Synthesis of polyisocyanurates by thermal rearrangement of polycyanurates

Abstract

Polyisocyanurates have been successfully prepared by the thermal rearrangement of polycyanurates, which were obtained from 2,4-dichloro-6-methoxy-1,3,5-triazine and bisphenol monomers. The thermal rearrangement was carried out in the presence of a small amount of tetrabutylammonium bromide (TBAB) as a catalyst at 200 C for 30 or 60 min in an argon atmosphere, and the degree of arrangement was greater than 95%. Transparent and amorphous polyisocyanurate films were obtained and showed a good thermal stability with a 5% weight loss temperature above 340 C in nitrogen and the glass transition temperature above 210 C. Films with a 10-mm thickness exhibited an excellent transparency above 90% at 400 nm. Furthermore, the thermal rearrangement of 2,6-bis(4-methoxyphenyl)-6-methoxy-1,3,5-triazine to 1,3-bis(4-methoxyphenyl)-5-methyl-1,3,5-triazinane-2,4,6-trione was investigated in detail. It was found that the complete thermal rearrangement was successfully accomplished in the presence of 2 wt % TBAB at 150 C for 20 min in an argon atmosphere.

Synthesis and characterization of polycyanurates as dismantlable adhesives

“…The molecular weights of the polycyanurates rapidly decrease during the thermal rearrangement to polyisocyanurates in air, as previously reported . Based on this finding, the DA with a high debonding temperature was developed.…”

“…The results are summarized in Table . A standard polycyanurate ( P1 ) was prepared by the phase‐transfer‐catalyzed polycondensation of DMT with M1 in the presence of quaternary ammonium salts following published procedures in previous articles . However, random copolymers, polycyanurates P2, P3, and P4 , were synthesized using M1 and a comonomer, M2 or M3 , respectively.…”

“…2,4‐Dichloro‐6‐methoxy‐1,3,5‐triazine ( DMT ) was kindly donated by Sankyo Chemical, and was recrystallized from n ‐hexane. P1 was prepared by the phase‐transfer‐catalyzed polycondensation of DMT with M1 in the presence of quaternary ammonium salts following procedures in previous articles …”

“…During the study of the synthesis of polycyanurates and their electric and optical applications, we found that the molecular weights of the polycyanurates rapidly decreased during the rearrangement to polyisocyanurates by a thermal treatment . For instance, the number‐average molecular weight ( M n ) value of a polycyanurate decreased from 104,000 to 23,000 after the thermal rearrangement at 180 °C for 5 min in air …”

“…In a previous study, we carefully investigated the thermal rearrangement of 2,4‐bis(4‐methoxyphenyl)‐6‐methoxy‐1,3,5‐triazine under various conditions, and found that the hydrolysis of aryl imidates in the presence of moisture occurred during the thermal rearrangement (Scheme ) …”