Processes for removing cyclic residuals from polyamide compositions

Abstract

A polyamide composition comprising a polyamide, less than 1.5 wt% cyclic residuals, based on the total weight of the polyamide composition; and less than 50 wppm catalyst composition, wherein the polyamide composition has an inert end group content ranging from 1 µeq / gram to 60 µeq / gram. The polyamide composition may be formed, at least in part, by performing solid phase polymerization (SSP) of a base polyamide composition under particular conditions, in which the base polyamide composition has an initial concentration of cyclic residuals that is greater than 1.5 wt%.

Description

PROCESSES FOR REMOVING CYCLIC RESIDUALS FROM POLYAMIDE COMPOSITIONSTECHNICAL FIELD

[0001] The present disclosure relates generally to polyamide formulations and to processes for producing such polyamides. More specifically, the present disclosure relates to processes for producing polyamides using a solid state polymerization (SSP) step that yields a polyamide composition having a low content of cyclic residuals and / or a desired relative viscosity and / or a desired relative viscosity build rate.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 677,524, filed on July 31 , 2024, the entire contents of which are hereby incorporated by reference in this application.BACKGROUND

[0003] Nylon-6; nylon-6, 6; and various copolymers thereof have been widely used in various applications, e.g., film formation, extrusion, injection molding, fiber, and food packaging films, because of their advantageous properties. These polymers / copolymers are formed via a polymerization reaction, as is well known.

[0004] In some cases, the caprolactam monomers used in the polymerization reaction may not entirely polymerize into polymers and higher molecular weight oligomers. These residual monomers have been found to contribute to, among other problems, production inefficiencies such as plating out on equipment (e.g., dies), problems relating to industry contamination limits for food contact applications, and an unpleasant volatile odor.

[0005] In conventional processes, residual caprolactam monomer may be removed by extraction with hot water. The monomeric caprolactam in the extraction water can be purified and cleaned to recapture caprolactam, which can be recycled to the polymerization reactor. However, these water extraction steps have not demonstrated effectiveness for other undesired components that are less water soluble.

[0006] U.S. Patent No. 4,053,457 discloses a process for the manufacture of polyamides from s- caprolactam and / or other polyamide-forming starting compounds by polymerization and subsequent extraction of the polymer. The extract containing solvent, monomer, and oligomers are concentrated in the absence of atmospheric oxygen. The surfaces that come into contact with the extract are made of materials that are inert under the conditions of the concentration process. The resultant concentrate,without further purification or separation, is polymerized by itself or together with other polyamide- forming starting compounds.

[0007] In many of these situations, it is desirable for a polymer / copolymer (collectively polymer(s)) to exhibit higher relative viscosity (RV) and molecular weight, in combination with low residual caprolactam concentration. Molecular weight may be increased by utilizing a solid state polymerization (SSP) process / operation, which is preferably employed after the crude polymer is polymerized and washed. As one example, SSP may be carried out by passing a hot inert gas flow through a heated bed of polymer pellets / granules. As another example, U.S. Patent No. 6,069,228 describes a process for preparing polyamide polymers via prepolymer formation in a reactor system including a reactor, flasher, and separator, crystallization of the prepolymer under controlled temperature conditions, and the subsequent conversion of these crystallized prepolymers to high molecular weight polymer via SSP. Also, U.S. Patent No. 6,476,181 discloses a process for increasing the molecular weight of nylon 6 while reducing its content of caprolactam and other volatiles by a two-staged heating process.

[0008] U.S. Patent No. 11,345,815 describes a base polyamide composition containing a nylon mixture having caprolactam units from 1 wppb to 50 wppm catalyst composition; and greater than 0.75 wt % residual caprolactam, wherein the base polyamide composition has a delta end group level ranging from 30 peq / gram to 90 pcq / grarn.

[0009] The compositional and performance properties of a polyamide polymer are often in conflict with one another, and processing to achieve a low concentration of cyclic residuals may have an adverse effect on molecular weight or RV build, among others. As one example, if residual caprolactam monomer were removed from a typical polyamide composition by performing SSP for an extended duration, then molecular weight of the resulting polyamide will undesirably overbuild and be excessively high at the end of the SSP operation. In some cases, the build rate of the RV and / or the molecular weight over time has a non-linear profile, which leads to control problems. Generally speaking, conventional polymer products have been unable to achieve a low concentration of cyclic residuals in combination with desirable molecular weight and / or relative viscosity, especially where the initial pre-SSP polymer has a high molecular weight and a high concentration of cyclic residuals.

[0010] There continues to be a need for a process for producing a polyamide composition having a low concentration of cyclic residuals, advantageous RV, specific RV build rates, and other beneficial pellet-related properties. The need also exists for a base polyamide composition that is capable of forming the aforementioned polyamide composition.SUMM RY

[0011] Embodiments disclosed herein relate to polyamide compositions and a solid state polymerization (SSP) process for manufacturing a post-SSP polyamide composition having a low concentration of cyclic residuals, a desired relative viscosity, and / or a desired relative viscosity build rate. In some cases, after SSP, the resulting polyamide composition includes: a polyamide; less than 1.5 wt% of cyclic residuals, e.g., l,8-diazacyclotetradecane-2, 7-dione; 1,8,15,22- tetraazacyclooctacosane-2,7,16,21-tetrone dimer; 1,8,15,22,29,36-hexaazacyclodotetracontane- 2,7,16,21,30,35-hexone; or 1,8,15,22,29,36,43,50-octaazacyclohexapentacontane-2,7,16,21,30,35,44,49-octone, or combinations thereof, optionally having a weight average molecular weight ranging from 50 to 4000; and less than 50 wppm of a catalyst composition optionally including phosphorous acid; phosphonic acid; alkyl-substituted phosphonic acids; aryl-substituted phosphonic acids; 2-pyridylethyl phosphonic acid; hypophosphorous acid; alkyl-substituted phosphinic acids; aryl-substituted phosphinic acids; alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous-containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; monosodium phosphate; or any combinations thereof; wherein the polyamide composition has an inert end group content ranging from 1 peq / gram to 60 peq / gram, e.g., from 15 peq / gram to 45 peq / gram, and / or a delta end group content ranging from 15 peq / gram to 90 peq / gram, e.g., from 35 peq / gram to 70 peq / gram, and / or demonstrates a color index ranging from -6 to 5, as measured by ASTM E313 (2018) and / or demonstrates a relative viscosity ranging from 100 to 500.

[0012] In some cases, the disclosure relates to a process for producing a polyamide composition having a low concentration of cyclic residuals, the process including the step of processing a base polyamide composition having an inert end group content ranging from 1 peq / gram to 60 peq / gram and an initial concentration of cyclic residuals greater than 1.5 wt%, based on a total weight of the base polyamide composition, optionally at a processing temperature ranging from 185 °C to 250 °C and / or a processing time ranging from 2 hours to 50 hours, to form a post-processing polyamide composition having a final concentration of cyclic residuals ranging from 0.01 wt% to 1 wt% cyclic residuals and demonstrating a color index ranging from -6 to 5, as measured by ASTM E313 (2018). The post-processing concentration of cyclic residuals may be at least 50% less than the concentration of cyclic residuals in the base polyamide composition before processing, and a relative viscosity of the base polyamide composition increases at a build rate ranging from 1 RV units / hour to 30 RV units / hour during processing.BRIEF DESCRIPTION OF THE DR WINGS

[0013] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present disclosure, are incorporated in and constitute a pail of this specification, illustrate embodiments of the present disclosure, and together with the detailed description, serve to explain principles of the embodiments discussed herein. No attempt is made to show structural details of this disclosure in more detail than may be necessary for a fundamental understanding of the embodiments discussed herein and the various ways in which they may be practiced. According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate embodiments of the disclosure.

[0014] FIG. 1 is a graphical representation that includes a plot demonstrating a correlation between yellow index (YI) and b* for example compositions, according to an embodiment.DETAILED DESCRIPTION

[0015] Conventional processes for producing polyamide compositions often employ a polymerization step to form a base polyamide composition, followed by solid state polymerization (SSP) of the base polyamide to form a post-SSP polyamide composition. Some polyamide compositions may have high concentrations of certain undesirable components, such as low molecular weight cyclic residuals. Further, conventional processes have been found to demonstrate undesirable RV and RV build rates and / or fail to remove a substantial portion of the low molecular weight cyclic residuals.

[0016] As used herein, the terms “low molecular weight cyclic residuals” or “cyclic residuals” refer to cyclic substances or compounds in a polyamide composition, which may include unreacted cyclic monomers and cyclic by-products, such as cyclic dimers, cyclic trimers, cyclic tetramers, and cyclic oligomers formed during or after polymerization.

[0017] The removal of some known cyclic residuals (e.g., residual caprolactam monomer) has been noted. However, the problem of other low molecular weight cyclic residuals is new and creates myriad processing and performance problems. Along those lines, the removal of the aforementioned low molecular weight cyclic residuals has not been disclosed or discussed in much, if any, detail. Importantly, separation schemes that rely on water extraction are not particularly effective for compounds that have poor solubility in water, e.g., low molecular weight cyclic residuals other than caprolactam. As such, there is a need for effective techniques for providing a polyamide compositionthat has a low concentration of cyclic residuals, along with advantageous RV, specific RV build rates, and other beneficial pellet-related properties.

[0018] Particular base polyamide compositions containing specific components and having particular properties, when processed via SSP (optionally under specific conditions such as elevated temperatures, e.g., over 190 °C or over 200 °C), enable the formation of polyamide compositions that demonstrate the aforementioned beneficial combinations of features, e.g., low cyclic residuals concentration and / or desirable RV and RV build rates, inter alia. Conventional base polyamide compositions and processes are incapable of yielding the post-SSP polyamide compositions described herein at least because cyclic residuals content remains high. The low cyclic residuals content disclosed herein is especially germane to food-related applications, e.g., utensils, where a “clean” polymer is advantageous due to a lesser propensity for migration of cyclic residuals out of the polymer. Legislation that will limit or eliminate the amount of such cyclic residuals is being pursued both in the U.S. and around the world, due to the potential extraction of these cyclic residuals from the utensils to the food. The European Federal Institute for Risk Assessment has opined that the limit for migration of certain cyclic residuals into food should be less than 5 mg / kg of food.

[0019] The use of specific inert end group (IEG) content and / or delta end group (DEG) content and / or catalyst content contributes to the desirable properties of the aforementioned post-SSP polyamide composition. For example, the base polyamides disclosed herein yield post-SSP polyamide compositions having an advantageous combination of low cyclic residuals content, e.g., less than 1 wt%, and a desirable RV and / or RV build, e.g., ranging from 30 to 600. RV may be measured via the 90% formic acid method, in accordance with ASTM D789 (9.34) (2018). Without being bound by theory, the disclosed ranges for IEG (and / or DEG content) contribute to particular amounts of matching end groups available for polymerization. The disclosed combination beneficially provides for control of the rate of RV / molccular weight increase whilst concurrently allowing the necessary time for diffusion of cyclic residuals out of pellets during SSP. Further, in some embodiments, the catalysts disclosed herein may serve as an anti-oxidant, which additionally contributes to an advantageous reduction in color formation (yellowness) during SSP.

[0020] In contrast, conventional base polyamide compositions, when processed via conventional SSP, may provide for one of these characteristics, but not more than one, e.g., not low cyclic residuals concentration and desired RV and / or RV build.

[0021] Processing of the base polyamide at specific temperatures resulted in unexpected removal of cyclic residuals. The combination of the disclosed base polyamide and processing via the disclosedprocess conditions (e.g., temperature, duration, inert gas flow rate), leads to surprising and unexpected purity and other compositional and performance characteristics. In some cases, the processing step includes SSP, and in such cases the SSP may involve heating the base polyamide. In some cases, the processing, e.g., the SSP processing, may be conducted at a temperature ranging from 190 °C to 260 °C, from 190 °C to 250 °C, from 190 °C to 240 °C, from 195 °C to 240 °C, from 200 °C to 240 °C, or from 205 °C to 230 °C. In terms of upper limits, the processing may be conducted at a temperature less than 260 °C, e.g., less than 250 °C, less than 240 °C, or less than 230 °C. In terms of lower limits, the processing may be conducted at a temperature greater than 190 °C, e.g., greater than 195 °C, greater than 200 °C, greater than 202 °C, greater than 210 °C, or greater than 215 °C. Other temperature and pressure ranges provided herein may be employed in the SSP process.

[0022] Additionally, in some implementations, the SSP processing may be performed under a flow of an inert gas (e.g., nitrogen). While not wishing to be bound by theory, it is believed that the inert gas flow may aid in the removal of low molecular weight cyclic residuals from the base polyamide composition during SSP. For example, in some implementations, SSP may be performed under a flow of nitrogen gas at a flow rate that ranges from 0 to 60 turns per minute, in which a “turn” refers to a sufficient volume of inert gas for one complete exchange of the interior volume of the SSP vessel with the inert gas. As such, turns per minute is equivalent to the volumetric flow of the inert gas divided by the internal volume of the vessel. For example, a flow rate of 20 cubic feet per minute (CFM) of nitrogen into a 40 cubic foot (ft3) vessel would result in 0.5 turns / min of N2. In some implementations, SSP may be performed under a flow of nitrogen gas at a flow rate that ranges from 0 to 0.3 turns per minute, or from 25 to 60 turns per minute.

[0023] The disclosed base polyamides provide for a consistent, controllable RV build rate during SSP, including but not limited to a substantially linear or linear build rate. This build rate contributes to advantageous control of RV build and simultaneous removal of cyclic residuals, such as by providing the ability to manipulate the RV-to-build time ratio. As an example, when the rate of SSP duration ranges from 1 to 30 hours, then the cyclic residuals have enough time to react or diffuse out of the polyamide composition - both the RV target and the cyclic residuals removal target may be achieved in similar time frames. As a result, the rate of RV build and the rate of cyclic residuals removal cooperate or synergize with one another. In contrast, the use of conventional base polyamide compositions detrimentally contributes to build rates that are too rapid, which do not allow sufficient time for removal of cyclic residuals. With conventional base polyamides and SSP processes, the removal of cyclic residuals takes too much or too little time, and RV builds to an undesirable level orfails to build to a desirable level. This is in contrast to some conventional process that have relied upon caprolactam and catalyst concentration (which affect build rate) to arrive at desirable RV and RV build rates.

[0024] In addition, the use of the base polyamides and SSP processes disclosed herein provide for a product having beneficial overall pellet quality, e.g., good color quality (low yellowing indices); low levels of black specks; and / or high degrees of pellet size uniformity. In particular, the use of the specific amounts of catalyst, if any, has surprisingly been found to retard yellowing. For example, in certain embodiments, the use of the low amounts of catalyst, if any, has surprisingly led to retardation of yellowing. Without being bound by theory, it is believed that lower catalyst concentrations (optionally in conjunction with caprolactam content) have a beneficial effect on color. For example, the related amount of hydrogen radicals donated by these catalysts, e.g., phosphite catalysts, may retard polymer oxidation, which leads to poor color qualities. The lower amounts of catalyst favor catalysis versus other color-causing side reactions, e.g., oxidation - the lower amounts of catalyst seem to demonstrate an anti-oxidizing benefit (in addition to the catalytic effects). Higher amounts of catalyst, in contrast, may provide hydrogen radicals in quantities that result in a build rate is too steep and / or non-linear. Thus, the disclosed amounts of catalyst advantageously both retard oxidation and provide for beneficial build rates (along with color-related and other benefits). As a result of the improved color quality, the resultant post-SSP polyamide compositions advantageously require little if any tinting agents, e.g., blue dyes, which are often employed in conventional polyamide compositions to offset poor color quality.

[0025] Polyamide Compositions with Low Concentrations of Cyclic Residuals

[0026] In some embodiments, the disclosure relates to polyamide compositions that, advantageously, demonstrate or contribute to beneficial combinations of features, e.g., low cyclic residuals concentration, e.g., less than 1.5 wt% of cyclic residuals, and / or desirable RV and RV build rates. Weight percentages may be based on the total weight of the polyamide composition unless otherwise specified. In some cases, the compositions contain low amounts of catalyst, e.g., less than 50 wppm catalyst composition or may contain no catalyst. In some cases, the polyamide compositions have a specific IED content, e.g., ranging from 1 microequivalent per gram (peq / gram) to 60 peq / gram. Additional features and details of the polyamide compositions are disclosed herein.

[0027] In some cases, the polyamide compositions may be formed via a process including the steps of processing a base polyamide composition comprising a polyamide, greater than 1.0 wt% of cyclic residuals, and an IED content, e.g., ranging from 1 peq / gram to 60 peq / gram to form the post-SSPpolyamide composition containing a reduced amount of cyclic residuals, e.g., from 0.01 wt% to 0.75 wt% cyclic residuals. Conventional processes that employ conventional base polyamide compositions have been found to be unable to yield the desired post-SSP polyamide compositions.

[0028] Cyclic Residuals

[0029] The disclosed cyclic residuals may vary widely. Generally speaking, the cyclic residuals may include monomers, dimers, and / or trimers of the repeating units of the polyamide. The cyclic residuals, in some cases, will be present in the post-SSP polymer composition(s), albeit in small concentrations. In certain embodiments, the cyclic residuals in the composition advantageously function as a compositional indicator of the process by which the composition was made. Thus, they provide a chemical fingerprint that can be used as an analytical tool in compositions and processes / applications in which the compositions are subsequently employed. For example, the presence of the disclosed cyclic residuals in the compositions may indicate a commercial grade or specific commercial product, which may allow a producer to better analyze its resultant products, e.g., its particular films or molded products.

[0030] One exemplary cyclic residual monomer is l,8-diazacyclotetradecane-2, 7-dione (CAS 4266- 66-4). One exemplary cyclic residual dimer is l,8,15,22-tetraazacyclooctacosane-2,7,16,21-tetrone dimer (CAS 4238-35-1). One exemplary cyclic residual trimer is 1,8,15,22,29,36- hexaazacyclodotetracontane-2,7,16,21,30,35-hexone (CAS 4174-07-6). One exemplary cyclic residual tetramer is l,8,15,22,29,36,43,50-octaazacyclohexapentacontane-2,7,16,21,30,35,44,49- octone (CAS 4266-65-3).

[0031] In some cases, the cyclic residuals include copolymer cyclic residuals, e.g., copolymers of PA-66-based copolymers such as PA-66 / 6 copolymers. As an example, the PA-66-based copolymer may include l,8,15,22,29,36,43,50-octaazacyclohexapentacontane-2,9,16,23,30,37,44,51-octone tetramer (CAS 16093-69-9).

[0032] In some cases, the cyclic residuals may be characterized by weight average molecular weight. In some cases, each of the cyclic residuals (pre-SSP and / or post-SSP) may have a respective weight average molecular’ weight ranging from 25 to 5000, e.g., from 50 to 4000, from 50 to 2500, from 100 to 2000, from 110 to 1850, from 150 to 1500, from 200 to 1200, or from 210 to 950. In terms of lower limits, each of the cyclic residuals may have a respective weight average molecular weight greater than 25, e.g., greater than 50, greater than 100, greater than 110, greater than 150, greater than 200, greater than 210, greater than 250, greater than 300, greater than 400, greater than 500, greater than 750, or greater than 1000. In terms of upper limits, each of the cyclic residuals may have a weightaverage molecular weight less than 5000, e.g., less than 4500, less than 4000, less than 3500, less than 3000, less than 2500, less than 2200, less than 2000, less than 1800, less than 1500, less than 1300, less than 1200, less than 1000 or less than 950.

[0033] In some embodiments, the cyclic residuals may be characterized by number average molecular weight, Mn, (initially, before processing) less than 18,000 grams per mol (g / mol), e.g., less than 15,000 g / mol, less than 13,000 g / mol, less than 12,000 g / mol, less than 11,000 g / mol, less than 1,000 g / mol, or less than 8,000 g / mol. In terms of ranges, the base polyamide composition may have a number average molecular weight, Mn, ranging from 2,000 g / mol to 18,000 g / mol, e.g., from 4,000 g / mol to 15,000 g / mol, from 5,000 g / mol to 12,000 g / mol, or from 7,000 g / mol to 11,000 g / mol. In terms of lower limits, the base polyamide composition may have a number average molecular weight greater than 2,000 g / mol, e.g., greater than 4,000 g / mol, greater than 5,000 g / mol, greater than 7,000 g / mol, or greater than 9,000 g / mol.

[0034] These characteristics may be applicable to the base and / or post-SSP polyamide compositions.

[0035] The base polyamide composition may further contain relatively high amounts of cyclic residuals prior to SSP processing. In some embodiments, the base polyamide composition contains from 0.5 wt% to 5 wt% cyclic residuals, e.g., from 0.75 wt% to 3 wt%, from 0.75 to 1.75 wt%, from 1 wt% to 1.5 wt%, or from 1 wt% to 1.3 wt%. In terms of lower limits, the base polyamide composition may contain greater than 0.5 wt% cyclic residuals, e.g., greater than 0.75 wt%, greater than 1 wt%, greater than 1.25 wt%, greater than 1.5 wt%, greater than 1.75 wt%, greater than 2 wt%, greater than 3 wt%, or greater than 5 wt%. In terms of upper limits, the base polyamide composition may contain less than 5 wt% cyclic residuals, e.g., less than 3 wt%, less than 2 wt%, less than 1.75 wt%, less than 1.5 wt%, less than 1.3 wt%, or less than 1.25 wt%.

[0036] It is noted that the concentration of cyclic residuals in the post-SSP polyamide composition may be less than the concentration of cyclic residuals in the base polyamide composition. In some embodiments, the post-SSP concentration of cyclic residuals is at least 5% less than the initial concentration of cyclic residuals in the base polyamide composition prior to SSP processing, e.g., at least 10% less, at least 15% less, at least 20% less, at least 25% less at least 35% less, at least 45% less, at least 50% less, at least 60% less, at least 70% less, at least 75% less, at least 90% less, or at least 100% less.

[0037] In some cases, the post-SSP polyamide composition may contain a lower amount of cyclic residuals relative to the base polyamide composition. In some embodiments, the post-SSP polyamide composition contains from 0.01 wt% to 2.5 wt% cyclic residuals, e.g., from 0.1 wt% to 1.5 wt%, from0.05 to 1 wt%, from 0.1 wt% to 0.75 wt%, from 0.1 wt% to 0.6 wt%; from 0.15 wt% to 0.45 wt%; from 0.19 wt% to 0.42 wt%; from 0.25 wt% to 0.75 wt%, from 0.2 wt% to 0.5 wt%, or from 0.3 wt% to 0.4 wt%. In terms of lower limits, the post-SSP polyamide composition may contain greater than 0.01 wt% cyclic residuals, e.g., greater than 0.05 wt%, greater than 0.07 wt%, greater than 0.1 wt%, greater than 0.15 wt%, greater than 0.19 wt%, greater than 0.2 wt%, or greater than 0.25 wt%. In terms of upper limits, the post-SSP polyamide composition may contain less than 2.5 wt% cyclic residuals, e.g., less than 1.5 wt%, less than 1 wt%, less than 0.75 wt%, less than 0.6 wt%, less than 0.5 wt%, less than 0.45 wt%, less than 0.42 wt%, less than 0.4 wt%, or less than 0.3 wt%.

[0038] In some cases, the post-SSP polyamide composition may contain a lower amount of residual cyclic monomers relative to the base polyamide composition. In some embodiments, the post-SSP polyamide composition contains from 0.01 wt% to 2.5 wt% residual cyclic monomers, e.g., from 0 wt% to 0.5 wt%, from 0.01 to 0.3 wt%, from 0.01 wt% to 0.2 wt%, from 0.01 wt% to 0.15 wt%; 0.001 wt% to 0.1035 wt%, or from 0 wt% to 0.0.1035 wt%. In terms of lower limits, the post-SSP polyamide composition may contain greater than 0.001 wt% residual cyclic monomers, e.g., greater than 0.01 wt%, greater than 0.05 wt%, greater than 0.07 wt%, greater than 0.1 wt%, greater than 0.05 wt%, greater than 0.1 wt%, greater than 0.15 wt%, or greater than 0.25 wt%. No residual cyclic monomer content is also contemplated. In terms of upper limits, the post-SSP polyamide composition may contain less than 2.5 wt% residual cyclic monomer, e.g., less than 1.5 wt%, less than 1 wt%, less than 0.75 wt%, less than 0.6 wt%, less than 0.5 wt%, less than 0.45 wt%, less than 0.42 wt%, less than 0.4 wt%, or less than 0.3 wt%.

[0039] In some cases, the post-SSP polyamide composition may contain a lower amount of residual cyclic dimers relative to the base polyamide composition. In some embodiments, the post-SSP polyamide composition contains from 0.01 wt% to 2.5 wt% residual cyclic dimers, e.g., from 0 wt% to 0.5 wt%, from 0.01 to 0.5 wt%, from 0.05 wt% to 0.4 wt%, from 0.1 wt% to 0.3 wt%; 0.11 wt% to 0.28 wt%, or from 0.13 wt% to 0.26 wt%. In terms of lower limits, the post-SSP polyamide composition may contain greater than 0.001 wt% residual cyclic dimers, e.g., greater than 0.01 wt%, greater than 0.05 wt%, greater than 0.07 wt%, greater than 0.1 wt%, greater than 0.05 wt%, greater than 0.1 wt%, greater than 0.11 wt%, greater than 0.13 wt%, greater than 0.15 wt%, or greater than 0.25 wt%. No residual cyclic dimer content is also contemplated. In terms of upper limits, the post- SSP polyamide composition may contain less than 2.5 wt% residual cyclic dimers, e.g., less than 1.5 wt%, less than 1 wt%, less than 0.75 wt%, less than 0.6 wt%, less than 0.5 wt%, less than 0.45 wt%, less than 0.42 wt%, less than 0.414 wt%, less than 0.4 wt%, less than 0.3 wt%, or less than 0.26 wt%.

[0040] In some cases, the post-SSP polyamide composition may contain a lower amount of residual cyclic trimers relative to the base polyamide composition. In some embodiments, the post-SSP polyamide composition contains from 0.01 wt% to 2.5 wt% residual cyclic trimers, e.g., from 0 wt% to 0.3 wt%, from 0.01 to 0.3 wt%, from 0.02 wt% to 0.25 wt%, from 0.03 wt% to 0.2 wt%; 0.04 wt% to 0.18 wt%, or from 0.06 wt% to 0.15 wt%. In terms of lower limits, the post-SSP polyamide composition may contain greater than 0.001 wt% residual cyclic trimers, e.g., greater than 0.01 wt%, greater than 0.02 wt%, greater than 0.03 wt%, greater than 0.04 wt%, greater than 0.05 wt%, or greater than 0.06 wt%. No residual cyclic trimer content is also contemplated. In terms of upper limits, the post-SSP polyamide composition may contain less than 2.5 wt% residual cyclic trimers, e.g., less than 1.5 wt%, less than 1 wt%, less than 0.75 wt%, less than 0.6 wt%, less than 0.5 wt%, less than 0.45 wt%, less than 0.4 wt%, less than 0.3 wt%, less than 0.25 wt%, less than 0.2 wt%, less than 0.18 wt%, or less than 0.15.

[0041] Base Polyamide

[0042] In some cases, a base polyamide composition or pre-SSP processing polyamide composition is disclosed herein. The base polyamide composition may include or consist of a polyamide, which may be a mixture of polyamides, as discussed herein.

[0043] The base polyamide composition may be produced by polymerizing caprolactam monomers (that may be within other mixtures such as nylon-6, 6 salt), which provides for at least some caprolactam unit content in the nylon mixture. Such caprolactam units are not considered to be “residual” caprolactam or a cyclic residual. In some embodiments, the base polyamide composition contains greater than 1.4 wt% caprolactam units, based on the total weight of the base polyamide composition, e.g., greater than 1.5 wt%, greater than 2 wt%, greater than 3 wt%, greater than 4 wt%, greater than 5 wt%, greater than 7 wt%, greater than 10 wt%, greater than 15 wt%, greater than 20 wt%, or greater than 25 wt%. In terms of ranges, the base polyamide composition may contain caprolactam units in an amount ranging from 1.4 wt% to 50 wt%, e.g., from 1.5 wt% to 45 wt%, from 2 wt% to 43 wt%, from 3 wt% to 40 wt%, from 4 wt% to 35 wt%, from 5 wt% to 30 wt%, from 10 wt% to 30 wt%, or from 10 wt% to 20 wt%. In terms of upper limits, the base polyamide composition may contain less than 50 wt% caprolactam units, e.g., less than 45 wt%, less than 43 wt%, less than 40 wt%, less than 35 wt%, less than 30 wt%, or less than 20 wt%.

[0044] In some embodiments, the base polyamide composition has a melting point ranging from 215 °C to 310 °C, e.g., from 235 °C to 290 °C, from 240 °C to 285 °C, from 245 °C to 280 °C, from 250 °C to 275 °C, from 255 °C to 270 °C, or from 260 °C to 265 °C. In terms of upper limits, the basepolyamide composition may have a melting point less than 310 °C, e.g., less than 290 °C, less than 285 °C, less than 280 °C, less than 275 °C, less than 270 °C, or less than 265 °C. In terms of lower limits, the base polyamide composition may have a melting point greater than 215 °C, e.g., greater than 235 °C, greater than 240 °C, greater than 245 °C, greater than 250 °C, greater than 255 °C or greater than 260 °C.

[0045] In some cases, the post-SSP polyamide composition will have similar melting point ranges and limits. In some cases, the post-SSP polyamide composition will have melting point ranges and limits that are ± 50% of the base polyamide, e.g., ± 25%, ± 15%, ± 10%, or ± 5%.

[0046] The use of base polyamide compositions having these melting point ranges enable an advantageous result when employed in the SSP processes discussed herein. While not wishing to be bound by theory, it is believed that base polyamide compositions having lower melting points may not be able to reach sufficient temperatures to achieve removal of the cyclic residuals. By employing higher melting point base compositions, the ability for cyclic residual removal during SSP is effectively facilitated. Also, if the melting point of the base polyamide compositions is too low, the composition will melt during SSP, thus rendering the product ineffective.

[0047] In some cases, the base polyamide composition is produced by melt polymerizing a polyamide composition and pelletizing the melted polyamide composition to form polyamide pellets.

[0048] End Groups

[0049] lEGs are non-reactive end groups, and they result from reaction of, for example, monoacids or monoamines with the polymer chain. For example, when acetic acid reacts with an amine end group on a chain, it forms an amide linkage with an non-reactive methyl group at the end of the chain.

[0050] In some cases, the base polyamide composition may have an inert end group content ranging from 1 peq / gram to 60 peq / gram, e.g., from 3 peq / gram to 55 peq / gram, from 10 peq / gram to 50 pcq / gram, from 15 peq / gram to 45 peq / gram, or from 20 peq / gram to 40 peq / gram. In terms of lower limits, the base polyamide composition may have an inert end group content greater than 1 peq / gram, e.g., greater than 3 peq / gram, greater than 5 peq / gram, greater than 10 peq / gram, greater than 12 peq / gram, greater than 15 peq / gram, greater than 17 peq / gram, greater than 20 peq / gram, greater than 22 peq / gram, or greater than 25 peq / gram. In terms of upper limits, the base polyamide composition may have an inert end group content less than 60 peq / gram, e.g., less than 55 peq / gram, less than 50 peq / gram, less than 47 peq / gram, less than 45 peq / gram, less than 42 peq / gram, less than 40 peq / gram, less than 37 peq / gram, or less than 35 peq / gram.

[0051] Exemplary monoacids include, but are not limited to, acetic acid, proprionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, palmitic acid, myristic acid, decanoic acid, undecanoic acid, dodecanoic acid, oleic acid, or stearic acid, or any combination thereof. Exemplary monoamines include but are not limited to benzylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, 2-ethyl-l -hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, amylamine, tert-butyl amine, tetradecylamine, hexadecylamine, or octadecylamine, or any combination thereof.

[0052] In some cases, IEG / DEG level may be obtained / achieved / controlled by controlling the amount of excess hexamethylene diamine (HMD) in the polymerization reaction mixture. HMD is believed to be more volatile than the dicarboxylic acids that are employed in the reaction, e.g., adipic acid. The HMD and the carboxylic acids act to balance the formula (based on the theoretical values for the end groups), and the balance between the two (and hence the DEG) can be adjusted to achieve desired properties in the polyamide compositions.

[0053] In some cases, the IEG / DEG level may be obtained / achieved / controlled via the incorporation of monoacids and / or monoamines, e.g., by “capping” some of the end structures to arrive at the desired DEG level, e.g., the desired end group balance.

[0054] In some cases, the utilization of monofunctional end capping provides the surprising benefit of controlling, e.g., slowing, the rate of polymerization in the SSP process. Without being bound by theory, it is believed that the capping (1) limits the amount of reactive ends; and (2) limits the degree of polymerization to a finite number. In some cases, the more end capping that is employed, the lower the (maximum) molecular weight can be (at 100% conversion). Both the former and latter may be achieved by creating high DEG systems. The monofunctional addition will increase DEG level.

[0055] In one embodiment, the monoacids and / or monoamines are incorporated at levels ranging from 1 and 40 pcq / gram, e.g., from 1 pcq / gram to 35 pcq / gram, from 3 pcq / gram to 35 pcq / gram, from 3 pcq / gram to 30 peq / gram, from 5 peq / gram to 30 peq / gram, from 5 peq / gram to 25 peq / gram, from 7 peq / gram to 25 peq / gram, from 7 peq / gram to 20 peq / gram, from 10 peq / gram to 20 peq / gram, or from 10 peq / gram to 15 peq / gram. In terms of upper limits, the monoacids and / or monoamines may be incorporated at levels less than 40 peq / gram, e.g., less than 35 peq / gram, less than 30 peq / gram, less than 25 peq / gram, less than 20 peq / gram, or less than 15 peq / gram. In terms of lower limits, the monoacids and / or monoamines may be incorporated at levels greater than 1 peq / gram, e.g., greater than 3 peq / gram, greater than 5 peq / gram, greater than 7 peq / gram, or greater than 10 peq / gram.

[0056] As used herein, delta end groups (DEG or DEGs) are defined as the quantity of amine end groups (-NH2) less the quantity of carboxylic acid end groups (-COOH). For example, in some cases, the quantity of amine end groups and the quantity of the carboxylic acid end groups may be determined in accordance with standard measurement techniques, such as using ISO 25761 to determine the quantity of the amine end groups and / or using ASTM D7409 to determine the quantity of the carboxylic acid end groups.

[0057] In some embodiments, the base polyamide composition has a delta end group (DEG) content ranging from 15 peq / gram to 90 peq / gram, based on the total weight of the base polyamide composition, e.g., from 25 peq / gram to 80 peq / gram, from 40 peq / gram to 70 peq / gram, from 35 peq / gram to 70 peq / gram, or from 45 peq / gram to 60 peq / gram. In terms of lower limits, the base polyamide composition may have a delta end group content greater than 15 peq / gram, e.g., greater than 20 peq / gram, greater than 25 peq / gram, greater than 30 peq / gram, greater than 35 peq / gram, greater than 40 peq / gram, greater than 45 peq / gram, greater than 50 peq / gram, greater than 55 peq / gram, or greater than 60 peq / gram. In terms of upper limits, the base polyamide composition may have a delta end group content less than 90 peq / gram, e.g., less than 85 peq / gram, less than 80 peq / gram, less than 75 peq / gram, less than 70 peq / gram, less than 65 peq / gram, less than 60 peq / gram, less than 55 peq / gram, or less than 50 peq / gram. Additional disclosure on end groups is provided below.

[0058] These characteristics, such as ranges and limits, may be applicable to the post-SSP polyamide composition as well.

[0059] Again, the utilization of the specific IEG and DEG levels provides for the unexpected combination of advantageous properties in the post-SSP polyamide compositions. These ranges and limits may be especially useful, for example, when the amine end balance may be important for secondary operations, e.g., tic layer bonding, adhesion, or secondary chemistry considerations, e.g., reactions with epoxies.

[0060] In some embodiments, the base polyamide composition has an RV (initially, before SSP processing) less than 55, e.g., less than 53, less than 50, less than 48, less than 45, less than 43, less than 40, less than 38, less than 35, less than 33, less than 30, less than 25, less than 20, or less than 15. In terms of lower limits, the post-SSP polyamide composition may have an RV greater than 1, e.g., greater than 3, greater than 5, greater than 8, greater than 10, greater than 12, greater than 15, or greater than 20. In terms of ranges, the post-SSP polyamide composition may have an RV ranging from 1 to 55, e.g., from 1 to 50, from 1 to 45, from 3 to 40, from 5 to 38, from 10 to 38, from 10 to 35, from 25to 40, from 25 to 50, from 20 to 40, from 30 to 40, from 15 to 40, from 15 to 30, or from 20 to 35. The RV values discussed herein may be measured by the formic acid method, e.g., ASTM D789 (9.34) (2018) using 90% formic acid, which is well known in the art.

[0061] In some embodiments, after SSP processing, the polyamide composition has an RV ranging from 30 to 600, e.g., from 40 to 500, from 75 to 500, from 100 to 500, from 125 to 475, from 150 to 400, from 150 to 450, from 200 to 400, from 200 to 350, or from 250 to 350. In terms of lower limits, the post-SSP polyamide composition may have an RV greater than 40, e.g., greater than 50, greater than 75, greater than 100, greater than 125, greater than 150, greater than 175, greater than 200, greater than 250, greater than 300, greater than 350, or greater than 400. In terms of upper limits, the post- SSP polyamide composition may have an RV less than 500, e.g., less than 475, less than 450, less than 425, less than 400, less than 375, less than 350, less than 325, less than 300, less than 275, less than 250, less than 225, or less than 200.

[0062] In some embodiments, the processing step increases the initial RV of the base polyamide composition and / or decreases the concentration of cyclic residuals in the base polyamide composition. In some cases, the post-SSP RV is at least 10% greater than the initial RV, e.g., at least 15% greater, at least 20% greater, at least 25% greater, at least 30% greater at least 35% greater, at least 40% greater, at least 50% greater, at least 60% greater, at least 75% greater, at least 90% greater, or at least 100% greater.

[0063] In addition to the base polyamide compositions themselves, the use of particular SSP parameters, in conjunction with the base polyamide compositions, provides for surprising compositional benefits in the post-SSP polyamide composition and for process related efficiencies. These SSP parameters and benefits are discussed in detail below.

[0064] Catalysts

[0065] The catalyst may vary widely, and there arc many suitable catalyst compositions known in the art. As some examples, the catalyst composition may include phosphorous acid; phosphonic acid; alkyl- and aryl- substituted phosphonic acids; 2-pyridylethyl phosphonic acid; hypopho sphorous acid; alkyl-, aryl- and alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous-containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; or monosodium phosphate; or any combination, e.g., 2 or more, thereof. Esters and salts of these phosphorous-containing acids include, but are not limited to, alkyl, aryl and alkyl / aryl esters, metal salts, ammonium salts, and ammonium alkyl salts. In certain embodiments, the catalystcomposition includes manganese hypophosphite, sodium hypophosphite, or any combination thereof. The aforementioned catalysts are commercially available products.

[0066] As noted above, the catalyst composition is present in specific amounts and contributes to surprising benefits. In some embodiments, the post-SSP polyamide composition contains from 1 wppb to 50 wppm catalyst composition, e.g., from 1 wppb to 40 wppm, from 1 wppb to 37 wppm, from 10 wppb to 37 wppm, from 10 wppb to 35 wppm, from 0.1 wppm to 35 wppm, from 0.1 wppm to 30 wppm, from 0.1 wppm to 25 wppm, from 0.1 wppm to 20 wppm, from 0.5 wppm to 15 wppm, from 0.5 wppm to 10 wppm; from 1 wppm to 20 wppm, from 2 wppm to 25 wppm, from 2 wppm to 20 wppm, from 1 wppm to 10 wppm, from 2 wppm to 15 wppm, from 3 wppm to 11 wppm, or from 4 wppm to 10 wppm. In terms of upper limits, the post-SSP polyamide composition may contain less than 50 wppm catalyst composition, e.g., less than 40 wppm, less than 35 wppm, less than 30 wppm, less than 25 wppm, less than 20 wppm, less than 15 wppm, less than 12 wppm, less than 11 wppm, less than 10 wppm, less than 8 wppm, less than 6 wppm, less than 5 wppm, less than 4 wppm, or less than 3 wppm. In terms of lower limits, the post-SSP polyamide composition may contain greater than 1 wppb catalyst composition, e.g., greater than 10 wppb, greater than 0.1 wppm, greater than 0.3 wppm, greater than 0.5 wppm, greater than 0.7 wppm, greater than 1 wppm, greater than 1.2 wppm, greater than 1.5 wppm, greater than 1.7 wppm, greater than 2 wppm, greater than 2.5 wppm, greater than 3 wppm, greater than 3.5 wppm, greater than 4 wppm, greater than 5 wppm, greater than 7 wppm, or greater than 10 wppm. These ranges and limits may be applicable to the base polyamide composition as well. In some cases, the catalyst concentration in the post-SSP polyamide composition may be less than the catalyst concentration in the base polyamide composition.

[0067] The units “wppm” and “wppb,” as used herein, mean weight parts per million or weight pails per billion, respectively, and are based on the total weight of the entire respective composition, e.g., the total weight of the entire base polyamide composition or the entire post-SSP polyamide composition. Likewise, weight percentages are based on the total weight of the entire respective composition.

[0068] In one embodiment, the catalyst composition contains an inorganic component, e.g., a phosphorus-containing component, such as inorganic phosphites. In these cases, the base polyamide composition contains from 1 wppb to 25 wppm phosphorus, e.g., from 1 wppb to 20 wppm, from 10 wppb to 20 wppm, from 0.1 wppm to 20 wppm, from 0.5 wppm to 20 wppm, from 1 wppm to 20 wppm, from 1 wppm to 15 wppm, from 2 wppm to 15 wppm, from 3 wppm to 12 wppm, from 3 wppm to 13 wppm from 4 wppm to 20 wppm; from 4 wppm to 15 wppm, from 4 wppm to 12 wppm, from10 wppm to 20 wppm, from 5 wppm to 15 wppm, from 5 wppm to 10 wppm, from 10 wppm to 16 wppm, or from 11 wppm to 15 wppm. In terms of upper limits, the base polyamide composition may contain less than 25 wppm phosphorus, e.g., less than 20 wppm, less than 18 wppm, less than 16 wppm, less than 15 wppm, less than 14 wppm, less than 13 wppm, less than 12 wppm, less than 11 wppm, less than 10 wppm, less than 9 wppm, less than 8 wppm, less than 7 wppm, less than 6 wppm, less than 5 wppm, less than 4 wppm, or less than 3 wppm. In teims of lower limits, the base polyamide composition may contain greater than 1 wppb phosphorus, e.g., greater than 10 wppb, greater than 0.1 wppm, greater than 0.3 wppm, greater than 0.5 wppm, greater than 0.7 wppm, greater than 1 wppm, greater than 1.2 wppm, greater than 1.5 wppm, greater than 1.7 wppm, greater than 2 wppm, greater than 2.5 wppm, greater than 3 wppm, greater than 3.5 wppm, greater than 4 wppm, or greater than 5 wppm.

[0069] Polyamide(s)

[0070] The polyamide may vary widely. In some embodiments, the polyamide may contain PA-6, PA-6,6, PA4,6, PA-6,9, PA-6,10, PA-6,12, PA11, PA12, PA9,10, PA9,12, PA9,13, PA9,14, PA9,15, PA-6,16, PA9,36, PA10,10, PA10,12, PA10,13, PA10,14, PA12,10, PA12,12, PA12,13, PA12,14, PA-6,14, PA-6,13, PA-6,15, PA-6,16, PA-6,13, PAMXD,6, PA4T, PA5T, PA-6T, PA9T, PA10T, PA12T, PA4I, PA5I, PA-61, PA10I, copolymers, terpolymers, or any mixtures thereof. Copolymers, terpolymers, and mixtures thereof are contemplated as feedstock components.

[0071] In some aspects, the polyamide may contain polyamides produced through ring-opening polymerization or polycondensation, including the copolymerization and / or copolycondensation, of lactams. For example, these polyamides may include, for example, those produced from propriolactam, butyrolactam, valerolactam, caprolactam, laurolactam, undecylolactam, and enantholactam. In some embodiments, the polyamide is a polymer derived from the polymerization of caprolactam, and as such, the nylon mixture includes some polymers having caprolactam units (nonresidual caprolactam).

[0072] In one embodiment, the polyamide composition may contain the polyamides produced through the copolymerization of a lactam with a nylon, for example, the product of the copolymerization of a caprolactam with PA-6,6.

[0073] In some cases, the polyamide composition may contain PA-66-based copolymers, e.g., copolymers that contain PA-66 as the major component (50% or greater of PA-66 units). In some cases, the PA-66-based copolymer contains PA-66 / 6, PA-66 / 6T, PA-66 / 610, or PA-66 / 612, or combinations thereof.

[0074] In some embodiments, the polyamide may be the condensation products of one or more dicarboxylic acids, one or more diamines, one or more aminocarboxylic acids, and / or ring-opening polymerization products of one or more cyclic lactams, e.g., caprolactam and laurolactam. In some aspects, the polyamide may include aliphatic, aromatic, and / or semi-aromatic polyamides and can be homopolymer, copolymer, terpolymer or higher order polymers. In some aspects, the polyamide includes blends of two or more polyamides. In some embodiments, the polyamide contains aliphatic or aromatic polyamides or blends of two or more polyamides.

[0075] In some aspects, the dicarboxylic acids may include one or more of adipic acid, azelaic acid, terephthalic acid, isophthalic acid, sebacic acid, and dodecanedioic acid. In some aspects, the dicarboxylic acids may include adipic, isophthalic and terephthalic acid. In some aspects, the dicarboxylic acids may include an aminocarboxylic acid, e.g., 11-aminododecanoic acid.

[0076] In some aspects, the diamines may include one or more of tetramethylenediamine, hexamethylenediamine, octamethylenediamine, nonamethylenediamine, 2- methylpentamethylenediamine, 2-methyloctamethylenediamine, trimethylhexamethylenediamine, bis(p-aminocyclohexyl)methane, m-xylylenediamine, p-xylylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, tridecamethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, and the like. Other examples of the aromatic diamine components, which are merely illustrative, include benzene diamines such as 1 ,4-diaminobenzene, 1,3-diaminobenzene, and 1,2-diaminobenzene; diphenyl(thio)ether diamines such as 4,4'-diaminodiphenylether, 3,4'-diaminodiphenylether, 3,3'- diaminodiphenylether, and 4,4'-diaminodiphenylthioether; benzophenone diamines such as 3,3'- diaminobenzophenone and 4,4'-diaminobenzophenone; diphenylphosphine diamines such as 3,3'- diaminodiphenylphosphine and 4,4'-diaminodiphenylphosphine; diphenylalkylene diamines such as 3,3'-diaminodiphcnylmcthanc, 4,4'-diaminodiphcnylmcthanc, 3,3'-diaminodiphcnylpropanc, and 4,4'- diaminodiphenylpropane; diphenylsulfide diamines such as 3,3 '-diaminodiphenylsulfide and 4,4'- diaminodiphenylsulfide; diphenylsulfone diamines such as 3,3'-diaminodiphenylsulfone and 4,4'- diaminodiphenylsulfone; and benzidines such as benzidine and 3,3 '-dimethylbenzidine.

[0077] In some aspects, the polyamide contains physical blends of aliphatic polyamides, semiaromatic polyamides, and / or aromatic polyamides to obtain intermediate or additive properties of each polyamide.

[0078] While much of the discussion above relates to polyamide, and in particular copolyamides of PA-6,6 and PA-6, it is contemplated that the processes and compositions described herein may includeor relate to polyamides ranging from aliphatic polyamides (traditionally PA-6,6 and PA-6 or other aliphatic nylons) to copolyamides with aromatic components (for example paraphenylenediamine and terephthalic acid), to copolymers such as adipate with 2-methyl pentmethylene diamine and 3,5- diacarboxybenzenesulfonic acid (or sulfoisophthalic acid in the form of its sodium sulfonate salt).

[0079] Other polyamides are described in International Application No. PCT / US2019 / 039579, which is incorporated by reference herein.

[0080] In one embodiment, the polyamide contains nylon-6 and nylon-6, 6. The nylon-6 may be present in the nylon mixture in an amount ranging from 1 wt% to 80 wt%, e.g., from 1 wt% to 60 wt%, from 1 wt% to 50 wt%, from 10 wt% to 60 wt%, from 5 wt% to 50 wt%, from 5 wt% to 40 wt%, from 7 wt% to 40 wt%, from 5 wt% to 35 wt%, from 10 wt% to 35 wt%, from 10 wt% to 30 wt%, or from 15 wt% to 30 wt%. In terms of upper limits, the nylon-6 may be present in the polyamide in an amount less than 80 wt%, e.g., less than 70 wt%, less than 60 wt%, less than 55 wt%, less than 50 wt%, less than 45 wt%, less than 40 wt%, less than 35 wt%, or less than 30 wt%. In terms of lower limits, the nylon-6 may be present in the polyamide in an amount greater than 1 wt%, e.g., greater than 2 wt%, greater than 3 wt%, greater than 4 wt%, greater than 5 wt%, greater than 7 wt%, greater than 10 wt%, greater than 12 wt%, greater than 15 wt%, greater than 20 wt%, greater than 25 wt%, or greater than 30 wt%.

[0081] The nylon-6, 6 may be present in the polyamide in an amount ranging from 20 wt% to 99 wt%, e.g., from 40 wt% to 95 wt%, from 50 wt% to 95 wt%, from 55 wt% to 85 wt%, from 65 wt% to 95 wt%, from 60 wt% to 90 wt%, from 65 wt% to 90 wt%, from 70 wt% to 90 wt%, from 75 wt% to 85 wt%, or from 70 wt% to 85 wt%. In terms of upper limits, the nylon-6, 6 may be present in the polyamide in an amount less than 99 wt%, e.g., less than 95 wt%, less than 90 wt%, less than 85 wt%, less than 80 wt%, less than 75 wt%, or less than 70 wt%. In terms of lower limits, the nylon-6, 6 may be present in the polyamide in an amount greater than 20 wt%, e.g., greater than 40 wt%, greater than 50 wt%, greater than 55 wt%, greater than 60 wt%, greater than 65 wt%, greater than 70 wt%, or greater than 75 wt%.

[0082] Processes for Producing a Polyamide with a Low Concentration of Cyclic Residuals

[0083] In conventional processes, some undesirable components, e.g., caprolactam, are often removed, e.g., by extraction. Extraction is normally carried out with hot water or with liquids that contain mostly water. From these extraction waters, the residual caprolactam can be recaptured, cleaned, and in some cases, reintroduced as a recycle stream to the polymerization process. These separate steps, however, detrimentally add equipment and operating costs and can add color to theresin. As noted above, the problem of lower molecular weight cyclic residuals is new and there is a need for effective techniques for providing a polyamide composition having a low concentration of cyclic residuals, along with advantageous post-SSP RV, specific RV build rates, and other beneficial pellet-related properties. The disclosure covers some such techniques to achieve an post-SSP polyamide composition that is free or substantially free of cyclic residuals.

[0084] Disclosed herein are processes for producing a post-SSP polyamide composition having a low concentration of cyclic residuals. One such process includes the steps of processing the base polyamide composition to form the post-SSP polyamide composition containing from 0.01 to 0.75 wt% of cyclic residuals. The base polyamide composition has an initial or pre-SSP concentration of cyclic residuals and an initial or pre-SSP RV (see discussion above). Likewise, the post-SSP polyamide composition has a final or post-SSP concentration of cyclic residuals and a final or post- SSP RV.

[0085] The processing may be conducted at specific operating parameters that provide for advantageous results when employed with the base polyamide compositions disclosed herein.

[0086] In some embodiments, the processing is conducted for a build time (e.g., a SSP duration) less than 50 hours, e.g. less than 40 hours, less than 38 hours, less than 36 hours, less than 35 hours, less than 34 hours, less than 32 hours, less than 30 hours, less than 28 hours, less than 26 hours, less than 25 hours, less than 24 hours, less than 22 hours, or less than 20 hours. In terms of ranges, the processing may be conducted for a build time ranging from 1 hour to 50 hours, e.g., from 2 hours to 50 hours, from 3 hours to 40 hours, from 2 hours to 38 hours, from 4 hours to 36 hours, from 5 hours to 35 hours, from 6 hours to 34 hours, from 8 hour to 32 hours, from 10 hours to 30 hours, from 12 hour to 28 hours, from 14 hours to 26 hours, from 16 hour to 25 hours, or from 18 hours to 24 hours. In teims of lower limits, the processing may be conducted for a build time greater than 1 hour, e.g., greater than 2 hours, greater than 3 hours, greater than 4 hours, greater than 6 hours, greater than 8 hours, greater than 10 hours, greater than 12 hours, greater than 14 hours, or greater than 15 hours.

[0087] In some embodiments, the aforementioned compositions and process conditions may contribute to an advantageous RV build rate, which provides sufficient time for beneficial removal of cyclic residuals and achieve a desirable post-SSP RV. In some embodiments, the RV build rate ranges from 0.1 RV units / hour to 30 RV units / hour, e.g., from 1 to 27 RV units / hour, from 1 to 25 RV units / hour, from 1 to 22 RV units / hour, from 1.5 to 19 RV units / hour, from 1.5 to 17 RV units / hour, from 1.5 to 15 RV units / hour, from 1 to 12 RV units / hour, from 1.5 to 12 RV units / hour, from 3 to 12, RV units / hour from 5 to 10 RV units / hour, from 1 to 9 RV units / hour, or from 1.5 to 9 RV units / hour.In terms of upper limits, the RV build rate may be less than 30 RV units / hour, e.g., less than 28 RV units / hour, less than 26 RV units / hour, less than 25 RV units / hour, less than 23 RV units / hour, less than 20 RV units / hour, less than 19 RV units / hour, less than 18 RV units / hour, less than 16 RV units / hour, less than 15 RV units / hour, less than 14 RV units / hour, less than 13 RV units / hour, less than 12 RV units / hour, less than 11 RV units / hour, less than 10 RV units / hour, less than 9 RV units / hour, less than 8 RV units / hour, less than 7 RV units / hour, less than 6 RV units / hour, or less than 5 RV units / hour. In terms of lower limits, the RV build rate may be greater than 0.1 RV units / hour, e.g., greater than 0.3 RV units / hour, greater than 0.3 RV units / hour, greater than 0.5 RV units / hour, greater than 0.7 RV units / hour, greater than 1 RV units / hour, greater than 1.2 RV units / hour, greater than 1.5 RV units / hour, greater than 2 RV units / hour, greater than 3 RV units / hour, greater than 4 RV units / hour, or greater than 5 RV units / hour. Of course, these ranges and limits related to only some embodiments. In other embodiments, higher RV build rates are contemplated, e.g., build rates greater than 30 RV units / hour.

[0088] In some embodiments, the processing may be conducted at a temperature mentioned above. It is noted that the ability of the base polyamide to be processed at higher temperatures contributes to the advantageous combination of features.

[0089] In some embodiments, the processing is conducted at a pressure below 1 atmosphere (atm), e.g., below 0.75 atm, below 0.5 atm, below 0.25 atm, or below 0.1 atm. In one embodiment, the processing is conducted at a pressure less than atmospheric pressure.

[0090] In a particular embodiment, the temperature, pressure, and build time are advantageously selected. For example, the processing may be conducted at temperature ranging from 150 °C to 250 °C, a build time less than 30 hours, and a pressure less than atmospheric pressure. In some cases, the entire process time (the “recipe time”) may range from 15 hours to 35 hours, e.g., from 5 hours to 30 hours, from 18 hours to 24 hours, or from 20 hours to 22 hours. Each of these factors may impact the RV and the cyclic residuals concentration of the post-SSP polyamide composition, and can be adjusted and / or balanced to achieve desired results.

[0091] The components of the base polyamide composition provide for these particular build times, which allow for both sufficient removal of cyclic residuals and sufficient RV and / or molecular weight build. Conventional base polyamide compositions have been unable to achieve this combination.

[0092] In other embodiments, the processing step include an extrusion RV build, e.g., using twin screw extrusion. However, the processing is not limited to these exemplary options. Other examplesinclude extraction and / or leaching. These steps may be carried out under low pressure or under vacuum.

[0093] Advantageously, the removal of cyclic residuals via SSP retards the propensity for plate-out of the cyclic residuals on metal surfaces. Plate-out typically occurs when the cyclic residuals volatilize from the polymer melt at high processing temperatures and then condenses on metal surfaces of the processing equipment. This plate-out generates harmful flaws and defects in the films and / or other end products. The reduction or elimination of cyclic residuals in the polyamide beneficially leads to reduction or elimination of plate-out. Additionally, SSP prevents cyclic residuals from blooming to the film surface, which can cause various problems, such as reduced adhesion with other polymer film layers, e.g., maleated polyethylene, poly(ethylene vinyl alcohol), and creating haze that limits film clarity.

[0094] As noted herein, the combination of the disclosed base polyamide composition and processing step provides for surprising benefits relating to pellet quality. In one embodiment, the post- SSP polyamide composition has a color index ranging from -6.0 to 5.0, as measured by ASTM E313 (2018), e.g., from -5.5 to 4.5, from -5.0 to 4.0, from -4.5 to 3.5, from -4.0 to 3.0, from -3.5 to 2.5, from -3.0 to 2.0, from -2.5 to 1.5, from -2.0 to 1.0, from -1.5 to 0.5, or from -1.0 to 0. In terms of upper limits, the post-SSP polyamide composition may have a color index less than 5.0, e.g., less than 5.5, less than 5.0, less than 5.5, less than 5.0, less than 4.5, less than 4.0, less than 3.5, less than 3.0, less than 2.5, less than 2.0, less than 1.5, less than 1.0, less than 0.5, or less than 0. In terms of lower limits, the post-SSP polyamide composition may have a color index greater than -6.0, e.g., greater than -5.5, greater than -5.5, greater than -5.0, greater than -4.5, greater than -4.0, greater than -3.5, greater than -3.0, greater than -2.5, greater than -2.0, greater than -1.5, greater than -1.0, greater than -0.5, or greater than 0.

[0095] In some cases, color index, e.g., yellowness index, is calculated according to ASTM E313 employing a spectrophotometer (an example brand is BYK Gardner). The yellowness index (YI) is an indicator of the whiteness or yellowness of an analyzed material, wherein lower values correspond to a whiter or less yellow material. In some cases, YI values may be calculated using an adjustment factor, so in some cases, it may be more useful to compare data on a b* basis, which depicts the yellowness or blueness of a sample. Lower or negative values correspond to blue or whitish pellets that have an absence of a yellow hue. FIG. 1 is a graphical representation that includes a plot demonstrating the BYK Gardner unit’s correlation between YI and b* for example compositions, in accordance with the present disclosure.

[0096] In some cases, the disclosed formulation and / or the SSP process contribute to the post-SSP polyamide composition having a consistent size, e.g., a high degree of pellet size uniformity, which may be expressed as weight per pellets (or per 100 pellets). Without being bound by theory, it is believed that the use of the disclosed parameters, e.g., RV ranges / limits, contributes to the elimination of bubbles from the molten polyamide strands, which results in less disruption in strand and diameter consistency. For example, the post-SSP polyamide composition may have a pellet weight ranging from 0.50 grams / 100 pellets to 1.4 grams / 100 pellets, e.g., from 0.55 grams / 100 pellets to 1.35 grams / 100 pellets, from 0.60 grams / 100 pellets to 1.30 grams / 100 pellets, from 0.65 grams / 100 pellets to 1.25 grams / 100 pellets, from 0.70 grams / 100 pellets to 1.20 grams / 100 pellets, from 0.75 grams / 100 pellets to 1.15 grams / 100 pellets, or from 0.80 grams / 100 pellets to 1.10 grams / 100 pellets. In terms of upper limits, the post-SSP polyamide composition may have a pellet weight less than 1.4 grams / 100 pellets, e.g., less than 1.35 grams / 100 pellets, less than 1.30 grams / 100 pellets, less than 1.25 grams / 100 pellets, less than 1.20 grams / 100 pellets, less than 1.15 grams / 100 pellets, or less than 1.10 grams / 100 pellets. In terms of lower limits, the post-SSP polyamide composition may have a pellet weight greater than 0.50 grams / 100 pellets, e.g., greater than 0.55 grams / 100 pellets, greater than 0.60 grams / 100 pellets, greater than 0.65 grams / 100 pellets, greater than 0.70 grams / 100 pellets, greater than 0.75 grams / 100 pellets, or greater than 0.80 grams / 100 pellets. In some cases, the post-SSP polyamide composition may have a pellet weight that varies by only + / - 25%, based on the average or target pellet weight, e.g., + / - 20%, + / - 15%, + / - 10%, + / - 5%, or + / - 2%.

[0097] In some cases, the improved color quality advantageously allows for the reduction or elimination of tinting agent(s) in the post-SSP polyamide composition. For example, the post-SSP polyamide composition may contain little or no tinting agent(s). In one embodiment, the post-SSP polyamide compositions contain from 0 wt% to 10 wt% tinting agent, based on the total weight of the post-SSP polyamide composition, e.g., from 0.0001 wt% to 10 wt%, from 0.001 to 10 wt%, from 0.005 wt% to 0.5 wt%, from 0.05 to 0.5 wt%, from 0.05 to 0.5 wt%, or from 0.005 to 0.1 wt%. In terms of upper limits, the post-SSP polyamide compositions contain less than 10 wt% tinting agent, e.g., less than 9 wt%, less than 8 wt% less than 7 wt%, less than 6 wt%, less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, less than 0.5 wt%, less than 0.1 wt%, or less than 0.05 wt%. In terms of lower limits, the post-SSP polyamide compositions contain greater than 0.0001 wt% tinting agent, e.g., greater than 0.005 wt%, greater than .001 wt%, greater than 0.05 wt%, greater than 0.01 wt%, or greater than 0.1 wt%. These ranges and limits are applicable to the base polyamide composition as well.

[0098] In one specific embodiment, the disclosed base polyamide composition and process are utilized. The base polyamide composition contains from 0.1 wppm to 30 wppm catalyst composition, from 1 wt% to 8 wt% residual caprolactam monomer and has a delta end group level ranging from 50 peq / gram to 75 peq / gram and has an initial RV less than 35. The post-SSP polyamide composition contains less than 0.5 wt% cyclic residuals (e.g., residual caprolactam monomer) and has a post-SSP RV greater than 45.

[0099] In another specific embodiment, the disclosed base polyamide composition and process are utilized. The base polyamide composition contains from 1 wppm to 15 wppm phosphorus, greater than 1.5 wt% residual caprolactam monomer and has a delta end group level greater than 50 peq / gram and has an initial RV less than 33. The processing is conducted at a pressure less than atmospheric pressure and a temperature ranging from 175 °C to 185 °C. The post-SSP polyamide composition contains less than 0.4 wt% cyclic residuals (e.g., residual caprolactam monomer) and has a post-SSP RV greater than 75.

[0100] Films and Other Applications

[0101] As noted above, one specific application for the disclosed polyamide compositions is in films, e.g., films for food-related applications. Also disclosed herein is a film formed from the post- SSP polyamide composition. Film production processes are well known, and the process for forming the film from the post-SSP polyamide composition may vary widely.

[0102] In other cases, the disclosed polyamide compositions may be particularly useful for molding-related applications. Other exemplary applications include extruded profiles, fiber, blow molding, and / or other applications that require low caprolactam concentration.

[0103] The films formed from the post-SSP polyamide compositions have surprising advantageous performance characteristics. For example, the films may demonstrate a puncture resistance greater than 3 Joules per millimeter (J / mm), as measured via ASTM F1366 (2018), e.g., greater than 4 J / mm, greater than 5 J / mm, greater than 7 J / mm, greater than 10 J / mm, or greater than 15 J / mm. In teims of ranges, the films may demonstrate a puncture resistance ranging from 3 J / mm to 50 J / mm, e.g., from 3 J / mm to 25 J / mm, from 5 J / mm to 50 J / mm, from 5 J / mm to 25 J / mm, from 5 J / mm to 20 J / mm, or 10 J / mm to 25 J / mm.

[0104] In some embodiments, the films may demonstrate an impact resistance greater than 1500 grams, as measured via ASTM D1709 A (2018), e.g., greater than 1700 grams, greater than 2000 grams, greater than 2200 grams, greater than 2500 grams, greater than 3000 grams or greater than 5000 grams. In terms of ranges, the films may demonstrate an impact resistance ranging from 1500grams to 20000 grams, e.g., from 1700 grams to 15000 grams, from 2000 grams to 15000 grams, from 2000 grams to 10000 grams, from 2500 grams to 10000 grams, or from 3000 grams to 10000 grams.

[0105] In some embodiments, the films may demonstrate a tear resistance greater than 50 grams, as measured via ASTM D1922 (2018), e.g., greater than 60 grams, greater than 70 grams, greater than 80 grams, greater than 90 grams, greater than 100 grams, greater than 125 grams, or greater than 150 grams. In terms of ranges, the films may demonstrate tear resistance ranging from 50 grams to 500 grams, e.g., from 60 grams to 450 grams, from 70 grams to 400 grams, from 80 grams to 300 grams, from 80 grams to 200 grams, or from 90 grams to 150 grams.

[0106] Surprisingly, the levels of IEG / DEG in the post-SSP polyamide composition contributed to films having better adhesion between layers when utilized in multi-layer film applications. In particular, these films have improved bonding strength with tie layers, e.g., maleic anhydride-based tie layers, of multi-layer film applications. This improvement in bonding has been shown to contribute to improved properties, e.g., puncture resistance, impact resistance, and / or tear resistance, in the multilayer film structures, as noted above. Without being bound by theory, it is postulated that the increased level amine ends (as reflected in higher DEG level) surprisingly improves adhesion between other layers, e.g., polyethylene, polyethylene terephthalate, and / or other polyamide layers. The amine ends allow more / better bonds to form with maleic anhydride-based tie layers, which results in significant improvements in lamination, e.g., reduction or elimination of delamination.

[0107] As used herein, “greater than” and “less than” limits may also include the number associated therewith. Stated another way, “greater than” and “less than” may be interpreted as “greater than or equal to” and “less than or equal to.” It is contemplated that this language may be subsequently modified in the claims to include “or equal to.” For example, “greater than 4.0” may be interpreted as, and subsequently modified in the claims as “greater than or equal to 4.0.”

[0108] In some embodiments, any or some of the components or steps disclosed herein may be considered optional. In some cases, the disclosed compositions may expressly exclude any or some of the aforementioned components or steps in this description, e.g., via claim language. For example, claim language may be modified to recite that the disclosed compositions, processes, streams, etc., do not utilize or comprise one or more of the aforementioned components, e.g., the base polyamide does not comprise catalyst and / or phosphoric acid. Such negative limitations are contemplated, and this text serves as support for negative limitations for components, steps, and / or features.

[0109] Experimental Examples

[0110] Laboratory-scale Experimental Examples

[0111] A set of laboratory-scale experiments were performed to evaluate example polyamide compositions and SSP processing conditions described herein. For these laboratory-scale experiments, the base (pre-SSP) polyamide composition (control) and post-SSP experimental examples 1 - 3 were prepared as disclosed herein. Experimental examples 1 - 3 employed the same base polyamide composition indicated for the control sample, which contained 0 wppm catalyst, had a DEG of 36 peq / gram, and had an IEG of 0 peq / gram. Experimental examples 1 - 3 were processed using SSP at the conditions indicated in Table 1, as well as an inert gas (N2) flow rate of 60 tums / min. The control and experimental examples were analyzed for post-SSP cyclic residual content, and the results are presented in Table 1. It may be appreciated that the indicated monomer, dimer, and trimer values indicated in Table 1 represent a breakdown of the various low molecular weight cyclic residuals, and as such, these values sum to yield the total cyclic residuals content for each sample. The results indicate performing SSP of this composition at suitable temperatures and for suitable durations results in removal of a substantial amount of low molecular’ weight cyclic residuals from the composition.

[0112] Table 1: SSP Conditions and Cyclic Residuals Content for Laboratory-Scale Experiments.

[0113] Pilot- scale Experimental Examples

[0114] A set of pilot- scale experiments were performed to evaluate example polyamide compositions and SSP processing conditions described herein. For these pilot-scale experiments, the base (pre-SSP) polyamide composition (control) and post-SSP experimental examples 4 - 14 were prepared as disclosed herein. Experimental examples 4 - 14 employed the same based polyamide composition as indicated for the control sample, which contained 0 wppm catalyst, had a DEG of 65 peq / gram, and had an IEG of 10.3 peq / gram. Experimental examples 4 - 14 were processed using SSP at the conditions indicated in Table 2, as well as an inert gas (N2) flow rate of 0 tums / min (e.g., a blanket of inert gas). The control and experimental examples were analyzed for post-SSP cyclic residuals content, and the results are presented in Table 2. It may be appreciated that the indicatedmonomer, dimer, and trimer values indicated in Table 2 represent a breakdown of the various low molecular weight cyclic residuals, and as such, these values sum to yield the total cyclic residuals content for each sample. Additionally, Table 2 indicates the increasing relative viscosity, in addition to the increased removal of low molecular weight cyclic residuals, resulting from increased SSP processing time.

[0115] Table 2: SSP Conditions and Results for Pilot-Scale Experiments.

[0116] Embodiments

[0117] At least the following embodiments are disclosed.

[0118] Embodiment 1: A (post-SSP) polyamide composition comprising: a polyamide; less than 1.5 wt% of cyclic residuals, based on a total weight of the polyamide composition; and less than 50 wppm of a catalyst composition; wherein the polyamide composition has an inert end group content ranging from 1 peq / gram to 60 cq / gram.

[0119] Embodiment 2: An embodiment of embodiment 1, wherein the cyclic residuals comprise l,8-diazacyclotctradccanc-2,7-dionc; l,8,15,22-tctraazacyclooctacosanc-2,7,16,21-tctronc dimer; l,8,15,22,29,36-hexaazacyclodotetracontane-2,7,16,21,30,35-hexone; or 1,8,15,22,29,36,43,50- octaazacyclohexapentacontane-2,7,16,21,30,35,44,49-octone; or any combination thereof.

[0120] Embodiment 3: An embodiment of embodiment 1 or 2, wherein the cyclic residuals are selected from the group consisting of l,8-diazacyclotetradecane-2, 7-dione; 1,8,15,22- tetraazacyclooctacosane-2,7,16,21-tetrone dimer; 1,8,15,22,29,36-hexaazacyclodotetracontane-2,7,16,21,30,35-hexone; and 1,8,15,22,29,36,43,50-octaazacyclohexapentacontane- 2,7,16,21,30,35,44,49-octone.

[0121] Embodiment 4: An embodiment of any one of embodiments 1 - 3, wherein each of the cyclic residuals has a weight average molecular weight ranging from 50 to 4000.

[0122] Embodiment 5 : An embodiment of any one of embodiments 1 - 4, wherein the polyamide composition has a delta end group content ranging from 15 pcq / gram to 90 peq / gram.

[0123] Embodiment 6: An embodiment of any one of embodiments 1 - 5, wherein the polyamide composition has a delta end group content ranging from 35 pcq / gram to 70 qcq / gram.

[0124] Embodiment 7: An embodiment of any one of embodiments 1 - 6, wherein the catalyst composition comprises phosphorous acid; phosphonic acid; alkyl- substituted phosphonic acids; arylsubstituted phosphonic acids; 2-pyridylethyl phosphonic acid; hypophosphorous acid; alkylsubstituted phosphinic acids; aryl-substituted phosphinic acids; alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous-containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; or monosodium phosphate; or any combination thereof.

[0125] Embodiment 8: An embodiment of any one of embodiments 1 - 7, wherein the catalyst composition is selected from the group consisting of phosphorous acid; phosphonic acid; alkylsubstituted phosphonic acids; aryl-substituted phosphonic acids; 2-pyridylethyl phosphonic acid; hypophosphorous acid; alkyl-substituted phosphinic acids; aryl-substituted phosphinic acids; alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous-containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; and monosodium phosphate.

[0126] Embodiment 9: An embodiment of any one of embodiments 1 - 8, wherein the polyamide composition demonstrates a color index ranging from -6 to 5, as measured by ASTM E313 (2018).

[0127] Embodiment 10: An embodiment of any one of embodiments 1 - 9, wherein the polyamide composition demonstrates a relative viscosity ranging from 100 to 500, as measured by ASTM D789 (9.34) (2018) using formic acid.

[0128] Embodiment 11: A process for producing a polyamide composition having a low concentration of cyclic residuals, the process comprising the step of: processing a base polyamide composition comprising a polyamide having an inert end group content ranging from 1 pcq / gram to 60 peq / gram and an initial concentration of cyclic residuals greater than 1.5 wt%, based on a totalweight of the base polyamide composition, to form a post-processing polyamide composition comprising a final concentration of cyclic residuals ranging from 0.01 wt% to 1 wt%.

[0129] Embodiment 12: An embodiment of embodiment 11, wherein the final concentration of cyclic residuals is at least 50% less than the initial concentration of cyclic residuals.

[0130] Embodiment 13: An embodiment of embodiment 11 or 12, wherein the base polyamide composition has an inert end group content ranging from 15 peq / gram to 45 peq / gram.

[0131] Embodiment 14: An embodiment of any one of embodiments 11 - 13, wherein the base polyamide composition has a delta end group content ranging from 35 peq / gram to 70 peq / gram.

[0132] Embodiment 15: An embodiment of any one of embodiments 11 - 14, wherein the postprocessing polyamide composition demonstrates a relative viscosity ranging from 100 to 500, as measured by ASTM D789 (9.34) (2018) using formic acid.

[0133] Embodiment 16: An embodiment of any one of embodiments 11 - 15, wherein, during the processing, a relative viscosity of the base polyamide composition increases at a build rate ranging from 1 RV units / hour to 30 RV units / hour.

[0134] Embodiment 17: An embodiment of any one of embodiments 11 - 16, wherein the cyclic residuals comprise l,8-diazacyclotetradecane-2, 7-dione; 1,8,15,22-tetraazacyclooctacosane- 2,7,16,21-tetrone dimer; l,8,15,22,29,36-hexaazacyclodotetracontane-2,7,16,21,30,35-hexone; or 1,8,15 ,22,29,36,43,50-octaazacyclohexapentacontane-2,7, 16,21 ,30,35 ,44, 49-octone; or any combination thereof.

[0135] Embodiment 18: An embodiment of any one of embodiments 11 - 17, wherein the cyclic residuals are selected from the group consisting of 1,8 -diazacyclo tetradecane-2, 7-dione; 1,8,15,22- tetraazacyclooctacosane-2,7,16,21-tetrone dimer; 1,8,15,22,29,36-hexaazacyclodotetracontane- 2,7,16,21,30,35-hexone; and 1,8,15,22,29,36,43,50-octaazacyclohexapentacontane-2,7, 16,21 ,30,35,44,49-octonc.

[0136] Embodiment 19: An embodiment of any one of embodiments 11 - 18, wherein the processing comprises heating the base polyamide composition to a temperature ranging from 185 °C to 250 °C.

[0137] Embodiment 20: An embodiment of any one of embodiments 11 - 19, wherein the processing comprises a processing duration ranging from 2 to 50 hours.

[0138] Embodiment 21: An embodiment of any one of embodiments 11 - 20, wherein the postprocessing polyamide composition demonstrates a color index ranging from -6 to 5, as measured by ASTM E313 (2018).

[0139] Embodiment 22: An embodiment of any one of embodiments 11 - 21, wherein the base polyamide composition comprises from 1 wppb to 50 wppm catalyst composition comprising phosphorous acid; phosphonic acid; alkyl- and aryl- substituted phosphonic acids; 2-pyridylethyl phosphonic acid; hypophosphorous acid; alkyl-, aryl- and alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous-containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; or monosodium phosphate; or any combination thereof.

[0140] Embodiment 23: An embodiment of any one of embodiments 11 - 22, wherein the base polyamide composition comprises from 1 wppb to 50 wppm catalyst composition selected from the group consisting of phosphorous acid; phosphonic acid; alkyl- and aryl- substituted phosphonic acids; 2-pyridylethyl phosphonic acid; hypophosphorous acid; alkyl-, aryl- and alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous-containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; and monosodium phosphate.

[0141] While the concept has been described in detail, modifications within the spirit and scope of the concept will be readily apparent to those of skill in the art. In addition, it should be understood that aspects of the concept and portions of various embodiments and various features recited herein and / or in the appended claims may be combined or interchanged either in whole or in pail. In the foregoing descriptions of the various embodiments, those embodiments which refer to another embodiment may be appropriately combined with other embodiments as will be appreciated by one of skill in the art. Furthermore, those of ordinary skill in the ail will appreciate that the foregoing description is by way of example only, and is not intended to limit the concept.

Claims

We Claim:

1. A polyamide composition comprising: a polyamide; less than 1.5 wt% of cyclic residuals, based on a total weight of the polyamide composition; and less than 50 wppm of a catalyst composition; wherein the polyamide composition has an inert end group content ranging from 1 peq / gram to 60 peq / gram.

2. The polyamide composition of claim 1, wherein the cyclic residuals comprise 1,8- diazacyclotetradecane-2, 7-dione; l,8,15,22-tetraazacyclooctacosane-2,7,16,21-tetrone dimer; l,8,15,22,29,36-hexaazacyclodotetracontane-2,7,16,21,30,35-hexone; or 1,8,15,22,29,36,43,50- octaazacyclohexapentacontane-2,7,16,21,30,35,44,49-octone; or any combination thereof.

3. The polyamide composition of claim 1, wherein each of the cyclic residuals has a weight average molecular weight ranging from 50 to 4000.

4. The polyamide composition of claim 1, wherein the polyamide composition has a delta end group content ranging from 15 peq / gram to 90 peq / gram.

5. The polyamide composition of claim 1, wherein the polyamide composition has a delta end group content ranging from 35 peq / gram to 70 peq / gram.

6. The polyamide composition of claim 1, wherein the catalyst composition comprises phosphorous acid; phosphonic acid; alkyl- substituted phosphonic acids; aryl-substituted phosphonic acids; 2- pyridylethyl phosphonic acid; hypophosphorous acid; alkyl-substituted phosphinic acids; arylsubstituted phosphinic acids; alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous-containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; or monosodium phosphate; or any combination thereof.

7. The polyamide composition of claim 1, wherein the polyamide composition demonstrates a color index ranging from -6 to 5, as measured by ASTM E313 (2018).

8. The polyamide composition of claim 1, wherein the polyamide composition demonstrates a relative viscosity ranging from 100 to 500, as measured by ASTM D789 (9.34) (2018) using formic acid.

9. A process for producing a polyamide composition having a low concentration of cyclic residuals, the process comprising the step of: processing a base polyamide composition comprising a polyamide having an inert end group content ranging from 1 peq / gram to 60 peq / gram and an initial concentration of cyclic residuals greater than 1.5 wt%, based on a total weight of the base polyamide composition, to form a post-processing polyamide composition comprising a final concentration of cyclic residuals ranging from 0.01 wt% to 1 wt%.

10. The process of claim 9, wherein the final concentration of cyclic residuals is at least 50% less than the initial concentration of cyclic residuals.

11. The process of claim 9, wherein the base polyamide composition has an inert end group content ranging from 15 peq / gram to 45 peq / gram.

12. The process of claim 9, wherein the base polyamide composition has a delta end group content ranging from 35 peq / gram to 70 peq / gram.

13. The process of claim 9, wherein the post-processing polyamide composition demonstrates a relative viscosity ranging from 100 to 500, as measured by ASTM D789 (9.34) (2018) using formic acid.

14. The process of claim 9, wherein, during the processing, a relative viscosity of the base polyamide composition increases at a build rate ranging from 1 RV units / hour to 30 RV units / hour.

15. The process of claim 9, wherein the cyclic residuals comprise l,8-diazacyclotetradecane-2,7- dione; l,8,15,22-tetraazacyclooctacosane-2,7,16,21-tetrone dimer; 1,8,15,22,29,36- hexaazacyclodotetracontane-2,7,16,21,30,35-hexone; or 1,8,15,22,29,36,43,50- octaazacyclohexapentacontane-2,7,16,21,30,35,44,49-octone; or any combination thereof.

16. The process of claim 9, wherein the processing comprises heating the base polyamide composition to a temperature ranging from 185 °C to 250 °C.

17. The process of claim 9, wherein the processing comprises a processing duration ranging from 2 to 50 hours.

18. The process of claim 9, wherein the post-processing polyamide composition demonstrates a color index ranging from -6 to 5, as measured by ASTM E313 (2018).

19. The process of claim 9, wherein the base polyamide composition comprises from 1 wppb to 50 wppm catalyst composition comprising phosphorous acid; phosphonic acid; alkyl- and arylsubstituted phosphonic acids; 2-pyridylethyl phosphonic acid; hypophosphorous acid; alkyl-, aryl- and alkyl- / aryl- substituted phosphinic acids; phosphoric acid; esters and salts of these phosphorous- containing acids; manganese hypophosphite; sodium hypophosphite; benzene phosphinic acid; or mono sodium phosphate; or any combination thereof.

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