Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-10-29
2003-03-18
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S125000, C528S126000, C528S128000, C528S172000, C528S173000, C528S176000, C528S179000, C528S183000, C528S188000, C528S220000, C528S229000, C528S350000, C528S351000, C528S353000, C264S319000, C264S320000, C264S325000, C428S402000, C428S473500
Reexamination Certificate
active
06534622
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyimide powder which contains a 2,3,3′,4′-biphenyltetracarboxylic acid component as an essential component and gives polyimide powder molded bodies that maintain a high level of heat resistance with particularly high flexural strength and tensile strength and high elongation, as well as to polyimide powder molded bodies and to a process for their production.
2. Description of the Related Art
Pyromellitic acid-based polyimide powder molded bodies obtained from a pyromellitic acid component and 4,4′-diaminodiphenyl ether have been widely used in the prior art as polyimide powder molded bodies because of their high toughness and satisfactory cutting workability.
However, pyromellitic acid-based polyimide molded bodies have high moisture absorption, considerable out gas and low chemical resistance and dimensional stability.
3,3′,4,4′-biphenyltetracarboxylic acid-based polyimide powder molded bodies have therefore been proposed.
Examples of such 3,3′,4,4′-biphenyltetracarboxylic acid-based polyimide powder molded bodies are described, for example, in Japanese Unexamined Patent Publication No. 57-200453, wherein there are obtained heated/compressed molded bodies of relatively large-sized aromatic polyimide powder with an imidation rate of 95% or greater obtained by polymerization and imidation of a 3,3′,4,4′-biphenyltetracarboxylic acid component and an aromatic diamine component in N-methyl-2-pyrrolidone.
Also, processes for production of aromatic polyimide powder molded bodies comprising a 3,3′,4,4′-biphenyltetracarboxylic acid component and para-phenylenediamine are described in Japanese Unexamined Patent Publication No. 61-241326 and Japanese Unexamined Patent Publication No. 1-266134.
However, although the processes described in the aforementioned publications are effective for production of polyimide powder comprising a 3,3′,4,4′-biphenyltetracarboxylic acid component and less than 30 mole percent of a 2,3,3′,4′-biphenyltetracarboxylic acid component and a para-phenylenediamine component, polyimides comprising, for example, a 2,3,3′,4′-biphenyltetracarboxylic acid component and a para-phenylenediamine component undergo gel precipitation when subjected to heated dehydrating ring closure in amide-based solvents, and with time become thoroughly lumpy and impossible to stir. Moreover, the molded bodies obtained from powder formed by crushing are brittle.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide polyimide powder molded bodies which contain a 2,3,3′,4′-biphenyltetracarboxylic acid component as an essential component and which exhibit both excellent heat resistance and satisfactory mechanical properties, polyimide powder as the starting material therefor, and a process for their production.
In other words, the invention provides a process for production of polyimide powder obtained by reacting an aromatic diamine with a partial ester of a biphenyltetracarboxylic dianhydride, which is a partial ester of a biphenyltetracarboxylic dianhydride with a primary alcohol of 1-5 carbon atoms of which at least 30 mole percent and especially at least 50 mole percent is a 2,3,3′,4′-biphenyltetracarboxylic acid component, in the presence of the primary alcohol, separating out and collecting the resulting solid polyimide precursor, and preferably heating at 150-300° C. for dehydrating ring closure.
The invention further provides polyimide powder obtained by the aforementioned process.
The invention still further provides biphenyltetracarboxylic acid-based polyimide powder molded bodies having a density of at least 1.3 g/mm
3
, a tensile strength of at least 800 Kg/cm
2
and a tensile break elongation of at least 10%, obtained by subjecting the aforementioned polyimide powder to heat and pressure in a die either simultaneously or separately.
The invention still further provides a process for production of polyimide powder molded bodies whereby the aforementioned polyimide powder is packed into a die and subjected to heat in a range of about 300-600° C. and pressure in a range of about 100-10,000 Kg/cm
2
either simultaneously or separately for molding.
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the invention.are listed below.
1) The aforementioned process for production of polyimide powder wherein the reaction is carried out in the presence of an imidazole.
2) The aforementioned process for production of polyimide powder molded bodies wherein the molding step is carried out by compression molding, wet CIP or dry CIP (CIP: Cold Isostatic Pressure) or HIP (HIP: Hot Isostatic Pressure).
According to the invention, the aromatic tetracarboxylic dianhydride component of the polyimide is 2,3,3′,4′-biphenyltetracarboxylic dianhydride alone or a biphenyltetracarboxylic dianhydride comprising at least 30 mole percent and especially at least 50 mole percent of 2,3,3′,4′-biphenyltetracarboxylic dianhydride and no greater than 70 mole percent and especially no greater than 50 mole percent of 3,3,4′,4′-biphenyltetracarboxylic dianhydride.
Part of the biphenyltetracarboxylic dianhydride may be replaced with another aromatic tetracarboxylic dianhydride such as pyromellitic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 2,2′-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride or bis(3,4-dicarboxyphenyl)ether dianhydride, so long as the effect of the invention is not hindered.
The diamine component used may be any aromatic diamine that gives a polyimide with a high Tg, such as para-phenylenediamine (p-phenylenediamine) or 4,4′-diaminodiphenyl ether.
According to the invention, it is necessary to use a partial ester, and preferably a half ester, of the aforementioned aromatic tetracarboxylic dianhydride with a primary alcohol of 1-5 carbon atoms such as methanol, ethanol, propanol, butanol or the like, and especially methanol.
The primary alcohol of 1-5 carbon atoms for the partial esterification is preferably used as the partial esterification solvent for the aromatic tetracarboxylic dianhydride.
In this case, the amount of the lower alcohol is preferably such that the total of the aromatic tetracarboxylic dianhydride and the diamine in the solution is 1-60 wt %.
Also, another solvent and the lower alcohol used for partial esterification may be used in admixture.
As suitable solvents there may be mentioned ketones and ethers with boiling points of no higher than 120° C., such as acetone, tetrahydrofuran and the like.
In this case, the amount of the lower alcohol is preferably a two-fold molar amount with respect to the aromatic tetracarboxylic dianhydride.
In the process of the invention, the aromatic tetracarboxylic dianhydride and the primary alcohol of 1-5 carbon atoms are preferably reacted under total reflux conditions for partial esterification, and especially half-esterification of the aromatic tetracarboxylic dianhydride, after which the resulting solution may be cooled, the aromatic tetracarboxylic acid component and an approximately equimolar amount of the aromatic diamine added thereto and reacted, and the solid polyimide precursor separated and collected from the reaction solution and then heated preferably at 150-300° C. for dehydrating ring closure to obtain polyimide powder.
The method of separating and collecting the solid polyimide precursor is not particularly restricted, and for example, solvent removal from the reaction solution may be carried out using an evaporator, a spray drier, distillation or the like.
In this case, the solvent removal temperature is preferably no higher than 250° C. and especially no higher than 120° C.
The imidation rate is preferably controlled by adding an imidation catalyst, and preferably an imidazole-based imidation catalyst, to the reaction system before the dehydrating ri
Aoki Fumio
Yamaguchi Hiroaki
Hampton-Hightower P.
Morgan & Lewis & Bockius, LLP
Ube Industries Ltd.
LandOfFree
Process for production of polyimide powder, polyimide... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for production of polyimide powder, polyimide..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for production of polyimide powder, polyimide... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3023946