MX2007012417A - Process for preparing precipitated calcium carbonate pigment, especially for use in inkjet printing paper coatings and precipitated calcium carbonate - Google Patents

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. 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. The invention provides an IgE-Retargeting, Function-Altering Molecules (ERFAM) construct of the formula A'-B', wherein A'represents a moiety that binds an IgE and B'represents a moiety that binds an inhibitory receptor;or a construct of the formula A'-X-B', wherein A'represents a moiety that binds an IgE, X represents a linker moiety, B'represents a moiety that binds an inhibitory receptor. Also provided are their methods of use in treating IgE-related disorders, e.g., allergy.

Description

PIGMENT OF PRECIPITATED CALCIUM CARBONATE, ESPECIALLY FOR USE IN PAPER COATINGS FOR PRINTING BY JET INK FIELD OF THE INVENTION The present invention relates to new mineral pigments of precipitated calcium carbonate (PCC) species. More specifically, the invention relates to new and innovative pigments of precipitated calcium carbonate (PCC) which can be used in coating formulations for manufacturing "multi-use" coated paper, in particular for ink jet printing applications, whose quality The printing would be identical or quite similar to that of high resolution commercial papers while maintaining low production costs. Multi-purpose paper is often used for different types of printing, such as black and white copies, laser printing or fax paper. Also, the invention relates to the production of said new mineral pigments of PCC species in suspension form, having a solids content suitable for making paper coatings for inkjet printing in low cost paper coaters, of Controlled Size (MSP, for its acronym in English).

Ref .: 186023 BACKGROUND OF THE INVENTION There is a demand for multi-purpose coated papers, and in particular for papers suitable for inkjet applications, which offer better print quality without this implying an increase in production costs. The multipurpose office paper currently available often has an unsatisfactory quality of inkjet printing. One of the main obstacles that has to be overcome in order to achieve an increase in the quality of the prints is to increase the optical density of the ink applied to the surface of the paper, in particular after the application of ink covering the entire color spectrum. Inkjet printers form images by applying a series of ink dots on the surface of the paper. The dyes used for inkjet printing are generally anionic and with a low solids formulation that is very mobile in nature. Only good print quality is obtained if the dye remains on the paper surface when the solvent of the ink penetrates the paper, leaving a uniform circular point at the application site. It is known that a difference is usually used of charge between the adsorbent and the adsorbate, respectively the surface of the paper and the dye molecules, to promote the adsorption of the dye. Therefore, a solution to increase the optical density is to increase the number of cationic points near the surface of the paper. If the surface of the paper is coated, the number of cations present near its surface can be increased by adding cationic additives to the coating formulation. However, adding cationic additives to obtain a given optical density significantly increases the final cost of the paper. The increase in part of the cationic additive that remains in a thin layer near the surface of the paper, characterized by the retention of the coating, is a second possibility to increase the optical density. Greater retention of the coating can be achieved by a smaller distribution of the size of the coating particles, which is a technically difficult and expensive solution. If the formulation of the coating contains PCC, the inherent adsorbent properties of the PCC particles towards the dyes used in the ink may offer another alternative to reduce the amount of cationic additives necessary to guarantee a certain density optics. For an equal amount of this pigment, decreasing the size of the primary PCC particles increases the surface of the positively charged pigment available to interact with and bind to the dye. This enhances the adsorption of the dye by the PCC particles near the point of application of the ink, which results in an increase in optical density. The separation of the larger dye molecules on the surface of the paper is also aided by the exclusion by size on the surface and by the highly porous coating, which allows the solvent to reach the support paper leg the dye molecules in the surface. This suggests the need for a porous formulation for the coating; thus, a theoretical solution is to introduce aggregates / agglomerates, such as aggregate pigments, into the coating formulation, while controlling the permeability and pore size distribution. However, as all experts in the art know, this theoretical solution is quite difficult to implement; in the case at hand, USP 5,750,086 (discussed below), produces very well divided PCC products, as well as many other patents, but not porous or aggregates / agglomerates. A second problem that must be solved to increase the quality of the prints is to reduce the phenomenonSee of ink run obserafter application of the ink on the surface of the paper. The shift of the ink from one color to another adjacent color occurs as a result of the latent fixation of the dye and its drying on the surface of the paper, which in turn is partly due to the delay in the absorption of the solvent from the ink on the support paper, which serves to put the dye in contact with the surface for quick fixing. This phenomenon of bleed has as a consequence that printed images appear distorted and less clear. In the same way, the migration effect also results in blurry images and occurs when the deposited ink follows the contour of the paper. As in the case of the bleed, it can be solby a rapid drying of the ink, the absorption of the ink being preferable to the adsorption when a porous medium is used. This implies that it is necessary to balance and control the adsorption of the ink on the surface of the pigment with the absorption in the available space of the pigment pores, since a high absorption results in a lesser shift and migration effect that nevertheless comes accompanied by a reduction in optical density, while high adsorption results in a better optical density but also a greater shift and migration effect.

A third challenge to obtain a high quality print is to reduce the irregularity of the printing on the final product on paper. The irregularity in the printing is the result of the heterogeneous penetration of the ink fixing elements (cationic additive or coating pigment) of the coating formulation into the backing paper. The formulations of the coating having a low solids content have a higher risk of the solvent moving the ink fixing elements away from the surface of the paper by two phenomena: when the solvent of the formulation reaches the backing paper after the coating and during the subsequent displacement of the solvent to the paper surface during drying. This irregularity of the surface can be reduced by using a suspension which has a high solids content and which limits the amount of solvent that reaches and leaves the support paper. However, this high solids content is incompatible with any of the aforementioned theoretical or objective solutions. When the coating formulation includes a pigment, it is preferable to use a high solids pigment suspension, since it is known that the starch fixative and other additives that are generally added to the multi-purpose paper coatings formulations are in the form of solution with low content in solid If the solids content of the coating suspension is not increased, the dilution by adding the fixative and other additives will be too high. The limitations mentioned above suggest the need to fix the dyes in homogeneously distributed points on the surface of the paper. Obviously, it is important that the coating formulation has a solids content; however, as is known in the art, reconcentration of aqueous suspensions containing aggregates often results in a significant reduction in pore size. Therefore, it was not considered that the theoretical solutions to the aforementioned problems could solve the defined problems and, on the contrary, this list suggests that they should be considered carefully and that extremely difficult solutions should be sought, if not impossible; However, this was one of the objectives of the invention and it is worthwhile having reached a global solution. A second aspect of concern for those skilled in the art is to achieve this balance by means of a cost-efficient solution. Any person with experience will appreciate that this requirement is always a factor that greatly complicates the definition of a technical solution, especially in this specific field. The multi-purpose papers for known inkjet printing are characterized by their surface treatment and slightly pigmented qualities, and by receiving a surface treatment or being coated in a cost-efficient chain-production coater, like the MSP or the film press, since they offer a great speed of application of the coating and a coating of lighter weight than the one of the options out of line. Specific papers for inkjet printing are characterized by a higher quality of high resolution printing versus multi-purpose papers. In general, these papers are coated with a heavyweight layer with formulations that include special, high-quality additives and fixatives by more expensive coating techniques, using for example Off-line Varibar ™, floating blade, curtain or knife. Due to the cost of the raw material, the rate of production, the weight and composition of the coating and the type of coating machine, the cost of the known multipurpose inkjet printing papers is lower than that of the high resolution matte paper for printing with ink jet, around 6 to 20 times higher. Therefore, persons skilled in the art will recognize the advantages of being able to obtain a high quality coating for the paper by means of a low cost coating solution. As indicated above, it is also desirable to reduce costs by reducing the amount of cationic additive used by the coating formulation versus the amount used for the current specialized pigments for ink jet printing. Also, it is interesting to reduce the amount of fixer required, since this component represents a high cost part in the composition of the coating and that its presence on the surface of the paper decreases the active area available to interact with the ink. One option is to use aggregates / agglomerates that have sufficiently small pores, in which case only the sufficient amount of fixative would have to be added to adsorb on the surface of the aggregates / agglomerates, since the fixative can not reach the surface of the particles main exposed in these pores. However, as indicated above, this proposal is only of a theoretical nature. With regard to the paper coating process, it can be achieved to reduce costs by promoting a faster drying of the paper after coating. A faster drying results in a faster machine speed and higher productivity, since the risk of the still wet coating being deposited in the paper making machine would be reduced. Faster drying can be achieved by using a coating formulation with higher solids content. Also, a coating formulation with a high solids content also reduces the costs associated with transporting said coating formulation from the pigment manufacturer to the paper mill and to the coating plant. A final concern of the persons with experience in the art is to guarantee a paper behavior (number of sheets produced without failures) greater or equal in the coaters. It is known that coatings such as MSP or the film press have a better paper performance when coating suspensions with higher solids content are used while maintaining a low viscosity (between 500 and 1500 mPas) of the suspension. As any person skilled in the art will observe, these are two additional technical problems that will have to be solved. Also, you will appreciate that many of the problems mentioned require conflicting solutions or that they conflict with each other, which could lead to important problems if an adequate balance is not found; this has been a difficult problem that has solved the present invention. As indicated above, the challenge and the overall technical problem is to develop a new class of PCC pigments designed for use in the coating process to manufacture a paper that is, from the technical point of view, a coated paper multipurpose, especially for ink jet printing applications, but whose properties are better compared to other coated papers of the same quality, while maintaining a low production cost. Last, but not least, it is obvious that the solution should be adapted to as many different types of printers as possible, but to all, which means a new complexity to solve. A person skilled in the art will recognize the commercial need for an innovative technology such as this one, the great technical challenge that it represents, and the considerable technical, commercial and financial advance that it would entail. Pigments for use in commercially available multi-use ink jet printing papers include specialized PCC pigments for ink jet printing, such as those of European Patent EP 0 815 174, or more expensive solutions such as silica smoked or precipitated. In addition to its considerable cost as a coating material, it is known that silica is generally limited to formulations with low solids content, the use of which considerably reduces the speed of the coating line, which in turn also increases the overall cost of the coating. covering. Accordingly, any man skilled in the art will have reasons to opt for the lower cost coating alternatives available in formulations with higher solids content. According to EP 0 815 174, which relates to a coating with a PCC, an organophosphonate, such as a phosphoric acid containing amine or ethanol bis (methylene phosphonic acid), which is added to a suspension of PCC in an amount 0.4-0.85% by weight in relation to the weight of the PCC. Subsequently, this suspension is matured by heat for a sufficient period of time (between 1 and 10 hours at a temperature not exceeding 75 ° C, or between 2 and 5 hours at 80-85 ° C) for a surface greater than 60 m2 / g. During the synthesis of the PCC, alumina or other inorganic components containing aluminum can be precipitated with a simple solution. In Example 1 of this patent, the addition of aluminum sulphate octadecahydrate is carried out just before the introduction of carbon dioxide. Optionally, up to 10% of the weight can also be added of hydrated aluminum sulfate. The maturation with heat and / or the grinding of the PCC are considered fundamental to achieve an adequate degree of fixation of the ink to the PCC. On the contrary, as will be seen later, the present invention does not require an expensive and long process of maturation with heat or grinding; in fact, in the present invention, maturation with heat even results in an inadmissible loss of the surface of the PCC. In addition, the solids content of the suspension revealed by the examples was low, close to 20%. EP 1 246 729 was presented as an improvement over the aforesaid patent, and it is said that the product of this patent obtains an area of 60 to 65 m2 / g, preferably 80 to 90 m2 / g, and generally does not exceed 95 to 100 m2 / g. It is said that this surface is obtained by heat maturation in the presence of an organophosphonate compound, as indicated above. It is said that the PCC particles are spherical in shape, with a diameter of the order of 0.02-0.03 pm. This PCC with a very specific surface that has a reduced particle size is obtained in a suspension with a low solids content (25%). The innovation claimed in EP 1 246 729 is based on the combination of a finely divided PCC that has a surface area greater than 60 m2 / g, in a large proportion, and a lower proportion of a silica type gel together with a fixative. The resulting composition can be coated with a blade or, less preferably, by means of a floating blade or a Meyer rod. The necessary presence of an expensive compound such as silica and the low solids content of the suspension represent the main negative aspects of the product defended by this patent. USP 5,750,086 describes a process for manufacturing ultrafine particles of colloid calcium carbonate (PCC), to which magnesium sulfate is added in 3-14% by weight by an aqueous suspension of calcium hydroxide, followed by a carbonation process by the introduction of zinc sulfate alone or with sulfuric acid. In the examples, the solutions of metal salts or sulfuric acid introduced have a concentration of 10% by weight. It is said that the process gives rise to ultrafine particles structured in chain of calcium carbonate colloid that have an average diameter of 0.01 μp? or lower, an average length of 0.05 μ? t? or lower and a specific BET surface area of 70 m2 / g or higher.

It is said that the ultrafine particles obtained "have a lower aggregation affinity". In fact, the applicant mainly refers to applications that require non-aggregated filler materials, such as applications in plastics, in which the dispersibility of the product is an important element. On the contrary, the present invention is directed to an aggregate product for paper applications for inkjet printing. However, the specific gas flow rate of 120 liters per minute per kilogram of calcium hydroxide indicated in the examples of USP 5,750,086 is significantly higher compared to the process conditions of the present invention, as indicated continuation. In fact, according to the following invention it has been concluded that, contrary to what was indicated by prior art and knowledge, by reducing the gas flow velocity around 30 or below 20 liters per minutes per kilogram of calcium hydroxide during precipitation, the discrete pigment described in USP 5,750,086 is not obtained, but rather the porous, mechanically stable and quite thick spherical aggregates / agglomerates of which said colloid calcium carbonate consists. As indicated above, although could theorize about the interest of the porous PCC with an adequate distribution of the pore size, probably obtained through a process of agglomeration, this was still theoretical until the aforementioned surprising innovation. It has also been observed that there is no indication in the prior art or in the available knowledge that by altering a parameter of the dozens of parameters of the PCC preparation process, porous agglomerates could be obtained. In addition, there were even fewer indications that these agglomerates could be stable and even less that the parameter that had to be modified was precisely the flow velocity. The process of USP 5,750,086 was reproduced with the aforementioned critical modification of the gas flow velocity. The properties of the product obtained are shown in Table 2, Example 1. As can be seen in Table 2, the product obtained by modifying the content of USP 5,750,086 according to the invention is not the discrete pigment described in the USP 5,750,086, if not quite thick agglomerates, which is quite surprising. However, a problem with the suspension produced in Example 1 is the low solids content, which is useful for certain applications in the aforementioned industries, but not for paper coatings. multipurpose in coaters like the MSP. This represented an additional problem that had to be solved, as will be discussed later. This surprising result is one of the fundamental starting points of the present invention. Additional prior art: Japanese patent 2004-229302 relates to an inkjet printing form that produces an "ink acceptance layer", which contains calcium carbonate as the main pigment, which would result in an improvement in what it refers to the migration effect and the ink shift. No specific indication is made as regards the properties or the structure of the calcium carbonate to be used. Instead, this document focuses on the use of a dispersant and the density of the cationic charge of said dispersant. EP 0 761 782, Japanese Patent 10-265 725 and Japanese Patent 2004-197 055 describe improved inks for ink jet printing, mainly by increasing the optical density, the migration effect and the ink shift when printing. None of these patents offers a specific indication on the coating pigment that will be used to prepare the sheet of paper. US 2003/0227 531 A1 refers to a paper coating of a polyvalent metal salt, such as calcium, magnesium or aluminum on a surface of the support paper, to improve the migration effect and the ink shift. BRIEF DESCRIPTION OF THE INVENTION The objectives of the invention can only be fully achieved through the combination of the specific process for preparing porous and stable PCC agglomerates, the decisive reduction of the gas flow rate used for carbonation, and certain steps of reconcentration to produce a suspension of PCC with high solids content suitable for paper coating applications. It is briefly recalled that PCC was generally obtained in the prior art by the following steps: first, a suspension of calcium hydroxide with a solid content of about 13% is prepared by a shutdown process; mixture of calcium oxide (also known as quicklime) in a stirred tank reactor. Then, said calcium hydroxide suspension is screened, for example with a 100 m filter, to remove any residual impurities and / or unprocessed or reactive lime, and subsequently passed to a stainless steel reactor equipped with a stirrer. The temperature is adjusted, generally to about 20 ° C, and then the suspension is passed to a carbonation tank or reactor in which the carbon dioxide is bubbled, optionally with air, precipitating the PCC. The PCC suspension is removed from the carbonation tank when it is considered appropriate after an adequate reduction in pH and / or conductivity. This procedure is known to those who have experience in the art; the following patents are included for reference: EP 0 768 344, WO 98/52870 (PCT / US98 / 09019) and WO 99/51691 (PCT / US99 / 07233). In general, the present invention resides in a series of first steps (Steps A) that result in the production of a suspension of PCC of low solids content, composed essentially of stable and porous agglomerates / aggregates of PCC particles, possibly followed of the reconcentration of said aqueous suspension (Steps B) without there being a loss of said agglomerates / aggregates. Steps A of the invention relate to a process for the preparation of stable and porous agglomerates / aggregates of PCC as a low solids suspension, and the PCC product thus obtained, which is a new industrial product. Accordingly, the invention relates to a new process for producing a PCC suspension by carbonation, with the characteristic that carbonation is carried out with a reduced gas flow rate to less than 30 liters per minute per kilogram of calcium hydroxide during precipitation (Steps A). The present invention also relates to a new process for producing a suspension of PCC by carbonation, also characterized in that the production of the PCC described in the previous paragraph is carried out in presence in magnesium sulfate, in combination with one or more sulphates Metals of the groups neither, said metal sulphates being said in particular with aluminum and / or zinc base, preferably with an aluminum base or with a zinc base. These steps are based on the steps described in USP 5, 750.086; however, a much lower gas flow rate for carbonation is used than in the aforementioned patent. The surprising result is that the obtained pigment is not a discrete product, with ultrafine particles and not agglomerating, but rather agglomerated / aggregates porous, stable and thick (between 1 and 5 m). Surprisingly, the agglomerates / aggregates are so stable that they retain their agglomerated / aggregate form during the next "reconcentration" step, and that unbelievably the finally produced PCC agglomerates / aggregates confer improved printing properties when incorporated into paper coatings. for ink jet printing versus the quality of printing presented by other papers of the same kind available in the market. In most preferred modalities, the Steps A of the present invention are also characterized by the use of the inventive combination of magnesium sulfate and aluminum sulfate, or magnesium sulfate and zinc sulfate. In the less preferred embodiments, the process of the invention uses 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 is added zinc sulfate. In addition, a less preferred application includes the use of magnesium sulfate sulfate and one or more metal sulfates of the n or ni groups. In addition, the invention also relates to the combination of the PCC production process (Steps A) with the subsequent specific process known as reconcentration (dehydration / redispersion) in the presence of a dispersant (Steps B). The use of this combination (production of PCC [Steps A] with the reconcentration process [Steps B]) for this type of application for ink jet printing is completely innovative. The final product is, which is quite surprisingly, a PCC in the form of stable agglomerates / aggregates having an average diameter of between 1 and 5 μ? t?, forming a PCC pigment that, when used in a standard formulation for coatings, results in higher print quality at a lower cost. The invention also relates to the novel PCC pigments themselves, as new industrial products, in the form of agglomerates / aggregates with an average diameter between 1 and 5 and m, obtained at the end of Steps A or at the end of Steps A and B. This is totally different from previous commercial technologies and patents. The invention also relates to the new pigment suspensions containing said pigments as new industrial products, namely the low solids suspension obtained at the end of Steps A and the suspension with high solids content obtained at the end of Steps A and B. The invention also relates to new coating formulations for coating ink jet printing paper containing said pigments or pigment suspension. Finally, the invention also relates to coated papers for ink jet printing, coated with the new coating formulations mentioned.

The invention relates to: a process for obtaining PCC useful for inkjet printing applications; of the type according to which the calcium hydroxide suspension is first prepared by mixing quick lime (CaO) with water in a stirred tank reactor or tank ("quenched lime"). Subsequently, the calcium hydroxide suspension is filtered, for example with a 100 μp filter, to remove any residual impurities and / or uncooked or reactive lime. Subsequently, the filtered suspension is passed to a stainless steel reactor equipped with a stirrer, the temperature is adjusted, generally to between 10 and 70 ° C, and subsequently the suspension is passed to a carbonation tank or reactor, in which it makes gas bubble with carbon dioxide content in the suspension. The suspension is removed from the carbonation tank when appropriate depending on the conductivity and pH, generally when the conductivity drops to the minimum and the pH drops below 8. The thicker particles are removed with a filter, for example with a filter 45 and m, so that the suspension only contains the ultrafine PCC agglomerates of the invention; characterized by the implementation of process steps that include a series of first steps relative to the production of the CCP in which: Al In a PCC production process as described above, carbonation is carried out with a gas flow rate of less than 30 liters per minute, at a standard temperature and pressure, kilogram of calcium hydroxide during precipitation. The invention also relates to the process defined above, characterized by: A2 In a production process of PCC as described in point Al, the suspension of calcium hydroxide which is extracted from said stainless steel reactor after said separation of said residual impurities and / or uncooled or reactive lime is treated by a combination of magnesium sulfate and metal sulphates of group n and / or of group n, preferably in the presence of an acid, said acid being preferably sulfuric acid, until agglomerates are obtained. stable aggregates with a solids concentration of 5-25%, preferably with a solids concentration of 15-20% ("precursor"). The invention also relates to the process defined above, characterized by: A3 In a PCC production process as described above at points A1 or A2, the calcium hydroxide suspension is first prepared by mixing quicklime with water in a stirred bucket reactor ("quenching") with a CaO: water ratio between 1: 3 and 1:20, preferably between 1: 5 and 1:12, and more preferably between 1: 7 and 1:10. The invention also relates to the process defined above, characterized by: A4 In a PCC production process as described in steps Al, A2 or A3, the temperature is preferably adjusted to between 15 and 50 ° C, more preferably between 15 and 30 ° C, before moving the suspension to the stirred tank reactor. BRIEF DESCRIPTION OF THE FIGURES These steps are presented schematically in the attached Figure 1. In said figure, the references have the following meanings: I: Water II: Quick lime III: Reactor, like a stirred tank reactor IV: Filter, like a filter of 100 and m V: Residual impurities and / or uncooked or reactive lime VI: Suspension of calcium hydroxide VII: Reactor, as a deposit or reactor of carbonation VIII: Dissolution of magnesium sulfate IX: Sulphate or metal sulphates of group n and / or of the group ni X: Optionally, acid, such as sulfuric acid XI: Gas with carbon dioxide content XII: Filter, like a 45 μp filter \ XIII: Coarse particles XIV: Suspension of PCC of the invention (in porous, agglomerated form) Steps They are followed by a process of reconcentration of the PCC produced during Steps A, in the presence of a cationic dispersant, anionic or the combination of both, under suitable conditions so that the aggregates / agglomerates are not substantially affected, up to a concentration of 25-60%, preferably within the range of 35-50%, and more preferably until reaching a concentration of solids with respect to the weight of 39-40%. The amount of dispersant added is controlled so that the PCC agglomerates / aggregates of the precursor are simply coated, this amount corresponding to that added before increasing the viscosity of the suspension. If the reconcentration process gives rise to a press filter cake, for example after having carried out the reconcentration process by means of a pressurized filter or a centrifuge, or by vacuum filtering, the concentrated material can optionally be washed with water and make a new dispersion until the final product is substantially aggregated / stable and porous agglomerates identical or very similar to those obtained during Steps A. The reconcentration process can be carried out by thermal evaporation as long as the final product substantially maintains the shape of the porous and stable agglomerates / aggregates obtained during Steps A. The process of reconcentration of part or all of the precursor may result in a dry product. In this case, the dried product will be redispersed until the final product consists of porous and stable agglomerates / aggregates identical or very similar to those obtained during Steps A. Figure 2 represents a dehydration process in a centrifuge, with: I: Suspension of PCC from Steps A II: Dehydrated Centrifuge III: IV Filtration: Press filter cake V: Dispersion unit VI: Dispersal enhancing solution (such as sodium salt of polyacrylic acid or sodium citrate / carboxymethylcellulose mixture) ) VII: Suspension of non-concentrated PCC Figure 3 represents an alternative dehydration process in a centrifuge, with: I: PCC Suspension of Steps A II: Dehydrated Centrifuge III: IV Filtration: Press Filter Cake V: Dispersion Unit VI: Dispersion Enhancing Solution (such as sodium salt of polyacrylic acid or sodium citrate / carboxymethylcellulose mixture) VII: Suspension of non-concentrated PCC Figure 4 represents a thermal reconcentration process in vacuum, with: I: Suspension of PCC from Steps A II: Thermal evaporator III: Suspension of non-concentrated PCC Figure 5 represents a thermal reconcentration process on a heating plate, with: I: Suspension of PCC from Steps A II: Heating plate III: Dispersal enhancing solution (as a cationic / hydroxyethylcellulose copolymer) IV: Suspension of non-concentrated PCC DETAILED DESCRIPTION OF THE INVENTION present optional and / or preferred aspects during Steps A that may be performed alone in combination.

The gas flow rate for carbonation should be selected within the range of 1 to 30, preferably between 10 and 20, and more preferably around 19.7 liters per minute, at standard temperature and pressure, per kilogram of calcium hydroxide during the precipitation. Said gas for carbonation is CO2 or a mixture of C02 and one or more different gases, such as air and / or nitrogen. The calcium hydroxide suspension should be treated more preferably by a combination of magnesium sulfate and aluminum sulfate, or by a combination of magnesium sulfate and zinc sulfate. According to the 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 carried out before carbonation. Magnesium sulfate can be added, in a less preferred option, either before adding other sulphates or during said addition. According to a second, less preferred option, magnesium sulfate can be added during carbonation together with aluminum sulfate and / or zinc sulfate. According to the less preferred option of the invention, it can be added magnesium sulfate during carbonation or just at the beginning of carbonation. The addition of aluminum sulfate and / or zinc sulfate takes place more preferably during the carbonation period. The addition of the acid, namely sulfuric acid, more preferably in the form of a sulfuric acid solution of 10% by weight, preferably takes place at the beginning of the carbonation. However, even more preferably, the addition of sulfuric acid occurs simultaneously with the addition of aluminum sulfate or zinc sulfate. The applicant considers, without being limited by any theory, that in the present invention, the presence, as described below, of sulfuric acid is necessary to obtain adequate results. In all of the above options, sulphates of group n and / or in addition to aluminum sulfate and / or zinc sulfate can be added, or as a substitute for aluminum sulfate and / or zinc sulfate. The temperature of the carbonation tank should be increased to between 40 and 80 ° C, preferably to between 50 and 60 ° C, and more preferably to between 56 and 57 ° C. The elimination of the residual impurities and / or of the uncooked or reactive lime is carried out by means of a filter of 45 μp? when the Brookfield viscosity of the material extracted from the carbonation tank is sufficiently low, specifically less than 100 mPas at 100 rpm. The suspension obtained at the end will essentially consist of stable and porous agglomerates / aggregates. Following are optional and / or preferred aspects during Steps B that may be performed alone or in combination. By "deagglomerated / disaggregated" is meant that the agglomerates / aggregates obtained at the end of Steps A are disintegrated by the specific process of the invention, the product being disintegrated ultrafine PCC of the same type (with the exception of metal salts contained or deposited ) than the one obtained in USP '086. By "soft or light conditions" it is understood that the deagglomeration / disaggregation of agglomerates / aggregates will be kept at a minimum level so that said agglomerates / aggregates are not "substantially affected". More specifically, it means that it is more preferable that during the reconcentration process, the increase in the area is limited to less than 50%, preferably to less than 25%, and / or that the increase in the fraction of particles less than 2 pm is limited to less than 50%, preferably to less than 25%, and more preferably to less than 10%, and / or that the reduction of the average diameter of the aggregate is limited to less than 50%, preferably less than 20%, and more preferably less than 15%, as measured by the means described below. The SEM images obtained before and after the reconcentration process are substantially identical, which means that the existing agglomerates / aggregates (obtained during the "precursor" Step A) are not substantially altered during said reconcentration process. The reconcentration process can be carried out by any thermal or mechanical separation technology for solid / liquid suspensions as long as the aggregates / agglomerates obtained during Steps A ("precursor") are sufficiently stable and not "substantially affected" for this technology. During the reconcentration process a common dispersant is added, with the usual proportions, in order to increase the solids content of the suspension without excessively increasing the viscosity of said suspension. Said dispersant may be cationic, anionic or a combination of both. The amount of dispersant added is controlled so that the PCC agglomerates / aggregates of the precursor are simply coated, this amount corresponding to that added before increasing the viscosity of the suspension. For example, approximately 5- 9% w / w of a 40% solution of sodium salt of polyacrylic acid on dry calcium carbonate to the suspension containing the pigment of the invention, which represents approximately 1.5-3.5% by weight of dry polyacrylic acid in calcium carbonate dry. More preferably, the reconcentration process is carried out in a centrifuge, or in a pressurized filter, or by vacuum filtration, or by thermal reconcentration, in the presence of a cationic, anionic dispersant or the combination of both. The final concentration of the suspension is approximately 39-40% solids by weight. Some degree of destruction of agglomerates / aggregates was expected. Often, these aggregates / agglomerates of the pigment are held together by relatively weak electrostatic or van der Waals attraction forces, which are overcome by centrifugal and / or shear forces created within the equipment associated with commercial reconcentration, especially in the centrifuge, rapid rotation decanter or high pressure filter press. Therefore, it is not at all obvious the result obtained that there is no significant destruction of aggregates / agglomerates despite achieving the required degree of reconcentration. The present invention relates to the aggregates / agglomerates of porous and stable PCC obtained at the end of Steps A alone ("precursor"), and the final stable porous and stable PCC aggregates / agglomerates obtained during the aforementioned processes, at the end of Steps A and in combination with Steps B, said PCC having remarkably innovative properties that are especially useful for ink jet printing applications. The stable and porous aggregates / agglomerates of PCC obtained at the end of Steps A as well as those obtained after the reconcentration process of Steps B can be characterized by a selection of the following elements: a specific surface of 30-100 m2 / g, preferably 50-80 m2 / g, and / or an aggregate diameter of the aggregate of 1-5 μ? t ?, with an average diameter of 2 m, and / or a fraction of fine particles of 2 m less than 20%, preferably less than 15%, and / or a primary acicular particle size of 20-50 nm, with an aspect ratio between 1: 2 and 1:10, and / or a solids content by weight of 5-25%, preferably 15-20% at the end of Steps A, and a solids content of 25-60%, preferably 35-50%, in particular a solids content of 39-40% at the end of Steps B. Final concentration of the suspension may be obtained partially or completely by the addition of one or more additional pigment suspensions or pigments during Steps B. The concentration of the final suspension can be obtained completely or partially through the addition of one or more pigments or pigment suspensions during steps B. The invention relates to the new pigments characterized by containing the aggregates / agglomerates of porous and stable PCCs described herein, and the new pigment or suspensions of PCC characterized by containing the aggregates / agglomerates of porous and stable PCC described herein. The invention also relates to novel PCC pigments and suspensions characterized by having a solids concentration relative to the weight of 5-25%, preferably 15-20% at the end of Steps A, and 25-60%, preferably 35-50%, in particular 39-40% at the end of Steps B. According to a preferred embodiment, the pigment suspension or the functional pigment with a large surface area and integrated cations is incorporated into the coating formulation of a form known to those skilled in the art, in order to specifically increase the optical density when printing without thereby increasing the migration effect or the ink shift: this is one of the main achievements of the invention.

Accordingly, the invention also relates to new formulations of coatings for the paper industry characterized by containing the new aggregates / agglomerates of PCC, the new pigments and / or the new suspensions described herein. The invention also relates to the formulations for coatings described herein and characterized in that the suspension of PCCs they contain has the following properties: a solids content of 25-60%, preferably 35-50%, in particular around 39-60%. 40% by weight, and / or large surface PCC, specifically with a specific surface area of 30-100 m2 / g, preferably 50-80 m2 / g. The invention also relates to the applications of the formulations for coatings according to claims 19 or 20 relating to the coating of paper for ink jet printing, specifically for the coating of "multi-purpose" paper for ink jet printing or for specialized and high quality paper. In summary, the preferred invention and the best method today is based on the selection of a gas flow rate for carbonation during the PCC precipitation that has been decisively reduced, the specific combination of cations introduced into the crystalline network of PCC during the synthesis of PCC, the use of a suspension for coating with high solids content, which follows a process called reconcentration after synthesis with dispersant up to 25-60%, preferably 35-50%, in particular around 39-40% solids content with respect to weight, in particular for use in coatings for paper to be coated in a film press or in an MSP, the use of a large surface PCC, within the range of 30-100 m2 / g, preferably 50-80 m2 / g, at the end of Steps A and / or at the end of Steps B, more preferably at the end of step B, the use of primary crystals of reduced diameter PCC, agglomerated / aggregated to form an agglomerate of porous PCC. Since the surface is a function of the particle size distribution, this distribution will have to be adjusted accordingly. The functional chemistry of the surface of the resulting pigment ensures a greater fixation of the ink and a greater surface of the pigment, which in turn provides a higher optical density or a lower need for cationic additives in the coating formulation for the same optical density . No increase or reduction in the migration and / or ink shift phenomena has been observed in relation to the alternatives available in the market. The possibility of obtaining a suspension with high Solids content with the pigment of the invention results in a better performance of the paper when it is incorporated into a paper coating formulation and coated with a coater, such as an MSP (less accumulation in the rolls of the MSP). The high solids content results in a lower need for energy for drying and a simpler and faster drying, which allows to increase the workload of the papermaking machine without this causing an increase in deposits on the rollers of the press after the drying section. The invention relates to a suspension for coatings with high solids content, which means a lower energy requirement during the drying phase and, thereby, a reduction in costs. In addition, the use of the aggregates / agglomerates of the invention makes it unnecessary to use both fixative, which also means a reduction in costs. Since the invention favors the formation of agglomerates / aggregates, applications will be limited to those relating to matte paper for inkjet printing. The agglomerates / aggregates of the invention are too thick to obtain a satin finish. Several of the processes of the invention will be better understood by the following description and the following non-limiting examples.

EXAMPLES: Examples of preparations of the innovative pigment for printing with inkjet and pigment data for the corresponding products: Examples 1, 5 and 7 were prepared according to Steps A of the invention. Examples 2, 3, 4, 6, 8 and 9 were reconcentrations from one of Examples 1, 5, and 7 according to the invention (Steps B). Example 1: Process of the invention, Steps A with magnesium sulfate and with zinc sulfate: 150 kg of quicklime were added to 1300 liters of tap water in a stirred tank reactor. Before adding the quicklime, the water temperature was adjusted to 40 ° C. The quicklime was quenched for 25 minutes with continuous stirring and the resulting suspension of calcium hydroxide ("whitewash") with 13.1% w / w solids was filtered with a 100 m filter. The precipitate of calcium carbonate was transferred to a cylinder reactor with baffles, stainless steel and 1000 liters capacity equipped with a gas agitator that had a gas dispersion unit, a stainless steel carbonation tube to direct a stream of air gas / carbon dioxide to the propellant, and test tubes to control the pH and conductivity of the suspension. The 700 liters of the calcium hydroxide suspension obtained in the shutdown step indicated above were added to the carbonation reactor and the temperature of the reaction mixture was adjusted to the desired initial temperature: 20 ° C. Before carbonation, 30 kg of 10% w / w aqueous solution of magnesium sulfate (MgSO4.7H20) was added to the lime slurry. Subsequently, the agitator was adjusted to 1480 rpm and the suspension was carbonated by passing a mixture of carbon dioxide gas at 26% volume to the air at 118 Nm3 / h, 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 sulphate (ZnS04.7H20) and 30 kg of 10% w / w aqueous solution of sulfuric acid were added to the reaction mixture continuously throughout the carbonation process. The carbonation finished after one hour and 55 minutes of reaction, this being indicated by a reduction 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 increase due to the nature Exothermic reaction up to a final temperature of the suspension of 57 ° C. Subsequently, the residual impurities and / or the uncooked or reactive lime they were removed by passing the aqueous suspension through a 45 μ filter. The aforesaid carbonation product was an aqueous suspension with a solids content of 15.6% w / w of ultrafine primary calcium carbonate particles bonded to form porous and stable spherical aggregates. The crystals as constituents of the aggregates had a particle diameter of 20-50 nm and an aspect ratio between 1: 2 and 1:10 according to the SEM images. The porous aggregates formed from these crystals had a diameter between 1 and 5 pm, with an average diameter of 2 μ ??, also in accordance with the SEM images. The pigment data of the product obtained in the above-described process are included in Example 1 of Table 2. The table of results of Example 1 confirms the large surface area of the aggregate / agglomerate and the appropriate dimensions of the aggregate / agglomerate, but a content of insufficient solids for subsequent coating applications. In fact, the results of a study on coating with a formulation with low solids content according to the general coating conditions described below demonstrate that, for an equal addition of solids per paper surface, coating with a formulation of lower solids content results in a decrease in the optical density (Table 1). Therefore, it is necessary to carry out the reconcentration process without significant loss or degradation of the aggregates. Table 1: Effect of the total solids content of the suspension on a 100% black optical density Content Metallic sulfate in total optical density type of the total content 100% black sulfate solids of the solid of the suspension metal suspension (% weight) (% weight) 13.7 10 ZnSO "* 7H20 2.44 36.7 10 ZnS (V7H20 2.72 Example 2: Process of the invention, reconcentration (Steps B) of the product of Example 1 2.210 g of the precipitated calcium carbonate suspension obtained according to the process of Steps A described in Example 1 were cooled to 25 ° C and dehydrated in Steps B by means of a filter Pressurized A press filter cake with a solids content of about 43% w / w is obtained. The filtrate was collected and used to re-disperse the filter press cake. 50 g of the filtrate obtained in the above-described dehydration step was added to a one liter dispersion unit equipped with a propellant and mixed with 16 g of a 40% w / w solution of the sodium salt of polyacrylic acid as the dispersant. In this mixture, the quicklime with a content of 57% w / w residual moisture, obtained in the dehydration process described above was gradually added to the dispersion unit under conditions of continuous mixing. After each addition of the filter press cake and the subsequent homogenization, the Brookfield viscosity of the suspension at 100 rpm was determined. The filter press cake was discontinued when the Brookfield viscosity reached a defined maximum limit of about 1000 mPas. At this time 680 g of filter press cake had been added. The product of the reconcentration process described above was an aqueous suspension with a solids content of 39.9% w / w of ultrafine particles of primary calcium carbonate bonded to form porous and stable spherical aggregates of 1-5 μta. The crystalline structure of the product was determined by SEM images. The pigment data of the product obtained in the above-described process are included in Example 2 of Table 2. From these data it can be concluded that the obtained pigment has a high specific BET surface value, which indicates that one has obtained the high surface required to interact and fix the ink, in addition to the appropriate dimensions of the aggregate / agglomerate (1-2 pm according to the SEM images) and of a suitable yellowing index. In addition, the final product also has a sufficient solids content for its application in paper coatings for ink jet printing. Example 3: Process of the invention, reconcentration (Steps B) of the product of Example 1 2,210 g of the precipitated calcium carbonate suspension obtained according to the process described in Example 1 were cooled to 25 ° C and dehydrated by means of a pressurized filter. The filtrate was collected and subsequently used to re-disperse the cake of Filter press. 30 g of the filtrate obtained in the above described dehydration step was added to a one liter dispersion unit equipped with a propellant and mixed with 6.4 g of a 35% w / w solution of sodium citrate and with 100 g of a solution at 6% w / w sodium salt of carboxymethylcellulose (CMC) as dispersant. In this mixture, the quicklime with a residual humidity of 57% w / w obtained during the dehydration process described above was gradually added to the dispersing unit under conditions of continuous mixing. After each addition of the press filter cake and the subsequent homogenization, the Brookfield viscosity of the suspension was determined at 100 rpm. The filter press cake was discontinued when the Brookfield viscosity reached a defined maximum limit of about 1000 mPas. At this time 590 g of filter press cake had been added. The product of the reconcentration process described above was an aqueous suspension with a solids content of 36.1% w / w of ultrafine particles of primary calcium carbonate bonded to form porous and stable spherical aggregates. The crystalline structure of the product was determined by SEM images.

The pigment data of the product obtained in the above-described process are included in Example 3 of Table 2. The comments in Example 2 are also applicable to these results. Example: Process of the invention, production of PCC (Step A, magnesium sulfate and zinc sulfate option) and reconcentration (Steps B) 150 kg of quicklime was added to 1300 liters of tap water in a stirred tank reactor. Before adding the quicklime, the water temperature was adjusted to 40 ° C. The quicklime was quenched for 25 minutes with continuous stirring and the resulting suspension of calcium hydroxide ("slurry") with 12.8% w / w solids was filtered with a 100 μ filter. The precipitation of calcium carbonate was transferred to a cylindrical reactor with deflectors, of stainless steel and 1000 liters of capacity equipped with a gas agitator that had a gas dispersion unit, a stainless steel carbonation tube to direct a stream of air gas / carbon dioxide to the propellant, and test tubes to control the pH and conductivity of the suspension. The 700 liters of hydroxide suspension Calcium obtained in the shut-off step indicated above were added to the carbonation reactor and the temperature of the reaction mixture was adjusted to the desired initial temperature: 20 ° C. Before starting carbonation, they were added kg of 10% w / w aqueous solution of magnesium sulphate (MgS04.7H20) to the whitewash. Subsequently, the agitator was adjusted to 1480 rpm and the suspension was carbonated by passing a mixture of carbon dioxide gas at 26% volume to the air at 118 Nm3 / h, 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 sulphate (ZnSC> 4.7H20) and 30 kg of 10% w / w aqueous solution of sulfuric acid were added continuously throughout the process of carbonation to the reaction mixture. The carbonation ended after one hour and 50 minutes of reaction, this being indicated by a reduction 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 increase, reaching up to 58 ° C due to the heat generated during the exothermic reaction.

Reconcentration step: Afterwards, the suspension was filtered with a 45 μp filter? before moving to the dehydrated centrifuge (which was adjusted to 4440 rpm) at a rate of 350 1 / h. A 4.75% w / w solution of a 40% w / w solution of a sodium salt of polyacrylic acid as a dispersion enhancer was added continuously to the uncondensed filter press cake generated by the dehydration centrifuge. Subsequently, the mixture was redispersed in a mixing unit and the reconcentrated product was recovered as an aqueous suspension of the pigment. The product of the above-mentioned carbonation and reconcentration steps was an aqueous suspension with a solids content of 39% w / w of ultrafine primary calcium carbonate particles bonded to form porous and stable spherical aggregates. The constituent crystals of the aggregates had an acicular particle shape, a diameter of 20-50 nm and an aspect ratio between 1: 2 and 1:10. The porous aggregates formed from these crystals had diameters between 1-5 μ ??, with an average diameter of 2 μp ?. The crystalline structure of the product was determined by SEM images. The pigment data of the product obtained in the above-described process are included in Example 4 of Table 2. The comments of Examples 2 and 3 are also applicable to these results. Example 5: Process of the invention, Steps A, magnesium sulfate and aluminum sulfate option: 115 kg of quicklime was added to 1000 liters of tap water in a stirred tank reactor. Before adding the quicklime, the water temperature was adjusted to 40 ° C. The quicklime was quenched for 25 minutes with continuous stirring and the resulting suspension of calcium hydroxide ("slurry") with 12.7% w / w solids was filtered with a 100 μm filter. The precipitate of calcium carbonate was transferred to a cylinder reactor with baffles, stainless steel and 1000 liters capacity equipped with a gas agitator that had a gas dispersion unit, a stainless steel carbonation tube to direct a stream of air gas / carbon dioxide to the propellant, and test tubes to control the pH and conductivity of the suspension. The 700 liters of the calcium hydroxide suspension obtained in the shutdown step indicated above were added to the carbonation reactor and the temperature of the reaction mixture was adjusted to the temperature desired initial: 20 ° C. Before starting carbonation, 30 kg of 10% w / w aqueous solution of magnesium sulfate (MgSO4.7H20) was added to the lime slurry. Subsequently, the agitator was adjusted to 1480 rpm and the aqueous suspension was carbonated by passing a mixture of carbon dioxide gas at 26% volume to the air at 118 Nm3 / h, 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 aluminum sulfate (Al2 (S04) 3 | 18H20) and 30 kg of 10% w / w aqueous solution of sulfuric acid were added continuously throughout the carbonation process to the reaction mixture. The carbonation finished after one hour and 48 minutes of reaction, this being indicated by a reduction in conductivity to a minimum accompanied by a drop in pH to a constant value lower than 8.0. During carbonation, the temperature of the suspension was increased, reaching up to 61 ° C due to the heat generated during the exothermic reaction. Subsequently, the suspension was filtered on a 45 im filter and the product was recovered as an aqueous suspension of the pigment.

The product of the carbonation process described above was an aqueous suspension with a solids content of 14.3% w / w of ultrafine particles of primary calcium carbonate bonded to form porous and stable spherical aggregates. The crystals constituting the aggregates had an acicular particle shape, a diameter of 20-50 nm and an aspect ratio between 1: 2 and 1:10. The porous aggregates formed from these crystals had a diameter between 1 and 5 μp ?, with an average diameter of 2 m. The crystalline structure of the product was determined by SEM images. The pigment data of the product obtained in the above-described process are included in Example 5 of Table 2. Example 6: Process of the invention, reconcentration (Steps B) of the product of Example 5 Ten liters of the carbonate suspension were filtered Precipitated calcium obtained according to the process described in Example 5 with a 45 m filter before transferring them to a thermal evaporator. The evaporator consisted of a cylindrical stainless steel bucket equipped with an agitator and a double heating unit layer at 120 ° C with hot synthetic oil as a heating medium. Before evaporation, 8.5% w / w of a 40% w / w solution of sodium salt of polyacrylic acid as a dispersion enhancer was added and mixed with the precipitated calcium carbonate suspension. The thermal reconcentration was carried out by evaporation in said laboratory evaporator at atmospheric pressure and with a suspension temperature of 90-95 ° C. Evaporation was stopped when the Brookfield viscosity reached a defined maximum limit of about 1000 mPas. The product of the reconcentration process described above was an aqueous suspension with a solids content of 35.5% w / w of ultrafine particles of primary calcium carbonate bonded to form porous and stable spherical aggregates. The crystalline structure of the product was determined by SEM images. The pigment data of the product obtained in the above-described process are included in Example 6 of Table 2. Example 7: Process of the invention, Steps A (option with magnesium sulfate and zinc sulfate): 115 kg of quicklime to 1000 liters of tap water in a stirred tank reactor. Before Add the quicklime, adjust the water temperature to 40 ° C. The quicklime was quenched for 25 minutes with continuous stirring and the resulting suspension of calcium hydroxide ("slurry") with 12.5% w / w solids was filtered with a 100 μm filter. The precipitate of calcium carbonate was transferred to a cylindrical reactor with deflectors, stainless steel and 1000 liter capacity equipped with a gas agitator that had a gas dispersion unit, a stainless steel carbonation tube to direct a stream of air / carbon dioxide gas to the propeller, and test tubes to control the pH and conductivity of the suspension. The 700 liters of the calcium hydroxide suspension obtained in the shutdown step indicated above were added to the carbonation reactor and the temperature of the reaction mixture was adjusted to the desired initial temperature: 20 ° C. Before starting carbonation, 30 kg of 10% w / w aqueous solution of magnesium sulfate (MgSO4.7H20) was added to the lime slurry. Subsequently, the agitator was adjusted to 1480 rpm and the suspension was carbonated by passing a mixture of carbon dioxide gas at 26% volume to the air at 118 Nm3 / h, corresponding to 19.7 liters per minute, at room temperature. standard pressure, per kilogram of calcium hydroxide, through the suspension. During carbonation, 100 kg of 10% w / w aqueous solution of zinc sulphate (ZnS0 .7H20) and 30 kg of 10% w / w aqueous solution of sulfuric acid were added continuously throughout the carbonation process to the reaction mixture. The carbonation finished after one hour and 43 minutes of reaction, this being indicated by a reduction of the conductivity to a minimum accompanied by a drop in pH to a constant value lower than 8.0. During carbonation, the temperature of the suspension was increased, reaching up to 62 ° C due to the heat generated during the exothermic reaction. Subsequently, the suspension was filtered on a 45 μm filter and the product was recovered as an aqueous suspension of the pigment. The product of the carbonation process described above was an aqueous suspension with a solids content of 13.7% w / w of ultrafine particles of primary calcium carbonate bonded to form porous and stable spherical aggregates. The crystals constituting the aggregates had an acicular particle shape, a diameter of 20-50 nm and an aspect ratio between 1: 2 and 1:10.

The porous aggregates formed from these crystals had a diameter between 1 and 5 im, with an average diameter of 2 and m. The crystalline structure of the product was determined by SEM images. The pigment data of the product obtained in the above-described process are included in Example 7 of Table 2. The comments in Example 1 are also applicable to these results. Example 8: Process of the invention, reconcentration (Steps B) of the product of Example 7 Ten liters of the precipitated calcium carbonate suspension obtained according to the process described in Example 7 were filtered with a filter of 45 and m before moving them to a thermal evaporator The evaporator consisted of a cylindrical stainless steel bucket equipped with a stirrer and a double-layer heating unit at 120 ° C with hot synthetic oil as a heating medium. Before evaporation, 8.5% w / w of a 40% w / w solution of sodium salt of polyacrylic acid as a dispersion enhancer was added and mixed with the precipitated calcium carbonate suspension.

The thermal reconcentration was carried out by evaporation in said laboratory evaporator at atmospheric pressure and with a suspension temperature of 90-95 ° C. Evaporation stopped when the viscosity of Brookfield reached a defined maximum limit of approximately 1000 mPas. The product of the reconcentration process described above was an aqueous suspension with a solids content of 36.7% w / w of ultrafine primary calcium carbonate particles bonded to form porous and stable spherical aggregates. The crystalline structure of the product was determined by SEM images. The pigment data of the product obtained in the above-described process are included in Example 8 of Table 2. Example 9: Process of the invention, production of PCC (Steps A, magnesium sulfate and zinc sulfate option) and reconcentration (Steps B) 115 kg of quicklime was added to 1000 liters of tap water in a stirred tank reactor. Before adding the quicklime, the water temperature was adjusted to 40 ° C. The quicklime was quenched for 25 minutes with shaking continuous and the resulting suspension of calcium hydroxide ("whitewash") with 13.5% w / w solids was filtered with a 100 μm filter. The precipitation of calcium carbonate was transferred to a cylinder reactor with deflectors, stainless steel and 1000 liters capacity equipped with a gas agitator that had a gas dispersion unit, a stainless steel carbonation tube to direct a stream of air gas / carbon dioxide to the propellant, and test tubes to control the pH and conductivity of the suspension. The 700 liters of the calcium hydroxide suspension obtained in the shutdown step indicated above were added to the carbonation reactor and the temperature of the reaction mixture was adjusted to the desired initial temperature: 20 ° C. Before starting carbonation, 30 kg of 10% w / w aqueous solution of magnesium sulfate (MgSO4.7H20) was added to the lime slurry. Later, the agitator was adjusted to 1480 rpm and the suspension was carbonated by passing a mixture of carbon dioxide gas at 26% volume to the air at 118 Nm3 / h, corresponding to 19.7 liters per minute, at standard temperature and pressure, kilogram of calcium hydroxide, through the suspension. During carbonation, 100 kg of % w / w aqueous solution of zinc sulphate (ZnS04.7H20) and 30 kg of 10% w / w aqueous solution of sulfuric acid were continuously added during the whole batching process to the mixture of the reaction. The carbonation ended after one hour and 44 minutes of reaction, this being indicated by a reduction 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 increase, reaching up to 56 ° C due to the heat generated during the exothermic reaction. Subsequently, the suspension was filtered on a 45 μm filter. Reconcentration step: Next, the filtered suspension was moved to a dehydrated centrifuge at a speed of 400 1 / h and adjusted to 4440 rpm. To the reconcentrated press filter cake and obtained from the dehydration centrifuge was added continuously 6% w / w of a 40% w / w solution of sodium salt of polyacrylic acid as a dispersion enhancer. Subsequently, the mixture was dispersed again in a mixing unit and the Concentrated product as an aqueous suspension of the pigment. The product of the above-described cation and reconcentration processes was an aqueous suspension with a solids content of 39.9% w / w of ultrafine particles of primary calcium carbonate bonded to form porous and stable spherical aggregates. The constituent crystals of the aggregates had an acicular particle shape, a diameter of 20-50 nm and an aspect ratio between 1: 2 and 1:10. The porous aggregates formed from these crystals had diameters between 1-5 μp ?, with an average diameter of 2 μm. The crystalline structure of the product was determined by SEM images. The pigment data of the product obtained in the above-described process are included in Example 9 of Table 2. In Table 2, the surface area (SSA) was measured by a Tristar 3000 analyzer, the particle size distribution ( PSD) using a Helos Sympatec device, the brightness using a Datacolor Elrepho 3000 Jerics device, the solids content using a Toledo HB43 Halongen ettler, and the viscosity using a Brookfield DVII viscometer, always in accordance with the manufacturer's recommendations.

Table 2: Characteristics of the pigments and aqueous suspensions with pigment content (all reconcentrations with anionic, cationic dispersants or the combination of both) Unit Test Ex. Ex. E]. Ex. Eg Ex. Eg Ex. Ex. 1 2 3 4 5 6 7 8 9 Surface m '/ g 58.9 69.0 64.2 71.2 59.5 64.1 75.2 68.4 62.8 specifies BET PSD (Helos Sympatec) < 2 pm% 31 38 38 33 16 20 12 16 36 < 1 pm% 8 11 11 9 5 6 4 4 10 Size pm 2.72 2.40 2.41 2.62 3.73 3.39 '4.25 3.81 2.49 particle average d50 Brightness (DIN 53140) R457 (ISO 96.1 96.0 95.8 96.0 95.7 95.5"95.6' 95.5 '95. 2469) index 1.5 1.5 1.7 '1.3' 1.6 '1.7' 1.6 '1.5' I. yellow (DIN 6167) Content ¾ 15.6 39.9 36.1 39.0 14.3 35.5 13.7 36.7 39.9 solids Viscosity mPas 34 '1030' 920 '770 33 765 22 720 994 Coating studies A selection of the aforementioned products of the invention was introduced into aqueous suspensions for paper coating and were used for coating base paper. Coating studies from the aqueous suspensions of Example 4, Example 6 and Example 8 Three aqueous suspensions were prepared for paper coating using one of the three PCC suspensions made according to the invention and with standard additives. Emox TSC is an oxidized potato starch from Emsland-Staerke GmbH, Basoplast PR8172 is a BASF fixative, Catiofast CS is a Poly-Dadmac cationic additive from BASF, and Lupamin 6005 is a polyvinyl formamide from BASF. Table 3: Composition of the formulation for coating (by parts) Suspension for Susp. Susp. Your coating of coated solids coated (% P / P) 1 2 3 PCC suspension of the invention Example 4 39.0 100 Example 6 35.5 100 Example 8 36.7 100 Emox TSC additives (Emsland-40 25 Staerke GmbH) 35 25 Basoplast PR8172 40 10 10 10 (BASF) Catiofast CS (BASF) 33 10 10 10 Lupamin 6005 (BASF) 30 1 1 Suspension characteristics final coatings Solids content 37.5 35.7 36.6 final pH of the suspension 9.0 8.4 final Viscosity of 160 580 460 Brookfield at 20 ° C Two other aqueous paper coating suspensions were prepared, each using the PCC suspensions to which the invention relates together with another selection of standard additives (Mo iol 26-88, Printofix Cartafix VXT01 and Cartabond TS1 from Clariant) . Table 4: Composition of the formulation for coating (by parts) Suspension for Susp. Susp. coated solids coating coated (% w / w) 4 5 Suspension of PCC of the invention Example 6 36.7 100 Example 8 35.4 100 Additives Mowiol 26-88 7.6 12 12 Printofix 43.0 5 5 Cartafix VXT01 20.0 3 3 Cartabond TS1 43.0 1.5 1.5 Characteristics of the coating suspension final pH of the aqueous - 8.3 8.0 final Content of 27.8 27.8 solids of the final suspension Viscosity of mPas 300 100 Brookfield of the final suspension at 20 ° C Subsequently, the aqueous solution for Coating 1 was used simultaneously on both sides of a backing paper, as described in Table 5, using a Jagenberg MSP press under the conditions indicated in Table 6. Table 5: Characteristics of backing paper coated with the coating suspension 1 Gram je: 84.1 g / m2 Filler content 23.9% (other): Lenght of tension: 4.75 km Contact angle with the 112.2 OS surface (1 o): Contact angle with the 106.6 OS surface (10 s): index of yellowing -25.6% OS: Table 6: Conditions of the Jagenberg MSP coating machine used with the coating suspension 1 Coating speed. : 560 m / min Application weight of 9.8 - 10.8 g / m2 coating: Coated moisture content. : 5.2 - 5.4% Temperature of 28 ° C Coating in color during coating: Right-sided heads coating 'Roll type C25' C25 coating Right-sided coated heads 200 rpm speed 200 rpm coating roller 1.5 bar pressure 1.5 bar coating roller 60 rpm speed 60 rpm pumping: 0.8 bar pressure 1.1 bar pumping: Calendered Number of NIPS: 1 Calendering speed: 200 m / min Calendering pressure: 65 kN / m Calendering temperature: 60 ° C The coating suspensions 2, 3, 4 and 5 were used to coat one side of the backing paper, which is described in Table 7, by means of the K-Coater in the conditions indicated in Table 8. Table 7: Characteristics of the coated paper coated with the aqueous coating suspensions 2, 4 and 5 Gramaj e 89.2 g / m2 Filler content 12.9% (other) Tension length 5.26 km Contact angle with 109.3 OS surface (1 o) Angle of contact with the 106.4 surface OS (10 s) Index of yellowing | 18.3% OS Table 8: Coater conditions with K-Coater machine with slotted wand for coating suspensions 2, 3, 4 and 5 Application weight of 8 g / m2 coating Content humidity of 5% coating Temperature of 23 ° C coating in color during the coating drying conditions of the Drying in a lab paper oven at 80 ° C for 4 minutes Ink jet printing studies Print studies were carried out with three different ink jet printers, namely an Epson Stylus Photo 950, an HP Deskjet 5550 and a Canon I950 to compare the inkjet printing of papers with pigments coatings of the invention compared to other commercially available ink jet printing papers. Printing test patterns were designed to evaluate the optical density, the degree of ink bleeding and the migration effect. HP Bright White and Epson S041214 papers are They market as multipurpose papers for inkjet printing. Zweckform 2585 and Epson S041061 papers are considered high-quality matte paper for inkjet printing and offer higher print quality than standard multi-purpose papers for inkjet printing. The optical density was measured using the Gretag D 186 densitometer according to the standard procedures indicated by the manufacturer. For an equal amount of applied ink, the higher the optical density, the better the coating keeps the dyes on the paper surface. Coated paper with suspension for coating 1: The following coating study (coating study 1) was carried out by coating the support paper described above with coating suspension 1, based on the PCC suspension of Example 4. The ink shift and the migration effect of a First type of print test pattern were measured by a PapEye team from ONLY Solution GmbH according to the standard procedures indicated by the manufacturer.

The lower the measured value, the better the results of ink shift and migration effect.

Table 9: Results of optical density and migration effect / ink shift of the coating paper with the pigment of the coating of the invention against other commercially available papers Type of printer Optical density Gretag-Macbeth D186 Epson Ma- Verde, i Blue, Red, stylus Ne- I Ne- Cian genta Amaric J my photo gro gold (C) (m) 'lio (y) 100%,: 100%, 100%, CorriMigra950 100%! 80% 100% | 100% 100% 1 and 100% I c 100% m 1001 tion Zweck- I I f orm 2585 2.23 .0 1.73 1 1.47 1.23 1.39 300.45 448.56 Epson j: S041061 I 2.29. 2.02 | 1.58; 1.42 1.11 ¡1.31 I 1.70 1.36 304.52 460.76 HP j i Bright j White '1.92; 1.71 1.31 [1.26 1.08 1.15 1.43 - 1.16 348.71 539.46 t Epson S041214 '1.58 · 1.39 0.97, 1.02 0.89 I 0.89 1.11 0.93 350.40 532.80 Coating study. 1 I 1.99 1.78 I 1.20 I 1.32 1.12 1.15 1.46 1.27 348.53 519.42 In the previous table it can be seen that the optical density obtained with the product of the invention was superior to that of other comparable and commercially available multipurpose papers, and that it approximates the quality of a higher quality paper for jet printing. ink. The ink run obtained with the product of the invention was equal to or lower than that obtained with other equivalent papers. The migration effect obtained with the product of the invention was lower than that obtained with other papers available in the market.

The higher optical density, the migration effect and the ink shift indicate a better balance of the absorption / adsorption properties of the paper coating compared to other comparable products available on the market. In addition, the structure of the pigment did not adversely affect the behavior of the paper; in fact, the paper's performance improved thanks to the lower accumulation of ink observed in the MSP press. Table 10: Results of optical density and migration effect / ink shift of the coating paper with the pigment of the coating of the invention against other commercially available papers Type of printer Color density Gretag-Macbeth DI86 Green Blue, eye, Ma , om And NeNeCian genta Amari100%, 100%, 100%, HP Deskjet gro gro (C) (m) llo (y) ycm CorriMigra¬ 5550 100% 80% 100% 100% 100% 100% 100% 100% tion Zweckform 2585 2.06 1.91 1.99 1.26 0.93 1.06 1.75 1.31 310.69 503.24 Epson S041061 1.95 1.81 1.85 1.19 0.92 1.03 1.67 1.28 312.92 520.78 HP Bright White 2.35 2.05 1.71 1.17 0.94 1.04 1.56 1.32 319.51 494.86 Epson S041214 1.85 1.68 1.39 1.01 0.83 0.89 1.28 1.02 331.35 514.59 Study of coating 1 2.57 2.35 1.86 1.23 1.01 1.08 1.69 1.19 314.12 510.20 The results relating to the optical density of the invention were superior to those obtained by other comparable papers and available on the market, and were even higher than those obtained with higher quality papers for inkjet printing. Also, a lower ink shift and a similar degree of migration effect were observed than in comparable papers and even in a higher quality one. Once again, the structure of the pigment did not adversely affect the behavior of the paper; in fact, the behavior of the paper improved thanks to the scarce accumulation of ink observed in the film press. Table 11: Results of optical density and migration effect / ink shift of the paper coated with the pigment of the coating of the invention against other commercially available papers Type of printer Color density Gretag-Macbeth D186 Green Blue, Red, Ma / NeNeCian genta Amari100%, 100%, 100%, gro gro (C) (m) llo (y) Y cm CorriMigra¬ Canon i950 100% 95% 100% 100% 100% 100% 100% 100% tion Zweckform 2585 2.21 1.95 1.41 1.84 1.00 0.99 2.16 1.59 299.66 470.13 Epson S041061 2.17 1.82 1.22 1.75 0.91 0.96 1.90 1.55 303.97 479.14 'HP Bright White 1.75 1.54 1.17 1.51 0.86 0.93 1.65 1.28 354.43 549.39 Epson S041214 1.42 1.29 0.99 1.28 0.77 0.77 1.24 1.07 348.44 527.03 Coating study1 1.87 1.66 1.23 1.63 0.90 0.91 1.68 1.36 340.32 548.72 The optical density results of the invention were generally superior to those of other comparable and commercially available papers, and approximated the values obtained by higher quality papers. A lower ink shift and migration effect similar to that of other comparable and commercially available papers was observed. Papers coated with coating suspensions 2 and 3: The following coating studies were carried out using the suspensions of PCC with aluminum and zinc base, each after a thermal reconcentration process. When coating the support paper with the suspensions for coatings 2 and 3, the results of coating studies 2 and 3, which appear below, were obtained respectively. A second study pattern was used to evaluate the optical density, the ink shift and the measurement effect. The ink shift and the migration effect were measured by the Personal IAS® (Image Analysis System) of the Quality Engineering Association, Inc. in accordance with the standard procedures indicated by the manufacturer. How much The lower the measured value, the better the results of ink shift and migration effect. Table 12: Results of optical density and migration effect / ink shift of the coated paper with the coating pigment of the invention versus other commercially available papers Type of printer Optical density Gretag-Macbeth D186 Blue, Red, MaAmaVerde, m And Epson Cyan 100%, 100%, stylus Black Black (C) (m) (Y) 100%, cm CorriMigraphoto 950 100% 80% 100% 100% 100% and 100% 100% 100% Zweckforra 2585 2 38 1.29 2.25 1.64 1.54 1.66 2.04 1.55 164.14 58.00 Epson S041061 2 45 1.23 2.09 1.59 1.49 1.54 1.85 1.51 166.34 67.63 HP Bright White 2 09 1.06 1.72 1.42 1.34 1.32 1.61 1.31 239.20 10 .37 Study of coating 2 2 21 1.13 1.81 1.69 1.58 1.25 1.49 1.67 216.30 j 74.91 Study of coating 3 2 30 1.19 1.84 1.70 1.62 1.32 1.57 1.68 209.09 89.94 Zweckform 2585 2 08 1.16 0.98 1.00 1.46 1.20 1.84 1.38 237.72 63.94 Epson S041061 1 92 1.09 0.97 0.97 1.47 1.18 1.73 1.47 193.69 66.95 HP Bright White 2 35 1.24 1.02 1.01 1.39 1.17 1.59 1.33 237.72 72.59 Coating study 2 2 75 1.32 1.04 1.04 1.44 1.33 1.88 1.34 204.01 69.55 Coating study 3 2 64 1.39 1.10 1.14 1.49 1.31 1.92 1.40 208.56 72.59 It can be seen from the previous table that the optical density obtained with the product of the invention was clearly superior not only to that of other products comparable and available in the market, but also sometimes to the highest quality papers. The ink run obtained with the product of the invention was equal to or lower than that obtained with other equivalent papers. The migration effect obtained with the product of the invention was lower or similar to that obtained with other comparable and commercially available papers. The brightness of the paper was similar to that of other papers available in the market. Table 14: Results of optical density and migration effect / ink shift of the coated paper with the coating pigment of the invention versus other commercially available papers Type of printer Optical density Gretag-Macbeth D186 Green Blue, Red, / cm And NeNeC an Magenta Amari100%, 100%, 100%, gro gro (C) (m) llo (y) ycm CorriMigra¬ Canon Í950 100% 80% 100% 100% 100% 100% 100% 100% tion Zweckform 2585 2.07 1.20 2.30 1.74 1.71 1.58 2.31 1.85 198.63 59.64 Epson S041061 2.06 1.17 2.06 1.80 1.66 1.42 1.82 1.68 204.45 63.72 HP Bright White 1.72 1.03 1.73 1.58 1.49 1.26 1.58 1.46 245.32 90.74 Coating study 2 2.06 1.17 1.91 2.00 1.75 1.56 1.94 1.89 225.42 72.14 Coating study 3 2.10 1.20 1.93 2.03 1.77 1.60 1.98 1.91 230.46 78.07 In the previous table it can be observed that the optical density obtained with the product of the invention was superior to that of other comparable papers available in the market, and that sometimes even exceeded the values obtained by higher quality papers. The ink run obtained with the product of the invention was equal to or lower than that obtained with other equivalent papers. The migration effect obtained with the product of the invention was lower than that of other comparable and commercially available papers. The brightness of the paper was similar to that of other papers available in the market. Papers coated with coating suspensions 4 and 5: The following coating studies were carried out using the PCC suspensions with aluminum and zinc base of Example 6 and Example 8, after a thermal reconcentration process. When coating the backing paper with the coating suspensions 4 and 5, the results of coating studies 4 and 5, which appear below, were obtained respectively. Ink shift and migration effect were measured by the second-impression study pattern and a Personal IAS® (Image Analysis System) of the Quality Engineering Association, Inc. in accordance with standard procedures indicated by the manufacturer. The lower the measured value, the better the results of ink shift and migration effect.

Table 15: Results of optical density and migration effect / ink shift of the coated paper with the coating pigment of the invention versus other commercially available papers Type of printer Optical density Gretag-Macbeth D186 Green 1 Blue, Red,, omy Epson Cian 'MagenAmari100%, 100%, 100%, stylus Black 1 Black 1 (C) ta (m) llo (y) ycm CorriMigraphoto 950 100% 1 80% 100% 100% 100% 100%! ioo% 100% tion 1. Zweckforra 1 2585 2 1.29 12.25, 1. 1.54 1.66 2.04 1.55 164.14 58.00 Epson S041061 2 45; 1.23 2.09 1.59 1.49 1.54 1.85 1.51 166.34 67.63 1 HP Bright White 2 09! 1.06 1.72 1.42 1 1.32 1.61 1.31 239.20 10 .37 Study of 1 * coating. 4 2 .27 1.18 1.96. 1.51 1.45 1.38 ¡1.69 1.42 195.99 67.10 Coating study 5 2 .21 11.15] 1.91 1.42 1.37 1.38 1.69 1.38 192.84 69.75 In the previous table it can be seen that the optical density obtained with the product of the invention was superior to that of other comparable and commercially available multipurpose papers, and that it approximates the quality of a higher quality paper for jet printing. ink. The ink run obtained with the product of the invention was equal to or lower than that obtained with other equivalent papers. The migration effect obtained with the product of the invention was lower than that obtained with other papers available in the market. The highest optical density, the effect of migration and the Ink shift indicates a better balance of absorption / adsorption properties compared to other comparable products available on the market. Table 16: Results of optical density and migration effect / ink shift of the paper coated with the coating pigment of the invention compared to other commercially available papers Type of printer Optical density Gretag - Macbeth D186 Blue, Red, Amarim and NeNeCian Mage rillo Verde, 100%, 100%, HP Deskjet gro gro (C) ta (m) (y) c 100%, cm CorrimienMigra¬ 5550 100% 80% 100% 100% 100% and 100% 100% 100% to tion Zweckform 2585 2.08 1.16 0.98 1.00 1.46 1.20 1.84 1.38 237.72 63.94 Epson S041061 1.92 1.09 0.97 0.97 1.47 1.18 1.73 1.47 193.69 66.95 HP Bright hite 2.35 1.24 1.02 1.01 1.39 1.17 1.59 1.33 237.72 72.59 Study of coating 4 2.72 1.25 1.09 1.07 1.39 1.21 1.78 1.36 193.32 81.32 Coating study 5 2.82 1.04 1.01 1.23 1.11 1.66 1.20 191.85 80.37 The results relating to the optical density of the invention were superior to those obtained by other comparable and commercially available papers as well as by higher quality papers for inkjet printing.

Also, a reduction of the ink shift was observed and an increase of the migration effect compared to other comparable papers.

Table 17: Results of optical density and migration effect / ink shift of the paper coated with the pigment of the coating of the invention against other commercially available papers Type of printer Optical density Gretag-Macbeth D186 Green Blue, Red,, cm And NeNeCian Amari100%, 100%, 100%, gro gro (C) Magenta llo (y) ycm CorriMigra¬ Canon i950 100% 80% 100% (m) 100% 100% 100% 100% 100% tion Zweckform 2585 2.07 1.20 2.30 1.74 1.71 1.58 2.31 1.85 198.63 59.64 Epson S041061 2.06 1.17 2.06 1.80 1.66 1.42 1.82 1.68 204.45 63.72 HP Bright White 1.72 1.03 1.73 1.58 1.49 1.26 1.58 1.46 245.32 90.74 Study of coating 4 1.83 1.15 2.01 1.73 1.62 1.42 1.66 1.61 208.92 Coating study. 5, 1.71 1.16 2.00 1.65 1.55 1.40 1.59 1.65 20 .01 The optical density results of the invention were always superior to those of other comparable and commercially available papers, and approached the values obtained by higher quality papers. A lower ink shift and migration effect similar to that of other comparable and commercially available papers was observed. The present invention also relates to the technical equivalents of the aforementioned description, as well as to the options that should necessarily be available to the person skilled in the art when reading the present application.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (23)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1.- Process for obtaining PCC useful for inkjet printing applications; of a type according to which the calcium hydroxide suspension is first prepared by mixing quicklime (CaO) with water in a stirred tank reactor ("quenched"), then the calcium hydroxide suspension is filtered, for example with a filter of 100 μp ?, to eliminate any residual impurities and / or uncooked or reactive lime; then, the filtered suspension is transferred to a stainless steel reactor equipped with an agitator, the temperature is adjusted, generally at 10-70 ° C, and subsequently the suspension is transferred to a carbonation tank or reactor, in which the gas with carbon dioxide content is made to bubble through the suspension, said suspension being extracted from the carbonation tank when it is considered appropriate depending on the conductivity and the pH, generally when the conductivity reaches a minimum value and the pH falls below 8, the coarse particles are separated by a filter, such as a 45 μ? T filter, so that the suspension only contains the ultrafine PCC agglomerates to which refers to the invention; characterized because it is carried out by the implementation of steps that include the following: A First steps, production of the PCC: At the step of carbonation is carried out with a gas flow rate of less than 30 liters per minute, at standard temperature and pressure , per kilogram of calcium hydroxide during precipitation.
2. 2.- Process in accordance with the claim 1, characterized in that: A2 the suspension of calcium hydroxide which is extracted from the stainless steel reactor after separation of said residual impurities and / or uncooked or reactive lime is treated by a combination of magnesium sulfate and groups II and / or group or more preferably in the presence of an acid with the acid being more preferably sulfuric acid until stable, the porous aggregates / aggregates are obtained at a concentration of 5-25% solids, preferably 15-20 % solids ("precursor").
3. 3. Process according to claims 1 or 2, characterized in that: A3 the calcium hydroxide suspension is first prepared by mixing quick lime with water in a stirred tank reactor ("quenched") with a CaO: water ratio between 1: 3 and 1:20, preferably between 1: 5 and 1:12, and more preferably between 1: 7 and 1:10.
4. 4. - Process according to any of claims 1 to 3, characterized in that:? 4 - the temperature is preferably set at 15-50 ° C, more preferably at 15-30 ° C, before transferring the suspension to the tank or carbonation reactor.
5. 5. - Process according to any of claims 1 to 4, characterized in that Steps A are followed by the following steps, known as Steps B: B Process of reconcentration of the "precursor": dehydration / redispersion steps after the "Steps" To "aforementioned - the reconcentration of the PCC produced during Steps A is carried out under suitable conditions so that aggregates / agglomerates are not substantially affected; with cationic, anionic dispersant or the combination of both; the amount of dispersant added is controlled so that the PCC agglomerates / aggregates of the precursor are simply coated, this amount corresponding to that added before increasing the viscosity of the suspension; until reaching a solids concentration by weight of 25-60%, preferably within the range of 35-50%, and more preferably of 39-40%;
6. 6. Process according to any of claims 1 to 5, characterized in that in Steps A applies at least one of the following parameters: the gas flow rate for carbonation should be selected within the range of 1 to 30, preferably between 10 and 20, and more preferably around 19.7 liters per minute, at standard temperature and pressure, per kilogram of calcium hydroxide during precipitation; the gas for carbonation is CO2 or a mixture of C02 and one or more different gases, such as air and / or nitrogen; the calcium hydroxide suspension is more preferably treated with a combination of magnesium sulfate and aluminum sulfate; or with a combination of magnesium sulfate and zinc sulfate.
7. 7. - Process according to any of claims 1 to 6, characterized in that in Steps A applies at least one of the following parameters: zinc sulfate can be added to the combination of magnesium sulfate and aluminum sulfate; aluminum sulfate can be added to the combination of magnesium sulfate and zinc sulfate - the addition of magnesium sulfate is most preferably carried out before carbonation; - magnesium sulfate can be added, in a less preferred option, either before adding other sulfates or during the addition; magnesium sulfate can be added, according to a less preferred option, during carbonation together with aluminum sulfate and / or zinc sulfate - magnesium sulfate can be added during carbonation or at the beginning of carbonation; the addition of aluminum sulfate and / or zinc sulfate takes place during carbonation; the addition of the acid, in particular sulfuric acid, more preferably in the form of a 10% H2SO4 solution in relation to the weight, takes place at the beginning of the carbonation; more preferably, the addition of H2SO4 occurs simultaneously with the addition of aluminum sulfate or zinc sulfate; in all the above options, sulphates of the group n and / or in addition to aluminum sulphate and / or zinc sulphate, or as a substitute for aluminum sulphate and / or zinc sulphate may be added - the temperature of the carbonation tank shall be increase up to 40-80 ° C, preferably up to 50-60 ° C, and more preferably up to between 56-57 ° C; The elimination of residual impurities and / or unburned or reactive lime is carried out using a 45 μ? t filter? when the Brookfield viscosity of the material extracted from the carbonation tank is sufficiently low, specifically less than 100 mPas at 100 rpm; the suspension obtained at the end will consist essentially of stable and porous agglomerates / aggregates.
8. 8. Process according to any of claims 1 to 7, characterized in that in Steps B: by "appropriate conditions" it is understood that the deagglomeration / disaggregation of the agglomerates / aggregates will be kept at a minimum level so that the agglomerates / aggregates are not "substantially affected"; the increase in area is limited to less than 50%, preferably less than 25%; and / or the increase of the fraction of smaller particles of 2 pm is limited to less than 50%, preferably less than 25%, and more preferably less than 10%; and / or the reduction of the average diameter of the aggregate is limited to less than 50%, preferably less than 20%, and more preferably less than 15%, measured by a Helos Sympatec equipment. by "deagglomerated / disaggregated" it is understood that the agglomerates / aggregates obtained at the end of Steps A are dispersed by the specific process of the invention; - the reconcentration process can be carried out by any thermal or mechanical separation technology for solid / liquid suspensions as long as the aggregates / agglomerates obtained during Steps A ("precursor") are stable enough and do not appear to be "substantially affected" " For technology.
9. 9. Process according to any of claims 5 to 8, characterized in that: the reconcentration process is carried out in a centrifuge, or in a pressurized filter, or by vacuum filtration, or by thermal reconcentration, in the presence of a cationic, anionic dispersant or the combination of both; and wherein the final concentration of the suspension is approximately 39-40% solids by weight.
10. 10. - Process according to any of claims 5 to 9, characterized in that: the reconcentration process gives rise to a press filter cake, when the process is carried out in a pressurized filter, in a centrifuge or by vacuum filtering, and in this case: the concentrated material can optionally be washed with water; a new dispersion is carried out - until the final material consists substantially of stable and porous agglomerates / aggregates, and identical or very similar to those obtained during Steps A of Claims 1 to 4; The reconcentration process can be carried out by thermal evaporation as long as the final product substantially maintains the shape of the porous and stable agglomerates / aggregates obtained during Steps A of Claims 1 to 4.
11. 11. Process of conformity with any of claims 5 to 9, characterized in that: the reconcentration of all or part of the precursor gives rise to a dry product and, in this case: a new dispersion is carried out until the final material consists substantially of stable and porous agglomerates / aggregates , and identical or very similar to those obtained during Steps A of Claims 1 to 4.
12. 12. Process according to any of claims 5 to 11, characterized in that approximately 5-9% w / w of a 40% solution. % of sodium salt of polyacrylic acid versus calcium carbonate is added as a dispersant to the suspension containing the pigment obtained in any of Claims 1 to 4 (Steps A) (corresponds to approximately 1.5-3.5% per weight of dry polyacrylic acid in dry calcium carbonate).
13. 13. - Process according to any of claims 5 to 12, characterized in that the final concentration of the suspension is obtained partially or completely by the addition of one or more original pigments or pigment suspensions during Steps B.
14. 14. - Stable and porous PCC aggregates / agglomerates characterized in that they are obtained according to any of claims 1 to 13.
15. 15. - Stable and porous aggregates / agglomerates of PCC characterized in that they have the following properties: a specific surface of 30-100 m2 / g, preferably 50-80 m2 / g; and / or an aggregate diameter between 1 and 5 μp ?, with an average diameter of 2 μm; I a fraction of fine particles of less than 2 μm less than 20%, preferably less than 15% (measured with a Helos Sympatec device); and / or a primary particle size of the acicular particles of 20-50 nm with an aspect ratio between 1: 2 and 1:10; and / or a solids content by weight of 5-25%, preferably 15-20% at the end of Steps A, and a solids content of 25-60%, preferably 35-50%, and in particular 39-40% at the end of Steps B.
16. 16. - New pigments characterized in that they contain porous and stable PCC aggregates / agglomerates in accordance with claims 14 or 15.
17. 17. - New pigment or PCC suspensions characterized by containing aggregates / porous and stable PCC agglomerates according to claims 14 or 15.
18. 18. - New PCC pigments or suspensions according to claim 17, characterized in that their concentration of solids is by weight: when they are in the form of a "precursor" to the end of Steps A, 5-25%, preferably 15-20%; when they are in the form of final PCC after reconcentration (Steps B), solids concentration of 25-60%, preferably of 35-50% and in particular of 39-40%.
19. 19. - Formulations for coatings for the paper industry characterized in that they consist of new aggregates / agglomerates of PCC, new pigments and / or new suspensions according to any of claims 16 to 18.
20. 20. - Fo rmu 1 aci one s for compliance coatings with the rei indication 19, characterized in that the PCC suspension contains characteristics of the following properties: a solids content by weight of 25-60%, preferably of 35-50%, and in particular of 39-40%; and / or PCC with a very specific surface, with a specific surface of 30-100 m2 / g, preferably 50-80 m2 / g.
21. 21. Ap 1 i ca c i ons of the formulations for coatings according to claim 19 or 20, characterized in that they are for the coating of paper for printing with ink jet.
22. 22. - Ap 1 i ca c i ons fo the formulations for coatings in accordance with claims 19 or 20, characterized in that they are for the coating of "multi-purpose" paper for printing with ink jet or specialized paper and high quality.
23. 23. - Paper for printing with ink jet, specifically "multi-use" paper for printing with ink jet or specialized and high-quality paper, characterized in that it is coated with at least one of the coating compounds according to claims 19 or 20.