DE2360502A1 - Solid water-contg. alkali silicates - treated with water vapour to improve solubility in water - Google Patents

Abstract

Prodn. of solid, water-contg. alkali silicates is improved in that granules of Na- or K-silicate, dried by spraying or hot-rolling, are subjected to the action of water vapour at 100-150 degrees C. pref. after preheating to a temp. between 100 degrees C and the treatment temp. The molar ratio SiO2:alkali metal oxide is 2 to 4:1 (pref. 3.2 to 4:1). these alkali silicates can be used in alkaline detergent compsns., esp. for industrial applications, and also in silicate-base glues and paitns. They dissolve in water more rapidly than untreated solid alkali silicates and, in contrast with the latter, leave hardly any undissolved residue (1% compared with i0% in the case of some known prods). They are more convenient that solns. of water glass because of the smaller water content, easy handling and transport, suitability for incorporation in solid detergent compsns., etc.

Description

4 Düsseldorf * November 30th, 1975 Hentoel & CfeGHibH

Henkel Str. 67 'Patent Department

Br-. £ la / B.

Patent shares

"Process for the production of solid, water-containing Alkali silicates "

The invention relates to a method for the production of solid ,, hydrous alkali silicates that are readily soluble in water.,

Alkali silicate solutions known to be converted by spray or roller drying in powder form © products "The resulting solid sodium and Kaliumsilikafce generally have a residual water content of about 14 to 20 Grew" - ^$.

Such spray- or roller-dried solid alkali silicates have the advantage over waterglass solutions of lower water ballast and relatively low reactivity to any added components. A disadvantage of these products is their relatively slow reading speed. This is all the smaller, the greater the SiOp: alkali metal oxide ratio and the smaller the water content. Above all, the solid alkali metal silicates produced by TrocLnungsprozesse not solve · residue. In water * The ^one portion of insoluble materials can be up to 20 Grew .- ^ and more.

Attempts have already been made to determine the ifose behavior of the products by a higher residual water content or by adding rod,

punches that favor a re-uptake of water, such as Polyglycols, to improve ·. Such products tend to be However, because of their higher water content for baking and / or increased hygroscopicity.

It has now been found that these disadvantages can be avoided by following the manufacturing process described below served by solid, water-containing alkali silicates with improved water solubility. The new procedure is characterized by that spray-dried or roller-dried, granular sodium or potassium silicates water vapor with a temperature of 100 to 1508 C allowed to act.

The granular sodium or potassium silicates are dehydrated from the usual Aikallsllikatlösung with a molar ratio SiOg ι alkali metal oxide in the range of 2 s 1 to 4 ϊ 1, preferably from 5.2: 1 to I: 1, and a SiOu concentration of 20 to 57 wt .- ^ obtained. In addition to roller drying, spray drying or atomization drying are particularly suitable for dehydration. The latter is generally used in spray towers: at temperatures above 100 ° C, preferably at from 120 to I50 ⁰ 0 performed.

The steam treatment of the granular alkali silicates can be carried out in an apparatus arrangement in which the material spread out on the sieve bottom is removed from the overheated steam from below is flowed through. Furthermore, the water vapor can be allowed to act on the solid silicate in the fluidized bed process. It is also possible, to carry out the process according to the invention in a trickle column, whereby the granular alkali silicate trickles from above against a stream of water vapor directed from below upwards. In any case, care must be taken that the surface of the alkali silicate grains as evenly as possible to the action of the water vapor is put on. In addition, a certain Minc'est-

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dwell time must not be exceeded. This minimum dwell time is generally 15 seconds to 2 minutes.

It has proven to be expedient to heat the solid alkali metal silicates to temperatures between 100 ° C. and the desired treatment temperature before they overheat Exposed to water vapor. This procedure remains the originally existing water content of the solid products is practically constant. Are the alkali silicates without previous Warming mr'.t treated water vapor so is a minor one Observe an increase in the residual water content.

When using the method described here on spray or roller-dried sodium and potassium silicates produce products with significantly improved dissolving properties. The one in the source material Any insoluble fraction present is eliminated by treatment with overheated Water vapor reduced to such an extent that it is neglected in practice can be. With appropriate process management, products can be obtained which are less than $ 1 insoluble Contain substance. In addition, the sodium and potassium silicates treated with superheated steam have a much higher rate of dissolution than the untreated products.

The alkali silicates which can be prepared in the manner described can in alkaline cleaning agents, especially in industrial cleaners, as well as in adhesives and paints based on silicate Find application.

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example 1

In each case 5 kg of spray-dried waterglass with a molar ratio SiO ₂ : Na ₂ O = 3.3 and a water content of 17.2 % were exposed on a sieve inside a heated vessel at normal pressure to flowing steam that was superheated to different degrees for 2 minutes. The temperature was measured with a thermocouple attached to the screen surface.

The insoluble residue of the starting material and the steamed products were obtained in the following manner determined: In each case 20 g of substance were suspended in 400 ml of water and stirred at 40 ° 0 for 10 minutes. The unsolved one The residue was filtered off through a filter crucible and calcined at 750 ° C. for 20 minutes.

To determine the water content, the starting material and the treated products were placed in a filter crucible Heated to 750 ° C for 20 minutes,

The test results are shown in Table 1.

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TABLE 1

Steam treatment of spray-dried water glass

Vers. No. Steam temp. water insoluble Setback ⁰ C % % untreated - 17.2 15.2 1 . 143 17.6 7.6 2 158 19.1 2.7 128 20.8 1.0 4th 119 ■ 21.6 .0.25 5 114 22.2 0.17

Example 2

In each case 5 kg of roll-dried waterglass with a molar ratio SiO ₂ : Na ₂ O = 3.3 and a water content of 18.5% were treated with superheated steam as described in Example 1.

The water content and the insoluble residue were determined in the same way as in Example 1.

The test results are shown in Table 2.

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TABLE 2

Steam treatment of roller-dried water glass

Vers. No. Steam temp.
⁰ C water insoluble Setback
. .. * untreated 18.5 14.0 1 144 17.6 5.6 2 134 20.3. 3.8 3 126 19.0 1.9 4th 118 21, " 0.9 5 111 22.4 0.8

Example 3

In each case 5 kg of spray-dried water glass with a molar ratio SiOp: Na "0 = 3.3 and a water content of 18.1 ^ were in the arrangement described in example 1 heated to 100-120 ° C. with the aid of a stream of hot air. The preheated goods was then treated with flowing steam at 126 ° C. for 3 minutes.

The test results are summarized in Table 3.

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TABLE J

Steam treatment of preheated, spray-dried Water glass

Vers.No. Preheating temp. water insoluble residue ° C * *. untreated 18.1 8.1 1 100 18.7 0.88 2 110 18.1 0.74 3 120 18.0 1.03

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Claims (2)

Henkel & Cie GmbH 4855 patent department patent claims 1) A process for the preparation of solid, water-containing alkali metal silicates with improved Wasserl-öslichkeit, characterized in that, allowed to act water vapor at a temperature of 100 to I50 C ⁰ to spray- or roller-dried granular sodium or potassium silicates. 2) Method according to claim 1, characterized in that t.ian the granular sodium or calcium silicates before the steam Effect on temperatures between 100 ° C and de: ' heat the desired temperature of the steam treatment "; 509824 / CU38