EP1286818A2

EP1286818A2 - Method for producing a container and container having barrier properties

Info

Publication number: EP1286818A2
Application number: EP01943154A
Authority: EP
Inventors: Klaus Hartwig; Wolf Jaksztat
Original assignee: KHS Corpoplast GmbH
Current assignee: KHS GmbH
Priority date: 2000-06-06
Filing date: 2001-05-22
Publication date: 2003-03-05
Also published as: DE10027924A1; BR0111416A; WO2001094097A3; WO2001094097A2; AU2001265815A1

Abstract

The invention relates to a container produced from a homogeneous thermoplastic material that has barrier properties in terms of a wall permeability to gases. The container is produced from a preform by blow-molding and its barrier characteristics correspond at least to a factor of > 2 BIF. The inventive container is deformation-resistant up to a temperature of at least 60 DEG C and has a bottle-shaped design with a bottom that curves inwards and that is enclosed by a supporting ring. The material used for the container comprises a main component and a barrier component with a substantially homogeneous distribution. The barrier component has a weight of not more than 30 % based on the weight of the main component. The container volume is not more than 1 liter and the supporting ring has a thickness of at least 1 mm. The container further comprises a base body and a container neck, the neck length accounting for at least 20 % of the container length. The maximum neck width is not more than 80 % of the maximum width of the base body.

Description

Process for manufacturing a container and containers with barrier properties

The invention relates to a method for producing a container from a thermoplastic by blow molding and biaxial orientation, in which a preform is inserted into a blow mold and expanded by the action of a pressure medium, and in which a blow mold comprising at least two blow mold segments and one is used to contour the container Floor insert is used.

The invention further relates to a container made of a homogeneous thermoplastic material with barrier properties with respect to a wall permeability for gases, which is produced by blow molding from a preform and whose barrier characteristic corresponds to at least one factor BIF> 2, and which is resistant to deformation up to the effect of temperature has at least 60 °, and the has a bottle-like design with an inwardly curved bottom, which is surrounded by a base ring.

Such containers are known in different embodiments. The barrier properties relate here in particular to resistance to the escape of carbon dioxide from an interior of the container into an environment and to the ingress of oxygen from the environment into a liquid stored inside the container. Typical methods for achieving a sufficient barrier property are, for example, plasma evaporation with silicon dioxide or carbon-containing materials. In addition, it is also known to use multi-layer containers, of which at least one layer is provided with the increased barrier properties. The barrier properties are generally measured compared to the use of standard PET material, and the BIF factor is determined. BIF means "Barrier Improvement Factor". A factor of BIF = 2 indicates a double barrier effect compared to the use of standard material.

The implementation of plasma coating processes requires a considerable outlay on equipment, and the use of carbon-containing coatings also addresses concerns about health risks. The use of multilayer preforms for the production of the containers causes a high outlay in the injection molding production of the preforms, which results in corresponding costs.

A general process for blow molding containers is described for example in DE-OS 43 40 291. Possibilities for controlling different blowing pressures are specified in DE-OS 41 13 874. A device for performing the method is described in DE-OS 42 12 583.

Containers made from preforms can have different properties and uses. Both disposable containers and refillable containers are known. In addition, containers are known which can also withstand elevated temperatures when filling or when carrying out washing and / or pasteurization processes.

Such a container can be shaped, for example, by first producing a preform from polyethylene terephthalate (PET) using the injection molding process and by heating the preform after intermediate storage and then feeding it to the blow molding station. However, it is also known to produce containers by the injection-blow process, in which the preform is fed to the blow molding station immediately after its production and after sufficient stability has been achieved, without interposition of heating. Finally, it is also known to produce preforms from pipe sections which are closed in the area of one end and provided with a suitable mouthpiece in the area of their other end.

Common to all methods is that the preform has a significantly smaller shape than the container to be produced. Compressed air is therefore applied to the preform within the blowing station in order to convert it into the container to be produced. In this inflation process, in addition to reducing the wall thickness by increasing the surface area, the material is oriented. This causes the thin Wall of the container has a very high dimensional stability, which makes the container suitable for a variety of uses.

Different methods are known for carrying out the blowing process. On the one hand, it is possible to use a uniform blowing pressure, which is introduced into the preform to be inflated and, after sufficient molding, is released from the finished container against an ambient pressure. It is also already known to first carry out a pre-expansion of the preform, which already approximates this relatively closely to the shape of the container to be produced, with a lower pressure, and only to express the finer contour of the container with a higher pressure. In this process, too, the blown air is vented against an ambient pressure after the container has been manufactured.

Depending on the application, different goals can be in the foreground when specifying the barrier properties. The main requirement for carbonated soft drinks is to prevent or reduce the escape of carbon dioxide through the container wall to the outside. In contrast, when storing, for example, fruit juices, beers or other oxygen-sensitive drinks or foods, the main requirement is to prevent or reduce the penetration of oxygen through the wall of the container into the stored liquid. In general, there is the problem that the substances suitable for improving the barrier properties can have a toxic effect and, therefore, in the case of filling liquids which are intended for consumption, there is direct contact between the liquids and the substances used to improve the barrier properties should be avoided.

In general, there is a high need to achieve the required barrier properties with little apperative effort, little time and at the lowest possible cost. Impairments to the product quality of beverages filled within the container must also be excluded. With the methods and devices that have become known so far, individual requirements can already be met relatively well, but a common satisfactory fulfillment of all requirements has not yet been achieved.

It is therefore an object of the present invention to improve a method of the type mentioned in the introduction in such a way that the properties of the containers produced are improved with respect to the shelf life of filled products without significant cost increases.

This object is achieved in that the blow mold segments are tempered to an average surface temperature in the range from 40 ° C to 170 ° C and that the floor insert is kept at a temperature below the average surface temperature of the blow mold segments.

Another object of the present invention is to provide a container of the type mentioned in the introduction in such a way that production with improved barrier properties is supported with inexpensive production.

This object is achieved in that a material main component and a barrier component with an essentially homogeneous distribution are used as the material for the container, the weight of the Barrier component maximum 30% of the weight of the main material component is that the container volume is a maximum of 1 liter. is and the base ring has a material thickness of at least 1 mm and that the container has a base body and a neck, wherein a neck length is at least 20% of the container length and a maximum neck diameter is at most 80% of a maximum diameter of the base body.

The bottle geometry explained above and the process sequence used in container manufacture make it possible to use a cheap preform to be produced from a homogeneous material and to avoid costly plasma coating processes to produce a plastic container which is more thermally and mechanically resistant than a standard PET bottle and which is provided with barrier properties which in particular support use for the reception of beer or beverages containing beer. The higher thermal resistance makes it possible to go through a pasteurization treatment. The increased barrier properties make it possible to prevent the penetration of critical amounts of oxygen, or at least to significantly reduce it, when bottling beer.

Product optimization can be achieved through the combination of the bottle design explained, a design of the shaping blow mold, a design of the preform used as the starting product, the selection of the bottle process to be used and the process sequence when carrying out the blowing process.

Improved material consolidation in the bottom area of the container can be achieved by a cooling time in the area of the floor insert is at least 2 seconds.

Improved contour stability can be achieved in that a contour flattening of the container base after blowing makes up a maximum of 25% of the distance of a container base to a center of the base before the blown container is removed from the blow mold.

It also proves to be advantageous with regard to the contour stability that the flattened base after pasteurizing accounts for a maximum of 55% of the distance from a container base to a center of the base before the blown container is removed from the blow mold.

An additional increase in stability can be achieved in that the material thickness in the area of the base ring is at least 1.2 mm.

Impairment of the quality of the filled product can be avoided by coloring the material at least in some areas.

Another possibility for reducing the penetration of gas amounts is that a substance for the accumulation of penetrating gases is arranged at least in some areas.

A simple closure possibility is that an external thread is arranged in the region of a mouth section of the container.

To avoid a sudden internal pressure discharge when opening the container, it is proposed that in At least one vent slot is arranged in the area of the external thread.

To reduce notch stresses, it is proposed that the ventilation slot be provided with a rounded contour.

An additional increase in stability can be achieved in that the mouth section has a reduced inner diameter in the area of the external thread.

Another closure possibility is that the mouth section is designed to arrange a crown cap.

It is also contemplated that the mouth section is designed for the arrangement of a clip closure.

In order to take into account a container expansion when exposed to an internal pressure, it is proposed that a side wall of the container is at least partially curved to an extent of 1% to 2% based on a container diameter in the direction of a container interior. In particular, starting from the bottom in the direction of the container shoulder, a conical course is also considered.

In particular, it proves advantageous that the inner curvature of the side wall is approximately 1.4%.

A penetration rate of harmful gases can be further reduced by arranging a substance for the attachment of at least one penetrating gas in the area of a container closure. A typical material selection is that PET is used as the main material component.

It is also thought that PP is used as the main material component.

Another variant is that PEN is used as the main material component.

Particularly good barrier properties can be achieved by using nylon as the barrier component.

It is also possible that EVOH is used as the barrier component.

Another variant can be seen in the fact that PEN is used as the barrier component.

An expanded range of materials is provided by using a PET as a barrier component

Copolymer with increased isophthalic acid content is used.

A barrier can be increased by embedding particles in the polymer matrix by using a polymer mixture with solid particles as the barrier component.

Exemplary embodiments of the invention are shown schematically in the drawing. Show it:

1: a longitudinal section through a preform, 2: a partial longitudinal section through a container designed as a bottle,

3 shows a perspective view of the container according to FIG. 2 when viewed obliquely from below,

Fig. 4: a longitudinal section through a blow mold in which a preform is stretched and expanded

and

Fig. 5: a sketch to illustrate a basic structure of a device for blow molding containers.

According to the embodiment in FIG. 1, a preform (1) consists of a mouth section (2), a support ring (4) separating the mouth section (2) from a neck area (3), and a neck area (3) into a wall section (5) overlapping shoulder area (6) and a floor (7). The support ring (4) projects beyond the mouth section (2) transversely to a preform longitudinal axis (8). In the region of the shoulder area (6), the outer diameter of the preform (1) widens from the neck area (3) in the direction of the wall section (5). In the case of a container (13) to be produced from the preform (1), the wall section (5) essentially forms the side wall of the container. The bottom (7) is rounded.

The mouth section (2) can, for example, be provided with an external thread (12) which enables a screw closure to be placed on the finished container (13). However, it is also possible to provide the mouth section (2) with an outer bead in order to create an area of attack for a crown cap. Beyond that too a variety of other designs conceivable to enable plug-in closures to be attached.

From the illustration in Fig. 1 it can be seen that the wall section (5) has an inner surface (9) and an outer surface (10). The inner surface (9) delimits a preform interior (11).

In the shoulder area (6) the thickness of a preform wall (14) can extend from the neck area (3) in the direction of the wall area (5) with increasing wall thickness. The preform (1) has a preform length (15) in the direction of the preform longitudinal axis (8). The mouth region (2) and the support ring (4) extend in the direction of the preform longitudinal axis (8) with a common mouth length (16). The neck area (3) has a neck length in the area of the preform longitudinal axis (8)

(17). The preform extends in the neck area (3)

(3) preferably with a constant wall thickness.

The preform (1) has a wall thickness (18) in the wall area (5) and a floor thickness (19) can be found in the area of the bottom (7). A further dimensioning of the preform (1) takes place with the help of an inner diameter (20) and an outer diameter (21), which are measured in the approximately cylindrical wall area (5).

In the bottle-shaped container (13) shown in FIG. 2, the mouth section (2) and the support ring (4) can be found essentially unchanged. The further region of the container (13) is expanded relative to the preform (1) by the biaxial orientation carried out both in the transverse direction and in the longitudinal direction. The container (13) has a container length (22) and has a container diameter (23) which, in view of the accuracies to be taken into account, is not to be differentiated below with regard to the specific inner diameter or outer diameter.

Fig. 2 shows, among other things, the bottom area of the blow-molded container (13). The container (13) has a side wall (24) and a container base (25). In the exemplary embodiment shown, the container bottom (25) consists of a standing ring (26) and a dome (28) which is curved inwards in the direction of a container interior (27). The dome (28) is formed from a dome slope (29) and a center (30).

The container (13) has a container mouth length (31) and a container neck length (32), at least the

Container mouth length (31) is usually equal to the mouth length (16) of the preform (1).

Heating the preform (1) before the orientation process is conceivable in different variations. When using a tunnel-like heating section, the temperature is only dependent on the length of stay. However, it is also conceivable to use radiant heaters which act on the preform (1) with infrared or high-frequency radiation. With the help of such radiators it is possible to generate a temperature profile in the area of the preform (1) in the direction of the longitudinal axis (8).

If such a radiant heater is formed from a plurality of independently controllable heating elements which are arranged one above the other in the direction of the longitudinal axis (8), more intensive control of the heating elements in the region of the upper extent of the preform (1) in the direction of the mouth section (2) in the thickened In the area of the wall section (5), a higher thermal energy is radiated than in the area of the wall section (5) which faces the floor (7). In the case of radiant heaters which can only be controlled uniformly, such heat profiling can also be achieved by arranging the heating elements at different distances in the direction of the longitudinal axis (8).

Fig. 3 shows the container (13) in a perspective view from below. In particular, in addition to the illustration in FIG. 2, it can be seen again that the container neck (33) widens starting from the support ring (4) in the direction of a container shoulder (34). To increase stability, the container shoulder (34), which widens starting from the container neck (33) towards a base body (35), is transferred from a shoulder (36) into the base body (35). To further increase stability, the base body (35) is transferred via a further shoulder (37) into a bottom taper (47) which is delimited by the standing ring (26) in the area of its extension facing away from the base body (35).

The basic structure of a device for shaping the preform (1) into the container (13) is shown in FIG. 4.

The device for forming the container (13) consists essentially of a blow molding station (38) which is provided with a blow mold (39) into which a preform (1) can be inserted. The preform (1) can be an injection molded part made of polyethylene terephthalate. In order to enable the preform (1) to be inserted into the blow mold (39) and to enable the finished container to be removed, the blow mold (39) consists of blow mold segments (40, 41) and a bottom insert (42) which can be positioned by a lifting device. The Preform (1) can be held in the area of the blowing station (38) by a transport mandrel (43) which, together with the preform (1), passes through a plurality of treatment stations within the device. However, it is also possible to insert the preform (1) directly into the blow mold (39), for example using pliers or other handling means.

To enable a compressed air supply line, a connection piston (not shown) is arranged below the transport mandrel (43), which supplies compressed air to the preform (1) and at the same time seals against the transport mandrel (43). In the case of a modified construction, it is generally also conceivable to use fixed compressed air supply lines.

The preform (1) is stretched using a stretching rod (44) which is positioned by a cylinder. In principle, however, it is also conceivable to carry out a mechanical positioning of the stretching rod (44) via cam segments which are acted upon by tapping rollers. The use of curve segments is particularly expedient when a plurality of blowing stations (38) are arranged on a rotating blowing wheel (53). The use of cylinders is expedient if there are blowing stations (38) arranged in a fixed position.

According to FIG. 4, the use of separate thread inserts (45) in the area of the blow mold (39) is provided to adapt to different shapes of the mouth section (2). In addition to the preform (1) and the finished blown container (13), a developing bladder (46) is also shown.

Fig. 5 shows the basic structure of a blow molding machine with a rotating heating wheel (52) and a rotating blowing wheel (53) is provided. Starting from a preform outlet (54), the preforms (1) are transported by transfer wheels (55, 56) into the area of the heating wheel (52). Radiant heaters (57) and blowers (58) are arranged along the heating wheel (52) in order to temper the preforms (1). After the preforms (1) have been adequately tempered, they are transferred to the blowing wheel (53), in the area of which the blowing stations (38) are arranged. The finished blown containers (13) are fed to a delivery section (59) by further transfer wheels.

In order to be able to form a preform (1) into a container (13) in such a way that the container (13) has material properties that ensure a long usability of food filled inside the container (13), in particular beverages, special process steps must be carried out the heating and orientation of the preforms (1) are observed. In addition, advantageous effects can be achieved by adhering to special dimensioning regulations.

Different plastics can be used as the thermoplastic material. For example, PET, PEN or PP can be used.

The preform (1) expands during the orientation process by supplying compressed air. The compressed air supply is divided into a pre-blowing phase, in which gas with a low pressure level is supplied, and a subsequent main blowing phase, in which gas with a higher pressure level is supplied. Compressed air with a pressure in the interval from 5 bar to 25 bar is used during the pre-blowing phase and compressed air with a pressure in the interval from 25 bar to 40 bar is fed in during the main blowing phase. Inside the blown Container usually results in a pressure in the range of about 2 bar to 10 bar during the pre-blowing phase.

To ensure an exact contour of the container (13), it is provided to provide the blow molding station (38) with a form locking device, which avoids a gap formation in the area of the boundary surfaces of the blow mold segments (40, 41) despite the internal pressure acting during the main blowing phase ,

According to a typical dimensioning, the length of the container neck (32) is at least 20% of the total length of the container (13). A maximum diameter of the container neck (33) is at most 80% of the maximum diameter of the container (13).

The preform (1) for the manufacture of the container (13) can be provided with a coloring in such a way that the transmission of light is reduced at least in a wave range which is harmful with regard to the product to be filled. The preform (1) has a long conical area below a short cylindrical section below the support ring (4). Ventilation slots (48) in the area of an external thread (49) of the mouth section (2) are preferably provided with a rounded contour in order to reduce notch effects when exposed to internal pressure. The thread can be reinforced by a reduced inside diameter in the region of the mouth section (2).

A typical container length (22) is in the range from 200 mm to 300 mm. A container length in the range of approximately -250 mm is preferred. The container neck length (32) is at least 20% of the container length (22). A diameter of the container neck (33) in the area of a transition to a container shoulder (50) is a maximum of 80% of a maximum Container diameter. An outer contour of the container neck with a conical configuration runs between the container shoulder (50) and the mouth section (2). The expansion takes place starting from the mouth section (2) towards the container shoulder (50).

The conical shape of the neck of the container takes place essentially along a circular contour with a radius of less than 500 mm. A radius in the range of approximately 350 mm is preferred. A curvature transition between the container neck and the container shoulder (50) takes place with a radius of curvature <30 mm. A typical curvature is in the range of a radius of curvature of 15 mm. In general, such a radius can preferably be in the range from 10 mm to 20 mm.

A course of curvature in the area of the container shoulder (50) typically runs with a radius of curvature of <60 mm. A curvature interval with a radius of curvature in the range from 25 mm to 35 mm is typical, for example the radius can be 30 mm.

For further stiffening, the container shoulder (50) is passed through a shoulder (51) into the side wall (24). An angle of inclination in the area of the shoulder (51) is typically below 60 °. The side wall (24) is transferred into a base part (61) via a further shoulder (60). Here too, the angle of inclination of the heel (60) is below 60 °.

A dome height of the dome (28) measured between a lower boundary of the base ring (60) and the center (30) is typically more than 8 mm. A value of about 12 mm is typical. A course of curvature in the region of the dome slope (29) typically has a radius of curvature of 20 mm to 60 mm. A value of around 40 is typical mm. Starting from the base ring (26), the contour of the dome slope (29) is defined in cross section by two eccentric radii. Respective associated circle centers have a lateral offset with respect to the longitudinal axis of the container. The lateral offset is at least 3 mm. A typical value is around 6 mm.

With regard to the radius of curvature of the dome slope (29), this can be defined in that the

Radius of curvature is at least 0.65 times the diameter of the base ring.

Claims

Patent claims

1. A method for producing a container from a thermoplastic by blow molding and biaxial orientation, in which a preform is inserted into a blow mold and expanded by the action of a pressure medium, and in which a blow mold made of at least two blow mold segments and a base insert is used to contour the container characterized in that the blow mold segments (40, 41) are tempered to an average surface temperature in the range from 40 ° C to 170 ° C and in that the bottom insert (42) is at a temperature below the average surface temperature of the blow mold segments (40, 41) is held.

2. The method according to claim 1, characterized in that a cooling time in the area of the bottom insert (42) is at least 1, 2 seconds.

3. The method according to claim 1 or 2, characterized in that a contour flattening of the container base (25) after blowing a maximum of 25% of the distance of a container base to a center

(30) of the bottom before removing the blown container (13) from the blow mold (39).

4. The method according to any one of claims 1 to 3, characterized in that the bottom flattening after a thermal treatment a maximum of 55% of the distance of a container base to a center (30) of the bottom before removal of the blown container (13) from the blow mold (39 ) matters.

5. Containers made of a homogeneous thermoplastic material with barrier properties with regard to a wall permeability for gases, which is produced by blow molding from a preform and whose barrier characteristic corresponds to at least one factor BIF> 2, and which is resistant to deformation up to a temperature effect of at least 60 ° C and which has a bottle-like design with an inwardly curved bottom, which is surrounded by a standing ring, characterized in that a material main component and a barrier component with a substantially homogeneous distribution are used as the material for the container (13), the weight of the Barrier component maximum 30% of the weight of the main material component is that the container volume is a maximum of 1 liter. is and the base ring has a material thickness of at least 1 mm and that the container (13) has a base body (35) and a container neck (33), one

Container neck length (32) is at most 80% of a maximum diameter of the base body (35).

6. Container according to claim 5, characterized in that the material thickness in the region of the standing ring (26) is at least 1.2 mm.

7. Container according to claim 5 or 6, characterized in that there is a material coloring at least in some areas.

8. Container according to one of claims 5 to 7, characterized in that a substance for the accumulation of penetrating gases is arranged at least in regions.

9. Container according to one of claims 5 to 8, characterized in that an external thread (49) is arranged in the region of a mouth section (2) of the container (13).

10. A container according to claims 9, characterized in that at least one vent slot (48) is arranged in the region of the external thread (49).

11. A container according to claim 10, characterized in that the ventilation slot (48) is provided with a rounded contour.

12. Container according to one of claims 5 to 11, characterized in that the mouth portion (2) in the region of the external thread (49) has a reduced internal diameter compared to a standard thread.

13. Container according to one of claims 5 to 11, characterized in that the mouth section (2) is designed for the arrangement of a crown cap.

14. Container according to one of claims 5 to 13, characterized in that the mouth section (2) is designed for arranging a clip closure.

15. Container according to one of claims 5 to 14, characterized in that a side wall (24) of the container (13) at least partially curved to an extent of 1% to 2% based on a container diameter in the direction of a container interior (27) is.

16. A container according to claim 15, characterized in that the inner curvature of the side wall (24) is approximately 1.4%.

17. Container according to one of claims 5 to 16, characterized in that a substance for the attachment of at least one penetrating gas is arranged in the region of a container closure.

18. Container according to one of claims 5 to 17, characterized in that PET is used as the main material component.

19. Container according to one of claims 5 to 18, characterized in that PP is used as the main material component.

20. Container according to one of claims 5 to 19, characterized in that PEN is used as the main material component.

21. Container according to one of claims 5 to 20, characterized in that nylon is used as the barrier component.

22. Container according to one of claims 5 to 21, characterized in that EVOH is used as the barrier component.

23. Container according to one of claims 5 to 22, characterized in that PEN is used as the barrier component.

24. Container according to one of claims 5 to 23, characterized in that a PET copolymer with a comonomer content of at least 1.5 mol% is used as the barrier component.

25. Container according to one of claims 5 to 24, characterized in that a PET copolymer with an isophthalic acid content of at least 1.5 mol% is used as the barrier component.

26. Container according to one of claims 5 to 25, characterized in that a polymer mixture with solid particles is used as the barrier component.

27. Container according to one of claims 5 to 25, characterized in that a curvature in the region of a dome slope (29) of the container base is defined by two circles arranged relative to a longitudinal axis of the container with eccentric circle centers.

28. A container according to claim 27, characterized in that an offset between the center of the circle and the longitudinal axis of the container is at least 3 mm.

29. Container according to one of claims 5 to 28, characterized in that a side wall (24) of the container starting from a bottom part (60) in Direction towards a container shoulder (50).

30. Container according to one of claims 5 to 29, characterized in that the side wall (24) via a shoulder (51) in the container shoulder (50) is transferred.