MXPA97007114A - Paper for registration with ink jet that incorporates novedous pigment of calcium carbonate precipit - Google Patents

Abstract

An improved thermal inkjet recording paper incorporating heat-cured and / or milled precipitated calcium carbonate ("PCC") and a binder is described, the thermo-curing and grinding processes yielding discrete particles of PCC with a surface and chemical morphology. which improve the ability of the PCC to bind to the ink jet without bonding so tightly to change the color of the ink, there have been produced papers for ink jet recording incorporating the PCC and binders of the present invention which are superior to the multi-purpose office papers with reduced embossing, dispersion and penetration or transparency of the backside, and improved optical density, drying time, and water fastness, the inkjet recording paper of the present invention is compared to the papers commercially based silicon, at a fraction of the cost

Description

POPEL FOR REGISTRATION WITH INK JET THAT INCORPORATES NOVEDOUS PIGMENT OF PRECIOUS CALCIUM CARBONATE FIELD OF THE INVENTION The present invention relates to novel pigments of ground precipitated and ground calcium carbonate which are used in papers for ink jet recording. More particularly, the present invention relates to an ink jet recording paper incorporating said pigments in at least one water-soluble binder that imparts enhanced print quality. The invention also relates to methods for applying these components to paper, and to methods for producing novel pigments.

BACKGROUND OF THE INVENTION The thermal ink jet process applies a dilute aqueous ink on the surface of a paper by heating a small volume of the ink in a small chamber with a hole that is directed towards the recording paper. The small volume of ink that is heated quickly reaches its boiling point, and the vapor bubble formed drives a small drop of liquid ink into the paper, where the drop produces an individual dot in a matrix of dots that form a character or image on the sheet. This procedure requires a + in + a that has a low content of solids and high boiling components, so that it is capable of rapid boiling + e without leaving a residue that can obstruct the heating element, and plugging the hole. Therefore, up to 36 percent of the ink from the inkjet printer is a mixture of water and low molecular weight glycols. Although this ink boils quickly when heated to ensure fast printing, and is not prone to clogging, it results in an applied ink that is very mobile and takes time to dry. Therefore, good print quality can only obtained if the ink + e of the ink remains on or near the outer surface of the paper, and does not extend or move from the point at which it was applied. Also important is that drying occurs quickly to prevent dyeing of the dye. In printers that are not equipped with heating elements, the water and glycol components of the ink must penetrate the paper body for proper drying of the colorant on the surface. If the colored phase is carried out on the paper with the liquid phase as it penetrates the paper, or if the dye appears on the surface of the paper, the quality of the resulting print or image will be poor. Also, the dye from the dry ink that is not permanently fixed on the paper will run or flow if the printed surface becomes wet or is marked with a rinse aid. Therefore, dry ink must have excellent properties in water and rinse-aid for optimum performance. In most applications, multi-purpose office papers provide inadequate or poor quality thermal ink jet printing. This is particularly true where multi-color printing is used with concomitant applications of superimposed ink. Poor print quality is complicated by printers that apply colors in one order when the print head moves to the right, and in the reverse order when the print head moves to the left. Multi-purpose office papers often allow the dye to penetrate the paper, which results in a reduced optical density of the printed image, and greater transparency on the reverse side of the paper. The office papers for multiple purposes that are highly prepared prevent the penetration of the liquid, resulting in a higher optical density of the ink and also, excessive dipping and scattering. One method to improve the quality of thermal inkjet printing is to apply a material to the surface of the paper that binds the ink dye to the surface, but allows the liquid water / glycol phase to enter the body of the paper , which accelerates drying. However, the ink dye is often a organic or unsaturated organic compound, and if the surface material interacts very strongly with the colorant, the color * of the ink may change. Therefore, a surface material must be obtained which prevents the tint dye from penetrating the paper, but which does not interact so strongly as to affect the dye, and cause a color change. Oshirna et al., Patent of E.U.A. No. 4,478,910, discloses a paper-based raw material that is coated with a highly specific surface area colloidal silica pigment and a polyvinyl alcohol binder, where the specific surface area of the colloidal silica is greater than 200? N2 / g. Migarnoto, patent of E.U.A. No. 4,576,867, and Kojirna et al., U.S. Patent. No. 4,830,911, teach that the application of a cationic quaternary ammonium polymer to a paper stock will improve the water firmness of the resulting paper. The application of said quaternary ammonium polymer in a sizing press is also described by Malhotra, patent of E.U.A. No. 5,223,338. However, commercial paper for thermal recording with high quality inkjet is produced with coatings that do not require a machine, that is, the paper is not treated in the sizing press of the machine manufacturer of pa, but must Removed and coated in an additional step using a separate coating procedure.

Precipitated calcium carbonate ("PCC") has been described as a pigment or useful pigment in inkjet paper, but is typically included in a long list of compounds that also include ground calcium carbonate. natural, a form of the compound that differs widely from the PCC in its physical and chemical properties; for example, the ground and natural calcium carbonate particles are much larger than those found in the PCC, and are normally anionic, while the PCC is naturally cationic. Kondo et al., Patent of E.U.A. No. 5,320,897, discloses coating paper for ink jet recording with pigments not included in the shelf, and a water-soluble binder. The pigments that are described as useful have an apparent specific gravity on the scale of 0.10 to 0.50 g / cm3, and produce a paper with a water contact angle of 45 ° to 100 °. Tsu isaka and others, patent of E.U.A. No. 5,007,964, describes a generic method of precipitation that incorporates a chelating agent to obtain a porous chain agglomeration similar to PCC particles with a specific surface area of BET in the range of 25 to 55 m2 g for use in a paper for registration. It is described that particles with a specific surface area of BET of more than 55 rn2 / g, are inconvenient because they have a higher density, are not porous and exhibit a low capacity for absorb oil and water. It is further described that the PCC can be used as a paste, or as a powder obtained by pounding the dried pulp, which is described does not affect the agglomeration of the particles. K? Nesh et al., Patent of E.U.A. No. 5,2.1.5,734, describes an accelerated heat-cure process for PCC that produces crystals with a specific surface area of about 3 about 15 m2 / g and a defined average particle size of about 0.2 to about 0.9 μr. PCC is used to improve the optical properties of paper. In view of the above, there is nothing in the prior art that suggests how to improve the print quality of the inkjet recording paper. The present invention provides said solution to this problem.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a paper for ink jet recording with improved properties incorporating novel pigments of precipitated calcium carbonate terrnocuradoe and / or milled, as well as a binder. The heat-cured PCC is prepared by carbonating a suspension of calcium hydroxide to form a suspension of precipitated calcium carbonate, sifting the suspension to remove impurities, adding an organophosphate compound, such as ethanolamine bis-rneti lenphosphonic acid), to the suspension, and drying the PCC suspension in the presence of the phosphate organ to produce an improved pigment for paper for ink-jet recording. The inkjet recording paper of the present invention is produced by coating at least one side of a paper base stock with a coating comprising heat-cured and / or milled PCC and a binder to form the paper for recording with ink-jet. The heat-cured and / or milled precipitated calcium carbonate is obtained by carbonation of a calcium carbonate suspension, by browning the PCC in the presence of an organophosphate compound and / or by grinding the PCC to produce defined PCC particles with a surface chemistry and morphology. improves the ability of the PCC to bind to the ink dye of the inkjet printer.

DETAILED DESCRIPTION OF THE INVENTION An inkjet recording paper has been obtained that provides total color print quality with inkjet approaching, or exceeding, that of the best specialized inkjet paper at a fairly low price. The selection of the particle size, surface area, surface chemistry and degree of aggregation of the PCC, and its combination with a formulation binder appropriate, allows each thermal inkjet print feature to be adjusted and optimized individually. The cationic PCCs of the present invention bind the dyes of the ink without the use of expensive cationic resins, and can be manufactured in the paper mill, which, unlike silica, do not need to be dried, shipped and then rehydrated for use . The present formulations are designed to be applied in a dosing sizing press, such as those installed in large, low cost papermaking machines per unit. Therefore, the PCC Compositions of the present invention can be applied as part of the papermaking operation, rather than as a separate additional step after the normal papermaking operations conclude, which increase the cost of the process and of the finished product. In view of the fact that the application of a dosing sizing press typically consists of two sides, both sides of a coated paper in said press are available for printing, rather than the one-sided coating found in expensive high-cost commercial papers. quality. Although polyvinyl alcohol is a preferred binder in the present invention, the treatment of a paper, for ink-jet registration with cold-cured and / or milled PCC provides a significant improvement in print quality with lower cost binders. Finally, the present formulations provide a role that is still appropriate for photocopied, which allows multiple uses «read paper. PCC is normally produced by bubbling a gas containing carbon dioxide through an aqueous suspension of calcium hydrogen. Other inorganic materials, in particular, inorganic materials containing aluminum, such as aluminum oxide, can be coprecipitated with the PCC, or can be precipitated on the surface of the PCC precipitate. However, it has been unexpectedly discovered that when said PCC is heat-cured and / or milled, treated with an appropriate binder, and then used in a composition to heat-treat paper for ink-jet recording, a recording paper is obtained with high-quality ink jet, which provides a print quality that compares favorably with that of commercial papers of thermally coated cost with silica, but at a fairly low cost. The milling and grinding procedures produce defined PCC particles with a surface chemistry and morphology that increases the ability of the PCC to bind to the inkjet ink dye without binding so strongly that the color of the ink changes. There have been produced papers for ink jet recording incorporating the PCC and the binders of the present invention which are superior for office papers for multiple purposes with reduced characteristics of immersion, dispersion and penetration or transparency of the back, as well as improved optical density, drying time and water fastness. The PCCs of the present invention are produced by the conventional method of precipitation which consists in introducing a gas containing carbon dioxide into a suspension of calcium hydroxide. The calcium carbonate precipitate is thermocured and / or milled before use. The print quality of an ink jet recording paper incorporating said PCC is controlled by the state of aggregation of the particles and the surface chemistry of the pigment and the binder. The chemical nature of the surface of the pigment is controlled by the specific synthetic route and the post-synthesis treatment of the pigment. A PCC particularly useful in the present invention is prepared by a process comprising introducing carbon dioxide into an aqueous suspension of calcium hydroxide at a temperature of about 7 ° to about 18 ° C. The suspension contains from about 0.2 to 1 weight percent, based on the calcium carbonate equivalent of the calcium hydroxide in the reaction suspension, of an anionic organopolyl phosphonate polyelectrolyte (typically, Briquest 221-50A, ethanolarnin acid). bis ~ met.ilenphosphonic), Albright & Uilson Americas, Inc., Richmond, VA) and from 0 to 10 weight percent of aluminum sulphate octadecahydrate (I2SO4-I6H2O). The introduction of carbon dioxide continues until the precipitation of calcium carbonate is substantial complete entity. This typically occurs when the conductivity of the carbonated suspension reaches a minimum at a pH of about 10 to 11. Except for the addition of aluminum sulfate octadecahydrate, the process up to this point is essentially that of US Patent No. 4,367,207, the teachings of which are incorporated by reference in the present invention The addition of aluminum sulfate octadecahydrate is described in US Patent No. 4,892,590, the teachings of which are also incorporated herein by reference. After a PCC of the desired particle size and specific surface area is obtained, the PCC is heat-cured or milled to obtain the PCC characteristics required for a low-cost, high-quality inkjet recording paper. The grinding breaks up the aggregates of the pigment into individual particles, which exposes the surfaces of the PCC that were attached, and are chemically different from the surface of the aggregate. The milling is typically carried out on a PCC with a scalenohedpca, acicular, prismatic or rhombohedral morphology. The thermocuration is usually carried out on a rhombohedral or prismatic PCC, and not only separates the aggregates, but also includes the additional precipitation on the particle surface. It is thought that the newly precipitated material may be chemically distinct from the rnat pal of additional surface; for example, the surface of a heat-cured or milled PCC may have a higher calcium-magnesium ratio. Conventional thermocuration, also known as Ostwald maturation, is a process by which crystals such as calcium carbonate, initially in a state of higher internal energy, and having relatively high phase solubilities, undergo a phase transformation by dissolving and redeposing themselves. on crystals in a state of lower internal energy. The process results in a final glass product characterized by a greater perfection of the crystal lattice structure, a narrower particle size distribution and a greater degree of particle distinction, and a lower surface energy. In the present invention, the heat cure of the PCC begins by terminating the reaction of carbon dioxide and calcium hydroxide when the conductivity of the suspension reaches a minimum, which is typically at a pH of about 10 to 11. The PCC is then sieved for removing impurities, and about 1 weight percent of an organophosphate, based on the weight of the PCC, is added to control the degree of heat cure. Other chemical agents that are surfactants with respect to calcium carbonate will also function as organophosphates to control the degree of heat cure. These agents include, but are not limited by the following, sodium polyphosphates, sodium silicates, sodium polyacrylates, various carboxylic acids such as mono-, di-, tn-, and polycarboxylic acids and their salts, various poly saccades, and various gums with repeated functionalities of carboxylic acid. The suspension is then heated to a temperature of at least about 75 ° C, and preferably about 80 ° C or more to cure the PCC particles. The thermo-cure step is carried out up to about 10 hours or more, depending on the temperature. At temperatures of about 80 to 85 ° C, the heating is carried out for about 2 to 5 hours. The pH of the suspension rises to about 10.5 due to the presence of unreacted calcium hydroxide. The thermocuration reaction is then monitored by measuring the surface area of the PCC at intervals every hour. The cold-cured PCC that is recovered as the final product of the process has a rhombohedral or prismatic morphology and a specific surface area of about 60 to about 100 rn2 / g, preferably about 65 to about 95 rn2 / g, and preferably of around 80 to 90 rn2 / g. The organophosphonates used in the present invention are organopoliphosphonates of variable molecular weight which are commonly used as inhibitors of scabs, sequestrants, deflocculators and detergent promoters. Such organophosphonates include, but are not limited to, Nitrile-nitrile-rnetylene-phosphonic acid, etilendianinotetra-rnetylene-phosphonic acid, diethylenetriane-phenylene-phosphonic acid, hydroxy-ethane-1, -di-phosphonic acid, ethanolarnine, ethanolamine bis-methylene-phosphonic acid, N, N-dimethylene-phosphonic acid and hexamethylene-dianinotetra-rnetylene-phosphonic acid. The preferred organophosphonate is ethanolamine bis-rneti-lyphosphonic acid. The grinding of a calcium carbonate can be carried out in a dry or wet grinding process in, for example, a conventional ball mill, jet mill, microline or media mill. The preferred grinding is carried out by introducing an aqueous suspension of PCC in a medium medium containing glass mill of a size of about 0.7 to 0.9 mm. The medium mill is equipped with mechanical agitation, and the preferred weight percentage of solids in the PCC suspension is from about 10 to 30%, based on the total weight of the PCC and water. When media milling is typically performed on PCC with a scalenohedral morphology, a PCC with a specific surface area of about 10 to about 40 rn2 / g, preferably about 15 to about 30 m2 / g, and a Glass shape less elongated. Examples of binders useful for coating compositions for ink-jet recording paper are those that hitherto are conventionally used in the art, and include polyvinyl alcohol ("PVOH") and derivatives from the same, oxidized starch, etherified starch, esterified starch, dextrin and similar starches, carboxymethyl cellulose, hydroxyethyl cellulose and similar cellulose derivatives, casein, gelatin, soy protein, maleic anhydride resin, styrene-butadiene copolymer crosslinks , copolymer of methyl methacrylate butadiene and similar polymers or copolymers of conjugated diene, and acrylate lattices and polymers or copolymers of methacrylate and similar acrylic polymers, and latex. When required, the coating composition may additionally be incorporated therein, in an amount conventionally used in the art, conventional pigment dispersants, adhesives, flow modifiers, defoaming agents, sputtering inhibitors, release agents, coloring agents. and similar. Ink-jet recording papers incorporating the PCC formulations of the present invention have been prepared and tested. The following is a brief description of the procedures and test methods used. Once a CCP is produced, the entire test procedure can be classified into four areas; pigment preparation, formulation with binder, paper coating and processing, and testing. The specific details for each of these procedures are given below.

Pigment preparation: The pigments to be tested are typically in the form of a suspension or a filter cake. The samples in the form of a suspension are concentrated in the desired solids by vacuum filtration. In some cases, such as with a molten PCC or with a specific surface area of approximately 10 to 53 m2 / g, the solids in the suspension are not altered in order to double the test conditions. Once the solids of the target formulation have been established, the pigment is diluted, if necessary, with water and mixed thoroughly. The pigment is characterized by the particle size distribution (Sedigraph 5100), specific surface area (Flowsorb), viscosity (Brookfield), and morphology by sieving electron microscopy ("SEM"). The surface area of the product was obtained using a rlicrOrneritics Flowsorb II 2300, which uses the theory of BET with nitrogen as the absorbent gas. The particle size was determined by a sedimentation technique using a Micromenties Sedigraph Model 5100 in an aqueous dispersion of the product at approximately 3 percent and using approximately 0.1 percent carboxylated polyelectrolyte (Daxad 30) as a dispersant.

Formulation: Typical binders are cationic starch (F? Lmcote-54R, National Starch), polyvinyl alcohol or PVOH (Airvol 107R, Air Products Inc.), and latex (press latex of experimental size from Dow). When a starch is used as a binder, the dried starch is dispersed in water at about 10-25 percent solids, and then cooked in an automatic laboratory oven at approximately 195 ° C for 50-190 minutes. The resulting viscous starch slurry is combined with the pigment, which has been properly prepared to obtain the target formulation solids, and mixed thoroughly in a Premier mill with an open cowles-type driving blade. The formulation is mixed for about 5 minutes until a completely homogeneous suspension is obtained, and the resulting formulation is characterized by the viscosity of Broo field (10, 20, 50 and 100 rpm) and solids. Polyvinyl alcohol is prepared in a manner similar to that used for starch. The PVOH is hydrated at approximately 200 ° C in a laboratory oven for 50-190 minutes at 10 percent solids. For latex binder (50 percent solids), no preparation is needed before testing. The formulation of these binders with the pigment is the same as with the starch. The formulation solids for the tests They were on the scale of approximately 20-28 percent, with a typical coating formulation that has approximately 20 percent solids.

Paper coating: In general, a non-sizing base material with a weight basis of 91.3-83.0 g / rn2 is used in the tests. The paper is cut into sheets of 30.48x43.18 crn and secured to the CSD Drawdown apparatus, which consists of a glass plate (30.48x43.18cm) mounted on a metal base with a spring clip on the top. A coating formulation is applied with a CSD stretch bar by placing the bar of choice, which depends on the weight of the target coating, on the top of the paper, adding a sample of 10-15 ml completely mixed with the formulation with a 30 nl syringe in a uniform line along the top of the paper, under the bar, and coating the paper by pulling the stretch bar from the top to the bottom using light pressure and a constant speed for about 2 hours second. The coating weight is determined by the stainless steel draw bars that are specifically scored to provide a predetermined coating volume to the paper surface. The bars with grooved grooves give a heavier coating weight, since spaces between the slots are wider. In turn, bars with a greater number of more tightly spaced grooves produce lighter coating weights. Typical coating weights are from about 2 to 10 g / rn2. Once a formulation has been applied, the paper is dried immediately with a heat gun held by hand for about 30-60 seconds, and then completely dried at room temperature over a period of about 2-24 hours. The dry papers are then cut into 21.59x27.94 cm sheets to test.

Paper test: Minimum print quality specifications with inkjet have been established by Hewlett Packard Corporation ("HP"). Therefore, most tests use HP methods to determine the following printing characteristics. The optical density is a measure of the reflection density of an image. A specific test pattern is printed on the paper, and the optical densities of pure black, mixed body black, cyan, magenta and yellow are measured using a reflection densitometer (Macbeth RD918). The resulting optical densities are compared to the minimum HP specifications.

Dispersion and smearing of the ink can increase the quality of the inkjet printing, the dispersion of the ink is defined as the growth or enlargement of printed areas. The embossing is the effect of the ink wick, which results in blurry images. This is measured by analyzing a specific portion of the same printed pattern used for optical density measurements. The specific portion is evaluated for the area of ink, dispersion, ink perimeter, and dipping. The resulting digital pattern is quantified and compared with a commercial inkjet paper. HP's test method for dispersing and smearing the ink was not used in these tests, since the HP test is subjective rather than quantitative. The ink drying time is a measure of the speed of ink absorption on a sheet of paper. A specific test pattern is printed, the image is smeared with ink, and the resulting optical density of the transferred black ink is measured. The results are adjusted to an exponential decomposition model of HP, and the ink drying time is calculated. The final drying times are compared with the minimum criteria established by HP. Water firmness is a measure of the amount of dye transferred from a printed area to an unprinted area when water is applied. The test pattern of the water firmness is printed on the paper, 250μl of water is applied throughout the print, and it is left to run over the area printed and unprinted area adjacent. The optical density of the black ink transferred in the non-printed areas is measured. The resulting optical densities are compared to the HP standards. Rinse Aid Firmness is the measure of dye transferred from a printed area to an unprinted area when it contacts two types of brighteners. The specific test pattern is printed on the paper and, using an alkaline rinse aid and an acid rinse aid, a perpendicular line is drawn through the test area. The optical density of the black ink transferred in non-printed areas is measured and compared to the minimum criterion of HP. A color evaluation is performed with a CIELAB system, which uses an Elrephro Datacolor 2000 colorimeter to determine the values of L *, a * and b * to mark the color appearance of printed areas of cyan, green yellow, blue, magenta and ro or. The results are compared with the HP diagrams for color quality. Tone adhesion is a xerographic, ink-free test that measures the degree of adhesion of tone to the coating. Tile adhesion is essential for use as a commercial multi-purpose paper, which will often be used as a copier paper. Here, a test pattern is copied onto the paper using a Xerox copier, the test areas are increased with a 2.27 kg roller, and the p > streaks of The resulting tone loss is compared to a series of rules. The degree of loss of tone is rated 1, loss better or no loss of tone, a ^ 10, loss of tone worse or severe. In the gloss test, the coated paper is tested for TAPPI brilliance using the Technidyne S-4 Brilliance Meter. The results are compared with the uncoated base material.

EXAMPLES The following non-limiting examples are merely illustrative of the preferred embodiments of the present invention, and should not limit the invention, the scope of which is defined by the appended claims.

EXAMPLE 1 The preparation of a calcium hydroxide suspension was carried out by combining 1 part of lime with 5 parts of water with mechanical stirring at an initial temperature of 50 ° C. The suspeneion was mixed for approximately 10 minutes, diluted with water to 1 part of lime to 15 parts of water, and sieved with a 60 mesh screen to remove the sand. Calcium carbonate was precipitated from the suspension in a 30 liter stainless steel reactor equipped with a variable speed agitation that has two pitch blade turbine impellers, heating and cooling the jackets, an * carbonation hub of stainless steel to direct a gas containing carbon dioxide to the impeller, and a probe to control the pH of the suspension. Twenty-six (26) liters of calcium hydroxide suspension, prepared as described above, was added to the reactor at the same time by stirring at 420 rpm. Six grams of organophosphonate (Briquest 221-50A, bi-rneti lenphosphonic ethanolamine acid, Albright to Uilliarns Americas, Inc., Rich ond VA), corresponding to 0.1 weight percent Briquest based on the calcium carbonate equivalent of the calcium hydroxide suspension. A 1 liter solution containing 95.0 g of AI2SO4 was then added. I6H2O. The temperature of the suspension was adjusted to 9.5 ° C, and gas containing carbon dioxide (28 volume percent CO2 on air) was introduced at a rate of 2.3 S.C.F.M. at the same time stirring at 615 rpm. The carbonation of the calcium hydroxide suspension was continued for 36 minutes with cooling until a minimum conductivity of the suspension was reached, indicating that the precipitation of calcium carbonate was completed. The final temperature of the suspension was 15.8 ° C. The specific surface area of the resulting calcium carbonate was determined as 115 m2 / g.

EXAMPLE 2 In the same manner as described in example 1, the precipitation of calcium carbonate by carbonation of a suspension of calcium hydroxide with a gas containing carbon dioxide in the presence of 0.1 weight percent Briquest and 3.15 weight percent weight of A1.2 O .I6H2O was carried out with the same equipment. The carbonation was completed in 35 minutes when a minimum conductivity was obtained. The final temperature of the suspension was 16.7 ° C, and the pH was 11.65. The specific surface area of the PCC was 102.3 m2 / g. The suspension of PCC was screened with a mesh of 325 sieves, and placed back into the reactor. While stirring, 45 g of Briquest 221-50A was added, which corresponds to 0.7 weight percent of Briquest, based on the weight of PCC present. The pH was adjusted to 9.5, the suspension was heated to 80 ° C, and the PCC was cured at 80 ° C for 5 hours. The specific surface area of the final product was 82.4 m2 / g.

EXAMPLE 3 In the same manner as described in example 2, a suspension of calcium hydroxide was carbon in the presence of 0.1 percent in Briquest peo and 3.15 percent by weight of AI2SO4.I6H2O where both percentages are based on the equivalent of Calcium carbonate of calcium hydroxide. He Carbonation time was 39 minutes, the final pH was 10.9, and a PCC with a specific surface area of 115.1 rn2 / g was obtained. While stirring the mixture, 0.7 weight percent of Bri uest 2 1-50A was added, based on the weight of PCC. The suspension was sieved with a mesh of 325 sieves, returned to the reactor and heated at 80 ° C for 2 hours. The specific surface area of the final product was 81.6 rn2 / g.

EXAMPLE 4 In the same manner as described in example 2, a suspension of calcium hydroxide was carbon in the presence of 0.7 weight percent of Briquest 221-50A and 3.15 weight percent of AI2SO4.I6H2O, both percentages based on the Calcium carbonate equivalent of calcium hydroxide. The charging time at the minimum conductivity was 36 minutes, and the final pH was 11.4. The specific surface area of the PCC was 99.1 m2 / g. The suspension passed through a mesh of 325 sieves, returned to the reactor, stirred, and 0.15 weight percent of Briquest 221-50A was added, based on the weight of PCC. The pH of the suspension was adjusted to 9.5, and the suspension was heated to 80 ° C. The PCC was thermoset at 80 ° C for 2 hours, and a PCC with a specific surface area of 63.8 mz / g was obtained.

EXAMPLE 5 A calcium carbonate suspension with a volume of 0.6 1 and a solids concentration of 20.2 percent by weight, based on the total weight of calcium carbonate and water, where the calcium carbonate was PCC scalenohedral with a Specific surface area of 11.57 m2 / g and an average particle size of 1.35μm was placed in an average 1.5 1 stainless steel mill containing 1.7 kg of glass globules of 0.7 to 0.9 mm. The medium mill was equipped with variable speed mechanical agitation. The suspension was ground during minutes with a stirring speed of 2450 rpm. The ground product had a specific surface area of 15.59 rn2 / g and an average particle size of 0.35 microns.

EXAMPLE 6 A calcium carbonate suspension having a volume of 0.6 1 and a solids concentration of 18.7 weight percent, based on the total weight of the calcium carbonate and water, wherein the calcium carbonate was a scalenohedral PCC with a Specific surface area of 26.07 rn2 / g and an average particle size of 0.88μm, was placed in a 1.5 1 stainless steel medium mill equipped with variable speed agitation and 1.7 kg glass globules of 0.7 to 0.9 mm. The suspension was milled for 10 minutes using a stirring speed of 2450 rpm. The ground PCC product had a specific surface area of 30.11 rn2 / g and an average particle size of 0.26 μm. The milled and heat-cured PCCs of Examples 1 to 6 were formulated with an appropriate binder, and the paper test sheets were coated with 5 g / m2 of the formulation in the manner described above. After drying, the paper sheets were tested for real black optical density, mixed body optical density, dispersion, penetration, drying time, and water solubility. The results of these tests are shown in table 1.

TABLE 1 These results demonstrate a significant improvement when compared to a typical uncoated commercial paper, which typically has a mixed black body optical density of approximately 0.9, an actual optical density of approximately 1.28, dispersion of approximately 108, a percent of penetration of about 38, a drying time of about 38, and a solubility in water of about 0.17. By comparison, the best high cost coated commercial paper has a mixed black body optical density of about 1.2, a true black optical density of about 1.56, dispersion of about 98, a penetration percent of about 28, a drying time about 12, and a water solubility of nearly 0. Thus, an ink jet recording paper produced in accordance with the present invention, and, in particular, a paper which is coated with a formulation based on the PCC produced in Example 2 is compared in inkjet printing quality with the best high cost commercial paper now available. While it is clear that the invention described herein is well calculated to meet the aforementioned objects, it will be appreciated that numerous modifications and modalities may be observed by those skilled in the art. It is intended that the annexed claims cover said modifications and modalities that fall within the scope of the true spirit and scope of the present invention.

Claims (17)

NOVELTY OF THE INVENTION CLAIMS

1. A process for preparing a precipitated calcium carbonate pigment comprising forming a suspension of precipitated calcium carbonate particles, adding an organophosphonate compound to the suspension, and heating the suspension to heat the particles of precipitated calcium carbonate and forming the improved pigment.

2. The process according to claim 1, further characterized in that the organophosphonate compound is an amine-containing phosphoric acid derivative and is added in an amount of between 0.1 and 1 weight percent.

3. The process according to claim 1, further characterized in that the organophosphonate compound is ethanolarnine bis-nitrate-phosphonic acid and is added in an amount of between 0.4 and 0.85 percent by weight.

4. The process according to claim 1, 2 or 3, further characterized in that the precipitated calcium carbonate particles are cured for a sufficient time to impart a specific BET surface area of more than 60 m2 / g. 5.- The procedure in accordance with any of claims 1, 2, 3 or 4, further characterized in that the precipitated calcium carbonate particles are cured between 10 and 10 hours at a temperature of at least 75 ° C. 6. The process according to any of claims 1,2,3,4 or 5, further characterized in that the particles of precipitated calcium carbonate are cured between about 2 and 5 hours at a temperature between about 80-85 ° C. 7. Heat-cured calcium carbonate particles when obtained by the process according to any of the preceding claims. 8. A method for making an inkjet recording paper comprising: coating at least one side of a paper base material with a coating comprising heat-cured calcium carbonate particles according to claim 7 and a binder to form the paper for ink jet recording. 9. The method according to claim 8, further characterized in that the coating is applied to each side of the paper base material. 10. The method according to claim 8 or 9, further characterized in that the coating is applied to the paper in a papermaking machine during the papermaking process. 11.- The procedure in accordance with the claim 8, 9 or 10, further characterized in that the binder is polyvinyl alcohol or a starch. 12. A method for making an ink jet recording paper having improved properties comprising: a) grinding precipitated calcium carbonate pigment to produce particles having a surface and chemical morphology that improve the ability of the particles to be bound to the ink; b) coating at least one side of a paper base material with a coating comprising said particles of the ground precipitated calcium carbonate pigment and a binder to form the paper for ink jet recording. 13.- The method according to the claim 12, further characterized in that the particles are milled to have a specific BET surface area of at least 15 m2 / g. 14. An ink jet recording paper comprising a paper base material, which also has a coating comprising a precipitated calcium carbonate precipitate, a precipitated calcium carbonate pigment ground, or a mixture of them, and a binder. 1

5. The ink jet paper according to claim 14, further characterized in that the ground precipitated calcium carbonate pigment has a BET specific surface area of at least about 15 rn / g. 1

6. The ink jet paper according to claim 14 or 15, further characterized in that the hot-cured precipitated calcium carbonate pigment has a specific BET surface area of at least about 60 rn2 / g. 1

7. The paper for recording with ink jet according to claim 14, 15 or 16, further characterized in that the binder is polyvinyl alcohol or a starch.