ADDITIVE FOR PAPER MAKING AND PAPER PRODUCED BY USING THE ADDITIVE

PROBLEM TO BE SOLVED: To provide an additive for paper making that is inexpensive and has excellent paper hardness and storage stability.SOLUTION: The additive for paper making comprises as a main component (C) a reaction product produced by reacting (A) starch modified with a crosslinkable vinyl monomer having a chain transfer substituent and (B) an acrylamide polymer in the presence of a peroxide. The use ratio of the modified starch (A) and the acrylamide polymer (B) [(A)/(B)] is 5/95 to 80/20. The chain transfer substituent of the vinyl monomer is N-substituted amide group and, for example, the vinyl monomer is at least one kind selected from N,N-dimethylacrylamide, N,N-diethylacrylamide and 2-acrylamide-2-methylpropanesulfonate.SELECTED DRAWING: None 【課題】安価でかつ優れた紙力強度および保存安定性を有する製紙用添加剤の提供。【解決手段】連鎖移動性置換基を有する架橋性ビニルモノマーで変性させた澱粉（Ａ）およびアクリルアミド系重合体（Ｂ）を、過酸化物の存在下で反応させて得られる反応生成物（Ｃ）を主成分として含有する製紙用添加剤。反応生成物（Ｃ）における前記変性澱粉（Ａ）およびアクリルアミド系重合体（Ｂ）の使用割合［（Ａ）／（Ｂ）］が、５／９５〜８０／２０である製紙用添加剤。前記ビニルモノマーの連鎖移動性置換基がＮ−置換アミド基であり、例えば、前記ビニルモノマーがＮ，Ｎ−ジメチルアクリルアミド、Ｎ，Ｎ−ジエチルアクリルアミドおよび２−アクリルアミド−２−メチルプロパンスルホン酸から選ばれる少なくとも１種である製紙用添加剤。【選択図】なし