US4703105A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Extraction of residues from styrenic polymers
Assignee: Dow Chemical Co
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Filing: 1985-12-23
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Granted: 1987-10-27
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Expires: 2005-12-23
Abstract
Abstract Bringing polymerizates, particularly those comprising styrene polymerized with an equal amount or more acrylonitrile and containing free styrene and acrylonitrile monomers, into contact with carefully selected gases in the near-critical to supercritical state substantially inhibits depolymerization and decomposition while substantially improving residue extraction.
Inventors
- 👤 Sambasiva R. Allada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 09:36
CPC Classifications
B; B01; B01D; B01D11/00; B01D11/02; B01D11/0203; C; C08; C08F; C08F6/00; C08F6/001; Y; Y02; Y02P; Y02P20/00; Y02P20/50; Y02P20/54
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
108 words
A method of making products formed of thermoplastic styrenic polymer comprising bringing molten polymerizate having acrylonitrile polymerized with styrene into contact with a solvent gas extractant having a critical temperature within the range of from 210° C. below to 20° C. above the process temperature or temperature at which the residual free styrene monomer can be extracted and at a pressure above the critical pressure of the solvent gas, separating the extractant and thereafter forming the polymerizate into packaging material; whereby depolymerization and decomposition is substantially inhibited; other residual monomers, oligomers, solvents, diluents and volatile condensation by-products are substantially reduced; and the need for chemical scavengers is negated.
Claim 2
Independent Claim
108 words
A method of making products formed of thermoplastic styrenic polymer comprising bringing molten polymerizate having acrylonitrile polymerized with styrene into contact with a solvent gas extractant having a critical temperature within the range of from 210° C. below to 20° C. above the process temperature or temperature at which the residual free styrene monomer can be extracted and at a pressure above the critical pressure of the solvent gas, separating the extractant and thereafter forming the polymerizate into packaging material; whereby depolymerization and decomposition is substantially inhibited; other residual monomers, oligomers, solvents, diluents and volatile condensation by-products are substantially reduced; and the need for chemical scavengers is negated.
Claim 3
Dependent Claim
118 words
An improved method for making products formed of thermoplastic styrenic polymer having acrylonitrile polymerized with styrene; the improvement comprising extracting the acrylonitrile/styrene polymerizate with a solvent gas in the supercritical state at an extraction temperature of from about 39.5° C. to not more than about 60° C., under supercritical pressure conditions, but not more than about 1,525 psi, for a period of from 30 minutes to about 120 minutes, separating the extractant and thereafter forming the polymerizate into packaging material; whereby the product is substantially free of residual acrylonitrile monomer and contains substantially reduced residual styrene monomer without the need for imparting excessively high pressures or long hours of extraction time, and without the need for chemical scavenger.
Claim 4
Dependent Claim
118 words
An improved method for making products formed of thermoplastic styrenic polymer having acrylonitrile polymerized with styrene; the improvement comprising extracting the acrylonitrile/styrene polymerizate with a solvent gas in the supercritical state at an extraction temperature of from about 39.5° C. to not more than about 60° C., under supercritical pressure conditions, but not more than about 1,525 psi, for a period of from 30 minutes to about 120 minutes, separating the extractant and thereafter forming the polymerizate into packaging material; whereby the product is substantially free of residual acrylonitrile monomer and contains substantially reduced residual styrene monomer without the need for imparting excessively high pressures or long hours of extraction time, and without the need for chemical scavenger.
Claim 5
Dependent Claim
21 words
The method of claim 2 wherein the polymerizate contains about 10-90% by weight polymerized styrene and 90-10% by weight polymerized acrylonitrile.
Claim 6
Dependent Claim
23 words
The method of claim 2 wherein from about 15 to 45 weight percent styrene is polymerized with 85 to 55 weight percent acrylonitrile.
Claim 7
Dependent Claim
28 words
The method of claim 2 wherein the critical temperature of the solvent gas is within the range of from 10° C. to 30° C. below the extraction temperature.
Claim 8
Dependent Claim
21 words
The method of claim 2 wherein the pressure is from 1.2 to 3 times the critical pressure of the solvent gas.
Claim 9
Dependent Claim
13 words
The method of claim 2 wherein the solvent gas is CO 2 .
Claim 10
Dependent Claim
31 words
The method of claim 2 wherein the extraction is conducted for a period of 2 hours using carbondioxide as the solvent gas at 60° C. under a pressure of 1500 psi.
Claim 11
Dependent Claim
22 words
The method of claim 2 wherein the extraction is conducted on granular form polymerizates having a particle size greater than 7 mesh.
References Cited (Backward Citations)
US4061566A
Cited
DE3323940A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-10-26 | 1991-04-27 | 1991-10-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-26 | 1995-04-27 | 1995-10-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-26 | 1999-04-27 | 1999-10-27 | $7700.00 | Window Closed / Lapsed |