VESSEL CLOSURE SEAL AND VESSEL CLOSURE

Abstract

The application relates to a vessel closure seal, in particular for fat-containing filling materials, comprising a polymer compound of which the seal consists essentially or entirely, a) wherein the polymer compound is PVC-free and comprises at least one TPS, and at least two different co-PPs, or at least one co-PP with a Shore A hardness of max. 80, a crystallisation enthalpy of max. 30 J/g and a melting point of at least 155° C., b) and the polymer compound has a Shore A hardness at 70° C. of between 30 and 85 and a Molt Flow Index (5 kg/190° C.) of less than 20 g/10 min.

Claims

1. Vessel closure seal, in particular for fat-containing filling materials, comprising a polymer compound of which the seal consists substantially or entirely, a) wherein the polymer compound is PVC-free and comprises at least one TPS, and at least two different co-PPs, or at least one co-PP with a Shore A hardness of max. 80, a crystallization enthalpy of max. 30 J/g and a melting point of at least 155° C., b) and the polymer compound has a Shore A hardness between 30 and 85 at 70° C. and a melt flow index (5 kg/190° C.) of less than 20 g/10 min.

2. Vessel closure seal according to claim 1, in which the at least one co-PP has a Shore A hardness of max. 75 and/or a crystallization enthalpy of max. 20 J/g and/or a melting point of at least 160° C.

3. Vessel closure seal according to claim 1, in which the polymer compound substantially does not comprise homo-PP.

4. Vessel closure seal according to claim 1, in which the polymer compound comprises at least one of SEBS, SEEPS or Polybutene.

5. Vessel closure seal according to claim 1, in which the polymer compound comprises a linear SEBS or SEEPS with a styrene content level between 26% and 34% styrene.

6. Vessel closure seal according to claim 1, in which the polymer compound comprises at least 20% TPS.

7. Vessel closure seal according to claim 1, in which the polymer compound contains a linear SEBS having a Shore A hardness of 50 to 90 and a 5% by weight solution in toluene has a dynamic viscosity of>50 mPa.Math.s (measured at 25° C.) and as a 10% by weight solution in toluene has a dynamic viscosity of>1000 mPa.Math.s.

8. Vessel closure seal according to claim 1, in which the polymer compound has a second SEBS with a styrene content of between 10% and 23%, a Shore A hardness between 30 and 60 and an MFI (2.16 kg/230° C.) between 2 and 30 g/10 min.

9. Vessel closure seal according to claim 1, in which the polymer compound comprises a first co-PP with a Shore D hardness below 25.

10. Vessel closure seal according to claim 1, in which the polymer compound comprises a first co-PP with an MFI (2.16 g/10 min.) of the first co-PP of below 30 g/10 min.

11. Vessel closure seal according to claim 1, in which the polymer compound comprises at least one co-PP with MFI (2.16 kg/230° C.) of at least 0.1 g/10 min.

12. Vessel closure seal according to claim 1, in which the DSC melting point of the first co-PP is higher than that of the second co-PP.

13. Vessel closure seal according to claim 1, in which the polymer compound comprises a first co-PP with a DSC melting point above 145° C.

14. Vessel closure seal according to claim 1, in which the polymer compound comprises between 20% and 70% co-PP.

15. Vessel closure seal according to claim 1, in which the polymer compound comprises at least one POE.

16. Vessel closure seal according to claim 15, in which the content of POE is between 10% and 50%.

17. Vessel closure seal according to claim 1, in which the polymer compound does not contain more than 10% of lubricants.

18. Vessel closure seal according to claim 1, in which the polymer compound does not contain more than 10% of liquid components at 20° C.

19. Vessel closure seal according to claim 1, which can be pasteurized at temperatures above 98° C.

20. Vessel closure, in particular vacuum vessel closure, made of metal or plastic, with a vessel closure seal according to claim 1.

21. Vessel closure according to claim 20, having a diameter of at least 28 mm.

Description

[0061] FIG. 1 shows an example of such a DSC curve.

[0062] It has proven helpful in describing the suitability of a sealing material for vacuum screw closures to design polymer compounds in such a way that the temperature of the exothermic peak is higher than the expected maximum operating temperature of the vessel closure. This exothermic peak temperature from the crystallization process is partly well below the temperature of the endothermic melt peak.

[0063] Basically, the invention prefers the use of such polymers having low degrees of crystallinity, while particularly crystalline polymers such as homo-PP, LLDPE, LDPE and HDPE are preferably not used at all or only to a reduced extent.

[0064] Preferred polymer compounds have a specific total crystallization enthalpy above room temperature of less than 45 J/g, more preferably a maximum of 38 J/g, more preferably a maximum of 30 J/g.

[0065] The TPS used according to the invention are preferably SEBS and/or SEEPS. In addition or as an alternative, at least one polybutene can be used.

[0066] In general, linear SEBS and/or SEEPS with styrene content levels between 26% and 34% are preferred. Particularly preferred are SEBS and/or SEEPS with styrene content levels between 29% and 33%, and usually preferred are SEBS and/or SEEPS with 31% to 32% styrene.

[0067] Preferred polymer compounds generally comprise up to 50%, more specifically up to 45%, more preferably up to 40% TPS. Preferably, such polymer compounds comprise at least 10%, specifically at least 20% and more preferably at least 30% TPS.

[0068] TPS are not in themselves particularly suitable polymers for sealing compounds that come into contact with fat-containing or oily fillers because they facilitate the entry of greases and oils into the seal. This is particularly true for products that are thermally treated, e.g., pasteurized or sterilized.

[0069] In accordance with EP 09 756 681, it is necessary to dispense with TPS contents in the polymer compound to the furthest extent possible.

[0070] However, it has surprisingly turned out that TPS can also be successfully used in sealing compounds for applications in greases and oils if the polymer compound contains certain polypropylene copolymers (co-PP). Apparently, the co-PP content prevents the absorption of fats and oils through the seal even in the presence of TPS and also in pasteurization and even sterilization (up to temperatures of 132° C.) Homo PPs are not used in favoured embodiments of the invention in place of co-PPs.

[0071] In preferred embodiments of the invention, the TPS portion of the polymer compound consists of at least two different TPS, in particular two different SEBS.

[0072] As the main component of this TPS content preferably linear SEBS serves a, which has a Shore A hardness of 50 to 90, preferably from 55 to 80 and as a 5% by weight solution in toluene has a dynamic viscosity of>50 mPa.Math.s (measured at 25° C.) and as a 10% by weight solution in toluene has a dynamic viscosity of>1000 mPa.Math.s.

[0073] Particularly preferred SEBS for this proportion are linear triblock copolymers of type S-E/B-S.

[0074] Products such as KRATON® G1651 and CALPRENE® 6174 are particularly suitable.

[0075] As a modifier then preferably serves a second SEBS with a styrene content of between 10% and 23%, a Shore A hardness between 30 and 60 and an MFI (2.16 kg/230° C.) between 2 and 30 g/10 min.

[0076] KRATON® G1645 or G1643 can be used in a mixture with KRATON® G1651 to increase the flexibility of the compound (in the sense of a plasticiser, instead of white oil).

[0077] The polymer compound further has a content of at least one co-PP.

[0078] The invention preferably uses contents of one or a plurality of co-PPs instead of contents of homo-PP in the polymer compound.

[0079] In a first variant of the invention, the polymer compound contains two different co-PPs.

[0080] The first co-PP preferably has a Shore D hardness below 25, more preferably below 20.

[0081] It preferably has a DSC melting point of above 145° C., more preferably above 155° C. The melting point of the first co-PP is preferably higher than that of the second co-PP.

[0082] The first co-PP preferably has a total enthalpy of crystallization of less than 30, more preferably less than 25 and usually preferably less than 20 J/g.

[0083] The MFI (2.16 g/10 min.) of the first co-PP is preferably below 30, more preferably below 20 and usually preferably below 10 g/10 min.

[0084] The second co-PP preferably has a Shore D hardness above 25, more preferably above 30, but below 45.

[0085] It preferably has a DSC melting point of above 140° C., more preferably above 145° C.

[0086] The second co-PP preferably has a total enthalpy of crystallization of less than 40, more preferably less than 35 J/g.

[0087] The MFI (2.16 g/10 min.) of the second co-PP is preferably below 35, more preferably below 25, and usually, preferably below 10 g/10 min.

[0088] The total amount of co-PP used in the compound is preferably generally 20%-65. The content level of the first co-PP is preferably greater than the content level of the second co-PP.

[0089] Particularly suitable products are the ADFLEX grades C290F and Q190F from LyondellBasell, DuClear QT80A from Ducor and TAFMER PN 3560 from Mitsui Chemicals.

[0090] In preferred embodiments of the invention, the co-PP can be partially replaced by other polymers, for example by LLDPE.

[0091] In a second variant of the invention, the polymer compound contains at least one co-PP with a Shore A hardness of max. 80, a crystallization enthalpy of max. 30 J/g and a melting point of at least 155° C.

[0092] Also in this second variant, the polymer material may contain another polymer, e.g., another co-PP or polyolefin.

[0093] As a further component of the polymer compound, the invention uses contents of at least one POE in certain embodiments.

[0094] Preferred POE contain PP units and randomly copolymerised ethylene units.

[0095] The content of POE is preferably between 10% and 50%, more preferably between 20% and 40%. VistaMAXX grades from ExxonMobil, e.g., VISTAMAXX 6202, are particularly suitable.

[0096] The polymer materials can withstand a hot filling of up to 100° C. for up to 60 min, starting from a hot filling of at least 60° C. in a maximum of 10 min and at least 1 min. The hot filling, starting from 60° C., can be carried out in steps from 5° up to 100° C. in 60 min.

[0097] Optionally, pigments, preferably inorganic pigments, can also be added to the formulations of the compounds to exclude pigment migration. It has also been shown that other additives such as waxes, silicones and in particular expanding agents can be added to the polymer compounds in order to improve, for example, the processing and the performance properties.

[0098] In the following, exemplary embodiments of the invention are described on the basis of the composition of the polymer compounds from which the vessel closure seal according to the invention was formed as stated above:

[0099] Exemplary Embodiment 1:

[0100] 15% first co-PP

[0101] 14% second co-PP

[0102] 33.4% SEBS 35% POE

[0103] 2.6% lubricants and additives

[0104] Exemplary Embodiment 2:

[0105] 20% first co-PP

[0106] 14% second co-PP

[0107] 33.4% SEBS

[0108] 30% POE

[0109] 2.6% lubricants and additives