PROBLEM TO BE SOLVED: To provide a water holding agent for a disposable body warmer in which the fall of the water capacity of gel is very little even if it is stored at a high temperature for a long period of time and moreover the gel, which is excellent in storage stability without varying the shape of the gel, is obtained.SOLUTION: In the water holding agent for the disposable body warmer which comprises an absorptive resin (X) which consists of a crosslinked polymer (A) comprising a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) which becomes water-soluble by hydrolysis, and an internal crosslinking agent (b) as indispensable constituent units, and respective values of the content of an unreacted vinyl monomer in (X) and the viscosity retention of the water absorption gel of the water holding agent satisfy specific ranges.COPYRIGHT: (C)2011,JPO&INPIT【課題】 高温で長期間保存してもゲルの保水量の低下が極めて少なく、またゲルの形状が変化することもなく保存安定性に優れたゲルが得られる、使い捨てカイロ用保水剤を提供する。【解決手段】 水溶性ビニルモノマー(a1)および/または加水分解により水溶性となる加水分解性ビニルモノマー(a2)、並びに内部架橋剤(b)を必須構成単位とする架橋重合体(A)からなる吸収性樹脂(X)を含有してなる使い捨てカイロ用保水剤であり、(X)中の未反応ビニルモノマーの含有量、および保水剤の吸水ゲルの粘度保持率の各値が特定の範囲をともに満足する使い捨てカイロ用保水剤。【選択図】 なし
