Soluble terminally modified imide oligomer using 2-phenyl-4,4'-diaminodiphenyl ether, varnish, cured product thereof, imide prepreg thereof, and fiber-reinforced laminate having excellent heat resistance

Abstract

Disclosed is a novel terminally modified imide oligomer having excellent solubility in organic solvents, excellent solution storage stability, and excellent molding properties such as low melt viscosity. Also disclosed are a varnish obtained by dissolving the terminally modified imide oligomer in an organic solvent; a cure product obtained by using the terminally modified imide oligomer and having excellent thermal and mechanical characteristics such as heat resistance, elastic modulus, tensile strength at break and tensile elongation at break; a prepreg; and a fiber-reinforced laminate. The soluble terminally modified imide oligomer is represented by general formula (1). In the formula, R1 and R2 each represents a divalent aromatic diamine residue; R3 and R4 each represents a tetravalentaromatic tetracarboxylic acid residue; R5 and R6 each represents a hydrogen atom or a phenyl group, with R5 or R6 being a phenyl group; m and n satisfy the following relations: m >= 1, n >= 0, 1 <= m+ n <= 20 and 0.05 <= m / (m + n) <= 1; and the repeating units may be arranged in blocks or randomly.

Description

technical field The present invention relates to terminal-modified imide oligomers, varnishes, and cured products thereof, and in particular, to materials usable for parts in a wide range of fields requiring easy formability and high heat resistance, including aircraft and space industry equipment. Background technique Aromatic polyimide has the highest level of heat resistance among polymer systems, and is also excellent in mechanical and electrical properties, so it is used as a raw material in a wide range of fields. On the other hand, aromatic polyimides generally lack processability, and are especially unsuitable for use as matrix resins for melt molding and fiber-reinforced composite materials. Therefore, imide oligomers whose ends are modified with thermal crosslinking groups have been proposed. Among them, imide oligomers whose ends are modified with 4-(2-phenylethynyl)phthalic anhydride are excellent in balance of formability, heat resistance and mechanical proper...

AI Technical Summary

Problems solved by technology

However, these end-modified imide oligomers are only 20% by weight or less dissolved in N-methyl-2-pyrrolidone (hereinafter referred to as NMP) and the like at room temperature (in this specification, room temperature refers to 23°C ± 2°C). Organic solvents, and when this varnish is stored, gelation is often observed after a few days, and there is a problem that it is difficult to store high-concentration varnishes stably for a long time

In addition, as one of the methods for improving solubility, for example, the use of acid anhydride monomers having a more curved and non-planar structure, such as 2,2,3',3'-linked The method of copolymerization of pyromellitic dianhydride, but it is usually observed that the elongation at break becomes smaller and the tendency to become brittle

In addition, diamine monomers having a sterically bulky structure described in Patent Document 4 and Patent Document 5, such as 9,9-bis(4-(4-aminophenoxy)phenyl)fluorene, can be cited. Copolymerization methods, but a lowering of their glass transition temperature and a tendency towards lower elongation at break and brittleness are also generally observed

In addition, for imide oligomers for pressure molding and transfer molding described in Patent Document 5, methods such as lowering the degree of polymerization or softening the diamine structure used in order to obtain high fluidity can be mentioned, but With this method, although the solubility of the imide oligomer increases, the glass transition temperature of the terminal cured product tends to decrease significantly