Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1997-01-02
1998-09-15
Medley, Margaret
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
423334, 23313AS, 264118, 510532, C10B 3332
Patent
active
058075291
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for the production of silicate-based or silicate-containing builder granules with apparent densities of at least 600 g/l which show improved performance properties and to detergents or cleaning compositions containing such granules.
2. Discussion of Related Art
Systems containing only silicates, such as the crystalline layer-form disilicates, or combinations of such components with other ingredients of detergents or cleaning compositions have recently been described for use as builders or co-builders. Combinations of sodium carbonates and sodium silicates are also known, cf. European patent applications EP-A-0 488 868 and EP-A-0 561 656.
U.S. Pat. Nos. 3,912,649, 3,956,467, 3, 838,193 and 3,879,527 describe amorphous sodium silicate compounds obtained by spray drying of aqueous waterglass solutions to form light silicates, subsequent grinding, compacting and spheronizing with further removal of water from the ground material (cf. for example FIG. 3 of U.S. Pat. No. 3,912,649) as builders. The products used have a water content of around 18 to 20% by weight for apparent densities well above 500 g/l.
Amorphous sodium disilicates with a low water content of 0.3 to 6% by weight are known from European patent application EP-A-0 444 415. The amorphous sodium disilicate is said preferably to contain 0.5 to 2% by weight of water. These amorphous disilicates with their very low water contents are produced by a multistage process in which a powder-form amorphous sodium silicate with a water content of 15 to 23% by weight is initially prepared. This material is treated in countercurrent with waste gas at temperatures of 250.degree. to 500.degree. C. in a revolving tube furnace. The amorphous sodium silicate leaving the revolving tube furnace is size-reduced to particle sizes of 0.1 to 12 mm by means of a mechanical crusher and is then ground in a mill to particle sizes of 2 to 400 pm.
EP-B-0 374 017 describes typical water-containing high-density silicates in granular form containing 1 to 10% by weight of cellulose derivatives which improves the dissolving rate of the compacted granules. There is no reference in this document to multiple wash cycle performance or, in particular, to the inhibition of incrustation.
According to the teaching of European patent application EP-A-0 542 131, a sodium silicate containing water of crystallization can be produced by treating a 40 to 60% by weight aqueous solution of the sodium silicate with hot air in a turbodryer equipped with percussive tools. The drying product passes through a pseudoplastic state with a free water content of 5 to 12% by weight, based on the paste, which is used to form a granular product. These granules are dried under conditions which preclude embrittlement of the outer shell of the granules and hence disintegration of the granule structure. It is possible in this way--while avoiding the so-called popcorn effect--to produce water-soluble sodium silicates with specific gravities of 0.5 to 1.2 which are distinguished by complete solubility in water at ambient temperature.
Earlier German patent application P 44 00 024.3 describes sodium silicates with a modulus (molar ratio of SiO.sub.2 to Na.sub.2 O) of 1.3 to 4 in the form of a fine-particle solid with a flake structure, these silicates being X-ray-amorphous and having absolute water contents of at most 15% by weight (overdried silicates) and apparent densities below 500 g/l. These X-ray-amorphous silicates are distinguished in particular by the presence of microcrystalline solid regions which can be detected by electron diffraction, but not by X-ray diffraction. By virtue of their flake structure, the silicates in question have a very high specific BET surface. The particle sizes are preferably in the range from 10 to 200 pm. Silicates with an apparent density below 400 g/l and, more particularly, in the range from 100 to 350 g/l are of particular advantage from the performance point of view.
The roll compacting of
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Bauer Volker
Breuer Wolfgang
Kottwitz Beatrix
Kruse Hans-Friedrich
Poethkow Joerg
Grandmaison Real J.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Medley Margaret
Szoke Ernest G.
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