Bismaleimide compounds

Details Bismaleimide compounds Bismaleimide compounds

1995-01-05

1997-04-01

Schofer, Joseph L.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

548423, C08F12240, C07D48702

Patent

active

056166664

DESCRIPTION:

BRIEF SUMMARY
This invention relates to bismaleimide compounds and polymers, particularly high temperature resistant polymers, prepared from them.
Bismaleimide derivatives of simple arydiamines can be used to prepare polyimides of good thermal stability. However, such bismaleimide derivatives are often difficult to process, and produce on curing, polymers with properties only marginally better than ethoxy derived materials. Furthermore, such bismaleimides compounds have either been derivatives of relatively simple diamino compounds or ill defined products made from the co-reaction of a number of polyfunctional materials.
GB 1,137,592 and U.S. Pat. No. 3,010,290 describe the preparation of bismaleimide compounds by reaction of maleic anhydride with some simple diarylamines. These products when converted to polymers with curing agents known in the art are generally more brittle than is desired for advanced composite use and as a result toughening agents are often necessary. This tends to lead to increased cost in processing and less reproducibility.
An alternative approach to improve toughness is to prepare thermally stable bismaleimide compounds of higher molecular weight so that on curing there will be greater molecular weight between crosslinks. However, it is a challenge to prepare relatively homogeneous materials and still retain some processibility and good thermal properties.
U.S. Pat. No. 3,998,786 discloses a method of preparing maleimide terminated oligo-imide materials. This method involves a one pot reaction for preparing the curable resin of an arylimide type, relying solely on stoichiometry of the reactants (dianhydride, dime and maleic anhydride) to determine the structure of the resulting maleimide.
U.S. Pat. No. 3,998,786 suggests that a wide range of possible diamines and dianhydrides are suitable starting materials in synthesis, and as a consequence, some of the claimed products are alleged to have structures corresponding to those of the present application. However in our attempts to duplicate the method described in U.S. Pat. No. 3,998,786 complex mixtures of chemicals, including considerable amounts of uncyclized and oligomeric material, were produced. This result is not unexpected, given the number of possible reactions, this type of synthesis would be expected to produce a complex mixture of different types of products which are very difficult to separate. Although no data is provided in U.S. Pat. No. 3,998,786, the resultant polyimides produced on curing such products could be inconsistent in properties from batch to batch including lower and variable Tg.
We have now found that substantially monomeric materials can be obtained by first preparing the monomeric diaminobisimides using the method disclosed in our International Patent Application No. PCT/AU91/00454.
According to one aspect of the present invention there is provided a bismaleimide compound of the formula (I) substantially free of oligomeric, amidic and uncyclized impurities which may be convened into a high molecular weight polyimide polymer having improved properties: ##STR2## wherein: Ar is an aromatic residue: and good conjugation between the nitrogen-containing groups shown in formula (I) or steric or other restrictions capable of moderating the reactivity of an unreacted amine moiety attached to said residue.
As used herein the term "good conjugation" means that during formation of the diaminobisimide precursor from a dime of formula (II): suppresses the reactivity of the other nitrogen atom during the reaction as disclosed in International Patent Application No. PCT/AU91/00454.
Suitable Ar groups include aryl, bridged or bonded di- or poly-aryl or heteroaryl groups. The Ar group may be substituted with one or more alkyl, haloalkyl, alkoxy, alkylthio, aryl, heteroaryl, aryloxy, carboxy, alkylamino, dialkylamino, amino, nitro, cyano or halo groups.
"Aryl" means an aromatic carbocyclic group, such as phenyl, naphthyl, and the like.
"Bridged or bonded di- or poly- aryl" means a group consisting of two or more aromatic carbocyclic rin

REFERENCES:
patent: 5262515 (1993-11-01), Kubo et al.

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