Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1999-05-25
2000-12-05
Edwards, Newton
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428395, D01F 662
Patent
active
061564257
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to filaments made of semicrystalline polyester and to a process for manufacturing such a filament.
The subject-matter of the invention is more particularly a filament made of semicrystalline polyester, such as a poly(ethylene glycol terephthalate) or poly(ethylene glycol naphthalate), exhibiting high mechanical properties and a process for drawing these filaments.
BACKGROUND OF THE INVENTION
Filaments, such as monofilaments or multifilament yarns, made of polyester are generally obtained by melt spinning a polyester and the monofilament obtained is subsequently subjected to a drawing operation, in order to orient the structure of the polyester and to obtain high mechanical properties, such as, for example, the Young's modulus or the tenacity. The drawing operation is carried out either in a single stage or in several stages. The total draw ratio applied is generally of the order of 6.
However, for applications of monofilaments as, for example, reinforcing components for straps, conveyor belts or tires or for the production of felts for paper machines or fabrics for screen printing, and the like, it is advantageous and desired to obtain still higher mechanical properties.
Current processes for the manufacture of monofilaments are limited because it is impossible to apply high draw ratios to the polyester filament without causing the latter to break; the maximum ratios are thus of the order of 7 to 8.
In fact, numerous processes for drawing polyester monofilament have been disclosed in the literature. Thus, mention may be made, by way of example, of Japanese Patent J02091212, which discloses a two-stage drawing operation, the first drawing operation being applied according to a ratio of between 3.5 and 5 and an overdrawing operation subsequently being applied. The overall draw ratio is then between 5 and 5.8.
U.S. Pat. No. 3,998,920 also discloses a two-stage drawing process with a first draw ratio of between 4 and 6 and a total draw ratio of between 6 and 7.5.
Drawing processes equivalent to those described above are also made known in U.S. Pat. Nos. 3,963,678, 4,009,511, 4,056,652, 5,082,611 and 5,223,187.
Furthermore, in the usual industrial processes, the drawing operation is generally carried out in a single stage, optionally followed by an overdrawing stage and/or by a relaxation stage.
The monofilaments obtained by these drawing processes exhibit a high level of mechanical properties, for example a breaking stress of the order of 600 MPa and an elongation at break of the order of 30%.
These filaments exhibit a stress at 4% elongation of less than 500 MPa and a small elastic range generally corresponding to an elongation of less than 4% and to a stress of less than 300 MPa.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
One of the aims of the invention is to provide a novel polyester filament exhibiting an even higher level of mechanical properties and a manufacturing process, more particularly a drawing process, which makes it possible to obtain such filaments.
The subject-matter of the invention is in particular a drawn polyester filament obtained by melt spinning exhibiting an elastic range for which the stress/elongation limits are respectively greater than 300 MPa and 4%, preferably greater than 600 MPa and 5%.
The limits of the elastic range correspond to the abscissa and ordinate of the point of the stress=f(elongation) curve which departs by 10% from the elastic straight line defined by stress=modulus of elasticity.times.elongation.
This stress=f(elongation) curve is prepared from an Instron.RTM. measuring device with a sample with a length of 50 mm at a temperature of 25.degree. C. and a relative humidity of 50%. The rate of elongation is 50 mm/min.
Stress should be understood as meaning the ratio of the force (unit: N) to the initial cross-section of the filament (unit: m.sup.2).
Filament should be understood as meaning filaments exhibiting a significant cross-section, for example a diameter of greater than 20 .mu.m, and generally used individually or in com
REFERENCES:
patent: 2556295 (1951-06-01), Pace
patent: 2615784 (1952-10-01), McClellan
patent: 4098864 (1978-07-01), Morris
patent: 5238740 (1993-08-01), Simons et al.
patent: 5558935 (1996-09-01), Tanaka et al.
Database WPI, Section Ch, Week 8533, Derwent Publications Ltd., London, GB; Class A23, AN 85-200368, XP002028124 & JP 60 126 317 A (Gosen KK), Jul. 5, 1985, see abstract.
Database WPI, Section Ch, Week 8508, Derwent Publications Ltd., London, GB, Class A23, AN 85-046075, XP00208125 & JP 60 002 710 A (Unitika KK), Jan. 9, 1985, see abstract.
Bouquerel Franck
Lapersonne Philippe
Roche Eric
Edwards Newton
Rhone-Poulenc Fibres et Polymeres S.A.
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