Abstract: Provided is a new granulator for preparing granules from a powdery material by agglomerating it through a kneading action, comprising a receptacle and two screws having screw blades disposed within the receptacle in parallel alignment to ensure intermeshing of the screw blades. The novel granulator consists of a feeding zone, a kneading zone divided into an upstream section and a downstream section, and a breaking zone. In the feeding zone, the blades on the two screws are forwardly conveying blades. In the upstream section of the kneading zone, on one screw a backwardly conveying blade is first provided and a forwardly conveying blade follows, and on the other screw, a forwardly conveying blade comes first and a backwardly conveying blade follows, said alternate arrangement occurring at least once in each screw. In the downstream section of the kneading zone, the blades on both of the screws are backwardly conveying screws.

Abstract: A process for producing sodium percarbonate which comprises reacting sodium carbonate with hydrogen peroxide in a working solution of sodium carbonate, hydrogen peroxide and water, said reaction being carried out in the presence of at least one N,N,N',N'-tetra(phosphonomethyl)diaminoalkane of the following formula ##STR1## wherein R is either ##STR2## and n is 0 or 1 to 4, and at least one salt selected from the group consisting of phosphates, silicates and magnesium salts.

Abstract: A process for producing sodium percarbonate which comprises reacting sodium carbonate with hydrogen peroxide in the presence of a stabilizer againsts the decomposition of hydrogen peroxide in a working solution of sodium carbonate, hydrogen peroxide and water, said stabilizer being at least one N,N,N',N'-tetra(phosphonomethyl)diaminoalkane of the following formula ##STR1## wherein R is either ##STR2## and n is 0 or 1 to 4.