| 摘要 |
<p>Polymers of methacrylic acid, partly esterified with mono-alkyl-polyalkylene glycol, are used as dispersants for aqueous compositions of anhydrous calcium sulfate; these dispersants make it possible to improve the maintenance of fluidity and to control the time of onset and/or end of setting. The use of a dispersant (I) for aqueous compositions of anhydrous calcium sulfate (II) which makes it possible to improve the maintenance of fluidity over time and to control the time of onset and/or completion of setting. This dispersant (I) comprises at least 75% (by number) of random linear chains made up of units of formula (1) and (2), with units of type (2) making up 5-60% of the total (1 + 2) and with oxypropylene groups being distributed randomly (or not) between the oxyethylene groups. X = H, alkali or alkaline earth metal, or ammonium; n = 1-250; m = 0-100 with m being less than n; R = 1-12C alkyl. Independent claims are also included for: (1) the use for the same application of a mixture of dispersants comprising 50-90 wt% (I) and 10-50 wt% of another dispersant (IA) containing at least 75% polymer chains with units of formula (3) and (4) (2) aqueous compositions of (II) containing (I) (3) aqueous compositions of (II) containing mixtures of (I) and (IA) as defined above (4) mixtures of (I) and (IA) as defined above. X1, p, q, R1 = as defined for X, n, m and R respectively (same or different in each case).</p> |
