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AssigneeNippon Shokubai Co., Ltd.
InventorsHirotama Fujimaru, Kunihiko Ishizaki, Nobuyuki Harada, Sei Nakahara
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The invention provides a hydrophilic resin and an absorbent article, both of which display still less coloring and discoloring when preserved for a long time. The hydrophilic resin is any one of: 1) a hydrophilic resin, obtained by a process including the step of polymerizing a monomer component including a major proportion of either one or both of acrylic acid and its salt which merely have a content of at most 0.20 ppm in total of hydroquinone and benzoquinone; 2) a hydrophilic resin, comprising a major proportion of an acrylic polymer and a minor proportion of either one or both of hydroquinone and benzoquinone, with the hydrophilic resin further comprising a quinhydronation inhibitor of 10˜1,000,000 times the total weight of hydroquinone and benzoquinone; 3) a hydrophilic resin, comprising a major proportion of an acrylic polymer and merely having a coloring degree (YI) of at most 20 after being left under conditions of the open system, 70° C., 65% RH for 1 week; and 4) a hydrophilic resin, which is a water-absorbent resin and is surface-crosslinked or surface-impregnated with a polyhydric alcohol and displays pH of 5.5 or less in a physiological salt solution and has an absorption capacity of 20 g/g or more for a physiological salt solution under a load of 50 g/cm2. In addition, the absorbent article comprises the above hydrophilic resin.
A crosslinked water-absorbent resin which is internally-crosslinked, which is obtained by aqueous solution polymerization or reverse-phase suspension polymerization, which has a water-soluble content of 25 weight % or below, which has an absorption capacity of 20 g/g or more for a physiological salt solution under a load of 50 g/cm2, over a period of 60 minutes, wherein the physiological salt solution is 0.9 wt % aqueous sodium chloride solution and which is obtained by a process comprising the steps of:
A crosslinked water-absorbent resin having a water-soluble content of 25 weight % or below, comprising a major proportion of an acrylic polymer which is obtained by a process including the step of polymerizing a monomer component including a major proportion of either one or both of acrylic acid and its salt, wherein the crosslinked water-absorbent resin has an absorption capacity of 20 g/g or more for a physiological salt solution under a load of 50 g/cm2 over a period of 60 minutes, wherein the physiological salt solution is 0.9 wt % aqueous sodium chloride solution, and wherein the coloring degree (YI) is at most 20 after the crosslinked water-absorbent resin is left exposed to the atmosphere at 70° C. and 65% RH for 1 week.
A crosslinked water-absorbent resin having a water-soluble content of 25 weight % or below and further having an absorption capacity of 20 g/g or more for a physiological salt solution under a load of 50 g/cm2 over a period of 60 minutes wherein the physiological salt solution is a 0.9 wt % aqueous sodium chloride solution, wherein the crosslinked water-absorbent resin is obtained by a process including the step of polymerizing a monomer component including a major proportion of either one or both of acrylic acid and its salt which have a content of at most 0.20 ppm in total of hydroquinone and benzoquinone “based on acrylic acid”.
A crosslinked water-absorbent resin which has an absorption capacity of 20 g/g or more for a physiological salt solution under a load of 50 g/cm2 over a period of 60 minutes wherein the physiological salt solution is a 0.9 wt % aqueous sodium chloride solution, which has a water-soluble content of 25 weight % or below and which is obtained by a process comprising the steps of:
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