Polymer compound for seals for use with fat-containing filling materials

Abstract

The invention relates to a polymer compound for a sealing insert for a container closure, in particular for fat-containing filling materials, which has a composition such that the migration of constituents of the compound into the filling material is reduced, characterized in that the Shore A hardness of the polymer compound is between 45 and 95 and in the compressive deformation test analogous to ASTM D395-97 Method B at 70 DEG C the polymer compound exhibits a compression set of 30-90%.

Claims

1. A method for producing press on and twist off caps for containers having an opening with an inner diameter above 2 cm that is to be closed by the container closure comprising a polymer-based sealing element which is arranged in the container closure in such a manner that it sealingly contacts the opening of the container in the closed state, in which method a polymer compound is made sufficiently flowable by heating and applied to the container closure in the region of the sealing element to be produced and brought mechanically into the desired shape which is maintained after it has cooled, wherein the Shore A hardness of the polymer compound is in the range of 40 to 90 and the polymer compound shows a compression set between 30% and 70% in the compressive deformation test according to ASTM after 22 hours at 70 C. and a compression of 25%, the polymer compound is PVC-free and wherein the polymer compound comprises a block copolymer which on the one hand comprises polyethylene units and on the other hand is built up from an alkene monomer, selected from the group consisting of propene, butene, hexene and octene, in the range of 20% to less than 100%; a random copolymer, that is composed of a linear or branched interpolymer of ethylene on the one hand and at least one C.sub.3-C.sub.20 alpha-olefin on the other hand, in the range of less than 80%; and other polyolefins up to 25%.

2. The method according to claim 1, wherein the Shore A hardness of the polymer compound is in the range of 60 to 75.

3. The method according to claim 1, wherein the polymer compound comprises not more than 10% of components that are liquid at the application temperature.

4. The method according to claim 1, wherein the copolymer is produced by using metallocene catalysts.

5. The method according to claim 1, wherein the polymer compound is composed such that the sealing insert is useable under conditions of pasteurization.

6. The method according to claim 1, wherein the polymer compound is composed such that the sealing insert is useable under conditions of sterilization.

7. The method according to claim 1, wherein the container closure has a gas barrier effect and/or an excess pressure valve effect in the closed state.

8. The method according to claim 1, wherein the container closure provides vacuum retention in the closed state.

9. The method according to claim 1, wherein the polymer material is provided as a granulate and is heated by an extruder.

10. The method according to claim 1, wherein the flowable polymer material is applied by a nozzle onto the inner side of the container closure.

11. The method according claim 10, wherein the applied polymer material is shaped by a stamp or the like.

12. The method according to claim 1, wherein the container closure corresponds to an inner diameter of the container opening of more than 2.5 cm.

13. A method for producing container closures for containers having an opening with an inner diameter above 2 cm that is to be closed by the container closure comprising a polymer-based sealing element which is arranged in the container closure in such a manner that it sealingly contacts the opening of the container in the closed state, in which method a polymer compound is made sufficiently flowable by heating and applied to the container closure in the region of the sealing element to be produced and brought mechanically into the desired shape which is maintained after it has cooled down, wherein the Shore A hardness of the polymer compound is in the range of 40 to 90 and the polymer compound shows a compression set between 30% and 70% in the compressive deformation test according to ASTM after 22 hours at 70 C. and a compression of 25%, the polymer compound is PVC-free, and wherein the polymer compound comprises a block copolymer which on the one hand comprises polyethylene units and on the other hand is composed of an alkene monomer, selected from the group consisting of propene, butene, hexene and octane, in the range of 20% to less than 100%; a random copolymer, that is composed of a linear or branched interpolymer of ethylene on the one hand and at least one C.sub.3-C.sub.20 alpha-olefin on the other hand, in the range of less than 80%; other polyolefins up to 25%.

14. The method according to claim 13, wherein the polymer compound comprises not more than 10% of components that are liquid at the application temperature.

15. The method according to claim 13, wherein the copolymer is produced by using metallocene catalysts.

16. The method according to claim 13, wherein the Shore A hardness of the polymer compound is in the range of 60 to 75.

17. The method according to claim 13, wherein the polymer compound is composed such that the sealing insert is useable under conditions of pasteurization.

18. The method according to claim 13, wherein the polymer compound is composed such that the sealing insert is useable under conditions of sterilization.

19. The method according to claim 13, wherein the container closure has a gas barrier effect and/or an excess pressure valve effect in the closed state.

20. The method according to claim 13, wherein the container closure provides vacuum retention in the closed state.

21. The method according to claim 13, wherein the polymer material is provided as a granulate and is heated by an extruder.

22. The method according to claim 19, wherein the flowable polymer material is applied by a nozzle onto the inner side of the container closure.

23. The method according to claim 1, wherein the other olefins comprise at least one of HDPE, co-PP, or styrene-ethylene/butylene-styrene (SEBS).

24. The method according to claim 13, wherein the other olefins comprise at least one of HDPE, co-PP, or styrene-ethylene/butylene-styrene (SEBS).

Description

(1) In a preferred embodiment of the present invention, the material of the sealing insert has only small amounts of, or more preferable no, constituents which are liquid at application temperature. The application temperature is usually equal to the ambient temperature, i.e. in the range of usual temperatures outdoors or in heated rooms.

(2) Therefore according to the invention, only small quantities or preferably no fluid extenders, such as white oil in particular, are added to the material of the sealing insert.

(3) In a preferred embodiment the material contains not more than 10%, preferably not more than 7%, more preferably not more than 4% and even more preferably not more than 1% of lubricants, which may pass into fat-containing filling materials in limited amounts in a migration test at 40 C. for 10 days.

(4) It is presently most preferred that the material contains (within the analytical limits given at the date of filing the application) absolutely no ingredients which are liquid at application temperature.

(5) Furthermore, it is preferred that the material of the sealing insert contains no plasticizers.

(6) Compounds for such sealing inserts without extenders are potentially difficult to process, especially if the diameter of the container closure exceeds 3 cm and if the material for instance as described in EP 0 503 124 is based on styrene-containing block copolymers with elastomeric chain segments. Therefore, according to the invention, materials are preferably used which do not contain these polymers.

(7) It is preferred that the material from which the sealing insert is formed neither contains said fluid extenders or plasticizers, nor styrene-containing block copolymers with elastomeric chain segments.

(8) Instead, it is preferred that the polymer material forming the main component of the sealing insert is based on certain polyalkylenes, which can be processed without extenders and the like to form seal inserts for container closures with diameters of more than 3 cm.

(9) t has been found that a block copolymer which on the one hand comprises polyethylene units and on the other hand is composed of an alkene monomer, selected from propene, butene, hexene and, in particular, octene, is particularly well suited for this purpose.

(10) Such copolymers can be produced with desired physical properties by using metallocene catalysts.

(11) Suitable polymers are described in EP-B10 714 427. There it is stated that these polymers as such can be processed to form sealing inserts, but no additives should be added. However, the invention is based inter alia on the finding that these polymers can be processed to form improved sealing inserts, when additives according to the invention are added. The problem of migration of material components in fat-containing filling materials is not addressed there.

(12) On the other hand, particularly suitable as a component of such compounds is a random copolymer, that is formed by a linear or branched interpolymer of ethylene on the one hand and at least one C.sub.3-C.sub.20 alpha-olefin on the other hand. Suitable random polymers are described for example in U.S. Pat. No. 6,235,822.

(13) According to the invention, it has been found that other formulation variations are possible, wherein the block copolymer is present in the range of 20-100%, the random copolymer is present in the range of 0-80%, and as additional ingredients, other polyolefins, in particular, styrene-ethylene/butylene-styrene (SEBS), HDPE or co-PP with up to 25% are present.

(14) According to the invention, the formula can comprise an ethylene-octene block copolymer, such as e.g. Infuse D9007 in the range of 37%-41%, an ethylene-octene random copolymer, such as e.g. Engage 8402 in the range of 58%-62%, an antioxidant, such as e.g. Irganox 1010 in the range 0.1%-0.3%, a stabilizer such as e.g. Irgafos 168 in the range of 0.0%-0.2%, a lubricant such as e.g. erucic acid amide in the range 0.2%-0.4%, and a lubricant such as oleamide in the range 0.2%-0.4%.

(15) An exemplary formulation for use for hot-filling and pasteurization comprises:

(16) Ethylene-octene block copolymer: 39.1%

(17) Ethylene-octene random copolymer: 60%

(18) Antioxidant: 0.2%

(19) Stabiliser: 0.1%

(20) Lubricant: 0.6%

(21) According to the invention, said material generally has a Shore A hardness of 45 to 95. In particular according to the formulation, it has a Shore A hardness of about 85 and a Shore D hardness of about 25. The compression set of the polymer compound (determined analogous to compressive deformation test ASTM D395-97 Method B) is between 50 and 80%.

(22) The polymeric materials according to the invention can resist hot-filling at up to 100 C. for up to 60 min, starting from a hot-filling of at least 60 C. at a maximum of 10 min and a minimum of 1 min. The hot-filling starting from 60 C. can be accomplished in 60 min to up to 100 C. in increments of 5 C.

(23) The apparent shear viscosity at 185 C. is 100 s.sup.1<100 Pa.Math.s and at 500 s.sup.1 is <50 Pa.Math.s. This was determined using a twin-bore capillary rheometer Porpoise P9 with a nozzle diameter of 0.5 mm.

(24) Optionally, pigments (preferably inorganic pigments, to prevent any pigment migration) can be added to the formulations of the compounds. It has also been shown that other additives such as waxes, silicones and in particular blowing agents may be added to the polymer compounds, for example to improve processing and performance characteristics.

(25) Furthermore, the polymer compounds show a compression set of 30-90% at 70 C. in the compressive deformation test analogous to ASTM D 395-97, Method B. For sterilized products, the compression set has higher values, up to 90%. For pasteurizable (but not sterilizable) products, the compression set may be at somewhat lower values, up to about 80%. For compounds with thermoplastic vulcanizates (TPV materials), the lower limit of the compression set may by down to 30%; for other materials the range of the compression set is preferably at least 50%.

(26) These materials can be processed to form large sealing elements for correspondingly large container closures with, for example, the described methods of our parallel international patent application (entitled Method of producing a vessel closure). Thus, it is for the first time possible to provide, for example, lug caps with diameters greater than 60 mm with a sealing insert which meets the regulations of the EC Directives 1935/2004 2023/2006, 2002/72/EC, 372/2007 and 2007/19/EC.

(27) In regard to these legal requirements, migration tests have to be carried out for container closures according to the invention as described in DIN EN 1186. There is no representation of this measurement method in the context of the present application but these tests are incorporated by reference to DIN EN 1186 in the disclosure of the present application.

(28) The use of said polymer material according to the invention not only allows that such produced sealing insert can be produced unproblematically and with the sealing properties as described above. Moreover, such container closures are pasteurizable, and they meet the above European legal regulations concerning the migration of constituents of the polymer material in the drink or food stuff, especially fat-containing filling materials, which are enclosed in containers sealed according to the invention.

(29) In this regard the regulations of said European law directives, particularly in connection with the test criteria of DIN EN 1186 are appropriate selection criteria for the polymer material that can be determined from a plurality of conceivable compounds by avoidance of components that are liquid at the application temperature and subsequent testing.