Rotary vacuum vessel closure with vessel closure seal

Abstract

The invention relates to a rotary vacuum vessel closure, in particular for fat-containing filling materials, with a vessel closure seal 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 one co-PP. b) and the polymer compound has a Shore A hardness (ASTM D2240, DIN ISO 7619-1) at 70°C between 30 and 85 and has an MFR (DIN ISO 1133, 5kg / 190°C) of less than 20g / 10 mm.

Description

[0001] Vacuum container twist lock with container seal

[0002] The invention relates to a PVC-free vessel closure seal according to the preamble of claim 1.

[0003] A major problem with polymer-based container seals is the migration of seal components into the contents. Migration problems occur particularly frequently with products containing fats or oils, as the migrating substances, such as plasticizers and extenders, are often fat-soluble.

[0004] Larger container closures of the type considered here are primarily cam-type twist-off closures, typically used to seal screw-top jars for food or beverages. These foods are often high-fat products such as ready meals, sauces, delicatessen items, fish in oil, antipasti, spice pastes, and the like, whose fat or oil content increases the risk of fat-soluble components of the packaging material leaching into the food. These requirements are particularly relevant for baby food, which is typically sold in jars with Press-On Twist-Off® closures (also referred to here as PT closures or PT caps).

[0005] The vessel closures in question typically have an opening width of at least 35 mm, e.g., 38 mm or more, e.g., 82 mm. Cam-type rotary closures may have 3, 4, 5, or more than 5 cams.

[0006] Conventional PVC-based container closures exhibit favorable sealing properties. Based on flexible PVC technology, it is also possible to formulate lower-migration sealing compounds, which often utilize polyadipates. Due to their molecular weight, these are less prone to migration when in contact with grease.

[0007] Migration assessment is carried out according to the rules defined in Regulation (EU) 10 / 2011 and DIN EN 1186. This applies particularly to storage at

[0008] It is postulated that room temperature testing after 10 days at 40°C is sufficient to determine migration. However, analytical practice shows that these test conditions are insufficient for plasticized PVC in sealing materials, and that after several months of storage at room temperature in contact with vegetable oil, migration limits are sometimes significantly exceeded.

[0009] Furthermore, the use of PVC-containing compounds in packaging materials is undesirable. The conventional incineration of household waste from halogenated plastics produces acidic gases, the release of which into the atmosphere is harmful. Moreover, even small amounts of PVC interfere with the material recycling of plastic waste. In addition, such PVC-based sealing elements require the use of plasticizers, which are also problematic due to the unacceptable alteration of the food product and—in the case of the use of epoxidized soybean oil as a plasticizer—the potential formation of epichlorohydrins, which are not yet toxicologically evaluated. Therefore, there is a need for PVC-free container closure seals that closely approximate the favorable properties of known PVC-containing seals.

[0010] According to the invention, PVC-free compounds are used. In the product according to the invention, migration can be largely or completely avoided by omitting liquid components and / or by using less migration-prone polymers, as well as by other measures.

[0011] The migration of packaging components (which may include the sealing liner of the container closure) into the food is not only generally undesirable, but also strictly regulated by legal provisions. Examples of such provisions are EC Regulations 1935 / 2004, 2023 / 2006, (EU) 10 / 2011, including amendments (EU) 321 / 2011, (EU) 1282 / 2011, (EU) 1183 / 2012, (EU) 202 / 2014, (EU) 174 / 2015, (EU) 2016 / 1416, (EU) 2017 / 752, (EU) 2018 / 79, (EU) 2018 / 213, (EU) 2018 / 831, (EU) 2019 / 37 and (EU) 2019 / 1338. Currently, maximum levels of 60 ppm of migrating constituents are permitted in infant formula.

[0012] The extent of any observed migration is measured using methods such as those defined in DIN EN 1186. Such methods are also used in the context of the present invention.

[0013] Providing PVC-free sealing inserts to container closures of the type considered here is not a trivial problem, especially when these closures must comply with the aforementioned regulations regarding the potential migration of their chemical components. Likewise, the sealing function must be guaranteed under filling conditions.

[0014] The requirements for sealing materials in container closures with larger inner diameters (at least 35 mm) of the container opening are more demanding, primarily due to the relatively larger quantities of material in the seal. For such applications, it is particularly important to combine sufficient flowability of the polymer material during the manufacturing of the sealing element with adequate sealing properties in the closed state. This includes the now-required tightness against the ingress or escape of gases, possibly combined with a pressure relief valve effect that prevents the container from bursting when heated or when overpressure develops inside the container for other reasons. Furthermore, especially for the typical applications of containers with larger opening diameters (e.g., canned goods), it is required that the sealing element also withstands pasteurization and, if applicable, other processes.It can even be used under sterilization conditions. Despite all these characteristics, the seals must also meet the aforementioned requirements regarding the potential migration of chemical components. A solution to these problems, which has since been successfully implemented, is disclosed in our application EP 09 756 681, now patent EP 2 470 435. The seal described therein is PVC-free and based on a combination of at least one olefin block copolymer (OBC) with at least one polyolefin elastomer (POE), high-density polyethylene (HDPE), or polypropylene or propylene copolymer ((co-)PP). It is not intended to contain TPS. The Shore A hardness at room temperature is between 45 and 95, and the compression set (CS) at 70°C is between 30% and 90%. The CS is determined according to EP 2 470 435, as well as in the context of the present invention, according to ASTM D395-97 Method B.To facilitate the processing of compounds previously known from EP 2 470 435, extenders and / or plasticizers were typically added. In particular, components that are liquid at application temperature, such as extender oils or plasticizers (preferably white oil), were used for this purpose. However, the formulation known from EP 2 470 435 essentially omits lubricants and components that are liquid at 20°C, as these can promote migration.

[0015] The product known from EP 2 470 435 is ideally suited for many applications, but could still be improved in some cases. For example, during automated sealing processes, the seal can be cut if the closing stroke is very short and the machine has limited adjustability. With very high-speed machines, the steaming time is sometimes insufficient to adequately heat the closure. It would therefore be desirable to have a seal that is thermally and mechanically more stable, yet softer, than the seals known from EP 09 756 681. This would allow for easier sealing with a reduced risk of cuts. Ideally, this seal should possess the advantageous properties of the known seal.

[0016] Seals should also have opening values ​​that are as low as possible to ensure that twist-off closures such as cam-type closures (Twist-off® closures), PT closures (Press-on Twist-off® closures), and other twist-off closures can be opened easily. It must be ensured, however, that the closure cannot be opened unintentionally, which is why the opening value cannot be too low.

[0017] With a standard 82 mm twist-off ® -For closures, the opening values ​​of PVC-containing seals are often in the range of 4.8 - 6.2 Nm (42-55 inch / lbs) or higher. Technically complex Orbit ® Closures with low-migration PVC-based seals, designed to reduce the opening torque required, have a torque of less than 4 Nm. For the known seal according to EP 09 756 681, typical opening torques for twist-off closures are [missing information]. ®- Closures at 4.3-5.1 Nm. A lower opening value would be advantageous for PVC-free closures.

[0018] Creating such a seal is a key objective of the invention. In principle, the invention solves this and other problems by means of the combinations of features specified in the independent claims.

[0019] As with the solution according to EP 09756681, the disclosure of which we incorporate in its entirety by reference into the disclosure of this application, the seal of the invention preferably comprises a polymer compound which, in a thermally rendered sufficiently flowable form, is introduced into a metal or plastic sealing blank and there is formed into the desired shape by stamping or the like, which it retains after cooling. In these cases, the finished seal usually consists entirely of the polymer compound. Machines for corresponding manufacturing processes are available, for example, from SACMI.

[0020] The terms "seal," "sealing insert," and "sealing element" are synonymous in the context of this description. In the vessel closures according to the invention, the sealing element is designed as an insert on the inner surface of the vessel closure in a similar manner to that found in known crown caps or screw caps. The manufacturing process according to the invention generally starts with a metal vessel closure blank, which is preferably pretreated on its inner surface with a suitable coating system. This pretreatment is not necessary for a plastic vessel closure. The coating system typically consists of a base coat and an adhesion promoter, both of which can be based on an epoxy-phenolic resin system or (usually for regulatory reasons) polyesters.

[0021] In particular, the coating systems of the company ACTEGA Rhenania (base coat TPE279 with adhesion coat TPE 1500 or ACTEcoat® TPE 515 with ACTEbond® TPE-655-MF) are suitable for this purpose, on which the compounds most preferred according to the invention adhere particularly well.

[0022] Alternatively, a suitable primer coating can be applied by lamination, lamination or possibly also by co-extrusion.

[0023] In some preferred embodiments, the polymer material intended to form the seal is applied to the inside of the pre-treated blank in a thermally flowable form. Extrusion is particularly suitable for this purpose, in which the sealing compound is heated to a temperature between 100 °C and 260 °C. The extrusion can be carried out approximately in the center of the blank's inner surface if the sealing insert is to be circular in shape. The polymer material for extrusion is metered by wiping a defined quantity of the polymer compound from a die. Subsequently, the sealing element is preferably formed from the extruded, still flowable material by appropriate stamping (analogous to the known compression molding process).

[0024] Alternatively, the polymer material can be extruded as a strand and cut to the appropriate length. The resulting strand section is then inserted into the preheated closure blank and, if necessary, stamped into the seal after further preheating. A baking step can follow to improve adhesion. The closure is then cooled. In other preferred embodiments of the invention, a melt ring made of sealant material can be extruded, inserted into the blank using an applicator, and formed into a seal, as described in US 9409324 B2.

[0025] While in known bottle closures (crown caps and the like) the sealing element is usually formed as a circular disc on the inside of the container closure, in larger container closures such as according to the invention it can be advantageous to form only a ring made of polymer material, which rests against the container wall in the opening area when the container is closed.

[0026] In a modified form, the sealing element can be formed outside the closure or closure blank by stamping a suitable polymer material onto it and then inserted into the closure or blank. This process is also known to SACMI as outshell molding.

[0027] The material of the sealing insert comprises, as its main or sole component, a polymeric component consisting of at least two different polymers, namely at least one TPS and at least one co-PP. The properties of this main polymeric component can be suitably modified by the addition of further components, for example, other polymers.

[0028] The invention thus departs from the concept known from EP 09 756 681, according to which the desired seal or the polymer compound of the seal must contain an OBC. An OBC may, but does not have to, be contained in the seal according to the invention.

[0029] A further significant difference in particularly preferred embodiments of the invention lies in the omission of relevant POEs. It has surprisingly been found that POEs in the known seal can be replaced by other polymers. This omission of POEs helps to solve a problem that occasionally arises with known seals: Glass containers are usually finished, for example by coating with PE waxes. Seals containing POE can, under certain conditions, exhibit an undesirable stickiness when used with such glass, which increases the opening value of the closure in an unacceptable way.

[0030] In preferred embodiments of the invention, the seal therefore contains no analytically detectable POE content. In other preferred embodiments, a small content of at least one POE may be present, but this is kept so low that the opening value of the seal does not change significantly compared to an identical seal without POE content.

[0031] Furthermore, the invention departs from the concept according to EP 09 756 681, according to which the seal or the sealing compound must not contain TPS.

[0032] The invention is based on the finding that thermally and mechanically stable, but softer, generic seals can be obtained when the polymer compound comprises certain types of TPS, in particular SEBS, in combination with certain types of co-PP. Not all known TPS are suitable for this purpose.

[0033] Types of TPS and not all known types of co-PP, as will be described below.

[0034] In preferred embodiments, the polymer compound according to the invention additionally comprises at least one OBC and / or at least one

[0035] Polyolefin, such as polyethylene, specifically LLDPE, is used. The polyolefin can often be replaced by another polymer with similar physical properties. The polymer compound may optionally contain other polymers. It is preferably intended that the sealing insert material has very low, and particularly preferably no, content of components that are liquid at application temperature. The application temperature is usually the same as the ambient temperature, i.e., within the range of typical ambient temperatures outdoors or in heated rooms. Typically, the application temperature is 20°C.

[0036] Therefore, preferably only small amounts or preferably no amounts at all of liquid extenders, such as white oil in particular, are added to the material of the sealing insert.

[0037] Preferably, the material contains no more than 10%, preferably no more than 7%, particularly no more than 4%, or even no more than 1% of lubricants, especially those that, in a migration test at 40°C for 10 days, migrate to the fatty contents to a limited extent (percentages in this application are always weight percentages, based on the total weight of the compound in the seal, unless expressly stated otherwise). Polymer compounds according to the invention generally have a Shore A hardness (ASTM D2240, DIN ISO 7619-1) at 70°C between 30 and 85, more specifically between 40 and 75. The lower the hardness, the easier the closures are to apply. When used on steam vacuum sealing machines, there is an increased risk of cuts if the hardness is below Shore A 30 at 70°C. Above Shore A 85, there is an increased risk of sealing failure.When used on cold vacuum sealing machines without preheating, a vacuum is not achieved at Shore A values ​​above 85. Preferably, the viscosity at maximum flow (DV) of the polymer compound (23°C, ASTM D395-97 Method B) is at most 50%, more preferably at most 40%, and particularly preferably at most 30%. In optimized embodiments, the DV can be 25% or lower. The polymer compound preferably has a relatively high melt viscosity, i.e., a melt mass flow rate (MFR) according to DIN ISO 1133 at a 5 kg platen weight and a measuring temperature of 190°C of less than 20 g / 10 min, preferably less than 15 g / 10 min. For processing on cold vacuum sealing machines, it may be advantageous to adjust for other viscosities.

[0038] After sealing, during and after the cooling process, and often even during storage of the sealed container, PVC-free compounds undergo crystallization processes within the polymer compound. These processes affect the hardness and elasticity of the seal, thus influencing the tension between the seal and the container, and the migration of the lubricant on the seal's surface. The slower the crystallization, the lower the tension, because the polymer compound has more time to relax. The smaller the crystalline fraction in the compound, the more favorable the lubricant migration.

[0039] The crystallinity of the polymer compound can be measured using known methods that provide values ​​for crystallinity area, start and end of the crystallization process, and maximum crystallinity.

[0040] The peak crystallization temperature and the crystallization enthalpy relative to the sample weight are determined from the first cooling curve using DSC (dynamic scanning calorimetry). The rules for this are described in the standard ISO 11357 and its sub-chapters (especially ISO 11357-3). These quantities were measured using a Mettler Toledo DSC1 system.

[0041] It has proven helpful for describing the suitability of a sealing material for vacuum twist closures to design polymer compounds such that the temperature of the exothermic peak is higher than the expected maximum operating temperature of the container closure. This exothermic peak temperature from the crystallization process is sometimes significantly lower than the temperature of the endothermic melting peak. The invention generally favors the use of polymers with low enthalpies of crystallization, while crystalline polyolefins such as homo-PP, LLDPE, LDPE, and HDPE are preferably not used or only used to a limited extent.

[0042] Preferred polymer compounds have a specific total enthalpy of crystallization above room temperature of less than 50 J / g, particularly preferably a maximum of 40 J / g, and more preferably a maximum of 30 J / g. The TPS used according to the invention are preferably SEBS. Linear SEBS with styrene contents between 26% and 34%, and especially between 29% and 33%, are generally preferred. SEBS with 31% to 32% styrene are most preferred. Particularly preferred SEBS are linear triblock copolymers of the SE / BS type. Products such as KRATON® G1651 and CALPRENE are particularly suitable. ® 6174. SEBS polymers with lower styrene contents than 25 wt% and simultaneously lower molecular weights than the above reference materials can be mixed with KRATON. ® G1651 can be used to improve the flexibility and flowability of the (in the sense of a plasticizer, instead of white oil).

[0043] To increase compounds.

[0044] Other TPS that can be used instead of or in conjunction with SEBS include SEEPS, polybutene, and similar TPS.

[0045] Preferred polymer compounds generally comprise up to 60%, more specifically up to 55%, and more preferably up to 50% TPS. Preferably, such compounds include

[0046] Polymer compounds containing at least 1%, specifically at least 5% and more preferably at least 10% TPS. Other preferred embodiments comprise at least 20%, more preferably at least 30% and most preferably at least 40% TPS.

[0047] Preferred TPS generally have styrene contents of 28 to 35%. A 10% solution in toluene has a viscosity of less than 2.5 Pa·s, measured with a Brookfield LVT viscometer. The density is preferably between 0.90 and 0.93 g / cm³.

[0048] TPS are not particularly suitable polymers for sealing compounds that come into contact with greasy or oily fillers because they facilitate the penetration of fats and oils into the seal. This is especially true for products that undergo thermal treatment, such as pasteurization or sterilization. According to EP 09 756 681, it is necessary to avoid TPS content in the polymer compound as much as possible.

[0049] However, it has surprisingly been found that TPS can also be successfully used in sealing compounds for applications involving fats and oils if the polymer compound contains certain polypropylene copolymers (co-PP). Apparently, the co-PP content prevents the absorption of fats and oils by the seal, even in the presence of TPS and even after pasteurization and sterilization (up to temperatures of 132°C). This is also possible with the use of homo-PPs, which, however, do not result in the required physical properties of the seal in such TPS-based compounds. Therefore, homo-PPs are not used instead of co-PPs in preferred embodiments of the invention.

[0050] Preferred co-PPs have a Shore D hardness of less than 55, preferably below 45, and particularly preferably below 40. The Shore D hardness is preferably greater than 15, better than 20, and particularly preferably greater than 30.

[0051] The MFR of co-PP is preferably at 2.16kg and 230°C measurement temperature at less than 30 g / 10 min, more preferably at less than 20 g / 10 min and even more preferably below 10 g / 10 min.

[0052] Co-PPs with an MFR (2.16kg / 230°C) of at least 0.1 are particularly preferred, more specifically at least 0.3 and even more specifically at least 0.5, and at most 15, more specifically at most 12 and even more specifically at most 10.

[0053] The melting point of co-PP is preferably below 165°C, more preferably below 160°C, and most preferably below 150°C.

[0054] The amount of co-PP used in the compound is preferably generally between 5% and 65%. Higher concentrations are possible.

[0055] The co-PP preferably has low crystallinity at a relatively high melting point. Preferred co-PPs have a total enthalpy of crystallization of less than 50 J / g, at melting points above 135°C, or even above 160°C.

[0056] Particularly suitable products can be found in the LyondellBasell ADFLEX series portfolio or in the Mitsui Chemicals TAFMER series. ExxonMobil's VISTAMAXX grades are also suitable.

[0057] In preferred embodiments of the invention, the co-PP can be partially replaced by other polymers, for example by LLDPE.

[0058] The polymer materials can withstand hot filling at up to 100 °C for up to 60 minutes.

[0059] Optionally, pigments, preferably inorganic pigments, can be added to the compound formulations to prevent pigment migration. It has also been shown that other additives such as (unsaturated) fatty acid amides, waxes, silicones, and other common additives can be added to the polymer compounds to improve, for example, processing and performance characteristics. The following describes exemplary embodiments of the invention based on the composition of the polymer compounds from which the vessel closure seal according to the invention was formed as described above: Example 1:

[0060] 40% co-PP 10% SEBS 47% OBC 3% lubricant

[0061] Example 2:

[0062] 30% co-PP, 40% SEBS, 30% LLDPE

[0063] Example 3:

[0064] 60% co-PP 40% SEBS

Claims

AMENDED CLAIMS received by the International Bureau on 13 November 2020 (13.11.2020) 1. Vacuum container screw cap, especially for fatty contents, with a container closure seal 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 TRS and at least one co-PP, b) and the polymer compound has a Shore A hardness (ASTM D2240, DIN ISO 7619-1) at 70°C between 30 and 85 and an MFR (DIN ISO 1133, 5kg / 190°C) of less than 20g / 10 min, and c) contains not more than 10% of components that are liquid at 20°C.

2. Vacuum container twist-off closure according to claim 1, wherein the polymer compound substantially does not comprise POE, 3. Vacuum container twist closure according to claim 1 or 2, wherein the polymer compound substantially does not comprise homo-PP.

4. Vacuum container twist-off closure according to one of claims 1 to 3, wherein the The polymer compound contains at least one SEBS, SEEPS or polybutene.

5. Vacuum container twist-off closure according to one of claims 1 to 4, wherein the The polymer compound comprises a linear XEB5 with styrene contents between 20% and 40%, preferably with styrene contents between 26% and 34%, specifically between 29% and 33%, and most preferably with 31% to 32% styrene.

6. Vacuum container twist-off closure according to one of claims 1 to 5, wherein the The polymer compound comprises at least 1%, specifically at least 5% and more preferably at least 10% TRX or 20%, more preferably at least 30% and most preferably at least 40% TRX.

7. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound comprises a TRX having a Shore A hardness (ASTM D2240, DIN ISO 7619-1) at 23°C of 50 to 90, preferably of 55 to 80.

8. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound comprises a co-PP with a Shore D hardness (ASTM D2240, DIN ISO 7619-1) at 23°C of less than 55, preferably below 45, particularly preferably below 40 and greater than 15, better greater than 20, particularly preferably greater than 30.

9. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound comprises a co-PP with an MFR of less than 30, more preferably less than 20, and even more preferably less than 10 g / 10 min measured at 2.16 kg / 230°C.

10. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound comprises a co-PP with MFR (2.16kg / 230°C) of at least 0.1, more specifically at least 0.3 and more specifically at least 0.5, and a maximum of 15, more specifically a maximum of 12 and more specifically a maximum of 10.

11. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound comprises a co-PP with a melting point of the co-PP below 165°C, more preferably below 160°C, most preferably below 150°C. AMENDED SHEET (ARTICLE 19) 12. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound comprises between 1% and 80%, preferably between 5% and 65% co-PP.

13. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound comprises at least one further polymer, in particular LLDPE, 14. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound contains no more than 10%, preferably no more than 7%, in particular no more than 4% and most preferably no more than 1% of lubricants.

15. Vacuum container screw cap according to one of the preceding claims, wherein the polymer compound contains no more than 7%, in particular no more than 4%, of components that are liquid at 20°C.

16. Vacuum container screw cap according to one of the preceding claims, which is pasteurizable, preferably also sterilizable.

17. Vacuum vessel twist-off closure according to one of the preceding claims, which exhibits vacuum retention.

18. Vacuum container twist closure according to one of the preceding claims, wherein the polymer compound has a DVR at 23°C (ASTM D395-97 Method B) of a maximum of 50%, more preferably a maximum of 40% and particularly preferably a maximum of 30%. AMENDED SHEET (ARTICLE 19)