It is preferable that at least one of R4, R5 or R6 represent a substituent other than hydrogen, and more preferable that the alkyl portion of the alkyl allyl amine represented in formula (2) below be a branched alkyl group, more preferably, a tertiary alkyl group, more preferably a tertiary butyl group, and most preferably a tertiary octyl group: The alkyl group may also include methylene spacers