JPH048450B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a prepreg for carbon fiber-reinforced composite materials having an addition-curing polyquinoxaline oligomer matrix, which has excellent heat resistance, water resistance, and mechanical properties. More specifically, the present invention relates to a prepreg for carbon fiber reinforced composite materials that has good heat resistance and excellent moldability and has an addition-curing polyquinoxaline oligomer matrix for carbon fiber reinforced composite materials (hereinafter abbreviated as CFRP). . [Prior art and problems to be solved by the invention] Conventionally, polyimide resins have been studied as matrix resins for heat-resistant CFRP. However, polyimide-based resins have excellent heat resistance but high water absorption, so polyimide-based composite materials have the disadvantage of absorbing moisture in the atmosphere and decreasing their heat resistance. On the other hand, polyquinoxaline resins have excellent heat resistance and water resistance, but their practical application has been delayed because they are difficult to mold compared to polyimide resins. In general, highly heat-resistant resins have high glass transition temperatures and melting points, and the fluidity of the molten resin is poor, so molding must be carried out at high temperatures and high pressures. Therefore, it has been extremely difficult to mold molded products with complex shapes or large parts. Therefore, in order to put heat-resistant composite materials into practical use, improving moldability has been an essential issue. Incidentally, polyphenylquinoxaline resin is soluble in organic solvents, has a glass transition temperature of about 300°C, has melt fluidity, and has good processability among heat-resistant polymers. However, composite materials having a matrix of high molecular weight polyphenylquinoxaline resin have extremely poor moldability due to the poor fluidity of the resin during molding. Therefore, with the aim of improving the moldability of polyphenylquinoxaline resins, research is being conducted on modifying them into addition-curing resins. For example, acetyl terminal [Natiol SAMPE Symposium, 21 (1976) 83],
Acetyl phenoxybendiyl terminal [National SAMPE Technical Conference,
8 (1976), 106], nitrile-terminated [National Sanpe Technical Conference
(National SAMPE Technical Conference),
8 (1976), 114], and biphenylene-terminated [Journal of Macromolecular Science
Chemistry (J, Macromol. Sci.Chem.),
A21 (8 & 9) (1984), 913] and other addition-curing polyphenylquinoxaline resins have been studied. In this way, by modifying the high molecular weight polyphenylquinoxaline resin into an addition-curing resin, the moldability was greatly improved. However, these addition-curing polyphenylquinoxaline resins have the disadvantage that molding machines and molding auxiliary materials are expensive due to high molding temperatures, and molded products with excellent physical properties cannot be obtained. . Therefore, there has been a strong desire to develop an addition-curing polyphenylquinoxaline resin that can be molded at low temperatures. Accordingly, the present inventors have conducted extensive research on polyquinoxaline resins that have excellent heat resistance, water resistance, and mechanical properties, and are also excellent in low-temperature moldability, and as a result, have arrived at the present invention. [Means for Solving the Problems] In order to solve the above problems, the present invention has the following configuration. That is, it is a prepreg for a carbon fiber reinforced composite material whose matrix is an addition-curing polyonoxaline oligomer represented by the general formula [] or/and []. R ₁ : nil, CH ₂ , O, CO, SO ₂ , S,

【formula】

【formula】

[Formula] Ar ₁ :

【formula】

【formula】

[Formula] Y ₁ : H, CH ₃ Conventional addition-curing polyquinoxaline resin oligomers require high temperatures of 290°C or higher for molding, and after-cure temperatures of 310°C or higher to develop sufficient heat resistance. As a result, molded products have large thermal residual strains during molding, and thermal cracks and microcracks due to thermal cycles often occur.
Therefore, there was a drawback that the physical properties of the composite material deteriorated. Therefore, the present inventors developed a low temperature curing polyquinoxaline resin. That is, a phenyl-N-maleimide type end-capping agent (general formula:

It has been found that a maleimide-terminated polyquinoxaline oligomer incorporating the formula has a low curing initiation temperature and can be molded at a low temperature of 230°C to 250°C, and that good molded products without the above-mentioned drawbacks can be obtained. Generally, the curing initiation temperature of maleimide-terminated resins is low; for example, in the case of bismaleimide, the molding temperature is
The temperature is 180℃ to 220℃, and if necessary, it is necessary to perform after-cure at 220℃ to 250℃ [National Sanpe Symposium
SAMPE Symposium), 29, (1984), 1043]. However, polyquinoxaline resin oligomers have a high glass transition temperature and are difficult to mold at temperatures below 200°C. Therefore, the present inventors conducted intensive research on end-capping agents for low-temperature curing polyquinoxaline resin oligomers, and found that molding at 230°C to 250°C was possible by using a phenyl-N-maleimide type end-capping agent. It made it possible. Now, phenyl-terminated polyquinoxane oligomers used in the present invention are synthesized.
N-maleimide type terminal capping agents include a diamine type having two amino groups at the ortho position of the benzene ring, and a phenylglyoxalyl type having two phenyl groups on the phenyl group.
Compounds of various types can be used. A diamine type terminal capping agent is produced by reacting 2-nitro-p-phenylenediamine and maleic anhydride in a dimethylacetamide solution to form a 1-
A diamine type terminal capping agent (1,2-amino-4-maleimidobenzene) is obtained by synthesizing amino-2-nitro-4-maleimidobenzene and reducing it using stannous chloride. . On the other hand, glyoxalyl-type end capping agents are produced by, for example, acetylating p-aminobenzaldehyde, condensing this and benzaldehyde with benzoin, oxidizing this with copper acetate and ammonium nitrate, and then deacetylating it. In particular, p-
Synthesize phenylglyoxalylaniline. A glyoxalyl-type terminal capping agent (1-phenylglyoxalyl-4-maleimidobenzene) was obtained by reacting p-phenylglyoxalylaniline obtained in the following with maleic anhydride in a dimethylacetamide solution. can get. When methyl-substituted maleic anhydride (citraconic anhydride) is used instead of maleic anhydride, the reaction initiation temperature of the terminal capping agent is slightly lowered, and the heat resistance of the cured product is slightly lowered, but the melting temperature of the oligomer is lowered. This improves moldability. Therefore, heat resistance and moldability can be controlled by mixing maleic anhydride and citranconic acid as necessary. Next, the maleimide-terminated addition-curable polyoxaline resin can be synthesized usually in the following order. For example, the oligomer represented by the general formula [ Obtained by completing . If the number of repeating units of the oligomer is n, then
By adjusting the molar ratio of tetraamine: bisglyoxalyl: terminal capping agent to n:(n+1):2, an oligomer having an arbitrary average molecular weight can be synthesized. On the other hand, the oligomer represented by the general formula [ ] can be synthesized by the same procedure as the above method except for using a glyoxalyl type terminal capping agent, but in this case, the proportion of each monomer is tetraamine: Bisglyoxalyl:
The molar ratio of the terminal capping agent is adjusted to be (n+1):n:2 mol. The maleimide-type terminal addition-curable polyquinoxaline oligomer used in the present invention is a resin with different heat resistance, physical properties, moldability, etc. by controlling the chemical structure of the tetraamine type monomer and bisglyoxalyl type monomer and the average molecular weight of the oligomer. However, in order to obtain a maleimide type terminal polyquinoxaline resin with excellent moldability and mechanical properties without impairing the excellent heat resistance and water resistance of the polyquinoxaline resin, 3, 3',4,4'-tetraaminodiphenyl [N],
3,3',4,4'-tetraaminobenzophenone [C], 3,3',4,4'-tetraamino diphenyl sulfone [S], 3,3',4,4'-tetraamino Diphenyl ether [E], 3,3',4,4'-tetraaminodiphenylmethane, 3,3',4,4'-
Tetraaminodiphenyl sulfide, 2,2'-bis[4-(3,4-diaminophenoxy)phenyl]propane, bis[4-(3,4-diaminophenoxy)phenyl]sulfone, 1 , 4-bis(3,4-diaminophenoxy)benzene, etc. are suitable, and examples of bisglyoxalyl type monomers include p-bis(phenylglyoxalyl)benzene [b], p-bis(phenylglyoxalyl) oxalyl)
diphenyl ether [e], p-bis(phenylglyoxalyl) diphenyl sulfide [s],
Preferred are p-bis(phenylglyoxalyl)diphenylbenzene and the like. Among the polyquinoxaline resins selected from these monomers, [N-e], [N-s], [N-e], [N-s], [N-e], [N-s], [ C-b], [C-e]
，
[E-b] etc. are suitable, especially [C-b], [E
-b] has excellent properties in terms of heat resistance and moldability. The mechanical properties of addition-curing polyquinoxaline resins improve as the average molecular weight of the oligomer increases, but heat resistance and moldability decrease, so it is suitable for the average number of repeating units n of the oligomer to be in the range of 0 to 10. A range of n from 0.4 to 4 is well-balanced in terms of heat resistance, moldability, and physical properties, and is suitable as an addition-curing polyquinoxaline oligomer. The maleimide-terminated addition-curing polyquinoxaline resin used in the present invention has excellent heat resistance and moldability, and can be molded at a lower temperature than conventionally known addition-curing polyquinoxaline resins, so it hardens during molding. It is characterized by excellent mechanical properties due to less distortion. However, the addition-curing polyquinoxaline resin according to the present invention also
As a matrix resin for composite materials having heat resistance of 250°C or higher, the glass transition temperature of the oligomer is approximately 170°C to 210°C. Therefore, during molding, the curing reaction of the terminal capping agent starts before the oligomer has sufficiently melted and flowed, making it difficult to mold molded products with complex shapes or large parts. Therefore, in order to further improve the moldability of the addition-curable polyquinoxaline having excellent heat resistance according to the present invention, it is effective to add a low molecular weight reactive diluent. The reactive diluent to be added to the maleimide-type polyquinoxaline resin oligomer of the present invention is a diallyl compound, particularly diallyl isophthalate, 3,3'-
Diallylbisphenol A and the like are preferred. Polyquinoxaline resin oligomers with maleimide-type terminals copolymerize with maleimide terminals and allyl compounds to create a three-dimensional crosslinked structure, making it possible to obtain quinoxaline-based resins with excellent moldability without sacrificing the performance required as heat-resistant resins. Not only is this possible, but it also has excellent mechanical properties. Moreover, since the tack and drape (softness) of the prepreg are improved by adding a reactive diluent, it has excellent properties as a composite material, especially as a matrix resin for CFRP. The mixing ratio of the maleimide-terminated polyquinoxaline resin oligomer and the reactive diluent is 1/0.1 in molar ratio.
A range of ~1/3 is desirable, and more preferably,
1/0.5 to 1/1.5 is desirable. As the amount of reactive diluent added increases, the fluidity of the resin improves, but on the contrary, the heat resistance decreases. Therefore, in order to maintain the performance required as a heat-resistant resin, the amount of reactive diluent added should not exceed 3 moles per mole of oligomer. On the other hand, if the amount added is too small, sufficient melt fluidity cannot be obtained, so the amount of reactive diluent added should be 0.1 mol or more per 1 mol of oligomer. As described above, the addition-curing polyquinoxaline resin used in the present invention has excellent heat resistance and mechanical properties, and also has excellent prepreg tack and drapability as well as excellent moldability. In addition to being excellent as a matrix resin for composite materials, it is also suitable as an adhesive or a molding material. In addition to the diallyl compound, bismaleimide, a dicyanate compound, a vinyl compound, etc. may be added in combination as a reactive diluent to the maleimide-terminated polyquinoxaline resin used in the present invention, if necessary. Furthermore, in the prepreg for carbon fiber-reinforced composite materials using the addition-curing polyquinoxaline oligomer of the present invention as a matrix, the most excellent effects can be obtained especially in the case of high-strength carbon fiber; however, in addition to carbon fiber as reinforcing fiber, It may be mixed with other fibers such as glass fibers, and the fibers may be in any form such as long fibers, woven fabrics, knitted fabrics, matte fibers, or cut fibers. [Example] The present invention will be explained in further detail by the following example. Example 1 2 moles of 3,3',4,4'-tetraaminodiphenyl ether and 3 moles of p-bis(phenylglyoxalyl) diphenyl ether were dissolved in dioxane and heated at boiling point for 3 hours. Made it react. Next, 2 moles of 1,2-diamino-4-maleimidobenzene was added to this solution, and the mixture was further reacted at the boiling point for 3 hours. A prepreg was produced by the drum winding method using the obtained reaction solution and "Torega" T400 manufactured by Toray Industries, Inc. The resin content of the obtained prepreg was 39.6%. The prepreg obtained there was cut into pieces of 30 cm in length and 20 cm in width, which were stacked and placed in an autoclave at 160°C and pressurized to 14 kg/ ^cm2 , then heated to 250°C, held for 2 hours, and then cooled. After that, the molded product was removed from the autoclave.
The obtained molded product was after-cured at 260° C. for 6 hours to obtain a molded product. The volume content of carbon fiber in the obtained molded product was 60.2%, and the glass transition temperature measured by the DSC method was 263°C, indicating that it had good heat resistance. Next, test pieces were cut out from the molded product obtained in accordance with ASTM, D-638 and D-790, and the tensile and bending properties were measured.
225Kg/mm ² , tensile modulus 14.3t/mm ² , bending strength 190
It had excellent mechanical properties with Kg/mm ² and flexural modulus of 13.8 t/mm ² . Example 2 2 moles of 3,3',4,4'-tetraaminobenzophenone, p-bis(phenylglyoxalyl)
Benzene is dissolved in dioxane in a proportion of 3 moles,
The reaction was carried out at boiling point for 3 hours. Then, 1,2-diamino-4-maleimidobenzene was added to this solution.
mol was added and further reacted for 3 hours at the boiling point.
1.0 mol of the obtained maleimide-type terminal polyoxaline oligomer and 3,3-diylbisphenol
Prepreg resin obtained by dissolving A in dioxane at a ratio of 0.8 mole and Toray Industries'"Torayca"
Prepreg was created using T400 using a wet method.
The resin content in the prepreg was 40.3%, and the carbon fiber basis weight was 252 g/m ² . The prepreg obtained there was cut into pieces of 30 cm in length and 20 cm in width, which were then laminated and pressurized to 7 kg/cm ² at 160°C in an autoclave, heated to 250°C, held for 2 hours, and then brought to room temperature. After cooling, the molded product was taken out from the autoclave. The obtained molded product was after-cured at 280° C. for 6 hours to obtain a molded product. The volume content of carbon fiber in the obtained molded product was 61.8%,
The glass transition temperature measured by the DSC method was 310°C, indicating that it had good heat resistance. Next, test pieces were cut out from the obtained molded product according to ASTM, D-638 and D-790, and the tensile properties and bending properties were measured.
230Kg/mm ² , tensile modulus 14.7t/mm ² , bending strength 197
It had excellent mechanical properties with Kg/mm ² and flexural modulus of 14.2 t/mm ² . Example 3 3,3',4,4'-tetraamino diphenyl ether and 2 moles of p-bis(phenylglyoxalyl)benzene were dissolved in dioxane and reacted at boiling point for 3 hours. Ta. Next, 2 moles of 1-phenylglyoxalyl-4-maleimidobenzene was added to this solution, and the mixture was further reacted at the boiling point for 3 hours. A ratio of 0.8 mol of the obtained maleimide-type terminal polyquinoxaline oligomer and 1.0 mol of 3,3'-diallylbisphenol A was dissolved in dioxane and stirred for a while at 50°C to reduce the dioxane content to 1%.
The resin for prepreg was obtained by concentrating to the following amount.
A prepreg was made using the hot melt method using the obtained prepreg resin and "Torayca" T400 manufactured by Toray Industries, Inc. The resin content in prepreg is
40.3%, and the basis weight of the carbon fiber was 249 g/m ² .
The prepreg obtained was cut into pieces of 30 cm long and 20 cm wide, which were then stacked and placed in an autoclave for 160 min.
After pressurizing to 7Kg/cm ² at ℃, the temperature was raised to 250℃,
After holding for 2 hours and cooling to room temperature, the molded product was taken out from the autoclave. The obtained molded product
A molded product was obtained by after-curing at 270°C for 6 hours. The volume content of carbon fiber in the obtained molded product is
59.8%, and the glass transition temperature measured by DSC method is
It was found that it had good heat resistance at 293°C. Next, test pieces were cut out from the obtained molded product according to ASTM, D-638 and D-790, and the tensile properties and bending properties were measured.
222Kg/mm ² , tensile modulus 14.3t/mm ² , bending strength 187
It had excellent mechanical properties with Kg/mm ² and flexural modulus of 13.8 t/mm ² . [Effects of the Invention] The prepreg for carbon fiber-reinforced composite materials using the addition-curing polyquinoxaline oligomer of the present invention as a matrix has excellent moldability, and the carbon fiber-reinforced composite materials obtained using the prepreg have good heat resistance. be.

Claims (1)

[Claims] 1. A prepreg for carbon fiber-reinforced composite material having an addition-curing polyquinoxaline oligomer represented by the general formula [] or/and [] as a matrix. R ₁ : nil, CH ₂ , O, CO, SO ₂ , S,
[Formula] [Formula] [Formula] Ar ₁ : [Formula] [Formula] [Formula] Y ₁ : H, CH ₃ .