Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1998-04-06
2000-08-15
Koslow, C. Melissa
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106485, 106486, 106491, 516111, 516106, 426423, 4263304, C01B 33157, C09C 130, C09D 700, C12H 1048
Patent
active
06103004&
DESCRIPTION:
BRIEF SUMMARY
Modern matting agents for coatings consist of highly porous, amorphous silicon dioxide which has been adjusted to a particle size which is appropriate for the required coating film thickness.
The most widely used matting agents originate from two processes: is formed, washing, drying, milling.
The best representatives of both processes show a high matting efficiency coupled with low thickening, good dispersibility and lacquer film transparency (clarity). SYLOID ED5, which is manufactured by Grace GmbH, Worms, Germany, is a typical representative of the first class and is used throughout this description as a standard for the state of the art.
Another type of matting agent has also been developed which exhibits an increased matting efficiency compared with the two aforementioned classes. This is attained by agglomerating in various ways a pyrolytic (pyrogenic, fumed) silicon dioxide (silica) (pyrolytic silicon dioxide is obtained by flame hydrolysis of SiCl.sub.4). This type of product (e.g. TS 100 from Degussa) exhibits a matting efficiency which is increased by 10 to 25% compared with the first two types. However, it is a major disadvantage of this type of product that it increases the viscosity of the paint (lacquer) in which it is used, even at the lower concentrations which are required in order to obtain the same gloss as with the other products. This increase in viscosity makes processing of the paint more difficult. A further disadvantage is the reduced dispersibility.
DE 12 09 108 describes the spray-drying of an aqueous suspension containing 20 to 60% pyrolytic silicon dioxide in order to obtain a spherical product having an average particle size of approx. 200 .mu.m.
DE 24 14 478 describes the production of a matting agent by aggregation of powdery pyrolytic silicon dioxide. The silicon dioxide is wetted by adding approx. 5% of water, based on silicon dioxide, and then dried in an oven or an air-jet mill. The surface of the powder is coated only with a very thin (monomolecular) layer because of low moisture absorption. During subsequent evaporation, aggregation takes place which leads to a product which has a relatively poor particle strength.
DE 28 31 561 describes the production of a catalyst support by spray-drying a suspension of pyrolytic silicon dioxide having a concentration of 10 to 33% and optionally by adding ammonia. The particle size is 40 to 80 .mu.m.
EP 0 341 383 describes a precipitated silicon dioxide with a high "structure", expressed as dibutyl phthalate (DBP) number of 3.0 to 4.0, which corresponds to a high pore volume. In the described process a spray-dryer is used. Given as a possible application is that as matting agents in paints (lacquers).
DE 41 32 230 describes the use of large particles (15 to 100 .mu.m) which were obtained by spray-drying a suspension of milled silicon dioxide hydrogel. These particles are used as texturing aid for coatings. The used additives have the purpose of producing particles which do not form solid deposits during sedimentation in the liquid paint (lacquer) as a result of standing for a relatively long time. They do not have binding properties. The stability of aggregates decreases with use.
It is the object of the present invention to obtain a matting agent which has an efficiency which is 25% greater than that of products known from the prior art, without exhibiting a correspondingly greater thickening at the same gloss. Other important properties such as dispersibility, surface roughness and transparency (clarity) of the resulting hardened film are not to be negatively impaired either.
This object is achieved by an aggregated silica gel which has been produced from silica gel particles (particle size: 1 to 20.mu., surface: 200 to 1000 m.sup.2 /g, specific pore volume: 0.4 to 2.5 ml/g) and binding agent selected from synthetic or natural layered silicate (phyllosilicate), pyrogenic silicon dioxide and organic polymers soluble in water or dispersible in water.
According to the invention a micronized silica gel having a pore volume of 0.4 to 2
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Belligoi Peter
Field Rex
Luers Georg
Schneider Rita
Cross Charles A.
Grace GmbH
Koslow C. Melissa
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