Container stopper material having only one kind of polymer

Abstract

Container closures, particularly vacuum screw closures, have a sealing insert comprising or consisting of a polymeric material (excluding PVC), said sealing insert essentially comprising only one type of copolymer, preferably only one type of copolymer and only conventional additives.

Description

Technical Field

[0001] The present invention generally relates to container closures having polymer-based seal inserts for bottles and other containers for holding beverages and foods. The container closures do not contain halogenated materials and are suitable for severe applications.

Background Art

[0002] For the purposes of transportation and storage or preservation, beverages and foods are filled into different types of containers. In many cases, these containers must be sealed so that the contents do not leak and are protected from the ingress of unwanted substances that could contaminate or damage the contents. In many applications, these are not just solid or liquid contaminants. If the contents are sensitive to gaseous substances, it is also necessary to prevent the ingress of gaseous substances. This is achieved by a properly configured container closure.

[0003] Container closures made from metal and / or plastic have been known previously. For example, in the form of screw caps, screw closures and crown corks, they serve to tightly seal containers such as bottles, glasses, etc. Such containers have a mouth that must be sealed by a container closure. In this regard, on the one hand, it is necessary to prevent the contents of the container from leaking, and on the other hand, to ensure a sufficiently tight closure of the container to protect the contents from the ingress of unwanted substances including gaseous substances such as oxygen, trichloroanisole, etc.

[0004] The necessary impermeability is usually achieved by a sealing insert that consists of a material that is sufficiently hard on the one hand and elastic on the other hand and is arranged in the container closure material in such a way that it comes into contact with the mouth of the container when the container closure material is placed on the container. The sealing insert is usually arranged inside the container closure material in the form of a disk or a ring. In the closed state of the container, the sealing insert seats on the mouth of the container and is pressed against the mouth by the container closure material, at which time it forms a seal by virtue of its hardness and its elasticity. In this regard, a good sealing insert compensates for the unevenness of the mouth of the container that always exists. Thus, the more uneven the mouth of the container is, the higher the requirements for the sealing insert become.

[0005] The seal by the sealing material can be further optimized by foaming if necessary. For foaming, chemical blowing agents such as citrate salts, bicarbonates, or microspheres filled with solvents (e.g., "Expancel"), and physical blowing agents such as CO2 or nitrogen (N2) introduced into the melt under high pressure during melting in an extruder can be used. In contrast, conventionally used chemical blowing agents based on semicarbazide or dicarboxamide are not desirable because the by-products generated during decomposition are toxicologically harmful when in contact with food.

[0006] An important factor for meeting such strict requirements is the proper selection of the material of the sealing insert. Many known materials are very suitable for relatively simple applications but are less or not at all suitable for more demanding seals.

[0007] In this regard, the sealing insert must also meet other requirements, for example, it must be capable of pasteurization or sterilization for various purposes. These should be able to withstand a considerable internal pressure (e.g., in the case of carbonated beverages), but when the pressure is exceeded, the pressure should be released in a controlled manner (operation of the pressure relief valve).

[0008] When the container closure is a screw closure, the sealing insert must not offer too much resistance to unscrewing the container closure from the mouth in a spiral manner when opening.

[0009] Also, the sealing insert should be as inexpensive as possible and easy to manufacture and should be attachable to the container closure. It is known to cut out disc-shaped sealing inserts from webs or films and attach them to the container closure ("outshell molding"), or, as a more preferred method in many cases, to introduce them in a flowable form into the container closure and overmold and solidify them there ("inshell molding"). Inshell molding also means that sealing inserts can be produced that are not disc-shaped but annular.

[0010] Inshell molding is usually carried out for polymer-based sealing inserts by introducing them as a liquid plastisol, subsequently molding (optionally), and drying at a temperature usually exceeding 190°C, or, in the case of thermoplastic materials, by heating and introducing them in a flowable state, subsequently molding, and cooling.

[0011] Previously, sealing inserts containing PVC were widely used, but currently, PVC and other halogenated materials raise major concerns. These are considered potentially harmful to health and are also difficult to dispose of. In many countries, the use of such halogenated materials is regulated or even prohibited by law or regulation.

[0012] Therefore, there is a significant need for container closures that do not contain halogenated materials and can be used without sacrificing the advantages of, for example, PVC-containing sealing inserts, with respect to processing, sealing properties, cost, etc.

[0013] Known seals inserts usually consist of different polymers, often a mixture of different types of polymers (also known as "compounds"). However, different polymers based on the same or homologous monomers will be described below as "different", but not as "different types". Thus, for example, all copolypropylenes containing only propylene and another olefin are different but not "different types", whereas a PP copolymer and SEBS are different types.

[0014] Known seals inserts usually include a substrate that is often a polyolefin and is itself close to having a catalog of the required properties. Next, the properties of the seals insert are specifically adjusted by mixing in other polymers in order to further optimize those properties with respect to the elasticity or heat resistance for the purpose.

[0015] In contrast, most compounds having only one type of polymer (apart from lubricants, stabilizers, etc.) are not suitable for the purposes of the present invention. Compounds having a non-elastomeric thermoplastic (e.g., most PP-based) as the only polymer in the seals insert are very hard and do not have sufficient elasticity. In contrast, compounds having only an elastomeric thermoplastic or a thermoplastic elastomer are usually too soft. SUMMARY OF THE INVENTION

[0016] Certain PP-based copolymers are an exception and, according to the present invention, can be processed into seals inserts together with a certain amount of a normal lubricant, etc. Such compounds are described in the claims.

[0017] The PP-based copolymer forms the main component of the sealing material and preferably does not contain (or contains only a very small amount of) other polymers. In other words, the only polymer (apart from conventional additives) forming the seals element substantially fully or fully participates in its properties.

[0018] Accordingly, according to the present invention, there is provided a container stopper material having a sealing element made of or containing a polymer material, in particular a vacuum screw stopper material, wherein the sealing element comprises substantially a single type of copolymer, preferably a single copolymer and only ordinary additives.

Embodiments for Carrying Out the Invention

[0019] In a preferred embodiment, the polymer material comprises or is a PP-based copolymer, in particular a bipolymer or a terpolymer.

[0020] Particularly preferably, the sealing insert comprises at least one PP / PE bipolymer (copolymer of propylene and ethylene). Alternatively, the sealing insert may comprise a PP / PE / BU terpolymer (copolymer of propene, ethene and butene).

[0021] In a preferred embodiment of the present invention, the container stopper material has a sealing insert in which the copolymer has an MFR (ASTM D 2240) of less than 10 g / 10 min, preferably less than 8 g / 10 min, particularly preferably ≦6 g / 10 min at 230 °C and a load of 2.16 kg.

[0022] Also, a preferred embodiment of the present invention provides a container stopper material in which the copolymer has a Shore A hardness (ISO 868) of less than 80, preferably 60 or more.

[0023] In another or the same preferred embodiment, there is provided a container stopper material in which the copolymer has a melting point (ISO 11357-3) of 140 °C to 190 °C, preferably 160 °C to 180 °C, particularly preferably at most 165 °C.

[0024] In a preferred embodiment of the present invention, the container stopper material is 0.8 to 1.0 g / cm 3 , preferably 0.86 to 0.9 g / cm 3 , particularly about 0.88 g / cm 3It contains a copolymer having a density (DIN EN ISO 1183-1).

[0025] In addition to the polymer, the sealing insert of the present invention preferably comprises conventional additives selected from lubricants, antioxidants, colorants and / or fillers.

[0026] Polymers suitable for carrying out the present invention can be purchased from the Mitsui Chemicals Group and LyondellBasell.

[0027] The sealing inserts made from the materials described can be used in fatty filling materials and are suitable for PT caps. They can also be sterilized. The suitability of the sealing material for sterilization can be determined by appropriate tests.

[0028] The prediction of this suitability is possible by known dynamic mechanical thermal analysis (DMTA). In principle, the heating curve is determined with respect to the phase angle (tanδ), and its inflection point must be sufficiently higher (usually at least 10 °C) than the intended sterilization temperature.

[0029] The verification of these tests is carried out by manufacturing the stopper material and testing it using appropriate application parameters such as the maximum sterilization temperature, the sterilization period (= time at the maximum sterilization temperature) and the back pressure.

Claims

1. A container stopper material, particularly a vacuum screw stopper material, having a seal insert containing or consisting of a polymer material (excluding PVC) that is a PP-based copolymer, wherein the seal insert contains substantially a single type of copolymer, preferably a single copolymer and only ordinary additives.

2. The container stopper material according to claim 1, wherein the polymer material contains a bipolymer or a terpolymer, or is a bipolymer or a terpolymer.

3. The container stopper material according to claim 1 or 2, containing at least one PP / PE bipolymer (a copolymer of propene and ethene).

4. The container stopper material according to any one of claims 1 to 3, containing a PP / PE / BU terpolymer (a copolymer of propene, ethene, and butene).

5. The copolymer of the container stopper material according to any one of claims 1 to 4 has an MFR (DIN EN ISO 1133) of less than 10 g / 10 min, preferably less than 8 g / 10 min, particularly preferably ≤ 6 g / 10 min at 230 °C and a load of 2.16 kg.

6. The copolymer of the container stopper material according to any one of claims 1 to 5 has a Shore A hardness (measured according to DIN ISO 7619-1) of less than 80, preferably 70 or more.

7. The copolymer of the container stopper material according to any one of claims 1 to 7 has a melting point (DIN EN ISO 11357-3) of 140 °C to 190 °C, preferably 160 °C to 180 °C, particularly preferably a maximum of 165 °C.

8. The copolymer has a density of 0.8 to 1.0 g / cm ３ , preferably 0.86 to 0.9 g / cm ３ , particularly about 0.88 g / cm ３ (DIN EN ISO 1183-1), and is the container stopper material according to any one of claims 1 to 7.

9. The additive of the container stopper material according to any one of claims 1 to 8 is selected from lubricants, antioxidants, colorants, and / or fillers.

10. Since the sealing material is a closed-cell foam, its density according to DIN EN ISO 1183-1 is lower than the initial density of the sealing material, but still at least 50%, preferably at least 70% of the initial density, of the container stopper material according to any one of claims 1 to 9.

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