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
2003-03-25
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
06538097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyimide powder which 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, Japanese Examined Patent Publication No. 39-22196 describes polyimide powder obtained by synthesizing a polyimide precursor in an amide-based solvent and reprecipitating the solution with a mixture of toluene, pyridine and acetic anhydride for imidation, and it is indicated that the polyimide powder obtained by this process gives molded bodies with satisfactory cohesion and high density. In addition, Japanese Unexamined Patent Publication No. 7-33873 describes a process for synthesis of a polyimide precursor powder in a water-soluble ketone, whereby removal of the solvent is facilitated, production of polyimide precursor powder with a high degree of polymerization is possible, and the molded bodies obtained from the polyimide precursor exhibit excellent dynamic properties and low residual solvent.
However, since it is difficult by the process described in Japanese Examined Patent Publication No. 39-22196 mentioned above to produce fine polyimide powder, and partial lump formation hampers efforts to achieve a uniform particle size, the molded bodies formed from the powder tend to be irregular. Moreover, employing the process of Japanese Unexamined Patent Publication No. 7-33873 tends to give fine powder with poor filtering properties, while the powder easily coheres together after filtration and during imidation in the solid phase. Also, polyimide powder obtained from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and para-phenylenediamine as the aromatic diamine component using this process has insufficient molecular weight, resulting in brittle molded bodies.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide polyimide powder molded bodies with excellent heat resistance and satisfactory mechanical properties which are obtained from polyimide powder whose particle size can be controlled and which exhibits satisfactory filtering properties and no cohesion between particles, as well as polyimide powder as the starting material therefor and a process for their production.
In other words, the present invention provides a process for production of polyimide powder which comprises reacting a biphenyltetracarboxylic dianhydride and an aromatic diamine in an amide-based solvent optionally containing a water-soluble ketone, in the presence of an imidazole at 1-100 equivalent percent and preferably 6-100 equivalent percent based on the carboxylic acid content of the polyimide precursor, separating and collecting the produced polyimide precursor powder from a water-soluble ketone solvent containing 3-30 wt % of an amide-based solvent, and heating the separated and collected polyimide precursor powder to an imidation rate of 90% or greater.
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 300-550° C. and pressure in a range of about 100-5000 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 2,3,3′,4′-biphenyltetracarboxylic dianhydride unit is included at 30 mole percent or greater.
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 tetracarboxylic acid component of the polyimide may be 3,3′,4,4′-biphenyltetracarboxylic dianhydride and/or 2,3,3′,4′-biphenyltetracarboxylic dianhydride, and is preferably a biphenyltetracarboxylic dianhydride containing at least 30 mole percent of 2,3,3′,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 such as, for example, para-phenylenediamine (p-phenylenediamine), 4,4′-diaminodiphenyl ether, 1,3-bis(4-aminophenoxy)benzene, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylethane, 4,4′-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]propane, 2,2′-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane or bis[4-(4-aminophenoxy)phenyl]ether, among which para-phenylenediamine (p-phenylenediamine) and 4,4′-diaminodiphenyl ether are preferably used.
According to the invention, it is necessary to react a biphenyltetracarboxylic dianhydride with an aromatic diamine in an amide-based solvent optionally containing a water-soluble ketone, in the presence of an imidazole at 1-100 equivalent percent and preferably 6-100 equivalent percent based on the carboxylic acid content of the polyimide precursor, separate and collect the produced polyimide precursor from a water-soluble ketone solvent containing 3-30 wt % of an amide-based solvent, and heat the separated and collected polyimide precursor powder to an imidation rate of 90% or greater to obtain the polyimide powder.
According to the invention, a biphenyltetracarboxylic dianhydride may be reacted with a molar equivalent of an aromatic diamine for about 30 minutes to 24 hours at 10-40° C. in a water-soluble ketone solvent containing 3-30 wt % of an amide-based solvent in the presence of the necessary amount of an imidazole, and then the high-molecularized precipitated polyimide precursor separated and collected. In this case, the total of the biphenyltetracarboxylic dianhydride and aromatic diamine in the solution is preferably 1-20 wt %.
Alternatively, a biphenyltetracarboxylic dianhydride may be reacted with a molar equivalent of an aromatic diamine for about 30 minutes t
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-3070530