Superfund Tax on Chemical Substances; Request To Modify List of Taxable Substances; Notice of Filing for Styrene Isoprene Block Copolymer; x+z=482, y=2,178.51, a=1.70

Issuing agencies

Abstract

This notice of filing announces that a petition has been filed requesting that styrene isoprene block copolymer ((C<INF>8</INF>H<INF>8</INF>)<INF>x</INF>- (C<INF>5</INF>H<INF>8</INF>)<INF>y</INF>- (C<INF>8</INF>H<INF>8</INF>)<INF>z</INF>- (C<INF>33</INF>H<INF>56</INF>N<INF>4</INF>OS<INF>2</INF>)<INF>a</INF>; x+z=482, y=2,178.51, a=1.70), also known as "SIS Rubber," be added to the list of taxable substances. This notice of filing also requests comments on the petition. This notice of filing is not a determination that the list of taxable substances is modified.

Full Text

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<title>Federal Register, Volume 91 Issue 189 (Thursday, October 1, 2026)</title>
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[Federal Register Volume 91, Number 189 (Thursday, October 1, 2026)]
[Notices]
[Pages 62595-62596]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-20061]


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DEPARTMENT OF THE TREASURY

Internal Revenue Service


Superfund Tax on Chemical Substances; Request To Modify List of 
Taxable Substances; Notice of Filing for Styrene Isoprene Block 
Copolymer; x+z=482, y=2,178.51, a=1.70

AGENCY: Internal Revenue Service (IRS), Treasury.

ACTION: Notice of filing and request for comments.

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SUMMARY: This notice of filing announces that a petition has been filed 
requesting that styrene isoprene block copolymer 
((C<INF>8</INF>H<INF>8</INF>)<INF>x</INF>-
(C<INF>5</INF>H<INF>8</INF>)<INF>y</INF>-
(C<INF>8</INF>H<INF>8</INF>)<INF>z</INF>-
(C<INF>33</INF>H<INF>56</INF>N<INF>4</INF>OS<INF>2</INF>)<INF>a</INF>; 
x+z=482, y=2,178.51, a=1.70), also known as ``SIS Rubber,'' be added to 
the list of taxable substances. This notice of filing also requests 
comments on the petition. This notice of filing is not a determination 
that the list of taxable substances is modified.

DATES: Written comments and requests for a public hearing must be 
received on or before November 30, 2026.

ADDRESSES: Commenters are encouraged to submit public comments or 
requests for a public hearing relating to this petition electronically 
via the Federal eRulemaking Portal at <a href="https://www.regulations.gov">https://www.regulations.gov</a> 
(indicate public docket number IRS-2026-1032 or styrene isoprene block 
copolymer; x+z=482, y=2,178.51, a=1.70) by following the online 
instructions for submitting comments. Comments cannot be edited or 
withdrawn once submitted to the Federal eRulemaking Portal. 
Alternatively, comments and requests for a public hearing may be mailed 
to: Internal Revenue Service, Attn: CC:PA:01:PR (Notice of Filing for 
Styrene Isoprene Block Copolymer; x+z=482, y=2,178.51, a=1.70), Room 
5203, P.O. Box 7604, Ben Franklin Station, Washington, DC 20044. All 
comments received are part of the public record and subject to public 
disclosure. All comments received will be posted without change to 
<a href="https://www.regulations.gov">https://www.regulations.gov</a>, including any personal information 
provided. You should submit only information that you wish to make 
publicly available. If a public hearing is scheduled, notice of the 
time and place for the hearing will be published in the Federal 
Register.

FOR FURTHER INFORMATION CONTACT: Jacob W. Peeples at (202) 317-6855 
(not a toll-free number).

SUPPLEMENTARY INFORMATION:

Request To Add Substance to the List

    (a) Overview. A petition was filed pursuant to Rev. Proc. 2022-26 
(2022-29 I.R.B. 90), as modified by Rev. Proc. 2023-20 (2023-15 I.R.B. 
636), requesting that SIS Rubber be added to the list of taxable 
substances under section 4672(a) of the Internal Revenue Code (List). 
The petition requesting the addition of SIS Rubber to the List is based 
on weight and contains the information detailed in paragraph (b) of 
this document. The information is provided for public notice and 
comment pursuant to section 9 of Rev. Proc. 2022-26. The publication of 
petition information in this notice of filing is not a determination 
and does not constitute Treasury Department or IRS

[[Page 62596]]

confirmation of the accuracy of the information published.
    (b) Petition Content.
    (1) Substance name: Styrene isoprene block copolymer 
((C<INF>8</INF>H<INF>8</INF>)<INF>x</INF>-
(C<INF>5</INF>H<INF>8</INF>)<INF>y</INF>-
(C<INF>8</INF>H<INF>8</INF>)<INF>z</INF>-
(C<INF>33</INF>H<INF>56</INF>N<INF>4</INF>OS<INF>2</INF>)<INF>a</INF>; 
x+z=482, y=2,178.51, a=1.70).
    The substance is also known as SIS Rubber.
    (2) Petitioner: Zeon Chemicals L.P. is an importer and exporter of 
SIS Rubber.
    (3) Proposed classification numbers:
    (i) HTSUS number: 4002.99.0000.
    (ii) Schedule B number: 4002.99.0000.
    (iii) CAS number: 25038-32-8.
    (4) Petition filing dates:
    (i) Petition filing date for purposes of making a determination: 
February 8, 2026.
    (ii) Petition filing date for purposes of section 11.02 of Rev. 
Proc. 2022-26, as modified by section 3 of Rev. Proc. 2023-20: April 1, 
2023.
    (5) Description from petition: SIS Rubbers are polyisoprene/
polystyrene elastomers with block structures that are primarily used in 
adhesive formulations. SIS Rubber is a triblock copolymer that consists 
of polystyrene sequences (or blocks) at each end of an isoprene 
sequence in the center. The imported SIS Rubber has a very low amount 
of residual cyclohexane (50 ppm). SIS Rubber is sold in pellet form 
with a small amount of silica or talc (~0.2%) used as an anti-
agglomeration agent. SIS Rubber is made from benzene, ethylene, 
propylene, butylene, nitric acid, methane, ammonia, chlorine, and 
sodium hydroxide. Taxable chemicals constitute 25.94 percent by weight 
of the materials used to produce this substance.
    (6) Process identified in petition as predominant method of 
production of substance: The predominant method of producing SIS Rubber 
is through a block polymerization of isoprene and styrene in 
cyclohexane in the presence of a catalyst. Styrene monomer is produced 
by the dehydrogenation of ethylbenzene. Ethylbenzene is produced via a 
Friedel-Crafts reaction of benzene and ethylene. 2,6-di-tert-butyl-4-
(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol is produced from 4-
amino-2,6-di-tert-butyl phenol and 1,3,5-Triazine, 2-chloro-4,6-
bis(octylthio). 4-amino-2,6-di-tert-butyl phenol is produced from 4-
nitro-2,6-di-tert-butyl phenol and hydrogen. 4-nitro-2,6-di-tert-butyl 
phenol is produced from 2,6-di-tert-butyl phenol and nitric acid. 2,6-
di-tert-butyl phenol is produced from phenol and butylene. Phenol is 
produced via the Hock process (i.e., the partial oxidation of cumene 
via the Hock rearrangement). Cumene is produced via the Friedel-Crafts 
alkylation of benzene with propylene. Hydrogen is produced from steam-
methane reforming. 1,3,5-Triazine, 2-chloro-4,6-bis(octylthio) is 
produced from 1,3,5-triazine, 2,4,6-trichloro and 1-octanethiol. 1,3,5-
triazine, 2,4,6-trichloro is produced from cyanogen chloride. Cyanogen 
chloride is produced by the oxidation of sodium cyanide with chlorine. 
Sodium cyanide is produced by treating hydrogen cyanide with sodium 
hydroxide. Hydrogen cyanide is produced by Andrussow oxidation (i.e., 
the reaction of methane and ammonia in the presence of oxygen). 1-
Octanethiol is produced by from halogen substituted octane and sodium 
hydrosulfide. Halogen substituted octane is produced by reacting octane 
and a halogen (e.g., iodine). Sodium hydrosulfide is produced by the 
reaction of sodium hydroxide with hydrogen sulfide.
    (7) Stoichiometric material consumption equation, based on process 
identified as predominant method of production: (x+z+a) 
C<INF>6</INF>H<INF>6</INF> (benzene) + (x+z) C<INF>2</INF>H<INF>4</INF> 
(ethylene) + y C<INF>5</INF>H<INF>8</INF> (isoprene) + a 
C<INF>3</INF>H<INF>6</INF> (propylene) + 2a C<INF>4</INF>H<INF>8</INF> 
(butylene) + a HNO<INF>3</INF> (nitric acid) + 15/4a CH<INF>4</INF> 
(methane) + 3a NH<INF>3</INF> (ammonia) + 3a Cl<INF>2</INF> (chlorine) 
+ 5a NaOH (sodium hydroxide) + 2a C<INF>8</INF>H<INF>18</INF> (octane) 
+ 11/2a O<INF>2</INF> (oxygen) + 2a I<INF>2</INF> (iodine) + 2a 
H<INF>2</INF>S (hydrogen sulfide) [rarr] 
(C<INF>8</INF>H<INF>8</INF>)<INF>x</INF>-
(C<INF>5</INF>H<INF>8</INF>)<INF>y</INF>-
(C<INF>8</INF>H<INF>8</INF>)<INF>z</INF>-
(C<INF>33</INF>H<INF>56</INF>N<INF>4</INF>OS<INF>2</INF>)<INF>a</INF> 
(SIS Rubber) + (x+z) H<INF>2</INF> (hydrogen) + 3a HCl (hydrochloric 
acid) + 31/2a H<INF>2</INF>O (water) + 3/4a CO<INF>2</INF> (carbon 
dioxide) + a C<INF>3</INF>H<INF>6</INF>O (acetone) + 3a NaCl (sodium 
chloride) + 2a HI (hydrogen iodide) + 2a NaI (sodium iodide).
    (8) Tax rate calculated by Petitioner, based on Petitioner's 
conversion factors for taxable chemicals used in production of 
substance:
    (i) Tax rate: $2.56 per ton.
    (ii) Conversion factors: 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.
    (9) Public docket number: IRS-2026-1032.

Michael H. Beker,
Senior Counsel (Energy, Credits, and Excise Tax), IRS Office of Chief 
Counsel.
[FR Doc. 2026-20061 Filed 9-30-26; 8:45 am]
BILLING CODE 4831-GV-P


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