US4981625A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Monodisperse, polymeric microspheres produced by irradiation of slowly thawing frozen drops
Assignee: California Institute of Technology
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Filing: 1988-03-14
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Granted: 1991-01-01
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Expires: 2008-03-14
Abstract
Abstract Monodisperse, polymeric microspheres are formed by injecting uniformly shaped droplets of radiation polymerizable monomers, preferably a biocompatible monomer, having covalent binding sites such as hydroxyethylmethacrylate, into a zone, impressing a like charge on the droplet so that they mutually repel each other, spheroidizing the droplets within the zone and collecting the droplets in a pool of cryogenic liquid. As the droplets enter the liquid, they freeze into solid, glassy microspheres, which vaporizes a portion of the cryogenic liquid to form a layer. The like-charged microspheres, suspended within the layer, move to the edge of the vessel holding the pool, are discharged, fall and are collected. The collected microspheres are irradiated while frozen in the cryogenic liquid to form latent free radicals. The frozen microspheres are then slowly thawed to activate the free radicals which polymerize the monomer to form evenly-sized, evenly-shaped, monodisperse polymeric microspheres.
Inventors
- 👤 Won-Kyu Rhim
- 👤 Michael T. Hyson
- 👤 Sang-Kun Chung
- 👤 Michael S. Colvin
- 👤 Manchium Chang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:43
CPC Classifications
A; A61; A61K; A61K9/00; A61K9/48; A61K9/50; A61K9/5094; A61K9/14; A61K9/16; A61K9/1605; A61K9/1629; A61K9/1635; A61K9/1682; A61K9/1694; B; B01; B01J; B01J2219/00; B01J2219/19; B01J2219/194; B01J2219/1941; B01J2219/1942; G; G01; G01N; G01N15/00; G01N15/10; G01N15/14; G01N15/149; Y; Y10; Y10S; Y10S526/00; Y10S526/909; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
106 words
A method of forming uniform, polymeric microspheres comprising the steps of: injecting a plurality of individual, uniformly sized liquid droplets comprising radiation polymerizable monomer into a zone defined by the walls of a container in a manner in which the droplets do not contact each other or the walls of the container; spheroidizing the droplets while in the zone to form uniformly-shaped liquid microspheres; freezing the microsphere droplets to convert the droplets into frozen uniformly shaped and sized microspheres; radiating the frozen microspheres to form latent free radicals; and slowly thawng the frozen microspheres to activate the free radicals and polymerize monomer to form the polymer.
Claim 2
Independent Claim
106 words
A method of forming uniform, polymeric microspheres comprising the steps of: injecting a plurality of individual, uniformly sized liquid droplets comprising radiation polymerizable monomer into a zone defined by the walls of a container in a manner in which the droplets do not contact each other or the walls of the container; spheroidizing the droplets while in the zone to form uniformly-shaped liquid microspheres; freezing the microsphere droplets to convert the droplets into frozen uniformly shaped and sized microspheres; radiating the frozen microspheres to form latent free radicals; and slowly thawng the frozen microspheres to activate the free radicals and polymerize monomer to form the polymer.
Claim 3
Dependent Claim
18 words
A method according to claim 1 in which the liquid droplets are frozen into a non-crystalline, glassy state.
Claim 4
Dependent Claim
19 words
A method according to claim 1 in which the injected droplets are charged by passing through an annular electrode.
Claim 5
Dependent Claim
16 words
A method according to claim 1 in which the droplets are injected into a vertical zone.
Claim 6
Dependent Claim
19 words
A method according to claim 1 in which the droplets are deployed into and levitated within a horizontal zone.
Claim 7
Dependent Claim
22 words
A method according to claim 4 in which the frozen microspheres are collected in a vessel containing a pool of cryogenic liquid.
Claim 8
Dependent Claim
27 words
A method according to claim 6 in which the frozen microspheres vaporize a portion of the cryogenic liquid to form a vapor layer which suspends the microspheres.
Claim 9
Dependent Claim
24 words
A method according to claim 7 in which the suspended, charged microspheres repel each other and move to the outer edge of the layer.
Claim 10
Dependent Claim
21 words
A method according to claim 8 further including the step of discharging the microspheres while at the edge of the layer.
Claim 11
Dependent Claim
26 words
A method according to claim 9 further including the step of collecting the discharged microspheres and radiating the discharged, frozen microspheres while immersed in cryogenic liquid.
Claim 12
Dependent Claim
17 words
A method according to claim 1 in which the radiation polymerizable monomer comprises a mono-unsaturated acrylic monomer.
Claim 13
Dependent Claim
94 words
A method according to claim 11 in which the acrylic monomer is selected from the group consisting of acrolein, acrylamide, methacrylamide, acrylic acid, methacrylic acid, dimethylamino-methacrylate or hydroxy-or amino-alkylacrylates of the formula: ##STR3## where R 1 is H or lower alkyl of 1 to 8 carbon atoms, R 2 is alkylene of 1 to 12 carbon atoms and Z is OH or R 3 -N-R 4 where R 3 and R 4 are individually selected from H, lower alkyl of 1 to 8 carbon atoms or lower alkoxy of 1 to 8 carbon atoms.
Claim 14
Dependent Claim
12 words
A method according to claim 12 in which the monomer is hydroxyethylmethacrylate.
Claim 15
Dependent Claim
22 words
A method according to claim 12 in which the liquid polymerizable monomer contains 0.1 to 10% of a radiation curable cross-linking agent.
Claim 16
Independent Claim
121 words
An apparatus for forming uniformly shaped and sized, polymeric microspheres comprising in combination: means for forming uniformly sized droplets of liquid monomer; means for applying a like charge to the droplets; means for spheroidizing the droplets to form evenly-shaped microspheres; a collection vessel for holding a pool of cryogenic liquid for receiving the evenly-shaped and evenly-sized, charged microspheres and freezing the microspheres to maintain said even size and shape; means for discharging the microspheres; irradiation means for applying free-radical generating radiation to the frozen microspheres for generating latent free radicals therein; and thawing means receiving the frozen microspheres for slowly thawing the microspheres whereby the latent free radicals are activated and polymerize the monomer into uniformly sized and shaped polymeric microspheres.
Claim 17
Independent Claim
121 words
An apparatus for forming uniformly shaped and sized, polymeric microspheres comprising in combination: means for forming uniformly sized droplets of liquid monomer; means for applying a like charge to the droplets; means for spheroidizing the droplets to form evenly-shaped microspheres; a collection vessel for holding a pool of cryogenic liquid for receiving the evenly-shaped and evenly-sized, charged microspheres and freezing the microspheres to maintain said even size and shape; means for discharging the microspheres; irradiation means for applying free-radical generating radiation to the frozen microspheres for generating latent free radicals therein; and thawing means receiving the frozen microspheres for slowly thawing the microspheres whereby the latent free radicals are activated and polymerize the monomer into uniformly sized and shaped polymeric microspheres.
Claim 18
Dependent Claim
19 words
An apparatus according to claim 15 in which the droplet forming means includes a piezoelectric crystal pulsed spray nozzle.
Claim 19
Dependent Claim
23 words
An apparatus according to claim 16 in which the charging means includes an annular D.C. electrode positioned below the outlet of the nozzle.
Claim 20
Dependent Claim
56 words
An apparatus according to claim 15 in which the charged, frozen microspheres vaporize a portion of the cryogenic liquid to form a vapor layer and the charged microspheres move to the outer edge of the layer and the discharge means comprises a plurality of electrodes positioned along the periphery of the collection vessel adjacent said layer.
Claim 21
Dependent Claim
24 words
An apparatus according to claim 18 in which the collection vessel includes a cover having a central aperture for passage of the frozen microspheres.
Claim 22
Dependent Claim
16 words
An apparatus according to claim 19 in which the discharge electrodes are mounted on said cover.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-12-31 | 1994-07-02 | 1995-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-31 | 1998-07-02 | 1999-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-31 | 2002-07-02 | 2003-01-01 | $7700.00 | Window Closed / Lapsed |