JPS6244771B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to an epoxy resin composition for carbon fiber prepreg that provides carbon fiber reinforced plastic (hereinafter abbreviated as CFRP) with excellent heat resistance and water resistance. (Prior art) CFRP, which takes advantage of carbon fiber's high specific strength and specific modulus, is widely used in industrial fields including aircraft. One of them is a centrifugal separator that rotates at ultra-high speed. used for such purposes
The properties required of CFRP include not only heat resistance and mechanical properties, but also water resistance and low-temperature hardening properties. In other words, CFRP undergoes dimensional changes due to the matrix resin, which causes it to lose its balance and cannot be rotated at high speeds. When rotating, it must be dehydrated, and since it takes a long time to dehydrate a product with poor water resistance, a product with good water resistance is required. Furthermore, if the curing temperature is high, thermal residual strain during molding is large, which tends to cause distortion in the molded product, making it difficult to balance rotation. Currently, the epoxy resin used for CFRP that requires heat resistance is N・N・N′・N′-tetraglycidyldiaminodiphenylmethane or a slightly modified version of this, and 4.4% as a hardening agent. This is an epoxy resin composition mixed with '-diaminodiphenyl sulfone. The disadvantage of this resin composition is that it has poor water resistance and curability. In other words, since the curing properties are poor, in order to sufficiently cure the
Because it requires curing at 210°C for 4 hours or more, not only is productivity low, but the resulting CFRP also suffers from large thermal distortions. On the other hand, in JP-A-54-77699, N・N・N′・N′−
N.
It is known that adding N.O-triglycidylmethaminophenol improves physical properties and curability. However, the cured product obtained from this resin composition has a high water absorption rate and is therefore not suitable for use in high-speed rotating objects. (Objective of the present invention) An object of the present invention is to obtain an epoxy resin having excellent water resistance and curability as well as heat resistance and mechanical properties. (Structure of the present invention) This object of the present invention is as follows: (1) Based on 100 parts by weight of the total epoxy resin, (A) 25 to 75 parts by weight of N・N・N ^-・N ^- -tetraglycidyldiaminodiphenylmethane. , (B) 5 to 25 parts by weight of N・N・O-triglycidyl metaaminophenol; (C) 15 to 60 parts by weight of brominated epoxy resin and/or novolak type epoxy resin; (D) of all epoxy resins. An epoxy resin composition for carbon fiber prepreg, comprising 0.6 to 1.4 equivalents of 4,4 ^- diaminodiphenyl sulfone per equivalent of epoxy group. achieved by. N・N・N′・N′-tetraglycidyldiaminodiphenylmethane used in the present invention is
It is commercially available under trademarks such as ELM434, YL913, and YH434. Since this epoxy resin is a tetrafunctional epoxy, the crosslinking density is high, and as a result, a cured product with high heat resistance and high elastic modulus can be obtained, but the elongation of the cured product is small. Also, since it contains nitrogen atoms in its molecules, it has poor water resistance. Taking these characteristics into consideration, the amount of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane added is determined by
When the epoxy resin excluding 4'-diaminodiphenyl sulfone is taken as 100 parts by weight, the amount is 25 to 75 parts by weight, more preferably 30 to 65 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 of the cured product will decrease. N・N・N′・N′-tetraglycidyldiaminodiphenylmethane, N・N・
Even if N'-triglycidyldiaminodiphenylmethane and a dimer obtained by reacting these glycidyl groups with each other are contained, the performance of the resin composition of the present invention is not impaired. N・N・O-triglycidyl metaaminophenol used in the present invention is ELM120, YDM120
It is sold under the trademarks such as. The more this epoxy resin has self-curing properties, the better its reactivity is. Also,
Since it is a trifunctional epoxy resin, the crosslinking density is high, resulting in a cured product with high heat resistance and high modulus of elasticity, but the elongation of the cured product is low. Furthermore, since the molecule contains nitrogen atoms, the water resistance of the cured product is poor. Considering these characteristics, the amount of N・N・O-triglycidyl metaaminophenol added is 5.
-25 parts by weight, preferably 10-20 parts by weight. If the amount exceeds this range, the water resistance will decrease and the shelf life of the prepreg will be shortened, and if it decreases, the curing properties will deteriorate. The Br epoxy resin used in the present invention is Br
A glycidyl ether type epoxy resin of brominated bisphenol A, and a glycidyl ether type epoxy resin of brominated phenol borax resin.
The content is 16-50% by weight. This brominated epoxy resin is Epicron 152, Epicron
It is commercially available under the trade names 1120, ESB340, EP1050, and BREN-S. This brominated epoxy resin becomes a cured product with high water resistance and elastic modulus, but since the epoxy equivalent is large, the crosslinking density is low, resulting in a cured product with 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 the brominated epoxy resin added is 15 to 60 parts by weight, more preferably 20 to 60 parts by weight.
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 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, N740, DER485,
It is commercially available under trade names such as ESCN220L and N673. This novolak type epoxy resin becomes a cured product with high heat resistance, high water resistance, and high elongation, but a cured product with low elastic modulus. Considering these characteristics, the amount of novolak type epoxy resin is 15 to 60 parts by weight.
More preferably, it is 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 glycidyl 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 necessary to adjust the curing speed and shelf life.
In view of the heat resistance, water resistance, and elongation of the resulting cured product, the amount of 4,4'-diaminodiphenyl sulfone added is 0.6 to 1.4 equivalents, more preferably 0.8 to 1.4 equivalents per equivalent of epoxy. It is 1.1 equivalent. Furthermore, in the present invention, 4,4'-diaminodiphenyl sulfone can of course be used in combination with other curing agents. 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 may be added to adjust the viscosity of the resin or the flow of the resin during curing to the extent that the properties of the resin composition of the present invention are not impaired. 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, hots, 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, such as glass fiber, boron fiber, and organic fiber, can be used. (Effects of the present invention) The epoxy resin composition of the present invention has good curability and water resistance. As a result, if cured at 180℃ for 2 hours, the water absorption is small and the glass transition temperature is 220~220℃.
A cured product with high heat resistance of 230℃ is obtained, and dimensional changes due to water absorption are small. Furthermore, since the cured product has high elastic modulus and elongation, it has the effect of providing CFRP with excellent physical properties. The present invention will be explained in more detail with reference to Examples below. Example 1 2250 g of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane (epoxy equivalent: 120)
2000 g of brominated epoxy resin (epoxy equivalent: 360) and 750 g of N・N・O-triglycidyl metaaminophenol (epoxy equivalent: 118) were mixed in advance at 100 g.
Add to a kneader heated to ℃ and mix thoroughly. After mixing, the temperature of the contents of the kneader was cooled to 60-65℃, and 1800 g of 4,4'-diaminodiphenylsulfone was added.
was added and thoroughly mixed to prepare an epoxy resin composition. This resin composition was impregnated into unidirectionally aligned carbon fibers "Torayca" T-300 (Toray trademark) by a hot melt method to produce a unidirectional prepreg having a resin content of 34% by weight. The obtained prepreg was cut into pieces of 30 cm in length and 30 cm in width, and 8 sheets were laminated, placed on a release-treated aluminum plate, covered with a nylon vacuum bag, and after vacuuming the inside of the bag, placed in an autoclave. , 6 Kg/cm ² , the temperature was increased at a rate of 1.5° C./min, and the mixture was heated at 180° C. for 2 hours to obtain a cured plate. The carbon fiber content of the obtained cured board was 59.5% by volume, and the thickness of the board was 1.15 mm. Further, the glass transition temperature was 224°C.
230mm in length and width from this hardened plate in the carbon fiber direction.
A 12.71 mm 0° tensile test piece was cut out. Glass tabs having a length of 50 mm and a width of 12.71 mm and having a tapered portion of 10 mm at one end were adhered to both ends of this test piece. A strain gauge was attached to the center of this tabbed test piece, and the tensile properties were measured at a tensile speed of 1 mm/min. The results are shown in Table 1. Also,
A test piece was cut out from this cured plate according to ASTM, D695, and its compressive properties were measured. The results are shown in Table 1.
Shown below. Length 150 in the direction of carbon fiber from this hardened plate
Cut out a test piece with a width of 20 mm and place it in hot water at 71℃.
After 14 days of immersion, the water absorption rate was 0.83%.
Furthermore, the prepreg was cut into pieces of 35 cm in length and 30 cm in width, and 16 sheets 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 59.2% by volume, and the thickness of the plate was 2.27 mm. A 90° tensile test piece having a length of 230 mm and a width of 25.41 mm was cut from this cured plate in a direction 90° to the carbon fiber. A strain gauge was attached to the center of this test piece, and the test piece was pulled at a pulling speed of 1 mm/min to measure the physical properties under 90° tension. The results are shown in Table 1. Further, a test piece was cut out from this cured plate according to ASTM, D2344, and the interlaminar shear strength was measured. The results are shown in Table 1.
Shown below. From these results, it was confirmed that the curability was good, and the water resistance, heat resistance, and composite physical properties were excellent.

[Table] Example 2 2000g of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane, 750g of N・N・O-triglycidylmethaminophenol, and novolac type epoxy (epoxy equivalent: 178) 2250 and 4.4 ′−
An epoxy resin composition was prepared by adding 050 g of diaminodiphenylsulfone to a kneader preheated to 60 to 65°C and thoroughly mixing. A prepreg was made in the same manner as in Example 1 using this resin composition. A cured plate was made using this prepreg in the same manner as in Example 1. The glass transition temperature of this cured plate was 225°C, and the water absorption rate was 0.92%. In the same manner as in Example 1, 0° and 90° tensile properties, compressive properties, and interlaminar shear strength were measured. These results are shown in Table 2, and it was confirmed that the curability was good, and the water resistance, heat resistance, and composite physical properties were excellent.

【table】

[Table] Comparative Example 1 4000 g of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane and 1920 g of 4,4′-diaminodiphenyl sulfone were added to a kneader preheated to 60 to 65°C and mixed thoroughly. An epoxy resin composition was prepared, and a prepreg was produced in the same manner as in Example 1. A cured plate was made in the same manner as in Example 1 using this prepreg. The glass transition temperature of this cured plate was 192°C, and the water absorption rate was 2.14. In the same manner as in Example 1, 0° and 90° tensile properties, compressive properties, and interlaminar shear strength were measured. These results are shown in Table 3, and the curing properties were poor and the physical properties of the composite were significantly lower than those of the Examples.

[Table] Comparative Example 2 3400 g of N・N・N′・N′-tetraglycidyldiaminodiphenylmethane, 600 g of N・N・O-triglycidylmethaminophenol, and 1920 g of 4,4′-diaminodiphenyl sulfone were prepared in advance.
The mixture was added to a kneader heated to 60 to 65° C. and thoroughly mixed to prepare an epoxy resin composition, and a prepreg was prepared in the same manner as in Example 1. A cured plate was made in the same manner as in Example 1 using this prepreg. The glass transition temperature of this cured plate was 224°C, and the water absorption rate was 1.93%. As in Example 1, 0° and
The 90° tensile properties, compressive properties, and interlaminar shear strength were measured. These results are shown in Table 4, indicating that the CFRP had good hardenability but poor water resistance.

【table】

【table】

Claims (1)

[Claims] 1. Based on 100 parts by weight of the total epoxy resin, (A) 25 to 75 parts by weight of N.N.N ^{-.N -} -tetraglycidyldiaminodiphenylmethane; (B) N.N.O. - 5 to 25 parts by weight of triglycidyl metaaminophenol; (C) 15 to 60 parts by weight of brominated epoxy resin and/or novolak type epoxy resin; (D) based on 1 equivalent of epoxy groups in the total epoxy resin.
An epoxy resin composition for carbon fiber prepreg, comprising 0.6 to 1.4 equivalents of 4,4 ^- diaminodiphenyl sulfone.