Polyimide, and preparation process of same

Abstract: This invention relates to a novel thermoplastic and amorphous polyimide which is readily soluble in organic solvent, a novel aromatic diamino compound used for the polyimide, and a preparation process thereof. The polyimide comprise a requisite structural unit having one or more recurring structural units of the formula: wherein m and n are individually an integer of 0 or 1, and R is The polyimide of the invention is essentially amorphous, excellent in melt flow stability in the decreased temperature as compared with conventionally known polyimide and has greatly improved processability. The polyimide of the invention obtained by using a novel aromatic diamino compound as a monomer can control various properties such as melt flow ability and solubility in solvents by side chains and not by principal chain of polyimide. Thus, excellent melt flow property and solubility in solvents can be obtained while maintaining high heat resistance and adhesive property which are derived from benzophenone structure of the diamino compound of the the invention.

Description: The present invention relates to a novel polyimide, a preparation process of the polyimide, a novel aromatic diamino compound used for preparation of the polyimide, and a preparation process the aromatic diamino compound. More particularly, the invention relates to a novel, thermoplastic and amorphous polyimide which is readily soluble in organic solvents and a preparation process of the polyimide. The novel aromatic diamino compound of the invention is useful for preparation of polyimide of the invention and can also be used for a raw material of other polyimides, polyamide, polyamideimide, bismaleimide and epoxy resin, and a curing agent of other maleimide compounds and epoxy compounds. Recently, materials of heat resistant resin have been required to satisfy thermal and mechanical properties and additionally flexibility for use in a composite and other properties such as processability. Polyimide resin has been focused attention to satisfy these requirements. Conventionally, polyimide has been excellent in mechanical properties, chemical resistance, flame retardance and electrical properties in addition to its essentially excellent heat resistance. Consequently, polyimide has been widely used in many fields such as processing materials, composite materials and electric and electronic devices. However, polyimide resin has high performance while it has a disadvantage of poor processability. A typically known polyimide is, for example, an aromatic polyimide prepared from 4,4'-diaminodiphenyl ether and pyromellitic dianhydride and having recurring structural units of the formula (A): (Trade Mark :Kapton and Vespel, manufactured by E.I. Du Pont de Nemours & . Co.). The polyimide is insoluble and infusible and must be molded by special technique such as sintering of powder. Molded articles having complex shapes are difficult to obtain by the technique and sintered products must be further finished by cutting or other operation to obtain satisfactory articles. Thus, the polyimide has a great disadvantage of high processing cost and cannot be used for polyimide varnish. Consequently, research and development on soluble or fusible (thermoplastic) polyimide have been extensively carried out in order to provide processability for polyimide. EP-A-0 047 501discloses polyimides obtained from bis(aminobenzoyl)benzene compounds and said to have good processability. Soluble polyimide is expected in future to be used for heat resistant varnish, coating and sealant. Solubilizing methods are summarized, for example, in "Polyimide Resin" published by Technical Information Association (1991). The methods include increase in molecular chain flexibility by introducing a flexible bond or by conducting copolymerization and increase in mutual action with a solvent by introducing an alkyl group. Most of the soluble polyimide, however, can be soluble only in high boiling point solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide and cresol as disclosed in, for example, Japanese Laid-Open Patent Sho 61-130342. The soluble polyimide also has a problem of containing a sulfonyl group which has a high moisture absorption. A series of recent Japanese Laid-Open Patents has disclosed polyimide which is soluble in low boiling point solvents such as acetone, toluene and dichloromethane. Such polyimide, however, has a disadvantage that an alkyl group having poor heat resistance is present in the molecular chain as disclosed in, for example, Japanese Lain-Open Patent Hei 1-263116, 1-263117 and 2-160832. On the other hand, various soluble (thermoplastic) polyimides have also been developed. For example, improvement of the raw materials diamine component has also been tried to improve in order to eliminate the above disadvantage. Polyimide has been known to be capable of controlling its transition temperature and melt flowability by changing a bonding radical in the monomer units or introducing folded structure into the molecule. For example, polyimide LARC TPI from NASA is prepared from 3,3'-diaminobenzophenone and benzophenonetetracarboxylic dianhydride and has a fundamental skeleton of the formula (B) below. The polyimide has been further improved and thermoplastic polyimide has been developed by reacting 1,3-bis(3-aminobenzoyl)benzene )benzene with various tetracarboxylic dianhydrides (Japanese Patent Application Hei 03-223930). Such polyimide exhibits excellent heat resistance and adhesive property. On the other hand, melt flow property is still insufficient and the polyimide is primarily used in the form of polyamic acid varnish. Such application to varnish has difficulty in treating the moisture formed in the final step of hot ring-closure from polyamic acid to polyimide, and leads to a problem of void generation in the adhesive layer. As a result, it is a disadvantage that the desired property is difficult to exhibit and application step to adhesive becomes complex. The present inventors have controlled the molecular weight of the polymer having the fundamental skeleton of the formula (B): by capping the reactive end of polymer chain and found polyimide which can be injection molded and extruded as disclosed in Japanese Laid-Open Patent Hei 2-018419. The polyimide powder thus obtained, however, has also a melting point of around 340 °C and must be converted to amorphous in order to use the powder for processing or adhesion. Further, the polyimide of the above formula (B) can be used for an adhesive having excellent heat resistance and is now primarily used for adhesion of metals, prepregs, ceramics and polyimide films of FPC base material and is expected to develop in a further broad field of adhesive by making the best use of the excellent thermoplasticity. Polyimide has been conventionally applied to adhesion by the following methods. 1) Varnish of polyamic acid precursor is applied to an adhesive surface and hot-pressed to perform adhesion through solvent removal and imidization. 2) A polyimide film is inserted between adhesive surfaces and hot-pressed to perform adhesion. 3) Polyimide powder is suspended in a volatile solvent, successively applied to the adhesive surface, subjected to solvent removal by evaporation and hot-pressed to perform adhesion. The method 3) is particularly advantageous in view of simple procedures and is often used. Development of polyimide which can be applied to the method has been desired. It is clear in the method that adhesion cannot be performed unless exceeding the melting point of the polyimide powder. In many researches, polyimide powder was suspended in a solvent, prepreg was prepared by impregnating the suspension into a carbon cloth, and a composite was prepared from the prepreg and used for a structured material. In such procedures, processing temperature exceeding the melting point of polyimide is required as in the case of the above method 3). Thus, development of polyimide having good solubility and fusibility has been strongly desired in view of processing temperature and adhesion temperature. Provision of polyimide having increased solubility in organic solvents or having a decreased melting point due to conversion of the polyimide powder from crystalline structure to amorphous structure as a substitute of polyimide of the formula (B) which is essentially excellent in various properties while insoluble in almost organic solvents has a great contribution to the improvement of processability and adhesive property of polyimide, extension of field for use, and improvement and rationalization of application methods. Embodiments of the invention desirably provide a thermoplastic and amorphous polyimide which has high solubility in organic solvents and good processability in addition to essentially excellent heat resistance of polyimide. More particularly, embodiments desirably provide the amorphous polyimide powder which has essentially excellent heat resistance of polyimide of the above formula (B) and additionally can be processed at temperature lower than convention, that is, at temperature lower than the melting point 340 °C of the polyimide of the formula (B). In preferred embodiments, the invention may provide a heat resistant adhesive and adhesion method which have essentially excellent heat resistance of polyimide of the formula (B) and additionally can conduct adhesion at temperature lower than convention, that is, at temperature lower than the melting point 340°C of the polyimide of the formula (B). In preferred embodiments, the invention may also provide polyimide having high solubility in low boiling point organic solvents. In preferred embodiments, the invention may also provide a novel aromatic diamino compound which can satisfy processability and flexibility of resulting polyimide and is useful for a raw material of polyimide for adhesive. The present inventors have found that polyimide derived from aromatic diamine having specific structure as a monomer ingredient is a thermoplastic and amorphous polyimide which may have high solubility and excellent processability without giving adverse effect on the essential properties of polyimide. Thus, the invention has been completed. The inventors have also found a novel aromatic diamino compound which is useful as a monomer of polyimide having these properties, succeeded in preparing the compound, and thus the present invention has been completed. That is, the aspect of the present invention is; 1) A polyimide comprising a requisite structural units consisting of one or more of recurring structural units of the formula (1): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2, R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms; R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms; and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member. 2) A polyimide comprising a requisite structural unit consisting of one or more of recurring structural units of the formula (1): wherein m, n, R and Ar are the same as above, and having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. 3) A polyimide of 1) or 2) wherein the polyimide having recurring structural units of the formula (1) is derived from a precursor polyamic acid having an inherent viscosity of 0.01 to 3.0 dℓ /g at 35°C in a dimethylacetamide solution at a concentration of 0.5 g/ dℓ . 4) A polyimide of 1) or 2) wherein the polyimide having recurring structural units of the formula (1) has an inherent viscosity of 0.01 to 3.0 dℓ /g at 35°C at a concentration of 0.5 g/ dℓ in a solvent mixture composed of 9 parts by weight of p-chlorophenol and 1 part by weight of phenol. 5) A polyimide comprising a requisite structural unit consisting of one or more of recurring structural units of the formula (2): wherein m and n are individually an integer of 0 or 1, R 8 is a hydrogen atom, halogen atom, alkyl having 1 to 4 carbon atoms, alkoxy or phenyl, and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member. 6) A polyimide comprising a requisite structural unit consisting of one or more of recurring structural units of the formula (2) : wherein m, n, R 8 and Ar are the same as above, and having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. 7) A polyimide comprising a requisite structural unit consisting of one or more of recurring structural units selected from the group consisting of 1 ○ the units of the formula (3); wherein R 9 is and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, 2 ○ the units of the formula (4): wherein R 9 and Ar are the same as above, and 3 ○ the units of the formula (5): wherein R 9 and Ar are the same as above, or said polyimide having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. 8) A polyimide copolymer comprising a requisite structural unit consisting of 1 to 99 % by mol of recurring structural units of the formula (1): wherein m, n, R and Ar are the same as above, 99 to 1 % by mol of recurring structural units of the formula (6): wherein n is an integer of 0 to 5, Q is a direct bond, -O-, -S-, -CO-, -SO 2 -, -CH 2 -, -C(CH 3 ) 2 - ) 2 - or -C(CF 3 ) 2 - and may be the same or different when aromatic rings are connected each other with two or more connecting radicals Q, and Ar' is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alcyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, or said polyimide copolymer having at the polymer chain end an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. 9) A polyimide copolymer comprising a requisite structural unit consisting of 1 to 99 % by mol of recurring structural units of the formula (2): wherein m and n are individually an integer of 0 or 1, R 8 is a hydrogen atom, halogen atom, alkyl of 1 to 4 carbon atoms, alkoxy or phenyl, and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and 99 to 1 % by mol of recrring structural units of the formula (6): wherein n, Q and Ar' are the same as above, or said polyimide copolymer having at the polymer chain end an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. 10) A polyimide copolymer comprising two or more recurring strutural units of the formula (1) described in claim 1 or said polyimide copolymer having at the polymer chain end an aromatic ring is which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. Another aspect of the present invention is a preparation process of these polyimide homopolymers and copolymers, that is : 11) A preparation process of a polyimide having a requisite structural unit consising of one or more of recurring structurel units of the formula (1): wherein m, n, R and Ar are the same as above, comprising reacting aromatic diamine essentially consisting of one or more aromatic diamino compound of the formula (7): wherein m, n and R are the same as above, with tetracarboxylic dianhydride primarily having the formula (8): wherein Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and thermally or chemically imidizing resultant polyamic acid. 12) A preparation process of a polyimide having a requisite structural unit consisting of one or more of recurring structural units of the formula (1): wherein m, n, R and Ar are the same as above, and having at the polymer chain end a radical which is essentially unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride, comprising reacting aromatic diamine essentially consisting of one or more of aromatic diamino of the formula (7): wherein m, n and R are the same as above, with tetracarboxylic dianhydride primarily having the formula (8): wherein Ar is the same as above, in the presence of aromatic dicarboxylic anhydride of the formula (9): wherein Z is a divalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and/or aromatic monoamine of the formula (10): Z 1 - NH 2 wherein Z 1 is a monovalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and thermally or chemically imidizing resultant polyamic acid. In these processes, preferred aromatic dicarboxylic anhydride is phthalic anhydride and preferred aromatic monoamine is aniline. Amount of aromatic dicarboxylic anhydride (phthalic anhydride) is 0.001 to 1.0 mol per mol of aromatic diamine. Amount of aromatic monoamine (aniline) is 0.001 to 1.0 mol per mol of aromatic tetracarboxylic dianhydride. Further aspect of the present invention is; 13) A composition, film and solution comprising polyimide of the present invention. Still another aspect of the present invention is a novel aromatic diamino compound and the raw material aromatic dinitro compound, that is, 14) An aromatic dinitro compound of the formula (11); wherein m, n and R are the same as in the formula (1). 15) An aromatic diamino compound of the formula (7): wherein m, n and R are the same as in the formula (1). 16) An aromatic diamino compound of the formula (12): wherein n is an integer of 0 or 1, and R 8 is a hydrogen atom, halogen atom, alkyl of 1 to 4 carbon atoms, alkoxy or phenyl. 17) An aromatic diamino compound of the formula (13): wherein R 9 is 18) An aromatic diamino compound of the formula (14): wherein R 9 is the same as above. 19) An aromatic diamino compound of the formula (15): wherein R 9 is the same as above. Still further aspect of the present invention is as preparation process of these aromatic diamino compound. 20)A preparation process of an aromatic diamino compound of the formula (7): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms; R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms; and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, comprising carrying out condensation of a dinitro compound of the formula (16): wherein X is a halogen atom, and m and n are individually an integer of 0 or 1, and a hydroxy compound of the formula (17): R - OH wherein R is the same as above, in an aprotic polar solvent in the presence of a base to obtain an aromatic dinitro compound of the formula (11): wherein m, n and R are the same as above, and successively reducing the aromatic dinitro compound. The polyimide of the invention is essentially amorphous, is excellent in melt flow stability in the decreased temperature as compared with conventionally known polyimide, has greatly improved processability and can be applied to structural materials because of high elastic modulus. That is, the polyimide of the invention obtained by using a novel aromatic diamino compound as a monomer can control various properties such as melt flow ability and solubility in solvents by side chains and not by principal chain of polyimide. Thus, excellent melt flow property and solubility in solvents can be obtained while maintaining high heat resistance and adhesive property which are derived from benzophenone structure of the diamino compound of the the invention. Further, the polyimide of the invention can exhibit satisfactory adhesive strength at relatively decreased temperatures and can hence be applied to adhesive. The polyimide is soluble in general purpose organic solvents such as chloroform and thus can also be used in the form of polyimide varnish. In the case of utilizing as adhesive, the polyimide is previously ring-closed and can be used as varnish in the state of imide. As a result, a conventional disadvantage of void generation due to moisture can also be eliminated. Hot press type adhesion can also be carried out by using a polyimide film. Embodiments of the invention are described below by way of example with reference to the drawings of which: Figure 1 illustrates an infrared absorption spectrum of 3,3'-dinitro-4-phenoxybenzophenone obtained in Example 3. Figure 2 illustrates an infrared absorption spectrum of 3,3'-diamino-4-phenoxybenzophenone obtained in Example 3. Figure 3 illustrates an infrared absorption spectrum of 3,4'-dinitro-4-biphenoxybenzophenone obtained in Example 4. Figure 4 illustrates an infrared absorption spectrum of 3,4'-diamino-4-biphenoxybenzophenone obtained in Example 4. Figure 5 illustrates an infrared absorption spectrum of 1,3-bis(3-nitro-4-phenoxybenzoyl)benzene obtained in Example 5. Figure 6 illustrates an infrared absorption spectrum of 1,3-bis(3-amino-4-phenoxybenzoyl)benzene obtained in Example 5. Figure 7 illustrates an infrared absorption spectrum of 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene obtained in Example 6. Figure 8 illustrates an infrared absorption spectrum of 3,3'-diamino-4,4'-dimethoxybenzophenone obtained in Example 7. Figure 9 illustrates an infrared absorption spectrum of polyimide powder in Example 8. Figure 10 is a drawing illustrating the relationships between the viscosity and the residence time of the polyimide powder obtained in Example 8 in the cylinder of a flow tester. Figure 11 illustrates an infrared absorption spectrum of the polyimide powder obtained in Example 31. Figure 12 is a drawing illustrating the relationships between the viscosity and the residence time of the polyimide powder obtained in Example 31 in the cylinder of a flow tester. The polyimide of the invention comprises a requisite structural unit consisting of one or more of recurring structural units of the formula (1): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms, and R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl of 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms, and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member. That is, the invention is a polyimide comprising a requisite structural unit having recurring structural units of the formula (1), and more specifically, can be a homopolymer having one of the recurring structural units of the formula (1) or can be a copolymer having two or more of the recurring structural units. The polyimide of the invention can also be a copolymer of recurring structural units of the formula (1) and other recurring structural units of polyimide in the range giving no adverse effect on the properties of polyimide of the invention. Further, the polyimide of the invention can have at the polymer chain end an aromatic ring which is essentially unsubstituted or substituted with a radical having no reactivity for amine and dicarboxylic anhydride. That is, the polyimide of the invention can be capped at the polymer chain end thereof with an aromatic dicarboxylic anhydride of the formula (9): wherein Z is a divalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and/or aromatic monoamine of the formula (16) : Z 1 - NH 2 wherein Z 1 is a monovalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member. Preferred aromatic polyimide is capped at the polymer chain end thereof with phthalic anhydride and/or aniline. The polyimide of the invention includes a polyimide homopolymer having one of the above recurring structural units, a polyimide copolymer having two or more of the above recurring structural units, a mixture of two or more of said polyimide homopolymer and/or said polyimide copolymers, a polyimide copolymer having the recurring structural units of the formula (1) and other recurring structural units which are comprised in a proportion giving no adverse effect on the essential properties of polyimide, and a mixture of polyimide having one or more recurring structural units of the formula (1) and polyimide having said other recurring structural units. Consequently, when the polyimide of the invention is a polyimide copolymer having two or more recurring structural units of the formula(1) or a mixture of polyimide, the polyimide has two or more recurring structural units wherein one or more radicals selected from m, n, Ar and R in the formula (1) are different each other. The polyimide of the invention can be prepared by reacting the raw material monomers, aromatic diamine and aromatic tetracarboxylic dianhydride in the absence or presence of aromatic dicarboxylic anhydride and/or aromatic monoamine and by thermally or chemically imidizing the resulting polyamic acid. Aromatic diamine used for preparing these polyimides essentially consists of one or more of aromatic diamino compound of the formula (7): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms, and R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms aryl, alkenyl, aralkyl or ω-alkyloxyoligo (alkyleneoxy) alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms. Preferred aromatic diamine is an aromatic diamine compound of formula (12): wherein n is an integer of 0 or 1, and R 8 is hydrogen atom, halogen atom, alkyl having 1 to 4 carbon atoms, alkoxy and phenyl. More preferred aromatic diamine is aromatic diamino compounds of the formula (13): wherein R 9 is the formula (14): wherein R 9 is same as above, and the formula (15): wherein R 9 is same as above. Exemplary aromatic diamino compounds which can be used are 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone and 3,4'-diamino-5'-biphenoxybenzophenone. These aromatic diamino compounds can be used singly or as a mixture. These aromatic diamino compounds can be prepared, for example, by the following process. An aromatic dinitro compound of the formula (16): wherein X is a halogen atom and m and n are individually an integer of 0 or 1 is subjected to condensation with a hydroxy compound of the formula (17): R - OH wherein R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom alkyl of 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy of 1 to 5 carbon atoms, and R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl of 1 to 8 carbon atoms aryl, alkenyl, aralkyl or ω-alkyloxyoligo(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms, in an aprotic polar solvent in the presence of a base to obtain an aromatic dinitro compound of the formula (11) : wherein m, n and R are the same as above. Successively, the thus-obtained dinitro compound is reduced to prepare the aromatic diamino compound of the formula (7) : wherein m, n and R are the same as above. Following aromatic halogeno dinitro compounds of the formula (16) are preferably used for preparing the aromatic dinitro compound of the formula (11) which is used in the process. Dihalogenodinitrobenzophenone of the formula (16-1) : wherein X is a halogen atom, includes, for example, 4,4'-dihalogeno-3,3'-dinitrobenzophenone. Monohalogenodinitrobenzophenone of the formula (16-2) : wherein X is a halogen atom, includes, for example, 4-halogeno-3,3'(or 4')-dinitrobenzophenone such as 4-chloro-3,3'-dinitrobenzophenone, 4-chloro-3,4'-dinitrobenzophenone, 4-bromo-3,3'-dinitrobenzophenone, 4-bromo-3,4'-dinitrobenzophenone, 4-fluoro-3,3'-dinitrobenzophenone and 4-fluoro-3,4'-dinitrobenzophenone and 4-iodo-3,3'-dinitrobenzophenone. 4-iodo-3,4'-dinitrobenzophenone. 4-Chloro-3,3'-dinitrobenzophenone or 4-chloro-3,4'-dinitrobenzophenone is more preferably used. 1,3(Or 1,4)-bis (3-nitro-4-halogenobenzoyl)benzene of the formula (16-3) : wherein X is a halogen atom, includes, for example, 1,3-bis(3-nitro-4-chlorobenzoyl)benzene, 1,4-bis(3-nitro-4-chlorobenzoyl)benzene, 1,3-bis(3-nitro-4-fluorobenzoyl)benzene, 1,4-bis(3-nitro-4-fluorobenzoyl)benzene, 1,3-bis(3-nitro-4-bromobenzoyl)benzene and 1,4-bis(3-nitro-4-bromobenzoyl)benzene and 1,3-bis(3-nitro-4-iodobenzoyl)benzene. 1,4-bis(3-nitro-4-iodobenzoyl)benzene. 1,3-Bis(3-nitro-4-chlorobenzoyl)benzene or 1,4-bis(3-nitro-4-chlorobenzoyl)benzene is more preferably used. The aromatic dinitro compound of the formula (11) can be prepared in high yield by reacting these aromatic halogenodinitro compounds with phenols or alcohols in an aprotic polar solvent in the presence of a base. The aromatic halogeno dinitrocompound used for a raw material of the process, for example, 4,4'-dihalogeno-3,3'-dinitrobenzophenone can be obtained with ease by nitration of 4,4'-dihalogenobenzophenone through a known process of Japanese Laid-Open Patent Sho 58-121256. Other aromatic dinitro compounds can also be prepared by similar processes. Exemplary phenols which can be used include, for example, phenol; cresol, dimethyl phenol and other alkylphenols; guaiacol, dimethoxyphenol and other alkoxyphenols; chlorophenol, fluorophenol, dichlorophenol, difluorophenol and other halogenophenols; phenylphenol, diphenylphenol and other arylphenols; phenoxyphenol, diphenoxyphenol and other aryloxyphenols; and naphthol, anthrol and other polycyclic phenols and alkyl, alkoxy, halogeno and aryl derivatives of these polycyclic phenols. Phenols and polycyclic phenols having two or more kinds of substituents such as halogenoalkylphenol and halogenoarylphenol can also be used. Alcohols which can be used include, for example, methanol, ethanol, isopropyl alcohol, tert-butyl alcohol and other alkyl alcohols; ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether and other oligoalkylene glycol monoalkyl ethers ; benzyl alcohol and other arylalkyl alcohols; and propenyl alcohol, isopropenyl alcohol and other alkenyl alcohols. Phenols and alcohols are not restricted to these enumerated compounds. The amount of these phenols or alcohols is 1.0 to 1.5 mols, preferably 1.03 to 1.3 mols per mol of the aromatic halogenodinitro compound of the formula (16) when aromatic monohalogenodinitro compound is used, and 2.0 to 3.0 mols, preferably 2.05 to 2.6 mols when aromatic dihalogenodinitro compound is used. Bases which can be used are carbonate, hydrogen carbonate, hydroxide and alkoxide of alkali metals, and include, for example, potassium carbonate, potassium hydrogen carbonate, potassium hydroxide, sodium carbonate, sodium hydroxide, sodium hydrogen carbonate, lithium carbonate, lithium hydroxide, sodium methoxide and potassium isopropoxide. The amount of these bases is more than equivalent, practically 1 to 2 equivalents per equivalent of a halogen radical in the aromatic halogenodinitro compound of the formula (16), (16-1), (16-2) or (16-3). Exemplary aprotic polar solvents used include N,N-dimethylformamid e, N,N-diethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, sulfolane and tetrahydrofuran. No particular limitation is imposed upon the amount of these solvents and the amount of 1 to 10 times by weight of the raw materials is usually sufficient. Catalysts which can be used for accelerating the reaction are copper powder, copper compounds and phase transfer catalysts such as crown ether, polyethylene glycol, quaternary ammonium base and quaternary phosphonium base. The reaction temperature is in the range of -10 °C to 250 °C, preferably -5 °C to 180 °C . The reaction time is in the range of 0.5 to 30 hours, preferably 1 to 10 hours. The reaction can be generally carried out by the following procedures. 1 ○ Prescribed amounts of a phenol or alcohol, a base and a solvent are charged to form an alkali metal salt of the phenol or alcohol, and the aromatic dinitro compound of the formula (16), for example, 4,4'-dihalogeno-3,3'-dinitrobenzophenone is successively added to carry out the reaction. 2 ○ The aromatic dinitro compound of the formula (16), for example, 4,4'-dihalogeno-3,3'-dinitrobenzophenone is charged to a solvent, and successively an alkali metal salt of the phenol or alcohol formed previously is added to the mixture to carried out the reaction. 3 ○ The whole materials including the aromatic dinitro compound of the formula (16), for example, 4,4'-dihalogeno-3,3'-dinitrobenzophenone are previously charged at one time and the mixture is heated as intact to carry out the reaction. The procedures are not limited to these embodiments and other suitable procedures can also be applied. When water is present in the reaction system, water is removed out of the reaction system by ventilating nitrogen gas during the reaction. However, a method for generally carried out is to azeotropically distill off water by addition of a small amount of benzene, toluene, xylene and chlorobenzene. End point of the reaction can be determined by decrease of the raw materials according to thin layer chromatography or high performance liquid chromatography. After finishing the reaction, the reaction mixture is poured as intact or after concentration into water to obtain the crude dinitro compound. The crude compound can be purified by recrystallization from or sludging in a solvent. The aromatic dinitro compound of the formula (11): wherein m, n and R are the same as above, which can be obtained by the above reaction is, for example, a compound of the formula (11-1): the formula (11-2): or the formula (11-3): In the formula (11-1), (11-2) and (11-3), R is the same as above, preferably The aromatic dinitro compound obtained above is reduced to give the aromatic diamino compound. That is, the aromatic diamino compound of the invention can be prepared by reducing the corresponding aromatic dinitro compound obtained by the above process. No particular restriction is placed upon the reduction method of dinitro compound. A method for reducing a nitro radical to an amino radical described, for example, in Shin Jikken Kagaku Koza, vol. 15, Oxidation and Reduction II, Published from Maruzen (1977), can be usually applied. Catalytic reduction is preferred in industry. Exemplary reducing catalysts which can be used include metal catalysts used generally for catalytic reduction, for example, nickel, palladium, platinum, rhodium, ruthenium, cobalt and copper. Palladium catalysts are preferred in industry. These catalysts are generally used, though can be used in the state of metal, by supporting on the surface of a carrier such as carbon, barium sulfate, silica gel, alumina and cerite, or also used in the form of a Raney catalyst of nickel, cobalt or copper. No particular limitation is put upon the amount of these catalysts. The amount is in the range of 0.01 to 10 % by weight for the raw material dinitro compound, usually 2 to 8 % by weight in the form of metal and 0.1 to 5 % by weight when supported on the carrier. In the case of iron powder reduction, the reaction temperature is in the range of 0 °C to 150 °C, preferably 0 °C to 70 °C. The reaction can be carried out by gradually adding iron powder to a solution or suspension of the raw material and a catalytic amount of hydrochloric acid, or by previously charging the raw materials containing iron powder into a solvent to conduct the reaction. No particular restriction is imposed upon the solvents used in the reduction so long as inactive for the reaction. Preferred solvents include, for example, methanol, ethanol, isopropyl alcohol and other alcohols; ethylene glycol, propylene glycol and other glycols; ether, dioxane, tetrahydrofuran, methyl cellosolve and other ethers. Other solvents which can also be used in some cases are hexane, cyclohexane and other aliphatic hydrocarbons; benzene, toluene, xylene and other aromatic hydrocarbons; ethyl acetate, butyl acetate and other esters; dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,2-trichloroethane, tetrachloroethane and other halogenated hydrocarbons; and N,N-dimethylformamide. No particular limitation is placed upon the amount of these solvents. These solvents are used in an amount enough to suspend or completely dissolve raw materials, that is, usually 0.5 to 10 times by weight for the weight of raw materials. No particular limitation is placed on the reaction temperature. The reaction temperature is in the range of usually 20 to 200°C, preferably 20 to 100°C. Reaction pressure is in the range of atmospheric pressure to 50 atm. Reducing reaction is usually carried out by suspending or dissolving the dinitro compound in a solvent, adding the catalyst and introducing hydrogen into the reaction system with stirring at a prescribed temperature. End point of the reaction can be determined by the amount of hydrogen, thin layer chromatography or high performance liquid chromatography. After finishing the reaction, the catalyst is removed by filtration and the solvent is distilled out of the filtrate to obtain the desired product. The polyimide of the invention can be prepared from the above aromatic diamino compound. More preferred recurring structural units of the polyimide include, for example, units of the formula (2): wherein m and n are individually an integer of 0 or 1, R 8 is a hydrogen atom, halogen atom, alkyl having 1 to 4 carbon atoms, alkoxy or phenyl, and Ar is tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, units of the formula (3) : wherein R 9 is and Ar is the same as in the formula (2), units of the formula (4) : wherein R 9 and Ar are the same as in the formula (3), and units of the formula (5) : wherein R 9 and Ar are the same as the formula (3). Another preferred polyimide is a copolymer comprising a requisite structural unit consisting of 1 to 99 % by mol of the recurring structural units of the above formula (1), (2), (3), (4) or (5) and 99 to 1 % by mol of the recurring structural units of the formula (6) : wherein n is an integer of 0 to 5, Q is a direct bond, -O-, -S-, -CO-, -SO 2 -, -CH 2 -, -C(CH 3 ) 2 - or -C(CF 3 ) 2 - and may be the same or different when aromatic rings are connected each other with two or more connecting radicals Q, and Ar' is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alcyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member. The polyimide of the invention is prepared by using the above aromatic diamines for the requisite raw material monomer. Other aromatic diamines can be used in combination with these diamines so long as giving no adverse effect on the good properties of the polyimide. Other aromatic diamines which can be used in combination include, for example, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis(3-aminophenyl)sulfide, (3-aminophenyl)(4-aminophenyl)sulfide, bis(4-aminophenyl)sulfide, bis(3-aminophenyl)sulfoxide, (3-aminophenyl)(4-aminophenyl)sulfoxide, bis(3-aminophenyl)sulfone, (3-aminophenyl)(4-aminophenyl)sulfone, bis(4-aminophenyl)sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]butane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1,4-bis(3-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene, 1,3-bis(3-amino-α,α-dimethybenzyl)benzene, 1,3-bis(4-amino-α,α-dimethybenzyl)benzene, 1,4-bis(3-amino-α,α-dimethybenzyl)benzene, 1,4-bis(4-amino-α,α-dimethybenzyl)benzene, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide bis[4-(4-aminophenoxy)phenyl]sulfide bis[4-(3-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethybenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethybenzyl)phenoxy]diphenyl sulfone, bis[4- {4-(4-aminophenoxy) phenoxy} phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethybenzyl]benzene, 1,4-bis[4-(3-aminophenoxy)-α,α-dimethybenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α,α-dimethybenzyl] benzene, 1,3-bis[4-(3-aminophenoxy)-α,α-dimethybenzyl]benzene, 3,3'-diamino-4,4'-difluorobenzophenone, 3,3'-diamino-5,5'-bis(trifluoromethyl)diphenyl ether, and 4,4'diamino-5,5'-bis (trifluoromethyl)diphenyl ether. These aromatic diamines can be used singly or as a mixture. Aromatic tetracarboxylic dianhydride which can be used in the invention is one or more of compounds of the formula (8): wherein Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member. In the aromatic tetracarboxylic dianhydride of the formula (8), Ar is specifically a tetravalent radical selected from the group consisting of an aliphatic radical having 2 to 10 carbon atoms, alicyclic radical having 4 to 10 carbon atoms, monoaromatic radical of the formula (a): condensed polyaromatic radical of the formula (b): and noncondensed aromatic radical being connected each other with a direct bond or a bridge member and having the formula (c): wherein X is a direct bond, -CO-, -0-, -S-, -SO 2 -, -CH 2 -, -C(CH 3 ) 2 -, -C(CF 3 ) 2 -, wherein Y is a direct bond, -CO-, -O-, -S-, -SO 2 -, -CH 2 -, -C(CH 3 ) 2 or -C(CF 3 ) 2 -. Exemplary tetracarboxylic dianhydride of the formula (8) which can be used in the invention include, ethylenetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 2,2-bis[4 {4-(1,2-dicarboxy)benzoyl} phenyl]propane dianhydride, 2,2-bis[4 {3-(1,2-dicarboxy)phenoxy} phenyl]propane dianhydride, bis[4- {4-(1,2-dicarboxy)phenoxy} phenyl]ketone dianhydride, bis[4- {3-(1,2-dicarboxy)phenoxy} phenyl]ketone dianhydride, 4,4'-bis[4-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, 4,4'-bis[3-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, bis[4- {4-(1,2-dicarboxy)phenoxy} phenyl]ketone dianhydride, bis[4- {3-(1,2-dicarboxy)phenoxy} phenyl]ketone dianhydride, bis[4- {4-(1,2-dicarboxy)phenoxy} phenyl]sulfone dianhydride, bis[4- {3-(1,2-dicarboxy)phenoxy} phenyl]sulfone dianhydride, bis[4- {4-(1,2-dicarboxy)phenoxy} phenyl]sulfide dianhydride, bis[4- {3-(1,2-dicarboxy)phenoxy} phenyl]sulfide dianhydride, 2,2-bis[4- {4-(1,2-dicarboxy )phenoxy} phenyl]-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis[4-(3-(1,2-dicarboxy)phenoxy } phenyl]-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, and 1,2,7,8-phenanthrenetetracarboxylic dianhydride. These dianhydrides can be used singly or as a mixture. The polyimide of the invention prepared by using the above aromatic diamine and aromatic tetracarboxylic dianhydride as monomer components comprises a requisite structural unit primarily having recurring structural units of the formula (1). That is, the invention includes polyimide which is derived from a selected aromatic diamine and a selected aromatic tetracarboxylic dianhydride in the above enumerated raw materials of the invention and has recurring structural units of the formula (1)∼(5), a polyimide copolymer which is derived from one or more selected aromatic diamines and one or more selected aromatic tetracarboxylic dianhydrides (both one, exclusive) in the above enumerated raw materials of the invention, and a polyimide copolymer which is derived from one or more selected aromatic diamines and one or more selected aromatic tetracarboxylic dianhydride in the above enumerated raw materials of the invention in combination with other diamines added in the range of giving no adverse effect on the properties of resulting polyimide. The aromatic polyimide copolymer comprising a fundamental skeleton consisting of recurring structural units of the formula (1) and recurring structural units of the formula (6) can be obtained by reacting aromatic diamino compound of the formula (7): in the presence of one or more diamine represented by the formula (6-1): H 2 N - X - NH 2 wherein X is wherein n is an integer of 0 to 5; Q is a direct bond, -O-, -S-, -CO-, -SO 2 -, -CH 2 -, -C(CH 3 ) 2 - or -C(CF 3 ) 2 - and may be the same or different when two or more Q connects three or more aromatic rings each other ; with one or more aromatic tetracarboxylic dianhydride selected from the above formula (8) or the formula (6-2): wherein Ar' is a tetravalent radical selected from the group consisting of wherein M is a divalent radical selected from the group consisting of and Exemplary aromatic diamines of the formula(6-1) used in the reaction include m-phenylenediamine, o-phenylenediamine and p-phenylenediamine, benzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2'-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)propane, 2-(3-aminophenyl)-2-(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, and 2-(3-aminophenyl)-2-(4-aminophenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene. 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(3-amino-α,α-dimethylbenzyl)benzene and 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene. 4,4'-bis(4-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 3,4'-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]ketone, bis[3-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[3-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, and 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane. These aromatic diamines can be used singly or as a mixture. Exemplary aromatic tetracarboxylic dianhydrides of the formula (6-2) include; pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis[4-(1,2-dicarboxy)phenoxy]benzene dianhydride, 1,4-bis[4-(1,2-dicarboxy)phenoxy]benzene dianhydride, 4,4'-bis[4-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, 4,4'-bis[4-(1,2-dicarboxy)phenoxy]benzophenone dianhydride, bis[4- {4-(1,2-dicarboxy)phenoxy} phenyl]sulfone dianhydride, 2,2-bis[4- {4-(1,2-dicarboxy)phenoxy} phenyl]sulfone dianhydride, and 2,2-bis[4- {4-(1,2-dicarboxy )phenoxy} phenyl]-1,1,1,3,3,3-hexafluoropropane dianhydride. The aromatic polyimide copolymer comprising 99 to 1 % by mol of the fundamental skeleton having recurring structural units of the formula (1),(2),(3),(4) or (5) and 1∼99 % by mol of the fundamental skeleton having recurring structural units of the formula (6) are prepared from corresponding monomers above. In addition to the requisite aromatic diamine and aromatic dicarboxylic dianhydride, other aromatic diamines or aromatic tetracarboxylic dianhydrides can be used in combination so long as giving no adverse effect on the good properties of the resulting homopolymer and copolymer of aromatic polyimide. The invention also includes capped polyimide having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity for amine and dicarboxylic anhydride. Further, the invention includes composition of these polyimides. Compositions have better properties than polyimides as such in some cases. The polyimide having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride can be obtained by capping the terminal radical of the polymer chain which is derived from aromatic amine of the above formula (7) and tetracarboxylic dianhydride primarily having the above formula (8), with aromatic dicarboxylic anhydride of the formula (9) wherein Z is a divalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member and/or aromatic monoamine of the formula (10) : Z 1 - NH 2 wherein Z 1 is a monovalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, preferably with phthalic anhydride and/or aniline. The polyimide can be prepared by reacting an aromatic diamine component with aromatic tetracarboxylic dianhydride in the presence of aromatic dicarboxylic anhydride of the formula (9) and/or aromatic monoamine of the formula (10), and successively by thermally or chemically imidizing the resultant polyamic acid Exemplary aromatic dicarboxylic anhydrides of the formula (9) include phthalic anhydride,2,3-benzophenonedicarboxylic anhydride, 3,4-benzophenonedicarboxylic anhydride, 2,3-dicarboxyphenylphenyl ether anhydride, 3,4-dicarboxyphenyl phenyl ether anhydride, 2,3-biphenyldicarboxylic anhydride, 3,4-biphenyldicarboxylic anhydride, 2,3-dicarboxyphenyl phenyl sulfone anhydride, 3,4-dicarboxyphenyl phenyl sulfone anhydride, 2,3-dicarboxyphenyl phenyl sulfide anhydride, 3,4-dicarboxyphenyl phenyl sulfide anhydride, 1,2-naphthalenedicarboxylic anhydride, 2,3-naphthalenedicarboxylic anhydride, 1,8-naphthalenedicarboxylic anhydride, 1,2-anthracenedicarboxylic anhydride, 2,3-anthracenedicarboxylic anhydride, and 1,9-anthracenedicarboxylic anhydride. These dicarboxylic anhydrides can be substituted with a radical having no reactivity for amine and dicarboxylic anhydride. Phthalic anhydride is most preferred in these dicarboxylic anhydrides in view of properties of resulting polyimide and practical use. Polyimide prepared in the presence of phthalic anhydride has excellent heat stability in high temperature and is very useful for a material of space and aeronautic instruments and electric and electronic devices. A portion of phthalic anhydride can be replaced with other dicarboxylic anhydrides in the range giving no adverse effect on the good properties of polyimide. The amount of dicarboxylic anhydride is suitably 0.001 to 1.0 mol per mol of aromatic diamine of the formula (7). When the amount is less than 0.01 mol, viscosity increases in high temperature processing. On the other hand, the amount exceeding 1.0 mol decreases mechanical properties of the product. Thus, the preferred amount is in the range of 0.01 to 0.5 mol. Aromatic monoamines which can be used include, for example, aniline, o-toluidine, m-toluidine, p-toluidine, 2,3-xylidine, 2,6-xylidine, 3,4-xylidine, 3,5-xylidine, o-chloroaniline, m-chloroaniline, p-chloroaniline, o-bromoaniline, m-bromoaniline, p-bromoaniline, m-nitroaniline, p-nitroaniline, o-aminophenol, m-aminophenol, p-aminophenol, o-anisidine, m-anisidine, p-anisidine, o-phenetidine, m-phenetidine, p-phenetidine, o-aminobenzaldehyde, m-aminobenzaldehyde, p-aminobenzaldehyde, o-aminobenzonitrile, m-aminobenzonitrile, p-aminobenzonitrile, 2-aminobiphenyl, 3-aminobiphenyl, 4-aminobiphenyl, 2-aminophenyl phenyl ether, 3-aminophenyl phenyl ether, 4-aminophenyl phenyl ether, 2-aminobenzophenone, 3-aminobenzophenone, 4-aminobenzophenone, 2-aminophenyl phenyl sulfide, 3-aminophenyl phenyl sulfide, 4-aminophenyl phenyl sulfide, 2-aminophenyl phenyl sulfone, 3-aminophenyl phenyl sulfone, 4-aminophenyl phenyl sulfone, α-naphthylamine, β-naphthylamine, 1-amino-2-naphthol, 2-amino-1-naphthol, 4-amino-1-naphthol, 5-amino-1-naphthol, 5-amino-2-naphthol, 7-amino-2-naphthol, 8-amino-1-naphthol, 8-amino-2-naphthol, 1-aminoanthracene, 2-aminoanthracene and 9-aminoanthracene. These aromatic monoamines can be substituted with a radical having no reacting for amine and dicarboxylic anhydride. The amount of aromatic monoamine is suitably 0.001 to 1.0 mol per mol of the aromatic tetracarboxylic dianhydride component. The amount less than 0.001 mol leads to viscosity increase in the high temperature processing and causes reduction of processability. On the other hand, the amount exceeding 1.0 mole lowers mechanical strengths of the product. Thus, preferred range is 0.001 to 0.5 mol. Consequently, preparation of capped polyimide of the invention which is terminated with an unsubstituted or substituted aromatic ring is carried out by using 0.9 to 1.0 mol of aromatic diamine and 0.001 to 1.0 mol of dicarboxylic anhydride or aromatic monoamine per mol of tetracarboxylic dianhydride. In the preparation of polyimide, the molar ratio of tetracarboxylic dianhydride to aromatic diamine is usually controlled in order to adjust molecular weight of formed polyimide. In order to obtain polyimide having good melt-flowability in the process of the invention, the molar ratio of aromatic diamine to tetracarboxylic dianhydride is suitably in the range of 0.9 to 1.0. Any process for preparing polyimide including known processes can be applied to the preparation of polyimide in the invention. Particularly preferred process is to carry out the reaction in an organic solvent. Exemplary solvent which can be used for the reaction include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, pyridine, picoline, dimethyl sulfoxide, dimethyl sulfone, tetramethylurea, hexamethylphosphoramide, phenol, o-cresol, m-cresol, p-cresol, m-cresylic acid, p-chlorophenol and anisole. These organic solvents can be used singly or as a mixture. In the process of the invention, the reaction is carried out by the addition of aromatic diamine, aromatic tetracarboxylic dianhydride and aromatic dicarboxylic anhydride or aromatic monoamine to the organic solvent according to the following procedures. (A) After reacting aromatic tetracarboxylic dianhydride with aromatic diamine, aromatic dicarboxylic anhydride or aromatic monoamine is added to continue the reaction. (B) After reacting aromatic diamine with aromatic dicarboxylic anhydride, aromatic tetracarboxylic dianhydride is added to continue the reaction. (C) After reacting aromatic tetracarboxylic dianhydride with aromatic monoamine, aromatic diamine is added to continue the reaction. (D) Aromatic tetracarboxlic dianhydride, aromatic diamine and aromatic dicarboxylic anhydride or aromatic monoamine are added at one time and the reaction is carried out. Any of the above addition procedures can be conducted. Reaction temperature is usually 250 °C or less, preferably 50 °C or less. No particular limitation is imposed upon the reaction pressure. Atmospheric pressure is satisfactory for carrying out the reaction. Reaction time differs depending upon the tetracarboxylic dianhydride, solvent and reaction temperature and sufficient time for carrying out the reaction is usually 4 to 24 hours. Further, polyamic acid thus obtained is thermally imidized by heating at 100 °C to 400 °C or chemically imidized by using an imidizing agent such as acetic anhydride to give polyimide having recurring structural units corresponding to those of polyamic acid. The desired polyimide can also be prepared by suspending or dissolving in an organic solvent aromatic diamine and aromatic tetracarboxylic dianhydride, and additionally aromatic dicarboxylic anhydride and/or aromatic monoamine in the case of terminating the polyimide with an aromatic ring, and successively heating the mixture to carry out formation and imidization of the polyimide precursor polyamic acid at the same time. Polyamic acid which is the precursor of polyimide of the invention has an inherent viscosity of 0.01 to 3.0 dℓ /g at 35 °C in a N,N-dimethylacetamide solution at a concentration of 0.5 g/ dℓ . The polyimide of the invention has an inherent viscosity of 0.01 to 3.0 dℓ /g at 35 °C in a solvent mixture composed of 9 parts by weight of p-chlorophenol and 1 parts of weight of phenol at a concentration of 0.5 g/ dℓ . The polyimide of the invention is soluble in general purpose solvents. Representative solvents include, for example, halogenated hydrocarbon solvents such as dichloromethane, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, tetrachloroethane, dibromomethane, trifroromethane, tetrabromomethane, dibromoethane, tribromoethane and tetrabromoethane; amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, N,N-dimethoxyacetamide and N-methyl-2-pyrrolidone; phenolic solvents such as phenol, cresol, halogenated cresol and xylenol; and aromatic hydrocarbon solvents such as benzene, toluene and xylene. These solvents can be used singly or as a mixture. The polyimide varnish obtained by dissolving the polyimide of the invention in these solvents can be employed for heat resistant varnishes, coatings and sealants. Further, polyimide film of the invention can be prepared by casting on a glass plate a varnish of polyamic acid precursor of the polyimide and heating to carry out imidization, by hot-pressing the polyimide powder as intact to form a film or by removing an organic solvent upon heating from the solution dissolved the polyimide to form a film. That is, films and powder of polyimide can be prepared by known methods. In the case of melt-processing the polyimide of the invention, other thermoplastic resins can be blended in a suitable amount depending upon the object for use so long as giving no adverse effect on the good properties of polyimides. Thermoplastic resin which can be blended include, for example, polyethylene, polypropylene, polycarbonate, polyarylate, polyamide, polysulfone, polyether sulfone, polyether ketone, polyphenylene sulfide, polyamideimide, polyetherimide, modified polyphenylene oxide and other kind of polyimide. Fillers which are used for common resin compositions can be added in the range not impairing the object of the invention. Exemplary fillers include graphite, carborundum, silica powder, molybdenum disulfide, fluoro resin and other wear resistance improvers; glass fiber, carbon fiber and other reinforcements; antimony trioxide, magnesium carbonate, calcium carbonate and other flame retardance improvers; clay, mica and other electrical property improvers; asbestos, silica, graphite and other tracking resistance improvers; barium sulfide, silica, calcium metasilicate and other acid resistance improvers; iron powder, zinc powder, aluminum powder, copper powder and other thermal conductivity improvers; and other miscellaneous materials such as glass beads, glass balloons, talc, diatomaceous earth, alumina, silicate balloons, hydrated alumina, metal oxides and colorants. The invention will hereinafter be illustrated further in detail by way of examples. These examples, however, are not be construed to limit the scope of the invention. Example 1 To a four necked flask equipped with a thermometer, reflux condenser and stirrer, 150 g of N,N-dimethylformamide (DMF), 20 g of toluene, 80 g (0.235 mol) of 4,4'-dichloro-3,3'-dinitrobenzophenone, 45.5 g (0.483 mol) of phenol and 39 g (0.282 mol) of potassium carbonate were charged. The mixture was heated to 130 °C with stirring and successively aged at 130 °C for 5 hours. After finishing the reaction, the reaction mixture was cooled to 80 °C and filtered to remove inorganic salts. The filtrate was mixed with 60 g of water and cooled to the room temperature to crystallize the desired product. The precipitated crystals were filtered and sludged with methanol to obtain 92 g (86 % yield) of desired 3,3'-dinitro-4,4'diphenoxybenzophenone. Melting point : 111.0 ∼112.8 °C 'H-NMR δ (CDCl 3 , ppm) : 7.175 (d, 4H (1)), 7.19∼7.69 (m, 6H (2)), 7.57 (d, 2H (3)) 8.06 (dd, 2H (4)), 8.52 (d, 2H (5)) (1)∼(5) illustrate positions on the following formula. Example 2 To a reaction apparatus equipped with a thermometer, reflux condenser and stirrer, 60 g (0.131 mol) of 3,3'-dinitro-4,4'-diphenoxybenzophenone, 150 g of methyl cellosolve and 3.0 g of 5 %-Pd/C (50 % moisture content) were charged and reacted in a hydrogen atmosphere at 70 ∼80 °C for 4 hours. After finishing the reaction, the catalyst was filtered and the filtrate was concentrated under reduced pressure to obtain 45 g (86 % yield) of 3,3'-diamino-4,4'-diphenoxybenzophenone as light yellow crystals. Melting point : 153.3 ∼154.0 °C 1 H-NMR δ (CDCl 3 , ppm) : 4.17 (s, 4H (1)), 6.96 (d, 4H (2)), 7.12∼7.63 (m, 6H (3)) 7.21∼7.25 (m, 4H (4)), 7.43 (d, 2H (5)) (1)∼(5) illustrate positions on the following formula. Elementary analysis (C 25 H 20 N 2 O 3 ) C H N Calculated (%) 75.74 5.18 7.07 Found (%) 75.62 5.20 7.01 Example 3 [The first step reaction] To a glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 61.3 g (0.2 mol) of 4-chloro-3,3'-dinitrobenzophenone, 19.7 g (0.21 mol) of phenol, 16.6 g (0.12 mol) of potassium carbonate, 220 g of N,N-dimethylformamide and 15 g toluene were charged. The mixture was heated to 140 °C with stirring and aged at 140 °C for 3 hours. After finishing the reaction, the reaction mixture was cooled to 100 °C and filtered to remove inorganic salts. The filtrate was mixed with 200 g of water and 50 g of methanol and cooled to the room temperature. The precipitated crystals were filtered and washed with isopropyl alcohol to obtain 69.1 g (94.8 % yield) of 3,3'-dinitro-4-phenoxybenzophenone. The purity measured by high performance liquid chromatography was 99.7 %. Melting point was 135.1∼136.0 °C. The IR spectrum is illustrated in Figure 1. [The second step reaction] To a sealed glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 54.6 g (0.15 mol) of the above obtained 3,3'-dinitro-4-phenoxy-benzophenone, 1.1 g of 5 % palladium / alumina catalyst (N.E. Chemcat Co.) and 270 g of N,N-dimethylformamide were charged. Hydrogen was introduced into the reaction vessel at temperature of 40∼50 °C with stirring, and 19.9 l of hydrogen was absorbed in about 8 hours. After finishing the reaction, the reaction mixture was filtered at the same temperature to remove the catalyst. The filtrate was concentrated under reduced pressure to obtain 37.0 g (81.2 % yield) of 3,3'-diamino-4-phenoxybenzophenone as light yellow crystals. Purity was 99.1 % by high performance liquid chromatography. Melting point was 111.6∼113.0 °C. The IR spectrum is illustrated in Figure 2. Elementary analysis (C 19 H 16 N 2 O 2 ) C H N Calculated (%) 75.0 5.3 9.2 Found (%) 73.9 5.6 10.1 Example 4 [The first step reaction] To a glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 61.3 g (0.2 mol) of 4-chloro-3,4'-dinitrobenzophenone, 35.7 g (0.21 mol) of p-phenylphenol, 16.6 g (0.12 mol) of potassium carbonate, and 235 g of N,N-dimethylformamide were charged. The mixture was heated to 140 °C with stirring and aged at 140∼ 150 °C for 1.5 hours. After finishing the reaction, the reaction mixture was cooled to 100 °C and filtered to remove inorganic salts. The filtrate was mixed with water and cooled to the room temperature. The precipitated crystals were filtered and washed with isopropyl alcohol to obtain 73.8 g (83.8 % yield) of 3,4'-dinitro-4-biphenoxybenzophenone. The purity measured by high performance liquid chromatography was 99.5 %. Melting point was 139.6∼140.6 °C. The IR spectrum is illustrated in Figure 3. [The second step reaction] To a sealed glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 44.0 g (0.1 mol) of the above 3,4'-dinitro-4-biphenoxy-benzophenone, 3.5 g of 5 % palladium / alumina catalyst (N.E. Chemcat Co.) and 220 g of N,N-dimethylformamide were charged. Hydrogen was introduced into the reaction vessel at temperature of 40 ∼50 °C with stirring, and 12.2 ℓ of hydrogen was absorbed in about 9 hours. After finishing the reaction, the reaction was filtered at the same temperature to remove the catalyst. The filtrate was mixed with 70 g of water to obtain 31.8 g (83.6 % yield) of 3,4'-diamino-4-biphenoxybenzophenone as light brown crystals. Purity was 99.1 % by high performance liquid chromatography. Melting point was 244.8∼245.1 °C. The IR spectrum is illustrated in Figure 4. Elementary analysis (C 25 H 20 N 2 O 2 ) C H N Calculated (%) 78.9 5.3 7.4 Found (%) 78.0 5.4 7.9 Example 5 [The first step reaction] To a glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 89.0 g (0.2 mol) of 1,3-bis(3-nitro-4-chlorobenzoyl)benzene, 59.3 g (0.63 mol) of phenol, 33.2 g (0.24 mol) of potassium carbonate and 450 g of N,N-dimethylformamide were charged. The mixture was heated to 110 °C with stirring and aged at 110∼ 120 °C for 1.5 hours. After finishing the reaction, the reaction mixture was filtered at the same temperature to remove inorganic salts. The filtrate was cooled to 80 °C, 225 g of water was dropwise added and the mixture was cooled to the room temperature. The precipitated crystals were filtered and recrystallized from 2-methoxyalcohol to obtain 103.7 g (92.5 % yield) of 1,3-bis(3-nitro-4-phenoxybenzoyl) benzene. The purity measured by high performance liquid chromatography was 99.8 %. Melting point was 162.3∼163.8 °C. The IR spectrum is illustrated in Figure 5. [The second step reaction] To a sealed glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 56.1 g (0.1 mol) of the above 1,3-bis(3-nitro-4-phenoxybenzoyl)-benzene, 2.0 g of 5 % palladium / alumina catalyst (N.E. Chemcat Co.) and 200 g of N,N-dimethylformamide were charged. Hydrogen was introduced into the reaction vessel at temperature of 25 °C with stirring, and 12.2 ℓ of hydrogen was absorbed in about 20 hours. After finishing the reaction, the reaction mixture was filtered at the same temperature to remove the catalyst. The filtrate was mixed with 150 g of water to obtain light brown crystals. The crystals were recrystallized from toluene to obtain 39.1 g (78.1 % yield) of 1,3-bis(3-amino-4-phenoxybenzoyl)benzene. Purity was 98.8 % by high performance liquid chromatography. Melting point was 128.∼ 129.0 °C. The IR spectrum is illustrated in Figure 6. Elementary analysis C H N Calculated (%) 76.8 4.8 5.6 Found (%) 74.0 4.9 6.1 Example 6 [The first step reaction] To a glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 44.5 g (0.1 mol) of 1,3-bis(3-nitro-4-chlorobenzoyl)benzene, 35.7 g (0.21 mol) of p-phenylphenol, 16.6 g (0.12 mol) of potassium carbonate and 220 g of N,N-dimethylformamide were charged. The mixture was heated to 90 °C with stirring and aged 3 hours at the same temperature. After finishing the reaction, the reaction mixture was filtered at the same temperature to remove inorganic salts. The filtrate was mixed with water. The precipitated crystals were filtered and recrystallized from toluene to obtain 64.7 g (90.5 % yield) of 1,3-bis(3-nitro-4-phenoxybenzoyl)benzene. The purity measured by high performance liquid chromatography was 99.2 %. Melting point was 190.6∼191.6 °C. [The second step reaction] To a sealed glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 35.7 g (0.05 mol) of the above 1,3-bis(3-nitro-4-biphenoxybenzoyl)-benzene, 33.5 g (0.06 mol) of iron powder and 400 g of a 90 % aqueous 2-methoxyethanol solution were charged and warmed to 50 °C. To the mixture a solution containing 1.1 g of 35 % hydrogen acid in 30 g of 90 % 2-methoxyethanol was dropwise added over 2 hours and further stirred for 15 hours at 50∼60 °C. After finishing the reaction, the reaction mixture was mixed with 250 g of water and cooled to 25 °C and filtered. The residue was dissolved in 230 g of N,N-dimethylformamide at 110 °C and filtered. The filtrate was mixed with water and cooled to 25 °C. The precipitated crystals were recrystallized from toluene to obtain 26.2 g (80.2 % yield) of 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene. Purity was 98.8 % by high performance liquid chromatography. Melting point was 186.7∼187.8 °C. The IR spectrum is illustrated in Figure 7. Elementary analysis C H N Calculated (%) 81.0 4.9 4.3 Found (%) 79.9 5.0 4.5 Example 8 [The first step reaction] To a glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 500 g of tetrahydrofuran and 100 g (0.293 mol) of 4,4'-dichloro-3,3'-dinitrobenzophenone were charged. The mixture was cooled to 0 °C with stirring, and then 34.8 g of sodium methoxide (28 % methanol solution, 0.645 mol) was added dropwise to the mixture taking 2 hours. Successively, the mixture was aged 3 hours at 20 °C. After finishing the reaction, the reaction mixture was filtered at the same temperature to remove insoluble matter. The filtrate was heated to 60 °C and mixed 990 mℓ of water and cooled to the room temperature to crystallize the desired product. The above insoluble matter obtained by filtration was sludgged with 300 g of water to obtain the desired product. These products obtained by the above procedures was combined and recrystallized from 1,2-dichloroethane (EDC) to obtain 84 g (86 % yield) of 3,3'-dinitro-4,4'-dimethoxybenzophenone. Melting point was 189.0∼189.9 °C. 1 H-NMR δ (DMSO- d 6 , ppm ) : 4.05 (S, 6H(1)), 7.53 (d, 2H(2)), 8.06(dd, 2H(3)), 8.26 (d, 2H(4)) (1)∼(4) illustrate positions on the following formula. Elementary analysis (C 25 H 12 N 2 O 7 ) C H N Calculated (%) 54.2 3.6 8.4 Found (%) 53.6 3.8 8.6 [The second step reaction] To a sealed glass reaction vessel equipped with a stirrer, thermometer and reflux condenser, 84 g (0.253 mol) of the above 3,3'-dinitro-4,4'-dimethoxybenzophenone, 420 g of N,N-dimethylformamide and 2.52 g of 5 % palladium / alumina catalyst (N.E. Chemcat Co.) were charged and reacted in a hydrogen atmosphere at 45∼55 °C for 3 hours. After finishing the reaction, the catalyst was filtered. The filtrate was heated to 80 °C and then 1275 g of water was added and cooled to the temperature to crystallize the desired product. The precipitated crystals were filtered and recrystallized from isopropylalcohol (IPA) to obtain 27 g (39 % yield) of 3,3'-diamino-4,4'-dimethoxybenzophenone as light yellow crystals. Melting point was 128.2∼129.2 °C. The IR spectrum is illustrated in Figure 8. Elementary analysis (C 15 H 16 N 2 O 3 ) C H N Calculated (%) 66.2 5.9 10.3 Found (%) 65.9 5.8 10.1 Properties of polyimide in the below examples were measured by the following methods. Tg, Tc and Tm : Measured in the air by DTG with Shimadzu DT-40 Series DSC--4019. 5% weight loss temperature : Measured by DTA-Tg(Shimazu DT-40 series, DSC-40M) in the air. Melt viscosity : Measured with a Shimadzu Koka type flow tester (CFT-500A) under 100 kg load. Melt flow initiation temperature : Measured with a Shimadzu Koka flow tester (SFT-500A) under 100kg load at a temperature rise rate of 5 °C /min. Adhesion test (Lap shear strength) : Paste was prepared by individually suspending polyimide powder in ethanol and coated on two cold rolled steel panels (JIS G-3141, SPCC, SD) having 1.6 × 25 × 100 mm 3 in size. The coated panels were hot pressed under pressure of 21 kg/cm 2 at temperature of 280, 300 and 350 °C, respectively. Tensile shear strength of the adhered specimens were measured in accordance with JIS K-6848. Inherent viscosity : Polyamic acid was dissolved in N,N-dimethylformamide. Polyimide was dissolved in a solvent mixture of p-chlorophenol/phenol (9/1 by weight). The viscosity was at 35 °C in a concentration of 0.5 g sample/100 mℓ solvent. Example 8 To a reaction vessel equipped with a stirrer, reflux condenser and nitrogen inlet tube, 39.65 g (0.1 mol) of 3,3'-diamino-4,4'-diphenoxybenzophenone, 31.58 g (0.098 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 0.592 g (0.04 mol) of phthalic anhydride, 1.40 g of γ-picoline and 284.92 g of m-cresol were charged. The mixture was heated to 150 °C with stirring in a nitrogen atmosphere and successively reacted at 150 °C for 4 hours while distilling out about 3.6 mℓ of water. After finishing the reaction, the reaction mixture was cooled to the room temperature and poured into about 2 ℓ of methyl ethyl ketone. Precipitated powder was filtered, washed with methyl ethyl ketone, and dried in the air at 50 °C for 24 hours and successively in a nitrogen atmosphere at 230 °C for 4 hours to obtain 66.25 g (97.1 % yield) of polyimide powder. The polyimide powder had an inherent viscosity of 0.56 dℓ /g, glass transition temperature of 246 °C and 5 % weight loss temperature of 524 °C. The X-ray diffraction pattern (XRD) of the polyimide powder indicated amorphous form. The IR absorption spectrum of the polyimide powder is illustrated in Figure 9. The spectrum atlas clearly indicated characteristic absorption bands of imide at around 1780 cm -1 and 1720 cm -1 . Results of elementary analysis on the polyimide powder were as follows. C H N Calculated (%) 73.89 3.25 4.10 Found (%) 73.59 3.19 4.15 Melt flow initiation temperature measured with a Koka type flow tester was 325 °C. Processing stability of the polyimide powder was also measured by changing the residence time in the cylinder of the flow tester. Results at 380 °C under 100 kg load are illustrated in Figure 10. Melt viscosity is almost constant even though residence time in the cylinder is extended and indicates good stability in processing the polyimide powder. An adhesion test (Lap shear strength measurement) was carried out by using the polyimide powder. Lap shear strength was 152 kg/cm 2 at press temperature of 280 °C, 230 kg/cm 2 at 300 °C and 332 kg/cm 2 at 350 °C , respectively. Further, solubility of the polyimide powder was examined at the room temperature. The polyimide powder was dissolved at a concentration of the 20 % by weight in chloroform, dichloromethane, carbon tetrachloride, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and o-, m-, and p-cresol. Comparative Example 1 To the same apparatus as used in example 7, 21.23 g (0.1 mol) of 3,3'-diaminobenzophenone, 31.58 g (0.098 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 0.592 g (0.004 mol) of phthalic anhydride, 1.40 g of γ -picoline and 211 g m-cresol were charged. The mixture was heated to 150 °C with stirring in a nitrogen atmosphere and reacted at 150 °C for 4 hours while distilling out about 3.6 mℓ of water. After finishing the reaction, the reaction mixture was cooled to 110 °C and 200 g of toluene was added dropwise to precipitate polyimide powder. The powder was filtered, washed with 300 g of toluene and dried in the air at 50 °C for 24 hours and successively in a nitrogen atmosphere at 250 °C for 4 hours to obtain 47.68 g (95.7 % yield) of polyimide powder. The polyimide powder thus obtained had an inherent viscosity of 0.55 dℓ /g, glass transition temperature of 243 °C, melting point of 315 °C and 5 % weight loss temperature of 537 °C. X-ray diffraction pattern of the polyimide powder indicated crystalline polyimide. Further, the polyimide powder had a melt flow initiation temperature of 335 °C and Lap shear strength of 0 kg/cm 2 at 280°C, 21 kg/cm 2 at 300 °C and 328 kg/cm 2 at 350 °C, respectively. The polyimide powder was partly dissolved only in cresol at a concentration of 10 % by weight at the room temperature, and quite insoluble in other organic solvents enumerated in Example 8. Examples 9 to 21, Comparative Examples 2 and 3 Various kinds of polyimide powder were prepared from the diamine components illustrated in Table 1 by carrying out the same procedures as described in Example 8. Table 1 illustrates diamine components, acid anhydride components, yield, fundamental properties such as inherent viscosity and Tg, and Lap shear strengths of these examples together with the results in Example 8 and Comparative Example 1. Table 2 illustrates results on dissolving the polyimide of these examples in various organic solvents together with the results in Example 8 and Comparative Example 1. Example 22 To a flask equipped with a stirrer, reflux condenser and nitrogen inlet tube, 39.65 g (0.1 mol) of 3,3'-diamino-4,4'-diphenoxybenzophenone and 287.5 g of N,N-dimethylacetamide were charged and 32.22g (0.1 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride was added by portions in a nitrogen atmosphere with caution to prevent temperature rise of the solution. Thereafter the mixture was stirred for about 30 hours at the room temperature. Polyamic acid thus obtained had an inherent viscosity of 0.74 dℓ /g. A portion of the polyimide solution was cast on a glass plate and heated at 100, 200 and 300 °C in order, respectively for an hour to obtain a film. The polyimide film thus obtained had Tg of 250 °C, tensile strength of 11.35 kg/cm 2 , elongation of 3.2 % and tensile elastic modulus of 384 kg/cm 2 . The polyimide film was dissolved in all organic solvents enumerated in Example 8 at a concentration of 20 % by weight. Examples 23 to 30, Comparative Examples 4 and 5 Various kinds of polyimide film were prepared from diamine components illustrated in Table 3 by carrying out the same procedures as described in Example 22. Table 3 illustrates diamine components, acid anhydride components, inherent viscosity of polyamic acids, Tg and mechanical properties of these films together with the results in Example 8. Table 3 also illustrates results on dissolving these films at a concentration of 20 % by weight in chloroform, N,N-dimethylacetamide and m-cresol. Example 31 To a reaction vessel equipped with a stirrer, reflux condenser and nitrogen inlet tube, 25.03 g (0.05 mol) of 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 15.47 g (0.048 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 0.592 g (0.004 mol) of phthalic anhydride, 0.70gγ-picoline and 162.0 g of m-cresol were charged. The mixture was heated to 150 °C with stirring in a nitrogen atmosphere and successively reacted at 150 °C for 4 hours while distilling out about 1.8 mℓ of water. After finishing the reaction the reaction mixture was cooled to the room temperature and poured into about 1ℓ of methyl ethyl ketone. Precipitated powder was filtered, washed with methyl ethyl ketone, and dried in the air at 50 °C for 24 hours and successively in a nitrogen atmosphere at 220 °C for 4 hours to obtain 37.88 g (96.4 % yield) of polyimide powder. The polyimide powder had an inherent viscosity of 0.51 dℓ /g, glass transition temperature of 233 °C and 5 % weight loss temperature of 522 °C. The X-ray diffraction pattern (XRD) of the polyimide powder indicated amorphous form. The IR absorption spectrum of the polyimide powder is illustrated in Figure 11. The spectrum atlas clearly indicated characteristic absorption bands of imide at around 1780 cm -1 and 1720 cm -1 . Results of elementary analysis on the polyimide powder were as follows. Melt flow initiation temperature measured with a Koka type flow tester was 330 °C. Processing stability of the polyimide powder was also measured by changing the residence time in the cylinder of the flow tester. Results at 380 °C under 100 kg load are illustrated in figure 12. Melt viscosity is almost constant even though residence time in the cylinder is extended and indicates good stability in processing the polyimide powder. Further, solubility of the polyimide powder was examined at the room temperature. The polyimide powder was dissolved at a concentration of 20 % by weight in chloroform, dichloromethane, carbon tetrachloride, 1,1,2-trichloroethane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and o-, m- and p-cresol. Comparative Example 6 To the same apparatus is used in example 31, 15.82 g (0.05 mol) of 1,3-(3-aminobenzoyl)benzene, 15.47 g (0.048 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 0.592 g (0.004 mol) of phthalic anhydride, 0.70 gγ -picoline and 125.2 g of m-cresol were charged. The mixture was heated to 150 °C with stirring in a nitrogen atmosphere and reacted at 150 °C for 4 hours while distilling out about 1.8 mℓ of water. After finishing the reaction, the reaction mixture was treated by the same procedures is Example 31. Polyimide powder thus obtained was 28.96 g (96.3 % yield) and had an inherent viscosity of 0.49 dℓ /g and 5 % weight loss temperature of 529 °C. Further, the polyimide powder had a flow initiation temperature of 325 °C. The polyimide powder was partly dissolved only in cresol at a concentration of 20 % by weight at the room temperature, and quite insoluble in other organic solvents enumerated in Example 31. Examples 32 to 34 and Comparative Example 7 Various kinds of polyimide powder were prepared from the diamine components illustrated in Table 4 by carrying out the same procedures as described in Example 31. Table 4 illustrates diamine components acid anhydride components, yield, fundamental properties such as inherent viscosity and Tg of these examples together with the results in Example 31 and Comparative Example 6. Table 5 further illustrates results on dissolving the polyimide of these examples in various organic solvents together with the results in Example 31 and Comparative Example 6. Example 35 To a flask equipped with a stirrer, reflux condenser and nitrogen inlet tube, 25.03 g (0.05 mol) of 1,3-bis(3-amino-4-phenoxybenzoyl)benzene and 164.6 g of N,N-dimethylacetamide were charged and 16.11 g (0.05 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride was added by portions in a nitrogen atmosphere with caution to prevent temperature rise of the solution. Thereafter the mixture was stirred for about 30 hours at the room temperature. Polyamic acid thus obtained had an inherent viscosity of 0.92 dℓ /g. A portion of the polyimide solution was cast on a glass plate and heated at 100, 200 and 300 °C in order, respectively for an hour to obtain a film. The polyimide film thus obtained had Tg of 231°C, tensile strength of 11.70 kg/cm 2 , elongation of 3.9 % and tensile elastic modulus of 336 kg/cm 2 . The polyimide film was dissolved in all organic solvents enumerated in Example 31 at a concentration of 20 % by weight. Example 36 and Comparative Example 8 Various Kinds of polyimide film were prepared from diamine components illustrated in Table 6 by carrying out the same procedures as described in Example 35. Table 6 illustrates diamine components, acid anhydride components, inherent viscosity of polyamic acids, Tg and mechanical properties of these films together with the results in Example 35. Table 6 also illustrates results on dissolving these films at a concentration of 20 % by weight in chloroform, N,N-dimethylacetamide and m-cresol. Example 37 To a reaction vessel equipped with a stirrer, reflux condenser and nitrogen inlet tube, 35.69 g (0.09 mol) of 3,3'-diamino-4,4'-diphenoxybenzophenone, 2.13 g (0.01 mol) of 3,3'-diaminobenzophenone, 31.58 g (0.098 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 0.592 g (0.0045 mol) of phthalic anhydride, 1.40 g ofγ -picoline and 284.82 g of m-cresol were charged. The mixture was heated to 150 °C with stirring in a nitrogen atmosphere and successively reacted at 150 °C for 4 hours while distilling out about 3.6 mℓ of water. After finishing the reaction, the reaction mixture was cooled to the room temperature and poured into about 2 ℓ of methyl ethyl ketone. Precipitated powder was filtered, washed with methyl ethyl ketone, and dried in the air at 50 °C for 24 hours and successively in a nitrogen atmosphere at 230 °C for 4 hours to obtain 65.18 g (98.0 % yield) of polyimide powder. The polyimide powder thus obtained had an inherent viscosity of 0.55 dℓ /g, glass transition temperature of 244 °C and 5 % weight loss temperature of 530 °C. The X-ray diffraction pattern(XRD) of the polyimide powder indicated amorphous form. Flow initiation temperature of the polyimide which was measured with a Koka type flow tester was 325 °C. In an adhesion test, the polyimide powder exhibited a lap shear strength of 152 kg/cm 2 at press temperature of 280°C, 230 kg/cm 2 at 300 °C , and 332 kg/cm 2 at 350 °C. Further, solubility of the polyimide powder was examined at room temperature. The polyimide powder was dissolved at a concentration of 20 % by weight in chloroform, dichloromethane, carbon tetrachloride, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and o-, m- and p-cresol. Examples 38 to 40 Various kinds of polyimide powder having a composition ratio illustrated in Table 7 were prepared by carrying out the same procedures as described in Example 37. The same evaluation as Example 37 was conducted. The results are illustrated in Table 7 together with the results of Example 37. Results on solubility test are illustrated in Table 8. Examples 41 to 61 Various kinds of copolyimide were prepared from various diamine component and various tetracarboxylic dianhydride illustrated in Tables 9 and 12 by carrying out the same procedures as described in Example 37. The same evaluation as Example 37 was conducted. The results are illustrated in Tables 10 and 13. Results on solubility test are illustrated in Tables 11 and 14. Example 62 To a vessel, 3 kg of polyimide powder obtained by the same procedures as Example 8, 3 kg of polyether sulfone VICTREX 4100G (Trade Mark of I.C.I. Ltd.) and 54 kg of m-cresol were charged and mixed for 24 hours at room temperature to obtain a polymer solution. To the polymer solution, 100 kg of methanol was added under strong stirring. Precipitated polymer powder was filtered, washed with methanol and at 150 °C for 8 hours in a nitrogen atmosphere. Polyimide powder thus obtained was pelletized by melt-extruding at 380 °C with a single screw extruder having a bore diameter of 30 mm. Pellets thus obtained were injection moled at cylinder temperature of 370 ∼380 °C, injection pressure of 500 kg/cm 2 and mold temperature of 180°C to obtain tensile test specimens. Tensile test was carried out in accordance with ASTM D-638. Results are illustrated in Table 15. Diamine g (mol) Diamine g (mol) Acid-anhydride g (mol) Acid-anhydride g (mol) Example 41 3,3'-DABP-DPO 19.82 (0.05) 3,3'-DABP-MPO 15.22 (0.05) BTDA 31.58 (0.098) no Example 42 3,3'-DABP-MPO 15.22 (0.05) 3,4'-DABP-MPO 15.22 (0.05) ↑ ↑ (0) Example 43 3,3'-DABP-DBO 27.43 (0.05) 3,4'-DABP-MBO 19.02 (0.05) ↑ ↑ (↑) Example 44 3,3'-DABP-DPO 19.82 (0.05) mm-ABB-DPO 25.03 (0.05) ↑ ↑ (↑) Example 45 mm-ABB-DPO 25.03 (0.05) mm-ABB-DBO 32.64 (0.05) ↑ ↑ (↑) Example 46 3,3'-DABP-DPO 39.64 (0.1) no BTDA 16.11 (0.05) PMDA 10.47 (0.048) Example 47 3,3'-DABP-MPO 30.44 (0.1) ↑ (0 ) ↑ BPDA 14.12 (↑) Example 48 mm-ABB-DPO 50.06 (0.1) ↑ (↑) ↑ PMDA 10.47 (↑) Example 49 mm-ABB-DBO 65.28 (0.1) ↑ (↑) ↑ BPDA 14.12 (↑ ) Example 50 3,3'-DABP-DPO 19.82 (0.05) 3,3'-DABP-MPO 15.22 (0.05) ↑ PMDA 10.47 (↑) Example 51 3,3'-DABP-DBO 27.43 (0.05) mm-ABB-DPO 25.03 (0.05) PMDA 10.91 (0.05) BPDA 14.12 (↑ ) Example 52 mm-ABB-DPO 25.03 (0.05) mm-ABB-DBO 32.64 (0.05) BTDA 16.11 (↑) PMDA 10.47 (↑) Note: Abbreviations in Table 9 are the same as Tables 1 and 4. Yield (%) η (dl/g) Tg (°C) Tm (°C) Td (5.0) (°C) Flow initiation temperature (°C) XRD PATTERN Example 41 98.3 0.51 248 no 536 325 Amorphous Example 42 97.6 0.53 246 ↑ 533 330 ↑ Example 43 97.2 0.57 245 ↑ 542 330 ↑ Example 44 97.4 0.49 248 ↑ 530 325 ↑ Example 45 98.5 0.55 249 ↑ 527 330 ↑ Example 46 99.0 0.56 246 ↑ 547 325 ↑ Example 47 97.2 0.55 250 ↑ 533 335 ↑ Example 48 96.8 0.50 240 ↑ 529 310 ↑ Example 49 97.7 0.59 235 ↑ 527 315 ↑ Example 50 97.9 0.47 246 ↑ 551 330 ↑ Example 51 98.1 0.55 247 ↑ 538 330 ↑ Example 52 98.3 0.53 233 ↑ 526 320 ↑ Diamine g (mol) Diamine g (mol) Acid anhydride g (mol) Acid anhydride g (mol) Example 53 3,3'-DABP-DPO 35.68 (0,09) 4,4'-ODA 2.00 (0.01) BTDA 31.58 (0.098) no Example 54 3,3'-DABP-MPO 15.22 (0.05) m-BP 18.42 (0.05) ↑ ↑ Example 55 3,3'-DABP-DBO 27.43 (0.05) APB 14.62 (0.05) ↑ ↑ Example 56 mm-ABB-DPO 25.03 (0.05) m-BP 18.42 (0.05) ↑ ↑ Example 57 3,3'-DABP-DPO 35.68 (0.09) 4,4'-ODA 2.00 (0.01) PMDA 21.38 (0.098) ↑ Example 58 3,3'-DABP-MBO 19.02 (0.05) m-BP 18.42 (0.05) ↑ ↑ Example 59 3,3'-DABP-DMO 13.67 (0.05) APB 14.62 (0.05) BPDA ↑ 28.83 (0.098) ↑ Example 60 3,3'-DABP-DPO 35.68 (0.05) m-BP 18.42 (0.05) PMDA 10.91 (0.05) BPDA 14.12 (0.048) Example 61 mm-ABB-DBO 32.64 (0.05) APB 14.62 (0.05) BTDA 16.11 (0.05) 6FDA ↑ 21.33 (0.048) Note: Other Abbreviations are the same as Table 1 Yield (%) η (dl/g) Tg (°C) Tm (°C) Td (5.0) (°C) Flow initiation temperature (°C) XRD PATTERN Example 53 97.3 0.52 253 mo 530 330 amorphous Example 54 95.2 0.56 247 ↑ 524 325 ↑ Example 55 96.7 0.55 232 ↑ 550 320 ↑ Example 56 97.3 0.48 238 ↑ 548 320 ↑ Example 57 97.2 0.54 258 ↑ 537 340 ↑ Example 58 98.0 0.51 252 ↑ 538 335 ↑ Example 59 96.7 0.50 228 ↑ 551 330 ↑ Example 60 97.1 0.55 240 ↑ 543 330 ↑ Example 61 99.0 0.54 225 ↑ 539 320 ↑ Note: Abbreviations in Table 9 are the same as Tables 1 and 4. Examples 63∼67 Blending was carried out as illustrated in Table 15 by the same procedures as described in Example 62. Evaluation was carried out by the same procedures as described in Example 62. Results are illustrated in Table 15 together with Example 62. Comparative Example 9 A mixture composed of 3 kg of the polyimide powder obtained by the same procedures as example 8 and 3 kg of polyether sulfone powder used in Example 62 were prepared by mixing these two materials as intact. The mixture was pelletized by extrusion as described in Example 62. The pellets thus obtained were pelletized again by melt-kneading with an extruder and injection molded to obtain tensile test specimens. Tensile properties were tested by the same procedures as described in Example 62 and results are illustrated in Table 15. Comparative Example 10 and 11 Blending was carried out as illustrated in Table 15 by the same procedures as Comparative Example 9. Properties of the mixture were evaluated and results are illustrated in Table 15. Polyimide Other resin Tensile test Example No. Amount (kg) polymer Amount (kg) TS * (kg/cm 2 ) El* (%) Example 63 8 3 polyether sulfone 3 1750 30 Example 64 8 4.5 ↑ 1.5 1200 20 Example 65 31 3 ↑ 3 1180 28 Example 66 31 4.5 ↑ 1.5 1230 23 Example 67 8 3 polyetherimide 3 1090 43 Comparative Example 9 8 3 polyether sulfone 3 730 10 Comparative Example 10 8 4.5 ↑ 1.5 820 8 Comparative Example 11 31 3 ↑ 3 840 10 Note :

Claims: A polyimide comprising a requisite structural unit consisting of one or more of recurring structural units of the formula (1) : wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms; R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo-(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms; and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member, said polyimide otionally having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. A polyimide of claim 1 wherein the polyimide having recurring structural units of the formula (1) is derived from a precursor polyamic acid having an inherent viscosity of 0.01 to 3.0 dℓ /g at 35°C in a dimethylacetamide solution at a concentration of 0.5 g/ dℓ . A polyimide of claim 1 wherein the polyimide having recurring structural units of the formula (1) has an inherent viscosity of 0.01 to 3.0 dℓ /g at 35°C at a concentration of 0.5 g/ dℓ in a solvent mixture composed of 9 parts by weight of p-chlorophenol and 1 part by weight of phenol. A polyimide comprising a requisite structural unit consisting of one or more of recurring structural units of the formula (2) : wherein m and n are individually an integer of 0 or 1, R 8 is a hydrogen atom, halogen atom, alkyl having 1 to 4 carbon atoms, alkoxy or phenyl, and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, said polyimide optionally having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. A polyimide comprising a requisite structural unit consisting of one or more of recurring structural units selected from the group consisting of 1 ○ the units of the formula (3) : wherein R 9 is and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member; 2 ○ the units of the formula (4): wherein R 9 and Ar are the same as above; and 3 ○ the units of the formula (5): wherein R 9 and Ar are the same as above; said polyimide optionally having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. A polyimide copolymer comprising a requisite structural unit consisting of 1 to 99 % by mol of recurring structural units of the formula (1): wherein m and n are individually an integer of 0 or 1, are R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms; R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo-(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms, and Ar is a tetravalent radical having 2 to 27 carbon atoms, and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and 99 to 1 % by mol of recurring structural units of the formula (6): wherein n is an integer of 0 to 5, Q is a direct bond, -O-, -S-, -CO-, -SO 2 -, -CH 2 -, -C(CH 3 ) 2 - or -C(CF 3 ) 2 - and may be the same or different when aromatic rings are connected each other with two or more connecting radicals Q, and Ar' is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alcyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member; said polyimide copolymer optionally having at the polymer chain end an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. A polyimide copolymer comprising a requisite structural unit consisting of 1 to 99 % by mol of recurring structural unit of the formula (2): wherein m and n are individually an integer of 0 or 1, R 8 is a hydrogen atom, halogen atom, alkyl of 1 to 4 carbon atoms, alkoxy or phenyl, and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alcyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and 99 to 1 % by mol of recurring structural units of the formula (6): wherein n is an integer of 0 to 5, Q is a direct bond, -O-, -S-, -CO-, - -SO 2 -, -CH 2 -, -C(CH 3 ) 2 - or -C(CF 3 ) 2 - and may be the same or different when aromatic rings are connected each other with two or more connecting radicals Q, and Ar' is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member; said polyimide copolymer optionally having at the polymer chain end an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. A polyimide copolymer comprising two or more recurring structural units of the formula (1) described in claim 1 said polyimide copolymer optionally having at the polymer chain end an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride. A preparation process of polyimide comprising a requisite structural unit consisting of one or more of recurring structural units of the formula (1): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms; R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms, and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, comprising reacting aromatic diamine essentially consisting of one or more aromatic diamino compound of the formula (7): wherein m, n and R are the same as above, with tetracarboxylic dianhydride primarily having the formula (8): wherein Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and thermally or chemically imidizing resultant polyamic acid. A preparation process of a polyimide having a requisite structural unit consisting of one or more of recurring structural units of the formula (1): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms; R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo-(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms, and Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and having at the polymer chain end thereof an aromatic ring which is unsubstituted or substituted with a radical having no reactivity with amine and/or dicarboxylic anhydride, comprising reacting aromatic diamine essentially consisting of one or more of aromatic diamino compound of the formula (7): wherein m, n and R are the same as above, with tetracarboxylic dianhydride primarily having the formula (8): wherein Ar is a tetravalent radical having 2 to 27 carbon atoms and being selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, in the presence of aromatic dicarboxylic anhydride of the formula (9) wherein Z is a divalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and/or aromatic monoamine of the formula (10): Z 1 - NH 2 wherein Z 1 is a monovalent radical having 6 to 15 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member, and thermally or chemically imidizing resultant polyamic acid. A preparation process of claim 10 wherein the aromatic dicarboxylic anhydride is phthalic anhydride. A preparation process of claim 10 wherein the aromatic monoamine is aniline. A preparation process of claim 10 wherein the amount of aromatic dicarboxylic anhydride is 0.001 to 1.0 mol per mol of aromatic diamine. A preparation process of claim 11 wherein the amount of phthalic anhydride is 0.001 to 1.0 mol per mol of mol of aromatic diamine. A preparation process of claim 10 wherein the amount of aromatic monoamine is 0.001 to 1.0 mol per mol of tetracarboxylic dianhydride. A preparation process of claim 12 wherein the amount of aniline is 0.001 to 1.0 mol per mol of tetracarboxylic dianhydride. A composition comprising the polyimide of claim 1. A polyimide film comprising the polyimide of claim 1. A solution comprising the polyimide of claim 1. An aromatic nitro compound of the formula (11): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms, and R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω -alkyloxyoligo-(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms. An aromatic diamino compound of the formula (7): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms, and R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or ω-alkyloxyoligo(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms. An aromatic diamino compound of claim 21 wherein the aromatic diamino compound of the formula (7) is represented by the formula (12): wherein n is an integer of 0 or 1, and R 8 is a hydrogen atom, halogen atom, alkyl of 1 to 4 carbon atoms, alkoxy and phenyl. An aromatic diamine compound of claim 21 wherein the aromatic diamino compound of the formula (7) is represented by the formula (13): wherein R 9 is An aromatic diamine compound of claim 21 wherein the aromatic diamino compound of the formula (7) is represented by the formula (14): wherein R 9 is An aromatic diamine compound of claim 21 wherein the aromatic diamino compound of the formula (7) is represented by the formula (15): wherein R 9 is A preparation process of an aromatic diamino compound of the formula (7): wherein m and n are individually an integer of 0 or 1, and R is wherein R 1 , R 2 , R 3 and R 4 are individually a hydrogen atom, halogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl or alkoxy having 1 to 5 carbon atoms, and R 5 , R 6 and R 7 are individually a hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl, alkenyl, aralkyl orω -alkyloxyoligo-(alkyleneoxy)alkyl having 1 to 10 carbon atoms and 1 to 3 oxygen atoms, comprising carrying out condensation of a dinitro compound of the formula (16): wherein X is halogen atom and m and n are individually an integer of 0 or 1, and a hydroxy compound of the formula (17): R - OH wherein R is the same as above, in an aprotic polar solvent in the presence of a base to obtain an aromatic dinitro compound of the formula (11): wherein R, m and n are the same as above, and successively reducing the aromatic dinitro compound.

Inventors: ISHIHARA YUKO, MATSUO MITSUNORI, OIKAWA HIDEAKI, OKAWA YUICHI, YAMAGUCHI AKIHIRO, YAMAGUCHI KEIZABURO, YAMASHITA WATARU, ISHIHARA, YUKO, MATSUO, MITSUNORI, OIKAWA, HIDEAKI, OKAWA, YUICHI, YAMAGUCHI, AKIHIRO, YAMAGUCHI, KEIZABURO, YAMASHITA, WATARU
Applicants: MITSUI TOATSU CHEMICALS, MITSUI TOATSU CHEMICALS, INC.
Application year: 1993
Main classification: C08G73
IPC codes: C07C225, C08L79, C07C205, C07C221, C08G73, C07C201, C08J5