Thermosetting resin composition

Abstract: 1. A thermosetting resin composition which comprises a bismaleimide derivative having the formula (I): and a diamine derivative having the formula (II): wherein R³ is a divalent radical represented by or where X is selected from a bond, a divalent hydrocarbon radical having 2 carbon atoms, hexafluorinated isopropylidene radical, carbonyl radical, thio radical and sulfinyl radical. A thermosetting resin prepolymer may be obtained by conducting heat-treatment of the thermosetting resin composition at a temperature of 70 to 220°C in the presence or absence of a solvent.

Description: The present application was divided out of application 87306106.3. The present invention relates to novel thermosetting resin compositions which are excellent in impact strength and flexibility. More particularly, it relates to thermosetting resin compositions and their prepolymers having aromatic bismaleimide derivatives and diamine derivatives as structural units. Conventional thermosetting resins having imide structure have been widely used in industry due to their excellent properties such as electrical insulation, high-temperature stability and dimensional stability of molded articles. The thermosetting resins, however, obtained by using aromatic bismaleimides as polymerization ingredients are insoluble and infusible, and have exhibited drawbacks of poor impact strength and flexibility, though these materials are excellent in the high-temperature stability. Therefore, as a method for improving the impact strength and flexibility of the aromatic bismaleimide resins, aromatic bismaleimides were tried to use in combination with aromatic diamines. For example, polyamino-bismaleimide resin which is composed of N,N'-(4,4'-methylenediphenylene)bismaleimide and 4,4'-diamino-diphenylmethane (trade mark KERIMID, a product from Rhône-Poulenc. Ind.) has superior impact strength and flexibility to the homopolymers of aromatic bismaleimide. Therefore the resin is used for impregnation varnish, laminated boards, molded articles, etc. The above thermosetting resins, however, have been still unsatisfactory in the impact strength and flexibility view point. FR-A-1 555 564 discloses compositions of bis-(4-maleimidephenyl)methane and a diamine B(NH 2 ) 2 where B is a radical having at least 30 carbon atoms. There is no teaching of selecting the diamine to enhance impact strength and flexibility. It is thus desirable to provide a tough thermosetting resin which maintains traditional high-temperature stability and is also excellent in the impact strength and flexibility. Preferred embodiments of the invention may make this possible. The present invention provides a thermosetting resin composition which comprises a bismaleimide derivative having the formula (I): and a diamine derivative having the formula (II): wherein R 3 is a divalent radical represented by or where X is selected from a bond, (CH 3 ) 2 C , hexafluorinated isopropylidene radical, carbonyl radical, thio radical and sulfinyl radical. Diamine derivatives II that may be used include for example: 1,3-bis(3-aminophenoxy)benzene, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfoxide. These diamine derivatives are used alone or in combination of two and more. These diamine derivatives can be technically and advantageously prepared in a high purity and good yield by conducting a condensation reaction of respectively corresponding bisphenols with m-dinitrobenzene in aprotic polar solvents in the presence of bases and successively reducing the resultant intermediates (Japanese Patent Application Nos. 32568/1985, 59560/1985). The illustrative bismaleimide derivative of the above formula (I) is bis(4-maleimidephenyl)methane. The compound can be easily prepared and applied, according to the usually known methods, by carrying out the condensation and dehydration reaction of bis(4-aminophenyl)methane and maleic anhydride. As the methods for preparing the thermosetting resin composition from the bismaleimide derivative of the above formula (I) and the diamine derivatives of the above formula (II), various methods may be employed as illustrated in the following. (1) Bismaleimides and diamines are ground and mixed in the solid state, or the resultant mixture is heat-treated to form the prepolymer and then ground to give pellets or powder. As the heat-treatment conditions, it is suitable to proceed with partial curing to the stage of prepolymer. The heat-treatment is carried out generally at a temperature of 70 to 220°C for 5 to 240 minutes, preferably at a temperature of 80 to 200°C for 10 to 180 minutes. (2) Bismaleimides and diamines are dissolved in organic solvents and then poured into bad solvents, the precipitated crystals are filtered and dried to give pellets or powder. Otherwise, after dissolving into the organic solvents, bismaleimides and diamines are partially cured to the stage of prepolymer and then poured into the bad solvents. The precipitated crystals are filtered and dried to give the pellets or the powder. The conditions of these procedures are the same as in (1). The organic solvents which may be used in this invention are restricted to those which are substantially unreactive to both components. The solvents are further desired to have good solubility to these reaction components. Suitable solvents which may be normally used for the reaction include, for example, halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethane and trichloroethylene; ketones such as acetone, methyl ethyl ketone, cyclohexanone and diisopropyl ketone; ethers such as tetrahydrofuran, dioxane and 2-methoxy ethanol; aromatic compounds such as benzene, toluene and chlorobenzene; and aprotic polar solvents such as acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone. In addition, the composition comprising bismaleimides and diamines of this invention may be added with one or more of ordinary additives in the range wherein the object of this invention is unharmed. These additives include antioxidants, heat-stabilizers, ultra violet absorbers, flame retardants, antistatic agents, lubricants colorants and so on. Furthermore other materials which may be incorporated in a suitable amount according to the object of addition include other thermosetting resins such as phenol resin, epoxy resin etc.; thermoplastic resins such as polyethylene, polypropylene, polyamide, polycarbonate, polysulfone, polyethersulfone, polyetheretherketone, modified polyphenyleneoxide, polyphenylenesulfide etc.; reinforcing materials such as glass fibre, carbon fibre, aromatic polyamide fiber, alumina fibre, potassium titanate fibre etc.; and fillers such as clay, mica, silica, graphite, glass beads, alumina, calcium carbonate etc. The bismaleimide derivative of the formula (I) and the diamine derivatives of the formula (II) are preferably used in a proportion ranging from 10:1 to 1:1.2 molar ratio. When the proportion of the diamine derivatives employed is small, cured products cannot obtain a good impact strength and flexibility. On the other hand too much proportion of the diamine derivatives results in an adverse effect on the thermal stability of cured product. The thermosetting resin compositions of this invention may be molded for practical use by known molding methods such as compression molding, transfer molding, extrusion molding, injection molding etc. and also applied to the raw materials for coating and adhesive, etc. The thermosetting resins of this invention thus obtained are excellent in the thermal stability, impact strength and flexibility. Therefore they are expected for a wide use in such areas as electric and electronic parts,various structural members, self-lubricating components etc. Accordingly their application provides a remarkable effect on the industry. The present invention will be described with reference to the following examples. Examples 1 - 4 In a stainless steel vessel fitted with a stirrer, reflux condenser and nitrogen inlet tube, bis(4-maleamidephenyl)methane and 4,4'-bis(3-aminophenoxy)biphenyl were charged in the feed molar ratios given respectively in Table 1 and reacted at 180°C for 20 minutes in a fused state. Thereafter, the resulting mixture was cooled to room temperature, and the reaction product thus-solidified in the form of a brown transparent glass was crushed, taken out of the vessel, ground in a mortar and screened through a 60-mesh sieve (250 µm opening), thereby obtaining a partially-cured polyaminobismaleimide-type thermosetting resin composition. Example 5 In a stainless steel vessel fitted with a stirrer, reflux condenser and nitrogen inlet tube, bis(4-maleimidephenyl)methane and 4,4'-bis(3-aminophenoxy)biphenyl were charged in the feed molar ratio given in Table 1. N-Methyl-2-pyrolidone was added to this mixture in such an amount that the resin concentration came to 55 wt.% so as to dissolve the both components. Then, reaction was carried out at 130°C for 50 minutes under heating. The resultant brown transparent varnish was charged dropwise into water under stirring and the precipitate thus-came out was filtered, washed with water and dried with hot air at 80°C for 15 hours. The precipitate was dried at 110°C for 20 minutes and then at 130°C for 20 minutes, ground in a mortar and screened through a 60-mesh sieve, thereby obtaining a partially-cured polyaminobismaleimide-type thermosetting resin composition. Examples 6 - 8 Using the bismaleimide and diamines given in Table 1 in the feeding molar ratio also given in Table 1, the following procedure was carried out to obtain the results shown in Table 1:- In a stainless steel vessel fitted with a stirrer, reflux condenser and nitrogen inlet tube, the bismaleimide (I) and the diamine (II) were charged in the feed molar ratios given respectively in Table 1 and reacted at 180°C for 20 minutes in a fused state. Thereafter, the reaction mixture was cooled to room temperature, and the reaction product thus-solidified in the state of a brown transparent glass was crushed, taken out of the vessel, ground in a mortar and screened through a 60-mesh sieve, thereby obtaining a partially-cured polyaminobismaleimide-type thermosetting resin composition. The composition was filled in a mold (10 x 80 x 4 mm) which had been heated to 180°C while being heated and molten and then compression-molded by keeping it at 200°C for 30 minutes under a pressure of 50 kg/cm 2 . Then, after being cooled to room temperature, the primary molded article was taken out of the mold and post-cured in a hot-air gear oven at 250°C for 4 hours to obtain specimens for testing Izod impact strength and flexural strength. The Izod impact strength (unnotched) was measured in accordance with ASTM D-256 while flexural strength was determined according to ASTM D-790. Concurrently, 5% weight decrease temperature of the molded specimens was determined. The results given in Table 1 were obtained. Comparative Examples 1 - 2 Using the bismaleimide and diamine given in Table 1 in the feed molar ratios also given in Table 1, the procedure of Examples 6-8 was repeated to obtain the results shown in Table 1. As is obvious from the results shown in Table 1, the thermosetting resin composition according to the present invention is excellent in flexural strength and modulus of flexural elasticity as well as Izod impact value. Therefore, the composition is a material having an outstanding impact resistance and flexibility. The composition is also excellent in high-temperature stability as indicated by 5% weight decrease temperature of not less than 390°C.

Claims: A thermosetting resin composition which comprises a bismaleimide derivative having the formula (I): and a diamine derivative having the formula (II): wherein R 3 is a divalent radical represented by or where X is selected from a bond, (CH 3 ) 2 C , hexafluorinated isopropylidene radical, carbonyl radical, thio radical and sulfinyl radical. The thermosetting resin composition of claim 1 wherein the bismaleimide derivative (I) and the diamine derivative (II) are used in a proportion ranging from 10:1 to 1:1.2 (molar ratio). A thermosetting resin prepolymer obtained by conducting heat-treatment of a thermosetting resin composition at a temperature of 70 to 220°C in the presence or absence of a solvent, said thermosetting resin composition being according to any preceding claim.

Inventors: KOGA NOBUHITO, OHTA MASAHIRO, YAMAGUCHI AKIHIRO, YAMAYA NORIMASA, KOGA, NOBUHITO, OHTA, MASAHIRO, YAMAGUCHI, AKIHIRO, YAMAYA, NORIMASA
Applicants: MITSUI TOATSU CHEMICALS, MITSUI TOATSU CHEMICALS, INC.
Application year: 1987
Main classification: C08G73
IPC codes: C08G73