Sealing material (Sh A 50-80) for vacuum rotary closures

Abstract

A container closure, in particular a vacuum rotary closure, has a sealing element, which comprises or consists of a polymer compound, in which the polymer compound comprises the following: at least one high vinyl styrene block copolymer; at least one isobutylene-containing, preferably rubber-like (co) polymer; at least one (co) PP-containing polymer in an amount greater than zero; and optionally other ingredients and additives.

Description

Field of the Invention

[0001] The present invention relates to a container closure, in particular a vacuum rotary closure, having a sealing element comprising or consisting of a polymer compound. More specifically, the present invention relates to a container closure for bottles and other containers for containing beverages and foodstuffs, having a polymer-based sealing gasket. The container closure does not have halogen-containing substances and is also suitable for demanding applications. Background Art

[0002] For transportation and storage or preservation, beverages and foodstuffs are filled into different types of containers. The containers usually have to be closable so that the contents do not leak out and are also protected against the entry of unwanted substances that could contaminate or damage the contents. In many applications, this does not only concern solid or liquid dirt. If the contents are sensitive to gaseous substances, these also have to be prevented from entering. This is achieved by a correspondingly designed container closure.

[0003] Container closures made of metal and / or plastic have long been known. These container closures are used, for example, in the form of screw caps, rotary closures and crown caps for sealingly closing containers such as bottles, glass jars and the like. Such containers have an opening that has to be closed by the container closure. Here, it must be ensured that the container is closed sufficiently tightly so that, on the one hand, the outflow of the container contents is prevented and, on the other hand, the container contents are protected against the entry of unwanted substances including gaseous substances such as oxygen, trichloroanisole and the like.

[0004] The necessary tightness is usually achieved by a sealing gasket, which is made of a material that is on the one hand sufficiently firm but on the other hand also elastic and is arranged in the container closure such that when the container closure is placed on the container, the sealing gasket contacts the opening of the container. The sealing gasket is mostly arranged in a disk-shaped or ring-shaped manner on the inside of the container closure. In the closed state of the container, the sealing gasket abuts against the container opening and is pressed against the opening by the container closure, wherein the hardness of the sealing gasket together with its elasticity causes the seal. A good sealing gasket compensates for the always present unevenness of the container opening here. Thus, the more uneven the container opening, the higher the requirements for the sealing gasket.

[0005] A key factor in meeting these requirements is the appropriate selection of the sealing gasket material. Many known materials are well suited for relatively simple applications, but are less suitable or not at all suitable for higher requirements for sealing.

[0006] Here, the sealing gasket must also meet other requirements, namely that the sealing gasket should be pasteurizable or even sterilizable by heat and, if necessary, pressure for many purposes of use. The sealing gasket (e.g. in carbonated beverages) should withstand a large internal pressure, but when the internal pressure is exceeded, it should be released in a controlled manner (overpressure - valve action).

[0007] If the container closure is a rotary closure, the sealing gasket allows the container closure to be twisted on the opening without excessive resistance when opening.

[0008] Furthermore, the sealing gasket must be manufactured as cost - effectively as possible and be able to be installed in the container closure. It is known to cut out a disc - shaped sealing gasket from a strip or film and then fasten it in the container closure ("Out - shellmolding"), or, more preferably, to introduce it in a flowable form into the container closure, where it is molded and cured ("In - shell molding"). In - shell molding also allows the production of sealing gaskets that are not disc - shaped but annular.

[0009] In the case of sealing gaskets based on PVC polymers, this is traditionally done by introducing them in the form of plastisols and subsequent gelation, where it is possible to profile the seal with a heated punch, or in the case of thermoplastics, this is done by introducing them in a heated, flowable state and subsequent shaping and cooling.

[0010] PVC - containing sealing gaskets were used on a large scale in the early days, while currently, PVC and other halogen - containing materials are facing great concerns. They are regarded as potentially health - damaging and cannot be disposed of without problems. In many countries, the use of these halogen - containing materials is regulated or even prohibited by laws or regulations.

[0011] Therefore, there is a great demand for container closures that can also cope without halogen - containing materials, without having to sacrifice the advantages that PVC - containing sealing gaskets have in terms of processing, sealing characteristics, cost, etc.

[0012] For this purpose, a large number of suggestions already exist in the prior art.

[0013] Therefore, it has been known for decades to manufacture sealing gaskets for rotary closures based on halogen - free polymers. The sealing gaskets are always "compounds", i.e. mixtures of one or (mostly) several polymers with additives that match the properties of the sealing gasket to a preset purpose of use, simplify its processing or use, etc.

[0014] Typical polymers among these compounds are thermoplastics, especially polyolefins, thermoplastic elastomers, elastoplastic thermoplastics, and synthetic rubbers. Typical additives are plasticizers, oils, lubricants, antioxidants, stabilizers, pigments, fillers, etc. Summary of the Invention

[0015] In this context, the object of the present invention is to provide a container closure that is improved, especially with regard to the properties of the sealing element.

[0016] The combination of features of the independent claims serves to achieve the object.

[0017] In particular, it is proposed according to the present invention that the sealing element contains a high-vinyl styrene block copolymer.

[0018] Advantageous refinements of the present invention are defined in the dependent claims. Detailed Description of the Invention

[0019] According to US1,0457,805 2B, "high vinyl" is understood to mean such a styrene block copolymer that has a vinyl content greater than 50 mol% before hydrogenation. After hydrogenation, the copolymer naturally contains little or even no longer contains unsaturation. However, this styrene block copolymer is also referred to as "high vinyl" because the styrene block copolymer can be derived from a precursor with such a high vinyl content.

[0020] "Rubber-like" is understood to mean such a polymer that is similar to known synthetic rubbers in its main mechanical properties (such as hardness and elasticity) for the sealing function. Butyl rubber (IIR), for example, commercially available products, is suitable as a reference substance.

[0021] The present invention specifically relates to a container closure, especially a vacuum rotary closure, which has a sealing element that includes or consists of a polymer compound, where the polymer complex includes the following:

[0022] At least one high-vinyl styrene block copolymer;

[0023] At least one isobutene-containing, preferably rubber-like (co)polymer;

[0024] At least one polymer based on (co)PP with a content greater than zero;

[0025] And, if necessary, other components and additives.

[0026] The styrene block polymer preferably has a styrene content of less than 25% by weight based on the total weight of the styrene block copolymer.

[0027] In particular, suitable are hydrogenated styrene block copolymers having a butadiene middle block (bonded 1,2- and / or 1,4), such as SEBS and high vinyl SEEPS.

[0028] The polymers differ from one another by the molecular middle blocks constructed from the hydrogenation sequences of (1,2- and / or 1,4-bonded) butadiene and / or isoprene.

[0029] Such copolymers can be obtained, for example, from Kraton Corp., TSRCCorp. or Dynasol. Typical suitable products are Kraton G1645, Kraton G1643, Vector 8245 or Calprene H6180, and in addition, for example, Hybrar 7000, in which, in addition to butadiene, isoprene is also copolymerized.

[0030] In a preferred embodiment of the container closure according to the invention, the high vinyl styrene block copolymer is present in a proportion of 20% to 40% by weight, based on the total weight of the polymer fraction in the sealing element.

[0031] The styrene block copolymer is preferably relatively soft and has a Shore A hardness of less than 60.

[0032] In a preferred embodiment of the invention, the styrene block copolymer has an MFI (190 °C, 5 kg) of ≥ 0 g / 10 min, where the material according to the invention cannot be melted or is only partially thermoplastic, if necessary.

[0033] In a preferred embodiment, the styrene block copolymer comprises SE(E)PS, which has a vinyl content of more than 50 mol% before hydrogenation and a styrene content of < 25% by weight, based on the total weight of the SE(E)PS.

[0034] According to the invention, the composition of the sealing element further contains a rubber-like (co)polymer containing isobutene, which preferably limits or completely prevents the passage of interfering substances, such as gases in the environment, i.e., has at least a small barrier effect.

[0035] According to the invention, the (co)polymer is selected from:

[0036] - IIR (butyl rubber);

[0037] - SIBS;

[0038] - PIB;

[0039] and mixtures thereof,

[0040] The copolymer preferably has a Shore A hardness between 20 and 60 and is preferably present in an amount of 10% to 40% by weight based on the total weight of the polymers in the sealing material.

[0041] In a preferred embodiment of the present invention, it is further proposed that the (co)PP-based polymer of the sealing element comprises or consists of a PP homopolymer or a PP copolymer having a Shore D hardness greater than 65, wherein the content of the polymer in the sealing material is preferably not more than 20% by weight based on the total weight of the polymers in the sealing material.

[0042] The main function of the (co)PP content is to give the sealing element sufficient resistance to heat treatment such as in pasteurization or sterilization, but also to ensure adhesion to the coating systems commonly used in metal closures or to the PP-based lid materials commonly used in plastic closures as well.

[0043] Currently preferred is that the PP-based polymer of the sealing element is a PP homopolymer, and PP copolymers with a low comonomer content (typically <5%, especially ethylene) are also suitable. Such materials are offered by a large number of manufacturers on the market.

[0044] Preferentially are materials whose melt flow index at 230 °C and at a coating weight of 2.16 kg does not exceed a value of 30 dg / min.

[0045] In an alternative embodiment of the present invention, it is proposed that the (co)PP-based polymer in the sealing element is a PP copolymer having a Shore D hardness less than 40, preferably between 20% and 70% by weight based on the total weight of the polymers in the sealing material. This more particular copolymer combines a low hardness for a PP-based copolymer with a melting point above 140 °C.

[0046] In this embodiment, the (co)PP has the same function as before, however, it is thus possible to achieve a material that can also cope with a lower content of the usually more expensive soft components described above.

[0047] In all embodiments, the PP-based polymer in the sealing element can be a PP / PE copolymer. In other preferred embodiments of the present invention, the sealing element can additionally or instead include at least one terpolymer, preferably a propylene-containing, ethylene-containing, and / or butene-containing terpolymer or consists of it. The sealing element does not contain PVC within the scope of the analytical methods commonly used in the application.

[0048] The sealing material preferably has a Shore A hardness (DIN ISO 7619-1) of 40 to 90, preferably 50 to 80, in general.

[0049] In a preferred embodiment, the sealing element comprises an additional polymer (in addition to PVC), in particular at least one (co)PE, preferably having a melting point above 100 °C (DIN EN ISO 11357-3), preferably having an MFI of ≤ 50 g / 10 min (DIN EN ISO 1133, 190 °C, 5 kg), and its content is at most 25% by weight, in particular with respect to the total weight of the polymers in the sealing material.

[0050] In a preferred embodiment of the present invention, the container closure further comprises common additives, such as at least one filler, such as talc, and its content is at most 20% by weight, in particular with respect to the total weight of the sealing element.

[0051] In particular when migration problems can be neglected, the hardness of the sealing element can be set by adding common plasticizing substances. In this embodiment, the composition of the sealing element contains at least one plasticizer that is liquid at 23 °C and ambient pressure, in particular white oil or a polyolefin-based synthetic oil, and its content is preferably at most 10% by weight with respect to the total weight of the sealing element.

[0052] In a preferred embodiment, the kinematic viscosity of the plasticizer (according to DIN EN ISO 3104) is higher than 60 mm 2 / s at 40 °C.

Claims

1. A container closure, in particular a vacuum rotary closure, having a sealing element, which sealing element comprises or consists of a polymeric compound, wherein the polymeric compound comprises the following: At least one high vinyl styrene block copolymer; At least one isobutene-containing, preferably rubber-like (co)polymer; At least one polymer containing (co)PP in an amount greater than zero; And optionally other ingredients and additives.

2. The container closure according to claim 1, wherein the styrene block copolymer has a styrene content of less than 25% by weight based on the total weight of the styrene-containing polymer.

3. The container closure according to claim 1 or 2, wherein the styrene block copolymer comprises SE(E)PS, which has a vinyl content of greater than 50 mol% before hydrogenation and a styrene content of <25% by weight based on the total weight of SEEPS.

4. The container closure according to any one of claims 1 to 3, wherein the styrene block copolymer is present in a proportion of 20% to 40% by weight based on the total weight of the polymer fraction in the sealing element.

5. The container closure according to any one of claims 1 to 4, wherein the styrene block copolymer has a Shore A hardness (DIN ISO 7619-1) of less than 60.

6. The container closure according to any one of the above claims, wherein the styrene block copolymer has an MFI (190 °C, 5 kg; DIN EN ISO 1133) of ≥0 g / 10 min or preferably >0 g / 10 min.

7. The container closure according to any one of the above claims, wherein the isobutene-containing (co)polymer is selected from isobutene copolymers, such as: - IIR (butyl rubber); - SIBS (styrene-isoprene / butadiene-styrene block copolymer); - PIB (polyisobutene); - And mixtures thereof; Wherein the isobutene-containing (co)polymer preferably has a Shore A hardness (DIN ISO 7619-1) between 20 and 60, and is preferably present in an amount of 10% to 40% by weight based on the total weight of the polymer in the sealing material.

8. The container closure according to any one of the above claims, wherein the polymer based on (co)PP comprises or consists of a PP homopolymer or a PP copolymer having a Shore D hardness greater than 65, and the content of the polymer in the sealing material is preferably not more than 20% by weight based on the total weight of the polymer in the sealing material.

9. The container closure according to any one of the above claims, wherein the polymer based on (co)PP comprises or consists of a PP copolymer having a Shore D hardness less than 40, and the content of the polymer in the sealing material is preferably between 20% and 70% by weight based on the total weight of the polymer in the sealing material.

10. The container closure according to any one of the preceding claims, wherein the PP copolymer comprises at least one terpolymer, preferably a propylene-containing, ethylene-containing and / or butene-containing terpolymer, and / or at least one propylene-containing and / or ethylene-containing copolymer or consists thereof.

11. The container closure according to any one of the preceding claims, wherein the sealing material generally has a Shore A hardness of 40 to 90, preferably 50 to 80 and particularly preferably 60 to 80.

12. The container closure according to any one of the preceding claims, the container closure further comprising at least one (co)PE, the (co)PE preferably having a melting point below 100 °C, the (co)PE preferably having an MFI (190 °C, 5 kg, DIN EN ISO 1133) of ≤ 50 g / 10 min, the content of the (co)PE being at most 25% by weight, in particular with respect to the total weight of the polymers in the sealing material.

13. The container closure according to any one of the preceding claims, the container closure further comprising at least one filler, in particular talc, the content of the filler being at most 20% by weight, in particular with respect to the total weight of the sealing element.

14. The container closure according to any one of the preceding claims, the container closure further comprising at least one plasticizer, in particular white oil or a polyolefin-based synthetic oil that is liquid at 23 °C and ambient pressure, the content of the plasticizer preferably being at most 10% by weight with respect to the total weight of the sealing element.

15. The container closure according to claim 14, wherein the kinematic viscosity of the plasticizer (according to DIN EN ISO 3104) is higher than 60 mm 2 / s at 40 °C.