Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-04-09
2003-03-11
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, C528S171000, C528S172000, C528S173000, C528S174000, C528S176000, C528S183000, C528S185000, C528S188000, C528S220000, C528S223000, C528S226000, C528S229000, C528S350000, C528S351000, C528S352000, C528S353000, C524S600000, C524S602000
Reexamination Certificate
active
06531568
ABSTRACT:
TECHNICAL FIELD
This invention relates to crosslinkable-group-containing polyamic acids, melt-moldable or formable, crosslinkable-group-containing polyimides, production processes thereof, and crosslinked thermoplastic polyimides obtained by heat-treating them. Specifically, the present invention is concerned with crosslinked thermoplastic polyimides having various excellent properties inherent to polyimides, namely, high heat resistance, excellent mechanical properties, superb sliding property, low water absorption property, outstanding electrical properties, high thermal oxidation resistance, high chemical resistance and high radiation resistance, especially those improved more markedly in heat resistance, chemical resistance and mechanical properties, crosslinkable-group-containing polyimides which are thermoplastic and melt-moldable or formable, crosslinkable-group-containing polyamic acids as precursors of the crosslinkable-group-containing polyimides, production proceses thereof, and their solutions or suspensions.
BACKGROUND ART
Polyimides have been used widely for many years as molding or otherwise forming materials, composite materials, or electrical or electronic materials in various fields, because in addition to their superb heat resistance, they are also excellent in mechanical properties and electrical properties.
For example, a polyimide (“Kapton”, “Vespel”, trade names; products of E.I. DuPont de Nemours & Co., Inc.) of the formula (A) is known as a representative polyimide:
This polyimide is non-thermoplastic and is insoluble and infusible, and hence has a drawback in moldability or formability. It is therefore accompanied by a problem that no mass production is practically feasible. As a specific processing method, a block is obtained using a special molding process called powder sintering molding, and then, mechanical working such as cutting, grinding and polishing is applied to the block to obtain a formed product.
As an amorphous thermoplastic polyimide with improved moldability or formability, a polyetherimide represented by the formula (B) (“Ultem”, trade name; product of General Electric Company) is known:
However, this polyimide is soluble in amide-type aprotonic polar solvents and halogenated hydrocarbon solvents and is inferior in chemical resistance. In addition, its glass transition temperature is 215° C., and a further improvement in heat resistance is desired depending on the application.
Further, a polyimide which is imparted with moldability or formability and is represented by the formula (C):
shows melt fluidity at its melting point and higher and permits melt molding or forming while retaining the inherent properties of polyimides because it has a melting point at 385° C. (U.S. Pat. No. 5,043,419). Although the glass transition temperature of this polyimide is relatively high, i.e., 250° C., marked reductions in properties, which are accompanied by deformation, softening or the like, take place when used at the glass transition temperature or higher. Further improvements are therefore desired depending on its application. Further, this polyimide is inferior in chemical resistance especially under stress, and an improvement is strongly desired in this respect.
Since the properties of a thermoplastic polyimide depend on the backbone structure of the polyimide, a variety of polyimides are selected in view of their inherent performance such as heat resistance, moldability or formability, mechanical properties and chemical resistance. Nonetheless, one or more of these individual properties may be found to be insufficient depending on the application, leading to an outstanding desire for the improvement of the above-described various properties.
On the other hand, a variety of thermosetting polyimides are available on the market. As a representative example of these polyimides, a polyimide available from monomers represented by the formula (D):
is known [“Kerimid-601”, trade name; product of Rhone-Poulenc SA; F. D. Darmory, “National SAMPLE Symposium”, 19, 693 (1974)]. As this polyimide is thermosetting, it is less susceptible to deformation or softening than thermoplastic polyimides and therefore, can be used under high temperature condition. However, this polyimide is not high in mechanical properties, especially in toughness and is weak against external force such as an impact. Due to its thermosetting property, no melt molding or forming is feasible. It is therefore necessary to carry out shaping at the stage of a prepolymer before its hardening and then to conduct heat treatment.
For the purpose of making improvements in the detrimental mechanical properties of these thermosetting polyimides, it is known to use a linear polyimide as a backbone and then to introduce crosslinking members into its ends and/or substituent groups. Reference may be had, for example, to U. S. Pat. No. 5,138,028, U.S. Pat. No. 5,478,915, U.S. Pat. No. 5,493,002, U.S. Pat. No. 5,567,800, U.S. Pat. No. 5,644,022, U.S. Pat. No. 5,412,066, and U.S. Pat. No. 5,606,014.
As technical details, U.S. Pat. No. 5,567,800, for example, discloses thermosetting polyimides available from heat treatment of imide oligomers having carbon-carbon triple bonds at their molecule ends, which can in turn be obtained from monomers represented by the formula (E):
and an end blocking agent, respectively. Although the polyimides disclosed in this patent have various excellent properties, they still do not permit melt molding or forming, and therefore, their molding or forming is limited to processing which makes use of solutions of polyamic acids as precursors. In general, subsequent to the shaping of a solution of a polyamic acid, removal of the solvent and a dehydrating imidation reaction are conducted by heating. As this processing involves the removal of the solvent, it is generally impossible to obtain a molded or formed product having a large thickness. This processing is therefore limited in shape to films or sheets, and further, involves problems such as foaming due to remaining solvent and a need for recovery of a great deal of solvent.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide crosslinkable-group-containing polyimides of various known thermoplastic polyimide backbone structures, which are provided with far better heat resistance, chemical resistance and mechanical properties than known polyimides of the structures without impairing advantages inherent to the structure, such as excellent moldability or formability, superb sliding property, low water absorption property, outstanding electrical properties, high thermal oxidation stability and high radiation resistance.
Specifically described, the terms “heat resistance”, “chemical resistance” and “mechanical properties” the improvements of which constitute one of themes sought for attainment by the present invention mean, for example, physical property values and test results such as those to be described below.
{circle around (1)} Concerning heat resistance, representative examples can include glass transition temperature; softening temperature, deflection temperature under load, and mechanical properties at high temperatures in thermal mechanical analyses; retentions of mechanical properties in thermal cycle tests; solder reflow heat resistance test; heat resistance test; and hot air aging test. Among these, the themes the attainment of which are sought for in the present invention can include especially deflection temperature under load, mechanical properties at high temperatures, retentions of mechanical properties in thermal cycle tests, and the like.
{circle around (2)} As to chemical resistance, representative examples can include solvent dissolution resistance test, solvent immersion test, under-stress solvent immersion resistance resistance test, and retentions of various physical properties after immersion in solvent under stress. Among these, the themes the attainment of which are sought for in the present invention can include especially under stress solvent immersion resistan
Kuroki Takashi
Oikawa Hideaki
Okawa Yuichi
Okumura Tomomi
Sakata Yoshihiro
Burns Doane , Swecker, Mathis LLP
Hampton-Hightower P.
Mitsui Chemicals Inc.
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