JPS62164504A - Manufacture of preform for oriented polyester vessel - Google Patents

Abstract

PURPOSE:To secure the strength of the neck part of a vessel as well as the multi-layer property of an expanded part by a method wherein one end of a pipe is expanded into the shape of a tranpet and the neck part, connected to the end of the pipe, is made separately by the injection molding of thermoplastic polyester while both of them are integrated by fusion welding. CONSTITUTION:An intermediate body, having the cylindrical part 6 and the bottom part 7 of a co-extrusion multi-layer pipe consisting of an intermediate gas barrier layer made of the copolymer of ethylene vinyl alcohol and inner and outer layers made of polyester, is formed. The open end of the intermediate body is expanded with a male mold 14 so as to coincide with the diameter of a final product or a neck part substantially while resin, such as polyethylene phthalate or the like, for forming the neck part is injected through runners 17, 19 to connect it to the expanded part. This preform 21 is heated preliminarily to the proper temperature of orientation, and it thereafter formed by blow forming into the final product. According to this method, a PET bottle excellent in gas barrier property can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application to which the Invention Pertains) The present invention relates to a method for producing a preformed product for a stretched polyester container. The present invention relates to a method for producing preforms for polyester containers, in particular wide-mouth containers.

(Prior Art) Molding of stretched polyester bottles is common today, and the resulting molded containers can be used for liquids such as liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc. due to their excellent transparency and suitable gas properties. In addition to product containers, they have recently come to be widely used in containers for carbonated drinks such as beer, cola, and cider, as well as soft drinks such as fruit juice and mineral water.

To manufacture this stretched polyester container, a preform of amorphous polyester with dimensions smaller than the final container is manufactured, and after preheating this preform to a stretching temperature, it is stretched in the axial direction and in the circumferential direction. A blow-stretching method is used for this purpose.

However, since stretched polyester bottles are also made of plastic, gas permeability can be considered to be zero for completely sealed items such as glass bottles and metal cans, whereas stretched polyester bottles are free from oxygen, carbon dioxide, etc. It has a slight permeability to carbon dioxide, making it inferior to cans and glass bottles in terms of food filling and storage stability, especially in the case of carbonated beverages, and in the case of beer, cola, cider, etc. It has clear storage period limits.

In order to improve the gas barrier properties of stretched polyester bottles, polyester is combined with a gas barrier resin such as ethylene-vinyl alcohol copolymer, and a multilayer bottomed preform in the form of a laminate is stretch-blown in the axial and circumferential directions. A method of forming the
Publication No. 62).

A co-injection method and a co-extrusion pipe method have been proposed for manufacturing multilayer bottomed preforms, but each has advantages and disadvantages.

First, in the co-injection method, polyester (PET) resin and
A multilayer preform is obtained by simultaneously injecting a gas barrier resin into a mold.

On the other hand, in the coextrusion vibrator method, two or more types of resins are heated and melted using a number of extruders corresponding to the types of resins, and then passed through a melt channel in a die head to obtain a multilayered, uniformly distributed pipe. Next, the pipe is sized with a sizing former and cooled through a cooling bath. The cooled pipe is then cut to a predetermined length. The cut pipe is then molded into a threaded portion and a closed bottom portion in the next step.

(Problems to be Solved by the Invention) However, in the conventional method for producing a preform, a problem occurs when producing a stretched polyester container having a wide mouth and neck.

In other words, in conventional preformed products, there is not much difference between the diameter of the mouth and neck part and the diameter of the body part. It becomes difficult to obtain a sufficiently large stretching ratio in the circumferential direction, and as a result, improvement in properties due to biaxial molecular orientation cannot be expected.

Of course, if a preform with a neck smaller in size than the final container neck is used, it is possible to impart circumferential molecular orientation to the body. Like the body, the body is also thinned, making it difficult to provide a strong sealing engagement with the lid.

From this point of view, it is desirable to use a preform whose mouth and neck have the same dimensions as the mouth and neck of the final container and whose body has a smaller diameter than the diameter of the body of the final container. Since there is a step between the two, this step must be connected by some means.

In the co-injection method, the resin flow becomes extremely turbulent at this stepped portion, making it difficult to mix a plurality of resin flows and clearly form a multilayer structure.

Also, in the coextrusion method, the problem is how smoothly to connect the stepped portions.

Therefore, the technical problem of the present invention is to solve the above-mentioned drawbacks of the conventional multilayer preform, and to provide a neck portion with a relatively large diameter and a body portion with a relatively small diameter, so that the stepped portions of the two are smoothly connected. In addition, it is an object of the present invention to provide a method for manufacturing a preformed product for a stretched container in which a multilayer structure is clearly formed also in the stepped portion (tapered portion).

(Means for Solving the Problems) According to the present invention, when producing a preformed product for a stretched polyester container, one end of a multilayer pipe formed by coextrusion is closed in advance, and the other end of the pipe is closed. heating to the softening temperature 1-
After that, the pipe is expanded into a trumpet shape to have a larger diameter than the original diameter of the pipe, and the neck and neck that are to be connected to the enlarged open end are manufactured by injection molding of thermoplastic polyester, and the body and neck are combined. Either the mouth and neck are fused and integrated in the injection mold at the same time as the mouth and neck are molded, or the trunk and the mouth and neck are fused and integrated outside the mold.

(Function) In the present invention, by coextruding to form a multilayer pipe and forming the body of the preform with this pipe, a reliable multilayer structure can be formed throughout the body of the preform. For example, a multilayer structure consisting of inner and outer layers of polyester and an intermediate bottle of gas barrier resin sandwiched therebetween can be reliably formed over the entire body. In addition, co-extrusion is much easier than co-injection, which controls the thickness of each layer and the distribution position within one layer, and can also increase the adhesive strength between each layer.

In addition, by forming the neck and neck part by injection of polyester, separately from forming the body part from the coextruded pipe,
``It is possible to form a mouth and neck portion with high dimensional accuracy, sufficient wall thickness, and rigidity to reliably engage and seal with the container lid.

Moreover, by enlarging the diameter of one end of the co-extruded multilayer pipe in a trumpet shape, it is possible to smoothly connect the small diameter body part and the large diameter part, and the enlarged connection part with this diameter becomes possible. The multilayer structure also provides the advantages of the multilayer structure, such as improved gas IJ properties.

(Effects of the Invention) When the multilayer polyester preform of the present invention is used, when manufacturing a wide-mouth stretch-molded container, the strength and rigidity of the neck and neck can be maintained within the necessary and sufficient range for sealing the lid, while the body of the container can be Stretching in the circumferential direction can be carried out at a sufficient magnification to increase the biaxial molecular orientation of the polyester, thereby improving the elastic modulus, impact resistance, transparency, and gas barrier properties. The entire body can have a multilayer structure to improve fragrance retention, gas barrier properties, etc.

(Preferred embodiment of the invention) The present invention will be explained in detail below regarding its preferred embodiments.

In addition, although an ethylene-vinyl alcohol copolymer will be explained below as an example of the gas barrier resin, the present invention is not limited to this example, as will be described later.

FIG. 1 is a book showing a multilayer pipe particularly suitable for the purpose of the present invention, which multilayer pipe 1 is made of polyester.
12, an outer layer 3, an intermediate gas barrier layer 4 of ethylene-vinyl alcohol copolymer, and adhesive layers 5α and 5h interposed therebetween.

It will be mentioned later that it is important to manufacture the pipe by coextrusion, but it is important to rapidly cool the extruded pipe by immersing it in water or the like in order to prevent crystallization of the polyester.

In the present invention, first, polyester and a gas barrier resin such as an ethylene-vinyl alcohol copolymer are
The first feature is coextrusion into pipes. That is, this co-extrusion is carried out by combining molten resin, molten ethylene and vinyl alcohol in a die, and extruding it through a ring-shaped orifice, but these two resins are both in a molten state. Because of the contact for a certain amount of time, the resins mix well at the interface between the two, and the thermal adhesion between the two is stronger than in the case of multilayer injection molding. This is exactly the same even when an adhesive resin is interposed between the polyester and the ethylene-vinyl alcohol copolymer (CEVOH).

As polyester, polyethylene terephthalate C
PET), mainly composed of ethylene terephthalate units,
Other copolyesters containing small amounts of modifying ester units, which are known per se, can also be used for the purpose of the invention. It is preferable that the polyester has a molecular weight sufficient to form a film.In the present invention, the gas barrier resin is preferably an ethylene-vinyl alcohol copolymer, -
A copolymer obtained by saponifying a copolymer of General 1c Mortide, especially 25 to 45 molar, with a degree of saponification of 96 or higher is advantageously used. The molecule i of this copolymer may be one having film-forming ability.

Although not necessary, a polyester layer and an ethylene-
Any adhesive known per se can be used to enhance the adhesion with the vinyl alcohol copolymer layer. Copolyester adhesives, polyester-ether adhesives, epoxy-edible thermoplastic resins, acid-modified thermoplastic resins, polyamide resins, etc. are used for this purpose.

The polyester group a (PET), ethylene-vinyl alcohol copolymer (EVOH), and adhesive layer (AD) can be used in a layer configuration of i, for example, with the outer layer on the left side and the inner layer on the right side, PET/EVOH ,EVOH/pET pET/AD/E〆OH,EVOH/AD/P
E.T.

PET/EVOH/PET, PET/AD/E〆OHA
It can be used in a layer structure such as D/P E T .

The layer thickness can vary, but generally pET:p
:rtOH=2:1 to 5:1, especially 3:1 to 4:1
The thickness ratio is preferably in the range of PET:AD=20:1 to 50:1, especially 60:1 when using an adhesive layer.
The thickness ratio is preferably in the range of 40:1 to 40:1.

According to the present invention, after cutting a pipe manufactured by co-pressing into a certain size, a closed bottom portion is formed at one end of the pipe, an enlarged diameter portion is formed at the other end of the pipe, and then an opening portion is formed. The neck is formed of polyester by injection method and integrated by heat fusion inside or outside of an injection mold.

This manufacturing process f’! This is shown in FIGS. 42 to 4.

That is, as shown in FIG. 2, the end portion 51 of the pipe 1 of a predetermined length held by the vibrator holding core 50 is heated and melted by the heater 452. At this time, in order to prevent the pipe holding core 50 from being directly heated, the pipe 1 is made to protrude by a distance S from the tip of the core 50 when the core 50 is inserted and mounted.

For this purpose, a positioning stopper is provided at a predetermined position on the core. This positioning stopper can be used, for example, in Fig. 2-l.
As shown in FIG. 2B, a part 56 of the core 50 is provided with a portion 56 that protrudes from the inner diameter of the pipe 1 by approximately 0.01 to 0.03 m, or as shown in FIG. This can be easily accomplished by providing balls 54 and the like arranged at regular intervals in the circumferential direction.

In the embodiment shown in FIG. 2-B, the ball 54 is supported so as to be able to reciprocate in the radial direction by a spring 55 extending toward the center of the core. 1 is inserted between a pair of injection split molds 56α, 56b and an injection bottom mold 57 (FIG. 6).

The injection split molds 56α and 56b have an inner circumferential surface corresponding to the outer circumferential surface of the pipe 1, and the injection bottom mold 57 has an inner circumferential surface corresponding to the outer circumferential surface of the closed bottom to be molded. ing.

Also, injection split mold 56α.

56b is provided so as to be openable and closable in the horizontal direction.

A gate 58 is formed in the center of the injection bottom mold 57, and the injection nozzle 59 passes through a runner 60 to the injection mold 57.
Ester is injected.

Further, the injection split molds 56α and 56b form an inner space having a diameter smaller than the outer diameter of the pipe 1 by about 0.1 to 0.2 rm when the molds are closed.

Therefore, by closing the mold as the core 50 descends, the pipe 1 supported by the core 50 can be moved over the positioning stopper (see FIGS. 2-A and 2-B). The state where the distance S becomes 0 (injection split mold 56α).

The predetermined mold clamping is completed in a state in which the end surface 61 of the pipe 56b is in contact with the lower end surface of the pipe (FIG. 4).

Next, injection molding of the closed bottom part is performed in the state shown in FIG.

That is, from the injection nozzle 59 to the runner 60 and the gate 58
The closed bottom portion 7 is formed integrally with the pipe 1 by injecting polyester into the space inside the injection mold.

Of course, instead of forming the closed bottom part by injection of polyester, a multi-layered vibrator with one end heated is held in the male mold and pressed between the male mold and female mold to fuse and integrate the vibrator itself to form a hemisphere. A shaped bottom may be formed.

Next, the other end of the bottomed cylinder formed as described above,
That is, a trumpet-shaped enlarged diameter portion is formed at the open end, and a mouth and neck portion is formed.

The mouth and neck portions are formed by injection molding of polyester. For example, the mouth and neck portions are formed by injection molding of polyester and are integrated by heat fusion inside or outside of an injection mold.

Figures 5-A and 5-B show a mode in which the injection of the mouth and neck part and the fusion to the body part are performed all at once in a mold (insert injection method)
In the drawings, FIG. 5-A shows a state in which the mold is opened, and FIG. 5-B shows a state in which the mold is closed.

First, prior to the injection of the mouth part, the end part 8 of the pipe-shaped body part 6 is injected in order to ensure the fit with the mouth and neck part to be injected.
A cutout 9 that ensures engagement in the axial and circumferential directions of the preform is provided by cutting, heat compression molding, or the like. Alternatively, if the end portion 8 instead of the notch 9 is heated to near the melting temperature of the resin, the fusion between the body end portion and the injected resin becomes more effective.

The injection mold includes a pair of split molds 16α and 16h having a parting line 11 and an inner peripheral surface 12 corresponding to the outer peripheral surface of the mouth and neck part to be molded, and a fixed male mold 1.
It consists of 4. The split molds 16α, 13h are provided so as to be horizontally openable/closeable and movable up and down. The male mold 14 has a tip 15α to be inserted into the pipe-shaped body 6, a tapered surface 15h that enlarges the open end 8 of the pipe-shaped body to a larger diameter, and an inner circumferential surface of the mouth and neck to be molded. It has an outer circumferential surface 16 corresponding to.

The fixed mold 14 has a runner 17,
A runner 19 connecting the runner 17 and the cavity 18 is provided at 3α.

Prior to the injection molding of the mouth and neck, the pipe-shaped body 6 is supported by a vertically movable support 20, and the open end 8 and the upper surface of the open end are heated to its softening temperature, generally from 9°C to 110°C. Next, the support 20 and the split molds 13α and 16b are raised. As a result, the tip 15α of the male mold 14 is inserted into the opening 8 of the pipe-shaped body 6, and as this insertion is forcibly performed, the tip 8 engages with the tapered surface 15b of the male mold 14. The diameter is gradually expanded, and finally the split molds 13α, 13b and the male taper surface 15 are formed as shown in Fig. 5-B.
It is formed into the shape of a trumpet-like connecting portion 25 defined by b. Also, split mold 13α.

A cavity 18 defined by M[f2 of fl, the outer circumferential surface 15 of the male mold 14, and the tip 8 of the pipe-shaped body 6 is formed.

By injecting the polyester into the cavity 18 through the runners 17 and 19, it is possible to form the neck and neck of the preform and to fuse and integrate this neck and neck with the pipe-shaped body 6.

In FIG. 6, which shows a multilayer bottomed preform obtained by the method of the present invention, the preform 21 is
It is formed by integrating a pipe-shaped body part 6 and a flange-like part 25 with an enlarged diameter formed by a multilayer coextrusion pipe method, and a closed bottom part 7 and a neck part 22 formed by injection of polyester. Moreover, a remarkable feature is that the opening end portion 24 provided with a sealing bead 26 is precisely formed in the mouth and neck portion 22.

In the specific example shown in FIGS. 5-A and 5-B, a notch or an engaging portion 9 is provided at the tip of the pipe-shaped body 6, but the neck portion 22 and the tip 8 of the pipe-shaped body 6 are It is not necessarily necessary to provide such a notch or an engaging portion as long as the fusion and integration with the material is completely achieved.

Furthermore, as shown in Figures 5-A and 5-B, it is desirable to perform the injection of the mouth and neck part and the fusion and integration of the pipe-shaped body part all at once, from the viewpoint of finishing accuracy of the joint surface, but as shown in Figure 7. As shown in
Lower end part 2 of neck and neck part 22 manufactured by injection of polyester
6α and the upper end 26b of the pipe 1 shown in FIG. A combination may be used to join the end faces together. Of course, when the pipe 1 is joined to the neck part 22, the bottom part shown in FIGS. 2 to 4 can also be formed after that.

The method described above has the characteristic that no excess resin is generated when a preformed product is obtained from a multilayer pipe or tube.

Next, the bottomed preform is preheated using hot air, an infrared heater, high frequency dielectric heating, etc. to a temperature appropriate for stretching the multilayer preform. In this case, the temperature range is 85° to 12 DC, preferably 95°C to 110°C. Insert the mandrel 27 into the mouth, and insert the mandrel 27 into the mouth of the pair of pot molds 28α, 28.
Clamp with b. A vertically movable stretching rod 29 is provided coaxially with the mandrel 27, between which there is an annular passage 60 for the injection of fluid.

In the present invention, the tip 61 of this stretching rod 29 is applied to the inside of the bottom part 7 of the preform 21, and this stretching rod 29
The preform 21 is moved downward to stretch it in the axial direction, and fluid is blown into the preform 21 through the passage 30, and the fluid pressure causes the preform to expand and stretch in the local direction.

According to the present invention, the neck of the final container and the neck of the preform are dimensionally equalized, and the diameter of the body of the preform is made sufficiently smaller than that of the final container. The stretching ratio in the circumferential direction is ensured.

According to the present invention, by carrying out the axial stretching and the circumferential stretching at the same time or almost simultaneously, even if the two-handed vinyl alcohol copolymer layer has a high vinyl alcohol content, the stretching can be carried out relatively easily. It has the advantage of being able to be stretched at low temperatures.

This is because even ethylene-vinyl alcohol copolymers containing high vinyl alcohol are extremely difficult to stretch.
When stretching a film, even if the temperature is at the appropriate stretching temperature, when the film is stretched sequentially in the vertical axis and then in the horizontal axis, as mentioned above (this is surprising given that the film ruptures during the stretching process). .

t, J-'+7 In stretch blow molding of a multilayer pipe of fluoropyrene and ethylene-vinyl alcohol copolymer, the ethylene-vinyl alcohol copolymer ff1a layer in the multilayer is stretched in a fairly high temperature range of 140C to 165C. Considering the fact that it is finally possible, the stretching temperature range of polyester resin is 85C to 120C, especially 95C to
It is a surprising fact that an ethylene-vinyl alcohol copolymer can be biaxially stretched in a temperature range as low as 110C.

The reason for this is that co-stretching is performed with the ethylene-vinyl alcohol copolymer layer placed on the polyester layer, and delamination between the two phase resin layers is suppressed during co-stretching, and that biaxial stretching is performed simultaneously. The multi-layer stretched polyester bottle thus obtained not only has excellent transparency, but also has a much higher gas barrier than a single polyester (stretched PET) bottle, which is superior to other plastic bottles. This bottle has a gas barrier property that can be adjusted as necessary, and is also pressure resistant, making it extremely easy to fill and store carbonated beverages, such as beer, cola, and cider. It is hygienic and when used containers are disposed of and incinerated, the gas generated is almost only carbon dioxide and water, and no harmful gases are generated. sex,
An ideal container that is lightweight and rupture resistant while having gas barrier properties and pressure resistance is provided.

Although the gas barrier resin has been explained using an ethylene-vinyl alcohol copolymer as an example, the gas barrier resin is not limited to this example, and may be a thermoplastic resin with good gas barrier properties, such as a gas barrier polyamide. (
Of course, it can also be applied to gas barrier copolyester (US Pat. No. 4,398°017), gas barrier initrile resin, vinyl chloride IJ densate resin, etc.

The invention is illustrated by the following example.

Example Extruder for inner and outer layers with a built-in full-flight screw with a diameter of 65 mm and an effective length of 1,430 mm, with a diameter of 50 mm
Cabinet, extruder for intermediate layer and extruder for adhesive layer with built-in full-flight screw with effective length of 1.100 m, 5
Using a ring-shaped layer die, the inner and outer layers were made of polyethylene terephthalate with an intrinsic viscosity of 1.0, the middle layer was made of ethylene-vinyl alcohol copolymer with a vinyl alcohol content of 70 molt, and the adhesive layer was made of polyamide (6-nylon/ 6
, 6 nylon copolymer) is extruded into water through a goo and cooled. The outer diameter of this pipe is 30 m, the inner diameter is 22 gates, and the thickness of each layer is 1.
．． 4 rtrm, the outer layer is 2.0++ m, the adhesive layer is 0.05 m each, and the middle layer is 0.5 W. This pipe is cut to a certain size (length 129 gates, weight 551 gates), and one end of the pipe is 4 and 5.
After inserting the pipe into a mold as shown in the figure, the mold is clamped, and the IJ'x tyrene terephthalate is individually injected to form a closed bottom and fused and integrated with the pipe, It was taken out from the mold after cooling.

Next, the open end and upper side of this bottomed pipe are heated to 102C to form a trumpet-shaped open end consisting of the top part with an outer diameter of 42 rm and the middle part with an outer diameter of 30 rm, as shown in Figure 5-A. 0 formed by heating only the open end of this pipe to a temperature of 25 DC,
The polyethylene terephthalate is inserted into the injection mold shown in FIG. 5-A and FIG. The product was fused and integrated, and the product was cooled and taken out from the mold.

This preformed product is heated to 105C, and is stretched in the vertical axis direction in a blow mold, while being blow-molded in the horizontal axis direction (with an internal volume of 1550 cm).
A multilayer stretched bottle of c was obtained.

The oxygen permeability of this bottle is approximately 1.5CC/i・24H-
atm<37c), and there was no damage when dropped onto concrete from a height of 120 crn, and no peeling occurred between the layers. Furthermore, since the neck of this bottle was formed with high precision by injection molding of polyester, no deformation or leakage occurred in the neck even when the bottle was filled with 96C liquid and sealed with a lid.

Effects of the Invention A container molded from a preform obtained by this method has the following characteristics.

(1) It has the same content preservation properties as the co-injection method and the co-extrusion pipe method.

(2) Since the closed bottom part is molded by the injection method, it has flexibility in shape and can be molded with good sealing performance.

(3) By unifying the shape of the mouth and neck, it becomes possible to use molds together.

(4) Multi-layer pipe molding can be done arbitrarily depending on the barrier properties, thickness, etc.
Since the pipe length can be easily changed, it is possible to quickly respond to customer needs by standardizing the neck and mouth molds.

(5) The mouth and neck can be made of PET alone and have very good transparency, and the color of the mouth and neck can be changed.

(6) The mouth and neck are wide, making it easier to take out the contents and make it easier to drink.

(7) Since the diameter of the multilayer pipe can be reduced,
Blow molding allows for a high horizontal stretching ratio of the container body,
The mechanical strength of the container, including drop impact strength, is significantly improved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a multilayer pipe used in the present invention, Figs. 2 to 4 are explanatory views of the process of forming a closed bottom, and Fig. 5-A is an explanatory view of the process of enlarging the open end of the pipe. , Fig. 5-a is an explanatory diagram illustrating the injection process of the mouth and neck part, Fig. 6 is a cross-sectional view of the multilayer preform used in the present invention, and Fig. 7 is a diagram showing the fusion of the pipe-shaped body part and the injection molding mouth neck part. FIGS. 8 and 9 are explanatory diagrams showing the integration process, in which the preform is held in a blow mold, and are a sectional view before blow molding and a sectional view after blow molding. 1 is a coextruded multilayer pipe, 2 and 3 are polyester inner and outer layers, 4 is an intermediate gas barrier layer, 6 is a pipe-shaped body,
7 is a closed bottom part, 21 is a kebbed 11 form, 22 is an injection polyester neck, 25 is a trumpet-shaped part, 50 is a pipe holding core, 52 is a heater, 56α and 56b are injection split molds, and 57 is an injection bottom mold. show. Patent applicant: Toyo Seikan Co., Ltd. Figure 1 Figure 2 Figure 4 Figure 5-4 Figure 5-8 Figure 6 Figure 7

Claims (3)

[Claims] (1) In a method for manufacturing a preformed product for a stretched polyester container, one end of a multilayer pipe formed by coextrusion is closed, the other end of the pipe is heated to a softening temperature, and then the original diameter of the pipe is The mouth and neck are expanded into a trumpet shape to have a large diameter, and the mouth and neck that are to be connected to the enlarged open end are manufactured by injection molding of thermoplastic polyester, and the body and the mouth and neck are molded in an injection mold. 1. A method for producing a preformed product for a stretched polyester container, which comprises fusing and integrating a body part and a neck part at the same time as molding, or by fusing and integrating a body part and a neck part outside a mold. (2) The method according to claim 1, wherein the multilayer pipe comprises polyester inner and outer layers and a gas barrier resin intermediate layer. (3) The method according to claim 1, wherein the gas barrier resin comprises an ethylene-vinyl alcohol copolymer or polyamide.