Butene (CO)polymer-based sealing material for container closures

Abstract

A container closure, in particular vacuum turn-lock closure, comprising a sealing element that contains or consists of a polymer compound (without PVC). The polymer compound comprises at least one polybutene-based polymer; at least one polymer that is derived from at least partially 1,2-linked isobutylene monomers; at least one (co)PP-based polymer and optionally other components and additives.

Description

[0001] Sealing material for vessel closures based on butene (co)polymers

[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-lock closures, and crown corks, for example, to tightly seal containers such as bottles, jars, and the like. Such containers have a mouth that must be sealed by the vessel closure. Vacuum (twist-lock) closures, including the so-called Twist-Off® and Press-on Twist-off® closures, occupy a special position. These closures must ensure vacuum retention for periods of up to three years instead of overpressure tightness.

[0005] The vessel must be sealed sufficiently tightly to prevent the contents from leaking out, and to protect the contents from the ingress of undesirable substances, including gaseous substances such as oxygen, trichloroanisole, and others, or from vacuum loss. The necessary tightness is usually achieved by a sealing insert made of a material that is sufficiently strong yet elastic and is arranged in the vessel closure so that it comes into contact with the vessel mouth when the vessel closure is placed on 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 and elasticity creating the seal.A good sealing insert compensates for the unevenness of the vessel mouth. Therefore, the more uneven the vessel mouth, the greater 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 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). In the case of vacuum (twist) closures, however, the sealing insert must also withstand externally applied overpressure during certain pasteurization and sterilization processes and maintain the negative pressure created in the container after cooling.

[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. For polymer-based sealing inserts, this is conventionally done by inserting them as a plastisol, followed by molding and gelling (curing by heating), or for thermoplastic materials by inserting them in a heated, flowable state, followed by molding and cooling.

[0010] 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.

[0011] 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.

[0012] There are already a number of proposals for this in the state of the art.

[0013] For decades, it has been known to produce sealing inserts for screw caps based on polymers that do not contain halogens.

[0014] 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.

[0015] Many well-known sealing inserts are based on polyolefins, mostly derived from PP, PE and their copolymers.

[0016] In contrast, sealing inserts based on poly(co)butenes have been proposed much less frequently.

[0017] EP 3 302 918 already discloses polymer compounds based, among other things, on special 1-butene copolymers, but which do not contain barrier polymers. These compounds are also said to be suitable for sealing inserts for vessel closures, but are consistently very hard. 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, whose seal is based on butene polymers.

[0018] The combination of features of the independent patent claim serves to solve this problem.

[0019] Advantageous further developments of the invention are defined in the dependent patent claims.

[0020] Vessel closures according to the invention, in particular vacuum screw closures, are provided with a sealing element comprising or consisting of a PVC-free polymer compound containing at least one polybutene-based polymer; at least one polymer derived from at least partially 1,2-linked isobutylene monomers; at least one (co)PP-based polymer, and optionally further components and additives.

[0021] In preferred embodiments of the invention, the polybutene-based polymer is a copolymer, especially with ethylene, i.e., a PB / PE copolymer. Such copolymers are known in the art and commercially available, e.g., from LyondellBasell.

[0022] In other embodiments, propylene may also be included.

[0023] The polybutene-based polymer is preferably present in the sealing element in a proportion of 50-75 wt.%, based on the total weight of the polymer components in the sealing element. It therefore usually forms the main component of the seal according to the invention.

[0024] In preferred embodiments of the invention, the polybutene-based polymer has a Shore A hardness of less than 85.

[0025] In preferred embodiments of the invention, the polymer derived from 1,2-linked isobutylene monomers is a copolymer, preferably a block copolymer. This copolymer preferably comprises units based on isoprene and / or styrene. The 1,2-linked polymer may contain 1,4-linkages in addition to the 1,2-linkages. The 1,2-linked polymer may have barrier properties that, in particular, limit the passage of oxygen.

[0026] Then the 1,2-linked polymer preferably has an oxygen permeability (OTR) at 23°C and 100% humidity of < 5000, preferably of a maximum of 2500, particularly preferably a maximum of 1000 cm 3 / m 2 .d.bar, normalized to 100 pm layer thickness.

[0027] Preferably, the 1,2-linked polymer is an isobutylene / isoprene copolymer or an isobutylene / styrene copolymer, particularly preferably selected from

[0028] High-vinyl SEEPS with a vinyl content of more than 50% by weight based on the total weight of SEEPS;

[0029] High-vinyl SEPS with a vinyl content of more than 50% by weight based on the total weight of SEPS;

[0030] HR (Isobutylene-Isoprene rubber; butyl rubber);

[0031] SIBS (styrene-isobutylene-styrene block copolymer);

[0032] PIB (polyisobutylene); and mixtures thereof, wherein the copolymer preferably has a Shore A hardness between 20 and 65 and is preferably present in a content of 10 to 30 wt.%, based on the total weight of the polymers in the sealing material.

[0033] Preferably, the 1,2-linked polymer is rubber-like.

[0034] By "highly vinylic," we mean, in accordance with US Pat. No. 1,0457,805 B2, those styrene block copolymers whose vinyl content is greater than 50 mol% before hydrogenation. After hydrogenation, the copolymer naturally contains hardly any, or even no, aliphatic double bonds.

[0035] Nevertheless, we also refer to such styrene block copolymers as “highly vinylic” because they can be derived from precursors with such high vinyl contents.

[0036] By "rubber-like," we mean polymers that resemble known synthetic rubbers in their mechanical properties essential for sealing (such as hardness, softness, and elasticity). Suitable reference substances include butyl rubber (IIR) or styrene block copolymers such as SBS or SEBS, for example, commercially available products.

[0037] The styrene block copolymer preferably has a styrene content of less than 25 wt.% based on the total weight of styrene block copolymer.

[0038] Particularly suitable are hydrogenated styrene block copolymers with butadiene middle blocks (1,2- and / or 1,4-linked), e.g. high-vinyl SEBS and high-vinyl SE(E)PS

[0039] 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.

[0040] Such copolymers can be obtained from, for example, Kraton Corp., TSRC Corp., Kuraray, or Dynasol. Typical suitable products are Kraton G1645, Kraton G1643, Vector 8245, or Calprene H6180. For applications requiring improved oxygen barrier properties, raw materials such as the Hybrar 7000 series, which copolymerizes isoprene in addition to butadiene, are also suitable.

[0041] In preferred embodiments of the vessel closure according to the invention, the high-vinyl styrene block copolymer is present in a proportion of 10 - 40 wt.%, based on the total weight of the polymer components in the sealing element.

[0042] The styrene block copolymer is preferably relatively soft and has a Shore A hardness of less than 65.

[0043] 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.

[0044] In these and other preferred embodiments of the invention, 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 between 10 and 20 wt.%, based on the total weight of the polymers in the sealing material.

[0045] Alternatively, the (co)PP-based polymer comprises a PP copolymer with a Shore D hardness of less than 40 or consists of such a PP copolymer, wherein the content of this polymer in the sealing material is preferably between 10 and 40 wt.%, based on the total weight of the polymers in the sealing material.

[0046] In preferred embodiments, the PP copolymer comprises or consists of at least one terpolymer, a butene-propene and / or ethene-containing copolymer optionally with proportions of hexene or octene.

[0047] The sealing material preferably has a total Shore A hardness < 80, measured after 10 d at 23°C, and an oxygen permeability (OTR) measured at 23°C and 100% humidity < 5000 cm 3 / m 2 .d.bar, normalized to 100 pm layer thickness.

[0048] The sealing material according to the invention or the sealing element made therefrom is preferably relatively soft and thus suitable for the intended use.

[0049] In addition to the above-mentioned components, the compound may contain other components that serve to adapt its sealing properties, improve its processing or for other purposes.

[0050] Preferred embodiments of the sealing material comprise at least one mineral filler, in particular talc, in particular in a content of up to 20 wt.% based on the total weight of the sealing element.

[0051] Further embodiments of the invention utilize at least one plasticizer, 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. This is generally unproblematic if the contents of the container are not greasy or oily. Otherwise, care should be taken to ensure that oil content in the seal may lead to migration problems, which may result in the partial or complete omission of components of the compound (e.g., oil) that contribute to such migration problems.

[0052] The following embodiments A1 to A1I illustrate the invention:

[0053] The PB-l-Et copolymer used in the examples except for Example A7 had an Et content of -15% determined by 'H-NMR.

[0054] The Pb-l-Et copolymer used in Example A7 had an Et content of -6% determined by 'H-NMR.

[0055] These copolymers were purchased from LyondellBasell under the names Purell KT MR 07 and Koattro DP 8310 M.

[0056] The SIBS used was Sibstar 102T-FD from Kaneka.

[0057] The HR used was X Butyl RB 101-3 from Arlanxeo.

[0058] The SEEPS used was Hybrar 7311 from Kuraray.

[0059] The random coPP used was RD 204 CF from Borealis

[0060] The homo-PP used was HD 204CF from Borealis.

[0061] The heterophasic coPP used was Dupure SL50 from Ducor Petrochemicals.

[0062] The Young's moduli for the materials in question were measured after 48 hours of storage on S2 test specimens punched from press plates, in accordance with DIN 53504. A test speed of 200 mm / min and a strain range of 0.05 to 0.25% were used to determine the Young's modulus.

[0063] Examples

[0064] Examples

[0065] PB-l-Et copolymer

[0066] PB-l-Et (low Et)

[0067] Copolymer

[0068] SIBS

[0069] IIR

Claims

AMENDED CLAIMS received by the International Bureau on 8 December 2023 (08.12.2023) 1. A vessel closure, in particular a vacuum screw cap, with a sealing element comprising or consisting of a polymer compound (without PVC), wherein the polymer compound comprises the following: at least one polybutene-based copolymer; at least one polymer derived from at least partially 1,2-linked isobutylene monomers; at least one (co)PP-based polymer, and optionally further components and additives.

2. A vascular closure according to claim 1, wherein the polybutene-based copolymer is a copolymer with ethylene.

3. Vessel closure according to claim 1 or claim 2, wherein the polybutene-based copolymer is present in a proportion of 50 - 75 wt.%, based on the total weight of the polymer components in the sealing element.

4. A vascular closure according to claim 1 or claim 2, wherein the polybutene-based copolymer has a Shore A hardness of less than 85.

5. Vascular closure according to one of the preceding claims, wherein the polymer compound comprises at least one isobutylene-based copolymer containing isoprene and / or styrene as comonomer and is preferably a block copolymer.

6. A vascular closure according to any one of the preceding claims, wherein the 1,2-linked polymer has 1,4-linkages in addition to the 1,2-linkages.

7. A vessel closure according to any one of the preceding claims, wherein the 1,2-linked polymer has a Shore A hardness of not more than 80.

8. A vascular closure according to any one of the preceding claims, wherein the 1,2-linked Polymer an oxygen transmission rate (OTR) measured at 23 °C and 100% AMENDED SHEET (ARTICLE 19) Humidity of < 5000, preferably a maximum of 2500, particularly preferably a maximum of 1000 cm 3 / m 2 .d.bar, normalized to 100 pm layer thickness.

9. A vascular closure according to claim 5, wherein the copolymer is selected from - High-vinyl SEEPS with a vinyl content of more than 50% by weight based on the total weight of SEEPS; - High-vinyl SEPS with a vinyl content of more than 50% by weight based on the total weight of SEPS; -HR. (Isobutylene-Isoprene rubber; Butyl rubber); - SIBS (styrene-isobutylene-styrene block copolymer); - PIB (polyisobutylene); 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 30 wt.%, based on the total weight of the polymers in the sealing material.

10. 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 greater than 65, wherein the content of this polymer in the sealing material is preferably between 10 and 20 wt.%, based on the total weight of the polymers in the sealing material.

11. Vessel closure according to one of the preceding claims, wherein the (co)PP-based polymer comprises or consists of a PP copolymer with a Shore D hardness of less than 40, wherein the content of this polymer in the sealing material is preferably between 10 and 40 wt.%, based on the total weight of the polymers in the sealing material.

12. Vascular closure according to claim 11, 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.

13. Vessel closure according to one of the preceding claims, wherein the sealing material has a total Shore A hardness < 80, measured after 10 d at 23°C, and a AMENDED SHEET (ARTICLE 19) Oxygen permeability (OTR) measured at 23°C and 100% humidity < 5000 cm 3 / m 2 .d.bar, normalized to 100 pm layer thickness.

14. Vessel closure according to one of the preceding claims, further comprising at least one mineral filler, in particular talc, in particular in a content of up to 20 wt.% based on the total weight of the sealing element.

15. 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, preferably in a content of up to 10 wt.% based on the total weight of the sealing element.

16. Vessel closure according to one of the preceding claims, in which the polymer compound has an oxygen permeability (OTR) measured at 23 °C and 100% humidity of < 5000, preferably of a maximum of 2500, particularly preferably a maximum of 1000 cm 3 / m 2 .d.bar normalized to 100 pm layer thickness. AMENDED SHEET (ARTICLE 19)

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