synopsisA study of a series of metal compounds as promoters of acyl peroxide and hydroperoxide dissociation in an unsaturated polyester-styrene resin solution has shownvanadic and vanadyl chelates to be the most active. All of the results were compared to a standard cobalt-methyl ethyl ketone peroxide promoter-catalyst system. It was found that the reactivity of 2 mg. of vanadium or vanadyl ion as vanadic or vanadyl acetyl acetonate with respect to 1% cumene hydroperoxide was greater than 24 mg. of cobalt as cobalt naphthenate with respect to 1% methyl ethyl ketone peroxide. This is significant, in that considerably less metallic promoter can be used at ambient temperatures for the fabrication of finished articles with considerably less associated color. Of the vanadium compounds studied, vanadic and vanadyl chelates were about equally reactive. Vanadyl acetyl acetonate was considered the promoter of choice, since vanadic acetyl acetonate solutions appeared to be air-oxidized readily. Study has shown that benzene solutions of vanadic acetyl acetonate lost some activity after a week, whereas chloroform solutions of vanadyl acetyl acetonate remained stable for a period of six to nine months. The utility of vanadium promoters for ambient temperature redox polymerization would be enhanced if they could be incorporated into unsaturated polyester resins at the time of preparation. However, results obtained indicated that both vanadic and vanadyl chelates limit the stability of such prepromoted resins, normally leading to gelation in about 17 days. A further indication of the utility of vanadium chelates as redox promoters was the observation that these materials are reactive towards diacyl peroxides as well as hydroperoxides. Vanadium chelates were the only materials studied which showed this wide spectrum of reactivity.
synopsisOf a series of copromoter metal species investigated, it waa found that several of these were strongly effective in synergizing the redox polymerization activity of vanadyl acetyl acetonate. Notable among these were Cu+2, Fe+3, Ti+3--Ti+6, Be+2, Alf3, and Th+4. Particularly notable was the effect of Ti +3-Ti +6, which strongly synergized the rate a t which complete polymerization was obtained, eg., within 15 min. as compared to 20 hr. when vanadyl acetyl acetonate was used alone. Synergism with copromoter metal species was noted with as low as 2 mg. titanium used in conjunction with 2 mg. of vanadyl ion as the chelate. A minimal concentration for synergistic effect was noted for those metal species thus studied. This was found to range from 0.18 to 0.41 mmole of copromoter metal species per 100 g. of resin system. Advantage was taken of the peculiar effect of manganic acetyl acetonate to prolong gel times without affecting the rate at which complete polymerization was obtained. By using manganic acetyl acetonate in conjunction with vanadyl acetyl acetonate, it was possible to prolong the shelf-life of a prepromoted resin from 17 to at least 110 days.
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