Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1998-11-17
2000-03-28
Edwards, Newton
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428395, 264184, D02G 300, D02F 600
Patent
active
060429410
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention pertains to a fibre of a para-aromatic polyamide polymer (p-aramid) comprising a quantity of sulphur bound to the aromatic nuclei of the polymer.
DESCRIPTION OF RELATED ART
Such fibres are known. For instance, EP 427 280 (Chiou) teaches a poly(paraphenylene terephthalamide) filament yarn having chemically bound sulphur (sulphonic acid or sulphonate) groups. The yarn contains 0.5 to 3.0% by weight of S thus bound. Also described is a process for the manufacture of such a yarn. In this process the p-aramid polymer is not spun directly from the conventional solution in concentrated sulphuric acid; rather, the substantially unsulphonated polymer is first exposed to fuming sulphuric acid in a concentration of 100.5 to 102.5% for 1 to 3 hours at 70 to 80.degree. C.
U.S. Pat. No. 4,075,269 and U.S. Pat. No. 4,162,346 (Jones) likewise disclose sulphonating p-aramid in fuming sulphuric acid. In the process described, poly(paraphenylene terephthalamide) containing 0.5 to 10% of S in the form of sulphonic acid and/or sulphonate groups bound to the aromatic nuclei is spun into a yarn.
As background art is further mentioned EP 442 399 (Keil), which discloses copolymers made from a mixture of monomers which comprises 7.5 to 30 mole-% of an alkylsulphonyl substituted aryl monomer. The exemplified sulphur content can be calculated to be about 1 wt. %.
Already in U.S. Pat. No. 3,767,756 (Blades) mention is made of the fact that fuming sulphuric acid can be used as solvent for spinning poly(paraphenylene terephthalamide). However, a warning is given here to carry out the treatment at a low temperature and in a short period of time, to avoid a decrease of the inherent viscosity and the tensile strength of the obtained fibres.
It is known that spinning p-aramid from concentrated sulphuric acid can produce fibres with excellent mechanical properties. It is also known from the aforementioned prior art that tensile strength in particular can be improved by sulphonation. Further, it is known that a p-aramid fibre containing extra sulphur is better able to withstand a heat treatment. In this connection Chiou teaches good strength retention after heat ageing, while Jones teaches that a significant increase in the tensile strength is found especially after a heat treatment.
In this familiar field of chemically (nucleus) bound sulphur-containing p-aramid fibres a novel, surprisingly improved fibre according to the invention has now been found. The invention in this connection consists of a p-aramid fibre of the aforementioned known type, with the quantity of nucleus-bound sulphur being 0.05 to 0.20% by weight, calculated on dry polymer. The fibre according to the present invention has an unexpectedly higher modulus. In addition, the fibre according to the invention has a substantially higher tensile strength, even without a heat treatment.
Preferably, the para-aramid is made up wholly or for the most part of poly(para-phenylene terephthalamide), hereinafter referred to as PPTA, and the quantity of nucleus-bound sulphur is 0.09 to 0.20% by weight. Further preference is given to a sulphur percentage of 0.09 to 0.15% by weight.
The PPTA can be made in a known manner by reacting stoichiometric quantities of para-phenylene diamine (PPD) and terephthalic acid dichloride (TDC) in an appropriate solvent (notably CaCl.sub.2 -containing N-methyl pyrrolidone). Suitable processes have been described in NL 157327 and WO 95121883.
To make fibres having the desired properties, use is made of an anisotropic solution of the PPTA, which preferably has a relative viscosity of at least 3.5, most preferably of more than 4.3. In this process at least 14% by weight, preferably about 17.0-20.5% by weight, is dissolved in an appropriate solvent such as concentrated sulphuric acid. Such anisotropic solutions are fully known for p-aramid in general and PPTA in particular. They can be prepared in a known manner, e.g., with the aid of a freezing process as described in NL 7904495. The spinning solution can be spun using a
REFERENCES:
patent: 3767756 (1973-10-01), Blades
patent: 4075269 (1978-02-01), Jones, Jr. et al.
patent: 4162346 (1979-07-01), Jones, Jr. et al.
patent: 4320081 (1982-03-01), Lammers
patent: 5128440 (1992-07-01), Keil et al.
Krins Bastiaan
Meeusen-Wierts Monique Helene Marielle
Van Der Werff Harm
Akzo Nobel nv
Edwards Newton
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