Precipitated Calcium Carbonate Pigment, Especially for Use in Inkjet Printing Paper Coatings
AssigneeOmya International AG
InventorsMichael Kaessberger, Michael Pohl
Life of this patent
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Abstract
The invention relates to novel and innovative PCC pigments, able to be used in a paper coating formulations to manufacture coated “multipurpose” papers, in particular for inkjet applications, whose print qualities would be identical or quite similar to high resolution commercial papers, while maintaining a reduced paper manufacturing and production cost. Said pigments are obtained by a carbonation process using a reduced flow rate of CO2/air, which leads to porous agglomerates of PCC of a very specific structure and unique properties, followed by an upconcentration step leading to substantially the same agglomerates but with a higher, appropriate, solids content.
Claims23
Process for providing PCC useful for ink-jet printing applications,
- of the type according to which a calcium hydroxide slurry is first prepared by mixing quicklime (CaO) with water in a stirring reactor or tank (“slake”), the calcium hydroxide slurry is then screened, such as on a 100 μm screen, to remove any residual impurities and/or non-reactive unburnt lime, the screened slurry is then directed towards a stainless steel reactor equipped with an agitator;
- the temperature is adjusted, generally to between 10 and 70° C., and subsequently the slurry is directed towards a carbonation reactor or tank, wherein carbon dioxide-containing gas is bubbled through the slurry, the slurry exits the carbonation tank when appropriate in view of conductivity and pH, generally when the conductivity reaches a minimum and the pH drops below 8, coarse particles are removed on a screen, such as a 45 μm screen, such that the slurry contains only the ultrafine PCC agglomerates of the invention,
- characterized by the implementation of process steps comprising the following:
- A First steps, production of the PCC:
- A1
- the carbonation step is performed at a carbonation gas flow rate of below 30 litres per minute at standard temperature and pressure per kilogram calcium hydroxide during precipitation.
Stable, porous aggregates/agglomerates of PCC characterized in that they feature the following properties:
- a specific surface area of 30 to 100 m2/g, preferably from 50 to 80 5 m2/g, and/or
- a mean aggregate diameter of 1 to 5 μm, with an average diameter of 2 μm, and/or
- a fraction of fines below 2 μm of less than 20%, preferably less than 15% (as measured on a Helos Sympatec), and/or
- a primary particle size of the acicular particles of 20 to 50 nm with an aspect ratio between 1:2 and 1:10 and/or
- a solids content, by weight from 5 to 25%, preferably 15 to 20% at the end of Steps A, and a solids content of 25 to 60%, preferably 35 to 50% solids, in particular 39 to 40% solids at the end of Steps B.
Dependencies are inferred from the claim text.