BRPI0609117B1 - Process for providing a PCC useful for inkjet printing applications, stable porous pcc aggregates / agglomerates, pigments, pcc suspensions, papermaking formulations for the papermaking industry, coating formulations applications, and paper for inkjet - Google Patents

Description

“PROCESS TO PROVIDE A USEFUL PCC FOR PCC INK JET PRINTING APPLICATIONS, STABLE POROS, PIGMENTS, PCC SUSPENSIONS, COATING FORMULATIONS, PAPER APPLICATION, APPLICATION AND APPLICATION INDUSTRY, TECHNICAL FIELD OF THE INVENTION The present invention relates to novel mineral pigments of the precipitated calcium carbonate (PCC) class.

More specifically, the invention relates to novel and novel PCC pigments which may be used in paper coating formulations for the manufacture of coated "multipurpose" papers, in particular for inkjet applications, the Printing qualities should be identical or quite similar to high-resolution commercial papers, while maintaining a low production cost. Multipurpose papers are typically used for a variety of printing types and include uses such as black and white copying, laser printing and fax paper. The invention further relates to the production of said novel suspension-like PCC class mineral pigments present in a solids content suitable for inkjet paper coating in a paper coating apparatus. such as the Oversized Size Press (MSP).

Technical Problems There is a demand for coated multipurpose papers, and particularly papers suitable for inkjet applications, which provide improved print quality without a corresponding increase in production cost.

Available multipurpose office papers are often associated with poor inkjet print quality.

One of the main obstacles to achieving an increase in print quality is to increase the optical density of ink applied to the paper surface, in particular following the application of broad color dye ink.

Inkjet printers form images by applying a series of ink dots to the paper surface. Pigment inks used in inkjet printing are generally anionic and in a naturally soluble, low solids formulation. Good print quality is only achieved if the ink dye remains on the paper surface as the ink solvent penetrates the paper, leaving a uniform circular point at the point of application. It is known that a charge difference between the adsorbent and the adsorbate, respectively for the paper surface and the dye molecules, is generally used to promote dye adsorption.

Therefore, one solution to increasing optical density lies in increasing the number of cationic sites near the paper surface. If the paper surface is coated, the number of cations present near the surface can be increased by adding cationic additives to the coating formulation. However, the addition of cationic additives to obtain a certain optical density significantly increases the cost of the final paper. Increasing the fraction of cationic additive retained in a thin layer near the paper surface, characterized by retention of the coating, is a second solution in order to increase the optical density. Higher coating retention through the use of a narrower coating particle size distribution, which is a technically difficult and expensive solution.

If PCC is present in the coating formulation, the inherent adsorptive properties of PCC particles relative to paint dyes may offer another alternative in order to reduce the amount of cationic additives required to ensure a certain optical density.

For an equal amount of this pigment, decreasing the primary PCC particle size increases the positively charged pigment surface area available to interact with and bind the dye. This promotes ink dye adsorption onto PCC particles near the paint application site, which leads to an increase in optical density. The segregation of large dye molecules on the paper surface is also aided by surface size exclusion and a high pore volume coating, allowing solvent to pass into the base paper while the molecules of dye are retained on the surface. This suggests the need for a porous coating formulation; A theoretical solution is therefore to introduce aggregates / agglomerates such that possibly aggregate pigments into the coating formulation with a carefully controlled pore volume distribution capillarity. However, as one skilled in the art knows, such a theoretical solution is quite difficult for the skilled engineer; in the specifically related domain, USP 5,750. 086 (discussed below) produces finely divided PCC, along with numerous other patents, but not porous products or aggregates / agglomerates.

A second challenge in increasing print quality is to reduce the bleed phenomenon, which is observed following the application of ink to the paper surface. The dye bleed from one color to another adjacent color occurs as a result of the latent ink dye binding and drying on the paper surface and is partly due to the absorption of the retarded ink solvent into the base paper. , which serves to bring the paint dye into contact with the surface for quick bonding. Bleeding has as a consequence the fact that printed images are distorted and appear less sharp.

Similarly, profiling also results in blurred images and occurs when the deposited ink follows the contours of the paper. As with ink bleed, this is rectified by rapid ink drying, preferably by dye absorption to adsorption when using porous media.

As implied in the above, there is a need to balance and control ink adsorption on the pigment surface, as opposed to the vacuum volume of the pigment holes, as absorption leads to decreased bleeding and profiling, but with a decrease. concomitant in optical density, while high absorption leads to improved optical density while increasing bleed and profiling.

A third challenge in achieving high quality printing is to reduce print inequality in the final paper product. Print inequality is the result of inhomogeneous penetration of the ink forming elements (cationic additive or coating pigment) of the coating formulation on the base paper.

Coating formulations that have a low solids content present an increased risk that the solvent will transport ink bonding elements off the paper surface during two phenomena: as the formulation solvent passes into the base paper following the paper coating and during the last solvent movement to the paper surface during drying. Such surface inequality may be limited by the use of a suspension having a high solids content, which limits the amount of solvent passing into and out of the base paper. However, such a high solids content is incompatible with some of the theoretical objectives or solutions.

When the coating formulation includes a pigment, the use of a high solids pigment suspension is desirable as it is known that starch binder and other additives generally added to multipurpose paper coating formulations, they are in the form of a low solids solution. If the solids content of the coating suspension is not maximized, dilution by the addition of binder and other additives will also be significant.

The above restrictions suggest the need for dye fixation in evenly distributed sites on the paper surface. It is clearly important that the coating formulation may have a high solids content, however it is known in the art that the high concentration of aggregate-containing suspensions often leads to a significant loss of pore volume.

As such, the theoretical solutions to the problems listed above have not been recognized as capable of solving the problems defined, and the above list, on the contrary, suggests that they need to be carefully considered, and extremely difficult, if not impossible, compromises. would be found; This was, however, one of the aims of this invention and it is the method of the invention that a global solution has finally been reached.

A second issue of one skilled in the art is to achieve this balance by employing a cost efficient solution. Any person skilled in the art will appreciate that such a requirement is always a factor of high complication in defining a technical solution, especially in the field considered.

Known multipurpose inkjet papers are characterized by a coiled surface or slightly pigmented qualities and generally a coiled or coated surface on a cost efficient inline coating apparatus such as Wool.MSP. ..or the Film Press, which allows for a high coating application speed and coating at a lower coating weight than its non-inline counterparts.

Special-class inkjet papers are characterized by superior high-resolution print quality over multipurpose papers. Such papers are generally coatings at a high coating weight, with formulations including high quality binders and additives, by means of more costly coating techniques, employing, for example, coating apparatus which is not in line with each other. curtain or blade, air trowel, Varibar ™.

Due to the high cost of the raw material, the production rate, weight and composition of the coating, and type of coating apparatus the cost of known multipurpose inkjet papers is lower than the cost of high quality matte inkjet papers. resolution by an order of magnitude that is roughly 6 to 20 times. Therefore, one skilled in the art recognizes the benefits of being able to achieve a high quality paper coating using a low cost coating solution.

As mentioned above, reducing the cationic additive demand of the coating formulation relative to current special inkjet pigments is also desirable in order to save costs.

In addition, it is also of interest to reduce the amount of binder required, as this component represents an expensive part of the coating composition and its presence on the paper surface reduces the active area available for ink interaction. One option is to use aggregates / agglomerates that have suitably small pores, in which case only enough binder to be adsorbed onto the surface of the aggregates / agglomerates needs to be added, as the binder cannot reach the surface of the primary particles exposed on the surface. inside Sos pores. However, as indicated above, this proposal is only theoretical.

With regard to the paper coating process, cost reduction can be achieved by promoting a faster paper drying stage. Following the coating. Faster drying translates into a higher paper machine speed and increased productivity as the risk of wet coating material being deposited on the papermaking machine is reduced. Faster drying is possible through the use of a coating formulation with a maximum solids content.

A high solids coating formulation also reduces the cost associated with transporting said coating formulation from the coating manufacturer to the paper mill, respectively the coating plant. One final aspect of the art is to ensure equal or improved processing capacity (number of sheets / yield without failure) in coating machines. Coating apparatuses such as MSP or Film Press are known to demonstrate improved processability when using increased solids content of the coating suspension while maintaining a low viscosity of the suspension ( 500 1500 mPAS).

As one skilled in the art will appreciate, these are additional technical problems to be solved. One skilled in the art will also recognize that many of these problems require conflicting or antagonistic solutions, leading to severe, if not properly balanced, problems; This was the difficult problem solved by this invention.

As mentioned above, the overall technical problem, and the technical challenge, is to develop a new class of PCC pigments structured to be used in a paper coating process to produce paper that is “from from a technical point of view ”, a coated multipurpose paper, particularly for inkjet applications, but whose printing properties would be enhanced over other coated papers of the same class while maintaining a low production cost.

Last but not least, the solution naturally needs to fit as many, if not all, printers as possible, adding another complexity to solve.

Anyone skilled in the art would recognize both the commercial need for such innovative technology and the supreme technical challenge it represents, and the considerable technical, commercial, and financial advancement it would provide. Background Art Pigment options for use in currently used multipurpose inkjet paper coatings include PCC inkjet pigments, such as those of EP 0 815 174, of expensive precipitated or fumigated silica.

In addition to its considerable cost as a coating material, it is known that silica is generally limited to low solids formulations, the use of which considerably reduces the speed of the coating line, further increasing it. the cost of the total coating. One of skill in the art is thus motivated to seek lower cost coating alternatives available in formulations with a higher solids content.

According to EP 0 815 174, which relates to the coating of a PCC, an organophosphonate compound, such as an amine-containing phosphoric acid or bis (methylenephosphonic acid) ethanol amine, is added to a PCC suspension in an amount 0.4 to 0.85 wt.% by weight of the PCC. Said suspension is then thermally cured for a sufficient period of time (1 to 10 hours at a temperature exceeding 75 ° C, or 2 to 5 hours at 80 to 85 ° C) to provide an area of specific surface area exceeding 60 m2 / g.

Alum, or other inorganic aluminum-containing compounds, may be co-precipitated during PCC synthesis. In example 1 of this patent, the addition of aluminum sulfate octadecahydrate is performed just prior to the introduction of carbon dioxide. Optionally, up to 10% by weight of hydrated aluminum sulfate may also be introduced. Thermal curing and / or milling of the PCC is considered critical so that an appropriate level of ink binding to the PCC is achieved.

In contrast, as will be seen below, neither time consuming heat curing nor grinding is required in the present invention; indeed, in the present invention, thermal curing even results in an inadmissible loss of the PCC surface area. In addition, the solids content of the suspension set forth in the examples was low, close to 20%. EP 1246 729 is presented as an improvement over the above-mentioned patent, and the product of this patent is said to be characterized by a surface area of 60 to 65 m2 / g, preferably 80 to 90 m2 / g, and generally not more than 95 to 100 m2 / g.

Such surface area is believed to be obtained by heat curing in the presence of an organophosphate compound as indicated above. PCC particles are believed to be individually spherical in shape, with a diameter on the order of 0.02 to 0.03 µm. This high specific surface area PCC, which has a narrow particle size, is obtained in a low solids (25%) suspension. The innovation alleged in EP 1 246 729 stems from the combination of a finely divided PCC having a surface area exceeding 60 m2 / g in a major proportion and a secondary proportion of silica gel together with a binder. . The resulting composition may be blade coated, or less preferably using an air spatula and a Meyer bar. The required presence of expensive silica and the low solids content of the suspension represent the main disadvantages. US 5,750,086 describes a process for the production of ultrafine colloidal calcium carbonate (PCC) particles in which magnesium sulfate is added in from 3 to 14% by weight of aqueous suspension of calcium hydroxide. followed by carbonation with the introduction of zinc sulfate alone or together with sulfuric acid.

In the examples, the introduced metal salt or sulfuric acid solutions have a concentration of 10% by weight. The process is considered to lead to ultra-finite colloidal calcium carbonate structured chain particles having an average diameter of 0.01 pm or less, an average length of 0.05 pm or less and a BET specific surface area of 70 m2 / g or greater.

The ultra-fine particles obtained are considered to have "lowest aggregation affinity". Indeed, the applicant primarily targets applications requiring unaggregated fillers, such as plastic applications, where the dispersibility of the end product is important. The present invention, by contrast, relates to an aggregate product for inkjet paper applications. The specific gas flow rate is 120 liters per minute per kilogram of calcium hydroxide as indicated in the examples of USP 5.750. 086, however, is significantly significantly higher compared to the process conditions of the present invention as will be seen below.

Indeed, it has been found in accordance with the present invention and contrary to prior art teaching and common knowledge that by reducing the specific gas flow to below about 30 or below about 20 liters per minute, per kilogram of calcium hydroxide during precipitation, not the distinct pigment described in USP 5,750,086 is obtained, but preferably mechanically porous coarse spherical agglomerates / aggregates consisting of said colloidal calcium carbonate.

As mentioned above, while it is possible to theorize as to the potential interest of porous PCC with an appropriate pore size distribution, possibly obtained through an agglomeration process, it remained theoretical until the surprising innovation above. It has also been noted that there is likewise no indication in the prior art or common knowledge that changing one parameter among many in the PCC preparation process would lead to porous clusters. There is also no indication that those clusters would be stable. There is even less indication that the parameter to be modified was precisely that of said flow rate. The process of USP S.750.086 was reproduced with the above-mentioned decisive modification for gas flow and the obtained product properties are given in Table 2, Example 1.

As can be seen from Table 2, the product obtained by changing the teaching of USP 5,750. 086 according to the invention is, quite surprisingly, not the distinct pigment described in USP 5,750. 086, but rather thick clumps.

However, a problem with the suspension produced in Example 1 is the low solids content, which is useful in some applications in the considered industries, but is not suitable for multipurpose paper coating in coating apparatus such as MSP. . This represented an added problem to be solved, as will be noted below. The surprising result is one of the key starting points of the present invention. Additional Prior Art Japanese Patent 2004-299302 teaches an inkjet registration form characterized by an "ink acceptance layer", said layer comprising calcium carbonate as a main pigment, which leads to profiling and bleeding. There is no specific indication as to the properties or structure of said calcium carbonate to be used. Rather, this document focuses on the use of a dispersant and the cationic charge density of said dispersant. EP 0 761 782, Japanese patent 10-265725 and Japanese patent 2004-197 055 describe improved inks for inkjet printing, ie used to improve optical density, bleed and / or profiling when printing . None of these patents provide specific indication of the coating pigment to be used when preparing the paper sheet. US 2003/0 227 531 A1 discloses a paper coating of a polyvalent metal salt, such as calcium, magnesium or aluminum, on a surface of the base paper to enhance profiling and bleeding. SUMMARY OF THE INVENTION The objectives of the invention can only be fully achieved by combining the specific process for preparing porous stable PCC agglomerates using a decisively reduced gas flow to the carbonation stage and the selected higher concentration stages. to produce a high solids PCC suspension for inkjet paper coating applications. It is briefly recalled that PCC is generally obtained in the prior art through the following stages: a suspension of calcium hydroxide in about 13% solids is first prepared by quenching: calcium oxide (also referred to as quicklime or virgin lime) is mixed with water in a stirring tank or reactor. Said calcium hydroxide suspension is then sieved, as in a 100 µm sieve, to remove any residual impurities and / or unreacted unburnt lime, and then directed to a stainless steel reactor equipped with a shaker. The temperature is generally adjusted to about 20 ° C and subsequently the suspension is directed to a carbonation tank or reactor, wherein carbon dioxide is bubbled therethrough, optionally with air, precipitating PCC. The PCC suspension leaves the carbonation tank where appropriate for an appropriate drop in pH and / or conductivity. The foregoing is known to one of skill in the art, and the following patents are incorporated herein by reference: EP 0 768 344, WO 98/52870 (PCT / IJS98 / 09019) and WO 99/51691 (PCT / US99 / 07233).

Generally speaking, the present invention resides in a series of early stages (Stages A) which lead to the production of a low solids PCC suspension comprising essentially essentially porous, stable porous agglomerates / aggregates. PCC, possibly followed by the higher concentration of said suspension (stages B) without the loss of said agglomerates / aggregates. Stage A according to the invention relates to a process for the preparation of stable, porous PCC agglomerates / aggregates as a low solids suspension, and the PCC product thus obtained, which is a new industrial product. The invention therefore encompasses a novel process for producing a PCC suspension via the carbonation pathway, characterized in that the carbonation stage is conducted with a carbonation gas flow rate reduced to below 30 liters per minute per kilogram of carbonation. calcium hydroxide during precipitation (Stage A). The present invention also encompasses a novel process for producing a PCC suspension via the carbonation pathway, further characterized in that the production of PCC as described in the above paragraph is conducted in the presence of magnesium sulfate in combination with one or more group II or II metal sulfates, said metal sulfate (s), in particular aluminum and / or zinc based, preferably aluminum or zinc based. These stages are based on those described in USP 5,750. 086, however with a much lower carbonation gas flow rate as mentioned above. The surprising result is that the pigment obtained is not a distinct, ultra-particular, non-binding product, but rather thick and stable porous agglomerates / aggregates (in the range of 1 to 5 pm).

The agglomerates / aggregates produced are surprisingly stable such that they are substantially kept in agglomerate / aggregate form during a subsequent "higher concentration" stage, and surprisingly the finally produced PCC agglomerates / aggregates confer printing properties. improved when incorporated into inkjet paper coatings as compared to the print quality of other market paper in the same class.

In most preferred embodiments, stage A of the present invention is further characterized by the use of the combination according to the invention of magnesium sulfate and aluminum sulfate, or magnesium sulfate and zinc sulfate.

In less preferred embodiments, the process according to the invention utilizes the combination of magnesium sulfate and zinc sulfate to which aluminum sulfate is added or the combination of magnesium sulfate and aluminum sulfate to which sulfate is added. Zinc In addition, a less preferred embodiment includes the use of magnesium sulfate and one or more group II and / or III metal sulfates. The invention further resides in the combination of the PCC production process (Stage A) with subsequent higher concentration (water removal / redispersion) stages in the presence of dispersant (Stage B).

It is entirely in accordance with the invention to use the combination: PCC production (Stage A) with the higher concentration process (Stage B) for this type of inkjet application. The final product is quite surprisingly a stable agglomerate / aggregate PCC having an average diameter in the range of μιη, ie between 1 and 5 pm, forming a PCC pigment which, when used in a formulation Standard coating leads to superior rfp print quality at a reduced cost. The invention also encompasses new PCC pigments themselves as new industrial products in the form of stable agglomerates / aggregates in the pm range, ie from 1 to 5 pm, as obtained in the final stage of Stage A or in the stage. Stage A and B. This is entirely different from previous commercial technologies and patents. The invention also encompasses new pigment suspensions containing said pigments as new industrial products, namely the low solids suspension obtained at the end of Stages A and the high solids suspension obtained at the end of stages A and B. A The invention further encompasses novel coating formulations for ink jet paper coating containing said pigment or pigment suspensions. The invention also encompasses inkjet papers coated with such novel coating formulations.

DETAILED DESCRIPTION OF THE INVENTION The invention relates to: a process for providing PCC useful for inkjet printing applications, of the type in which a calcium hydroxide suspension is first prepared by the virgin lime mixture. (CaO) with water in a stir reactor or tank (“quenched lime”). The calcium hydroxide suspension is then sieved, as in a 100 µm sieve, to remove residual impurities and / or unreacted unburned lime. The screened suspension is then directed to a stainless steel reactor equipped with a stirrer; the temperature is generally adjusted to between 10 and 70 ° C, and subsequently the suspension is directed to a carbonation tank or reactor, wherein carbon dioxide-containing gas is bubbled through the suspension. The suspension leaves the carbonation tank, where appropriate, for conductivity and pH, generally when conductivity reaches a minimum and the pH drops below 8. Coarse particles are removed in a sieve such as ma 45 µm sieve such that the suspension contains only the ultrafine PCC agglomerates of the invention. - characterized by the implementation of process stages, which comprise a series of first stages, relating to the production of the CCP, in which: Al In a CCP production process, as described above, the carbonation stage is performed at a flow of carbonation gas of below about 30 liters per minute at standard temperature and pressure per kilogram of calcium hydroxide during precipitation. The invention also relates to a process as defined above characterized in that: A2 In a PCC production process as described above under 1, the suspension of calcium hydroxide leaving said reactor of Stainless steel after said separation of the residual impurities and / or non-reactive unburnt lime is treated by the combination of magnesium sulfate and Group II and / or Group III metal sulfates, more preferably in the presence of an acid, said acid being more preferably sulfuric acid until stable porous agglomerates / aggregates are obtained at a concentration of 5 to 25% solids, preferably 15 to 20% solids ("precursor"). The invention also relates to a process as defined above characterized in that: A3 In a PCC production process as described above under Al and A2, the sodium hydroxide suspension is first prepared by mixing virgin lime with water in an ignition tank or reactor (- ^ caTextint ”) at a CaO: water weight ratio of between 1: 3 and 1:20, preferably between 1: 5 and 1: 12, so most preferred from 1: 7 to 1:10. The invention also relates to a process as defined above characterized in that: A4 In a PCC production process as described above under Al, A2 or A3, the temperature is preferably adjusted to between 15 to 50 ° C, more preferably at 15 to 30 ° C, before the suspension is directed to the carbonation tank or reactor.

These stages are shown schematically in the attached Figure 1. In that figure, the references have the following meanings: I: Water II: Virgin lime III: Reactor, such as a stirring tank or reactor IV: Sieve, such as a 100 pm sieve V: Residual impurities and / or Non-reactive unburned lime VI: Sodium hydroxide suspension VII: Reactor, such as a carbonation tank or reactor VIII: Magnesium Sulphate Solution IX: Group II and / or Group III Metal Sulfate (s) X: Optionally acid such as sulfuric acid XI: Carbon dioxide-containing gas XII: Sieve such as a 45 pm sieve XIII: Coarse particles XIV: PCC suspension (in a porous, agglomerated form) Stage A is followed by higher concentration of PCC produced during Stage A, in the presence of a cationic, anionic or combination dispersant, under conditions sufficiently mild or mild that aggregates / agglomerates are not substantially destroyed, or to a concentration of 25 to 60 %, preferably in the range of 35 to 50%, preferably 39 to 40%, by weight, of solids, is achieved. The amount of dispersant added is controlled such that the precursor PCC agglomerates / aggregates are only coated, this amount corresponding to that added prior to an increase in suspension viscosity.

If the higher concentration leads to a filter cake, such as following the higher concentration performed using a pressurized filter, or a centrifuge, or by vacuum filtration, the concentrated material is optionally washed with water and a redispersion is performed. until the final material substantially consists of stable porous agglomerates / aggregates identical to or very similar to those obtained in Stages A. The upper concentration may be performed at a thermal evaporation stage with the final material remaining substantially in the form of stable porous agglomerates / aggregates obtained at Stage A. Higher concentration of part or all of the precursor may lead to a dry product, and in such a case the dry product is again dispersed until the final material consistently. stable porous aggregates / agglomerates identical to or very similar to those obtained in Stage A. Fig. Figure 2 represents a water removal process in a centrifuge, with: I: Stage A PCC Suspension II: Water Removal Centrifuge III: Filtered IV: Filter Pie V: Dispersion Unit VI: Solution of a Dispersion (such as a Sodium Salt of a Polyacrylic Acid or a Sodium Citrate / Carboxy Methyl Cellulose Mixture) VII: Higher Concentration PCC Suspension Figure 3 is an alternate water removal process in a centrifuge with: I : Stage A PCC Suspension II: Water Removal Centrifuge III. Filtered IV. Filter Pie V. Dispersing Unit VI. Solution of a Dispersion Aide (such as Sodium Salt of a Polyacrylic Acid or a Sodium Citrate / Carboxy Methyl Cellulose Mixture) VII: PCC Suspension with Higher Concentration Figure 4 represents a higher thermal concentration stage soD vacuo, with: I: Stage A PCC Suspension II: Thermal Evaporator III: Higher Concentration PCC Suspension Figure 5 represents a higher thermal concentration on a heating plate, with: I: Stage A PCC Suspension II: Heating III: Solution of a Dispersion Aid (such as a Cationic Copolymer / Hydroxy Ethyl Cellulose) IV: PCC Suspension with Higher Concentration The following are optional and / or preferred features in Stage A to be taken alone or in combination. . The carbonation gas flow rate is preferably selected from 1 to 30, preferably from 10 to 20, more preferably about 19.7 liters per minute at conventional temperature and pressure per kilogram of sodium hydroxide during precipitation. Said carbonation gas is CO2 and a mixture of CO2 and one or more gases, such as air and / or nitrogen. The sodium hydroxide suspension is more preferably treated by a combination of magnesium sulfate and aluminum sulfate, a combination of magnesium sulfate and zinc sulfate.

According to less preferred options, zinc sulfate may be added to the combination of magnesium sulfate and aluminum sulfate or aluminum sulfate may be added to the combination of magnesium sulfate and zinc sulfate. The addition of magnesium sulfate is more preferably performed prior to carbonation. Magnesium sulfate may be added, at a less preferred option, either prior to addition to other sulfates or during addition. In a second less preferred option, magnesium sulfate may be added during carbonation, together with aluminum sulfate and / or zinc sulfate. As at least one preferred option of the invention, magnesium sulfate may be added during carbonation or just at the beginning of carbonation. Addition of aluminum sulfate and / or zinc sulfate most preferably occurs during the carbonation period. Addition of acid, i.e. sulfuric acid, more preferably in the form of a 10% by weight solution of sulfuric acid, preferably occurs at the onset of carbonation. Even more preferably, however, the addition of sulfuric acid occurs simultaneously with the addition of aluminum sulfate or zinc sulfate.

Without being bound by any theory, the applicant is of the opinion that in the present invention the presence, as described below, of sulfuric acid is necessary for proper results to be achieved.

In all of the above, Group II and / or III sulfates may be added in addition to aluminum sulfate and / or zinc sulfate, or as a substitute for aluminum sulfate and / or zinc sulfate. It is observed that the temperature in the carbonation tank is raised to between 40 and 80 ° C, preferably at 50 to 60 ° C, more preferably at 56 to 57 ° C. Removal of residual impurities and / or unreacted unburnt lime occurs on a 45 pm mesh screen when Brookfield viscosities in the material that comes out of the carbonation tank are sufficiently low, ie less than 100 mPas at 100 rpm. . The product of the final suspension consists substantially of porous / stable agglomerates / aggregates.

The following are optional and / or preferred Stage B features to be taken alone or in combination.

By deagglomeration / disaggregation it is considered that the agglomerates / aggregates obtained at the end of Stage A through the specific process of the invention are disintegrated, the disintegrated product being ultrafine PCC of the same type (with the exception of deposited or contained metal salts) as obtained. in US 5,750,086.

By "soft or mild" conditions it is considered that the disagglomeration / disaggregation of the agglomerates / aggregates is kept to a minimum such that said agglomerates / aggregates are not "substantially destroyed". More precisely, this means that it is more preferred that during the higher concentration stages the increase in surface area is limited to less than 50%, preferably less than 25%, and / or the increase in surface area. in the particle fraction below 2 pm is limited to less than 50%, more preferably less than 25%, more preferably less than 10%, and / or decreased mean aggregate diameter is limited. less than 50%, preferably less than 20%, more preferably less than 15%, as measured according to the means described below.

SEM images before and after the higher concentration are substantially identical, meaning that the existing clusters / aggregates (as obtained in the precursor Stage A) are not remarkably altered during the higher concentration. The upper concentration stage may be performed in the form of any thermal or mechanical separation technology for solid / liquid suspensions, provided that the aggregates / agglomerates obtained in Stage A (“precursor”) are sufficiently stable and not “substantially destroyed”. by said technology.

During the higher concentration process, a common dispersant is added in usual proportions to increase the solids content without excessively increasing the viscosity of the suspension. Said dispersant may be cationic, anionic or a combination thereof. The amount of dispersant added is controlled such that the precursor PCC agglomerates / aggregates are only coated, this amount corresponding to that added prior to an increase in suspension viscosity. For example, approximately 5 to 9% w / w of a 40% solution of polyacrylic acid sodium salt to dry calcium carbonate is added to the suspension containing the pigment of the invention, corresponding to approximately 1.5 to 3, 5% dry weight polyacrylic acid in dry calcium carbonate.

More preferably, the higher concentration is performed in a centrifuge, or on a pressurized filter, or by vacuum filtration or through higher thermal concentration, in the presence of a cationic, anionic dispersant, or in combination. The concentration of the final suspension is about 39 to 49% solids by weight. A degree of destruction of clusters / aggregates is expected. Such pigment aggregates / agglomerates are often held together by relatively weak Van der Waals or relatively electrostatic attractive forces, which are overcome by centrifugal and / or shear forces created within equipment associated with the higher commercial concentration, or either inside the centrifuge, fast rotating settling apparatus or high pressure filter press. The result that no noticeable destruction of aggregates / agglomerates is observed while achieving the required higher degree of concentration is therefore not entirely obvious. The present invention encompasses the stable porous PCC aggregates / agglomerates produced at the end of Stage A alone ("precursor") and the final porous stable PCC aggregates / agglomerates as obtained by the above processes at the end of Stage A in In combination with Stage B, said PCC is characterized by very innovative properties, which in turn make it particularly vapor for inkjet applications.

The stable porous PCC aggregates / agglomerates obtained at the end of Stage A, as well as those obtained after the higher concentration of Stage B, can be characterized by a selection of the following: a specific surface area of 30 to 100 m 2 / g preferably 50 to 80 m 2 / g, and / or an average aggregate diameter of 1 to 5 pm, with an average diameter of 2 pm, and / or a fines fraction below 2 pm, or less than 20 µm. %, preferably less than 15%, and / or a primary acicular particle size of 20 to 50 nm, with an aspect ratio of 1: 2 to 1:10, and / or a solids content by weight from 5 to 25%, preferably from 15 to 20% at the end of Stage A, and a solids content of 25 to 60%, preferably 35 to 50% solids, in particular from 39 to 40% solids at the end of stage B. The concentration of the final suspension may be obtained either partially or totally by the addition of one or more additional pigments or suspensions. The invention encompasses novel pigments, characterized in that they comprise porous PCC aggregates / agglomerates as described herein, and novel pigment or PCC suspensions, characterized in that they comprise aggregates / agglomerates. porous PCC as described herein. The invention also encompasses novel PCC pigments and suspensions, characterized in that their solids concentration is by weight 5 to 25%, preferably 15 to 20% solids at the end of Stage A and 25%. 60%, preferably 35 to 50%, in particular 39 to 40% solids at the end of Stage B.

According to a preferred embodiment, the pigment or functional pigment suspension with a high surface area and integrated cations is incorporated into the coating formulation, in a manner known per se to that skilled in the art, to effectively increase the density. optical when printing, without an increase in bleed or profiling: this is one of the major embodiments of the invention. The invention therefore also encompasses novel coating formulations for the papermaking industry, characterized in that it comprises new PCC aggregates / agglomerates, new pigments and / or suspensions described therein. The invention also encompasses coating formulations as described herein, characterized in that the PCC suspension it contains is characterized by the following properties: A solids content of 25 to 60%, preferably 35 to 50%, in particular around 39 to 40%, and / or a high surface area PCC effectively characterized by a specific surface area of 30 to 100 m2 / g, preferably 50 to 80 m2 / g. The invention also encompasses applications of the coating formulations according to any of claims 19 or 20, relating to inkjet paper coating, i.e. "multipurpose" inkjet paper coating, or special paper. high-quality.

To summarize, the most preferred invention and the best mode today is based on the selection of a decisively reduced carbonation gas flow during PCC precipitation, the specific combination of cations introduced into the PCC crystal lattice, and the use of a high content. 60% solids, preferably 35 to 50%, in particular around 39 to 40% solids by weight, in particular for use in paper coatings to be coated on MSP or Film Press, to use a high surface area PCC in the range of 30 to 100 m 2 / g, preferably 50 to 80 m / g, at the end of Stage A and / or the end of Stage B, more preferably at the end of stage B, in the use of small diameter primary PCC crystals, agglomerates / aggregates to form a porous PCC agglomerate.

Since surface area is a function of the particle size distribution, this distribution should be adjusted accordingly. The surface chemistry of the resulting functional pigment ensures increased ink dye fixation and increased pigment surface area, resulting in increased optical density or lower cationic additive demand in coating formation for equal optical density. There is no increase or even decrease in bleeding and / or profiling in relation to commercial alternatives. The possibility of obtaining a high solids suspension with the pigment according to the invention leads to improved processability when incorporated into a paper coating formulation and coated on a coating apparatus such as an MSP. (less buildup on MSP rollers. High solids content leads to lower drying energy demand and faster and easier drying; a higher paper machine speed is possible with increased deposits on rollers in the post drying section of the paper machine The invention leads to a high solids coating suspension, meaning that less energy needs to be introduced during the drying stage, thereby reducing cost.

In addition, the use of aggregates / agglomerates according to the invention limits the amount of binder required, thereby limiting the cost.

Due to the fact that the invention will favor agglomerates / aggregates, applications will be limited to matte inkjet paper applications. The agglomerates / aggregates according to the invention are too thick to obtain a glossy finish. EXAMPLES: Examples of innovative inkjet pigment preparations and pigment data for the corresponding products: Examples 1, 5 and 7 were prepared according to Stages A of the invention. Examples 2, 3, 4, 6, 8 and 9 constituted higher concentrations of one of the higher concentrated Examples 1, 5 and 7 according to the invention (Stage B).

Example 1: Process of the invention, Stage A with magnesium sulfate and zinc sulfate ......... 150 kg of virgin lime was added to 1300 liters of spout water in a stir reactor. Prior to the addition of lime, the water temperature was adjusted to 40 ° C. Virgin lime was quenched for 25 minutes under continuous agitation and the resulting suspension of 13.1% w / w solids calcium hydroxide ("lime milk") was then sieved through a ΙΟΟμηι sieve. Precipitation of calcium carbonate was conducted in a 1000 liter baffled cylindrical stainless steel reactor equipped with a gasification stirrer having a gas dispersion unit, a stainless steel carbonation tube to direct a gaseous gas stream. carbon dioxide / air inside the impeller, and probes for monitoring pH and suspension conductivity. 700 liters of extinction stage calcium hydroxide suspension as mentioned above were added to the carbonation reactor and the temperature of the reaction mixture was adjusted to the desired starting temperature at 20 ° C.

Prior to carbonation, 30 kg of aqueous solution to 10% magnesium sulfate (MgSCV 7 H2 O) was added to the lime milk. The stirrer was then adjusted to 1480 rpm, and the suspension was carbonated by passing a 26 percent volume gas mixture of carbon dioxide in air at 118 nm3 / hour, corresponding to 19.7 liters per minute at standard temperature and pressure per kilogram of calcium hydroxide through the suspension. During carbonation, 100 kg of 10% w / w aqueous solution of zinc sulfate (ZnSO4.7H20) and 30 kg of 10% w / w aqueous sulfuric acid solution were added to the reaction mixture from a continuously for the total carbonation time period.

Carbonation was achieved after 1 hour and 55 minutes of reaction time and a decrease in conductivity to a minimum was indicated, accompanied by a drop in pH at a constant value below 8.0.

During carbonation, the temperature of the suspension was allowed to rise due to the exothermic nature of the reaction to a final suspension temperature of 57 ° C.

Residual impurities and / or unreacted unburned lime were then removed by passing the aqueous suspension through a 45 µm sieve. The above carbonation product was an aqueous solids suspension of 15.6% w / w of ultra-primary primary calcium carbonate particles bonded together to form stable porous spherical aggregates.

Single crystals as constituents of the aggregates were characterized by a particle diameter of 20 to 50 nm and an aspect ratio of between 1: 2 and 1: 10 according to the SEM figures. The porous aggregates formed from these single crystals had diameters of between 1 and 5 pm, with an average diameter of 2 pm, also according to the SEM figures.

The product pigment data obtained in the process described above are listed as Example 1 in Table 2.

The results from the table for Example 1 confirm the high aggregate / agglomerate surface area and appropriate aggregate / agglomerate dimensions, but an insufficient solids content for subsequent coating applications. Indeed, the results of a low solids formulation run coating test according to the general coating conditions described below demonstrate that for an equal solids addition per paper surface area, Coating with a lower solids formulation leads to a decrease in optical density (Table 1). It is therefore necessary to achieve a higher concentration without noticeable loss or degradation of aggregates.

Table 1: Effect of total suspension solids content on 100% black optical density Example 2: Process of the invention, higher concentration (Stage B) of the product of Example 1 2210 g of precipitated calcium carbonate suspension obtained according to Stage A of the process as described in Example 1 was cooled to 25 ° C and removed from water in Stage B using a pressurized filter. A filter cake of about 43% solids w / w is obtained. The filtrate was collected and used for the redispersion of the filter cake. 50 g of the filtrate obtained at the water removal stage as described above was added in a 1 liter dispersion unit equipped with a propellant and mixed with 16 g of a 40% w / w sodium salt solution of polyacrylic acid as a dispersant.

Within this mixture, the filter cake having a residual moisture content of 57% w / w as obtained at the above water removal stage was gradually added to the interior of the dispersion unit under continuous mixing. .

After each addition of the filter cake and subsequent homogenization, the viscosity of the Brookfield suspension at 100 rpm was determined. The addition of the filter cake was stopped when Brookfield viscosity reached a defined upper limit of approximately 1000 mPas.

At this point, 680 g of the filter cake was then added. The product of the above concentration process described above was an aqueous suspension with a solids content of 39.8% w / w of ultra-primary primary calcium carbonate particles bonded together to form stable porous spherical aggregates of 1 to 5 pm. The crystal structure of the product was determined by SEM figures.

The product pigment data obtained in the process described above are listed as Example 2 in Table 2. From these data, it can be seen that the obtained pigment is characterized by a high BET specific surface area value, which shows that the high surface area required to interact and bind the paint together with the appropriate aggregate / agglomerate dimensions (1-2 µm according to SEM) and yellowing index were obtained. The final product is further characterized by a sufficient solids content for subsequent inkjet paper coating applications.

Example 3: Process of the invention, higher concentration (Stage B) of the product of Example 1 2210 g of the precipitated calcium carbonate suspension obtained according to the process described in Example 1 was cooled to 25 ° C and removed from water using a pressurized filter. The filtrate was collected and used for subsequent redispersion of the filter cake. 30 g of the filtrate obtained at the water removal stage as described above was added to a 1 liter dispersion unit equipped with a propellant and mixed with 6.4 g of a 35% w / w Citrate solution Sodium and 100 g of a 6% w / w sodium Carboxy Methyl Cellulose (CMC) sodium salt solution as dispersant.

Within this mixture, a filter cake having a residual moisture of 57% w / py obtained at the above described water removal stage was gradually added to the dispersion unit under continuous mixing. After each filter cake addition and subsequent homogenization, the Brookfield viscosity of the suspension at 100 rpm was determined. The addition of the filter cake was stopped when Brookfield viscosity reached a defined upper limit of approximately 1000 mPas.

At this time, 590 g of the filter cake had been added. The product of the above concentration process described above was an aqueous suspension having a solids content of 36.1% w / w of ultrafine primary calcium carbonate particles bonded together to form stable porous spherical aggregates. The crystal structure of the product was determined by the SEM figures.

The product pigment data obtained in the process described above are listed as Example 3 in Table 2.

The results reproduce the same comments as in Example 2.

Example 4: Process of the invention, production of PCC (Stage A, Magnesium Sulphate and Zinc Sulphate Option) and higher concentration (Stage B) 150 kg of virgin lime was added to 1300 liters of spout water in a agitation. Prior to the addition of lime, the water temperature was adjusted to 40 ° C. The virgin lime was quenched for 25 minutes under continuous agitation and the resulting suspension of calcium hydroxide ("lime milk") in a solids content of 12X8% w / w was sieved in a 100 µm sieve. Precipitation of calcium carbonate was conducted in a 4000 liter baffled cylindrical stainless steel reactor equipped with a gasification stirring having a gas dispersion unit, a stainless steel carbonation tube, in a gas stream. carbon dioxide / air to the propellant, and probes to monitor the PH and conductivity of the suspension. 700 liters of the calcium hydroxide suspension obtained at the quenching stage as mentioned above were added to the carbonation reactor and the reaction mixture temperature was adjusted to the desired starting temperature of 20 ° C.

Prior to the onset of carbonation, 30 kg of a 10% w / w aqueous solution of magnesium sulfate (MgSO 4, 7H 2 O) was added to the lime milk. The stirrer was then adjusted to 1480 rpm, the suspension was carbonated by passing a carbon dioxide gas mixture in a volume of 26 percent in air at 119 Nm3 / h, corresponding to 19.7 liters per minute at a conventional temperature and pressure per kilogram of calcium hydroxide through the suspension.

During carbonation, 100 kg of a 10% w / w aqueous zinc sulfate solution (ZnSO 4 .7H 2 O) and 0 kg of a 10% w / w aqueous sulfuric acid solution were added continuously to the over the total carbonation time to the reaction mixture.

Complete carbonation was achieved after 1 hour and 50 minutes of reaction time and indicated by a drop in conductivity to a minimum, accompanied by a drop in pH to a constant value below 8.0.

During carbonation, the temperature of the suspension was allowed to rise resulting in a final suspension temperature of 58 ° C due to the heat generated during the exothermic reaction.

Higher Concentration Stage: The suspension was then sieved through a 45 pm sieve before being fed to a water removal centrifuge (operating at 4440 rpm) at a rate of 350 l / hour. The higher concentration filter cake discharged by the water removal centrifuge added 4.75% w / w of a 40% w / w solution of a polyacrylic acid sodium salt as a dispersion aid continuous. The mixture was then again dispersed in a mixing unit and the higher concentration product was recovered as an aqueous pigment suspension. The product of the higher concentration carbonation stages, as mentioned above, was an aqueous suspension with a solids content of 39% w / w of ultrafine primary calcium carbonate particles bonded together to form porous spherical aggregates. stable. The single crystals as constituents of the aggregates had an acicular particle shape with a diameter of 20 to 50 nm and aspect ratios of between 1: 2 and 1:10. The porous aggregates formed from these single crystals had diameters of between 1 and 5 pm, with an average diameter of 2 pm. The crystal structure of the product was determined by SEM figures.

Product pigment data obtained in the process described above are listed as Example 4 in Table 2.

The results reproduce the same comments as Examples 2 and 3.

Example 5: Process of the Invention, Stage A, Magnesium Sulphate Option and 115kg Virgin Lime Aluminum Sulphate were added to 1000 liters of spout water in a stir reactor. Prior to the addition of lime, the water temperature is set to 40 ° C. The virgin lime was quenched for 25 minutes under stirring conditions, and the resulting suspension of calcium hydroxide ("lime milk") at a solids content of 12.7% was then sieved in a 100 µm sieve. The calcium carbonate precipitate was conducted in a baffled cylindrical stainless steel reactor equipped with a gasification stirrer having a gas dispersion unit, a stainless steel carbonation tube to direct a carbon dioxide gas stream / air to the propellant and probes to monitor the pH and conductivity of the suspension. 700 liters of the calcium hydroxide suspension obtained at the quenching stage as mentioned above was added to the carbonation reactor, and the reaction mixture temperature was adjusted to the desired starting temperature of 20 ° C.

Prior to the onset of carbonation, 30 kg of a 10% w / w aqueous solution of magnesium sulfate (MgSCV 7H20) was added to the lime milk. The stirrer was then adjusted to 1480 rpm, and the suspension was carbonated by passing a gaseous mixture of carbon dioxide in a volume of 26 percent in air at 118 Nm3 / hour, corresponding to 19.7 liters per minute in a standard temperature and pressure per kilogram of calcium hydroxide through the suspension.

During carbonation, 100 kg of 10% w / w aqueous solution of aluminum sulfate (H2 SO4. 18 Η20) and 30 kg of 10% w / w aqueous sulfuric acid solution were added continuously. to the reaction mixture over the total carbonation time period.

Carbonation was achieved after 1 hour to 48 minutes of reaction time and was indicated by a drop in conductivity to a minimum, accompanied by a drop in pH at a constant value below 8.0.

During carbonation, the temperature of the suspension was allowed to rise resulting in a final suspension temperature of 61 ° C due to the heat generated during the exothermic reaction. The suspension was then sieved in a 45 µm sieve, and the product was recovered as an aqueous pigment suspension. The carbonation stage product described above was an aqueous suspension with a solids content of 14.3% of ultrafine primary calcium carbonate particles bonded together to form stable porous spherical aggregates.

Unique crystals as constituents of the aggregates are characterized by acicular particle shapes with a diameter of 20 to 50 nm and aspect ratios of between 1: 2 and 1:10.

The porous aggregates formed from these single crystals had diameters of between 1 and 5 pm, with an average diameter of 2 pm. The crystal structure of the product was determined by SEM figures.

The product pigment data obtained in the process described above are listed as Example 5 in Table 2.

Example 6: Process of the invention, higher concentration (Stage B) of the product of Example 5 10 liters of precipitated calcium carbonate suspension, obtained according to the process described in Example 5, were sieved in a 45 pm sieve before be fed to a thermal evaporator. The evaporator consisted of a cylindrical stainless steel vessel equipped with a stirrer and a double-blanket heating unit operating with synthetic oil at 120 ° C as a heating medium.

Prior to evaporation, 8.5% w / w of a 40% w / w solution of a sodium salt of polyacrylic acid as a dispersion aid was added to the precipitated calcium carbonate suspension and mixed therewith. Higher thermal concentration was achieved by evaporation in said laboratory evaporator under atmospheric pressure at suspension temperatures in the range of 90 to 95 ° C. Evaporation was stopped when Brookfield viscosity reached a defined upper limit of approximately 100 ° C. mPas. The product of the above-defined higher concentration process was an aqueous suspension having a solids content of 35.5% w / w of ultrafine primary calcium carbonate particles bonded together to form stable porous spherical aggregates. . The crystal structure of the product was determined by SEM figures.

Product pigment data obtained in the process described above are listed as Example 6 in Table 2.

Example 7: Process of the invention, Stage A (Magnesium Sulphate and Zinc Sulphate Option) 115 kg of virgin lime was added to 1000 liters of spout water in a stir reactor. Prior to the addition of lime, the water temperature was adjusted to 40 ° C. The virgin lime was quenched for 25 minutes under stirring conditions and the resulting suspension of calcium hydroxide (“lime milk”) at a content of 12.5% w / w solids were then sieved in a 100 µm sieve. The calcium carbonate precipitate was led to a reactor. stainless steel, cylindrical, baffled, equipped with a gasification stirrer having a gas dispersion unit, a stainless steel carbonation tube to direct a carbon dioxide / air gas stream to the impeller, and probes to monitor the pH and the conductivity of the suspension. 700 liters of the extinction stage calcium hydroxide suspension, as mentioned above, were added to the carbonation reactor, and the reaction mixture temperature was adjusted to the desired starting temperature of 20 ° C.

Prior to the onset of carbonation, 30 kg of a 10% w / w aqueous solution of magnesium sulfate (MgSO4.7H20) was added to the lime milk. The stirrer was then adjusted to 1480 rpm and the suspension was carbonated by passing a gaseous mixture of carbon dioxide in a percent volume of 26 percent in air at 118 Nm3 / hour, corresponding to 19.7 liters per minute in standard temperature and pressure per kilogram of calcium hydroxide through the suspension.

During carbonation, 100 kg of a 10% w / w aqueous zinc sulfate solution (ZnSCh, 7H2o) and 30 kg of a 10% w / w aqueous sulfuric acid solution were added continuously to the reaction mixture during the total carbonation period.

It was achieved that carbonation was completed after 1 hour and 43 minutes of reaction time and indicated by a drop in conductivity to a minimum, accompanied by a drop in pH to a constant value below 8.0.

During carbonation, the temperature of the suspension was allowed to rise, resulting in a final suspension temperature of 62 ° C, due to the heat generated during the exothermic reaction. The suspension was then sieved through a 45 μιη sieve and the product recovered as an aqueous pigment suspension. The carbonation stage product described above was an aqueous suspension, having a solids content of 13.7% w / o of ultrafine primary calcium carbonate particles bonded together to form stable porous spherical aggregates. .

Single crystals as constituents of the aggregates were characterized by acicular particle shapes, with a diameter of 20 to 50 nm and aspect ratios of between 1: 2 and 1: 10.

The porous aggregates, formed from these unique crystals, presented diameters of between 1 and 5 μτη, with an average diameter of 2 gm. The crystal structure of the product was determined by SEM figures.

The product pigment data obtained in the process described above are listed as Example 7 in Table 2.

These results reproduce the same comments as for Example 1.

Example 8: Process of the invention, higher concentration (Stage B) of the product of Example 7 10 liters of the precipitated calcium carbonate suspension according to the process described in Example 7 were sieved in a 45 gm sieve and then fed to a thermal evaporation apparatus. The thermal evaporation apparatus consisted of a cylindrical stainless steel vessel equipped with a stirrer and a double blanket heating unit operating with a hot synthetic oil at 120 ° C as a heating medium.

Prior to evaporation, 8.5% w / w of a 40% w / w solution of a polyacrylic acid sodium salt as a dispersion aid was added to the precipitated calcium carbonate suspension and mixed therewith. Higher thermal concentration was achieved by evaporation in said laboratory evaporator under atmospheric pressure at suspension temperatures in the range of 90 to 95 ° C. Evaporation was stopped when Brookfield viscosity reached a defined upper limit of approximately 1000 mPas. The product of the above concentration process described above was an aqueous suspension having a solids content of 36.7% w / w of ultrafine primary calcium carbonate particles bonded together to form stable porous spherical aggregates. The crystal structure of the product was determined by SEM figures.

The product pigment data obtained in the process described above are listed as Example 8 in Table 2.

Example 9: Process of the invention, PCC production (Stage A, Magnesium Sulphate and Zinc Sulphate Option) and higher concentration (Stage B). 115 kg of virgin lime was added to 1000 liters of water from the spout in a stir reactor. Prior to the addition of lime, the water temperature was adjusted to 40 ° C. The virgin lime was quenched for 25 minutes under continuous agitation and the resulting suspension of calcium hydroxide ("lime milk" at a solids content of 13.5% w / w was then sieved in a 100 µm sieve Calcium carbonate precipitation was conducted in a 1000 liter baffled cylindrical stainless steel reactor equipped with a gasification stirrer, characterized by a gas dispersion unit, a stainless steel carbonation tube to direct a carbon dioxide / air gaseous stream to the propellant, and probes to monitor the pH and conductivity of the suspension 700 liters of a calcium hydroxide suspension obtained at the quenching stage as mentioned above have been added to the carbonation reactor and The temperature of the reaction mixture was adjusted to the desired starting temperature of 20 ° C.

Prior to the onset of carbonation, 30 kg of a 10% w / w aqueous solution of magnesium sulfate (MgSO4.7H20) was added to the lime milk. The stirrer was then adjusted to 1480 rpm, and the suspension was carbonated by passing a 26 percent volume of carbon dioxide gas mixture in air at 118 nm3 / hour, corresponding to 19.7 liters per minute, at a standard temperature and pressure per kilogram of sodium hydroxide through the suspension. During carbonation, 100 kg of a 10% w / w aqueous zinc sulfate solution (ZnSCV 7H20) and 30 kg of a 10% w / w aqueous sulfuric acid solution were added continuously to the mixture. reaction over the total carbonation time period.

Carbonation was achieved after 1 hour and 44 minutes of reaction time, and was indicated by a drop in conductivity to a minimum, accompanied by a drop in pH to a constant value below 8.0.

During carbonation, the temperature of the suspension was allowed to rise, resulting in a final suspension temperature of 56 ° C due to the heat generated during the exothermic reaction. The suspension was then sieved in a 45 gm sieve. Higher Concentration Stage The sieved suspension was then fed at a rate of 4001 / hour to a water removal centrifuge operating at 4440 rpm. To the higher concentration filter cake discharged by the water removal centrifuge was added 6% w / w of a 40% solution of the polyacrylic acid sodium salt as a dispersion aid continuously. The mixture was then again dispersed in a mixing unit and the higher concentration product was recovered as an aqueous pigment suspension. The product of the carbonation stages and higher concentration described above was an aqueous suspension with a solids content of 39.9% w / w of ultra-primary primary calcium carbonate particles bonded together to form porous spherical aggregates. . The single crystals as constituents of the aggregates had an acicular particle shape with a diameter of 20 to 50 nm and aspect ratios of 1: 2 to 1:10. The porous aggregates formed from these unique crystals had diameters of between 1 and 5 pm, with an average diameter of 2 pim. The crystal structure of the product was determined by SEM figures.

Product pigment data obtained in the process described above are listed as Example 9 in Table 2.

In Table 2, specific surface area (SSA) was measured using a Tristar 3000 Analyzer, particle size distribution (PSD) using a Helos Sympatec, gloss using a Datacolor Elrepho 3000 Jerics, solids content using a Mettler Toledo HB43 scale. , and viscosity using a Brookfield DVII Viscosimeter, all according to the manufacturer's recommendations.

Table 2: Characteristics of Pigments and Suspensions Containing Invention Pigment (all higher concentrations with cationic anionic disoersants or in combination) Coating Tests A selection of the above products has been introduced into paper coated and paper coated suspensions.

Suspension-based Coating Tests of Examples 4, 6 and 8 Three paper coating suspensions were prepared, each using one of the three PCC suspensions prepared according to the invention, along with conventional additives.

Emox TSC is an oxidized potato starch from Emsland-Staerke GmbH, Basoplast PR 8172 is a BASF binder, Catiofast CS is a Poly-Dadmac cationic additive of BASF, and Lupamin 6005 is polyvinylformamide from BASF.

Table 3: Dartesl Coating Formulation Doses Two additional paper coating suspensions were prepared, each using one of two PCC suspensions prepared according to the invention, along with another selection of standard additives (Mowiol 26 -88, Printofix). Cartafix VXT01 and Cartabond TS1 from Clariant).

Coating formulation compositions (parts) Coating suspension 1 was then coated simultaneously on both sides of a base paper, which is described in Table 5 using the Jargenberg MSP under the conditions listed in Table 6.

Table 5: Features of Coated Base Paper Using Coating Suspension 1 Table 6: Machine Conditions at Jagenberg MSP Using Coating Suspension 1 Coating Suspension 1 Coating suspensions 2, 3, 4 and 5 were coated on one side of a base paper, which is described in Table 7 using Coating Apparatus K under the conditions listed in Table 8. Table 7: Coated Base Paper Characteristics in Coating Suspensions 2, 3 4 and 5 Table 8: Machine Conditions Coating over a Coating Device K with a splined rod for Coating Suspensions 2,3, 4 and 5.

Inkjet printing tests Tests on three different inkjet printers, namely the Epson Stylus Photo 950, HP Deskjet 5550, and Canon i950, were used to compare the inkjet printability of coated paper. with the pigments of the invention as opposed to inkjet papers on the market. Print-test cards are designed to evaluate optical density as well as profiling and bleed.

HP Bright White and Epson S041214 papers are marketed as multipurpose inkjet papers. Zweckform 2585 and Epson S041061 papers are considered to represent high quality matte inkjet papers that offer higher print quality than conventional multipurpose inkjet papers. Optical density was measured using the Gretag D 186 densitometer according to the manufacturer's standard procedures. For an equal amount of ink applied, the higher the optical density, the better the coating keeps the dyes on the paper surface.

Coating Suspension 1 Coated Paper: The following coating assay (Coating Assay 1) was performed by coating Coating Suspension 1, based on the PCC suspension of Example 4, onto the base paper as described above. . Bleeding and profiling on a first type of test print card were measured using PapEye instrumentation from ONLY Solution GmbEIm according to standard procedures provided by the manufacturer. The lower the measured value, the better the bleed and profiling.

Table 9: Optical Density and Bleeding / Profiling Results of Coated Paper of the Invention Coating Opposition to Market Papers The table below shows that the optical density obtained with the product of the invention is higher than market papers for comparable purposes and approximates the quality of superior inkjet paper. The bleed obtained with the product of the invention is equal to or less than other equivalent market papers. The profile obtained with the product of the invention is inferior to other papers on the market. Improved optical density, bleed and profiling attest to an improved balance of paper coating absorption / adsorption properties against competitive market products.

In addition, the pigment structure did not negatively influence the processing capacity. The processing capacity was effectively improved as less dry accumulation was observed on the MSP.

Table 10: Optical Density and Bleeding / Profiling Results of Paper Coated with the Invention Coating Pigment Opposed to Market Papers.

The optical density results of the invention were superior to comparable market papers and in some cases also to higher quality inkjet papers. A decreased bleed and a similar degree of profiling compared to and comparable to one of the highest quality papers was also observed.

Again, pigment structure did not negatively influence processing capacity; processing capacity was improved as less dry buildup was observed on the film press. Table 11: Optical Density and Bleeding / Profiling Results of the Coating Pigment Coated Paper of the Invention Opposing Market Papers The optical density results of the invention were mainly superior to those of comparable market papers, and approached values provided by higher quality papers. Coating Papers with Coating Suspensions 2 and 3 The following coating tests were performed using zinc and aluminum based PCC suspensions, each thermally concentrated. Coating the naphtha and Coating Suspensions 2 and 3, respectively, led to the results of Coating Test 2 and 3 below. A second type of test card was used to evaluate optical density, bleed and profiling. Bleeding and profiling were measured using Quality Engineering Association Inc.'s Personal IAS® (Image Analysis System) instrumentation according to conventional procedures provided by the manufacturer. The lower the measured value, the better the bleed and profiling.

Table 12: Optical Density and Bleeding Results / Profiling Paper Coated with Coating Pigment of the Invention Opposing Market Papers The table above shows that the optical density obtained with the product of the invention is higher than comparable market papers. , and sometimes even exceeded even higher quality paper values. The bleed observed with the product of the invention is inferior to other equivalent market papers. The profiling obtained with the product of the invention is lower than that of other comparable market papers. The brightness of the paper was similar to market papers.

Table 13: Results of Optical Density and Bleeding / Profiling Paper Coated with the Invention Coating Pigment in Onosicão Market Papers. The table above shows that the optical density obtained with the product of the invention was clearly superior not only to comparable market papers, but sometimes also to higher quality paper. The bleed obtained with the product of the invention is equal to or less than other equivalent market papers. The profiling obtained with the product according to the invention is lower than or similar to other comparable market papers. The brightness of the paper was similar to market papers.

Table 14: Results of Optical Density and Bleeding / Profiling Paper Coated with the Coating Pigment of the Invention Opposing Market Papers. The table above shows that the optical density obtained with the product of the invention is higher than comparable market papers, and sometimes even exceeded higher quality paper values. The bleed obtained with the product according to the invention is equal to or less than other equivalent market papers. The profiling obtained with the product of the invention is lower than that of other comparable market papers. The brightness of the paper was similar to that of market papers.

Coating Papers with Coating Suspensions 4 and 5: The following coating assays were performed using zmco based PCC suspensions from Examples 6 and 8, thermally concentrated higher. Coating the base paper with Coating Suspensions 4 and 5 led, respectively, to the results of Coating Tests 4 and 5 below. Bleeding and profiling were measured using the second print test card and Quality Engineering Association, Inc. Personal IAS® (Image Analysis System) instrumentation according to standard procedures provided by the manufacturer. The lower the measured value, the better the bleed and profiling.

Table 15: Results of Optical Density and Bleeding / Profiling of Coating Pigment Coated Paper of the Invention, Opposing to Market Papers The table above shows that the optical density obtained with the product of the invention is higher than market papers for comparable purposes, and approaches the quality of superior inkjet paper. The bleed obtained with the product of the invention is equal to or less than other equivalent market papers. The profiling obtained with the product of the invention is inferior to other market papers. Improved optical density, bleed and profiling attest to an improved balance of absorption / adsorption properties relative to competitive market products. Table 16. Optical Density and Bleeding Results / Profiling of Coated Pigment Coated Paper of the Invention, on Market Papers The optical density results of the invention were superior to comparable market papers as well as to top quality inkjet papers. A decreased bleed and an increase in profiling relative to comparable roles were also observed. Table 17: Results of Optical Density and Bleeding / Profiling Paper Coated with the Coating Pigment of the Invention Opposed to Market Papers.

The optical density results of the invention were always superior to those of other comparable papers on the market, and approached the values provided by higher quality papers. A decreased bleed and a similar degree of profiling relative to comparable market papers was observed. The present invention also encompasses the technical equivalents of the above description as well as options that would be readily available to one skilled in the art upon reading the present application.

Claims (18)

Process for providing a useful PCC for inkjet printing applications, - of the type in which a calcium hydroxide suspension is first prepared by mixing virgin lime (CaO) with water in a tank or reactor. ("quenching"), the calcium hydroxide suspension is then sieved, as in a 100 µm sieve, to remove any residual impurities from unreacted unburnt lime, the sieved suspension is then directed to a stainless steel reactor equipped with a stirrer; the temperature is generally adjusted to between 10 and 70 ° C, and subsequently the suspension is directed to a carbonation tank or reactor, wherein carbon dioxide-containing gas is bubbled through the suspension, the suspension leaves the carbonation tank. carbonation where appropriate, in view of conductivity and pH, generally when conductivity reaches a minimum and pH drops below 8, coarse particles are removed in a sieve such as a 45 μηι sieve such that that the suspension contains only the ultrafine PCC clusters of the invention, characterized in that the implementation of the process stages comprises the following: A - first stages, production of the PCC; AI - the carbonation stage is performed at a carbonation gas flow rate of below 30 liters per minute at standard temperature and pressure per kilogram of calcium hydroxide during precipitation, and - the calcium hydroxide suspension is treated by a combination of magnesium sulfate and aluminum sulfate and / or a combination of magnesium sulfate and zinc sulfate; A2 the calcium hydroxide suspension, which leaves said stainless steel reactor after said separation of said residual impurities and / or non-reactive unburnt lime, is treated by a combination of magnesium sulfate and metal sulfates of the Group II and / or Group III, - most preferably in the presence of an acid, - said acid being, more preferably, sulfuric acid - until stable porous aggregates are obtained at a concentration of 5 to 25% solids, preferably 15 to 20% solids ("precursor"); A3 - said calcium hydroxide suspension is first prepared by mixing virgin lime with water in a tank or stirring reactor ("quenching") at a CaO: water ratio of 1: 3 to 1 : 20, preferably from 1: 5 to 1:12, more preferably from 1: 7 to 1:10; A4 - the temperature is preferably adjusted to between 15 and 50 ° C, more preferably between 15 and 30 ° C, before the suspension is directed to a carbonation tank or reactor, wherein Stage A is followed by the following stages, Stage B; B. Higher concentration of “precursor”: water removal / redispersion stages following “Stage A” above, - higher concentration of CCP produced during Stage A with a cationic, anionic dispersant or in combination, - until a concentration of 25 to 60%, preferably in the range of 35 to 50%, more preferably 39 to 40% solids by weight, is reached. Process according to Claim 1, characterized in that at Stage A at least one of the following parameters is applied: - the carbonation gas flow rate is preferably selected in the range 1 to 2. 30, preferably 10 to 20, more preferably 19.7 liters per minute, at standard temperature and pressure, per kilogram of calcium hydroxide during precipitation, said carbonation gas is CO2, or a mixture CO2 and one or more other gases, such as air and / or nitrogen, - the calcium hydroxide suspension is more preferably treated by a combination of magnesium sulfate and aluminum sulfate, - or a combination of magnesium sulfate and zinc sulfate. Process according to either of Claims 1 and 2, characterized in that at Stage A at least one of the following parameters is applied: - Zinc sulfate may be added to the combination of magnesium sulfate and sulfate. - aluminum sulfate may be added to the combination of magnesium sulfate and zinc sulfate, - the addition of magnesium sulfate is more preferably performed before carbonation, - magnesium sulfate may be added, in a less preferred option, or before or during the addition of other sulfates, - magnesium sulfate may be added, in a less preferred option, during carbonation together with aluminum sulfate and / or zinc, - magnesium sulfate may be added. be added during carbonation or at the beginning of carbonation, - the addition of aluminum sulphate and / or zinc sulphate occurs during carbonation, - the addition of acid, ie sulfuric acid, most preferably in the form of a 10 wt% H 2 SO 4 solution, occurs at the onset of carbonation, - more preferably, the addition of H 2 SO 4 occurs simultaneously with the addition of aluminum sulfate or zinc sulfate, - in all of the above, Group II and / or III sulfates may be added in addition to aluminum and / or zinc sulfates, or as a substitute for aluminum and / or zinc sulfates, - is It is observed that the temperature in the carbonation tank is raised to between 40 to 80 ° C, preferably to 50 to 60 ° C, more preferably to 56 to 57 ° C, - the removal of residual impurities and / or Non-reactive unburned lime occurs in a 45 pm mesh screen when the Brookfield viscosity of the material leaving the carbonation tank is sufficiently low, ie less than 100 mPas at 100 rpm, - the product of the final suspension. consists of stable porous clusters / aggregates. Process according to any one of Claims 1 to 3, characterized in that in Stage B, the increase in surface area is limited to less than 50%, preferably less than 25%, and / or - the increase in the particle fraction below 2 pm is limited to less than 50%, preferably less than 25%, more preferably less than 10%, and / or - the decrease in mean aggregate diameter. is limited to less than 50%, preferably less than 20%, more preferably less than 15% as measured using a Helos Sympatec apparatus, - by "disaggregation / disaggregation" it is understood that agglomerates / aggregates obtained at the end of stage A through the specific process of the invention are disintegrated, - the higher concentration stage can be performed in the form of any thermal or mechanical separation technology for solid / liquid suspensions. Process according to any one of Claims 1 to 4, characterized in that: - the higher concentration is carried out in a centrifuge, or on a pressurized filter, or by vacuum filtration or by higher thermal concentration, in presence of a cationic dispersant, anionic or in combination, - and wherein the concentration of the final suspension is 39 to 40% solids by weight. Process according to any one of Claims 1 to 5, characterized in that: - the higher concentration leads to a filter cake, such that by the higher concentration in a pressurized filter or a centrifuge through vacuum filtration, and in such a case: - the concentrated material is optionally washed with water, - a redispersion is formed, - until the final material consists of stable porous agglomerates / aggregates as those obtained in Stage A of claim 1, - the higher concentration may be performed at a thermal evaporation stage, the final material remaining as stable porous agglomerates / aggregates obtained in Stage A of claim 1. Process according to any one of Claims 1 to 5, characterized in that: - the higher concentration of part or all of the precursor leads to a dry product, and in such a case, - a redispersion is performed, - until that the final material consists of stable porous agglomerates / aggregates such as those obtained in Stage A of claim 1. Process according to any one of claims 1 to 7, characterized in that 5 to 9% w / w of a 40% sodium salt solution of a polyacrylic acid relative to dry calcium carbonate is added. as a dispersant to the suspension containing the pigment obtained as defined in claim 1 (Stage A) (corresponding to 1.5 to 3.5% by weight of dry polyacrylic acid on dry calcium carbonate). Process according to any one of claims 1 to 8, characterized in that the concentration of the final suspension is partially or wholly obtained by the addition of one or more additional pigments or pigment suspensions during Stage B. Stable porous PCC aggregates / agglomerates as defined in any one of claims 1 to 9, characterized in that they have the following properties: - a specific surface area of 30 to 100 m2 / g, preferably 50 to 80 m2 / g, and / or - an average aggregate diameter of 1 to 5 pm, with an average diameter of 2 pm, and / or - a fines fraction below 2 pm of less than 20%, preferably less than 15% (as measured on a Helos Sympatec), and / or - an acicular particle primary particle size of 20 to 50 nm, with an aspect ratio of between 1: 2 and 1: 10 and / or - a solids content by weight of 5 to 25%, preferably 15 to 20% at the end of Stage A, and a solids content of 25 to 60%, preferably 35 to 50% solids, in particular 39 to 40% solids, at the end of Stage B. Pigments, characterized in that they comprise stable porous PCC aggregates / agglomerates as defined in claim 10. PCC suspensions, characterized in that they comprise stable porous PCC aggregates / agglomerates as defined in claim 10. PCC suspensions according to claim 12, characterized in that their solids concentration is by weight: - when in the form of the "precursor" at the end of Stage A, from 5 to 25%, such that from 15 to 20% solids, when in the form of the final higher concentrated PCC (Stage B), from 25 to 60% solids, preferably from 35 to 50% solids, in particular from 39 to 40% solids. Coating formulations for the papermaking industry, characterized in that they comprise new PCC aggregates / agglomerates, new pigments and / or new suspensions as defined in any one of claims 11 to 13. Coating formulations according to claim 14, characterized in that the PCC suspension they contain has the following properties: - a solids content of 25 to 60%, preferably 35 to 50%. , in particular from 39 to 40% by weight, and / or high specific surface area PCC, with a specific surface area of 30 to 100 m 2 / g, preferably 50 to 80 m 2 / g. Applications of the coating formulations as defined in any one of claims 14 or 15, characterized in that they are for coating inkjet paper. Applications of the coating formulations as defined in any one of claims 14 or 15, characterized in that they are for the coating of "multipurpose" inkjet paper or high quality specialty paper. Inkjet paper, that is, "multipurpose" inkjet paper or special high quality paper, characterized in that it is coated with at least one coating composition as defined in claims 14 or 15.