US 5519092

I'll search for litigation/assignment context on this specific patent number, then summarize from the authoritative full text provided.

US Patent 5,519,092 — Summary

Note on sourcing: The bibliographic and text details below come from the authoritative full patent text supplied (Google Patents, https://patents.google.com/patent/[US5519092](/patent/US5519092)/en). My supplementary searches confirmed the same record (Justia, EveryPatent) but returned no evidence of any CAFC 2026 docket, district-court suit, or IPR involving this specific patent number. I treat that as "no authoritative information found" rather than "no litigation exists."

Bibliographic data

Family members (same priority): EP0736548A2/A3, JPH08283340A, KR960037705A, CN1140719A, BR9601278A, AR001516A1, HUP9600899A2/A3, MY132244A, SG77562A1, GB9507305D0.

Abstract (as issued)

A process for making substituted acylating agents by reacting an enophile bearing at least one carboxyl group with a polyolefin selected from polypropylene and poly(iso)butene, in which the reaction mixture also contains either (a) an olefin of formula (R)(R¹)C=C(R²)(R³) where at least one of R–R³ is hydrogen and at least one of the others is an alkyl group of at least 3 carbons, or where R²/R³ together with R¹ form a cycloaliphatic ring such that the olefin has at least 5 carbons in a linear hydrocarbyl chain, or (b) an adduct of that olefin with the reactant enophile. The product contains substantially less resin.

Independent claim 1 — plain language

Claim 1 (the only independent claim) covers a process with three elements:

1. What is made and how: substituted acylating agents (e.g., maleinised polyolefins such as poly(iso)butenyl succinic anhydride, PIBSA), produced by thermal reaction (no free-radical initiator needed).
2. The two reactants: (i) an enophile containing at least one carboxyl group that is capable of forming resins under the reaction conditions (e.g., maleic anhydride or maleic acid), and (ii) a polyolefin selected from polypropylene and poly(iso)butene.
3. The mandatory additive: added to the reaction mixture is "at least" either:
   • (a) one olefin of formula (I): (R)(R¹)C=C(R²)(R³), wherein at least one of R, R¹, R², R³ is hydrogen, and at least one of the remaining three is either (i) an alkyl group having at least 3 carbon atoms, or (ii) at least one of R² and R³ together with R¹ forms a cycloaliphatic ring, such that the olefin has at least 5 carbon atoms in a linear hydrocarbyl chain; or
   • (b) one adduct of that olefin with the reactant enophile (e.g., an alkenyl succinic anhydride).

In plain terms: it is a one-step thermal succination (maleinisation) process in which a relatively long-chain or ring-containing olefin — or its pre-formed adduct with the enophile — is deliberately co-fed to suppress "tar"/resin formation. The word "at least" before (a)/(b) means the claim tolerates additional, unnamed components in the mixture; it does not require both (a) and (b).

The dependent claims (2–10), briefly

• 2: Enophile is a carboxylic acid or anhydride with an active unsaturated linkage capable of enophilic addition.
• 3: Enophile is maleic acid or maleic anhydride.
• 4: Polyolefin is a poly(iso)butene with >20% terminal-unsaturation chains and Mn ≥ 500.
• 5: The formula (I) olefin(s) have 5–30 carbon atoms.
• 6: Additive amount is 0.1–10% w/w of total polyolefin.
• 7: Additive may be added before or during the reaction.
• 8: Reaction temperature 100–240 °C.
• 9: Reaction run in substantial absence of free radicals/free-radical precursors (e.g., oxygen/air).
• 10: Product is a polypropenyl succinic anhydride or poly(iso)butenyl succinic anhydride.

Substance of the disclosure

• The problem: thermal maleinisation of poly(iso)butene tends to resinify maleic anhydride, giving fines/turbidity, reactor fouling, and a discrepancy between real and apparent succinylation ratios. The chlorination route avoids this but introduces chlorine, which is environmentally undesirable and can yield chlorinated by-products in engine service.
• The solution: co-feed a linear (≥C5 chain) or appropriately substituted olefin, or its enophile adduct, at typically 0.1–5% w/w of polyolefin. Olefins from the Shell "SHOP" process are cited as a typical mixture.
• Comparative Tests CT1–CT3 (no additive) show ~10.8–11.9 g tar per 100 g PIB at superatmospheric pressure; inventive Examples 1–6 (octadecene, dodecene, or dodecenyl succinic anhydride "DD-SA") show ~2.25–8.1 g. At atmospheric pressure, CT7/CT8 show ~3.4 and ~1.08 g tar/100 g vs. Examples 7–8 at ~1.15 and ~0.25 g.
• Notably adverse: short-chain adducts — isobutenyl succinic anhydride (CT4) and allyl succinic anhydride (CT5, CT6, CT9) — are shown to be neutral or detrimental (19.3–22.7 g tar per 100 g PIB), which is the basis for the ">3 carbon atoms / ≥5 carbon linear chain" limitation.
• The disclosure also notes that unreacted maleic anhydride recovery is improved, and that any alkenyl succinic anhydride by-product may contribute slightly to detergency of downstream succinimides.

Uncertainty / caveats

• Litigation: I found no authoritative record of this patent being litigated at the CAFC (or PTAB/district court) in 2026. Given the patent lapsed in 2004 for non-payment of maintenance fees, an active 2026 assertion would be surprising; I cannot affirmatively rule out a non-assertion-related appearance (e.g., cited as prior art) without direct docket access.
• Related family member US 5,644,001 ("Resin-free succinimides…", BP Chemicals) and cited art US 5,134,978 / US 5,071,919 (Ethyl Petroleum Additives) and US 5,286,799 / US 5,319,030 (Chevron) appear in the citation records, but I have not verified their current status or any litigation involving them.
• The OCR of the supplied text contains obvious typos ("herein from branched chains," "titans," "miniraise," "enopohilc"); I have interpreted these as transcription artifacts, not technical terms.

I'll search litigation-focused sources for this specific patent number.

Initial results were mostly false positives (e.g., a "'092 Patent" that is actually US 10,385,092, and reexam litigation reports for other patents). Let me search more specifically.

Still no direct hits. Let me query dedicated litigation databases and the related family patents.

Litigation search — US Patent 5,519,092

Bottom line

I found no litigation of any kind involving US Patent 5,519,092. No district-court infringement action, no declaratory-judgment action, no CAFC appeal, no PTAB proceeding (IPR/PGR/CBM), and no ITC § 337 investigation appears in any of the sources I searched. I am reporting this as "no litigation known," not as an affirmative proof of non-existence.

What I searched and what came back

Two additional searches (Docket Alarm / Unified Patents-style docket queries, and a search on the related family member US 5,644,001) could not be completed — my search budget was exhausted mid-query. Those channels remain unverified, and I flag that as a gap.

Near-miss results that are NOT this patent

To prevent misattribution, these BP Chemicals cases surfaced in searches but involve different patents, so none belongs in a '092 litigation list:

• Hoechst Celanese Corp. v. BP Chemicals Ltd., 65 F.3d 188 / 78 F.3d 1575 (Fed. Cir. 1995) — asserted Celanese's '806 patent (resin swelling); BP's Purolite® resin accused. Not '092.
• BP Chemicals Ltd. v. Union Carbide Corp., 91-1256 (Fed. Cir. 1993) — declaratory-judgment action over Carbide's '399 patent (LLDPE); dismissed for lack of an actual controversy. Not '092.
• Lubrizol Corp. v. Esso Petroleum Co. [1998] R.P.C. 727 (Eng. C.A.) — UK action over substituted acylating agent / PIBSA claim construction. Adjacent subject matter, but a different patent and a different jurisdiction.

I found nothing tying '092 itself to any of these.

Corroborating but non-dispositive indications

• The Google Patents record supplied as the authoritative text lists "Cited By (8)" and "Citations (5)" — i.e., patent-document citations only. If '092 had been asserted in a US suit, litigation databases typically surface at least a docket reference; none appeared.
• The patent's legal-status chain shows only prosecution/assignment/maintenance events (assignment 1995-09-25; certificate of correction 1996-10-08; fee payments 1998/1999) and then lapse for non-payment of maintenance fees effective 2004-05-21, with a final "patent expired due to nonpayment of maintenance fees under 37 CFR 1.362" entry. A patent that lapsed in 2004 would be an unusual target for a later assertion.
• The US family tree shows only one US family application, US 08/462,008 (no continuations, no reissues, no reexaminations), so there is no reissue/reexam track that might generate separate proceedings.

Caveats and confidence

• Confidence that no litigation exists: moderate, not high. My searches were general web searches, not a direct PACER, Docket Navigator, Lexis CourtLink, or Unified Patents portal query, and two intended database-specific searches were cut off. Free/aggregated sources can miss older, sealed, or thinly reported cases.
• Time window matters: the patent issued 1996-05-21 and lapsed 2004-05-21. Any US enforcement would necessarily fall in roughly that eight-year window. I found no such case.
• Foreign proceedings are a separate question. The family includes EP0736548, JP H08283340, KR960037705, CN1140719, BR9601278, AR001516, HU P9600899, MY132244, and SG77562. The Lubrizol v. Esso UK decision noted above shows this technical field was litigated in Europe, but I found no evidence tying any such action to this family. An EPO opposition search was not run.
• I did not verify current status or litigation history of the art cited against '092 (US 5,137,978; US 5,071,919; US 5,286,799; US 5,319,030; US 5,454,964) or the later-resolving family member US 5,644,001.

Recommended next steps to close the gap

1. Query Unified Patents (portal.unifiedpatents.com/litigation/caselist), Docket Navigator, or Lexis CourtLink directly on 5519092 and on BP Chemicals as assignee, restricted to 1996–2004.
2. Run a PACER party search for "BP Chemicals" in D. Del., S.D.N.Y., D.N.J., and E.D. Pa. for that window.
3. Check EPO Register / opposition file for EP0736548 and JPO for JP H08283340.

If you can point me at a specific docket source or a party name you suspect, I can re-run narrowly on that.

I'll verify the structured "no proceedings" signal against the public record before writing.

Proceedings overview

There are zero AIA trial proceedings on file against US 5,519,092 — no IPRs, no PGRs, no CBMs, no derivation proceedings — so there is no petitioner to estop, no FWD to quote, and no claim of this patent has been canceled or sustained by the Board. The bottom-line defensive posture is not "the patent has survived and is hardened"; it is "the patent is expired and unenforceable, so there is nothing for an AIA trial to do" — any demand letter asserting US 5,519,092 in 2026 should be treated as a red flag against the sender, not a litigation threat to be answered with an IPR.

I reached this conclusion from the canonical structured block ("The USPTO ODP API returns no AIA trial proceedings for this patent as of the most recent ingest") and confirmed it with independent web searching: queries on the patent number in combination with "IPR," "PTAB," "proceeding," and "petition" returned no PTAB docket, no petition paper, and no Board decision. Per the operating rules, I treat this as "no proceedings found," not as an affirmative proof of nonexistence — but the structural analysis below makes the negative result highly credible rather than merely unverified.

There are no proceedings to describe — here is why that is structural, not accidental

The usual "most-impactful first" ordering is vacuous here, so I am substituting the reason the list is empty. Four independent gates each individually foreclose an AIA trial on this patent:

Practical consequence: the AIA statute's three petition types (IPR, PGR, CBM) did not exist during any moment when this patent was both alive and economically worth challenging. That is a complete, mechanism-level explanation for the zero count — and it is a stronger signal than a mere "we didn't find anything."

Cross-check on the "no proceedings" negative

• Family-wide: the co-pending family member records in the structured data (EP0736548A3, JPH08283340A, KR960037705A, CN1140719A, SG77562A1, MY132244A, AR001516A1, BR9601278A, HUP9600899A2/A3) show regional prosecution events only. No AIA-trial-style opposition mechanism applies at the USPTO to any of them, and no Board proceeding is listed for any family member.
• Cited-by set: the Board-facing citation trail runs to US5644001 (BP Chemicals, "Resin-free succinimides") and the Chevron US5286799 / US5319030 family, plus EP0602863B1 — these are cited references, not proceedings against the '092 patent. Do not mistake an entry in a "Cited By" table for a PTAB filing.
• Not to be confused with: search noise surfaced similar-looking but unrelated numbers — 5,519,882 (in a prior-art table), 5,495,291 (the Harmonic v. Avid patent, IPR2013-00252/2015-1072), and 5,644,001 (BP family member). None of these is US 5,519,092. Per the operating rules I am not auto-correcting or conflating them.

(No per-proceeding write-ups follow, because there is no proceeding number, petitioner, panel, institution decision, FWD, settlement, or appeal to report. I will not synthesize placeholder entries.)

Strategic summary

Claim status: all 10 claims are UNTESTED at the PTAB — and now expired. No claim of US 5,519,092 has been canceled, narrowed, or confirmed by the Board. Claim 1 (the sole independent claim, covering a thermal maleinisation process with a ≥C5-chain or cycloaliphatic-olefin/adduct anti-resin additive) and dependent claims 2–10 all stand exactly as issued, subject to the 1996-10-08 certificate of correction noted in the record. Because the patent lapsed on 2004-05-21, "surviving claims" is a formal rather than practical status: the claims exist on paper but cannot be enforced for any act occurring on or after 2004-05-21, and post-expiration 35 U.S.C. § 286 recovery is now time-barred. If a demand letter cites claims 1–10 of the '092 patent as a live basis for royalties on current PIBSA production (e.g., thermal maleinisation of NAPVIS®/PARAPOL®/ULTRAVIS® poly(iso)butene with maleic anhydride), the correct answer is not a prior-art defense — it is that the asserted right expired two decades ago.

Estoppel landscape: empty, and it will stay empty. 35 U.S.C. § 315(e)(2) estopsel binds only petitioners, real parties in interest, and privies who lost an IPR. There has been no petitioner, so no entity is estopped from anything, and no prior-art ground is "consumed." Conversely, there is also no FWD to borrow for a defendant's benefit. The practical asymmetry is that a defendant gains nothing from the Board here because it does not need the Board: the complete invalidity/expiration defense is available in any forum, from the face of the patent and the fee record. Note also that § 315(b)'s one-year bar, § 315(a)'s civil-action bar, and § 325(a)'s PGR equivalents are all inoperative for want of any proceeding to anchor them.

Pattern signals: none. There is no repeat petitioner, no patent-owner PTAB appeal practice, and no defensive aggregator (no Unified Patents, RPX, or similar) in the chain — the structured NPE/aggregator indicators are silent, and the assignee of record is the operating chemical company BP Chemicals Limited, not a monetization vehicle. The 1995-09-25 assignment (reel/frame 007653/0366, Blackborow → BP Chemicals Limited, effective 1995-06-01) is the only ownership event on file. The 1996-10-08 certificate of correction is the sole post-issuance Office event other than the fee lapse. EP family member EP0736548A3 was "Ceased," consistent with a family the owner abandoned selectively rather than policed.

One cross-reference caveat for the file: the previously generated Patent Summary and bibliography are consistent with everything I verified (priority 1995-04-07, issue 1996-05-21, 10 claims with claims 2–10 depending on claim 1, lapse 2004-05-21). I found no contradiction between the prior sections and the record. The prior summary's caveat — that it could not affirmatively rule out a non-assertion appearance — is the right posture, and I adopt it here.

Recommended next steps

1. If a demand letter asserts US 5,519,092: do not file an IPR. Confirm the lapse against the primary sources and put the sender on notice of the 2004-05-21 maintenance-fee lapse and the 2018-01-25 STCH expiration event, both visible in the Legal Events table at https://patents.google.com/patent/US5519092/en. A petition to cancel already-expired claims would spend money to solve a problem that expiration already solved, and the claim-by-claim records a petitioner would need to build do not exist to borrow.

2. Verify the negative yourself before relying on it (the record could change, and my searches are a supplement, not the canonical source):

   • USPTO PTAB E2E / Patent Trial and Appeal Board End-to-End, search by patent number 5519092 — https://ptacts.uspto.gov/ptacts/
   • USPTO PTAB Decisions — https://www.uspto.gov/patents/ptab/decisions
   • Open Data Portal trial-proceedings endpoint (the ingest behind the structured block), and USPTO PatentCenter (https://patentcenter.uspto.gov/) for the application 08/462,008 maintenance-fee and STCH history.
   • CourtListener / Free Law Project and the Federal Circuit docket for any appeal naming the '092 patent (https://www.courtlistener.com/). My searches surfaced no CAFC appeal, which is unsurprising given the absence of any Board decision to appeal.

3. If the real target is a different number, flag it before doing any PTAB work. The risk of confusion is real and I saw it in the search results: 5,519,882, 5,495,291, 5,644,001, and 5,134,978 / 5,071,919 all surfaced as near-miss citations. Re-confirm the exact number against the asserting party's letter — the operating rules require literal treatment of identifiers, and a one-digit substitution here would send you to an entirely different PTAB history (e.g., Harmonic v. Avid on the '291 patent does have a substantial IPR and Federal Circuit record).

4. If the patent resurfaces in a chain of title or an IPR is somehow filed: the trigger points to watch are (a) any ex parte reexamination request (the only Office-side validity mechanism available during the patent's enforceable life, and I found no evidence one was filed) and (b) any revival petition for the lapsed maintenance fee. Absent a revival, the expiration is final; absent a reexamination, "no AIA trial activity" remains the accurate and durable answer.

Bottom line for a defendant: the absence of PTAB activity is not a gap in the record — it is the expected consequence of a patent that issued in 1996, was abandoned in 2004, and was never economically worth challenging in the twelve years that the AIA trial mechanisms have existed. There is no FWD to link to, no claim-level disposition to quote, and no § 315(e)(2) estoppel to navigate. The defense is expiration, and it does not require the Board.

I'll verify the assignment chain against indexed sources before finalizing.

Let me check whether any indexed assignment database shows post-issuance records for this patent.

US 5,519,092 — Assignment / Ownership Reconstruction

Source note (read first): The USPTO Assignment Center (https://assignmentcenter.uspto.gov/) and its legacy mirror (https://assignment.uspto.gov/patent/index.html) are JavaScript applications that do not expose their record set to plain retrieval, so I could not pull the underlying reel/frame images directly. The findings below rest on (i) the legal-events and assignment metadata in the authoritative full patent text supplied, and (ii) supplementary searches of indexed assignment databases. Where a field (notably the recording correspondent) was not recoverable, I say so rather than guess. Verify at: https://assignment.uspto.gov/patent/index.html?patentNumber=[5519092](/patent/5519092) (search by patent number).

Inventors

• The patent names exactly one inventor. There is no multi-inventor team here, so the classic "all inventors departed within 12 months" tell cannot arise.
• Pattern assessment: the inventor-to-employer assignment was executed 1995-06-01 — four days before the 1995-06-05 US filing date — the textbook employee pre-filing assignment to the operating company. Nothing in the record suggests the inventor left, assigned to a third party, or that rights were brokered. No unusual departure pattern observed.
• Caveat: I have not independently verified Blackborow's employment contract with BP Chemicals; the inference comes from the assignee identity and near-filing execution date, which is strong but not documentary proof of employment.

Original assignee

• Entity on the issued patent: BP Chemicals Limited (England), principal office Britannic House, 1 Finsbury Circus, London EC2M 7BA.
• Line of business: UK petrochemicals — the olefins/derivatives and polyolefins businesses of the BP group at the time. The patent's own description markets BP's HYVIS®, NAPVIZ® and ULTRAVIS® polyisobutene products (see the specification), and the comparative tests use Parapol® (Exxon), Hyvis® and Ultravis® polybutenes — i.e., the assignee's own commercial product families are the reactants.
• Product embodying the claims: Yes, in substance. The claimed process makes PIBSA (polyisobutenyl succinic anhydride), a detergent/dispersant precursor for lubricant and fuel succinimides. BP Chemicals was a commercial supplier of both the PIB feedstock (HYVIS/NAPVIS/ULTRAVIS) and PIBSA-type intermediates. So this is an operating-company process patent, not a paper asset.
• Current status: BP Chemicals Limited was never dissolved and did not go bankrupt. Its petrochemicals assets were spun into Innovene (2005), which INEOS acquired in a $9 bn cash deal completed December 2005; BP later sold the remaining aromatics/acetyls business to INEOS in 2020. Separately, BP Chemicals did record bulk patent assignments to O&D Trading Limited (later renamed Innovene Europe Limited, then INEOS Europe Limited) around 2005 — e.g., the record described in the Pakistan IPO Gazette for Patent No. 138748, deed dated 1 April 2005.
• Important negative: That Innovene/INEOS conveyor belt appears to have bypassed US 5,519,092 — its maintenance fee lapsed 2004-05-21, before the Innovene spin-off and INEOS sale. A lapsed US patent is not a transferable asset, consistent with the absence of any post-2004 assignment of record.

Assignment timeline

There is exactly one recorded assignment in this chain. No post-issuance transfers, security interests, mergers, name changes, or releases are recorded.

• 1995-06-01 (executed) / recorded 1995-09-25 — Reel 007653 / Frame 0366
  • Conveyance: Assignment (ASSIGNMENT OF ASSIGNORS INTEREST)
  • Assignor: Blackborow, John Richard (sole inventor)
  • Assignee: BP Chemicals Limited (England)
  • Correspondent: ⚠️ Not recoverable from the supplied record. The legal-events entry does not carry the recording correspondent's name/firm, and the Assignment Center record could not be pulled. I decline to name a correspondent rather than fabricate one. (For context only: unrelated BP trademark/assignment filings in the same era show correspondents such as "Donald C. ___" and the New York firm "Weiss, Dawid, Fross et al."; I have no evidence either acted on reel 007653/0366, so this is not a finding.)
  • Context: Initial inventor→employer assignment of the entire right, title and interest; standard operating-company acquisition of an employee invention, executed days before the US filing.

No further records. The Assignment Center shows no downstream links, which — combined with the 1995 sole assignment — means BP Chemicals Limited (and its successors in the Innovene/INEOS chain, if any residual interest existed) remained the record owner for the patent's enforceable life. The rights then expired for non-payment of the 2004 maintenance fee (LAPS event 2004-05-21; FP "Lapsed due to failure to pay maintenance fee" effective 2004-05-21; STCH entry 2018-01-25 confirming expiration under 37 CFR 1.362). A certificate of correction (CC) issued 1996-10-08 — a bibliographic fix, not an ownership event.

Because there is a recorded assignment (the original), I proceed with the remaining sections per the task instructions rather than stopping.

Timeline diagram

timeline
    title Ownership of US 5519092
    1995 : Inventor assigns rights to BP Chemicals Ltd
    1996 : Patent issues 21 May
         : Certificate of correction issued
    2004 : Maintenance fee lapses 21 May
    2018 : USPTO records patent as expired

NPE / troll-pattern signals

Net: The record is the cleanest possible negative result — a single operating-company assignment, no downstream links, and a self-inflicted lapse. It is the opposite of a troll pattern.

Verdict

Insufficient data — applying the rubric's explicit definition ("no records, or only the original assignment"). Only one assignment is of record: inventor Blackborow → BP Chemicals Limited, executed 1995-06-01, recorded 1995-09-25 at Reel 007653 / Frame 0366.

Substantively, this is not an NPE case: all eight troll-pattern signals are not present, the assignee was a genuine operating petrochemical producer that made the reactants named in the specification, and the patent simply lapsed on 2004-05-21 for non-payment of the maintenance fee (LAPS/FP events) before any BP portfolio divestiture could have carried it into the Innovene/INEOS chain. There is no evidence — in Google Patents legal events, indexed assignment databases, or litigation directories — of any security interest, shell transfer, aggregator acquisition, or assertion of this patent. Verification: https://assignment.uspto.gov/patent/index.html?patentNumber=5519092.

I'll search the USPTO and related databases for US 5,519,092 and each of its cited references.

Now let me search the remaining cited references.

Prior-Art Analysis — US 5,519,092 ("Substituted acylating agents")

Analyst's verification note: I searched for the specific number 5,519,092. The USPTO-mirroring records (Google Patents, https://patents.google.com/patent/US5519092/en; Justia, https://patents.justia.com/patent/5519092) confirm it is a real, granted US patent (filed 1995-06-05, issued 1996-05-21, BP Chemicals Ltd). I could not directly open the USPTO Patent Public Search (PatFT/PatentCenter) interface through the tools available, so bibliographic confirmations rely on the authoritative full text already supplied plus the Google Patents/Justia records, which reproduce the USPTO front page. I did not find a matching number that could be confused with 5,519,092.

Important framing correction: US 5,519,092 was filed 1995-06-05 with a GB priority of 1995-04-07, i.e. pre-AIA. Therefore 35 U.S.C. §§ 102(a), (b), (e) as they existed before the AIA (i.e., pre-2013) govern. I use those standards below, not the post-AIA 102(a)(1)/(a)(2) scheme.

The purpose of all cited art here is essentially the same: it is background/examiner art in the "chlorine-free thermal maleinisation of poly(iso)butene" field. As shown below, no cited reference discloses the single element that gives claim 1 its novelty — the mandatory co-fed additive (a formula-(I) olefin or its enophile adduct) — so none anticipates any claim. They are § 103 (obviousness) references, not § 102 references.

Which documents count as "citations" of 5,519,092

The record contains two distinct lists, and they are not interchangeable:

• Front-page "[56] Patent Citations (5)" — cited by the examiner during prosecution of 5,519,092.
• "Family Cites Families (6)" — art cited by examiners against foreign family members sharing the GB 9507305 priority (EP 0736548, JP H08283340, etc.), not necessarily considered against the US case.

A. Front-page examiner citations (the 5 documents)

B. "Family Cites Families (6)" — art cited against family members

These were considered against EP 0736548 / JP H08283340 / KR 960037705 etc., so their US-law relevance to 5,519,092 is indirect.

C. Consolidated § 102 verdict

No cited reference anticipates any of claims 1–10.

The reason is structural, not incidental. Claim 1 is the sole independent claim, and it is a process claim that positively requires adding "at least … (a) one olefin of formula (I) [R,R¹,R²,R³ with ≥3-carbon alkyl or ≥5-carbon linear hydrocarbyl chain / cycloaliphatic ring], or (b) one adduct of said olefin with the reactant enophile." Every one of the cited documents describes a maleinisation process in which the only olefin present is the polyolefin reactant itself (or, in the Chevron cases, free-radical initiation). None discloses a separate, deliberately co-fed long-chain/ring olefin or its preformed enophile adduct as a resin-suppressing additive. Under § 102, a reference must disclose every element arranged as in the claim — so the additive gap is fatal to anticipation for all claims 1–10.

Additional element-level mismatches worth recording:

• Claim 9 (substantial absence of free radicals): US 5,286,799 and US 5,319,030 (teach the opposite — a free-radical initiator is essential). These references therefore not only fail to anticipate but affirmatively teach away from claim 9's condition.
• Claim 4 (>20 % terminal unsaturation, Mn ≥500): US 5,137,978 / US 5,071,919 / US 5,454,964 do disclose PIB with high vinylidene content and Mn in the hundreds-to-thousands; US 5,286,799 / US 5,319,030 disclose PIB Mn 500–5000 but with <10 % alkylvinylidene. None of this matters for anticipation because claim 4 depends from claim 1.
• Claim 8 (100–240 °C): US 5,286,799, US 5,319,030, US 5,454,964 all disclose overlapping temperature ranges — again irrelevant to anticipation absent the claim-1 additive.

D. The references' real role: § 103, not § 102

The five front-page citations, and US 5,071,919 within the family list, are best understood as obviousness/background art showing that (i) chlorine-free thermal maleinisation of PIB to PIBSA was known; (ii) the "tarry-residue / fouling / yield-loss" problem was well recognized (US 5,137,978 and US 5,454,964 both frame it explicitly); and (iii) the field was actively seeking tar mitigation. They supply the motivation and state of the art but not the claimed additive. One supplementary document surfaced in my search but which is not on either citation list — EP-A-0014288 (mentioned in the EP 0623631 B1 discussion, describing an ene reaction of a C4–C10 unsaturated dicarboxylic material with a C30–C700 olefin "in the presence of at least a sediment-reducing amount of an oil-soluble organic acid") — is topical to the tar/sediment problem and worth checking separately if a full § 103 attack is being built.

E. Anomalies, caveats and confidence

• US 542,757 A ("Chimney-cap," 1895) is reported literally per the no-auto-correction rule but is not credible prior art and should be treated as a citation-table artifact for US 5,519,092. Flagging it rather than "fixing" it.
• US 5,454,964 A appears in the citation list although it issued 1995-10-03 — after the 5,519,092 filing (1995-06-05). Its usefulness as prior art therefore rests on its 1993-05-04 filing date (§ 102(e)) and its earlier GB publication, not on its US issue date. I have flagged this rather than assuming it is § 102(b) art.
• Logical inconsistencies in the source text: The authoritative patent text I was given lists US 5,454,964 both as a "Patent Citation" of 5,519,092 and the 5,519,092 record lists it among "Similar Documents"; both patents share inventor Blackborow and assignee BP Chemicals. I treat these as co-pending/sibling BP cases, which is consistent with the examiner citing them for field context.
• Descriptions of items 6–11 rely on Google Patents citation titles plus the brief full-text snippets returned by search, not on a full read of each reference's claims; where I write "no formula-(I) additive disclosed," that is my assessment from the available text and should be confirmed against the complete specifications if a formal § 102/§ 103 opinion is required.
• Dates for items 1–5 and 10–11 were taken from the authoritative 5,519,092 record; for items 1–3 I additionally verified the dates against the reference patent PDFs/snippets (Google Patents, patentimages). One date-sensitive conclusion — that US 5,319,030 misses the § 102(b) one-year bar by about two days — depends on the exact critical date and should be double-checked (using the GB priority of 1995-04-07 pushes the bar to 1994-04-07, which would make US 5,319,030 § 102(b) art after all; using the US filing of 1995-06-05, it is not). I flag this rather than assert it as settled.

I'll ground this analysis in the actual disclosures of the cited art. Let me pull the key references.

Now the Chevron references and the BP Chemicals family member.

Let me pull the two remaining cited references and the closest family-adjacent art.

I have enough to run the §103 analysis against the references actually listed on the US 5,519,092 record. Below, all identifiers are reproduced literally as they appear on the page, and I flag anything I could not verify from primary text.

Obviousness analysis — US 5,519,092 under 35 U.S.C. § 103

1. The claim to be attacked (scope)

Claim 1 is the only independent claim. Reduced to elements:

Two scope observations that matter for §103:

• Formula (I) has no upper bound on the "alkyl" group. A vinylidene- or trisubstituted-terminated polyisobutene chain is itself an "alkyl group having at least 3 carbon atoms." Claim 1 therefore reaches a genus much broader than claim 5's C5–C30 range; the applicant's actual data (octadecene, dodecene, dodecenyl succinic anhydride) sit only in the narrow C12–C18 window.
• Element D requires the olefin/adduct to be added, and the patent distinguishes it from the polyolefin reactant in element C. This is the only real point of novelty, and it is exactly the point on which the cited art is weakest.

Level of ordinary skill (PHOSITA): a chemist or chemical engineer with an ordinary degree and ~2–5 years of experience in lubricant/fuel-additive chemistry, specifically in the "ene"/maleinisation reaction of polyolefins with maleic anhydride to make PIBSA intermediates. This is a mature, crowded, and highly documented art (the '092 specification itself concedes "It is well known in the art to make poly(iso)butenyl succinic anhydrides…").

2. The prior art on the face of this record, and its § 102 status

The '092 record lists Citations (5) on the U.S. face, Family Cites Families (6), plus the "Similar Documents" table. The U.S. filing date is 1995-06-05, so the pre-AIA § 102(b) critical date is 1994-06-05 (measured from the U.S. filing date, per In re Hilmer; foreign priority GB 9507305 of 1995-04-07 cannot antedate § 102(b) art).

Also useful as secondary art (though it is not on the '092 face, it is quoted in the family background of the BP '964 line, at the EP 0623631 A2 document):

• EP-A-0014288 — described in that background as an ene reaction of a C4–C10 unsaturated dicarboxylic material with an olefin of 30–700 carbons "carried out in the presence of at least a sediment-reducing amount of an oil-soluble organic acid."
• EP-A-0082601 — polyalkenyl succinic anhydrides made by incremental maleic anhydride addition maintaining a single homogeneous phase.

Both are "add an auxiliary material / control the feed to manage sediment" teachings in the very same ene reaction.

3. Combination A — the primary § 103 case against claim 1

US 5,071,919 / US 5,137,978 (Ethyl) in view of US 5,286,799 (Chevron).

What Ethyl supplies (elements A, B, C): the reaction of "polyisobutenes" with an acidic reactant of formula R–CO–CH=CH–CO–R′ where R/R′ are OH, O-lower alkyl, halogen, or together a single oxygen (maleic acid, fumaric acid, maleic anhydride, itaconic/citraconic analogues), by a thermal route with no chlorine and no free-radical initiator, under superatmospheric pressure, at 220–265 °C, with unreacted maleic anhydride recovered for recycle (https://www.freepatentsonline.com/[5071919](/patent/5071919).html; https://patents.google.com/patent/[US5071919A](/patent/US5071919A)/en). It is therefore a direct, enabling disclosure of A, B and C, including the poly(iso)butene species, and it covers claim 8's 100–240 °C window by overlap.

Why Ethyl also supplies the motivation: the same document states that "thermal stabilizers or other additive materials to reduce tar formation are not required," and immediately identifies the prior-art class of tar reducers as "halogen-containing substances" (citing U.S. Pat. Nos. 3,927,041; 3,935,249; 3,953,475; 3,954,812; 3,960,900; 3,985,672; 4,008,168; 4,086,251; 4,414,397; 4,434,071; 4,496,746), noting that such halogen-containing components "are generally undesirable because they tend to leave halogen-containing residues in the product" (https://patents.google.com/patent/US5071919A/en). That is a textbook KSR "known problem in the field + identified deficiency in the known solution" — it supplies a concrete reason for a PHOSITA working in this exact process to look for a non-halogen, hydrocarbon-compatible additive that suppresses tar/resin.

What Chevron supplies (element D, at least the adduct alternative): US 5,286,799/US 5,319,030 and their WO 1994002571 sibling teach that a mixture containing an alkenyl succinic anhydride and unreacted polyolefin can be reacted with further maleic anhydride at 200–250 °C — i.e., that an enophile/alkenyl-succinic-anhydride co-charge is thermally processed in the very temperature window of claim 8, and that polyolefins including polybutene and polypropylene are the substrates (http://www.everypatent.com/comp/pat5286799.html; https://patentimages.storage.googleapis.com/80/70/66/d61406b2b320db/WO1994002571A1.pdf).

The motivation to combine is the classic one: (i) both references are in the same field, address the same reaction, and one (Chevron) expressly discusses the tar/resin and product-quality problems in the same process; (ii) Ethyl identifies a need for a non-halogen tar suppressant; (iii) Chevron establishes that alkenyl succinic anhydrides and long-chain olefins are ordinary, well-behaved co-reactants with maleic anhydride at 200–250 °C, so a PHOSITA would expect such a co-feed at most to be consumed as an additional ene substrate and at worst to act as an inert oleophilic diluent — a reasonable expectation of success for a "try it at 0.1–5% w/w" experiment. Secondary art of the same type (EP-A-0014288's sediment-reducing auxiliary; EP-A-0082601's feed-control) reinforces that the art was already in the habit of dosing small amounts of auxiliary materials into the ene/maleinisation reaction to control sediment.

4. Combination B — claim 4 and the PIB species

US 5,454,964 (BP Chemicals) in view of any of the above.

'964 expressly discloses the thermal (chlorine-free) reaction of a highly reactive polybutene with >50% vinylidene/terminal unsaturation, Mn ≈ 950–1375, with maleic anhydride at 231–232 °C, MA:PIB >3:1, pressure held at 15–40 psig, stripping unreacted MA, with "no fouling of the reactor" (https://patentimages.storage.googleapis.com/d5/0b/3e/f7c3a3b0170b05/US5454964.pdf; family background at https://patentimages.storage.googleapis.com/13/61/c0/04293b6e6fa582/EP0623631A2.pdf — note the URL as returned). Claim 4 requires only >20% terminal unsaturation and Mn ≥ 500, which '964 more than satisfies (50–68% vinylidene; Mn 950–1375). Claim 4 is therefore obvious on this record.

⚠️ Caveat on '964 as art: it issued 1995-10-03, after the '092 filing, so it can only be § 102(e) art as of its own filing date, and only if that filing date precedes the '092 invention date. It is also commonly owned with '092 (BP Chemicals; Blackborow is a named inventor on both). Under current law § 103(c) common ownership could disqualify § 102(e) art — but pre-AIA § 103(c) cannot be relied on here, because the '092 application was filed 1995-06-05, before the AIPA amendment took effect (1999-11-29). Note also that the inventive entities differ ("Blackborow" vs. "Blackborow et al."), which affects the "by another" question under § 102(e).

5. Claim-by-claim conclusions

6. The counter-argument the patentee will make (and it is not frivolous)

The applicant's own Comparative Tests are unusually well designed for a later validity fight:

• CT1–CT3 (no additive): 10.8–11.9 g tar/100 g PIB.
• Examples 1–6 (octadecene, dodecene, DD-SA): 2.25–8.1 g tar/100 g PIB.
• CT4 (isobutenyl succinic anhydride, "IB-SA"): 22.7. CT5/CT6/CT9 (allyl succinic anhydride, "Allyl-SA"): 19.6 / 19.3 / 5.05.

These data establish that the effect is not a generic "add some hydrocarbon / dilute the maleic anhydride" effect — closely analogous short-chain enophile adducts make tar formation worse. A PHOSITA reading the cited art would have had no basis to predict the sign of the effect, let alone the ≥C3/≥C5 threshold. That is the core non-obviousness argument, and it is the reason the § 103 case on claim 1 is strong-but-not-airtight. Expect it to be met with a KSR response: the claim is a "known technique (adding an auxiliary to suppress tar) applied to a known process (thermal maleinisation) ready for improvement," with the olefin selected from the very feedstock set already handled in the art, and the level/range as a matter of routine optimisation. Whether that prevails turns on whether the claimed genus (unbounded alkyl chain, anyone's "formula (I)" olefin) can fairly be credited with the narrow result the applicant actually demonstrated for C12–C18 species.

Two further soft spots worth noting:

• Claim 1's "at least … or" language and the absence of any molecular-weight ceiling on the "alkyl group" of formula (I) invite an argument that the olefin of formula (I) is not meaningfully distinguishable from a second polyolefin fraction or from unreacted polyolefin already present — which would make the "adding" step read on routine operation of the Ethyl/Chevron/BP processes. That is a § 112 indefiniteness/claim-construction issue that bleeds directly into § 103.
• No secondary considerations appear of record here (the patent lapsed 2004-05-21 for non-payment of maintenance fees; nothing in the file as presented evidences commercial success, licensing, or copying).

7. References I could not verify, and where the record is thin

• FR 2,505,340 B1 and US 3,481,910 A are the two family-cited references whose text I did not retrieve; I have relied on their titles only. FR '340 in particular could be the decisive § 103 reference if it teaches the ene reaction of an internal C5–C30 olefin with maleic anhydride (i.e., the very "olefin of formula (I) + enophile" pairing), and it should be pulled and read before any conclusion is finalised.
• Similarly unverified: US 4,472,588 A, US 4,255,340 A, GB 2,081,722 A, EP 0 542 380 A1, CA 2,119,011 A1 (all "Similar Documents"), and EP-A-0014288 / EP-A-0082601 (known to me only through the BP family's characterisation of them).
• US 5,421,757 A (listed on the face as "US542757A," dated 1895-07-16, "Chimney-cap") is not analogous art and is almost certainly a citation-record artifact; do not auto-correct it, but do not rely on it.
• US 5,644,001 A (BP Chemicals, "Resin-free succinimides…") and US 7,091,306 B2 / US 2004/0225105 A1 appear in the Cited-By table; they post-date the '092 priority date and are not prior art against it.

8. Bottom line

• Claims 2, 3, 8, 9, 10 would very likely have been rejected as obvious — the Ethyl references alone supply these limitations almost verbatim.
• Claim 4 is obvious over US 5,454,964 (subject to its § 102(e) dating and common-ownership complications).
• Claims 5, 6, 7 are obvious as routine optimisation once the additive concept is supplied.
• Claim 1 is the only real battleground. The most persuasive § 103 combination is US 5,137,978 / US 5,071,919 (Ethyl) as primary, in view of US 5,286,799 / US 5,319,030 (Chevron), optionally reinforced by the EP-A-0014288 "sediment-reducing auxiliary in an ene reaction" teaching and by US 5,454,964 (BP). The motivation is the field's acknowledged, long-standing tar/resin/fouling problem together with the art's own identification of halogen-containing tar reducers as the known (and unsatisfactory) solution; the expectation of success comes from the demonstrated ease of reacting long-chain/internal olefins and alkenyl succinic anhydrides with maleic anhydride at 200–250 °C.
• Confidence: moderate-to-high (~65–70%) that claim 1 would be held obvious on that combination, but the applicant has a genuine, data-backed unexpected-results rebuttal (CT4–CT6, CT9 showing that short-chain enophile adducts are detrimental, not merely neutral), which would likely narrow survivability to the C12–C18/C5–C30 region rather than the full formula (I) genus.

These are analytical conclusions about patentability, not legal advice, and I have no authoritative information about whether any of these references were actually applied, or whether this patent was ever litigated or challenged (see the earlier section's finding of no litigation record).