Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-02-25
2001-02-13
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, C528S126000, C528S128000, C528S170000, C528S172000, C528S173000, C528S179000, C528S183000, C528S185000, C528S188000, C528S220000, C528S229000, C528S350000, C528S353000
Reexamination Certificate
active
06187899
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to novel polyamic acid microfine particles and polyimide microfine particles and to a technology for producing them.
BACKGROUND OF THE INVENTION
Polyimides are not only favorable in mechanical properties but also satisfactory in other properties such as heat resistance, resistance to chemicals, and electric insulating properties and have, therefore, been used broadly as electrical/electronic materials, car component materials, and substitutes for metals and ceramics, among other applications.
The conventional process for synthesizing a polyimide comprises reacting a tetracarboxylic dianhydride with a diamine in a solvent such as N,N-dimethylformamide (DMF) to give a polyamic acid which is a precursor of the objective polyimide in the form of a varnish, and subjecting this varnish to precipitation to provide the objective polyimide as fine particles.
However, this technology has the drawback that the polyimide particles separating out with the progress of polymerization reaction undergo coalescence/coagulation, thus failing to give a monodispersed polyimide system.
An alternative technology comprises polymerizing a tetracarboxylic dianhydride with an organic diamine in an organic solvent under heating to give a polyamic acid solution, pouring this solution in a poor solvent for the polymer, recovering the resulting precipitate, and subjecting it to thermal cyclization reaction to provide the objective polyimide.
However, when polyimide microfine powder is to be produced by this technology, the polymer block must be recovered after the imidation reaction and mechanically pulverized, thus introducing a complicating factor into the production process. Moreover, mechanical pulverization yields only more or less coarse particles and can hardly provide a monodispersed system of discrete particles. In addition, the above technology does not lend itself well to the control of particle morphology and size distribution.
Thus, there has been a standing demand for development of a technology for producing polyimide microfine powder capable of providing a monodispersed system.
SUMMARY OF THE INVENTION
With a view to overcoming the above drawbacks of the prior art, the inventors of this invention explored in earnest for a way to meet the demand and discovered that the demand can be satisfied by using a process including a certain procedure herein defined. This invention has been developed on the basis of the above finding.
This invention, therefore, is directed to a process for producing polyamic acid microfine particles from a tetracarboxylic anhydride and a diamine compound, said process being characterized by comprising
(a) a first step which comprises preparing a first solution containing said tetracarboxylic anhydride and a second solution containing said diamine compound, respectively, and
(b) a second step which comprises mixing said first and second solutions under constant ultrasonic agitation to let polyamic acid microfine particles precipitate from the mixed solution (first invention).
This invention is further directed to a process for producing polyimide microfine particles from a tetracarboxylic anhydride and a diamine compound, said process being characterized by comprising
(a) a first step which comprises preparing a first solution containing said tetracarboxylic anhydride and a second solution containing said diamine compound, respectively,
(b) a second step which comprises mixing said first and second solutions under constant ultrasonic agitation to let polyamic acid microfine particles precipitate from the mixed solution, and
(c) a third step which comprises subjecting said polyamic acid microfine particles to imidation reaction to thereby produce polyimide microfine particles (second invention).
This invention is further directed to polyamic acid microfine particles having an average particle diameter of 0.03-0.7 &mgr;m as obtainable by the above process for producing polyamic acid microfine particles (third invention).
The invention is further directed to polyimide microfine particles having an average particle diameter of 0.03-0.7 &mgr;m as obtainable by the above process for producing polyimide microfine particles (fourth invention)
REFERENCES:
patent: 3607838 (1971-09-01), Strickrodt
patent: 4098800 (1978-07-01), Banucci et al.
patent: 57200453 (1982-08-01), None
patent: 61-45651 (1986-10-01), None
Translation of Article in The Chemical Daily dated Mar. 14, 1997. Tri Osaka Develops New Process for Producing Uniform Polyimide Microfine Particles Having Diameter of 1 &mgr;m or Less and Unaffected Heat Resistance. pp. 1-2.
Asao Katsuya
Saito Hidenori
Armstrong, Westerman Hattori, McLeland & Naughton
Hampton-Hightower P.
Osaka Prefectural Government
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