THERMOSETTING RESIN COMPOSITION

Abstract: Thermosetting resin compositions are provided which comprise aromatic bismaleimide derivatives, for example, 2,2 bis[4(3-maleimidephenoxy)phenyl]propane and diamine derivatives, for example, 4,4′-bis(3-­ aminophenoxy)biphenyl. Prepolymers are also prepared by conducting heat-treatment of said compositions. The compositions of this invention are used for thermo-­ forming such as compression molding etc. as well as raw materials of adhesives and coatings. The composi­ tions provide molded articles which are excellent, for example, in impact strength, flexibility and high-­ temperature stability.

Description: 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 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. 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. EP-A-0 107897 discloses thermosetting resins derived from (a) a bis-maleimide compound having para -substituted benzene rings linking the maleimide nitrogen to a central linker, e.g. N,N'-[4,4'-diphenoxy-1,4-benzene]- bis -maleimide; and (b) a diamine, e.g. 4,4'-diaminodiphenylmethane. We have found that the use of similar components but in which the bis-maleimide has meta -substitution can give resins with particularly good mechanical properties (Izod impact strength and flexural strength). The present invention provides a thermosetting resin composition which comprises (i) a bismaleimide derivative having the formula (I): wherein R¹ is a divalent radical represented by or where X is a bond, a divalent hydrocarbon radical having 1 to 10 carbon atoms, hexafluorinated isopropylidene radical, carbonyl radical, thio radical, sulfinyl radical, sulfonyl radical or oxide; and (ii) a diamine derivative having the formula (II): wherein Y is methylene or -O-R²-O-, where R² is a divalent radical represented by or wherein X is as defined above, and wherein nitrogen atom is para-located to methylene when Y is methylene, or meta-located to ether linkage when Y is -O-R²-O-. The following compounds are employed as raw materials for preparing the above thermosetting resin composition: 1,3-bis(3-maleimidephenoxy)benzene, bis[4-(3-maleimidephenoxy)phenyl]methane, 1,1-bis[4-(3-maleimidephenoxy)phenyl]ethane, 1,2-bis[4-(3maleimidephenoxy)phenyl]ethane, 2,2-bis[4-(3-maleimidephenoxy)phenyl]propane 2,2-bis[4-(3-maleimidephenoxy)phenyl]butane, 2,2-bis[4-(3-maleimidephenoxy)phenyl] 1,1,1,3,3,3-hexafluoropropane, 4,4′-bis(3-maleimidephenoxy)biphenyl, bis[4-(3-maleimidephenoxy)phenyl]ketone, bis[4-(3-maleimidephenoxy)phenyl]sulfide, bis[4-(3-maleimidephenoxy)phenyl]sulfoxide bis[4-(3-maleimidephenoxy)phenyl]sulfone, bis[4-(3-maleimidephenoxy)phenyl]ether, etc. These bismaleimide derivatives are used alone or in combination of two and more. The aforementioned bismaleimide derivatives may easily be prepared, usually according to conventional methods, by conducting a condensation and dehydration reaction of diamine derivatives having the following formula (III) with maleic anhydride. wherein R is a divalent radical represented by or where X is a radical selected from a bond, a divalent hydrocarbon radical having 1 to 10 carbon atoms, hexafluorinated isopropylidene radical, carbonyl radical, thio radical, sulfinyl radical, sulfonyl radical, or oxide. Diamine derivatives used include for example: 1,3-bis(3-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]butane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 4,4′-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfoxide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, etc. 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 diamine derivative wherein Y is methylene in the above formula (II) is 4,4'-diaminodiphenylmethane. It is industrially and favorably produced from aniline and formaldehyde, and can be utilized for the present invention. As the methods for preparing the thermosetting resin composition from the bismaleimide derivatives 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 derivatives 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. Synthesis Example 1 In a reaction flask equipped with a stirrer and a thermometer were charged 43.2 g (0.44 mole) of maleic anhydride and 130 g of acetone to prepare a solution. To the solution, a solution of 73.6 g (0.2 mole) of 4,4′-bis(3-aminophenoxy)biphenyl in 515 g of acetone was added dropwise at room temperature and the resulting solution was stirred at 23 - 27°C for 3 hours. After completion of the reaction, the crystals thus-formed were filtered, washed with acetone and dried to obtain bismaleamic acid in the form of yellowish crystals. Amount: 110.6 g (Yield: 98.0%), m.p.: 183 - 185°C IR (KBr, cm⁻¹): 1720 (carbonyl group) 1255 (ether linkage) The bismaleamic acid thus-obtained (112 g) was suspended in 300 g of acetone, added with 9.6 g of triethylamine and then stirred at room temperature for 30 minutes. After addition of 0.4 g of magnesium (II) oxide and 0.04 g of cobalt (II) acetate tetrahydrate, the resulting mixture was added with 52.0 g of acetic anhydride dropwise at 25°C over 30 minutes and further stirred for 3 hours. After completion of the reaction, the crystals thus-formed were filtered, washed and dried to obtain 4,4′-bis(3-maleimidephenoxy)biphenyl as light yellowish crystals. Amount: 84.5 g (Yield: 80.0%), m.p.: 207 - 209°C IR (KBr, cm⁻¹): 1720 and 1710 (imide linkage) 1250 (ether linkage) MS (FD method, m/e): 528 (M⁺) 5% Weight decrease temperature (in air): 459°C Synthesis Example 2 In a reaction flask equipped with a stirrer and a thermometer were charged 10.8 g (0.11 mole) of maleic anhydride and 32 g of acetone to prepare a solution. To the solution, a solution of 20.5 g (0.05 mole) of 2,2-bis[4-(3-aminophenoxy)phenyl]propane in 41 g of acetone was added dropwise at room temperature and the resulting solution was stirred at 23 - 27°C for 3 hours. After completion of the reaction, the crystals thus-formed were filtered, washed with acetone and dried to obtain bismaleamic acid in the form of yellowish crystals. Amount: 29.7 g (Yield: 98.0%), m.p.: 169 - 171°C IR (KBr, cm⁻¹): 3280 and 3220 (NH), 1700 (carboxyl group), 1580 and 1550 (amide linkage) MS (FD method): m/e 608(M+2), 510, 491, 411 The bismaleamic acid thus-obtained (38 g) was suspended in 92 g of acetone, added with 3 g of triethylamine and stirred at room temperature for 30 minutes. After addition of 0.13 g of magnesium(II) oxide and 0.013 g of cobalt(II) acetate tetrahydrate, the resulting mixture was added with 16 g of acetic anhydride dropwise at 25°C over 30 minutes and further stirred for 4 hours. After completion of the reaction, the crystals thus-formed were filtered, washed with methanol and dried at 40°C under reduced pressure to obtain 2,2-bis[4-(3-maleimidphenoxy)phenyl]propane as light-yellowish crystals. Amount: 30 g (Yield: 83.9%), m.p.: 161 - 164°C IR (KBr, cm⁻¹): 1775 and 1715 (imide linkage) 1255 (ether linkage) MS (FD method, m/e): 571 (M+l) 5% Weight decrease temperature (in air): 447°C Synthesis Example 3 In a reaction flask equipped with a stirrer and a thermometer were charged 37.8 g (0.385 mole) of maleic anhydride and 113 g of acetone to prepare a solution. To the solution, a solution of 70 g (0.175 mole) of bis[4-(3-aminophenoxy)phenyl]sulfide in 140 g of acetone was added dropwise at room temperature and further stirred at 25°C for 3 hours. The crystals thus-formed were filtered, washed and dried to obtain bismaleamic acid in the form of light-yellowish crystals. Amount: 104 g (Yield: 99.6%), m.p.: 202 - 204°C IR (KBr, cm⁻¹): 3280 (NH), 1690 (carbonyl group), 1240 (ether linkage) MS (FD method, m/e): 596, 400 In a reaction flask equipped with a stirrer and a thermometer, 104 g of the bismaleamic acid thus-obtained was suspended in 300 g of acetone. After addition of 8.4 g of triethylamine, the resulting mixture was stirred at 25°C for 30 minutes. After further addition of 0.35 g of magnesium (II) oxide and 0.035 g of cobalt(II) acetate tetrahydrate, the resultant mixture was added with 45.5 g of acetic anhydride dropwise and further stirred at 25°C for 2 hours. After completion of the reaction, the reaction liquid was fed dropwise into 1 liter of water with stirring. The crystals thus-formed were filtered, washed with water and dried to obtain bis[4-(3-maleimidephenoxy)phenyl]sulfide as light-yellowish crystals. Amount: 92 g (Yield: 93.8%) The crystals were recrystallized from acetone to obtain a purified product. m.p.: 64 - 67°C IR (KBr, cm⁻¹): 1770 sh and 1730 (imide linkage) 1260 (ether linkage) MS (FD method, m/e): 560 5% Weight decrease temperature (in air): 434°C Examples 1 - 4 In a stainless steel vessel fitted with a stirrer, reflux condenser and nitrogen inlet tube, 4,4′-bis(3-maleimidephenoxy)biphenyl 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 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/cm² (0.05 Nm-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. Example 5 In a stainless steel vessel fitted with a stirrer, reflux condenser and nitrogen inlet tube, 4,4'-bis(3-maleimidephenoxy)biphenyl and 4,4'-bis(3-aminophenoxy)biphenyl were charged in the feed molar ratio given in Table 1. N-Methyl-2-pyrrolidone was added to this mixture in such an amount that the resin concentration came to 55 wt.% so as to dissolve 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 (250µm opening), thereby obtaining a partially-cured polyaminobismaleimide-type thermosetting resin composition. Then, the procedure of Examples 1-4 was repeated to obtain the results given in Table 1. (The same sentence shall apply to the following Examples and Comparative Examples as final paragraph, although omitted in these Examples.) Examples 6-20 Using the bismaleimides and diamines given in Table 1 in the feed molar ratios also given in Table 1, the procedure of Examples 1-4 was repeated to obtain the results shown in Table 1. Examples 21-24 In a stainless steel vessel fitted with a stirrer, reflux condenser and nitrogen inlet tube, 4,4'-bis(3-maleimidephenoxy)biphenyl and bis(4-aminophenoxy)methane were charged in the feed molar ratios given respectively in Table 1 and reacted at 180°C for 20 minutes in a fused state. Then, the resulting mixture was cooled to roomtemperature, 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 (250µm opening), thereby obtaining a partially-cured polyaminobismaleimide-type thermosetting resin composition. Example 25 In a stainless steel vessel fitted with a stirrer, reflux condenser and nitrogen inlet tube, 4,4'-bis(3-maleimidephenoxy)biphenyl and bis(4-aminophenoxy)methane 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 (250 µm opening), thereby obtaining a partially-cured polyaminobismaleimidetype thermosetting resin composition. Examples 26-28 Using the bismaleimides and diamine given in Table 1 in the feed molar ratio also given in Table 1, the procedure of Examples 1 - 4 was repeated to obtain the results shown in Table 1. 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 1 - 4 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 (i) a bismaleimide derivative having the formula (I): wherein R¹ is a divalent radical represented by or where X is a bond, a divalent hydrocarbon radical having 1 to 10 carbon atoms, hexafluorinated isopropylidene radical, carbonyl radical, thio radical, sulfinyl radical, sulfonyl radical or oxide; and (ii) a diamine derivative having the formula (II): wherein Y is methylene or -O-R²-O-, where R² is a divalent radical represented by or wherein X is as defined above, and wherein nitrogen atom is para-located to methylene when Y is methylene or metalocated to ether linkage when Y is -O-R²-O-. 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. The thermosetting resin composition of claim 1 or 2 which comprises a said diamine derivative having the formula: wherein R² is as defined in claim 1. The thermosetting resin composition of claim 1 or 2 which comprises bis(4-aminophenyl)methane. 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
Applicants: MITSUI TOATSU CHEMICALS, INC.
Application year: 1987
Main classification: C08G73
IPC codes: C08G73