Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-14
2001-11-06
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06313200
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a process for feeding additives into a polymer melt stream, wherein a substream is taken from the polymer melt stream, mixed with additives, and thereafter supplied into the polymer melt stream again.
2. Summary of the Related Art
Feeding additives into a polymer melt stream is know. A process for feeding additives into a polymer melt stream is described in
Chemiefasern/Textilindustrie
[Manmade Fibers/Textile Industry], vol. 36/88, January 1986, pages 24 to 29, with a substream of approximately 5% to 10% being removed from an unmodified main melt stream discharged from a final reactor or extruder and sent through a twin screw extruder equipped with special kneading elements. Suitable additives are added to the twin-screw extruder with a continuous metering system and incorporated homogeneously into the melt. Then the melt loaded with additives is mixed back into the main melt stream, with a uniform distribution of additives being achieved by means of static mixing elements.
German Patent No. 4,039,857 describes a process and a device for direct continuous modification of polymer melts. A substream of melt, to be optionally modified, is taken from the main stream of melt and sent into a twin screw extruder. The additives pass through a delivery pump into the twin screw extruder. The modified melt substream is then sent back to the main melt stream.
European Patent No. 532,988 describes a process for producing random copolyesters. According to a preferred embodiment, a polyester (B) and 10 to 50 wt % of a polyester (A) are sent to a mixing extruder, and the extrudate is then mixed with the remaining 90 to 50 wt % of polyester (A) in a static mixer.
It is known from Franz Fourné,
Synthetische Fasern
[Synthetic Fibers], Hanser Verlag, 1995, pages 316 through 318, that planet wheel spinning pumps can be used to convey polymer melts. These planet wheel pumps usually have three to eight pump gear wheels arranged in one plane about a planet gear wheel that serves as the drive. The only melt inlet is in the form of a flow channel in the middle, and each of the n outlets is arranged in one gear wheel wedge.
SUMMARY OF THE INVENTION
The present invention comprises a process for feeding additives into a polymer melt stream, wherein a homogeneous premixing of additives and part of the polymer melt is achieved. This is ensured even when the additives have different Theological properties than the polymer melt.
According to the invention, a substream of a polymer melt stream is split off and directed to a planet wheel pump with n pump gear wheels. Before entering the planet wheel pump, the substream is optionally split into from 2 to n−1 substreams, which are each directed into a separate pump gear wheel. Additives are directed into from one to all of the remaining pump gear wheels. The additives and the substream(s) are mixed in the planet wheel pump and then directed back into the polymer melt stream.
Optionally, the substream/additive mixture is passed through a static mixer before returning to the polymer melt stream and/or the polymer melt stream is passed through a static mixer after the substream/additive mixture is added to it.
The foregoing merely summarizes certain aspects of the invention and is not intended, nor should it be construed to limit the invention, which is disclosed in more detail below. All patents and other publications, including priority document German Patent Application 198 41 376.9 are hereby incorporated by reference in their entirety.
REFERENCES:
patent: 5376702 (1994-12-01), Stibal et al.
patent: 30 38 580 (1981-06-01), None
patent: 40 39 857 C2 (1990-04-01), None
patent: 41 34 682 (1995-02-01), None
patent: 532 988 B1 (1995-11-01), None
Signer, Arno, (1992)Plastverarbeiter, 43, JG. NR. 11, with English translation.
Fourne, Franz, (1995)Schmelzpinnanlagen, 4.6, pp. 316-318, with English Translation.
Luckert et al., (1986)Chemlefasern/Textillindustrie, vol. 36, No. 88, pp. 24-29 with English Translation.
Cain Edward J.
Lurgi Zimmer Aktiengesellschaft
McDonnell & Boehnen Hulbert & Berghoff
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