Container closure made of metal or plastic

Abstract

A closure made of metal or plastic for a container for accommodating beverages or food has a mouth opening which is to be closed by the container closure. The container closure has a sealing insert which is arranged such that it closes the mouth opening with sealing action when the container closure is fitted on the container. The container closure, including the sealing insert, does not contain any halogen-containing material, and the sealing insert comprises at least two different polymers, of which at least one is a barrier polymer with a Shore D hardness of at most 40 and oxygen permeability of at most 1000 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar and, without the Shore D hardness being limited, with oxygen permeability of at most 10 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar.

Claims

1. A container closure of metal or plastic for a container for accommodating beverages or food having a mouth opening to be closed by the container closure, with a sealing insert that is arranged in the container closure such that it closes the mouth opening with sealing action when the container closure is fitted onto the container, wherein the container closure, including the sealing insert, contains no halogen-containing materials, and the sealing insert comprises a combination of at least two different barrier polymers, each of which is a barrier polymer with a Shore D hardness of at most 40 and an oxygen permeability of at most 1000 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, or, without the Shore D hardness being limited, with an oxygen permeability of at most 10 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, wherein the oxygen permeability, in accordance with DIN 53380-3, is determined at an oxygen concentration of 100%, relative humidity of 100%, atmospheric pressure, and a measuring temperature of 26° C. and is relative to a layer thickness of 100 μm.

2. The container closure as claimed in claim 1, wherein the sealing insert comprises the at least two different barrier polymers in a mixture with one another.

3. The container closure as claimed in claim 1, wherein the sealing insert has the at least two different barrier polymers in different layers of a multilayer structure.

4. The container closure as claimed in claim 1, wherein the barrier polymers include one or more of butyl rubber (IIR); polyisobutylene (PIB); a styrene block copolymer; polyamide (PA); an ethylene-vinyl alcohol copolymer-(EVOH); and a thermoplastic vulcanizate (TPE-V), wherein the total content of isobutylene-based polymers in the sealing insert does not exceed 60% by weight.

5. The container closure as claimed in claim 1, wherein the sealing insert comprises two different barrier polymers and additionally at least one further polymer that is not a barrier polymer.

6. The container closure as claimed in claim 5, wherein the at least one further polymer comprises a polyolefin.

7. The container closure as claimed in claim 1, wherein the sealing insert comprises TPE including one or more of SBS, SEBS, SIBS, SIS, SEP, SEPS, and SEEPS.

8. The container closure as claimed in claim 1, wherein the sealing insert contains a mixture of butyl rubber (IIR) and styrene-isobutylene-styrene (SIBS).

9. The container closure as claimed in claim 8, wherein the sealing insert additionally contains at least one polyolefin.

10. The container closure as claimed in claim 1, wherein the sealing insert contains at least one additive.

11. The container closure as claimed in claim 1, wherein the sealing insert contains up to 25% by weight butyl rubber, up to 65% by weight of SIBS, and up to 60% by weight of one or more of PE-HD, PE-LD, and PE-LLD.

12. The container closure as claimed in claim 11, wherein the one or more of PE-HD, PE-LD, and PE-LLD has a melt flow rate (MFR at 5 kg/190° C.) of greater than 1 g/10 min.

13. The container closure as claimed in claim 1, wherein the sealing insert has a Shore D hardness of less than 50.

14. The container closure as claimed in claim 1, wherein the sealing insert has a Shore D hardness of between 15 and 40.

15. The container closure as claimed claim 1, wherein the Shore A hardness of the sealing insert is between 55 and 100.

16. The container closure as claimed in claim 1, wherein the sealing insert has an oxygen permeability of less than 940 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar.

17. The container closure as claimed in claim 16, wherein the sealing insert has an oxygen permeability of less than 670 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar.

18. The container closure as claimed in claim 1, wherein the sealing insert has a melt flow rate (MFR) under a 5 kg load and at 190° C. of at least 1 g/10 min.

19. The container closure as claimed in claim 1, wherein the sealing insert has a compression set (CS) at 25% compression, 23° C., and 22-hour storage of between 20% and 70%.

20. The container closure as claimed in claim 1, wherein the sealing insert has a CS at 25% compression, 40° C., and 22-hour storage of between 45% and 70%.

21. The container closure as claimed in claim 1, wherein the sealing insert has a CS at 25% compression, 70° C., and 22-hour storage of between 50% and 80%.

22. The container closure as claimed in claim 1, wherein the sealing insert has an oxygen permeability of less than 700 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar at a CS (23° C., 22-hour storage, 25% compression) of between 40% and 65% and a melt flow rate of more than 1 g/10 min under a 5 kg load and at 190° C.

23. The container closure as claimed in claim 22, wherein the sealing insert contains butyl rubber, SIBS, and at least one polyolefin.

24. The container closure as claimed in claim 1, wherein the container closure is a screw cap, a peelable aluminum closure, or a crown cap.

25. The container closure as claimed in claim 1, wherein the sealing insert is pasteurizable.

26. The container closure as claimed in claim 1, wherein the sealing insert is configured as a ring or disk and has a sealing lip around its circumference that protrudes when the container closure is in an attached state in the direction of the mouth opening of the container.

27. The container closure as claimed in claim 1, wherein the sealing insert comprises two different elements, a first element of the two different elements being ring-shaped or disk-shaped and connected to the container closure of metal or plastic and a second element of the two different elements being ring-shaped or disk-shaped and arranged on the first element at least in the area in which the container closure is configured to contact the mouth opening of the container.

28. The container closure as claimed in claim 27, wherein the first and the second elements are composed of different materials, and the material of the second element comprises at least one barrier polymer.

29. The container closure as claimed in claim 1, wherein the sealing insert comprises two different materials, a first material of the two different materials forming a disk-shaped element sandwiched between layers of a second material of the two different materials, wherein the second material is a compound including at least one barrier polymer and having a Shore D hardness of less than 40 and the first material is a compound or a pure polymer having a Shore D hardness of greater than 40.

30. The container closure as claimed in claim 29, wherein the first material comprises a barrier polymer.

31. The container closure as claimed in claim 1, wherein the sealing insert contains an oxygen-binding compound (scavenger).

32. The container closure as claimed in claim 1, wherein the sealing insert includes a metal film.

33. The container closure as claimed in claim 1, wherein the sealing insert comprises a foamed polymer compound.

34. The container closure as claimed in claim 10, wherein the at least one additive includes one or more of a plasticizer; a stickiness-reducing agent (anti-blocking agent), and a lubricant, with the proviso that a plasticizer content is less than 70% by weight, or the sealing insert is free of plasticizers.

35. The container closure as claimed in claim 30, wherein the barrier polymer includes one or more of ethylene-vinyl alcohol copolymer (EVOH) and (optionally modified) polyamide (PA).

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 illustrates two embodiments of sealing insert; and

(2) FIG. 2 illustrates three embodiments of sealing insert.

DETAILED DESCRIPTION OF THE INVENTION

(3) According to the invention, a container closure of metal or plastic for a container for accommodating beverages or food that has a mouth opening to be closed by said container closure is provided with a sealing insert that is arranged in the container in such a manner that it closes the mouth opening with sealing action when the container closure is fitted onto the container.

(4) In a first preferred embodiment, the sealing insert comprises a polymer compound that contains at least two different barrier polymers, but no halogen-containing polymers. Such sealing inserts can be used in a wide variety of applications, particularly those in which the sealing insert formerly contained only one polymer. Because of the interaction among the plurality of barrier polymers, there is improved adjustability of the hardness and elasticity of the sealing insert with an overall improved barrier function.

(5) For in-shell molding processes, the sealing insert preferably comprises the at least two different barrier polymers in a mixture with one another.

(6) For out-shell molding in particular, as discussed below with reference to FIG. 1, it can instead be provided that the sealing insert has at least two different barrier polymers that are essentially unmixed with one another (and e.g. occur in different layers of a multilayer structure).

(7) The barrier polymers used according to the invention are generally selected from the group comprising butyl rubber (IIR); polyisobutylene (PIB); styrene block copolymers, more particularly styrene-isobutylene-styrene (SIBS), styrene-isoprene-styrene (SIS), styrene-vinyl isoprene-styrene, and hydrogenated styrene-vinyl isoprene-(co-)isoprene-styrene; polyamide (PA); ethylene-vinyl alcohol copolymers (EVOH); and thermoplastic elastomers (TPE-V), more particularly allyl-styrene with an isobutene content of >50% in the rubber components, wherein the total content of isobutylene-based polymers in the sealing insert preferably does not exceed 60% by weight, more preferably 55% by weight, and particularly preferably 50% by weight in order to keep the stickiness of the polymer compounds within practicable limits.

(8) The sealing insert contains at least one further (other) polymer that is not a barrier polymer and is used for adjustment of the hardness and elasticity of the sealing insert, but can also optionally contribute to the barrier effect of the sealing insert. This further (other) polymer generally comprises a polyolefin, more particularly polyethylene and/or a polyethylene copolymer, preferably PE-HD, PE-LD, PE-LLD (C.sub.4, C.sub.6 or C.sub.8) and/or VLDPE, MD-LDPE, EVA, EEA, EMA, EAA, EBA, polypropylene and/or propylene copolymer.

(9) Alternatively or additionally, the sealing insert may comprise a TPE, more particularly SBS, SEBS, SIBS, SIS, SEP, SEPS, or SEEPS.

(10) In preferred embodiments, the sealing insert contains a mixture of butyl rubber (IIR) and styrene-isobutylene-styrene (SIBS). The butyl rubber has particularly favorable barrier properties and is preferably soft, but not very elastic (CS), and tends to undergo cold flow (retardation). The SIBS has a somewhat higher oxygen permeability and is harder, but more elastic, and also has less of a tendency to undergo cold flow.

(11) The combination of butyl rubber and SIBS is superior to the individual components with respect to softness and elasticity (and thus its sealing action). The sealing functionality can be further improved if at least one polyolefin (see above) is also included. This reduces creep tendency and improves processability.

(12) In particularly preferred embodiments, the sealing insert contains up to 25% by weight of butyl rubber, up to 65% by weight of SIBS, and preferably up to 60% by weight, more preferably up to 55% by weight, and particularly preferably up to 50% by weight of PE-HD, PE-LD, and/or PE-LLD.

(13) The polymer compound that forms the sealing insert preferably contains at least one additive such as a plasticizer, e.g. polybutene oil or white oil; a stickiness-reducing agent (anti-blocking agent), and/or a lubricant, wherein the plasticizer content is preferably less than 70% by weight, more preferably less than 60% by weight, even more preferably less than 50% by weight, particularly preferably less than 40% by weight, especially less than 30% by weight, especially less than 20% by weight, and especially less than 10% by weight, more preferably less than 5% by weight, and even more preferably less than 1% by weight or the sealing insert is free of plasticizers.

(14) The polyolefin contained in the polymer compound generally has a melt flow rate (MFR) under a 5 kg load and at 190° C. of greater than 15 g/10 min, preferably at least 20 g/10 min.

(15) It is generally preferable if the sealing insert has a Shore D hardness of less than 50, preferably less than 40, and particularly preferably less than 30, wherein the Shore D hardness is often between 15 and 40, and preferably between 25 and 40.

(16) In this case, the Shore A hardness of the sealing insert is preferably between 55 and 100.

(17) In general, the sealing insert should show an OTR of less than 940 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, more particularly less than 850 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, more preferably less than 800 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, especially less than 770 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, and more particularly less than 700 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, wherein (more particularly for applications in wine closures) an OTR of less than 670 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, especially less than 630 cm.sup.3, 100 μm/m.sup.2.Math.d.Math.bar, preferably less than 600 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, and particularly preferably less than 560 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar is preferred.

(18) Sealing inserts according to the invention preferably have a melt flow rate (5 kg, 190° C.) of at least 5, preferably at least 10, and particularly preferably at least 15 g/10 min. Melt flow rates of at least 20 g/10 min are particularly preferred.

(19) In order to achieve the desired elasticity, the sealing insert should preferably have a compression set (CS) at 25% compression, 23° C., and 22-hour storage of between 20% and 70%, and more particularly between 40% and 65%, a CS at 25% compression, 40° C., and 22-hour storage of between 45% and 70%, and a CS at 25% compression, 70° C., and 22-hour storage of between 50% and 80%, which can be achieved by means of the qualitative and quantitative composition of the polymer compound.

(20) In particularly advantageous embodiments, the sealing insert contains butyl rubber, SIBS, and at least one polyolefin, preferably in the above-mentioned content ranges, and has an oxygen permeability of less than 700 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar at a CS (25% compression, 23° C., 22-hour storage) of between 40% and 65% and a melt flow rate (5 kg/190° C.) of more than 1 g/10 min, more particularly more than 10 g/10 min.

(21) The container closure can generally be any desired screw- or pry-off closure. However, it is preferably a screw cap, more particularly an aluminum screw cap with a diameter of 28 mm, 30 mm or 38 mm, more particularly 28×15 mm or 30×60 mm (long cap), or a crown cap, more particularly with a sheet thickness of less than 0.21 mm.

(22) The container closure is preferably pasteurizable together with its sealing insert, more particularly at temperatures in the range of 62° C. to 70° C.

(23) The sealing insert is preferably configured as a ring or disk and has a sealing lip running around its circumference that protrudes when the container closure is in an attached state in the direction of the mouth opening of the container. FIG. 2 shows schematic sections of several variants of this preferred embodiment, in which an in principle disk-shaped sealing insert (3, 5, 7) has one or two sealing lips (4, 6, 8, 9) around its circumference that are preferably formed during in-shell molding of the sealing insert. In this case, a single sealing lip can be provided that is radially arranged such that it engages with the container mouth opening (not shown) internally (4) or externally (6). However, two sealing lips (8, 9) can also be arranged such that together, they engage with the mouth opening of the container both internally and externally.

(24) In other preferred embodiments, the sealing insert is composed of two different elements, with one being a ring-shaped or (preferably) disk-shaped first element that is preferably connected to the metal or plastic material of the closure body and the other being a (preferably) ring-shaped or disk-shaped second element that is arranged on the first element at least in the area in which the attached container closure is in contact with the mouth opening of the container. FIG. 1 shows a particularly preferred embodiment in which the first element (1) is disk-shaped and the second element (2) is ring-shaped.

(25) Both elements may be composed of the same polymer compound, e.g. if it is advantageous to produce the sealing insert by means of out-shell molding, for example because it is desired to arrange another metal film or the like between the elements.

(26) Alternatively, it may be advantageous for the first and the second element to be composed of different materials, wherein the material of the second element comprises at least one barrier polymer, and preferably at least two barrier polymers.

(27) In another preferred embodiment (FIG. 1), the sealing insert is composed of two different materials, with the first material (1a) forming a disk-shaped element that is sandwiched between layers of the second material (2a), wherein the second material is a compound with at least one barrier polymer and a Shore D hardness of less than 40 and the first material is a compound or a pure polymer with a hardness greater than Shore D 40. If the second material has sufficient softness, the first material may also preferably comprise a barrier polymer, preferably selected from ethylene-vinyl alcohol copolymer (EVOH) and (optionally modified) polyamide (PA), or other hard materials having a high barrier effect.

(28) The sealing insert may contain an oxygen-binding compound (scavenger), more particularly sodium sulfite. In order to improve the barrier effect, it may be provided, and more particularly laminated with a metal film, more particularly if it is produced in the out-shell molding process.

(29) In order to further improve the sealing, the sealing insert may comprise a foamed polymer compound (in the area in contact with the container mouth opening).

(30) The polymer compounds according to the invention preferably comprise at least two barrier polymers that differ in at least one physical parameter (for example Shore hardness). In general, this is preferably achieved in that the barrier polymers belong to different substance classes. Here, the term “substance classes” is to be understood as it is commonly understood in the case of plastics belonging to “different” substance classes that differ in functional groups or have a different basic structure. For this reason, for example, butyl rubber and SIBS belong to different substance classes. Accordingly, although they differ in several physical parameters, PE-HD and PE-LD do not belong to different substance classes.

(31) Preferred polymer compounds contain at least one, and preferably at least two barrier polymers that are thermoplastic elastomers.

(32) In this case, preferred barrier polymers are e.g. butyl rubber (IIR); polyisobutene (PIB); styrene block copolymers, more particularly styrene-isobutylene-styrene (SIBS), styrene-isoprene-styrene (SIS), styrene-vinyl isoprene-styrene and hydrogenated styrene-vinyl isoprene-(co-)isoprene-styrene; polyamide (PA); ethylene-vinyl alcohol copolymers (EVOH); and thermoplastic vulcanizates (TPE-V), more particularly those with an isobutene content of >50% in the rubber components, wherein the total content of isobutene-based polymers in the sealing insert preferably does not exceed 60% by weight, more preferably 55% by weight, and particularly preferably 50% by weight.

(33) The oxygen permeability of a barrier polymer according to the invention is preferably at most 900 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, more preferably at most 800 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, especially preferably at most 700 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, and even more preferably at most 600 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar when the Shore D hardness of the barrier polymer is not greater than 40, preferably at most 8 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar, and even more preferably at most 6 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar.

(34) Of particular significance in the context of this invention is the use of a container closure of the above-described type for closing a wine, sparkling wine, or champagne bottle.

(35) In this case, a polymer material comprising at least one barrier polymer is used as a sealing insert in a closure, more particularly a screw cap and especially an aluminum screw cap, preferably having the dimensions 30×60 mm (long cap), for a wine, sparkling wine, or champagne bottle. Similar closures can be advantageously used for spirits (having an alcohol content of greater than 18% by volume, and more particularly greater than 24% by volume).

(36) In another preferred use of the container closures described here, these are configured as crown caps with a sheet thickness of less than 0.21 mm, preferably less than 0.20 mm, and particularly preferably less than 0.18 mm.

EMBODIMENTS

(37) In a series of tests (runs 1 to 12), various compounds were produced and tested for their suitability as sealing inserts. For this purpose, the compounds were produced in the conventional manner by mixing under heat in an extruder and then molded into test pieces meeting the specifications of the respective measuring method to be used (cf. above under “Definitions and measuring methods”). The results are shown in Table 1.

(38) TABLE-US-00001 Run 0 Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Run8 Run 9 Run 10 Run 11 Run 12 Butyl rubber 24.46 19.7 19.7 19.7 19.7 9.7 9.7 10 10 SIBS 50 35 40 60 37.5 40 30 50 36 35 30 30 PE-HD MFR 2 24.2 PE-ED MFR 30 49.85 29.5 49.2 29.5 29.2 51.7 33.5 49.5 39.2 44.5 44.5 30.6 30.6 PE-LD MFR 20 10 10 10 10 28.6 PE-LLD MFR 20 10 28.6 SEBS EH 504 10 10 Polybutene oil 5 Talc 0.74 Titanium dioxide 0.25 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Irganox 1010 0.05 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Irgafos 168 0.2 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Erucamide 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Total 100 100 100 100 100 100 100 100 100 100 100 100 100 Shore A 68 — 80 83 94 86 94 92 94 95 95 96 Shore D 50 16 — 25 26 36 25 34 35 36 36 37 38 MFR [190° C./5 kg] 17.1 4.8 — 8.2 7.8 19.4 9.2 16.0 15.2 18.7 17.7 18.7 20.0 OTR 25° C., 100% 475 678 — 660 764 658 604 541 621 533 553 622 588 RH [cm.sup.3 * 100 μm/m.sup.2-d] Compression set — — — 50 — — — 57 37 — — — — at 28° C. Compression set — — — 59 — — — 60 57 — — — — at 40° C. Compression set — — — 67 — — — 62 65 — — — — at 70° C. Processability Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Stickiness No High — Medium No No Low No No No No No No

(39) In some of these compounds (runs 0, 2, 4, 5 and 8), the sealing insert comprises only one barrier polymer, and in the other compounds (runs 1, 3, 6, 7, 9 to 12) the sealing insert comprises two barrier polymers.

(40) Butyl rubber (X Butyl RB 101-3) and SIBS (Sibstar 102T FD) were used as barrier polymers.

(41) Two different PE-HDs (MFR=2 or 30, density 0.954 g/cm.sup.3), PE-LD (MFR=20, density 0.924 g/cm.sup.3) and PE-LLD (MFR=20, density 0.924 g/cm.sup.3), were used as polyolefin components.

(42) In run 0, talc (Luzenac) was used in order to reduce stickiness.

(43) Irganox 1010 and Irgafos 168 were used as stabilizers or antioxidants.

(44) Finawax E is erucamide, a lubricant.

(45) The tests allow the following general conclusions to be drawn, which are relevant for all polymer compounds according to the invention and the sealing inserts produced from said compounds:

(46) Run 0 is a compound with butyl rubber as the sole barrier compound. The oxygen permeability is low, but the Shore D hardness is too high for application in wine bottle closures. However, such compounds having only one barrier compound can be used for example in crown caps with reduced sheet thickness.

(47) Run 1 has a total content of butyl rubber and SIBS of almost 70% by weight and is significantly softer than run 0. However, the compound is highly sticky, and the granulate tends to undergo blocking. The other runs, with a lower total content of isobutylene-based polymers (cf. run 4, with 60% by weight SIBS), were less sticky. No more blocking was observed below a total content of 50% by weight of isobutene-based polymers.

(48) Run 2 has a relatively low content of SIBS as the sole barrier polymer and contains SEBS together with polybutene oil. This batch was not processable. Based on a comparison with run 5, which was similarly designed and was processable, this is assumed to be due to the oil components.

(49) Run 3, with approx. 60% by weight, has a very high total content of isobutene-based barrier polymers compared to run 0 and very low hardness, with favorable, but not optimum, barrier properties. The batch was processable, but the product shows only moderate stickiness.

(50) Run 4 also has around 60% by weight of barrier polymer, but only one (SIBS). The compound is harder than run 3, and oxygen permeability is higher. The combination of two barrier polymers (run 3) results in lower oxygen permeability.

(51) Run 5 contains a relatively low content of SIBS as a single barrier polymer. The batch contains no softening oil and was processable; the product is not sticky. The polymer compound is harder and characterized by a higher oxygen barrier than in run 4. This is due to the higher PE-HD content. Despite the lower SIBS content, the barrier effect is better than in run 4.

(52) Run 6 corresponds in the content of barrier polymers to run 3, with slightly modified polyolefin components. The use of a higher content of PE-HD causes the hardness of the polymer compound to increase. The oxygen permeability changes only slightly. To a certain extent, the hardness and barrier effect can therefore be adjusted by means of the polyolefin content.

(53) Run 7 is similar to run 3 and run 6, with somewhat lower SIBS content and increased content of PE-HD. With increasing PE-HD content and decreasing SIBS content, the hardness of the polymer compound increases, while the oxygen permeability decreases slightly. Run 7 offers an insight into elastic behavior by means of the CS data. This compound represents a particularly preferred type of sealing inserts, especially for use in wine bottle caps (long caps).

(54) Run 8 contains only SIBS as a barrier polymer and is to be compared to run 4. The compound contains less SIBS, but more PE-HD, and is accordingly harder. The oxygen permeability is slightly lower. The barrier function is significantly better, despite the reduced content of barrier polymers.

(55) Run 9 is comparable to run 8 with respect to hardness and oxygen permeability. The total content of barrier polymers is lower, and the polyolefin content is higher. The barrier effect is outstanding, with comparable hardness. This is also a compound that can be particularly favorably used for sealing inserts that achieve the objects of the invention.

(56) Run 10 differs from run 9 in the replacement of PE-LD by PE-LLD. With the same hardness, the barrier function is somewhat reduced, but still favorable.

(57) Run 11 has a similar composition with respect to the barrier polymers to that of run 9 and run 10, but has an increased content of PE-LD. Because of the low crystallinity of PE-LD relative to PE-HD, the oxygen permeability increases. This would lower the material costs, but at the cost of even greater hardness and a significantly lower barrier effect. It should be noted that a compound such as that of run 11 can also be used as a sealing insert for long caps. According to the invention, the limits for hardness and barrier function are preferably Shore D=at most 50 and OTR=at most 940 cm.sup.3.Math.100 μm/m.sup.2.Math.d.Math.bar.

(58) Run 12 is similar to run 11, wherein the PE-LD is replaced by PE-LLD. The two are comparable with respect to hardness and oxygen permeability.

(59) In general, compounds with at least two barrier polymers are found to be superior to those that comprise only one barrier polymer (of the same type). It is also found that the properties of the sealing insert produced from the compound can be adapted and improved by the addition of other polymers, more particularly polyolefins. However, the comparison with runs 0 and 2 shows that a high content of polyolefins alone is not the decisive factor.

(60) Compounds such as those in runs 0, 4, 5, and 8 with only one barrier polymer can be used in any case as sealing inserts for crown caps with reduced sheet thickness.

(61) The findings presented here, obtained using test pieces composed of homogeneous compounds, can be applied to sealing inserts that are not molded from one homogenous polymer compound, but as described above, have a multilayer structure, as shown in FIG. 1 by way of example.