Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-09-21
2001-09-11
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S125000, C528S128000, C528S170000, C528S172000, C528S173000, C528S176000, C528S179000, C528S188000, C528S220000, C528S229000, C528S350000, C525S935000, C524S600000, C524S607000, C428S411100, C428S473500
Reexamination Certificate
active
06288209
ABSTRACT:
ORIGIN OF THE INVENTION
The invention described herein was made by an employee of the United States Government and may be manufactured and used by or for the Government without the payment of any royalties thereon or therefor.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyimide copolymers which contain 1,3-bis(3-aminophenoxy)benzene with reactive endgroups that are useful as adhesives, composite matrices, moldings, films and coatings.
2. Description of Related Art
Wholly aromatic polyimides are known for their exceptional thermal, thermo-oxidative and chemical resistance, but are generally difficult to process as structural adhesives or composite matrices. Several polyimides such as Kapton® (DuPont), PI-2080 (Dow Chemical, licensed to Lenzing), XU-218 (Ciba-Geigy), Ultem® (General Electric) and LAC™-TPI (Mitsui Toatsu) are commercially available and used as fibers, films, moldings, adhesives or composite matrices.
Currently available equipment to process polyimides into useful parts are limited in their pressure and temperature capability and certain applications require co-curing of adhesives and composites with other structures such as foam or honeycomb. Because of the equipment limitations (especially autoclaves) and co-curing requirements, it is extremely important to provide materials that are processable at 250 psi or below and 371 ° C. or below. Because of the foams and honeycombs that are being proposed for use in some applications, reductions in pressure below 250 psi are also very significant.
While improved processing conditions are very important, the polyimides must also display better mechanical and adhesive properties to meet the needs of future applications. Especially important for these applications are properties measured at temperatures of 177° C. or slightly higher for use over long time periods at those elevated temperatures.
Thermoplastic polymers currently available are either difficult to process into high quality parts or have limited mechanical performance at the elevated temperatures for short or long periods of time. The related art that comes closest to meeting the needs of future applications is a thermoplastic polyimide known as LARC™-IA, as described by St. Clair and Progar in U.S. Pat. No. 5,147,966. However, this polyimide requires higher processing conditions than desired and/or provides lower mechanical and adhesive properties than desired, depending on the tests performed.
The incorporation of ethynyl groups in polyimides have been reported in the literature, typically as terminal groups to yield acetylene-terminated imide oligomers (ATI). Therimid-600, an oligoimide with acetylene end groups was first developed at the Hughes Aircraft Co. [N. Bilow, A. L. Landis and L. J. Miller, U.S. Pat. No. 3,845,018 (1974); A. L. Landis, N. Bilow, R. H. Boschan, R. E. Lawrence and T. J. Aponyi,
Polym. Prepr.,
15, 537(1974); N. Bilow and A. L. Landis,
Natl. SAMPE Tech. Conf Ser
., 8, 94(1976)]. Several reviews on polyimides or acetylene-terminated prepolymers are published and discuss other acetylene containing polyimides [P. M. Hergenrother, in (H. Mark, ed.)
Encyclopedia of Polymer Science and Engineering
, 2nd. ed., vol. 1, John Wiley and Sons, Inc., New York, 61(1985); P. M. Hergenrother in (H. Mark, ed.)
Encyclopedia of Polymer Science and Engineering
, 2nd. ed., vol. 7, John Wiley and Sons, Inc., New York, 639(1987); T. Takekoshi, in (C. G. Overberger, ed.)
Advances in Polymer Science
, 2(1990)]. Polyinudes containing pendent ethynyl groups have been reported but one reference contains an abstract only with no experimental details or polymer properties [F. W. Harris, S. M. Padaki and S. Varaprath,
Polym. Prepr
., 21(1), 3(1980)]. Another disclosure on polyimides containing pendent ethynyl groups contains detailed experimental information and polymer properties [B. J. Jensen, P. M. Hergenrotber and G. Nwokogu,
Polym. Prepr
., 33(1), 914 (1992) and B. J. Jensen, P. M. Hergenrother and G. Nwokogu,
Polymr
, 34(3), 630, (1993)]
Maleimide terminated polymers (bismaleimides) have been known for many years [G. F. D. Alelio, U.S. Pat. No. 3,929,713 (1975)]. They are a leading class of thermosetting polyimides because of their excellent processability and balance of thermal and mechanical properties, making them extremely popular in advanced composites and electronics. Many different bismaleimides have been synthesized with a variety of connecting groups between the maleimide rings [D. Wilson, H. D. Stenzenberger and P. M. Hergenrother,
Polyimides
, Blackie & Son Ltd., Bishopbriggs, Glasgow, United Kingdom, 1990].
Norbornene terminated polyiniides have also been known for many years [H. R. Lubowitz, U.S. Pat. No. 3,528,950 (1970)]. The norbornene groups reacts to form thermo-oxidatively stable polyimides which have found use as high temperature composite matrix resins [D. Wilson, H. D. Stenzenberger and P. M. Hergenrotber,
Polyimides
, Blackie & Son Ltd., Bishopbriggs, Glasgow, United Kingdom, 1990].
An object of this invention is to provide polyimide copolymers of virtually any molecular weight terminated with reactive groups.
Another object is to provide polyimides terminated with reactive groups which can be processed at low pressures to provide polyimides with improved solvent resistance, modulus and elevated use temperatures.
Another object is to provide polyimide copolymers terminated with reactive groups of molecular weight between ~1000 and ~15000 g/mole.
Another object is to provide polyimide copolymers terminated with reactive groups of molecular weight between ~2500 and ~10000 glmole.
Another object is to provide polyimides terminated with reactive groups with improved melt processability.
Another object is to provide a system that can be processed without the evolution of volatiles.
Another object is to provide a system that is melt stable at high temperatures.
Another object is to provide a system that has improved adhesive properties.
Another object is to provide a system that has improved composite properties.
Another object is to provide a system that has improved solvent resistance.
SUMMARY OF INVENTION
According to the present invention, polyimide copolymers were obtained containing 1,3-bis(3-aminophenoxy)benzene (APB) and other diamines and dianhydrides and terminating with the appropriate amount of reactive endcapper. The reactive endcappers studied include but should not be limited to 4-phenylethynyl phthalic anhydride (PEPA), 3-aminophenoxy-4′-phenylethynylbenzophenone (3-APEB), maleic anhydride (MA) and nadic anhydride (5-norbornene-2,3-dicarboxylic anhydride, NA). Homopolymers containing only other diamines and dianhydrides which are not processable under conditions described previously can be made processable by incorporating various amounts of APB, depending on the chemical structures of the diamines and dianhydrides used. Polyimides that are more rigid in nature require more APB to impart processability than polyimides that are less rigid in nature. Some of these more rigid polyimides may never reach low enough melt viscosity to be processed by methods such as resin transfer molding even with very high (>95%) loading levels of APB. The exact amount of APB required to impart processability is not predictable and is determined by the exact processing parameters and methods that the copolymers will see. For example, resin transfer molding requires lower melt viscosity than resin powder infusion, which requires lower melt viscosity than autoclave processing in composite preparation. The copolymers that result from using APB to enhance processability have a unique combination of properties that include low pressure processing (200 psi and below), long term melt stability (several hours at 300° C. for the phenylethynyl terminated polymers), high toughness, improved solvent resistance, improved adhesive properties, and improved composite mechanical properties. These copolyimides are eminently s
Edwards Robin W.
Hampton-Hightower P.
The United States of America as represented by the Administrator
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