JPS6244770B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a high-performance epoxy resin for carbon fiber prepreg. [Prior Art] Carbon fiber reinforced plastics (hereinafter abbreviated as CFRP) has high specific strength and specific modulus, so it is being considered as a structural material for reducing the weight of aircraft bodies in the civil aircraft field, and it has already been used. As a first step, it is used as a secondary structural material. Furthermore, recently, high-strength and elongation carbon fibers have been developed, and CFRP using them has begun to be considered as a primary structural material. The epoxy resin used in CFRP for aircraft is mainly composed of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane, and the curing agent is 4.
4'-diaminodiphenyl sulfone has been used. Such resins are disclosed in detail in, for example, Japanese Patent Publication No. 55-25217. This resin composition is
Since it has a high modulus of elasticity and a high heat distortion temperature, the CFRP obtained from this resin composition has excellent heat resistance, interlaminar shear strength, and compressive strength when dry. However, since this resin composition has a low elongation of the cured product and poor water resistance, the resulting CFRP has the following defects. In other words, since the elongation of the resin is small, CFRP
The 90° tensile elongation is small at 0.4-0.5%. As a result,
The tensile properties of laminates such as 0°/90° and 0°/±45°/90° are low, and the excellent properties of carbon fibers are not fully utilized. Furthermore, recently developed high strength and elongation carbon fibers cannot exhibit sufficient 0° tensile properties. On the other hand, since the water resistance is poor, the heat resistance decreases significantly after water absorption. As a result, the compressive strength at high temperatures after water absorption, which is an important physical property for aircraft structural materials, decreases. In order to meet the compression strength in this state, CFRP
CFRP has to be made thicker, which reduces the efficiency of CFRP in reducing the weight of the aircraft. [Object of the present invention] Therefore, the present inventors conducted intensive studies to find an epoxy resin that exhibits excellent tensile properties and water resistance without impairing the heat resistance, interlaminar shear strength, and compressive strength of CFRP. We have arrived at the present invention. [Structure of the present invention] That is, the present invention provides: (1) 20 to 80 parts by weight of the total epoxy resin;
parts by weight of N・N・N ^-・N ^- -tetraglycidyldiaminodiphenylmethane and 15 to 60 parts by weight of
An epoxy resin composition (hereinafter referred to as the present invention A) characterized by containing a brominated epoxy resin and 4,4 ^- diaminodiphenylsulfone in an amount of 0.8 to 1.2 equivalents per equivalent of epoxy group. (2) 15 to 60 parts by weight of total epoxy resin
parts by weight of N・N・N ^-・N ^- -tetraglycidyldiaminodiphenylmethane and 15 to 60 parts by weight of
An epoxy resin composition comprising a brominated epoxy resin, 15 to 60 parts by weight of a novolac type epoxy resin, and 0.8 to 1.2 equivalents of 4,4 ^- diaminodiphenylsulfone per equivalent of epoxy group. (hereinafter referred to as the present invention B). Regarding. That is, the epoxy resin composition of the present invention A is
As a result of increasing the elongation of the cured product without impairing the elastic modulus of the cured product, the resulting CFRP has a greatly improved 90° tensile elongation of 0.70 to 0.95% without impairing the interlaminar shear strength and compressive strength. 0゜/
Since the physical properties of the laminate at angles of 90°, 0°/±45/90° are improved, the excellent performance of carbon fiber can be fully expressed. It also fully exhibits the 0° tensile properties of recently developed high strength and elongation carbon fibers. Furthermore, we have improved water resistance without compromising the heat resistance of the cured product.
The compressive strength of the obtained CFRP at high temperature after water absorption is
It has become fully satisfactory as a structural material for aircraft. Furthermore, in order to improve the heat resistance of the present invention A and the elongation of the cured product, the present invention B is preferred, in which a novolak type epoxy resin is added to the present invention A. Invention B is obtained as a result of improving heat resistance and elongation of the cured product without impairing other physical properties.
CFRP has improved tensile properties and heat resistance without compromising interlaminar shear strength and compressive strength. N・N・N′・N′-tetraglycidyldiaminodiphenylmethane used in the present invention is
It is commercially available under trade names such as ELM434, YL913, and YH434. Since this epoxy resin is a tetrafunctional epoxy resin, it has the advantage that it has a high crosslinking density and a cured product having a high elastic modulus and high heat resistance can be obtained. On the other hand, the elongation of the cured product is low and the water resistance of the cured product is poor because the molecule contains nitrogen atoms. Considering these characteristics, N・N・
The amount of N′・N′-tetraglycidyldiaminodiphenylmethane added is determined by adding only the epoxy resin excluding the curing agent 4・4′-diaminodiphenyl sulfone.
In the case of 100 parts by weight, it is 15 to 60 parts by weight, more preferably 20 to 50 parts by weight. If the amount exceeds this range, the elongation and water resistance of the cured product will decrease, and if it decreases, the heat resistance and elastic modulus of the cured product will decrease. Obtained by lowering the elastic modulus
The interlaminar shear strength and compressive strength of CFRP decrease. Even if N・N・N′・N′-tetraglycidyldiaminodiphenylmethane contains N・N・N′-triglycidyldiaminodiphenylmethane and a dimer in which these glycidyl groups have reacted with each other, The performance of the resin composition of the present invention is not impaired. The Br epoxy resin used in the present invention is Br
Glycidyl ether type epoxy resin of brominated bisphenol A, glycidyl ether type epoxy resin of brominated phenol novolak resin, with a Br content of 16 to 50% by weight, Epiclon 152,
Epicron 1120, ESB340, EP1050, BREN-S
It is marketed under the trade name. This brominated epoxy resin has the advantage of forming a cured product with high water resistance and high elastic modulus, but has the disadvantage that the large epoxy equivalent weight results in a cured product with low crosslinking density and low heat resistance. Furthermore, since it has steric hindrance due to Br atoms, increasing the concentration of the Br-containing epoxy resin lowers the elongation of the cured product. Considering these characteristics, the amount of brominated epoxy resin added is:
The amount is 15 to 60 parts by weight, more preferably 20 to 50 parts by weight. If the amount exceeds this range, the heat resistance and elongation of the cured product will decrease, and if it decreases, the water resistance and elastic modulus of the cured product will decrease. The novolak type epoxy resins used in the present invention are glycidyl ether type epoxy resins of phenol novolak resin and cresol novolak resin, including EP152, EP154, DER485, N740,
It is commercially available under trade names such as N673 and ESCN220L. This novolak type epoxy resin has the advantage of forming a cured product with high heat resistance, high water resistance, and high elongation, but has the disadvantage of forming a cured product with low elastic modulus. Taking these characteristics into consideration, the amount of novolak type epoxy resin added is 15 to 60 parts by weight, more preferably 20 to 50 parts by weight. If the amount exceeds this range, the elastic modulus of the cured product will decrease, and if it decreases, the water resistance and elongation of the cured product will decrease. Furthermore, EP828,
The addition of glycidyl ether type epoxy resins of bisphenol A, which are commercially available under trade names such as EP1001, EP1004, YD128, Epiclon 855, Epiclon 1050, and ELA128, increases the elongation of the cured product. The addition of ether type epoxy resins is highly preferred. 4,4'-diaminodiphenyl sulfone as a curing agent used in the present invention has a relatively long shelf life as an amine-based curing agent, and
It provides a cured product with high heat resistance. 4・4′−
Theoretically, the addition amount of diaminodiphenylsulfone should be 1 equivalent of amine per 1 equivalent of epoxy, but it is important to adjust the curing speed and shelf life, and the heat resistance, water resistance, and elongation of the resulting cured product. Therefore, the amount of 4,4'-diaminodiphenyl sulfone added is in the range of 0.8 to 1.2 equivalents per equivalent of epoxy. If the amount exceeds this range, the curing speed will be faster and the shelf life will be shorter. Furthermore, the water resistance and heat resistance of the cured product decrease. When the amount is less than this range, the curing speed becomes extremely slow and the heat resistance and elongation of the cured product decrease. Furthermore, in the present invention, 4,4'-diaminodiphenyl sulfone can of course be used in combination with other curing agents or curing accelerators. In particular, the combined use with a boron trifluoride amine complex is very preferable because it increases the curing speed without impairing other properties. In the present invention, in order to obtain a resin viscosity suitable for prepreg, the resin viscosity may be adjusted by prepolymerizing with 4,4'-diaminodiphenyl sulfone or 4,4'-diaminodiphenylmethane. Furthermore, a thermoplastic resin or the like may be added to adjust the resin viscosity and resin flow during curing to an extent that does not impair the performance of the resin composition of the present invention. The epoxy resin composition of the present invention is preferably used as CFRP, but the carbon fibers used in this case can be in any form such as tapes, sheets, mats, textiles, etc. arranged in a certain direction. It can also be applied to carbon fiber. Furthermore, all the materials normally used as reinforcing materials for FRP can be used, such as glass fiber, boron fiber, and organic fiber. [Effects of the present invention] As a result of the epoxy resin composition of the present invention increasing the elongation of the cured product without impairing the elastic modulus of the cured product, the obtained CFRP has a high elongation without impairing the interlaminar shear strength and compressive strength. , 90° tensile elongation 0.7~
Because of the significant improvement of 0.95%, 0°/90°, 0
Since the physical properties of the laminate, such as ゜/±45゜/90゜, are improved, the excellent performance of carbon fiber can be fully expressed. It also fully exhibits the 0° tensile properties of recently developed high strength and elongation carbon fibers. Furthermore, we have improved the water resistance without impairing the heat resistance of the cured product.
The compressive strength of CFRP at high temperatures after water absorption has become sufficiently satisfactory as a structural material for aircraft. Invention B is obtained as a result of improving heat resistance and elongation of the cured product without impairing other physical properties.
CFRP has improved tensile properties and heat resistance without compromising interlaminar shear strength and compressive strength. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 1750 g of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane (epoxy equivalent: 120)
Add 1,500 g of brominated epoxy resin (epoxy equivalent: 360) and 1,750 g of glycidyl ether type epoxy resin of bisphenol A (epoxy equivalent: 189) to a kneader preheated to 100° C. and mix thoroughly. After mixing, the temperature of the contents of the kneader was cooled to 60 to 65 degrees, and 1,600 g of 4,4'-diaminodiphenylmethane and 25 g of boron trifluoride monoethylamine were added and thoroughly mixed to prepare an epoxy resin composition. . Carbon fiber "trading card" T made of this resin composition aligned in one direction
-500 (Trademark of Toray Industries, Inc.) by the hot melt method to create a unidirectional prepreg with a resin content of 34% by weight. The obtained prepreg is 30cm long and wide.
After cutting 30 cm pieces and laminating 8 sheets, the laminated material was placed on release-treated aluminum and set for autoclave molding using a nylon bag. This set material was placed in an autoclave, pressurized to 6 kg/cm ² , heated at a rate of 1.5° C./min, and heated at 180° C. for 2 hours to obtain a cured plate. The carbon fiber content of this cured board was 58% by volume, and the thickness of the board was 1.13 mm. A 0° tensile test piece having a length of 230 mm and a width of 12.72 mm was cut out from this cured plate in the direction of the carbon fibers. Length 50 on each side of both ends of this specimen
A glass tab with a width of 12.72 mm and a taper of 10 mm at one end was glued. A strain gauge was attached to the center of this tabbed test piece, and tensile properties were measured at a tensile speed of 1 mm/min. The measurement results are shown in Table 1. Also, from this hardened plate,
Test pieces were cut out and compressive properties were measured according to ASTM, D695. The results are shown in Table 1. Next, the prepreg was cut into pieces of 35 cm and width of 30 cm, and 16 pieces were laminated. A cured plate was made from this laminated product in the same manner as above. The carbon content of this cured plate was 60% by volume, and the thickness of the plate was 2.19 mm. From this hardened plate, the length is 230 mm and the width is 90° to the carbon fiber.
A 25.43 mm 90° tensile test piece was cut out. A strain cage was attached to the center of this test piece, and the tensile properties were measured at a tensile rate of 1 mm/min. The results are shown in Table 1. Furthermore, from this hardened plate,
A test piece was cut out according to ASTM, D2344, and the interlaminar shear strength was measured. The results are shown in Table 1. From these measurement results, it was confirmed that especially water resistance, heat resistance, and tensile properties were excellent.

【table】

[Table] Example 2 N・N・N′・N′-tetraglycidyldiaminodiphenylmethane 1500g and brominated epoxy resin
Add 1,500 g and 2,000 g of novolac type epoxy resin (epoxy equivalent: 176) to a kneader preheated to 100°C and mix thoroughly. After mixing, the temperature of the contents of the kneader was cooled to 60 to 65°C, and 1600 g of 4,4'-diaminodiphenylsulfone and 25 g of boron trifluoride monoethylamine were added and thoroughly mixed to prepare an epoxy resin composition. . Using this resin composition,
A unidirectional prepreg with a resin content of 34% by weight was produced in the same manner as in Example 1. Using this prepreg, the 0° and 90° tensile properties, compressive properties, and interlaminar shear strength were measured in the same manner as in Example 1. These results are shown in Table 2, and it was confirmed that the water resistance, heat resistance, and tensile properties were particularly excellent.

[Table] Example 3 N・N・N′・N′-tetraglycidyldiaminodiphenylmethane 1500g and brominated epoxy resin
1250g, 1500g of novolac type epoxy resin, and 750g of glycidyl ether type epoxy resin of bisphenol A (epoxy equivalent: 188) were mixed in advance with 100g of novolac type epoxy resin.
The mixture was added to a kneader heated to ℃ and thoroughly mixed. After mixing, the temperature of the contents of the kneader was cooled to 60-65°C, and 1650 g of 4,4'-diaminodiphenylsulfone was added.
and 25 g of boron trifluoride monoethylamine were added and thoroughly mixed to prepare an epoxy resin composition. Using this resin composition, a unidirectional prepreg with a resin content of 34% by weight was produced in the same manner as in Example 1. Using this prepreg, 0° and 90° tensile properties, compressive strength, and interlaminar shear strength were measured in the same manner as in Example 1. These results are shown in Table 3.
In particular, it was confirmed that the water resistance, heat resistance, and tensile properties are excellent.

[Table] Comparative Example 1 5000 g of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane, 2400 g of 4,4′-diaminodiphenylsulfone, and 25 g of boron trifluoride monoethylamine were heated to 60 to 65°C in advance. The mixture was added to a heated kneader and thoroughly mixed to prepare an epoxy resin composition, and a prepreg was prepared in the same manner as in Example 1. Using this prepreg, 0° and 90° tensile properties, compressive properties, and interlaminar shear strength were measured in the same manner as in Example 1. These results are shown in Table 4, and only CFRP with poor tensile properties and water resistance was obtained.

【table】

Claims (1)

[Claims] 1 20 to 80 parts by weight of the total epoxy resin
Parts by weight of N・N・N ^-・N ^- -tetraglycidyldiaminodiphenylmethane and 15 to 60 parts by weight of Br
epoxy resin and 1 equivalent of epoxy group
An epoxy resin composition containing 0.8 to 1.2 equivalents of 4,4 ^- diaminodiphenylsulfone. 2 15 to 60 parts by weight of the total epoxy resin
Parts by weight of N・N・N ^-・N ^- -tetraglycidyldiaminodiphenylmethane and 15 to 60 parts by weight of Br
epoxy resin, 15 to 60 parts by weight of novolak type epoxy resin, and 0.8 parts per equivalent of epoxy group.
An epoxy resin composition comprising ~1.2 equivalents of 4,4 ^- diaminodiphenyl sulfone.