Polyamide compositions with reduced yellowing properties and methods of making the same

Abstract

This disclosure relates to a polyamide composition containing a polyamide and small amounts of (a) a combination a sterically hindered phenolic primary antioxidant and an organophosphate antioxidant and / or (b) a blue dye, that unexpectedly provide color improvements to the resulting polyamide composition, both after the antioxidants have been introduced and for a sustained period of time thereafter.

Description

POLYAMIDE COMPOSITIONS WITH REDUCED YELLOWING PROPERTIES AND METHODS OF MAKING THE SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Application No.63 / 738,011, filed December 23, 2024, which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present disclosure generally relates to polyamide compositions that demonstrate reduced yellowing. More specifically, the present disclosure relates to polyamide compositions containing anti-yellowing agents, in which the polyamide compositions demonstrate substantially less yellowing after aging compared to polyamide compositions lacking such anti-yellowing agents.BACKGROUND

[0003] Polyamide resins and methods for their preparation are well known. When manufactured according to conventional processes but in the absence of conventional pigments, these resins tend to exhibit varying degrees of undesired yellowness, with the yellowness increasing over time. Polyamide resins also generally exhibit increased yellowness when exposed to the high temperatures associated with subsequent commonly employed melt processing operations. Since many of these polyamide resins are stored for extended periods of time, and in view of the potential for repeated cycles of melting during molding and extrusion, there is an incentive to provide improved polyamide resins which initially show low color, and which continue to show low color over time.

[0004] Antioxidants are compounds that inhibit oxidation (usually occurring as autoxidation), a chemical reaction that can produce free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants are frequently added to industrial products, such as polymers, fuels, and lubricants, to extend their usable lifetimes. Foods are also treated with antioxidants to forestall spoilage often produced by the rancidification of oils and fats. In cells, antioxidants such as glutathione, mycothiol, and bacillithiol, as well as antioxidants in enzyme systems like superoxide dismutase, have all been shown to prevent damage from oxidative stress.SUMMARY

[0005] Provided here are compositions and methods to address these shortcomings of the art and provide other additional or alternative advantages. The disclosure herein provides for polyamide compositions containing particular anti-yellowing agents. Embodiments also include the use of particular anti-yellowing agents, including certain antioxidants and blue dyes, in amounts conventionally thought to be too low to be effective for their conventional uses. These agents are surprisingly effective in preparing low-color polyamides that retain the low color (e.g., low yellowness index) over an extended period of time, even when aged under harsh conditions (e.g., high temperatures, high humidity).

[0006] Embodiments described herein include a polyamide composition containing a polyamide, a sterically hindered phenolic primary antioxidant, and an organophosphate antioxidant. The sterically hindered phenolic primary antioxidant is present in amounts from 0.01 wt.% to 1 wt.%, such as 0.05 wt.% to 0.5 wt.%; and the organophosphate antioxidant is present in amounts from 0.01 wt.% to less than 1 wt.%, such as 0.05 wt.% to 0.5 wt.%. In some embodiments, the sterically hindered phenolic primary antioxidant contains a hydroxyphenyl group having one or more tertbutyl groups, such as a di-tert-butyl-hydroxyphenyl propionate group. In some embodiments, the organophosphate antioxidant contains one or more phenyl groups, each having one or more tertbutyl groups, and / or may be a diphosphite compound. The composition unexpectedly demonstrates a yellowness index, as measured in accordance with ASTM E313-20, which is less than 15 (e.g., between -10 and 15) after 1500 hours, and / or a yellowness index that is at least 25% lower after 1500 hours compared to the same composition that lacks the sterically hindered phenolic primary antioxidant and the organophosphate antioxidant.

[0007] In some embodiments, the di-tert-butyl-hydroxyphenyl propionate group is 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate. In some embodiments, the organophosphate antioxidant is a diphosphite compound having two 2,4-di-tert-butylphenyl groups. In some embodiments, the composition further contains hypophosphorous acid. In some embodiments, the yellowness index is at least 25% lower, compared to the same composition that lacks the sterically hindered phenolic primary antioxidant and the organophosphate antioxidant. In some embodiments, the polyamide includes PA6,6; PA6I / 6T; PA6; PA610; PA611; PA612; PA10; PAI 1; or PA12; or combinations thereof. In some embodiments, the polyamide composition further contains between 50 ppb and3000 ppb (e.g., from 200 ppb to 2000 ppb or 500 ppb to 1500 ppb) of a blue dye, such as copper(IT) phthalocyanine.

[0008] Embodiments described herein include a polyamide composition containing a polyamide, and between 50 ppb and 3000 ppb (e.g., from 200 ppb to 2000 ppb or 500 ppb to 1500 ppb) of a blue dye, such as a blue dye containing copper(II) phthalocyanine. The composition unexpectedly demonstrates a yellowness index, as measured by ASTME313-20, which is less than 15 after 1500 hours. In some embodiments, the polyamide includes PA6,6; PA6I / 6T; PA6; PA610; PA611; PA612; PA10; PA11; or PA12; or combinations thereof. In some embodiments, the polyamide composition contains from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant; and from 0.01 wt.% to less than 1 wt.% of an organophosphate antioxidant.

[0009] Embodiments described herein include a method for producing a polymer composition that maintains a low yellowness index. The method includes combining a polyamide or polyamide precursors with (a) from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant and from 0.01 wt.% to 1 wt.% of an organophosphate antioxidant, and / or (b) between 50 ppb and 3000 ppb of a blue dye, to form a preliminary polyamide composition. The preliminary polyamide composition demonstrates a yellowness index, as measured by ASTM E313-20, which is less than 15 after 1500 hours. In some embodiments, the process involves polymerizing the preliminary polyamide composition to form a polyamide composition. In some embodiments, the sterically hindered phenolic primary antioxidant includes a hydroxyphenyl group having one or more tertbutyl groups, and the organophosphate antioxidant includes one or phenyl groups having one or more tert-butyl groups. In some embodiments, the blue dye includes copper(II) phthalocyanine, and combining includes combining from 200 ppb to 2000 ppb of copper(II) phthalocyanine with the polyamide precursors.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure, and together with the detailed description, serve to explain principles of the embodiments discussed herein.

[0011] FIG. 1 is a graphical representation of the yellowness index values determined for example polyamide compositions after aging, in accordance with an embodiment.

[0012] FIG.2 is a graphical representation of the yellowness index values determined for example polyamide compositions after aging, in accordance with an embodiment.DETAILED DESCRIPTION

[0013] As discussed above, Applicant developed compositions with low amounts of particular antioxidants and / or particular blue dyes that can act as anti-yellowing agents to provide improved color to the polyamide composition. The reduced yellowing is demonstrated as either a yellowness index having a low value (e.g., less than 15) or a reduction in yellowness index (e.g., 25% or more) relative to a polyamide composition lacking such anti-yellowing agents. These embodiments had surprisingly reduced yellowing that may be observed immediately after introduction of the antiyellowing agents into a polyamide composition or a polyamide precursor composition, after polymerization, and / or after aging. In some embodiments, a significant reduction in yellowing is not seen immediately after introduction or polymerization; however, the anti-yellowing agents described herein provide maintenance of the post-introduction color, allowing the polyamide composition to avoid color degradation and yellowing during usage or storage. Additionally, the resulting polyamide compositions exhibit reduced yellowing after aging for a substantial amount of time at elevated temperatures and in humid environments.

[0014] In the following description, numerous details are set forth in order to provide a thorough understanding of the various embodiments. In other instances, well-known processes, devices, and systems may not have been described in particular detail in order not to unnecessarily obscure the various embodiments. Additionally, illustrations of the various embodiments may omit certain features or details in order to not obscure the various embodiments.

[0015] The description may use the phrases “in some embodiments,” “in various embodiments,” “in an embodiment,” or “in certain embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.

[0016] The use of the words “a” or “an” when used in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0017] The term “about” refers to a range of values including the specified value, which a person of ordinary skill in the art would consider reasonably similar to the specified value. In embodiments, “about” refers to values within a standard deviation using measurements generally acceptable in the art. In one non-limiting embodiment, when the term “about” is used with a particular value, then “about” refers to a range extending to ±10% of the specified value, alternatively ±5% of the specified value, or alternatively ±1% of the specified value, or alternatively ±0.5% of the specified value. In embodiments, “about” refers to the specified value.

[0018] The terms “reducing,” “reduced,” or any variation thereof, when used in the claims and / or the specification includes any measurable decrease or complete removal to achieve a desired result.

[0019] The terms “wt.%”, “vol.%”, or “mol.%” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, which includes the component. In a non-limiting example, 10 grams of a component in 100 grams of the material is 10 wt.% of such component. The term “ppm” refers to part-per-million by weight, and the term “ppb” refers to parts-per-billion by weight.Polyamide composition

[0020] The polyamide composition comprises a polyamide, which, in some embodiments, is a polyamide suitable for producing fibers and fabrics. In one embodiment, the polyamide composition comprises a polyamide in an amount ranging from 50 wt.% to 100 wt.%, such as from 50 wt.% to 99.98 wt.%, from 50 wt.% to 99 wt.%, from 50 wt.% to 98 wt.% from 55 wt.% to 100 wt.%, from 55 wt.% to 99.98 wt.%, from 55 wt.% to 99 wt.%, from 55 wt.% to 98 wt.%, from 60 wt.% to 100 wt.%, from 60 wt.% to 99.98 wt.%, from 60 wt.% to 99 wt.%, from 60 wt.% to 98 wt.%., from 65 wt.% to 100 wt.%, from 65 wt.% to 99.98 wt.%, from 65 wt.% to 99 wt.%, or from 65 wt.% to 98 wt.%). In terms of upper limits, the polymer composition may comprise less than 100 wt.% of the polymer (e.g., less than 99.98 wt.%, less than 99 wt.%, or less than 98 wt.%). In terms of lower limits, the polymer composition may comprise greater than 50 wt.% of the polymer (e.g., greater than 55 wt.%, greater than 60 wt.%, or greater than 65 wt.%). In some cases, the composition comprises the zinc and other additives, as discussed herein.

[0021] Suitable polyamides include semi-aromatic and aliphatic polyamides, such as nylons and aramids. For example, the polyamide may comprise PA-4T / 4I; PA-4T / 6I; PA-5T / 5I; PA-6; PA-6,6; PA-6,6 / 6; long chain polyamide, such as PA-10; PA-11, PA-12; PA-6,10; PA-6,11; PA-6,12, as well as other known long-chain variants optionally including aromatic components (e.g., T andI components); PA-6,6 / 6T; PA-6T / 6I; PA-6T / 6T / 6; PA-6T / 6; PA-6T / 6I / 66; PA-6T / MPMDT (where MPMDT is polyamide based on a mixture of hexamethylene diamine and 2-methylpentamethylene diamine as the diamine component and terephthalic acid as the diacid component); PA-6T / 66; PA-6T / 610; PA-10T / 612; PA-10T / 106; PA-6T / 612; PA-6T / 10T; PA-617101; PA-9T; PA-10T; PA-12T; PA-10T / 10I; PA-10T / 12; PA-10T / 11; PA-6T / 9T; PA-6T / 12T; PA-6T / 10T / 6I; PA-6T / 6I / 6; PA-6T / 61 / 12; PA-6I / 6T, and copolymers, blends, mixtures and / or other combinations thereof.

[0022] In one embodiment, the polyamide is PA6,6; PA6; PA610; PA611; PA612; PA10; PA11; or PA12; or a combination thereof. For instance, the polyamide is PA6,6; PA6 or a combination of PA6,6 and PA6. In one embodiment, the polyamide is PA6,6 or PA6I / 6T. In some embodiments, the polyamide is an aliphatic polyamide formed from non-aromatic polyamide monomers.

[0023] The polyamide composition may include other polymers, such as polyester, rayon, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), co-PET, polylactic acid (PLA), polytrimethylene terephthalate (PTT), or combinations thereof. In some cases, the polyamide composition may include polycarbonate (PC). For example, the polyamide composition may comprise a blend of polycarbonate with other polymers, such as a blend of polycarbonate and acrylonitrile butadiene styrene (PC-ABS), a blend of polycarbonate and polyvinyl toluene (PC-PVT), a blend of polycarbonate and polybutylene terephthalate (PC-PBT), a blend of polycarbonate and polyethylene terephthalate (PC-PET), or combinations thereof.Antioxidants

[0024] In some embodiments, the polyamide composition contains at least one sterically hindered phenolic primary antioxidant and at least one organophosphate antioxidant. Primary antioxidants are substances that directly provide antioxidant properties without prior chemical conversion to an active form, as opposed to secondary antioxidants, which are chemically converted to an active form before providing antioxidant properties.

[0025] In one embodiment, the sterically hindered phenolic primary antioxidant comprises a hydroxyphenyl group having one or more tert-butyl groups, such as two, three, or four tert-butyl groups. In some embodiments, the sterically hindered phenolic primary antioxidant comprises two hydroxyphenyl groups, each having one or more tert-butyl groups, such as two, three, or four tertbutyl groups.

[0026] In some embodiments, the sterically hindered phenolic primary antioxidant comprises one or more propionate groups (Structure 1) or one or more propionyl ami de groups (Structure 2). While represented in ionic form in Structures 1 and 2, the illustrated anions of the propionate group or the propionylamide group (i.e., the anionic oxygen of Structure 1, the anionic nitrogen of Structure 2) may be bonded to a hydrogen atom, a substituted or unsubstituted, straight-chain or branched chain alkyl group, a substituted or unsubstituted, straight-chain or branched chain alkenyl group, a substituted or unsubstituted, straight-chain or branched chain alkynyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. In one embodiment, the moiety bonded to the propionate or propionylamide group is a straight-chain alkyl group, such as an alkyl group having 1-30 carbon atoms (e.g., 2-20, 3-18, 4-18, 5-18, or 6-18 carbon atoms). Alternatively, the anion of the propionate or propionylamide group may be bonded to a substituted or unsubstituted, straight-chain or branched chain alkane group, for instance alkane group having 2-30 carbon atoms (e.g., 2-20, 3-18, 4-18, 5-18, or 6-18 carbon atoms). The alkane portion of the propionate group or the propionylamide group (i.e., methylene carbon and / or the methyl carbon of Structures 1 and 2) may be bonded to another propionate or propionyl ami de group as part of the sterically hindered phenolic primary antioxidant.Structure 1:Propionate GroupStructure 2:Pro ionyl am ide Group

[0027] The propionate groups or propionylamide groups may part of the sterically hindered phenolic primary antioxidant that also contains a hydroxyphenyl group having one or more tertbutyl groups, or the propionate groups or propionyl ami de groups may part of a sterically hindered phenolic primary antioxidant that does not otherwise contain a hydroxyphenyl group. For instance,the sterically hindered phenolic primary antioxidant may contain a 3 -(3, 5 -di -tert-butyl -4-hydroxyphenyl) propionate group or a 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionylamide group.

[0028] Suitable sterically hindered phenolic primary antioxidants include Irganox 1098, commercially available from BASF, and Irganox 1076, also commercially available from BASF.

[0029] In an embodiment, the sterically hindered phenolic primary antioxidant is present in amounts ranging from 0.01 wt.% to 1 wt.%, such as 0.02 wt.% to 1 wt.%; 0.03 wt.% to 1 wt.%; 0.04 wt.% to 1 wt.%; 0.05 wt.% to 1 wt.%; 0.01 wt.% to 0.9 wt.%; 0.01 wt.% to 0.8 wt.%; 0.01 wt.% to 0.7 wt.%; 0.01 wt.% to 0.6 wt.%; 0.01 wt.% to 0.5 wt.%; 0.02 wt.% to 0.8 wt.%; 0.03 wt.% to 0.7 wt.%; 0.04 wt.% to 0.6 wt.%; or 0.05 wt.% to 0.5 wt.%. In terms of lower limits, the polyamide composition may contain greater than 0.01 wt.% sterically hindered phenolic primary antioxidant (e g., greater than 0.02 wt.%, greater than 0.03 wt.%, greater than 0.04 wt.%, or greater than 0.05 wt.%). In terms of upper limits, the polyamide composition may contain less than 1 wt.% sterically hindered phenolic primary antioxidant (e.g., less than 0.9 wt.%, less than 0.8 wt.%, less than 0.7 wt.%, less than 0.6 wt.%, or less than 0.5 wt.%).

[0030] The organophosphate antioxidant may be an organophosphate that comprises one or more phenyl groups, each having one or more tert-butyl groups, such as two, three, four, or five tertbutyl groups. In an embodiment, the organophosphate antioxidant comprises two phenyl groups, each having one or more tert-butyl groups, such as two, three, four, or five tert-butyl groups.

[0031] The organophosphate antioxidant may be a diphosphite compound. The diphosphite may be part of the organophosphate antioxidant that also contains a phenyl group having one or more tert-butyl groups, or the diphosphite may be part of an organophosphate antioxidant does not otherwise contain a phenyl group. For instance, the organophosphate antioxidant may be a diphosphite compound having one or more tert-butyl phenyl groups, such as two 2,4-di-tert-butylphenyl groups. Examples of suitable organophosphate antioxidants include Ultranox 626, commercially available from SI Group.

[0032] In an embodiment, the organophosphate antioxidant is present in amounts ranging from 0.01 wt.% to 1 wt.%, such as 0.02 wt.% to 1 wt.%; 0.03 wt.% to 1 wt.%; 0.04 wt.% to 1 wt.%; 0.05 wt.% to 1 wt.%; 0.01 wt.% to 0.9 wt.%; 0.01 wt.% to 0.8 wt.%; 0.01 wt.% to 0.7 wt.%; 0.01 wt.% to 0.6 wt.%; 0.01 wt.% to 0.5 wt.%; 0.02 wt.% to 0.8 wt.%; 0.03 wt.% to 0.7 wt.%; 0.04 wt.% to 0.6 wt.%; or 0.05 wt.% to 0.5 wt.%. In terms of lower limits, the polyamide compositionmay contain greater than 0.01 wt.% organophosphate antioxidant (e.g., greater than 0.02 wt.%, greater than 0.03 wt.%, greater than 0.04 wt.%, or greater than 0.05 wt.%). In terms of upper limits, the polyamide composition may contain less than 1 wt.% organophosphate antioxidant (e.g., less than 0.9 wt.%, less than 0.8 wt.%, less than 0.7 wt.%, less than 0.6 wt.%, or less than 0.5 wt.%).

[0033] It should be appreciated that, while sterically hindered phenolic primary antioxidants and organophosphate antioxidants are known to be used to improve the heat stability of polyamides, Applicant found that these components surprisingly provide an anti-yellowing effect for polyamide compositions even after substantial aging under harsh conditions, as described herein. Furthermore, Applicant unexpectedly found that this anti-yellowing effect is observed when these antioxidants are used in lower amounts than those used to provide conventional heat stability effects.Blue dye

[0034] Additionally, Applicant has developed compositions containing certain blue dyes, which when used in particular amounts, can surprisingly act as an anti-yellowing agent for polyamide compositions. In an embodiment, the polymer composition contains a polyamide, and between 50 ppb and 3000 ppb of a blue dye. The composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20. In general, the purpose of the blue dyes described herein is not to introduce a blue color into the polyamide to merely mask yellowing. In other words, the blue dyes described herein may be used in amounts too small to provide a noticeable blue color within the polyamide, except where a blue color may be desirable. While not wishing to be bound by theory, the blue dyes described herein represent chemical structures that possess antioxidant properties that are believed to block or prevent yellowing of polyamide compositions, even when present in amounts that only introduce a negligible amount of blue color to be introduced into the polyamide.

[0035] In one embodiment, the blue dye comprises phthalocyanine and / or copper(II). An example of a suitable blue dyes includes phthalocyanine blue, also known as phthalocene blue. In one embodiment, the blue dye may include methylene blue. In some embodiments, the blue dye may be a natural blue dye, such as an anthocyanin, phycocyanin, genipin, or gardenia blue. In some embodiments, the polyamide contains between 50 ppb and 3000 ppb of the blue dye (e.g., between 100 ppb and 2500 ppb, between 150 ppb and 2000 ppb, between 200 ppb and 2000 ppb, between 250 ppb and 1500 ppb, between 500 ppb and 1500 ppb, or between 500 ppb and 2500 ppb). Interms of lower limits, the polyamide composition may contain greater than 50 ppb of the blue dye (e.g., greater than 100 ppb, greater than 150 ppb, greater than 200 ppb, greater than 250 ppb, or greater than 500 ppb). In terms of upper limits, the polyamide composition may contain less than 3000 ppb of the blue dye (e.g., less than 2500 ppb, less than 2000 ppb, or less than 1500 ppb).

[0036] As can be seen in the data below, the addition of 175 ppb of phthalocyanine blue dye produces a polyamide having a yellowness index of 16.3, while the addition of 1.75 ppm (1750 ppb) produces a polyamide having a yellowness index of 4.44. The addition of 35 ppm (35,000 ppb) produces a polyamide having a yellowness index of -64.3. As such, for an embodiment in which a yellowness index of -10 to 15 is desired, a polyamide may contain phthalocyanine blue dye in an amount greater than 175 ppb and less than 3000 ppb (e.g., from 200 ppb to 2000 ppb).

[0037] In some embodiments, a polyamide composition may include two or more of a sterically hindered phenolic primary antioxidant, an organophosphate antioxidant, and a blue dye. For example, in one embodiment, a polyamide composition may include a combination of a sterically hindered phenolic primary antioxidant, an organophosphate antioxidant, and a blue dye. It is believed that using one or both of the types of antioxidants described herein in combination with a blue dye described herein provides a combined or synergistic anti-yellowing effect. While not wishing to be bound by theory, for such embodiments, it is believed that the blue dyes described herein primarily limit or reduce the initial yellowness index of such polyamide compositions prior to or immediately following polymerization, while the antioxidants described herein are believed to primarily help to limit or reduce the yellowness index thereafter.Yellowness Index

[0038] These particular antioxidants and / or blue dyes, when used in specific ranges, provide improved color to the polyamide composition, demonstrated as a reduction in yellowing. The polyamides have been shown to have a yellowness index of less than 15, which can be seen immediately after polymerization of the polyamide composition (when the antioxidants are introduced in the polymerization process) as well as 1500 hours, or more, thereafter. The conditions relating to the 1500-hour time period can vary in terms of temperature and relative humidity. Typically, the polyamide is maintained for the time period, in this case 1500 hours, at a temperature of 55 °C and a relatively humidity of 95%, however other temperatures, both higher and lower than this (for instance, temperatures from 20 °C to 100 °C) and other relative humidities may also be used.

[0039] Yellowness index is measured by ASTM E313-20. ASTM E313 is entitled “Standard Practice for Calculating Yellowness and Whiteness Indices from Instrumentally Measured Color Coordinates.” The term “ASTM E313” as used herein refers to the practice (a) for providing numbers that correlate with visual ratings of yellowness or whiteness of white and near-white or colorless object-color specimens, viewed in daylight by an observer with normal color vision, and (b) provides recommended equations for single-number scales of yellowness or whiteness and discusses their derivations and uses, and limits to their applicability.

[0040] More specifically, for the experimental data described herein, the yellowness index (YI) was calculated for Illuminant C using the CIE 1964 standard colorimetric observer (10°) in accordance with Equation 1, in which Cx has a value of 1.2769 and Czhas a value of 1.0592, and in which the X, Y, and Z values are the measured tristimulus values of the specimen. The L*, a*, and b* values indicated herein are determined as indicated by the ASTM E313-20 standard.Equation 1: YI = 100 (Cx X - Cz Z) / Y

[0041] The polyamide compositions demonstrate a yellowness index of less than 15, after introduction, after polymerization, and / or after aging, as measured by ASTM E313-20. Achieving a yellowness index of less than 15 indicates that yellowing is substantially absent from the composition. Applicant has demonstrated that the use of particular antioxidants in specific ranges has unexpectedly enabled the production of polyamide compositions having a yellowness index of 15 or lower, such as less than 12, less than 10, less than 7, or less than 5. In terms of lower limits, polyamide compositions have demonstrated a yellowness index greater than -10. For example, in some embodiments, the desirable yellowness index ranges from -10 to 15 (e.g., -8 to 12, -5 to 10, -2 to 7, or 0 to 5).

[0042] The polyamide compositions have also demonstrated a yellowness index of less than 15, after a significant period of time, such as 500 hours, 1000 hours, or 1500 hours, as measured by ASTM E313-20. While the use of certain dyes and pigments can improve the color of polyamides for a short period of time, demonstrating the improvement of a sustained period of time, has increased commercial value.

[0043] In some embodiments, the polyamide composition has a yellowness index that is at least 25% lower, compared to the same composition, but lacking the anti-yellowing agents described herein. For instance, the polyamide can have a yellowness index that is 30% lower, 35% lower, 40% lower, 45% lower, or 50% lower, compared to the same composition, but lacking the anti-yellowing agents described herein. In certain cases, the reduction in yellowness index is even more dramatic. In those instances, the yellowness index may be at least five-fold (5x) lower, such as sixfold (6x), seven-fold (7x), or eight-fold (8x) lower, compared to the same composition, but lacking the anti-yellowing agents described herein. A reduction in yellowness index values between these values described above is also contemplated, such as 100% lower, 200% lower, 300% lower, or 400% lower yellowness index compared to the same composition, but lacking the anti-yellowing agents described herein.

[0044] Additionally, the resulting polyamide compositions has been demonstrated to exhibit the reduced yellowing (e.g., yellowness index of less than 15) even after extensive aging at elevated temperatures (e.g., 55 °C and higher) and in humid environments (e.g., 95% relative humidity and higher).Antiviral / Antimicrobial agents

[0045] In some embodiments, the polyamide composition may include antiviral or antimicrobial agents, such as zinc compounds, copper compounds, silver compounds, and / or phosphorus compounds to provide structural and / or antimicrobial / antiviral benefits. As used herein, “zinc compound” refers to a compound having at least one zinc molecule or ion (likewise for copper compounds). As used herein, “phosphorus compound” refers to a compound having at least one phosphorus molecule or ion. Zinc content may be indicated by zinc or zinc ion (the same is true for copper and silver). The ranges and limits may be employed for zinc content and for zinc ion content, and for other metal content (e.g., copper content). The calculation of zinc ion content based on zinc or zinc compound can be made by the skilled chemist, and such calculations and adjustments are contemplated.

[0046] With regard to the zinc, copper, silver and / or phosphorus, the polyamide composition may contain zinc, copper, silver, and / or phosphorus in amounts ranging from 5 ppm to 20,000 ppm, such as from 5 ppm to 17,500 ppm, from 5 ppm to 17,000 ppm, from 5 ppm to 16,500 ppm, from 5 ppm to 16,000 ppm, from 5 ppm to 15,500 ppm, from 5 ppm to 15,000 ppm, from 5 ppm to 12,500 ppm, from 5 ppm to 10,000 ppm, from 5 ppm to 5000 ppm, from 5 ppm to 4000 ppm, from 5 ppm to 3000 ppm, from 5 ppm to 2000 ppm, from 5 ppm to 1000 ppm, from 5 ppm to 500 ppm, from 10 ppm to 20,000 ppm, from 10 ppm to 17,500 ppm, from 10 ppm to 17,000 ppm, from 10 ppm to 16,500 ppm, from 10 ppm to 16,000 ppm, from 10 ppm to 15,500 ppm, from 10 ppm to 15,000 ppm, from 10 ppm to 12,500 ppm, from 10 ppm to 10,000 ppm, from 10 ppm to 5000 ppm,from 10 ppm to 4000 ppm, from 10 ppm to 3000 ppm, from 10 ppm to 2000 ppm, from 10 ppm to 1000 ppm, from 10 ppm to 500 ppm, from 50 ppm to 20,000 ppm, from 50 ppm to 17,500 ppm, from 50 ppm to 17,000 ppm, from 50 ppm to 16,500 ppm, from 50 ppm to 16,000 ppm, from 50 ppm to 15,500 ppm, from 50 ppm to 15,000 ppm, from 50 ppm to 12,500 ppm, from 50 ppm to 10,000 ppm, from 50 ppm to 5000 ppm, from 50 ppm to 4000 ppm, from 50 ppm to 3000 ppm, from 50 ppm to 2000 ppm, from 50 ppm to 1000 ppm, from 50 ppm to 500 ppm, from 100 ppm to 20,000 ppm, from 100 ppm to 17,500 ppm, from 100 ppm to 17,000 ppm, from 100 ppm to 16,500 ppm, from 100 ppm to 16,000 ppm, from 100 ppm to 15,500 ppm, from 100 ppm to 15,000 ppm, from 100 ppm to 12,500 ppm, from 100 ppm to 10,000 ppm, from 100 ppm to 5000 ppm, from 100 ppm to 4000 ppm, from 100 ppm to 3000 ppm, from 100 ppm to 2000 ppm, from 100 ppm to 1000 ppm, from 100 ppm to 500 ppm, from 200 ppm to 20,000 ppm, from 200 ppm to 17,500 ppm, from 200 ppm to 17,000 ppm, from 200 ppm to 16,500 ppm, from 200 ppm to 16,000 ppm, from 200 ppm to 15,500 ppm, from 200 ppm to 15,000 ppm, from 200 ppm to 12,500 ppm, from 200 ppm to 10,000 ppm, from 200 ppm to 5000 ppm, from 200 ppm to 4000 ppm, 5000 ppm to 20000 ppm, from 200 ppm to 3000 ppm, from 200 ppm to 2000 ppm, from 200 ppm to 1000 ppm, from 200 ppm to 500 ppm, from 10 ppm to 900 ppm, from 200 ppm to 900 ppm, from 425 ppm to 600 ppm, from 425 ppm to 525 ppm, from 350 ppm to 600 ppm, from 375 ppm to 600 ppm, from 375 ppm to 525 ppm, from 480 ppm to 600 ppm, from 480 ppm to 525 ppm, from 600 ppm to 750 ppm, or from 600 ppm to 700 ppm. In terms of lower limits, the polyamide composition may contain greater than 5 ppm of zinc / copper / silver / phosphorus, such as greater than 10 ppm, greater than 50 ppm, greater than 100 ppm, greater than 200 ppm, greater than 300 ppm, greater than 350 ppm, greater than 375 ppm, greater than 400 ppm, greater than 425 ppm, greater than 480 ppm, greater than 500 ppm, or greater than 600 ppm. In terms of upper limits, the polyamide composition may contain less than 20,000 ppm of zinc / copper / silver / phosphorus, such as less than 17,500 ppm, less than 17,000 ppm, less than 16,500 ppm, less than 16,000 ppm, less than 15,500 ppm, less than 15,000 ppm, less than 12,500 ppm, less than 10,000 ppm, less than 5000 ppm, less than less than 4000 ppm, less than 3000 ppm, less than 2000 ppm, less than 1000 ppm, less than 500 ppm, less than 400 ppm, less than 330 ppm, less than 300.

[0047] The zinc of the polyamide composition may be present in or provided via a zinc compound, which may vary widely. The zinc compound may comprise zinc oxide, zinc ammonium adipate, zinc acetate, zinc ammonium carbonate, zinc stearate, zinc phenyl phosphinic acid, or zincpyrithione, or combinations thereof. In some embodiments, the zinc compound comprises zinc oxide, zinc ammonium adipate, zinc acetate, or zinc pyrithione, or combinations thereof. In some embodiments, the zinc compound comprises zinc oxide, zinc stearate, or zinc ammonium adipate, or combinations thereof. In some aspects, the zinc is provided in the form of zinc oxide.

[0048] The copper of the polyamide composition, if present, is not particularly limited. Suitable copper compounds include copper iodide, copper bromide, copper chloride, copper fluoride, copper oxide, copper stearate, copper ammonium adipate, copper acetate, or copper pyrithione, or combinations thereof. The copper compound may comprise copper oxide, copper ammonium adipate, copper acetate, copper ammonium carbonate, copper stearate, copper phenyl phosphinic acid, or copper pyrithione, or combinations thereof. In some embodiments, the copper compound comprises copper oxide, copper ammonium adipate, copper acetate, or copper pyrithione, or combinations thereof. In some embodiments, the copper compound comprises copper oxide, copper stearate, or copper ammonium adipate, or combinations thereof. In some aspects, the copper is provided in the form of copper oxide.

[0049] The silver of the polyamide composition, if present, is optionally provided via a silver compound. As used herein, “silver compound” refers to a compound having at least one silver molecule or ion. The silver may be in ionic form.

[0050] The phosphorus of the polyamide composition may be present in or provided via a phosphorus compound, which may vary widely. The phosphorus compound may comprise benzene phosphinic acid, diphenylphosphinic acid, sodium phenylphosphinate, phosphorous acid, benzene phosphonic acid, calcium phenylphosphinate, potassium B-pentylphosphinate, methylphosphinic acid, manganese hypophosphite, sodium hypophosphite, monosodium phosphate, hypophosphorous acid, dimethylphosphinic acid, ethylphosphinic acid, diethylphosphinic acid, magnesium ethylphosphinate, triphenyl phosphite, diphenylmethyl phosphite, dimethylphenyl phosphite, ethyldiphenyl phosphite, phenylphosphonic acid, methylphosphonic acid, ethylphosphonic acid, potassium phenylphosphonate, sodium methylphosphonate, calcium ethylphosphonate, and combinations thereof. In some embodiments, the phosphorus compound comprises hypophosphorous acid.

[0051] Applicant recognized that certain of the aforementioned antiviral / antimicrobial agents, such as certain antiviral / antimicrobial agents containing silver or copper, can promote yellowing of polyamide compositions. As such, Applicant further recognized that the anti-yellowing agentsdescribed herein may beneficially reduce or prevent the yellowing of polyamide compositions that include such antiviral / antimicrobial agents.Additional Components

[0052] In some embodiments, the polyamide composition may contain additional additives, such as pigments, hydrophilic or hydrophobic additives, anti-odor additives, and antimicrobial / anti-fungal inorganic compounds.

[0053] In some embodiments, the polyamide composition can be combined with color pigments for coloration for the use in fabrics or other components formed from the polyamide composition. For instance, the polyamide composition can contain UV additives to withstand fading and degradation in fabrics exposed to significant UV light, or additives to make the surface of the fiber hydrophilic, hydrophobic, or hygroscopic. In some aspects, the polyamide composition can contain additives to make the fabric flame retardant, flame resistant, or stain resistant. The polyamide composition may further contain colored materials, such as carbon black, copper phthalocyanine pigment, lead chromate, iron oxide, chromium oxide, and ultramarine blue. In some embodiments, the polyamide composition may be free of any pigments, or may only include the blue dye in the amounts described herein.

[0054] The additional additives may be in the form of a delusterant. A delusterant additive may improve the appearance and / or texture of the synthetic fibers and fabric produced from the polyamide composition. In some embodiments, inorganic pigment-like materials can be utilized as delusterants. The delusterants may comprise one or more of titanium dioxide, barium sulfate, barium titanate, zinc titanate, magnesium titanate, calcium titanate, zinc oxide, zinc sulfide, lithopone, zirconium dioxide, calcium sulfate, barium sulfate, aluminum oxide, thorium oxide, magnesium oxide, silicon dioxide, talc, mica, and the like.

[0055] In one embodiment, the polyamide composition contains the delusterant, or any of the other additives, in an amount ranging from 0.0001 wt.% to 3 wt.%, such as 0.0001 wt.% to 2 wt.%, from 0.0001 wt.% to 1.75 wt.%, from 0.001 wt.% to 3 wt.%, from 0.001 wt.% to 2 wt.%, from 0.001 wt.% to 1.75 wt.%, from 0.002 wt.% to 3 wt.%, from 0.002 wt.% to 2 wt.%, from 0.002 wt.% to 1.75 wt.%>, from 0.005 wt.% to 3 wt.%, from 0.005 wt.% to 2 wt.%, from 0.005 wt.% to 1.75 wt.%. In terms of upper limits, the polyamide composition may contain less than 3 wt.% delusterant / additional additives, such as less than 2.5 wt.%, less than 2 wt.% or less than 1.75 wt.%. In terms of lower limits, the polyamide composition may contain greater than 0.0001 wt.%delusterant / additional additives (e ., greater than 0.001 wt.%, greater than 0.002 wt.%, or greater than 0.005 wt.%).Process embodiments

[0056] Another embodiment relates to a process for producing a polyamide that demonstrates and / or maintains a low yellowness index. The process includes the step of combining a polyamide (or one or more polyamide monomers / precursors) with from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant, and from 0.01 wt.% to 1 wt.% of an organophosphate antioxidant, to form a preliminary polyamide composition, wherein the preliminary polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20. The process may additionally involve polymerizing the preliminary polyamide composition to form a polyamide composition. Alternatively, the polyamide composition may be polymerized independently of the antioxidants, and the antioxidants can be added postpolymerization.

[0057] Another embodiment relates to a process for producing a polyamide that demonstrates and / or maintains a low yellowness index. The process includes the step of combining a polyamide (or one or more polyamide monomers / precursors) with between 50 ppb and 3000 ppb of a blue dye, to form a preliminary polyamide composition, wherein the preliminary polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20. The process may additionally involve polymerizing the preliminary polyamide composition to form a polyamide composition. Alternatively, the polyamide composition may be polymerized independently of the blue dye, and the blue dye can be added post-polymerization.

[0058] Another embodiment relates to a process for producing a polyamide that demonstrates and / or maintains a low yellowness index. The process includes the step of combining a polyamide (or one or more polyamide monomers / precursors) with (a) from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant and from 0.01 wt.% to 1 wt.% of an organophosphate antioxidant and / or (b) between 50 ppb and 3000 ppb of a blue dye, to form a preliminary polyamide composition. The process may additionally involve polymerizing the preliminary polyamide composition to form a polyamide composition. The polyamide composition maintains the postpolymerization yellowness index after 1500 hours, as measured by ASTM E313-20. Maintaining the yellowness index in this context, may be demonstrated by having a change in yellowness index of less than 10%, for instance, less than 5%, less than 2%, or less than 1% after aging up to 1500hours, relative to the yellowness index of the composition as measured after polymerization and prior to aging.

[0059] For each of the process embodiments noted above, the polyamide, sterically hindered phenolic primary antioxidant, organophosphate antioxidant, and blue dye can be represented by the embodiments discussed above, relating to the polyamide composition.Articles

[0060] The polyamide compositions having improved anti-yellowing properties can be used in a variety of commercial applications, including neat resins for cable tie products, fdm packaging, fasteners, circuit breakers, terminal blocks, connectors, automotive parts, furniture parts, appliance parts, cable ties, sports equipment, gun stocks, window thermal breaks, aerosol valves, food film packaging, automotive / vehicle parts, textiles, industrial fibers, carpeting, and el ectri cal / electronic parts.Examples

[0061] In a first experimental example, Examples 1-1 to 1-7 were prepared by combining the components listed in Table 1 (amounts listed in grams) to form a PA 6I / 6T polyamide prepared by the process described below.

[0062] Table 1: Example Polyamide Compositions

[0063] Polymerization of the formulations of Examples 1-1 to 1-7 was performed through the following procedure. First, a nylon salt was prepared. For Examples 1-1 to 1-7, separate components of 61 salt (equimolar salt of hexamethylene diamine with isophthalic acid, I) and 6T salt (equimolar salt of hexamethylene diamine (HMD) and terephthalic acid, T) were combined. Alternatively, a tertiary salt may instead be made by first combining hexamethylene diamine and diluting in deionized water, and then isophthalic and terephthalic acids (at 60 / 40 to 70 / 30 I / T ratio) may be added to the aqueous HMD solution while stirring and maintaining the mixture at a temperature of 50-70 °C. In either case, this yields a diamine / diacid equimolar salt solution at a final concentration of 35-50 wt.% aq.

[0064] After salt solution was formed and pH was checked to ensure equimolar balance, the salt solution was pumped to an evaporator, where the solution was heated to 135-155 °C for 30-90 minutes to increase the solids concentration to 70-90 wt.%. Additives such as catalyst, antioxidants, blue dye, antifoam, etc. (see Table 1), were also added in the evaporation step. Alternatively, the additives may be introduced prior to the evaporation step or after the evaporation step.

[0065] Once concentrated, the solution was then pumped into the polymerization reactor where it underwent multiple reaction stages under agitation / stirring. Polymer additives may also be optionally added during the polymerization stages instead of during the evaporation step. The reactor was pressurized to 125-300 psia under an inert atmosphere and heated to 220-265 °C for 30-90 minutes. In the first stage, oligomers are short chains that are formed, tying up all volatile diamines under pressure to prevent loss and limit undesired viscosity build.

[0066] Next, pressure was reduced to atmospheric pressure over 30-60 minutes while the polymer reaction mixture was heated to 260-295 °C. Once at atmospheric pressure, the reaction was carried out for an additional finishing time of 10-40 minutes. Reduced pressure can optionally be applied through vacuum to increase reaction rate. After finishing, pressure was applied using nitrogen gas, reactor die valves were opened, and molten strands were directed to a water tray to quench. Thestrands were cut into pellets. Alternatively, underwater pelletizing could be used in the place of strand cutting. The pellets were screened, conveyed to a blender, and packaged. Pelletizing times were between 20 and 60 minutes.

[0067] Table 2 : Yellowness Index Analysis of Modified Polyamide Compositions

[0068] Examples 1-1 to 1-7 were analyzed for yellowing index. The results are presented in Table 2. In Table 2, YI represents the Yellowness Index, measured by ASTM E313-20; b* represents the blue to yellow region of the color space. Negative b* values mean that the pellets or parts have a more blue tone, whereas positive b* values mean that the pellets or parts have a more yellow tone; VNs (viscosity number measured in sulfuric acid) represents the molecular weight or chain length of the material, measured in mL / g as determined in accordance with ISO307; NH2 represents the amine end-group content of the polyamide composition, measured in peq / g; P represents the phosphorus content of the polyamide composition, measured in ppm; and NA4 represents the amount of acetic acid capped inert end groups, measured in ppm. The acetic acid is introduced to cap a small portion of amine chain ends to limit moderate viscosity build and improve consistency of VNs.

[0069] As can be seen in Table 2, the addition of a sterically hindered phenolic primary antioxidant (Irganox 1076) slightly increased the yellowness index of the polyamide composition from 19.2 to 20.5 (compare Example 1-1 with Example 1-2). Similarly, the addition of an organophosphate antioxidant (Ultranox 626) slightly decreased the yellowness index of the polyamide composition from 19.2 to 18.8 (compare Example 1-1 with Example 1-6). However, when the sterically hindered phenolic primary antioxidant (Irganox 1076) and organophosphate antioxidant (Ultranox626) were combined together, the yellowness index of the polyamide composition surprisingly and unexpectedly dropped from 19.2 to 13.4, a 30% decrease (compare Example 1-1 with Example 1-3). Based on the results of the same individual antioxidants being added at the same amounts, this significant decrease in yellowness index would not have been expected to one skilled in the art. This synergistic result demonstrates improvement beyond the expected additive effect.

[0070] As indicated in Table 2, the addition of a blue dye (phthalocene blue) also improved the yellowness index of the polyamide compositions. The addition of 175 ppb of a blue dye (phthalocene blue) produces a polyamide having a yellowness index of 16.3 (from 19.2), the addition of 1.75 ppm (1750 ppb) of a blue dye (phthalocene blue) produces a polyamide having a yellowness index of 4.44, and the addition of 35 ppm (35,000 ppb) of a blue dye (phthalocene blue) produces a polyamide having a yellowness index of -64.3 (compare Example 1-1 with Examples 1-7, 1-5, and 1-4, respectively). While a decrease in yellowness index to 16.3 is satisfactory, the desired threshold level of 15 was not achieved for this example. On the other hand, achieving a yellowness index of -64.3 indicates that the color of the composition has been significantly altered by the blue dye the polyamide composition, which can lead to the undesired aesthetic appearance of blue-green tones.

[0071] In a second experimental example, two polyamides were prepared, namely Examples 2-1 and 2-2. Example 2-1 was prepared using 231.3 kg (510 lbs.) of Nylon 6,6 monomer salt, 56 g of a 2 wt.% antifoam emulsion, 379 g of an aqueous solution containing acetic acid and sodium phosphinate, 350 g of 80 wt.% acetic acid, and 500 g of an aqueous solution containing 50 wt.% HMD. Example 2-2 was prepared using the same formulation as Example 2-1, except that the formulation also included 240 g of Irganox 1098 and 240 g of Ultranox 626. As such, Example 2-1 represents a neat polyamide 6,6 composition that does not contain any antioxidants, while Example 2-2 represents the same polyamide 6,6 composition, but containing 0.2 wt.% of a sterically hindered phenolic primary antioxidant (Irganox 1098) and 0.2 wt.% of an organophosphate antioxidant (Ultranox 626). The polyamides of Examples 2-1 and 2-2 were prepared using the process described above with respect to the first experimental example.

[0072] FIG. 1 is a graphical representation of the yellowness index of Examples 2-1 and 2-2 evaluated after aging. Each example was measured for its yellowness index at 0 hours, 168 hours, 500 hours, 1000 hours, and 1500 hours. For each time period, the polyamide compositions were held at a temperature of 55 °C and a relatively humidity of 95%. As indicated in FIG. 1, Example2-1 demonstrated a yellowness index ranging from about 25 to about 35, with the yellowness increasing at each aging platform. In contrast, Example 2-2, demonstrated a significantly reduced yellowness index of about 2 at zero hours, which increased by less than 5, at each aging platform. Indeed, Example 2-2 demonstrated an yellowness index of 5 or less over all aging platforms.

[0073] In a third experimental example, three polyamides were prepared, namely Examples 3-1, 3-2, and 3-3. Example 3-1 was prepared using 231.3 kg (510 lbs.) of Nylon 6,6 monomer salt, 56 g of a 2 wt.% antifoam emulsion, 379 g of an aqueous solution containing acetic acid and sodium phosphinate, 350 g of 80 wt.% acetic acid, and 500 g of an aqueous solution containing 50 wt.% HMD. Example 3-2 was prepared using the same formulation as Example 3-1, except that the formulation also included 240 g of Irganox 1098 and 240 g of Ultranox 626. Example 3-3 was prepared using the same formulation as Example 3-1, except that the formulation also included 480 g of Irganox 1098 and 480 g of Ultranox 626. As such, Example 3-1 represents a neat polyamide 6,6 composition that does not contain any antioxidants; Example 3-2 represents the same polyamide 6,6 composition, but containing 0.2 wt.% of a sterically hindered phenolic primary antioxidant (Irganox 1098) and 0.2 wt.% of an organophosphate antioxidant (Ultranox 626); and Example 3-3 represents the same polyamide 6,6 composition, but containing 0.4 wt.% of a sterically hindered phenolic primary antioxidant (Irganox 1098) and 0.4 wt.% of an organophosphate antioxidant (Ultranox 626). The polyamides of Examples 3-1, 3-2, and 3-3 were prepared using the process described above with respect to the first experimental example.

[0074] FIG. 2 is a graphical representation of the yellowness index of Examples 3-1, 3-2, and 3-3 evaluated after aging. Each example was measured for its yellowness index at 0 hours, 168 hours, 250 hours, 500 hours, 1000 hours, and 1500 hours. For each time period, the polyamide compositions were held at a temperature of 55 °C and a relatively humidity of 95%. As indicated in FIG.2, Example 3-1 demonstrated a yellowness index ranging from about 12 to about 27, with the yellowness index increasing at each aging platform. In contrast, Examples 3-2 and 3-3 demonstrated a significantly reduced yellowness after ageing. While Examples 3-2 and 3-3 started out having the same yellowness index as Example 3-1 or higher, the yellowness index of these examples increased only slightly at each aging platform. Particularly, for the aging range from 200 hours to 1500 hours, the yellowness index increased by an amount of 2 or less at each aging platform, increasing to a final yellowness index not more than about 12 after 1500 hours.

[0075] These results demonstrate that (a) the combination of a sterically hindered phenolic primary antioxidant and an organophosphate antioxidant and / or (b) a blue dye, not only produce a significant reduction in yellowness index immediately after addition or polymerization, but that the modified polyamide composition is able to maintain that lowered yellowness index at 500, 1000, and 1500 hours. Maintaining the lower yellowness index upon aging renders the polyamide compositions particularly suitable for commercial products in which it is desirable to maintain the reduced color of the polyamide composition during storage or usage, even under elevated temperature and high humidity conditions. It should be appreciated that, while the upper limit of the aging experiments was 1500 hours, the compositions described herein are expected to provide lower yellowness index values relative to compositions that lack the described anti-yellowing agents, even after aging for longer than 1500 hours.

[0076] When ranges are disclosed herein, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, reference to values stated in ranges includes each and every value within that range, even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0077] Other objects, features and advantages of the disclosure will become apparent from the foregoing drawings, detailed description, and examples. These drawings, detailed description, and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. It should be understood that although the disclosure contains certain aspects, embodiments, and optional features, modification, improvement, or variation of such aspects, embodiments, and optional features can be resorted to by those skilled in the art, and that such modification, improvement, or variation is considered to be within the scope of this disclosure.Embodiments

[0078] The following embodiments are contemplated. All combinations of features and embodiments are contemplated.

[0079] Embodiment 1: A polyamide composition comprising: a polyamide; from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant; and from 0.01 wt.% to less than 1 wt.% of an organophosphate antioxidant. The polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20.

[0080] Embodiment 2: A polyamide composition of embodiment 1, wherein composition comprises from 0.05 wt.% to 0.5 wt.% of the sterically hindered phenolic primary antioxidant.

[0081] Embodiment 3: A polyamide composition of any of the above embodiments, wherein the sterically hindered phenolic primary antioxidant comprises a hydroxyphenyl group having one or more tert-butyl groups.

[0082] Embodiment 4: A polyamide composition of any of the above embodiments, wherein the sterically hindered phenolic primary antioxidant comprises a di-tert-butyl-hydroxyphenyl propionate group.

[0083] Embodiment 5: A polyamide composition of any of the above embodiments, wherein the di-tert-butyl-hydroxyphenyl propionate group is 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0084] Embodiment 6: A polyamide composition of any of the above embodiments, wherein the composition comprises from 0.05 wt.% to 0.5 wt.% organophosphate antioxidant.

[0085] Embodiment 7: A polyamide composition of any of the above embodiments, wherein the organophosphate antioxidant comprises one or more phenyl groups, each having one or more tertbutyl groups.

[0086] Embodiment 8: A polyamide composition of any of the above embodiments, wherein the organophosphate antioxidant is a diphosphite compound.

[0087] Embodiment 9: A polyamide composition of any of the above embodiments, wherein the organophosphate antioxidant is a diphosphite compound having two 2,4-di-tert-butylphenyl groups.

[0088] Embodiment 10: A polyamide composition of any of the above embodiments, wherein composition further comprises hypophosphorous acid.

[0089] Embodiment 11 : A polyamide composition of any of the above embodiments, wherein the yellowness index is at least 25% lower, compared to the same composition that lacks the sterically hindered phenolic primary antioxidant and the organophosphate antioxidant (or the same composition that comprises only polyamide).

[0090] Embodiment 12: A polyamide composition of any of the above embodiments, wherein the polyamide comprises PA6,6; PA6I / 6T; PA6; PA610; PA611; PA612; PA10; PA11; or PA12; or combinations thereof.

[0091] Embodiment 13: A polyamide composition of any of the above embodiments, comprising between 50 ppb and 3000 ppb of a blue dye.

[0092] Embodiment 14: A polyamide composition comprising: a polyamide, and between 50 ppb and 3000 ppb of a blue dye. The polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20.

[0093] Embodiment 15: A polyamide composition of embodiment 14, wherein composition comprises from 500 ppb to 1500 ppb of the blue dye.

[0094] Embodiment 16: A polyamide composition of embodiment 14 or embodiment 15, wherein the blue dye comprises copper(II) phthalocyanine dye.

[0095] Embodiment 17: A polyamide composition of any one of embodiments 14-16, wherein the polyamide comprises PA6,6; PA6V6T; PA6; PA610; PA611; PA612; PA10; PA11; or PA12; or combinations thereof.

[0096] Embodiment 18: A polyamide composition of any one of embodiments 14-17, comprising from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant; and from 0.01 wt.% to less than 1 wt.% of an organophosphate antioxidant.

[0097] Embodiment 19: A method for producing a polymer composition that maintains a low yellowness index, the method comprising the step of combining a polyamide (or one or more polyamide monomers / precursors) with (a) from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant, and from 0.01 wt.% to 1 wt.% of an organophosphate antioxidant, and / or (b) between 50 ppb and 3000 ppb of a blue dye, to form a preliminary polyamide composition. The preliminary polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20.

[0098] Embodiment 20: The method of embodiment 19, further comprising the step of polymerizing the preliminary polyamide composition to form a polyamide composition.

[0099] Embodiment 21 : The method of embodiment 19 or embodiment 20, wherein the sterically hindered phenolic primary antioxidant comprises a hydroxyphenyl group having one or more tertbutyl groups, and wherein the organophosphate antioxidant comprises one or phenyl groups having one or more tert-butyl groups.

[0100] Embodiment 22: The method of any one of embodiments 19-21, wherein the blue dye comprises copper(II) phthalocyanine, and wherein the combining comprises combining from 200 ppb to 2000 ppb of copper(II) phthalocyanine with the polyamide precursors.

Claims

CLAIMSWhat is claimed is:

1. A polyamide composition comprising:a polyamide;from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant; and from 0.01 wt.% to less than 1 wt.% of an organophosphate antioxidant,wherein the polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20.

2. The polyamide composition of claim 0, wherein composition comprises from 0.05 wt.% to 0.5 wt.% of the sterically hindered phenolic primary antioxidant.

3. The polyamide composition of any one of claims 1 or 2, wherein the sterically hindered phenolic primary antioxidant comprises a hydroxyphenyl group having one or more tert-butyl groups.

4. The polyamide composition of any one of claim 1-3, wherein the sterically hindered phenolic primary antioxidant comprises a di-tert-butyl-hydroxyphenyl propionate group.

5. The polyamide composition of claim 4, wherein the di-tert-butyl-hydroxyphenyl propionate group is 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

6. The polyamide composition of any one of claims 1-5, wherein the composition comprises from 0.05 wt.% to 0.5 wt.% of the organophosphate antioxidant.

7. The polyamide composition of any one of claims 1-6, wherein the organophosphate antioxidant comprises one or more phenyl groups, each having one or more tert-butyl groups.

8. The polyamide composition of any one of claims 1-7, wherein the organophosphate antioxidant is a diphosphite compound.

9. The polyamide composition of any one of claims 1-8, wherein the organophosphate antioxidant is a diphosphite compound having two 2,4-di-tert-butylphenyl groups.

10. The polyamide composition of any one of claims 1-9, wherein the composition further comprises hypophosphorous acid.

11. The polyamide composition of any one of claims 1-10, wherein the yellowness index is at least 25% lower, compared to the same composition that lacks the sterically hindered phenolic primary antioxidant and the organophosphate antioxidant.

12. The polyamide composition of any one of claims 1-11, wherein the polyamide comprises PA6,6; PA6I / 6T; PA6; PA610; PA611; PA612; PA10; PA11; orPA12; or combinations thereof.

13. The polyamide composition of any one of claims 1-12, comprising between 50 ppb and 3000 ppb of copper(II) phthalocyanine dye.

14. A polyamide composition comprising:a polyamide; andbetween 50 ppb and 3000 ppb of a blue dye,wherein the polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20.

15. The polyamide composition of claim 14, wherein composition comprises from 500 ppb to 1500 ppb of the blue dye.

16. The polyamide composition of any one of claims 14 or 15, wherein the blue dye comprises copper(II) phthalocyanine dye.

17. The polyamide composition of any one of claims 14-16, wherein the polyamide comprises PA6,6; PA6I / 6T; PA6; PA610; PA611; PA612; PA10; PAI 1; or PA12; or combinations thereof.

18. The polyamide composition of any one of claims 14-17, comprising:from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant; and from 0.01 wt.% to less than 1 wt.% of an organophosphate antioxidant.

19. A method for producing a polymer composition that maintains a low yellowness index, the method comprising:combining polyamide precursors with (a) from 0.01 wt.% to 1 wt.% of a sterically hindered phenolic primary antioxidant and from 0.01 wt.% to 1 wt.% of an organophosphate antioxidant, and / or (b) between 50 ppb and 3000 ppb of a blue dye, thereby to yield a preliminary polyamide composition, wherein the preliminary polyamide composition demonstrates a yellowness index less than 15 after 1500 hours, as measured by ASTM E313-20.

20. The method of claim 19, further comprising the step of polymerizing the preliminary polyamide composition to form a polyamide composition.

21. The method of any one of claims 19 or 20, wherein the sterically hindered phenolic primary antioxidant comprises a hydroxyphenyl group having one or more tert-butyl groups, and wherein the organophosphate antioxidant comprises one or phenyl groups having one or more tert-butyl groups.

22. The method of any one of claims 19-21, wherein the blue dye comprises copper(II) phthalocyanine, and wherein combining comprises combining from 200 ppb to 2000 ppb of copper(II) phthalocyanine with the polyamide precursors.

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