Powdered preparations of surface active alkylglycosides

Powder-form preparations of surface-active alkyl glycosides contain 5 to 65% by weight of a surface-active alkyl glycoside and 35 to 95% by weight of an inert inorganic support. They are produced by mixing the crude product obtained in the industrial production of the alkyl glycosides with water and an inorganic particulate support, for example silica, chalk or sodium chloride, and drying the resulting mixture. Preferred powder-form preparations contain 20 to 50% by weight of the alkyl glycoside and 50 to 80% by weight of an inert inorganic support.

This invention relates to free-flowing powder-form preparations of 
surface-active alkyl glycosides and to a process for their production by 
drying of an aqueous mixture of alkyl glycoside and inert particulate 
support materials. 
Surface-active alkyl glycosides in the context of the present invention are 
the reaction products of sugars and aliphatic primary alcohols preferably 
containing 8 to 22 carbon atoms. The sugar components, which are referred 
to hereinafter as glycoses, are preferably glucose and also fructose, 
mannose, galactose, talose, gulose, allose, altrose, idose, arabinose, 
xylose, lyxose, ribose and mixtures thereof. 
The acetalization products of glucose with fatty alcohols obtainable, for 
example, from natural fats and oils by known methods, i.e. with linear, 
primary, saturated and unsaturated C.sub.8-22 alcohols, are preferred by 
virtue of their ready availability and their good performance properties. 
Accordingly, the invention preferably relates to these types of alkyl 
glycosides which are also referred to hereinafter as alkyl glucosides. 
Where they are produced by known methods for example in accordance with 
U.S. Pat. No. 3,839,318 or EP 132 046 A1, alkyl glycosides are accompanied 
by different residual quantities of unreacted starting products, among 
which the fatty alcohol is particularly troublesome in many applications. 
The crude acetalization products are solid, solidified melts which cannot 
be cast or dispersed at normal temperature. 
In one particularly preferred production process, glucose is acetalized 
with fatty alcohol, water being continuously distilled off from the 
mixture under reduced pressure. In this production process, which is 
described in detail in German patent application P 38 33 780.0, the crude 
alkyl glucoside is obtained in the form of a solidified melt containing 
approximately 63% by weight fatty alkyl monoglucoside, 15% by weight fatty 
alkyl diglucoside, 6% by weight fatty alkyl triglucoside, 3% by weight 
alkyl tetraglucoside, 6% by weight polyglucose and 2 to 4% by weight 
residual fatty alcohol. Attempts to convert this melt by spray drying, 
flaking or granulation into a particulate product which flows freely at 
normal temperature resulted in the formation of tacky, moisture-sensitive 
materials. In addition, the unreacted residual fatty alcohol still present 
in the product is noticeable by its unpleasant taste where the alkyl 
glucosides are used in oral and dental hygiene preparations. However, oral 
and dental hygiene preparations represent a preferred application for 
surface-active alkyl glycosides by virtue of their compatibility with 
mucous membrane. 
Accordingly, the problem addressed by the invention was to convert 
surface-active alkyl glycosides into a pourable, free-flowing form in 
which they could readily be stored, transported, distributed and 
incorporated without difficulty in other products, particularly in oral 
and dental hygiene preparations. 
Accordingly, the present invention relates to powder-form preparations of 
surface-active alkyl glycosides which are characterized in that the 
contain 5 to 65% by weight of a surface-active alkyl glycoside and 35 to 
95% by weight of an inert support and which are obtained by drying of a 
pourable, aqueous mixture of crude alkyl glycoside and support. 
In the context of the invention, a crude alkyl glycoside is understood to 
be the crude product obtained in the known production process with the 
secondary constituents attributable to the process, more particularly the 
reaction mixture containing 2 to 5% by weight unreacted fatty alcohols 
obtained by the acetalization process described above. 
Suitable supports are any chemically and physiologically inert, inorganic 
support materials which show a substantially neutral or, at best, mildly 
basic reaction in water and which accumulate in powder form after drying. 
Particularly preferred supports are substances which are not troublesome 
when used in oral and dental care preparations, for example in 
toothpastes, for example because they are already required in another 
capacity in such preparations. Suitable supports of this type are, for 
example, the known polishing agent components, such as chalk, silicas, 
dicalcium phosphate, calcium pyrophosphate, insoluble sodium 
metaphosphate, aluminium oxide and aluminium oxide hydrates. However, 
neutral and physiologically acceptable water-soluble salts, such as for 
example sodium chloride or sodium sulfate, or mixtures of two or more of 
these supports are also suitable. Other suitable inert supports are 
alumosilicates, for example layer silicates, talcum, zeolites, magnesium 
aluminium silicate (Veegum.RTM.), calcium sulfate, magnesium carbonate or 
magnesium oxide. 
Particularly preferred supports are silicas which, by virtue of their large 
inner surface, give a good free-flowing preparation in small quantities of 
from about b 0.5 part by weight per part by weight alkyl polyglycoside. 
With other supports, for example chalk and sodium chloride and sodium 
sulfate, the ratio by weight of support to alkyl glycoside should be at 
least 1:1 and, better still, from 1 to 4:1 in order to obtain preparations 
combining favorable performance properties with an adequate storage life. 
Accordingly, preferred preparations according to the invention contain 20 
to 50% by weight of a surface-active alkyl glycoside and 50 to 80% by 
weight of an inert, inorganic support. 
The finely divided abrasive silicas already used as polishes for 
toothpastes are preferably used as supports. These silicas are, for 
example, the precipitated silicas which are known from DE 31 14 492 and DE 
31 14 493 or from DE 24 46 038 and which are commercially available; the 
water-containing gel silicas known from DE 27 04 504 and DE 28 53 647 and 
the xerogel silicas known, for example, from U.S. Pat No. 3,538,230. 
However, thickening silicas and pyrogenic silicas, for example Aerosil, 
may also be used either on their own or in conjunction with other silicas 
in cases where particularly low powder densities are required. 
The physical and performance properties of the powder-form preparations 
according to the invention may be controlled within wide limits through 
the choice of the type and quantity of support and through combinations of 
different supports. For preparations which are to be suitable as an 
additive for toothpastes and which contain a water-insoluble abrasive as 
support, the particle size of the support should be largely below 50.mu. 
and, on average, should preferably be from 0.1 to 10.mu.. 
The preparations according to the invention are produced by mixing 5 to 65 
parts by weight of a crude alkyl glycoside obtained in industrial 
production with 35 to 95 parts by weight of an inorganic support and such 
a quantity of water that a mixture which still flows freely at a 
temperature below +80.degree. C. is formed and then removing the water 
from this mixture by evaporation to such an extent that a powder-form, 
free-flowing product is obtained. The 30 to 60% aqueous paste of the alkyl 
glucoside obtained after bleaching of the crude alkyl glucoside by the 
process according to German patent application P 38 33 780.0 may also be 
introduced into this mixture. It has been found to be favorable to use 
approximately 1.5 to 4 parts by weight water to 1 part by weight solid in 
the production of this mixture. This mixture is generally a paste or 
slurry which shows poor flow at normal temperature which can be converted 
by heating to temperatures of up to 80.degree. C. into a readily pumpable 
and sprayable form. The water-soluble constituents are largely dissolved 
or swollen in the paste while the water-insoluble components are stably 
dispersed therein. 
The water may be removed from the mixture, i.e. the paste or slurry can be 
dried, in any way, for example on cylinder or belt dryers, in a fluidized 
bed of already formed preparation or by spraying into a hot air stream. 
The last process, so-called spray drying, is the preferred embodiment for 
the drying of the preparations according to the invention. The water is 
removed to such an extent that a powder-form, free-flowing product is 
formed. In most cases, this is the case with water contents of less than 
1% by weight. In the cases where the support binds part of the water as 
water of crystallization, this recommended residual water content is based 
on the free water which is not bound in the crystal lattice. In cases 
where relatively large agglomerates are formed during drying, for example 
on cylinder and belt dryers, it may be necessary to disintegrate these 
agglomerates in a following grinding step. Where the water is removed by 
spray drying, the preparations according to the invention do not have to 
be subsequently disintegrated. For use in toothpastes, the preparations 
according to the invention should not contain any agglomerates larger than 
200.mu. in diameter while the average primary particle size should be no 
more than 50.mu.. 
The preparations according to the invention flow freely and remain 
free-flowing in storage, even in moist air. Another advantage of the 
powder-form preparations is that the content of residual fatty alcohol is 
greatly reduced by the production process according to the invention. 
Accordingly, the preparations may also be used for the production of oral 
and dental hygiene preparations without any adverse effect on their taste.