Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Specific organic component
Reexamination Certificate
1999-12-14
2002-01-22
Gitomer, Ralph (Department: 1623)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Specific organic component
C536S018700, C536S022100, C536S004100, C536S120000, C536S124000, C536S127000
Reexamination Certificate
active
06340665
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for the simultaneous drying and granulation of water-containing, alkaline sugar surfactant pastes in a thin layer evaporator/dryer.
Sugar surfactants, for example alkyl oligoglucosides or fatty acid-N-alkyl glucamides, are distinguished by excellent detergent properties and high ecotoxicological compatibility. For this reason, these classes of non-ionic surfactants are acquiring increasing significance. Although, hitherto, they have generally been used in liquid formulations, for example dishwashing detergents or hair shampoos, there is now also a market need for solid, water-free formulations which may even be incorporated, for example, in powder-form detergents or syndet soaps.
On an industrial scale, liquid surfactant formulations are generally dried by conventional spray drying, in which the water-containing surfactant paste is sprayed in the form of fine droplets at the head of a tower, the droplets encountering hot drying gases flowing in countercurrent. Unfortunately, this technology cannot readily be applied to sugar surfactant pastes because the temperatures required for drying are above the caramelization temperature, i.e. the decomposition temperature, of the sugar surfactants. The conventional drying of sugar surfactant pastes results in the formation of carbonized products, in addition to which caking occurs on the walls of the spray drying tower so that they have to be cleaned at considerable expense at short intervals.
Attempts have been made in the past to overcome this problem. For example, German patent application DE-A1 41 02 745 (Henkel) describes a process in which a small quantity of 1 to 5% by weight of alkyl glucosides is added to fatty alcohol pastes which are then conventionally spray dried. Unfortunately, the process can only be carried out in the presence of a large quantity of inorganic salts. According to German patent application DE-A1 41 39 551 (Henkel), pastes of alkyl sulfates and alkyl glucosides which may contain at most only 50% by weight of the sugar surfactant are sprayed in the presence of mixtures of soda and zeolites. However, this process only gives compounds with a low surfactant concentration and an inadequate bulk density. Finally, International patent application WO 95/14519 (Henkel) reports on the drying of sugar surfactant pastes with superheated steam. Unfortunately, this is technically very complicated. In fact, there has not yet been a reliable process which enables high-quality, substantially water-free sugar surfactant powders or granules to be produced, but which does not entail the use of carriers during the drying process. Another problem of known processes is that they do not lead to the particularly preferred heavy powders with a bulk density above 500 g/l and, at the same time, a greatly reduced dust content. However, it is precisely these two parameters which are so important on economical, applicational and safety grounds.
German patent DE-C1 195 34 371 (Henkel) describes a process for the production of sugar surfactant granules in which water-containing pastes of alkyl glucosides or fatty acid-N-alkyl glucamides are dried in a thin layer evaporator. The preparations are highly alkalized (pH=11-12) for antimicrobial stabilization. However, a neutral to slightly acidic pH value is required for cosmetic product formulations. The discontinuous nature of the neutralization step in the paste is very time-consuming and can only be reproduced to a limited extent on account of the considerable buffer effect so that frequent readjustment is necessary. In addition, if the pH falls below the neutral point, the paste foams vigorously with evolution of carbon dioxide. In addition, a subsequent heat treatment during drying leads to a poorly reproducible increase in the pH value so that neutral granules cannot readily be produced by this method.
Accordingly, the complex problem addressed by the present invention was to convert water-containing, alkaline sugar surfactant pastes with minimal outlay on equipment into substantially water-free and dust-free granules with a neutral or slightly acidic pH value which, compared with known products, would be distinguished simultaneously by improved colour quality and storage stability, by a high bulk density and by good flow properties
DESCRIPTION OF THE INVENTION
The present invention relates to a process for the production of neutral sugar surfactant granules, in which water-containing pastes of
a) alkyl and/or alkenyl oligoglycosides and/or
b) fatty acid-N-alkyl polyhydroxyalkylamides
with a solids content of at least 20% by weight and preferably in the range from 25 to 75% by weight are dried in a horizontally arranged thin-layer evaporator or dryer with rotating internals to a residual water content below 2% by weight, preferably below 1.5% by weight and, more preferably, below 1% by weight and, at the same time, converted into particulate form, characterized in that the sugar surfactant pastes are neutralized immediately before entering the thin-layer evaporator/dryer.
It has surprisingly been found that the introduction of the neutralizing agent immediately before the alkaline pastes enter the thin-layer evaporator/dryer leads to rapid and uniform neutralization and ultimately to products which are far more light-colored and color-stable than known products. Conversely, this means that neutralized sugar surfactant pastes can be dried at distinctly higher temperatures, i.e. at increased product throughputs, and that granules equivalent in their color quality to known granules can still be obtained. The products have a high apparent density of 550 to 650 g/l and an average particle diameter of 2 to 4 mm which leads to a reduction in the unwanted absorption of water and in the caking of the particles. High stability in storage is also achieved in this way. At the same time, the particles are dust-free, i.e. the percentage of particles smaller than 200 &mgr;m in diameter is less than 5% by weight, and considerably harder than comparable granules which has a favorable effect on their flow properties.
Alkyl and/or alkenyl oligoglycosides
Alkyl and alkenyl oligoglycosides are known nonionic surfactants which correspond to general formula (I):
R
1
O—[G]
p
(I)
where R
1
is an alkyl and/or alkenyl radical containing 4 to 22 carbon atoms, G is a sugar unit containing 5 or 6 carbon atoms and p is a number of 1 to 10. They may be obtained by the relevant methods of preparative organic chemistry. EP-A1-0 301 298 and WO 90/03977 are cited as representative of the extensive literature available on this subject.
The alkyl and/or alkenyl oligoglycosides may be derived from aldoses or ketoses containing 5 or 6 carbon atoms, preferably glucose. Accordingly, the preferred alkyl and/or alkenyl oligoglycosides are alkyl and/or alkenyl oligoglucosides. The index p in general formula (I) indicates the degree of oligomerization (DP degree), i.e. the distribution of mono- and oligoglycosides, and is a number of 1 to 10. Whereas p in a given compound must always be an integer and, above all, may assume a value of 1 to 6, the value p for a certain alkyl oligoglycoside is an analytically determined calculated quantity which is generally a broken number. Alkyl and/or alkenyl oligoglycosides having an average degree of oligomerization p of 1.1 to 3.0 are preferably used. Alkyl and/or alkenyl oligoglycosides having a degree of oligomerization of less than 1.7 and, more particularly, between 1.2 and 1.4 are preferred from the applicational point of view. The alkyl or alkenyl radical R
1
may be derived from primary alcohols containing 4 to 11 and preferably 8 to 10 carbon atoms. Typical examples are butanol, caproic alcohol, caprylic alcohol, capric alcohol and undecyl alcohol and the technical mixtures thereof obtained, for example, in the hydrogenation of technical fatty acid methyl esters or in the hydrogenation of aldehydes from Roelen's oxosynthesis. Alkyl oligoglucosides having a chain length of C
8
to C
10
(DP
Gutsche Bernhard
Hensen Hermann
Lueder Thomas
Scholinakis Konstantinos
Seipel Werner
Drach John E.
Gitomer Ralph
Henkel Kommanditgesellschaft auf Aktien
Khare Devesh
Murphy Glenn E. J.
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