Patent Description:
Conventional polyamides are generally known for use in many applications including, for example, textiles, automotive parts, carpeting, and sportswear.

In some of these applications, the polyamides in question may be exposed to high temperatures, e.g., on the order of <NUM> to <NUM>. It is known that, when exposed to such high temperature, a number of irreversible chemical and physical changes affect the polyamide, which manifest themselves through several disadvantageous properties. The polyamide may, for example, become brittle or discolored. Furthermore, desirable mechanical properties of the polyamide, such as tensile strength and impact resilience, typically diminish from exposure to high temperatures. Thermoplastic polyamides, in particular, are frequently used in the form of glass fiber-reinforced molding compounds in construction materials. In many cases, these materials are subjected to increased temperatures, which lead to damage, e.g., thermooxidative damage, to the polyamide.

In some cases, heat stabilizers or heat stabilizer packages may be added to the polyamide mixture in order to improve performance, e.g., at higher temperatures. The addition of conventional heat stabilizer packages has been shown to retard some thermooxidative damage, but typically these heat stabilizer packages merely delay the damage and do not permanently prevent it. As mentioned above, examples of the thermooxidative damage include decreases in tensile strength and impact resilience.

In addition, conventional stabilizer packages have been found to be ineffective over higher temperature ranges, e.g., over particular temperature gaps such as from <NUM> to <NUM> or from <NUM> to <NUM>. In particular, the use of many known stabilizer packages yields polyamides that have stability/performance gaps over broad temperature ranges, e.g., the aforementioned temperature gaps. For example, polyamides that employ copper-based stabilizers yield polyamides that have performance gaps at temperatures above <NUM>. Similarly, polyamides that employ polyol-based stabilizers yield polyamides that have performance gaps at temperatures above <NUM>. Thus, when polyamides are exposed to these temperatures, the polyamides perform poorly, e.g., in terms of tensile strength and/or impact resilience, inter alia. Further, while many of these stabilizers may improve performance at some temperatures, each stabilizer package often presents its own set of additional shortcomings. Stabilizer packages that utilize iron-based stabilizers, for example, are known to require a high degree of precision in the average particle size of the iron compound, which presents difficulties in production. Furthermore, these iron-based stabilizer packages demonstrate stability issues, e.g., the polyamide may degrade during various production stages. As a result, the residence time during the various stages of the production process must be carefully monitored. Similar issues are present in polyamides that utilize zinc-based stabilizers.

As one example of a conventional stabilizer package, <CIT> discloses a polyamide molding compound comprising: (A) a polyamide mixture (<NUM>-<NUM> wt. %) comprising (A1) at least one semiaromatic, semicrystalline polyamide having a melting point of <NUM> - <NUM>, and (A2) at least one caprolactam-containing polyamide that is different from the at least one semiaromatic, semicrystalline polyamide (A1) and that has a caprolactam content of at least <NUM> wt. %; (B1) at least one filler and reinforcing agent (<NUM>-<NUM> wt. %); (C) at least one thermal stabilizer (<NUM>-<NUM> wt. %); and (D) at least one additive (<NUM>-<NUM> wt. The polyamide molding compound comprises: (A) a polyamide mixture (<NUM>-<NUM> wt. %) comprising (A1) at least one semiaromatic, semicrystalline polyamide having a melting point of <NUM> - <NUM>, and (A2) at least one caprolactam-containing polyamide that is different from the at least one semiaromatic, semicrystalline polyamide (A1) and that has a caprolactam content of at least <NUM> wt. The sum of the caprolactam contained in polyamide (A1) and polyamide (A2) is <NUM>-<NUM> wt. %, with respect to the polyamide mixture. The polyamide mixture further comprises: (B1) at least one filler and reinforcing agent (<NUM>-<NUM> wt. %); (C) at least one thermal stabilizer (<NUM>-<NUM> wt. %); and (D) at least one additive (<NUM>-<NUM> wt. No metal salts and/or metal oxides of a transition metal of the groups VB, VIB, VIIB or VIIIB of the periodic table are present in the polyamide molding compound.

GB <NUM>,<NUM> discloses a stabilized polyamide containing as stabilizers <NUM> to <NUM>% by weight of hypophosphoric acid and/or a hypophosphate and <NUM> to <NUM>% by weight of a water soluble cerium (III) salt and/or a water-soluble titanium (III) salt. Specified hydrophosphates are lithium, sodium, potassium, magnesium, calcium, barium, aluminium, cerium, thorium, copper, zinc, titanium, iron, nickel and cobalt hypophosphates. Specified water-soluble cerium (III) and titanium (III) salts are the chlorides, bromides, halides, sulphonates, formates and acetates. Specified polyamides are those derived from caprolactam, caprylic lactam, o -amino-undecanoic acid, the salts of adipic, suberic, sebacic or decamethylene dicarbonic acid with hexamethylene or decamethylene diamine, of heptane dicarboxylic acid with bis-(<NUM>-aminocyclohexyl)-methane, of tetramethylene diisocyanate and adipic acid and of aliphatic w-aminoalcohols and dicarboxylic acids each with <NUM> to <NUM> carbon atoms between the functional groups. The stabilizers may be added to the polyamides during or after the polycondensation reaction. Delustrants, e.g. cerium dioxide, titanium dioxide, thorium dioxide or ytrium trioxide may also be added to the polyamides. Examples (<NUM>) and (<NUM>) describe the polymerization of:-(<NUM>) hexamethylene diammonium adipate in the presence of disodium dihydrogen hypophosphate hexahydrate and (a) titanium (III) chloride hexahydrate, (b) cerium (III) chloride; (<NUM>) caprolactam in the presence of (a) thorium hypophosphate and titanium (III) chloride hexahydrate, whilst in Example (<NUM>) polycaprylic lactam is mixed with tetrasodium hypophosphate, titanium (III) acetate and titanium dioxide.

Also, <CIT>, discloses the use of a radical catcher for the stabilization of organic polymer against photochemically, thermally, physically and/or chemically induced dismantling through free radical, preferably against UV-light exposure. Cerium dioxide is used as an inorganic radical catcher. Independent claims are included for: (<NUM>) a polymer composition comprising cerium dioxide, a UV-absorber and/or a second radical catcher; (<NUM>) agent for the stabilization of organic polymer comprising a combination of cerium dioxide, a UV-absorber and/or at least a second radical catcher; and (<NUM>) a procedure for the stabilization of organic polymer, preferably in the form of polymer based formulation, lacquer, color or coating mass against photochemically, thermally, physically and/or chemically induced dismantling through free radical, comprising mixing cerium dioxide as inorganic radical catcher, optionally in combination with the UV-absorber or with the second radical catcher.

And, <CIT> discloses a flame retardant molding composition. The composition contains a polymeric component, preferably a polyamide, red phosphorus, zinc borate, talcum and a lanthanide compound. The composition is characterized by its combined flame resistance and good mechanical properties. The composition may also contain fillers or reinforcing substances, an impact modifier and further conventional additives.

<CIT> relates to polyamide molding compounds which have an improved resistance to heat-aging and comprise the following compositions: (A) <NUM> to <NUM> wt. % of at least one polyamide, (B) <NUM> to <NUM> wt. % of at least one filler and reinforcing means, (C) <NUM> to <NUM> wt. % of at least one inorganic radical interceptor, (D) <NUM> to <NUM> wt. % of at least one heat stabilizer which is different from the inorganic free-radical scavenger under (C), and (E) <NUM> to <NUM> wt. % of at least one additive.

Even in view of the references, the need exists for an improved polyamide compound that demonstrates superior performance over a broad temperature range, in particular, that demonstrates significant improvements in tensile strength and impact resilience (among other performance characteristics) at higher temperature ranges, e.g., above <NUM> or from <NUM> to <NUM> (temperature gaps), which is where many polyamide structures are utilized, for example in automotive applications that deal with engine heat.

The present disclosure relates to a heat-stabilized polyamide composition comprising from <NUM> wt. % to <NUM> wt. % of an amide polymer (optionally a first amide polymer and a second amide polymer), from <NUM> wt. % to <NUM> wt. % of a cerium-based heat stabilizer, a second heat stabilizer, e.g., a copper-based compound, optionally present in an amount ranging from <NUM> wt. % to <NUM> wt. %a halide additive, and less than <NUM> wt. % of a stearate additive. A weight ratio of halide additive to stearate additive is less than <NUM>, e.g., less than <NUM>. The polyamide composition may have a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of <NUM> and measured at <NUM> or when heat aged for <NUM> hours over a temperature range of from <NUM> to <NUM>, and measured at <NUM>. The cerium-based heat stabilizer may be a cerium ligand compound selected from the group consisting of cerium hydrates, cerium acetates, cerium oxyhydrate, cerium phosphate, and combinations thereof and the activation temperature of the cerium-based heat stabilizer is at least <NUM>% greater than the activation temperature of the second heat stabilizer. In some cases, the cerium-based heat stabilizer is a cerium-based ligand compound; the second heat stabilizer is a copper-based heat stabilizer, and the polyamide composition has a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>.

In some embodiments, the disclosure relates to a heat-stabilized polyamide composition comprising from <NUM> wt. % to <NUM> wt. % of an amide polymer, from <NUM> wt. % to <NUM> wt. % of a cerium-based heat stabilizer, and a second heat stabilizer. The amide polymer may comprise greater than <NUM> wt. %, based on the total weight of the amide polymer, of a low caprolactam content polyamide; and less than <NUM> wt. %, based on the total weight of the amide polymer, of a non-low caprolactam content polyamide and/or a non-low melt temperature polyamide. The low caprolactam content polyamide may comprise PA-<NUM>,<NUM>/<NUM>; PA-6T/<NUM>; PA-<NUM>,<NUM>/6T/<NUM>; PA-<NUM>,<NUM>/6I/<NUM>; PA-6I/<NUM>; or 6T/6I/<NUM>; or combinations thereof and may comprise less than <NUM> wt. % caprolactam. The low melt temperature polyamide may have a melt temperature below <NUM>. The polyamide composition may have a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours over a temperature range of from <NUM> to <NUM>, and measured at <NUM>.

In some embodiments, the disclosure relates to a heat-stabilized polyamide composition comprising from <NUM> wt. % to <NUM> wt. % of an amide polymer, from <NUM> wt. % to <NUM> wt. from <NUM> ppm to <NUM> ppm, of cerium oxide and/or cerium oxyhydrate, a second heat stabilizer, a halide additive, and less than <NUM> wt. % of a stearate additive. A weight ratio of halide additive to stearate additive may be less than <NUM>, and the polyamide composition may optionally have a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>. The polyamide composition may also comprise iodide (ion) present in an amount ranging from <NUM> wppm to <NUM> wppm. The amide polymer may comprise greater than <NUM> wt. %, based on the total weight of the amide polymer, of a low caprolactam content polyamide; and less than <NUM> wt. %, based on the total weight of the amide polymer, of a non-low caprolactam content polyamide or a non-low melt temperature polyamide. The polyamide composition may have a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours over a temperature range of from <NUM> to <NUM>, and measured at <NUM>.

This disclosure relates to heat-stabilized polyamide compositions that comprise unique and synergistic heat stabilizer packages, which provide for significant improvements in performance, e.g., tensile strength and/or impact resilience, at higher temperatures. Conventional heat stabilizer packages suffer from stability/performance gaps over broad temperature ranges, and these performance gaps often occur at temperatures at which polyamide structures, e.g., automotive component applications are employed. As a result, the polyamide structures demonstrate performance and/or structural failures. The disclosed polyamide compositions and structures made therefrom allow for uses in applications that require exposure to higher temperatures. Improvement in heat-aging resilience is particularly desirable, because it can result in longer lifespans for thermally loaded polyamide components. Furthermore, improved heat-aging resilience may diminish the failure risk of thermally loaded polyamide components.

It has now been discovered that the use of synergistic heat stabilizers (heat stabilizer packages), preferably in specific amounts, unexpectedly provides for superior performance over broad temperature ranges. More specifically, the polyamide compositions disclosed herein have been surprisingly found to achieve significant performance improvements at temperatures ranging from <NUM> to <NUM>, e.g., <NUM> to <NUM>, especially when exposed to such temperatures for prolonged periods of time. Importantly, this temperature range is where many polyamide structures are utilized, for example in automotive applications. Exemplary automotive applications may include a variety of "under-the-hood" uses, such as cooling systems for internal combustion engines. In particular, many polyamide structures are employed in turbo chargers and charge air cooler systems, which expose the polyamide to high temperatures. Due to the unexpectedly superior performance of the heat-stabilized polyamide compositions, they are particularly well-suited to these applications.

In addition, the inventors have found that the use of particular (greater) quantities of low caprolactam content polyamide, e.g., PA-<NUM>/<NUM> copolymer, e.g., greater than <NUM> wt. %, (and thus lower amount of higher caprolactam content polyamides, e.g., PA-<NUM>) surprisingly provides for better heat stability over the aforementioned temperature ranges, especially when employed along with the synergistic heat stabilizer packages. Also, it has unexpectedly been found that the use of particular (greater) quantities of polyamides having low melt temperatures, e.g., below <NUM>, (and thus lower amounts of higher melt temperature polyamides, e.g., PA-<NUM>) actually improves heat stability. Traditionally, it has been believed that the use of low caprolactam content polyamides and/or low melt temperature polyamides would be detrimental to the ultimate high temperature performance of the resultant polymer composition, e.g., since these low temperature polyamides have lower melt temperatures than high caprolactam content polyamides. The inventors have unexpectedly found that the addition of certain quantities of low caprolactam content polyamides and/or low melt temperature polyamides actually improves high temperature heat performance. Without being bound by theory, it is postulated that, at higher temperatures, these amide polymers actually "unzip" and shift toward the monomer phase, which surprisingly leads to the high heat performance improvements. Further, it is believed that the use of the polyamides having low melt temperatures actually provides for a reduction of the temperature at which the unzipping occurs, thus unexpectedly further contributing to improved thermal stability.

Some polyamides may be low caprolactam content polyamides as well as low melt temperature polyamides, e.g., PA-<NUM>/<NUM>. In other cases, low melt temperature polyamides may not include some low caprolactam content polyamides, and vice versa.

In some cases, the heat-stabilized polyamide compositions disclosed herein comprise an amide polymer and a particular stabilizer package comprising a first heat stabilizer and a second heat stabilizer. These components are present in the heat-stabilized polyamide composition at the specific amount, limits, and ratios discussed herein. The first heat stabilizer may comprise a cerium-based compound, e.g., a cerium-based compound. The second heat stabilizer may vary, and, in preferred embodiments, it is a copper-based compound, e.g., a copper halide. In some embodiments, the cerium-based heat stabilizer is employed in particular amounts or concentration ranges. In some cases, the cerium-based heat stabilizer and the second heat stabilizer are utilized in amounts such that the weight ratio of the cerium-based heat stabilizer to the second heat stabilizer falls within a certain range or limit, as discussed herein.

In some embodiments, the heat stabilizer comprises specific oxide/oxyhydrate compounds, preferably cerium oxide and/or cerium oxyhydrate. In some cases , cerium oxyhydrate and cerium oxide may have a CAS number of <NUM>-<NUM>-<NUM>; cerium hydrate may have a <NPL>.

The polyamide further comprises (in addition to the cerium-based compound and the second heat stabilizer) a halide additive, e.g., a chloride, a bromide, and/or an iodide. In some cases, the purpose of the halide additive is to improve the stabilization of the polyamide composition. Surprisingly, the inventors have discovered that, when employed as described herein, the halide additive works synergistically with the stabilizer package by mitigating free radical oxidation of polyamides. Exemplary halide additives include potassium chloride, potassium bromide, and potassium iodide. In some cases, these additives are utilized in amounts discussed herein.

The heat-stabilized polyamide comprises the stearate additives, e.g., calcium stearates or zinc stearates, in an amount of less than <NUM> wt. Generally, stearates are not known to contribute to stabilization; rather, stearate additives are typically used for lubrication and/or to aid in mold release. Because synergistic small amounts are employed, the disclosed heat-stabilized polyamide compositions are able to effectively produce polyamide structures without requiring high amounts of stearate lubricants typically present in conventional polyamides, thus providing production efficiencies. Also, the inventors have found that the small amounts of stearate additive is reduces the potential for formation of detrimental stearate degradation products. In particular, the stearate additives have been found to degrade at higher temperatures, giving rise to further stability problems in the polyamide compositions.

The inventors have also discovered that when the weight ratio of the halide additive to the stearate additive is maintained within certain ranges and/or limits, the stabilization is synergistically improved. In some embodiments, the weight ratio of halide additive, e.g., bromide or iodide, to stearate additive, e.g., calcium stearate or zinc stearate is less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of ranges, this weight ratio may range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of lower limits, this ratio may be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>.

In some cases, the ratio of the weight ratio of the second heat stabilizer, e.g., copper-based stabilizer, to the halide additive is less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of ranges, the weight ratio of the cerium-based heat stabilizer to the halide may range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of lower limits, the weight ratio of the cerium-based heat stabilizer to the halide is at least <NUM>, e.g., at least <NUM>, at least <NUM>, or at least <NUM>.

Importantly, the weight ratio of the cerium-based heat stabilizer to the second heat stabilizer, e.g., a copper-based heat stabilizer, may be less than <NUM>:<NUM>, preferably the weight ratio of the cerium-based heat stabilizer to the second heat stabilizer ranges from <NUM> to <NUM>. This weight ratio may be referred to herein as the "cerium ratio. " Preferably the second heat stabilizer does not comprise a stearate compound, e.g., calcium stearate, and the ratio is calculated as such. In other embodiments, the cerium ratio is greater than <NUM>. Additional limits and ranges for the cerium ratio are provided herein. Without being bound by theory, it is believed that the use of the specific amounts of cerium-based heat stabilizer (as mentioned herein) affect the activation of the stabilizer package. And the activation provided by the aforementioned stabilizer packages synergistically contributes to improvements in the profile of the stabilization, especially over broader (higher) temperature ranges. In some cases, the cerium-based heat stabilizer may have a particular activation temperature and the second heat stabilizer may have a particular activation temperature different from the cerium-based heat stabilizer. The cerium-based heat stabilizer, for example, may have a higher activation temperature than the second heat stabilizer, e.g., a copper-based compound. The synergistic combination of the two heat stabilizers (at the aforementioned cerium ratios) allows the cerium-based heat stabilizer to prevent thermal damage to the polyamide composition, particularly at higher temperatures, while the second heat stabilizer supplements the prevention of thermal damage at (slightly) lower temperatures. Thus, the weight ratio of the cerium-based heat stabilizer to the second heat stabilizer has been found to have an effect on the performance properties, e.g., tensile strength and impact resilience, of the resultant polyamide.

In contrast, although some conventional heat stabilizer packages employ cerium and other stabilizers, there is little or no instruction as to the importance of the weight ratio of cerium-based heat stabilizer to second (non-stearate) heat stabilizer, as disclosed herein. Further, some conventional stabilizer packages may rely on combinations of second heat stabilizers, e.g., combinations of copper-based compounds and stearates such as calcium stearate. Many of these packages, however, utilize much lower amounts of copper-based compound and high amounts of stearates and/or hypophosphoric acid and/or a hypophosphate, and as a result do not provide improvements in the profile of the stabilization, e.g., the consistent retardation of thermal damage over the broad temperature ranges discussed herein. Phosphorus-based compounds are generally known in the art as a class of antioxidant stabilizers. It has been found, however, that these phosphorous stabilizers provide only short-term stability, and as such are not desirable. The disclosed stabilizer packages have been found to function effectively without the need for additional phosphorus-based stabilizers such as hypophosphoric acid and/or a hypophosphate. As a result, the use of these additives in heat-stabilized polyamides can be beneficially eliminated and the stabilization package simplified.

As one result of using these components, preferably in the specified ranges, limits, and/or ratios, the heat-stabilized polyamide compositions demonstrate unexpectedly high tensile strength after exposure to high temperatures. Thus, by incorporating the heat stabilizer packages disclosed herein, the inventors have found that the performance of polyamide compositions can be improved, e.g., at higher temperatures, and that damage typically suffered by polyamide compositions at higher temperatures, e.g., theremooxidative damage, is mitigated. As one example, the polyamide compositions beneficially have a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM> (as measured using ISO <NUM>-<NUM> (<NUM>) for tensile strength and ISO <NUM> (<NUM>) for heat age). These heat stabilizer packages thus allow for the improved use and functionality of polyamide compositions in environments of higher temperature, e.g., in automotive applications. Whereas polyamide compositions already known in the art become much more brittle after being exposed to such high temperatures, the compositions disclosed herein are able to maintain a substantially higher tensile strength.

The heat stabilizer packages disclosed herein improve the utility and functionality of polyamide compositions by mitigating, retarding, or preventing the effects damage, e.g., thermooxidative damage, that results from exposure of polyamides to heat. In one embodiment, the heat stabilizer package comprises the cerium-based heat stabilizer, e.g., the cerium-based heat stabilizer, and the second heat stabilizer. In some cases, the amount of the cerium-based heat stabilizer is present in an amount greater than the second heat stabilizer. In some cases, the polyamide composition beneficially comprises little or no stearates, e.g., calcium stearate or zinc stearate. In some cases the weight ratio of the halide additive to the stearate additive and/or the weight ratio of the second heat stabilizer to the halide additive are maintained within certain ranges and/or limits.

The cerium-based heat stabilizer, e.g., the cerium-based heat stabilizer, may vary widely. In some cases, the cerium-based heat stabilizer is a compound that comprises cerium. In some cases, the cerium-based heat stabilizer is generally of the structure CeXn, where X is a ligand and n is a non-zero integer. That is to say, in some embodiments, the cerium-based heat stabilizer is a cerium-based ligand compound. The inventors have found that particular cerium ligands are able to stabilize polymides particularly well, especially when utilized in the aforementioned amounts, limits, and/or ratios. In some cases, the ligand may be an oxide and/or an oxyhydrate.

In some embodiments, the ligand(s) may be selected from the group consisting of acetates, hydrates, oxyhydrates, phosphates, bromides, chlorides, oxides, nitrides, borides, carbides, carbonates, ammonium nitrates, fluorides, nitrates, polyols, amines, phenolics, hydroxides, oxalates, sulfates, aluminates, and combinations thereof. In some preferred embodiments, the cerium-based heat stabilizer may comprise a cerium hydrate, or cerium acetate, or a combination thereof. In some cases, the cerium-based heat stabilizer may comprise cerium hydrate, cerium acetate, cerium oxyhydrate, or cerium phosphate, or combinations thereof. The inventors have found that, surprisingly, employing these specific cerium-based heat stabilizers results in a heat stabilizer package that provides for the benefits discussed herein. By selecting multiple cerium-based heat stabilizers, one may be able to synergistically improve the heat stabilization effect of the individual heat stabilizer. Furthermore, a polyamide composition comprising multiple cerium-based heat stabilizers may provide improved heat stability over a broader range of temperatures or at higher temperatures. In some cases, the polyamide composition may not utilize cerium phosphate.

In some embodiments, the polyamide composition comprises the cerium-based heat stabilizer in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of lower limits, the polyamide composition may comprise greater than <NUM> wt. % cerium-based heat stabilizer, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt. In terms of upper limits, the polyamide composition may comprise less than <NUM> wt. % cerium-based heat stabilizer, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt.

In some cases, the polyamide composition comprises little or no cerium hydrate, e.g., less than <NUM> wt. % cerium hydrate, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In some cases, the polyamide composition comprises substantially no cerium hydrate, e.g., no cerium hydrate.

In some embodiments, the polyamide composition comprises cerium oxide (optionally as the only cerium-based heat stabilizer), or cerium oxyhydrate (optionally as the only cerium-based heat stabilizer), or a combination of cerium oxide and cerium oxyhydrate in an amount ranging from <NUM> ppm to <NUM> wt. %, e.g., from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, or from <NUM> ppm to <NUM> ppm.

In terms of lower limits, the polyamide composition may comprise greater than <NUM> ppm cerium oxide, or cerium oxyhydrate, or a combination thereof, e.g., greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, greater than <NUM> ppm, or greater than <NUM> ppm. In terms of upper limits, the polyamide composition may comprise less than <NUM> wt. % cerium oxide, or cerium oxyhydrate, or a combination thereof, e.g., less than <NUM> ppm, less than <NUM> ppm, less than <NUM>, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, or less than <NUM> ppm.

In some embodiments, where cerium oxide, or cerium oxyhydrate, or a combination of cerium oxide and cerium oxyhydrate is utilized, the polyamide comprises cerium (not including ligand) in an amount ranging from <NUM> ppm to <NUM> ppm, e.g., from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, from <NUM> ppm to <NUM> ppm, or from <NUM> ppm to <NUM> ppm.

In terms of lower limits, the polyamide composition comprises cerium (not including ligand) in an amount greater than <NUM> ppm, e.g., greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, greater than <NUM> wppm, or greater than <NUM> wppm. In terms of upper limits, the polyamide composition comprises cerium (not including ligand) in an amount less than <NUM> ppm, e.g., less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, less than <NUM> ppm, or less than <NUM> ppm.

The second heat stabilizer may vary widely. The inventors have found that particular second heat stabilizers unexpectedly provide for synergistic results, especially when utilized in the aforementioned amounts, limits, and/or ratios and with the cerium-based stabilizer, stearate additive, and halide additive.

In some embodiments, the second heat stabilizer may be selected from the group consisting of phenolics, amines, polyols, and combinations thereof. In some cases, the second heat stabilizer may comprise such phenolics as N,N'-hexamethylene-bis-<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)-propionamide, bis-(<NUM>,<NUM>-bis-(<NUM>'-hydroxy-<NUM>'-tert-butylphenyl)-butanoic acid)-glycol ester, <NUM>,<NUM>'-thioethylbis-(<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)-propionate, <NUM>-<NUM>'-butylidene-bis-(<NUM>-methyl-<NUM>-tert-butylphenol), or triethyleneglycol-<NUM>-(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)-propionate, or combinations thereof.

In preferred embodiments, the second heat stabilizer comprises a copper-based stabilizer. The inventors have surprisingly found that the use of the copper-based stabilizer and the cerium-based stabilizer in the amounts discussed herein has a synergistic effect. Without being bound by theory, it is believed that the combination of the activation temperatures of the cerium-based heat stabilizer and the copper-based stabilizer unexpectedly provide for thermooxidative stabilization at particularly useful ranges, e.g., <NUM> to <NUM> or from <NUM> to <NUM>. This particular range has been shown to present a performance gap when conventional stabilizer packages are employed. By utilizing the combination of the copper-based stabilizer and the cerium-based stabilizer in the amounts discussed herein thermal stabilization is unexpectedly achieved.

By way of non-limiting example, the copper-based compound of the second heat stabilizer may comprise compounds of mono- or bivalent copper, such as salts of mono- or bivalent copper with inorganic or organic acids or with mono- or bivalent phenols, the oxides of mono- or bivalent copper, or complex compounds of copper salts with ammonia, amines, amides, lactams, cyanides or phosphines, and combinations thereof. In some preferred embodiments, the copper-based compound may comprise salts of mono- or bivalent copper with hydrohalogen acids, hydrocyanic acids, or aliphatic carboxylic acids, such as copper(I) chloride, copper(I) bromide, copper(I) iodide, copper(I) cyanide, copper(II) oxide, copper(II) chloride, copper(II) sulfate, copper(II) acetate, or copper (II) phosphate. Preferably, the copper-based compound is copper iodide and/or copper bromide. The second heat stabilizer may be employed with a halide additive discussed below. Copper stearate, as a second heat stabilizer (not as a stearate additive) is also contemplated.

In some embodiments, the polyamide composition comprises the second heat stabilizer in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of lower limits, the polyamide composition may comprise greater than <NUM> wt. % second heat stabilizer, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt. In terms of upper limits, the polyamide composition may comprise less than <NUM> wt. % second heat stabilizer, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt.

In cases where the second heat stabilizer is a copper-based stabilizer, the copper-based stabilizer may be present in the heat stabilizer package (and in the polyamide composition) in the amounts discussed herein with respect to the second heat stabilizer generally.

As noted above, the cerium ratio has unexpectedly been found to greatly affect the overall heat stability of the resultant polyamide composition. In some embodiments, the cerium ratio is less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of ranges, the cerium ratio may range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>; from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of lower limits, the cerium ratio may be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>.

In some embodiments, the cerium ratio is greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. In terms of ranges, the cerium ratio may range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>; from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the cerium ratio may be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>.

In some embodiments, the cerium ratio is greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. In terms of ranges, the cerium ratio may range from <NUM> to <NUM>, e.g., from <NUM> to <NUM>; from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the cerium ratio may be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>.

The halide additive may vary widely. In some cases, the halide additive may be utilized with the second heat stabilizer. In some cases, the halide additive is not the same component as the second heat stabilizer, e.g., the second heat stabilizer, copper halide, is not considered a halide additive. Halide additive are generally known and are commercially available. Exemplary halide additives include iodides and bromides. Preferably, the halide additive comprises a chloride, an iodide, and/or a bromide.

In some embodiments, the halide additive is present in the polyamide composition in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., <NUM> wt. % to <NUM> wt. %, <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of upper limits, the halide additive may be present in an amount less than <NUM> wt. %, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of lower limits, the halide additive may be present in an amount greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt.

In some cases, for example, where cerium oxides/oxyhydrates are employed as the first heat stabilizer, the weight ratio of cerium oxide/oxyhydrate stabilizer to iodide has been shown to demonstrate unexpected heat performance. Without being bound by theory, it is postulated that iodide is important to the regeneration of the cerium, possibly providing the ability of some cerium ions to return to the original state, which leads to improved and more consistent heat performance over time. In some cases, when cerium oxide and/or cerium oxyhydrate are employed, particular (higher) amounts of iodide are used in conjunction therewith. Beneficially, when these amounts of iodide and cerium oxide/oxyhydrate and/or weight ratios thereof are employed, the use of bromine-containing components can advantageously be eliminated. In addition, iodide ion may play a role in stabilizing higher oxidation states of cerium which could further contribute to the heat stability of cerium oxide/oxyhydrate system.

In some embodiments, iodide (total iodide ion, e.g., chloride and/or bromide) is present in an amount ranging from <NUM> wppm to <NUM> wppm, e.g., from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, or from <NUM> wppm to <NUM> wppm. In terms of lower limits, the iodide may be present in an amount at least <NUM> wppm, e. at least <NUM> wppm, at least <NUM> wppm, at least <NUM> wppm, at least <NUM> wppm, at least <NUM> wppm at least <NUM> wppm, or at least <NUM> wppm. In terms of upper limits, the iodide may be present in an amount less than <NUM> wppm, e.g., less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, or less than <NUM> wppm.

In some embodiments, when cerium oxide and/or cerium oxyhydrate are employed, iodide is present in an amount ranging from <NUM> wppm to <NUM> wppm, e.g., from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, from <NUM> wppm to <NUM> wppm, or from <NUM> wppm to <NUM> wppm. In terms of lower limits, the iodide may be present in an amount at least <NUM> wppm, e. at least <NUM> wppm, at least <NUM> wppm, at least <NUM> wppm, at least <NUM> wppm, or at least <NUM> wppm. In terms of upper limits, the iodide may be present in an amount less than <NUM> wppm, e.g., less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, less than <NUM> wppm, or less than <NUM> wppm.

Total iodide content includes iodide from all iodide sources, e.g., first and second heat stabilizers, e.g., copper iodide, and additives, e.g., potassium iodide.

The stearate additive may vary widely and is present in the composition in an amount of less than <NUM> wt. Stearate additive are generally known and are commercially available. Exemplary stearate additives include zinc stearate and calcium stearate. Preferably, the halide additive comprises an iodide and/or a bromide.

The stearate additive may be present in synergistic small amounts. For example, the polyamide composition may comprise less than <NUM> wt. % stearate additive, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of ranges, the polyamide composition may comprise from <NUM> wppm to <NUM> wt. % stearate additive, e.g., from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, or from <NUM> wppm to <NUM> wt. In terms of lower limits, the polyamide composition may comprise greater than <NUM> wppm stearate additive, e.g., greater than <NUM> wppm, greater <NUM> wppm, or greater than <NUM> wppm. In some embodiments, the polyamide composition comprises substantially no stearate additive, e.g., comprises no stearate additive.

In some cases, the polyamide composition comprises little or no antioxidant additives, e.g., phenolic antioxidants. As noted above, antioxidants are known polyamide stabilizers that are unnecessary in the polyamide compositions of the present disclosure. Preferably, the polyamide composition comprises no antioxidants. As a result, there is advantageously little need for antioxidant additives, and production efficiencies are achieved. For example, the polyamide composition may comprise less than <NUM> wt. % antioxidant additive, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of ranges, the polyamide composition may comprise from <NUM> wt. % to <NUM> wt. % antioxidants, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of lower limits, the polyamide composition may comprise greater than <NUM> wt. % antioxidant additive, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM>, or greater than <NUM> wt.

It has been discovered that when preparing the heat-stabilized polyamide compositions disclosed herein, the cerium-based heat stabilizer can beneficially be selected on the basis of that activation temperature. It has also been discovered that the cerium-based heat stabilizer's ability to stabilize may not fully activate at lower temperatures. In some cases. the cerium-based heat stabilizer may have an activation temperature greater than <NUM>. e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. In terms of ranges, the cerium-based heat stabilizer may have an activation temperature ranging from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of upper limits, the cerium-based heat stabilizer may have an activation temperature less than <NUM>. e.g., less than <NUM>, less than <NUM>, or less than <NUM>. In preferred embodiments, the cerium-based heat stabilizer has an activation temperature of approximately <NUM>.

The activation temperature of a polyamide heat stabilizer may be an "effective activation temperature. " The effective activation temperature relates to the temperature at which the stabilization functionality of the additive becomes more active than the thermo-oxidative degradation of the polyamide composition. The effective activation temperature reflects a balance between the stabilization kinetics and the degradation kinetics.

In some cases, when a heat stabilization target is known, the cerium-based heat stabilizer, or the combination of cerium-based heat stabilizers, can be selected based on the heat stabilization target. For example, in some embodiments, the cerium-based heat stabilizer is preferably selected such that the cerium-based heat stabilizer has an activation temperature falling within the ranges and limits mentioned herein.

In some embodiments, the second heat stabilizer may have an activation temperature less than <NUM>. e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. In terms of lower limits, the second heat stabilizer may have an activation temperature greater than <NUM>. e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. In terms of ranges, the second heat stabilizer may have an activation temperature ranging from <NUM> to <NUM>, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. Effective activation temperatures may be within these ranges and limits as well.

In preferred embodiments, the second heat stabilizer is selected such that it has an activation temperature lower than the activation temperature of the cerium-based heat stabilizer. By utilizing a second heat stabilizer with a lower activation temperature than that of the cerium-based heat stabilizer, the resultant polyamide composition may show increased heat stability and/or heat stability over a broader range of temperatures. In some embodiments, the activation temperature of the cerium-based heat stabilizer, as measured in degrees centigrade, is greater than the activation temperature of the second heat stabilizer, e.g., the copper-based stabilizer, as measured in degrees centigrade, e.g., at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, at least <NUM>% greater, or at least <NUM>% greater.

In some cases, the activation temperature of the cerium-based heat stabilizer, as measured in degrees centigrade, is greater than the activation temperature of the second heat stabilizer, e.g., the copper-based stabilizer, as measured in degrees centigrade, e.g., at least <NUM> greater, at least <NUM> greater, at least <NUM> greater, at least <NUM> greater, at least <NUM> greater, or at least <NUM> greater.

As noted above, some conventional stabilizer packages may rely on combinations of second heat stabilizers, e.g., stearates (such as calcium stearate or zinc stearate), hypophosphoric acids, and/or hypophosphates. It has been discovered that the use of the aforementioned cerium-based heat stabilizer and lower amounts, if any, of these compounds has been surprisingly found to improve the stabilization profile of the resultant polyamide composition. In some embodiments, the polyamide composition comprises less than <NUM> wt. % of hypophosphoric acid and/or a hypophosphate, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of ranges, the polyamide composition may comprise from <NUM> wppm to <NUM> wt. % of hypophosphoric acid and/or a hypophosphate, e.g., from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, or from <NUM> wppm to <NUM> wt. In a preferred embodiment, the polyamide composition comprises no hypophosphoric acid and/or a hypophosphate.

In some embodiments, the polyamide composition comprises less than <NUM> wt. % of cerium dioxide, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of ranges, the polyamide composition may comprise from <NUM> wppm to <NUM> wt. % of cerium dioxide, e.g., from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, from <NUM> wppm to <NUM> wt. %, or from <NUM> wppm to <NUM> wt. In a preferred embodiment, the polyamide composition comprises no cerium dioxide.

In a particular embodiment, the second heat stabilizer is a copper-based compound and the polyamide has an impact resilience of at least <NUM>%.

In another particular embodiment, the cerium-based heat stabilizer is a cerium-based ligand, the second heat stabilizer is a copper-based heat stabilizer, the polyamide composition has a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>, and optionally the cerium ratio ranges from <NUM> to <NUM>.

In another particular embodiment, the cerium-based heat stabilizer is a cerium-based ligand; the second heat stabilizer is a copper-based heat stabilizer, the polyamide composition has a relative viscosity ranging from <NUM> to <NUM>, and the polyamide composition has a tensile strength from <NUM> MPa to <NUM> MPa , when heat aged for <NUM> hours at a temperature ranging from <NUM> to <NUM> and measured at <NUM>.

In another particular embodiment, the cerium-based heat stabilizer is a cerium-based ligand, the second heat stabilizer is a copper-based heat stabilizer, the polyamide composition has a relative viscosity ranging from <NUM> to <NUM>, and the polyamide composition has a tensile strength from <NUM> MPa to <NUM> MPA, when heat aged for <NUM> hours at a temperature ranging from <NUM> to <NUM> and measured at <NUM>.

Some embodiments of the heat-stabilized polyamide compositions comprise a filler, e.g., glass. In these cases, the filler may be present in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of lower limits, the polyamide compositions may comprise at least <NUM> wt. % filler, e.g., at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, or at least <NUM> wt. In terms of upper limits, the polyamide compositions may comprise less than <NUM> wt. % filler, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. The ranges and limits for the other components are based on a "filled" composition. For a neat composition, the ranges and limits may need to be adjusted to compensate for the lack of filler. The material of the filler is not particularly limited and may be selected from polyamide fillers known in the art. By way of non-limiting example, the filler may comprise glass- and/or carbon fibers, particulate fillers, such as mineral fillers based on natural and/or synthetic layer silicates, talc, mica, silicate, quartz, titanium dioxide, wollastonite, kaolin, amorphous silicic acids, magnesium carbonate, magnesium hydroxide, chalk, lime, feldspar, barium sulphate, solid or hollow glass balls or ground glass, permanently magnetic or magnetisable metal compounds and/or alloys and/or combinations thereof, and also combinations thereof.

In other cases, the heat-stabilized polyamide compositions is a "neat" composition, e.g., the polyamide composition comprises little or no filler. For example the polyamide compositions may comprise less than <NUM> wt. % filler, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of ranges, the polyamide compositions may comprise from <NUM> wt. % to <NUM> wt. % filler, e.g., from <NUM> wt. % to <NUM> wt. % or from <NUM> wt. % to <NUM> wt. In such cases, the amounts of other components may be adjusted accordingly based on the aforementioned component ranges and limits. It is contemplated that a person of ordinary skill in the art would be able to adjust the concentration of the other components of the polyamide composition in light of the inclusion or exclusion of a glass filler.

Both the filled and neat embodiments each demonstrate the surprising improved mechanical properties. For unfilled resins of polyamides, however, thermal stability is not typically measured by references to the tensile strength of the polyamide composition; rather, thermal stability is often measured using relative thermal index (RTI). RTI refers to the thermal classification of a material by comparing the performance of the material against the performance of a known or reference material. Often, RTI assesses the ability of the material to withstand exposure to high temperatures by measuring the ability of the material to maintain at least <NUM>% of its tensile strength when exposed to various temperatures for set amounts of time. The non-glass-filled embodiments of the heat-stabilized polyamide compositions demonstrate improved RTI.

The aforementioned heat-stabilized polyamide compositions demonstrate surprising performance results. For example, the polyamide compositions demonstrate superior tensile strength over broad temperature ranges, even over known performance gaps, e.g., temperature gaps (for example from <NUM> to <NUM>). These performance parameters are exemplary and the examples support other performance parameters that are contemplated by the disclosure. For example, other performance characteristics taken at other heat age temperatures (in particular, over ranges in heat age temperatures, for example from <NUM> to <NUM>) and heat age durations are contemplated and may be utilized to characterize the disclosed polyamide compositions.

In some embodiments, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the tensile strength may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa.

In some embodiments, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the tensile strength may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa.

In some embodiments, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours over an entire temperature range of from <NUM> to <NUM>, and measured at <NUM>.

Such heat age performance over the <NUM> to <NUM> range (as shown throughout this section) illustrates the unexpected performance of the disclosed polyamide compositions, especially in the temperature gap. This is applicable to the performance characteristics as well, e.g., tensile retention or impact resilience. Other temperature ranges, e.g., from <NUM> to <NUM> or from <NUM> to <NUM>, are also supported by the examples and contemplated, but all of these specific performance characteristics are not specifically listed (in the interest of brevity and conciseness).

In some embodiments, the polyamide composition demonstrates a tensile strength retention of at least <NUM>%, e.g., at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>%, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the tensile strength retention may range from <NUM>% to <NUM>%, e.g., from <NUM>% to <NUM>%, from <NUM>% to <NUM>%.

In some embodiments, the polyamide composition demonstrates a tensile strength retention of at least <NUM>%, e.g., at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>%, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the tensile strength retention may range from <NUM>% to <NUM>%, e.g., from <NUM>% to <NUM>%, from <NUM>% to <NUM>%.

In some embodiments, the polyamide composition demonstrates a tensile strength retention of at least <NUM>%, e.g., at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>%, when heat aged for <NUM> hours over an entire temperature range of from <NUM> to <NUM>, and measured at <NUM>.

Tensile strength is not the only mechanical property of polyamides that suffers from exposure to high temperatures. The damage to polyamides caused by heat manifests itself in a number of ways. It has been found that the heat-stabilized polyamide compositions also show improved resilience to other forms of damage. That is to say, the polyamide compositions exhibit other desirable mechanical properties after having been exposed to high temperatures.

In some embodiments, the polyamide composition demonstrates a tensile elongation of at least <NUM>%, e.g., at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>%, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the tensile elongation may range from <NUM>% to <NUM>%, e.g., from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%.

In some embodiments, the polyamide composition demonstrates a tensile elongation of at least <NUM>%, e.g., at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>%, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the tensile elongation may range from <NUM>% to <NUM>%, e.g., from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>%<NUM> to <NUM>%.

In some embodiments, the polyamide composition demonstrates a tensile elongation of at least <NUM>%, e.g., at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>%, when heat aged for <NUM> hours over an entire temperature range of from <NUM> to <NUM>, and measured at <NUM>.

In some embodiments, the polyamide composition demonstrates a tensile modulus of at least <NUM> MPa, e. at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the tensile modulus may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa.

In some embodiments, the polyamide composition demonstrates a tensile modulus of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>,. In terms of ranges, the tensile modulus may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa.

In some embodiments, the polyamide composition demonstrates a tensile modulus of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours over an entire temperature range of from <NUM> to <NUM>, and measured at <NUM>.

In some embodiments, the polyamide composition demonstrates an (unnotched) impact resilience of at least <NUM> kJ/m<NUM>, e.g., at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, or at least <NUM> kJ/m<NUM>, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the impact resilience may range from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, e.g., from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, or from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>.

In some embodiments, the polyamide composition demonstrates an (unnothced) impact resilience of at least at least <NUM> kJ/m<NUM>,e.g., <NUM> kJ/m<NUM>,, at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, or at least <NUM> kJ/m<NUM>, when heat aged for <NUM> hours at a temperature of at least <NUM>, e.g., <NUM> or <NUM>, and measured at <NUM>. In terms of ranges, the impact resilience may range from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, e.g., from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, or from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>.

In some embodiments, the polyamide composition demonstrates an (unnotched) impact resilience of at least <NUM> kJ/m<NUM>, e.g., at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, at least <NUM> kJ/m<NUM>, or at least <NUM> kJ/m<NUM>, when heat aged for <NUM> hours over an entire temperature range of from <NUM> to <NUM>, and measured at <NUM>.

Some embodiments of the heat-stabilized polyamide composition exhibit an impact resilience of greater than <NUM> kJ/m<NUM>, e.g., greater than <NUM> kJ/m<NUM>, greater than <NUM> kJ/m<NUM>, greater than <NUM> kJ/m<NUM>, greater than <NUM> kJ/m<NUM>, greater than <NUM> kJ/m<NUM>, greater than <NUM> kJ/m<NUM>, greater than <NUM> kJ/m<NUM>, or greater than <NUM> kJ/m<NUM>, when measured by ISO <NUM> (<NUM>). In terms of ranges, the heat-stabilized polyamide composition exhibit an impact resilience ranging from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>, or from <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM>.

Generally, tensile strength, tensile elongation, and tensile modulus measurements may be conducted under ISO <NUM>-<NUM> (<NUM> or <NUM>), and heat aging measurements may be conducted under ISO <NUM> (<NUM> or <NUM>).

Tensile strength retention may be measured by measuring tensile strength before and after treatment and calculating a ratio of the measurements.

Impact resilience may be measured in accordance with ISO <NUM>/1eU (<NUM> or (<NUM>).

Furthermore, the heat stabilizer packages have been shown to retard the damage to the polyamides even when exposed to higher temperature. When tensile strength is measured at higher temperatures, the tensile strength of the heat-stabilized polyamide compositions remains surprisingly high. Typically, tensile strength of polyamide compositions is much lower when measured at higher temperatures. While that trend remains true of the heat-stabilized polyamide compositions disclosed herein, the actual tensile strength remains surprisingly high even when measured at temperatures. In some cases, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>. In terms of ranges, the tensile strength may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa. Polyamide compositions that demonstrate such high tensile strength after having been exposed to temperatures such as these constitute a marked improvement over other methods of heat-stabilizing polyamides known in the art.

In one embodiment, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>. In terms of ranges, the tensile strength may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa. Although these tensile strengths decrease, these values are still surprisingly higher than those of conventional polyamide compositions that employ conventional stabilizer packages.

In one embodiment, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa when heat aged for <NUM> hours at a temperature ranging from <NUM> to <NUM> and measured at <NUM>. In terms of ranges, the tensile strength may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa.

In one embodiment, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, at least <NUM> MPa, or at least <NUM> MPa, when heat aged for <NUM> hours at a temperature at least <NUM> and measured at <NUM>. In terms of ranges, the tensile strength may range from <NUM> MPa to <NUM> MPa, e.g., from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, from <NUM> MPa to <NUM> MPa, or from <NUM> MPa to <NUM> MPa. Although these tensile strengths decrease, these values are still surprisingly higher than those of conventional polyamide compositions that employ conventional stabilizer packages.

As noted above, the present disclosure relates to heat-stabilizing additives for polyamides. Many varieties of natural and artificial polyamides have already been utilized in various applications due to their high durability and strength. Common polyamides include nylons and aramids. For example, the polyamide may comprise PA-4T/4I; PA-4T/6I; PA-5T/5I; PA-<NUM>; PA-<NUM>,<NUM>; PA-<NUM>,<NUM>/<NUM>; PA-<NUM>,<NUM>/6T; PA-<NUM>,<NUM>/6T(<NUM>)/<NUM>(<NUM>); PA-<NUM>,<NUM>/6T(<NUM>)/<NUM>(<NUM>); PA-6T/6I; PA-6T/6I/<NUM>; PA-6T/<NUM>; PA-6T/6I/<NUM>; PA-6T/MPDMT (where MPDMT is polyamide based on a mixture of hexamethylene diamine and <NUM>-methylpentamethylene diamine as the diamine component and terephthalic acid as the diacid component); PA-6T/<NUM>; PA-6T/<NUM>; PA-10T/<NUM>; PA-10T/<NUM>; PA-6T/<NUM>; PA-6T/10T; PA-6T/10I; PA-9T; PA-10T; PA-12T; PA-10T/10I; PA-<NUM>,<NUM>; PA-10T/<NUM>; PA-10T/<NUM>; PA-6T/9T; PA-6T/12T; PA-6T/10T/6I; PA-6T/6I/<NUM>; or PA-6T/<NUM>/<NUM>; or combinations thereof.

The heat-stabilized polyamide compositions may comprise a combination of polyamides. By combining various polyamides, the final composition may be able to incorporate the desirable properties, e.g., mechanical properties, of each constituent polyamides.

The heat-stabilized polyamide composition may comprise from <NUM> wt. % to <NUM> wt. % of the amide polymer (as a whole), based on the total weight of the heat-stabilized polyamide composition. In some cases, the heat-stabilized polyamide composition may comprise amide polymer in an amount from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, and from <NUM> wt. % to <NUM> wt. , or from <NUM> wt. % to <NUM> wt. In terms of lower limits, the heat-stabilized polyamide composition may comprise amide polymer in an amount less than <NUM> wt. %, e.g., less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of lower limits, the heat-stabilized polyamide composition may comprise amide polymer in an amount greater than <NUM> wt. %, e.g. greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt.

Without being bound by theory, the combination of polyamides could comprise any number of known polyamides. For example, in some embodiments, the polyamide comprises a combination of PA-<NUM> with PA-<NUM>,<NUM>, and/or PA-<NUM>,<NUM>/6T. In these embodiments, the polyamide may comprise from <NUM> wt. % to <NUM> wt. % PA-<NUM>, from <NUM> wt. % to <NUM> wt. % PA-<NUM>,<NUM>, and/or from <NUM> wt. % to <NUM> wt. % PA-<NUM>,<NUM>/6T. In particular, the PA-<NUM> may be present in an amount from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, and from <NUM> wt. % to <NUM> wt. In terms of upper limits, the PA-<NUM> may be present in an amount up to <NUM> wt. %, e.g., up to <NUM> wt. %, up to <NUM> wt. %, up to <NUM> wt. %, up to <NUM> wt. %, up to <NUM> wt. %, and up to <NUM> wt. The PA-<NUM>,<NUM> and/or PA-<NUM>,<NUM>/6T may be present in an amount from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, and from <NUM> wt. % to <NUM> wt. In terms lower limits, the PA-<NUM>,<NUM> and/or PA-<NUM>,<NUM>/6T may be present in an amount greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, great than <NUM> wt. %, and greater than <NUM> wt. In some embodiments the polyamide comprises one or more of PA-<NUM>, PA-<NUM>,<NUM>, and PA-<NUM>,<NUM>/6T.

The heat-stabilized polyamide compositions may also comprise polyamides produced through the ring-opening polymerization or polycondensation, including the copolymerization and/or copolycondensation, of lactams. Without being bound by theory, these polyamides may include, for example, those produced from propriolactam, butyrolactam, valerolactam, and caprolactam. For example, in some embodiments, the polyamide is a polymer derived from the polymerization of caprolactam. In those embodiments, the caprolactam is preferably at least <NUM> wt. % of the polymer, e.g., at least <NUM> wt. %, at least <NUM> wt. %, at least <NUM> wt. %, and at least <NUM> wt. In terms of ranges, the polymer comprises from <NUM> wt. % to <NUM> wt. % caprolactam, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of upper limits, the polymer comprises less than <NUM> wt. % capropactam, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt.

In some embodiments, as noted herein, a low caprolactam content polyamide is utilized, e.g., a polyamide comprising less than <NUM> wt. % caprolactam, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. In terms of ranges, the low caprolactam content polyamide may comprise from <NUM> wt. % to <NUM> wt. % caprolactam, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of lower limits, the low caprolactam content polyamide may comprise greater than <NUM> wt. % caprolactam, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt.

In some embodiments, a low melt temperature polyamide is utilized, e.g., a polyamide having a melt temperature below <NUM>, e.g., below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, below <NUM>, or below <NUM>.

In some embodiments, the low caprolactam content polyamide comprises PA-<NUM>,<NUM>/<NUM>; PA-6T/<NUM>; PA-<NUM>,<NUM>/6T/<NUM>; PA-<NUM>,<NUM>/6I/<NUM>; PA-6I/<NUM>; or 6T/6I/<NUM>, or combinations thereof. In some cases, the low caprolactam content polyamide comprises PA-<NUM>,<NUM>/<NUM> and/or PA-<NUM>,<NUM>/6T/<NUM>. In some embodiments, the low caprolactam content polyamide comprises PA-<NUM>,<NUM>/<NUM>.

In some embodiments, the low melt temperature polyamide comprises PA-<NUM>,<NUM>/<NUM>; PA-6T/<NUM>; PA-<NUM>,<NUM>/6I/<NUM>; PA-6I/<NUM>; or 6T/6I/<NUM>, or combinations thereof. In some cases, the low caprolactam content polyamide comprises PA-<NUM>,<NUM>/<NUM>. In some cases, the melt temperature of the low melt temperature polyamide may be controlled by manipulating the monomer components.

In some cases, the polyamide includes particular (high) concentrations of low caprolactam content polyamide and/or low melt temperature polyamide. For example, the polyamide may comprise greater than <NUM> wt. % of low caprolactam content polyamide and/or low melt temperature polyamide, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt. In terms of ranges, the polyamide may comprise from <NUM> wt. % to <NUM> wt. % low caprolactam content polyamide and/or low melt temperature polyamide, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of upper limits, the polyamide may comprise less than <NUM> wt. % low caprolactam content polyamide and/or low melt temperature polyamide, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt.

In some cases, the polyamide includes particular (low) concentrations of other non-low caprolactam content and/or high melt temperature polyamides, e. For example, the polyamide may comprise less than <NUM> wt. % of non-low caprolactam content polyamide and/or low melt temperature polyamide, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. % or less than <NUM> wt. In terms of ranges, the polyamide may comprise from <NUM> wt. % to <NUM> wt. % other non-low caprolactam content and/or high melt temperature polyamides, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or from <NUM> wt. % to <NUM> wt. In terms of lower limits, the polyamide may comprise greater than <NUM> wt. % of non-low caprolactam content polyamide and/or low melt temperature polyamide, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt.

Furthermore, the heat-stabilized polyamide compositions may comprise the polyamides produced through the copolymerization of a lactam with a nylon, for example, the product of the copolymerization of a caprolactam with PA-<NUM>,<NUM>.

In addition to the compositional make-up of the polyamide composition, it has also been discovered that the relative viscosity of the amide polymer in combination with the stabilizer package has been found to have many surprising benefits, both in performance and processing. For example, if the relative viscosity of the amide polymer is within certain ranges and/or limits, production rates and tensile strength (and optionally impact resilience) are improved.

In the heat-stabilized polyamide compositions, the polyamide may have a relative viscosity ranging from <NUM> to <NUM>, e.g. from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In terms of lower limits, the relative viscosity of the polyamide may be greater than <NUM>, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM>. In terms of upper limits, the relative viscosity of the polyamide may be less than <NUM>, e.g., less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>. Relative viscosity may be determined via the formic acid method.

Some embodiments of the heat-stabilized polyamide compositions further comprise a supplemental heat stabilizer (in addition to the cerium-based heat stabilizer and the second heat stabilizer. The addition of a supplemental heat stabilizer can synergistically improve the capability of the heat-stabilize polyamide compositions to maintain desirable mechanical properties after exposure to high temperatures. In particular, the additional of the supplemental heat stabilizer may result in a polyamide composition that has a higher tensile strength after having been exposed to high temperatures. In some embodiments, the supplemental heat stabilizer may comprise any heat stabilizer, or combinations thereof, known in the art. For example, the supplemental heat stabilizer may be selected from the group consisting of phenolics, amines, polyols, copper-based stabilizers, and combinations thereof.

Processes of producing the heat-stabilized polyamide compositions are described hereinafter. A preferred method includes providing a polyamide, determining a desired heat stabilization target, selecting a cerium-based stabilizer based on the desired heat stabilization target, and adding the cerium-based stabilizer to the polyamide to form a heat-stabilized polyamide composition. For example, if a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature ranging from <NUM> to <NUM> or from <NUM> to <NUM> (and measured at <NUM>) is desired, the cerium-based stabilizer having acetate and/or hydrate ligands, e.g., cerium acetate and/or cerium hydrate, may be utilized to achieve the desired performance in the specific heat age temperature range (the other heat age temperature ranges and limits discussed herein and other ligands discussed herein may be similarly employed in this manner). By doing so the heat stabilizer package with the selected cerium-based stabilizer and second heat can be employed to produce a polyamide composition that exhibits heat stability at the desired temperature.

The method can also include the further steps of selecting a second heat stabilizer based on the desired heat stabilization target and the cerium-based stabilizer. The cerium-based heat stabilizer can be selected on the basis of its activation temperature. Similarly, the second heat stabilizer can also be selected on the basis of the desired heat stabilization level and/or the selected cerium-based heat stabilizer. The resultant polyamide composition will have the beneficial performance characteristics discussed herein.

In preferred embodiments of this process, the cerium-based stabilizer is a cerium based ligand and the second heat stabilizer is a copper-based heat stabilizer. In these embodiments, the selection of the cerium-based ligand may further comprise the selection of a ligand component of the cerium-based ligand based on the desired heat stabilization level.

Preferably, the result of this process is a heat-stabilized polyamide composition that has a tensile strength of at least <NUM> MPa, e.g., at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>.

The process may comprise the steps of providing an amide polymer; adding to the polymer a cerium-based heat stabilizer and a second heat stabilizer, as discussed herein, to form an intermediate polyamide composition, heating the intermediate polyamide composition to a predetermined temperature, e.g., at least <NUM>, and cooling the heated intermediate polyamide composition to form the heat-stabilized polyamide composition. Beneficially, the heating of the polyamide serves to activate the stabilizer package, which in turn heat stabilizes the intermediate polyamide composition. As a result, the (cooled) heat-stabilized polyamide composition will have improved performance characteristics, as discussed herein.

Some embodiments of the process include the intermediate steps of grinding the amide polymer and adding the cerium-based heat stabilizer to the ground amide polymer. The remaining components are then added to the resultant ground amide polymer and cerium-based heat stabilizer mixture. The inventors have discovered that this process advantageously results in a more uniform dispersion of the cerium-based heat stabilizer throughout the final heat-stabilized polyamide compositions.

The following embodiments are contemplated. All combinations of features and embodiments are contemplated.

Embodiment <NUM>: A heat-stabilized polyamide composition may comprise: from <NUM> wt. % to <NUM> wt. %% of an amide polymer, from <NUM> wt. % to <NUM> wt. % of a cerium-based heat stabilizer, a second heat stabilizer, from <NUM> wt. % to <NUM> wt. % of a filler, halide additive, and less than <NUM> wt. % of a stearate additive, wherein a weight ratio of halide additive to stearate additive is less than <NUM>, and optionally wherein the polyamide composition has a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>, or wherein the polyamide composition optionally has a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours over a temperature range of from <NUM> to <NUM>, and measured at <NUM>.

Embodiment <NUM>: The polyamide composition may comprise less than <NUM> wt. % of an antioxidant additive.

Embodiment <NUM>: The polyamide composition may comprise less than <NUM> wt. % of hypophosphoric acid and/or a hypophosphate.

Embodiment <NUM>: The cerium-based heat stabilizer may be present in an amount greater than the second heat stabilizer.

Embodiment <NUM>: The second heat stabilizer may be present in an amount ranging from <NUM> wt. % to <NUM> wt.

Embodiment <NUM>: The weight ratio of the cerium-based heat stabilizer to the second heat stabilizer may range from <NUM> to <NUM>.

Embodiment <NUM>: The second heat stabilizer may comprise a copper-based compound.

Embodiment <NUM>: The polyamide composition may comprise greater than <NUM> wppm copper-based compound.

Embodiment <NUM>: The relative viscosity of the amide polymer may range from <NUM> to <NUM>.

Embodiment <NUM>: The weight ratio of halide additive to the stearate additive may be less than <NUM>.

Embodiment <NUM>: The cerium-based heat stabilizer may be a cerium ligand selected from the group consisting of acetates, hydrates, oxyhydrates, phosphates, bromides, chlorides, oxides, nitrides, borides, carbides, carbonates, ammonium nitrates, fluorides, nitrates, polyols, amines, phenolics, hydroxides, oxalates, sulfates, aluminates, and combinations thereof.

Embodiment <NUM>: The cerium-based heat stabilizer may be a cerium ligand selected from the group consisting of cerium hydrates, cerium acetates, and combinations thereof.

Embodiment <NUM>: The cerium-based heat stabilizer may be cerium acetate.

Embodiment <NUM>: The cerium-based heat stabilizer may have an activation temperature ranging from <NUM> to <NUM>.

Embodiment <NUM>: The polyamide composition may comprise less than <NUM> wt. % cerium dioxide.

Embodiment <NUM>: The polyamide composition may comprise no cerium dioxide.

Embodiment <NUM>: The polyamide composition may have a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>.

Embodiment <NUM>: The polyamide composition may have a tensile strength ranging from <NUM> MPa to <NUM> MPa, when heat aged for <NUM> hours at a temperature ranging from <NUM> to <NUM> and measured at <NUM>.

Embodiment <NUM>: The polyamide composition may have a tensile strength ranging from <NUM> MPa to <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>.

Embodiment <NUM>: The polyamide composition may have an impact resilience of at least <NUM> kJ/m<NUM>, as measured by ISO <NUM> (<NUM>).

Embodiment <NUM>: The second heat stabilizer may be a copper-based compound and wherein the polyamide may have an impact resilience of at least <NUM>%.

Embodiment <NUM>: The activation temperature of the cerium-based heat stabilizer, as measured in degrees centigrade, may be at least <NUM>% greater than the activation temperature of the second heat stabilizer, as measured in degrees centigrade.

Embodiment <NUM>: The cerium-based heat stabilizer may be a cerium-based ligand; wherein the second heat stabilizer may be a copper-based heat stabilizer, and wherein the polyamide composition may have a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of at least <NUM> and measured at <NUM>.

Embodiment <NUM>: The cerium-based heat stabilizer may be a cerium-based ligand; wherein the second heat stabilizer may be a copper-based heat stabilizer; and wherein the polyamide composition may have a relative viscosity ranging from <NUM> to <NUM>; and wherein the polyamide composition may have a tensile strength from <NUM> MPa to <NUM> MPa , when heat aged for <NUM> hours at a temperature ranging from <NUM> to <NUM> and measured at <NUM>.

Embodiment <NUM>: The cerium-based heat stabilizer may be a cerium-based ligand; wherein the second heat stabilizer may be a copper-based heat stabilizer; and wherein the polyamide composition may have a relative viscosity ranging from <NUM> to <NUM>; and wherein the polyamide composition may have a tensile strength from <NUM> MPa to <NUM> MPA, when heat aged for <NUM> hours at a temperature ranging from <NUM> to <NUM> and measured at <NUM>.

Embodiment <NUM>: The second heat stabilizer may be selected from the group consisting phenolics, amines, polyols, and combinations thereof.

Embodiment <NUM>: the amide polymer may comprise: from <NUM> wt. % to <NUM> wt. % PA-<NUM>,<NUM>; from <NUM> wt. % to <NUM> wt. % PA-<NUM>,<NUM>/6T; and from <NUM> wt. % to <NUM> wt. % PA-<NUM>.

Embodiment <NUM>: The amide polymer may comprise a first amide polymer and a second amide polymer.

Embodiment <NUM>: The amide polymer may have a caprolactam content of at least <NUM> wt.

Embodiment <NUM>: The polyamide composition may comprise a filler, preferably present in an amount ranging from <NUM> wt. % to <NUM> wt.

Embodiment <NUM>: The polyamide composition may comprise less than <NUM> wt. % of the filler, preferably less than <NUM> wt.

Embodiment <NUM>: the low caprolactam content polyamide may comprise PA-<NUM>,<NUM>/<NUM>; PA-6T/<NUM>; PA-<NUM>,<NUM>/6T/<NUM>; PA-<NUM>,<NUM>/6I/<NUM>; PA-6I/<NUM>; or 6T/6I/<NUM>; or combinations thereof.

Embodiment <NUM>: The low caprolactam content polyamide may comprise less than <NUM> wt. % caprolactam.

Embodiment <NUM>: The polyamide composition may comprise cerium oxyhydrate in an amount ranging from <NUM> ppm to <NUM> ppm.

Embodiment <NUM>: The weight ratio of cerium oxide and/or cerium oxyhydrate to second heat stabilizer may range from <NUM> to <NUM>.

Examples <NUM> - <NUM> and Comparative Examples A - D were prepared by combining components as shown in Table <NUM> and compounding in a twin screw extruder. Polymers were melted, additives were added to the melt, and the resultant mixture was extruded and pelletized. Percentages are expressed as weight percentages.

The second heat stabilizer package comprised a blend of CuI (<NUM>%), KBr(<NUM>%), Zinc Stearate <NUM>%), and ethylene bis(stearamide) (<NUM>%).

The samples were heat aged and tested for tensile strength. The results are summarized in Tables 2a - 2e.

The samples were heat aged and tested for tensile strength retention. The results are summarized in Tables 3a - 3e.

The samples were heat aged and tested for tensile elongation. The results are summarized in Tables 4a - 4e.

The samples were heat aged and tested for tensile modulus. The results are summarized in Tables 5a - 5e.

The samples were heat aged and tested for impact resilience. The results are summarized in Tables 6a - 6e.

As shown in the Tables, Examples <NUM> - <NUM> generally demonstrated unexpected, synergistic results in for all of the measured performance characteristics - tensile strength, tensile strength retention, tensile elongation, tensile modulus, and impact resilience.

Importantly, the disclosed polyamide compositions show significant improvements iover the (entire) temperature range of <NUM> - <NUM> (the "temperature gap"). Also, the improvements in performance are even more significant as the heat age time is greater than <NUM> hours, e.g. greater than <NUM> hours or greater than <NUM> hours. The temperature gap and these extended heat age times are important and significant because they represent conditions under which polyamide compositions are typically employed, e.g. automotive under-the-hood applications.

The average values and ranges for the working Examples are higher than the values for the respective Comparative Examples, especially in the temperature gap and at higher heat age times. For example, for tensile strength measured at <NUM> and <NUM> hours of heat aging, the range for tensile strength range for the working Examples was <NUM> - <NUM> MPa, while the range for the Comparative Examples was significantly less, <NUM> - <NUM> MPa. The comparison is even more stark at <NUM> and <NUM> hours of heat aging. The range for tensile strength range for the working Examples was <NUM> - <NUM> MPa (if Example <NUM> is discarded), while the range for the Comparative Examples was an order of magnitude less, <NUM> - <NUM> MPa. Again, this demonstrates the improvements in performance in the temperature gap and at higher heat age times.

As another example, for impact resistance measured at <NUM> and <NUM> hours of heat aging, the range for the working Examples was <NUM> - <NUM> kJ/m<NUM>, while the range for the Comparative Examples was significantly less, <NUM> - <NUM> kJ/m<NUM>. The comparison is even more stark at <NUM> and <NUM> hours of heat aging. The range for impact resistance for the working Examples was <NUM> - <NUM> kJ/m<NUM> (if Example <NUM> is discarded), while the range for the Comparative Examples was <NUM> - <NUM> kJ/m<NUM> MPa.

Also, the polyamide composition demonstrates a tensile strength of at least <NUM> MPa (if Example <NUM> is discarded), when heat aged for <NUM> hours over the entire temperature range of from <NUM> to <NUM>, and measured at <NUM>. Such heat age performance over the <NUM> to <NUM> range illustrates the unexpected performance of the disclosed polyamide compositions over the entire temperature gap.

Individual comparisons also support the showing of the synergies of the disclosed formulations. As one example, the comparison of Example <NUM> and Comparative Example A demonstrate the surprising, synergistic effect of the disclosed stabilizer package. Comparative Example A utilizes only a copper stabilizer, while Example <NUM> utilizes a copper stabilizer and a cerium-based stabilizer. At <NUM>, tensile strength for Comparative Example A was <NUM> MPa and <NUM> MPa for <NUM> and <NUM> hours, respectively. Surprisingly, Example <NUM> demonstrated tensile strengths of <NUM> MPa (<NUM>% increase) and <NUM> MPa (<NUM>% increase) under the same test conditions. The magnitude of these improvements is unexpected.

As another example, at <NUM>, impact resistance for Comparative Example A was <NUM> kJ/m<NUM> and <NUM> kJ/m<NUM>for <NUM> and <NUM> hours, respectively. Surprisingly, Example <NUM> demonstrated impact resistances of <NUM> kJ/m<NUM> (<NUM>% increase) and <NUM> kJ/m<NUM> (<NUM>% increase) under the same test conditions.

Importantly, in many cases, performance surprisingly improves as temperature increases. For example, in Table 2c, at <NUM> and <NUM> hour tensile strengths for the working Examples ranged from <NUM> - <NUM> MPa, but at <NUM> (Table 2e), tensile strengths for the working Examples ranged from <NUM> - <NUM> MPa. Heat age performance increases at higher temperature is highly unexpected.

Claim 1:
A heat-stabilized polyamide composition comprising:
from <NUM> wt% to <NUM> wt% of an amide polymer, optionally comprising a first amide polymer and a second amide polymer;
from <NUM> wt% to <NUM> wt% of a cerium-based heat stabilizer;
a second heat stabilizer, optionally present in an amount ranging from <NUM> wt% to <NUM> wt%,
a halide additive, and
less than <NUM> wt% of a stearate additive,
wherein a weight ratio of halide additive to stearate additive is less than <NUM>, and wherein the polyamide composition optionally has a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours at a temperature of <NUM> and measured at <NUM> or
wherein the polyamide composition optionally has a tensile strength of at least <NUM> MPa, when heat aged for <NUM> hours over a temperature range of from <NUM> to <NUM>, and measured at <NUM>,
wherein the tensile strength measurement is conducted under ISO <NUM>-<NUM> (<NUM> or <NUM>), and the heat aging measurement is conducted under ISO <NUM> (<NUM> or <NUM>).