Copolyamide active-passive oxygen barrier resins

IS 2 170 478 T3

DESCRIPTION

Copolyamide resins as active-passive barriers against oxygen.

This application is a continuation in part of a previous American application filed on September 23, 1996, Serial Number 08 / 717,370. It is also a continuation in part of a PCT application filed on September 22, 1997, with Application Number US97 / 16712.

Field of the invention

This invention relates generally to compositions, articles, and methods for packaging oxygen-sensitive substances, especially edible products. The invention is directed at barrier materials against oxygen that have improved properties as passive barriers against oxygen and also that have properties as active oxygen scavengers. The active oxygen scavengers of this invention are condensation copolymeric substances that can be used for bottles and for packaging and have the ability to consume, eliminate or reduce the amount of oxygen in or from a certain environment in a solid state at ambient temperatures. Formulas are discovered from which plastic bottles and other items and lamines for packaging can be made. Background of the invention

Plastic materials have produced significant progressive advancements in the packaging industry due to the design flexibility of their materials and their ability to be manufactured in various sizes and shapes commonly used in the packaging industry. The deployment of plastic materials in articles for packaging such as sheets, trays, bottles, jars, cans, coatings and liners is already common in the packaging industry. Although plastics materials offer numerous benefits to the packaging industry, with an unlimited degree of design flexibility, the utility of plastics materials has continued to be reduced in situations where barrier properties against atmospheric gases are required. (mainly oxygen) to ensure an adequate commercial life of the product. When compared to traditional packaging materials, such as glass or steel, plastics offer lower barrier properties, limiting their acceptability for use in packaging products that are sensitive to atmospheric gases, particularly when exposed to atmospheric gases. atmospheric gases will take long periods of time. The packaging industry continued to search for packaging materials that offer the design flexibility of plastics while exhibiting the barrier properties of glass and steel.

The packaging industry has developed technology to improve the barrier properties of plastic containers by developing containers that offer improved barrier properties that approximate, but are not comparable to, those of glass, steel and aluminum. By a very wide margin, polyethylene terephthalate (PET) and similar packaging polyeosters have gained wide acceptance, especially in bottling applications, in view of the clarity and stiffness characteristics associated with PET bottles. PET has made significant inroads into bottling and packaging applications at the expense of the use of glass containers, but primarily in applications where the needs for barrier properties are modest. A significant example is the use of PET for soft drink bottles. However, the barrier properties of PET have limited its use in the packaging of oxygen-sensitive products.

It is generally accepted in the packaging industry that polyamides exhibit superior passive barrier properties against oxygen when compared to similar polyester packaging constructions. A polymer useful as a passive barrier against oxygen is one that exhibits the ability to retard the permeability of oxygen through oil when compared to the permeability of oxygen through other resins. Furthermore, it has been described that a polyamide known as MXD-6 has a certain capacity as an active barrier against oxygen. MXD-6 is poly (m-xylene adipamide) which is a polyamide made up of equal amounts in molarity of the two monoomers (1) metaxylenediamine and (2) adopic acid. An active barrier resin against oxygen is a substance capable of intercepting and trapping oxygen (through its participation in a reaction with oxygen) when it tries to pass through the packaging. This method also allows the opportunity to remove unwanted oxygen from within the container cavity, into which such oxygen may have been inadvertently introduced during packaging or filling. This method of providing oxygen barrier properties in which the substance consumes or reacts with oxygen is known as an "active oxygen barrier" and involves a different concept from passive oxygen barriers that try to hermoetically seal a product away. of oxygen through an approximation

ES 2 170 478 T3 passive.

When MXD-6 (about 4% by weight) is mixed with PET (about 96% by weight, the resulting mixture is approximately 70% as permeable to oxygen as a similar unmodified construction of PET. Presumably, this 30% improvement over unmodified PET can be attributed to the improvement of the passive barrier properties of the aforementioned mixture When an oxidation catalyst is added to the mixture (eg. about 50-200 ppm of cobalt relative to the weight of the mixture), the mixture acquires improved properties to actively trap oxygen. The O2 permeability of the mixture is reduced under these conditions until the ability of the mixture to actively trap oxygen is exhausted. The barrier properties acquired by the blend are only suitable for minor packaging requirements and only with heavy use of the blend. However, MXD-6 is a relatively expensive polyamide and the use of large amounts of it in a package serves to prevent the economic viability of the package from being determined. More common lower cost polyamides, such as the well known poly (hexamethylene adipamide), exhibit the improved passive barrier properties of polyamides but are free of active barrier properties. What is needed is a polyamide-based resin as an active-passive barrier of polyamide against oxygen, which can be produced at a reasonable cost and exhibits sufficient barrier and trapping properties to offer the possibility of reaching commercial lives of level 6. months to two years in oxygen sensitive products. This invention addresses such a need. Summary of the Invention and Review of the Art

In a common and co-pending assignment application, filed on September 23, 1996, with Serial Number 08 / 717,370, it was discovered that certain hydrocarbons, such as polyolefins (especially polydienes), present in small amounts as oligomer blocks of polyolefins in a polymorphic block of copolyester, they added substantial ability to actively trap oxygen from oxygen to packaging polyosters that did not show any ability to actively trap oxygen in the absence of the polyolefin oligoomer blocks. The oxygen-scavenging copolyesters of the aforementioned application consisted mainly of polyester packaging segments with only a quantity of oxygen-scavenging polyolefin oligoomer segments present to supply the oxygen-trapping capacity required for the packaging application. the one that was destined. The copolyethers of the application carrying Serial Number 08 / 717,370 were topically in the range of about 0.5-12% by weight of polyolefin oligoomer segments with the remainder comprised of polyester segments. An especially preferred representation was a copolyether of about 4% by weight of polyolefin oligoomer segments with the remainder polyester segments. These types of copolyether blocks comprising low weight percent levels of polyolefin oligoomer segments exhibit properties (such as melting point, viscosity, and clarity) very similar to the unmodified polyester from which the polyester segments were derived. In particular, layers in laminar and bottling coatings having one or more layers of unmodified polyester and one or more layers of oxygen-scavenging copolyester block, as noted above, were self-adhesive and the packaging articles appeared to be a monolotic construction ( more than formed by different layers).

For this invention, the applicants have extended the concept of implanting segments of polyolefin oligoomers with high capacity to trap oxygen in polyamides that form blocks of copolyamides formed predominantly of polyamide segments and a certain number of segments of polyolefin oligoomers to trap oxygen. . As was the case with the copolyethers discovered in the application of Serial Number 08 / 717,370, the copolyamides of this invention have properties that are very similar to the polyamide from which the polyamide segments were derived. A topical use of such polyamides comprises a layered construction, such as a packaging foil or the wall of a bottle having outer and inner layers of polyamide and an interlayer of copolyamide (in which the polyamide segments of the copolyamide are derived of those of the polyamides of the inner and / or outer layers and the oxygen trapping segments comprise a polyolefin oligoomer). This arrangement serves to provide properties to the copolyamide layer that are very similar to the properties of unmodified polyamide layers, which is an important concept of this invention for sheet constructions. A main concept of this invention, however, is the incorporation of segments of polyolefin oligoomers, highly efficient as oxygen scavengers, in the copolyamide, leaving the copolyamide with properties very similar to those of the polyamide unmodified. The high capacity of the copolyamides as active oxygen scavengers which is discovered derives from the capacity as active oxygen scavengers of the polyolefin oligoomer segments. As noted above, polyamides, per se, are generally considered to exhibit superior passive barrier properties against oxygen than polyesters. Therefore

ES 2 170 478 T3 Another important concept of this invention is the combination of superior properties such as passive barriers with the active capacity to trap oxygen, when compared to the use of only unmodified polyester or only unmodified polyamide.

An active barrier resin against oxygen is a substance capable of intercepting and trapping oxygen (through its participation in a reaction with oxygen) when it tries to pass through the packaging. This method also allows the opportunity to remove unwanted oxygen from the interior of the container cavity into which such oxygen may have been inadvertently introduced during packaging or filling. This method of providing oxygen barrier properties in which the substance consumes or reacts with oxygen is known as an "active oxygen barrier" and involves a different concept from passive oxygen barriers that try to hermoetically seal a product away. of oxygen through a passive approach. Only active oxygen scavengers can remove unwanted oxygen (inadvertently introduced during packaging) from the container cavity. The active trapping of oxygen implies, therefore, the consumption of a material incorporated in the wall of a container. This material is progressively consumed, so that the ability to actively trap oxygen is eventually depleted or at least reduced. However, this eventual depletion of the active oxygen scavenger medium can be adjusted so that removal occurs only well after the time required for the commercial oxygen-free life of the packaged product has passed, which is typically one year or two. less.

US Patent 5,021,515 (CMB Patent) discloses the OxBar system for trapping oxygen from CMB. The CMB patent discloses the use of a polyamide mixed with a polyester for bottling, such as PET and also requires the presence of a catalyst, such as a transition metal. These mixtures are subsequently unfolded so that at least one layer is formed on a wall of a single or multi-layer container or bottle. According to the CMB patent, the polyamide in the mixture is responsible for the ability of the mixture as an active oxygen scavenger. In a preferred embodiment of the CMB Patent, 96% by weight of PET is mixed with 4% by weight of a polyamide often designated MXD-6. MXD-6 is a polyamide made up of equal amounts in molarity of the two monoomers (1) metaxylene diamine and (2) adopic acid. The PET / MXD-6 mixture is topically deployed in the presence of 200 ppm cobalt, which serves to catalyze the active trapping function of oxygen.

EP-A-0 507 207 discloses a composition for trapping oxygen comprising a polymer of an ethylenically unsaturated hydrocarbon and a transition metal as a catalyst.

The current invention is directed to the use of copolyamides capable of trapping oxygen in the solid state, formed mainly by polyamide segments and an oxygen-trapping amount of polyolefin oligoomer segments. The copolyamides of this invention are topically deployed in the presence of a catalyst, such as a transition metal, and comprise at least one layer of a single or multi-layer container or bottle wall. Significant differences between this invention and the CMB patent include that (1) the present invention was directed to a copolyamide that primarily comprises polyamide segments, while the CMB patent discloses a polyester / polyamide blend that is primarily polyester (the CMB patent does not disclose the use of polyolefin in any way), (2) the polyolefin oligoomer segments in the copolyamides of this invention are the fractions that react with oxygen and trap it, while in the CMB patent it is polyamide that reacts with oxygen and traps it, (3) the oxygen-trapping ability of the copolyamides of this invention is considerably greater than that of the PET / MDX-6 blend and (4) the copolyamides of this invention are used topically in polyamide-based containers and bottles, while the PET / MDX-6 mix is ​​aimed at containers and bottles based on polyester (PET). Brief description of the drawings

Figure 1 is a cross-sectional view of the preferred construction of the oxygen trap wall and foil of a bottle.

Figure 2 is a graph showing the oxygen trapping propensity of a set of resins of this invention versus other control resins.

Detailed description of the preferred representations

As previously noted, polyamides, in general, have superior properties

ES 2 170 478 T3 as passive oxygen barriers when compared to similar polyester packaging constructions. This is true both for the less expensive and better known polyamides, such as poly (hexamethylene adipamide), and for the more exotic and rather expensive polyamides, such as MDX-6. The polyamides used to make plastic bottles and other packaging items can be the same polyamides from which the polyamide segments are derived in the oxygen scavenging copolyamides discovered in this invention. It is well known in the polyamide art to prepare polyamides by copolymerizing (typically on an equal molar basis in the presence of a suitable catalyst) of the monoamers of two separate chemical substances as shown in Formula I and in Fig. Formula II, to give rise to the repetition of the polyamide unit shown in Formula III.

OO

II II

I. HOC-R1-COH

II. H2N-R2-NH2

OO

II

III. (-NC-R1-CN-R2) ||

NH

In some more detail, preferred polyamide resins for use in the present invention include linear polyamides such as those included in Formula I by selecting the dicarboxylic acid component from a list that includes aliphatic diacids, such as adapic acid, acid phthalic, isophthalic acid, terephthalic acid, the various dicarboxylic acids of naphthalene, and mixtures of the compounds from the previous list. Preferred diamines of Formula II include polyalkene diamines, such as hexamethylene diamine, aromatic amines, such as xylene diamines, and mixtures of the foregoing.

Polyamides prepared from the above mentioned components are well known in the art, and can be prepared by polymerization reaction between dicarboxylic acid (or suitable derivatives) of Formula I and diamine (or suitable derivatives) of Formula II. . In many cases, polyamides suitable for use in this invention are available for purchase from various suppliers such as the Amodel® Series of polyamides available from Amococo Chemical Company and the Zytel® Series of polyamides available from Du Pont. In selected representations, the present invention also contemplates the use of recycled polyamides as part or as all of the polyamide for food.

Other suitable polyamides for use in the present invention include branched polyamides. These branched species can be prepared using mainly difunctional dicarboxylic acid monoamers together with certain carboxylic acid monomer with a number of functional groups greater than two and then polymerizing these acids with polyamines. Alternatively branched species can be prepared by primarily using diamine monoamers together with certain polyamines with more than two amino groups and then polymerizing these polyamines with acidic monoamers with various functional groups. Examples of acids with a functional group number greater than two include trimellatic acid and pyromeltic acid (or their anhydrides).

When the monoamers of Formula I and the monomers of Formula II react to give the repeating structure of Formula III, this type of polymerization is known as polycondensation or condensation polymerization. A definition of condensation polymerization is given on page 67 in the book "Glossary of chemical terms" by CA Hampel and GG Hawley, Von Nostrand, 1976. According to this reference, a condensation polymer is a linear or three-dimensional macromolecule obtained by reacting two organic molecules, generally with water or alcohol formation as a by-product. The reaction is repetitive or multi-stage as the macromolecule is formed. These repetitive stages are known as polycondensation. Examples given as condensation polymers are polyesters and polyamides. In 1929 Carothers (wh Carothers, J.Am. Chem. Soc. 51, 2548 (1929)) proposed a generally useful differentiation between two broad classes of polymers. One of Carothers' classes was the condensation polymers in which the formula

ES 2 170 478 T3 molecular structure of the (repeating) structural unit or structural units in the polymer lacks certain aotoms present in the monomer or monoomers from which it has been formed, or which must be degraded by cheomic means. The other class of Carothers were the addition polyomers in which the molecular formula of the structural (repeating) unit or structural units in the polymer is identical to that of the monomer from which the polymer is derived. The polyomers and copolymers of importance in this invention are those that Carothers would have considered condensation polyomers in view of their polymerization characteristics and the formulas of the repeating units of the polyomers versus those of the monoomers that form them. In one aspect of this invention, novel condensation copolymers formed predominantly of polyamide segments and oxygen-trapping hydrocarbon segments are discovered in an amount effective to provide the required oxygen-trapping ability. As explained in more detail below, these hydrocarbon segments of the condensation copolymer are actually oligoomers of an addition polymer.

Of course, it was necessary for the applicants to focus on the evaluation and selection of appropriate hydrocarbon segments that could be incorporated into a copolyamide and would provide the necessary capacity as oxygen scavengers without detriment to the outstanding characteristics and properties of the hydrocarbons. container polyamides and segments derived from them for the copolymer. The applicants recognized and established that hydrocarbons such as polyolefins (especially polydienes) provided good ability as oxygen scavengers when added as blocks in a copolyether. As was verified in the examples section of this specification, subsequent analysis and experimentation confirmed that the polyolefin segments in the copolyamides added to the polyamides the capacity as active oxygen scavengers in a similar way to that observed for copolyethers having oligoomer blocks. polyolefin. Generally, the oxygen trapping capabilities of the polyamides were better when low molecular weight polyolefin oligoomers were used, having topically molecular weights in the range of 100-10000. Polyolefin oligoomers with molecular weights in the range 1000-3000 are particularly preferred. Preferred polyolefin oligoomers for use as hydrocarbon segments in oxygen scavenging copolyamides are polypropylene, poly (4-methyl) 1-pentene, and polybutadiene. While not a hydrocarbon as such, the oligoomer of propylene glycol oxide was also identified as a substance of potential use as an oxygen scavenger. Of these the polybutadiene oligoomer is especially preferred insofar as it has a high propensity to trap oxygen and also because it is commercially available in the form necessary to make the oxygen-trapping copolyamides of this invention by the preferred method of this invention.

As stated above, the polyolefin oligoomer segments should be present in the copolyamides of this invention only in the amount necessary to provide the desired oxygen trapping ability. One reason for keeping the polyolefin oligoomer segments only at the necessary level is to satisfy the objective of keeping the copolyamide as similar to the polyamide homopolymer as possible. In practice, the presence of polyolefin oligomer segments in a range between 0.5% by weight and 12% by weight, based on the weight of the copolyamide, has been found to be a% by weight range for topical use. The presence of polyolefin oligoomer segments in a range between about 2% by weight and about 8% by weight, based on the weight of the copolyamide, is preferred. Especially preferred is the presence of polyolefin oligoomer segments in a range between about 2% by weight and about 6% by weight, based on the weight of the copolyamide.

The copolyamides of this invention have the ability to absorb oxygen in the crystalline solid state at ambient temperatures from 0 ° C to 60 ° C. This functional range for copolyamides is below the crystal transition temperature T_(c) of these compositions. This behavior is in stark contrast to earlier art oxygen scavengers that absorb oxygen at ambient (or even cooler) temperatures but still above the T_(c)It is simply understood that gas permeability is greatly increased above the T_(c) when the material is no longer a solid and therefore serves to nullify the trapping utility of these traps. Another major advantage of the copolymers of this invention, particularly when compared to other oxidizable metal / electrolyte formulations, is that they trap oxygen in the absence of water or moisture (as well as in the presence of water or moisture). This allows the use of the oxygen scavenging copolymers of this invention for the packaging of dry materials such as electronic components, dry snack foods, medical articles. This ability to trap oxygen in a dry environment represents a further distinction of the oxygen trap copolymers of this invention over many prior art trappers that require the presence of water or, at least, a huomer environment.

IS 2 170 478 T3

Generally the preparation of the oxygen scavenging copolyamides discovered above will involve a step comprising adding functional groups to at least one or more (preferably more) of the available end sites in the scavenger polyolefin oligoomer to be incorporated as segments into the copolyamides. . The terminal functional group added must be a moiety capable of participating in polycondensation reactions and forming polycondensation bonds when incorporated into a polymer. It will be understood that there may be more than two end sites available to add functional groups when crosslinking or branching occurs in the polyolefin oligoomer. In cases in which the addition of two or more functional groups is contemplated, they will generally be multiples of the same functional group, that is, all hydroxy groups, all carboxy groups or all amino groups added in multiple terminal sites of the oligomer molecule. polyolefin. Those of ordinary skill in the art will recognize that this invention can be practiced even when different but chemically compatible end functional groups are present at multiple end sites of polyolefin oligaomer molecules. As shown above, the only requirement is that the terminal functional groups must be capable of participating in polycondensation reactions. A non-exhaustive list of terminal functional groups includes hydroxy, carboxylic acid, carboxylic acid anhydrides, alcohol, alkoxy, phenoxy, amino, and epoxy groups. Preferred end groups are hydroxy, carboxylic acid, and amino. It will be obvious that this stage of preparation can be avoided by using polyolefin oligoamers which are already properly functionalized and commercially available in this way. In this regard, hydroxy terminal functional groups are of special preference to applicants in the sense that polyolefin oligaomers with the terminal hydroxy group suitable for incorporation into the oxygen-scavenging copolyamides of this invention are commercially available and offer attractive properties. . A greater understanding of the process can be achieved by considering the chemical species represented in Faormulas IV, V and VI.

OO

II II

IV. HOC- (POO) -COH

V. H2N- (POO) -NH2

SAW. HO- (POO) -OH

In formulas IV, V and VI (POO) represents a fraction composed of a divalent polyolefin oligoomer. Although Phaormulas IV, V and VI show double functionality, (POO) can be found with only one functional group or with more than two functional groups when the crosslinking or branching of (POO) offers more than two terminal sites. for functionalization. In Formula IV the (OOP) is finished dicarboxy. In Formula V the (POO) is dihydroxy terminated and in Formula VI the (POO) is diamino terminated. Although Formulas IV, V and VI show the hydrogenated forms of these species, those with a certain knowledge of the technique will understand that from one to the total of the hydrogens in each of Formulas IV, V and VI may be replaced by a organic radical such as an alkyl, cycloalkyl, phenyl group and remain valid for the same purpose in the preparation of the oxygen scavenging copolyamides of this invention. Using the substituted forms of the species of Formulas IV, V and VI will simply produce different by-products in the copolymer formations. As previously highlighted, this invention can be carried out with only one functional group per (OOP) or with more than two functional groups per (OOP). In Formulas IV, V and VI a case of difunctionality is shown but it represents one of the many possible levels of functionality. The method of formation of these functional group terminated species is not important to the findings of this invention. Commercially available forms of Formula V (which is especially preferred) include the α, ω-polybutadiene diols R20LM and R45HT products from Elf Attochem.

The similarity in the chemical structure of the species represented in Faormulas I and IV can be easily appreciated. Taking into account that polycondensation takes place by reaction of the terminal groups, polycondensates composed predominantly of polyamide segments with some segments of polyolefin oligoamers can be formed. For a simpler understanding of the composition, it may be useful to think in terms of substituting the desired amount of the Formula IV species for an equivalent amount (based on moles) of the Formula I species, producing polycondensates that both have polyamide. and polyolefin oligamer segments. How has it

ES 2 170 478 T3 mentioned above, the copolymers are true polycondensates with the unusual characteristic that some of the segments consist of an addition polymer (actually oligomer). In the same way, the similarity between the species of Fíormulas II and VI can be easily appreciated. Copolycondensates can be formed by substituting the desired amount of the Formula VI species with an equivalent molar amount of the Formula II species. The nature of the polycondensation reaction that forms the copolycondensates for these two types of segment substitutions would be similar to that found in the formation of true or unmodified polyamide. It would be expected that the by-products formed were also similar. The Formula V species is hydroxy terminated. A desired amount of this species can be substituted for an equivalent amount of the Formula II species to produce a slightly different type of copolymer. When prepared in this way a condensation copolymer is formed in which the bonds proximal to the polyolefin oligoimer segments are polyester bonds. As will be shown below, these represent only a small percentage, for example, of non-polyamide bonds and the copolycondensates produced that have some polyester bonds are as suitable for our purposes as are the copolycondensates of this invention prepared with a 100% polyamide bonds between the segments. The significant fact is that the oxygen-trapping polyolefin oligiomer has been implanted as segments thus providing the ability to trap oxygen to the formed product, while retaining virtually all of the outstanding characteristics of the original packaging / polyamide. bottle. These techniques for introducing the desired polyolefin oligomer into the polycondensate when used at the low levels discovered by applicants provide a very accurate and effective means of distributing the oxygen scavenging fraction throughout the copolycondensate. Achieving a uniform dispersion of the oxygen scavenging fraction of the copolycondensate while maintaining the properties of the precursor polyamide is a key feature of this invention that allows a further distinction of the copolycondensates of this invention from prior art. Trying to produce oxygen-trapping materials by performing a physical combination of non-functionalized polyolefin oligoimers and polyamide generally produces a non-rigid emulsion that is not useful for packaging. However, when functional group terminated polyolefin oligoimers are mixed or blended with polyamide at temperatures exceeding 200 ° C to melt the polyamide, the copolycondensates of this invention will be formed, at least to some extent, by transesterification. Therefore, mixtures and combinations of polyolefin oligomers with terminal functional groups with polyamide, even if designated as such, may be within the scope of this invention when producing the combination and mixing processes at melting temperatures of the polyamide. of copolycondensates of this invention.

The preferred source material as a polyolefin oligoimer is the terminated dihydroxy (POO) species, with a molecular weight in the range of 100-10000. The especially preferred source material as a polyolefin oligomer is the terminated dihydroxy (POO) species, with a molecular weight in the range of 1000-3000. Copolymers formed using PBDs with a molecular weight within the preferred range will generally have a unique T_(C)(measured by differential scanning calorimetry) of approximately 100-130 C and offer the ability to absorb oxygen at temperatures below T_(C). Although copolymers with a single unit of T_(C), those with an ordinary knowledge of the technique would understand that copolymers with multiple T's can also be applied._(C) provided that the lowest transition temperature of the glass is a temperature that is above the temperature of use of the container. The advantage of having a T_(C) Above the temperature of use of the container is to allow flexibility of container design related to the rigidity of the container. It is well understood that the stiffness of the container can also be controlled by a wall thickness that allows flexible lamines to be produced by reduction of thickness thanks to the use of said copolymers.

An objective of this invention is to produce copolyamides having predominantly polyamide segments and an oxygen scavenging amount of polyolefin oligomer segments that are capable of absorbing oxygen at ambient temperatures below their glass transition temperatures. This means that copolymers trap oxygen like solids. It is this characteristic that distinguishes copolymers from most prior art oxygen scavengers that are used as scavengers above their glass transition temperatures, that is, not as solids. Those skilled in the art would recognize the many advantages of solid oxygen scavengers, including the ability to have a foil or container that can be made entirely of the copolymer and still maintains its shape at ambient temperatures. For this invention, ambient temperatures means typical storage temperatures in the range from about 0 ° C to about 30 ° C. In order to tolerate hot fill applications, the ambient temperature range would be between about 0 ° C and about 60 ° C.

IS 2 170 478 T3

The copolymers of this invention can be produced using any form of polycondensation processes including the direct continuous and / or batch reaction methods commonly used for the manufacture of polyamides. The only deviation in the process is that instead of using, for example, 50% by mole of the Formula I species and 50% by mole of the Formula II species, some of at least one of the species of Formulas IV, V or VI is included and a corresponding mole amount of the species of Formulas I or II is kept out of the polymerization process. Alternatively, the copolycondensates can be prepared by taking a polyamide and polymerizing it further with the functional group terminated polyolefin oligoomer, by heating the components to achieve homogenization of the melt in an extruder. Heating in the extruder can be achieved under vacuum and non-vacuum conditions. Those of ordinary skill in the art will recognize this form of processing as reactive extrusion. In this type of reactive extrusion process, polycondensation takes place and the product obtained is, partially or totally, a copolymer formed by segments of the initial polyamide and segments of the polyolefin oligoomer, rather than a simple melt mixture of the individual components of departure. Reactive extrusion, as described above, is the preferred method for making the polycondensates of this invention.

In direct polycondensation processes, substituting the desired amount of the terminally functional polyolefin oligoomer with an approximately equivalent amount of one of the unmodified condensation polymer monoomers produces a higher molecular weight copolymer. In this case the desired amount of the terminally functional polyolefin oligoomer can replace molar equivalent amounts of one of the polyamide monoomers. In the case of direct polycondensation, the amount of end-functional polyolefin oligomer that absorbs oxygen can be widely modified as long as the resulting copolymer exhibits the desired properties in the final state such as the trapping capacity and clarity required for its intended end use. . Generally, when they are prepared before their incorporation into articles for packaging, it is necessary to keep the copolycondensates in an inert environment during their conservation. In most cases, the ability to trap oxygen in copolycondensates was present as soon as they were formed and after a period of induction due to exposure to oxygen. The potential to trap oxygen can be significantly reduced if they are left exposed to oxygen (or air) for long periods of time. In addition, prolonged exposure to high temperature in the presence of oxygen may further reduce the ability to absorb oxygen from copolymers when making a packaging article and introduce the possibility of toxicity breakdown and degradation if produced in excess. The premature loss of the ability to trap oxygen before converting the copolymers into a packaging article can be controlled by storing them in an inert environment or by adding suitable stabilizing agents.

Although the copolycondensates of this invention can be manufactured by any suitable process, the preferred method for the manufacture of the copolycondensates of this invention is by reactive extrusion as briefly described above and as will be described in more detail below and again again in the examples section of this specification. As part of the reaction extrusion process either alone or in combination with the manufacturing step, the source polyamide is kept under an inert atmosphere in the extruder, preferably one provided by a layer of nitrogen. The terminally functional polyolefin oligoomer is transported separately to the extruder and introduced into the mixing zone of the extruder. The rate of introduction of polyamide to the extruder is adjusted to allow sufficient residence time to melt the polyamide and cause it to react with the terminally functional polyolefin oligoomer to produce a copolymer by transesterification. The preferred residence time is from about 3 to about 5 minutes at the preferred temperature range of from about 260 to 300 ° C. The end-functional polyolefin oligomer is fed into the extruder through a separate port and the rate of introduction of the polyolefin oligomer is adjusted to provide the amount of polyolefin oligoomer segments needed to achieve the desired capacity as scavengers. oxygen of the polycondensates. A topical range of polyolefin oligoomer segments is from about 0.5% by weight to about 12% by weight of the total weight of the polycondensate product. A catalyst (transesterification / transamidation) that helps to achieve the transformation, such as a carboxylate of a transition metal, can optionally also be used in the extruder in an amount comprised in the range between 10-300 ppm of the mixture in the extruder. Cobalt carboxylates are the transesterification catalysts and cobalt octoate is especially preferred since it causes the reaction to occur rapidly and is commercially available at a reasonable cost and in concentration levels for direct use. As noted above, the transesterification reaction was allowed to occur.

ES 2 170 478 T3 in the extruder for about 3-5 minutes at a temperature of about 260-30 () C. Under these conditions the terminally functional polyolefin oligoomer forms a copolymer with the polyamide through transesterification. For the purposes of your understanding, transesterification can be understood as a reaction whereby the terminally functional polyolefin oligoomer species are replaced by some of the above polyamide monomeric species originally present in the starting polyamide. Regardless of the mechanism, a copolymer is formed with the polyolefin oligoomer species with single or multiple terminal functionality.

When prepared through a reactive extrusion process in which pellets are formed and then stored, the amount of moisture captured by the copolymer is most desirable in order to minimize the need for drying prior to article manufacture. for packaging. Control of captured moisture can be achieved through a two-stage process. First, the extruded copolymer can be cooled using a process consisting of immersing it in a nonaqueous solution before being chopped into pellets as disclosed in US Patent No. 5,536,793. This process allows the preparation of low humidity pellets. Then the balls are sealed directly in containers that do not allow moisture to pass (for example cans) for storage.

The pellets can be used directly from storage in subsequent melt stages commonly used in the packaging industry, such as air extrusion molding, amine forming, sheet extrusion, injection molding, coating melt. If drying is required it is desirable to dry the pellets in a vacuum oven or in a desiccant oven with a nitrogen coating.

In order to minimize the loss of utility as an oxygen scavenger of the copolymer, the copolymer can be produced during the casting stage used to make the packaging article. This depends on the flexibility of the manufacturing process and is topically preferred for extrusion type processes such as forming extrusion or sheet extrusion. As explained later, copolymers are relatively safe against obvious attack by oxogen once they are incorporated into a bottle or sheet.

Additives that may also be present in the copolycondensates of this invention include heat stabilizers, antioxidants, colorants, crystallization nucleating agents, aerating agents (when foam is needed), fillers, biodegradation accelerators, branching agents, spreading agents. chain.

As those of ordinary skill in the art will appreciate, the inclusion of these additives produces copolyomers that are within the spirit of this invention. The copolymers of this invention also serve for use in opaque applications such as rigid opaque crystalline copolycondensate trays containing low levels of crystallizing nucleating agents such as polyolefins. Furthermore, the copolymers of this invention could be used to prepare cellular structures in which the copolymers are foamed to reduce their density allowing the cost of the container to be further reduced. For certain applications, mixtures of the copolycondensates of this invention would be useful. Topically the mixing of the copolymers of this invention will take place with other polycondensates, especially polyamides. However, even non-miscible tiles may be appropriate for certain applications.

Although the applicants prefer to manufacture the copolymers of this invention using polycondensation methods, those skilled in the art will recognize that the copolymers could be formed, under certain circumstances, by a process of addition polymerization or by a combination of polycondensation and additional polymerization. It was previously noted that R1 in Formula I and / or R2 in Formula II may contain at least one olephonic unsaturation site. The availability of olephonic unsaturation sites in the polyamide backbone creates a condition whereby polyolefin oligoomer segments can be incorporated into the polyamide through an addition polymerization process. Alternatively, the availability of olephonic unsaturation sites in the polyamide backbone creates a condition whereby unsaturated fractions capable of participating in polycondensation can be attached to the polyamide backbone by an additive type reaction. Maleic anhydride and acrylic acid are both olephonically unsaturated and are good examples of these types of fractions that can be added to the polyamide backbone at unsaturated sites and create polycondensation sites at the other end of the molecules. These recently added polycondensation sites could later undergo a condensation reaction with species such as those represented in Formulas IV, V and VI, thus adding polyolefin segments to the polyamide. Even when R1 and R2 of Formulas I and II

ES 2 170 478 T3 are both saturated, another possible route is available for the addition of polyolefin oligoomer segments. The saturated polyamide chain can be reacted with an agent, such as maleic anhydride, capable of reacting with polyamide, for example at the polycondensation sites available at the ends of polyamide macromoecules. Such treatment of polyomers is well known in the art and it is often referred to as "malleation". Once attached by condensation to the polyamide (either along the main chain or at the ends of the polyamide molecules), the attached maleic anhydride creates olephonic unsaturation sites to which olefin oligoomers are incorporated by a reaction of addition. Copolyamides having polyolefin oligoomer segments that are manufactured by any of these various methods are well appreciated by applicants and considered to be within the scope of this invention.

The packaging polyamides of this discovery are well known in the art. They are generally prepared by polycondensation of one or more dioacidal species with one or more diamine species under polycondensation conditions and in the presence of a suitable polycondensation catalyst. Said polycondensations to form polyamides are also well studied and well known in the art and are not part, per se, of this invention. Although most polyamides could be considered with the benefit of being included in this invention, certain polyamides are most commonly used in the packaging industry and are therefore the preferred polyamides of this invention. These preferred polyamides include those that have diacidic moieties such as adopic acid, phthalic acid, isophthaolic acid, terephthalene acid, naphthalene dicarboxylic acid, substituted derivatives of the foregoing, and mixtures of the foregoing. Those skilled in the art will recognize that various derivatives of the diacids and diamines mentioned above can be used and still result in the formation of the same polyamides under polycondensation conditions. Generally, the segments of the polyamides of the copolyamides of this invention will be composed of segments of the polyamides that result from the condensation of the dioacids and diamines listed above.

When prepared by a transesterification / transamidation reaction in a reaction extruder as described above, the polycondensates of this invention are topically made into pellets and subsequently processed to make containers, bottles or loamines. The preferred type of container wall, bottle wall, or sheet construction comprises a three-layer representation as shown in Figure 1. The exterior of the bottle or container wall 24 is formed by a thicker layer 26 of unmodified packaging polyamide and may comprise recycled polyamide as it does not contact the container cavity or packaging material. The interior of the wall of the bottle or container 22 that defines the container cavity is formed by a thinner layer 28 of unmodified packaging polyamide. Intermediate layer 30 comprises the polyamides of this invention. Although the representation of Figure 1 may require special extrusion equipment, it is preferred for the following reasons: (1) creates a structure with a relatively thick layer of exposed polyamide that serves as a good passive barrier against oxygen in the air, (2) the inner layer in contact with the packaged material is also polyamide, which has a long history of use and acceptance as a material for the packaging of consumables, (3) by placing the copolyamides of this invention between two layers of unmodified polyamide with good properties as passive barriers against oxygen, it adds oxygen-trapping copolymers from direct contact with air or oxygen and retains its ability as oxygen-trapping agents by applying it. only against oxygen penetrating unmodified polyamide layers, and (4) the copolyamide and unmodified polyamides are so similar that they bond when extruded together without using a bonding adhesive layer.

The preferred three-layer representation described above is achieved in the simplest way by joint extrusion of a copolymer layer with the two unmodified polyamide layers. The copolymer is so chemically similar to unmodified polyamide that the three layers uniformly adhere to each other and form a monolotic structure on cooling. Adhesive bonding layers are not required. However, in articles of manufacture of this invention where recycling is not important, additional layers of materials other than polyamide can be incorporated to improve adhesion, improve barrier properties, reduce costs. It may be feasible to achieve the preferred three-layer representation by techniques other than co-extrusion, such as solution coating or heat-fusing the layers. Any method other than extrusion can have the disadvantages of: (1) reduction of trapping potential due to unwanted or inadvertent exposure of oxygen-trapping copolymers to air or oxygen; and (2) additional processing steps. For the manufacture of bottles the bonding of the three layers by means of adhesives would go against the objective of recyclability, unless the adhesive was based on polyamide or was compatible with polyamide. For the production of foils and wrappers, recyclability is not as important a consideration as in the case of bottles. In fact for laminates it may even be desirable to use layers of the copolymers of this discovery in conjunction with

ES 2 170 478 T3 layers of other materials such as layers of polyethylene vinyl alcohol and layers of polyolefins. Although immediate co-extrusion of these copolymers may be your preferred use, other options for use are also available. For example, the copolymers could be mixed in the form of a concentrate with other polyamides for the manufacture of sheets or bottles, or be used as an inner coating or layer in a multilayer construction, for example, for the packaging of electronic components.

In a broad representation, this invention discloses a laminar composition that includes at least one layer of a packaging material and at least one layer of an active oxygen-trapping copolyamide of this invention wherein said copolyamide is predominantly composed of polyamide segments and an active oxygen scavenger amount of polyolefin oligaomer segments. Predominantly, as used above, it means that the copolyamide is at least 50% by weight polyamide segments. Typically, the polyolefin oligoamer segments comprise between about 0.5% by weight and about 12% by weight of the copolyamide, preferably between about 2.0% by weight and about 8.0% by weight, and most preferably between about 2.0% by weight and about 6.0% by weight of the copolyamide. The packaging material layer is typically a thermoplastic packaging material. A list of preferred thermoplastic materials can be found in USA 21 CFR §177.1010 - 177.2910, revised on April 1, 1997. However, the copolyamides of this invention can be used as active oxygen scavengers to consume oxygen from the space. head shaped inner liner on cans or glass jars / bottles. In these applications, the packaging material layer will be composed of metal or glass. A layer of packaging material is preferably composed of polyamide and especially preferred are the polyamides from which the polyamide segments of the copolyamide have been derived. Another layer of packaging material preferably is composed of polyesters, especially polyesters such as those listed in USA 21 CFR §177.1590, revised on April 1, 1997. The use of the copolyamides of this invention in a laminar construction that also includes a polyester layer is especially attractive when passive gas barrier properties are required above those available, for example, with PET. In particular, beer bottles must be able not only to keep oxygen out and remove oxygen from the headspace, but must also serve to prevent carbon dioxide from escaping from the bottled beer. A polyamide based oxygen scavenger layer will provide a higher passive barrier than that provided by a polyester based oxygen scavenger layer to reduce the escape of carbon dioxide from the beer.

When desired for certain applications, methods are available to make the oxygen scavenging properties of these copolymers even more effective. For example, optionally, an oxidation catalyst may be added to the copolymer during the product manufacturing step. This is a separate catalyst additive to help uptake oxygen and is in addition to residual oxidation catalyst, if any, that may remain from the copolymer formation. The presence of such a catalyst, when added and used in an amount comprised in the range between 10 and 2,000 ppm with respect to the weight of the copolymer, serves to facilitate the level of captured oxygen, often very markedly. Preferred catalysts are multivalent transition metals, such as iron and manganese. Cobalt is especially preferred.

The copolymers of this invention can be used in conjunction with other oxygen consuming systems. For example, a representation to obtain a greater capacity to trap oxygen for manufactured products of this invention involves the optional inclusion of photo-activators (such as small amounts of benzophenone) in the manufactured products together with the copolymers of this discovery. Manufactured products, such as bottles, containing the optional photoactive materials, in addition to the copolymers of this discovery would be exposed to UV light sufficiently to activate the photoactive materials to capture oxygen prior to use (i.e. filling the bottle) or shipping the manufactured product.

In a different and improved representation, additional oxygen scavenging materials are deployed within the cavity along with the use of the copolymers of this discovery that would comprise the packaging material. Typically these additional oxygen scavengers would take the form of a sachet, especially for oxygen sensitive non-consumable materials such as electronic components. For oxygen sensitive consumables, the additional oxygen scavenging materials could take the form of a matte surface as is often used in butchers under a cut of meat or poultry. An additional oxygen scavenger can also be deployed in the form of a cape for a bottle cap. In many representations of this technique, the additional oxygen scavenger employed is one that constitutes a completely different system from the

ES 2 170 478 T3 copolyamides of this invention.

In a different and improved embodiment, the copolymers of this discovery are deployed as an internal coating for a glass or metal container or can, alone or in conjunction with known polyomers for coating glass / metal containers. In either situation, both types of oxygen barriers, active and passive, are present, since the glass / metal container is itself a passive barrier against oxygen. In either case, the copolymers of this discovery are prepared to constitute a thermoset resin, or a blending resin, which can be used to coat the inside of the container walls by means of a spray. A spray dispensable resin could be made in the simplest way by mixing a small amount of a copolymer of this invention with a thermosetting resin normally used for coating cans. It may be necessary to prepare the copolymer with a percentage of polyolefin oligomer segments greater than 12% by weight such that only a minimal amount of the copolymer is required mixed with the resin that can be dispensed by a spray. The advantage of a glass / metal container liner consisting of an active oxygen scavenger is that it offers the opportunity to dissipate oxygen from the headspace. Using a can liner to remove oxygen from the headspace in a can containing an edible product is much more attractive than using a sachet or other item that the consumer must separate from the product and dispose of.

As has already been stated on several occasions, the recycling of bottles made using the copolymers of this discovery is an important inventive aspect of this discovery. Furthermore, the manufactured bottles must be suitable for recycling with other polyamide bottles without the need for special processing, such as delamination or depolymerization. A quick review of the materials present in the manufactured bottles of this invention shows how the recycling requirements have been met. Figure 1 shows a cross section of the preferred construction of the bottle wall. In Figure 1, layers 26 and 28 are preferably comprised of unmodified packaging polyamide. The outer surface 24 is defined by the thickest layer of polyamide (which may already be recycled polyamide) and the inner surface 22 (i.e., the container or bottle cavity) is defined by the thin layer 28 of topically virgin polyamide. Intermediate layer 30 was formed from the oxygen scavenging copolyomers of this invention. For a topical bottle of approximately one-half liter capacity, the oxygen-scavenging copolymer layer of the bottle represents about 5% by weight of the total bottle. The remaining 95% of the bottle is unmodified polyamide. Under the highest percentage copolymer conditions, which are about 12% by weight polyolefin oligoomer, the copolymer layer is even 88% by weight polyamide / polyamide segments and is topically 96% by weight of polyamide when the most preferred percentages of polyolefin oligoomers are used. This means that the final bottle manufactured is at least 99.4% by weight polyamide and topically 99.8% by weight polyamide. It is this high percentage of polyamide in the manufactured bottle that makes it suitable for recycling with other polyamide bottles.

The main application of the oxygen scavenging copolymers of this discovery will be their use for the manufacture of container walls and packaging articles, already mentioned several times previously in this discovery. A fundamental use of these manufactured articles is the packaging of perishable food and perishable objects. A non-limiting list of perishable foods particularly suitable for the type of packaging described in this discovery would include dairy products, such as milk, yogurt, ice cream and cheese; prepared foods, such as casseroles and soups; Meat products such as hot dogs, assorted cold cuts, chicken and beef jerky; individual products, such as ready meals or ready-made side dishes; ethnic offerings such as pasta and spaghetti sauce; condiments, such as barbecue sauce, ketchup, mustard, and mayonnaise; beverages, such as fruit juices; dry foods, such as dried fruits, dried vegetables, and breakfast cereals; baked goods, such as bread, crackers, pasta, cookies, and muffins; finger foods such as candy, potato chips, and cheese snacks; spreads such as peanut butter, peanut butter and jelly combinations, jams and jellies, and dressings whether dry or fresh. Generally, the copolymers discovered and the packages made with them can be used to improve the barrier properties in packaging materials intended for any type of product, be it food or drink or others, that degrade in the presence of oxygen. In essence, manufactured packages including the active copolyamides of this invention serve to extend the shelf life of oxygen sensitive products. The copolyamides of this invention can also be applied to their use for the packaging of a wide variety of non-food products since they have the ability to trap oxygen, either in the presence or in the absence of water or humidity.

IS 2 170 478 T3

Series N ° 1 Examples

Preparation of the copolyamide and properties

The copolyomers referenced in Tables 1 and 2, unless otherwise indicated, were prepared in the manner described herein. The preparations were made on a Werner and Pfleiderer ZSK-30 co-rotating twin thread extruder with fully intertwined threads with a length of 45: 1 to thread diameter. The TSK-30 extruder was also equipped with a KTRON weight loss pellet feeder. The amorphous polyamides used were either AMODEL® 2010 or ZYTEL® 330 resin pellets, which were previously dried overnight at 125^°C in a desiccant oven. AMODEL¹® 2010 is a polyphthalamide comprising over 40% by molarity of terephthalic diacid and over 60% by molarity of isophthalic diacid as derivative fractions and 100% by molarity of hexamethylene diamine (HMDA) as diamine fraction. ZYTEL¹® 330 is a polyphthalamide that comprises over 30% by molarity of terephthalic diacid and over 70% by molarity of isophthalic diacid as derivative fractions and 100% by molarity of hexamethylene diamine (HMDA) as fraction of diamine.

The dry polyamide pellets were introduced into the feed section of the extruder under a blanket of nitrogen gas. The polybutadiene oligomer (PDB) with a terminal hydroxy group was kept in a viscous fluid vessel under pressure of nitrogen gas, transported separately from the gas by a positive displacement pump to the molten polyamide through an injection port in the extruder. The cyclomer used was a PDB diol with a molecular weight of approximately 1230 (R20LM available from Elf Attochem). The polyamide feed rate was established at 6.7 kg / hr (14.8 lb / hr) while the PDB was added at a rate of 28 g / hr (0.062 lb / hr) to obtain a copolyamide with about 96% by weight of polyamide segments and about 4% by weight of PDB segments. The residence time of the extrusion was in the range of 3-4 minutes and the temperature profile of the reactive extrusion was maintained in the range of 280-300.^°C. The volatiles generated in the reaction were removed by means of a vacuum pump. The copolymer extrudate was quenched on a Sandvik metal belt and pelletized. The finished pellets were packaged in moisture and gas resistant aluminum foil bags. To keep the copolymer free from contamination with oxygen, the entire line of the extrusion process was kept under a layer of nitrogen gas including a previous injection on the bags for storage. It should be noted that the copolyamides for this series were prepared in the absence of a transesterification catalyst. Optionally, a transition metal can be used as a transesterification catalyst in the extruder mixture in a concentration comprised in the range between 50-300 ppm with respect to the weight of the extruder mixture.

Reactive extrusion resins prepared as indicated above were evaluated for their oxygen absorptive capacity, thermic properties, inherent viscosity values, molecular weight distribution, mechaonic properties, and dynaomic mechaonic properties. Some of the resulting data are summarized in Table 1. Some of the beads were treated with osmium tetraoxide, which stains only the polyolefin oligoomer (POO) segments of the copolymers. Fine sections of product pellets stained with osmium tetraoxide were also obtained in Transmission Electron Micrographs which showed the dioameter segments of the OOPs clustered in a size range less than about 15 nm. The results are in accordance with the formation of polyamide copolyether entities in the extruder because (1) the IVs (inherent viscosity) values ​​for extrusion resins were higher than those of the source materials, (2) due to T_(c)s (glass transition temperatures) slightly reduced, and also (3) due to the size of the OOP diameter segments.

In Table 1, resin 117-2B was prepared using a 50-50% by weight mixture of 117-1A and 117-2. The t_(c) It was determined by differential scanning calorimetry. IV was determined using the ASTM D2857 method in phenol-TCE solvent and at 25^°C and is given in units of dl / g. Mn and Mw by gel permeate chromatography (ASTM D3593 and ASTM 4001) using columns of Shodex A-80MS and hexafluoro isopropanol with sodium triacetate buffer as solvent. Izod impact force was determined by the ASTM D-256 method and is given in units of kg m / cm (ft lb / inch) of shear.

IS 2 170 478 T3

TABLE 1

<td rowspan="2">Id Resin and series Property</td><td rowspan="2">AMODEL® only Id No. 117-1A</td><td colspan="2">AMODEL® 4% wt PBD</td><td rowspan="2">AMODEL® 2% wt PBD Id No. 117-2B</td><td rowspan="2">ZYTEL® only Id No. 119-1</td><td rowspan="2">ZYTEL® 4% wt PBD Id No. 119-2</td>

<td>No.</td><td>Id 117-2</td>

<td>Glass transition temperature (T (_c)), ° C</td><td> 107.7</td><td colspan="2"> 121.2</td><td></td><td> 118</td><td> 122</td>

<td>Intrinsic viscosity (IV)</td><td> 0.85</td><td colspan="2"> 1.04</td><td></td><td> 0.72</td><td> 0.78</td>

<td>Molecular weight, (Mn, X 10^-3)</td><td> 17.8</td><td colspan="2"> 20.9</td><td></td><td> 15.9</td><td> 17.3</td>

<td>Molecular weight, (Mw, X 10^-3)</td><td> 59.3</td><td colspan="2"> 91.1</td><td></td><td> 42.2</td><td> 50.8</td>

<td>Mn / Mw</td><td> 3.33</td><td colspan="2"> 4.36</td><td></td><td> 2.66</td><td> 2.94</td>

<td>Izod impact force</td><td> 0.116 (2.14)</td><td colspan="2"></td><td> 0.115 (2.11)</td><td> 0.073 (1.35)</td><td> 0.097 (1.79)</td>

Oxygen entrapment by copolyamide - series 1

The resins of the Series 1 preparations were evaluated to study the captured oxygen by placing 25 g of pellets in 500 mL ball jars equipped with a septa for sampling. The samples were stored at 60 ° C in an oven and the oxygen content of the jars was monitored on a Mocon HS750 oxygen analyzer by drawing 2 cc gaseous aliquots at periodic intervals. The data obtained are shown in Table 2 and have been represented graphically in Figure 2. The identification numbers of the resins in Figure 2 and also in Table 3 are preceded by the character sequence "19440" which was an internal control number of the project and which should be ignored when interpreting the results, it can be discerned from Simply put from these results that the copolyamides of this invention have a substantial ability to trap oxygen. In this way a main objective of this invention has been achieved in the sense that capacity as an active scavenger of oxygen has been added to a material based on polyamide, which already inherently exhibits superior properties as a passive barrier against oxygen when compared to constructions of similar polyester.

The numerical values ​​in rows 2-7 and in columns 2-6 of Table 2 list the percentage of oxygen remaining in the air sample trapped in the ball jars along with the 25 g resin sample. Resin identification number 120-1 corresponds to an oxygen scavenger resin discovered in US Patent Application No.^° 08 / 717,370 and is included for comparison purposes together with unmodified AMODEL® and ZYTEL® control samples. It should be noted that the tests carried out in Table 2 were carried out in the absence of cobalt or other transition metal (s) as promoters / catalysts of the reaction with oxygen and its cataciation by the copolymer. In practice, the copolyamides of the invention are typically deployed in the presence of about 102000 ppm (with respect to the weight of the copolymer) of a transition metal as a catalyst. The catalyst transition metal is typically added to the copolymer during manufacture of the packaging article. Cobalt is the preferred catalyst, with cobalt added in the form of cobalt carboxylate being especially preferred, and cobalt octoate being most especially preferred.

IS 2 170 478 T3

TABLE 2

<td>Id Resin and analysis Day number</td><td>AMODEL® only Id No. 117-1A</td><td>AMODEL® 4% wt PBD N^° Id 117-2</td><td>AMODEL® 2% wt PBD Id No. 117-2B</td><td>only Id No. 119-1</td><td>ZYTEL® 4% wt PBD Id No. 119-2</td>

<td> 0</td><td> 20.9</td><td> 20.9</td><td> 20.9</td><td> 20.9</td><td> 20.9</td>

<td> 2</td><td> 20.9</td><td> 20.6</td><td> 20.8</td><td> 20.5</td><td> 19.3</td>

<td> 5</td><td> 20.8</td><td> 20.3</td><td> 20.7</td><td> 18.5</td><td> 16.7</td>

<td> 7</td><td> 20.8</td><td> 20.1</td><td> 20.6</td><td> 17.5</td><td> 15.5</td>

<td> 14</td><td> 20.7</td><td> 19.1</td><td> 20.5</td><td> 15.2</td><td> 12.7</td>

<td> 21</td><td> 20.5</td><td> 17.4</td><td> 20.3</td><td> 13.5</td><td> 10.9</td>

<td> 28</td><td> 20.5</td><td> 16.3</td><td> 20.3</td><td> 12.5</td><td> 9.8</td>

Series N ° 2 Examples

Preparation of the copolyamide and properties

A second series of copolymer preparations was made using MDX-6 as the polyamide in the extruder and therefore as the source of polyamide segments in the copolyamide. MXD-6 is pol (mxylenadipamide) and has been previously described in this application. Preparation for Series 2 was the same as for Series 1 throughout the extrusion except that MXD-6 was used instead of AMODEL® or ZYTEL®. The MXD-6 Series 2 copolymer was extruded through a 6-inch slot die manufactured by Extrusion Dies, Inc. (EDI) (a 6-inch EDI slot die) onto a cooling stack of two rollers and then recovered as sheets on a constant tension winder. After recovery, the samples were placed in heat sealable metal bags. The bags were purged with nitrogen gas and sealed. The values ​​of polymer feed rate, thread speed, extruder temperature, degree of vacuum, and residence time were adjusted to provide stable extrusion of the MXD6 copolyamide lamina. Table 3 shows the extrusion process data used for the two Series of resins, Series 1 and Series 2. The MXD-6 loamine alone was designated by the identification number 157-1 and the MDX-6 copolymer with 4% by weight of PBD was designated by the identification number 158-1. In Table 3 all the pressures listed in Columns 10-13 are as indicated by the pressure gauge used. Oxygen entrapment by copolyamide - series 2

The resins of the Series 2 preparations were evaluated to study the captured oxygen by placing only 10 g of loamines (instead of 25 g of pellets as in Series 1) in 500 mL Ball jars equipped with septa for sampling. . Samples were stored at 60^°C in an oven and the oxygen content of the jars was monitored on a Mocon HS750 oxygen analyzer by drawing 2cc gaseous aliquots at periodic intervals. The data obtained have also been represented graphically in Figure 2 together with the data of the Series 1 resins. From Figure 2 it can be extracted that 10 g of copolyamide in the form of sheets are almost as effective as 25 g of copolyamide in pelletized in terms of captured oxygen. There are several factors involved that make direct comparisons difficult. Sheet samples allow greater access to the oxygen scavenger present compared to pelletized samples. Furthermore, polyamides are better as passive barriers against oxygen than polyamides, making it more difficult for oxygen to access the trapping fraction in a copolyamide than in a copolyether. In practice, the copolyamide sheets are also topically unfolded in the presence of about 10-2000 ppm (based on the weight of the copolymer) of a transition metal as a catalyst. The transition metal as a catalyst is typically added to the copolymer during manufacture of the packaging article. As above, cobalt is the preferred catalyst, with cobalt added in the form of cobalt carboxylate being especially preferred, and cobalt octoate being most especially preferred.

IS 2 170 478 T3

TABLE 3 - EXTRUSION WEIGHT DATA

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IS 2 170 478 T3

As can be learned from the data in the examples, the copolyamides of this invention exhibit a substantial ability to trap oxygen, which serves to increase their already superior properties as passive oxygen barriers compared to polyester. The copolymers discovered herein are advantageously deployed as one layer in a multi-layer packaging construction, particularly when an additional layer is present as a passive oxygen barrier to protect the active oxygen scavenging copolymers from obvious attack by oxygen. (from oxygen present in the air) and also when an adjacent layer is chemically similar to copolyamides. Those skilled in the art, however, will appreciate that variations on this basic form of deployment are possible and should be considered within the scope of this invention.