Plastic and nonmetallic article shaping or treating: processes – Vacuum treatment of work – To degas or prevent gas entrapment
Patent
1997-10-27
1999-03-16
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Vacuum treatment of work
To degas or prevent gas entrapment
264184, 26421122, 26421123, B29C 4776, D01D 110, D01F 660
Patent
active
058825630
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for making fibres from a polyamide consisting wholly or for the most part of poly(p-phenylene terephthalamide) in which a spinning mass is prepared by cooling concentrated sulphuric acid of at least 98 wt. % content to below its coagulation point, subsequently combining the thus cooled sulphuric acid with the polyamide and mixing them to form a solid mixture containing, calculated on the weight of the mixture, at least 15% of the polyamide having an inherent viscosity of at least 2.5, and then heating the resulting solid mixture and passing it, under pressure, to spinning orifices, and spinning it by means of an air gap spinning process.
Such a process is known from Netherlands patent application 7904495 laid open to public inspection. It was found that with the aid of this so-called freezing process proper mixing of sulphuric acid and poly(p-phenylene terephthalamide) could be achieved. However, the resulting sandy solution lacks sufficient homogeneity for immediate processing after being melted. For this reason the sandy solution is heated in an extruder prior to being spun. Not all drawbacks are obviated by this procedure, however. Since not every polymer granule will absorb the same quantity of sulphuric acid, the sulphuric acid:polymer ratio on a microscopic scale differs from the set macroscopic scale ratio. This will give inhomogeneities during melting. Furthermore, it was found that favourable results in actual practice are highly dependent on precise settings for the pressure build-up and the variation in temperature in the extruder. In consequence, there is a considerable risk of failure of the extruder process. It was also found to be advisable in actual practice to compress the sandy solution in the cold state, which severely curtails the options to increase or change the process capacity.
It has also been proposed to prevent inhomogeneities in the poly(p-phenylene terephthalamide) spinning solution by means of an improved process of dissolving poly(p-phenylene terephthalamide) in sulphuric acid. A two-step mixing process to this end in which poly(p-phenylene terephthalamide) and sulphuric acid are successively mixed in a small twin-screw mixer operated at high speed and a large twin-screw mixer operated at low speed is known from Research Disclosure 232 004. Such a process has nothing to do with eliminating the drawbacks to the known freezing process, nor does it have the advantages provided by said process.
From WO 92/07120 it is known to modify a poly(p-phenylene terephthalamide) spinning solution by the addition thereto of solution containing additives. A static mixer unit is employed to this end. This process has nothing to do with improving the aforementioned freezing process either.
DESCRIPTION OF THE INVENTION
The invention has for its object to eliminate the drawbacks to the known freezing process. To this end the invention consists in that in a process of the known type mentioned in the opening paragraph the heating and pressurising of the solid mixture is carried out in a device in which the polymer solution passes through at least two successive zones, i.e., a melting zone and a pressure build-up zone, with the polymer solution being kneaded as well as mixed in at least the melting zone.
Since in the melting zone the polymer solution is transformed from a granular structure (containing many voids) into a liquid, the degasification of the polymer solution by means of a vacuum preferably takes place in this zone.
The conventional extruders combine a number of functions, i.e., kneading, mixing, melting, degasification, and pressure build-up. It was found that not only the process capacity and controllability, but also the homogeneity of the spinning solution, the quality of the yarn, and the loop and cord strengths can be enhanced by dividing these functions between at least two separate zones, a melting zone and a pressure build-up zone.
Further, it was found that the process according to the present invention allows t
REFERENCES:
patent: 3414645 (1968-12-01), Morgan, Jr.
patent: 3873072 (1975-03-01), Blackmon
patent: 4016236 (1977-04-01), Nagasawa et al.
patent: 4320081 (1982-03-01), Lammers
patent: 5094690 (1992-03-01), Zikeli et al.
patent: 5121992 (1992-06-01), List et al.
patent: 5147135 (1992-09-01), List et al.
patent: 5246776 (1993-09-01), Meraldi et al.
patent: 5534113 (1996-07-01), Quigley et al.
Derwent Patent Abstract 91-036767/05 (1991).
Derwent Patent Abstract 19,369Q (1969).
Derwent Patent Abstract 91-304786/42 (1991).
Derwent Patent Abstract 87-228715 (1987).
Derwent Patent Abstract 90-107892 (1990).
Derwent Patent Abstact 83-751004/35 (1983).
Derwent Patent Abstract 90-061032/09 (1990).
Roelofs Wilhelmus Marie
Spieker Antonius Hendrikus Maria
Waringa Johannes Gerrit
Akzo Nobel nv
Fennelly Richard P.
Tentoni Leo B.
LandOfFree
Process for making fibres from poly(p-phenylene terephthalamide) does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for making fibres from poly(p-phenylene terephthalamide), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for making fibres from poly(p-phenylene terephthalamide) will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-814216