JPS6338050B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a high-performance carbon fiber prepreg resin. (Prior art) Carbon fiber reinforced plastics (hereinafter abbreviated as CFRP) have high specific strength and specific modulus, so they are being considered as a structural material to reduce the weight of aircraft bodies in the field of civil aircraft, and they are already being used as structural materials to reduce the weight of aircraft bodies. As a first step, it is used as a secondary structural material. Furthermore, recently, high strength and elongation carbon fibers have become relevant, and CFRP using them has begun to be considered as a primary structural material. 4,4'-diaminodiphenylsulfone is used as a curing agent for epoxy resins used in aircraft CFRP. An epoxy resin composition using this curing agent has a high modulus of elasticity and a high heat distortion temperature, so the resulting CFRP has excellent heat resistance, interlaminar shear strength, and compressive strength. However, the epoxy resin composition using this curing agent has a low elongation of the cured product, so the resulting CFRP
The 90° tensile elongation of is also small corresponding to the resin elongation. As a result, the tensile properties of 0°/90° and 0°/±45/90° laminates 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. For this reason, there is a strong desire to develop a curing agent for epoxy resins that provides a cured product with high elongation without impairing the heat resistance and elastic modulus of the cured product. (Purpose of the present invention) Therefore, the present inventors conducted intensive studies to find a curing agent for epoxy resin that exhibits excellent tensile properties without impairing the heat resistance, interlaminar shear strength, and compressive strength of CFRP. As a result, we have arrived at the present invention. (Structure of the present invention) That is, General formula (In the formula, R is a residue of an alkylene glycol having 2 to 10 carbon atoms or an alicyclic diol having 5 to 14 carbon atoms.) Epoxy resin for carbon fiber prepreg containing the compound shown as a curing agent. Regarding the composition. Here, the term "residue" refers to an alkylene glycol or an alicyclic diol from which the hydroxyl group has been removed. The compound represented by the general formula of the present invention can be obtained by a known method. For example, it is obtained by reacting an alkylene glycol having 2 to 10 carbon atoms or an alicyclic diol having 5 to 14 carbon atoms with P-nitrobenzoyl chloride, and then reducing the product with hydrazine in the presence of a palladium catalyst. be able to. Examples of alkylene glycols having 2 to 10 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,
2-butanediol, 1,4-butanediol,
2,3-butanediol, 1,5-pentanediol, 2,4-pentanediol, neopentyl glycol, 1,3-dimethyl-1,3-propanediol, 1,5-hexanediol, 1,6
-Hexanediol, 2-ethyl-2-methyl-
1,3-propanediol, 2-methyl-2,4
-Pentanediol, 1,7-heptanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propane Diol, 2-methyl-2-propyl-1,3
-Propanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol,
Examples include linear or side chain alkylene glycols such as 1,9-nonanediol and 1,10-decanediol. Alkylene glycols may contain heteroatoms such as oxygen and sulfur, and include, for example, diethylene glycol, triethylene glycol, thiodiethanol, and the like. Examples of the alicyclic diol having 5 to 14 carbon atoms include 1,3-cyclopentanediol, 1,4
-Cyclohexanediol, 1,4-cyclohexanedimethylol, 1,5-decalindiol,
Examples include diols such as tricyclodecane dimethylol. Among these alkylene glycols and alicyclic diols, a cured epoxy resin having particularly excellent tensile properties can be obtained by using a linear or side chain alkylene glycol having 4 to 6 carbon atoms. Theoretically, the amount of this compound to be added should be 1 equivalent of amine per 1 equivalent of epoxy. In view of elongation, etc., the amount of this compound added is 0.5 to 1.5 equivalents, more preferably 0.8 to 1.2 equivalents, per 1 equivalent of epoxy. Moreover, in the present invention, it is of course possible to use this compound in combination with other curing agents. British patent 118237 is a combination of this compound with a single epoxy resin. However, with such a combination, the performance of this compound cannot be fully expressed. Only the combination of this compound with a mixture of multiple epoxy resins can fully exhibit the performance of this compound. The epoxy resin used in the present invention may be any commercially available epoxy resin, but the following epoxy resins and addition amounts are most preferred in order to fully exhibit the performance of this curing agent. N,N,N,N'-tetraglycidyldiaminodiphenylmethane is ELM434, YL913,
It is commercially available under product names such as YH434. Since this epoxy resin is tetrafunctional, it has the advantage that it has a high crosslinking density and a cured product with high elastic modulus and high heat resistance can be obtained. On the other hand, the cured product has the drawbacks of low elongation and poor water resistance. Taking these characteristics into consideration, the amount of N,N,N',N'-tetraglycidyldiaminodiphenylmethane added is 15 to 70% by weight in the epoxy resin component. More preferably, it is 25 to 55% by weight. If the amount exceeds this range, the elongation and water resistance will decrease, and if it decreases, the heat resistance and elastic modulus of the cured product will decrease. When the elastic modulus of the resin is reduced, the interlaminar shear strength and compressive strength of the obtained CFRP are reduced. The brominated epoxy resin is brominated bisphenol A.
These are the glycidyl ether type epoxy resin and the glycidyl ether type epoxy resin of brominated phenol novolak resin. Br content is 16-50% by weight, Epicron 152, Epicron
It is commercially available under trade names such as 1120, EBS340, Ep1050, BRENS, etc. Although the cured product obtained from this resin has high water resistance and elastic modulus, it has a high epoxy equivalent weight, so the crosslinking density is low and the heat resistance is low.
Furthermore, resin elongation is low due to steric hindrance caused by Br atoms. Taking these characteristics into account, the amount of brominated epoxy resin added should be 15 to 15% in the epoxy resin component.
It is 55% by weight. More preferably, it is 20 to 40% by weight. If the amount exceeds this range, the heat resistance and water resistance of the cured product will decrease. On the other hand, when the amount is decreased, the elastic modulus and water resistance of the cured product decrease. Bisphenol A type epoxy resin is Ep828,
Ep1001, YD128, Epicron 855, Epicron
It is commercially available under trade names such as 1050, ELA128, DER331, etc. A cured product obtained from this resin has a high resin elongation, but a low elastic modulus. Taking these characteristics into consideration, the amount of bisphenol A type epoxy resin added is 5 to 50% by weight, more preferably 10 to 40% by weight, based on the epoxy resin component. When the amount exceeds this range, the elastic modulus of the cured product decreases. On the other hand, when the amount is decreased, the elongation of the cured product decreases. N,N,O-triglycidyl metaaminophenol is commercially available under trade names such as ELM120 and YDM120. The more this epoxy resin has self-curing properties, the better its reactivity is. Furthermore, since it is a trifunctional epoxy resin, the crosslinking density is high, resulting in a cured product with high heat resistance and high elastic modulus. On the other hand, the cured product has low elongation and poor water resistance. Considering these characteristics, the amount of N,N,O-triglycidyl metaaminophenol added is 5 to 30% by weight, more preferably 10 to 20% by weight, based on the epoxy resin component. If the amount exceeds this range, the water resistance will decrease and the shelf life of the prepreg will be shortened. On the other hand, when the amount is decreased, the curability deteriorates and the elastic modulus decreases. Novolac type epoxy resin is a glycidyl ether type epoxy resin of phenol novolac resin and cresol novolac resin.
Ep154, DER485, N740, N673, ESCN220L,
It is commercially available under the trade name. This novolak type epoxy resin has the advantage of forming a cured product with high heat resistance and high water resistance, but has the disadvantage of forming a cured product with a low modulus of elasticity. Taking these characteristics into consideration, the amount of novolac type epoxy resin added is 15 to 60 parts by weight, more preferably 20 to 50% 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. In the present invention, in order to obtain a resin viscosity suitable for prepreg, the resin viscosity is adjusted by prepolymerizing with a compound represented by the general formula, 4,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenylmethane. I don't mind. Further, a thermoplastic resin may be added to adjust the resin viscosity or the resin flow during curing to an extent that does not impair the properties of the resin composition of the present invention. The epoxy resin composition of the present invention is preferably used as CFRP, and the carbon fibers used in this case are carbon fibers in any form such as tapes, sheets, mats, textiles, etc. arranged in a certain direction. It can also be applied to 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) As a result of the cured product of the epoxy resin composition according to the present invention increasing elongation without substantially impairing heat resistance and elastic modulus, the obtained CFRP loses interlaminar shear strength and compressive strength. Since the tensile elongation at 90° is greatly improved without bending, the physical properties of laminates such as 0°/90°, 0°/±45°/90° are greatly improved, making carbon fiber superior. fully demonstrate its performance. In addition, the 0° tensile properties of recently developed high strength and elongation carbon fibers are fully expressed. Hereinafter, the present invention will be explained in more detail with reference to Examples. Production example of the general formula (when R is a neopentyl glycol residue) In a four-neck flask equipped with a reflux condenser, thermometer, and stirrer, 360 c.c. of pyridine, 371 g (smol) of P-nitrobenzoyl chloride, Prepare 104g (1 mol) of neopentyl glycol and heat,
Refluxed for an hour. Then, the reaction solution was poured into ice water from step 2, and the precipitate was overdried to obtain 389 g of neopentyl dipnitrobenzoate having a melting point of 149-152°C.
In a similar reactor, neopentyl glycol-di-p
120.6 g (0.3 mol) of nitrobenzoate to 500 c.c.
After dispersing the solution in isopropyl alcohol and purging the solution with nitrogen for 30 minutes, 5 g of 10% palladium-carbon was added. Then 80% hydrazine hydrate 66
g (1.05 mol) was added dropwise over 30 minutes, and after the completion of the addition, the mixture was refluxed for 3 hours. Then, after removing the catalyst through the opening paper,
Neopentyl glycol cooled to 163-165℃
93 g of dipaminobenzoate was obtained. The same operation was performed by changing the alkylene glycol and the alicyclic diol to produce the compounds shown in Table 1. Example 1 40 g of N,N,N',N'-tetraglycidyldiaminodiphenylmethane (epoxy equivalent: 120), 40 g of brominated epoxy resin (epoxy equivalent: 360), and N,N,O-triglycidylmethaminophenol (epoxy Equivalent weight 118) 20g at 155℃~
After heating and mixing at 160°C, 48g of propylene glycol-dip-aminobenzoate was added and completely dissolved. This epoxy resin composition was poured into a mold with a thickness of 2 mm and cured at 180°C for 1 hour, and then at 190°C for 4 hours to obtain a cured product. Table 1 shows the tensile strength, elastic modulus, elongation, glass transition point, and absorption rate of this cured product after immersion in boiling water for 20 hours. Example 2 45 g of N,N,N',N'-tetraglycidyldiaminodiphenylmethane and 40 g of brominated epoxy resin
After heating and mixing 15 g of N,N,O-triglycidyl metaaminophenol at 155°C to 160°C in advance, 52 g of neopentyl glycol-dip-aminobenzoate was added, completely dissolved, and cured in the same manner as in Example 1. I got something. Table 1 shows the physical properties of this cured product. Example 3 40 g of N,N,N',N'-tetraglycidyldiaminodiphenylmethane and 30 g of brominated epoxy resin
g, N,N,O-triglycidylmethaminophenol 15g and bisphenol A type epoxy resin (epoxy equivalent 189) 15g in advance at 155°C to 160°C.
After heating and mixing at .degree. C., 53 g of neopentyl-dip-aminobenzoate was added and completely dissolved, and a cured product was obtained in the same manner as in Example 1. Table 1 shows the physical properties of this cured product. Examples 4 to 6 The curing agent was replaced with 1,6-hexanediol-dip-aminobenzoate, 1,4-cyclohexanemethylol-dip-aminobenzoate, and tricyclodecanedimethylol-dip-aminobenzoate, A cured product was obtained in the same manner as in Example 3. Table 1 shows the physical properties of these cured products. Comparative Example 1 100g of N,N,N',N'-tetraglycidyldiaminodiphenylmethane was heated to 155℃~160℃ in advance.
After heating to ℃, neopentyl glycol dip
After adding and completely dissolving 71 g of -aminobenzoate, a cured product was obtained in the same manner as in Example 1. Table 1 shows the physical properties of this cured product. Comparative Examples 2 to 5 Cured products were obtained in the same manner as in Comparative Example 1 using various dipaminobenzoates with different diols. Table 1 shows the physical properties of this cured product. From Table 1, it was clearly confirmed that the epoxy resin composition of the present invention had excellent performance. Example 7 2000 g of N,N,N',N'-tetraglycidyldiaminodiphenylmethane and brominated epoxy resin
1500g, N,N,O-triglycidylmethaminophenol 1000g and bisphenol A type epoxy resin (epoxy equivalent 189) 500g
Add to a kneader heated to ℃ and mix thoroughly. After mixing, cool the temperature of the kneader contents to 60-65℃,
54 g of neopentyl glycol dipaminobenzoate was added and thoroughly mixed to prepare an epoxy resin composition. This resin composition was impregnated into unidirectionally aligned carbon fibers "Torayca" T-500 (trademark of Toray Industries, Inc.) by a hot melt method to produce a unidirectional prepreg with 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, and set for autoclave molding using a nylon bag. This set material was placed in an autoclave, pressurized to 6 kg/cm ² and then heated at 180° C. for 2 hours to obtain a cured plate. The carbon fiber content of this cured plate was 59.3% by volume, and the thickness of the plate was 1.11 mm. Length 230mm from this hardened plate in the carbon fiber direction,
A 0° tensile test piece with a width of 12.73 mm was cut out. Glass tabs having a length of 50 mm, a width of 12.73 mm, and 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 test piece was pulled at a pulling speed of 1 mm/min to measure the tensile properties. The measurement results are shown in Table 2.
Further, a test piece was cut out from this cured plate according to ASTM, D695, and its compression properties were measured. The results are shown in Table 2. Next, prepreg is 35cm long and 30cm wide.
16 sheets were stacked together. A cured plate was made from this laminated product in the same manner as above. The carbon content of this hardened plate is 598% by volume, and the thickness of the plate is 2.20
It was warm in mm. From this hardened plate to carbon fiber
A 90° tensile test piece with a length of 230 mm and a width of 25.45 mm was cut in the 90° direction. 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 tensile properties. The results are shown in Table 2. moreover,
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 2. These measurement results show that, in particular,
It was confirmed that the material had excellent tensile properties, water resistance, and heat resistance.

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Claims (1)

[Scope of Claims] 1 Contains N,N,N',N'-tetraglycidyldiaminodiphenylmethane, brominated epoxy resin, and further contains N,N,O-triglycidylaminophenol, bisphenol A type epoxy resin ,
It also contains at least one epoxy resin selected from the group consisting of phenol novolac type epoxy resins, and has the general formula (In the formula, R is a residue of an alkylene glycol having 2 to 10 carbon atoms or an alicyclic diol having 5 to 14 carbon atoms) as a curing agent.Epoxy resin composition for carbon fiber prepreg thing.