Sealing material (sh a 50 - 80) for vacuum screw closures

Abstract

A container closure, in particular vacuum screw closure, having a sealing insert which comprises or consists of a polymer compound, the polymer compound comprising the following: at least one highly vinylic styrene block copolymer; at least one isobutylene-containing, preferably rubber-type (co-)polymer; a content of more than zero of at least one (Co)PP-containing polymer and optionally other constituents and additives.

Description

[0001] Sealing material (Sh A 50 - 80) for vacuum screw caps

[0002] The invention relates to a vessel closure, in particular a vacuum screw cap, with a sealing element comprising or consisting of a polymer compound. More specifically, the invention relates to vessel closures with a polymer-based sealing insert for bottles and other containers for holding beverages and food. The vessel closures are free of halogen-containing substances and are also suitable for demanding applications.

[0003] Beverages and foodstuffs are filled into various types of containers for transport, storage, and preservation. These containers often need to be sealable to prevent leakage and to protect them from unwanted substances that could contaminate or damage the contents. In many applications, these contaminants are not limited to solid or liquid contaminants. If the contents are sensitive to gaseous substances, these must also be prevented from entering. This is achieved by an appropriately designed container closure.

[0004] Metal and / or plastic vessel closures have been around for a long time. They are used in the form of screw caps, twist locks, and crown corks, for example, to tightly seal vessels such as bottles, jars, and the like. Such vessels have a mouth that must be sealed by the vessel closure. A sufficiently tight closure of the vessel must be ensured, on the one hand, to prevent the vessel contents from leaking out and, on the other hand, to protect the vessel contents from the entry of unwanted substances, including gaseous substances such as oxygen, trichloroanisole, and others.

[0005] The necessary tightness is usually achieved by a sealing insert made of a material that is both sufficiently strong and elastic and is arranged in the vessel closure so that it contacts the vessel mouth when the vessel closure is attached to the vessel. The sealing insert is usually disc-shaped or ring-shaped and arranged on the inside of the vessel closure. When the vessel is closed, it rests against the vessel mouth and is pressed against the mouth by the vessel closure, with its hardness combined with its elasticity creating the seal. A good sealing insert compensates for the unevenness that is always present in the vessel mouth. Therefore, the more uneven the vessel mouth is, the higher the demands placed on the sealing insert.

[0006] A key factor in meeting such requirements is the appropriate choice of gasket material. Many common materials are well-suited for relatively simple applications, but less so, or not at all, for more demanding seals.

[0007] The sealing insert must also meet additional requirements, for example, it must be pasteurizable or even sterilizable by heat and, if necessary, pressure for many applications. It must withstand considerable internal pressure (e.g., in carbonated beverages), but release in a controlled manner if this pressure is exceeded (overpressure valve effect).

[0008] If the vessel closure is a twist-lock closure, the sealing insert must not offer excessive resistance to the twisting of the vessel closure on the mouth when opening.

[0009] In addition, the sealing insert must be as easy to manufacture and install as possible in the vessel closure. It is known to cut disc-shaped sealing inserts from sheets or films and then attach them to the vessel closure ("out-shell molding") or, as is often preferred, to insert them in a flowable form into the vessel closure, where they are formed and solidified ("in-shell molding"). In-shell molding also allows the production of sealing inserts that are not disc-shaped, but rather ring-shaped.

[0010] In the case of PVC polymer-based gasket inserts, this is conventionally done by introduction as a plastisol with subsequent gelling, whereby profiling of the gasket is possible using heated stamps, or in the case of thermoplastic materials by introduction in a heated, flowable state, subsequent shaping and cooling.

[0011] While PVC-based gasket inserts were once widely used, PVC and other halogen-containing materials now raise significant concerns. They are considered potentially harmful to health and are not easily disposed of. In many countries, the use of such halogen-containing materials is regulated or even prohibited by law or regulation.

[0012] There is therefore a significant need for vessel closures that do not require halogen-containing materials, without having to forego the advantages that, for example, PVC-containing sealing inserts have in terms of processing, sealing properties, costs, and the like.

[0013] There are already a number of proposals for this in the state of the art.

[0014] For decades, it has been known to produce sealing inserts for screw caps based on polymers that do not contain halogens. These sealing inserts are generally "compounds," i.e., mixtures of one or (usually) several polymers with additives that adapt the properties of the sealing insert to the intended application, facilitate its processing or use, and so on.

[0015] Typical polymers in such compounds are thermoplastics, especially polyolefins, thermoplastic elastomers, elastic thermoplastics, and synthetic rubbers. Typical additives include plasticizers, oils, lubricants, antioxidants, stabilizers, pigments, fillers, and the like.

[0016] Against this background, it is an object of the invention to propose improved vessel closures, particularly with regard to the properties of the sealing element.

[0017] The combination of features of the independent patent claim serves to solve this problem.

[0018] In particular, the invention provides that the seal contains high-vinyl styrene block copolymers.

[0019] Advantageous developments of the invention are defined in the dependent patent claims. By "highly vinylic," we mean, in accordance with US Pat. No. 1,0457,805 (2B), those styrene block copolymers whose vinyl content is greater than 50 mol% before hydrogenation. After hydrogenation, the copolymer naturally contains little or no unsaturation. Nevertheless, we also refer to such styrene block copolymers as "highly vinylic" because they can be derived from precursors with such high vinyl contents.

[0020] By "rubber-like," we mean polymers that resemble known synthetic rubbers in their mechanical properties essential for sealing (such as hardness and elasticity). Butyl rubber (IIR), e.g., the commercially available product, is a suitable reference substance.

[0021] The invention specifically relates to a vessel closure, in particular a vacuum screw closure, with a sealing element comprising or consisting of a polymer compound, wherein the polymer compound comprises the following: at least one high-vinyl styrene block copolymer; at least one isobutylene-containing, preferably rubber-like (co)polymer; a content greater than zero of at least one (co)-PP-based polymer, and optionally further components and additives.

[0022] The styrene block copolymer preferably has a styrene content of less than 25 wt.% based on the total weight of styrene block copolymer.

[0023] Particularly suitable are hydrogenated styrene block copolymers with butadiene middle blocks (1,2- and / or 1,4-linked), e.g. SEBS and high-vinyl SEEPS

[0024] These polymers differ from each other in their molecular middle blocks, which are composed of hydrogenated sequences of butadiene (1,2 and / or 1,4-linked) and / or isoprene.

[0025] Such copolymers can be obtained, for example, from Kraton Corp., TSRC Corp., or Dynasol. Typical suitable products are Kraton Gl 645, Kraton Gl 643, Vector 8245, or Calprene H6180, among others, e.g., Hybrar 7000, which copolymerizes isoprene in addition to butadiene. In preferred embodiments of the vessel closure according to the invention, the high-vinyl styrene block copolymer is present in a proportion of 20-40 wt.%, based on the total weight of the polymer components in the sealing element.

[0026] The styrene block copolymer is preferably relatively soft and has a Shore A hardness of less than 60.

[0027] In preferred embodiments of the invention, the styrene block copolymer has an MFI (190°C, 5 kg) of >0 g / 10 min, whereby the materials according to the invention may not be meltable or may be only partially thermoplastic.

[0028] In preferred embodiments, the styrene block copolymer comprises an SE(E)PS having a vinyl content before hydrogenation of more than 50 mol% and a styrene content of <25 wt% based on the total weight of SE(E)PS.

[0029] According to the invention, the compound of the sealing element further contains an isobutylene-containing rubber-like (co)polymer, which preferably limits or completely prevents the passage of disruptive substances, e.g. gases from the environment, thus having at least a small barrier effect.

[0030] According to the invention, the (co)polymer is selected from

[0031] IIR (butyl rubber);

[0032] - SIBS;

[0033] - PIB; and mixtures thereof, wherein the copolymer preferably has a Shore A hardness between 20 and 60 and is preferably present in a content of 10 to 40 wt.%, based on the total weight of the polymers in the sealing material.

[0034] In a preferred embodiment of the invention, it is further provided that the (co)PP-based polymer of the sealing element comprises or consists of a PP homopolymer or a PP copolymer with a Shore D hardness of more than 65, wherein the content of this polymer in the sealing material is preferably not greater than 20 wt.%, based on the total weight of the polymers in the sealing material.

[0035] The main function of this (co)PP content is to give the sealing element sufficient resistance to heat treatment such as pasteurization or sterilization, but also to ensure adhesion to the lacquer systems commonly used in metal closures or the cap material, which is also usually PP-based, in plastic closures.

[0036] Currently, it is preferred that the PP-based polymer of the sealing element be a PP homopolymer, although PP copolymers with low comonomer contents (typically <5%, especially ethylene) are also suitable. Such materials are available on the market from a variety of manufacturers.

[0037] Preference is given to those whose melt flow index at 230°C and 2.16 kg coating weight does not exceed 30 dg / min.

[0038] In an alternative embodiment of the invention, the (co)-PP-based polymer in the sealing element is a PP copolymer with a Shore D hardness of less than 40, preferably between 20 and 70 wt.%, based on the total weight of the polymers in the sealing material. Such more specialized copolymers combine a low hardness for PP-based copolymers with melting points above 140°C.

[0039] In this embodiment, the (co-)PP has the same function as before, but it allows materials to be produced that require lower contents of the often expensive soft components described above.

[0040] In all embodiments, the PP-based polymer in the sealing element can be a PP / PE copolymer. In other preferred embodiments of the invention, the sealing element can additionally or instead comprise or consist of at least one terpolymer, preferably a propene-, ethene-, and / or butene-containing terpolymer. The sealing element does not contain PVC within the scope of the analytical methods customary on the date of filing. The sealing material preferably has a total Shore A hardness (DIN ISO 7619-1) of 40 to 90, preferably 50 to 80.

[0041] In preferred embodiments, the sealing element comprises additional polymers (excluding PVC), in particular at least one (co)PE, preferably with a melting point (DIN EN ISO 11357-3) above 100°C, preferably with an MFI (DIN EN ISO 1133, 190°C, 5 kg) of < 50g / 10 min., in particular in a content of up to 25 wt.% based on the total weight of the polymers in the sealing material.

[0042] In preferred embodiments of the invention, the vessel closure further comprises conventional additives, e.g., at least one filler such as talc, in particular in a content of up to 20 wt.% based on the total weight of the sealing element.

[0043] Particularly when migration problems are negligible, the hardness of the sealing element can be adjusted by conventional additions of plasticizing substances. In these embodiments, the compound of the sealing element contains at least one plasticizer that is liquid at 23°C and ambient pressure, in particular white oil or a synthetic polyolefin-based oil, preferably in a content of up to 10 wt.% based on the total weight of the sealing element.

[0044] In preferred embodiments, the kinematic viscosity (according to DIN EN ISO 3104) of the plasticizer at 40°C is above 60 mm 2 / s.

Claims

AMENDED CLAIMS received by the International Bureau on 21 May 2024 (21.05.2024) 1. A vessel closure, in particular a vacuum screw cap, with a sealing element comprising or consisting of a polymer compound, wherein the polymer compound comprises: at least one high-vinyl styrene block copolymer; at least one isobutylene-containing, preferably rubber-like (co)polymer, namely HR (butyl rubber); a content greater than zero of at least one (co)PP-containing polymer, and optionally further components and additives.

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

3. A vessel closure according to claim 1 or claim 2, wherein the styrene block copolymer comprises a SE(E)PS having a vinyl content before hydrogenation of more than 50 mol% and a styrene content of <25 wt% based on the total weight of SEEPS.

4. Vessel closure according to one of claims 1 to 3, in which the styrene block copolymer is present in a proportion of 20 - 40 wt.%, based on the total weight of the polymer components in the sealing element.

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

6. Vessel closure according to one of the preceding 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. A vascular closure according to any one of the preceding claims, wherein the isobutylene-containing (co)polymer is selected from isobutylene copolymers such as -IIR (butyl rubber); AMENDED SHEET (ARTICLE 19) - SIBS (styrene-isoprene / butadiene-styrene block copolymer); - PIB (polyisobutylene); - and mixtures thereof; wherein the isobutylene-containing (co)polymer preferably has a Shore A hardness between 20 and 60 (DIN ISO 7619-1) and is preferably present in a content of 10 to 40 wt.%, based on the total weight of the polymers in the sealing material.

8. Vessel closure according to one of the preceding claims, wherein the (Co)PP-based polymer comprises or consists of a PP homopolymer or a PP copolymer having a Shore D hardness of more than 65, wherein the content of this polymer in the sealing material is preferably not greater than 20% by weight, based on the total weight of the polymers in the sealing material.

9. Vessel closure according to one of the preceding claims, wherein the (Co)PP-based polymer comprises or consists of a PP copolymer having a Shore D hardness of less than 40, wherein the content of this polymer in the sealing material is preferably between 20 and 70 wt.%, based on the total weight of the polymers in the sealing material.

10. Vascular closure according to one of the preceding claims, wherein the PP copolymer comprises or consists of at least one terpolymer, preferably a propene-, ethene- and / or butene-containing terpolymer, and / or at least one propene- and / or ethene-containing copolymer.

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

12. Vessel closure according to one of the preceding claims, further comprising at least one (co)PE, preferably with a melting point below 100°C, preferably with an MFI (190°C, 5 kg, DIN EN ISO 1133) of ≤ 50g / 10 min., in particular in a content of up to 25 wt.% based on the total weight of the polymers in the sealing material. AMENDED SHEET (ARTICLE 19) 13. Vessel closure according to one of the preceding claims, further comprising at least one filler, in particular talc, in particular in a content of up to 20 wt.% based on the total weight of the sealing element.

14. Vessel closure according to one of the preceding claims, further comprising at least one plasticizer, in particular white oil or a synthetic oil based on polyolefin which is liquid at 23 °C and ambient pressure, preferably in a content of up to 10 wt.% based on the total weight of the sealing element.

15. Vessel closure according to claim 14, wherein the kinematic viscosity (according to DIN EN ISO 3104) of the plasticizer at 40°C is above 60 mm 2 / s is located. AMENDED SHEET (ARTICLE 19)