The Curing of Epoxy Resins with the Aluminium AcetylacetonateOrganoboron Compounds Catalyst System

J-STAGE
  • IIJIMA Takao
    Department of Applied Chemistry, Faculty of Engineering, Yokohama National University
  • SASHIDA Nobuyuki
    Department of Applied Chemistry, Faculty of Engineering, Yokohama National University
  • KAKIUCHI Hiroshi
    Department of Applied Chemistry, Faculty of Engineering, Yokohama National University

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Other Title
  • アルミニウムアセチルアセトナート-有機ホウ素化合物系触媒によるエポキシ樹脂の硬化反応

Description

Novel catalysts were found for the curing of epoxy resins. The catalysts consisted of aluminum acetyl-acetonate (Alacac3) and organoboron compounds, and had a wide reactivity range. The organoboron compounds used were trialkyl borates (B (OR) 3, R = CH3, C2H5, i-C3H7 and n-C4H9) and diisopropyl phenylboronates (R′PhB (Oi-Pr), R′=, ο-NO2, m-NO2, p-NO2, p-Cl, H and p-OMe). The catalysts was more effective for the curing of 3, 4-epoxycyclohexylmethyl 3, 4-epoxycyclohexanecarboxylate (Celoxide 2021) than for that of bisphenol A-diglycidyl ether (Epikote 828). The Alacac3-trialkyl borates catalyst system showed the same activities, independent of the kind of the esters. The gel time of Celoxide 2021 was 6 min at 100°C using the catalyst composed of Alacac3 1.0 phr and B (OBu) 3 4.0 phr. The Hammett plot for the curing rate of Celoxide 2021 was linear in the Alacac3-diisopropyl phenylboronates catalyst system. The introduction of electron-attracting groups into the benzene ring accelerated the curing rate and vice versa. The gel time of Celoxide 2021 with Alacac3 (1.0 phr) -diisoproryl p-nitrophenylboronate (1. 6 phr) was 2 minat 100°C in the same curing conditions as that with the Alacac3-B (OBu) 3. The reactivities of 2-aryl-4-phenyl-1, 3-2-dioxaborolane decreased to a con-siderable extent owing to their hydrolytic stabilities. The active species was estimated as the following structure, based on the reaction of Alacac3 and phenylboronic acids.<BR>acac2A1 OH B R' O

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