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US4397799A
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US
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Process for drying and expanding microspheres
Assignee: Kemanord AB
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Filing: 1981-12-18
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Granted: 1983-08-09
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Expires: 2001-12-18
Abstract
Abstract The present invention relates to a process for drying and expanding microspheres whereby first a dispersion of the microspheres in an inert liquid is prepared. This dispersion is then atomized in a hot inert gas. The process of the invention is advantageously carried out in a spray dryer.
Inventors
- 👤 Anders T. Edgren
- 👤 Lars-Olof Svedberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 04:36
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/22; C08J9/228; B; B01; B01J; B01J13/00; B01J13/02; B01J13/20; C08J9/32; Y; Y10; Y10S; Y10S264/00; Y10S264/06
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
141 words
A process for drying and expanding microspheres having thermoplastic shells encapsulating a blowing agent, comprising the steps of (a) providing a dispersion of the unexpanded microspheres, in sizes between 1 μm and 1 mm, in a volatile liquid that is inert to and a non-solvent for the thermoplastic microspheres, (b) atomizing the dispersion having an amount up to 50% of the unexpanded microspheres in a stream of hot, inert gas having a temperature sufficient to: (i) in a first stage said volatile liquid is vaporized and (ii) in a second stage the microspheres are expanded by evaporation of the blowing agent at a temperature which initiates expansion of the microspheres, (c) feeding the gas stream containing the expanded microspheres to a separator for the microspheres, and (d) collecting from the separator of a product of dry, free-flowing and discrete microsphere particles.
Claim 2
Dependent Claim
141 words
A process for drying and expanding microspheres having thermoplastic shells encapsulating a blowing agent, comprising the steps of (a) providing a dispersion of the unexpanded microspheres, in sizes between 1 μm and 1 mm, in a volatile liquid that is inert to and a non-solvent for the thermoplastic microspheres, (b) atomizing the dispersion having an amount up to 50% of the unexpanded microspheres in a stream of hot, inert gas having a temperature sufficient to: (i) in a first stage said volatile liquid is vaporized and (ii) in a second stage the microspheres are expanded by evaporation of the blowing agent at a temperature which initiates expansion of the microspheres, (c) feeding the gas stream containing the expanded microspheres to a separator for the microspheres, and (d) collecting from the separator of a product of dry, free-flowing and discrete microsphere particles.
Claim 3
Dependent Claim
18 words
A process according to claim 1 in which the liquid is water and the inert gas is air.
Claim 4
Dependent Claim
21 words
A process according to claim 1 in which the dispersion of microspheres has a dry content of 25 to 50 percent.
Claim 5
Dependent Claim
27 words
A process according to claim 1 in which the temperature in the mixture of microspheres and gas at the final stage of expansion is 80-150 degrees centigrade.
Claim 6
Dependent Claim
20 words
A process according to claim 4 in which the temperature at the final stage of expansion is 90-120 degrees centigrade.
Claim 7
Dependent Claim
21 words
A process according to claim 1 in which the temperature of the entering gas is between 140 and 300 degrees centrigrade.
Claim 8
Dependent Claim
21 words
A process according to claim 6 in which the temperature of the entering gas is between 160 and 250 degrees centrigrade.
Claim 9
Dependent Claim
21 words
A process according to claim 7 in which the temperature of the entering gas is between 180 and 200 degrees centigrade.
Claim 10
Dependent Claim
22 words
A process according to claim 1 in which the shell of the microspheres consists of a copolymer of vinylidene chloride and acrylonitrile.
Claim 11
Dependent Claim
13 words
A process according to claim 1 in which the blowing agent is iso-butane.
Claim 12
Dependent Claim
21 words
A process according to claim 1 in which the atomization is carried out with the aid of atomizing discs or nozzles.
Claim 13
Dependent Claim
17 words
A process according to claim 1 in which the process is carried out in a spray dryer.
Claim 14
Dependent Claim
27 words
A process according to claim 1 in which the expanded microspheres are collected in a collecting device which separates air, such as a filter or a cyclone.
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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) | 1986-08-08 | 1987-02-07 | 1987-08-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-08-08 | 1991-02-07 | 1991-08-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-08-08 | 1995-02-07 | 1995-08-09 | $7700.00 | Window Closed / Lapsed |