US4882108A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for producing polypropylene foam
Assignee: Mitsubishi Chemical Corp
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Filing: 1988-04-07
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Granted: 1989-11-21
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Expires: 2008-04-07
Abstract
Abstract A method of producing a crosslinked, uniformly foamed article of a polypropylene resin is provided. The polypropylene resin containing a crosslinking agent and a foaming agent is extruded through a long-land die which is provided with a choking die at an intermediate portion thereof; a lubricant is provided on the inner surface of the long-land die; the crosslinking agent is decomposed in the front stage of the long-land die; and the foaming agent is decomposed in the rear stage of the long-land die. An ethylene-propylene random copolymer resin which contains 2 to 10 wt. % of ethylene and has a melt flow rate of 5 g/10 minutes or more at 230° C. and a melt expansion ratio of 1.4 of less at 190° C. is used as the polypropylene resin.
Inventors
- 👤 Yoshio Nakajima
- 👤 Takao Kimura
- 👤 Yoshinobu Nagaoka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:55
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/04; C08J9/06; C08J9/10; B; B29; B29C; B29C44/00; B29C44/34; B29C44/36; B29C44/46; B29C44/50; B29C48/00; B29C48/25; B29C48/94; C08L; C08L23/00; C08L23/02; C08L23/10; C08L23/14; C08L23/142; B29C48/03; B29C48/09; B29K; B29K2023/00; B29K2023/10; B29K2023/12; C08J2323/00; C08J2323/02; C08J2323/16; Y; Y10; Y10S; Y10S264/00; Y10S264/16; Y10S264/18
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
228 words
A method for producing a polypropylene foamed article, comprising the steps of: uniformly melt-mixing a polypropylene resin with a crosslinking agent and a foaming agent; extruding the thus-obtained melted resin into a long-land die provided with a choking die in an intermediate portion thereof so as to apply back pressure to the melted resin in a front stage of said long-land die; supplying a lubricant to an interface between said long-land die and the melted resin from a portion near an inlet of said long-land die; heating the resin to cause crosslinking by the resin by thermal decomposition of the crosslinking agent in said front stage of said long-land die; heating the resin to a temperature above the decomposition temperature of the foaming agent in a rear stage of said long-land die; foaming the resin by extruding it from said long-land die, wherein said polypropylene resin is an ethylene-propylene random copolymer which contains 2 to 10 wt % of ethylene with a melt flow rate of 5 g/10 minutes or more at 230° C. and a melt expansion ratio of 1.4 or less at 190° C.; extracting the lubricant from a surface of the resin at an end of said front stage of said long-land die; and supplying the extracted lubricant to an interface between said long-land die and the resin at an end of the intermediate portion.
Claim 2
Independent Claim
228 words
A method for producing a polypropylene foamed article, comprising the steps of: uniformly melt-mixing a polypropylene resin with a crosslinking agent and a foaming agent; extruding the thus-obtained melted resin into a long-land die provided with a choking die in an intermediate portion thereof so as to apply back pressure to the melted resin in a front stage of said long-land die; supplying a lubricant to an interface between said long-land die and the melted resin from a portion near an inlet of said long-land die; heating the resin to cause crosslinking by the resin by thermal decomposition of the crosslinking agent in said front stage of said long-land die; heating the resin to a temperature above the decomposition temperature of the foaming agent in a rear stage of said long-land die; foaming the resin by extruding it from said long-land die, wherein said polypropylene resin is an ethylene-propylene random copolymer which contains 2 to 10 wt % of ethylene with a melt flow rate of 5 g/10 minutes or more at 230° C. and a melt expansion ratio of 1.4 or less at 190° C.; extracting the lubricant from a surface of the resin at an end of said front stage of said long-land die; and supplying the extracted lubricant to an interface between said long-land die and the resin at an end of the intermediate portion.
Claim 3
Dependent Claim
22 words
A method of producing a polypropylene foamed article according to claim 1, wherein a crosslinking accelerator is mixed with said polypropylene resin.
Claim 4
Dependent Claim
31 words
A method of producing a polypropylene foamed article according to claim 2, wherein said crosslinking accelerator is an organic compound having two or more vinyl-type double bonds in its molecular structure.
Claim 5
Dependent Claim
43 words
A method of producing a polypropylene foamed article according to claim 2, wherein said crosslinking accelerator comprises a combination of an aromatic hydrocarbon having one vinyl group and an organic compound having two or more acryloyloxy or methacryloyloxy groups in its molecular structure.
Claim 6
Dependent Claim
66 words
A method of producing a polypropylene foamed article according to claim 1, wherein a choking ratio A/B of said choking die, wherein A denotes the cross-sectional area of said front stage of said long-land die and B denotes the cross-sectional area of the maximum choking portion of said choking die, in a direction perpendicular to the direction of movement of the resin is 2/1 to 10/9.
Claim 7
Dependent Claim
55 words
A method of producing a polypropylene foamed article according to claim 1, wherein said lubricant is extracted from the surface of said resin at an end of said front stage of said long-land die and is again supplied to an interface between said long-land die and said resin at an end of said intermediate portion.
Claim 8
Dependent Claim
36 words
A method of producing a polypropylene foamed article according to claim 1, wherein resin passages in rear stages of said long-land die have cross sections which gradually increase in the direction of movement of the resin.
References Cited (Backward Citations)
US4552708A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-11-20 | 1993-05-22 | 1993-11-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-11-20 | 1997-05-22 | 1997-11-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-11-20 | 2001-05-22 | 2001-11-21 | $7700.00 | Window Closed / Lapsed |