Montedison S.p.a.

Montedison Fibre S.p.a.

Giuseppe Sironi

Francesco Ferrero

Bruno Viviani

Camillo Paffoni

Giuseppe Ribaldone

Renato Grecu

Giuliano Fagherazzi

Franco Montino

Luigi Colombo

A process is disclosed for the preparation of black and brown thermostable pigments consisting essentially of mixed phases of iron and manganese oxides, characterized in that: (a). pyrolusite, in the form of particles having a mean diameter not exceeding 20 microns, is mixed and maintained in contact together with heptahydrated ferrous sulphate at a temperature between room temperature and 95.degree. C.; and (b). the mass thereby obtained is dried, crushed and screened, and then calcined in the presence of air in a fluidized bed reactor at a temperature between 800.degree. and 900.degree. C. The starting pyrolusite/heptahydrated ferrous sulphate mixture may be additioned with one or more compounds selected from the group consisting of FeCl.sub.2, SiO.sub.2, FeCl.sub.3, Na.sub.2 SiO.sub.3, Fe.sub.3 O.sub.4, NaAlO.sub.2, KAl(SO.sub.4).sub.2 and NaBO.sub.2. The total quantity of additives is between 0.5% and 5% by weight based on the final product. The starting pyrolusite/heptahydrated ferrous sulphate mixture may also be additioned with water in a quantity not exceeding 20% by weight. The residence time of the solids in the fluidized bed reactor is between 1 and 6 hours. The black and brown thermostable pigments obtained from the process are also claimed.

Process for the preparation of thermostable black and brown pigments and

The present invention relates to a new class of compounds belonging to the anthraquinone series, having the general formula: ##STR1## wherein R, R', R', R'', R' are indifferently H or Chlorine, ##STR2## Such compounds exhibit a color varying from yellow to violet depending on the nature and position of substituents R, R', R', R'', R'.sup.v and, in virtue of their excellent stability characteristics, they are particularly useful as pigments and vat dyes. This invention relates furthermore to the preparation of compounds having general formula (I) and to the utilization thereof, particularly in the following applications:

Anthraquinone compounds and process for preparing same

A process is disclosed for preparing .alpha.-Fe.sub.2 O.sub.3 in the form of acicular particles substantially free from occluded boils or cavities, and containing from 0.2 to 2% by weight of SiO.sub.2, and having a mean axial ratio between 6 and 8, and an intrinsic coercive force of 320 - 370 Oe. An aqueous solution of FeSO.sub.4. 7H.sub.2 O is treated with alkali, in the presence of air, thus forming acicular .alpha.-FeOOH, which is then dehydrated, reduced at Fe.sub.3 O.sub.4 under fluidizing conditions, and oxidized to .gamma.-Fe.sub.2 O.sub.3 at 200.degree.-350.degree. C under fluidizing conditions. The formation of the acicular .alpha.-FeOOH is carried out at a yield of 0.5-2.5 kg of ferric Fe per hour per m.sup.3 of reactor; the reaction product is filtered and washed and the .alpha.-FeOOH particles are coated with 0.2-2% by weight of SiO.sub.2, from an aqueous suspension of .alpha.-FeOOH brought to a temperature ranging from 50.degree. to 90.degree. C, adding Na.sub.2 SiO.sub.3, and adjusting the final pH to 5.5-6.5; the .alpha.-FeOOH treated with SiO.sub.2 is dehydrated and simultaneously reduced to Fe.sub.3 O.sub.4 at a temperature between 480.degree. and 550.degree. C with a gaseous mixture selected from the class consisting of H.sub.2 + H.sub.2 O, CO + CO.sub.2, and H.sub.2 + CO + H.sub.2 O + CO.sub.2.

Process for preparing ferrimagnetic acicular ferric oxide

A process is disclosed for producing magnetite having an equiaxial morphology in the state of a hyperfine powder, starting from a solution of a bivalent iron solution, characterized in that:

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Novara, Italy

Giuseppe Sironi