Patent Application
20240140665
This invention relates to the scavenging of oxygen and particularly, although not exclusively, relates to the scavenging of oxygen in containers, for example food or beverage containers.
Polymers such as poly(ethylene terephthalate) (PET) are versatile materials that enjoy widespread use for fibres, films and three-dimensional structures. A particularly important application for polymers is for containers, especially for food and beverages. This application has seen enormous growth and continues to enjoy increasing popularity. Despite this growth, polymers have some fundamental limitations that restrict their applicability. One such limitation is that all polymers exhibit some degree of permeability to oxygen. The ability of oxygen to permeate through polymers such as PET into the interior of the container is a significant issue, particularly for foods and beverages that are degraded by the presence of even small amounts of oxygen. For the purpose of this disclosure, permeable means diffusion of small molecules through a polymeric matrix by migrating past individual polymer chains, and is distinct from leakage, which is transport through macroscopic or microscopic holes in a container structure.
To address the aforementioned problem, products may be packaged in plastic packages which incorporate passive barriers to oxygen and/or oxygen scavengers. Generally, greater success has been achieved utilizing oxygen scavengers; however, oxygen scavenging materials heretofore have suffered from a number of issues. Some oxygen scavengers utilized to date rely on the incorporation of an oxidizable solid material into the package. Technologies utilized include oxidation of iron (incorporated either in sachets or in the container sidewall), oxidation of sodium bisulfite, or oxidation of an oxidizable polymer (particularly poly(butadiene) or m-xylylenediamine adipamide). All of these technologies suffer from slow rates of reaction, limited capacity, limited ability to trigger the scavenging reaction at the time of filling the container, haze formation in the package sidewall, and/or discoloration of the packaging material. These problems have limited the use of oxygen scavengers in general, and are especially significant for transparent plastic packaging (such as PET) and/or where recycling of the plastic is considered important.
Applicant's publication number WO2008/090354A1 discloses a container comprising an active substance which is incorporated in the container and is arranged to react with moisture in the container to release molecular hydrogen. The document describes a wide range of potential active substances including metals and/or hydrides, with sodium borohydride being exemplified as the active material which is arranged to generate hydrogen by reaction with water. The hydrogen released reacts, in the presence of a Group VIII metal, preferably palladium or platinum, catalyst in the closure or bottle wall with ingressing oxygen in the container, to produce water.
WO2010116192 addresses a problem associated with use of sodium borohydride described in WO2008090354A, in that sodium borohydride can react with aldehydes which are important flavour components of foods and beverages. An increased loss of these flavour components by reaction with the active substance may have a detrimental effect on the flavour of the food or beverage—i.e. the flavour is scalped and such scalping may get worse over time. To address this problem, WO2010116192 proposes use of calcium hydride. However, even when using calcium hydride, it cannot be ruled out that reaction of flavour components will not produce “non-intentionally-added-substances” (NIAS).
Even though calcium hydride is a non-reducing hydride, it has been found that, when catalyst is in the vicinity of hydrogen being generated, flavour molecules may migrate and be catalytically reduced, with a risk that NIAS may be produced. For example, if a packaged food or beverage contains benzaldehyde then, in the presence of hydrogen and catalyst, there is a possibility the benzaldehyde could react to produce benzyl alcohol which may theoretically further react to produce toluene. If this happened, toluene would be an undesirable NIAS. Preferred embodiments of the present invention have, as one object, the mitigation of any perceived risk of production of NIAS by catalytic reaction of components in a contained food or beverage.
In addition to the aforesaid, Applicant has previously described how, when palladium catalyst is distributed in the wall of a PET container for catalysing the reaction of hydrogen and oxygen, for example as described in WO 2008/090354A1, there is a risk the catalyst may be poisoned by constituents of the resin. This problem may be particularly acute for PET resins made using an antimony-based catalyst, since the antimony tends to poison the palladium catalyst. This problem has made it difficult to exploit the oxygen scavenging invention described in WO 2008/090354A1 using containers comprising PET resins made using an antimony-based catalyst. It is an object of preferred embodiments of the present invention to address the aforesaid problem.
Thus, it is an object of preferred embodiments of the present invention to address the above described problems.
According to a first aspect of the invention, there is provided a closure for a container, the closure comprising:
According to a second aspect of the invention, there is provided a container comprising:
Unless otherwise stated, a reference to “ppm” herein refers to “parts per million” by weight.
For purposes of this disclosure, a container suitably includes any package that surrounds a product and that contains no intentional microscopic or macroscopic holes that provide for transport of small molecules between the interior and the exterior of the package.
In the first aspect, the TPV may be the amount of toluene in mg calculated as described when the closure is subjected to the following process:
When the closure does not include a closure shell and may for example comprise a film and/or laminate, the film and/or laminate in a substantially flat state is fully immersed in said benzaldehyde solution in a container, wherein the cross-sectional area of the container in which the film and/or laminate is positioned is only slightly greater (eg no more than 10% greater area) than the cross-sectional area of the film and/or laminate. For example, such a film and/or laminate may be positioned as shown in
Steps (i) to (iv) are undertaken at ambient temperature which may be fixed at 20° C.
Steps (i) to (v) may be repeated, except that step (iii) is extended to 72 hours to calculate TPV after that time.
The TPV per unit area (herein the “TPV-UA”) of said closure may be less 0.00200 mg/cm2 (preferably less than 0.00150 mg/cm2, after 24 hours; and/or the TPV per unit area of said closure may be less than 0.01000 mg/cm2 (preferably less than 0.00500 mg/cm2, more preferably less than 0.0045 mg/cm2) mg/cm2 after 72 hours, wherein:
The following statements apply to the first and/or second aspects.
Said barrier means is suitably positioned between a position in said container wherein product is contained in normal use and said catalyst. Preferably, the barrier means is arranged so that there is substantially no path for passage of a component of a product contained in use in said container to the catalyst except via said barrier means.
Preferably, substantially the entirety of said catalyst is shielded from product and/or components thereof contained in use in said container by said barrier means, preferably so there is substantially no path unimpeded by said barrier means for passage of product and/or components thereof to said catalyst.
Preferably, the distance between catalyst and barrier means is less than 10 mm, less than 5 mm or less than 1 mm. In some case, the catalyst and barrier means abut so the distance may be zero mm.
Preferably, at least 80 wt %, more preferably at least 95 wt %, especially at least 99 wt % of said catalyst in said container is within a linear distance of less than 10 mm or less than 5 mm or less than 2 mm of said barrier means.
Preferably, said barrier means comprises:
Preferably, said barrier means is arranged to restrict passage of organic molecules as described based on physical properties, for example of organic molecules relative to the barrier means. Benzaldehyde may be used as a reference material for organic molecules as descried herein, in which case, said barrier means is suitably arranged to restrict passage of benzaldehyde molecules.
Said barrier means is preferably arranged to restrict passage of organic molecules, for example, benzaldehyde, on the basis of a physical property of said barrier means. Said physical property may be based on size or may be based on polarity of the barrier means.
When the function of said barrier means to restrict organic molecules, for example benzaldehyde, is based on size, said barrier means may be porous with the pore size being such as to restrict, for example, exclude organic molecules, for example benzaldehyde; but, preferably, the pore size is such as to allow passage of other desired molecules, for example oxygen, hydrogen and water as described herein.
When the function of said barrier means to restrict organic molecules, for example benzaldehyde, is based on polarity, said barrier means may have a sufficiently different polarity compared to the polarity of organic molecules, especially benzaldehyde (suitably used as a reference, irrespective of whether a product contained, in use, in the container includes benzaldehyde).
When said barrier means is as described in (AA), said barrier means may restrict passage of organic molecules, especially benzaldehyde, due to the difference in the HSP of the barrier means compared to benzaldehyde which has a HSP of 19.2 MPa1/2. Preferably, the difference between the HSP of benzaldehyde and a barrier material of said barrier means is at least 3.2 MPa1/2, preferably at least 4.0 MPa1/2. Said difference may be less than 10 MPa1/2 or less than 7.0 MPa1/2.
Said barrier material of said barrier means may have a HSP of less than 16.0 MPa1/2, preferably less than 15.8 MPa1/2, more preferably less than 15.6 MPa1/2 and, especially, less than 15.2 Mpa1/2. In some cases, said HSP may be less than 14.0 MPa1/2 or less than 13.2 MPa1/2. Said barrier material may have a HSP of at least 5.0 MPa1/2, preferably, at least 8.0 MPa1/2, more preferably at least 10.0 MPa1/2.
Said barrier means may comprise a layer of said barrier material. Said layer is preferably substantially continuous. Said layer suitably has a thickness of less than 1 mm, preferably less than 0.5 mm. In some case, for example wherein a barrier material surrounds individual particles of catalyst so that a mass of composite particles is defined, said layer may be less than 0.1 mm or preferably less than 0.01 mm. Said layer preferably has a thickness which varies by less than 1mm across its extent. Preferably, the ratio of the maximum thickness of said layer divided by the minimum thickness of said layer is less than 2.0. Said layer preferably has a substantially constant thickness across its extent.
In an embodiment (A1), said layer may be in a lamina form. For example, said layer may not be endless. It may have at least one end. It may have at least one edge. The end or edge is suitably an outer surface of the layer (e.g. which defines the thickness of the layer), wherein the end or edge extends transverse to, for example perpendicular to, a main area of the layer, wherein the main area of the layer is suitably defined by a surface of the layer which has the greatest area. Said main area may have an area of at least 2 cm2 or at least 3.5 cm2. Said layer may have first and second spaced apart ends.
A said layer in accordance with embodiment (A1) may be arranged as a layer in a closure of the container or may be a layer of a container body of said container. Said layer may comprise a fluorinated polymer as described in Example 17 et seq.
In an embodiment (A2), said layer may define a coating, for example, an enclosure, suitably on and/or around catalyst for example catalyst particles. Said layer may be endless. It may be continuous. It may fully enclose catalyst. Said layer may have a thickness of no greater than 0.01 mm, preferably across substantially its entire extent. Said layer may define a barrier material which surrounds individual particles of catalyst so that a mass of composite particles is defined, each of which composite particles comprises catalyst surrounded by said barrier material. Said layer may comprise a fluorinated polymer as described in Example 23; or may comprise a silicone-based material, for example one made using a platinum catalyst such as a dimethicone polymer, manufactured using a platinum catalyst in a hydrosilylation reaction.
When said barrier means is as described in (BB), said porous material is suitably selected to restrict passage of organic molecules, especially benzaldehyde, on the basis of the size of pores in the porous material relative to the size of organic molecules, especially benzaldehyde (suitably used as a reference compound). Preferably, said porous material is selected to allow and/or not substantially act as a barrier to hydrogen, oxygen and water molecules. Thus, said barrier means may restrict passage of organic molecules, especially benzaldehyde, to the catalyst associated with the barrier means, whilst allowing passage of hydrogen and oxygen to catalyst and water away from the catalyst.
Said catalyst is preferably embedded in the porous material, for example in a pore structure thereof. Said porous material is suitably microporous and suitably includes pores with free diameters of less than 2 nm. The pores may have free diameters of at least 0.4 nm.
Said porous material is preferably inorganic.
Said porous material preferably has a zeolithic structure.
Said porous material may have a relatively hydrophilic internal environment. Said porous material may comprise a zeolite with a Si/Al ratio of less than 2. Said porous material may comprise, preferably consists essentially of, a zeolite which may be selected from NaX, CaX or CaA zeolites.
Said porous material preferably includes at least 0.05 wt %, for example at least 0.15 wt % of catalyst. The amount of catalyst in said porous material may be less than 1.00 wt % or less than 0.50 wt %.
When said barrier means is as described in (CC), said barrier material of said barrier means may restrict passage of organic molecules, especially benzaldehyde, due to a physical property of the barrier means wherein, suitably, the physical property is based on size or polarity differences between molecules it is desired to allow to pass through the barrier material and organic molecules (especially benzaldehyde), the passage of which through the barrier material is to be restricted. Said barrier material may have a HSP as described in (AA) or may have porosity, for example as described with reference to the barrier material described in (BB).
Said barrier material (and suitably associated catalyst) may be associated with a polymeric material (XX). Polymeric material (XX) is preferably not the same as any polymeric material which may be a component of said barrier material and/or said barrier means. When said barrier material has a HSP of less than 16.0 MPa1/2, said polymeric material (XX) preferably has a HSP which is higher than the HSP of the barrier material and/or is greater than 16.0 MPa1/2, preferably greater than 16.1 MPa1/2, more preferably greater than 16.5 MPa1/2. The difference between the HSP of polymeric material (XX) and the HSP of the barrier material may be at least 0.5 MPa1/2, preferably at least 1.0 MPa1/2, more preferably at least 1.5 MPa1/2.
Said polymeric material (XX) may have a HSP in the range 16.1 to 30.0 MPa1/2. Said polymeric material (XX) preferably defines a layer, for example, of a closure.
Said barrier material may be associated with said polymeric material (XX) in a number of different ways. In an embodiment (B1), said barrier material may be distributed, for example, dispersed, within polymeric material (XX). In this case, a combination comprising said barrier material and associated catalyst may be dispersed in said polymeric material (XX).
In an example (B1-i), the barrier means may be as described in (AA), for example as described in embodiment (A2), and may comprise a layer of said barrier material and said layer may define a coating, for example, an enclosure, suitably around catalyst, for example catalyst particles. The aforementioned combination of barrier material and catalyst may be distributed, for example dispersed within polymeric material (XX).
In an example (B1-ii), the barrier means may be as described in (BB) and porous material and associated catalyst may be distributed, for example dispersed within, polymeric material (XX). Preferably, as described with reference to (BB), the catalyst is embedded in the pore structure of the porous material which suitably has a zeolithic structure. The combination of catalyst and porous material is preferably dispersed in polymeric material (XX).
In an alternative embodiment (B2) wherein barrier material and said polymeric material (XX) are associated, said barrier material may overlie the polymeric material (XX) and may contact, for example make face-to-face contact with, said polymeric material (XX). In some cases, said barrier material and said polymeric material (XX) may define distinct and/or separable layers. For example, said barrier material may be as described in (AA) and said polymeric material (XX) may be different to said barrier material. In another case, for example wherein said barrier means and/or barrier material is defined by functionalising (e.g. fluorinating) a surface region of a polymeric material (XX) (e.g. as described in Example 17 hereafter), there may be no distinct layer of barrier material which can be separated from polymeric material (XX).
In embodiment (B2), catalyst may be dispersed in one or both of said barrier material and polymeric material (XX). It is suitably dispersed in both materials.
Polymeric material (XX) may be selected from HDPE, PP, LLDPE, LDPE, PS, PET, EVA, SEBS, Nylon (e.g. Nylon-6), thermoplastic elastomers (TPEs) and olefinic block copolymers (OBCs) and mixes of these and other polymers. Polymeric material (XX) is preferably a polyolefin polymer for example a polyethylene.
In a preferred embodiment, said barrier material does not comprise HDPE, PP, LLDPE, LDPE, PS, PET, EVA, SEBS, Nylon (e.g. Nylon-6), thermoplastic elastomers (TPEs) or olefinic block copolymers (OBCs).
Said catalyst may be associated with a closure of the container and/or may be associated with a container body of the container. Preferably, said container comprises a closure and a container body. The container body suitably defines a volume in which a product is contained, in use, in the container; and said closure cooperates with the container body to close and/or seal the container. In some cases, said closure may be releasably securable to the container body in which case, suitably, the closure and container body are screw-thread to allow screw-threaded engagement of the closure to the container body. Alternatively, said closure may not be releasable securable and/or may be a single use closure such as may be defined by a film closure which is adhered to the container body. Such a film closure may be associated with a tray or may comprise a foil liner which is arranged to close a bottle, such as a ketchup bottle or the like.
The shape, construction, or application of the containers described is not critical. In general, there is no limit to the size or shape of a container. For example, the container may be smaller than 1 milliliter or greater than 1000 liter capacity. The container preferably has a volume in the range 20 ml to 100 liter, more preferably 100 ml to 5 liter or 100 ml to 2 liter. A container may be selected from a sachet, bottle, jar, bag, pouch, tray, pail, tub, barrel or blister pack. Preferably, said container is a bottle or tray.
Said catalyst is selected to catalyse the reaction between molecular hydrogen and molecular oxygen, to produce water. A large number of catalysts are known to catalyze the reaction of hydrogen with oxygen, including many transition metals, metal borides (such as nickel boride), metal carbides (such as titanium carbide), metal nitrides (such as titanium nitride), and transition metal salts and complexes. Of these, Group VIII metals are particularly efficacious. Of the Group VIII metals, palladium and platinum are especially preferred because of their low toxicity and extreme efficiency in catalyzing the conversion of hydrogen and oxygen to water with little or no by-product formation. The catalyst is preferably a redox catalyst.
Unless otherwise stated, the amounts (e.g. ppm, wt %, etc.) of catalyst referred to herein are the amounts of active species, for example metal, which are able to catalyse the reaction between molecular hydrogen and molecular oxygen, excluding any coordinated groups. Thus, when palladium acetate is used to deliver palladium, the ppm, wt %, etc. referred to herein refer to the ppm or wt % etc., of palladium delivered, excluding the acetate moieties.
Said catalyst is preferably a metal, preferably a transition metal, preferably selected from Group VIII metals, for example palladium and platinum.
Suitably, references to catalyst for catalysing a reaction between hydrogen and oxygen refer to all such catalysts, even if different types of such catalyst are included in said container. However, preferably said container includes a single type of catalyst.
A reference to “ppm” herein refers to “parts per million” by weight.
Said hydrogen generating means suitably includes a matrix material with which said active material is associated. In this case, the ratio of the weight of active material to matrix material may be at least 0.01, preferably at least 0.02. Preferably, the matrix comprises a polymeric matrix and said active material is dispersed therein. In general, once an active material is dispersed into a polymer, the rate of release of hydrogen is limited by the permeation rate of water into the polymeric matrix and/or by the solubility of water in the chosen matrix. Thus, selection of polymeric materials based on the permeability or solubility of water in the polymer allows one to control the rate of release of molecular hydrogen from active materials. However, by selection of appropriate control means, the rate determining step for release of hydrogen may be determined by properties of said control means, as described herein.
The matrix may include at least 1 wt % of active material, preferably at least 2 wt %. The matrix may include less than 70 wt % of active material. Suitably, the matrix includes 1-60 wt %, preferably 2-40 wt % of active material, more preferably 4-30 wt % of active material. The balance of material in the matrix may predominantly comprise a said polymeric material. It may include other additives, for example fillers (e.g. oils) and materials to make the appearance of the matrix appear more visually uniform.
Said active material may comprise a metal and/or a hydride. A said metal may be selected from sodium, lithium, potassium, magnesium, zinc or aluminum. A hydride may be inorganic, for example it may comprise a metal hydride or borohydride; or it may be organic.
Active materials suitable for the release of molecular hydrogen as a result of contact with water include but are not limited to: sodium metal, lithium metal, potassium metal, calcium metal, sodium hydride, lithium hydride, potassium hydride, calcium hydride, magnesium hydride, sodium borohydride, and lithium borohydride. While in a free state, all of these substances react very rapidly with water; however, once embedded into a polymeric matrix, the rate of reaction proceeds with a half-life measured in weeks to months, for example when stored at ambient temperature.
Selection of suitable active substances for incorporation into a polymeric matrix can be based on a number of criteria, including but not limited to cost per kilogram, grams of H2 generated per gram of active substance, thermal and oxidative stability of the active substance, perceived toxicity of the material and its reaction byproducts, and ease of handling prior to incorporation into a polymeric matrix. Of the suitable active substances, hydrides are preferred; sodium borohydride is exemplary because it is commercially available, thermally stable, of relatively low cost, has a low equivalent molecular weight, and produces innocuous byproducts (sodium metaborate).
Calcium hydride is the most preferred active substance. Preferably, said hydrogen generating means comprises calcium hydride. Preferably, said hydrogen generating means comprises calcium hydride dispersed in said polymeric matrix. Preferably, the polymeric matrix includes at least 10 wt % or at least 20 wt % of calcium hydride. Said polymeric matrix preferably includes 10 to 35 wt %, more preferably 18 to 28 wt % of calcium hydride; and preferably includes 65 to 90 wt %, more preferably 72 to 82 wt %, of said polymeric matrix. A preferred polymeric matrix is a polyolefin, with polyethylene being especially preferred.
Preferably, a closure of said container includes said hydrogen generating means.
Said container preferably includes a control means for controlling the passage of moisture, for example water or water vapour (e.g. from a product contained in the container) to said active material arranged to generate molecular hydrogen. Providing a control means as described introduces substantial flexibility which allows control of the rate of production of hydrogen by the hydrogen generating means and tailoring of the time over which hydrogen is generated, which determines the shelf-life of the container. For example, to achieve a long shelf-life a relatively large amount of active material may be associated with a matrix and by controlling passage of moisture to the hydrogen generating means, the rate of hydrogen generation is controlled as is the rate of consumption of the active material. In contrast, in the absence of the control means, the relatively large amount of active material would produce hydrogen at a quicker rate and would be consumed quicker meaning the shelf-life of the container would be less.
Said control means is preferably arranged to control a first evolution ratio, wherein the first evolution ratio is defined as:
Said first evolution ratio is suitably less than 4, preferably less than 3, more preferably less than 2. The ratio is suitably greater than 0.5, preferably greater than 0.8, and more preferably 1 or greater.
Said selected initial 5 day period may be within 45 days, suitably within 30 days, 15 days, 10 days or 5 days of filling of the container, for example with a beverage.
Said control means is preferably arranged to control a second evolution ratio, wherein the second evolution ratio is defined as:
Said second evolution ratio is suitably less than 4, preferably less than 3, more preferably less than 2. The ratio is suitably greater than 0.5, preferably greater than 0.8, and more preferably 1 or greater
Said control means is preferably arranged to control a third evolution ratio, wherein the third evolution ratio is defined as:
Said third evolution ratio is suitably less than 4, preferably less than 3, more preferably less than 2. The ratio is suitably greater than 0.5, preferably greater than 0.8, and more preferably 1 or greater.
Both the first and second evolution ratios may apply. Preferably, the first, second and third evolution ratios apply.
Suitably, in said container, the only path for passage of moisture, in use, from product in the container to the hydrogen generating means is via said control means. Said control means preferably defines an uninterrupted barrier between the hydrogen generating means and a source of moisture in the container.
Unless otherwise stated, water permeability described herein is measured using (American Society for Testing Materials Annual Book of Standards) ASTM procedure E96 Procedure E at 38° C. and relative humidity of 90%.
A said control means is suitably selected so that it defines the rate determining step for passage of moisture, for example water vapour, from a product in the container to the active material. Suitably, the rate of passage of moisture through the control means, towards the hydrogen generating means, is no faster than (e.g. it may be slower than) the rate of passage of water through the hydrogen generating means (e.g. through a matrix material thereof). Preferably, to achieve the aforesaid, the ratio of the water vapour permeability (g·mm/m2·day) of the control means divided by the water vapour permeability of the matrix material may be 1 or less, preferably 0.75 or less, more preferably 0.5 or less. In some situations, the control means and said matrix material comprise the same material, in which case the water vapour permeability through the respective materials may be substantially the same. In other situations, water vapour permeability of the control means may be such that the rate of passage of moisture through the control means, towards the hydrogen generating means, is faster than the rate of passage through the hydrogen generating means. Nonetheless in such situations the control means is still found to exercise control over hydrogen generation because the moisture “backs up” in the material of the control means; and it is found that the rate of hydrogen generation in the presence of such a control means is less than in the absence of such a control means.
In one embodiment, the ratio of the water vapour permeability (g·mm/m2 day) of the control means divided by the water vapour permeability of the matrix material of the hydrogen generating means is 15 or less, 10 or less, 3 or less, or 2.6 or less. It may be in the range 0 to 15, 0 to 10 or 0 to 3.
At least part of said control means is preferably provided in a first layer. A second layer may comprise said hydrogen generating means. Said second layer may abut and/or contact (e.g. make face to face contact with) the first layer. Where the control means includes more than one layer, part of the control means may be defined by said first layer and part defined by another layer.
Said second layer may incorporate hydrogen generating means which may comprise a matrix with which said active material is associated, for example embedded or preferably dispersed. Said matrix may comprise a matrix material, for example a polymeric matrix material. Suitable matrix materials have a water vapour permeability of greater than 0.1 g·mm/m2·day, suitably greater than 0.2 g·mm/m2·day, preferably greater than 0.4 g·mm/m2·day, more preferably greater than 0.6 g·mm/m2·day, and especially greater than 0.8 g·mm/m2·day. In some cases, said water vapour permeability may be greater than 1.0 g·mm/m2·day. Said matrix material may comprise a blend comprising, for example, at least two polymeric materials. The water vapour permeability of said matrix material may be less than 5 g·mm/m2·day, less than 4 g·mm/m2·day or less than 3 g·mm/m2·day. Suitable polymeric matrix materials include but are not limited to ethylene vinyl acetate, styrene-ethylene-butylene (SEBS) copolymers, Nylon 6, styrene, styrene-acrylate copolymers, polybutylene terephthalate, polyethylene and polypropylene.
As described above, said catalyst may be associated with a closure of the container and/or may be associated with a container body of the container. When said catalyst is associated with a closure, said catalyst is preferably provided in a layer of said closure. When said closure includes a first layer and a second layer as described, said catalyst may be provided in said first and/or second layers and/or provided in a layer (e.g. a third layer) which may be as described in embodiment (A1). In any case, preferably, a barrier means, for example barrier material, is provided between a container body in which product is contained, in use, and catalyst in the closure, wherein said barrier means, for example barrier material, is suitably an integral part of the closure and, therefore, is removed from association with the container body if the closure is disengaged from the container body. Said barrier means may be as described in (AA), (BB) and/or (CC). When said barrier means comprises a barrier material as described in (AA), said barrier material may be provided as a separate layer and may, for example, define a first layer as described. When said barrier means comprises a barrier material as described in (BB) or (CC), in preferred embodiments, said catalyst may be arranged as described in embodiment (A2) or may be associated with a porous material as described in (BB). In both cases, composite particles may be defined, each of which comprises catalyst and barrier material. The composite particles may be dispersed within said first and/or said second layer of said closure. Preferably, said first layer includes said composite particles.
As described, in some embodiments, said barrier material may be associated with polymeric material (XX). Polymeric material (XX) may comprise, for example define, the first or second layers and, more preferably, defines said first layer which suitably provides said control means. Barrier means and/or barrier material may be associated with polymeric material (XX) as described in Examples (B1-i) and Example (B1-ii).
When said catalyst is associated with said container body, the container body may include a sidewall constructed from a composition that includes a polymer resin first component and a second component comprising a catalyst capable of catalyzing a reaction between molecular hydrogen and molecular oxygen. The catalyst suitably includes a barrier means, for example a barrier material, as described herein.
Because of the extremely high reaction rates obtainable with a number of catalysts, very small amounts of catalyst may be required. A container body may include 0.01 ppm to 1000 ppm, suitably 0.01 ppm to 100 ppm, preferably 0.1 ppm to 10 ppm, more preferably at least 0.5 ppm of catalyst relative to the weight of said container body (excluding any contents thereof). In preferred embodiments, 5 ppm or less of catalyst is included. Unless otherwise stated reference to “ppm” refer to parts per million parts by weight.
The small amount of catalyst needed allows even expensive catalysts to be economical. Moreover, because very small amounts are required to be effective, there can be minimal impact on other package properties, such as color, haze, and recyclability. For example, when palladium is utilized as the catalyst, concentrations less than about 1 ppm of finely dispersed Pd may be sufficient to achieve acceptable rates of oxygen scavenging. In general, the amount of catalyst required will depend on and can be determined from the intrinsic rate of catalysis, the particle size of the catalyst, the thickness of the container walls, the rates of oxygen and hydrogen permeation, and the degree of oxygen scavenging required.
In a preferred embodiment, the catalyst is incorporated into a wall of the container body. It is preferably associated with, for example dispersed in, a polymer which defines at least part of the wall of the container body. In a preferred embodiment, the catalyst is associated with material which defines at least 50%, preferably at least 75%, more preferably at least 90% of the area of the internal wall of the container body. In a preferred embodiment, the catalyst is distributed substantially throughout the entire wall area of the container body.
The container body may be a monolayer or a multilayer construction. In a multi-layered construction, optionally one or more of the layers may be a barrier layer. A non-limiting example of materials which may be included in the composition of the barrier layer are polyethylene co-vinyl alcohols (EVOH), poly(glycolic acid), and poly(metaxylylenediamine adipamide). Other suitable materials which may be used as a layer or part of one or more layers in either monolayer or multilayer containers include polyester (including but not limited to PET), polyetheresters, polyesteramides, polyurethanes, polyimides, polyureas, polyamideimides, polyphenyleneoxide, phenoxy resins, epoxy resins, polyolefins (including but not limited to polypropylene and polyethylene), polyacrylates, polystyrene, polyvinyls (including but not limited to poly(vinyl chloride)) and combinations thereof.
In a preferred embodiment, the container body includes walls defined by polyester, for example PET. When said catalyst is associated with said container body, preferably catalyst is dispersed within the polyester. Advantageously, due to the provision of the barrier material, the risk the catalyst may be poisoned by constituents of the resin is reduced. Consequently, catalyst and associated barrier material may solve the problem described in the introduction particularly in relation to container bodies comprising PET made using an antimony-based catalyst.
Said container body may include a permeable wall comprising of one or more polymers that have in the absence of any oxygen scavenging a permeability between about 6.5×10−7 cm3-cm/(m2-atm-day) and about 1×104 cm3-cm/(m2-atm-day).
According to a third aspect of the invention, there is provided a closure for a container according to the second aspect, the closure comprising:
Preferably, said closure includes a barrier means comprising:
Other features of the barrier means and/or closure may be as described any statement according to the second aspect.
In a preferred embodiment, at least part of a said control means is provided in a first layer and a second layer comprises said hydrogen generating means. A said catalyst is preferably provided in a layer of said closure. When said closure includes a first layer and a second layer as described, said catalyst may be provided in said first and/or second layers and/or provided in another layer (e.g. a third layer). In any case, preferably, a barrier means, for example barrier material, is suitably an integral part of the closure and, therefore, is arranged to be removed from association with a container body if the closure is disengaged from the container body.
According to a fourth aspect of the invention, there is provided a container body for a container of the second aspect, the body comprising:
Preferably, said container body includes a barrier means comprising:
Said container body suitably comprises polyester as described herein in combination with said barrier material. Said barrier material may define an internal layer of the container which is suitably inwards of said polyester layer.
Other features of the barrier means and/or container body may be as described any statement according to the second aspect.
According to a fifth aspect of the invention, there is provided a method of restricting passage of organic molecules, for example benzaldehyde, from a product contained, in use, in a container to a catalyst which is part of the container and is arranged to catalyse a reaction between molecular hydrogen and molecular oxygen, the method comprising: providing a barrier means for restricting passage of organic molecules, for example benzaldehyde, said barrier means being positioned between a volume of said container in which the product is positioned in use and said catalyst for restricting passage of organic molecules, for example benzaldehyde, from a product contained, in use, in the container, to the catalyst.
The method of the fifth aspect may include any feature of any invention of any other aspect.
According to a sixth aspect of the invention, there is provided a method of constricting a barrier means for a closure or container body of a container, the method comprising:
(CCC) selecting a barrier material which surrounds individual particles of catalyst so that a mass of composite particles is defined, wherein each of said composite particles comprises catalyst surrounded by said barrier material and arranging said composite particles in said closure or arranging said composite particles in said container body.
According to a seventh aspect of the invention, there is provided the use of a barrier means as described herein for restricting passage of organic molecules, for example benzaldehyde from a product.
Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein mutatis mutandis.
Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
In the figures, the same or similar parts may be annotated with the same reference numerals.
The following materials are referred to hereinafter:
Hildebrand Solubility Parameters are described herein. The Hildebrand solubility parameter (δ) provides a numerical estimate of the degree of interaction between materials. The Hildebrand solubility parameter is the square root of the cohesive energy density:
The cohesive energy density is the amount of energy needed to completely remove unit volume of molecules from their neighbours to infinite separation (an ideal gas). This is equal to the heat of vaporization of the compound divided by its molar volume in the condensed phase. In order for a material to dissolve, these same interactions need to be overcome, as the molecules are separated from each other and surrounded by the solvent. Materials with similar solubility parameters will be able to interact with each other, resulting in solvation, miscibility or swelling.
Unless otherwise stated herein, parts per million (ppm) or parts per billion (ppb) or similar expressions herein refer to the parts on a weight-weight basis.
A preform 10 illustrated in
Referring to
In use, with container 38 including a beverage and closure 40 in position, the headspace in the container will be saturated with water vapor. This vapor passes into liner 46 and contacts the calcium hydride associated with the liner. As a result, the calcium hydride produces molecular hydrogen which undergoes a catalyzed reaction with oxygen which may have entered the container through its permeable walls, to produce water. Thus, oxygen which may ingress the container is scavenged and the contents of the container are protected from oxidation. The scavenging effect may be maintained for as long as hydrogen is produced in the container and such time may be controlled by inter alia varying the amount of hydride in the liner.
It has, however, been found that not only does the catalyst catalyse the reaction of hydrogen and oxygen to produce water but it may also catalyse other undesirable oxidization, reduction and/or isomerisation reactions involving organic components of the beverage contained in the container. Such organic components may migrate into and out of, for example, layers 50, 52 of insert 48 and reaction products may enter the beverage.
Clearly, the products of catalysed reactions depend on what molecules are present in a particular beverage provided in a container. By way of example, many fruit beverages include benzaldehyde. A container which includes a closure comprising a palladium catalyst for catalysing a reaction between hydrogen and oxygen as aforesaid, was assessed. The container was first filled with a benzaldehyde solution to simulate a product including a flavour component. It was found, after storage for 60 days, there was a 6.9% conversion of benzaldehyde to benzyl alcohol (via a hydrogenation reaction) and 0.4% conversion to toluene (via hydrogenolysis of benzyl alcohol). Both of the reactions are undesirable. As a generality, it is desirable to limit/prevent any and all palladium catalysed reactions of components of products provided in containers of the type described.
The description and examples which follow illustrate how undesirable reactions of components present in beverages in a container may be investigated and/or how they may be reduced to limit the production of potentially undesirable contaminants, whilst not substantially impeding the required oxygen scavenging reaction involving hydrogen and oxygen.
In general terms, preferred embodiments provide a barrier between a product in a container (in particular small organic molecules which are components of the product and may be released therefrom) and a catalyst associated with a closure or body wall of the container. In preferred embodiments, the catalyst is provided in a closure. The barrier may be provided as described in (A) to (C) below.
In general terms, a catalyst may be incorporated in the pore structure of a microporous material to produce a combination which can be mixed into a thermoplastic polymer and extruded or moulded to produce a film which may then be incorporated into a closure, for example as layer 52 which is provided outside hydride-containing layer 50, as shown in
The pore size of the microporous material, for example zeolite, may be in the 5-10 Angstroms.
Zeolithic structures may be formed by a range of elements including germanium, gallium, indium, phosphorous and carbon. Preferred microporous materials are natural or synthetic zeolites.
Preferred microporous materials have a relatively hydrophilic environment inside the material, for example zeolite, which helps to exclude organic molecules and encourage passage of, for example water. The hydrophilic environment may be inherent or an additional material may be associated with the zeolite to create the desired environment.
Preferred zeolites have a hydrophilic internal environment which may be created by presence of Group I or Group II aluminates. The Si/Al ratio affects the hydrophilicity of zeolites. Preferred zeolites have a Si/Al ratio of less than 2, for example less than 1.5. Preferably, the counter-ion to the AlO2−− moieties are Na or Ca. Preferred zeolites are NaX, CaX or CaA. CaA tends to be highly hydrophilic and may be preferred in some cases.
Whilst the microporous material, for example zeolite, may be microporous/zeolitic throughout the body of the structure, zeolitic particles having a zeolitic exterior but an amorphous/non-zeolitic interior may be used in preparation of the zeolite/catalyst combination.
The mechanism of action of microporous materials to restrict passage of organic molecules may be two-fold—firstly, based on the porous structure restricting the molecules based on size; and, secondly, based on hydrophilic/hydrophobic properties of the porous structure.
In general terms, a catalyst may be encapsulated in a suitable polymer and then the catalyst/polymer combination can be dispersed in a suitable thermoplastic matrix polymer (e.g. a polyolefin) and extruded or moulded to produce a film which may then be incorporated into a closure, for example as layer 52 in
The encapsulated catalyst may be made as described in Reference Example 1 of U.S. Pat. No. 9,561,171 and the content of column 13, line 56 to column 14, line 19 of U.S. Pat. No. 9,561,171 is incorporated herein by this reference. As will be appreciated, the example describes preparation of silicone rubber particles of average diameter 6.2 μm, containing 7.2 ppm by mass of platinum metal (Pt).
In general terms, the silicone resin used may be based on any vinyl-substituted silicone or silicon hydride, such as polymethylhydrosiloxane.
The catalyst may be used in the polymerisation process to produce the silicone resin. The catalyst remains in the silicone resin after catalysing the polymerisation process and is therefore available for catalysing the reaction of hydrogen and oxygen as described.
The encapsulated catalyst, suitably having an average (D50) particle size in the range 1 to 100 μm, suitably in the range 3 to 30 μm, may be mixed with thermoplastic matrix polymer as described to provide 1 to 1000 ppm, suitably 10 to 50 ppm, of catalyst in the film produced which is then used for layer 52 of the closure.
It is found that the encapsulated platinum catalyst is dispersed in the silicone at a molecular level with no detectable clusters. As a result, the activity of the catalyst is optimised and lower amounts of catalyst may be used in the thermoplastic matrix polymer of layer 52 than in comparable situations wherein the catalyst is less well dispersed.
Other polymers with sufficiently different Hildebrand Solubility Parameters compared to the organic molecules it is desired to restrict from contacting the catalyst may be used as alternatives to silicone resins. For example, catalyst may be dispersed in a fluoropolymer resin, such as PTFE which has a solubility parameter of 12.7 MPa1/2. Such a combination may be used to produce a film which may then be incorporated in a closure, for example as layer 52 in
As an alternative to the arrangement described in (B), referring to
The organophobic layer 62 may be provided as a discrete layer upon underlying layer 52 by suitable means. For example, layer 62 may be applied by compression moulding, injection moulding, co-extrusion or solvent deposition. As an alternative, the outer surface of a layer 52 may be functionalised to increase its organophobicity and/or lower its Hildebrand Solubility Parameter.
In one embodiment, layer 62 may comprise a fluoropolymer layer which may be applied as a discrete layer onto layer 52. Alternatively, the outer surface of layer 52 may be post-fluorinated, for example by exposure of a closure including layer 52 to fluorine gas for example as described in US20190040219 A1, the content of which as regards the fluorination method is incorporated herein by reference.
Although the barriers referred to in (A) to (C) have been described as restricting passage of organic molecules to catalyst in a closure, when catalyst is provided in a side wall of a container body 22, for example as described in WO2008/090354A1, a barrier may be associated with the side wall to restrict passage of organic molecules as aforesaid. For example, catalyst may be encapsulated in a microporous material as described in (A) or in a polymer as described in (B) and incorporated in the side wall. Alternatively, the side wall of the container body may include an internal layer as described in (C). Such a layer may be conveniently provided by post-fluorination of the innermost layer of a container body.
The general procedures referred to above are further illustrated in the following examples.
Referring to
In general terms, test materials are prepared by dry blending a mixture of a selected catalyst composition with pulverised Petrothene (polyethylene) and Vistamaxx (propylene) pellets. This mixture is then melt compounded in a twin-screw extruder with a barrel temperature of 180° C. and a residence time of 43 seconds. The extrudate is cooled in a water bath, the surface moisture is removed with an air knife and the dried strand is pelletized. The pellets are stored in a foil-lined bag to prevent moisture uptake prior to manufacture of test samples.
The following steps are undertaken:
As an alternative, the ion-exchanged product from step (vi) may be sent directly to a drier to reduce moisture content to about 20%, followed by step (x).
The procedure of Example 2 was used, replacing Pt(NH3)4Cl2 with Pd(NH3)4Cl2.
Following the general procedure described in Example 1, the following test samples were prepared:
Following the general procedure of Example 1, the test materials of Examples 4 to 11 were made into closures as described in
Referring to
At the point of test, each jar 72 was opened and 6 g (+/−0.02 g) of solution was transferred from the facing of the closure to a 9 ml high-recovery GCMS vial. The vial was then capped with a magnetic closure and placed in an autosampler tray ready for extraction and testing. Note that a small quantity of condensation was present inside each jar through the test, which is largely unavoidable when storing samples at room temperature.
The aqueous samples were extracted using a written automated program carried out by a Gerstel MPS Autosampler. Dispersive Liquid-Liquid micro-extraction was carried out on each sample by addition of 300 μl of dichloromethane and 150 μl of isopropyl alcohol followed by vortex mixing and finally centrifugation to form an extractant solvent droplet (lower layer). A large volume injection (LVI) (10 μl+) of the extractant solvent was carried out into a cooled GC inlet (PTV) to minimise both thermal degradation of the analytes and evaporative losses. Controlled evaporation in the GC inlet removes the solvent and concentrates the analyte for detection. A solvent-sample ‘sandwich’ injection approach was used to improve injection reproducibility and optimise the concentration of analytes on the column.
Detection of toluene was confirmed using selected reaction monitoring (SRM). An SRM approach on a triple quadrupole instrument selects a precursor ion using the MS1 quadrupole and following collision at a controlled energy in the collision cell, a characteristic product ion is selected by the MS2 quadrupole. This combination of procedures allows specific and accurate ppb quantification of the analyte.
The results of the tests described in Example 13 are provided in the table below.
In the table the values represent the toluene concentration (in parts per billion by weight (ppb)) in the benzaldehyde solutions taken at intervals from the closures following storage for up to 14 days (336 hours).
In the table the column headed “Bulk sol.” refers to benzaldehyde solution alone. The following is noted:
The catalyst material of Examples 8 to 10 may, in alternative embodiments, be provided with a barrier means of a type as described herein.
TPV and TPV-UA as described herein may be calculated as follows from data for Examples 7 and comparative example 5.
The test material in each case has a 25.4 mm diameter facing layer with a surface area of 5.067 cm2.
The volume of 300 ppm benzaldehyde solution added was 2 ml per cm2 of surface area=5.067*2=10.134 ml of benzaldehyde solution added.
60% of volume of benzaldehyde solution removed after fixed time period (24 hours or 72 hours as applicable)=6.08 ml for testing.
Calculation of TPV for the Example 7 closure.
TPV (24 hrs)=0.00375(0.00037*10.134 [volume of benzaldehyde solution added to closure in ml])
TPV (72 hrs)=0.00821(0.00081*10.134 [volume of benzaldehyde solution added to closure in ml])
Calculation of TPV for the Example 5 closure.
TPV (24 hrs)=0.0109(0.00108*10.134 [volume of benzaldehyde solution added to closure in ml])
TPV (72 hrs)=0.0647(0.00638*10.134 [volume of benzaldehyde solution added to closure in ml])
Calculation of TPV-UA for the Example 7 closure.
Calculation of TPV-UA for the Example 5 closure.
1.27 × 10−2
Examples 14 to 20 describe an alternative barrier of a type described in (C) above.
Palladium acetate was dispersed into acetyl tributyl citrate at a 1 wt % loading, and the resulting dispersion was melt-blended with a 23% LDPE/77% Vistamaxx elastomer resin at a let-down ratio of 0.2% to provide a polyolefin blend containing 20 ppm Pd (hereinafter referred to as “HyCat”). Separately, calcium hydride was blended with LDPE to provide a hydride compound containing 21.6 wt % CaH2 (hereinafter referred to as “HyCom”).
38 mm closures were compression molded with a 25 mil thick HyCom base layer.
Some of the closures from Example 15 were subsequently overmolded with a 15 mil thick HyCat layer.
Some of the closures from Example 16 were subjected to fluorination to a fluorination level of 1 (equivalent to decreasing the permeation rate of benzaldehyde by a factor of 2). Fluorination was carried out as described in US2019/0040219 A1.
Some of the closures from Example 16 were subjected to fluorination as described in Example 17, to a fluorination level of 5 (equivalent to decreasing the permeation rate of benzaldehyde by a factor of 10).
Some of the closures from Example 16 were subjected to fluorination as described in Example 17, to a fluorination level of ˜10.
Some of the closures from Example 16 were subjected to fluorination as described in Example 17, to a fluorination level of ˜20 .
Closures from Examples 15-20 were fitted onto 500 ml heatset PET bottles that had each been fitted with an OxyDot™ and brim-filled with air-saturated water. The oxygen concentration of the water was tracked over time. The results are presented in
To 500 ml heat-set PET bottles was added a water solution of ˜300 ppm benzaldehyde at 84° C. The bottles were then capped with 38 mm closures containing no HyCat or HyCom (Virgin Liner), or with closures from Examples 15-20. The bottles were then stored at 40° C. for 14 days and analyzed for the presence of benzaldehyde, benzyl alcohol, and toluene. The results were normalized to 100 ppm benzaldehyde.
As can be seen from the results, in the absence of HyCat and HyCom (Virgin Liner), no hydrogenation of benzaldehyde was observed. In the presence of HyCom only (Example 15), there was a trace of benzyl alcohol formed, likely resulting from a base-catalyzed Cannizzaro reaction. In Example 16 (HyCat+HyCom) there was a small but significant amount of hydrogenation of benzaldehyde to benzyl alcohol, and further hydrogenolysis of benzyl alcohol to toluene. In Example 17 (HyCat+HyCom+level 1 fluorination) the amount of benzyl alcohol and toluene formation is markedly decreased. In Example 18 (HyCat+HyCom+level 5 fluorination) the amount of hydrogenation is reduced even further. Examples 19 and 20 show that further increasing the level of fluorination results in ever-decreasing rates of formation of toluene. These results demonstrate the efficacy of the fluorinated barrier material in decreasing the degree of byproduct formation in the oxygen scavenging reaction.
A 1% solution of palladium acetate in acetyl tributyl citrate is compounded into poly(vinylidene fluoride) at a let down ratio of 1.0%. The resulting fluoropolymer compound is melt-blended with LDPE at a 20:80 ratio to prepare a HyCat blend containing 20 ppm Pd. This HyCat blend is compression molded onto closures from Example 15 and the resulting closures are tested for oxygen scavenging and benzaldehyde reduction. The closures are found to exhibit reduced benzaldehyde hydrogenation (and reduced production of toluene) relative to closures from Example 18.
In the following, Example 24 describes an alternative method of preparing a catalyst/zeolite combination and subsequent examples describe use and testing of alternative materials combinations.
The method of Example 2 is generally followed, with the following changes:
In steps (iii) and (v), distilled water is used instead of 3% NH3-H2O; step (vi) is carried out for about 48 hours; and calcination in step (x) is carried out at 300° C. instead of 230° C.
In addition, Pt(NH3)(NO3)2 may be substituted for Pt(NH3)Cl2, although Pt(NH3)Cl2 was used in the examples which follow.
Following the general procedure described in Example 1, the following test samples were prepared:
Following the procedure described in Example 21, closures based on materials of Examples 25 to 27 were assessed and the results are presented in
Following the procedure described in Example 22, bottles were analysed for the presence of benzaldehyde, benzyl alcohol, and toluene and the results are provided below.
Results show that all three Vistamaxx grades described herein offer acceptable oxygen scavenging and resistance to flavor scalping performance. Grades 6202 and 6502 are higher MFI grades and are found to provide improved processability in a closure compression molding process by virtue of promoting extrudate tack, thereby eliminating the potential for compound extrudate pellet from bouncing out from the underside of closures just prior to compression molding.
The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/061945 | 12/17/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63129763 | Dec 2020 | US |
