Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1997-03-03
1998-12-08
Marcheschi, Michael
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
423335, 423338, 423339, C01B 3312
Patent
active
058463119
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of international application number PCT/FR96/00461, filed Mar. 28,1996.
The present invention relates to a new process for the preparation of precipitated silica, to precipitated silicas which are in particular in the form of powder, of substantially spherical beads or of granules, and to their application as a reinforcing filler for elastomers.
It is known that precipitated silica has been employed for a long time as a white reinforcing filler in elastomers.
However, like any reinforcing filler, it is appropriate that it should be capable of, on the one hand, being handled and above all, on the other hand, of being easily incorporated into the mixtures.
It is known in general that, to obtain the optimum reinforcing properties conferred by a filler, it is appropriate that the latter should be present in the elastomer matrix in a final form which is both as finely divided as possible and distributed as homogeneously as possible. However, such conditions can be achieved only insofar as, on the one hand, the filler has a very good ability to be incorporated into the matrix during mixing with the elastomer (incorporability of the filler) and to disintegrate or to deagglomerate into the form of a very fine powder (disintegration of the filler) and as, on the other hand, the powder resulting from the abovementioned disintegration process can itself, in its turn be perfectly and homogeneously dispersed in the elastomer (dispersion of the powder).
Moreover, for reasons of mutual affinities, silica particles have an unfortunate tendency, in the elastomer matrix, to agglomerate with each other. These silica/silica interactions have a detrimental consequence of limiting the reinforcing properties to a level that is substantially lower than that which it would be theoretically possible to expect if all the silica/elastomer interactions capable of being created during the mixing operation were actually obtained (this theoretical number of silica/elastomer interactions being, as is well known, directly proportional to the external surface of the silica employed).
Furthermore, in the raw state, such silica/silica interactions tend to increase the stiffness and the consistency of the mixtures, thus making them more difficult to process.
The problem arises of having available fillers which, while being capable of being relatively large in size, improve the rheological properties of elastomers and advantageously have a good dispersibility in elastomers.
The aim of the present invention is to overcome the abovementioned disadvantages and to solve the abovementioned problem.
More precisely, its aim is especially to propose a new process for the preparation of precipitated silica which, advantageously, has a good dispersibility (and disintegratability) and very satisfactory reinforcing properties, in particular which, when employed as a reinforcing filler for elastomers, imparts excellent Theological properties to the latter while providing them with good mechanical properties.
The invention also relates to precipitated silicas which, preferably, are in the form of powder, of substantially spherical beads or, optionally, of granules, and which, while being of relatively large size, have very satisfactory reinforcing properties and, in an advantageous manner, very good dispersibility (and disintegratability).
It relates, finally, to the use of the said precipitated silicas as reinforcing fillers for elastomers.
In the description which follows, the BET specific surface is determined according to the Brunauer-Emmett-Teller method described in the Journal of the American Chemical Society, Vol. 60, page 309, February 1938 and corresponding to NFT standard 45007 (November 1987).
The CTAB specific surface is the outer surface determined according to NFT standard 45007 (November 1987) (5.12).
The DOP oil uptake is determined according to NFT standard 30-022 (March 1953) by using dioctyl phthalate.
The packing density (PD) is measured according to NFT standard 030100.
The pH is measured according to ISO stand
REFERENCES:
patent: 4040858 (1977-08-01), Wason
patent: 4161455 (1979-07-01), Wason
patent: 5403570 (1995-04-01), Chevallier et al.
patent: 5413844 (1995-05-01), Persello
Bomal Yves
Chevallier Yvonick
Prat Evelyne
Marcheschi Michael
Rhone-Poulenc Chimie
Solomon Andrew M.
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