CS270316B1 - Process for preparing sodium tripolyphosphate - Google Patents

Abstract

Before injection into the slurry, phosphoric acid ester is added to the mixture of orthophosphate solutions in an amount of up to 0.05% by weight, based on the finished sodium tripolyphosphate.

Description

The invention relates to a process for the production of granular sodium tripolyphosphate (Νβ.Ρ, Ο. - pentasodium triphosphate) with a bulk density of more than Soo kg / rn and an increased abrasion resistance of the particles.

At present, granular sodium polyphosphate with a low bulk density is increasingly used as a component in the manufacture of laundry detergents by dry route, where the other components are sprayed and admixed dry to the granular sodium tri-polyyl phosphate.

In order to save energy and prevent the hydrolysis of sodium tripolyphosphate, this manufacturing process is gaining importance in the washing powder industry.

Sodium tripolyphosphate suitable for these purposes must, in particular, meet the following requirements: the sodium tripolytostate particles must, as far as possible, be resistant to handling, in particular pneumatic conveying, be as granular as possible and contain only a small proportion of dust and must be available in a wide range rozmez! bulk scales.

Sodium tripolyphosphate with increased particle strength can be produced by granulating ground tripolyl phosphate with the addition of water or phosphate solutions on granulating plates or granulating drums. Usually, the granulation is followed by sui-ning, respectively calibrating and separating the individual fractions on the sieves. The tripolyphosphate thus obtained exhibits increased granule strength, but the product thus obtained exhibits a high bulk density of from 600 to 1000 kg / m.

A preferred method for producing sodium tripolyphosphate from the emission of solutions of mononatlumine phosphate and dllumine phosphate having a molar ratio of P 1 Na - 1.666 is their drying in spraying suits and subsequent calcination to give sodium tripolyphosate. In this process, sodium triol polyeate is obtained in the form of granular beads. These beads are tight-walled and exhibit poor handling resistance. Reduction of the bulk density can be achieved by the addition of substances which decompose at elevated temperatures with the formation of gases which are formed! the balls continue to inflate. The beads then have thinner walls and are less rigid. For example, urea or phosphorus compounds with a power of less than 5 are used as blowing agents.

Increased handling resistance of the beads can be achieved by the addition of alkaline earth compounds, especially sulfates, inorganic boron compounds, by adding polyphosphates to the mixture of orthophosphate solutions prior to spraying them into the spray spray and hydrating the tripolyphosphate.

It has been found that the addition of phosphoric acid esters to solutions of orthophosphates prior to spraying in amounts of up to 0.1% by weight, based on halo tripolyphosphate, reduces the bulk density of the produced tripolyphosphate without reducing the mechanical strength of the particles, the particle size of which varies largely below 0. 2 mm, which increases their resistance to damage during handling, in particular during pneumatic transport.

In this way it is possible to produce sodium tripolyphosphate with a bulk density less than

O

500 kg / m and increased particle strength without the need to substantially modify or expand the process equipment and change the process mode to a larger extent.

Claims (2)

PURPOSE OF THE INVENTION 1. A process for producing sodium tripolyphosphate having a bulk density of less than Soo kg / m < 2 > and increased particle strength, characterized in that phosphoric acid ester is added in amounts of up to 0.5% by weight based on the finished sodium tripolyphosate. CS 27o316 Bl 2. 1. The process of claim 1 wherein the phosphoric acid ester is added to the mixture of the orthophosphate solutions prior to spraying into the oven in an amount of up to about 0.5% by weight and an alkaline earth metal salt of up to about 0.5% by weight based on the finished tripolyphosphate. sodium.