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

The disclosure relates to a container closure, in particular a vacuum screw closure, having a sealing element comprising or consisting of a polymer compound. More particularly, the 5 disclosure relates to container closures having a polymer-based sealing insert for bottles and other containers for holding beverages and foodstuffs. The container closures are free of halogen-containing substances and are also suitable for demanding applications. Beverages and foodstuffs are filled into various types of containers for transport and storage. 0 These containers often need to be sealable so that the contents do not leak and are also protected against the ingress of undesirable substances that would contaminate or damage the contents. In many applications, these are not just 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. 15 Container closures made of metal and / or plastic have long been known. In the form of screw caps, screw closures and crown caps, for example, they are used to seal containers such as bottles, jars and the like. Such containers have a mouth that must be closed by the container closure. A sufficiently tight closure of the container must be ensured in order to prevent the 20 contents of the container from leaking and to protect the contents of the container from the ingress of undesirable substances, including gaseous substances such as oxygen, trichloroanisole and others. The necessary tightness is usually achieved by a sealing insert, which is made of a material that 25 is both sufficiently strong and elastic and is arranged in the container closure in such a way that it contacts the mouth of the container when the container closure is arranged on the container. The sealing insert is usually arranged in the shape of a disc or ring on the inside of the container closure. In the closed state of the container, it lies against the mouth of the container and is pressed against the mouth by the container closure, wherein its hardness together with its 30 elasticity creates the seal. A good sealing insert compensates for the unevenness that is always present at the mouth of the container. The more uneven the container mouth is, the higher the demands placed on the sealing insert. 2022491254   08 Sep 2026 A key factor in meeting such requirements is the appropriate choice of the sealing insert material. Many well-known materials are well suited for relatively simple applications, but less so or not at all for more demanding seals. 5 The sealing insert must also meet other requirements, for example it should be pasteurisable or even sterilisable for many applications by applying heat and, if necessary, pressure. It should be able to withstand considerable internal pressure (e.g. for carbonated drinks), but give way in a controlled manner if this pressure is exceeded (overpressure valve effect). 0 If the container closure is a screw closure, the sealing insert must not offer too much resistance to the twisting of the container closure on the neck during opening. In addition, the sealing insert must be as easy as possible to produce and fit in the container closure. It is known to cut disc-shaped sealing inserts from sheets or films and then attach them 15 to the container closure ("out-shell moulding") or, which is often preferred, to insert them into the container closure in a flowable form, mould them there and solidify them ("in-shell moulding"). In-shell moulding also makes it possible to produce sealing inserts that are not disc-shaped but ring-shaped. 20 In the case of PVC polymer-based sealing inserts, this is conventionally done by insertion as plastisol with subsequent gelling, wherein profiling of the seal is possible using heated stamps, or in the case of thermoplastic materials by insertion in a heated flowable state, subsequent moulding, and cooling. 25 While sealing inserts containing PVC were used extensively in the past, PVC and other halogen-containing materials are now the subject of considerable concern. They are considered to be potentially harmful to health and are also not easy to dispose of. In many countries, the use of such halogen-containing materials is regulated or even banned by laws or regulations. 30 There is therefore a considerable need for container closures that do not require halogencontaining materials without having to forego the advantages that PVC-containing sealing inserts, for example, have in terms of processing, sealing properties, costs and the like. There are already a number of proposals for this in the prior art. 2022491254   08 Sep 2026 It has been known for decades to manufacture sealing inserts for screw closures on the basis of polymers that do not contain halogens. These sealing inserts are all "compounds", i.e. mixtures of one or (usually) several polymers with additives that adapt the properties of the sealing insert 5 to the intended application, facilitate its processing or use and the like. Typical polymers in such compounds are thermoplastics, especially polyolefins, thermoplastic elastomers, elastic thermoplastics and synthetic rubbers. Typical additives are plasticisers, oils, lubricants, antioxidants, stabilisers, pigments, fillers and the like. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims. 15 Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 20 Against this background, it is a preferred aim to propose improved container closures, in particular with regard to the properties of the sealing element. The combination of features of the independent claim serves to solve this problem. 25 In particular, the disclosure provides that the seal contains highly vinylic styrene block copolymers. Advantageous developments of the disclosure are defined in the dependent claims. 30 Based on US 1 0457 805 2B, the term "highly vinylic" refers to styrene block copolymers of which the vinyl content is more than 50 mol % before hydrogenation. After hydrogenation, the copolymer naturally contains little or even no unsaturation. Nevertheless, we also refer to such styrene block polymers as "highly vinylic" because they can be derived from precursors with such high vinyl contents. By "rubber-type" we mean polymers that are similar to known synthetic rubbers in terms of 5 their mechanical properties (such as hardness and elasticity) that are essential for the sealing function. Butyl rubber (IIR), e.g. the commercially available product, is suitable as a reference substance. 2022491254   08 Sep 2026 In a first aspect disclosed herein, is a container 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 highly vinylic styrene block copolymer; at least one iso-butylene-containing, preferably rubber-type (co-)polymer; specifically IIR (butyl rubber); 15          a content of more than zero of at least one (co)-PP-based polymer, and optionally other constituents and additives. The styrene block copolymer preferably has a styrene content of less than 25 wt.%, based on the total weight of styrene block copolymer. 20 Hydrogenated styrene block copolymers with butadiene centre blocks (1,2- and / or 1,4-linked), e.g. SEBS and highly vinylic SEEPS, are particularly suitable. These polymers differ from each other in the molecular centre blocks, which are made up of 25 the hydrogenated sequences of butadiene (1,2- and / or 1,4-linked) and / or isoprene. Such copolymers can be obtained from Kraton Corp., TSRC Corp. or Dynasol, for example. Typical suitable products are Kraton G1645, Kraton G1643, Vector 8245 or Calprene H6180, among others, e.g. Hybrar 7000, in which isoprene is copolymerised in addition to butadiene. 30 In preferred embodiments of the container closure according to the disclosure, the highly vinylic 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. 2022491254   08 Sep 2026 The styrene block copolymer is preferably relatively soft and has a Shore A hardness of less than 60. In preferred embodiments of the disclosure, the styrene block copolymer has an MFI (190°C, 5   5 kg) of >0 g / 10 min, wherein the materials according to the disclosure may not be meltable or are only partially thermoplastic. In preferred embodiments, the styrene block copolymer comprises an SE(E)PS having a vinyl content prior to hydrogenation of more than 50 mol % and a styrene content of <25 wt.%, based on the total weight of SE(E)PS. According to the disclosure, the compound of the sealing element further comprises an isobutylene-containing rubber-type (co-)polymer, which preferably limits or completely prevents the passage of interfering substances, e.g. gases from the environment, i.e. has at least 15 a small barrier effect. According to the disclosure, the (co-)polymer further comprises - SIBS; - PIB; 20        or mixtures thereof, wherein the copolymer preferably has a Shore A hardness of between 20 and 60 and preferably in a content of 10 to 40 wt.%, based on the total weight of the polymers in the sealing material. 25 In a preferred embodiment of the disclosure, 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 the sealing material in this polymer is preferably not more than 20 wt.%, based on the total weight of the polymers in the 30 sealing material. The main function of this (co)PP content is to give the sealing element sufficient resistance to heat treatment such as pasteurisation or sterilisation, but also to ensure adhesion to the coating 2022491254   08 Sep 2026 systems commonly used in metal closures or the cap material in plastic closures, which is also usually PP-based. It is currently preferred that the PP-based polymer of the sealing element is a PP homopolymer, 5 wherein PP copolymers with low comonomer contents (typically <5%, especially ethylene) are also suitable. Such materials are available on the market from a large number of manufacturers. Preference is given to those of which the melt flow index does not exceed 30 dg / min at 230°C and 2.16 kg coating weight. 0 In an alternative embodiment of the disclosure, it is provided that 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 specialised copolymers combine a low hardness for PP-based copolymers with melting 15 points above 140°C. In this embodiment, the (co-)PP has the same function as before, but materials can be realised that manage with lower contents of the often expensive soft components described above. 20 In all embodiments, the PP-based polymer in the sealing element may be a PP / PE copolymer. In other preferred embodiments of the disclosure, the sealing element may 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. 25 The sealing material preferably has an overall Shore A hardness (DIN ISO 7619-1) of 40 to 90, preferably 50 to 80. In preferred embodiments, the sealing element comprises additional polymers (except PVC), in 30 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 < 50 g / 10 min, in particular in a content of up to 25 wt.%, based on the total weight of the polymers in the sealing material. 2022491254   08 Sep 2026 In preferred embodiments of the disclosure, the container 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. 5 In particular, if migration problems are negligible, the hardness of the sealing element can be adjusted by conventional additions of plasticising substances. In these embodiments, the compound of the sealing element contains at least one plasticiser 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. In preferred embodiments, the kinematic viscosity (according to DIN EN ISO 3104) of the plasticiser at 40°C is above 60 mm2 / s.

Claims

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

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

153. The container closure according to claim 1 or claim 2, in which the styrene block copolymer comprises an SE(E)PS having a vinyl content prior to hydrogenation of more than 50 mol% and a styrene content of <25 wt.%, based on the total weight of SEEPS.20   4. The container closure according to any one of claims 1 to 3, in which the styrene blockcopolymer is present in a proportion of 20 - 40 wt.%, based on the total weight of the polymer components in the sealing element.

5. The container closure according to any one of claims 1 to 4, in which the styrene block 25      copolymer has a Shore A hardness of less than 60 (DIN ISO 7619-1).

6. The container closure according to any one of the preceding claims, in which 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.

307. The container closure according to any one of the preceding claims, in which the isobutylene-containing (co-)polymer further comprises- SIBS (styrene-isoprene / butadiene-styrene block copolymer); or- PIB (polyisobutylene);2022491254   08 Sep 2026- or mixtures thereof;wherein the iso-butylene-containing (co-)polymer preferably has a Shore A hardness of between 20 and 60 (DIN ISO 7619-1) and is preferably present in a content of 10 to 405          wt.%, based on the total weight of the polymers in the sealing material.

8. The container closure according to any one of the preceding claims, in which the (Co)PP-based polymer comprises or consists of a PP homopolymer or a PP copolymer with a Shore D hardness of more than 65, wherein the content of the sealing material in this polymer0       preferably is not more than 20 wt.%, based on the total weight of the polymers in the sealingmaterial.

9. The container closure according to any one of the preceding claims, in which the (Co)PP-based polymer comprises or consists of a PP copolymer having a Shore D hardness of less15       than 40, wherein the content of said polymer in the sealing material is preferably between20 and 70 wt.%, based on the total weight of polymers in the sealing material.

10. The container closure according to any one of the preceding claims, wherein the PP copolymer comprises or consists of at least one terpolymer, preferably a propene-, ethene-20       and / or butene-containing terpolymer, and / or at least one propene- and / or ethene-containingcopolymer.

11. The container closure according to any one of the preceding claims, wherein the sealing material has an overall Shore A hardness of 40 to 90, preferably 50 to 80 and particularly25       preferably 60 to 80.

12. The container closure according to any 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 < 50 g / 10 min, in particular in a content of up to 2530       wt.%, based on the total weight of the polymers in the sealing material.

13. The container closure according to any 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.2022491254   08 Sep 202614. The container closure according to any one of the preceding claims, further comprising at least one plasticiser, in particular white oil or a synthetic polyolefin-based oil which is liquid at 23°C and ambient pressure, preferably in a content of up to 10 wt.%, based on the total5       weight of the sealing element.

15. The container closure according to claim 14, in which the kinematic viscosity (according to DIN EN ISO 3104) of the plasticiser at 40°C is above 60 mm2 / s.