Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-02-05
2002-10-01
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
Reexamination Certificate
active
06458912
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermoplastic polyimide, and an aromatic diamine compound used in the production of the polyimide.
The thermoplastic polyimide of the present invention has at least excellent characteristics {circle around (1)} to {circle around (4)} described below.
{circle around (1)} It is superior in thermal stability on melting. That is, the degree of lowering of the fluidity on melting with a lapse of time is small. It was difficult to realize this feature in the prior art.
{circle around (2)} It has high heat resistance. That is, it has excellent mechanical strength even at the temperature higher than a glass transition temperature (Tg) because of its high crystallizability.
{circle around (3)} It is superior in productivity. That is, since a crystallization rate is large, it is crystallized during a normal short molding cycle without requiring a special heat-treating operation such as operation of slowly cooling in a mold on molding, operation of heat-treating after molding or the like.
{circle around (4)} It is superior in dimensional accuracy. That is, since a crystallization rate is large and it is crystallized in a mold on molding, the degree of shrinkage after molding is small.
The aromatic diamine compound of the present invention has at least excellent characteristics {circle around (5)} to {circle around (6)} described below.
{circle around (5)} The content of an azo compound is very small.
{circle around (6)} A polyimide resin having excellent thermal stability on melting can be obtained.
BACKGROUND ART
a) Filed of the Invention
{circle around (1)} Characteristics and application of polyimide
Polyimide has widely been used in the fields of molding materials, composite materials, electric/electronic parts, etc. because of its excellent characteristics such as mechanical properties, chemical resistance, flame retardance, electric characteristics, etc., including excellent heat resistance.
{circle around (2)} “Vespel” (manufactured by Du Pont Co.) and “Upimol” (manufactured by Ube Industries, Ltd.)
As the polyimide for molding material and composite material, “Vespel” (trade name, manufactured by Du Pont Co.) and “Upimol” (trade name, manufactured by Ube Industries, Ltd.) are known, but both polyimides were inferior in moldability because they are insoluble and infusible. That is, to obtain a molded article of the polyimide, it was necessary to mold from polyamic acid as a polyimide precursor by using a special means such as sintering. The problem is that it is difficult to obtain a product having a complicated shape by sintering. To obtain the product having a complicated shape, a desired shape must be skived from a block by using a cutting machine such as NC lathe and the like. Therefore, there was a problem about the cost required to complicated machining and forming steps.
{circle around (3)} “Ultem” (manufactured by General Electric Co.)
As an injection-moldable thermoplastic polyimide having improved moldability, for example, “Ultem” (trade name, manufactured by General Electric Co.) is known (U.S. Pat. Nos. 3,847,867 and 3,847,869).
However, since this polyimide is completely non-crystalline and has a glass transition temperature (Tg) of 215° C., it has not sufficient heat resistance, necessarily, when assuming use at a high temperature range.
That is, when it is evaluated by a deflection temperature under load (DTUL) which indicates s substantial working limit of temperature, the temperature of neat “Ultem” is 200° C. and that of (CF30) “Ultem” containing 30% by weight of carbon fibers is 212° C. Therefore, when assuming use at a high temperature range, both of them are not a high numerical value as a super engineering plastic.
{circle around (4)} “AURUM” (manufactured by Mitsui Chemicals, Inc.)
As the injection-moldable thermoplastic polyimide having improved moldability, for example, “AURUM” (trade name, manufactured by Mitsui Chemicals, Inc.) was newly developed (Japanese Patent Laid-Open No. 62-68817).
This polyimide is superior in thermal stability on melting and is suitably applied to melt molding such as extrusion molding and injection molding. Regarding “AURUM”, a melt viscosity ratio MVR calculated by the numerical formula (1) is within a numerical range shown in the numerical formula 2.
The glass transition temperature (Tg) of this polyimide is 245° C. and, when it is evaluated by the reflection temperature under load (DTUL), the temperature of neat “AURUM” is 238° C. and that of (CF30) “AURUM” containing 30% by weight of carbon fibers is 248° C. Therefore, “AURUM” is superior in heat resistance to “Ultem”.
“AURUM” is essentially crystalline and can be crystallized by heat-treating (annealing treatment, annealing) after molding. Regarding DUTL of “AURUM” when it is crystallized, the temperature of neat “AURUM” is 260° C. and that of (CF30) “AURUM” containing 30% by weight of carbon fibers is 349° C. Therefore, “AURUM” has a markedly higher heat resistance than the case where it is not crystallized.
As described above, “AURUM” is crystalline and has high glass transition temperature and high melting point, and has highest heat resistance among thermoplastic resins. However, this polyimide is slowly crystallized, that is, it takes a long time to complete the crystallization is long. Furthermore, a molded article obtained by a general molding cycle, e.g. injection molding cycle of about 30 to 60 seconds, is amorphous.
Therefore, the molded article thus obtained has such a feature that it is superior in dimensional accuracy and flexural modulus as far as it is used at a temperature lower than the glass transition point.
On the other hand, when the molded article thus obtained is used under the conditions of a temperature higher than the glass transition point, the modulus is drastically lowered and the shape of the molded article can not be retained, thereby making it impossible to use it continuously.
When this molded article made of “AURUM” is continuously used under the conditions of a temperature higher than the glass transition point, the amorphous molded article may be crystallized by subjecting to a heat treatment. However, a heat-treating operation requiring a long time drastically lowers the productivity and, furthermore, shrinkage along with crystallization causes problems such as dimensional change, deformation, surface roughening and the like.
If the molded article obtained by molding “AURUM” is sufficiently crystallized without requiring a special heat treatment (e.g. slow cooling in mold, heat treatment after molding, etc.), these problems do not occur. Therefore, there has been developed a technique of accelerating the crystallization by adding to “AURUM” an organic low-molecular weight compound and a crystalline resin having low heat resistance (Japanese Patent Laid-Open Nos. 9-104756 and 9-188813).
However, these methods have such a problem that the heat and chemical resistances are lowered because the low-molecular weight compound and resin having low heat resistance are added.
{circle around (5)} Polyimide having a repeating unit represented by the chemical formula (1).
Polyimide having a repeating unit represented by the chemical formula (1) is disclosed in Japanese Patent Laid-Open Nos. 61-143433, 62-11727 and 63-172735, and crystallizability and fast crystallization are shown.
Accordingly, if this polyimide can be applied to injection molding and can be crystallized in a mold during a conventional molding cycle, it is assumed that the resulting molded article has high heat resistance and high dimensional accuracy.
However, since molecular terminal of the polyimide produced in accordance with such a disclosure is not deactivated, the thermal stability on melting is drastically low and the fluidity is lowered quickly within a short time. Therefore, it was not practical to apply the polyimide to melt molding such as extrusion molding, injection molding or the like.
{circle around (6)} Polyimide having a repeating unit represented by the chemical formula (1), molecular terminal of which is compose
Kido Hiroyasu
Kuroki Takashi
Oikawa Hideaki
Okawa Yuichi
Okumura Tomomi
Boykin Terressa M.
Burns Doane Swecker & Mathis L.L.P.
Mitsui Chemicals Inc.
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