Phthalic Anhydride

Stepan is a mainstay of the phthalic anhydride (PA) industry with a history of over 50 years as a leading PA producer. We provide the most efficient conversion of orthoxylene to molten PA with the newest reactor in the North American market.

PA is manufactured at Stepan's Millsdale site, located in Elwood, Illinois and in compliance to ISO 9001:2015 standards. We supply the North American merchant market, as well as use PA to manufacture our extensive STEPANOL® polyester polyol product line.

Stepan is committed to service excellence, as demonstrated in our safe, secure and reliable supply of molten PA. We are also highly dedicated to our sustainability program and that includes using the steam created from making PA as the main heat source for our Millsdale site.

If you would like more information or have a question about Stepan PA, please contact

End Use Markets

  • Polyester resins
  • Plasticizers
  • Alkyd resin and coatings
  • Polyester polyols
  • Pigments and dyes
  • Engineered plastics
  • Flame retardants

Common Uses and Applications

  • Boat hulls
  • Shower stalls
  • Flexible tubing and containers in the medical industry
  • Wire coating and insulation
  • Garden hoses
  • Commercial and residential paint coatings
  • Vinyl wallpaper

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