Process for preparing granules of pigments by means of double extrusion
AssigneePPG Industries Ohio, Inc.
InventorGiovanni Broggi
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Abstract
A process for the production of a particle composition containing, at least one resin and at least one pigment is described, said process comprising the following steps: •extrusion of a mixture containing said at least one resin and said at least one pigment without induced heating; •subsequent extrusion, with induced heating, of the mixture obtained from the preceding extrusion; •granulation of the mixture thus obtained. With the abovementioned process it is possible to obtain a composition having granules with an average diameter less than 2 microns and a greater homogeneity than the known processes.
Claims24
A process for the production of a particle composition containing at least one of aldehyde, ketone and acrylic resin, and at least one pigment, comprising the following steps:
- (a) extrusion, in a co-rotating twin-screw extruder, of a mixture containing said at least resin and said at least one pigment without induced heating, using only the heat developed naturally by the cutting and friction forces inside the extruder, wherein the temperature inside the extruder according to step (a) varies from 5 to 50° Celsius, and the screws of the extruder according to step (a) have a length 20-40 times the diameter;
- (b) subsequent extrusion, with induced heating, of the mixture obtained from the extrusion according to step (a), wherein the temperature inside the extruder according to step (b) varies from 80 to 130° Celsius, and the screws of the extruder according to step (b) have a length 30-60 times the diameter;
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- (c) granulation of the mixture thus obtained.
Dependencies are inferred from the claim text.