The Dow Chemical Company

Carl P Strange

Clark W Gibson

Gordon Y Liu

George K Greminger, Jr

Albert C Tsang

Christopher D Messelt

Harold B Martin, Jr

Samuel A Pence, Jr

Non-gelling cellulose ethers are purified by mixing same with a dialdehyde under acidic conditions and under high agitation, forming a slurry of the treated cellulose ether, rapidly transferring the slurry to a filter and then dewatering said slurry.

Process for preparing cellulose ethers

Higher reaction efficiencies are seen in cellulose etherification reactions when the reagents are continuously added to alkali cellulose at elevated temperatures. In particular, mixed hydroxyalkylcellulose ethers are prepared with higher reaction efficiencies using this process. In an especially preferred embodiment, hydroxypropylmethylcellulose is prepared by continuously adding propylene oxide to heated cellulose containing a small amount of caustic, adding more caustic and then continuously adding methyl chloride at elevated temperatures.

Process for preparing hydroxyalkylcellulose ethers

Cellulose derivatives having a controlled molecular weight are prepared by adjusting oxygen concentration as measured by analyzing the quantity of oxygen in the head space of the reaction vessel to a level such that the cellulose derivative prepared therein has a desired solution viscosity. The cellulose derivative is then prepared in the reaction vessel without substantially increasing the quantity of oxygen in said reaction vessel.

Process for preparing cellulose derivatives

Polysaccharide ethers are prepared in a novel continuous process in which a slurry of a polysaccharide, an alkali metal hydroxide, and an etherifying agent, with or without an inert diluent, are mixed in the substantial absence of molecular or free oxygen and fed through a sinuous tubular reactor under pressure, so that the etherification reaction is continuous. The apparatus for preparing the reaction mixture is also novel.

Method of preparing polysaccharide ethers and apparatus

Novel compositions comprise homogeneous mixtures of liquid carbon dioxide and an anhydrous lower alkanol gelled to a viscosity of at least 10 centipoises with a hydroxypropyl methylcellulose having a methoxyl degree of substitution of from 0.2 to 1.0 and a molar substitution of hydroxypropoxyl of at least 1.2. The compositions are employed in a method of treating a subterranean formation penetrated by a wellbore by injecting same under pressure down the wellbore and into the formation to stimulate production of natural gas or petroleum.

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Walker, LA, United States of America

Carl P Strange