CH712945A1 - Method for producing a flat closure element with at least one thin point for closing a container opening. - Google Patents

Abstract

It is a method for producing a closure element (6) for closing a container opening, which has at least one thin point (61) of a predetermined minimum wall thickness, described in which a predetermined amount of a plasticized plastic material (P) in a mold cavity (5) of an injection mold ( 10) of an injection molding device introduced, the plastic material (P) brought to solidification by cooling or a crosslinking reaction and after opening the injection mold (10), the closure element (6) is configured. The plasticized plastic material (P) is thereby introduced into the mold cavity (5) of the not yet completely closed injection mold (10). The injection molding tool (10) is closed during or after the injection process, wherein the predetermined minimum wall thickness of the at least one thin point (61) is formed by the closing of the injection mold (10).

Description

Description: The invention relates to a method for producing a flat closure element for a container opening with at least one thin point according to the preamble of patent claim 1.

Flowable or liquid foods, but also bulk goods, such as sugar, flour, coffee, powder for instant beverages, milk powder, toddler food, etc. are often kept in containers that have a relatively large opening in relation to the outer dimensions of the container , Examples of such containers are milk or yoghurt containers but also small capsule-like containers for coffee machines. With many foods, but also with different bulk goods, it must be prevented that oxygen and / or water vapor get into the interior of the container and the content degrades or spoils during storage. For certain products, the diffusion of aromas or the effect of radiation such as visible light or ultraviolet light should also be prevented. For this purpose, the container walls are often constructed from composite materials and have one or more barrier layers which are intended to prevent the penetration of oxygen and / or water vapor or the diffusion of aromas. The container opening is usually covered with a closure part made of a composite material in the form of a film, which forms a barrier layer against oxygen and / or water vapor and is usually connected to the opening edge by gluing or sealing. For example, such closure parts include various types of polymers, such as polyamide (PA), polypropylene (PP) or polyethylene (PE). So that the contents of the container can be poured out, removed or otherwise emerge from the container, the closure part made of composite material must be pulled off, cut open, pressed in or perforated in a suitable form. The connection of the closure part at the opening of the container is therefore often provided with a desired release point. Desired release points are always a weak point, because there is a risk that the closure part will loosen itself over time and the seal against oxygen and water vapor can no longer be guaranteed. Containers are also known which are equipped with a piercing or cutting device for the closure part made of composite material, which can be arranged within a closure cap which can be screwed onto the opening. However, such solutions are very complex and expensive.

To facilitate the breaking open of the closure part attached to the container opening, closure parts with thin points have also already been proposed. For example, such closure parts can be produced in an injection molding process. When the plastic is injection molded, an attempt is also made to form thin points on the closure part which will later serve as predetermined breaking points. However, the thin area limits the size of the molded part, since the plasticized plastic material solidifies too quickly at the thin area or causes an excessive pressure loss. In order to still be able to manufacture larger closure parts, the thin point must be made relatively thick-walled, which can lead to problems when the closure part is later broken open. The plastic material must be very thin for the injection molding of closure parts with thin spots. Unfortunately, the plastics that are suitable for this and can be justified by the costs often do not have particularly good barrier properties against oxygen and / or water vapor. The injection molding process must be carried out with very high pressures and very short injection times. Pressures from 1,800 to 2,500 bar and injection times from 0.1 to 0.4 seconds are typical. This leads to very high mechanical stress on the injection mold and the injection molding device.

The closure part for attachment to the opening of the container is produced in a separate working step and must be brought together with the container at the right time, usually at the bottler, in order to be able to carry out the closing process. This requires a not inconsiderable logistical and equipment outlay, which increases the cost of manufacturing and filling the containers. In addition, the separate film usually consists of composite materials that are different from the materials from which the containers are made. This can prove to be disadvantageous when recycling and is therefore undesirable for ecological reasons.

The object of the present invention is therefore to modify a method for producing a closure element for a container opening with at least one thin point in such a way that even higher-viscosity materials can be processed. A method for producing a closure element is to be created, which allows the closure element to be integrally formed on the pouring opening of the container or to be formed integrally with the pouring opening.

The solution to these problems consists in a method for producing a closure element for a container opening with at least one thin point, which has the features listed in claim 1. Further developments and / or advantageous variants of the invention are the subject of the dependent claims.

The invention proposes a method for producing a closure element for closing a container opening, which has at least one thin point of a predetermined minimum wall thickness, in which a predetermined amount of a plasticized plastic material is introduced into a mold cavity of an injection mold of an injection molding device, the plastic material by cooling or solidify a crosslinking reaction and the closure element is formed after opening the injection mold. The procedure according to the invention is characterized in that the plasticized plastic material is introduced into the mold cavity of the injection mold, which is not yet completely closed, and that the injection mold is completely closed during or after the plasticized plastic material is introduced, the predetermined minimum wall thickness of the at least being closed by closing the injection mold a thin spot is formed.

CH 712 945 A1 The plastic melt is introduced into the virtually pressure-free, not completely closed injection mold. The injection mold is completely closed during or after the injection process. The closing pressure that builds up evenly ensures that the injected plastic is distributed within the mold cavity and thus for the final formation of the closure part. The closing pressures that occur are lower than in the injection molding processes of the prior art. Since the injection mold is not yet completely closed when the plastic melt is introduced, the minimum wall thicknesses of the at least one thin point of the flat closure element are not limiting with regard to the plastic materials that can be used, in particular their viscosity, and the size of the closure element. This means that higher-viscosity materials can also be used. Because the injection mold is not yet completely closed, the gap width at the at least one thin point can still be set so large that the risk of the plastic melt freezing out at the thin point or an excessive pressure loss is practically eliminated. In addition, the inner wall of the mold cavity can also be heated. As a result, it is possible to work with significantly lower injection pressures and longer injection times, which has an advantageous effect on the mechanical stress on the injection molding system and on the mechanical stability of the molded part. The at least one thin point on the closure element can be formed very precisely in the embossing process following the material introduction by completely closing the injection molding tool. By setting the final wall thickness only through the stamping process, lower minimum wall thicknesses of the thin area can also be achieved. This can prove to be very advantageous, in particular in the case of closure elements with a predetermined breaking point. Under certain circumstances, separate breaking or cutting tools can be dispensed with, or they can be made less solid. After the embossing and solidification of the closure element in its final form has been completed, the injection mold is opened. The closure element can be removed for further processing or remain in the injection mold. For example, in a subsequent station, a functional part with a pouring opening, which can be closed, for example, by a twist lock, and a shoulder can be molded onto the closure part. After the functional part has solidified, the molded part comprising the closure element and the functional element can be removed from the injection mold.

A method variant of the invention can provide that the injection mold for the introduction of the plasticized plastic material is closed at least to the extent that leakage of the introduced plastic material from the mold cavity of the injection mold can be prevented. This is not absolutely necessary; for example, a reservoir for excess plastic melt could be provided. However, by preventing the plastic melt from escaping from the mold cavity, unintentional contamination of the injection molding system can be avoided.

Depending on the shape of the mold cavity and the molded part to be produced, the injection mold can remain open to different extents. For the production of a flat closure part, it may be expedient if the injection mold is closed at least 5% for the introduction of the plasticized plastic material.

The inventive method allows the very precise formation of very thin-walled thin spots. In a further method variant, the at least one thin point can be formed with a wall thickness of 0.02 mm to 1 mm. In a further variant, the at least one thin point can be formed with a wall thickness of 0.05 mm to 0.8 mm. Finally, an alternative method variant can provide that the at least one thin point is formed with a wall thickness of only 0.1 mm to 0.4 mm. The listed wall thickness ranges for the thin area are not to be considered conclusively. For example, wall thickness ranges of only 0.02 mm to 0.05 mm or any wall thickness ranges within the specified limits for minimum and maximum wall thicknesses can be produced if it is necessary and appropriate for an intended molded part or closure element.

In a further variant of the method, the closure element is produced with a barrier material to prevent oxygen and / or water vapor and / or radiation and / or aromas from diffusing out. Such a flat closure element can be used, for example, to break open an opening in a food packaging, the contents of which are to be protected against the ingress of oxygen and / or water vapor and / or radiation and / or aroma diffusion. Radiation can be visible light or ultraviolet light.

Such food packaging can e.g. Milk packages or yogurt containers, but also capsule-like packages for powdered or liquid coffee concentrates for coffee machines.

In one variant of the method, the barrier material of the closure element is embedded on all sides in a plastic material, which can be different from the barrier material. This process variant can be particularly advantageous in the case of barrier materials which are otherwise difficult to attach to a container opening. The barrier material can, for example, be embedded in a material that can be very easily connected to the container material. The embedding also allows a barrier material to be used which would react chemically with the contents of the container, such as EVOH.

Another variant of the process control can provide that the embedding of the barrier material is carried out in a two-component or multi-component injection molding process. 2-component or multi-component injection molding processes have been tried and tested and allow the production of molded parts that consist of two or more

CH 712 945 A1

Plastic materials are made. In the simplest case, the plastic materials only differ in their color in order to achieve a certain design. The 2-component or multi-component injection molding process, in particular, allows the use of different materials in order to combine different properties in a targeted manner. In this way, for example, barrier materials against oxygen and / or water vapor and / or radiation / and / or diffusing out can be combined with low-density polyethylene (LDPE) or with high-density polyethylene (HDPE) or with polypropylene.

In one process variant, polyamide (PA), polyethylene furanoate (PEF), polypropylene furanoate (PPF), polyethylene vinyl alcohol (EVOH), polyethylene vinyl acetate (EVA), their copolymers and mixtures of the plastics mentioned can be used as barrier materials. Particularly with barrier materials encapsulated on all sides, there are hardly any restrictions with regard to the choice of material for the oxygen and / or water vapor and / or diffusion and / or radiation barrier.

The procedure according to the invention also allows the processing of higher-viscosity plastic materials. In a further variant of the method, the plastic material introduced into the mold cavity of the injection mold can have a melt flow index of> 1 g / 10 min or even greater than 3 g / 10 min. Examples of such plastic materials are polypropylene (PP), high density polyethylene (HDPE), which are otherwise primarily used for the plastic blowing process.

[0018] The method according to the invention also creates the conditions for simple further processing of the injection-molded closure part. In a further variant of the method, for example, a functional part can be molded onto the closure part before demolding. The functional part can be part of a closure, for example. It can be a dome-shaped section of a packaging part which can be connected in a liquid-tight manner to an essentially cylindrical container. For example, the molded functional part can be designed for connection to a plastic-coated cardboard container of a milk packaging. In an alternative embodiment variant, the functional part can be designed as a capsule-like container. The previously produced closure element with a thin point can be designed in such a way that the thin point opens under the influence of temperature and pressure after a predetermined time.

The injection molding of the functional part on the closure part is expediently carried out with the aid of a cube tool, rotary plate tool or another form of 2-component or multi-component tools. Injection molding systems with die tools are space-saving and allow high productivity through simultaneous execution of different manufacturing steps on the available sides of the die tool. The cube tool can be, for example, a 180 ° tool or a 90 ° tool.

Further advantages and features of the invention will become apparent from the following description of an exemplary procedure with reference to the schematic drawings, which are not to scale.

1 shows a section of an injection molding tool in the not yet fully closed state immediately after the introduction of a plastic melt;

FIG. 2 shows an enlarged view of a detail from FIG. 1 with the thin area indicated;

FIG. 3 shows the injection mold from FIG. 1 in the completely closed state;

FIG. 4 shows, in analogy to FIG. 2, an enlarged view from FIG. 3 with the thin point indicated; and

Fig. 5 shows a flat closure element for a container opening with a thin point and molded functional part.

In the figures, the same components or elements are each provided with the same reference numerals.

In Fig. 1, a portion of an injection mold is shown schematically, which is provided with the reference numeral 10 in its entirety. The injection molding tool comprises a first tool part 1 and a second tool part 2, which is displaceably mounted relative to the first tool part 1. The first tool part 1 can, for example, be a rotatably mounted central segment of a cube tool. The second tool part 2 can be displaced horizontally relative to the first tool part 1 and has an inlet 3 for a plasticized plastic material P which can be supplied via a feed channel 4, for example a hot channel. The first tool part 1 and the second tool part 2 delimit a mold cavity 5 in the closed state, which defines the shape of an injection-molded closure element 6, as can be seen better in FIG. 2. The reference numerals 9 designate ejectors for the closure element 6 formed within the mold cavity 5.

Fig. 1 shows the first tool part 1 and the second tool part 2 in a not yet fully closed state. In this case, the two tool parts 1, 2, for example, are fed towards one another to such an extent that leakage of the plasticized plastic material P injected into the mold cavity 5 is avoided. For example, the two tool parts 1, 2 are approximated to one another to at least 5% of the closed state. The distance is d

CH 712 945 A1 of a first contact surface 11 on the first tool part 1 and a second contact surface 21 on the second tool part 2, which bear against one another by a maximum of 3 mm when the injection mold 10 is closed.

The mold cavity 5, which defines the closure element 6 for closing a container opening, which has at least one thin point 61, is expanded by the distance d between the first tool part 1 and the second tool part 2. As can be seen in particular from FIG. 2, the at least one thin point 61 does not have its final minimum wall thickness, but is also expanded by the distance d between the first and the second tool parts 1, 2. The at least one thin point 61 can be designed, for example, in the form of a ring. However, it goes without saying that the shape, the number and the arrangement of the thin spots can be chosen differently depending on the respective requirements. 1 and 2 further show that the mold cavity 5 is not completely filled, so that when the two tool parts 1, 2 are completely closed, there is sufficient space for the displaced plastic material.

Since the mold cavity 6 and in particular the at least one thin point 61 is extended by the distance d between the first and second contact surfaces 11, 21, in addition to the usual plastic materials which are relatively thin in the melt state, plastics can also be processed which have a melt flow index of> Have 1 g / 10 min. The processable materials therefore include high density polyethylene (HOPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene homopolymer (PP-H), block copolymer polypropylene (PP-B), random copolymer polypropylene (PP-R), polyethylene terephthalate (PET), polyethylene furanoate (PEF), polypropylene furanout (PPF), polystyrene (PS), polylactide (PLA), polyamide (PA), acrylonitrile-butadiene-styrene copolymer (ABS), polyoxymethylene (POM ), their copolymers and mixtures of the plastics mentioned.

3 and in the detailed representation in FIG. 4, the injection mold 10 from FIGS. 1 and 2 is shown in the fully closed state. The first and second contact surfaces 11, 12 on the first and second tool parts 1, 2 abut one another and can be pressed together with a closing force of up to 10,000 N. The mold cavity 5 is reduced to its nominal volume. The plastic melt P displaced thereby completely fills the mold cavity 5. The injection mold is closed completely during or after the injection of the introduced plastic melt. The flat closure element 6 defined by the mold cavity 5 is pressed or embossed into its final shape by the closing process. The at least one thin spot 61 also receives its minimum wall thickness w predetermined by the mold cavity 5. This can be from 0.02 mm to 1 mm. In a variant, the at least one thin spot 61 can be formed with a wall thickness w of 0.05 mm to 0.8 mm. Finally, an alternative method variant of the invention can provide that the at least one thin spot 61 is formed with a wall thickness w of 0.1 mm to 0.4 mm. The stated wall thickness ranges for the thin section 61 are not to be considered conclusively. For example, wall thickness ranges from only 0.02 mm to 0.05 mm, or 0.05 mm to 0.1 mm, or 0.4 mm to 0.8 mm, or 0.8 mm to 1 mm, or any other additional wall thickness ranges within the specified limits for minimum and maximum wall thicknesses should be created, should it be necessary and appropriate for an intended molded part. By pressing the plastic melt introduced into the mold cavity 5, there are almost no limits to the minimum wall thickness w of the thin area 61 and the spatial extent of the closure element 6.

Fig. 5 shows an embodiment of a closure element 6 with at least one thin point 61, to which a functional part 8 has been injection molded. The functional part 8 is, for example, a dome-like packaging part that is liquid-tight with a container, e.g. can be connected to a plastic-coated cardboard container of a milk packaging. The flat closure part 6 extends within the functional part 8 at a transition from a shoulder section 81 to a neck section 82, which can be provided, for example, with an external thread 83 or the like. In FIG. 5 it is also indicated that an internal thread 84 can also be formed on the neck section. The internal thread can be provided in addition to or as an alternative to the external thread. The external thread mounting a twist lock on the neck portion 82 and the internal thread 84 allow mounting a piercing element. The at least one thin point 61 is, for example, annular and forms a predetermined breaking point of the closure element 6 in order to access the contents of the container connected to the functional part. For example, the closure element 6 can be broken open at the thin point 61 by pressure, or can be cut open or pierced with the aid of an aid. A thickened area in the center of the flat closure element 6 represents an injection point 62 of the closure part 6.

The injection molding of the functional part 8 on the closure element 6 can be carried out with the aid of a cube tool. Injection molding machines of this type are space-saving and allow high productivity through simultaneous execution of different manufacturing steps on the available sides of the die tool. The cube tool can be, for example, a 180 ° tool or a 90 ° tool. The further production steps can accordingly be carried out on two opposite sides of the cube or on all four sides of the cube.

The flat closure element 6 can comprise a barrier material against oxygen and / or water vapor, and / or a barrier material prevents the diffusion of aromas or the effect of radiation such as visible light or ultraviolet light and is embedded in a plastic that is different from the barrier material. However, the closure element 6 can also be made entirely of such a barrier material. Such a flat closure element 6 can be used, for example, to break open an opening in a food packaging, the contents of which are to be protected against the ingress of oxygen and / or water vapor.

CH 712 945 A1

Such food packaging can e.g. Milk packs or yogurt containers, but also capsule-like packaging for powdered or liquid coffee concentrates for coffee machines.

The barrier material of the closure element 6 can be embedded on all sides in a plastic material which is different from the barrier material. This can be of particular advantage in the case of barrier materials which are otherwise difficult to attach to a container opening or which react chemically with the container contents. The barrier material can, for example, be embedded in a material that can be very easily connected to the container material.

Embedding the barrier material of the closure element 6 can be carried out in a 2-component or multi-component injection molding process. 2-component or multi-component injection molding processes have been tried and tested and allow the production of molded parts that consist of two or more plastic materials. In the simplest case, the plastic materials only differ in their color in order to achieve a certain design. The 2-component or multi-component injection molding process, in particular, allows the use of different materials in order to combine different properties in a targeted manner. In this way, for example, barrier materials against oxygen and / or water vapor can be combined with low-density polyethylene (LDPE) or with high-density polyethylene (HDPE) or with polypropylene.

[0032] Polyamide (PA), polyethylene furanoate (PEF), polypropylene furanoate (PPF), polyethylene vinyl alcohol (EVOH), polyethylene vinyl acetate (EVA), their copolymers and mixtures of the plastics mentioned can be used as barrier materials. In the case of barrier materials encapsulated on all sides, there are hardly any restrictions with regard to the choice of material for the oxygen and / or water vapor barrier.

In a further embodiment variant of the invention, not shown, the functional part molded on with at least one thin point after the inventive production of the closure element can be designed as a capsule-like container. The previously produced closure element with a thin point can be designed in such a way that the thin point opens under the influence of temperature and pressure after a predetermined time. Capsule-like containers of this type can be used, for example, as so-called coffee capsules in connection with automatic coffee machines.

The above description only serves to explain the method according to the invention and is not to be regarded as restrictive. Rather, the invention is defined by the patent claims and the equivalents which are obvious to the person skilled in the art and which are encompassed by the general inventive concept.

Claims (15)

claims 1. A method for producing a closure element (6) for closing a container opening, which has at least one thin point (61) of a predetermined minimum wall thickness (w), in which a predeterminable amount of a plasticized plastic material (P) into a mold cavity (5) of an injection mold ( 10) of an injection molding device, the plastic material (P) is solidified by cooling or a crosslinking reaction and after the opening of the injection molding tool (10) the closure element (6) is formed, characterized in that the plasticized plastic material (P) is inserted into the mold cavity ( 5) of the injection mold (10), which is not yet completely closed, and that the injection mold (10) is completely closed during or after the introduction of the plasticized plastic material, the predetermined minimum wall thickness (w) of the at least being closed by the injection mold (10) a thin spot (61 ) is trained. 2. The method according to claim 1, characterized in that the injection mold (10) for the introduction of the plasticized plastic material (P) is closed at least to the extent that leakage of the introduced plastic material (P) from the mold cavity (5) of the injection mold (10) prevents become. 3. The method according to claim 1 or 2, characterized in that the injection mold (10) for the introduction of the plasticized plastic material (P) is closed to at least 5%. 4. The method according to any one of the preceding claims, characterized in that the at least one thin site (61) is formed with a minimum wall thickness (w) of 0.02 mm to 1 mm. 5. The method according to any one of the preceding claims, characterized in that the at least one thin site (61) is formed with a minimum wall thickness of 0.05 mm to 0.8 mm. 6. The method according to any one of the preceding claims, characterized in that the at least one thin site (61) is formed with a minimum wall thickness (w) of 0.1 mm to 0.4 mm. 7. The method according to any one of the preceding claims, characterized in that the closure element (6) with a barrier material against the entry of oxygen and / or water vapor and / or radiation and / or diffusion of aromas is produced. 8. The method according to claim 7, characterized in that the barrier material of the closure element (6) is embedded on all sides in a plastic material which is different from the barrier material. 9. The method according to claim 8, characterized in that the closure element (6) is produced in a 2-component or multi-component injection molding process. CH 712 945 A1 10. The method according to any one of claims 7 to 9, characterized in that the barrier material used is polyamide (PA), polyethylene furanoate (PEF), polypropylene furanoate (PPF), polyethylene vinyl alcohol (EVOH), polyethylene vinyl acetate (EVA), their copolymers and mixtures of the plastics mentioned become. 11. The method according to any one of the preceding claims, characterized in that the plastic material (P) introduced into the mold cavity of the injection mold has a melt flow index of> 1 g / 10 min. 12. The method according to any one of the preceding claims, characterized in that prior to removal from the mold, a functional part (8) is molded onto the closure part (6). 13. The method according to claim 12, characterized in that the injection molding of the functional part (8) on the closure part (6) with the aid of a cube tool, a turntable tool or another form of 2-component or multi-component tools. 14. The method according to claim 12 or 13, characterized in that the functional part (8) is designed as a dome-like packaging part. 15. Molding manufactured according to one of the preceding claims, characterized in that it has a closure element (6) and a functional part (8) and is designed as a container or is provided for a liquid-tight connection to a container body. CH 712 945 A1