Viscosifier & fluid loss control system

Claim 1

A composition capable of imparting to aqueous systems a combination of pseudoplasticity and fluid loss control comprising a mixture of: (a) a hydroxy containing aluminum component formed by mixing in an aqueous medium and under a high degree of agitation a water-soluble basic agent selected from the group consisting of an alkali metal aluminate, alkali metal hydroxide, ammonium hydroxide and mixtures thereof with a water-soluble acidic agent selected from an inorganic acid, aluminum chloride, aluminum sulfate, aluminum nitrate, their hydrates and mixtures thereof; at least one of said basic and acidic agents being an aluminum containing compound: said acidic and basic agents being reacted in a ratio such that the resultant product is capable of imparting to an aqueous medium a pH of from at least about 8 to about 10.3 in combination with (b) a cross-linked hydroxyalkyl cellulose reaction product, said reaction product formed by contacting in an aqueous medium a hydroxy C 1 -C 3 alkyl cellulose and from about 1 to 200 percent of stoichiometry based on the hydroxy groups of the cellulose of an agent capable of cross-linking said cellulose, said agent being epihalohydrin or said agent being a compound having at least one aldehyde group therein or a compound capable of generating an aldehyde group in situ; wherein the amount of component (a) to component (b) is in the ratio of at least about 0.75:1 to 3:1; the reaction between said hydroxyalkyl cellulose and epihalohydrin being carried out in an aqueous basic medium having a pH of about 9.5 or more and the reaction between said hydroxyalkyl cellulose and said compound having or capable of generating at least one aldehyde group therein being carried out in an aqueous acidic medium having a pH of about 5.5 or less.