US4424287A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Polymer foam process
Assignee: Pactiv LLC
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Filing: 1981-06-10
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Granted: 1984-01-03
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Expires: 2001-06-10
Abstract
Abstract Thermoplastic foams of polystyrene, for example, are prepared with a blowing agent which is a mixture of an organic plasticizing blowing agent, such as pentane, and an atmospheric gas, such as carbon dioxide. Typically, such foams prepared with organic blowing agent alone were aged prior to thermoforming the foam into articles. Foams prepared with the mixed blowing agent of this invention exhibit the advantage of reduced atmospheric emissions on aging.
Inventors
- 👤 D. Emil Johnson
- 👤 Charles M. Krutchen
- 👤 G. Vincent Sharps, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 12:10
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/04; C08J9/12; C08J9/127; B; B29; B29C; B29C44/00; B29C44/34; B29C44/3442; B29C44/3446; C08J2203/00; C08J2203/14; C08J2325/00; C08J2325/02; C08J2325/04; C08J2325/06; Y; Y10; Y10S; Y10S264/00; Y10S264/05
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
80 words
A method for the formation of a thermoplastic foam which comprises introducing to a molten thermoplastic resin a blowing agent comprising at least one atmospheric gas and at least one volatile plasticizing blowing agent in amounts sufficient to plasticize said thermoplastic resin; extruding said thermoplastic in the form of a foam; and thermoforming said foam into articles; wherein the atmospheric gas is present in sufficient amounts to allow thermoforming immediately after the extrusion of the foam without substantial intermediate aging.
Claim 2
Independent Claim
80 words
A method for the formation of a thermoplastic foam which comprises introducing to a molten thermoplastic resin a blowing agent comprising at least one atmospheric gas and at least one volatile plasticizing blowing agent in amounts sufficient to plasticize said thermoplastic resin; extruding said thermoplastic in the form of a foam; and thermoforming said foam into articles; wherein the atmospheric gas is present in sufficient amounts to allow thermoforming immediately after the extrusion of the foam without substantial intermediate aging.
Claim 3
Dependent Claim
14 words
A method in accordance with claim 1, wherein said atmospheric gas is carbon dioxide.
Claim 4
Dependent Claim
27 words
A method in accordance with claim 1 wherein said volatile plasticizing organic blowing agent comprises an alkane with 4 to 6 carbon atoms or a mixture thereof.
Claim 5
Dependent Claim
22 words
A method in accordance with claim 1 wherein said volatile plasticizing organic blowing agent consists essentially of n-pentane, isopentane or mixtures thereof.
Claim 6
Dependent Claim
14 words
A method in accordance with claim 1 wherein said thermoplastic consists essentially of polystyrene.
Claim 7
Dependent Claim
14 words
A method in accordance with claim 1 wherein said thermoplastic consists essentially of polyparamethylstyrene.
Claim 8
Dependent Claim
46 words
A method in accordance with claim 1 wherein the thermoplastic resin consists essentially of polystyrene, the volatile blowing agent comprises up to about 5 parts by weight of a pentane hydrocarbon and up to 5 parts by weight of carbon dioxide per 100 parts of resin.
Claim 9
Dependent Claim
33 words
A method in accordance with claim 1 wherein a mixture of citric acid and sodium bicarbonate, in an amount effective for nucleating foam cells, is added to said thermoplastic prior to extrusion thereof.
Claim 10
Dependent Claim
19 words
A method in accordance with claim 1 wherein said thermoplastic is extruded in the form of a foam tube.
Claim 11
Dependent Claim
20 words
A method in accordance with claim 1 wherein said volatile plasticizing organic blowing agent consists essentially of a halogenated hydrocarbon.
Claim 12
Dependent Claim
26 words
A method in accordance with claim 1 wherein the system is started-up without the atmospheric gas; then, atmospheric gas is bled into the blowing agent stream.
Claim 13
Dependent Claim
19 words
A method in accordance with claim 1 wherein the extruded foam is thermoformed into articles without any substantial aging.
Claim 14
Dependent Claim
28 words
The process of claim 1 wherein the atmospheric gas is present in a sufficient amount to substantially eliminate sagging of the extruded foam upon thermoforming without substantial aging.
Claim 15
Dependent Claim
22 words
The process of claim 1 wherein said atmospheric gas is liquified and fed to admixture with said thermoplastic resin in liquid form.
Claim 16
Independent Claim
81 words
A method for the formation of a thermoplastic foam which comprises: (a) introducing to a molten thermoplastic resin a blowing agent comprising at least one atmospheric gas and at least one volatile plasticizing blowing agent in amounts sufficient to plasticize said thermoplastic resin; (b) extruding said thermoplastic in the form of a foam; and (c) thermoforming said foam into articles; wherein the atmospheric gas is present in sufficient amounts to substantially reduce emission of the organic blowing agents into the environs.
Claim 17
Independent Claim
81 words
A method for the formation of a thermoplastic foam which comprises: (a) introducing to a molten thermoplastic resin a blowing agent comprising at least one atmospheric gas and at least one volatile plasticizing blowing agent in amounts sufficient to plasticize said thermoplastic resin; (b) extruding said thermoplastic in the form of a foam; and (c) thermoforming said foam into articles; wherein the atmospheric gas is present in sufficient amounts to substantially reduce emission of the organic blowing agents into the environs.
Claim 18
Dependent Claim
24 words
The process as claimed in claim 15 wherein said atmospheric gas is liquified and fed to admixture with said thermoplastic resin in liquid form.
Claim 19
Dependent Claim
28 words
The process of claim 15 wherein said volatile plasticizing organic blowing agent is a C 4 to C 6 alkane and wherein said atmospheric gas is carbon dioxide.
Claim 20
Dependent Claim
31 words
The process of claim 17 wherein the alkane and carbon dioxide are continuously metered at a predetermined flow rate and blended in a weight ratio of about 3:1 to 1:1 respectively.
Claim 21
Dependent Claim
13 words
The process of claim 17 wherein alkane:carbon dioxide ratio is about 2:1 respectively.
Claim 22
Dependent Claim
18 words
A process in accordance to claim 17 wherein said alkane consists essentially of n-pentane, isopentane, or mixtures thereof.
Claim 23
Dependent Claim
39 words
The process of claim 15 wherein the reduction in the amount of organic blowing agent emission into the environs is greater than the expected reduction which is equivalent to the decrease in the amount of organic blowing agent used.
Claim 24
Dependent Claim
114 words
A continuous process for thermoplastic foam production comprising the steps of: (a) feeding a thermoplastic resin to a screw-type extruder and heating the thermoplastic resin to a first temperature substantially above melting temperature of the resin; (b) introducing volatile hydrocarbon and atmospheric gas blowing agent in liquid phase concurrently into the resin while mixing the resin at the first temperature; (c) cooling the mixture of molten resin and blowing agent to a second temperature below the first temperature and above the melting temperature; (d) extruding a foamed sheet of the thermoplastic resin by passing the molten mixture through an orifice into a zone of reduced pressure; and (e) thermoforming said extruded foam into articles.
Claim 25
Dependent Claim
114 words
A continuous process for thermoplastic foam production comprising the steps of: (a) feeding a thermoplastic resin to a screw-type extruder and heating the thermoplastic resin to a first temperature substantially above melting temperature of the resin; (b) introducing volatile hydrocarbon and atmospheric gas blowing agent in liquid phase concurrently into the resin while mixing the resin at the first temperature; (c) cooling the mixture of molten resin and blowing agent to a second temperature below the first temperature and above the melting temperature; (d) extruding a foamed sheet of the thermoplastic resin by passing the molten mixture through an orifice into a zone of reduced pressure; and (e) thermoforming said extruded foam into articles.
Claim 26
Dependent Claim
14 words
The process of claim 22 wherein said atmospheric gas consists essentially of carbon dioxide.
Claim 27
Dependent Claim
17 words
The process of claim 22 wherein said volatile hydrocarbon consists essentially of n-pentane, isopentane or mixtures thereof.
Claim 28
Dependent Claim
12 words
The process as claimed in claim 22 wherein said orifice is annular.
Claim 29
Dependent Claim
26 words
The process of claim 22 wherein the system is started-up without the atmospheric gas; then, the atmospheric gas is gradually bled into the blowing agent stream.
Claim 30
Dependent Claim
20 words
The process claimed in claim 26 wherein said atmospheric gas is bled into said blowing agent stream in liquid form.
Claim 31
Dependent Claim
86 words
A thermoplastic foam article containing in its porous interstices at least one atmospheric gas and at least one volatile plasticizing organic blowing agent, said organic blowing agent being present in an amount sufficient to allow thermoforming of said foam article without substantial aging as compared to thermoformed thermoplastic foam which does not contain said atmospheric gas within its porous interstices; said foam article emitting a reduced quantity of said organic blowing agent to the atmosphere during the formation of said foam article and thereafter thermoforming thereof.
Claim 32
Dependent Claim
86 words
A thermoplastic foam article containing in its porous interstices at least one atmospheric gas and at least one volatile plasticizing organic blowing agent, said organic blowing agent being present in an amount sufficient to allow thermoforming of said foam article without substantial aging as compared to thermoformed thermoplastic foam which does not contain said atmospheric gas within its porous interstices; said foam article emitting a reduced quantity of said organic blowing agent to the atmosphere during the formation of said foam article and thereafter thermoforming thereof.
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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) | 1987-01-02 | 1987-07-04 | 1988-01-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-01-02 | 1991-07-04 | 1992-01-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-01-02 | 1995-07-04 | 1996-01-03 | $7700.00 | Window Closed / Lapsed |