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US-12624185-B2 - Recycling method for elastomer toughened thermoplastic polymers

US12624185B2US 12624185 B2US12624185 B2US 12624185B2US-12624185-B2

Abstract

Toughened thermoplastic polymers having elastomeric domains in thermoplastic polymer may be recycled by a method comprising dissolving the thermoplastic polymer in a solvent to form a solution, wherein the elastomer is dispersed within the solution as elastomer particulates or droplets, applying a sufficient centrifugal force to the solution to separate the elastomeric particulates or droplets from the solution to form a separated system and (c) recovering the thermoplastic polymer and elastomeric polymer by removing one or both from the separated system. The recovered elastomer and thermoplastic polymer may then be reused in the same type, similar or differing plastics avoiding degradation typically found when recycling toughened thermoplastic polymers.

Inventors

  • Abidin Balan
  • Gilbert Bouquet
  • Elroy Eekman
  • Pascal Lakeman

Assignees

  • TRINSEO EUROPE GMBH

Dates

Publication Date
20260512
Application Date
20240613
Priority Date
20201228

Claims (20)

  1. 1 . A method of recycling a toughened thermoplastic polymer having therein an elastomeric polymer that is present as dispersed elastomer domains comprising, (a) dissolving the thermoplastic polymer of the toughened thermoplastic polymer in a solvent to form a solution, forming elastomeric polymer particles or droplets from the elastomeric polymer and suspending the elastomeric polymer particles or droplets in the solution, wherein there is a density difference of at least about 2% between density of the solution and density of the elastomer particles or droplets in the solution; (b) applying a centrifugal force to the solution to separate the elastomeric polymer particles or droplets from the solution to form a separated system; and (c) recovering the thermoplastic polymer and elastomeric polymer by removing one or both from the separated system.
  2. 2 . The method of claim 1 , wherein an inorganic particulate that is insoluble in the solvent is added to the thermoplastic polymer, prior to or during the dissolving of the thermoplastic polymer.
  3. 3 . The method of claim 2 , wherein the inorganic particulate has an average size that is larger than the elastomer droplets or particulates average size.
  4. 4 . The method of claim 3 , wherein the inorganic particulate average size is at least 5 time greater than the elastomer droplets or particulates average size.
  5. 5 . The method of claim 1 , wherein the density difference is at least about 5%.
  6. 6 . The method of claim 1 , wherein the density of the solution is less than the density of the elastomeric polymer particles or droplets in the solution.
  7. 7 . The method of claim 1 , wherein the solvent has a density that is at least 10% lower than density of the thermoplastic polymer.
  8. 8 . A method of recycling a toughened thermoplastic polymer having therein an elastomeric polymer that is present as dispersed elastomeric polymer domains comprising: (a) dissolving thermoplastic polymer of the toughened thermoplastic polymer in a solvent to form a solution, forming elastomeric polymer particles or droplets from the elastomeric polymer and suspending the elastomeric polymer particles or droplets in the solution, wherein there is a density difference between density of the solution and density of the elastomeric polymer particles or droplets; (b) introducing a second solvent that swells or dissolves the elastomeric particles; (c) applying a centrifugal force to the solution to separate the elastomeric polymer particles or droplets from the solution to form a separated system; and (d) recovering the thermoplastic polymer and elastomeric polymer by removing one or both from the separated system.
  9. 9 . The method of claim 8 , wherein the second solvent increases the density of said swelled or dissolved particles.
  10. 10 . The method of claim 8 , wherein the solvent comprised of a first solvent and the second solvent has a density of at most about 0.9 g/ml.
  11. 11 . The method of claim 10 , wherein the second solvent has a density of at least 1.2 g/cc.
  12. 12 . The method of claim 10 wherein the second solvent causes the density difference to increase.
  13. 13 . The method of claim 11 , wherein the second solvent is a halohydrocarbon.
  14. 14 . The method of claim 11 , wherein greater than 0 to about 1.5 wt % of the second solvent is introduced.
  15. 15 . The method of claim 8 , wherein an inorganic particulate that is insoluble in the solvent is added to the thermoplastic polymer, prior to or during the dissolving of the thermoplastic polymer.
  16. 16 . A method of recycling a toughened thermoplastic polymer having therein an elastomeric polymer that is present as dispersed elastomeric polymer domains comprising: (a) dissolving thermoplastic polymer of the toughened thermoplastic polymer in a solvent to form a solution, forming elastomeric polymer particles or droplets from the elastomeric polymer and suspending the elastomeric polymer particles or droplets in the solution, wherein there is a density difference between density of the solution and density of the elastomeric polymer particles or droplets, wherein the solvent has a density of at most about 0.9 g/cc; (b) applying a centrifugal force to the solution to separate the elastomeric polymer particles or droplets from the solution to form a separated system,; and (c) recovering the thermoplastic polymer and elastomeric polymer by removing one or both from the separated system.
  17. 17 . The method of claim 16 , wherein the solvent is comprised of at least 2 solvents, and each solvent has a density of less than 0.9 g/cc.
  18. 18 . The method of claim 17 , wherein each of the at least 2 solvents have the density of less than 0.85 g/cc.
  19. 19 . The method of claim 16 , wherein an inorganic particulate that is insoluble in the solvent is added to the thermoplastic polymer, prior to or during the dissolving of the thermoplastic polymer.
  20. 20 . The method of claim 18 , wherein the density difference is at least 5%.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 18/269,100 filed Jun. 22, 2023, which is a National Stage 371 entry of International Application No. PCT/EP2021/085220, filed on Dec. 10, 2021, published as WO2022/144158, which claims priority from European Patent Application No. 20217398.5, filed on Dec. 28, 2020, the entire disclosures of which are hereby incorporated by reference. TECHNICAL FIELD The invention relates to recycling of thermoplastic polymers toughened with elastomer domains/particulates. In particular, the invention relates to the recycling and separation of elastomers from elastomer toughened thermoplastics such as high impact polystyrene (HIPS) and acrylonitrile butadiene styrene (ABS) polymers. BACKGROUND The recycling of thermoplastic polymers has generally been accomplished by mechanically pulverizing and incorporating into a composite or by dissolution and physical separation of insoluble materials (e.g., fillers, insoluble polymers, pigments and the like). Examples of such recycling include selective polymer dissolution in solvents and super critical fluids with or without the application of heat and removal of insoluble particles, including polymer precipitates by filtration or other means such as centrifugal decanting such as described in the following patents and patent publications: U.S. Pat. Nos. 5,233,021, 5,278,282, 8,138,232, 8,338,563, US20030191202, WO2001072900, WO2005026244 and WO2015076868. Thermoplastic polymers toughened with elastomeric domains/particles (e.g., HIPS and ABS) are widely used for their impact strength and chemical resistance in a wide array of devices such as appliances (e.g., refrigerators) and electronic devices (e.g., televisions and computers). It is known that recycling of these type of plastics is problematic, because the recycled plastics fail to achieve the same properties and introduce substantial variability even when mixed with virgin polymers such as described by Japanese Application publications: JP2003231119 and JP2004323825A. Accordingly, it would be desirable to provide an improved recycling method allowing greater use of thermoplastic polymers toughened with elastomeric domain/particles such as HIPS and ABS polymers. SUMMARY Applicants have surprisingly discovered that in certain toughened thermoplastic polymers having elastomeric domains/particles dispersed therein such as ABS or HIPS polymer may be selectively dissolved and the thermoplastic polymer may be substantially separated from the elastomer. This enables the use of the separate use of each of these in subsequent applications like the original application by blending with other components (e.g., virgin polymer or virgin rubber particles) reconstituting the characteristics of the recycled polymer. Alternatively, the recycled polymer may be used in other applications not requiring the same characteristics (e.g., applications of polystyrene “PS” or styrene-acrylonitrile “SAN” type polymers) where the recycled material may be used to enhance the properties due to the presence of a small amount of elastomer within the recycled PS or SAN. A first aspect of the invention is a method of recycling a toughened thermoplastic polymer having therein an elastomeric polymer that is present as dispersed elastomer domains comprising, (a) dissolving the thermoplastic polymer in a solvent to form a solution, wherein the elastomer is dispersed within the solution as elastomer particulates or droplets, the solution and elastomer particles or droplets each having a density such that said densities have a density difference;(b) applying a centrifugal force to the solution to separate the elastomeric particulates or droplets from the solution to form a separated system,(c) recovering the thermoplastic polymer and elastomeric polymer by removing one or both from the separated system. A second aspect of the invention is a thermoplastic polymer comprised of a virgin thermoplastic polymer blended with the recovered thermoplastic polymer of the first aspect. In this aspect, a thermoplastic polymer of virgin monomers is blended, for example, by melt blending with the recovered thermoplastic polymer (e.g., make an SAN thermoplastic polymer). A third aspect of the invention is an impact modified thermoplastic polymer comprising the recovered thermoplastic polymer of the first aspect and a virgin impact modifier dispersed therein. In this aspect it has been discovered that the recovered thermoplastic polymer may be compounded in the same fashion as virgin thermoplastic polymer to realize an impact modified thermoplastic polymer having essentially the same characteristics and properties as such polymers made with virgin thermoplastic polymer. A fourth aspect of the invention is an impact modified thermoplastic polymer comprising a thermoplastic polymer blended with the recovered elastomer of the first aspect. In an embodiment of this aspect, the elas