Abstract: The invention relates to a process for polymerizing block polymers of general formula (I): ##STR1## in which process the following are brought into contact with each other: an ethylenically unsaturated monomer of formula:CYY'(.dbd.CW--CW').sub.a .dbd.CH.sub.2,a precursor compoun of general formula (II): ##STR2## a radical polymerization initiator.

Abstract: The invention relates to a new process for the preparation of precipitated silica which has a good dispersibility and very satisfactory reinforcing properties. It also relates to new precipitated silicas which are in the form of powder, of substantially spherical beads or of granules, these silicas being characterized by the fact that they have a CTAB specific surface of between 90 and 250 m.sup.2 /g, a BET specific surface of between 90 and 250 m.sup.2 /g, a DOP oil uptake lower than 300 ml/100 g, a zinc content of between 1 and 5% by weight, and by the fact that the number N of stearic acid molecules consumed per nm.sup.2 of silica surface, when stearic acid is reacted with this silica in xylene for 2 hours at 120.degree. C., is at least 1. The invention also relates to the use of the said silicas as reinforcing fillers for elastomers, especially for improving their rheological properties.

Abstract: The invention relates to a new process for the preparation of precipitated silica which has a good dispersibility and very satisfactory reinforcing properties. It also relates to new precipitated silicas which are in the form of powder, of substantially spherical beads or of granules, these silicas being characterized by the fact that they have a CTAB specific surface of between 90 and 250 m.sup.2 /g, a DOP oil uptake lower than 300 ml/100 g, a pore distribution such that the pore volume consisting of the pores whose diameter is between 175 and 275 .ANG. represents less than 50% of the pore volume consisting of the pores of diameters smaller than or equal to 400 .ANG., a zinc content of between 1 and 5% by weight and by the fact that the number N of molecules of stearic acid consumed per nm.sup.2 of silica surface, when stearic acid is reacted with the said silica in xylene for 2 hours at 120.degree. C., is at least 1.

Abstract: The present invention relates to multifunctionalized alkoxy, the alkoxy functionality Y being introduced onto a suitable polyhydrooorganosiloxane by a dehydrogenation/condensation reaction from the alcohol from which Y derives and then the functionality W by a hydrosilylation reaction from the olefinic compound from which W derives. The multifunctionalized alkoxy polyorganosiloxanes can be used as antiadhesion modulators in silicone compositions and as silica covering agents in silicone compositions containing fillers.

Abstract: Improved method for obtaining organosilanes comprising: a redistribution reaction between a chlorinated organohydrogenosilane and an organo-substituted and optionally chlorinated silane, the distribution reaction taking place in the presence of a sufficient amount of a catalyst consisting of a Lewis acid of formula (3) M(X).sub.d in which: M represents a metal selected among Ti, Fe, Cu, Ag, Zn, Cd, Hg, Al, Ga, In, B, Sn, Pb, Sb, and Bi; X represents a halogen atom; d represents the valency of metal M; and separation by distillation of the chlorinated organohydrogenosilane produced by redistribution; the said method being characterized in that, after redistribution, a redistribution catalyst inhibiting compound is used. This catalyst is selected among the fluid polyorganosiloxanes (POS) having a viscosity at 25.degree. C. not exceeding 5000 mPa.cndot.

Abstract: The present invention relates to a composition based on a sulphur compound, zinc and optionally a transparent oxide, to a process for its preparation and to its use as a dye pigment. The composition of the invention is characterized in that it comprises a support based on at least one sulphur compound, and a zinc compound, deposited on the support and obtained by reaction of a zinc precursor with aqueous ammonia and/or an ammonium salt. The composition may also comprise a layer based on at least one transparent oxide deposited at the surface of the support and/or fluorine atoms. It may be prepared in particular by a process in which the support, a zinc precursor, aqueous ammonia and/or an ammonium salt and, if necessary, a transparent oxide precursor and a fluorinating agent are placed in contact and the zinc compound is deposited on the support and, where appropriate, the transparent oxide is precipitated on the said support.

Abstract: Composite particles having a core consisting of an organic polymer and a coating including at least one aluminum, silicon, zirconium and/or transition metal oxide and/or hydroxide, and optionally containing calcium carbonate, as well as methods for preparing same, are disclosed. The use of said composite particles for preparing hollow particles with a shell of the same kind as the above-mentioned coating is also disclosed. Finally, the use of said hollow composite particles as fillers or additives in plastics and elastomers is disclosed.

Abstract: The invention discloses a method for preparing particles comprising a dense silica shell and a core of another material, through rapid precipitation of active silica from a an aqueous alkaline metal silicate solution with pH adjustment by means of an acidifying agent, on a material support other than silica, separation of the silica slurry formed and drying of the recovered silica suspension. These composite particles consisting of a shell formed of dense silica and a non-polymer organic material core with biological, in particular phytosanitary, activity can be used for the slow release of the said solid non-polymer organic material with biological, in particular phytosanitary, activity, by slow diffusion through the silica shell.

Abstract: The invention concerns the use as thermothickeners of multi-block copolymers of general formula (I) or (II): ##STR1## wherein E designates a polyoxyalkylene sequence; A designates a water-soluble polymer sequence; X is a sulphur or oxygen atom; Y is an oxygen atom or an --N--R' group, R' being a linear or branched alkyl; R is a linear or branched alkyl, aralky or alkylaryl group; and n is such that the molecular mass of the multi-block copolymers Mp is greater than 250,000 g/mol.

Abstract: The present invention relates to a process for the acylation of an aromatic thioether. In its preferred variant, the invention resides in a process for the condensation of acetic anhydride or acetyl chloride with thioanisole. The process for the acylation of an aromatic thioether according to the invention is characterised in that it consists in reacting said thioether with an acylating agent chosen from the group formed by the halides of carboxylic acids and the anhydrides of carboxylic acids, in the presence of an effective quantity of an acid zeolite.

Abstract: Cellulose microfibrils, in particular for use as a reinforcing filler or structuring agent in composite materials, a method for making same, and composite materials containing said microfibrils, are disclosed. Specifically, said microfibrils are surface-modified cellulose microfibrils with an L/D ratio higher than 20, preferably higher than 100, and an average diameter of 1-50 nm, where L is the length of the microfibril and D is its average diameter. At least 25% by number of the hydroxyl functions on the surface of the microfibrils are esterified by at least one organic compound including at least one function capable of reacting with the hydroxyl groups of the cellulose. As a result, when the organic compound is a compound that includes acetyl groups such as acetic acid, said microfibrils are used as a reinforcing filler in a material comprising cellulose acetate as the polymeric matrix. The filled composite material may be shaped to provide films, moldings, fibers or yarns.

Abstract: The subject-matter of the present invention is a process of use in perfluoroalkylation and a reactant for making use of this process. This process is defined in that it comprises a stage in which a material of formula RfH and a base (or a species capable of generating a base) are brought into contact, in a polar and anhydrous medium, with a substrate carrying at least one electrophilic functional group. Application to organic synthesis.

Abstract: The present invention lies in the field of the manufacture of phenol from cumene. The subject of the invention is a process for the continuous preparation of cumene hydroperoxide by oxidation, in the liquid phase, of cumene in the presence of oxygen. The process according to the invention is carried out in the presence of at least one agent chosen from the hydroxide or the carbonate of an alkali metal and/or alkaline-earth metal; the said agent being used in an amount of between 2 and 10 ppb (expressed as sodium hydroxide) with respect to the amount of cumene introduced. The invention likewise relates to the use of the hydroperoxide thus obtained for preparing phenol.

Abstract: A method for hydrogenating aromatic nitro compounds by reacting at least one aromatic nitro compound with hydrogen in two adiabatically operated fixed-bed catalytic reactors arranged in series, wherein one part of the reaction mixture from the first reactor is recirculated therein while the other part is fed into the second reactor.

Abstract: The invention relates to a substrate provided, on at least a portion of one of its faces, with a coating with a photocatalytic property based on titanium dioxide which is at least partially crystalline and which is incorporated in the said coating partly in the form of particles predominantly crystallized in the anatase form. The invention also relates to a process for the preparation of this substrate and organic dispersions of titanium dioxide particles used in the said process for the preparation of the substrate.

Abstract: Water-redispersible granules including at least one active material in the form of a hydrophobic liquid, at least one non-ionic surfactant selected from polyoxyalkylene derivatives, and at least one water-soluble compound selected from polyelectrolytes belonging to the weak polyacid family are disclosed. A method for preparing such granules by preparing an aqueous emulsion of at least one active material, at least one non-ionic surfactant and at least one water-soluble compound, and drying the resulting emulsion, is also disclosed.

Abstract: The invention relates to a colloidal dispersion, characterized in that it comprises a cerium oxide and at least one additive chosen from .beta.-diketones, monocarboxylic acids containing a hydroxyl function in the .alpha.- or .beta.-position and diols. It also relates to a redispersible composition in the form of a colloidal dispersion based on cerium oxide and the same above mentioned additives. The colloidal dispersion of the invention can be obtained by a process which is characterized in that at least one above mentioned additive is added to a colloidal dispersion of cerium oxide as the starting material. Finally, the invention relates to the use of a dispersion of the above type or of the type obtained by redispersing a redispersible composition, on a substrate as an anticorrosion agent, in a cosmetics composition, in catalysis, in particular for automobile post-combustion, in lubrication or in ceramics.

Abstract: A cosmetic composition for the hair and/or skin comprising a water-dispersible sulfone copolyester with polyorganosiloxane units incorporating a plurality of recurrent sulfone polyester units and polyorganosiloxane units which have: a molecular mass number between 5000 and 45,000; a sulfur weight content of 0.5 to 6% compared with the said sulfone copolyesters with polyorganosiloxane units; and a silicium content of 0.05 to 20% by weight compared with the said sulfone copolyesters with polyorganosiloxane units.

Abstract: The invention relates to a descaling formulation comprising cellulose microfibrils, in which at least 80% of the cells have primary walls and not more than 20% of the cells have secondary walls, with a degree of crystallinity of not more than 50%. The pH of the formulation is less than or equal to 1 and more particularly less than or equal to 0.5.

Abstract: The subject of the present invention is a composition comprising:at least one masked or unmasked polyisocyanate in the form of an aqueous emulsion whose mean size is between 0.1 and 10 micrometers and preferably smaller than 2 and larger than 0.2 micrometers,at least one polyhydroxylated polymer, advantageously a polyol, in the form of a second aqueous dispersion whose mean size is between 10 and 200 nanometers.This composition is defined in that the quantity of polyol in the mixture is chosen so as to meet one of the following two constraints:the polyol content, expressed in mass per cent, is at least equal to 35-0.75 R, advantageously at least equal to 40-0.75 R, preferably to 45-0.75 R;the polyol content, expressed in mass per cent, does not exceed 45-2 R, advantageously does not exceed 40-2 R, preferably 35-2 Rwith R equal to the ratio of the mean size (d.sub.50) of the emulsion to that of the polyol dispersion.Application to organic synthesis.