US3721649A
Expired / Lapsed
US
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Phtalein-fluoran semiconductive polymers
Assignee: 3M Co
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Filing: 1970-06-19
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Granted: 1973-03-20
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Expires: 1990-06-19
Abstract
Abstract A semiconductive phthalein-fluoran polymer adapted for use in a friction element in an electrostatic device of the Johnsen-Rahbek type. The semiconductive polymer is produced produced by a Friedel-Crafts type condensation reaction, e.g. of an alpha hydroxyanthraquinone or an alpha hydroxynaphthalene with phthalic anhydride, 1,8-naphthalic anhydride, or 3,4,5,6tetrahydrophthalic anhydride, at a reaction temperature in the range of from 259* to 268* C.
Inventors
- 👤 Burguette M Dominguez
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:11
CPC Classifications
H; H02; H02N; H02N13/00; C; C08; C08G; C08G61/00; C08G65/00; C08G65/34
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
25 words
The method of claim 1 further comprising purifying said polymer by extraction to remove substantially all of the zinc chloride and the unreacted starting materials.
Claim 2
Dependent Claim
50 words
The method of claim 1 further comprising heat-treating said semiconductive material by heating it between 170* and 180*C. in an oxygen-containing atmosphere for a time sufficient to lower its resistivity, or heating it between 210*C. and 270*C. in the absence of oxygen for a time sufficient to raise its resistivity.
Claim 3
Dependent Claim
9 words
The organic semiconductive material of the process of claim
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) | 1976-03-19 | 1976-09-18 | 1977-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-19 | 1980-09-18 | 1981-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-19 | 1984-09-18 | 1985-03-20 | $7700.00 | Window Closed / Lapsed |