| 摘要 |
A plaster composition is disclosed having a long setting time, which composition comprises a gypsum-based plaster and an effective amount of a setting retarding agent comprising a polymer having a molecular weight of less than 1000 of the formula: <IMAGE> (I) wherein R1 is hydrogen or methyl, R2 is COOH, COOR4, wherein R4 is C1 to C4 alkyl, CONH2 or CN, R3 is hydrogen or methyl, X is a sodium, potassium, lithium, calcium, magnesium, or ammonium ion, and x and y designate the molar ratio of the two monomers forming the setting retarding agent of the formula I.
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