Transparent backing compound

Abstract

A polymeric compound for a PVC-free sealing insert or liner of a container closure for a food or beverage container comprising: at least one hydrocarbon barrier polymer in an amount of 1 to 35 wt% based on the total compound, the at least one hydrocarbon barrier polymer being selected from styrene-isobutylene-butadiene-styrene (SIBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene / propylene-styrene (SEEPS), butyl rubber, and polyisobutylene (PIB); LDPE in an amount of 40 to 95 wt% based on the total compound weight; LLDPE and / or SEBS and / or olefin block copolymer (OBC), the total amount of (LLDPE and / or SEBS and / or OBC) being 0 to 30 wt% based on the total compound weight; a non-zero amount of oxygen scavenging material up to 2 wt% based on the total compound weight.

Description

Technical Field

[0001] This invention relates to PVC-free polymer composites, particularly for the production of linings, sealing elements, and fittings for container closures. When these PVC-free polymer composites are packaged in containers, such as beverage bottles, for oxygen-sensitive materials, such as food and especially beverages, they optimize the protection of such oxygen-sensitive materials from oxygen through a combination of inert oxygen-blocking substances and oxygen-binding substances (scavengers). More specifically, this invention relates to linings that exhibit improved resistance to loss of transparency, for example, due to becoming cloudy or turbid, and thus exhibit improved long-term transparency. Background Technology

[0002] Typical food or beverage containers include a closure to prevent loss or contamination of their contents. Also typically, this closure is lined with or formed of a sealing material that ensures a tight and durable seal between the container and the closure. Examples of such closures include crown stoppers, screw-on crowns, pull-tab closures, and screw caps.

[0003] The fundamental function of the complex discussed here is to create such sealing inserts or linings in container closures. This not only prevents leakage of the contents (including gases such as CO2 or N2), but also protects them from contamination by substances that the filled and sealed container may be exposed to, for example, during storage and transportation.

[0004] Therefore, container seals or linings are specifically designed to prevent oxygen from reaching the filler. Another important function is to limit the unwanted entry of volatile compounds, which can originate from, for example, the outer packaging, such as shrink wrap, cardboard, or wooden pallets. In particular, it is important to seal bottled beverages (beer, juice, mineral water) with caps to inhibit the entry of TCA (trichloroanisole) and other volatile organic carbon (VOC) compounds.

[0005] In conventional container seals, substances such as oxygen, TCA, etc., can enter the sealed container because the seal cannot prevent this. Contaminants migrate through the seal (e.g., due to their solubility in the compound) into the container and thus reach the filler. The opposite effect, where filler components seep into the seal, is also undesirable. This can be a problem for, for example, oily filler materials or flavored beverages.

[0006] General sealing materials for overcoming such problems are known from our prior application WO 2015 / 010718, the entire contents of which are incorporated herein by reference, particularly relating to the types and properties of polymers contained in the polymer complexes from which sealing materials are produced.

[0007] These compounds are typically PVC-free because PVC can cause problems during handling or incineration and may hinder the mechanical recycling of plastic waste. Soft PVC-based sealants often also contain plasticizers, which is a concern for health reasons. Known sealants generally have performance characteristics compatible with PVC-based linings and can therefore be used as alternatives to PVC-based seals.

[0008] A common practice is to use the container closure to provide information, such as the beverage manufacturer's name. For example, the exterior of the closure (e.g., the top outer surface of a crown stopper) can be used to display the manufacturer's name, the product's trademark, etc.

[0009] In industry, it is also desirable to utilize the inside of the enclosure (i.e., the side facing the contents) to provide information. This information becomes available to the user after the enclosure is removed from the container.

[0010] Therefore, it is known to provide a QR code on the inside of a closure with a transparent liner, for example, by printing the QR code on the surface of the closure facing the inside of the container. The print will remain in contact with the filled items because it is separated from these items by the transparent liner. If the liner is transparent enough, the QR code can be seen and scanned through the liner after the closure is removed from the container. It should be understood that the invention is not limited to the use of QR codes; in fact, it is not limited to any particular type of information, a particular type of closure, or a particular kind of packaging material.

[0011] However, the aforementioned technologies still have a variety of problems and drawbacks that may hinder their usefulness.

[0012] Scanning a QR code (or similar information item) through a closed liner requires the liner to be sufficiently transparent; otherwise, the scanner will not be able to scan the code clearly and completely.

[0013] The aforementioned WO 2015 / 010718 discloses lining materials typically suitable for such scans. These lining materials also provide highly improved protection against oxygen ingress. However, in some cases, the lining material may become less transparent over time, apparently due to deterioration of the material used in the lining. While this generally does not affect the sealing and oxygen-barrier properties of the lining, it makes it less transparent than expected during scanning, especially after prolonged storage.

[0014] Therefore, a universal liner that remains transparent for a longer period of time is required. We have found that increased long-term transparency can be provided by appropriately selecting the type and amount of polymer and by including a cleaning agent material in the composite from which the liner is produced. Summary of the Invention

[0015] The appended independent claims define suitable compounds that can be used for such linings. The appended dependent claims define advantageous embodiments of such compounds.

[0016] In the following text, a polymer complex, or simply a complex (as is commonly used in industry), is understood as a blend of one or more polymers with other components (e.g., viscosity modifiers, extenders, fillers, pigments, scavengers, antioxidants, lubricants) used to adjust desired application properties. These application properties relate to the behavior of the complex from its preparation to its use in the production of container closures (e.g., when placed in a closure preform to produce a sealing insert), and the properties of the closure during container filling and storage and its intended use by consumers (e.g., opening, removing beverages or food, resealing the container).

[0017] The composite of the present invention is essentially composed of a mixture of substances containing at least two or more different polymers, and in some cases, conventional additives (antioxidants, lubricants, pigments, etc.), wherein a certain amount of scavenging material is added to the mixture of substances.

[0018] The composite of the present invention comprises at least one chemically uncrosslinked rubbery polymer. Hydrocarbon polymers such as butyl rubber, polyisoprene, polyisobutylene, SIBS (styrene-isobutylene-butadiene-styrene block copolymer), or polybutene can be used for this purpose.

[0019] One or more rubbery polymers can provide sufficient barrier properties, as with SIBS. If the rubbery polymer cannot provide sufficient barrier properties, such properties are typically provided by adding a suitable non-rubbery polymer. Polyolefins, such as certain LLDPEs, can be used for this purpose.

[0020] Within the scope of this invention, a barrier polymer is a polymer that is not mixed with other substances and provides a film thickness of 100 μm and a resistance of less than 2000 cm⁻¹ at 23°C and 100% relative humidity. 3 / m 2 .d as defined in ISO 15105-2 OTR.

[0021] SIBS is preferred as the barrier polymer.

[0022] The overall barrier properties of the composite should enable it to provide a film thickness of 100 μm and a barrier strength of less than 2000 cm⁻¹ at 23°C and 100% relative humidity. 3 / m 2 .d as defined in ISO 15105-2 OTR.

[0023] To achieve the desired hardness (and other properties), the composite preferably also contains a thermoplastic polymer, particularly a polyethylene-based thermoplastic polymer. More specifically, in addition to a barrier polymer such as SIBS, the composite preferably contains a polyolefin as a hardness modifier for the composite. Typically, this is based on LDPE and forms the main component of the composite.

[0024] The composite may also contain an LLDPE component, particularly an LLDPE component produced using metallocene technology. In some preferred embodiments, the LLDPE component incorporates a copolymer, particularly a copolymer with octene as a comonomer.

[0025] In other preferred embodiments, the polyolefin component comprises SEBS (especially at low molecular weights, e.g., a solution viscosity of about 550 cP or less in toluene for 20 wt% SEBS) and / or SE(E)PS. Preferably, the composite using the SEBS softener contains less than 1 wt% oil or no oil at all. Preferred composites with the SBS softener may contain up to 10 wt% and preferably less than 10 wt% oil (unless otherwise explicitly defined, all percentages of composition in this specification are by weight).

[0026] The relative total content of polyolefins is preferably higher than the relative total content of the barrier polymer, especially SIBS. In a particularly preferred embodiment, the relative content of SIBS is higher than 5% by weight and lower than 30% by weight. More preferably, the relative content of SIBS is from 5% by weight to 15% by weight, especially about 10% by weight. In contrast, the relative total content of polyolefins is generally at least 30% by weight, preferably at least 50% by weight and optionally at least 70% by weight or more (always based on the total weight of the final composite).

[0027] A particularly preferred embodiment has about 10% by weight of the barrier complex, especially SIBS; about 15% by weight of LLDPE and at least 70% by weight of LDPE. The LLDPE content can be 0% by weight, that is, LLDPE can be completely absent, but more preferably has a minimum (non-zero) content of LLDPE.

[0028] In some preferred embodiments, LLDPE is partially replaced by SEBS and / or SBS. Preferably, the relative amount of SEBS and / or SBS is less than the relative amount of LLDPE. The total amount of non-LDPE polyolefin is preferably up to 30% by weight, and preferably less than 20% by weight.

[0029] Typically, the physical properties (hardness, elasticity) of the composite correspond to the physical properties of the composite disclosed in WO2015 / 010718 A1 above. In a preferred embodiment, the Shore D hardness of the composite is less than 45. The barrier properties can be defined according to the oxygen permeability (OTR), which is determined, for example, using a Mocon OX-TRAN 2 / 60 device at 23°C and 100% relative humidity and normalized to a film thickness of 100 μm. The relative amount of the barrier polymer in the composite is typically as high as 20% by weight, preferably from 5% to 15% by weight, and most preferably about 10% by weight.

[0030] The polymer composite of the present invention contains a scavenging component that specifically inhibits oxygen from approaching or entering packaged food or beverages.

[0031] Inorganic sulfites, such as sodium sulfite, are particularly suitable as such scavengers. Other known scavengers, such as ascorbic acid, may also be used. Suitable scavenger materials, for example in terms of type, quantity and application, are described in our application WO 2011 / 069520, which is incorporated herein by reference.

[0032] As is known from WO 2011 / 069520, the use of PVC-free polymeric composites containing added oxygen-consuming components (which are a scavenger) is particularly beneficial for spiral crown caps. Preferably, these components are sulfite particles with a specific average particle size. The reduction in oxygen ingress is achieved through sulfites, while the composite itself (i.e., regardless of its scavenger content) does not actually need to possess any specific barrier function.

[0033] The compounds mentioned in WO 2011 / 069520 are based on polypropylene and polyethylene (especially LDPE and LLDPE) and SEBS contents. SEBS does not have useful barrier properties. These compounds contain a significant amount of oil. In this embodiment, white oil, at 34%, is the largest single component. This oil content is necessary to obtain the desired physical parameters of the compound.

[0034] However, for many applications, any such oil content in container seals is undesirable. Oil can facilitate the migration of substances into and through the container seal, reducing its barrier properties. The resulting increased entry of oxygen and other volatiles can negatively impact product characteristics.

[0035] To suppress such effects, WO 2011 / 060803 proposes, for example, oil-free compounds, especially when using fatty contents. However, the barrier properties, optionally improved by scavenging agents, are ineffective. In WO 2011 / 06083, the durable transparency of the lining is also not an issue.

[0036] The cleaning agent content of the composite of the present invention is preferably low, typically from 0.2% to 2% by weight, more preferably from 0.5% to 1.5% by weight. Using as little cleaning agent as possible is considered advantageous, as the cleaning agent content may lead to a loss of transparency in the lining made of the composite. Detailed Implementation

[0037] Comparative tests have been conducted to illustrate various aspects of the invention. In these tests, four different lining compositions were prepared from commercially available materials. The composites formed from these materials were used as linings in conventional crown stopper closures on conventionally filled bottles (beer, and mineral water) so that the lining material remained in contact with the filled article.

[0038] The inside of the enclosure provides information, namely a QR code (15 mm × 15 mm) printed on the surface of the primer layer applied to the lining in the conventional manner.

[0039] Tests were conducted to determine whether the closure provided the expected oxygen barrier properties and whether the QR code could be successfully scanned through the liner after the container was opened by removing the closure at intervals extended up to 6 months after capping (typical beer shelf life).

[0040] Use a commercially available smartphone with a scanning function to scan the code. The QR code contains an internet link to an internet address. If the phone can successfully use the link to contact that address, the scan is considered mobile-readable.

[0041] The results can be seen in the table below:

[0042]

[0043] (All quantities above are based on the weight percentage of the total complex.)

[0044] In Example 1, the scan was successful, but the blocking effect of the complex was insufficient.

[0045] In Example 2, a blocking effect is provided, but the liner is too opaque for scanning.

[0046] In Example 3, the composite was not blocking enough, and the liner was too opaque for scanning.

[0047] Example 4 is one embodiment of the present invention. It provides sufficient barrier effect (below 2000 cm² at a thickness of 100 μm, 23°C, and 100% relative humidity). 3 / m 2 It can be used for OTR (.d files) and scanning is possible.

[0048] The compounds of this invention can be used in all kinds of bottle closures, such as crown stoppers, screw crowns, aluminum closures, and caps (e.g., plastic caps with internal threads). They can also be used in pull-tab caps and similar closures.

[0049] Implementation Plan Examples

[0050] SIBS 10% by weight

[0051] Metallocene-catalyzed LLDPE, C8 15% by weight

[0052] LDPE 73% by weight

[0053] 2% by weight of conventional additives

[0054] Liners with good sealing properties can be prepared from the composites in the implementation examples. These linings have and maintain scan suitability for the required duration (i.e., more than one month under typical use conditions).

Claims

1. A PVC-free sealing insert or liner for a container closure body for food or beverage containers, comprising: The amount is 5% to 15% by weight of styrene-isobutylene-butadiene-styrene (SIBS) based on the total complex. The amount is 65% to 95% by weight of LDPE based on the total weight of the composite; The total amount of LLDPE and / or SEBS and / or olefin block copolymers (OBC) is from 0% to 30% by weight based on the total weight of the composite. The oxygen scavenging material has a non-zero amount of up to 2% by weight of the total composite weight.

2. The composite according to claim 1, wherein the oxygen transmissibility (OTR) of the styrene-isobutylene-butadiene-styrene (SIBS) to a 100 μm thick film at 23°C and 100% relative humidity is less than 2000 cm⁻¹. 3 / m 2 .d.

3. The composite according to claim 2, comprising styrene-isobutylene-butadiene-styrene (SIBS) having a styrene content of less than 31% by weight.

4. The complex according to any one of claims 1 to 3, wherein the amount of LLDPE and / or SEBS and / or OBC is non-zero.

5. The complex according to any one of claims 1 to 3, comprising C4 to C8 LLDPE.

6. The complex according to claim 5, wherein the amount of C4 to C8 LLDPE is 5% to 15% by weight based on the total complex.

7. The composite according to claim 5, wherein the C4 to C8 LLDPE is a random copolymer of polyethylene and octene.

8. The complex according to any one of claims 1 to 3, comprising at least 70% by weight of LDPE based on the total complex.

9. The complex according to any one of claims 1 to 3, comprising not more than 15% by weight of a substance that is liquid at a pressure of 1 bar and at 20°C.

10. The complex according to any one of claims 1 to 3, comprising not more than 10% by weight of a substance that is liquid at a pressure of 1 bar and at 20°C.

11. The complex according to any one of claims 1 to 3, comprising not more than 5% by weight of a substance that is liquid at a pressure of 1 bar and at 20°C.

12. The complex according to any one of claims 1 to 3, comprising not more than 1% by weight of a substance that is liquid at a pressure of 1 bar and at 20°C.

13. The complex according to any one of claims 1 to 3, having no substance at a pressure of 1 bar and at 20°C within a suitable analytical detection limit.

14. The complex according to any one of claims 1 to 3, comprising 0.5% to 2% by weight of sodium sulfite as the oxygen scavenging material based on the total complex.

15. The complex according to claim 14, wherein the average particle size of the sodium sulfite, as determined by laser diffraction, is about 10 μm.

16. The complex according to any one of claims 1 to 3 further comprises an amount of up to 35% by weight of ethylene / octene-based OBC based on the total complex.

17. A PVC-free enclosed liner made from a compound as defined in any one of claims 1 to 16.

18. A container closure comprising a liner made of a composite as defined in any one of claims 1 to 16.

19. The container enclosure according to claim 18, wherein the container is a beer bottle.

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