EPOXY RESIN COMPOSITION

Abstract: Resin compsns. comprises of (a) difunctional epoxy cpds., (b) trifunction epoxy cpds., (c) phenols of the formula (A) and (d) 4,4-diaminodiphenylsulfone or 3,3-diaminodiphenylsulphone; (X1-X8 are Br, Cl or H, at least 4 among X1-X8, are Br or Cl; R1-R2 are H or CH3). Specifically the epoxy resin (a) includes bisphenol type epoxy resin or brominated epoxy resin. The epoxy resin (b) includes tri-glycidylamine type epoxy resin. The phenol includes tetrabromo-bisphenol-F or hexabromobisphenol-A. Fibres e.g. C fibres, glass fibres, aramide fibres or boron fibres may be applied.

Description: TECHNICAL FIELD The present invention relates to an epoxy resin composition for prepreg having excellent hot wet property and improved compression strength after impact. Composite materials obtained from said resin composition can be used in air planes, automobiles and general industrial applications. BACKGROUND ART As the matrix resin for composite material, there have hitherto been widely used epoxy resins for their adhesivity and high rigidity. As the high performance structural matrix resin, in particular, there has been widely used, since 1972, a composition comprising, as main components, N,N,N',N'-tetraglycidyldiaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone. PROBLEMS TO BE SOLVED BY THE INVENTION Composite materials obtained from this composition, however, are low in elongation although relatively high in high-temperature compression strength after moisture absorption; accordingly, they have had a draw back that their elongation at break is smaller than recently developed high-elongation reinforcing fibers, for example, a carbon fiber having an elongation at break of 1.5% or more, an aramid fiber and a glass fiber. Also, said composite materials are very low in compression strength after impact and have been completely insufficient for use as a primary structural material. In view of the above, the present inventors made investigation on an epoxy resin composition for prepreg giving a composite material having excellent hot wet property, high utilization as a reinforcing material and improved compression strength after impact and, as a result, have reached the present invention. MEANS FOR SOLVING THE PROBLEMS According to one aspect, the present invention provides a process for the preparation of an epoxy resin composition derived from the following essential components (A), (B), (C) and (D): (A) a bifunctional epoxy resin; (B) a trifunctional epoxy resin selected from the group consisting of N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-4-amino-m-cresol, N,N,O-triglycidyl-5-amino-o-cresol, and a mixture of two or more of them, (C) a phenol compound represented by the formula where X 1 to X 8 each represents Br, Cl or H and at least four of X 1 to X 8 each represents Br or Cl; and R 1 and R 2 each represents H or CH 3, (D) 4,4'-diaminodiphenyl sulfone or 3,3'-diaminodiphenyl sulfone, wherein the molar ratio of the epoxy groups of (A)/(B) is 1/0.1 to 1/0.7; the amount of (C) used is such that the ratio of the epoxy groups of (A) and (B) to the phenolic OH-groups of (C) is 1/0.1 to 1/0.5, and the amount of (D) used is such that the ratio of the moles obtained by subtracting the moles of the phenolic OH groups of (C) from the moles of the epoxy groups of (A) and (B) and the moles of the NH groups of (D) is 1/0.5 to 1/1.2, comprising the steps of: mixing 14 to 71% of (A) with all of (B) ; subjecting the resulting mixture and all of (C) to a preliminary reaction to allow 80% or more of the phenolic OH of (C) to undergo a preliminary reaction; cooling; and adding the balance of (A) and the component (D). The present invention further provides an epoxy resin composition in accordance with Claim 6. As the bifunctional epoxy resin (A) used in the present invention, there can be mentioned glycidyl ether compound derived from bisphenol A, glycidyl ether compound derived from bisphenol F, a brominated epoxy resin obtained by brominating either of them and glycidyl ether compound derived from bisphenol S. In order to obtain improved toughness, it is preferable to use, in particular, glycidyl ether compound derived from bisphenol A or glycidyl ether compound derived from bisphenol F as a main component. As the phenol compound (C) used in the present invention, there can be mentioned tetrabromobisphenol A, tetrabromobisphenol F, octabromobisphenol A and hexabromobisphenol A. As the curing agent which is the component (D), 4,4'-diaminodiphenyl sulfone is used preferably. The epoxy resin composition may further comprise a reinforcing fiber as an additional component (E). As examples of this component there can be mentioned a carbon fiber, a glass fiber, an aramid fiber, a boron fiber or a silicon carbide fiber. The amount of (C) used is such that the ratio of the epoxy groups of (A) and (B) to the phenolic OH-groups of (C) is 1/0.1 to 1/0.5. When the phenolic OH groups are larger than 1/0.1, no sufficient water resistance and toughness is obtained, and this is not proper. When they are smaller than 1/0.5, the resulting epoxy resin composition is lower in degree of crosslinking, so sufficient heat resistance and solvent resistance are not obtained, and this is not preferable. They are more preferably 1/0.3 to 1/0.6. A part of the epoxy resin (A), all of (B) and all of (C) are subjected to a preliminary reaction to allow 80% or more, more preferably 90% or more of the phenolic OH of (C) to undergo the preliminary reaction. When the reaction proportion is lower than the above, the impact resistance of the resulting resin composition is not improved sufficiently; therefore, it is preferable to effect the preliminary reaction to an extent as mentioned above. The molar ratio of the epoxy groups of the part of (A) and all of (B), both used in the preliminary reaction with (C) preferably is (A)/(B) = 1/0.2 to 1/1.4, more preferably 1/0.4 to 1/1.2. When the ratio is larger than 1/0.2, no sufficient heat resistance, water resistance and solvent resistance can be obtained; therefore, such a ratio is not preferable. When the ratio is smaller than 1/1.4, gelation occurs during the preliminary reaction; therefore, such a ratio is not preferable. Further, the ratio of the total epoxy moles and the (C) phenolic OH moles used in the preliminary reaction, i.e. (the total moles of the epoxy groups of (A) and (B) used in the preliminary reaction)/(the moles of the phenolic OH of (C) used in the preliminary, reaction) is preferably 1/0.2 to 1/1, more preferably 1/0.3 to 1/0.8. When the ratio is larger than 1/0.2, no sufficient water resistance and toughness can be obtained; therefore, such a ratio is not preferable. When the ratio is smaller than 1/1, the mixture under preliminary reaction becomes too viscous to be handled efficiently. Meanwhile, the amount of (D) used, relative to (A), (B) and (C) is such that the ratio of the moles obtained by subtracting the moles of the phenolic OH of (C) from the moles of the total epoxy groups and the moles of the NH groups of (D) is 1/0.5 to 1/1.2. When the ratio is larger than 1/0.5, curing is insufficient and solvent resistance and heat resistance of the cured resin are not sufficient. When the ratio is smaller than 1/1.2, water resistance and solvent resistance are reduced. The resin composition of the present invention may further use, as other components, an inorganic filler, for example, a silica powder, Aerosil and microballons; a flame retardant such as antimony trioxide; a flow controlling agent, for example, a phenol-terminated polyethersulfone, a polysulfone, a poly(vinyl butyrate) and a polyetherimide. Also, it is possible to use the reinforcing fiber in the form of milled fiber, chopped fiber, unidirectional fiber or fabric. EXAMPLES The present invention is explained specifically, below by way of Examples. Parts refer to parts by weight. Example 1 30 parts of bisphenol F diglycidyl ether [Epikote 107 (trade name) having an epoxy equivalent of 170, manufactured by Yuka Shell Epoxy K. K.], 18.7 parts of N,N,O-triglycidyl-p-aminophenol (epoxy equivalent: 106) and 41.6 parts of 2,2-bis(3,5-dibromo4-hydroxyphenyl)propane were mixed and heated at 130°C for 2 hours, and then reaction product was cooled to 60°C. Thereto were added the balance (70 parts) of Epikote 807, 37.9 arts of 4,4'-diaminodiphenyl sulfone and further 2.4 parts of Aerosil 380. The mixture was sufficiently stirred in a kneader (maintained at 60°C) to obtain a resin composition (I). This resin composition (I) was placed between glass plates so as to give a 2-mm plate. Curing was effected at 180°C for 2 hours to obtain a resin plate. Also, the resin composition (I) was coated on a release paper with a doctor knife under heating at 60°C to prepare a hot melt film of 78 g/m 2 . A unidirectional prepreg having a fiber areal weight of 145 g/m 2 and a resin content of 35 wt% was made from the hot melt film and unidirectionally arranged carbon fibers (Pyrofil ® M-1, manufactured by Mitsubishi Rayon K.K.) by a hot melt process. This prepreg was stacked to obtain [0°] 16 and [+45°/0°/-45°/90] 4S laminates; the laminates were cured in an autoclave of 0.49 MPa (5 Kgf/cm 2 ) at 180°C for 2 hours to obtain composite material panels. They were measured for properties as follows and the results were shown in Table 1. Hot water resistance of composite material was measured by immersing the composite laminate of [0°] 16 in water of 71°C for 14 days and then subjecting it to a 0° compression test at 82°C according to ASTM D-3410. Also, impact resistance was measured by fixing a plate having a panel dimension of 10 cm x 15 cm (4" x 6") on a stand having a hole of 7.5 cm x 12.5 cm (3" x 5"), dropping a 4.9-kg weight having a nose of 1.3 cm (1/2") R on the center of the plate to apply an impact of 67 J/cm (1,500 lb. in per inch) of plate thickness, then subjecting the panel to a compression test, according to NASA RP 1092. Handleability of resin was determined by examing the softness of the resin composition (I) at room temperature. Methyl ethyl ketone resistance (MEK resistance) was determined by immersing a cured resin in methyl ethyl ketone at room temperature for 7 days and then examining the change of its appearance, wherein ○ refers to no change and X refers to big change. Examples 2-9 Comparative Examples 1-5 Experiments were effected in the same manner as in Example 1 except that the mixing ratio of Epikote 807, N,N,O-triglycidyl-p-aminophenol, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane and 4,4'-diaminodiphenyl sulfone used in Example 1 was changed. The results were shown in Table 1. It is also appreciated that when there is effected a preliminary reaction, proper ranges exist in A/B epoxy molar ratio, A+B/C (the ratio of the total epoxy moles of A and B used in the preliminary reaction and the phenolic OH moles of C), A+B+A'/C (the ratio of the epoxy total moles used and not used in the preliminary reaction and the phenolic OH moles of C) and A+B+A'-C/D (the ratio of the moles obtained by subjecting the phenolic OH moles of C from the total epoxy moles and the NH functional group moles of amine D). Example 10 A test was effected in the same manner as in Example 1 except that the bifunctional epoxy resin used in the preliminary reaction in Example 1 , i.e. Epikote 807 was replaced by Epikote 828. The results were shown in Table 1. Comparative Example 6 100 parts of bisphenol F diglycidyl ether [Epikote 807 (trade name) having an epoxy equivalent of 170, manufactured by Yuka Shell Epoxy K.K.], 18.7 parts of N,N,O-triglycidyl-p-aminophenol (epoxy equivalent: 106) and 41.6 parts of 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane were mixed at 120°C. The mixture was cooled to 60°C, and 37.9 parts of 4,4'-diaminodiphenyl sulfone and 2.4 parts of a fine powder of silicon oxide (Aerosil 380 manufactured by Nippon Aerosil K.K.) were added. The mixture was sufficiently stirred by a kneader to obtain a resin composition (I). This resin composition (I) was placed between glass plates so as to give a 2-mm plate. Curing was effected at 180°C for 2 hours to obtain a resin plate. Also, the resin composition (I) was coated on a release paper with a doctor knife under heating at 60°C to prepare a hot melt film of 78 g/m 2 . A unidirectional prepreg having a fiber areal weight of 145 g/m 2 and a resin content of 35 wt% was made from the hot melt film and unidirectionally arranged carbon fibers (Pyrofil® M-1, manufactured by Mitsubishi Rayon K.K.) by a hot melt process. This prepreg was stacked to obtain [0°] 16 and [+45°/0°/-45°/90] 4S laminates; the laminates were cured in an autoclave of 0.49 MPa (5 Kgf/cm 2 ) at 180°C for 2 hours to obtain composite material panels. They were measured for properties in accordance with Example 1 above. Molar ratios, and results for this Comparative Example are as follows: A/B molar ratio A+B/C molar ratio A+B-C/D molar ratio Handle-ability MEK resistance 0° Compression strength after water absorption 82°C (Kg/mm 2 ) Compression strength after impact room temperature (Kg/mm 2 ) 1/0.3 1/0.2 1/1 O O 110 31

Claims: A process for the preparation of an epoxy resin composition derived from the following essential components (A), (B), (C) and (D): (A) a bifunctional epoxy resin; (B) a trifunctional epoxy resin selected from the group consisting of N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-4-amino-m-cresol, N,N,O-triglycidyl-5-amino-o-cresol, and a mixture of two or more of them, (C) a phenol compound represented by the formula where X 1 to X 8 each represents Br, Cl or H and at least four of X 1 to X 8 each represents Br or Cl; and R 1 and R 2 each represents H or CH 3, (D) 4,4'-diaminodiphenyl sulfone or 3,3'-diaminodiphenyl sulfone, wherein the molar ratio of the epoxy groups of (A)/(B) is 1/0.1 to 1/0.7; the amount of (C) used is such that the ratio of the epoxy groups of (A) and (B) to the phenolic OH-groups of (C) is 1/0.1 to 1/0.5, and the amount of (D) used is such that the ratio of the moles obtained by subtracting the moles of the phenolic OH groups of (C) from the moles of the epoxy groups of (A) and (B) and the moles of the NH groups of (D) is 1/0.5 to 1/1.2, comprising the steps of: mixing 14 to 71% of (A) with all of (B) ; subjecting the resulting mixture and all of (C) to a preliminary reaction to allow 80% or more of the phenolic OH of (C) to undergo a preliminary reaction; cooling; and adding the balance of (A) and the component (D) A process according to claim 1, characterized in that the bifunctional epoxy resin (A) is a glycidyl ether compound derived from bisphenol A or a glycidyl ether compound derived from bisphenol F. A process according to claim 1, characterized in that the component (C) is tetrabromobisphenol A. A process according to claim 1, characterized in that the molar ratio of the epoxy groups of (A)/(B) used in the preliminary reaction is 1/0.5 to 1/1.2 and the amount of (C) used is such that the molar ratio of the total moles of the epoxy groups of (A) and (B) and the moles of the phenolic OH of (C) is 1/0.3 to 1/0.8. A process according to any preceding claim, wherein the epoxy resin composition further comprises (E) a reinforcing fiber. An epoxy resin composition comprising the following components (I), (II) and (III) as essential components: (I) a preliminary reaction product obtainable by subjecting (A) a bifunctional epoxy resin, (B) a trifunctional epoxy resin selected from the group consisting of N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-4-amino-m-cresol, N,N,O-triglycidyl-5-amino-o-cresol, and a mixture of two or more of them, and (C) a phenol compound represented by the formula : wherein X 1 to X 8 each represents Br, Cl or H and at least four of X 1 to X 8 each represents Br or Cl; and R 1 and R 2 each represents H or CH 3, to a preliminary reaction in which 80% or more of the phenolic OH of (C) undergo reaction, the molar ratio of the epoxy groups of (A) to (B) being from 1/0.4 to 1/1.2, the ratio of the total epoxy moles of (A) and (B) to the (C) phenolic OH moles being from 1/0.3 to 1/0.8, (II) bifunctional epoxy resin (A) (hereinafter referred to as (A')), (III) 4,4'-diaminodiphenyl sulfone or 3,3'-diaminodiphenyl sulfone (hereinafter referred to as (D)), wherein the ratio of moles of (A') to moles of (A) is 0.4-6.0:1, and the ratio of moles obtained by subtracting moles of the phenolic OH of (C) from moles of the total epoxy groups of (A), (A') and (B) to moles of the NH groups of (D) is 1:0.5-1.2.

Inventors: AGATA AKIRA, KUBO TAKATOSHI, MURATA TAKASHI, SARUTA MASAHIRO, TADA HISASHI, AGATA, AKIRA, KUBO, TAKATOSHI, MURATA, TAKASHI, SARUTA, MASAHIRO, TADA, HISASHI, AGATA, AKIRA MITSUBISHI RAYON CO., LTD., KUBO, TAKATOSHI MITSUBISHI RAYON CO., LTD., MURATA, TAKASHI MITSUBISHI RAYON CO., LTD., SARUTA, MASAHIRO MITSUBISHI RAYON CO., LTD., TADA, HISASHI MITSUBISHI RAYON CO., LTD.
Applicants: MITSUBISHI RAYON CO, MITSUBISHI RAYON CO., LTD.
Application year: 1988
Main classification: C08G59
IPC codes: C08G59