The invention relates to a granular surfactant composition comprising sodium silicate and other constituents, to a process for its preparation and to its use.
Crystalline layered sodium silicates (phyllosilicates), in particular those of the formula NaMSixO2x+1.yH2O, where M is sodium or hydrogen, x is a number from 1.9 to 4, and y is a number from 0 to 20, and preferred values for x are 2, 3 or 4, have proven to be suitable replacements for the builders phosphate and zeolite, especially in detergents and cleaners.
The use of the abovementioned crystalline phyllosilicates for softening water is described, for example, in EP-A-0 164 514. Preferred crystalline phyllosilicates are those in which M is sodium and x assumes the values 2 or 3.
Preferred materials are either beta- or delta-sodium disilicates (Na2Si2O5.yH2O), it being possible to obtain beta-sodium disilicate, for example, by the process in PCT/WO 91/08171.
A commercially available crystalline sodium disilicate which corresponds to the abovementioned formula is, for example, SKS-6 from Clariant GmbH. This product is composed of the various polymorphous phases of sodium disilicate and thus consists of alpha-disodium disilicate, beta-disodium disilicate and delta-disodium disilicate. Preference is given to as high as possible a content of delta-disodium disilicate. The commercial product may also comprise components of noncrystallized sodium silicate.
The above mentioned sodium disilicates are normally used together with surfactants in the many diverse fields. These surfactants also include the known anionic linear alkylbenzenesulfonates (also referred to as LAS).
In detergent production, the abovementioned known anionic linear alkylbenzenesulfonates (LAS) in liquid water-containing form, together with other detergent ingredients such as soda, water glass etc., are generally converted into a dry pulverulent form in a spray drying process. The material normally has a low bulk density since the spray droplets expand in the spray tower as a result of the evaporation of water to form hollow spheres/beads. This product form makes the preparation of compact detergents difficult, and the resulting powder lacks good flowability, which hinders transportation during the detergent production process.
The spray-drying process is, moreover, energy-intensive since all of the components must be dissolved in water to give an aqueous slurry, and this water must be evaporated in the spray tower, which is energy-intensive. The required bulk density can in most cases only be achieved by means of a further additional agglomeration step.
The object of the invention is now to provide surfactant compositions which have high flowability. It is likewise the object of the invention to convert linear alkylbenzenesulfonates from the liquid form into a solid, granular, readily flowable form.
This object is achieved by a granular surfactant composition comprising sodium silicate and other constituents of the type mentioned at the outset, which comprises from 20 to 95% by weight of sodium silicate and from 5 to 80% by weight of at least one linear alkylbenzenesulfonate, and has a mean particle diameter of xe2x89xa750 xcexcm and an ffc value of xe2x89xa77.