040111 FE / AL
1
Use of a cationic silicon dioxide dispersion as a -textile
finishing agent
The invention relates to a cationic silicon dioxide dispersion for use as a textile finishing agent.
It has long been known to use silica as an non-slip agent for textiles (Ullmann's Encyclopedia of Industrial Chemistry, Vol. A26, p. 328, 5th edition). These silica sols may have specific surface areas of more than 1000 m2/g. They generally assume the form of isolated, spherical particles with diameters of a few nanometres. In order to prevent gelation, they are generally stabilised by the addition of aluminium salts or polymers. In the case of use as an non-slip agent, it has proved disadvantageous that, in order to achieve the desired effect of slip resistance, it is sometimes necessary to use large quantities of silica sol or cationised silica sol. This is possibly due to the spherical structure of the silica sol particles. Better results may be obtained with partially aggregated silica sol particles, as described in WO 2004/007367. The low degree of aggregation of the silica sol particles is disadvantageous here. Furthermore, the bond between the silica sol particles is not so strong that the energy introduced in the event of any external force applied to the particles is sufficient to separate the aggregates again.
The object of the present invention is to provide a dispersion containing silicon dioxide which may be used as a textile finishing agent and avoids the disadvantages of the prior art.
The present invention provides an aqueous dispersion for use as a finishing agent for textiles, wherein the dispersion contains a pyrogenically produced, aggregated silicon dioxide powder and a cationic polymer which is soluble in the dispersion, wherein the cationic polymer is

040111 FE / AL
2
present in a quantity such that the particles of the silicon dioxide powder exhibit a positive zeta potential.
Pyrogenically produced silicon dioxide powders should be taken to mean those which are obtainable by flame hydrolysis or flame oxidation. In these processes, primary particles of approx. 5 to 50 nm are initially formed, which, as the reaction proceeds, combine to form aggregates. These aggregates form a three-dimensional network. The aggregates cannot generally be broken back down into the primary particles.
The specific surface area of the pyrogenically produced silicon dioxide powder in the aqueous dispersion is not limited. It may preferably have a specific surface area of 50 to 300 m2/g.
A preferred dispersion may be one in which the pyrogenically produced silicon dioxide powder is doped with up to 1 wt-% of aluminium oxide or potassium. Such powders are described, for example, in EP-A-995718 and EP-A-1216956.
The content of pyrogenically produced silicon dioxide powder in the dispersion may preferably amount to 3 to 50 wt.%.
Selection of the cationic polymer is not limited according to the present invention, but the quantity thereof is. The cationic polymers must be present in the dispersion in a quantity such that the surface of the particles of the silicon dioxide powder is completely covered with cationic polymer and consequently exhibits a positive zeta potential.
The content of cationic polymer is preferably between 0.1 and 15 wt.% and particularly preferably between 0.8 and 5 wt.%, relative to the quantity of cationic polymer and silicon dioxide powder.

040111 FE / AL
3
Cationic polymers with a molecular weight of less than 100 000 g/mol are preferred.
Preferred cationic polymers may be: polymers with at least one quaternary ammonium group, a phosphonium group, an acid adduct of a primary, secondary or tertiary amine group, a polyethyleneimine, a polydiallylamine or a polyallylamine, a polyvinylamine, a dicyandiamide condensation product, a dicyandiamide-polyamine cocondensation product, a polyamide-formaldehyde condensation product.
Preferred polymers may be those based on a diallyl ammonium compound, particularly preferably those based on a dialkyldiallyl compound which may be obtained by a free-radical cyclisation reaction of diallylamine compounds and exhibit structure 1 or 2. Structures 3 and 4 represent copolymers based on dialkyldiallyl compounds.
In these structures, R1 and R2 represent a hydrogen atom, an alkyl group with 1 to 4 C atoms, methyl, an ethyl, an n-propyl, an iso-propyl, an n-butyl-, an iso-butyl or a tert.-butyl group, wherein R1 and R2 may be identical or different. A hydrogen atom of the alkyl group may furthermore be substituted by a hydroxy group. Y represents a free-radically polymerisable monomer unit, such as for example sulfonyl, acrylamide, methacrylamide, acrylic acid or methacrylic acid. X" represents an anion.
A poly(diallyldimethyl ammonium chloride) solution (PDADMAC solution in water) may be mentioned by way of example.


040111 FE / AL
4

The aggregate size of the silicon dioxide particles is not limited, but may preferably be smaller than 0,. 5 um. At this size it is, for example, possible to influence the handle and lustre of the textiles.
The pH value of the dispersion may preferably be between 2 and 8.
The dispersion may, for example, be produced as described in EP-A-1013605 or EP-A-1331254.
The dispersion exhibits the advantage over prior art dispersions containing silica sols which are either not aggregated or may be paresent in partially aggregated form so that less silicon dioxide need be used in order to bring about, for example, the same slip resistance in the textiles. Additionally, the aggregate size of the particles and thus the handle and lustre of the textiles may be adjusted by suitable dispersion techniques. The advantages are probably attributable to the aggregated structure of the pyrogenically produced silicon dioxide powder.
Examples:
Cationic Silica-Dispersion according to the invention