IRS Seeks Comments on Adding SIS Rubber to Superfund Tax List
The petition filed by Zeon Chemicals L.P. asks the IRS to treat styrene isoprene block copolymer as a taxable substance, with comments due by Nov. 30, 2026.
The Internal Revenue Service issued a notice of filing (FR Doc 2026-20061) announcing a petition to add styrene isoprene block copolymer (SIS Rubber) to the list of taxable substances under section 4672(a) of the Internal Revenue Code. The public docket number is IRS-2026-1032, and written comments or requests for a hearing must be received on or before November 30, 2026.
The petition, filed by Zeon Chemicals L.P., identifies the substance as ((C8H8)x-(C5H8)y-(C8H8)z-(C33H56N4OS2)a) with the parameters x+z=482, y=2,178.51, a=1.70. Classification numbers proposed are HTSUS 4002.99.0000, Schedule B 4002.99.0000, and CAS 25038-32-8. The petition lists a filing date of February 8, 2026 for determination purposes and a filing date of April 1, 2023 for Rev. Proc. 2022-26 compliance.
SIS Rubber is described as a triblock copolymer used primarily in adhesive formulations, sold in pellet form with about 0.2% silica or talc as an anti-agglomeration agent. Taxable chemicals account for 25.94 percent by weight of the inputs. The petitioner calculated a tax rate of $2.56 per ton, applying conversion factors of 0.19 for benzene, 0.07 for ethylene, 0.0004 for propylene, 0.001 for butylene, 0.0005 for nitric acid, 0.0005 for methane, 0.0004 for ammonia, 0.002 for chlorine, and 0.002 for sodium hydroxide.
Comments are to be submitted electronically via regulations.gov referencing docket IRS-2026-1032 or mailed to the IRS office at Room 5203, P.O. Box 7604, Ben Franklin Station, Washington, DC 20044. Jacob W. Peeples (202) 317-6855 is the designated contact, and Michael H. Beker, Senior Counsel, signed the notice.
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