JPS62270315A - Manufacture of oriented polyester vessel - Google Patents

Abstract

PURPOSE:To prevent the deformation of the neck part of a vessel and permit the accurate molding of a screw part by a method wherein the cylindrical part of the vessel, formed by co-extruding thermoplastic polyester resin and thermoplastic gas barrier resin, thereafter, molding it through biaxial orientation blow molding, and the neck part, manufactured by the injection molding of thermoplastic polyester, are integrated by fusion welding in an injection mold. CONSTITUTION:A preform with bottom, formed by an method wherein a multilayer pipe, formed by joining the co-polymer of molten polyester and molten ethylene vinyl alcohol in a dice and extruding through and annular orifice, is cut into a predetermined size, thereafter, is heated to melt and form the preform, is preheated by hot air of the like and biaxial orientation blow molding is effected to form the cylindrical part 30 of a vessel. The cylindrical part 30 of the vessel is supported by a supporting fitting 40, movable up-and-down, and the tip end thereof is heated, thereafter, the supporting fitting as well as split molds 33a, 33b are elevated to insert the tip end of a male mold 34 into the opening of the cylindrical part 30 of the vessel. On the other hand, polyester is injected into a cavity 38 to mold a neck part 50, thereafter, the neck part 50 is integrated with the cylindrical part 30 of the vessel by fusion welding.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a stretched polyester container, and more specifically, it relates to a method for manufacturing a stretched polyester container, and more specifically, a container formed by coextrusion or an eve method. The present invention relates to a method for producing a stretched polyester container, which comprises biaxially stretching blow molding a bottomed preform to form a container body, and then forming a container neck.

(Prior Art) Stretched polyester containers are used for liquid detergents, shampoos, cosmetics, etc. due to their excellent transparency and suitable gas barrier properties.
In addition to containers for liquid products such as soy sauce and sauces, in recent years beer,
It has come to be widely used in containers for carbonated drinks such as cola and cider, and soft drinks such as fruit juice and mineral water.

As a method for manufacturing this stretched polyester container, a so-called coextrusion pyzo method has been proposed.

(Japanese Unexamined Patent Publication No. 59-199237) In this method, thermoplastic polyester, thermoplastic gas, glycerin resin, etc. are heated and melted using extruders with a number corresponding to class 4 of the resin, and the melt inside the die head is heated and melted. Is the channel uniformly distributed in too many layers? get the song.

The Harrison is then sized using a sizing former and cooled through a cooling bath. Next, the cooled strips are cut into predetermined lengths. The next step is to form the threaded part and bottom of the cut pipe. The molding method begins by heating one end of the mother tube to an appropriate temperature, placing it in a mold, and blowing high-pressure air to mold the bottom.

Next, the other end of the pipe is heated to an appropriate temperature, placed in a screw mold, and high-pressure air is blown into it to form the threaded part.

At this time, it goes without saying that it is also possible to mold the threaded portion first and then mold the bottom portion.

After the preform thus obtained is heated to an appropriate temperature, it is placed in a blow mold, and high-pressure air is blown into the preform to form a container.

(Problems to be Solved by the Invention) However, in the above manufacturing method, the container neck is molded as one piece with a predetermined preform, and this is applied to blow molding, so the mold structure As a result, the wall thickness of the preform cannot be adjusted, and as a result, it is difficult to reduce the thickness of the shoulder portion during blow molding.

Another drawback is that the mouth and neck are easily deformed due to heat, pressure, etc. during blow molding, and it is difficult to achieve dimensional accuracy for screws in the mouth and neck.

Therefore, the technical object of the present invention is to solve the above-mentioned drawbacks of the conventional method when manufacturing a stretched polyester container by the co-extrusion mA-ib method.

(Means for Solving the Problems) The method for manufacturing a stretched polyester container of the present invention includes (4) forming a pipe by coextrusion of a thermoplastic polyester and a thermoplastic gas barrier resin, and (B) biaxial stretch blow molding of the bottomed preform in the axial direction and circumferential direction to form a container body; manufacturing step, (C) manufacturing a neck part having an opening at the upper end and a fitting part or a fitting part with the lid on the outer periphery by injection molding of thermoplastic polyester, and combining the container body with the mouth neck part; The process consists of: fusing and integrating the parts within or outside the injection mold.

(Function) In the production method of the present invention, polyester and ethylene-
In order to co-extrude the gas barrier tallow, such as a vinyl alcohol copolymer, into the pipe, the two resins are brought into contact with each other in a molten state for a certain period of time. Therefore, the thermal adhesion between the two is
For example, the process is more robust 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.

In addition, after cutting this coextruded multilayer material into a certain length, one end is fused and closed to form a bottom part to form a bottomed preform. It becomes possible to perform blow stretching at the same time or almost simultaneously with the axial stretching while pressing the stretching rod against the film.

That is, the occurrence of cracks and resident cracks in the ethylene-vinyl alcohol copolymer layer that are observed in the case of sequential stretching can be effectively eliminated.

To explain this point, the ethylene-vinyl alcohol copolymer has a problem in that it is significantly lacking in stretchability, especially biaxial stretchability, at the appropriate stretching temperature for z IJ ester. That is, when a coextruded multilayer pipe of polyester and ethylene-vinyl alcohol copolymer is held with clamps and stretched in the axial direction, and then blow-stretched, a large number of cracks are formed in the ethylene-vinyl alcohol copolymer layer in the axial direction. There is a tendency for cracks or latent cracks to occur. This is thought to be because a phenomenon similar to fibrillation occurs in the ethylene-vinyl alcohol copolymer layer during axial stretching, and cracks, etc., occur during the subsequent stretching operation.

According to the present invention, such a fibrillation phenomenon can be avoided by simultaneously stretching and blowing a coextruded laminate.

In the manufacturing method of the present invention, the bottomed preform is biaxially stretched and blow-molded to form a container body, and then a container mouth neck having a predetermined threaded portion and the like is formed by injection molding of polyester.

Therefore, it is possible to adjust the wall thickness of the bottomed preform using an appropriate mold, and the shoulder portion can be easily thinned during blow molding.

Further, the container neck is formed by injection molding with high dimensional accuracy, and furthermore, the neck of the container is effectively prevented from being deformed by heating or the like during blow molding.

(Preferred embodiment of the invention) The present invention will be described in detail below with respect to its preferred embodiments.

In the following, an ethylene-vinyl alcohol copolymer will be explained as an example of the varnish resin, but the present invention is not limited to this example, as will be described later.

Manufacture of preform (Step (A)) In the present invention, a pipe is first formed by coextruding polyester and a gas barrier resin such as an ethylene-vinyl alcohol copolymer. Build a preform fcM.

This coextrusion is carried out by combining the molten polyester and the molten ethylene-vinyl alcohol copolymer in a die and extruding them through a ring-shaped orifice.

In this case, an adhesive resin may be interposed between the polyester and the ethylene-vinyl alcohol copolymer if necessary.

FIG. 1 shows a multilayer motherboard 1 which is particularly suitable for the purposes of the present invention, comprising an inner layer 2 and an outer layer 3 of polyester, and an intermediate layer of ethylene-vinyl alcohol copolymer. It consists of one layer 4 and adhesive layers 5a, 5b interposed between them.

The extruded mother eve is rapidly cooled by immersion in water or the like in order to prevent crystallization of the stream ester.

After cutting this seide into a certain size, as shown in Fig. 2-A, one end 1a'' is heated and melted with a heater 10a to form, for example, a semicircular original shape as shown in Fig. 2-8. Female mold 1 having a cavity 10b corresponding to any bottom shape
0c and a male mold 10@ having a protrusion 10d,
As shown in FIG.
form.

) The other end Sa of the main tube-shaped body 6 is in an open state.

The bottomed preform thus formed is subjected to two-wheel stretch blow molding, which will be described later.

As polyesters, polyethylene terephthalate, copolyesters mainly containing ethylene terephthalate units, and also containing some modification ester units, which are known per se, are used for the purpose of the present invention. This polyester only needs to have a molecular weight sufficient to form a film.

In the present invention, the sparring resin used is preferably an ethylene-vinyl alcohol copolymer, generally a copolymer obtained by saponifying a copolymer of ethylene and a vinyl ester such as vinyl acetate, and the molding process Considering the properties and barrier properties, the ethylene content is 15 to 50 mol, especially 25 to 45 mol, and the degree of saponification is 9.
Those with 6q6 or more are advantageously used. The molecular weight of this copolymer may be any as long as it has film-forming ability.

Although not necessarily necessary, 1. T? Any adhesive known per se can be used to enhance the adhesion between the IJ ester layer and the ethylene-vinyl alcohol copolymer layer. Copolyester adhesive, polyester-
Ether adhesives, dioxymodified thermoplastic resins, acidic thermoplastic resins, and the like are used for this purpose.

The polyester substrate (PET), ethylene-vinyl alcohol copolymer (EVAC), and adhesive layer (AD) can be used in various layer configurations, for example, with the outer layer on the left and the inner layer on the right, paT/EvAc , EvAc/pETPF:T/AD/
W.A.C.

EVAC/AD/PET, PET/EVAC/1
)ET, PET/AD/'EVACAD/PET, and the like.

The thickness of the layer can vary, but generally PET:
EVAC=2:1 to 5:1, especially 3:1 to 4
:1, and when using an adhesive layer, PET:AD = 20:1 to 50:1.
In particular, it is recommended that the thickness ratio be in the range of 30:1 to 40:1. Used for molding.

This pre-forming is performed to adjust the wall thickness of the preform and to provide an appropriate flange at the tip of the mouth of the preform, and can be easily performed by means such as heat compression molding using an appropriate mold. It is done.

In particular, this flange part fixes the preform during blow molding, and is formed by injection molding, which will be described later, to fully engage and bring the preform into close contact with the mouth and neck of the container.

According to the present invention, such a bottomed preform is preheated to a temperature appropriate for stretching the multilayer preform using hot air, an infrared heater, high-frequency induction heating, etc., and biaxial stretch blow molding is performed.

The temperature range for preheating is generally 85-120°C, especially 95°C.
~110°C.

Stretch! 3 and 4 for explaining the row molding operation, a mandrel 21 is inserted into the mouth of a preform 20, and the mouth is inserted into a pair of split molds 22m, 2.
Clamp with 2b.

A vertically movable stretching rod 23 is provided coaxially with the mandrel 21, and between this stretching rod 23 and the mandrel 21 there is an annular passage 24 for the injection of fluid.

In the present invention, the tip 25 of the stretching rod 23 is applied to the inside of the bottom 26 of the preform 20, and while the stretching rod 23 is stretched downward, fluid is introduced into the preform 20 through the passage 24. The fluid pressure causes the preform to expand and stretch in the circumferential direction.

According to the present invention, the body of the bottomed preform is formed by a coextrusion/matrix method, and the container body is formed by two-way stretch blow molding. It is formed by an injection method and integrated by heat fusion inside or outside the injection mold.This shows a mode in which the injection of the mouth and neck and the fusion to the body are performed all at once in the mold (insert injection method). 5th-
In Fig. A and Fig. 5-B, Fig. 5-A shows a state in which the mold is open, and Fig. 5-B shows a state in which the mold is closed.

The injection mold consists of a pair of split molds 33a and 33b each having a two-ring line 31 and an inner circumferential surface 32 corresponding to the outer circumferential surface of the mouth part to be molded, and a fixed 7" male mold. It consists of a mold 34. Split molds 33a and 33bl
'j: Provided so that it can be opened and closed in the horizontal direction and can be moved up and down. The male mold 34 has an outer peripheral surface 35 corresponding to the inner periphery UkU of the mouth and neck to be molded, and a tip 36 to be inserted into the container body 30.

The fixed mold 34 has a runner 37, and the split mold 33aK
is the runner 39 connecting the runner 37 and the cavity 38
are provided for each.

Prior to injection molding of the mouth part, the container body 30 is supported by a vertically movable support 40, and if necessary, the tip 30'
After heating to a temperature that causes fusion with the mouth and neck portion to be injected, the split molds 33a and 33b are closed, and the support 40 and the split molds 33a and 33b are raised. As a result, the tip end 36 of the male mold 34 is inserted into the opening of the container body 30. Further, a cavity 38 defined by the inner peripheral surface 32 of the split molds 33a, 33b, the outer peripheral surface 35 of the male mold 34, and the tip 30' of the container body 30 is formed.

By injecting polyester into the cavity 38 through the runners 37 and 39, it is possible to form a container mouth 50 and to fuse and integrate this neck 50 with the container body 30.

(Operation and Effect) Thus, the stretching obtained by the method of the present invention? A polyester container has a neck part formed by injection of polyester that is integrated into the container body, and an open end for sealing, a surrounding threaded part, a support ring, etc. are formed with precision on this neck part. A notable feature is that

In particular, according to the present invention, since the container neck is formed after blow molding, it will be understood that deformation of the container neck due to heating during blow molding is reliably prevented.

Further, since the threaded portion is formed by an injection method, it has flexibility in shape and can be formed with high precision.

Furthermore, during blow molding, since the preform does not have a neck and a neck, it is possible to freely adjust the wall thickness of the preform.

(Example) Extruder for inner and outer layers with a built-in full-flight screw with a diameter of 65 and an effective length of 1.430 m, a diameter of 50 m
, the effective length is 1. Using a Loom full-flight screw extruder for the base intermediate layer, an extruder for the adhesive layer, and five ring-shaped dies, the inner and outer layers are polyethylene terephthalate with an intrinsic viscosity of 1.0, and the intermediate layer is cahinyl alcohol. Contains! 70 mol ethylene-vinyl alcohol copolymer, and the adhesive layer is a copolymerized nylon of 85 mol nylon 6 and 15 mol nylon 646.
Lamination of layers! The eve is extruded through a die into water and cooled.

The outer diameter of this tube is 30 mm, the inner diameter is 22 mm, and the thickness of each layer is 1.4 mm for the inner layer and 2.0 mm for the outer layer.
, adhesive increase is 0.05m5a and medium VJ layer is 0.
．． 5m, and this pipe has a certain size (length 129,
One end of the pipe was heated to approximately 220°C to form a blockage at the bottom of the semicircular shape.

A flange part is formed at the open end of this pipe by hot compression molding, and then the preform is heated to 105°C and vertically placed in a blow mold as shown in Figures 3 and 4. While stretching in the axial direction, plow and main stretching in the horizontal direction,
A stretched bottle body with a content f11550cc was obtained t0. Then, only the upper end opening of this stretched bottle was heated to a temperature of 230°C, and the stretched bottle was inserted into the injection mold shown in Figures 5-A and 5-B, and the polyethylene Terephthalate alone is injected to form a north neck with a sealing opening end, a threaded part, and a support ring, and is fused and integrated with the bottle wings. After cooling, the bottle is removed from the mold to obtain a stretched bottle container. Just in case.

The oxygen permeability of this gas is approximately 1.5 cc/, 12.2
4H atm (37℃), no damage when dropped onto concrete from a height of 120m, and no peeling between layers.In addition, the neck of this bottle is precisely formed by injection molding of polyester. 93
Even when filled with liquid at ℃ and sealed with a lid, no deformation or leakage of the neck occurred.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the multilayer 9 ide used in the present invention, and Figure 2-
Figures A, 2-B and 2-C are explanatory diagrams of the bottom forming process, and Figures 3 and 4 are diagrams of the bottomed preform before glow molding with it held in the blow mold. A cross-sectional view and a cross-sectional view after blow molding are shown, respectively, and Figures 5-A and 5
-B is an explanatory diagram showing the process of fusing and integrating the stretch-molded container body and the injection molding mouth neck.

Claims (1)

[Claims] (1), (A) A pipe is formed by coextrusion of thermoplastic polyester and thermoplastic gas barrier resin, and after cutting the pipe to a certain size, one end is fused and closed to form a bottomed preform. (B) A step of manufacturing a container body by biaxially stretching the bottomed preform in the axial direction and the circumferential direction. (C) Fitting the bottomed preform with an opening and a lid on the outer periphery. A step of manufacturing a mouth and neck having a joint or a threaded joint by injection molding of thermoplastic polyester, and fusing and integrating the container body and the mouth and neck within or outside the injection mold. A method for producing a stretched polyester container characterized by comprising: