Patent US3821157A successfully refreshed from Google Patents.
US3821157A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Thermoplastic binders for continuously produced leads for pencils,copying pencils and coloured pencils
Assignee: Bayer AG
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Filing: 1973-05-17
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Granted: 1974-06-28
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Expires: 1993-05-17
Abstract
Abstract Leads for writing purposes comprising a graft polymer of an ethylene/vinyl acetate copolymer, a vinyl chloride and a graft copolymer of a styrene and an acrylonitrile type monomer onto a butadiene polymer and graphite or a scouring agent.
Inventors
- 👤 K Muller
- 👤 H Rohr
- 👤 K Ott
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 17:00
CPC Classifications
C; C09; C09D; C09D13/00
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
21 words
The pencil lead of claim 1 wherein (A) has a vinyl acetate content of from 30 to 55 percent by weight.
Claim 2
Dependent Claim
16 words
The pencil lead of claim 1 wherein graphite is the pencil coloring agent capable of chalking.
Claim 3
Dependent Claim
87 words
The pencil lead of claim 1 wherein (A) comprises a graft polymer of 40 percent by weight of vinyl chloride, 23 percent by weight of vinyl acetate and 37 percent by weight of ethylene and (B) comprises a mixture of 30 percent by weight of a graft polymer comprising 30 percent by weight of styrene and 50 percent by weight of acrylonitrile grafted on 50 percent by weight of polybutadiene and 70 percent by weight of a copolymer of styrene and acrylonitrile in a ratio of 70:30.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-27 | 1977-12-27 | 1978-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-27 | 1981-12-27 | 1982-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-27 | 1985-12-27 | 1986-06-28 | $7700.00 | Window Closed / Lapsed |