Production of sodium tripolyphosphate
AssigneeHoechst Aktiengesellschaft
InventorsRaban v.Schenck, Cent M. Eegdeman
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Abstract
The invention relates to a process for making sodium tripolyphosphate from wet-processed phosphoric acids which contain organic impurities, are neutralized and concentrated to give an orthophosphate solution or suspension which is sprayed in a spray tower in contact with one or more oxidants. More particularly, sodium tripolyphosphate, which is suitable for use in detergent slurries and causes the temperature determined after 1 and 5 minutes, respectively, in the hydration test (ROH) to be increased by at least 7.degree. C., is made; to this end, the wet-processed phosphoric acids are first admixed with the oxidants and then concentrated.
Claims6
In the process of making sodium tripolyphosphate in the presence of one or more oxidants, from wet-processed phosphoric acids containing organic impurities and having initially a P.sub.2 O.sub.5 content of less than 20 weight%, by neutralizing the phosphoric acid to a molar ratio of Na:P of 5:3 and one step spray drying the resulting orthophosphate solutions or suspensions in a spray tower, the improvement which comprises:
- (a) adding the oxidant to the phosphoric acid,
- (b) thereafter concentrating the acid to a P.sub.2 O.sub.5 content of 27 to 32 weight %,
- (c) neutralizing the concentrated acid and
- (d) subjecting the orthophosphate solution or suspension obtained to a one step spray drying process at temperatures within the range of 300.degree. to 500.degree. C. with the resultant formation of a sodium tripolyphosphate suitable for use in detergent slurries and yielding in the hydration test (ROH) a rise of temperature of at least 7.degree. C. between temperatures determined after 1 and 5 minutes.
Dependencies are inferred from the claim text.