EP0453687A1
Expired / Lapsed
EP
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Process and apparatus for molding foamed plastic article
Assignee: ABC Technologies Inc
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Filing: 1990-12-12
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Granted: —
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Expires: 2010-12-12
Abstract
Abstract In the production of foamed plastic articles using a screw extruder, it is known to introduce a gaseous foaming agent into the plastic while the latter is passing through the extruder. It has been found that a foamed thermoplastic with pores or cells of uniform size and distribution can be produced by passing a gaseous foaming agent, e.g. nitrogen gas through a central passage (8) extending substantially the entire length of the extruder screw (1), discharging the agent into the thermoplastic proximate the discharge end of the extruder, and mixing the foaming agent with the plastic immediately prior to discharge of the mixture into a mold.
Inventors
- 👤 Changize Sadr
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 01:26
CPC Classifications
B; B29; B29C; B29C44/00; B29C44/34; B29C44/3442; B29C44/3446; B29C44/3449; B29C44/36; B29C44/46; B29C44/50; B29C48/00; B29C48/25; B29C48/252; B29C48/2522; B29C48/256; B29C48/2564; B29C48/285; B29C48/29; B29C48/298; B29C48/36; B29C48/50; B29C48/505; B29C48/53; B29C48/565; B29C48/022; B29C48/03; B29C48/288; B29C48/2886; B29K; B29K2105/00; B29K2105/0005; B29K2105/06; B29K2105/16
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
85 words
A method of molding a foamed thermoplastic article comprising the steps of introducing a thermoplastic into an extruder barrel containing a screw extending the length of the barrel; introducing a gaseous foaming agent under pressure into a driven end of the screw for passage along substantially the entire length of the screw; discharging the foaming agent radially into the thermoplastic proximate the discharge end of the barrel; and mixing the foaming agent with the thermoplastic immediately prior to discharge of the thermoplastic from the barrel.
Claim 2
Dependent Claim
131 words
An extruder screw for use in an extruder of the type including an elongated barrel and an inlet for introducing plastic into the barrel near one end thereof comprising elongated cylindrical body means for rotation in the barrel, helical flight means on substantially the entire length of said body means for feeding the plastic through the barrel during rotation of said screw means; first axial passage means in said body means extending from said one end to proximate the other end of said body means for carrying gaseous foaming agent through said body means; and second generally radially extending passage means in said body means proximate said other end for discharging the gaseous foaming agent from the screw for intimate mixing with the plastic immediately prior to extrusion from the barrel.
Claim 3
Dependent Claim
43 words
A screw according to claim 2, including head means defining said other end of said body means, said head means containing a discharge end of said first passage means and said second passage means for discharging the foaming agent from the body means.
Claim 4
Dependent Claim
51 words
A screw according to claim 3, wherein said head means includes bolt means at the upstream end thereof in the direction of foaming agent flow for threadedly engaging the remainder of said body means, said bolt means containing the downstream end of said first passage means and said second passage means.
Claim 5
Dependent Claim
63 words
A screw according to claim 4 including a radially extending passage in said bolt means communicating with said first passage means; an annular passage in said head means around said bolt means for receiving foaming agent from said radial passage; and radially extending orifice means for discharging foaming agent from said annular passage into the plastic between the screw body and the barrel.
Claim 6
Dependent Claim
39 words
A screw according to claim 4, wherein said second passage means includes a plurality of inclined passages in said head means for discharging the foaming agent in a downstream direction from the downstream end of said first passage means.
Claim 7
Dependent Claim
88 words
A screw according to claim 4, including annular insert means on said bolt means between said head means and the downstream end of said body means defining an annular passage around said bolt means; a radially extending passage in said bolt means for feeding foaming agent from the downstream end of said first passage means to said annular passage; and a plurality of radially extending orifices in said insert means for discharging foaming agent from said annular passage into the plastic between said body means and the barrel.
References Cited (Backward Citations)
FR2098326A1
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DE2053646A1
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DE2402203A1
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US3986709A
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DE2340499C2
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DE3139024A1
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EP0329934A2
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