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

Abstract

A container closure, particularly a vacuum turnlock closure, comprises a sealing element containing or made of a polymer compound (excluding PVC). The polymer compound comprises at least one polybutene polymer, at least one polymer derived from at least partially 1,2-bonded isobutylene monomer, at least one (co)PP polymer, and optionally other components and additives. In a preferred embodiment, the polybutene polymer is a copolymer with ethylene in particular. In a preferred embodiment, the polybutene polymer has a Shore A hardness of less than 85.

Description

Technical Field

[0001] The present invention relates to a container closure comprising a sealing element containing or consisting of a polymeric compound, particularly a vacuum turn-lock closure. More specifically, the present invention relates to a container closure having a polymeric-based sealing insert for bottles and other containers for holding beverages and foods. The container closure does not contain halogenated substances and is suitable for severe applications.

Background Art

[0002] Beverages and foods are filled into various types of containers for transportation and storage. These containers often need to be sealable so that the contents do not leak and are protected from the ingress of unwanted substances that can contaminate or damage the contents. In many applications, the problem is not only solid or liquid contaminants. If the contents are sensitive to gaseous substances, these must also be prevented from entering. This is achieved by a properly designed container closure.

[0003] Container closures made of metal and / or plastic have been known for many years. For example, in the form of screw caps, twist-off caps and crown caps, container closures are used to seal containers such as bottles, jars, etc. Such containers have an opening that must be closed by the container closure. Vacuum (turn-lock) closures, including Twist-off® and Press-on Twist-off® closures, occupy a special position in this regard as they must guarantee vacuum retention over a period of up to three years instead of overpressure sealing.

[0004] Containers must be sufficiently sealed to prevent leakage of the contents and protect the contents from the ingress of unwanted substances including gaseous substances such as oxygen, trichloroanisole, etc. or loss of vacuum.

[0005] The required seal is typically achieved by a sealing insert made of a material that is sufficiently strong on the one hand but also elastic on the other, and is positioned within the container closure so as to contact the opening of the container when the container closure is placed on top of the container. In most cases, the sealing insert is disc-shaped or ring-shaped and is positioned inside the container closure. When the container is closed, the sealing insert is positioned in contact with the container opening and pressed against the opening by the container closure, and its hardness, along with its elasticity, provides a seal. A good sealing insert compensates for any irregularities that are always present at the container opening. The greater the irregularities at the container opening, the higher the requirements placed on the sealing insert.

[0006] A crucial factor in meeting such requirements is the appropriate selection of material for the sealing insert. Many well-known materials are suitable for relatively simple applications but are unsuitable, or not suitable at all, for more demanding sealing.

[0007] Sealing inserts must also meet other requirements in many applications, such as being pasteurizable and even sterilizable. They must not only withstand considerable internal pressure (for example, in carbonated beverages), but also yield in a controlled manner (overpressure valve effect) even when this pressure is exceeded. On the other hand, in the case of vacuum (turnlock) closures, the sealing insert must also withstand external overpressure during specific pasteurization and sterilization processes and maintain the vacuum generated inside the container after cooling.

[0008] If the container closure is a turn-lock closure, the sealing insert should not provide excessive resistance to twisting of the container closure over the opening when opening.

[0009] Furthermore, sealing inserts must be as easy as possible to manufacture and install into container closures. Known methods include cutting disc-shaped sealing inserts from a web or film and then installing them into container closures ("out-shell molding"), or, often preferred, inserting them into container closures in a fluid form in which they are molded and solidified ("in-shell molding"). In-shell molding also allows for the manufacture of ring-shaped sealing inserts instead of disc-shaped ones.

[0010] In the case of polymer-based sealing inserts, this is conventionally done by introducing a plastisol, followed by molding and gelling (curing by heating), or, in the case of thermoplastic materials, by introducing the material in a heated, fluid state, followed by molding and cooling.

[0011] While PVC-containing sealing inserts have been widely used in the past, PVC and other halogen-containing materials now pose considerable concerns. They are considered potentially harmful to health and are difficult to dispose of. In many countries, the use of such halogen-containing materials is regulated or even prohibited by law or regulation.

[0012] Therefore, there is a considerable need for container closures that do not contain halogenated materials, without sacrificing the advantages that PVC-containing sealing inserts offer in terms of processing, sealing properties, cost, etc.

[0013] There are already numerous proposals for this purpose in the prior art. For example, the manufacture of sealing inserts for screw caps based on halogen-free polymers has been known for decades.

[0014] Typical polymers in such compounds are thermoplastics, particularly polyolefins, thermoplastic elastomers, thermoelastic thermoplastics, and synthetic rubbers. Typical additives include plasticizers, oils, lubricants, antioxidants, stabilizers, pigments, and fillers.

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

[0016] On the other hand, poly(co)butene-based sealing inserts have not been widely proposed.

[0017] Patent Document 1 already discloses polymer compounds based on particularly special 1-butene copolymers, but these do not contain barrier polymers. These compounds are also said to be suitable for sealing inserts for container closures, but they are all very rigid. [Prior art documents] [Patent Documents]

[0018] [Patent Document 1] European Patent No. 3302918 [Overview of the project] [Problems that the invention aims to solve]

[0019] Against this backdrop, the object of the present invention is to propose a container closure that is improved in terms of the properties of the sealing element, particularly with respect to the properties of the butene polymer-based sealing element.

[0020] The combination of features in the independent claims helps to achieve this objective.

[0021] Advantageous variations of the present invention are defined in the dependent claims. [Means for solving the problem]

[0022] The container closure according to the present invention, in particular a vacuum turnlock closure, comprises a sealing element containing or consisting of a PVC-free polymer compound, the polymer compound comprising at least one polybutene-based polymer and at least one polymer derived from at least partially 1,2-bonded isobutylene monomers, at least one (co)PP-based polymer, optionally other components and additives, and comprises.

[0023] In a preferred embodiment of the present invention, the polybutene-based polymer is in particular a copolymer with ethylene, i.e. a PB / PE copolymer. Such copolymers are known in the prior art and are commercially available, for example, from LyondellBasell.

[0024] In other embodiments, for example, propylene may also be included.

[0025] The polybutene-based polymer is preferably present in the sealing element in a proportion of 50 to 75% by weight relative to the total weight of the polymer components in the sealing element. Thus, it usually forms the main component of the seal according to the present invention.

[0026] In a preferred embodiment of the present invention, the polybutene-based polymer has a Shore A hardness of less than 85.

[0027] In a preferred embodiment of the present invention, the polymer derived from 1,2-bonded isobutylene monomers is a copolymer, preferably a block copolymer. Preferably, this copolymer contains units based on isoprene and / or styrene. The 1,2-bonded polymer may have 1,4-bonds in addition to the 1,2-bonds.

[0028] The 1,2-bonded polymer may have barrier properties that particularly restrict the passage of oxygen. In this case, the 1,2-bonded polymer preferably has an oxygen permeability (OTR) measured at 23°C and 100% humidity, which is normalized to a layer thickness of 100 μm and 5000 cm². 3 / m 2 It is less than or equal to d.bar, preferably a maximum of 2500 cm². 3 / m 2 It is a d.bar, and particularly preferably up to 1000 cm 3 / m 2 It is .d.bar.

[0029] Preferably, the 1,2-bonded polymer is isobutylene / isoprene copolymer or isobutylene / styrene copolymer, and particularly preferably, • High-vinyl SEEPS having a vinyl content of more than 50% by weight relative to the total weight of SEEPS, • High-vinyl SEPS having a vinyl content of more than 50% by weight relative to the total weight of SEPS, IIR (isobutylene-isoprene rubber; butyl rubber), • SIBS (styrene-isobutylene-styrene block copolymer), • PIB (Polyisobutylene), • A mixture of those, Selected from, The copolymer preferably has a Shore A hardness of 20 to 60. Preferably, it is present in an amount of 10 to 30% by weight relative to the total weight of the polymer in the sealing material.

[0030] Preferably, the 1,2-bonded polymer is rubbery.

[0031] "High vinyl" refers to styrene block copolymers with a vinyl content exceeding 50 mol% before hydrogenation, according to U.S. Patent No. 1,0457,805. After hydrogenation, the copolymer naturally contains little to no aliphatic double bonds.

[0032] Nevertheless, such styrene block copolymers are also called "high-vinyl" because they can be derived from precursors with a high vinyl content.

[0033] "Rubber-like" refers to a polymer that is similar to known synthetic rubber in terms of mechanical properties essential for sealing function (hardness or flexibility and elasticity, etc.). Suitable reference materials are styrene block copolymers such as butyl rubber (IIR), SBS, or SEBS, for example, commercially available products.

[0034] The styrene block copolymer preferably has a styrene content of less than 25% by weight relative to the total weight of the styrene block copolymer.

[0035] Particularly preferred are hydrogenated styrene block copolymers having a butadiene intermediate block (1,2- and / or 1,4-linkage), such as high-vinyl SEBS and high-vinyl SE(E)PS.

[0036] These polymers differ from one another in that they consist of molecular intermediate blocks composed of hydrogenated sequences of butadiene (1,2 and / or 1,4-linked) and / or isoprene.

[0037] Such copolymers can be obtained, for example, from Kraton Corp., TSRC Corp., Kuraray, or Dynasol. Typical suitable products include Kraton G1645, Kraton G1643, Vector 8245, or Calprene H6180, and raw materials such as the Hybrar® 7000 series, which copolymerize isoprene in addition to butadiene, when improved oxygen barrier properties are required.

[0038] In a preferred embodiment of the container closure according to the present invention, the high vinyl styrene block copolymer is present in a proportion of 10 to 40% by weight relative to the total weight of the polymer components in the sealing element.

[0039] The styrene block copolymer is preferably relatively soft and has a Shore A hardness of less than 65.

[0040] In preferred embodiments of the present invention, the styrene block copolymer has an MFI (190°C, 5kg) of 0g / 10min or more, and the material according to the present invention may be non-meltable or only partially thermoplastic.

[0041] In these and other preferred embodiments of the present invention, the (co)PP polymer includes or consists of a PP homopolymer or PP copolymer having a Shore D hardness of 65 or higher, and the content of this polymer in the sealing material is preferably 10 to 20% by weight relative to the total weight of the polymer in the sealing material.

[0042] Alternatively, the (co)PP polymer may include or consist of a PP copolymer having a Shore D hardness of less than 40, and the content of this polymer in the sealing material is preferably 10 to 40% by weight relative to the total weight of the polymer in the sealing material.

[0043] In preferred embodiments, the PP copolymer comprises or consists of at least one terpolymer, butene-propene and / or ethene-containing copolymer, optionally in proportion to hexene or octene.

[0044] The sealing material preferably has a total Shore A hardness of 80 or less measured after 10 days at 23°C, and an oxygen permeability (OTR) of 5000 cm² measured at 23°C and 100% humidity, standardized to a layer thickness of 100 μm. 3 / m 2 It is below .d.bar.

[0045] Therefore, the sealing material or sealing element made therefrom according to the present invention is preferably relatively soft and thus suitable for the intended application.

[0046] In addition to the above components, the compound may also contain further components that adjust its sealing properties, improve its processing, or serve other purposes.

[0047] A preferred embodiment of the sealing material further comprises at least one mineral filler, in particular talc, in an amount of up to 20% by weight relative to the total weight of the sealing element.

[0048] Further embodiments of the present invention further include at least one plasticizer, in particular white oil or polyolefin-based synthetic oil, preferably in an amount of up to 10% by weight relative to the total weight of the sealing element. In any case, this is usually not a problem unless the filling material in the container is oily or greasey. Otherwise, care must be taken as oil in the sealing may cause migration problems, and components of compounds (e.g., oil) that contribute to such migration problems may be partially or completely removed. [Examples]

[0049] The following examples A1 to A11 illustrate the present invention. With the exception of Example A7, the Et content of the PB-1-Et copolymer used in the examples was approximately 15%, as measured by 1H-NMR. The Et content of the Pb-1-Et copolymer used in Example A7 was approximately 6%, as measured by 1H-NMR.

[0050] These copolymers were obtained from LyondellBasell under the names Purell KT MR 07 and Koattro DP 8310 M.

[0051] The SIBS used was the Kaneka Sibstar (registered trademark) 102T-FD. The IIR used was Arlanxeo's X_Butyl RB 101-3. The SEEPS used was Kuraray's Hybrar(registered trademark) 7311. The random coPP used was the Borealis RD204CF. The homogeneous push-pull (PP) used was the Borealis HD204CF. The heterogeneous coPP used was Ducur Petrochemicals' Dupure SL50.

[0052] The elastic modulus of the material was measured according to DIN 53504 after storing S2 test specimens punched from a press plate for 48 hours. A test speed of 200 mm / min and an elongation range of 0.05–0.25% were used to determine the elastic modulus.

[0053] (Examples) [Table 1]

Claims

1. A container closure comprising a sealing element containing or made of a polymer compound (excluding PVC), particularly a vacuum turnlock closure, wherein the polymer compound is At least one polybutene copolymer, At least one polymer derived from an isobutylene monomer that is at least partially 1,2-bonded, At least one (co)PP-based polymer, Optionally, other ingredients and additives, A container closure, including a container closure.

2. The container closure according to claim 1, wherein the polybutene copolymer is a copolymer with ethylene.

3. The container closure according to claim 1 or 2, wherein the polybutene copolymer is present in a proportion of 50 to 75% by weight relative to the total weight of the polymer components in the sealing element.

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

5. The container closure according to any one of claims 1 to 4, wherein the polymer compound comprises at least one isobutylene copolymer containing isoprene and / or styrene as a comonomer, and is preferably a block copolymer.

6. The container closure according to any one of claims 1 to 5, wherein the 1,2-bonded polymer also has 1,4-bonds in addition to 1,2-bonds.

7. The container closure according to any one of claims 1 to 6, wherein the 1,2-bonded polymer has a Shore A hardness of up to 80.

8. The oxygen permeability (OTR) of the 1,2-bonded polymer, measured at 23°C and 100% humidity, was normalized to a layer thickness of 100 μm and measured at 5000 cm². ３ / m ２ d. bar or less, preferably a maximum of 2500 cm ３ / m ２ d. bar, and particularly preferably up to 1000 cm ３ / m ２ d. A container closure according to any one of claims 1 to 7, wherein the bar is d.

9. The aforementioned copolymer is • High-vinyl SEEPS having a vinyl content of more than 50% by weight relative to the total weight of SEEPS, • High-vinyl SEPS having a vinyl content of more than 50% by weight relative to the total weight of SEPS, IIR (isobutylene-isoprene rubber; butyl rubber), SIBS (styrene-isobutylene-styrene block copolymer), PIB (Polyisobutylene) and - A mixture of those, Selected from, The copolymer preferably has a Shore A hardness of 20 to 60. Preferably, the container closure according to claim 5, which is present in an amount of 10 to 30% by weight relative to the total weight of the polymer in the sealing material.

10. The container closure according to any one of claims 1 to 9, wherein the (co)PP polymer includes or consists of a PP homopolymer or PP copolymer having a Shore D hardness of 65 or more, and the content of this polymer in the sealing material is preferably 10 to 20% by weight relative to the total weight of the polymer in the sealing material.

11. The container closure according to any one of claims 1 to 10, wherein the (co)PP polymer includes or comprises a PP copolymer having a Shore D hardness of less than 40, and the content of this polymer in the sealing material is preferably 10 to 40% by weight relative to the total weight of the polymer in the sealing material.

12. The container closure according to claim 11, wherein the PP copolymer comprises or consists of at least one terpolymer, preferably a terpolymer containing propene, ethene and / or butene, and / or at least one copolymer containing propene and / or ethene.

13. The sealing material has a total Shore A hardness of 80 or less measured after 10 days at 23°C, and its oxygen permeability (OTR), measured at 23°C and 100% humidity, is normalized to a layer thickness of 100 μm and is 5000 cm². ３ / m ２ d. A container closure according to any one of claims 1 to 12, wherein the bar is less than or equal to d.

14. A container closure according to any one of claims 1 to 13, further comprising at least one mineral filler, in particular talc, in an amount of up to 20% by weight relative to the total weight of the sealing element.

15. The container closure according to any one of claims 1 to 14, further comprising at least one plasticizer, in particular white oil or polyolefin-based synthetic oil, preferably in a content of up to 10% by weight relative to the total weight of the sealing element.

16. The oxygen transmission rate (OTR) of the polymer compound, measured at 23°C and 100% humidity, is standardized to a layer thickness of 100 μm and is 5000 cm ３ / m ２ .d.bar or less, preferably at most 2500 cm ３ / m ２ .d.bar, and particularly preferably at most 1000 cm ３ / m ２ .d.bar. The container closure according to any one of claims 1 to 15

Images