CA2120781A1

CA2120781A1 - Polyimide oligomers

Info

Publication number: CA2120781A1
Application number: CA002120781A
Authority: CA
Inventors: Michael Amone; Mark Southcott
Original assignee: Individual
Current assignee: Huntsman Advanced Materials Switzerland GmbH
Priority date: 1993-04-09
Filing date: 1994-04-07
Publication date: 1994-10-10
Also published as: US5478915A; EP0626412A1; DE69405646T2; DE69405646D1; EP0626412B1; US5412065A; ES2108406T3; JPH06329794A

Abstract

Polyimide Oligomers Abstract Polyimide oligomers are described which comprise the condensation product of: at least one phenylindane diamine and at least one aromatic bis(ether anhydride). The polyimide oligomers of the invention are readily processed to form solution prepregable polyimide composites having high glass transition temperatures and high temperature and oxidative stability. More particularly, the present invention provides for crosslinkable polyimide oligomers prepared by reacting, in a suitable solvent under an inert atmosphere, a mixture of monomers comprising: (A) an aromatic diamine component comprising from about 25 to 100 mole % of at least one phenylindane diamine; (B) a dianhydride component comprising from about 25 to 100 mole % of at least one aromatic bis(ether anhydride);
and (C) at least one end-cap monomer selected from the group consisting of mono-anhydrides, acyl halides and aromatic amines, wherein each end-cap monomer contains at least one crosslinkable funtional group in the molecule. The crosslinkable polyimide oligomers of the present invention are characterized by a number average molecular weight of from about 1000 to about 15000.

Description

f-~UK-19530LA/CGC 1698 Pobimide Oli~omers The present invendon relates to polyimide oligomers having high thermal and oxidadve stability and to methods for their manufacture. More particularly, the present invendon relates to polyimides oligomers that can be readily prepregged and cured to form advanced composites having aerospace applicadons.

Polymer based composite materials are used in applicadons requiring perforrnance at temperatures ranging from below ambient to 260C. -Typical applicadons include:
compressor blades, ducts, splitters and thrust-vectoring flaps for jet engines, rnissile fins, wing components, radar domes, and other aerospace structures. Polyimide resins have bcen employed in such applicadons due to their high temperature and thermal stability properdes.

.
Polyimide resins are generally produced dth by condensadon polymerizadon direcdy or by addidon polymerizadon followed by a condensation rearrangement reacdon to form the heterocyclic rings. Accordingly, H2O is a reacdon product in either case and ereates inherent difficulda in produeing void-free composites. Voids have a deleterious effeet on the shear strength, flexural strength, and dieleetric properdes of polyimide based composites.

In ordor to aehieve hi8h performance it has been previously proposed to use fully prereaeted thermoplasde polyimides as the composite matnx. However, in this case the softening point or T~ of the polyimide resin must be substandally above the intended use-temperature. Accordingly, a very high pmeessing temperature is required which has the dsk of eausing pyrolyde degradadon of the resin. Moreover, the pressure needed to aehkve the required resin ~low often is higher than commercially available equipment is eapable of sustaining.

In recent years, attempts have been made to resolve certain of these disadvantages. For example, in U.S. patents 3,528,9S0, 3,745,149 and 3,083,081, polyimides are prepared from coreacdng certain polyfunctional amines, polyfunctional anhydrides and end-eapping ~ :-monoanhydrides in an attempt to alleviate processing, stability and economic dis-advantages.

More recently, certain soluble polyimides, such as those described in Bateman et al U.S.
Patent 3,856,752 which is assigned to the same assignee as the present invendon, have been described. Such polyimides are prepared by utilizing diaminodiphenylindane and aromatic dianhydrides. The resultant polyimides exhibit numerous advantages over the polyimides of the pdor art but still encounter certain processing problems due to reduced solubility and flow characteristics.

Polyimide materials that are derived from in situ reacted monomers and oligomers have been used successfully in high performance environments. ~rocessing problems normally associated with resin flow are less severe for such materials owing to their low molecular weight relad~e to fully plereacted thermoplastic polyimides. One such material is PMR-15 which is described in U.S. patent 3,745~149. The acronym PMR stands for in Situ poly-merization of monomeric reactants. The -15 refers to a formulated molecular weight of 1500. PMR-15 is an addition polyimide derived from the dimethyl esterof benzophenone tetracarboxylic dianhydride (BTDE), the monomethyl ester of nadic anhydride (NE) and 4,4' -methylene dianiline (MDA). Addition polymerizadon is made possibb by the use of the nadic end groups, which react without further evoludon of voladla at 25~350C.

While PMR~15 provides significant benefits, this resin and in~diate materials (e.g., prepregs) deri~ed from it havc certain disadvantages. Among these are toxicity, short shelf life, and handling difficuldes dunng processing. The toxicity originates from MDA which is considered a suspect human carcinogen by the U.S. Environmental Protectdon Agency.
Such red orperceivedrisks associated with PMR-15 are expected to hamper subsequent -applications for this material.

Accordingly, there condnues to be a need for polyimides for high performance applica- i dons, such as aerospace needs, which rcquire elevated temperature perfonnance in -combinadon with chemical stability and greater ease in processing.
.
The present invendon relata to polyimide oligomers comprising the condensadon product of at least one phenylindane diamine and at kast one aromatic bis(ether anhydride~. The ~ -~
present invendon also relates to the discovery that such polyimide oligomers can be readily pmcessed to form soludon prepregable polyimide composites having high glass -212078~

transition temperatures and high temperature and oxidative stability. More particularly, the present invention provides for crosslinkable polyimidb oligomers prepared by reacting, in a suitable solvent under an inert atmosphere, a mixture of monomers comprising: (A) an aromatic diamine component comprising from about 25 to 100 mole % of at least one phenylindane diamine; (B) a dianhyd~ide component comprising from about 25 to 100 mole % of at bast one aromatic bis(ether anhydridb); and (C) at least one end-cap mono-mer selected from the group consisting of monoanhydrides, acyl halidbs and aromadc amines, wherein each end-cap monomer contains at least one crosslinkable funcdonal group in the molecule. The crosslinkable polyimide oligomers of the present invendon are characterized by a number average molecular wdght of from about 1000 to about 15000.

Unless otherwise indicated, the terms used in this specificadon and in the appended claims are intended to be interpreted in their art recognized generic sense. Certain terms which are used in this specification and the appended claims are defined below.

The term "polyimide oligomer(s)" is intended to describe oligomeric materials that are produced by the condensation of the at bast th ee dissimilar monomers (A), (B) and (C), but does not excludb the presence of addidonal monomers unless otherwise clearlyindicated herein.

The term "aromatic" when used in conjunction with a chemical group such as "aromadc ~ -radical", "aromadc diamine", "aromadc bis(ether anhydride)", etc., is intended to describe organic compounds or radicals thereof containing at least one closed homocyclic or heterocyclic nucleus that possess a closed loop of electrons (the so-called aromadc sextet).
For exampb, organic compounds or radicals thereof containing a single aromadc nucleus (e.g., benzene, pyridine, thiophene, 1,2,3,~tetrahydronaphthalene, etc.) as well as compounds or radicals containing polynuclear aromadc moiedes are intended. The -polynuclear aromadc moiedes can be of:
(i) the fused type wherein at Ieast two aromadc nucld are fused such as found, for ~ -example, in naphthalene, anthracene, the azanaphthalenes, etc. or ~ -(ii) the linked type wherein at least two aromadc nuclei (either mono or polynuclear) are linked through bridging linkages to each other as found, for example, in bisphenol A, benzidine, diphenyl çther, diphenyl sulfone, etc. Suitable bridging linkages are well known to those skilled in the art and include, for example, carbon-to-carbon single bonds, ether, keto, alkylene, sulfonyl, sulfinyl, amino, sulfide, and mixtures of such divalent bridginglinkages.
.:
, ~

1' 1 .,' " ' ' . , :, ' ~ ~ ' ',, ' ' , ' ,f~

The term "hydroearbyl" when used in conjunction with a chemical group such as "hydro~
carbyl radical" is intended to describe organic compounds or radieals thereof whieh include hydrocarbon as well as substantially hydrocarbon groups. This includes aromatie (defimed above) as well as aliphade and alicyelie (both saturated and unsaturated) groups, radicals or subsdtuents.

"Substandally hyd~oearbon" desclibes organie eompounds or radicals thereof that have a predominant amount of earbon and hydrogen atoms (i.e., at least about 50 mole %), but whieh also eontain non-hydrocarbon subsdtuents or heteroatoms in a ring or chain other-wise eomposed of earbon atoms. Those skilled in the art will be aware of suitab1e non-hydroearbon subsdtuents (e.g., halogen, hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, sulfoxy, ete.). In addition, suitable heteroatoms will be apparent to those of ordinary skill in the art and include, for example, sulfur, oxygen, nitrogen, etc.
., The term "crosslinkable" is intended to deseribe the chemical funedonality of eertain sub-sdtuent groups of the end-eap monomers (C) and the polyimide oligomers, whieh groups -are eapable of interaedng with, e.g., reaedve sites in the backbone of a polymer, an oligomer moleeule, or a substrate material, to form a primary, covalent chemical bond dunng a erosslinlcing orcuring proeess. In general, such crosslinkable funcdonal groups will eontain at least one unsaturadon site, but also can inelude in lieu of or in addidon to at ~ -least one unsaturadon site, funcdons eapable of: hydroxyl-transether~leadon crosslinking;
amine-amide erosslinking; oxirane ring opening; and hydroxyl-isocyante erosslinking or urethane formadon.
,~:
The term "at kast one" when used in eonjunedon with a ehemieal g~oup, recumng unit or the like, is intended to provide for the presence of one or more than one of such groups or units in the moleeule, oligomer or a monomer mixture, as the case may be. In other words, tho present invendon eontemplates both individua1 ehemical groups and units as well as mixtures of sueh materials as defined herein.

The term "divalent aromade radieal" is intended to deseribe aromade ehemical groups whieh have two free valences attached to an aromatie ling; dther both valences are on the same ring or each valenee is on a differenet aromade ring in the radieal.

The term "lower" as used in the present speeifieation and elaims, when used in -, ., . .-,, ., : : . ~-conjuncdon with groups such as allcyl is intended to describe such groups which contain a total of up to 7 carbon atoms.

In one embodiment of the present invention, polyimide oligomers are synthesized from a mixture of monomers comprising: -(A) an aromatic diamine component selected from:

(A-i) from about 25 to about 100 mol % of at least one phenylindane diamine represented by the formula (RS)4 NH2 (I) ~ .

:
wherein Rl, R2 and R3 independently ate hydrogen or lower alkyl, and each R4 and : :
each R5 independently are hydrogen, halogen or lower allcyl; and ~ ;
(A-ii) f om O to about 75 mob % of at least one aromadc diamine, other than a phenylindane diamine, rcpresented by the formula whetein R is a divalent aromatic radical; ~.

(B) a dianhydride component selected from:
-(B-i) from about 25 mole % to about 100 mol % of at least one aromatic bis(ether anhydride) represented by the formula ~ , ..
. ~
:. ',,:

212~781 o o o~-Y-~ ~1) o wherein Y is a divalent aromatic radical; and (B-ii) from O mol % to about 75 mol % of at least one dianhydride, other than anaromatic bis(ether anhydride), represented by the formula O O " -o)~z)l\o (IV) whein Z is a tetravalent hyd~byl radical; and (C) at least one end-cap monomer selected from the gmup consisting of monoanhydrides, acyl haL~ and _ whein each end-cap monomer (C~ contains at least one CfOSS-lin~bk lor~onal g~oup in the molecule.

The molar ~un~ for dle various monomcrs (A), (B) and (C~ in the mixture are selected so that the ~ultant polyimide oligomer has a numbcr avaage molecular weight of from about 1000 to about lSOOO and, more particularly, from about 3000 to about 10000. The reaction typicdly occurs by mi~ung aU the monomers in a suitabb solvent under an inert ~pl~rc. Hating the mixture incfeases the reacoion rate.

Excess alomatic diamine (A) or dianhydride (B) may be provided, although substantiaUy stoichiometric amounts of such materials m~y also be used (i.e., the equivalence of arnine calculatod tQ equal the equivalence of the total anhydride content). In general, a sufficient amount of the end-cap monomer (C~ is employed so that polyimidc oligomers are obtained which have a crnsslinkable end-cap at each distal end of the oligomer molecule. In one embodiment, a stochiometric excess of (C) is employed to ensure that each oligomer molecule contains two end-caps.

In one embodiment, when the end-cap monomer (C) is a monoanhydride or an acylhalide, the aromatic diamine component (A) generally will be present in a stoichiometric or molar excess relative to the dianhydride component (B) so that the resultant polyimide oligomer molecules will terminate with amine functions that can react with the monoanhydride and/or acylhalide end-cap monomer. In a specific embodiment, the molar ratio of monomers (A):(B):(C) generally is (1):(1-n):(-2.1n), where n is a number of from about 0.03 to about 0.25 and the symbol (~) means +/- 10%. In a more specific embodiment, the molar ratio (A):(B):(C) is from about 1.00:0.75-0.97:0.0~0.50, more particularly, about 1.00:0.840.93:0.140.32 and, most particularly, about l.00:0.80-0.88:0.240.40.

In like manner, in embodiments wherein the end-cap monomer (C) is an amine, the dianhydride component (B) gene~ally will be present in a stoichiometric or molar excess relative to the aromadc diamine component (A) so that the resultant polyimide oligomer molecules will terminate with funcdonal groups capable of reacdng with the amine (C). In a specific embodiment, the molar rado of monomers (A):(B):(C) generally is (l-n):(1):(~2.1n), where n is a number of from about 0.03 to about Q25 and the symbol (~) means +/- 10%. ~ a more specific embodiment, the molar ratio (A):(B):(C) is from about 0.75~0.97:1:00:0.06 0.50, more pardcularly"Ibout 0.840.93:1.00:0.140.32 and, most particularly, about O.80~.88:1.00:0.240.40.
'~':':":"' Those skilled in the art will appreciate that the molar rado and mole % values for the recurring structural units in the polyimide oligomers of the inventdon will correspond generally to the molar amounts for the various monomers (A), (B) and (C) used in the reacdon mixture.

(A) Aromadc diamunes One of the essendal components used in the preparadon of the polyimide oligomers of this invendon is (A) an aromadc diamine component consisdng of (A-i) at least about 25 mob % of at least one phenylindane diamine, and (A-ii) up to about 75 mole % of at least one aromatic diamine, other than a phenylindane diamine.

In one embodiment, the aromadc diarnine component (A) will consist of about 212~781 50-75 mole % (A-i) and about 25-50 mole % (A-ii), more particularly, about 7S mole %
(A-i) and about 25 mole % (A-ii).

In another embodiment, the aromatic diamines (A-ii) will not be present, in which case the aromatic diamine component (A) will contain about 100 moh % of at least one phenylindane diamine (A-i).

In one embodiment, the applicable phenylindane diamines (A-i) correspond to the formula (R5)4 ~ NH2 (Ia) wherein Rl and R2 independently are hydrogen or Cl-Cs alkyl, and each R4 and each Rs independently are hydrogen, halogen (especially chloro, bromo and fluoro), or Cl-C4 aL~yl, and the amino group on the indane ring is at the S or 6 posidon.

The phenylindane diamines (A-i) ean eonsist of any combinadon of the isomerie orsubsdtuted isomerie phenyL~ndane diamine eompounds. For e~cample, the phenylindane diamines (A-i) ean eomprise from O to 100 mob % of 5-amino-1-(4' -aminophenyl~
1,3,3-trimethylindane in eombinadon with from 100 to O pereent of 6-amino-1-(4' -amino-phenyl)-1,3,3-trimethylindane. FuTther, eitha or both of these isomers can be subsdtuted ova the entire range from O to 100 pereent by any of the subsdtuted diamino isomers without impairing the novel soluble natu~ of the polyin~ides. Examples of sueh subsdtu-ted diamino isomers are S-amino-6-methyl-1-(3' -amino-4' -methylphenyl)-1,3,3-tri-methylindane, S-amino-1-(4' -amino-Ar' ,Ar' -dichlo~phenyl)-Ar,Ar-dichloro-1,3,3-trimethylindane, 6-amino-1-(4' -amino-Ar' ,Ar' -dichlor~phenyl~Ar,Ar-dichloro-1,3,3-trimethylindane, 4amino-6-methyl-1-(3' -amino-4' -methyl-phenyl)-1,3,3-tnmethyl-indane and Ar-amino-1-(Ar' -amino-2' ,4' -dimethylphenyl)-1,3,3,4,6-pentamethylindane.
The prefixes Ar and Ar' in the above fonnulae indicate indeSnite posidons for the given subsdtuents in the phenyl rings.

Among the phenylindane diamines (A-i), there can be mendoned those in which Rl and R2 r~

independently are hydrogen or methyl, and each R4 and each R5 independently is hydrogen, methyl, chloro or bromo. In particular, suitable phenylindane diamines are those in which R1 is hyd~gen or methyl, and R4 independently are hydrogen, methyl, chloro or bromo, and the amino groups are at positions 5, 6, or 7 and at positions 3' or 4' .
Because of reladve availability, the phenylindane diamines which are particularly suitable include compounds wherein R1 and R2 are methyl, R4 and Rs are hydrogen, and the amino groups are at positions S or 6 and at position 4' are known as DAPI. DAPI has the structural formula DAPI ~ ~ -'' ' :. ' in which the amino on thc indanc ring is at the S or 6 position.

Thc phenylindanc diamincs and-rncthods for their prcparadon are disclosed in U.S. patents 3,856,752 and 3,983,092, which patcnts are fully incorporatcd by rcfcrcnce hcrcin with respect to thcir disclosurc pertaining to the prcparadon of such materials.

The aromadc diamincs, other than a phenylindane diamine, (A-ii) correspond to the fonnula wherein R is a divalent aromadc radical, more pardcularly, a divalent C6-C24 aromadc radical. It will bc understood that the amino groups of formula II are attached to an aromadc ring; eithcr both amino grDups reside on thc same aromadc ring or cach amino group is attached to a diffcrent aromadc ring in thc moleculc.
In one embodiment, R i8 a divalent aromadc radical selected from thc group consisting of --~'~.

~0~, ~S~

~cH~and ~o~so2~~.

wherein R6, R7 and R8 independently are hydrogen or lower al~yl and, more particularly, hydrogen or al~yl having 1 to 4 a~rbon atoms.

Rcpresentadve exampla of usefid aroma~c diamines (A-ii) include:
para-phenylenediamine, meta-phenyknediamine, 4,4' ~di~diphenylpropane, 4,4' ~iamino-diphenylmethane, benzidine, 4,4' ~iamino~iphenyl sulfide, 4,4' ~i-amino diphcnyl sulfone, 3,3' ~di~diphcnyl sulfone, 4,4' -diamino diphcnyl ether,1,5 diamir~naphth~lcnc, 3,3' -ditncthoxy benzidinc, 2,4bis(bcta-amino-t-butyl)tolucne, bis-(pa~a-bcta-amino-t-butylphcnyl)cthcr,bis-(para-bcta-methyl-delta-amino-pcntyl~
benzcne, bis-(para-l,l~nethyl-S-amino-pentyl)benzene, l-isopropyl-2,4metaphenylene diamine, m-xylene diamine, N,N,N' ,N' -tetramethyl-4,4' -diaminodiphenylmcthane,3,3'~me~ylbenzidino,etc.andmixturesthereo Among the f~regoing compounds, there can be particula~ly mentioned C6-C14 aromatic diamines such as p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether (ODA), 4,4' -diamino diphenyl su1fone, m-xylylenediamine and bis(p aminophenyl) methane.

Those sl~11ed in the art w~ll appreciate that the divalent aromatic radical R will include the divalent residues of any of the aforemendoned diamines after the amino functional groups have bcen removed.

Methods for preparing the aromatic diamines (A-ii) are within the knowledge of the art 212~781 and many suitable aromadc diamines are commercia11y available.

(B) Dianhydrides A further required component for the preparadon of the polyimide oligomers of this invention is (B) a dianhydride component consisdng of (B-i) at least about 25 mole % of at least one aromatic bis(ether anhydride), and (B-ii) up to about 75 mole % of at least one dianhydride, other than aromadc bis(ether anhydr;ide).

In one embodiment, the dianhydride component (B) will consist of about 50-75 mole %
(B-i) and about 25-50 mole % (B-ii), more pardcularly, about 75 mole % (B-i) and about 25 mob % (B-ii).

In anotherembodiment, the dianhydrides (B-ii) will n~t be present, in which case the dianhydride component (B) will contdn about 100 mole % of at least one aromadc bis(ether anhydride) (B-i).

The aromadc bis(ether anhydrides) (B-i) can be prepared by a number of known methods ~ -and many are commercially available. Forexample, the bis(ether anhydrides) (B-i) are preparod by coupling an ~iuc xybne derivadve, such as a 4haloxylene or the alkali metal phenoxide of ~xylenol, with an appropr~te halide or aryloxide, via the Ullman synthesis. This rescdon empbys a coppercatalyst, followed by oxidadon of the arDmadc methyl g oups and dehydradon to effect ring closure as described in U.S. patent 4,480,009 which is incafporated by reference herein for its disclosure pertdning to this reacdon. The reacdon can be schemadcally exemplified as follows: ~~
, ' ':' ~ ' ' ~j ~ NaO--Y--ONa H3C~~Halo I~c ~ -' '' '- '.

,r~
212~78~

~ O--Y--O ~CH3 H3 I KM",04 CH3 ~ la~i~ ~COOH

O O
o~O-Y-O~O (m).
O O
In a onc embodiment, group Y is a divalent aromadc Tadical of the formula CH3 : ~ i ;~wherein X is a divalcnt radical selected from the group consisting of +, CH3 H + ~ F3 -~ ::

CN3 ~ S' --c--;andnisOorl.

~': ', . ' , ' . ., : . ~ , ' ' 2l2~78l ' In a more specif1c embodiment, X is sclected from the group consisdng of +, +, + ,and cl ; andnis l.

Illustra~ive aromatic bis(ether anhydridcs) (B-i) includc 2,2-bist4,4'-di(3,4-dicarboxyphenoxy)phenyl]propane dianhydridc (BPADA), --2,2-bisl4,4'-di(2,3-dicarboxyphenoxy)phenyllpropane dianhydride, 1,1-bist4,4'-di(3,4-dicarboxyphenoxy)phenylhthane dianhydride and 1,3-trifluoro-2,2-bist4,4'-di(3,4-dicarboxyphcnoxy)phenyllpropane dianhydride.

BPADA is particularly suitable and is rcpresented by the structural formula O o -' ~' C ~O~c~_O_[~ ,0 BPADA.

' ~The dianhydrides, other than an aromadc bis(ether anhydride), (B-ii) correspond to the ~ -~
forrnula :~, O O
O~z)~O

, ' ' ;~
wherein Z i8 a tetravalent hydrocarbyl radical.

In one embodiment, Z is a tetrava1ent aromadc radical of, for example, (B-ii.l) substituted or unsubsdtuted phenyl, naphthyl or biphenyl rings; (B-ii.2) two phenyl rings linked by a :

21207~1 direct bond, O, S, SO2, carbonyl or alkylene; or (B-ii.3) aromatic rings containing heterocyclic atoms such as pyrazine or thiophene.
In another embodiment, the dianhydrides (B-ii) correspond to the formulae O O

0~0 (IVa) wherein Rg is hydrogen or lower aLt~yl;
O O

O~ ~XI~ /~ (IVb) O O
.wherein X1 is selected from the group consisting of a direct carbon-to-carbon bond, O, SO2, S and a divalent carbonyl radical (--c--) Swtable dianhydrides (B~ also can be aliphatic in nature, such as cyclopentane tetracarboxylic acid dianhydride, cyclohexane tetracarboxylic acid dianhydride and butane tetracarboxylic acid dianhydride.

Among the useful dianhydrides (B-ii) there can be mentioned:

pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic dianhydride, 2,2',3,3'-diphenyl tetracarboxylic dianhydride, 2,2-bis-(3,4~dicarboxyphenyl) propane dianhydride, .

".~ . , .: .
- :.s~ .
..... . , .. . ~ . .
~ ~ , ~ . , . ! . ' 2,2-bis-(2,3-dicarboxyphenyl) propane dianhydride, bis-(3,4-dicarboxyphenyl) ether dianhydride, bis-(3,4-dicarboxyphenyl) sulfone dianhydride, bis-(3,4-dicarboxyphenyl) sulfide dianhydride, 1,1-bis-(2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis-(3,4-dicarboxyphenyl) ethane diMhydride, bis-(2,3-dicarboxyphenyl) methMe dianhydride, bis-(3,4-dicarboxyphenyl) methane dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1 ,2,4,5-naphthalene tetracarboxylic diMhydride, 1 ,2,5,6-naphthalene tetracarboxylic diMhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, ~:
thiophene-2,3,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, decahydronaphthalene- 1 ,4,5,8-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene- 1 ,4,5,8-tetracarboxylic dianhydride, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, cyclopentane- 1 ,2,3,4-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, 1,2,3,4-butane tetracarboxylic dianhydride, 3,4,3',4'-benzophenone tetracarboxylic dianhydride, azobenzene tetracarboxylic dianhydride, 2,3,4,5-tetrahydrofuran dianhydride, etc., and mixtures thereof.

Among the foregoing dianhydrides, there can be particularly mentioned aromatic dianhydrides (B-ii) including:

pyromel1itic dianhydride, 3,3' ,4,4' -benzophenone tetracarboxylic acid dianhydride, 3,3' ,4,4' -biphenyl tetracarboxylic acid dianhydride, 3,3~ ,4,4' -diphenylsulfone tetracarboxylic dianhydride, and 4,4' -oxydiphthalic dianhydride.

Those skilled in the art will appreciate the tetravalent hydrocarbyl radical Z will include the tetravalent residues of any of the aforementioned dianhydrides after the anhydride functional groups have been removed.

In gencral, the dianhydrides (B-ii) and methods foq their preparation are within the slcill of the art. For example, certain dianhydrides and methods for their preparation are disclosed, for example, in U.S. patents 3,745,149 and 3,856,752 which patents are incorporated by reference herein for their teachings related to such materials.

(C) E~nd-cap monomer A key component of the monomer mixture is an end~ap monomer (C) which is selected from the group consisdng of (C-i) monoanhydrides, (C-ii) acyl halides and (C-iii) aromatic amines, wherein each end-cap monomer (C) contains at least one crosslinkable group in the molecule. In gen~al, the crosslinkable group reacts without evoludon of volatiles, due to imidizadon, during the curing of the polyimide oligomers. Illustrative crosslinkable groups include vinyl, ethynyl, maleimido, cyano, nadic and acetylenic functdons.

In one embodiment, the end-cap monomers (C) contain from about 1 to about 2 crosslinkable groups in the molecule. More panicularly, the monomers (C) will contain 1 crosslinkable functional group.

In one embodiment, the aromadc amines (C-iii) contain from 6 to about 30 carbon atoms. -Illustradve end-cap monomers (C) include, for example, those represented by the following formulae (1) through (9):
o C~C~ (1), N~C~O a).

21207~1 o ~ ~0 --C~NU2 (4) uc_c~ t5), ~NU2 (6), ~ (7). ~C-CI (8) and Rl~o (9);

wherein Rlo is aUyl or methallyl; and Rll is hydrogen or lower allcyl, more parlicularly, wherein Rlo is allyl and Rl, is hydrogen (i.e., allyl nadic anhydride or ANA).

Suitable end-cap monomers (C) are prepared by a variety of hlown methods and many suitable end-capping agents are commercially available. For example, methods forpreparing nadic anhydrides (9) wherein Rlo is allyl or methallyl and Rll is hydrogen are disclosed in U.S. patent 3,105,839 which is ;ncorporated by reference herein for its disclosure related to the preparadon of such materials.

Polyimide Oli~eomcrs The polyimide oligomers of the present invendon can be prepared by any of a number of - - . . - .: : . . : . ~ ~ , . ~ .

212~7~1 methods known in the art including those set forth in Kirk-Othmer, EncYclopedia of Chemical Technology, Vol. 18, ThW ed., pp. 706-710 (1982). In one embodiment, the polyimide oligomers of the present invention are prepared by a solution polymerization process wherein the monomers (A), (B), and (C) are reacted in an organic reaction medium which is a solvent for at least one of the reactants, preferably under substantially anhydrous conditions and under an inert atmosphere. The initial reaction conditions are generally reflux, particularly at a temperature below about 100C and conveniently at room temperature.

Those sldlled in the art will be aware of suitable solvents which include, for example, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidinone and m-cresol.

As noted above, it is usually desirable to follow the conventional procedure of eliminating oxygen from the atmosphere with which the monomeric solutions are in contact while the polymerization reaction is occurring. This can be accomplished by the usual procedure of purging the polymerization vessel with argon, nitrogen or other inert oxygen-free gas and closing the vessel, or foq an open vessel continuing a slow flow of the inert gas through the vessel throughout the reacdon. Any conventional mixing device can be used such as a rotator or propeller to achieve a rapid and complete mixing of the reactants (A), (B) and (C).

The initial product of the reaction is a polyamic acid which contains, inter alia, structural units represented by the formula:

~N--C ~} ~C--N
H O O H

The polyamic acid is subsequently converted to the polyimide by several methods which include (1) heating the polyamic acid solution at temperatures between 100C and 240C
depending on the boiling point of the organic solvent (in this stage an azeotropic solvent, e.g. toluene can be used), until imidization is complete or, (2) by chemical means, e.g. by :;",, , ~

. , . . . :
-. . :
; ' .: . ' . ~ ..... ~ .
.

21207~1 adding to the polyamic acid solution a dehydrating agent such as acetic anhydride alone or in combination with a tertiary amine catalyst such as pyridine or triethylamine, and conveniently at room temperature.

More specifically, the preparation of the polyamic acid which is subsequently converted to the polyirnide oligomers of the present invention can be conveniently carried out in a number of ways. The aromadc diamine(s) (A), dianhydride(s) (B) and end-capping agent(s) (C) can be premixed as dry solids in appropriate molar amounts and the resulting mixture can be added, in small portions and with agitation, to an organic solvent.
Alternately, this order of addidon can be reversed, e.g., after prernixing the diamine(s) (A), the dianhydride(s) (B) and the end-capping agent(s) (C), the solvent may be added to the mixture with agitation. It is also possible to dissolve the diamine(s) (A) in the solvent while agitating and to add slowly the dianhydlide(s) (B) and end-capping agents (C) in portions that provide a controllable rate of reaction. However, this order of addition can also be varied. Still another process involves dissolving the diamine(s) (A) in one portion of a solvent and the dianhydride(s) (B) and end-capping agents (C) in another portion of the same or another solvent and then mixing the two soludons.

In one embodiment, to effect the conversion of the polyarnic acids to the polyimides, the polyamic acids are heated above 50C in an inert atmosphere and, more pardcularly, to between 110 to 240C in an inert atmosphere. In a typical process, the polyamic acids are prepared at a temperature below 50C and maintained at this temperature undl maximum viscosity is obtained, denotdng maximum polymerizatdon. The polyamic acid, in solution and under an inert atmosphere, is subsequently heated to about 100C to 240C to convert the polyamic acid to the polyimide. The polyimide may be alternatively prepared by mixing the diamine(s) (A), dianhydTide(s) (B) and end-capping agent(s) (C) at room temperature in a solvent such as nitrobenzene and then rapidly headng the mixture to reflux for about 2 to 12 hours.
~' The total reacdon time period from monomer mixture to polyimide oligomer is generally within the range of about 2 to about 16 hours and more frequently is approximately 4 to about 8 hours.

The polyimide oligomers are precipitated from their reacdon solutions by use of a nonsol-vent for the oligomer such as methanol, water, or acetone. The polyirnide oligomers are then oven dried, vacuum tumble dried or spray dlied and dle like. The resulting polyimide - . ~ ~.. ..... .

. ; , .

21207~1 oligomers are characterized by superior processability and are readily processed to form solution prepregable polyimide composites having high glass transition temperatures and high temperature and oxidative stability. The polyimide oligomers also can be used as a powder thermoset molding type composition. Other appropriate ingredients can be added to the polyimide oligomer solutions or molding powders including fillers, dyes, pigments, thermal stabilizers, as well as standard reinforcing materials, such as glass fiber, graphite, carbon fibers, chopped glass, chopped carbon fibers, clay, silica, boron and the like, depending on the end use.

Composites are made from the polyimide oligomers of the invention by the following method and exhibit high Tg's and unlike most polyimides are solution prepregable (i.e.
soluble in common solvents). Suitable solvents include, for example, N-methylpyrroli-dinone, dimethylformamide, 1,3-dioxalane, dimethylsulfoxide, a-butyral lactone, diglyme, chloroform, methylene chloride, etc.

In another embodiment, the present invention pertains to polyimide oligomers that comprise:

(A-1) at least about 10 mole % of a recurring moiety represented by-the formula (I.l) _ (R5)4 ] (1.1) wherein R1, R2 and R3 independently are hydrogen or lower alkyl, and each R4 and each Rs independently are hydrogen, halogen or lower alkyl, more particularly, wherein Rl and R2 independently are hydrogen or C1-Cs alkyl, R3 is C1-C4 aLIcyl (e.g., methyl) and each R4 and each Rs independently are hydrogen, halogen (especially chloro, bromo andfluoro), or Cl-C4 alkyl;

(A-2) from 0 to about 40 mole % of a recur~ing moiety represented by the formula (II.1) -[R]
(II.l) . :

... . ~

~', .
:, - ' ' - ~ ' : . -, .. . ..

wherein R is divalent aromatic radical, more particularly, a divalent C6-C24 aromatic radical and, most particularly, R is a divalent aromadc radical selected from the group consisting of ~'~.

~ so2~, ~

and ~o~ so2~0~, wherein R6, R7 and R8 independently are hydrogen or lower aL~yl and, more par~cularly, hydrogen or aL~cyl having 1 to 4 carbon atoms;

(B-1) at least about 10 mole % of a recurring moiety represented by the fonnula (m.l) O O

~N~3--O-Y-O~N (m.l) wherein Y is a divalent aromadc radical and, more specifically, a divalent aromadc radical of the forrnula ~ ~ (IIIa) ,, .
. .

: . :' '- , ~

21207~1 wherein X is a divalent radical selected from the group consisting of +, CH3 +, + . ~ --P-- f C2N5 }33 ~3 ~3 r, [~ ,-p, cl ,-S- zlld --c--; and n is O or 1 and, more specifically, X is selected from the group consisting of CH3 Cl H3 H CP3 + ~ , +, and Ic ; and n is l;
CH3 ~2Hs CP3 (B-2) from O to about 40 mole % of a recurring moiety represented by the formulae aV.l) ~Z N~

O O

whcrein Z is a tetravalent aromatic radical, particularly, a tetravalent aromatic radical of :
substituted or unsubstituted phenyl, naphthyl or biphenyl rings; phenyl rings linked by a direct bond, O, S, SO2, carbonyl or alkylene; or aromatic rings containing heterocyclic atoms such as pyrazine or thiophene; more particularly, (B-2) is from O to about 40 mole % of at least one recu~ing moiety of the formulae (IV.2) - (IV.3) :

: : :, , :: ,, , - . . , ~ .~

O O ~
t t wherein R9 is hydrogen or lower aLkyl;
~ O O ~
tll~x~l~ ~3, O O ::

wherein Xl is selected from the group consis~ng of a direct carbon-to-carbon bond, O, S2~ S and a divalent carbonyl radical (_ c _); and (C-l) at least about 3 mole % of at least one monovalent end-cap moiety selected from N-amides, N-imides and monovalent aromatic radicals having from 6 to about 30 carbon atoms, which end-cap moieties contain at least one crosslinkable functional group.

Those skilled in the art will appreciate that the N-amides and N-irnides (C-1) a~e the monovalent residues of corresponding monoanhydride and acylhalide end-cap monomers (C). The monoanhydride and acylhalide monomer will cap polymer chains that terminate with a reacdve nitrogen funcdon, e.g. monomers (A). Likewise, it will be appreciated that the C6-C30 monovalent aromadc radicals are the residues of 30 corresponding aromatic amine end-cap monomers (C). The aromadc amine end-cap monomers (C) will cap polymer chains that terminate with a reactive anhydride function, e.g. monomer (B).

In one embodiment, the end-cap moiety (C-l) corresponds to at least one monovalent radical represented by the formulae:

. . . . .. , . ~ .
- .; ... .
. ~

.

212~7~1 o C~N-- (la) HC_ C ~ (2a), o ~c-c~ ~c=c~
~JJ ~ ~(3a)~ ~ ~(4a), o ~c 3 (5a), [~3 (6a), ¢~N- (7a) H
338 N (8~), aod It~ (9a) wherein Rlois allyl or methallyl; and Rll is hyd~ogen or lowa aL~yl.
:, . . .
The molar ratio of recu~ing structural units in the polyimide oligomer molecule (A-l)-(A-2):(B-1)-(B-2): (C-1) generally is about (1):(1-n):2n to about (1-n):(1):2n, where n is a number of from about 0.03 to about 0.25.

In a more specific embodiment, the reculTing moiety (A-l) is present in the oligomer in an amount of from 10 to about S0 mole %, m~re preferably, from about 2S to about S0 mole % and, most preferably, from about 40 to about 50 mole %.

In another embodiment of the invention, about 30 to about 40 mole % of the recurring .

:~i 2~207~1 moiety (A-2) is present in the oligomer. More particularly, moiety (A-2) is prescnt in the polyimide oligomer in an amount of from about 20 to about 30 mole % and, most particularly, from 0 to about 10 mole %.

In like manner, it is preferred that the recurring moiety (B-l) is present in the oligomer in an amount of from about 10 to about 50 mole %, more preferably, from about 20 to about 50 mole %, and, most preferably, from about 40 to about 50 le %.

With regard to (B-2), this recurring moiety generally is present in the polyimide oligomer in an amount of from about 30 to about 40 mole %, more particularly, f~om about 20 to about 30 mole %, and, most preferably, from 0 to about 10 le %.

In a specific embodiment, the end-cap moiety (C-2) genera11y is present in the polyimide oligomer in an amount of from about 3 to about 25 mole %. More specifically, the end-cap moiety is present in the range of about S to about lS mole %.

The polyimide oligomers which are prepa~d as described above have a number average molecular wdght (M,~) of from about 1000 to about 15000, more particularly, about 3000 to about 10000.

In one embodiment, the present invention pertains to polyimides oligomers that are obtained from a reaction mixture which is substantially free from monome~ic components other than (A), (B) and (C).

In another embodiment, the present invendon contemplates mixtures of polyimide oligomers having varying degrees of polymerization.

For purposes of this invention, the molecular weight values, both Mn and Mw, are deter-mined by gel permeation chromatography (GPC). This separation method involves column chromatography in which the stationary phase is a rigid, heteropourous, solvent-swollen polymer network (in particle form) of a polystyrene gel (e.g., crosslinked styrene/-divinyl benzene copolymers) varying in permeability over many orders of magnitude. The liquid or "mobile" phase is a solvent containing the sample polymer. As the sample passes through the gel, the polymer molecules diffuse into all palts of the gel not mechanically barred to them. The smaller molecules "permeate" more completely and spend more time in the column; the larger molecules "permeate" less and pass through the column more . ' '' ~ ' . ~ ' '' ' ~ , rapidly.

The Mn and Mw values of the polyimide oligomers of the present invention can be obtained by one of ordinary skill in the art by comparing the GPC distribution data obtained for the polyimide oligomers to a series of GPC calibration standards of polymers having a known molecular weight distribution. For example, polystyrene standards of varying molecular weights are used and N-methylpyrrolidinone treated with P205 is used as the mobile phase. This bile phase may be obtained by the method described in S. H.
Kim et al, Journal of Polym. Sci. Part B: Polymer Physics, Vol. 29, 109-117 (1991). For example, the mobile phase is prepared æ follows:
3 liters of N-methylpyrrolidone are poured into each of three 4 liter erlenmeyer flæks.
Approximately 10 g of P205 is added to each of the flæks along with a magnetic stir bar.
The solutions are stirred for a minimum of 12 hours. The solutions are then filtered into a 20 liter round bottom ~lask. The combined solution is then agitated via a magnedc stir bar for a minimum of 2 hours to make the soludon homogeneous. The resultant P2Os treated NMP soludon is filtered through a 0.5 ,~lm filter before use.

The GPC sample preparation consists of, inter alia, dissolving 20-30 mg of the polyimide oligomer sample in P20s treated NMP and then filtering the solution through a 0.45 ~,Im polytetrafluoroethylene filter in to a GPC sample vial. GPC columns are used which have retention volumes of 105, 104, 103 and 500 A, respectively, and a 10 ~m particle size. The mobile phæe flow rate is 0.8 mVmin and the detector advantageously is a Waters Associates RI detector.

The polyinude oligomers of the present invendon can be prepregged by numerous techniques well-known to those skilled in the art. For example, one such procedure is to prepare prepregs from unsized AS-4 carbon fibers and polyimide/NMP soludons withviscqsides ranging from 2000 to 10000 mPa-s, using a drum winder. The prepregs are allowed to dry on the drum and then stored in plasdc bags at room temperature. Under this procedure, residual solvent contents are typically in the range of 10 to 20% by weight and the thickness of the prepregs is approximately 0.56 mm. In general, some prepregs are tacky, while others are dry due to precipitation of the polyimide oligomer.

Alternadvely, a treater line can be employed using sized fiber and various organic solvents, alone or in combinadon, such as diglyme, dimethylformamide, N-methylpyrroli-done, methylethyLketone, dioxalane and the like with a resin content ranging from about :.; . . .. ... ,: ~ , : - , 2~207~

35 to 42% by weight and residual solvents of about 20 to 35% by weight.

The prepregged polyimide oligomers of the present invention can be processed into composite laminates by numerous techniques well-known to those skilled in the art. Por example, the prepregs are laid up, vacuum bagged and compression Ided into unidirectional laminates based on the following schedule:

1. Cure: a press is heated from room temperature to about 290-295C with 30 inch vacuum applied when the temperature reaches about 270-290C, and held for 2 hours .

2. Post-cure: the press is gradually heated up to about 316C and 6.9 kPa (200 psi) pressure is applied when the temperature reaches 280C.

3. After about 16 hours at about 316C, the press is cooled slowly (1.5C/min) to about 65C and the laminate is demolded.

The resin content of the resultant laminate is obtained, for example, according to the ASTM-D3171 method.

In order that those sldlled in the art will be better able to practice the invention, the following examples are given by way of illustration and not by way of limitation. In the following examples, as well as elsewhere in the specification and claims, temperatures are in degrees Celsius, the pressure is atmospheric and all parts are by weight, unless odlerwise clearly indicated.

212~781 Example A: Svnthesis of Dinadicimidobenzoic acid 2 ~ I ~C--OH ~ ~C--OH

C25H2(jN206 444Al In a 6 liter sulfonadon flask, equipped with s~rer, condenser and thermometer, 2800 ml acetic acid 100% (glacia1) and 393.9 g of nadicanhydride (2.40 mole) are placed under nitrogen. While sdning, 182.6 g of 3,5-diaminobenzoic acid (1.20 mole) is added and the reacdon mixture is heated to reflux (113C). The now daTlc soludon is sdrred at reflux for 6 hours and then cooled to 100C. A portion of charcoal is adsled and the mixture is sti~red for 15 minutes. The hot soludon is then filtered through a preheated-buchner-funnel. Su~
sequently, the mixture is coobd, under s~ing, to room temperature (at 80C a precipitate -crystallizes). The white precipitate is filtered off, washed twice with 200 ml of acetic acid and then with approximately 31 of water (about neut~al). The product is dried under vacuum at 80-90C overnight.

Yield: 440 g (82%) Calc. Found C: 67.56% 67.40%
H: 4.54% 4.45%
N: 6.30% 6.28%
Fp: 238C

f~

212~7~1 Example B: Svnthesis of Dinadicimidobenzoic acid chloride (DNBCI

~ C--OH ~_ ~3C CI

C25Hl9N20 0 462.89 In a 2.5 Iiter sulfonation flask, equipped with sdrrer, thermometer, condenser (cooled with ice-water), and gas absoIpdon ~ap, is placed 1350 ml methylene chloride, 333.3 gdinadicimidobenzoic acid (0.75 mole) and 11.0 g N,N-dimethylformamide. The mixture is heated to reflux with stirring. Over a period of 3 hours, 111.5 g of distilled thionyl chloride (0.938 mole, theory + 25%) is added from a dropping funnel under the surface of dle reacdon mixture. The mixture is sdrred for an addidonal 10-12 hours until no further HCVSO2 is evolved. Then, dle slighdy brownish soludon is t~ansferred into a 2.5 liter round bottom flask and the soludon is concentrated on a rotary evaporator to approximate-ly 600 ml. Subscquendy, dle concentrated soludon is added, under sdning, to 2500 rnl of cyclohexane and dhe combined solution is sdrred for 15 minutes. DNBC is recovered as a white precipitate, is filte~d, washed with 300 ml of cyclohexane and dried in a vacuum oven at 40-50C overnight.

Yield: 346 g (100%) Calc. Found C: 64.87% 64.83 H: 4.14% 4.20 N: 6.05% 6.11 Cl: 7.66% 7.45 Example 1 Synthesis of a 5000 MW D~BPADA/ANA Polyimide Oligomer (5/6~amino-1-(4' -aminophenyl~1,3,3-trimethylindane (DAPI), 39.96 g (0.1500 mole), 9.450 g (0.04630 mole) of allylnadic anhydride (ANA), and 300 ml of N-methylpyrrolidi-none (NMP) is charged into a one liter flask. The solution is stilred under ni~ogen at room ~: . ~ - . . .:

.

c .

21207~3~

temperature (25C) for five hours. To the stirring solution is added 65.88 g (0.1266 mole) of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 150 ml of NMP. The solution is then stirred overnight (12-15 hours) at ambient temperature. The polyamic-acid is then imidized chemically over a six hour period, while stirring, by adding 67.40 g (0.660 mole) of acetic anhydride and 33.39 g (0.3300 mole) of triethylamine. The product is then precipitated by pouring the solution into methanol and the resulting precipitate collected via vacuum filtration. The polyimide is then soaked in methanol followed by a hot water (70C) soak overnight. The polyimide is then dried in an air circulating oven overnight and afterwards in a vacuum oven at 150C. The polyimide has an intlinsic viscosity of 0.17 and molecular weights (GPC using polystyrene standards):
MW=12533, Ms,=5129, MW/M"=2.44; Tg=256C via DSC. The molar ratios are 1: 0.84:
0.31 DAPVBPADA/ANA.

Example 2 Synthesis of a 5000 MW DAPI/13PADA/DNBC PolYimide Oli omer Into a reacdon vessel is placed 106.98 g (0.4016 mole) of DAPI, 175.28 g (0.3368 mole) of BPADA, and 1.25 liters of NMP. The soludon is stirred at ambient temperature, under a stream of nitrogen, for 1.5 hours. To the soludon is added 87 g of toluene. The reaction mixture is then azeotropically refluxed to 155C, collecdng the water in a Dean ~L Stark trap. The reacdon mixture is cooled down after the theoredcal amount of water isremoved. Upon reaching room temperature 13.70 g (0.1354 mole) of triethyl amine and 63.8 g (0.1379 mole) of 3,5-Dinadic benzoyl chloride (DNBC) from Example B are added to the reacdon, and the reacdon mixture is stirred for 4 hours. The work-up and isoladon is done as shown in example 1. The corresponding polyimide oligomer has an in~insicviscosity of 0.18 and molecular weights (GPC using polystyrene standards): MW=12077, M"=6235, M~ ,=1.93; Tg=254C. The molar rados are 1.0: 0.84: 0.34 DAPVBPADA/DNBC.

Example 3 Svnthesis of a 10000 MW DAPVBPADA/DNBC Polvimide Oli~omer The same procedure is used as is shown in example 2 except for the amounts of matenals used (i.e. molar ratios). 206.05 g (0.3959 mole) of BPADA, 111.88 g (0.4200 mole) of .:. : ' : -;~ ' , : . :

212~7~1 DAPI, 24.00 g (0.0518 mole) of DNBC, 5.770 g (0.0569 mole) of triethylamine, and 1.5 liters of NMP are employed. The corresponding polyimide has an intrinsic viscosity of 0.27 and molecular weights (GPC using polystyrene standards): MW--22053, M"=10638, MW~M"=2.07; Tg=234C. The molar ratios are 1.0: 0.94: 0.12 DAPVBPADA/DNBC.

Examples 4-7 Following procedures similar to those outlined in examples 1-3, polyimide oligomers are prepared from BPADA, DAPI and the end-capping monomers shown in Table I

Table I

Example End~ap monomer 4 a~cl o IlC-C~O

6 0-c-c~

O

7 ¢ ~jo o ..

; .. .
''.` . ' ' :' , ;' ~ ' : ` ' - ', '`
;., ,' ' ' ' , :., ' ~ ' - , , Examples 8-10 Following procedures similar to those outlined in examples 1-3, with the exception that the molar ratio of DAPI and BPADA are reversed, polyimide oligomers are prepared from BPADA, DAPI and the end-capping monomers shown in Table II

Tab1e II

Example End-cap monomer 8 ~c_c~3 g HC_C~

[ ~NH2 Example 11 Svnthesis of a 5000 MW DAPJUBPADA/BTDA/DNBC Polvimide Oli~omer Into a reaction vessel is placed 186.459 g (0.7000 mole) of DAPI, 159.606 g (0.30667 mole) of BPADA, 98.813 g (0.30667 mole) of 3,3' ,4,4' -benzophenone tetracarboxylic acid dianhydride (BTDA) and 1.30 liters of NMP. The solution is stir ed at ambient temperature, under a stream of nitrogen, for 1.5 hours. To the solotion is added 100 ml of toluene. The reactdon mixture is then azeotropically refluxed to 155C, collecting the water in a Dean ~c Stark trap. The reacdon mixture is cooled down after the theoredcal amount of wata is removed. Upon reaching room temperature 96.676 g (0.9554 mole) of triethyl amine and 84.2 g (0.18207 mole) of 3,5-Dinadic benzoyl chloride (I)NBC) are added to the reaction, and the reaction mixture is stirred for 4 hours. The work-up and isoladon is done as shown in cxample 1. The corresponding polyimide oligomer hasmolecular weights (GPC using polystyrene standards)~ ,=17583, Ml~=7792, f~
212078~

M~/M"=2.26; Tg=296C.

Exarnples 12-17 Polyimide oligomers are prepared by repeating the synthesis of example 11 wherein 25 mole % of the aromatic amine DAPI is replaced with the aromatic diamines shown in Table m:

Table m Example Aromatic diamine 12 p-phenylenediamine, 13 m-phenylenediamine, 14 4,4'-diaminodiphenyl ether (ODA), 4,4' -diamino-diphenyl sulfone, 16 m-xylylenediamine, 17 bis(p-aminophenyl) methanc.

ExamPles 18-21 Polyimide oligomers are prepared by repeating the synthesis of example 11 wherein BTDA is replaced with the dianhydTides shown in Table IV:

Table IV

ExamPlc Dianhydride 18 pyromellitic dianhydride, 19 3,3' ,4,4' -biphenyl tetracarboxylic acid dianhydride, -3,3' ,4,4' diphenylsulfone tetracarb~xylic acid dianhydride, 21 4,4' -oxydiphthalic dianhydride.

, ... , . . - , - . . , . . . ,: . , -Example 22-25 Following procedures similar to those outlined in example 11, polyimide oligomers are prepared from DAPI, BPADA, BTDA, and the end-capping monomers shown in Table V:

Table V

Example End-cap monomer 22 ~c~

23 uc~c~o 24 ~c_c~O

~5 ~o Exam~les 2~28 Following procedures similar to those outlined in example 11, with the exception that the molar ratio of DAPI and the dianhydride component (BPADA/BTDA) are reversed, :-polyimide oligomers are prepared from DAPI, BPADA, BTDA and the end-capping : : .
. monomers shown in Table VI: ~

- , ~ . - -. -21207~1 Table VI
Example End-cap monomer 26 ~c_c~3 27 HC--C ~12 .

28 C~3NH2 Example 29 Composites are made from the polyimide o~igomers of the invention by the following - ~ -method:

Either N-methylpyrolidinone, 1,3~ioxolane or CH2Cl2 (180 g) is added to a polyimide oligomer (120 g) of the foregoing examples. The polyimide oligomer is stirred until fully dissolved. The resulting soludon is drum wound onto Carbon Fiber (AS4, unsized) to give a prepreg with 40% w/w resin content. The prepreg is cur~d using the cure cycle shown below:

1. Cure: a press is heated from room temperature to aboul 290-295C with 30 inch vacuum applied when the temperature reaches about 270-290C, and held for 2 hours .

2. Post~ure: the press is gradually heated up to about 316C and 6.9 kPa (200 psi) pressure is applied when the temperature reaches 280C.

3. After about 16 hours at about 316C, the press is cooled slowly (1.5C/min) to about 65C and the laminate is demolded.

212~7~1 - 36~

The resin content of the resuleant laminate is obtained according to the ASTM-D3 171 method.

As mentioned above, the major advantage of the polyimide oligomers of the present invention is that they are solution prepregable (i.e. soluble in common solvents). It also has been observed that the composites made from the polyimide oligomers of the invention exhibit high Tg's as well as high temperature and oxidative stability.
While the invention has been explained in relation to its preferred embodiments, it is to be understood that various modifications thereof will become apparent to those sldlled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims.

,' . `, , :

Claims

1. A polyimide oligomer comprising the condensation product of at least one phenylindane diamine and at least one aromatic bis(ether anhydride).

2. A polyimide oligomer comprising the condensation product of (A) an aromatic diamine component comprising at least about 25 mole % of at least one phenylindane diamine;
(B) a dianhydride component comprising at least about 25 mole % of at least one aromatic bis(ether anhydride); and (C) at least one end-cap monomer selected from the group consisting of monoanhydrides, acyl halides and aromatic amines, wherein each end-cap monomer contains at least one crosslinkable functional group in the molecule.

3. A polyimide oligomer according to claim 2, wherein the aromatic diamine component (A) is selected from:

(A-i) from about 25 to about 100 mole % of at least one phenylindane diamine represented by the formula (I) wherein R1, R2 and R3 independendy are hydrogen or lower aLkyl, and each R4 and each R5 independently are hydrogen, halogen or lower alkyl; and (A-ii) from 0 to about 75 mole % of at least one aromatic diamine, other than a phenylindane diamine, represented by the formula H2N-R-NH2 (II) wherein R is a divalent aromatic radical.

4. A polyimide oligomer according to claim 2, wherein the dianhydride component (B) is selected from:

(B-i) from about 25 to about 100 mole % of at least one aromatic bis(ether anhydride) represented by the formula (III) wherein Y is a divalent aromatic radical; and (B-ii) from 0 to about 75 mol % of at least one dianhydride, other than an aromatic bis(ether anhydride), represented by the formula (IV) wherein Z is a tetravalent hydrocarbyl radical.

5. A polyimide oligomer according to claim 3, wherein the phenylindane diamines (A-i) are represented by the formula (Ia) wherein R1 and R2 independently are hydrogen or C1-C5 alkyl, and each R4 and each R5 independently are hydrogen, halogen or C1-C4 alkyl.

6. A polyimide oligomer according to claim 5, wherein the phenylindane diamines (A-i) are represented by the formula in which the amino on the indane ring is at the 5 or 6 position.

7. A polyimide oligomer according to claim 3, wherein (A-ii) is an aromatic diamine of formula II and R is a divalent aromatic radical selected from the group consisting of , , , , and , wherein R6, R7 and R8 independently are hydrogen or lower alkyl.

8. A polyimide oligomer according to claim 7, wherein (A-ii) is an aromatic diamine selected from the group consisting of p-phenylenediamine, m-phenylenediamine, 4,4'-di-aminodiphenyl ether, 4,4' -diamino-diphenyl sulfone, m-xylylenediamine and bis(p-aminophenyl) methane.

9. A polyimide oligomer according to claim 4, wherein (B-i) is an aromatic bis(ether anhydride) of formula III and group Y is a divalent aromatic radical represented by the formula (IIIa) wherein X is a divalent radical selected from the group consisting of , ,,,, -O-, -SO2-, , -P-, , -S-, and ; and n is 0 or 1.

10. A polyimide oligomer according to claim 9, wherein X is selected from the group consisting of , -, and ; and n is 1.

11. A polyimide oligomer according to claim 10, wherein (B-i) is an aromatic bis(ether anhydride) represented by the formula .

12. A polyimide oligomer according to claim 4, wherein the dianhydrides (B-ii) arc selected from a compound represented by the formulae (IVa) wherein R9 is hydrogen or lower alkyl; or (IVb) wherein X1 is selected from the group consisting of a direct carbon-to-carbon bond, O, SO2, S, and a divalent carbonyl radical ().

13. A polyimide oligomer according to claim 12, wherein the dianhydrides (B-ii) are selected from the group consisting of pyromellitic dianhydride, 3,3' ,4,4' -benzophenone tetracarboxylic acid dianhydride, 3,3 ' ,4,4' -biphenyl tetracarboxylic acid dianhydride, 3,3' ,4,4' -diphenylsulfone tetracarboxylic dianhydlide, and 4,4' -oxydiphthalicdianhydride.

14. A polyimidc oligomer according to claim 2, whercin (C) is at least one end-cap monomer selected from the group consisting of monoanhydrides, acyl halides and amines, wherein each end-cap monomer (C) contains at least one crosslinkable group in the molecule selected from the group consisdng of vinyl, ethynyl, maleimido, cyano, nadic and acetylenic functions.

15. A polyimide oligomer according to claim 2, wherein (C) is at least one end-cap monomer selected from the group consisting of a compound represented by the following formulae (1) through (9):

(1), (2), (3), (4), (5), (6), (7), (8), and (9);

wherein R10 is allyl or methallyl; and R11 is hydrogen or lower alkyl.

16. A polyimide oligomer according to claim 2, which has a number average molecular weight of from about 1000 to about 15000.

17. A polyimide oligomer according to claim 16, which has a number average molecular weight of from about 3000 to about 10000.

18. A polyimide oligomer according to claim 2, wherein the molar ratio (A):(B):(C) is (1):(1-n):(~2.1n), wherein n is a number from about 0.03 to about 0.25 and the symbol (-) means +/- 10%.

19. A polyimide oligomer according to claim 2, wherein the molar ratio (A):(B):(C) is (1-n):(1):(~2.1n), wherein n is a number from about 0.03 to about 0.25 and the symbol (~) means +/- 10%.

20. A polyimide oligomer which comprises:
(A-1) at least about 10 mole % of a recurring moiety represented by the formula (I.1) (I.1) wherein R1, R2 and R3 independently are hydrogen or lower alkyl, and each R4 and each R5 independently are hydrogen, halogen or lower alkyl;

(A-2) from 0 to about 40 mole % of a recurring moiety represented by the formula (II.1) -[R]- (II.1) wherein R is divalent aromatic radical;

(B-1) at least about 10 mole % of a recurring moiety represented by the formula (III.1) (III.1) wherein Y is a divalent aromatic radical;

(B-2) from 0 to about 40 mole % of a recurring moiety represented by the formulae (IV.1) (IV.1) wherein Z is a tetravalent aromatic radical; and (C-1) at least about 3 mole % of at least one monovalent end-cap moiety selected from N-amides, N-imides and monovalent aromatic radicals having from 6 to about 30 carbon atoms, which end-cap moieties contain at least one crosslinkable functional group.

21. A polyimide oligomer according to claim 20, wherein R is divalent aromatic radical selected from the group consisting of , , , , and , wherein R6, R7 and R8 independently are hydrogen or lower alkyl.

22. A polyimide oligomer according to claim 20, wherein Y is a divalent aromatic radical represented by the formula (IIIa) wherein X is a divalent radical selected from the group consisting of , ,,,, -O-, -SO2-, , -P-, , -S- and ; and n is 0 or 1.

23. A polyimide oligomer according to claim 20, wherein (B-2) is from 0 to about 40 mole % of at least one recurring moiety represented by the formulae (IV.2) - (IV.3) (IV.2) wherein R9 is hydrogen or lower alkyl;
(IV.3) wherein X1 is selected from the group consisting of a direct carbon-to-carbon bond, O, SO2, S and a divalent carbonyl radical ().

24. A polyimide oligomer according to claim 20, wherein the molar ratio of recurring structural units (A-1)-(A-2):(B-1)-(B-2):(C-1) is about (1):(1-n):2n to about (1-n):(1):(2n), where n is a number of from about 0.3 to about 0.25.

25. A thermoset molding powder composition comprising a polyimide oligomer according to claim 20.

26. A prepreg comprising a reinforcing fiber, and a matrix resin comprising a polyimide oligomer according to claim 20.

27. A composite structure comprising a reinforcing fiber, and a matrix material comprising a crosslinked polyimide oligomer according to claim 20.