Color stable and low wear polymer composition and articles made therefrom

{
  "publication_number": "US11661512B2",
  "country": "US",
  "kind": "B2",
  "title": "Color stable and low wear polymer composition and articles made therefrom",
  "abstract": "A colorized and tribologically modified polyoxymethylene polymer composition is disclosed. The polyoxymethylene polymer composition is comprised of a polyoxymethylene polymer in combination with at least one tribological modifier. The tribological modifier may include a fluoropolymer. The polymer composition further contains at least one coloring agent in combination with a color stabilizer. The color stabilizer has been found to dramatically improve color consistency. Polymer articles molded from the polymer composition not only have excellent surface appearance but have excellent low friction characteristics when tested against aluminum.",
  "claims": [
    "1. A polymer composition comprising separate components that are suited for being extruded together comprising: a polyoxymethylene polymer; a first tribological modifier comprising a fluoropolymer, the fluoropolymer being present in the composition in an amount of at least 2% by weight, the fluoropolymer comprising polytetrafluoroethylene particles having an average particle size of from about 1 micron to about 10 microns when tested according to ISO Test 13321; and a precompound comprising: one or more coloring agents compounded with a color stabilizer, the color stabilizer comprising a non-oxidized polymer wax, the color stabilizer comprising a polyethylene polymer having a molecular weight of less than about 10,000 g/mol or comprising an ethylene bis-stearamide, the one or more coloring agents being present in the polymer composition in an amount from about 0.1% to about 2% by weight and wherein the color stabilizer is present in the polymer composition in an amount from about 0.5% to about 2% by weight.",
    "2. A polymer composition as defined in claim 1, wherein the color stabilizer is combined with the one or more coloring agents such that the polymer composition, when molded into an article, is color stabilized such that a difference in surface brightness over a surface of an article molded at a temperature between 185° C. and 250° C. varies by no more than 0.5.",
    "3. A polymer composition as defined in claim 1, wherein the color stabilizer is combined with the one or more coloring agents such that the polymer composition, when molded into an article, is color stabilized such that a difference in surface brightness over a surface of an article molded at a temperature between 185° C. and 250° C. varies by no more than 0.3.",
    "4. A polymer composition as defined in claim 1, wherein the color stabilizer is combined with the one or more coloring agents such that the polymer composition, when molded into an article, is color stabilized such that a difference in surface brightness over a surface of an article molded at a temperature between 185° C. and 250° C. varies by no more than 0.25.",
    "5. A polymer composition as defined in claim 1, wherein the color stabilizer comprises the polyethylene polymer.",
    "6. A polymer composition as defined in claim 5, wherein the polyethylene polymer has a density of from about 0.92 g/cm 3 to about 0.94 g/cm 3.",
    "7. A polymer composition as defined in claim 1, wherein the color stabilizer comprises the ethylene bis-stearamide.",
    "8. A polymer composition as defined in claim 1, wherein the polymer composition contains a second tribological modifier comprising a high density polyethylene.",
    "9. A polymer composition as defined in claim 1, wherein the polymer composition, when molded, has a dynamic coefficient of friction against a counter material of less than about 0.2, the counter material comprising aluminum.",
    "10. A polymer composition as defined in claim 1, wherein the polymer composition further contains a copolyamide.",
    "11. A polymer composition as defined in claim 1, wherein the polymer composition further contains an acid scavenger.",
    "12. A polymer composition as defined in claim 11, wherein the acid scavenger comprises tricalcium citrate.",
    "13. A polymer composition as defined in claim 1, wherein the polymer composition further contains a nucleant, wherein the nucleant comprises a polyoxymethylene terpolymer.",
    "14. A polymer composition as defined in claim 13, wherein the one or more coloring agents comprises titanium dioxide, carbon black, a pigment, or mixtures thereof.",
    "15. A polymer composition as defined in claim 1, wherein the polyoxymethylene polymer is present in the composition in an amount of at least 85% by weight."
  ],
  "description_excerpt": "Polyacetal polymers, which are commonly referred to as polyoxymethylene polymers, have become established as exceptionally useful engineering materials in a variety of applications. For instance, because polyoxymethylene polymers have excellent mechanical properties, fatigue resistance, abrasion resistance, chemical resistance, and moldability, they are widely used in constructing polymer articles, such as articles for use in the automotive industry and the electrical industry.\n\nThe mechanical properties of polyoxymethylene molding compositions are the reason for their use in numerous applications. To improve their properties, polyoxymethylene polymers are often provided with additives to adapt the properties for a specific application, for example by using reinforcing fibers or tribological modifiers. For instance, polyoxymethylene polymers have been combined with a tribological modifier for producing polymer compositions well suited for use in tribological applications where the polymer article is in moving contact with other articles, such as metal articles, plastic articles, and the like. These tribological applications can include embodiments where the polymer composition is formed into gear wheels, pulleys, sliding elements, and the like. The addition of a tribological modifier can provide a composition with a reduced coefficient of friction and low wear.\n\nIn the past, high molecular weight polyolefins have been used to improve the wear resistance of polyoxymethylene resins. For instance, U.S. Pat. No.",
  "cpc": [
    "C08L 61/02",
    "B65G 15/32",
    "B65G 17/40",
    "B65G 2207/48",
    "C08L 2201/08",
    "C08L 2205/03",
    "C08L 2205/14",
    "C08L 59/02"
  ],
  "ipc": [
    "B65G 15/32",
    "C08L 61/02"
  ],
  "assignees": [
    "Celanese International Corp"
  ],
  "inventors": [
    "Qamer Zia",
    "Thomas Seelmann",
    "Kirsten Markgraf"
  ],
  "filing_date": "2019-12-12",
  "publication_date": "2023-05-30",
  "grant_date": "2023-05-30",
  "priority_date": "2018-12-12",
  "application_number": "US-201916711925-A",
  "family_id": "71072416",
  "cited_by_count": 0,
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    "US20180100113A1",
    "US10538717B2",
    "US20200148968A1"
  ]
}