Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1995-07-21
1998-01-13
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528125, 528126, 528128, 528170, 528172, 528173, 528179, 528183, 528186, 528188, 528220, 528229, 528310, 528322, 528351, 525935, 524600, 524607, 428395, 4284111, 4284735, C08G 7310, C08G 6926
Patent
active
057081271
DESCRIPTION:
BRIEF SUMMARY
The invention is concerned with polymerizable monomeric reactants (PMR) type resins containing bisnadimide and high temperature resistant matrix polymers for composites made therefrom.
In recent years the most practical of the high temperature thermostable polyimide matrix resins developed for the aerospace industry has been the polymerizable monomeric reactants (PMR) type, produced by workers in NASA, USA. These resins are monomeric mixtures of aromatic diamines with nadic anhydride and aromatic dianhydride based esters. These mixtures were reported to react at intermediate temperature to give nadimide capped oligomers of Formula (I) as shown below. ##STR4##
At higher cure temperatures, these oligomers melt and crosslink to form a continuous stable matrix in advanced composite structures. Recent work (J. N. Hay, J. D. Boyle, P. G. James, J. R. Walton, and D. Wilson, "Polymerisation Mechanisms in PMR 15 Polyimide,", in Polyimides: Materials, Chemistry and Characterization, C. Feger, M. M. Khojasteh, and J. E. McGrath Eds., Elsevier, Amsterdam, 1989, pages 305 to 320) has shown that the oligomers formed have much more complex structures with unreacted ester and acid groups as well as uncyclized structures. This complexity and partial reaction means that consistent resin properties are not possible and also lead to brittleness, microcracking and voids in the final composites. The aromatic diamine monomers present in the resins often have toxicity and stability problems, for example, diaminodiphenylmethane--the most commonly used aromatic diamine in industry.
An alternative approach to improve composite toughness, etc., has been to use higher molecular weight or fluorinated monomers in the initial resin mixtures and hence improve molecular mobility and processability. The difficult challenge however is to prepare relatively homogeneous materials without increasing material costs greatly.
International Patent Publication No. WO 92/06078 by the present applicant, which is incorporated herein by reference, describes a process for the low cost production of novel, high molecular weight monomeric diaminobisimides (hereinafter referred to as "DABIs") of well defined structure and substantially free of oligomeric, amidic and uncyclized impurities. These aromatic diamines have also been found to be non-toxic and stable. International Patent Publication No. WO 92/06078 also discloses the use of DABIs as hardeners for epoxy resins.
In European Patent Publication No. 0 479 722 A2, Kramer et al disclose oligomeric polyimides of Formula (I) as defined above wherein Ar is C.sub.6 H.sub.2 and 5<n<150. These polyimides are stated to be soluble and useful as tougheners in crosslinked resin systems.
We have now found that DABIs produced by the process disclosed in International Patent Publication No. WO 92/06078 can be used to make PMR type resins which crosslink on heating to give thermally stable polyimides having much better properties than the standard PMR matrix resins.
According to one aspect of the present invention there is provided a PMR type resin which comprises a mixture of: ##STR5## (b) a diaminobisimide of Formula (Ib) ##STR6## (c) an aromatic tetracarboxylic acid of Formula (Ic) or a derivative thereof ##STR7## the components (a), (b) and (c) being present in the approximate molar proportions of 2:n:n-1 respectively; and substituted aryl, optionally substituted bridged or bonded di- or poly-aryl or optionally substituted heteroaryl group; for good conjugation between the nitrogen containing groups; and
Preferably 5>n>2.
As used herein the term "good conjugation" means that during formation of the diaminobisimide precursor from a diamine of Formula (III) shown below, substitution of an electron-withdrawing group on one of the nitrogen atoms suppresses the reactivity of the other nitrogen atom during the reaction.
Preferably the aromatic diamine of the Formula (III) is sterically hindered, such as in compounds of Formulae (V) and (VI) ##STR8## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are the same
REFERENCES:
patent: 3998786 (1976-12-01), D'Alelio
patent: 5041526 (1991-08-01), Riel et al.
patent: 5041527 (1991-08-01), Riel et al.
patent: 5041528 (1991-08-01), Riel et al.
Eibl Robert
Hodgkin Jonathan Howard
Commonwealth Scientific and Industrial Research Organisation
Hampton-Hightower P.
Seidleck James J.
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