CS270569B2 - Method of hollow containers production from multi-layer plastics - Google Patents

Abstract

A multilayer plastic container is produced using two or more layers. The outer layer is introduced into a mould and an inner layer is extruded into the mould. The bottom edges are joined together by clamping, whilst one layer is in the melt phase. - Compressed air blown through the clamping section forces sealing between the two layers over the entire surface. The mould is then closed and both layers forced against the inner surface of the mould.

Description

The invention also relates to a process for the manufacture of hollow containers of multilayer plastics, in which an inner and an outer layer, one of which is in the melt phase, are fed into an open mold and, after closing the mold, pressed against the mold wall under pressure.

Such a process is known from Japanese Patent Application Publication No. 45-39189. In the known method, the inner and outer layers are fed into the open mold, whereupon the mold is closed and first the inner layer is pressed against the outer strand by pressurized media and then the layers are pressed together against the inner side of the mold.

In the unformed state, the outer layer may not fully surround the inner layer, such as when a cylindrical inner layer, such as a rounded film or a film extruded in such a shape, and two flat or curved films are placed in an open mold against each other and on both sides of the inner layer.

In the known method, it is well possible that the air at least partially remains trapped between the compressed layers, which constitutes a serious technical drawback in the numerous applications of such obtained products.

The present invention is based on a process for the manufacture of hollow containers of multi-layered plastics material in which an inner and an outer layer, one of which is in the melt phase, is fed into an open mold in tubular formations surrounding the outer tubular structure. the tubular formation of the inner layer a faces towards the side walls of the mold cavity, the layers being pressed after the mold is closed under pressure against the walls of the mold _f, this pressure being exerted by a pressurized fluid medium characterized in that at least one of the layers is introduced into an open mold in the form of an extruded tube which is still in the melt phase and is extruded at a first position above the mold, the first and second layers being clamped at a second position below the mold, and layers into each other touch it for at least 99% of their surface by inflating the laminated tubular body from the inside toward the sides so that their contact surfaces are glued together before closing the mold, whereupon the mold is closed and the inner layer is further inflated, whereby the inner and outer layers are pressed against the wall of the mold.

With this solution, the inner and outer layers are perfectly joined and there is no risk of air pockets and the resulting defects such as occur in the prior art.

The method of the invention can be used in the manufacture of hollow articles having walls of two or more layers. All these layers may be of different plastics, but this is not necessary.

According to one embodiment of the invention, at least one of the layers is fed into the open mold as a film comprising at least two layers of different materials.

Preferably, air is evacuated from the space between the inner and outer layers during inflation of the layers from the inside.

The inner layer can also be fed into the open mold as a balloon-shaped film, and the balloon is reduced before the outer layer is brought into the mold by aspirating the gas contained in its cavity.

The method in which a multi-layer or balloon film is used is particularly advantageous when the end product is subject to gas or vapor permeability requirements and / or mechanical properties. suitable for the production of containers for the storage of chemicals such as solvents and also for the production of technical products such as the production of oil tanks · For applications where permeability is as low as possible, it may be advantageous for at least one layer to be a film. or at least one layer comprises such a film. Films with 8 barrier properties are generally known and need not be characterized in detail. Any one of ordinary skill in the art can readily make a choice of numerous known films with barrier properties. The content or absence of a barrier film is not critical to the process of the invention, and therefore the use of any such suitable barrier film is within the scope of the invention.

In principle, any polymeric plastics may be used in the process of the invention, or adhesives may be used to achieve a suitable bond.

Particularly suitable plastics are, for example, for one layer of high density polyethylene β (HDPE) or linear low density polyethylene 8 (LLDPE) in connection with the β second layer, which is a multilayer film consisting of: HDPE-Plexar-Nylon 6-Plexar-HDPE or HDPE-Surlyn-Polyester-Surlyn-HDPE where:

Plexar - modified vinyl acetate resin,

Nylon 6 - polycaprolactam,.

Surlyn - ionomers based on ethylene and methacrylic acid.

When using a multilayer film, LLDPE can also be used instead of DHPE, whereby polyester can be replaced by Eval (copolymer of ethylene and vinyl alcohol), Nylon-Eval mixed, Nylon 6.12 (condensation product of hexamethyldiamine and lauric acid) and copolymers of these materials. However, the invention is not limited to these compositions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the accompanying drawings, in which: FIGS. 1 to 4 show the working phases of a first embodiment of the method of the invention, wherein the inner layer is an extruded blank and the outer layer is two flat films or a tubular film; 5 to 8 a working phase of another embodiment of the method according to the invention, wherein the inner layer comprises a balloon-like, multi-layer tubular film and the outer layer a single-layer semifinished product.

In Fig. 1 the mold 1 consists of two mold halves 2, has an extrusion nozzle 3, Д, an extrusion gap 5 and a tran 6 is actuated by a spindle 7 ·

The device 8 consists of a fixed central part 9 and two movable parts 10 and 11. The pressure 12 supplies a pressure medium, for example air, to the buffer vessel 13. While it is also possible to supply cooled air, this is generally less desirable.

When the valve 14 is opened and the second valve 15 is closed, the pressurized environment can be introduced via the pipes 16 and 17 into the opening 18 in the central part 9 of the clamping device 8.

When the valve 14 is closed and the second valve 15 is opened, the environment from the cavity 20 can be discharged via the pipes 17 and 19 and the orifice 18, and possibly underpressure against the environment can be created.

The pressurized liquid medium can also be supplied through the orifice 21 in the spindle 7 which extends into the mandrel 6, or the medium can be discharged from the cavity 20.

2 to 8 show the same apparatus as in FIG. 1, except for the support tube 26, which is provided with openings 29 (see FIGS. 5 to 8).

1 to 4. First, the outer layer 22 (see FIG. 1) is introduced into the open mold 1. Then the extruder 4 feeds the inner blank 23 in the direction of the arrows 24 into the open mold. (see fig.

2). Then, the inner layer 22 and the outer layer 23 are pressed near their lower edges 31 and 32 by the clamping device 8 (see Fig. 3) and the valve 14 is opened for a time (see Fig. 4) to pressurize the pressurized fluid medium, e.g. The mold halves 2 and 3 are moved against each other and the mold is closed in a manner not shown, whereupon the layers are pressed together against the inner mold wall by pressure environment. After cooling, the mold can open and the object is removed from it.

The invention can also be carried out in a manner the phases of which are illustrated in FIGS

First, the balloon-shaped multilayer film 25 (see FIG. 5) is introduced into the open mold 1 and supported by the central portion 9 of the clamping device 8. Then the second valve 15 opens, the valve 14 is closed, and vacuuming reduces the balloon volume. The support tube 28 supports the collapsed balloon 26 to the sides (see FIG. 6). Then, the extruder 4 feeds the blank 27 shown in FIG. 7 into the open mold 1, whose bottom edge (not shown) is pressed against the bottom edge (not shown) of the multilayer balloon-shaped film 25 by the clamping device 8 (see FIG. 7). and the valve _14f is opened so that the pressure medium passes from the buffer vessel 13 to the cavity of the multi-layer balloon-shaped film 25 (FIG. 8).

When the collapsed balloon 26 is inflated to the extent that it contacts the outer layer of the blank 27 almost everywhere and both layers are sufficiently rigid, the two mold halves are moved together and the mold 1 is closed and the two layers are pressed together against the inner the mold wall 1 using a pressurized environment.

The air between the inner and outer layers may be expelled through the aperture 21. The air between the mold halves 1 and the outer layer must be able to escape in a manner known to those skilled in the art.

Various variations are possible within the scope of the invention. For optimum results, it is desirable that not only the pre-inflation, i.e. the contacting of the layers by a pressurized medium such as air, and their bonding before the mold is closed, takes place quickly, especially in a few seconds or less, but also with some force, that is, the pre-inflation takes place under pressure. In a suitable embodiment, it may be desirable to surround the multilayer blank with a support sleeve such that when the pre-inflation pressure is increased, the outer layer is pressed against the support sleeve and thereby retains its shape. By pre-inflating at high speed and at elevated pressure, the removal of air between layers can be further improved.

The support sleeve may have any desired shape and construction and may consist of one element or two or more connectable elements. The support sleeve may also be made of an air permeable material so that not only the outer layer may be tightly pressed against it, but the outer film may even be sucked into the support sleeve using partial vacuum in the region of the support sleeve; if this outer film is perforated, the removal of air from the space between the two layers can be further improved. Such a support sleeve may also be heatable to achieve optimal bonding of the inner and outer layers.

Obviously, when such a support sleeve is used, the apparatus for carrying out the method of the invention must include means for removing the support sleeve after pre-inflation and before closing the mold so that the mold can then be closed and the bonded layers pressed against the mold wall.

The introduction of the gaseous medium, usually air, during pre-inflation can also be effected by various means. It is usually desired to inflate at one location so that the inner and outer layers are pressed against each other and then displaced instead of the inflated air, resulting in some development of one layer relative to the other. This can be achieved, for example, by injecting the inflation environment through a nozzle in a direction diverted from the perpendicular to the axial direction. Such a nozzle may be, for example, in the center section 9 of Figure 1. If the nozzle is axially movable, it may move from bottom to top or otherwise, blowing in the nozzle. · Turbine-shaped nozzle is particularly advantageous. Using such a device, it is possible to press the inner layer against the outer layer at the location determined by the mechanism and to bring the layers in contact in the desired direction gradually ·

Claims (4)

SUBJECT OF THE INVENTION A method for manufacturing hollow containers 2 of a multilayer plastics material, in which an inner and an outer layer, one of which is in the melt phase, is fed into an open mold, in tubular formations, of which the outer tubular formation surrounds the tubular inner layer structure. facing towards the side walls of the mold cavity, the layers being pressed after the mold is closed by applying pressure against the walls of the mold, the pressure being exerted by a pressurized fluid medium, characterized in that at least one of the layers is fed to the open mold in the extruded tube it is still in the melt phase and is extruded at a first point above the mold, the first and second layers being clamped at a second point below the mold and wherein the layers are contacted for at least 99% of their area by inflating before closing the mold laminated tubular shape from the inside towards the sides, bringing their contact surfaces are glued together before closing the mold, whereupon the mold is closed and the inner layer is further inflated, whereby the inner and outer layers are pressed against the wall of the mold · 2. The method of claim 1, wherein at least one of the layers is fed to the open mold as a film comprising at least two layers of different materials. Method according to claim 1 or 2, characterized in that, during the inflation of the layers from the inside, air is extracted from the space between the inner layer and the outer layer. 4. A method according to any one of claims 1 to 3, wherein the inner layer is fed into the open mold as a balloon-shaped film and the balloon is reduced before the outer layer is brought into the mold by aspirating the gas contained in its cavity.