N-vinyl lactam-based crosslinked polymer, cosmetic, absorbent agent for ink, and absorbent composite

Abstract

The invention aims to provide a crosslinked polymer having excellent moisture retention properties, an excellent ethanol absorption capacity, excellent adhesiveness to the skin when applied to the skin as a cosmetic, and a high concentration of an effective component. The invention relates to a N-vinyl lactam-based crosslinked polymer including: a structural unit derived from a N-vinyl lactam; and a structural unit derived from a crosslinking agent, the N-vinyl lactam-based crosslinked polymer having an ethanol absorption capacity of 3 to 40 g per 1 g of the N-vinyl lactam-based crosslinked polymer, the N-vinyl lactam-based crosslinked polymer containing a particle having an aspect ratio determined by the following method of 1.15 to 10 in a proportion of 10% to 100% (by number) of the total number of the N-vinyl lactam-based crosslinked polymer and having a proportion of an extractable of 35 mass % or less in 100 mass % of the entire polymer, the method being 'method of measuring aspect ratio' in which the aspect ratio is determined as a value obtained by measuring the major and minor axes of a primary particle of the N-vinyl lactam-based cross-linked polymer with an optical or electron microscope and dividing the major axis by the minor axis.