Abstract:
Moldable polyimide resin composition which has melt-flowability and excellent processability in addition to essential heat-resistant of polyimide and comprises an aromatic bisimide compound and polyimide to resin. A further aspects relates to, a carbon fiber reinforced polyimide resin composition which has excellent mechanical strengths and comprises a carbon fiber coated with aromatic bisimide compound on the surface and the polyimide to resin, A still further aspect relates to and a novel bisimide compound which is very useful as the aromatic bisimide compound in the composition.

Description:
This application is a divisional of application Ser. No. 07/934,681, filed as PCT/JP92/0039, Jan. 20, 1992, now U.S. Pat. No. 5,457,154. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a bisimide compound, a polyimide resin composition comprising the bisimide compound, and a carbon fiber reinforced polyimide composition comprising a carbon fiber coated on the surface with the bisimide compound. 
     2. Description of the Related Art 
     Materials having more excellent high-temperature characteristics have recently been required in order to enhance performance and reduce weight on various industrial materials in the fields of electric and electronic devices, space and aeronautical equipment and transport machinery. In these materials, polyimide has mechanical strength, dimensional stability, flame retardance and electrical insulation properties in addition to its excellent high-temperature resistance, and hence been widely used in the above industrial fields. Polyimide of has a high molecular weight, however, has generally high softening point and is insoluble in almost organic solvents. As a result, many difficulties have been encountered for the use of polyimide. 
     ULTEM(Trade mark of General Electric Co.), a representative thermoplastic polyimide resin, has superior heat resistance and mechanical strength compared to general purpose engineering plastics. Consequently, it is called a super engineering plastic and widely investigated for use in electric and electronic devices, machines and automobiles. 
     Accompanied with the recent progress of technology, it has been demanded to develop a novel thermoplastic polyimide resin having heat-resistance and mechanical characteristics which are superior to ULTEM. 
     For example, U.S. Pat. No. 4,847,349 discloses a process for preparing polyimide resin by reacting etherdiamine with tetracarboxylic acid dianhydride. Japanese Laid-Open Patent Hei 2-018419 proposes a process for preparing polyimide resin by reacting 3,3&#39;-diaminobenzophenone and tetracarboxylic acid dianhydride. Both patents have provided novel polyimides having heat resistance and mechanical characteristics which are superior to conventional polyimide. 
     The above polyimides are much superior in heat resistance and other characteristics to common engineering plastics represented by polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polysulfone and polyphenylene sulfide. However, increased molecular weight lowers melt flowability and melt processability of the polyimide is still inferior to these engineering plastics. 
     In order to enhance the characteristics of polyimide resin, mechanical strength in particular, fibrous reinforcement, particularly carbon fiber, is generally incorporated. 
     Carbon fiber is frequently used for carbon fiber reinforced plastics which use epoxy resin as a matrix and hence epoxy resin is commonly used for the collecting agent of carbon fiber. As a result, the epoxy resin collecting agent is effective when thermosetting resin such as epoxy resin is used for the matrix. However, epoxy resin has poor adhesion to polyimide a resin and resin composition having good mechanical strength cannot be obtained. 
     A process of using polyimide resin for the collecting agent of carbon fiber has been disclosed, for example, in Japanese Laid-Open Patent Sho 53-106752. However, polyimide resin must be generally processed at temperatures higher than 300° C. and the collecting agent decomposes by heat in the processing step to cause problems such as formation of voids and reduction of weld strength. Further, Japanese Laid-Open Patent Sho 56-120730 describes a process for using a carbon fiber collected with aromatic polysulfone resin. However, the process leads to merely a small increase in mechanical strengths and has not yet fully satisfied desired characteristics. 
     An object of the invention is to provide a compound having outstanding processability in addition to excellent heat resistance. 
     Another object of the invention is to provide a processable polyimide-based resin composition having very excellent melt flowability without impairing the essential characteristics of polyimide. 
     A further object of the present invention is to provide a polyimide-based resin composition having excellent mechanical strength. 
     SUMMARY OF THE INVENTION 
     As a result of an intensive investigation in order to accomplish the above objects, the present inventors have found that a polyimide resin composition comprising an aromatic bisimide compound is excellent in melt flowability and processability and that a polyimide resin composition comprising a carbon fiber coated with the aromatic bisimide compound on the surface has excellent mechanical strength, and further have found a novel bisimide compound which is very useful for the composition. Thus, the present invention has been completed. 
     That is, one aspect of the invention is a bisimide compound represented by the formula (1): ##STR1## wherein A is a divalent radical selected from the group consisting of radicals having the formulas: ##STR2## wherein X is a direct bond, a divalent hydrocarbon radical having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio or sulfonyl, and Y 1  ˜Y 4  are individually hydrogen atom, lower alkyl radical, lower alkoxy radical, chlorine or bromine atom, ##STR3## ; and R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member. 
     Practical compounds are a bisimide compound represented by the formula (2): ##STR4## wherein X is a direct bond, a divalent hydrocarbon radical having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio or sulfonyl, Y 1  ˜Y 4  are individually hydrogen, lower alkyl radical, lower alkoxy radical, chlorine or bromine atom, and R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member; a bisimide compound represented by the formula (3): ##STR5## wherein R is a divalent radical 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; 
     a bisimide compound represented by the formula (4): ##STR6## wherein R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member; 
     a bisimide compound represented by the formula (5): ##STR7## wherein R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member; 
     a bisimide compound represented by the formula (6): ##STR8## wherein R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member; and a bisimide compound represented by the formula (7): ##STR9## wherein X is a direct bond, a divalent hydrocarbon radical having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio or sulfonyl, Y 1  ˜Y 4  are individually hydrogen, lower alkyl radical, lower alkoxy radical, chlorine or bromine atom, and R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member. 
     Another aspect of the invention is a polyimide resin composition comprising the aromatic bisimide compound and polyimide, for example, a polyimide resin composition comprising as requisite components 1 the bisimide compound represented by the above formula (1) and 2 polyimide, particularly the polyimide having recurring structural units of the formula (8): ##STR10## wherein A&#39; is a divalent radical having the formula: ##STR11## wherein X is a direct bond, a divalent hydrocarbon radical having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio or sulfonyl, and Y 1  ˜Y 4  are individually hydrogen atom, lower alkyl radical, lower alkoxy radical, chlorine or bromine atom; or the formula: ##STR12## and R&#39; is a tetravalent radical having 2 or more carbon atoms and 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. 
     Following polyimide resin compositions are exemplified as preferred combinations of the aromatic bisimide compound and polyimide. 
     (1) A polyimide resin composition wherein the polyimide has recurring structural units represented by the formula (9): ##STR13## wherein R&#39; is the same as in the formula (8) and the aromatic bisimide compound is represented by the formula (10): ##STR14## wherein B is a direct bond, a radical selected from divalent hydrocarbon radical having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio, ether and sulfonyl, each nitrogen atom is individually para-, ortho- or meta-located to B and R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical, noncondensed aromatic radical connected to each other with a direct bond or a bridge member, and/or by the formula (2): ##STR15## wherein X, Y 1  ˜Y 4  and R are the same as above. 
     (2) A polyimide resin composition wherein the polyimide has recurring structural units represented by the formula (11): ##STR16## wherein X is a direct bond, a divalent hydrocarbon radical having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio or sulfonyl, Y 1  ˜Y 4  are individually hydrogen atom, lower alkyl radical, lower alkoxy radical, chlorine or bromine atom, and R&#39; is a tetravalent radical having 2 or more carbon atoms and 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; and the aromatic bisimide compound is represented by the above formula (10) and/or the formula (2). 
     (3) A polyimide resin composition wherein the polyimide has recurring structural units of the formula (9): ##STR17## wherein R&#39; is the same as above, and the aromatic bisimide compound is represented by the formula (3): ##STR18## wherein R is the same as above. 
     (4) A polyimide resin composition wherein the polyimide has recurring structural units of the formula (11): ##STR19## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above, and the aromatic bisimide compound is represented by the formula (7): ##STR20## wherein X, Y 1  ˜Y 4  and R are the same as above, the formula (12): ##STR21## wherein R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical, and noncondensed aromatic radical connected to each other with a direct bond or a bridge member, and two isopropylidene radicals are located each at para- or meta-position on a benzene ring, the formula (4): ##STR22## wherein R is the same as above, the formula (13): ##STR23## wherein R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member, and the two carbonyl radicals are located on meta- or para-position to the central ether bond, and the other two ether bonds on the outside are located on meta- or para-position to said carbonyl radicals, respectively, the formula (14): ##STR24## wherein Z is a radical selected from the group consisting of carbonyi or sulfonyl, and R is a divalent radical having 2 or more carbon atoms and 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, the formula (15): ##STR25## wherein R is a divalent radical 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; the two carbonyl radicals are located at meta- or para-position on the central benzene ring; when the two carbonyl radicals are located on para-position on the central benzene ring, both terminal nitrogen atoms are located at para- or meta-position to the ether linkages, respectively; and when the two carbonyl radicals are located on meta-position on the central benzene ring, both terminal nitrogen atoms locate on para- or meta-position to the ether linkages, respectively, or the formula (16): ##STR26## wherein R is a divalent radical selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or bridge member, and the two isopropylidene radicals are located on para- or meta-position on the central benzene ring. 
     (5) A polyimide resin composition wherein the polyimide has recurring structural units represented by the formula (17): ##STR27## wherein R&#39; is a tetravalent radical having 2 or more carbon atoms and 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; and the aromatic bisimide compound is represented by the above formula (10), (2), (7), (12), (4), (13), (14), (15) or (16). 
     A further aspect of the invention is 1 a carbon fiber reinforced polyimide resin composition comprising a carbon fiber coated on the surface with an aromatic bisimide compound, preferably a bisimide compound represented by the above formula (2): ##STR28## wherein X, Y 1  ˜Y 4  and R are the same as above, and polyimide, particularly the polyimide having recurring structural units represented by the above formula (11): ##STR29## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above, or the polyimide having recurring structural units represented by the formula (9): ##STR30## wherein R&#39; is the same as above; or 2 a carbon fiber reinforced resin composition comprising a carbon fiber coated on the surface with an aromatic bisimide compound represented by the formula (10): ##STR31## wherein B and R are the same as above, and the polyimide having recurring structural units represented by the formula (11): ##STR32## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above. 
     The bisimide of the invention can simultaneously provide good heat resistance and processability for polyimide and is useful for heat resistant coatings, heat resistant adhesives, sizing agents of glass fiber and carbon fiber, and plasticizers of heat resistant resin. 
     Addition of the bisimide compound to polyimide resin can greatly reduce melt-viscosity of the resin and improve processability. Particularly, the polyimide resin composition comprising the bisimide compound of the invention has remarkably improved processability. 
     The polyimide resin composition comprising the carbon fiber coated with the bisimide compound of the invention has excellent mechanical strength and can be widely used as a material for members of electric and electronic devices, automotive trim, space and aeronautical equipment and general instruments in industry. Therefore, the invention is very valuable in industry. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is an IR absorption spectrum atlas of bisimide obtained in Example. FIG. 2 is an IR absorption spectrum atlas of bisimide obtained in Comparative Example 1. FIG. 3 is an IR absorption spectrum atlas of bisimide obtained in Example 5. FIG. 4 is an IR absorption spectrum atlas of bisimide obtained in Example 6. 
     FIG. 5 is an IR absorption spectrum of bisimide obtained in Example 8. FIG. 6 is an IR absorption spectrum atlas of bisimide obtained in Example 10. FIG. 7 is an IR absorption spectrum atlas of bisimide obtained in Example 12. FIG. 8 is an IR absorption spectrum atlas of bisimide obtained in Example 14. FIG. 9 is an IR absorption spectrum atlas of bisimide obtained in Example 16. FIG. 10 is an IR absorption spectrum atlas of bisimide-3 obtained in the Synthesis Example. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The bisimide compound of the invention is represented by the above formula (1) and practical compounds are respectively represented by the formulas(2), (3), (4), (5), (6) and (7). 
     The bisimide compound can be prepared by reacting a diamine compound represented by the formula (1-a): ##STR33## wherein A is a divalent radical selected from the group consisting of radicals having the formulas: ##STR34## wherein X is a direct bond, a divalent hydrocarbon radical having from 1 to 10 carbon atoms, hexafluorinated isopropylidene, carbonyl, thio or sulfonyl, and Y 1  ˜Y 4  are individually hydrogen atom, lower alkyl radical, lower alkoxy radical, chlorine or bromine atom, ##STR35## with a dicarboxylic acid anhydride represented by the formula (18): ##STR36## wherein R is a divalent radical 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. 
     The diamine compounds used for preparing the bisimide compound of the invention are represented by the formula (2-a): ##STR37## wherein X and Y 1  ˜Y 4  are the same as in the formula (2). 
     Exemplary diamine compounds which are represented by the formula (2-a) include: 
     bis[4-(3-aminophenoxy)phenyl]methane, 
     1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]propane, 
     2-[4-(3-aminophenoxy)phenyl]-2-[4-(3-aminophenoxy)-3-methylphenyl]-propane, 
     2,2-bis[4-(3-aminophenoxy)-3-methylphenyl]propane, 
     2-[4-(3-aminophenoxy)phenyl]-2-[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane, 
     2,2-bis[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]butane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 
     4,4&#39;-bis(3-aminophenoxy)biphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3-methylbiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dimethylbiphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3,5-dimethylbiphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3,3&#39;,5,5&#39;-tetramethylbiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dichlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,5-dichlorobiphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3,3&#39;,5,5&#39;-tetrachlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dibromobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,5-dibromobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;,5,5&#39;-tetrabromobiphenyl, 
     bis[4-(3-aminophenoxy)phenyl]ketone, 
     bis[4-(3-aminophenoxy)phenyl]sulfide, 
     bis[4-(3-aminophenoxy)-3-methoxyphenyl]sulfide, 
     [4-(3-aminophenoxy)phenyl][4-(3-aminophenoxy)-3,5-dimethoxyphenyl]-sulfide, 
     bis[4-(3-aminophenoxy)-3,5-dimethoxyphenyl]sulfide, and 
     bis[4-(3-aminophenoxy)phenyl]sulfone. 
     Other diamine compounds which can be used are 3,3&#39;-diaminobenzophenone of the formula (3-a): ##STR38## bis[4-{4-(4-aminophenoxy)phenyl} phenyl]sulfone of the formula (4-a): ##STR39## 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene of the formula (5-a ): ##STR40## and bis[3-{4-(4-aminophenoxy)benzoyl} phenyl]ether of the formula (6-a): ##STR41## 
     Further diamine compounds which can be used for preparing the bisimide compound are represented by the formula (7-a): ##STR42## wherein X and Y 1  ˜Y 4  are the same as in the formula (7). 
     Exemplary diamine compounds which are represented by the formula (7-a) include: 
     1,1-bis[4-(4-aminophenoxy)phenyl]methane, 
     1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 
     2,2-bis[4-(4-aminophenoxy)phenyl]propane, 
     2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3-methylphenyl]propane, 
     2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 
     2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 
     2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 
     2,2-bis[4-(4-aminophenoxy)phenyl]butane, 
     2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 
     4,4&#39;-bis(4-aminophenoxy)biphenyl, 
     4,4&#39;-bis(4-amlnophenoxy)-3-methylbiphenyl, 
     4,4&#39;-bis(4-amlnophenoxy)-3,3&#39;-dimethylbiphenyl, 
     4,4&#39;-bis(4-amlnophenoxy)-3,5-dimethylbiphenyl, 
     4,4&#39;-bis(4-aminophenoxy)-3,3&#39;,5,5&#39;-tetramethylbiphenyl, 
     4,4&#39;-bis(4-aminophenoxy)-3,3&#39;-dichlorobiphenyl, 
     4,4&#39;-bis(4-amlnophenoxy)-3,5-dichlorobiphenyl, 
     4,4&#39;-bis(4-amlnophenoxy)-3,3&#39;,5,5&#39;-tetrachlorobiphenyl, 
     4,4&#39;-bis(4-amlnophenoxy)-3,3&#39;-dibromobiphenyl, 
     4,4&#39;-bis(4-aminophenoxy)-3,5-dibromobiphenyl, 
     4,4&#39;-bis(4-aminophenoxy)-3,3&#39;,5,5&#39;-tetrabromobiphenyl, 
     bis[4-(4-aminophenoxy)phenyl] ketone, 
     bis[4-(4-aminophenoxy)phenyl] sulfide, 
     bis[4-(4-aminophenoxy)-3-methoxyphenyl] sulfide, 
     [4-(4-aminophenoxy)phenyl] [4-(4-aminophenoxy)-3,5-dimethoxyphenyl] sulfide, 
     bis[4-(4-aminophenoxy)-3,5-dimethoxyphenyl] sulfide, and bis[4-(4-aminophenoxy)phenyl] sulfone. 
     The diamine compounds enumerated above can be used singly or as a mixture. 
     The aromatic dicarboxylic acid anhydrides used for the preparation of bisimide compounds of the invention are represented by the formula (18) and include, for example, 
     phthalic anhydride, 
     3-methylphthalic anhydride, 
     4-methylphthalic anhydride, 
     2,3-benzophenonedicarboxylic anhydride, 
     3,4-benzophenonedicarboxylic anhydride, 
     2,3-dicarboxyphenyl phenyl 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 anhydrides are used singly or as a mixture. 
     No particular restriction is imposed upon the reaction of the diamine with the dicarboxylic acid anhydride. The reaction is preferably carried out in organic solvents in particular. 
     Exemplary solvents 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, m-cresol, p-cresol, p-chlorophenol and anisole. 
     These organic solvents can be used singly or as a mixture. 
     Reaction temperature is usually 200° C. or less, preferably 50° C. or less. No particular limitation is placed on the reaction pressure. The reaction can be satisfactorily carried out under atmospheric pressure. The reaction time varies depending upon the kind of solvents and reaction temperature. The reaction is usually carried out for sufficient time to complete formation of bisamic acid which is the precursor of the bisimide compound of the invention. The reaction time of from 10 minutes to 24 hours is usually sufficient for the reaction. 
     The reaction can provide bisamic acids which correspond to the desired bisimide compounds of the invention, that is, the bisamic acid having the formula (2-b ): ##STR43## and corresponding to the bisimide compound of the formula (2), the bisamic acid having the formula (3-b): ##STR44## and corresponding to the bisimide compound of the formula (3), the bisamic acid having the formula (4-b); ##STR45## and corresponding to the bisimide compound of the formula (4), the bisamic acid having the formula (5-b): ##STR46## and corresponding to the bisimide compound of the formula (5), the bisamic acid having the formula (6-b): ##STR47## and corresponding to the bisimide compound of the formula (6), and the bisamic acid having the formula (7-b ): ##STR48## and corresponding to the bisimide compound of the formula (7). 
     The bisamic acids thus obtained are heat-imidized at temperature of 80° to 400° C. or by chemically imidized with an imidizing agent such as acetic anhydride to give bisimide compounds having the formulas (1) to (7). 
     Alternatively, the above diamine compound and the above dicarboxylic acid anhydride are suspended or dissolved in an organic solvent, and formation and dehydrating imidization of the resulting bisamic acid can be simultaneously carried out by heating from 50° to 400° C. to give corresponding bisimide compounds. 
     The bisimide compounds having the formulas (2) and (7) which are prepared from the diamine compounds having the formulas (2-a) and (7-a) have a melting point of 290° C. or less. The bisimide compounds having the formula (3) which are prepared from the diamine compounds having the formula (3-a) have a melting point of 260° C. or less. Thus the bisimide compounds obtained in the invention have lower melting points, can be melt-processed with ease and have excellent processability as compared with high molecular weight polyimide. The bisimide compounds also have solubility of 5% by weight or more in halogenated hydrocarbon solvents such as dichloromethane, chloroform and carbon tetrachloride, and can be used in the form of solutions in these solvents. 
     The polyimide resin composition of the invention is a novel polyimide resin composition comprising the aromatic bisimide compound and the polyimide as requisite components. The polyimide resin composition prepared by using the novel bisimide compound having the formula (1) of the invention is preferred in particular. 
     No particular restriction is imposed upon the polyimide used in the polyimide resin composition of the invention. Various kinds of polyimide can be used and particularly preferred polyimide has recurring structural units represented by the formula (8): ##STR49## wherein A&#39; and R&#39; are the same as above. Useful kinds of polyimide include, for example, the polyimide having recurring structural units of the formula (9): ##STR50## wherein R&#39; is the same as above, the polyimide having recurring structural units of the formula (11): ##STR51## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above, and the polyimide having recurring structural units of the formula (17): ##STR52## wherein R&#39; is the same as above. 
     Consequently, representative embodiments of combination composed of the polyimide resin component and the bisimide compound component include: 
     (1) the combination of the polyimide having recurring structural units of the formula (9): ##STR53## wherein R&#39; is the same as above, with the bisimide compound having the formula (10): ##STR54## wherein B and R are the same as above, and/or the formula (2): ##STR55## wherein X, Y 1  ˜Y 4  and R are the same as above, 
     (2) the combination of the polyimide having recurring structural units of the formula (11): ##STR56## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above, with the bisimide compound having the formula (10): ##STR57## wherein B and R are the same as above, and/or the formula (2): ##STR58## wherein X, Y 1  ˜Y 4  and R are the same as above, 
     (3) the combination of the polyimide having recurring structural units of the formula (9): ##STR59## wherein R&#39; is the same as above, with the bisimide compound having the formula (3): ##STR60## wherein R is the same as above, 
     (4)˜(17) the combination of the polyimide having recurring structural units of the formula (11) or (17): ##STR61## wherein R&#39; and Y 1  ˜Y 4  are the same as above, with the bisimide compound having the formula (7): ##STR62## wherein R and Y 1  ˜Y 4  are the same as above, the formula (12): ##STR63## wherein R is the same as above, the formula (4): ##STR64## wherein R is the same as above, the formula (13): ##STR65## wherein R is the same as above, the formula (14): ##STR66## wherein R and Z are the same as above, the formula (15): ##STR67## wherein R is the same as above, or the formula (16): ##STR68## wherein R is the same as above. 
     The polyimide used in the composition of the invention can be prepared by reacting a diamine compound with a tetracarboxylic acid dianhydride of the formula (19): ##STR69## wherein R&#39; is a tetravalent radical having 2 or more carbon atoms and 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, and successively by carrying out dehydrating cyclization of the resultant polyamic acid. 
     The polyimide can be practically prepared with ease by the processes disclosed in Japanese Laid-Open Patent Hei 2-022422, 2-133427 and 2-229124. 
     Various diamine compounds can be used as raw materials for providing the desired polyimide. For example, the following diamine compounds can be used. 
     In order to obtain polyimide having recurring structural units of the above formula (9), 3,3-diaminobenzophenone is used. 
     Exemplary diamines which can provide the polyimide having recurring structural units of the above formula (11) include 
     bis[4-(3-aminophenoxy)phenyl]methane, 
     1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]propane, 
     2-[4-(3-aminophenoxy)phenyl]-2-[4-(3-aminophenoxy)-3-methylphenyl]propane, 
     2,2-bis[4-(3-aminophenoxy)-3,5-dimethylbenzoyl]propane, 
     2,2-bis[4-(3-aminophenoxy)-3-methylphenyl]propane, 
     2-[4-(3-aminophenoxy)phenyl]-2-[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]butane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 
     4,4&#39;-bis(3-amlnophenoxy)biphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3-methylbiphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3,3&#39;-dimethylbiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,5&#39;-dimethylbiphenyl 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;,5,5&#39;-tetramethylbiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dichlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,5&#39;-dichlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;,5,5&#39;-tetrachlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dibromobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,5&#39;-dibromobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;,5,5&#39;-tetrabromobiphenyl, 
     bis[4-(3-aminophenoxy)phenyl]ketone, 
     bis[4-(3-aminophenoxy)phenyl]sulfide, 
     bis[4-(3-aminophenoxy)-3-methoxyphenyl]sulfide, 
     [4-(3-aminophenoxy)phenyl][4-(3-aminophenoxy)-3,5-dimethoxyphenyl]sulfide, 
     bis[4-(3-aminophenoxy)-3,5-dimethoxyphenyl]sulfide, and 
     bis[4-(3-aminophenoxy)phenyl]sulfone. 
     These diamine compounds can be used singly or as a mixture. 
     In order to obtain the polyimide of the above formula (17), bis[4- {4-(4-aminophenoxy)phenoxy} phenyl]sulfone is used. 
     Tetracarboxylic acid dianhydrides used in the invention and represented by the formula (19) include, for example, 
     ethylenetetracarboxylic dianhydride, 
     butanetetracarboxylic dianhydride, 
     cyclopentanetetracarboxylic dianhydride, 
     pyromellitic 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)propane dianhydride, 
     2,2-bis(2,3-dicarboxyphenyl)propane 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, 
     3,3&#39;,4,4&#39;-benzophenonetetracarboxylic dianhydride, 
     2,2&#39;,3,3&#39;-benzophenonetetracarboxylic dianhydride, 
     3,3&#39;,4,4&#39;-biphenyltetracarboxylic dianhydride, 
     2,2&#39;,3,3&#39;-biphenyltetracarboxylic dianhydride, 
     bis(3,4-dicarboxyphenyl)ether dianhydride, 
     bis(2,3-dicarboxyphenyl)ether dianhydride, 
     bis(3,4-dicarboxyphenyl)sulfone dianhydride, 
     4,4&#39;-(p-phenylenedioxy)diphthalic dianhydride, 
     4,4&#39;-(m-phenylenedioxy)diphthalic 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 tetracarboxylic acid dianhydrides can be used singly or as a mixture. 
     In the preparation of the polyimide resin, a part of the above diamine can be replaced with other aromatic diamines in the range giving no adverse effect on the good properties of the polyimide of the invention, for example, in the range of usually 50% by weight or less, preferably 30% by weight or less for the amount of the above diamine. 
     In preparing the polyimide resin, it is preferred in view of improving heat stability to carry out the reaction in the presence of dicarboxylic acid anhydride or monoamine. 
     Exemplary aromatic diamines which can replace the above diamines include 
     m-phenylenediamine, o-phenylenediamine, 
     p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 
     bis(3-aminophenyl)ether, 
     (3-aminophenyl)(4-aminophenyl)ether, 
     bis(4-aminophenyl)ether, 
     bis(3-aminophenyl)sulfide, 
     (3-aminophenyl)(4-aminophenyl)sulfide, 
     bis(4-aminophenyl)sulfide, 
     bis(3-aminophenyl)sulfoxide, 
     (3-aminophenyl)(4-aminophenyl)sulfoxide, 
     bis(4-aminophenyl)sulfoxide, 
     bis(3-aminophenyl)sulfone, 
     (3-aminophenyl)(4-aminophenyl)sulfone, 
     bis(4-aminophenyl)sulfone, 
     3,4&#39;-diaminobenzophenone, 4,4&#39;-diaminobenzophenone, 
     bis[4-(4-aminophenoxy)phenyl]methane, 
     1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 
     1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 
     2,2-bis[4-(4-aminophenoxy)phenyl]propane, 
     2,2-bis[4-(4-aminophenoxy)phenyl]butane, 
     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, 
     4,4&#39;-bis(4-aminophenoxy)biphenyl, 
     bis[4-(4-aminophenoxy)phenyl]ketone, 
     bis[4-(4-aminophenoxy)phenyl]sulfide, 
     bis[4-(4-aminophenoxy)phenyl]sulfoxide, 
     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, 
     bis[4-(3-aminophenoxy)phenyl]methane, 
     1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]propane, 
     2-[4-(3-aminophenoxy)phenyl]-2-[4-(3-aminophenoxy)-3-methylphenyl]propane, 
     2,2-bis[4-(3-aminophenoxy)-3-methylphenyl]propane, 
     2-[4-(3-aminophenoxy)phenyl]-2-[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane, 
     2,2-bis[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]butane, 
     2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 
     4,4&#39;-bis(3-aminophenoxy)biphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3-methylbiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dimethylbiphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3,5&#39;-dimethylbiphenyl, 
     4,4&#39;-bis(3-amlnophenoxy)-3,3&#39;,5,5&#39;-tetramethylbiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dichlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,5&#39;-dichlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;,5,5&#39;-tetrachlorobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;-dibromobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,5&#39;-dibromobiphenyl, 
     4,4&#39;-bis(3-aminophenoxy)-3,3&#39;,5,5&#39;-tetrabromobiphenyl, 
     bis[4-(3-aminophenoxy)phenyl]ketone, 
     bis[4-(3-aminophenoxy)phenyl]sulfide, 
     bis[4-(3-aminophenoxy)-3-methoxyphenyl]sulfide, 
     [4-(3-aminophenoxy)phenyl][4-(3-aminophenoxy)-3,5-dimethoxyphenyl]sulfide, sulfide, 
     bis[4-(3-aminophenoxy)-3,5-dimethoxyphenyl]sulfide, and 
     bis[4-(3-aminophenoxy)phenyl]sulfone. 
     The polyimide resin powder of the above formula (9) has an inherent viscosity in the range of usually from 0.10 to 1.50 dl/g, preferably from 0.30 to 1.22 dl/g. The viscosity lower than 0.10 dl/g cannot provide the desired mechanical strengths. On the other hand, the viscosity higher than 1.50 dl/g leads to high melt viscosity and poor processability. 
     The polyimide resin powder of the above formula (11) has an inherent viscosity in the range of usually from 0.10 to 1.50 dl/g, preferably from 0.25 to 1.22 dl/g. The viscosity lower than 0.10 dl/g cannot provide the desired mechanical strengths. On the other hand, the viscosity higher than 1.50 dl/g leads to high melt viscosity and poor processability. 
     The inherent viscosity indicated herein is measured at 35° C. in a solution containing 0.5 g of the polyimide resin in 100 ml of a solvent mixture of p-chlorophenol/phenol in a ratio of 90/10 by weight. 
     The aromatic bisimide compounds which can be used as fluidization accelerators in the composition of the invention include the compound of the formula (1), the compounds illustrated by the lower concept, that is, the formula (2), (3), (4), (5), (6) or (7), and other various aromatic bisimide compounds. 
     In the aromatic bisimide compounds which are used for a component of the composition of the invention, the bisimide compound of the invention can be prepared by the above preparation process and the processes described in detail in the examples. 
     Other bisimide compounds used for the composition of the invention, that is, the bisimide compounds of the formulas (10), (13), (14), (15) and (17) are prepared by the following processes. 
     The bisimide compound represented by the formula (10) and/or the formula (2) can be prepared with ease by reacting the diamine represented by the formula (10-a): ##STR70## wherein B is the same as in the formula (10), and/or the diamine represented by the formula (2-a), with the aromatic dicarboxylic acid anhydride represented by the formula (19) and successively by carrying out dehydrating cyclization of the resultant bisamic acid. 
     Useful diamines represented by the formula (10-a) include, for example, 
     3,3&#39;-diaminodiphenyl ether, 3,4&#39;-diaminodiphenyl ether, 
     4,4&#39;-diaminodiphenyl ether, 3,3&#39;-diaminodiphenyl sulfide, 
     3,4&#39;-diaminodiphenyl sulfide, 4,4&#39;-diaminodiphenyl sulfide, 
     3,3&#39;-diaminodiphenyl sulfone, 3,4&#39;-diaminodiphenyl sulfone, 
     4,4&#39;-diaminodiphenyl sulfone, 3,3&#39;-diaminobenzophenone, 
     3,4&#39;-diaminobenzophenone, 4,4&#39;-diaminobenzophenone, 
     3,3&#39;-diaminodiphenylmethane, 3,4&#39;-diaminodiphenylmethane, 
     4,4&#39;-diaminodiphenylmethane, 1,1-bis(3-aminophenyl)ethane, 
     1,1-bis(4-aminophenyl)ethane, 
     1,1-(3-aminophenyl)(4-aminophenyl)ethane, 
     2,2-bis(3-aminophenyl)propane, 
     2,2-bis(4-aminophenyl)propane, 
     2,2-(3-aminophenyl)(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 
     2,2-(3-aminophenyl)(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane. 
     These diamines can be used singly or as a mixture. 
     The diamines of the formula (2-a) which can be used are compounds practically enumerated above. These diamines can be used singly or as a mixture. 
     The diamines of the formula (10-a) can be previously mixed with the diamines of the formula (2-a) in the preparation of the bisimide compound. 
     The aromatic dicarboxylic acid anhydrides which can be used are compounds represented by the formula (18) and include, for example, 
     phthalic anhydride, 3-methylphthalic anhydride, 
     4-methylphthalic anhydride, 2,3-benzophenonedicarboxylic anhydride, 
     3,4-benzophenonedicarboxylic anhydride, 
     2,3-dicarboxyphenyl phenyl ether anhydride, 
     3,4-dicarboxyphenyl phenyl ether anhydride, 
     3,4-biphenyldicarboxylic anhydride, 
     2,3-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 compound can be used singly or as a mixture. 
     The diamine compounds used for preparing the other bisimide compounds of the formula (12) are represented by the formula (12-a): ##STR71## and include, for example, 1,3-bis(4-amino-α,α-dimethylaminobenzyl) benzene and 1,4-bis(4-amino-α,α-dimethylaminobenzyl)benzene. 
     Exemplary diamine compounds used for preparing the bisimide compounds of the formula (13) are represented by the formula (13-a): ##STR72## and include bis[3{4-(4-aminophenoxy)benzoyl}phenyl]ether, 
     bis[4-{4-(4-aminophenoxy)benzoyl}phenyl]ether, 
     bis[4-{3-(4-aminophenoxy)benzoyl}phenyl]ether and 
     bis[3-{3-(4-aminophenoxy)benzoyl}phenyl]ether. 
     Representative diamine compounds used for preparing the bisimide compounds of the formula (14) are represented by the formula (14-a): ##STR73## wherein Z is the same as above, and include 4,4&#39;-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone and 
     bis[4-{4-(4-amino-α,α-dimethylbenzyl)phenoxy}phenyl]sulfone. 
     Useful diamine compounds for use in the preparation of the bisimide compounds of the formula (15) are represented by the formula (15-a): ##STR74## and include, for example, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 
     1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 
     1,3-bis[4-(3-aminophenoxy)benzoyl]benzene and 
     1,3-bis[3-(3-aminophenoxy)benzoyl]benzene. 
     The diamine compounds which can be used for the preparation of the bisimide compounds of the formula (16) are represented by the formula (16-a): ##STR75## and include, for example, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene and 
     1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl)benzene. 
     The aromatic dicarboxylic acid anhydride are represented by the above formula (18) and any of the compounds practically enumerated can be used. 
     No particular restriction is imposed upon the method for reacting the diamine compound with the dicarboxylic acid anhydride. Known methods can be arbitrarily employed. The method for preparing the above bisimide compound of the invention can also be employed. 
     In processing the resin composition of the invention, the aromatic bisimide compound is used in the range of from 0.5 to 100 parts by weight for 100 parts by weight of the polyimide. The effect of the aromatic bisimide compound as a fluidization accelerator can be observed in a relatively small amount. Even an amount of 0.5 part by weight of the bisimide compound for 100 parts by weight of the polyimide is also effective. An amount of 1 part by weight or more is particularly effective. However, an amount of the aromatic bisimide compound exceeding 100 parts by weight tends to impair the mechanical strength of the resulting polyimide resin composition, and the range of 100 parts by weight or less is thus preferred. 
     Preparation of the polyimide resin composition of the invention can be carried out by usually known methods. For example, following methods are preferred. 
     1. Polyimide resin powder and the aromatic bisimide compound is premixed into powder with a mortar, Henschel mixer, drum blender, tumbling blender, ball mill or ribbon blender. 
     2. Polyimide resin powder is previously dissolved or suspended in an organic solvent, the aromatic bisimide compound is added to the resulting solution or suspension and uniformly suspended or dissolved, and thereafter the solvent is removed to obtain powder. 
     3. An aromatic bisimide compound and/or its aromatic bisamic acid precursor are dissolved or suspended in an organic solvent solution of polyamic acid which is the precursor of the polyimide and successively heat-treated at 100° to 400° C. or chemically imidized with a usual imidizing agent. Solvent is removed from the resulting mixture to obtain the powder. 
     The resin composition thus obtained in the form of powder can be used as intact for various processes such as injection molding, compression molding, transfer molding and extrusion. The powder is more preferably processed after melt-kneading. 
     Melt-kneading can be carried out with equipment for melt-kneading common rubbers or plastics, for example, hot rolls, Banbury mixer, Brabender and extruder. Melt-kneading temperature is usually set higher than melting temperature of the blending system and lower than decomposition initiating temperature of the system. The temperature is usually from 280° to 420° C., preferably from 300° to 400° C. 
     Injection molding and extrusion forming which can perform uniform melt-kneading and have high productivity are suitable for processing the resin composition of the invention. However, transfer molding, compression molding, sinter molding, and other processing methods can also be applied. 
     Prepreg for composite materials can be prepared by melt-impregnating carbon fiber or glass fiber with the above uniformly kneaded resin composition or by impregnating various fibers with a uniform solution or dispersion of the polyimide resin and aromatic bisimide compound, and successively by removing the solvent. 
     Various kinds of additives can be incorporated with the resin composition of the invention. 
     Useful additives include, for example, solid lubricants such as molybdenum disulfide, graphite, boron nitride, lead monoxide and lead powder; reinforcements such as glass fiber, carbon fiber, aromatic polyimide, silicon carbide fiber, potassium titanate fiber and glass beads; and other common auxiliary agents such as antioxidants, heat stabilizers, ultraviolet absorbers, flame retardants, antistatic agents, lubricants and colorants. These additives can be used singly or as a mixture in an amount giving no adverse effect on the properties of the resin composition of the invention. 
     A further embodiment of the invention is a polyimide resin composition comprising the polyimide resin and carbon fiber coated on the surface with the aromatic bisimide compound. As result of more detailed investigation by the inventors, the invention is a polyimide resin composition comprising a carbon fiber coated as a collecting agent on the surface with a bisimide compound represented by the above formula (10): ##STR76## wherein B and R are the same as above, and a polyimide having recurring structural units represented by the formula (11): ##STR77## wherein X, Y 1  ˜Y 2  and R&#39; are the same as above; or a polyimide resin composition comprising a carbon fiber coated as a collecting agent on the surface with a bisimide compound represented by the formula (2): ##STR78## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above, and a polyimide having recurring structural units represented by the formula (11): ##STR79## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above, or a polyimide having recurring structural units represented by the formula (9): ##STR80## wherein R&#39; is the same as above. 
     The bisimide compound which is applied to the carbon fiber in the invention is represented by the formula (10) or the formula (2) which is obtained by reacting the diamine with the dicarboxylic acid anhydride as described above. 
     The polyimide resin which can be used for the composition of the invention has recurring structural units represented by the formula (11): ##STR81## wherein X, Y 1  ˜Y 4  and R&#39; are the same as above, or recurring structural units represented by the formula (9): ##STR82## wherein R&#39; is the same as above. 
     When the bisimide compound of the formula (15) is applied to the carbon fiber, the polyimide having recurring structural units of the formula (11) is preferably used in particular. When the bisimide compound of the formula (2) is applied to the carbon fiber, the polyimides having recurring structural units of the formula (11) and recurring structural units of the formula (9) are preferably used. 
     The polyimide used for the composition of the invention and the bisimide compound applied to the carbon fiber can be prepared by using the same or different diamine as a raw material component. That is, X and Y 1  ˜Y 4  in the formula (11) can be the same as or different from X and Y 1  ˜Y 4  in the formula (2). 
     Exemplary carbon fibers which can be coated with the bisimide compound include acrylic carbon fiber, rayon-based carbon fiber, lignin-based carbon fiber and pitch-based carbon fiber. Acrylic carbon fiber is most preferably used in the invention because of its highest fiber strength. 
     The form of carbon fiber can be any kind such as chopped strand, roving and woven fabric. The surface of carbon fiber is more preferably oxidation-treated in advance by ozone or electrolytic oxidation. 
     In order to apply the bisimide compound to carbon fiber, the bisimide compound is dissolved in a solvent such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, dimethyl sulfoxide, N,N-dimethylacetamide, N-methyl-pyrrolidone, methyl ethyl ketone, 1,1,2-trichloroethane, m-cresol, p-cresol, o-cresol, p-chlorophenol, o-chlorophenol, m-chlorophenol and phenol. 
     Carbon fiber is immersed in the resulting bisimide solution and successively dried by removing the solvent to obtain the bisimide coated carbon fiber. 
     The bisimide compound of the formula (2) which can be used in the invention has a melting point of 290° C. or less and the bisimide compound of the formula (15) has a melting point of 350° C. or less. Both bisimide compounds can be melt processed and thus the bisimide coated carbon fiber can also be prepared by a melt-immersion method. 
     The coating amount of the bisimide compound on the carbon fiber is preferably in the range of from 0.1 to 10 parts by weight, more. preferably from 0.5 to 9 parts by weight, most preferably from 1 to 8 parts by weight for 100 parts by weight of the coated carbon fiber. 
     Various methods can be used for mixing the bisimide coated carbon fiber thus obtained and the polyimide resin. For example, the coated carbon fiber is cut into a length of 3 to 8 mm. The cut fiber thus obtained and the polyimide resin can be separately fed to an extruder and melt-mixed, or are previously blended in a mixer such as a Henschel mixer, super mixer and ribbon blender, and successively fed to the extruder. Alternatively, the coated carbon fiber roving can be directly fed to the extruder and mixed with the polyimide resin. 
     The amount of the bisimide coated carbon fiber and the polyimide resin matrix in the composition of the invention is from 5 to 50 parts by weight, preferably from 10 to 50 parts by weight of the carbon fiber and from 95 to 50 parts by weight, preferably from 90 to 50 parts by weight of the polyimide resin. When the amount of the carbon fiber is less than 5 parts by weight, increase of tensile strength of the resulting resin composition is unfavorably small. When the amount of the carbon fiber exceeds 50 parts by weight, uniform mixing of molten resin composition becomes difficult and melt-flowability is severely decreased to impair processability such as injection molding ability. 
     Other additives can be incorporated, if desired, with the composition of the invention in addition to the polyimide resin and the bisimide coated carbon fiber. Exemplary additives include talc, calcium carbonate, mica, glass beads and other fillers, glass fiber, potassium titanate fiber, aramide fiber, ceramic fiber and other fibrous reinforcements, stabilizers and colorants. These additives can be used in an amount giving no adverse effect on the quality and performance of the composition of the invention. 
     As mentioned above, the resin composition of the invention comprising the bisimide coated carbon fiber and the polyimide resin can be processed into desired articles by injection molding, extrusion forming, transfer molding, compression molding and other known processing methods. The resin composition of the invention thus processed has excellent mechanical strength, at high temperatures in particular, and is hence used for mechanical members and automotive parts which require high mechanical strength at high temperatures, for example, gear, cam, bushing, pulley and sleeve, and also for members of internal combustion engines, for example, gas exhausting parts for a silencer such as an impeller and manifold of an integrated centrifugal compressor, valve guide, valve stem, piston skirt, oil pan, front cover and locker cover. 
     The carbon fiber reinforced polyimide resin composition of the invention is usually used in the form of pellets which can be handled with ease. Molded articles are prepared by injection molding. The pellets are prepared by kneading and extruding the polyimide resin and the carbon fiber strand with a known single or twin screw extruder and successively by cutting the resulting strand of the composition. 
     Injection molding of the pellets thus obtained is carried out with a common injection molding machine at a cylinder temperature of 360° to 420° C. and a mold temperature of 160° to 210° C., preferably 180° to 200° C. Complex shaped members of internal combustion engines such as an impeller of an integrated centrifugal compressor can also be prepared with ease. 
     The present invention will hereinafter be illustrated in detail by way of examples and comparative examples. 
     EXAMPLE 1 
     To a reaction vessel equipped with a stirrer, reflux condenser and a nitrogen inlet tube, 368 g(1.0 mole) of 4,4&#39;-bis(3-aminophenoxy) biphenyl and 5.215 g of N,N-dimethylacetamide were charged, and 311 g(2.1 moles) of phthalic anhydride was added at room temperature and stirred for 2 hours. 
     Successively, 404 g(4 moles) of triethyl amine and 306 g(3 moles) of acetic anhydride were added dropwise to the resulting solution and stirred for 2 hours. The slurry thus formed was poured into methanol. The precipitate was filtered, dispersed in methanol, and filtered again. The procedures were repeated again. The filtered precipitate was dried at 150° C. for 2 hours to obtain 475 g of white powder. The powder had a melting point of 286° C. by DSC, a melt-initiation temperature of about 280° C. and good melt processability. 
     Results of elemental analysis were as follows. 
     
         ______________________________________Elemental analysis(C.sub.40 H.sub.24 N.sub.2 O.sub.6)     C          H      N______________________________________Calculated (%)       76.40        3.82   4.46Found (%)   76.27        3.80   4.49______________________________________ 
    
     An IR-absorption spectrum atlas is illustrated in FIG. 1. In the spectrum atlas, characteristic absorption band of imide at around 1780 cm -1  and 1720 cm -1  and characteristic absorption band of ether at around 1240 cm -1  were remarkably found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum atlas, the powder thus obtained was bisimide having the structure of the formula (20): ##STR83## The bisimide had solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride, and also had good processability. 
     EXAMPLES 2˜4 
     Each bisimide powder was prepared by carrying out the same procedures as conducted in Example 1 except that diamines were used as illustrated in Table 1. 
     The melting point and results of elemental analysis on the powder thus obtained are illustrated in Table 1 
     Any bisimide compound had solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     
                       TABLE 1______________________________________                         Melting     Diamine             pointExample   Amount g (mole)     (°C.)______________________________________2         bis[4-(3-aminophenoxy)phenyl]                         270     ketone     396.5 (1.0)3         bis[4-(3-aminophenoxy)phenyl]-                         230     sulfide     400.5(1.0)4         2,2&#39;-bis[4-(3-aminophenoxy)phenyl]                         250     propane     410.5(1.0)______________________________________Elemental analysis (%)       C      H          N    S______________________________________Calculated  75.00  3.66       4.27 0Found       74.85  3.60       4.31 0Calculated  72.70  3.64       4.24   4.85Found       72.56  3.60       4.34   4.88Calculated  77.01  4.48       4.18 0Found       76.92  4.42       4.21 0______________________________________ 
    
     COMPARATIVE EXAMPLE 1 
     The same procedures were carried out as conducted in Example 1 except that 368 g of 4,4&#39;-bis(3-aminophenoxy)biphenyl was replaced by 195.6 g(2.1 moles) of aniline and 311 g of phthalic anhydride was replaced by 218.1 g(2.1 moles) of pyromellitic dianhydride. Light yellow powder thus obtained was 360 g. 
     Results on the elemental analysis of the powder are as follows. 
     
         ______________________________________Elemental analysis(C.sub.22 H.sub.12 N.sub.2 O.sub.4)     C          H      N______________________________________Calculated (%)       71.74        3.26   7.61Found (%)   71.70        3.20   7.65______________________________________ 
    
     An IR absorption spectrum of the powder is illustrated in FIG. 2. In the spectrum atlas, the characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1 , and the characteristic absorption band of ether around 1240 cm -1  were remarkably found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum atlas, the powder thus obtained was bisimide having the structure of the formula (21): ##STR84## The bisimide had solubility of 0.01% by weight or less in dichloromethane, chloroform and carbon tetrachloride, was poor in processability and had a very high melting point of 442° C. 
     EXAMPLE 5 
     To the same reaction vessel as used in Example 1, 212 g(1.0 mole) of 3,3&#39;-diaminobenzophenone and 5215 g of N,N-dimethylacetamide were charged and 311 g(2.1 moles) of phthalic anhydride was added at room temperature and stirred for 2 hours. 
     Successively, 404 g(4 moles) of triethylamine and 306 g(3 moles) of acetic anhydride were added dropwise to the resultant solution and stirred for 2 hours at room temperature. The reaction mixture was poured into methanol. The precipitate was filtered, dispersed in methanol and filtered again. The procedures were repeated again. The precipitate thus obtained was dried at 150° C. for 2 hours. White powder thus obtained was 453 g, had a melting point of 240° C. and a melt initiation point of about 230° C., and was good in melt processability. 
     Results on the elemental analysis are as follows. 
     
         ______________________________________Elemental analysis (C.sub.29 H.sub.16 N.sub.2 O.sub.5)     C          H      N______________________________________Calculated (%)       73.73        3.39   5.93Found (%)   73.61        3.30   5.96______________________________________ 
    
     An IR absorption spectrum of the powder is illustrated in FIG. 3. In the spectrum atlas, characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably observed. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus obtained was bisimide having the structure of the formula (22): ##STR85## 
     The bisimide had solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride, and also had good processability. 
     EXAMPLE 6 
     To the same reaction vessel as used in Example 1, 616.7 g(1.0 mole of bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone and 1850 g of m-cresylic acid were charged, and 325.6 g(2.2 moles) of phthalic anhydride was added at room temperature. The mixture was heated to 140° C. and reacted for 2 hours. 
     Successively, the reaction mixture was poured into methanol and resulting precipitate was filtered, washed 3 times with methanol and dried at 150° C. for 2 hours to obtain 873.7 g(96.4% yield) of white powder having a melting point of 217° C. 
     Following results were obtained on elemental analysis. 
     
         ______________________________________Elemental analysis (C.sub.52 H.sub.32 N.sub.2 S.sub.1 O.sub.10)       C    H          N     S______________________________________Calculated (%)         71.2   3.6        3.2 3.6Found (%)     70.8   3.7        3.3 3.6______________________________________ 
    
     An IR absorption spectrum of the powder is illustrated in FIG. 4. In the spectrum atlas, the characteristic absorption spectrum of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus obtained was bisimide having the structure of the formula (23): ##STR86## 
     The bisimide thus obtained had solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     EXAMPLE 7 
     The same procedures as conducted in Example 6 were carried out except that 325.6 g(2.2 moles) of phthalic anhydride was replaced by 436 g(2.2 moles) of 2,3-naphthalenedicarboxylic anhydride. White powder thus obtained was 938 g(96% yield) and had a melting point of 218° C. Following results were obtained on the elemental analysis. 
     
         ______________________________________Elemental analysis(C.sub.60 H.sub.36 N.sub.2 S.sub.1 O.sub.10)       C    H          N     S______________________________________Calculated (%)         73.8   3.7        2.9 3.3Found (%)     73.6   3.5        3.0 3.3______________________________________ 
    
     In an IR absorption spectrum atlas, characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus obtained was bisimide having the structure of the formula (24): ##STR87## 
     The bisimide had solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     EXAMPLE 8 
     To the same reaction vessel as used in Example 1, 344.5 g(1.0 mole) of 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene and 3426 g of m-cresylic acid were charged and 325.6 g(2.2 moles) of phthalic anhydride was added at room temperature. The mixture was heated to 140° C. and reacted for 2 hours. Successively, the reaction mixture was poured into methanol. The precipitate was filtered, washed several times with methanol and dried at 100° C. for 16 hours under reduced pressure. White powder thus obtained was 590.6 g(97.7% yield) and had a melting point of 240° C. Following results were obtained on elemental analysis. 
     
         ______________________________________Elemental analysis (C.sub.40 H.sub.32 N.sub.2 O.sub.4)     C          H      N______________________________________Calculated (%)       79.47        5.30   4.64Found (%)   79.73        5.43   4.60______________________________________ 
    
     An IR absorption spectrum atlas is illustrated in FIG. 5. In the spectrum atlas, the characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, the characteristic absorption band of amic acid around 1550 cm -1 , the characteristic absorption band of diamine around 3200˜3400 cm -1 , and the characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus formed is bisimide having the structure of the formula (25): ##STR88## 
     The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride, and also had good processability. 
     EXAMPLE 9 
     The same procedures as conducted in Example 8 were carried out except that 325.6 g(2.2 moles) of phthalic anhydride was replaced by 436 g(2.2 moles) of 2,3-naphthalenedicarboxylic anhydride. White powder obtained was 687 g(97% yield), had a melting point of 241° C., and gave following results on elemental analysis. 
     
         ______________________________________Elemental analysis(C.sub.48 H.sub.40 N.sub.2 O.sub.4)     C          H      N______________________________________Calculated (%)       81.36        5.65   3.95Found (%)   81.05        5.58   3.94______________________________________ 
    
     In an IR absorption spectrum atlas, characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, characteristic absorption band of amic acid around 1550 cm -1 , characteristic absorption band of diamine around 3200˜3400 cm -1 , and characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum atlas, the powder thus obtained is bisimide having the structure of the formula (26): ##STR89## The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     EXAMPLE 10 
     To the same reaction vessel as used in Example 1, 592.7 g(1.0 mole of bis[3-{4-(4-aminophenoxy)benzoyl}phenyl]ether and 4832 g of m-cresylic acid were charged and 325.6 g(2.2 moles) of phthalic anhydride was added at room temperature. The mixture was heated to 140° C. and reacted for 2 hours. 
     Successively, the reaction mixture was poured into methanol. The precipitate formed was filtered, washed several times with methanol and dried at 100° C. for 16 hours under reduced pressure. 
     Yellow powder thus obtained was 820.3 g(96.2% yield). The powder had a melting point of 202° C. 
     Following results were obtained on the elemental analysis of the powder. 
     
         ______________________________________Elemental analysis(C.sub.54 H.sub.32 N.sub.2 O.sub.9)     C          H      N______________________________________Calculated (%)       76.06        3.76   3.29Found (%)   76.18        3.85   3.42______________________________________ 
    
     An IR absorption spectrum atlas is illustrated in FIG. 6. In the spectrum atlas, the characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, the characteristic absorption band of amic acid around 1550 cm -1 , the characteristic absorption band of diamine around 3200˜3400 cm -1 , and the characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus formed is bisimide having the structure of the formula (27): ##STR90## 
     The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride, and also had good processability. 
     EXAMPLE 11 
     The same procedures as conducted in Example 10 were carried out except that 325.6 g(2.2 moles) of phthalic anhydride was replaced by 436 g(2.2 moles) of 2,3-naphthalenedicarboxylic anhydride. Yellow powder obtained was 909 g(95% yield), had a melting point of 176° C., and gave following results on elemental analysis. 
     
         ______________________________________Elemental analysis (C.sub.62 H.sub.32 N.sub.2 O.sub.9)     C          H      N______________________________________Calculated (%)       77.82        3.35   2.93Found (%)   77.68        3.45   3.02______________________________________ 
    
     In an IR absorption spectrum atlas, characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, characteristic absorption band of amic acid around 1550 cm -1 , characteristic absorption band of diamine around 3200˜3400 cm -1 , and characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum atlas, the powder thus obtained is bisimide having the structure of the formula (28): ##STR91## The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     EXAMPLE 12 
     To the same reaction vessel as used in Example 1, 368.4 g(1.0 mole) of 4,4&#39;-bis(4-aminophenoxy)biphenyl and 3561 g of m-cresol were charged and 325.6 g(2.2 moles) of phthalic anhydride was added at room temperature. The mixture was heated to 140° C. and reacted for 2 hours. 
     Successively, the reaction mixture was poured into methanol. The precipitate formed was filtered, washed several times with methanol and dried at 100° C. for 16 hours under reduced pressure. 
     Yellow powder thus obtained was 600.1 g(95.5% yield). The powder had a melting point of 292° C. 
     Following results were obtained on the elemental analysis of the powder. 
     
         ______________________________________Elementary analysis (C.sub.40 H.sub.24 N.sub.2 O.sub.4)     C          H      N______________________________________Calculated (%)       76.40        3.82   4.46Found (%)   76.72        3.92   4.51______________________________________ 
    
     An IR absorption spectrum atlas is illustrated in FIG. 7. In the spectrum atlas, the characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, the characteristic absorption band of amic acid around 1550 cm -1 , the characteristic absorption band of diamine around 3200˜3400 cm -1 , and the characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus formed is bisimide having the structure of the formula (29): ##STR92## 
     The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride, and also had good processability. 
     EXAMPLE 13 
     The same procedures as conducted in Example 12 were carried out except that 325.6 g(2.2 moles) of phthalic anhydride was replaced by 436 g(2.2 moles)of 2,3-naphthalenedicarboxylic anhydride. Light yellow powder obtained was 696 g(95% yield), had a melting point of 293° C., and gave following results on elemental analysis. 
     
         ______________________________________Elemental analysis (C.sub.48 H.sub.32 N.sub.2 O.sub.6)     C          H      N______________________________________Calculated (%)       78.69        4.37   3.83Found (%)   78.70        4.28   3.61______________________________________ 
    
     In an IR absorption spectrum atlas, characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. 
     On the other hand, characteristic absorption band of amic acid around 1550 cm -1 , characteristic absorption band of diamine around 3200˜3400 cm -1 , and characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum atlas, the powder thus obtained is bisimide having the structure of the formula (30): ##STR93## The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     EXAMPLE 14 
     To the same reaction vessel as used in Example 1, 410.5 g(1 mole) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 3800 g of m-cresol were charged and 325.6 g(2.2 moles) of phthalic anhydride was added at room temperature. The mixture was heated to 140° C. and reacted for 2 hours. 
     Successively, the reaction mixture was poured into methanol. The precipitate formed was filtered, washed several times with methanol and dried at 100° C. for 16 hours under reduced pressure. 
     Light yellow powder thus obtained was 612.8 g(91.4% yield). The powder had a melting point of 218° C. 
     Following results were obtained on the elemental analysis of the powder. 
     
         ______________________________________Elementary analysis(C.sub.43 H.sub.30 N.sub.2 O.sub.6)     C          H      N______________________________________Calculated (%)       77.01        4.48   4.18Found (%)   76.84        4.55   4.26______________________________________ 
    
     An IR absorption spectrum atlas is illustrated in FIG. 8. In the spectrum atlas, the characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, the characteristic absorption band of amic acid around 1550 cm -1 , the characteristic absorption band of diamine around 3200˜3400 cm -1 , and the characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus formed is bisimide having the structure of the formula (31): ##STR94## 
     The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     EXAMPLE 15 
     The same procedures as conducted in Example 14 were carried out except that 325.6 g(2.2 moles) of phthalic anhydride was replaced by 436 g(2.2 moles) of 2,3-naphthalenedicarboxylic anhydride. White powder obtained was 697 g(90% yield), had a melting point of 219° C., and gave following results on elemental analysis. 
     
         ______________________________________Elementary analysis (C.sub.51 H.sub.38 N.sub.2 O.sub.6)     C          H      N______________________________________Calculated (%)       79.07        4.91   3.62Found (%)   78.72        5.05   3.54______________________________________ 
    
     In an IR absorption spectrum atlas, characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, characteristic absorption band of amic acid around 1550 cm -1 , characteristic absorption band of diamine around 3200˜3400 cm -1 , and characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum atlas, the powder thus obtained is bisimide having the structure of the formula (32): ##STR95## The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     EXAMPLE 16 
     To the same reaction vessel as used in Example 1, 400.5 g(1.0 mole) of bis[4-(4-aminophenoxy)phenyl]sulfide and 3743 g of m-cresol were charged and 325.6 g(2.2 moles) of phthalic anhydride was added at room temperature. The mixture was heated to 140° C. and reacted for 2 hours. 
     Successively, the reaction mixture was poured into methanol. The precipitate formed was filtered, washed several times with methanol and dried at 100° C. for 16 hours under reduced pressure. 
     White powder thus obtained was 612.9 g(92.8% yield). The powder had a melting point of 252° C. 
     Following results were obtained on the elemental analysis of the powder. 
     
         ______________________________________Elemental analysis (C.sub.40 H.sub.24 N.sub.2 O.sub.6 S)       C    H          N     S______________________________________Calculated (%)         72.70  3.64       4.24                               4.85Found (%)     72.66  3.73       4.26                               4.99______________________________________ 
    
     An IR absorption spectrum atlas is illustrated in FIG. 9. In the spectrum atlas, the characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, the characteristic absorption band of amic acid around 1550 cm -1 , the characteristic absorption band of diamine around 3200˜3400 cm -1 , and the characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus formed is bisimide having the structure of the formula (33): ##STR96## 
     The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride, and also had good processability. 
     EXAMPLE 17 
     The same procedures as conducted in Example 16 were carried out except that 325.6 g(2.2 moles) of phthalic anhydride was replaced by. 436 g(2.2 moles) of 2,3-naphthalenedicarboxylic anhydride. White powder obtained was 703 g(92% yield), had a melting point of 253° C., and gave following results on elemental analysis. 
     
         ______________________________________Elemental analysis (C.sub.48 H.sub.32 N.sub.2 O.sub.6 S)       C    H          N     S______________________________________Calculated (%)         75.39  4.19       3.66                               4.19Found (%)     75.52  4.26       3.42                               3.88______________________________________ 
    
     In an IR absorption spectrum atlas, characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  was remarkably found. On the other hand, characteristic absorption band of amic acid around 1550 cm -1 , characteristic absorption band of diamine around 3200˜3400 cm -1 , and characteristic absorption band of acid anhydride around 1850 cm -1  were not found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum atlas, the powder thus obtained is bisimide having the structure of the formula (34): ##STR97## The bisimide had a solubility of 5% by weight or more in dichloromethane, chloroform and carbon tetrachloride and also had good processability. 
     Synthesis Example 
     Synthesis of Polyimide-1 
     According to the example described Japanese Laid-Open Patent Hei 2-18419, 3,3&#39;-diaminobenzophenone was reacted with 3,3&#39;,4,4&#39;-benzophenonetetracarboxylic dianhydride in the presence of phthalic anhydride to obtain polyimide powder. 
     The polyimide powder had an inherent viscosity of 0.52 dl/g, glass transition temperature of 250° C. and melting point of 298° C. 
     The inherent viscosity was measured at 35° C. in a solution containing 0.5 g of the polyimide in a solvent mixture of p-chlorophenol/phenol in a ratio of 90/10 by weight. The melting point was measured by DSC. The measuring methods will be the same hereinafter. 
     Synthesis of Polyimide-2 
     The same procedures as conducted in Synthesis of Polyimide-1 were carried out except that the ratio of the diamine to the tetracarboxylic acid dianhydride and phthalic anhydride was changed. The polyimide powder thus obtained had an inherent viscosity of 0.85 dl/g, glass transition temperature of 262° C. and melting point of 298° C. 
     Synthesis of Polyimide-3 
     According to the description in Japanese Laid-Open Patent Hei 1-110530, 4,4&#39;-bis(3-aminophenoxy)biphenyl was reacted with pyromellitic dianhydride and phthalic anhydride to obtain polyimide powder. 
     The polyimide powder obtained had an inherent viscosity of 0.53 dl/g, glass transition temperature of 250° C. and melting point of 390° C. 
     Synthesis of Polyimide-4 
     The same procedures as conducted in Synthesis of Polyimide-3 were carried out except that the ratio of the diamine to tetracarboxylic acid dianhydride and phthalic anhydride was changed. 
     The polyimide powder thus obtained had an inherent viscosity of 0.78 dl/g, glass transition temperature of 254° C. and melting point of 390° C. 
     Synthesis of Polyimide-5 
     The same procedures as conducted in Synthesis of Polyimide-3 were carried out by using bis[4-(3-aminophenoxy)phenyl]sulfide, pyromellitic dianhydride and phthalic anhydride. 
     The polyimide thus obtained had an inherent viscosity of 0.49 dl/g and glass transition temperature of 235° C. 
     Synthesis of Polyimide-6 
     The same procedures as conducted in Synthesis of Polyimide-3 were carried out by using bis[4-(3-aminophenoxy)phenyl]ketone, bis(3,4-dicarboxyphenyl)ether dianhydride and phthalic anhydride. 
     The polyimide thus obtained had an inherent viscosity of 0.51 dl/g and glass transition temperature of 201° C. 
     Synthesis of Polyimide-7 
     According to Japanese Laid-Open Patent Hei 1-221428, bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone was reacted with pyromellitic dianhydride and phthalic anhydride. 
     The polyimide thus obtained had an inherent viscosity of 0.57 dl/g, glass transition temperature of 285° C. and melting point of 420° C. 
     Synthesis of Polyimides-8˜12 
     The same procedures as conducted in Synthesis of Polyimide-7 were carried out except that tetracarboxylic acid dianhydride was changed to obtain various kinds of polyimide. 
     The raw materials and properties of these polyimides and the results on Polyimide-7 are summarized in Table 2. 
     
                       TABLE 2______________________________________Raw Material               Tetracarboxylic                            DicarboxylicPolyimide   Diamine     acid dianhydride                            acid anhydride______________________________________ 7      bis[4-{4-(4-               pyromellitic phthalic   aminophenoxy)               dianhydride  anhydride   phenoxy}   phenyl]sulfone 8         ↑     ↑   ↑ 9         ↑  3,3&#39;,4,4&#39;-biphenyl-                            ↑               tetracarboxylic               dianhydride10         ↑  bis(3,4-dicarboxy-                            ↑               phenyl)ether               dianhydride11         ↑  3,3&#39;,4,4&#39;-   ↑               benzophenone-               tetracarboxylic               dianhydride12         ↑  4,4&#39;-(p-     ↑               phenylenedioxy)               diphthalic               dianhydride______________________________________  Polymer properties    Inherent    Glass transition    viscosity   temperature                           Melting pointPolyimide    (dl/g)      (°C.)                           (°C.)______________________________________ 7       0.57        285        420 8       0.70        288        420 9       0.60        263        --10       0.59        237        --11       0.60        245        --12       0.59        220        --______________________________________ 
    
     Synthesis of Bisimide Compound-1 
     Bisimide was prepared from 4,4&#39;-bis(3-aminophenoxy)biphenyl and phthalic anhydride by carrying out the same procedures as Example 1. The bisimide compound obtained had a melting point of 286° C. 
     Synthesis of Bisimide Compound-2 
     Bisimide was prepared from bis[4-(3-aminophenoxy)phenyl]sulfide and phthalic anhydride by the same procedures as conducted in Synthesis of Bisimide Compound-1. 
     The bisimide compound thus obtained had a melting point of 230° C. 
     Synthesis of Bisimide Compound-3 
     To a reaction vessel equipped with a stirrer, reflux condenser and nitrogen inlet tube, 200 g(1.0 mole) of 4,4&#39;-diaminodiphenyl ether and 4000 g of m-cresol were charged and 311 g(2.1 moles) of phthalic anhydride was added at room temperature. The mixture was then heated to 200° C. and stirred for 2 hours at the same temperature. 
     Successively, the reaction mixture was poured into methanol. The precipitate formed was filtered, washed several times with methanol and dried at 150° C. for 2 hours. The white powder thus obtained was 450 g, had a melting point of 295° C. and melt-initiation point of about 290° C., and also had good melt-processability. 
     Following results were obtained on elemental analysis. 
     
         ______________________________________Elemental analysis (C.sub.28 H.sub.16 N.sub.2 O.sub.4)     C          H      N______________________________________Calculated (%)       73.36        3.06   6.11Found (%)   73.30        3.10   6.16______________________________________ 
    
     An IR absorption spectrum atlas is illustrated in FIG. 10. In the spectrum atlas, the characteristic absorption band of imide around 1780 cm -1  and 1720 cm -1  and the characteristic absorption band of ether around 1240 cm -1  were remarkably found. 
     According to the identification by the preparation process, results of elemental analysis and IR absorption spectrum, the powder thus obtained is bisimide having the structure of the formula (35): ##STR98## 
     Synthesis of Bisimide Compound-4 
     Bisimide was prepared from 3,3&#39;-diaminobenzophenone and phthalic anhydride by carrying out the same procedures as conducted in Example 5. 
     The bisimide compound obtained had a melting point of 240° C. 
     Synthesis of Bisimide Compound-5 
     Bisimide was prepared from 4,4&#39;- bis(4-aminophenoxy)biphenyl and phthalic anhydride by carrying out the same procedures as conducted in Example-12. 
     Synthesis of Bisimide Compounds-6˜12 
     The same procedures as conducted in Synthesis of Bisimide Compound-5 were carried out except that diamines were changed to obtain various kinds of bisimide. 
     Table 3 summarizes the raw materials and properties of the bisimide and also results on Aromatic Bisimide Compound-5. 
     
                       TABLE 3______________________________________                       BisimideRaw material                Melting                    Dicarboxylic                               pointBisimide  Diamine           acid anhydride                               (°C.)______________________________________5      4,4&#39;-bis(4-aminophenoxy)                    Phthalic   292  biphenyl          anhydride6      2,2-bis[4-(4-aminophenoxy)                    ↑    218  phenyl]propane7      1,3-bis(4-amino-α,α-                    ↑    240  dimethylbenzyl)benzene8      bis[4-{4-(4-aminophenoxy)                    ↑    217  phenoxy}phenyl]sulfone9      bis[3-{4-(4-aminophenoxy)                    ↑    202  benzoyl}phenyl]ether10     bis[4-{4-amino-α,α-                    ↑    160  dimethylbenzyl)phenoxy}  phenyl]sulfone11     1,4-bis[4-(3-aminophenoxy)-                    ↑    220  benzoyl]benzene12     1,3-bis[4-{4-aminophenoxy)-                    ↑    180  α,α-dimethylbenzyl]benzene______________________________________ 
    
     EXAMPLES 18˜20 
     COMPARATIVE EXAMPLE 2 
     Polyimide-1 and Bisimide Compound-1 were dry blended in proportions illustrated in Table 4. Melt viscosity of the resin composition obtained was measured with a Koka type flow tester CFT-500 (Trade mark of Shimadzu Seisakusho Co.) by using an orifice having a diameter of 0.1 cm and a length of 1 cm. The resin composition was maintained in the cylinder at 380° C. for 5 minutes and then extruded under a load of 100 kg. Results are illustrated in Table 4. 
     Melt viscosity rapidly decreased with increase in the proportion of the bisimide compound, and thus illustrated improvement of processability. 
     EXAMPLES 21˜23 
     COMPARATIVE EXAMPLE 3 
     Polyimide-2 and Bisimide Compound-2 were dry blended in proportions illustrated in Table 4. Melt viscosity of the resulting composition was measured by the same procedures as conducted in Examples 18˜20, Comparative Example 2 except that the resin composition was maintained at 400° C. for 5 minutes in the cylinder of the flow tester. Results obtained are illustrated in Table 4. 
     EXAMPLES 24˜26 
     The same procedures as conducted in Examples 18˜20 were carried out except that Bisimide Compound-3 was used in place of Bisimide Compound-1 and dry blended in proportions illustrated in Table 4. Melt viscosity was measured by extruding under 100 kg load after maintaining at 380° C. for 5 minutes. Results are illustrated in Table 4. 
     
                       TABLE 4______________________________________         (wt.             (wt. Melt viscosityPolyimide     part)  Bisimide  part)                               (poise)______________________________________Example 18   Polyimide-1             100    Bisimide                            1    8000Example 19        100    Compound-1                            5    6300Example 20        100            20   1800Comparative       100            0    10500Example 2Example 21   Polyimide-2             100    Bisimide                            2    91400Example 22        100    Compound-2                            10   51400Example 23        100            50   2500Comparative       100            0    120000Example 3Example 24   Polyimide-1             100    Bisimide                            5    6400Example 25        100    Compound-3                            20   1800Example 26        100            70   **&lt;100______________________________________ **Melt viscosity is less than 100 poise and a measurement of melt viscosity was not possible. 
    
     EXAMPLES 27˜32 
     COMPARATIVE EXAMPLE 4 
     Polyimide-3 and Bisimide Compound-1 or Bisimide Compound-3 were dry blended in proportions illustrated in Table 5. Melt viscosity of the resin composition obtained was measured with a Koka type flow tester CFT-500 (Trade mark of Shimadzu Seisakusho Co.) by using an orifice having a diameter of 0.1 cm and a length of 1 cm. The resin composition was maintained in the cylinder at 400° C. for 5 minutes and then extruded under a load of 100 kg. Results are illustrated in Table 5. 
     Melt viscosity rapidly decreased with increase in the proportion of the bisimide compound, and thus illustrated improvement of processability. 
     EXAMPLES 33˜35 
     COMPARATIVE EXAMPLE 5 
     Polyimide-5 and Bisimide Compound-2 were dry blended in proportions illustrated in Table 5. Melt viscosity of the resulting composition was measured by the same procedures as conducted in Examples 27˜32, Comparative Example 4 except that the resin composition was maintained at 360° C. for 5 minutes in the cylinder of the flow tester. Results obtained are illustrated in Table 5. 
     EXAMPLE 36˜38 
     COMPARATIVE EXAMPLE 6 
     Polyimide-6 and Bisimide Compound-1 were dry blended in proportions illustrated in Table 5. Melt viscosity of the resulting composition was measured by extruding under 100 kg load after maintaining at 340° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 5. 
     
                       TABLE 5______________________________________         (wt.             (wt. Melt viscosityPolyimide     part)  Bisimide  part)                               (poise)______________________________________Example 27   Polyimide-3             100    Bisimide                            1    5100Example 28        100    Compound-1                            5    3600Example 29        100            20   1000Comparative       100            0    6000Example 4Example 30   Polyimide-3             100    Bisimide                            2    4900Example 31        100    Compound-3                            10   2700Example 32        100            50   150Example 33   Polyimide-5             100    Bisimide                            5    5500Example 34        100    Compound-2                            20   1500Example 35        100            70   **&lt;100Comparative       100            0    9000Example 5Example 36   Polyimide-6             100    Bisimide                            1    6400Example 37        100    Compound-1                            5    4500Example 38        100            20   1300Comparative       100            0    8000Example 6______________________________________ 
    
     EXAMPLES 39˜42 
     COMPARATIVE EXAMPLE 7 
     Polyimide-1 and Bisimide Compound-4 were dry blended in proportions illustrated in Table 6. Melt viscosity of the resin composition obtained was measured with a Koka Type flow tester CFT-500 (Trade mark of Shimadzu Seisakusho Co.) by using an orifice having a diameter of 0.1 cm and a length of 1 cm. The resin composition was maintained in the cylinder at 380° C. for 5 minutes and then extruded under a load of 100 kg. Results are illustrated in Table 6. 
     Melt viscosity rapidly decreased with increase in the proportion of the bisimide compound, and thus illustrated improvement of processability. 
     EXAMPLES 43˜45 
     COMPARATIVE EXAMPLE 8 
     Polyimide-2 and Bisimide Compound-4 were dry blended in proportions illustrated in Table 6. Melt viscosity of the resulting composition was measured by the same procedures as conducted in Examples 39˜42 except that the resin composition was maintained at 400° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 6. 
     
                       TABLE 6______________________________________         (wt.             (wt. Melt viscosityPolyimide     part)  Bisimide  part)                               (poise)______________________________________Example 39   Polyimide-1             100    Bisimide                            1    8100Example 40        100    Compound-4                            5    5700Example 41        100            20   1600Example 42        100            70   **&lt;100Comparative       100            0    10500Example 7Example 43   Polyimide-2             100    Bisimide                            2    7700Example 44        100    Compound-4                            10   43700Example 45        100            50   2300Comparative       100            0    120000Example 8______________________________________ 
    
     EXAMPLES 46˜51 
     COMPARATIVE EXAMPLE 9 
     Polyimide-3 and Bisimide Compound-5 or Bisimide Compound-7 were dry blended in proportions illustrated in Table 7. Melt viscosity of the resin composition obtained was measured with a Koka Type flow tester CFT-500 (Trade mark of Shimadzu Seisakusho Co.) by using an orifice having a diameter of 0.1 cm and a length of 1 cm. The resin composition was maintained in the cylinder at 400° C. for 5 minutes and then extruded under a load of 100 kg. Results are illustrated in Table 7. 
     Melt viscosity rapidly decreased with increase in the proportion of the bisimide compound, and thus illustrated improvement of processability. 
     EXAMPLES 52˜57 
     COMPARATIVE EXAMPLE 10 
     Polyimide-4 and Bisimide Compound-5 or Bisimide Compound-11 were dry blended in proportions illustrated in Table 7. Melt viscosity of the resulting composition was measured by the same procedures as conducted in Examples 46˜51, Comparative Example 9. 
     EXAMPLES 58˜63 
     COMPARATIVE EXAMPLE 11 
     Polyimide-5 and Bisimide Compound-6 or Bisimide Compound-8 were dry blended in proportions illustrated in Table 7. Melt viscosity of resulting polyimide composition was measured by extruding under load of 100 kg after maintaining at 360° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 7. 
     EXAMPLES 63˜71 
     COMPARATIVE EXAMPLE 12 
     Polyimide-6 and Bisimide Compounds-9, -10 or -12 were dry blended in proportions illustrated in Table 7. Melt viscosity of the resulting polyimide composition was measured by extruding under load of 100 kg after maintaining at 340° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 7. 
     
                       TABLE 7______________________________________         (wt.             (wt. Melt viscosityPolyimide     part)  Bisimide  part)                               (poise)______________________________________Example 46   Polyimide-3             100    Bisimide                            1    5200Example 47        100    Compound-5                            5    3500Example 48        100            20   1100Comparative       100            0    6000Example 9Example 49        100    Bisimide                            2    4800Example 50        100    Compound-7                            10   2500Example 51        100            40   200Example 52   Polyimide-4             100    Bisimide                            2    83000Example 53        100    Compound-5                            10   46000Example 54        100            25   6000Comparative       100            0    370000Example 10Example 55        100    Bisimide                            5    72000Example 56        100    Compound-11                            15   15000Example 57        100            30   1300Example 58   Polyimide-5             100    Bisimide                            2    7400Example 59        100    Compound-6                            10   3800Example 60        100            15   2400Comparative       100            0    9000Example 11Example 61        100    Bisimide                            5    5800Example 62        100    Compound-8                            20   1500Example 63        100            30   640Example 63   Polyimide-6             100    Bisimide                            2    6800Example 64        100    Compound-9                            5    5200Example 65        100            10   3400Comparative       100            0    8000Example 12Example 66        100    Bisimide                            10   3300Example 67        100    Compound-10                            20   1400Example 68        100            55   **&lt;100Example 69        100    Bisimide                            1    7200Example 70        100    Compound-12                            5    5200Example 71        100            10   3200______________________________________ 
    
     EXAMPLES 72˜77 
     COMPARATIVE EXAMPLE 13 
     Polyimide-7 and B is imide Compound-1 or Bisimide Compound-3. were dry blended in proportions illustrated in Table 8. Melt viscosity of the resin composition obtained was measured with a Koka Type flow tester CFT-500 (Trade mark of Shimadzu Seisakusho Co.) by using an orifice having a diameter of 0.1 cm and a length of 1 cm. The resin composition was maintained in the cylinder at 420° C. for 5 minutes and then extruded under a load of 100 kg. Results are illustrated in Table 8. 
     Melt viscosity rapidly decreased with increase in the proportion of the bisimide compound, and thus illustrated improvement of processability. 
     EXAMPLES 78˜83 
     COMPARATIVE EXAMPLE 14 
     Polyimide-8 and Bisimide Compound-5 or Bisimide Compound-7 were dry blended in proportions illustrated in Table 8. Melt viscosity of the resulting composition was measured by the same procedures as conducted in Examples 72˜77, Comparative Example 13. 
     EXAMPLES 84˜89 
     COMPARATIVE EXAMPLE 15 
     Polyimide-9 and Bisimide Compound-1 or Bisimide Compound-8 were dry blended in proportions illustrated in Table 8. Melt viscosity of resulting polyimide composition was measured by extruding under load of 100 kg after maintaining at 380° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 8. 
     EXAMPLES 90˜93 
     COMPARATIVE EXAMPLE 16 
     Polyimide-10 and Bisimide Compounds-9 or -11 were dry blended in proportions illustrated in Table 8. Melt viscosity of the resulting polyimide composition was measured by extruding under load of 100 kg after maintaining at 360° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 8. 
     EXAMPLES 94˜96 
     COMPARATIVE EXAMPLE 17 
     Polyimide-11 and Bisimide Compound-12 were dry blended in proportions illustrated in Table 8. Melt viscosity of the resulting composition was measured by extruding under load of 100 kg after maintaining at 370° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 8. 
     EXAMPLES 97˜99 
     COMPARATIVE EXAMPLE 18 
     Polyimide-12 and Bisimide Compound-10 were dry blended in proportions illustrated in Table 8. Melt viscosity was measured by extruding under load of 100 kg after maintaining at 340° C. for 5 minutes in the cylinder of the flow tester. Results are illustrated in Table 8. 
     By the addition of bisimide, melt viscosity of the resin was remarkably decreased and processability was improved. 
     
                       TABLE 8______________________________________         (wt.             (wt. Melt viscosityPolyimide     part)  Bisimide  part)                               (poise)______________________________________Example 72   Polyimide-7             100    Bisimide                            1    7200Example 73        100    Compound-1                            5    5000Example 74        100            10   3200Comparative       100            0    8500Example 13Example 75        100    Bisimide                            5    5400Example 76        100    Compound-3                            15   2400Example 77        100            25   1000Example 78   Polyimide-8             100    Bisimide                            2    46000Example 79        100    Compound-5                            10   17000Example 80        100            30   1300Comparative       100            0    68000Example 14Example 81        100    Bisimide                            5    34000Example 82        100    Compound-7                            15   8000Example 83        100            30   1000Example 84   Polyimide-9             100    Bisimide                            10   4200Example 85        100    Compound-1                            30   700Example 86        100            60   **&lt;100Comparative       100            0    10000Example 15Example 87        100    Bisimide                            5    5400Example 88        100    Compound-8                            10   3600Example 89        100            20   1500Example 90   Polyimide-             100    Bisimide                            2    5000Example 91   10        100    Compound-9                            5    3400Comparative       100            0    6000Example 16Example 92        100    Bisimide                            10   2200Example 93        100    Compound-11                            15   1200Example 94   Polyimide-             100    Bisimide                            10   3000Example 95   11        100    Compound-12                            30   300Example 96        100            50   **&lt;100Comparative       100            0    9500Example 17Example 97   Polyimide-             100    Bisimide                            2    4000Example 98   12        100    Compound-10                            5    2800Example 99        100            10   1400Comparative       100            0    5500Example 18______________________________________ 
    
     EXAMPLES 100˜102 
     The bisimide compound which was prepared by reacting 4,4&#39;-bis(3-aminophenoxy)biphenyl with phthalic anhydride according to Example 1 and had an inherent viscosity of 0.52 dl/g, glass transition temperature of 250° C. and melting point of 298° C.(hereinafter referred to simply as Bisimide-A) was used as a raw material. A bisimide solution compound of 20% by weight of Bisimide-A, 40% by weight of dichloromethane and 40% by weight of 1,1,2-trichloroethane was prepared. 
     An oxidation-treated acrylic carbon fiber roving, HTA(Trade mark of Toho Rayon Co.; used as carbon fiber in the below examples and comparative examples, unless otherwise noted) was continuously immersed in the bisimide solution at a rate of 60 m/hr, dried to remove the solvents and cut into a length of 3 mm to obtain chopped strand. The adhered amount of the bisimide was 5% by weight for the weight of the carbon fiber. The carbon fiber chopped strand thus obtained was dry blended with Polyimide-4 in proportions illustrated in Table 9. The resin composition thus obtained was fed to an extruder having a bore diameter of 40 mm, melt-kneaded at 400° C. and extruded to obtain uniformly blended pellets. 
     The above uniform pellets were injection molded with a common injection molding machine at a cylinder temperature of 410° C. and mold temperature of 200° C. to form dumbbell specimens. Tensile strength of the dumbbell specimens was measured at 23° C. at a pulling rate of 5 mm/min. 
     Results are illustrated in Table 9. 
     COMPARATIVE EXAMPLES 19˜20 
     The same procedures as conducted in Examples 100˜102 were carried out except that the carbon fiber chopped strand coated with the bisimide compound was replaced by an epoxy resin collected acrylic carbon fiber. Dumbbell specimens of carbon fiber reinforced polyimide resin thus prepared were subjected to tensile strength test and results are illustrated in Table 9. 
     
                       TABLE 9______________________________________CompositionPolyimide resin   Carbon fiber  Tensile         Amount  Collecting                           Amount                                 strengthKind of resin (wt. %) agent     (wt. %)                                 (kg/cm.sup.2)______________________________________Example 100   Polyimide-1             80      Bisimide A                             20    2610Example 101       70              30    3060Example 102       60              40    3400Comparative   Polyimide-4             80      epoxy resin                             20    1880Example 19Comparative       70              30    2060Example 20Comparative       60              40    2200Example 21______________________________________ 
    
     EXAMPLES 103˜105 
     The bisimide compound which was prepared by reacting bis[4-(3-aminophenoxy)phenyl]sulfide with phthalic anhydride according to Example 3 and had a melting point of 230° C. (hereinafter referred to simply as Bisimide-B) was used as a raw material. 
     As oxidation-treated carbon fiber roving was continuously immersed in molten Bisimide-B at 240° C. at a rate of 30 m/hr and cut into a length of 3 mm to obtain chopped strand. The amount of adhered bisimide compound was 7% by weight for the weight of carbon fiber. 
     The carbon fiber chopped strand thus obtained was dry blended with Polyimide-5 in proportions illustrated in Table 10. The resin composition obtained was fed to an extruder having a bore diameter of 40 mm, melt-kneaded at 360° C. and extruded to obtain uniformly blended pellets. 
     The above uniform pellets were injection molded with a common injection molding machine at a cylinder temperature of 360° C. and mold temperature of 180° C. to form dumbbell specimens. Tensile strength of the dumbbell specimens was measured at 23° C. at a pulling rate of 5 mm/min. Results are illustrated in Table 10. 
     COMPARATIVE EXAMPLES 22˜23 
     The same procedures as conducted in Examples 102˜104 were carried out except that proportions of the bisimide coated carbon fiber were changed. Results are illustrated in Table 10. Pellets containing 60% by weight of carbon fiber had poor melt flowability and hence dumbbell specimens could not be prepared by injection molding. 
     
                       TABLE 10______________________________________CompositionPolyimide resin   Carbon fiber  Tensile         Amount  Collecting                           Amount                                 strengthKind of resin (wt. %) agent     (wt. %)                                 (kg/cm.sup.2)______________________________________Example 103   Polyimide-5             80      Bisimide-B                             20    2970Example 104       70              30    3450Example 105       60              40    3880Comparative   Polyimide-5             40      epoxy resin                             60    moldingExample 22                              impossibleComparative       98              20    1650Example 23______________________________________ 
    
     EXAMPLES 106˜108 
     The same procedures as conducted in Examples 100˜102 were carried out except that Polyimide-4 was replaced by Polyimide-6 and the composition was melt-kneaded at 320° C. to obtain uniformly blended pellets. The pellets thus obtained was injection molded with a common injection molding machine at a cylinder temperature of 330° C. and mold temperature of 160° C. to prepare dumbbell specimens. Tensile strength of the dumbbell specimens was measured at 23° C. at a pulling rate of 5 mm/min. Results are illustrated in Table 11. 
     COMPARATIVE EXAMPLE 24 
     Dumbbell specimens were prepared by carrying out the same procedures as conducted in Examples 106˜108 except that the polyimide resin was used alone without carbon fiber. Results are illustrated in Table 11. 
     
                       TABLE 11______________________________________CompositionPolyimide resin   Carbon fiber  Tensile         Amount  Collecting                           Amount                                 strengthKind of resin (wt. %) agent     (wt. %)                                 (kg/cm.sup.2)______________________________________Example 106   Polyimide-6             80      Bisimide-A                             20    2600Example 107       70              30    2910Example 108       60              40    3260Comparative   Polyimide-6             100     Bisimide-A                             0     1180Example 24______________________________________ 
    
     EXAMPLES 109˜111 
     Uniformly blended pellets were prepared by carrying out the same procedures as conducted in Examples 106˜108 except that Polyimide-6 is replaced by polyimide-1 and the composition was melt-kneaded at 360° C. 
     Dumbbell specimens were prepared from the uniformly blended pellets by injection molding at a cylinder temperature of 380° C. and mold temperature 180° C. Tensile strength of the specimens was measured at 23° C. at a pulling rate of 5 mm/min. Results are illustrated in Table 12. 
     COMPARATIVE EXAMPLE 25˜27 
     Dumbbell specimens of carbon fiber reinforced polyimide resin were prepared by carrying out the same procedures as conducted in Examples 109˜111 except that the carbon fiber chopped strand coated with the bisimide compound was replaced by an acrylic carbon fiber collected with an epoxy resin. Tensile strength of the specimens was measured under the same conditions as in Examples 109˜111 and results are illustrated in Table 12. 
     
                       TABLE 12______________________________________CompositionPolyimide resin   Carbon fiber  Tensile         Amount  Collecting                           Amount                                 strengthKind of resin (wt. %) agent     (wt. %)                                 (kg/cm.sup.2)______________________________________Example 109   Polyimide-1             80      Bisimide-A                             20    2680Example 110       70              30    3120Example 111       60              40    3510Comparative   Polyimide-1             80      epoxy resin                             20    1930Example 25Comparative       70              30    2100Example 26Comparative       60              40    2270Example 27______________________________________ 
    
     EXAMPLES 112˜114 
     A bisimide solution composed of 40% by weight of dichloromethane, 40% by weight of 1,1,2-trichloroethane and 20% by weight of Bisimide Compound-3(hereinafter referred to simply as Bisimide-C) was prepared. An oxidation-treated acrylic carbon fiber roving, HTA(Trade Mark of Toho Rayon Co.) was continuously immersed in the bisimide solution at a rate of 60 m/hr, dried to remove the solvents and cut into a length of 3 mm to obtain chopped strand. The adhered amount of the bisimide was 5% by weight for the weight of the carbon fiber. 
     The carbon fiber chopped strand thus obtained was dry blended with polyimide-4 in proportions illustrated in Table 13. The resin composition thus obtained was fed to an extruder having a bore diameter of 40 mm, melt-kneaded at 400° C. and extruded to obtain uniformly blended pellets. 
     The above uniform pellets were injection molded with a common injection molding machine at a cylinder temperature of 400° C. and mold temperature of 200° C. to form dumbbell specimens. Tensile strength of the dumbbell specimens was measured at 23° C. at a pulling rate of 5 mm/min. Results are illustrated in Table 13. 
     COMPARATIVE EXAMPLES 28˜30 
     The same procedures as conducted in Examples 112˜114 were carried out except that the carbon fiber chopped strand coated with the bisimide compound was replaced by an epoxy-resin collected acrylic carbon fiber. Dumbbell specimens of carbon fiber reinforced polyimide resin thus prepared were subjected to tensile strength test and results are illustrated in Table 13. 
     
                       TABLE 13______________________________________CompositionPolyimide resin   Carbon fiber  Tensile         Amount  Collecting                           Amount                                 strengthKind of resin (wt. %) agent     (wt. %)                                 (kg/cm.sup.2)______________________________________Example 112   Polyimide-4             80      Bisimide-C                             20    2630Example 113       70              30    3080Example 114       60              40    3430Comparative   Polyimide-4             80      epoxy resin                             20    1880Example 28Comparative       70              30    2060Example 29Comparative       60              40    2200Example 30______________________________________ 
    
     EXAMPLES 115˜117 
     A carbon fiber roving which was previously oxidation-treated on the surface was continuously immersed in molten Bisimide-C at a rate of 30 m/hr and cut into a length of 3 mm to obtain chopped strand. 
     The adhered amount of the bisimide was 5% by weight for the weight of the carbon fiber. 
     The carbon fiber chopped strand thus obtained was dry blended with polyimide-5 in proportions illustrated in Table 14. The resin composition thus obtained was fed to an extruder having a bore diameter of 40 mm, melt-kneaded at 360° C. and extruded to obtain uniformly blended pellets. 
     The above uniform pellets were injection molded with a common injection molding machine at a cylinder temperature of 360° C. and mold temperature of 180° C. to form dumbbell specimens. Tensile strength of the dumbbell specimens was measured at 23° C. at a pulling rate of 5 mm/min. Results are illustrated in Table 14. 
     COMPARATIVE EXAMPLES 31˜32 
     The same procedures as conducted in Examples 115˜117 were carried out except that the proportion of the polyimide to the carbon fiber coated with the bisimide was changed. Results are illustrated in Table 14. 
     The pellets containing 60% by weight of carbon fiber had poor melt flowability and hence dumbbell specimens could not be prepared by injection molding. 
     
                       TABLE 14______________________________________CompositionPolyimide resin   Carbon fiber  Tensile         Amount  Collecting                           Amount                                 strengthKind of resin (wt. %) agent     (wt. %)                                 (kg/cm.sup.2)______________________________________Example 115   Polyimide-5             80      Bisimide-C                             20    2980Example 116       70              30    3500Example 117       60              40    3950Comparative   Polyimide-5             40      Bisimide-C                             60    moldingExample 31                              impossibleComparative       98              2     1650Example 32______________________________________ 
    
     EXAMPLES 118˜120 
     Uniformly blended pellets were prepared by carrying out the same procedures as conducted in Examples 112˜114 except that Polyimide-4 is replaced by Polyimide-6 and melt-kneading was carried out at 320° C. The uniform pellets obtained were injection molded with a common injection molding machine at a cylinder temperature of 320° C. and mold temperature of 160° C. to prepare dumbbell specimens. 
     Tensile strength of the specimens was measured at 23° C. at a pulling rate of 5 mm/min. Results are illustrated in Table 15. 
     COMPARATIVE EXAMPLE 33 
     Dumbbell specimens were prepared by carrying out the same procedures as conducted in Examples 118˜120 except that polyimide resin was used alone without carbon fiber. Results are illustrated in Table 15. 
     
                       TABLE 15______________________________________CompositionPolyimide resin   Carbon fiber  Tensile         Amount  Collecting                           Amount                                 strengthKind of resin (wt. %) agent     (wt. %)                                 (kg/cm.sup.2)______________________________________Example 118   Polyimide-6             80      Bisimide-C                             20    2630Example 119       70              30    3000Example 120       60              40    3320Comparative   Polyimide-6             100     Bisimide-C                             0     1180Example 33______________________________________ 
    
     The polyimide resin composition of the present invention is a composition comprising an aromatic bisimide compound in polyimide resin and has improved processability. 
     The resin composition of the invention composed of an improved carbon fiber and polyimide resin can be processed into a desired shape by injection molding, extrusion forming, transfer molding, compression molding and other known processing methods. 
     The resin composition of the invention thus processed has excellent mechanical strength, particularly mechanical strength at high temperatures, and hence can be used for mechanical members and automotive parts which require high mechanical strengths at high temperatures, for example, gear, cam, bushing, pulley and sleeve, and also for members of internal combustion engines, for example, gas exhausting parts for a silencer such as an impeller and manifold of an integrated centrifugal compressor, valve guide, valve stem, piston skirt, oil pan, front cover and locker cover. 
     The carbon fiber reinforced polyimide resin composition of the invention is usually used in the form of pellets which can be handled with ease. Molded articles are prepared by injection molding. The pellets are prepared by kneading and extruding the polyimide resin and the carbon fiber strand with a known single or twin screw extruder and successively by cutting the resulting strand of the composition. 
     Injection molding of the pellets thus obtained is carried out with a common injection molding machine at a cylinder temperature of 360° to 420° C. and a mold temperature of 160° to 210° C., preferably 180° to 200° C. Complex shaped members of internal combustion engines such as an impeller of an integrated centrifugal compressor can also be prepared with ease. 
     The carbon fiber reinforced polyimide resin composition of the invention has excellent mechanical strength and can be widely used as a material for members of electric and electronic devices, automotive trim, space and aeronautical equipment and general instruments in industry. Thus, the polyimide resin composition is valuable in industry. 
     Further, the bisimide compound of the invention is very useful for the preparation of the polyimide resin composition having these excellent properties.