NZ258488A

NZ258488A - Preparation of bisnadimides (n,n'-bis(aryl)aryl diimides) from an n,n'-bis (aminoaryl)aryldiimide and nadic acid; curable compositions and fibre reinforced cured composites

Info

Publication number: NZ258488A
Application number: NZ258488A
Authority: NZ
Inventors: Jonathan Howard Hodgkin; Mervyn Benjamin Jackson; Trevor Charles Morton
Original assignee: Commw Scient Ind Res Org
Priority date: 1992-12-07
Filing date: 1993-12-07
Publication date: 1997-02-24
Also published as: CA2150566A1; EP0672044A4; AU5619094A; JPH08504196A; EP0672044A1; WO1994013669A1

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number £58488 New Zealand No. 258488 International No. PCT/AT93/00622 Pi 10! ity Date{s): Complete Specification Filed: Class: (6) Gctf.DW-8 7..[04..; C08 G 7 3.11.9.;.. Xo.to fj\} "3 J. .«+}.? j„. 3>OVP. ® .1 \ Publication Date:.... .2..4..f£fl 1997... i f'.O. Journal No: ;,*\v .7*7 « ? " r<-*. * ^ NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention: Bisnadimides Name, address and nationality of applicant(s) as in international SSh SCIENTIFIC & INDUSTRIAL RESEARCH ORGANISATION, of Limestone Avenue, Campbell, ACT 2601, Australia WO 94/13669 PCT/AU93/00622 - 1 - 258 4 B ® BISNADIMIDES 5 The invention is concerned with bisnadimides and polymers, particularly 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 15 anhydride and aromatic dianhydride based esters. These mixtures were reported to react at intermediate temperatures to give nadimide capped oligomers of Formula (I) as shown below. 10 O 20 0 25 t 30 0 O O O Y r 0 O O o Formula (I) WO 94/13669 PCT/AU93/00622 258 48 8 At higher cure temperatures, these oligomers melt and crosslink to form a continuous stable matrix in advanced composite structures. Recent work (J.N. Hay, JX). Boyle, P.G. James, J.R. Walton, and D. Wilson, "Polymerisation Mechanisms in PMR 15 Polyimide,", in Pctyimides: Materials, Chemistry and Characterization, C. 5 Feger, MAI. Khojasteh, and J£. 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. 10 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 15 higher molecular weight or fluorinated monomers in the initial resin mixtures and hence improve molecular mobility and process ability. The difficult challenge however is to prepare relatively homogeneous materials without increasing material costs greatly. 20 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 "DAB Is") of well defined structure and substantially free of oligomeric, amidic and uncyclized impurities. These aromatic diamines have also been found 25 to be non-toxic and stable. International Patent Publication No. WO 92/06078 also discloses the use of DAB Is 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 and 30 5<n<150. These polyimides are stated to be soluble and useful as tougheners in • crosslinked resin systems. 253488 -3- We have now found that DABIs produced by the process disclosed in International Patent Publication No. WO 92/06078 can be used to make bisnadimides which crosslink on heating to give thermally stable polyimide resins having superior properties. 10 15 20 25 30 According to one aspect of the present invention there is provided a method for the preparation of a bisnadimide of Formula (II) substantially free of oligomeric, amidic and uncyclized impurities O 0 0 -Ar'—N' Ar N- V V O O •Ar'—N ) m Formula (II) wherein Ar is an optionally substituted aryi, optionally substituted bridged or bonded di- or poly aryi or optionally substituted heteroaryl group; Ar' is an optionally substituted aryi or heteroaryl group which provides for good conjugation between the nitrogen containing groups; each X is independently selected from hydrogen, or an alkyl g| m is 0 to 6 which comprises reacting a diaminobisimide of the Formula (DI) 0 II c. H,N Af1 -N / 0 II .c \ Ar c- !l .0 •c II 0 \ / N—Ar'-NHj Formula (III) 258488 -4- wherein Ar and Ar' are as defined in Formula (II) above with nadic acid or a reactive derivative thereof which is optionally substituted with or an alkyl group. As used herein the term "good conjugation" means that during formation of 5 the diaminobisimide precursor from a diamine of Formula (IV) shown beiow, substitution of an electron-withdrawing group on one of the nitrogen atoms suppresses the reactivity of the other nitrogen atom during the reaction. 10 H2N-Ar/-NH2 Formula (IV) 15 Preferably the aromatic diamine of the Formula (IV) is sterically hindered, such as in compounds of Formulae (V) and (VI) R3 20 25 30 Formula (V) R4 NH* Formula (VI) wherein R^, R^, R^ and are the same or different and each may be selected from alkyl, aryi, heteroaryl, nitro and halogen groups. 94/13669 PCT/AU93/00622 -5- Ar or Ar' may be substituted with one or more alkyl, alkoxy, alkylthio, aryi, heteroaryl, aryloxy, carboxy, alkylthio, alkylamino, dialkylamino, amino, nitro, cyano or halo groups. 5 "Aryi" means an aromatic carbocyiic group, such as phenyl, naphthyl, and the like. "Bridged or bonded di- or poly aryi" means a group consisting of two or more aromatic carbaxylic ring systems, such as phenyl, naphthyl or the like joined by a 10 bond, such as in biphenyl, or a bridging group, such as in sulphonyldiphenyl. "Bridging group" includes for example SO2, CO, CH2 and O such as in compounds of the Formula (Vila) 15 Formula (Vila) 20 wherein is a divalent group such as -SO2-, -CO-, -CH^r and -O-. Generally the group Ar' may be selected from the groups listed above for Ar. However, because of the constraints imposed by the requirement of "good conjugation11 (as defined above) some bridged di- or poly aryi groups may not be 25 suitable. Thus for Ar', the bridging group (if present) must provide good conjugation between the amino groups of the diamine moiety (IV). For example in groups of the Formula (VHb) H2N ^NH2 30 Formula (VHb) WO 94/13669 PCT/AU93/00622 -6- wherein R* is CH2 or ^ere diamine is 3,3 '^ulphonyldianiline, there is insufficient conjugation and oligomeric diaminoimides are present in the precursor diaminobisimides. In contrast, benzidine and 4,4 '-sulphonyldianilines have sufficient 5 conjugation and give the desired predominantly monomeric diaminobisimide compound and hence a substantially monomelic bisnadimide. "Heteroaryl" means aromatic monocyclic or polycyclic groups containing at least one heteroatom such as nitrogen, oxygen or sulfur. Examples of suitable 10 "heteroaryl" groups are: 3- to 8- membered, more preferably 5- or 6- membered heteromonocyclic groups containing 1 to 4 nitrogen atom(s), for example, pyrrol)!, imidazolyi, pyrazolyi, pyridyl, pyrimidyl, pyrazinyl, pyridazrnyl, triazinyl; condensed heterocyclic groups containing 1 to 5 nitrogen atom(s), for example, indolyl, isoindolyl, indolizinyi, benzimidazolyl, quinolyl, isoquinolyi, indazolyl, benzotriazolyl, 15 etc.; 3- to 8- membered heteromonocyclic groups containing 1 or 2 sulfur atom(s) and 1 to 3 nitrogen atom(s), for example, thiazolyi, isothiazolyi, thiadiazolyi, etc.; 3-to 8- membered heteromonocyclic groups containing 1 to 2 sulfur atom(s), for example thienyl, eta; condensed heterocyclic groups containing 1 to 2 sulfur atom(s) and 1 to 3 nitrogen atom(s), for example, benzothiazolyi; benzothiadiazolyi, etc.; 3 20 to 8- membered heteromonocyclic groups containing an oxygen atom, for example, furyl, etc.; condensed heterocyclic groups containing 1 to 2 sulfur atom(s), for example, benzo thienyl, etc.; and condensed heterocyclic groups containing 1 or 2 oxygen atom(s), for example, benzofuranyl, etc. 25 The alkyl group may be straight chain or branched and contain 1 to 20 carbon atoms. Suitable alkyl groups are methyl, ethyl, propyl, iso-propyl, /rbutyl, iso-butyl, tert-butyl, n-pentyl, iyo-pentyl, neo-pentyl, msctyl, fro-octyl, decyl, cetyl, stearyl, and the like. 30 "Alkoxy" and "alkylthio" mean groups in which the alkyrl moiety is a branched or unbranched saturated hydrocarbon group containing from one to eight carbon WO 94/13669 PCT/AU93/00622 -7- atoms, such as methyl, ethyl, propyl, iso-propyl, /rbutyl, iso-butyl, tert-butyl and the like. 5 "Alkanoyl" may be formyl, acetyl, propionyi, butyryl, valeryl, frovaleryl, pivaloyl, hexanoyl, and the like. Preferably, the diaminobisimide of the Formula (III) is produced by the process disclosed in International Patent Publication No. WO 92/06078 as such a 10 compound is substantially free of oligomeric, amidic and uncyclized impurities. However, it will be appreciated that the diaminobisimide of the Formula (III) used in the method of the invention may be produced by any suitable known process. The reaction is preferably carried out using nadic anhydride or an alkyl-15 substituted nadic anhydride in the molten state as the solventThe reaction may also be performed in the presence of a solvent such as an organic solvent, for example, dimethyl form amide, dimethyiacetamide or xylene. If a solvent is used, because pure cyclized bisnadimides are formed and can be separated from the solvent as solids, unlike the case in standard PMR type resins, the products can be cured into final 20 resins and composites without the porosity problems caused by strongly bound solvents. Preferably the reaction is performed at elevated temperatures, such as, for example, above about 120 *C. The method of the invention allows very high yields 25 of substantially pure bisnadimides, even with very insoluble DABIs, to be prepared. Excess optionally substituted nadic anhydride may be removed from the final product by washing with a suitable solvent, such as, for example, ethanol or hot water. The bisnadimides of Formula (13) are also novel and form another aspect of 30 the present invention. WO 94/13669 PCT/AU93/0Q622 -8- The invention also provides bisnadimides of Formula (II) -whenever prepared by a method as defined above. The bisnadimides of the invention, which are substantially free of oligomeric, S amidic and uncyclized impurities, may be used in a curable formulation to produce impregnated fibre reinforced materials and to form crosslinked polyimide polymers which can be used in advanced composite materials. By utilising the present invention, the PMR composition containing a toxic, 10 reactive diamine of conventional practice is replaced by a safe, stable bisnadimide which can be readily handled during composite fabrication. Furthermore, on a weight of resin basis, much lower quantities of volatile cydization products are evolved during the curing step as at least half the groups are already cyclized. IS The bisnadimides of the invention can be reacted with or -without curing agents to form crosslinked polyimide polymers which are useful for a variety of applications including adhesives, bars, films, electronic encapsulation, moulded components and composites. On curing at elevated temperatures, the bisnadimides of Formula (II) may be converted into crosslinked polyimide polymers having 20 improved properties. Thus, the invention further provides a curable formulation which comprises a bisnadimide of the Formula (II) as defined above. 25 The bisnadimides of the invention are particularly useful in the manufacture of fibre reinforced composite materials. For example, curable formulations containing the bisnadimides of the invention maybe applied to reinforcing cloth such as uni-directional or woven carbon fibre either from solution (preferably a lower aliphatic ketone or halogenated hydrocarbon solvent) or from a hot melt. 30 Application may be performed manually or by machine and includes techniques involving transfer from a precoated transfer medium. WO 94/13669 FCT/AU93/00622 -9 - Therefore, the present invention also provides an impregnated fibre reinforced material (commonly known as a "prepreg") -wherein the fibre reinforcements are coated with a curable formulation as defined above. 5 Thus, according to another aspect of the present invention there is provided a crosslinked polyimide polymer which is formed from a bisnadimide monomer of Formula (II) as defined above. 10 According to a further aspect of the present invention there is provided a method for the preparation of the crosslinked polyimide polymer defined above which comprises heating a bisnadimide of Formula (II) as defined above. The bisnadimides are preferably heated to temperatures above about 250 °C. 15 The heating may occur under pressure. While the prior art describes very few co-react ants for curing PMR type resins, it has been found that trans-stilbene is a particularly good curing additive for the bisnadimides of the invention. Such additives provide cyclizable and 20 aromatizable double bond compounds which are capable of reacting -with reactive groups liberated by the bisnadimide type cure. Another additive particularly useful • in the production of void-free resin bars from the bisnadimides of the invention is the addition of a small percentage of hydroquinone or other additives to prevent "skinning" and hence entrapment of residual volatiles during the early stages of cure. 25 The impregnated fibre reinforced material defined above are also suitable for use in the production of advanced composite materials. The impregnated fibre materials may be laid down by any suitable known method for making composite materials, such as, for example, vacuum bagging on a caul plate or an appropriate 30 tool. WO 94/13669 PCT/AU93/00622 - 10 - Accordingly, the present invention also provides an advanced composite material which comprises an assembly of reinforcing fibres in a matrix of a crosslinked polyimide polymer as defined above. 5 Alternatively, the bisnadimides of the invention can be used in an appropriate resin formulation for resin transfer moulding or for the manufacture of sheet moulded material. Another envisaged application is in pultrusion. The invention is illustrated by the following Examples. These Examples are 10 not to be construed as limiting the invention in any way. The systematic names used in the Examples are based on the Chemical Abstracts names of related compounds. 15 Example 1 Bisnadimide resin, CBR-116, Formula (II) wherein X is H,Ar is C$H^COC^H3 and Ar' is 1J ^substituted methyldietfyiphenyi A mixture of 400g of nadic anhydride and 200g of 5j5'-carbonylbis {2-[3-20 amino(methyldiethyl)phenyl]}-lH-isoindols-13(2H)-dione prepared by the method described in International Patent Publication No. WO 92/06078 were mixed together as finely divided solids and then heated slowly with stirring to 180 °C. The nadic anhydride melted at about 160 "C and dissolved the diamine as well as reacting with it to liberate water. After heating with stirring for 8 hours the toffee-like mixture 25 was cooled, ground and washed with very hot water to remove the large excess of unreacted anhydride. The remaining solid was dried and then dissolved in the minimum amount of methylene chloride and poured into excess ethanol to give the pure solid bisnadimide 30 as i. light brown powder with infrared spectra showing peaks at 1776,1724,1710cm~* (imide), 1182,1106 and 723cm" V WO 94/13669 PCT/A3 !93/00622 -11 - Example 2 Bisnadimide resin CBR-412, Formula (II) wherein X is CH^, Ar is C^2 an^ Ar' is IJ-disubstUuted methyidiethylphenyl 5 (a) Neat 2,6-bis(3-amino(methyldiethyl)phenyl)-benzo[l,2-c:4,5c']-dipyrrole-13»5,7(lH,6H)-tetrone (CBH-103) (2.6g, 0.0049 mole) prepared by the method described in International Patent Publication No. WO 92/06078 was added to liquid methyl nadic anhydride (1.8g, 0.01 mole) and the stirred solution heated at 180 °C 10 for 2 hours and at 200 °C for 2 hours and allowed to cool. The FTIR was consistent with the expected product which was soluble in CH2CI2' acetone, THF and DMF and insoluble in ethanol. The GPC showed one main peak with Mn» 830 (expected value 858). It had no sharp melting point, but softened with decomposition at about 300 °C. Recrystallization from CHC^/ethanol made no difference to the properties. 15 Curing a sample in the DSC resulted in an endotherm centred at 260 °C, attributed to the retro Diels-Alder reaction, and a broad exotherm commencing at about 300 #C (b) In DMF 20 A solution of CBH-103 (10.7g, 0.02 mole) and methyl nadic anhydride (6.9 ml, 0.048 mole) in DMF (50 ml) was refluxed with stirring under nitrogen for 4 hours. After cooling, it was poured into cold water (500 ml) with stirring, the precipitate filtered off, washed repeatedly with water and dried in vacuo at 40 °C to constant weight It was purified by dissolving in chloroform and precipitated into ethanol. 25 Its properties were the same as those of the material prepared without solvent. (c) In xylene solvent A mixture of CBH-103 (5.35g, 0.01 mole) and methyl nadic anhydride (3.45 ml, 0.024 mole) in xylene (50 ml) was refluxed in a flask fitted with a Dean Stark 30 trap until the theoretical amount of water had been evolved and then cooled and the product filtered off and dried in vacuo at 40 °C to constant weight 94/13669 PCT/AU93/00622 -12- Its properties were the same as those of the material prepared without solvent. Examples 3 to 10 5 Other bisnadimides prepared by methods similar to those described in Examples 1 and 2 are shown in Table 1. Their infrared and nuclear magnetic resonance spectra and their gel permeadon chromatographs were in agreement with the proposed structures. 10 Table 1: Other Bisnadimides of Fonnula (II) 15 20 Example Number X Ar Ar' 3 H (C6H3OC6H4)2C(CH3)2 1,4 disubstituted phenyl 4 H (C6H3OC6H4)2C(CH3)2 13 disubstituted methyl diethylphenyl 5 H C6H3CH2C6H3 1,4 disubstituted phenyl 6 ch3 (CgHgOCgH^CHg^ 1,4 disubstituted phenyl 7 ch3 (C6H3OC6H4)2C(CH3)2 13 disubstituted methyl diethylphenyl 8 gh3 c6h3coc6h3 13 disubstituted methyl diethylphenyl 9 ch3 c6h3ch2c6h3 1,4 disubstituted phenyl 10 CH.3 CfiH3C(CH3)2C6H3 1,4 disubstituted phenyl 25 Example 11 A matrix resin formulation was prepared for coating carbon fibre by dissolving 78% of the resin of Example 1, 18.0% trans-stilbene and 4% hydroquine in four volumes of dichloromethane with stirring. After coating with this solution to give 30 a 40% total resin content on the fibres after drying, the cloth was laid up in a 5 layer test part and cured in a heated press as follows. 25 °C to 250 °C in 3 hrs, 250 - 310 °C WO 94/13669 PCT/AU93/00622 -13 - in 1 hr, 310 °C for 1 hr and then cooled to room temperature over 2 hrs. Measurements by DMTA indicated a Tg of 386 "C. Example 12 5 A 20% (w/v) solution of the bisnadimide of Example 6 in methylene chloride was coated on to a carbon fibre cloth to give approximately a 40% resin content on the fibres after drying, the cloth was laid up in a 5 layer test part and cured in a heated press from 25 °C to 180 *C in 0.5 h, 180 'C/l h, 200 °C/1.5 h, 250 #C/6 h and 10 315°C/2h. Examples 13 to 18 Other bisnadimides were applied to carbon fibre cloth and cured by methods 15 similar to those of Example 12. Some of the properties of the cured laminates are listed in Table 2. The value of the Tg for most of the examples can be increased by up to 50% by a post cure at 315 °C for several hours. • • • m Table 2: Preparation and properties of some cured bisnadimide 5-ply carbon fibre laminates Example Bisnadimide of Example Number Prepregging Solvent Maximum Cure CC) WtX Resin Thickness of laminate (mm) T_ by DMTA (°C) Hater uptake at 71#C after 7 days (%) Height Loss at 250°C after 7 days (X) 12 6 CH2CI2 315 42 00 • H 263 0.9 0.37 13 / 6 DHF 315 30 1.07 294 2.7 0.8 14 6 NMP 315 30 1.10 295 4.1 1.2 15 3 DMF 315 35 1.05 325 3.7 0.6 16 4 CH2CI2 315 42 1.13 312 1.4 2.3 17 7 CH2CI2 315 42 1.09 286 1.4 2.4 18 9 CH2CI2 315 • 42 1.18 374 1.7 0.31 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> WO 94/13669 PCT/AU93/00622 -15 - Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group 5 of integers but not the exclusion of any other integer or group of integers. 258 488 - 16 - CLAIMS 

1. A method for the preparation of a bisnadimide of Formula (II) siibstantially free of oligomeric, amidic and uncyclized impurities N Ar'—N Ar N Af—N \/ \/ 15 20 Formula (II) wherein Ar is an optionally substituted aryi, optionally substituted bridged or bonded di- or poly- aryi or optionally substituted heteroaryl group, Ar' is an optionally substituted aryi or heteroaryl group which provides for good conjugation between the nitrogen containing groups; each X independently selected from hydrogen, or an alkyl group; and m is 0 to 6 which comprises reacting a diaminobisimide of the Formula (m) 0 II c 25 H:N—Ar -f/ "T Ar * • * C II .0 \ / N—Ar'-NH} Formula (HI) 30 wherein Ar and Ar' are as defined in Formula (II) above with nadic acid or a reactive derivative thereof which is optionally substituted with an alkyl group. WO 94/13669 258488 PCT / AU93/00622 -17-
2. A method according to Qaim 1, wherein the nadic acid derivative is nadic anhydride or an alkyl ester of nadic acid. S
3. A method according to Qaim 1 or Qaim 2, wherein the reaction is performed at an elevated temperature.
4. A method according to Qaim 3, wherein the temperature is above 120-C. 10
5. A method according to any one of the preceding claims, wherein the reaction is performed in the presence of a solvent.
6. A method according to Qaim S, wherein the solvent is an organic solvent. 15
7. A method according to Qaim 5 or Qaim 6, wherein the solvent is dimethylforrnamide, dimethyl ace tamide or xylene.
8. A bisnadimide of Formula (II) as defined in Qaim 1 whenever prepared by 20 the method of any one of the preceding claims.
9. A bisnadimide of Formula (II) as defined in Qaim 1.
10. A curable formulation which comprises a bisnadimide of the Formula (II) as 25 defined in Qaim 8 or Qaim 9.
11. A crosslinked polyimide polymer which is formed fro \ monomer of Formula (II) as defined in Qaim 8 or Qaim 9. 30
12. A method for the preparation of a crosslinked polyimide polymSfHHPdgfmed in Qaim 11 which comprises heating a bisnadimide of Formula (Q) as defined in Qaim 8 or Qaim 9. WO 94/13669 PCT/AU93/00622 -18 -
13. A method according to Claim 13, wherein the heating occurs in the presence of a curing additive. 5
14. A method according to Qaim 13, wherein the curing additive is trans-stilbene and/or hydroquinone.
15. An adhesive, bar, film or moulded component which is composed wholly or partly of the crosslinked polyimide polymer defined in Qaim 11. 10
16. An impregnated fibre reinforced material wherein the fibre reinforcements are coated with the curable formulation defined in Qaim 10.
17. An advanced composite material which comprises an assembly of reinforcing IS fibres in a matrix of the crosslinked polyimide polymer defined in Qaim 11. </div>