EP0656857A1

EP0656857A1 - Plastic closure unit and process for producing the same

Info

Publication number: EP0656857A1
Application number: EP94920463A
Authority: EP
Inventors: Elmar Mock
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 1993-06-30
Filing date: 1994-06-26
Publication date: 1995-06-14
Also published as: US5863655A; JPH08500802A; AU7124594A; WO1995001288A3; WO1995001288A2; CA2142274A1

Abstract

A closure unit consists of a pouring part (10) and of a closure part (20) linked to the pouring-part even in the open state. In the closed state of the closure unit, both parts are sealed with respect to each other by a pair of sealing surfaces. The closure unit has an area made of a pouring-part material (A) and an area made of a closing-part material (B). Both areas are joined together by a joint line. The path of the joint line through the closure unit is such that at least parts of the sealing surface at the side of the pouring-part are made of the pouring-part material and at least parts of the sealing surface at the side of the closure part are made of the closure-part material. The closure unit is produced by a simultaneous casting process. The materials are matched and the casting parameters of both simultaneous casting processes are set in such a way that both materials meet at the position of the future joint line and form a joint line (31). The position and form of the joint line may further be determined by movable casting mould parts (slides).

Description

Closure unit made of plastic and process for its production

The invention relates to a closure unit made of plastic according to the preamble of the first independent claim and a method for its production according to the preamble of the corresponding method claim.

The invention relates in the second place also to a closure made of plastic with an opening part and a closure part which are designed such that in the closed state of the closure unit at least one sealing surface on the opening part is mechanically pressed against a corresponding sealing surface on the closure part, and in a third place a method for the production of this closure, which is produced by casting in the open state and is closed after production. Closure units made of plastic, which have a pouring part and a closure part, are known, for example, in applications on containers made of glass, metal, etc. Advantageously, such closure units are designed in such a way that the closure part is connected to the pouring part even in the open state, and that it also follows can be closed somewhat tightly the first time it is opened.

Closure units of this type are usually produced using injection molding processes. If the closure unit is made of a material and is cast in the open state, the production consists of a single casting step and is therefore very economical. However, since the function of the pouring part is different from the function of the closure part, it is obvious that with a closure unit made of only one material, this material cannot optimally fulfill both functions, i.e. in other words, compromises have to be made in the choice of material. These compromises often result, for example, in a not very good tightness of the closed or reclosed closure unit.

Closure units made from two or more different materials are also known, with which the disadvantage mentioned above can be avoided. Closure units of this type then usually consist of a pouring part and a closure part or parts of these parts which are produced separately and from different materials, the pouring part and closure part then not being fastened to one another, for example when the closure unit is open, and an actual unit only in the closed state form. The individual parts are then usually connected to one another in an additional assembly step, for example by combining the form-fitting means provided, by gluing, welding, etc., which of course makes production more expensive.

It is the object of the invention to create a closure unit in which the advantage of a closure unit made of at least two materials is combined with the advantages of a closure unit made of only one material. In other words, this means a closure unit on which the individual parts perform their function as optimally as possible thanks to a suitable material and which can nevertheless be produced in a simple casting process and without additional assembly steps for connecting individual parts.

This object is achieved by the closure unit and the manufacturing method as defined by the claims. The closure unit according to the invention has a pouring part and a closure part which are connected to one another even when the closure unit is open, and it consists of at least two materials, the regions of the two materials being connected to one another by a flow seam. This flow seam is located, for example, in the connection area between the pouring part and the closure part, such that the pouring part consists entirely of a pouring material, the closure part entirely of a closure material. The flow seam can also extend through one of the parts, such that this part consists of both materials. In any case, the flow seam runs between the areas of the two materials such that the pair of sealing surfaces, by means of which the closure unit is kept sealed in the closed state, consists at least partially of a sealing surface on the spout part made of the spout material and a sealing surface on the part of the closure part made of the closure material

The flow seam between the two materials is created by pouring the two materials together. It can be a front flow seam that arises from the fact that the two materials meet in a pourable or flowable state. It can also be a cold flow seam that arises from the fact that one of the materials in a pourable or flowable state meets the other, already somewhat cooled material. A shear flow seam is also conceivable.

The closure unit is produced by pouring the two materials from two or more different pouring openings into a casting cavity, which essentially represents the negative of the closure unit in the open state, and by setting the casting parameters in such a way that the two materials are at the point for the flow seam intended location of the cavity meet in the intended state. As will be described in more detail below, it can be advantageous or necessary to provide slides in the casting cavity which are moved during the casting. The relevant casting parameters for the location and quality of the flow seam are the corresponding casting temperatures, casting speeds, temporal coordination of the two quasi-simultaneous casting processes and the duration and extent of the reprint or reprints for each pair of materials and each form of closure unit.

The pouring material is adapted to the manner in which the closure unit is to be attached to the container, ie in other words, it can be welded, glued, etc. The material combination of the pouring material and the closure material is selected such that they form a well-sealing pair of sealing surfaces can; that is, advantageously only one of the materials is rigid, while the other is flexible and conformable Bθispiθlsweisθ has properties such that the pouring part has sufficient stability to give the closure unit mechanical strength sufficient for use, transportation, etc. The closure material has properties such that it is sufficiently flexible and elastic to be able to nestle against sealing surfaces of the pouring material for the tightest possible connection, and that it is sufficiently elastic to withstand the deformations that are unavoidable when opening and closing the closure unit. Furthermore, the closure material can have properties for desired decorative functions, for example.

However, the closure material can also be more rigid than the pouring material.

For recycling reasons, it is advantageous to choose the two materials from the same group of plastics. However, this is not a mandatory requirement for the production. Amorphous and partially crystalline polypropylene (PP) or low-density polyethylene (LD-PE) and high-density polyethylene (HD-PE) are proposed as material pairs. Soft and hard polyvinyl chloride (PVC) are also suitable for chemically resistant closure units. Material pairs consisting of a polymer filled with inorganic substances (e.g. glass) and the same polymer without filler or the same polymer in solid and foamed form can also be used. For closure units with a high gas density, material pairs consisting of, on the one hand, polyester (PET), polypropylene (PP) or polyethylene (PE) as the base material and, on the other hand, ethylene-vinyl alcohol copolymer (EVOH), semicrystalline polyamide (MXD-6) produced by Polycondensation of metaxylenediamine and adipic acid, liquid crystal polymer (LCP), polyethylene naphthalate (PEN), polyacrylonitrile (PAN), amorphous polyamide (APA), polyvinyl diene chloride (PVDC) or a polymer filled with scavenger as a barrier material.

It turns out that good flow seams can be produced in a material combination with a crystalline or partially crystalline and an amorphous plastic if a glass transition point of the crystalline material lies in the melting range of the amorphous material and the two materials meet in this temperature range. An example of such a material pairing is the combination of partially crystalline and amorphous polypropylene already mentioned above.

In addition to the connection of the two materials by means of the flow seam, this can be designed in such a way that it also represents a positive connection

The closure, to which the invention relates in the second place, also has a part with a opening (opening part) and a part closing the opening of the opening part (closure part). The opening part is, for example, an entire plastic container with an opening or the pouring part of a closure unit, as is used, for example, on glass or metal containers. The closure is closed by placing the closure part on the opening part, or opened by lifting or pivoting the closure part away. Closure units made of plastic, which have a pouring part (opening part) and a closure part, are, as already indicated above, manufactured by injection molding: either in one piece with a connecting part which permanently connects the pouring part and closure part, or in two parts as a separate pouring part and separate closure part. Plastic containers and associated closure parts (lids) are also usually manufactured separately. Such closures are usually produced in the open state and then closed in a further production step before or after assembly on the container and / or its filling.

The casting molds for the opening part and the closing part of such closures are designed in such a way that both parts have sealing surfaces which are pressed against one another by a mechanical closing process, a positive connection being produced for this closing process by means of provided form-locking means between the closing part and the opening part. The positive connection is effected, for example, by a thread or, in the case of snap closures, by a corresponding deformation of at least one part. The seal that can be achieved by such sealing surfaces pressed against one another is usually absolutely sufficient for powders and liquids and also remains well sealed after numerous openings and closings. On the other hand, their tightness for gases and germs is not sufficient, especially after long storage.

In order to achieve a seal for gases and germs, aluminum foils, for example, are inserted into the closures described above as an additional sealant or gas barrier, which then have to be removed when they are opened for the first time.

It is now the second object of the invention to provide a plastic closure with an opening part and a closure part which, without additional sealing means, has a gas and germ tightness at least until the first opening, which essentially corresponds to the gas and germ tightness of the closure material. In other words, the tightness of the closure according to the invention should be about the same as when the opening part and closure part were provided as an inseparable part. It is also the third object of the invention to demonstrate a method according to which the closure unit according to the invention will be produced.

This last-mentioned object is achieved for the plastic closure with an opening part and a closure part which are designed such that in the closed state of the closure unit at least one sealing surface on the opening part is mechanically pressed against a corresponding sealing surface on the closure part, in that before the first opening of the closure unit At least one sealing surface on the closure part and a corresponding sealing surface on the opening part adhere to one another such that the first opening process requires more force than each subsequent opening process, but that the sealing surfaces are not damaged during the first opening process. The method considered in the third place is further characterized in that at least one pair of sealing surfaces is thermally treated in such a way that its sealing surfaces adhere to one another in such a way that they can be separated from one another with a reasonable amount of force when first opened without the sealing surfaces being damaged.

The closure according to the invention considered in second place has at least one pair of sealing surfaces, the sealing surfaces of which, before being opened for the first time, are not only pressed mechanically against one another but also adhere to one another. This additional adhesive connection is essentially produced by a thermal treatment of at least one of the sealing surfaces of the pair of sealing surfaces. The heat treatment is carried out with sealing surfaces pressed together, i.e. performed with the closure closed or immediately before the closure. The choice of the materials of the opening part and the closure part and the choice of the parameters of the heat treatment is such that the adhesive connection can be released with a reasonable effort by the consumer when the closure is first opened, the adhesive connection being irreversibly destroyed, the mechanical sealing ability of the pair of sealing surfaces but is not diminished.

If the closure is closed again after the first opening, the pair of sealing surfaces (or the pairs of sealing surfaces) is mechanically pressed again. The additional adhesive bond is then missing.

Another advantage of a closure with an adhesive connection between the sealing surfaces of the opening part and the closure part is that the inside or the outside of the closure can be coated with a barrier material, for example silicon oxide or aluminum, for a further increase in gas tightness, the risk of that the coating is damaged by a relative movement between the two parts is greatly reduced. It is also possible that the mechanical sealing function is quasi separated from the adhesive connection in such a way that one pair of sealing surfaces effects a good mechanical seal, while a second pair of sealing surfaces represents a less good mechanical seal and mainly takes over the additional seal by means of an adhesive connection

To create the adhesive connection, the sealing surfaces are lightly welded as a pair, for example after the closure of the closure. One or both sealing surfaces can also be heated by warm air or with a flame immediately before the closure unit is closed, with the use of an appropriate flame affected surfaces are deoxidized at the same time. Heating by high-voltage discharge is also conceivable. Friction welding is also conceivable to create the adhesive connection between the sealing surfaces.

The two sealing surfaces to be connected by the heat treatment can be made of the same plastic or of different plastics. Different plastics are advantageous if the requirements for the two parts differ, for example in terms of flexibility, as can be the case with a snap lock. Examples of material pairs that can be used for this purpose are again semi-crystalline and amorphous polypropylene, high and low density polyethylene, hard and soft polyvinyl chloride, polymer filled and unfilled with an inorganic substance (e.g. glass), solid and foamed polymer. Other possible material combinations are polyester (PET), polypropylene (PP) or polyethylene (PE) as the one material and ethylene-vinyl alcohol copolymer (EVOH), semi-crystalline polyamide (MXD-6) produced by polycondensation of metaxylenediamine and adipic acid, liquid crystal -Poiymer (LCP), polyethylene naphthalate (PEN), polyacrylonitrile (PAN), amorphous polyamide (APA), polyvinyldiene chloride (PVDC) or a polymer filled with scavenger than the other material.

With the aid of the following figures, the closure unit according to the invention and the method for its production will now be described in more detail using exemplary embodiments. Show:

Figure 1 shows an exemplary embodiment of the closure unit according to the invention in the immediately manufactured, ie open state (section); Figure 2 shows the closure unit of Figure 1 in the closed state (section);

Figure 3 shows a detail of a casting cavity with slide;

Figures 4 to 6 further exemplary embodiments of the closure unit according to the invention; Figures 7 and 8 to explain the manufacture of the closure unit according to Figure 6 is a section by the closure unit to show the slide movement (Figure 7) and a timing diagram of the casting process (Figure 8);

FIG. 9 shows a quasi-endless band of closure units according to the invention;

FIG. 10 shows a diagram of an arrangement for producing the closure units according to the invention; and

FIG. 11 shows in section and in the closed state a plastic closure according to the invention in the form of a closure unit for mounting on a container, for example, without a neck. This closure unit represents an exemplary embodiment of the closure. As already explained at the beginning, many further embodiments are conceivable.

Figure 1 shows an exemplary embodiment of the closure unit according to the invention in section, as it is manufactured, that is, in the open state. The closure unit has a pouring part 10, a closing part 20 and a connecting part 30, wherein the pouring part consists of a pouring material A and the closing part consists of a closing material B. The two parts are connected to one another in the region of the connecting part 30 by a flow seam 31. Possible positions of the two pouring openings in the casting cavity for producing the closure unit shown are indicated by the two arrows A and B.

Figure 2 shows the same closure unit as Figure 1 in the closed state. It can be seen from a comparison of FIGS. 1 and 2 that when the closure unit is closed and when it is opened, the connecting part 30 and the regions 22 of the closure part which serve to seal between the pouring part and the closure part are strongly deformed. In order for the closure unit to survive numerous opening and closing operations without damage, and so that the closure unit still closes sufficiently tightly after many such operations, the material of these areas must be correspondingly soft and elastic. On the other hand, however, this means that the material of the pouring part is correspondingly rigid in order to ensure the mechanical stability of the closure unit. If the closure unit can be fastened to a container by welding, the pouring material must also be weldable.

All of the above conditions are met by the material pair polypropylene crystalline and amorphous, with which a firm flow seam 31 between the two materials A and B can also be produced in the area of the connecting part 30.

The closure unit is manufactured by essentially simultaneously pouring the two materials into a casting cavity which holds the negative of the closure unit in the open state represents, for example, by a casting entrance in the area of the pouring part (arrow A) and the closure part (arrow B). The exact starting point and the speeds of the two simultaneous casting processes are set up in such a way that the two materials meet in the area of the connecting part.

The exact position of the flow seam between the two materials and their shape are determined by the shape of the casting cavity, by the starting point and speed of the two simultaneous casting processes and by the condition of the two materials that meet (temperature, viscosity). The position and shape of the flow line are therefore subject to a process-related spread. To avoid this inaccuracy or to produce a certain shape of the seam, sliders can also be provided in the casting cavity at the positions provided for the flow seam, which are pulled immediately after the arrival of at least one of the two materials at the flow seam position. A flow seam made with a slider is precisely positioned and has an exact, predetermined shape. However, your liability will be lower than with a corresponding flow seam that was produced without a slide.

A slider is particularly necessary if the one material for producing a cold flow seam is to have cooled down somewhat when it meets the other material and, for this reason, is to reach the seam position somewhat earlier. Sliders can also be used if the contact surface of the two materials is to be shaped in such a way that the two material areas are also positively connected to one another.

FIG. 3 shows in detail the area of the flow seam in a casting cavity for producing a form-fitting flow seam. Two slides 40 are provided at the predetermined position of the flow line. The movement of these slides is coordinated with the casting process in such a way that they are removed from the casting cavity after the arrival of material A, but before the arrival of material B (arrows S). This means that the material A receives an interface which corresponds to the shape of the slide and forms a molding 41. After removal of the slide, this is cast around by material B, which creates a positive connection between the two materials in addition to connecting the flow seam.

FIG. 4 shows very schematically another exemplary embodiment of the closure unit according to the invention. In this embodiment, the pouring part 10 consists entirely of pouring material A, the closing part 20 partly from closing material B, partly from pouring material A. The flow seam 31.1 runs over the entire closing part, such that for the Manufacture of this closure unit requires only a very small amount of the closure material B. Positions for the pouring opening are again indicated by arrows A and B.

A closure unit, as shown in FIG. 4, is advantageous if the closure material B is expensive, as is the case for EVOH, for example. However, EVOH is extremely advantageous because of its high gas tightness as a barrier layer material for closure units, which are used, for example, for carbonated drinks. For these reasons, the embodiment according to FIG. 4, with PET as the pouring material and EVOH as the closure material, represents a good, gas-tight closure unit in terms of expenditure on material.

To produce the embodiment according to FIG. 4, a slide 42 is necessary in the casting mold, which is also indicated in the figure. At the beginning of the casting process, this is in a position which is higher by the thickness of the material A in the closure part than that in the figure 4 shown position of the slide. The two, quasi-simultaneous casting processes of materials A and B are coordinated in such a way that the casting process of material B is completed and the slide 42 is moved into its lower position (arrow S) before the material A reaches the region of the closure part. The resulting flow seam is a cold flow seam

FIG. 5 shows, again very schematically, a further exemplary embodiment in which the area of the closure material B is further reduced. The closure material B actually only forms those areas of the closure part 20 that form the sealing surfaces for the closed closure unit. A movable slide 42 in the casting cavity is also necessary to produce this closure unit. The individual parts of the closure unit and the manufacture essentially correspond to those of the closure unit according to FIG. 4 and are therefore also designated with the same reference numbers.

Figure 6 shows a further, exemplary embodiment of the closure unit according to the invention, in which the area of the pouring material A is now essentially reduced to the sealing surfaces, in such a way that the pouring material A only forms a sealing ring 11 connected to the actual pouring part 10 by a flow seam, and the Rest of the closure unit, in particular the sealing surface on the closure part side, consists of the closure material B.

FIGS. 7 and 8 show schematically how the closure unit according to FIG. 6 is produced, with a sectional drawing from which the slide movement can be seen (FIG. 7), and a time diagram (FIG. 8) of the two quasi-simultaneous casting processes (A and B) and the Slider movement (S). The slide 43 is arranged in the region of the closure part 10 and has two positions, an upper position o, as is necessary for the casting of the pouring material A, or the sealing ring 11 and is shown towards the right in the figure, and a lower position u , in which the sealing ring 11 assumes its definitive position in relation to the pouring part 10, or in relation to the casting cavity for the remaining parts of the closure unit, and which is shown on the left.

As can be seen from the timing diagram (FIG. 8), the pouring of material B begins with a delay of t compared to the pouring of material A. The slide 43 is moved from its upper (o) to its lower (u) position as soon as the material A has been cast and the material B has not yet reached the area of the sealing ring. The time range t represents the compression time under pressure, which is followed by the cooling range. The casting cycle also includes opening the mold, ejecting the closure unit and reclosing the mold, during which the slide 43 is also moved back into its upper position. All of these processes do not differ from the corresponding processes when casting with only one material and are not shown in the time diagram

In a similar manner to how a sealing ring is produced in accordance with FIGS. 6 to 8, which is connected to the pouring part by a flow seam, it is conceivable to produce a sealing ring which is fastened in the closure part with a flow seam.

FIG. 9 schematically shows a quasi endless band of closure units according to the invention. These are lined up on two threads 50. Such a band is produced by leading the pair of threads through the casting cavity and advancing them in a coordinated manner with the casting cycle. Advantageously, the threads are not completely cast in, since in this case they would have to be cut during further processing of the closure units or the closure units would be at risk when loosening the threads, but the threads are only partially cast over, so that the closure units are securely attached to them that they can be separated easily and without damage.

Such a quasi-endless band of closure units can simply be stored in the rolled-up state, can be fed continuously into an apparatus for further processing, for example for fastening the closure units to appropriate containers, and the threads can be reused.

Instead of a pair of threads, only one thread, several threads or a film strip can also be used as a transport and storage aid for the closure units according to the invention come.

FIG. 10 also shows schematically an arrangement for producing closure units according to the invention in the form of a quasi-endless band, as is shown, for example, in FIG. The arrangement has an injection molding machine 60 which is known per se and which is set up and controlled accordingly for the simultaneous casting of two materials A and B. A pair of threads 50 or another quasi endless transport and storage aid is fed by means of feed rollers 62 from a supply roller 61 through the casting cavity Machine pulled. The pair of threads 50 conveys the cast closure units from the casting machine in the form of a quasi-continuous belt 51. This is deflected via a deflection roller 63 and wound up on a bearing transport roller 64

The closure unit according to the further embodiment of FIG. 11 consists of a pouring part (opening part) 1, a closing part 2 and a connecting part 3. Between the closing part and the pouring part there is an inner pair of sealing surfaces 21 and an outer pair of sealing surfaces 22a. For example, the pouring part consists of an essentially rigid material, the closure part consists of a flexible and elastic material, the two materials being connected to one another in the region of the connecting part 3 by means of a flow seam. When the closure unit is closed and when it is opened, the closure part is deformed in such a way that the pairs of sealing surfaces are pressed against one another in the closed state.

For the embodiment of the closure according to the invention shown in FIG. 11, the outer pair of sealing surfaces 22a is particularly suitable as a mechanical seal. The inner pair of sealing surfaces 21 is more accessible, particularly in the closed state of the closure unit, for thermal treatment, so that there the additional connection can be produced by adhesion, for example by welding the sealing surfaces which are already stacked and pressed against one another.

Of course, only the outer pair of sealing surfaces could also be provided, for example, and the sealing surfaces could be connected to one another by an adhesive connection.

It can be seen that closure units, as shown in FIG. 1, have good properties if their pouring part is made of a crystalline or semi-crystalline material and their closure part is made of an amorphous material. Crystalline and amorphous polypropylene is particularly suitable.

Claims

Patent claims

1. closure unit made of plastic, which has a pouring part (10), a closure part (20) connected to the pouring part even when the closure unit is open, and a pair of sealing surfaces sealing the two parts (10 and 20) against one another in the closed state of the closure unit, characterized in that the closure unit has a region made of a pouring material (A) and a region made of a closure material (B), the sealing surface pair of the sealing surface pair on the pouring part at least partially consisting of the pouring material (A) and the sealing surface side of the sealing part pair at least partly on the sealing part the closure material (B), and that the two material areas are connected to one another by a flow seam (31).

2. Closure unit according to claim 1, characterized in that the pouring part (10) consists entirely of the pouring material (A), that the closure part (20) consists entirely of the closure material (B) and that the flow seam (31) in the area of one Pouring part lies flexibly with the connecting part (30) connecting the closing part

3. Closure unit according to claim 1, characterized in that the pouring material extends into the closure part and the flow seam extends into the closure part or the closure material extends into the pouring part and the flow seam extends in the pouring part

4. Closure unit according to claim 3, characterized in that one of the materials forms a sealing ring (11) which is fastened by the flow seam in the pouring part or in the closure part.

5. Closure unit according to one of claims 1 to 4, characterized in that one of the materials is more flexible and elastic than the other.

6. Closure unit according to claim 5, characterized in that one of the materials is essentially crystalline or partially crystalline, the other is essentially amorphous and that a glass transition point of the crystalline or partially crystalline material lies in the melting range of the amorphous material.

7. Closure unit according to claim 5, characterized in that the two materials are a filled with an inorganic substance, preferably glass and a non-filled polymer.

8. Closure unit according to claim 5, characterized in that one of the two materials is polyester (PET), polypropylene (PP) or polyethylene (PE) and the other material is ethylene-vinyl alcohol copolymer (EVOH), semi-crystalline polyamide (MXD-6 ) made by polycondensation of metaxylenediamine and adipic acid, liquid crystal polymer (LCP), polyethylene naphthalate (PEN), polyacrylonitrile (PAN), amorphous polyamide (APA), polyvinyldiene chloride (PVDC) or a polymer filled with scavenger

9. closure unit with an opening part (1) and a closure part (2), which are designed such that in the closed state of the closure unit at least one sealing surface on the opening part is mechanically pressed against a corresponding sealing surface on the closure part, characterized in that before the first opening of the Closure unit stick at least one sealing surface on the closure part (2) and a corresponding sealing surface on the opening part (1) so that the first opening process requires more force than each subsequent opening process, but that the sealing surfaces are not damaged during the first opening process.

10. Closure unit according to claim 9, characterized in that the pair of materials for the sealing surfaces partially crystalline and amorphous polypropylene, high and low density polyethylene, hard and soft polyvinyl chloride, a filled with an inorganic substance and an unfilled polymer or a solid and a foamed polymer is

11. A method for producing the closure unit according to one of claims 1 to 10, characterized in that in a casting cavity, which essentially represents the negative of the closure unit in the open state, the pouring material (A) essentially simultaneously through a pouring opening in the region of the pouring part. and through a pouring opening in the. Area of the closure part, the closure material (B) is poured in and that the two casting processes are coordinated in such a way that the two materials (A, B) meet at the location of the casting cavity intended for the flow seam and form a flow seam (31).

12. The method according to claim 11, characterized in that for positioning and / or shaping the flow seam individual parts of the mold moved during the casting process and that the movable mold parts are preferably designed such that the cold flow seam (31) between the two materials (A, B) also represents a positive connection.

13. A method for producing a closure unit according to one of claims 1 to 12, wherein the closure is made in the open state by casting and closed after manufacture, characterized in that at least one pair of sealing surfaces (21) is thermally treated.