Plastic and nonmetallic article shaping or treating: processes – Vacuum treatment of work
Patent
1996-07-09
1998-02-10
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Vacuum treatment of work
264184, 2642105, 2642108, 26421115, 26421116, 264233, D01D 506, D01F 674
Patent
active
057165670
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the process for production of aromatic polyimide fibres featuring high fire- and heat-resistance, and can be used for making products that are to operate, partly or completely, in a direct contact with an open fire, or are subjected to a thermal shock at a temperature of from 700.degree. to 1200.degree. C., or wherever it is impermissible to release into the atmosphere the polymer destruction products or fume particles resulting from local overheating of textile materials.
Improved-quality polyimide fibres are made use of for making: means for firemen and members of search-and-rescue crews, those of crews of aircraft and sea vessels, workers of the gas, oil, coal, and metallurgical industries, as well as those of some other services concerned with fire hazard and contact with a naked flame; fire-resistant cords, ropes, cables, and so on; fabric, knitted fabric from polyimide fibres or threads, and the bottom layer consists of any other natural or man-made fibre.
The top layer protects completely against an open fire and thermal shock, while the bottom layer provides for other properties, such as comfort when using natural fibres. Moreover, the chemisorption ability of the polyimide fibres enables such sunk-loop fabrics to be used for making masks and caps protecting the respiratory system and the organ of vision against fumes and combustion products when evacuating people from the zone of accidental fires in public places (such as hotels, saloons of sea vessels, production and public-amenity premises).
High level of thermal stability of polyimide materials enables one to use them to good advantage in extra-reliable filtering units operating at 250.degree.-350.degree. C., as well as in articles adapted to operate at such temperatures in the open air.
2. The Prior Art
According to a state-of-the-art process for producing polyimide fibres, polyamide acid is synthesized from pyromellitic dianhydride and 4,4'-diaminodiphenylmethane or metaphenylenediamine in a dimethyl- formamide solution, followed by a wet spinning in an aqueous-settling bath, whereupon the freshly spun fibres are subjected to plasticization drafting and heat-treatment (cf., e.g., U.S. Pat. No. 3,179,614, C1. 524-726, published in 1965).
However, the fibres produced by the method discussed before features but low mechanical characteristics (that is, their strength is as low as 25-27 cN/tex) and low thermal stability.
Higher consumer's and service properties are displayed by the polyimide fibres produced on the base of pyromellitic dianhydride and 4,4'-diaminodiphenyloxide. Such a polyimide fibre is produced by a wet spinning of a concentrated solution of said polyamide acid in N-methylpyrrolidone, followed by plasticization drafting, chemical and thermal imidization; it has a strength of 55 cN/tex, an elastic modulus of 1280 kgf/sq.mm, and a percentage elongation at rupture of 7% (cf., e.g., Japanese Application 59-163,416, C1. DO1F 6/74 published in 1984).
The fibre produced by the aforedescribed process has an oxygen index of 36%; however, its thermal stability is also low, that is, after having been heated at 300.degree. C. for 100 hours, the fibre loses 35-45% of its initial strength.
The polyimide fibres of the aforespecified chemical structure are produced by dry spinning of an appropriate polyamide acid in a dimethylformamide solution, followed by thermal imidization (cf., e.g., U.S. Pat. No. 3,415,782, C1. 260-47, published in 1968).
The fibre has a strength of about 60 cN/tex and an oxygen index of 35%. After having been heat in the air at 300.degree. C. for 100 hours the fibre loses 40-42% of its initial strength.
A most similar to the present invention is a process for producing polyimide fibres from polyamide acid of the following general formula: ##STR1## where Q is the residue of the dianhydrides of pyromellitic, 3,3',4,4'- diphenyltetracarboxylic, 3,3',4,4'-diphenyloxidetetracarboxylic, and 3,3',4,4'-benzophenonetetracarboxylic acids, hydroqu
REFERENCES:
patent: 3179614 (1965-04-01), Edwards
patent: 3415782 (1968-12-01), Irwin
patent: 4640972 (1987-02-01), Irwin
patent: 4869861 (1989-09-01), Inoue et al.
Andriashin Alexandr Ivanovich
Musin Ruslan Rustemovich
Musina Tamara Kurmangazievna
Oprits Zinaida Grigorievna
Schetinin Alexandr Mikhailovich
Tamara Kurmangazievna Musina
Tentoni Leo B.
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