Claims
- 1. A method of making a polymeric foam comprising polyacrylonitrile comprising:
- (a) forming a free-flowing particulate polymer comprising polyacrylonitrile and having from about 5 percent to about 20 percent by weight of an absorption aid therein;
- (b) mixing a liquid fugitive plasticizer with the particulate polymer to produce a free-flowing particulate polymer wherein the plasticizer is uniformly absorbed in the particulate polymer; and
- (c) extruding the particulate polymer at sufficient temperature and with sufficient blowing agent to form a foamed polymer.
- 2. A method according to claim 1 wherein the blowing agent comprises the vaporized absorption aid produced from the absorption aid present in the polymer.
- 3. A method according to claim 1 wherein the absorption aid is removed before extrusion and a blowing agent is introduced at the extrusion step.
- 4. A method according to claim 1 wherein the fugitive plasticizer comprises ethylene carbonate, propylene carbonate, or acetonitrile.
- 5. A method according to claim 1 wherein the absorption aid is water or a lower aliphatic alcohol.
- 6. A method according to claim 3 wherein the blowing agent comprises CO.sub.2, pentane, a halocarbon or a compressed gas.
Parent Case Info
This application is a continuation of application Ser. No. 08/191,171, filed Feb. 3, 1994, now abandoned, which is a divisional of application Ser. No. 07/822,288, filed Jan. 21, 1992, now U.S. Pat. No. 5,304,590.
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822288 |
Jan 1992 |
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Continuations (1)
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191171 |
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