Abstract: A process for producing a stable acidic aqueous alumina sol containing columnar secondary particles having a length of 50 to 400 nm which are formed by face-to-face coagulation of rectangular plate-like primary particles having a length of one side of 10 to 40 nm and a thickness of 2.5 to 10 nm when observed through an electron microscope, by use of an aqueous alkali aluminate solution and liquid or gaseous carbon dioxide as starting materials. The obtained acidic aqueous alumina sol has a low viscosity and is stable for salts. The dried gel obtained from the sol is characterized in that the gel structure thereof is rigid even though it is porous.

Abstract: A process for producing a stable acidic aqueous alumina sol containing columnar secondary particles having a length of 50 to 400 nm which are formed by face-to-face coagulation of rectangular plate-like primary particles having a length of one side of 10 to 40 nm and a thickness of 2.5 to 10 nm when observed through an electron microscope, by use of an aqueous alkali aluminate solution and liquid or gaseous carbon dioxide as starting materials. The obtained acidic aqueous alumina sol has a low viscosity and is stable for salts. The dried gel obtained from the sol is characterized in that the gel structure thereof is rigid even though it is porous.

Abstract: The present invention relates to a process for preparing an aqueous solution of sulfonated melamine-formaldehyde resin, and a cement composition in which the solution and a setting retarder are added to a concrete, a mortar, a cement paste or the like. And the process comprises the following step (A), step (B) and step (C): Step (A): a step of adjusting an aqueous solution containing melamine (a), formaldehyde (b), sulfanilic acid (c) and an alkali substance (d) to (a):(b):(c)=1:2.5-3.5:0.5-1.5 in molar ratio and its pH to 8.0-13.5, and thereafter heating the aqueous solution at 50-90° C. to conduct the reaction until free sulfanilic acid decreases to 40-90 mol % of the amount of sulfanilic acid charged; Step (B): a step of adding an inorganic acid to the reaction liquid obtained in the step (A) to adjust its pH to 6.0-8.0, and thereafter heating the reaction liquid at 50-90° C.

Abstract: The present invention relates to a process for preparing an aqueous solution of sulfonated melamine-formaldehyde resin, and a cement composition in which the solution and a setting retarder are added to a concrete, a mortar, a cement paste or the like. And the process comprises the following step (A), step (B) and step (C): Step (A): a step of adjusting an aqueous solution containing melamine (a), formaldehyde (b), sulfanilic acid (c) and an alkali substance (d) to (a):(b):(c)=1:2.5-3.5:0.5-1.5 in molar ratio and its pH to 8.0-13.5, and thereafter heating the aqueous solution at 50-90° C. to conduct the reaction until free sulfanilic acid decreases to 40-90 mol % of the amount of sulfanilic acid charged; Step (B): a step of adding an inorganic acid to the reaction liquid obtained in the step (A) to adjust its pH to 6.0-8.0, and thereafter heating the reaction liquid at 50-90° C.

Abstract: A product obtained by reacting a sulfonated amino resin and an amino group-containing substance in a weight ratio of from 1:0.05 to 1:3.

Abstract: A device for rethreading and cleaning threaded pipe studs having an elongated casing having an outside surface provided with flat portions for attaching to a torquing means, which casing is provided with a straight channel therethrough shaped to allow passage of the pipe stud with at least a portion of the channel sidewalls having an inside diameter slightly larger than the outside diameter of the pipe studs, and having multiple threading dies attached to the channel sidewalls at one open end with the teeth protruding perpendicularly from the channel sidewalls, wherein the teeth on each threading die projects consecutively shallower into the channel as they progress from the open end.