| 摘要 |
PROBLEM TO BE SOLVED: To improve water reducing property, slump loss preventing property and strength exhibiting property by absorbing a specified copolymer in fine porous silica powder. SOLUTION: A polyoxyalkylene compd. represented by the formula R<1> O (AO)n R<2> [where R<1> is 2-5C alkenyl, AO is 2-4C oxyalkylene including >=50mol% oxyethylene, R<2> is H or 1-18C hydrocarbon and (n) is 1-500 as the average mol number of added alkylene oxide] is copolymerized with maleic anhydride, maleic acid or its salt in a molar ratio of 3:7 to 7:3 in water or an org. solvent in the presence of a polymn. initiator to obtain a copolymer. Fine porous silica powder having <=0.03μm primary average particle diameter, 50-400m<2> /g specific surface area, 0.10-0.30g/ml apparent specific gravity and 10-300ml/100g oil absorption is mixed with an aq. soln. of the copolymer and this copolymer is absorbed in the fine porous silica powder.
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