| 摘要 |
A novel copolymer obtained by copolymerizing (A) 20 to 90 wt.% N-vinylacetamide, (B) 7 to 70 wt.% 2-acrylamido-2-methylpropanesulfonic acid and/or salt thereof, and (C) 3 to 40 wt.% vinyl monomer other than the ingredients (A) and (B) [the total amount of the ingredients (A), (B), and (C) is 100 %]; and a regulator for digging mud, characterized by comprising the copolymer. The regulator can impart satisfactory flowability, lubricating properties, and resistance to loss of water to digging mud even under high-temperature high-pressure conditions and even when the mud contains salt in a large amount.
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