Heat-resistant resin composition

Abstract: Disclosed is a heat-resistant resin composition prepared by mixing (A) a resin composition and (B) a hardener of an epoxy resin, followed by heating the mixture for curing, said composition (A) being prepared by heating a mixture of (a) a polymaleimide resin represented by the following general formula: (wherein R₁ represents an organic group having a valency of n, X a and X b represent monovalent atoms or groups which are the same or different and selected from a hydrogen atom, a halogen atom, and an organic group, and n represents 1 to 4), (b) an epoxy resin having at least two epoxy groups in a molecule thereof, and (c) a compound containing at least one hydroxyl group, at least one carboxyl group, or both at least one hydroxyl group and at least one carboxyl group in a molecule thereof.

Description: The present invention relates to a liquid, thermosetting, solventless heat-resistant resin composition excellent in storage stability, a heat-resisting property, and workability. In recent years, strong demand has increasingly arisen for increasing the heat resistance of resin components such as adhesives in electronic equipment and mechanical parts. For these application purposes, a lot of attempts have been made for resins whose adhesive properties are improved by modifying a maleimide resin excellent in heat-resisting property with an epoxy resin. Among them all, in order to improve the storage stability, when a bismaleimide resin is modified with an epoxy resin only, precipitation tends to undesirably occur. In order to improve the resin in this respect, Published Unexamined Japanese Patent Application No. 1-229029 discloses a resin composition obtained such that a polymaleimide resin and an epoxy resin are modified with a compound, as a third component, containing one hydroxyl group and at least one epoxy group. The resin composition obtained by modifying the polymaleimide and epoxy resins with the compound containing one hydroxyl group and at least one epoxy group as disclosed in Published Unexamined Japanese Patent Application No. 1-229029 is excellent in heat-resisting property, but the heat-resisting property is degraded by a degree corresponding to the addition of this modified product. The present invention has been made to solve the above conventional problem, and has as its object to provide a liquid, thermosetting, solventless heat-resistant resin composition excellent in storage stability, a heat-resisting property,'and workability. The present invention has been achieved by extensive studies of the present inventors to achieve the above object of the present invention. There is provided a liquid, solventless heat-resistant resin composition which contains a minimum amount of the above-mentioned modified product, is less toxic, and is soluble in a general purpose solvent. That is, the present invention provides a heat curable two-part heat-resistant resin composition comprising (A) a resin composition as a first part and (B) a hardener of an epoxy resin as a second part, said composition (A) being prepared by heating a mixture of (a) a polymaleimide resin represented by the following general formula: (wherein R 1 represents an organic group having a valency of n, X a and X b represent monovalent atoms or groups which are the same or different and selected from a hydrogen atom, a halogen atom, and an organic group, and n represents 1 to 4), (b) an epoxy resin having at least two epoxy groups in a molecule thereof, and (c) a compound containing at least one hydroxyl group, at least one carboxyl group, or both at least one hydroxyl group and at least one carboxyl group in a molecule thereof, wherein an amount of the compound as the component (c) of composition (A) falls within a range of 0.1 to 5 parts by weight based on 100 parts by weight of the polymaleimide resin as the component (a) of composition (A) and said composition (A) is prepared by heating at 110°C to 160°C the mixture of components (a), (b) and (c) of composition (A). Examples of the polymaleimide as one component (a) of the composition (A) are N,N'-4,4'-diphenyletherbismaleimide, N,N'-4,4'-diphenylsulfonebismaleimide, N,N'-4,4'-diphenylmethanebismaleimide, N,N'-phenylenebismaleimide, N,N'-3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethanebis maleimide, a trinuclide thereof, and a tetranuclide thereof. These materials can be used singly or in a mixture of at least two thereof. Examples of the epoxy resin as one component (b) of the composition (A) are a bisphenol A epoxy resin represented by the following formula: (n = 0 : 87.2%, n = 1 : 11.1%, n = 2 : 1.5%) and derived from bisphenol A and epichlorohydrin a bisphenol F epoxy resin represented by the following formula: (n = 0 : 87.2%, n = 1 : 11.1%, n = 2 : 1.5%) and derived from bisphenol F and epichlorohydrin, a cresol novolak type epoxy resin, a phenol novolak type epoxy resin, an epoxy resin consisting of glycidylated amine, an aliphatic or alicyclic epoxy resin, an epoxy resin having a heterocyclic ring, and an epoxy resin containing a siloxane bond. These epoxy resins can be used singly or in a combination of at least two thereof. Compounds (c)-1, (c)-2, and (c)-3 below can be used as one component (c) of the composition (A). These compounds can be singly used or in a combination of at least two thereof. (c)-1 Compound Containing at least one Hydroxyl Group Examples of this compound are phenol, cresols, xylenols, hydroxyl methyl benzoate, nonyl phenol, methoxy phenol, p-octyl phenol, t-butyl phenol, phenyl phenol, polyoxyethylene alkylphenyl ether, tetrahydronaphthol, menthol, phenylethyl alcohol, benzyl alcohol, cyclohexanol, hydroxyacetophenone, hydroxybenzaldehyde, hydroxybenzyl alcohol, hydroxybiphenyl, hydroxymethoxybenzaldehyde, hydroxymethoxyacetophenone, hydroxymethoxydiphenyl, hydroxymethoxypropenyl benzene, hydroxymethyl pyrone, hydroxypropiophenone, dihydroxybenzaldehyde, resorcinol, hexyl resorcinol, methyl resorcinol, pyrogallol, methyl pyrogallol, dihydroxyacetophenone, dihydroxybenzophenone, dihydroxybiphenyl, dihydroxynaphthalene, cyclohexanediol, dihydroxybenzyl alcohol, hydroxyphenethyl alcohol, butanediol, hexanetriol, catechol, hydroquinone, dihydroxytoluene, hexynediol, inositol, pentanediol, hexanediol, phloroglucinol, purpurin, quinizarin, anthrarufin, bishydroxyphenylpropane, bishydroxyphenylsulfone, propanediol, butyl pyrocatechol, chlorohydroquinone, dicyanohydroquinone, dihydroxyacetone, tetrahydroxyanthracene, dihydroxydiphenylmethane, dodecanediol, methylpentanediol, 1,3-bis(3-hydroxylpropyl)tetramethyldisiloxane, vanillyl alcohol, various phenol resins, and various alcohols. (c)-2 Compound Containing at least one Carboxyl Group Examples of this compound are benzoic acid, phenylacetic acid, phenylpropanoic acid, phenylbutyric acid, bromobenzoic acid, toluic acid, methoxybenzoic acid, cyclohexane carboxylic acid, dicarboxydiphenyl, malonic acid, mellitic acid, pyromellitic acid, trimellitic acid, phthalic acid, and isophthalic acid. (c)-3 Compound Containing at least one Hydroxyl Group and at least one Carboxyl Group Examples of this compound are benzilic acid, caffeic acid, camphoric acid, cresotinic acid, gallic acid, dihydroxybenzoic acid, hydroxymethoxybenzoic acid, mandelic acid, hydroxymethylbenzoic acid, phenolphthalin, protocatechuic acid, quinic acid, hydroxynaphthoic acid, hydroxyphenylacetic acid, hydroxyphenylisovaleric acid, hydroxyphenylpropionic acid, hydroxytoluic acid, and tropic acid. The components (A)(a), (A)(b), and (A)(c) are simultaneously mixed under heating at 110°C to 200°C for 0.3 to 24 hours. Gelling and precipitation cannot be prevented by the presence of the component (A)(c) only for the polymaleimide resin as the component (A)(a). However, when the component (A)(b) is added and mixed under heating with the above mixture, a solventless composition (A) which is a liquid at room temperature to a temperature of about 80°C can be prepared. The amount of the component (A)(c) falls within the range of 0.1 to 5 parts by weight based on 100 parts by weight of the polymaleimide resin as the component (A)(a). When the heat-resisting property of the objective composition is taken into consideration, the amount of the epoxy resin as the component (A)(b) falls within the range of preferably 20 to 500 parts by weight based on 100 parts by weight of the polymaleimide resin as the component (A)(a). However, for the purpose of retaining good physical properties during heating and preventing precipitation, the amount of the epoxy resin as the component (A)(b) falls within the range of more preferably 50 to 300 parts by weight. The components (A)(a), (A)(b), and (A)(c) are heated at a temperature of 110°C to 160°C. By employing the above conditions, a more preferable composition (A) can be obtained. The following general epoxy resin hardeners can be used as the hardener as the component (B). (B)-1 Polyamine Examples of the polyamine are general, liquid or solid aromatic and alicyclic polyamines (e.g., diaminodiphenylmethane, diaminodiphenylsulfone, metaphenylenediamine, diaminodiphenylether, and xylylenediamine). (B)-2 Acid Anhydride Examples of the acid anhydride are methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, and methylcyclohexene dicarboxylic anhydride. (B)-3 Polyhydric Phenol Examples of the polyhydric phenol are bishydroxyphenylpropane, bishydroxyphenylmethane, and a novolak phenol resin. (B)-4 Imidazole Examples of the imidazole are 2-methylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole. In addition to the above hardeners, epoxy resin hardeners such as amine, dicyandiamide, polymercaptan, and onium salt can be used, as needed. These hardeners can be used singly or in a combination of at least two thereof. The amount of the component (B) falls within the range of preferably 0.2 to 60 parts by weight based on 100 parts by weight of the composition (A). The composition (A) and the component (B) are mixed, and the resultant mixture is heated for curing at a temperature of preferably 80°C to 250°C, and more preferably 170°C to 230°C to obtain a heat-resistant resin composition. The heating time can be properly selected in accordance with the target performance. In order to reduce the shrinkage and the thermal expansion during curing and improve various properties such as abrasion resistance, mechanical strength, thermal conductivity, and electrical conductivity, an inorganic filler, and a metal powder, may be added. Within the range which does not impair the object of the present invention, in order to improve toughness and flexibility, at least one of silicone resin, various solid or liquid rubber materials can be added. In addition, in order to reduce the viscosity of the objective composition, in the composition (A) of the present invention, at least one of the following compounds may be freely added within the range which does not impair the heat-resisting property which is the object of the present invention. Examples of such a compound are allyl alcohol, furfuryl alcohol, divinyl benzene, vinyl toluene, styrene, N-vinyl pyrrolidone, triallyl trimellitate, triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, various acrylates (e.g., trimethylolpropane triacryalte), various methacrylates (e.g., glycidyl methacrylate), and hydroxycyclopentadiene. When a polymaleimide (particularly, general purpose bismaleimide) and an epoxy resin are mixed under heating at a high temperature (e.g., 150°C), the mixture can be set in a homogeneous liquid state. However, when the mixture is cooled to room temperature, a large amount of precipitate tends to settle. The present invention has been made to improve this drawback and overall compatibility. That is, when a compound containing at least one hydroxyl group, at least one carboxyl group, or both at least one hydroxyl group and at least one carboxyl group is added in a small amount, precipitation of the maleimide is suppressed. It is assumed that a charge transfer complex formed between the compound and maleimide, used as an initiating radical species, causes maleimide radical polymerization. The resultant reaction product is assumed to be present together with the nonreacted epoxy resin with good compatibility. A prepolymer of the resultant composition (A) is cured by the epoxy resin hardener as the component (B), thereby obtaining a heat-resistant resin composition having good workability. Examples 1-8 and Comparative Examples 1 - 4 In Examples 1 - 8 and Comparative Examples 1 to 4, components (A), i.e., compositions (A) and components (B) and their mixing amounts shown in Tables 1 and 2 were used. Components (A) were obtained such that polymaleimide resins as components (A)(a), epoxy resins as components (A)(b), and compounds as components (A)(c) each containing at least one hydroxyl group, at least one carboxyl group, or both at least one hydroxyl group and at least one carboxyl group in each molecule thereof, all of which were shown in Tables 1 and 2, were charged in 1ℓ autoclaves and were reacted at 145°C for 2 hours. In Comparative Example 1, a component (A) was obtained except that a component (A)(c) was excluded. In Comparative Examples 2 to 4, components (A) were obtained such that components (A)(a) and (A)(c) were excluded. In Comparative Examples 2 to 4, therefore, only components (A)(b) were used as the components (A). Although homogeneous liquid products were obtained as the components (A) in Examples 1-8 , the component (A) excluding the component (A)(c) in Comparative Example 1 resulted in precipitation of the component (A)(a), and a homogeneous liquid reaction product could not be obtained. Each mixture consisting of the components (A) and (B) was heated for curing at 80°C for 2 hours, then at 120°C for an hour, and finally at 200°C for 35 hours. The glass transition points Tg [measured by the TMA (thermomechanical analysis) method] and the flexural strengths (measurement temperature: 150°C or 200°C) of the resultant cured compositions in Examples 1 to 7, and Comparative Examples 2 to 4 were measured, and the results are shown in Tables 1 and 2. In Tables 1 and 2, when Examples are compared with the Comparative Examples using only the epoxy resins as the components (A), the heat-resisting properties of the resin compositions in Examples are apparently improved due to the addition of the polymaleimide resins. Component (A) (parts by weight) Comparative Example 1 2 3 4 N,N'-4,4'-diphenylmethanebismaleimide 143 - - - Epikote 828 (1) 300 100 - - Epiclon 830 (2) 300 - 100 - ERL4221 (3) - - - 100 3-(p-hydroxyphenyl) propionic acid - - - - 3,4-dihydroxytoluene - - - - 1,4-butanediol - - - - isophthalic acid - - - - gallic acid - - - - hydroquinone - - - - o-hydroxybenzylalcohol - - - - 2-hydroxy-m-toluic acid - - - - CKM-5254 (4) - - - - 1,4-cyclohexanediol - - - - phenol - - - - cyclohexanol - - - - benzoic acid - - - - reaction condition - - - - Precipitation after 2 weeks x...occurring o...not occurring x - - - Component (B) (parts by weight) Comparative Example 1 2 3 4 diaminodiphenylmethane (5) - 25 25 - HN-2200 (6) - - - 68 K54 (7) - - - 2 Tg (TMA method)(°C) (8) - 168 138 160 flexural strength (9) (N/cm 2 )(200°C) (9) - - - 650 flexural strength (N/cm 2 ) (150°C) (9) - 3910 390 - Notes: (1) to (9); Same as Table 1 A heat-resistant resin composition according to the present invention is a heat-resistant resin composition obtained by homogeneously modifying with good compatibility a polymaleimide resin and an epoxy resin with the use of a small amount of a third component. This modified composition is also excellent in storage stability. Therefore, the heat-resistant resin composition according to the present invention can be used with good workability in a variety of applications such as adhesives and castings which are excellent in heat-resisting property.

Claims: A heat curable two-part heat-resistant resin composition comprising (A) a resin composition as a first part and (B) a hardener of an epoxy resin as a second part, said composition (A) being prepared by heating a mixture of (a) a polymaleimide resin represented by the following general formula: (wherein R 1 represents an organic group having a valency of n, X a and X b represent monovalent atoms or groups which are the same or different and selected from a hydrogen atom, a halogen atom, and an organic group, and n represents 1 to 4), (b) an epoxy resin having at least two epoxy groups in a 15 molecule thereof, and (c) a compound containing at least one hydroxyl group, at least one carboxyl group, or both at least one hydroxyl group and at least one carboxyl group in a molecule thereof, wherein an amount of the compound as the component (c) of composition (A) falls within a range of 0.1 to 5 parts by weight based on 100 parts by weight of the polymaleimide resin as the component (a) of composition (A) and said composition (A) is prepared by heating at 110°C to 160°C the mixture of components (a), (b) and (c) of composition (A). A composition according to claim 1, characterized in that the composition (A) further contains at least one member selected from the group consisting of allyl alcohol, furfuryl alcohol, divinyl benzene, vinyl toluene, styrene, N-vinyl pyrrolidone, triallyl trimellitate, triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, acrylates, methacrylates, and hydroxycyclopentadiene. A composition according to claim 1, further containing at least one member selected from the group consisting of an inorganic filler and a metal powder. A composition according to claim 1, further containing at least one member selected from the group consisting of a silicone resin, solid rubber, and liquid rubber. A composition according to claim 1, characterized in that the polymaleimide resin as the component (a) of composition (A) is at least one member selected from the group consisting of N,N'-4,4'-diphenyletherbismaleimide, N,N'-4,4'-diphenylsulfonebismaleimide, N,N'-4,4'-diphenylmethanebismaleimide, N,N'-phenylenebismaleimide, N,N'-3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethanebismaleimide, a trinuclide thereof, and a tetranuclide thereof. A composition according to claim 1, characterized in that the epoxy resin as the component (b) of composition (A) is at least one member selected from the group consisting of a bisphenol A epoxy resin, a bis-phenol F epoxy resin, a cresol novolak type epoxy resin, a phenol novolak type epoxy resin, an epoxy resin consisting of glycidylated amine, an aliphatic and alicyclic epoxy resins, an epoxy resin having a heterocyclic ring, and an epoxy resin containing a siloxane bond. A composition according to claim 1, characterized in that the compound containing at least one hydroxyl group as the component (c) of composition (A) is at least one member selected from the group consisting of phenol, cresols, xylenols, hydroxyl methyl benzoate, nonyl phenol, methoxy phenol, p-octyl phenol, t-butyl phenol, phenyl phenol, polyoxyethylene alkylphenyl ether, tetrahydronaphthol, menthol, phenylethyl alcohol, benzyl alcohol, cyclohexanol, hydroxyacetophenone, hydroxybenzaldehyde, hydroxybenzyl alcohol, hydroxybiphenyl, hydroxymethoxybenzaldehyde, hydroxymethoxyacetophenone, hydroxymethoxydiphenyl, hydroxymethoxyproenpyl benzene, hydroxymethyl pyrone, hydroxypropiophenone, dihydroxybenzaldehyde, resorcinol, hexyl resorcinol, methyl resorcinol, pyrogallol, methyl pyrogallol, dihydroxyacetophenone, dihydroxybenzophenone, dihydroxybiphenyl, dihydroxynaphthalene, cyclohexanediol, dihydroxybenzyl alcohol, hydroxyphenethyl alcohol, butanediol, hexanetriol, catechol, hydroquinone, dihydroxytoluene, hexynediol, inositol, pentanediol, hexanediol, phloroglucinol, purpurin, quinizarin, anthrarufin, bishydroxyphenylpropane, bishydroxyphenylsulfone, propanediol, butyl pyrocatechol, chlorohydroquinone, dicyanohydroquinone, dihydroxyacetone, tetrahydroxyanthracene, dihydroxydiphenylmethane, dodecanediol, methylpentanediol, 1,3-bis(3-hydroxylpropyl)tetramethyldisiloxane, vanillyl alcohol, phenol resins, and alcohols. A composition according to claim 1, characterized in that the compound containing at least one carboxyl group as the component (c) of composition (A) is at least one member selected from the group consisting of benzoic acid, phenylacetic acid, phenylpropanoic acid, phenylbutyric acid, bromobenzoic acid, toluic acid, methoxybenzoic acid, cyclohexane carboxylic acid, dicarboxydiphenyl, malonic acid, mellitic acid, pyromellitic acid, trimellitic acid, phthalic acid, and isophthalic acid. A composition according to claim 1, characterized in that the compound containing at least one hydroxyl group and at least one carboxyl group as the component (c) of compo sition (A) is at least one member selected from the group consisting of benzilic acid, caffeic acid, camphoric acid, cresotinic acid, gallic acid, dihydroxybenzoic acid, hydroxymethoxybenzoic acid, mandelic acid, hydroxymethylbenzoic acid, phenolphthalin, protocatechuic acid, quinic acid, hydroxynaphthoic acid, hydroxyphenylacetic acid, hydroxyphenylisovaleric acid, hydroxyphenylpropionic acid, hydroxytoluic acid, and tropic acid. A composition according to claim 1, characterized in that the epoxy resin hardener as the component (B) is at least one member selected from the group consisting of a polyamine, an acid anhydride, a polyhydric phenol, an imidazole, an amine, dicyandiamide, polymercaptan, and an onium salt. A composition according to claim 9, characterized in that the polyamine is at least one member selected from the group consisting of diaminodiphenylmethane, diaminodiphenylsulfone, metaphenylenediamine, diaminodiphenylether, and xylylenediamine. A composition according to claim 9, characterized in that the acid anhydride is at least one member selected from the group consisting of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, and methylcyclohexene dicarboxylic anhydride. A composition according to claim 9, characterized in that the polyhydric phenol is at least one member selected from the group consisting of bishydroxyphenylpropane, bishydroxyphenylmethane, and a novolak phenol resin. A composition according to claim 9, characterized in that the imidazole is at least one member selected from the group consisting of 2-methylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole. A composition according to claim 1, characterized in that an amount of the epoxy resin as the component (b) of composition (A) falls within a range of 20 to 500 parts by weight based on 100 parts by weight of the polymaleimide resin as the component (a) of composition (A). A composition according to claim 1, characterized in that an amount of the epoxy resin as the component (b) of composition (A) falls within a range of 50 to 300 parts by weight based on 100 parts by weight of the polymaleimide resin as the component (a) of composition (A). A composition according to claim 1, characterized in that an amount of the epoxy resin hardener as the component (B) falls within a range of 0.2 to 60 parts by weight based on 100 parts by weight of the composition (A). A composition according to claim 1, characterized in that the mixture of the composition (A) and the component (B) is heated at 80°C to 250°C. A composition according to claim 1, characterized in that the mixture of the composition (A) and the component (B) is heated at 170°C to 230°C.

Inventors: HAMACHI KENJI, NOJIRI HISAO, SATO SHINICHI, HAMACHI, KENJI, NOJIRI, HISAO, SATO, SHINICHI
Applicants: KONISHI CO LTD, KONISHI CO., LTD.
Application year: 1992
Main classification: C08L79
IPC codes: C08L79, C08L63, C08G59, C08L35, C08L33