Patent ID: 7041168

Claim:
A process of preparing a construction material system, comprising extruding a construction material with an additive comprising an irreversibly crosslinked cellulose derivative, wherein the irreversibly crosslinked cellulose derivative is prepared by a process comprising, (a) alkalizing cellulose with aqueous alkali metal hydroxide solution in the presence of a suspension medium, (b) reacting the alkalized cellulose with one or more alkylene oxides, (c) reacting the alkalized cellulose of step-(b) with an alkyl halide present in the suspension medium, (d) subsequently or simultaneously reacting the alkalized cellulose with a crosslinker in an amount of 0.0001to 0.05 eq, where the unit “eq” represents the molar ratio of the crosslinker relative to the anhydroglucose unit (AGU) of the cellulose used, and (e) optionally performing at least one of steps (i), (ii), (iii) and (iv), (i) adding a material selected from the group consisting of alkali metal hydroxide, alkylating agent and combinations thereof, (ii) separating off the irreversibly crosslinked cellulose derivative from the reaction mixture, (iii) purifying the irreversibly crosslinked cellulose derivative, and (iv) drying the irreversibly crosslinked cellulose derivative.