive strength of 20 to 40 g / 10 mm wide and hardly bonded, impact delamination may be less likely to occur than a container having a high adhesive strength. As described above, the impact delamination is a difficult problem because the cause is not clear, and improvement is desired.

[0003] On the other hand, Japanese Patent Application Laid-Open No. 1-176554 proposes to improve the impact delamination by blending a polyamide-ester-based thermoplastic resin with EVOH, but the improvement effect is not sufficient, and further improvement is desired. ing.

[0004] In some cases, the plastic container is used by hot-filling a beverage with a PES layer and an EV.
Delamination may occur due to the difference in the thermal shrinkage of the OH layer, and it has been difficult to use this container in this field.
However, there are a large number of beverages that use hot-fill filling, and many of them increase the commercial value by improving the barrier properties. Therefore, development of a barrier container that can be used in this field has been strongly desired. .

[0005]

A PES-based multi-layer container, especially a co-injection stretch blow-molded container, which does not contain an independent adhesive resin and is laminated with EVOH as a gas barrier resin, is an empty container, a normal pressure filling container or a high pressure container. When a shock is applied to a container filled with the contents described above, delamination occurs between the PES layer and the EVOH layer, resulting in a problem of poor appearance of the container. Furthermore, when the beverage is hot-filled into the container, the shrinkage ratios are different, and the interlayer adhesion is insufficient. Therefore, the present inventors have intensively studied a method for preventing the delamination.

[0006]

Means for Solving the Problems The inventors of the present invention have proposed a method in which PES is applied to the inner and outer layers by a multi-layer preform, in particular, a co-injection molding method.
OH or PES and EVOH produce a multilayer preform having an intermediate layer completely encapsulated by the inner and outer layer surface layers, and when the multilayer parison is stretch blow-molded to produce a container, the composition of EVOH is eagerly studied. As a result of the investigation, surprisingly, the EVOH (C) was mixed with a polyamide resin (D) and an ethylene / unsaturated carboxylic copolymer resin (E), and the EVOH composition (B) was used. As a result, they found that the shock delamination resistance was greatly improved, and completed the present invention.

More surprisingly, the co-injection stretch blow container molded with the above composition not only significantly improves the impact delamination property, but also has a vertical streak-like shape which is likely to be generated on the container body, the bottom, and the periphery of the opening. It was also found that the thickness unevenness of the EVOH layer was significantly improved. In general, in the co-injection and co-stretching operations of PES and EVOH, EVOH has poor stretchability as compared with PES. Therefore, when the above-mentioned EVOH composition (B) is used, it is not clear why the vertical stripes are greatly improved, but the polyamide resin (D) and the ethylene / unsaturated carboxylic copolymer resin (E) are converted to EVOH (E). C) and the EVOH composition (B) has improved stretchability by blending with PES.
It is presumed that the interlayer adhesion between (A) was increased and that the generation of streaks was prevented. This fact is apparent from the embodiments described below. In the present invention, it is not particularly necessary to provide an independent adhesive resin layer between (A) and (B), but it is free to provide this layer, for example, to provide a thin layer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS PES (A) used in the present invention
As the polymer, a polycondensate containing an aromatic dicarboxylic acid or an alkyl ester thereof and a glycol as main components is used. In particular, to achieve the object of the present invention, PES mainly containing ethylene-terephthalate is preferable. And processability, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, dicarboxylic acid components such as sebacic acid or their alkyl ester derivatives and propylene glycol as copolymer components as long as the strength is not significantly impaired.
It is also possible to use a copolymer obtained by copolymerizing glycol components such as 4-butanediol, cyclohexanedimethanol, neopentyl glycol, bisphenol A and diethylene glycol. And phenol 50
It is preferable that the resin be dissolved in a mixed solvent of 50% by weight and 50% by weight of tetrachloroethane and have an intrinsic viscosity [η] (unit: dl / g) of 0.5 to 1.5 measured at a temperature of 30 ° C.

[0009] EVOH resin (B) used in the present invention
Is a saponified product of an ethylene-vinyl ester copolymer, and has an ethylene content of 15 to 70 mol%, preferably 25 to 70 mol%.
65 mol%, optimally 25 to 60 mol%, and the degree of saponification of the vinyl ester component is 85% or more, preferably 90%
The above can be used. If the ethylene content is less than 15 mol%, the melt moldability is poor, while if it exceeds 70 mol%, the gas barrier properties are insufficient. In addition, the degree of saponification is 85
%, The gas barrier property and the thermal stability deteriorate.

In the present invention, vinyl acetate is a typical vinyl ester used in the production of EVOH, but other fatty acid vinyl esters (such as vinyl propionate and vinyl pivalate) can also be used. In addition, EVOH may contain 0.0002 to 0.2 mol% of a vinylsilane compound as a copolymerization component. Here, as the vinylsilane-based compound, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane,
γ-methacryloxypropylmethoxysilane. Among them, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used. Further, other comonomers [eg, propylene, butylene, unsaturated carboxylic acid or its ester ((meth) acrylic acid, methyl (meth) acrylate], ethyl) may be used as long as the object of the present invention is not hindered. ｝, Vinylpyrrolidone (such as N-vinylpyrrolidone) can also be copolymerized. Also,
The preferred melt index (MI) of the EVOH used in the present invention (at 190 ° C. under a load of 2160 g) is 0.1 to 5
0 g / 10 min, optimally 0.5-20 g / 10 min. However, those having a melting point of around 190 ° C. or exceeding 190 ° C. were measured at a plurality of temperatures equal to or higher than the melting point under a load of 2160 g, and the reciprocal of the absolute temperature was plotted as abscissa and MI as ordinate log on a semilogarithmic graph. Expressed as a value extrapolated to ° C.

The polyamide resin (D) used in the present invention
Is a polymer having an amide bond, for example, polycaproamide (nylon-6), polyundecaneamide (nylon-11), polylauryl lactam (nylon-12), polyhexamethylene adipamide (nylon-
6,6), polyhexamethylene sebacamide (nylon-
6,12), caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / aminoundecanoic acid polymer (nylon-6 / 1)
1), a caprolactam / ω-aminononanoic acid polymer (nylon-6, 9), a caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,
6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6,6 / 6,12), polymer of adipic acid and meta-xylylenediamine, or hexamethylenediamine And aromatic nylon which is a polymer of m, p-phthalic acid and the like. These polyamide resins can be used alone or in combination of two or more. Also, E
Among these polyamide resins, polyamides containing a nylon 6 component (for example, nylon-6,12, nylon-6 / 12, nylon-6 /
6,6, etc.), and more preferably a polyamide containing 6 components of nylon. Since EVOH and nylon react / gel during the melting process, it is preferable to use nylon having a melting point of 240 ° C. or less, preferably 230 ° C. or less, from the viewpoint of suppressing thermal deterioration of the blend composition.

An ethylene / unsaturated carboxylic acid copolymer resin used in the same manner is an ethylene / unsaturated carboxylic acid copolymer or an ionomer (E) which is a metal salt thereof.
) And the unsaturated carboxylic acid content is preferably from 2 to
It is a copolymer with 15 mol%, more preferably 3 to 12 mol% of ethylene. As unsaturated carboxylic acids,
For example, there are acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, monomethyl maleate, monoethyl maleate, and maleic anhydride, and acrylic acid or methacrylic acid is particularly preferable. Other monomers that may be contained in the copolymer include vinyl acetate, vinyl esters such as vinyl propionate, methyl acrylate, ethyl acrylate, isopropyl acrylate,
Examples include unsaturated carboxylic esters such as isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, isobutyl methacrylate, diethyl maleate, and carbon monoxide.

The metal ion in the ionomer is an alkali metal such as lithium, sodium and potassium, and an alkaline earth metal such as zinc, magnesium and calcium. Particularly, zinc is preferably used. The degree of neutralization in the ionomer is 100% or less, particularly 90%
Below, especially the range of 70% or less is desirable. The lower limit of the degree of neutralization is usually 5% or more, more preferably 10% or more, furthermore 30% or more. Further, the suitable melt index (MI) (at 190 ° C. under a load of 2160 g) of the ethylene / unsaturated carboxylic acid copolymer resin used in the present invention is not particularly limited, but by satisfying the following formula: This is preferable because the effect of improving impact delamination is improved. 0.1 ≦ MI (E) / MI (C) ≦ 100. . . (III) More preferably, 0.3 ≦ MI (E) / MI (C) ≦ 70. . . (V) MI (C): Melt index of EVOH resin (C) (2160 g, 190 ° C.) (g / 10 min) MI (E): Melt index of resin (E) (2160)
g, 190 ° C) (g / 10 minutes)

The composition ratio of the EVOH composition of the present invention must satisfy the following formula. 0.5 ≦ Wc / (Wc + Wd + We) ≦ 0.99. . . (I) 0.02 ≦ Wd / (Wd + We) ≦ 0.7. . . (II) preferably 0.55 ≦ Wc / (Wc + Wd + We) ≦ 0.93. . . (VI) 0.03 ≦ Wd / (Wd + We) ≦ 0.6. . . (VII) More preferably, 0.58 ≦ Wc / (Wc + Wd + We) ≦ 0.95. . . (VIII) 0.05 ≦ Wd / (Wd + We) ≦ 0.5. . . (IX) Wc: weight of saponified ethylene-vinyl ester copolymer (C) Wd: weight of polyamide resin (D) We: weight of ethylene / unsaturated carboxylic copolymer resin (E) EVOH resin ( When C) is less than 0.5 of the total composition,
The gas barrier property is remarkably reduced, and deviates from the gist of the present invention. On the other hand, if it exceeds 0.99, the effect of improving impact delamination is insufficient. Polyamide resin (D) and ethylene
When the blending ratio of the unsaturated carboxylic copolymer resin (E) is less than 0.02, the compatibility of the blend with EVOH is reduced. When the blending ratio is more than 0.7, the chemical reaction between the polyamide and EVOH is performed. The thermal stability of the blend becomes worse.

It is known that the ethylene / unsaturated carboxylic copolymer resin (E) can provide a certain degree of adhesive strength to the PES resin (A).
When a multi-layer container is obtained by using a blend system containing only the VOH resin (C), the bottle becomes slightly cloudy (haze increases), and in this case, the effect of improving the impact delamination is insufficient.
However, by adding a polyamide resin (D) to the ethylene / unsaturated carboxylic copolymer resin (E) and the EVOH resin (C) as in the present invention, the transparency is improved, and the effect of improving the impact delamination is further improved. Will be enough. Although the cause is not clear, the compatibility between the ethylene / unsaturated carboxylic copolymer resin (E) and the EVOH resin (C) is insufficient, but the polyamide resin (D) acts as a compatibilizer, It is presumed that the dispersed particle diameter is small.
As a result, it can be understood that light scattering by the dispersed particles inside the composition is reduced and the transparency is improved. Further, the effect of improving the impact delamination is presumed that the ethylene / unsaturated carboxylic copolymer resin (E) in the blend layer comes into contact with the PES at the interface between the PES and the EVOH composition layer to generate an adhesive force. At this time, in the two-component blend of the ethylene / unsaturated carboxylic copolymer resin (E) and the EVOH resin (C), the contact points are large in area, small in number, and “coarse”.
In contrast to the structure, the three-part blend has a “fine” structure with a large number of contacts, so it is presumed that the three-part blend provides a better impact delamination improvement effect.

The method of blending the EVOH resin (C), the polyamide resin (D) and the ethylene / unsaturated carboxylic copolymer resin (E) is not particularly limited, and these resins are dry blended and used as they are. And re-pelletizing and drying the dry blended pellets using a Banbury mixer, a single screw extruder or a twin screw extruder.

Among these blending methods, a method of previously blending or reacting a polyamide resin (D) and an ethylene / unsaturated carboxylic copolymer resin (E) and then blending with the resin (C) is known as a method of impact delamination. The result that the improvement effect is further improved has been obtained. This is because the compatibility between the polyamide resin (D) and the EVOH (C) is good, but the compatibility between the resin (E) and the EVOH resin (C) is slightly inferior. Is blended, more polyamide resin (D) adheres sufficiently around resin (E), and therefore the compatibility between EVOH resin (C) and resin (E) is improved. It is inferred.

The method of blending or reacting the polyamide resin (D) and the ethylene / unsaturated carboxylic copolymer resin (E) in advance and then blending with the EVOH resin (C) is not particularly limited. For example, the resin (D) and the resin (E) are dry-blended, and the dry-blended pellets are pelletized and dried by a Banbury mixer, a single-screw extruder or a twin-screw extruder to obtain a blended product. A method of dry blending with C) and using it for co-injection molding, or a method of pelletizing again by the same method, and the like. It is also effective to blend and mix or react the resin (D) and the resin (E) in a common solution, dry the solvent, and appropriately blend with the resin (C).

One or more antioxidants such as hindered phenols, hindered amines, metal soaps (eg, calcium stearate, magnesium stearate), ultraviolet absorbers, and coloring agents may be used as long as the object of the present invention is not impaired during blending. It is free and effective to add two or more kinds. In the present invention,
PH of a layer (intermediate layer) of a composition comprising these blends
Is adjusted to 3 to 6 so that the PES of the intermediate layer and the inner and outer layers can be adjusted.
This is preferable because the adhesion to the layer is improved. The pH can be adjusted by including organic acids (acetic acid, propionic acid, caprylic acid, lauric acid, etc.) and inorganic acids (phosphoric acid, etc.)
It can be carried out

Further, as a means for improving the impact delamination property of the co-injection stretch blow container, the polyamide resin (D) 1 to 100 parts by weight is added to the thermoplastic polyester resin 100 parts by weight.
Use a resin in which 20 parts by weight and 1 to 20 parts by weight of an ethylene / unsaturated carboxylic copolymer resin (E) are blended, that is, (D) and (E) are replaced with PES and EV.
It is more effective to blend with both OH. However,
In this case, the transparency is slightly reduced.

Container Precursor Having a Multilayer Structure (Parison)
Usually performs a single clamping operation on a single mold using a molding machine having two injection cylinders, and alternately and / or alternately shifts the molten PES and EVOH resin composition from each injection cylinder at a different timing. It is obtained by simultaneously injecting the concentric nozzles. For example (1)
Inject PES for inner and outer layers first, then become intermediate layer
Injecting the EVOH composition, PES / EVOH composition / PE
A method of making a three-layer container of S, or (2) first injecting the PES for the inner and outer layers, then injecting the EVOH composition, and simultaneously or again injecting the PES as the central layer again, PES / EVOH composition / PES / EVO
The inner layer is obtained by a general method of a bottomed parison in which the inner layer is completely enclosed by the innermost and outermost PES layers, such as a method of making a five-layer container of the H composition / PES, and is not particularly limited in terms of equipment. The multi-layer parison is heated in a warm state directly or after being heated to 75 to 150 ° C. by a heating element such as a block heater or an infrared heater, sent to a stretching blow step, and stretched 1 to 5 times in the vertical direction. PES or / and EV blown 1-4 times with compressed air
The OH composition is uniaxially or biaxially stretched to obtain a multilayer polyester stretch blow container. The heating and stretching step is not particularly limited in terms of equipment.

The heat treatment of the stretch blow container greatly affects the impact delamination of the multi-layer bottle, and it is more desirable to satisfy the following formula (IV). (Tp-20)>Tc> 100. . . (IV) Tp: Melting point of PES (° C) Tc: Heat treatment temperature of bottle (° C)

When Tc is larger than Tp-20, the outermost layer PE
The strength of the bottle becomes poor, probably because S is softened and the stretching orientation is lowered. On the other hand, when Tc is lower than 100 ° C., no improvement in the impact delamination property of the multilayer container is observed. Heat treatment time is 1
About 100 seconds is good, and the heat treatment method is not particularly limited, but generally, a method of increasing the mold temperature in the blowing step or a method of heating again under pressure and conducting heat treatment in a mold, Alternatively, a method of performing heat treatment with hot air or a heat medium may be used. In addition, when removing the bottle having a high temperature after the heat treatment, a method of rapidly cooling the heating mold or the heating medium, or a method of introducing the bottle again into the cooling mold and cooling it with a cooling mold under pressure and the like can be mentioned.

The multilayer container of the present invention is composed of PES and E
Using two types of resins, one or more intermediate layers of the EVOH composition layer, or the EVOH composition layer and the PES
And a PES layer as an inner / outer layer completely enclosing an intermediate layer including at least one layer, and generally a PES / EVOH composition / PES, a PES / EVOH composition / PES / PE.
S, PES / EVOH composition / PES / EVOH composition / PES and the like. Regarding the thickness of the parison, the total thickness is 2 to 5 mm, and the total thickness of the EVOH composition layer is 1 mm.
In general, the thinner the EVOH composition layer, the smaller the number of EVOH composition part layers, and the closer the position of the EVOH composition layer closer to the outer layer side to the outer layer surface, the more impact delamination of the container. Easy to occur. The total thickness of the container body is generally 100 to 3000 μm, and can be properly used depending on the application. At this time, the total thickness of the EVOH composition is 2 to 200 µ, preferably 5 to 100 µ.

The multilayer plastic container of the present invention includes:
The above-mentioned co-injection-stretched multilayer plastic container is particularly suitable, but other co-extrusion direct blow containers, co-extrusion-stretched multilayer plastic containers, thermoformed containers such as cups formed from multilayer sheets, and the like are also included.

Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

[0027]

【Example】

Example 1 EVOH resin containing a small amount of acetic acid, ethylene content of 32 mol%, saponification degree of 99.6%, MI (melt index: 190 ° C.-2160 g) 1.3 g / 10
With respect to 70 parts by weight of EVOH (C) having a melting point of 181 ° C., 10 parts by weight of nylon 6 (Ube nylon 1011FB, melting point of 225 ° C.) as a polyamide resin (D) and ethylene as an unsaturated carboxylic acid copolymer resin (E) -Methacrylic acid copolymer (methacrylic acid 4.3 mol%, melting point 98 ° C)
20 parts by weight of a melt-kneaded material are dry-blended, and a 30 mmφ twin screw extruder (TEX3 manufactured by Nippon Steel Works, Ltd.) is used.
In step 0), pelletization was performed at a die exit resin temperature of 220 ° C. and a screw rotation speed of 300, and then dried under reduced pressure at 80 ° C. for 16 hours to obtain an EVOH-based resin composition (B). Polyethylene terephthalate (PET) having an intrinsic viscosity of 0.71 is used as a thermoplastic polyester resin, and a co-injection stretch blow device (50-
HT type 750ml, 2 pieces), PET extruder tip temperature 270 ° C, EVOH extruder tip temperature 200
C., hot-runner block where PET and EVOH merge at 260.degree. C. to perform co-injection stretch blow molding, the average thickness of the body is 90 .mu.m of inner layer PET, 20 .mu.m of intermediate EVOH composition,
A multilayer co-injection blow-molded bottle with an outer PET of 190μ was obtained. In order to easily cause impact delamination on this bottle body, the mold was set to a vertical 50 mm x horizontal 15 mm, thickness 1.0 mm,
2.0 mm and 4.0 mm irregularities were provided.

Water is filled in 10 of the multi-layer containers, and
When the body was repeatedly dropped with the body level from the height of m, delamination occurred on average 20 times. Also, the bottle was filled with an aqueous solution of carbon dioxide gas and the inside of the bottle was filled with 4 gas Vol. When the sample was repeatedly dropped in the same manner, delamination occurred 33 times on average.

When the container was stretched and blown from a parison, the temperature of the blow mold was set to 120 ° C., and a heat treatment was performed for 30 seconds. In the deramification test, delamination was performed 30 times at normal pressure and carbon dioxide gas aqueous solution was used. In the pressure filling system, delamination does not occur even if it is dropped more than 50 times,
Improvement of impact delamination by heat treatment was observed. Table 1 shows the results.

Examples 2 to 4 Experiments were conducted in the same manner as in Example 1 except that the compositions were as shown in Table 1. Table 1 shows the performance of the obtained bottles. Note that EVOH used in Example 3 contains a small amount of acetic acid.

Comparative Example 1 In Example 1, only the EVOH resin containing no polyamide resin and no unsaturated carboxylic acid copolymer resin was used.
An experiment was performed in the same manner as in Example 1. As a result, delamination occurred in the container when the container was filled with atmospheric pressure water on average for the second time, and delamination occurred on average for the fifth time even when the container was filled with carbon dioxide gas under pressure.
In addition, when the delamination test was performed on the heat-treated bottle in the same manner as in Example 1, the delamination was caused by the third drop on average under normal pressure water filling,
Even under pressure filling with an aqueous solution of carbon dioxide, delamination occurred at the average of the fourth drop, and no heat treatment effect was observed.

Comparative Examples 2 to 7 Experiments were carried out in the same manner as in Example 1 with the compositions shown in Table 1. Table 1 shows the performance of the obtained containers.

Example 5 In Example 1, the co-injection molding conditions were changed, and the average thickness of the body of the container was changed from the inner side to the order of PET 90 μ / EVOH composition 10 μ / PET 100 μ / EVOH composition 10 μ / PE.
A bottle of T90μ having two types and five layers was obtained. In this container, delamination occurred on average 26 times under normal pressure water filling, and delamination occurred on average 41 times in carbon dioxide gas aqueous pressure filling. Also, as in Example 1, when heat treatment was performed, no delamination occurred even if the atmosphere was dropped 50 times or more under both normal pressure and carbon dioxide pressure. The pH of the intermediate layer (EVOH composition layer) in Examples 1 to 5 (pH of the extract obtained by crushing the intermediate layer and immersing it in water at 120 ° C.) was 4.

[0034]

[Table 1]

[0035]

According to the present invention, it is possible to obtain a multilayer plastic container having significantly improved impact delamination and hot-fill filling delamination.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B32B 27/32 101 B32B 27/32 101 27/34 27/34 27/36 27/36 C08L 29/04 C08L 29/04 S 67/00 67 / 00 // (C08L 29/04 77:00 33:06) B29L 9:00 22:00

Claims (5)

[Claims] 1. An ethylene-vinyl alcohol copolymer (C) comprising an inner / outer layer of a thermoplastic polyester (A) and an intermediate layer of a resin (B), wherein said resin (B) has an ethylene content of 15 to 70 mol%. ), A polyamide resin (D) and an ethylene / unsaturated carboxylic copolymer resin (E),
A multilayer plastic container which is a composition satisfying the following formulas (I) and (II). 0.5 ≦ Wc / (Wc + Wd + We) ≦ 0.99. . . (I) 0.02 ≦ Wd / (Wd + We) ≦ 0.7. . . (II) where Wc: weight of ethylene-vinyl alcohol copolymer (C) Wd: weight of polyamide resin (D) We: weight of ethylene / unsaturated carboxylic copolymer resin (E) 2. The multilayer plastic container according to claim 1, which satisfies the following formula (III). 0.1 ≦ MI (E) / MI (C) ≦ 100. . . (III) MI (C): Melt index of resin (C) (2160 g, 190 ° C.) (g / 10 min) MI (E): Melt index of resin (E) (2160)
g, 190 ° C) (g / 10 minutes) 3. The method for producing a multilayer plastic container according to claim 1, wherein coextrusion stretch blow molding is performed. 4. After co-injection stretch blow molding, the following formula (IV)
The method for producing a multilayer plastic container according to claim 1, wherein the heat treatment is performed at a temperature satisfying the following. (Tp-20)>Tc> 100. . . (IV) However, Tp: Melting point of thermoplastic polyester (A) (° C) Tc: Heat treatment temperature of plastic container (° C) 5. A polyamide resin (D) as the resin (B).
) And ethylene-unsaturated carboxylic copolymer resin (E
2. The method for producing a multilayer plastic container according to claim 1, wherein a composition obtained by pre-blending the above) and blending this with an ethylene-vinyl alcohol copolymer (C) is used.