for the purposes of this description , the term “ calcium carbonate powder ” and any variations thereof , is intended to encompass any powdered material of calcium carbonate , including ground calcium carbonate and precipitated calcium carbonate . the term “ aqueous citric acid ” is intended to encompass a solution of citric acid in liquid form with any amount of water present . as noted above , however , the concentration of the citric acid within such a solution should be adjusted accordingly when added to the calcium carbonate powder such that the amount of citric acid actually reacted with the powder is from 0 . 1 to 5 parts per hundred parts of the calcium carbonate . the inventive method is relatively simple to follow , which is yet another advantage . basically , a starting calcium carbonate powder is obtained initially . to this powder is added the aqueous citric acid in the concentrations as noted above . such introduction of citric acid may be performed through any means , including , without limitation , drop - wise addition while stirring , if in smaller batch sizes , or in repetitive streams of the liquid solution at set intervals and in set volumes for each repeated introduction . the rate of addition should be performed in a range of anywhere between 0 . 1 to 100 ml / min per 350 g of calcium carbonate ( or , between 0 . 000285 to 0 . 285 ml / min per gram of calcium carbonate ), preferably slower , of from 1 to 25 ml / min per 350 g of calcium carbonate . this repetitive introduction step is potentially preferred as it permits reaction of the citric acid in discrete areas within the provided calcium carbonate powder to best ensure , while stirring , that substantially uniform reaction and resultant granulation occurs . spraying of the citric acid solution on the powder while or with subsequent stirring is also possible . generally , it has been found that introduction of the aqueous citric acid quickly may result in lack of proper granulation . as uniformity ( or at least substantial uniformity ) in granulated materials is the aim in this method , the slow addition while stirring is preferred . the granulation may be performed in any apparatus known in the industry such as mixers having low shear or high shear , fluid bed technology , and the like . the amount of citric acid to be added to the provided calcium carbonate powder may be of the range of 0 . 1 to 5 parts per hundred parts of the calcium carbonate , with 0 . 5 to 5 parts preferred , and even more specific preferred amounts noted within the examples , below . specific volumes to be added are not critical as the important feature is to properly introduce the citric acid at intervals or through a steady , slow stream while the powder is properly stirred . the concentration of the citric acid in solution will determine the amount of such a reactant to be introduced to the calcium carbonate powder , in essence . subsequent to reaction of the two components , the wet mixture is then collected and dried . this drying step may be performed within any well known apparatus , including , without limitation , a spray dryer , a rotary dryer , an oven , a fluid bed drier , and the like . the purpose for drying is to remove the excess water through evaporation to leave a granulated solid calcium carbonate in particulate form . such a dried particulate may then be milled , again with any standard well known apparatus , including , without limitation , a hammer mill , a ball mill , an air mill , a bead mill and the like . the milled particulate can then either be separated through a sieve to provide narrow ranges of particle size materials , or coupled with any fines separated through sieving . such sieving thus may be utilized as either a particle size sequestration means , or to ensure the granulates are reduced to their smallest particle sizes . it is then possible , if so desired , to react more citric acid with the remaining fmes , or with the fmes coupled with the larger particle size materials , in order to further granulate the materials to reduce any waste thereof . the closest prior art to such a novel method is taught within u . s . pat . no . 5 , 759 , 575 to gergely et al . such a disclosure encompasses the production of an effervescent tablet including granulated materials comprising citric acid present in an amount in excess of calcium carbonate , far different from the very low amounts within the present inventive method . other granulated calcium carbonate teachings include the presence of salts of edible acids , not edible acids alone . such teachings concern the prevention of premature acid - base reactions of the calcium carbonate and edible acid by requiring the salt of such acids . once produced , the desired particles can then be introduced into desired end use formulations and / or forms . for instance , the resultant granulated calcium carbonate materials may be used as produced and introduced into gelatin capsules to provide a calcium supplement for a patient / user . such a supplement may be utilized as an antacid or as a delivery system for calcium ( for various reasons and / or purposes , such as a manner of treating osteoporosis , as one non - limiting example ). tablets or lozenges may also be produced from such materials through compression techniques as well . such tablets may utilize solely the inventive granulated calcium carbonate materials , or may include certain binders or other additives that act as compression aids to improve the friability of such a tablet formulation . such binders or compression aids may include , without limitation , gum acacia , maltodextrin , alginic acid , gelatin , guar gum , povidone , pregelatinized starch , glucose , ethylcellulose , carboxymethyl cellulose , microcrystalline cellulose , and hydroxypropyl methylcellulose . other additives may be present within either a tablet or capsule form including the inventive calcium carbonate materials depending on the nature of the end use selected . thus , pharmaceutical actives may be present , including any number of analgesics , acid scavengers , cold remedies and the like . additional dietary supplement ingredients may be present such as essential minerals ( potassium , magnesium , selenium , iron , and the like ), vitamins , folic acid , niacin and the like . excipients may be added to tablets to aid in quick tablet disintegration when placed in the buccal cavity as well . such excipients include , without limitation , crospovidone , mcc , sodium starch glycolate and calcium silicate , such as rxcipient ® fm 1000 from j . m . huber corporation . other additives possible within such formulations include coatings ( such as cellulose ethers , gums , and the like ) over the tablet or lozenge surface , sweeteners , diluents , flavoring agents , colorants , preservatives , other antacid compounds ( such as aluminum hydroxide , magnesium hydroxide , magnesium carbonate , and the like ), and other typical additives for such orally administered calcium carbonate tablet compositions . the calcium carbonate granules were made by adding 350 g of ground calcium carbonate ( gcc ), hubercal ® 250 available from j . m . huber corporation , quincy , ill ., to a hobart mixing tank . to the gcc , a citric acid solution as binder , prepared by dissolving a specified amount of anhydrous citric acid in 40 g of water was added either manually or utilizing a masterflex flow meter with microprocessor pump drive at a pumping rate of 10 ml / min . the manual addition used in example 1 was a drop by drop addition and was completed within about 20 to 25 minutes . for examples 6 and 7 , an additional binder , 3 . 5 g maltodextrin for example 6 and 3 . 5 g acacia gum for example 7 , mixed with the citric acid to provide a treatment level of 1 % citric acid and 1 % additional binder . during the addition of citric acid solution , the hobart mixer was stirred at medium speed . after all the binder was added , the formed granules were oven dried overnight at 100 ° c . the granules were put through a 20 mesh ( 850 μm ) u . s . sieve and the granules which did not pass through 20 mesh sieve were gently milled using a mortal and pestle and combined with the granules which previously passed through the 20 mesh sieve . the variables used to make examples 1 - 7 granules are summarized in table 1 . for comparison , granules were formed by granulating 350 g hubercal ® 250 gcc with 40 ml water and no other binder by the same method as described above in examples 1 - 7 . the variables used to make comparative example 1 are summarized in table 1 . the particle distribution and flow characteristics of the granules produced above were measured according to the methods described below with the results summarized in table 2 . the particle size distribution was evaluated by placing the 50 g of granules on a stack of 20 mesh ( 850 μm ), 50 mesh ( 180 μm ), 100 mesh ( 150 μm ), 140 mesh ( 105 μm ), and 200 mesh ( 75 μm ) u . s . sieves with the sieves having the largest openings at the top , i . e . in the order listed with the 20 mesh sieve on top and 200 mesh sieve at the bottom . the sieves were placed on a boerner portable sieve shaker , model rx - 24 , available from w . s . tyler , inc ., mentor , ohio , and shaken for 5 minutes after which the screens were separated and the granules on each sieve were weighed . the intrinsic flowability , which is the property of a powder to flow evenly under the action of gravity and other forces , was determined using a flodex ® tester available from hanson research , chatsworth , calif . the flodex tester is comprised of a funnel with stopper to hold the test powder , under which is a straight - walled open cylinder and finally one of a series of plates with increasing orifice sizes . the flodex tester was assembled with the plate having the smallest orifice size and 50 g of the sample was placed in the stoppered funnel . after 30 seconds the stopper was removed and if the sample flowed through the orifice , the size of the orifice diameter , in mm , was recorded as the flodex index . if the sample did not flow through the orifice , the sample was placed back in the funnel and the experiment was repeated with plates of increasing orifice size until the sample flowed through an orifice . the diameter of the smallest orifice needed for flow was recorded as the flodex index . this test simulates how materials will flow , i . e . to feed a tableting machine . a flodex index measurement of 15 mm indicates good flowability as a solid ; preferably , this measurement should be even lower , with a 10 mm more preferable , and even lower , such as below 7 most preferable . such a result indicates that the products made within the inventive method exhibit excellent flow characteristics as a granulate material . granules made in example 5 were compressed into tablets and several properties of the formed tablets were evaluated . tablets were prepared by weighing all formulation ingredients ( 97 . 5 % gcc and 2 . 0 % croscarmellose sodium ) together , except the lubricant magnesium stearate , on a weighing pan . typically , a tablet formulation was 300 g to 500 g total weight , in order to prepare multiple testing . the combined ingredients were passed through a 20 mesh ( 850 82 m ) sieve to lumps and then the resulting mixture was transferred to a pk - v blender ( twin shell dry blender model 014 - 215 - 0053 , available from patterson kelly , east stroudsburg , pa .) and mixed for 5 minutes . the magnesium stearate lubricant ( 0 . 5 %) was then geometrically diluted with the mixture and then added back to the pk blender and all ingredients mixed together for an additional 2 minutes . tablets were formed from the resulting formulation on an 8 - station piccola rotary tablet press available from riva s . a ., argentina , fitted with 10 mm standard concave die punches compacting at 15 kn and 30 kn compression forces . tablet weight was maintained between 750 mg to 800 mg by adjusting the tablet press . tablet ejection force was measured by the tableting press . all tablets were prepared 24 hours before testing hardness , disintegration time and friability . tablet hardness , expressed in kp , was measured on 5 tablets utilizing a erweka tbh30 instrument ( milford , conn .) and the result reported was an average of 5 measurements . tablet disintegration time ( dt ) was determined according to the usp test for uncoated tablets by placing 3 tablets ( each tablet in a separate tube ) in an erweka zt72 disintegrator ( milford , conn .). the tablets were repeatedly immersed in 37 ° c . deionized water at a rate of 30 strokes per minute until the tablets disintegrated , as detected and recorded by the instrument . the reported result was an average of the 3 measurements . tablet friability was determined by placing 10 tablets in a distek , inc . friabilator df - 3 ( north brunswick , n . j .) set for 100 revolutions . the % friability is calculated from the amount of tablet weight lost ( friable ) by weighing the tablets before and after rotation . when this granulation was compressed at 30 kn compaction pressure the tablets demonstrated acceptable performance . tablet hardness , friability and ejection forces were acceptable for tablets compressed on 10 mm tooling . such results indicate the acceptability of the resultant calcium carbonate materials of the inventive method as a source for compressed tablets . while the invention will be described and disclosed in connection with certain preferred embodiments and practices , it is in no way intended to limit the invention to those specific embodiments , rather it is intended to cover equivalent structures structural equivalents and all alternative embodiments and modifications as may be defined by the scope of the appended claims and equivalence thereto .
a new and useful method of granulating calcium carbonate is provided . such a method entails the inclusion of very low amounts of an aqueous solution citric acid to a calcium carbonate material , with subsequent , mixing , drying , milling , and sieving to provide the correct target particle size range for the resultant granulated materials . such granulated calcium carbonate materials exhibit very high available calcium levels , excellent flow characteristics , capability for compression into tablets , and a drastic reduction in needed binders to effectuate the desired granulation itself . products including such granulated calcium carbonate materials are also encompassed within this invention .