CA2394799C - Ink jet recording paper incorporating novel precipitated calcium carbonate pigment - Google Patents

Abstract

Disclosed is an ink jet recording paper comprising a paper base stock, having thereon a coating comprising a heat aged precipitated calcium carbonate pigment, and a binder, the pigment produced by heat aging a slurry of precipitated calcium carbonate particles in the presence of an effective amount of an organophosphonate compound to control the extent or degree of heat aging.

Description

INK JET RECORDINC3 PAPER INCORPORaITIN(~
NOVEL PRECIPITATED CALCIDM CARBONATE PI~1T
This is a divisional application of Canadian Patent Application Serial No. 2,215,500 filed on March 14, 1996.
The subject matter of this divisional application is directed to an ink jet recording paper described more in detail hereinunder. The subject matter of the parent application was restricted to a process for preparing precipitated calcium carbonate particles. However, it should be understood that the expression "the invention" and the like encompasses the subject matter of both the parent and the divisional application.
Field of the Invention The present invention relates to novel heat aged and milled precipitated calcium carbonate pigments for use in ink jet recording papers. More particularly, the present invention relates to an ink jet recording paper which incorporates Buch pigments and at least one water soluble binder to impart enhanced print quality. The invention also relates to ZO methods of applying these components to paper, and to methods of producing the novel pigments.
Backarouad of the Invention The thermal ink jet process applies a dilute aqueous iuk onto the surface of a paper by heating a sill volume of the ink is a small chamber with an orifice that is directed at the recording paper. The small volume of ink that is heated rapidly reaches its boiling point, sad the steam bubble formed propels a tiny drop of liquid ink at the paper, where the drop Produces a single dot is a dot matrix that forms a character or image on the sheet. This process requires an ink that is law in solids and high boiling components so that it is capable of boiling rapidly without leaving a residue that can foul the heating element, sad clog the orifice. Therefore, up to 96 percent of ink jet printer ink is a mixture of water and low molecular weight glycols. Although such an ink boils quickly when heated to ensure rapid printing, and is not prone to clog, it results is as applied ink that is very mobile and slow to dry. Therefore, good print quality can be obtained only if the ink colorant or dye remains on or near the outer surface of the paper, and does not spread or move from the point at which it was applied_ It is also important that drying occurs rapidly to prevent smearing of the colorant. In printers that are not equipped with heating elements, the water and glycol comoponents of the ink must penetrate into the body of the paper for proper drying of the colorant on the surface. If the colored phase is carried into the paper with the liquid phase as it penetrates into the paper, or if the colorant migrates across the surface of the paper, the quality of the resulting priest or image will be poor. Also, dry ink colorant that is not permanently fixed on the paper will blot or run if the printed surface becomes wet or is marked with a highlighter. Therefore, the dry ink should have excellent water sad highlighter fastness properties for optimum perforrmaace.
Ia moat applications, multipurpose office papers provide inadequate or poor thermal ink jet print quality. This is particularly true where multicolor printing with concomitant superimposed ink applications is utilised. The poor print quality is compounded in printers that apply the colors in one order when the print head moves to the right sad the reverse order when the print head moves to the left. Multipurpose office papers often allow the colorant to penetrate into the paper, which results in reduced optical density of the printed image, and increased ahowthrough on the reverse side of the paper. Multipurpose office papers that are highly sized prevent liquid penetration. leading to higher ink optical density, but, also. excessive feathering and spreading.
One method of improving thermal ink jet print WO 96119369 PCTlUS96103546 quality is to apply a material to the paper surface that binds the ink colorant to the surface, but allows the water/glycoi liquid phase to pass into the body of the paper, which speeds drying. However, the ink colorant often is an unsaturated or aromatic organic compound, sad if the surface material interacts too strongly with the colorant the color of the ink can change. Therefore, a surface material must be obtained that prevents the ink colorant from penetrating the paper, but does not interact so strongly as to effect the colorant, sad cause a color change.
Oshima et al., U.S. Patent No. 4,478,910, discloses a paper base stock that is coated with a high specific surface area colloidal silica pigment and a polyvinyl alcohol binder, where the specific surface area of the colloidal silica is greater than 200 mZ/g.
Migamoto, ~.S. Patent No. 4,576,867, sad Rojima et al., tl.S. Patent No. 4,830,911, teach that application of a cationic quaternary aamaonium polymer to a paper stock will improve the water fastness of the resulting paper. Application of such a quaternary animoafum polymer is a size press is also disclosed by Malhotra, tl.S. Patent No. 5,223,338. However, high quality, cammnercial thermal ink jot recording paper is produced with off machine Boaters, i.e., the paper is not treated in the size press of the paper making machine, but moat be removed sad coated in as additional step using a ~eparata coating process.
Precipitated calcium carbonate ("PCC") has been disclosed as a useful pigment or filler is ink jet paper, but is typically included in a long list of compounds that also includes natural ground calcium carbonate, a form of the compound that differs greatly - from PCC is its physical sad chemical properties; e.g., natural ground calcium carbonate particles are far larger than those found is PCC, sad are normally anionic, whereas PCC is naturally cationic.

WO 96119369 PCTlUS96103546 Koado et al., U.S. Patent No. 5,320,897, describes coating ink jet recording paper with off-the-shelf pigments sad a water soluble binder. The pigments which are disclosed as being useful have an apparent specific gravity is the range of 0.10 to 0.50 g/em3. and produce a paper with a water contact angle of 45° to I00°.
Tbukisaka et al., U.S. Patent No. 5,007,964, disclose a generic precipitation method incorporating a chelatiag agent to obtain a porous agglomeration of chain like PCC particles with a HET specific surface area is the range of 25 to 55 mZ/g for use is a recording paper. Particles with a BST specific surface area of greater than 55 m2/g, are disclosed as being I5 undesirable because they have a higher density, are not porous, sad exhibit a low ability to absorb oil sad water. It is further disclosed that PCC can be used as a paste, or as a powder obtained by pulverizing the dried paste, which is disclosed as not affecting the agglomeration of the particles.
Ruaesh et al., U.S. Pataat No. 5,215,734, disclose an accelerated heat aging process for PCC that produces crystals with a specific surface area of about 3 to about 15 mZ/g and an average discrete particle size of about 0.2 to about 0.9 ~. The PCC is used to improve the optical properties of paper.
In view of the above, there is nothing in the prior art to suggest how to improve the print quality of ink jet recording paper. The present invention provides one such solution to this probla~m.
Summary of the Invention The present invention relates to as ink jet recording paper with anhaaced properties that incorporates novel heat aged and/or milled precipitated calcium carbonate pigments sad a binder. The heat aged PCC is prepared by carbonating a slurry of calcium hydroxide to form a slurry of precipitated calcium carbonate, screening the slurry to remove impurities, adding an organophosphonate compound, such as ethanolamine bis-(methylenephosphonic acid), to the slurry, and heat aging the PCC slurry in the presence of the 5 organophosphonate to produce an improved pigment for ink jet recording paper.
The ink jet recording paper of the present invention is produced by coating at least one side of a paper base stock with a coating comprising heat aged and/or milled PCC
and a binder to form the ink jet recording paper. The heat aged and/or milled precipitated calcium carbonate is made by carbonating a slurry of calcium carbonate, heat aging the PCC in the presence of an organophosphonate compound and/or milling the PCC to produce discrete particles of PCC
with a surface morphology and chemistry that enhances the ability of the PCC to bind to the ink jet printer ink colorant.
The present invention also provides an ink jet recording paper comprising a paper base stock, having thereon a coating comprising a heat aged precipitated calcium carbonate pigment, and a binder, the pigment produced by heat aging a slurry of precipitated calcium carbonate particles in the presence of an effective amount of an organophosphonate compound to control the extent or degree of heat aging.
The present invention also provides a process for making an ink jet recording paper comprising:
a) precipitating calcium carbonate particles from a slurry of calcium hydroxide by introducing carbon dioxide;
b) heat aging the precipitated calcium carbonate particles in the presence of an organophosphonate compound Sa to produce particles having a BET specific surface area of at least about 60 m2/g; and c) coating at least one side of a paper base stock with a coating comprising heat aged calcium carbonate particles and binder to form the ink jet recording paper.
The present invention also provides a process for making an ink jet recording paper comprising:
a) preparing precipitated calcium carbonate particles having a BET specific surface area of at least 60 m2/g and b) coating at least one side of a paper base stock with a coating comprising the precipitated calcium carbonate particles and a binder to form the ink recording paper.
Detailed Description of the Invention An ink jet recording paper has been obtained that provides full color ink jet print quality that approaches or surpasses that of the best ink jet specialty paper at a greatly reduced price. The selection of PCC particle size, surface area, surface chemistry, and degree of aggregation, and its combination with an appropriate formulation binder allows each thermal ink jet print characteristic to be individually adjusted and optimized.
The cationic PCCs of the present invention bind ink colorants without the use of expensive cationic resins and can be manufactured on-site at the paper mill, so that, unlike silica, they do not need to be dried, shipped, and then rewetted for use. The present formulations are designed for application in a metering size press, such as those installed on large, low unit cost paper machines. Therefore, the PCC
compositions of the present invention can be applied as part of the paper making operation, rather than as a separate, additional step after normal papermakiag operations are co~plsted that increases the cost of the process and the finished product. As a metered size press application is typically two sided, both sides of a paper coated on such a press are available for printing, rather than the single sided coating that is found in expensive, high quality comimarcial papers.
Although polyvinyl alcohol is a preferred binder in the present invention, treating as ink jet recording paper with heat aged and/or milled PCC provides a significant improve~meat is print quality with lower cost binders.
Finally, the present formulations provide a paper that is still suitable for photocopying, which allows multiple uses of the paper.
PCC is normally produced by bubbling a gas containing carbon dioxide through as aqueous suspension of calcium hydroxide. Other inorganic materials, in particular, inorganic materials coataiaiag aluminum, such as alum, can bs coprecipitated with PCC, or can be precipitated onto the surface of the PCC precipitate.
It has been unexpectedly discovered, however, that when such a PCC ie heat aged and/or milled, trsatad with as appropriate binder, sad then used in a composition for treating thezmal ink jet recording paper, a high quality ink jet recording paper is obtained, which provides a print quality that eomopares favorably with that of high coat, cemomareial, silica coated thermal ink jet papers, but at a greatly reduced cost.
The heat aging and milling processes produce discrete particles of PCC with a surface morphology sad chemistry that enhances the :bility of the PCC to bind to the ink jet ink colorant without binding so strongly that the color of the ink is changed. Ink jet recording papers incorporating the PCC sad binders of the present invention have bean produced that are superior to multipurpose office papers with reduced feathering, spreading, and penetration or backside showthrough, as well as improved optical density, dry time, and water fastness.
The PCCs of the present invention are produced by the conventional precipitation method of introducing a gas containing carbon dioxide into a suspension of calcium hydroxide: The calcium carbonate precipitate is then~heat aged and/or milled before use.
The print quality of an ink jet recording paper incorporating such a 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 pigment surface is controlled by the specific synthetic pathway and post synthesis treatment of the pigment.
A PCC particularly useful is the present invention is prepared by a process which comprises introducing carbon dioxide into an aqueous slurry of calcium hydroxide at a temperature of from about 7° to 2a about 18°C. The slurry contains from about 0.02 to 1 weight percent, based oa the calcium carbonate equivalent of the calcium hydroxide in the reaction slurry, of an anionic organopolyphosphonate polyelectrolyte (typically, Briquest Z21-50A, ethanolamfae bis-(methyleaephosphoaic acid), Albright Wilson Americas, Iac., Richmond, VA) and from 0 to 10 weight percent of aluminum aulfate-octadacahydzate (A1ZS04-I6H2~?). The introduction of carbon dioxide is continued until precipitation of the calcium carbonate ie substantially -complete. This typically occurs when the conductivity of the carbonated slurry reaches a minimum at a pH of about 10 to 11.
8xcept for the addition of aluminum sulfate octadecahydrate; the process to this point is essentially tbat of U.S. Patent No. 4,367,207.
The addition of aluminum sulfate octadecahydrate is disclosed in U.S. Patent No.
4,892,590, Once a PCC of the desired particle size and specific surface area is obtained, the PCC ie heat-aged or milled to obtain the PCC characteristics required-for a high-quality.~low cost ink jet recording paper.
Milling breaks pigment aggregates into individual particles, which expoeeB PCC surfaces that were joined, and are chemically different from the aggregate surface. Milling is typically performed on a PCC with a ecalenohedral, acicular, prismatic, or rhombohedral morphology. Heat aging is normally performed on a rhombohedral oz prismatic PCC, and not only separates aggregates, but also involves further precipitation on the particle surface. It is believed that the newly precipitated material may be chemically different from the original surface material; e.g., the surface of a heat aged or milled PCC may have a higher calcium-magnesium ratio.
Conventional heat aging, also known as Oatwald ripnaiag, is a process whereby crystals such as calcium carbonate, initially at a higher internal energy state, and having relatively high phase solubilities, undergo a phase transformation by dissolving and redepositing on crystals at a lower internal energy state. The process results in a final crystal product characterized by greater perfection of the crystal lattice structure, a narrower particle size distribution, a greater degree of particle discreteness, and a lower surface energy.
In the present invention, heat aging of PCC
starts by ending the reaction of carbon dioxide and calcium hydroxide when the conductivity of the Blurry reaches a minimum, which is typically at a pH of about 10-11. The PCC is then screened to remove impurities, and up to about 1 percent by weight of an WO 96!29369 PCTIUS96103546 _ g orgaaophoephonate, based oa the weight of PCC, is added to control the extent or degree of heat aging. Other chemical agents that are surface active with regard to calcium carbonate will also serve as well as orgaaophosphoaates to control the extent or degree of heat aging. Such agents include, but are not limited to the following, sodium polyphosphates, sodium silicates, sodium polyacrylatss, various carboxylic acids, such as mono, di, tri, and polycarboxylic acids, and their salts, various polysaccharides, and various gums with repeating carboxylic acid funetioaalities.
The slurry is then heated to a temperature of at least about 75°C. and preferably about 80°C. or higher to heat age the PCC particles. The heat aging step is conducted for up to about 10 hours or more, depending upon the temperature. At temperatures of about 80 to 85°C., the heating is conducted for about 2 to 5 hours.
The pH of the slurry rises to approximately 10.5 due to the presence of uareacted calcium hydroxide. The aging reaction is then monitored by measuring the surface area of the PCC at hourly intervals. The heat aged PCC
that ie recovered as the final product of the process has a rhomobohedral or prismatic morphology and a specific surface area of about 60 to about 100 m2/g, preferably about 65 to about 95 mZ/g, and most preferably from about 80 to 90 mZ/g.
The organophosphonates employed is the present invention are organopolyphosphonates of varying molecular weights commonly used as scale inhibitors, ssquesteraats, dsflocculants, and detergent proaroters.
Such orgsnophosphonates include, but are not limited to, aitrilo tris (methyleae phosphonic acid), ethyleaediaminetetra (methylane phosphoaic acid), diethylenetriaminepaata (methyleae phosphoaic acid), hydroxy ethane-l, 1-dipbosphonic acid, ethaaolamine, ethanolamine bis-(methylaaephosphonic acid), N,N-dimethyleae phosphoaic acid, and hexamethyleae-diamiaetetra (methyleae phosphoaic acid). The preferred organophosphonate is ethsaolamine bis-(methylenephosphoaic acid).
The milling of a calcium carbonate may be carried out in either a wet or dry milling process in, for example. a coavaatioaal ball mill, jet mill, micro mill,. or media mill. The preferred milling is carried out by introducing an aqueous slurry of PCC into a media mill contaiaiag glass media of a size from about 0.7 to 0.9 mm. The media mill is equipped with mechanical agitation, and the preferred weight percent solids of the PCC slurry is frown about 10 to 30 percent, based on the total weight of the PCC and the water. When media milling is typically performed on PCC with a scalanohedral morphology, a PCC with a specific surface area of frown about 10 to about 40 m2/g, preferably from about 15 to about 30 m2/g, and a less elongated crystal shape is produced.
Examples of binders useful for coating compositions for ink jet recording paper are those heretofore conveatioaally used in the art, and include polyvinyl alcohol ("PVOH") and derivatives thereof, oxidized starch, etherified starch, estarified starch, dextrin.and like starches, carboxymethylcellulose, hydroxyethylcellulose and like cellulose derivatives, cassia, gelatin, soybsaa protein, malefic anhydride resin, lattices of usual styrenebutadieae copolymer, methyl methacrylate-butadiene copolymer and like conjugated diene polymers or copolymers, and latticsa of acrylate and methacrylate polymers or copolymers and like acrylic polymers, and latex. When required, the coating composition may have further incorporated therein is an amount conventionally used is the art of conventional pigment dispersaats, tackifiere, flowability modifiers, defoaming agents, foaming inhibitors, release agents, coloring agents, and the like.

Ink jet recording papers incorporating the PCC formulations of the present invention have been prepared and tested. The following is a summary of the procedures sad testing methods used. Once a PCC is produced, the entire testing process can be categorized into four areas; pigment preparation,_formulation with binder, paper coating sad processing, and testing.
Specific details for each of these procedures are given below.
Pigment Preparation:
Pigments to be tested are typically in the form of a slurry or a filter cake. Samples in the form of a slurry are concentrated to the desired solids by vacuum filtration. In some instances, such ae with a media milled PCC with a specific surface area of about 10 to 35 m2/g, the slurry solids are not further altered is order to duplicate trial conditions. Once the target formulation solids is set, the pigment is diluted, if necessary, with water and thoroughly mixed.
The pigment is characterized by particle size distribution (Sedigraph 5100), specific surface area (Flowsorb), viscosity (Brookfield), and morphology by scanning electron microscopy ("SEM°).
The surface area of the product was obtained using a Micromeritics Flowsorb II 2300, which employs BET theory with nitrogen as the absorbing gas. The particle size was determined by a sedimentation technique using a Micrameritics Sedigraph Model_5100 on as aqueous dispersion of the product at about 3 percent and using about 0.1 percent carboxylated TM
polyelectrolyte (Daxad 30) as a dispersant.
Formulation:
Typical binders are cationic starch (Filmcote-54~. National Starch), polyvinyl alcohol or PVOH (Airvol 1074, Air Products Iac.). and latex (Dow experimental size press latex). When a starch is used as a binder, the dry starch is dispersed in water at WO 96129369 PCTlUS96/03546 about 10-25 percent solids, and then cooked in an auta~ated laboratory cooker at about 195°C. for 50-190 minutes. The resulting viscous starch slurry is combined with the pigment, which has been appropriately prepared to attain the target formulation solids, and mixed thoroughly oa a Preanier mill with.a Cowles type open impeller blade. The formulation is mixed for about 5 minutes until a completely homogenous slurry is obtained, and the resulting formulation is characterized by Hrookfield viscosity (10, 20, 50, and 100 r.p.m.) and solids.
Polyvinyl alcohol fs prepared is a manner similar to that used for starch. The PVOH is hydrated at about 200°C. in a laboratory cooker for 50-190 minutes at 10 percent solids. For the latex binder (50 percent solids), no preparation is necessary before testing. The formulation of these binders with the pigment is the same as with the starch.
Formulation solids for the tests were in the range of about 20-2B percaat, with a typical coating formulation having about 20 percent solids.
Pager Coatiac:
C3eaerally, as uasised base stock with an 81.3-83.0 g/st2 basis weight is used is the tests. The paper is cut into 12x1?" sheets and secured to the CSD
Drawdown Apparatus, which coasirts of a glass plate (12x1?") mounted oa metal base with spring clip at the top. A coating formulation is applied with a CSD
drawdowa rod by placing the rod of choice, which depends on target coat weight, at the top of the paper, adding a thoroughly mixed 10-15 ml sample of the fosmulation with a 30 ml syringe is a uniform line across the top to the paper, below the rod, and coating the paper by pulling the drawdowu rod from top to bottom using light pressure and a constant, steady rate for about 2 seconds.
The coat weight is determine by the stainless steel drawdowa rods, which are specifically grooved to deliver a predetermined coating volume to the paper surface. Rods with fewer grooves deliver a heavier coat weight, since the spaces between the grooves are wider. In tuna, rode with a greater number of more tightly~spaced grooves produce lighter coat weights.
Typical coat weights are about~2 to 10 g/m2.
Dace a formulation has bean applied, the paper is immediately dried with a hand held heat gun for about 30-60 seconds, and then completely dried at room temperature over a period of about 2-24 hours.
The dried papers are they cut into 8 1/2 x 11" sheets for testing.
Payer Testing:
Minimum ink jet print quality specifications have been established by Hewlett Packard Corporation (wgpwy, ~erefore, most tests utilize HP methods to determine the following print characteristics.
Optical density is a measure of the reflection density of as image. A specific test pattern is printed onto the paper, gad the optical densities of pure black, composite black, cyan, magenta, gad yellow are measured using a reflection deasitometer (Macbeth RD918). The resulting optical densities are compared to minimum HP specifications.
Ink spreading gad feathering can both decrease the quality of ink jet print. Ink spreading is defined as the growth or widening of printed areas.
Feathering is the wicking of ink, which results in fuzzy 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 ink area, spreading, gad ink perimeter, - feathering. The resulting, digitized patters is quaatitated gad co~pared to a commercial premnium ink jet paper. The HP test method for ink spreading gad feathering was not used in these tests, since the HP

test is subjective rather than quantitative.
Ink Dry Time is a measure of the rate of ink absorption into a sheet of paper. A specific test pattern is printed, the image is blotted, and the resulting optical density of the transferred black ink is measured. The results are fitted to a decaying exponential model from 8P, and the ink dry time is calculated. The final dry times are comnpared to minimum criteria set by 8P.
Waterfastaess is a measure of the amount of colorant transferred from a printed area to as unprinted area when water is applied. The waterfastaess test pattern is printed onto the paper, 2501 of water is applied across the print, and allowed to run over the printed area and adjacent uaprinted area. The optical density of the transferred black ink oa the unprintsd areas is measured. Resulting optical densities are compared to HP standards.
Highlighter smearfastnsss is the measure of ZO colorant transferred from a printed area to as uaprinted area when contacted by two types of highlighters. The specified test patters is printed onto the paper sad, using as alkaline highlighter sad an acid highlighter, a perpendicular line is drawn Z5 across the test area. The optical density of tr~sferred black ink oa uaprinted areas is measured and compared to BP minimum criteria.
1~ color evaluation is performed with a CIBLAH
system, which uses as 8lrephro Dataeolor 2000 30 colorimeter to determine L*, a*, sad b* values to score color appearance of cyan, green yellow, blue, magenta, and red printed areas. The results are compared to HP -diagrams for color quality.
Toner adhesion is a non-ink jet xerographic 35 test, which measures the degree of toner adhesion to the coating. Toner adhesion is esaeatial for use as a casmmercial multipurpose paper, which will often be used as a copier paper. Here, a test pattern ie copied onto the paper using a Xerox copier, the test areas are creased with a 5 pound roller, and the resulting toner loss patterns are compared to a set of standards. The degree of toner loss is rated from l, best or no toner loss, to I0, worst or severe toner loss.
In the brightness teat, the coated paper is tested for TAPPI brightness using the Technidyne S-4 brightness meter. Results are compared to the uncoated base stock.
EgAMPLSS
The following non-limiting examples are merely illustrative of the preferred embodiments of the present invention, and are not to be construed as limiting the invention, the scope of which is defined by the appended claims.
B.xample 1 The preparation of a slurry of calcium hydroxide was carried out by combining 1 part lime with 5 parts water with mechanical agitation at an initial temperature of 50°C. The slurry was mixed for about 10 minutes, diluted with water to 1 part lime to 15 parts water, and screened with a 60-mesh screen to remove grit.
Calcium carbonate was precipitated from the slurry in a 30 liter. stainless'steel reactor equipped with variable speed agitation having two pitched blade turbine impellers, heating and cooling jackets, a stainless steel carbonation tube to direct a carbon dioxide containing gas to the impeller, and a probe for monitoring the pH of the suspension.
Tweaty-six (26) liters of calcium hydroxide slurry, prepared ae described above, were added to the reactor while stirring at 420 r.p.m. To the slurry was then added 6 grams of organophosphonate (Hriquest 221-50A, ethaaolamine bi-(methylenephosphonic acid), Albright & Williams Americas, Iac., Richmond VA), corresponding to 0.1 percent by weight of Hriquest M
based on the calcium carbonate equivalent of the calcium hydroxide slurry. A I liter solution containing 95.0 g A12S04-168Z0 was then added. The slurry temperature was adjusted to 9.5°C., and a gas containing carbon dioxide (28 percent by volume C02 in air)_was introduced at a rate of 2.3 S.C.F.M. while stirring at~615 r.p.m. Carbonation of the calcium hydroxide slurry was continued for 36 minutes with cooling until a minimum slurry conductivity was reached, indicating that the calcium carbonate precipitation was complete. The final temperature of the slurry was 15.8°C. The specific surface area of the resulting calcium carbonate was determined to be 115 m2/g.
Example 2 In the same manner as described in Example 1, calcium carbonate precipitation by carbonation of a calcium hydroxide slurry with a carboy dioxide a0 containing gas is the presence of 0.1 percent by weight Hriquest and 3.15 percent by weight A1ZS04~168Z0 was carried out with the same equipment. The carbonation was complete is 35 minutes when a minimum conductivity was attained. The final temperature of the slurry was 16.7°C.. and the p8 was 11.65. The specific surface area of the PCC was 102.3 mZ/g. The PCC slurry was screened with a 325-mash screen, and placed back into the reactor. While stirring, 45 g of Hriquest 221-50A, corresponding to 0.7 percent by weight Briquest. based on the weight of PCC present, was added. The pH was adjusted to 9.5. the slurry was heated to 80°C., and the PCC was heat aged at 80°C. for 5 hours. The specific surface area of the final product was 8Z.4 m2/g.
8xample 3 In the same manner as described in Example 2, a calcium hydroxide slurry was carbonated in the TM
presence of 0.1 percent by weight Hriquest and 3.15 percent by weight A12S04-16H20, where bath percentages are based on the calcium carbonate equivalent of the calcium hydroxide. The carbonation time was 39 minutes, the final pH was,10.9, and a PCC with a specific surface area of 115.1 m2/g was obtained.
While stirring the mixture, 0.7 percent by weight TM
Briquest 221-50A, based on the weight of PCC was added.
The slurry Was screened with a 325 mesh screen, returned to the reactor, and heated to 80°C. for 2 hours. The specific surface area of the final product was 81.6 m2/g.
Example 4 In the same manner as described in Example 2, a calcium hydroxide slurry was carbonated in the TM
presence of 0.? percent by weight Hriquest 221-50A and 3.15 percent by weight A12S04~16H20, both percentages based on the calcium carbonate equivalent of calcium hydroxide. The batch time to 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 slurry was passed through a 325 mesh screen, returned to the reactor, stirred, and 0.15 percent by weight HriquestTM
221-50A, based on the weight of PCC, was added. The pH
of the slurry was adjusted to 9.5, and the slurry was heated to 80°C. The PCC was heat aged at 80°C. for 2 hours, and a PCC with a specific surface area of 63.8 m2/g was obtained.
Example 5 A calcium carbonate slurry 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 a scalenohedral PCC with a specific surface area of 11.57 m2/g and an average particle size of 1.35 Ecm was placed into a 1.5 1 stainless steel media mill containing 1.7 kg of glass beads of 0.7 to 0.9 mm. The media mill was WO 96129369 PCTlUS96l03546 equipped with variable speed mechanical agitation. The slurry was milled for 10 minutes with as agitation speed of 2450 rpm. The milled product had a specific surface area of 15.59 m2/g and as average particle size of 0.35 microns.
. 8xample 6 A calcium carbonate slurry having a volume of 0.6 1 and a solids concentration of 18.7 percent by weight, based oa the total weight of the calcium carbonate sad the water, where the calcium carbonate was a scalenohedral PCC with a specific surface area of 26.07 m2/g and an average particle size of 0.88 ~cm, was placed in a 1.5 1 stainless steel media mill equipped with variable speed agitation sad 1.7 kg of 0.7 to 0.9 amn glass beads. The slurry was milled for 10 minutes using a 2450 rpm agitation speed. The milled PCC
product had a specific surface area of 30.11 m2/g sad an average particle size of 0.26 ~cm.
The heat aged end media milled PCC's of ales 1 to 6 were formulated with sa appropriate binder, sad paper test sheets were coated with 6 g/m2 of the formulation in the manner described above.
After drying, the paper hand sheets were tested for true black optical density. composite optical density, spreading, penatration, dry time, and water solubility.
The results of these tests are given is Table 1.

~, M
N

v o w ~n M e n o ~ ~ M M o 0 M o N u~

f" N M M

v o ~n ~ w H

~r1 ,p o r1 . ,.i .-1 0~ d~ o .

y M o .-t o d1 ml e-~

d~ If1 N

y -1 N t0 r-1 e1 d~ H O v-~1 ~ 1C N rl O

d M O ri N

y x" M N CD

a r-1 N e~ o~ o ~

M ,~ o .-i ~ t o ,~ o y M O N ~i N

N

p N It1 CD CD O

~

N O e-1 rl O rl !~ O

M O N r1 ri e~l ~D N

p ri M 1D ~ O
.

~

N If1 v-1 rl ri t~1 O O

r1 O n1 x" N r1 tf1 p N M V~ ~ e-1 w N ~ O ~-1 ei O CO N O

y M O N

al r1 N

0t M N ~ O

~

rl O O r-1 O M O O

M O M

ri 'd~ N

01 M M tf1 O

~

ri p If1 O r1 r1 V~ O O
,~

ri O M

O P

~i ~ O O a-) ~0 O O O

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These results demonstrate a significant improvement when compared to a typical uacoated commercial paper, which, typically, has a composite black optical density of about 0.9, a true optical density of about 1.28, spreading of about 108, a percent. penetration of about 38, a drying time of about 38, sad a water solubility of about 0.17. Hy comparison, the best high cost, coated commercial paper has a composite black optical density of about 1.2, a true black optical density of about 1.56, spreading of about 98, a percent penetration of about 28, a drying time of about I2, sad a water solubility of nearly 0.
Therefore, as ink jet recording paper produced according to the present invention, and, is particular, a paper that is coated with a formulation based oa the PCC produced is Example 2, is comparable is ink jet priest quality to the beat high cost commercial paper now available.
While it is apparent that the invention herein disclosed is well calculated to fulfill the objects above stated, it will be appreciated that numerous modifications sad embodiments may be devised by those skilled is the art. It ie intended that the appended claims cover all such modifications and embodiments as fall within the true spirit and scope of the present invention.

Claims (16)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An ink jet recording paper comprising a paper base stock, having thereon a coating comprising a heat aged precipitated calcium carbonate pigment, and a binder, said pigment produced by heat aging a slurry of precipitated calcium carbonate particles in the presence of an effective amount of an organophosphonate compound to control the extent or degree of heat aging.

2. The ink jet paper of claim 1, wherein the heat aged precipitated calcium carbonate pigment has a Brunaner, Emmett and Teller (BET) specific surface area of at least 60 m2/g.

3. The ink jet recording paper of claim 1 or 2, wherein the binder is polyvinyl alcohol or a starch.

4. A process for making an ink jet recording paper comprising:

a) precipitating calcium carbonate particles from a slurry of calcium hydroxide by introducing carbon dioxide;

b) heat aging the precipitated calcium carbonate particles in the presence of an organophosphonate compound to produce particles having a BET specific surface area of at least 60 m2/g; and c) coating at least one side of a paper base stock with a coating comprising heat aged calcium carbonate particles and binder to form the ink jet recording paper.

5. The process of claim 4, wherein the organophosphonate compound is an amine-containing phosphoric acid derivative and is added in an amount of between 0.1 and 1 percent by weight.

6. The process of claim 4, wherein the organophosphonate compound is ethanolamine bis-(methylenephosphonic acid) and is added in an amount of between 0.4 to 0.85 percent by weight.

7. The process of claim 4, 5 or 6, wherein the precipitated calcium carbonate particles are aged for a sufficient time to impart a BET specific surface area of greater than 60 m2/g.

8. The process of any one of claims 4 to 7, wherein the precipitated calcium carbonate particles are aged for between 1 and 10 hours at a temperature of at least 75°C.

9. The process of claim 8, wherein the precipitated calcium carbonate particles are aged for between 2 and 5 hours at a temperature of between 80°-85°C.

10. The process of any one of claims 4 to 9, wherein the coating is applied to each side of the paper base stock.

11. The process of any one of claims 4 to 10, wherein the coating is applied to a paper on a papermaking machine during the papermaking process.

12. The process of any one of claims 4 to 11, wherein the binder is polyvinyl alcohol or a starch.

13. A process for making an ink jet recording paper comprising:

a) preparing precipitated calcium carbonate particles having a BET specific surface area of at least 60 m2/g and b) coating at least one side of a paper base stock with a coating comprising said precipitated calcium carbonate particles and a binder to form the ink recording paper.

14. The process of claim 13, wherein the precipitated calcium carbonate particles are prepared by adding an organophosphonate compound to a slurry of calcium carbonate particles, and heating the slurry to heat age the particles and impart a BET specific surface area of at least 60 m2/g.

15. The process of claim 13 or 14, wherein the precipitated calcium carbonate particles are prepared with a BET specific surface area of at least 80 m2/g and the coated paper has a water solubility of 0.45 or less.

16. The process of claim 13, 14 or 15, wherein the ink jet recording paper has a composite black optical density of at least 0.98, true black optical density of at least 1.31, a spreading value of 107.7 or less, a penetration of 34.5 or less, a drying time of 22 or less, and a water solubility of 0.45 or less.