Flame retardant high-temperature-resistant polyimide fibers and

Details Flame retardant high-temperature-resistant polyimide fibers and Flame retardant high-temperature-resistant polyimide fibers and

1989-10-20

1993-12-21

Lesmes, George F.

Plastic and nonmetallic article shaping or treating: processes

With twining, plying, braiding, or textile fabric formation

264258, 26433112, 264DIG71, 528125, 528126, 528128, 428287, 428288, 428296, A29D 2800, D02G 120, B32B 3104, C08G 802

Patent

active

052718891

DESCRIPTION:

BRIEF SUMMARY
BRIEF SUMMARY OF THE INVENTION

The present invention relates to flame-retardant, high-temperature-resistant polyimide fibers based on recurring structural elements of the general formula ##STR1## in which R is the group ##STR2## and/or the group ##STR3## a nonwoven made from such fibers, as well as the fibers and molded articles prepared by heating said fibers to about their glass transition temperature.
Copolyimide fibers having the above structural elements are known. E.g., U.S. Pat. Nos. 3,985,934 and 4,801,502. It is also known in the art that most stretched synthetic fibers shrink when heated close to the fiber's stretching temperature. For example, special polyolefin, polyester, polyvinyl chloride, and polyamide fibers shrink by about 50% when heated to such a temperature. The manufacturing process imparts this property to these fibers. Synthetic fibers are commonly stretched after spinning to orientate the polymer molecules. Strong intermolecular forces prevent the stretched molecules from contracting and convoluting (i.e., relaxing). At elevated temperatures, these forces are progressively overcome, allowing the fiber to reach a state of correspondingly higher entropy, thus developing a contracting force which shrinks the fiber.
Synthetic fibers having a high shrinkage capacity are used to thermally compact random nonwovens. This process is described, for example, in German Application 1,785,165, and in U.S. Pat. Nos. 4,188,690, and 4,237,180.
The German Application 1,785,165 discloses a procedure for the manufacture of felts from a random nonwoven consisting of at least two types of fibers. One of the fiber types shrinks considerably more than the other when the nonwoven is heated to an elevated temperature.
U.S. Pat. No. 4,237,180 discloses insulating materials comprising a mixture of inorganic and organic fibers. The organic fibers shrink when heated to an elevated temperature. This shrinkage compacts the fiber web.
U.S. Pat. No. 4,188,690 discloses the manufacture of a structureless nonwoven from a web of highly shrinkable organic fibers which by heat treatment shrink the web area approximately 50%.
Fibers having a high shrinkage capacity are also used as components for high-bulk yarns (R. W. Moncrieff, Man Made Fibers 5th ed., 1970, Heywood Books, pp. 461, 514, and 641).
To make highly stable molded articles from nonwovens, the nonwoven's fibers should have a high shrinkage capacity. It is also desirable that such molded articles exhibit high temperature resistance and flame-retardant properties. Such fibers and nonwovens are useful in the airplane, electrical engineering and automotive industries. Prior to the present invention fibers having a high shrinkage capacity, high temperature resistance and flame-retardant properties had not been identified.
Some polyamide fibers, such as, e.g., a conventional shrinkable meta-aramide fiber (NOMEX T 463, made by Du Pont), have good thermal properties. However, these fibers do not shrink sufficiently which restricts their utility.
Polyimide fibers having the structural elements described above are known to possess excellent thermal properties. Moreover, the gases produced at the decomposition temperature of these fibers exhibit a low smoke density and the toxicity of these fumes is slight. An object of the present invention is to make polyimide fibers that are useful in the manufacture of molded articles having a high tensile strength, a high temperature resistance, and flame-retardant properties, and yet also have a relatively low density. Furthermore, such molded articles should be machinable and able to be further molded.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cut-away view of a three-dimensional molded article according to the present invention;
FIGS. 2a and b are charts which show the functional relationship between the contraction force and the load (in cN/tex) for a specific temperature;
FIG. 3 is a chart which shows the functional relationship between fiber shrinkage and temperature for a meta-aramide fiber and a polyimide fiber acco

REFERENCES:
patent: 2991537 (1961-07-01), Moler et al.
patent: 3870677 (1975-03-01), Farrissey, Jr. et al.
patent: 3930097 (1975-12-01), Alberino et al.
patent: 3985934 (1976-10-01), Farrissey, Jr. et al.
patent: 4188690 (1980-02-01), Suzuki et al.
patent: 4237180 (1980-12-01), Jaskowski
patent: 4265954 (1981-05-01), Romanek
patent: 4474846 (1984-10-01), Doerer et al.
patent: 4476183 (1984-10-01), Holtrop et al.
patent: 4818586 (1989-04-01), Smith et al.
patent: 5229184 (1993-07-01), Campbell et al.
New Materials Offer Undreamed of Opportunities For The Aerospace Industry.
Roughly translated, Lightweight Fiber for Aviation and Space Industry.
K. G. Buller, Heat and Thermoresistant Polymers (roughly translated); M., Chemija, 1984, 7.1.1.9, p. 744
Nauka, 1983, p. 290.

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