US3997360A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for cleaning vinyl chloride polymerization reactors
Assignee: Societa Italiana Resine SpA SIR
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Filing: 1975-08-11
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Granted: 1976-12-14
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Expires: 1995-08-11
Abstract
Abstract Polymeric deposits formed on internal surfaces of the reactors during polymerization or copolymerization of vinyl chloride are removed by dissolving them at a temperature above 60° C with a solvent mixture comprising from 0 to 7% by weight of water, the remainder consisting of toluene and dimethylformamide in a weight ratio of toluene to dimethylformamide of from 50:50 to 90:10.
Inventors
- 👤 Francesco Testa
- 👤 Antonio Bigliani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 21:40
CPC Classifications
C; C08; C08J; C08J11/00; C08J11/04; C08J11/06; C08J11/08; B; B08; B08B; B08B3/00; B08B3/04; B08B3/08; C08J2327/00; C08J2327/02; C08J2327/04; C08J2327/06; Y; Y02; Y02W; Y02W30/00; Y02W30/50; Y02W30/62
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
109 words
In a method for cleansing surfaces of equipment used for the polymerization of vinyl chloride by removing polymeric deposits therefrom by contact with a solvent, the improvement which comprises contacting polymeric deposits formed on said surfaces at a temperature of at least 60° C with a solvent mixture containing water in amounts up to 7% by weight of the mixture, the remainder consisting of toluene and dimethylformamide in a weight ratio of toluene to dimethylformamide of from 50:50 to 90:10, for a time sufficient to dissolve at least a portion of said polymeric deposits, and subsequently removing said solvent mixture containing dissolved polymeric solids from contact with said surfaces.
Claim 2
Dependent Claim
109 words
In a method for cleansing surfaces of equipment used for the polymerization of vinyl chloride by removing polymeric deposits therefrom by contact with a solvent, the improvement which comprises contacting polymeric deposits formed on said surfaces at a temperature of at least 60° C with a solvent mixture containing water in amounts up to 7% by weight of the mixture, the remainder consisting of toluene and dimethylformamide in a weight ratio of toluene to dimethylformamide of from 50:50 to 90:10, for a time sufficient to dissolve at least a portion of said polymeric deposits, and subsequently removing said solvent mixture containing dissolved polymeric solids from contact with said surfaces.
Claim 3
Dependent Claim
14 words
The method of claim 1, wherein said weight ratio is from 55:45 to 75:25.
Claim 4
Dependent Claim
18 words
The method of claim 1, wherein said solvent mixture comprises from 0.7 to 7% by weight of water.
Claim 5
Dependent Claim
18 words
The method of claim 1, wherein said solvent mixture comprises from 1 to 3% by weight of water.
Claim 6
Dependent Claim
14 words
The method of claim 1, wherein said temperature is from 60° to 100° C.
Claim 7
Dependent Claim
14 words
The method of claim 1, wherein said temperature is from 70° to 100° C.
References Cited (Backward Citations)
US3764384A
Cited
US3784477A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-12-14 | 1980-06-14 | 1980-12-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-12-14 | 1984-06-14 | 1984-12-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-12-14 | 1988-06-14 | 1988-12-14 | $7700.00 | Window Closed / Lapsed |