The Importer Asked to Have Its Own Rubber Taxed
An IRS notice going into tomorrow's Federal Register carries a petition from Zeon Chemicals to add SIS rubber, the backbone of hot melt pressure sensitive adhesives, to the Superfund list of taxable substances. The proposed rate is $2.56 a ton and 72 percent of it is benzene. The statutory deadline for deciding it expired on August 7, and the number that can actually cost you money is not the $2.56.
At 8:45 this morning, an IRS notice went onto public inspection asking the public to comment on a petition that would put a new federal excise tax on a rubber that goes into tape, labels and diaper construction adhesive.
The petitioner is the company that imports it.
Zeon Chemicals L.P. is described in the notice, in the IRS's own words, as "an importer and exporter of SIS Rubber." It is asking the Secretary to add styrene isoprene block copolymer to the list of taxable substances under section 4672(a), which is the list that decides who owes tax under section 4671 when the stuff clears customs.
"Why would the importer of a substance ask the government to start taxing it?"
The notice publishes in tomorrow's Federal Register as FR Doc 2026-20061. It runs five pages, it is signed by a senior counsel in the IRS Office of Chief Counsel, and it says on its face that it "is not a determination that the list of taxable substances is modified." Comments run to November 30 under docket IRS-2026-1032.
If you formulate hot melt pressure sensitive adhesives, or you buy them, the classification line to go look at is HTSUS 4002.99.0000, and the CAS number is 25038-32-8.
What Is Actually in the Petition
SIS is the triblock: polystyrene end blocks with an isoprene block in the middle, made by block polymerization of isoprene and styrene in cyclohexane over a catalyst. The notice calls out that the imported material carries 50 ppm residual cyclohexane and ships as pellets with about 0.2 percent silica or talc as an anti-agglomeration agent.
That last detail is worth holding onto for a minute.
The test a substance has to clear to join the list is in section 4672(a)(2)(B): taxable chemicals have to be more than 20 percent of the weight (or of the value) of the materials used to produce it. Zeon's petition puts SIS at 25.94 percent by weight, which clears it with room to spare.
Nine taxable chemicals are named: benzene, ethylene, propylene, butylene, nitric acid, methane, ammonia, chlorine and sodium hydroxide. Isoprene is in the stoichiometric equation and is not in that list, because isoprene has never been a taxable chemical under section 4661.
So the polymer's own defining monomer contributes nothing to its tax. The styrene half pays for both.
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