CA2158969C - Zirconium silicate grinding medium and method of milling - Google Patents
Zirconium silicate grinding medium and method of milling Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
- B02C17/18—Details
- B02C17/20—Disintegrating members
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
- B02C23/18—Adding fluid, other than for crushing or disintegrating by fluid energy
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- Food Science & Technology (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
- Crushing And Grinding (AREA)
- Pigments, Carbon Blacks, Or Wood Stains (AREA)
- Disintegrating Or Milling (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
- Silicon Compounds (AREA)
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- Polishing Bodies And Polishing Tools (AREA)
Abstract
A grinding medium including naturally occurring zirconium silicate sand characterized by a density in the range of from about 4 g/cc absolute to about 6 g/cc absolute is provided. Also provided is a method for milling a powder which includes steps of forming a milling slurry including a naturally occurring zirconium silicate sand grinding medium having a density in the range of from about 4 g/cc absolute to about 6 g/cc absolute.
Description
PATENT
ZIRCONIUM SILICATE GRINDING MEDIUM
BackQrouad of the Invention 1. Field of the Invention The invention relates to grinding media and more Sparticularly to zirconium silicate grinding media.
ZIRCONIUM SILICATE GRINDING MEDIUM
BackQrouad of the Invention 1. Field of the Invention The invention relates to grinding media and more Sparticularly to zirconium silicate grinding media.
2 Descr~tion of the Prior Art Many applications such as the production of ceramic parts, production of magnetic media and manufacture of paints require that the ceramic, magnetic or pigment powder, respectively, be as completely dispersed within the particular binder appropriate for a given application as possible.
Highly dispersed ceramic powders result in ceramic parts of higher density and higher strength than those prepared from less completely dispersed solids. The data storage l5capabilities of magnetic media are limited by particle size and completely dispersed, finely divided powder magnetic media achieve maximum information storage. The optical properties of paints, such as hiding power, brightness, color and durability are strongly dependent on the degree of pigment dispersal achieved. Finely divided powders are required to achieve such complete powder dispersal. Typically, milling devices such as disc mills, cage mills, and/or attrition mills are used with a milling medium to produce such finely divided powders, ideally to reduce the powder to its ultimate state of 25division such as, for example, to the size of a single powder crystallite.
Milling of some powders involves a de-agglomeration process according to which chemical bonds, such as hydrogen-bonded surface moisture, Van der Waals and 30electrostatic forces, such as between particles, as well as any other bonds which are_keeping the particles together, must ~ 15 8 9 6 9 PATENT
be broken and/or overcome in order to obtain particles in their state of ultimate division. One pigment powder which entails a de-agglomeration milling process to reduce it to a finely divided powder is titanium dioxide. Optimal dispersal Sof titanium dioxide pigment powder results in optimized performance properties, particularly improved gloss, durability and hiding power.
De-agglomeration processes are best performed using a grinding medium characterized by a small particle size which l0is the smallest multiple of the actual size of the product particles being milled which can still be effectively separated from the product powder. In a continuous process, the grinding medium can be separated from the product particles using density separation techniques. In a typical l5bead or sand mill operated in a continuous process, separation of the grinding medium from the product can be effected on the basis of differences between settling rate, particle size or both parameters existing between the grinding medium and product powder particles.
20 Commercial milling applications typically use silica sand, glass beads, ceramic media or steel balls, for example, as grinding media. Among these, the low density of about 2.6g/cc, of sand and glass beads and the low hardness of glass beads restricts the materials which can be milled using sand 25or glass beads. The use of steel shot is restricted only to those applications where iron contamination resulting from wear products of the steel shot during the milling process can be tolerated.
Thus, there exists a need for a relatively inexpensive, 30dense and non-toxic grinding medium which is characterized by a small particle size, a density sufficiently high for separation purposes to allow it to be used for the milling of a wide range of materials and which does not generate wear byproducts which result in contamination of the product powder.
Summary of the Invention The invention provides a relatively inexpensive, dense and non-toxic, naturally occurring zirconium silicate sand grinding medium which has small particle size and a sufficiently high density to make it suitable for grinding a wide range of materials, while not contaminating the product powder with its wear byproducts as well as a method for milling a powder using this grinding medium.
According to one aspect of the invention, a naturally occurring zirconium silicate sand characterized by a density in the range of from about 4g/cc absolute to about 6g/cc absolute, more preferably in the range of from about 4.6g/cc absolute to about 4.9g/cc absolute and most preferably in the range of from about 4.75g/cc absolute to about 4.85g/cc absolute is provided, together with a liquid medium selected from the group consisting of water, oil, organic compounds, and mixtures thereof.
Another aspect of the invention provides a method for milling a powder comprising steps of providing a starting powder characterized by a starting powder particle size and a naturally occurring zirconium silicate sand grinding medium characterized by a grinding medium density in the range of from about 4.Og/cc absolute to about 6.Og/cc absolute and a particle size in the range of from about 100 microns to about 500 microns, and mixing the starting powder and the grinding medium with a liquid medium to form a milling slurry; milling the milling slurry in a high energy mill for a time sufficient to produce a product slurry including a product powder having a desired product powder particle size and having substantially the same composition as the starting powder and separating the product slurry from the milling slurry.
Highly dispersed ceramic powders result in ceramic parts of higher density and higher strength than those prepared from less completely dispersed solids. The data storage l5capabilities of magnetic media are limited by particle size and completely dispersed, finely divided powder magnetic media achieve maximum information storage. The optical properties of paints, such as hiding power, brightness, color and durability are strongly dependent on the degree of pigment dispersal achieved. Finely divided powders are required to achieve such complete powder dispersal. Typically, milling devices such as disc mills, cage mills, and/or attrition mills are used with a milling medium to produce such finely divided powders, ideally to reduce the powder to its ultimate state of 25division such as, for example, to the size of a single powder crystallite.
Milling of some powders involves a de-agglomeration process according to which chemical bonds, such as hydrogen-bonded surface moisture, Van der Waals and 30electrostatic forces, such as between particles, as well as any other bonds which are_keeping the particles together, must ~ 15 8 9 6 9 PATENT
be broken and/or overcome in order to obtain particles in their state of ultimate division. One pigment powder which entails a de-agglomeration milling process to reduce it to a finely divided powder is titanium dioxide. Optimal dispersal Sof titanium dioxide pigment powder results in optimized performance properties, particularly improved gloss, durability and hiding power.
De-agglomeration processes are best performed using a grinding medium characterized by a small particle size which l0is the smallest multiple of the actual size of the product particles being milled which can still be effectively separated from the product powder. In a continuous process, the grinding medium can be separated from the product particles using density separation techniques. In a typical l5bead or sand mill operated in a continuous process, separation of the grinding medium from the product can be effected on the basis of differences between settling rate, particle size or both parameters existing between the grinding medium and product powder particles.
20 Commercial milling applications typically use silica sand, glass beads, ceramic media or steel balls, for example, as grinding media. Among these, the low density of about 2.6g/cc, of sand and glass beads and the low hardness of glass beads restricts the materials which can be milled using sand 25or glass beads. The use of steel shot is restricted only to those applications where iron contamination resulting from wear products of the steel shot during the milling process can be tolerated.
Thus, there exists a need for a relatively inexpensive, 30dense and non-toxic grinding medium which is characterized by a small particle size, a density sufficiently high for separation purposes to allow it to be used for the milling of a wide range of materials and which does not generate wear byproducts which result in contamination of the product powder.
Summary of the Invention The invention provides a relatively inexpensive, dense and non-toxic, naturally occurring zirconium silicate sand grinding medium which has small particle size and a sufficiently high density to make it suitable for grinding a wide range of materials, while not contaminating the product powder with its wear byproducts as well as a method for milling a powder using this grinding medium.
According to one aspect of the invention, a naturally occurring zirconium silicate sand characterized by a density in the range of from about 4g/cc absolute to about 6g/cc absolute, more preferably in the range of from about 4.6g/cc absolute to about 4.9g/cc absolute and most preferably in the range of from about 4.75g/cc absolute to about 4.85g/cc absolute is provided, together with a liquid medium selected from the group consisting of water, oil, organic compounds, and mixtures thereof.
Another aspect of the invention provides a method for milling a powder comprising steps of providing a starting powder characterized by a starting powder particle size and a naturally occurring zirconium silicate sand grinding medium characterized by a grinding medium density in the range of from about 4.Og/cc absolute to about 6.Og/cc absolute and a particle size in the range of from about 100 microns to about 500 microns, and mixing the starting powder and the grinding medium with a liquid medium to form a milling slurry; milling the milling slurry in a high energy mill for a time sufficient to produce a product slurry including a product powder having a desired product powder particle size and having substantially the same composition as the starting powder and separating the product slurry from the milling slurry.
_ 215 ~ 9 6 9 PATENT
An object of this invention is to provide a naturally occurring zirconium silicate sand grinding medium.
Another object of this invention is to provide a method for milling a powder using a naturally occurring zirconium Ssilicate sand grinding medium.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon reading the description of preferred embodiments which follows.
Description of Preferred Bmbodimeats As used herein in the specification and in the claims which follow, the term "naturally occurring" indicates that the zirconium silicate sand is mined in the form of zirconium silicate sand of a particular particle size and is l5distinguished from zirconium silicate materials which are synthesized, manufactured or otherwise artificially produced by man. The zirconium silicate sand grinding medium of the invention occurs in nature in the appropriate size and shape which can be sorted to obtain the appropriate fraction for use 20in a particular grinding operation. The mined zirconium silicate sand is sorted to isolate the appropriate fraction of zirconium silicate sand, based on particle size considerations, to be used as a grinding medium. The term "grinding medium" as used herein in the specification and in 25the claims which follow refers to a material which is placed in a milling device, such as a disc mill, cage mill or attrition mill, along with the powder to be ground more finely or de-agglomerated to transmit shearing action of the milling device to the powder being processed to break apart particles 30 of the powder .
a The invention provides a grinding medium including naturally occurring zirconium silicate sand characterized by a density in the range of from about 4g/cc to about 6g/cc, more preferably in the range of from about 4.6g/cc to about 4.9g/cc Sand most preferably in the range of from about 4.75g/cc to about 4.85g/cc.
The naturally occurring zirconium silicate sand tends to be single phase, while synthetic zirconium silicate ceramic beads are typically multiphase materials. Surface lOcontaminants such as aluminum, iron, uranium, thorium and other heavy metals as well as TiOz can be present on the surfaces of the naturally occurring zirconium silicate sand particles. Once the surface contaminants are removed by any surface preconditioning process known to one skilled in the l5art, such as, for example, washing and classifying, chemical analyses indicate that any remaining contaminants are within the crystal structure of the zirconium silicate and do not adversely affect the powder being milled.
Since the density of the naturally occurring zirconium 20silicate sand as described above exceeds the 3.8g/cc density typically characteristic of manufactured zirconium silicate beads, naturally occurring zirconium silicate sand grinding medium of a smaller particle size than that of manufactured zirconium silicate beads can be used, without the zirconium 25silicate sand floating out of the milling slurry, thus ceasing to be effective as a grinding medium.
The zirconium silicate sand grinding medium can be characterized by a particle size which is the smallest multiple of the particle size of the finished product particle 30size, the milled product powder particle size, which can be effectively separated from the milled product powder.
Typically, the naturally occurring zirconium silicate sand _ 215 8 9 6 9 PATENT
particle size is greater than 100microns and can be in the range of from about 100microns to about 1500microns, more preferably in the range of from about 100microns to about 500microns and most preferably in the range of from about 5150microns to about 250microns. The mined, naturally occurring zirconium silicate sand can be screened using techniques well known to one skilled in the art to isolate a coarse fraction of sand having particles of an appropriate size to function as an effective grinding medium.
The grinding medium can be any liquid medium compatible with the product being milled and the milling process and can include water, oil, any other organic compound or a mixture thereof, and can be combined with the naturally occurring zirconium silicate sand to form a slurry. The liquid medium l5is selected depending upon the product being milled. The milled product powder may or may not be separated from the liquid medium after the milling process is complete; however, the grinding medium is usually separated from the liquid medium after the milling process is complete.
If the powder being milled is a pigment for use in an oil based paint or ink, the liquid medium can be an oil such as a naturally derived oil like tung oil, linseed oil, soybean oil or tall oil or mixtures thereof. These naturally occurring oils can be mixed with solvents such as mineral spirits, 25naphtha or toluol or mixtures thereof which can further include substances such as gums, resins, dispersants and/or drying agents. The liquid medium can also include other materials used in the manufacture of oil based paints and inks such as alkyd resins, epoxy resins, nitrocellulose, melamines, 30urethanes and silicones.
If the powder being milled is a pigment for use in a water based paint, such as a latex paint, the liquid medium 215 8 9 s 9 PATENT
can be water, optionally including antifoaming agents and/or dispersants. Also, if the powder is a ceramic or magnetic powder, the medium can be water and can also include dispersants.
The naturally occurring zirconium silicate sand and the liquid medium can be combined to form a grinding slurry which is further characterized by a grinding slurry viscosity which can be in the range of from about l.Ocps to about 10,000cps, more preferably in the range of from about l.Ocps to about 10500cps and most preferably in the range of from about l.Ocps to about 100cps. In general, the grinding slurry viscosity is determined by the concentration of solids in the grinding slurry and, thus, the higher the concentration of solids in the grinding slurry, the higher will be the grinding slurry l5viscosity and density. There is no absolute upper limit to grinding slurry viscosity; however, at some viscosity, a point is reached where no grinding medium is needed, as is the case for plastics compounded in extruders, roll mills, etc. without a grinding medium.
20 The invention also provides a method for milling a powder including steps of providing a starting powder characterized by a starting powder particle size; providing a grinding medium including naturally occurring zirconium silicate sand characterized by a grinding medium density in the range of 25from about 4.Og/cc absolute to about 6.0 g/cc absolute;
providing a liquid medium; mixing the starting powder with the liquid medium to form a milling slurry; milling the milling slurry for a sufficient time to produce a product slurry including a product powder characterized by a desired product 30powder particle size and having substantially the same composition as the starting powder; and separating the product slurry including the product powder from the milling slurry.
f ~ ~ CA 02158969 1999-OS-25 The starting powder used in the method of the invention can be an agglomerated and/or aggregated powder. The agglomerated powder can be characterized by an agglomerated powder particle size less than about 500microns and more Spreferably can be in the range of from about O.Oimicron to about 200microns. For titanium dioxide pigment powders, the agglomerated powder has a particle size of in the range of from about 0.05micron to about 100microns which can be milled to approach the particle size of an individual titanium lOdioxide crystallite.
The starting powder can also be characterized by a starting powder density in the range of from about 0.8g/cc absolute to about 5.Og/cc absolute. The method of the invention is suitable for organic powders which typically have l5densities on the lower end of the above range as well as for inorganic powders such as titanium dioxide, calcium carbonate, bentonite or kaolin or mixtures thereof. The titanium dioxide starting powder can be an agglomerated titanium dioxide pigment which has a density in the range of from about 3.7g/cc 20to about 4.2g/cc.
The naturally occurring zirconium silicate sand used in the method of the invention can also be characterized by a zirconium silicate sand particle size greater than about 100microns and can be in the range of from about 100microns to 25about 1500microns, more preferably in the range of from about 100microns to about 500microns and most preferably in the range of from about 150microns to about 250microns.
The liquid medium used in the method of the invention can be oil or water selected according to the criteria already 30 described.
Milling the milling slurry can be carried out in any suitable milling device which employs a grinding medium, such as, but ' CA 02158969 1999-OS-25 not limited to, a bead mill, cage mill, disc mill or pin mill designed to support a vertical flow or horizontal flow. The milling process can be a batch or continuous process.
The process of separating the product slurry from the milling slurry can be accomplished by distinguishing the product slurry, which contains the product powder along with liquid medium from the milling slurry on the basis of a difference between starting powder and grinding medium physical properties and product powder particle physical lOproperties such as particle size, particle density and particle settling rate. As already described, the product powder may or may not be separated from the liquid medium after the milling process is complete;.however, the grinding medium is usually separated from the liquid medium after the l5milling process is complete. The product powder can be separated from the product slurry and subjected to further processing such as dispersing the powder in a dispersing medium to form a dispersion. Depending upon whether the dispersion is an oil based paint or ink or a water based paint 20or ink or a ceramic or magnetic powder dispersion, the dispersing medium can be selected according to the same criteria as already described for the selection of the liquid medium. If the product powder is to be used in the product slurry, no further dispersing steps are needed.
25 In order to further illustrate the present invention, the following examples are provided. The particular compounds, processes and conditions utilized in the examples are meant to be illustrative of the present invention and are not limited thereto.
PATENT
Example 1 The following example is provided to compare the performance as a grinding medium of conventional, commercially available synthetic zirconium silicate ceramic beads with the Sperformance of standard 10-40 mesh (U.S.)silica sand.
Sand mills having nominal grinding chamber capacities of 275 gallons and overall capacities of 500 gallons were loaded separately with 3000 pounds of synthetic zirconium silicate ceramic beads of nominal 300micron and 210micron size and with 101200 pounds of standard 10-40 mesh (U.S.) silica sand, the highest mill loading feasible with silica sand. The mills loaded with 3000 pounds of synthetic zirconium silicate ceramic beads as well as the mill loaded with 1200 pounds of 10-40 mesh (U.S.) silica sand were operated at 16, 23 and 30 l5gallon per minute flow rates. The feed slurries fed through all mills had a density of 1.35g/cc and contained titanium dioxide, approximately 40% of which was less than 0.5micron in size in water. The size of the titanium dioxide particles in the product slurry was measured using a Leeds and Northrupp 209200 series Microtracl''' particle size analyzer in water with 0.2% sodium hexametaphosphate surfactant at ambient temperature. The results are summarized in Table 1 and indicate that the grinding efficiency of the synthetic zirconium silicate ceramic beads as indicated by the 25percentage of product powder less than or equal to 0.5micron in size compares favorably with the grinding efficiency of 10-40 mesh (U. S.) silica sand.
Table 1 Nhll Flow Rate(gal/min)Grinding Medium %Product<_0.5micron A 30 300micron synthetic66.57 zirconium silicate ceramic beads 30 300micron synthetic64.42 zirconium silicate ceramic beads A 23 300micron synthetic zirconium silicate ceramic beads 23 300micron synthetic70.41 zirconium silicate ceramic beads A 16 300micron synthetic79.96 zirconium silicate ceramic beads g 16 300micron synthetic71.26 zirconium silicate ceramic beads A 30 210micron synthetic85.29 zirconium silicate ceramic beads 30 210micron synthetic74.72 zirconium silicate ceramic beads A 23 210micron synthetic91.51 zirconium silicate ceramic beads g 23 210micron synthetic83.11 zirconium silicate ceramic beads A 16 210micron synthetic95.22 zirconium silicate ceramic beads 16 210micron synthetic95.22 zirconium silicate ceramic beads A 30 10-40 mesh (U.S.)65.17 silica sand g 30 10-40 mesh (U.S.)~ 54.28 silica sand Mill Flow Rate(gal/min)Grinding Medium %Product_<O.Smicron 23 10-40 mesh (U. 61.96 S. ) silica sand g 23 10-40 mesh (U. 57.76 S. ) silica sand 16 10-40 mesh (U. 67.09 S. ) silica sand g 16 10-40 mesh (U. 59.48 S. ) silica sand Furthermore, when the properties of finished pigments processed with the 210micron synthetic zirconium silicate ceramic beads were compared with those of pigments processed Swith silica sand, several improvements with respect to the properties of finished pigments processed with silica sand were observed. The improvements included an approximately 57%
reduction in break time, which is defined as time to incorporate the pigment into an alkyd resin, an approximately 10420 lowering in consistency, which is defined as the torque required to mix an alkyd resin paint system once the pigment is incorporated therein, an approximate 6 unit increase in B235 semi-gloss which is defined as a 60 degree gloss measurement in a latex paint system, a lowering by l5approximately 12 units of B202H haze, which is defined as the relative depth an image can be perceived on a paint surface and an increase of approximately 2 units in B202 gloss, which is defined as a measurement at 20 degrees of reflected light from a paint system made in an acrylic resin.
20 It is noted that the naturally occurring zirconium silicate sand grinding medium, because of its higher density and single phase microstructure, can produce a pigment powder having superior properties to those obtained using the synthetic zirconium silicate ceramic beads as described above.
~~~8969 PATENT
Example 2 Example 2 is provided to compare the performance of synthetic zirconium silicate ceramic beads with the performance of the naturally occurring zirconium silicate sand 5grinding medium of the invention. It is noted that the naturally occurring zirconium silicate sand has a higher density than the 3.8g/cc density of synthetic zirconium silicate products which allows use of smaller naturally occurring zirconium silicate sand particles by comparison with the synthetic zirconium silicate product particle sizes, thereby providing greater grinding efficiency.
Plant trials using the naturally occurring zirconium silicate sand grinding medium having a particle size in the range of from about 180-210microns in a cage mill showed that l5naturally occurring zirconium silicate sand can be used successfully at production flowrates to effect removal of coarse particles, having a particle size greater than 0.5micron in a titanium dioxide pigment. No appreciable loss of media from the mill was observed.
Example 2 was conducted by changing flowrates in mill B, operating with conventional silica sand, and of mill C, operating with naturally occurring zirconium silicate sand.
Sand loadings in mill B and mill C were similar to those used in Example 1, i.e., 1200 pounds of silica sand in mill B and 253000 pounds of naturally occurring zirconium silicate sand in mill C. Samples were obtained concurrently from both sand mills. Mill feed was also sampled to measure any particle size variability in feed particle size.
Particle size data, as provided in Table 2, shows that at 30either a low flowrate (approximately 13 gallons/minute) or at a high flowrate (approximately 35 gallons/minute) the naturally occurring zirconium silicate sand is much more _ 215 8 9 6 9 PATENT
efficient in reducing particle size, compared with the performance of the conventional silica sand.
After a period of continuous operation, both mill overflows were sampled for pigment optical quality and Scontamination.
Contamination of the pigment product from the naturally occurring zirconium silicate sand grinding medium was minimal as measured by x-ray fluorescence examination of the pigment solids found in the mill overflow. Metal contaminant levels l0also measured by x-ray fluorescence were similar to those observed in pigments milled using a conventional silica sand grinding medium. The optical quality of the pigment milled with the naturally occurring zirconium silicate sand as measured by the B381 dry color and brightness test which is l5defined as the total light reflected from a powder compact surface and the spectrum of reflected light i.e. color, was comparable to that obtained for samples milled using conventional silica sand. Results of these tests are summarized in Table 3.
PATENT
Table 2 Pigment Particle Size Data Parameter M~1 B Mill C
Flowrate 13.2 13.2 ~g~~) Median Particle Diameter0.37 0.24 Fraction ofParticles<86.94 99.55 O. Smicron Flowrate 35.2 35.2 ~g~~) Median Particle Diameter0.38 0.37 Fraction of Particles75.64 87.55 <
O. Smicron Table 3 Pigment Chemical Composition and Optical Properties Property Mill B
0.71 0.72 %ZrOZ O.O 1 O.O 1 Calgon 0.06 0.06 Fe ppm 35 34 Ni ppm 10 8 B381 Brightness 97.87 97.94 B381 Color 1.14 1.09 After nineteen days of operation with the naturally occurring zirconium silicate sand, mill C was inspected for signs of wear on the rubber lining using a fiber optic probe inserted through a flange in the underside of the mill.
lOEssentially no signs of wear on the rubber lining were observed as indicated by the condition of the weavelike pattern on the rubber mill lining which is normally present on the surface of freshly lined mills. By contrast, in a mill which had been operated for only one week using a conventional silica sand grinding medium, the mill lining showed considerable wear, especially to the leading edges of the mill rotor bars where the weavelike,pattern had been almost 5completely worn away.
Example 3 The following example is provided to show the differences in particle size, impurity content and grinding performance among naturally occurring zirconium silicate sands obtained lOfrom different natural sources.
Three naturally occurring zirconium silicate sand samples, hereinafter referred to as Sample 1, Sample 2 and Sample 3 were evaluated for particle size using a screen analysis conducted for thirty minutes on a Rotapz'''. Based on l5the data presented in Table 4, Sample 2 and Sample 3 are similar with respect to particle size, while Sample 1 is smaller, which can make it difficult to retain Sample 1 sand in a cage mill during a continuous process.
Table 4 20 Particle Sizes of Zirconium Silicate Sand Samples Sample Origin Sample 1 Sample 2 Sample 3 180 microns 0.61 75.1 67.2 150microns 5.73 16 32.1 less than 93.66 8.9 ~ 0.7 150microns The three naturally occurring zirconium silicate sand samples were also subjected to elemental analysis using x-ray fluorescence techniques. The results of the elemental 25analysis are given in Table 5.
2 I 5 8 9 6 ~ PATENT
Table 5 Elemental Chemical Analysis of Zirconium Silicate Sands Sample Origin Sample 1 Sample 2 Sample 3 Element %Na 0.38 0.41 0.2 0.16 0.16 0.73 %Si 15.15 15.43 14.5 %C1 0.2 0.24 0.1 %Ti 0.13 0.13 0.21 %Y 0.2 0.19 0.19 48.16 47.69 48.88 %~ 0.92 0.99 0.93 %O 34.49 35 34.07 Trace Analysis p (ppm) 659 ___ ___ IC (ppm) ___ ___ 134 Ca (ppm) 327 614 689 Cr (ppm) ___ 177 ___ ~ ~ppm) ___ 201 ___ Fe (ppm) 729 714 711 Sr (ppm) 81 ___ ___ Pb (ppm) 50 ___ ___ Th (ppm) 90 200 180 U (ppm) 180 200 220 A laboratory scale grinding study was also performed with Sthe three naturally occurring zirconium silicate sands. The study was conducted in a cage mill under a standard laboratory sand load of 1.8:1 zirconium sand to pigment load. Table 6 shows the percent of particles passing 0.5micron, i.e., particles having sizes smaller than 0.5micron, after 2, 4 and 108 minutes of grinding, as well as the median particle diameter at these times. The pigment was an untreated interior enamel grade titanium dioxide pigment. Particle sizes were .. _ ' ~ CA 02158969 1999-OS-25 determined using a Microtrac"' particle size analyzer as has been described before.
Table 6 Pigment Grinding Performance Sample Sample Sample Sample Origin 1 2 3 Particle Particle Particle Size Size Size Time Median %Passing Median %Passing M~ %Passing Diameter O.SmicronDiameterO.Smicron Diameter O.Smicron Feed (0 1 21.09 1 21.09 1 21.09 minutes) 2 minutes0.45 61.93 0.48 53.45 0.48 53.66 4 minutes0.38 80.96 0.42 69.84 0.42 71.53 8 minutes0.33 94.02 0.35 87.97 0.36 88.66
An object of this invention is to provide a naturally occurring zirconium silicate sand grinding medium.
Another object of this invention is to provide a method for milling a powder using a naturally occurring zirconium Ssilicate sand grinding medium.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon reading the description of preferred embodiments which follows.
Description of Preferred Bmbodimeats As used herein in the specification and in the claims which follow, the term "naturally occurring" indicates that the zirconium silicate sand is mined in the form of zirconium silicate sand of a particular particle size and is l5distinguished from zirconium silicate materials which are synthesized, manufactured or otherwise artificially produced by man. The zirconium silicate sand grinding medium of the invention occurs in nature in the appropriate size and shape which can be sorted to obtain the appropriate fraction for use 20in a particular grinding operation. The mined zirconium silicate sand is sorted to isolate the appropriate fraction of zirconium silicate sand, based on particle size considerations, to be used as a grinding medium. The term "grinding medium" as used herein in the specification and in 25the claims which follow refers to a material which is placed in a milling device, such as a disc mill, cage mill or attrition mill, along with the powder to be ground more finely or de-agglomerated to transmit shearing action of the milling device to the powder being processed to break apart particles 30 of the powder .
a The invention provides a grinding medium including naturally occurring zirconium silicate sand characterized by a density in the range of from about 4g/cc to about 6g/cc, more preferably in the range of from about 4.6g/cc to about 4.9g/cc Sand most preferably in the range of from about 4.75g/cc to about 4.85g/cc.
The naturally occurring zirconium silicate sand tends to be single phase, while synthetic zirconium silicate ceramic beads are typically multiphase materials. Surface lOcontaminants such as aluminum, iron, uranium, thorium and other heavy metals as well as TiOz can be present on the surfaces of the naturally occurring zirconium silicate sand particles. Once the surface contaminants are removed by any surface preconditioning process known to one skilled in the l5art, such as, for example, washing and classifying, chemical analyses indicate that any remaining contaminants are within the crystal structure of the zirconium silicate and do not adversely affect the powder being milled.
Since the density of the naturally occurring zirconium 20silicate sand as described above exceeds the 3.8g/cc density typically characteristic of manufactured zirconium silicate beads, naturally occurring zirconium silicate sand grinding medium of a smaller particle size than that of manufactured zirconium silicate beads can be used, without the zirconium 25silicate sand floating out of the milling slurry, thus ceasing to be effective as a grinding medium.
The zirconium silicate sand grinding medium can be characterized by a particle size which is the smallest multiple of the particle size of the finished product particle 30size, the milled product powder particle size, which can be effectively separated from the milled product powder.
Typically, the naturally occurring zirconium silicate sand _ 215 8 9 6 9 PATENT
particle size is greater than 100microns and can be in the range of from about 100microns to about 1500microns, more preferably in the range of from about 100microns to about 500microns and most preferably in the range of from about 5150microns to about 250microns. The mined, naturally occurring zirconium silicate sand can be screened using techniques well known to one skilled in the art to isolate a coarse fraction of sand having particles of an appropriate size to function as an effective grinding medium.
The grinding medium can be any liquid medium compatible with the product being milled and the milling process and can include water, oil, any other organic compound or a mixture thereof, and can be combined with the naturally occurring zirconium silicate sand to form a slurry. The liquid medium l5is selected depending upon the product being milled. The milled product powder may or may not be separated from the liquid medium after the milling process is complete; however, the grinding medium is usually separated from the liquid medium after the milling process is complete.
If the powder being milled is a pigment for use in an oil based paint or ink, the liquid medium can be an oil such as a naturally derived oil like tung oil, linseed oil, soybean oil or tall oil or mixtures thereof. These naturally occurring oils can be mixed with solvents such as mineral spirits, 25naphtha or toluol or mixtures thereof which can further include substances such as gums, resins, dispersants and/or drying agents. The liquid medium can also include other materials used in the manufacture of oil based paints and inks such as alkyd resins, epoxy resins, nitrocellulose, melamines, 30urethanes and silicones.
If the powder being milled is a pigment for use in a water based paint, such as a latex paint, the liquid medium 215 8 9 s 9 PATENT
can be water, optionally including antifoaming agents and/or dispersants. Also, if the powder is a ceramic or magnetic powder, the medium can be water and can also include dispersants.
The naturally occurring zirconium silicate sand and the liquid medium can be combined to form a grinding slurry which is further characterized by a grinding slurry viscosity which can be in the range of from about l.Ocps to about 10,000cps, more preferably in the range of from about l.Ocps to about 10500cps and most preferably in the range of from about l.Ocps to about 100cps. In general, the grinding slurry viscosity is determined by the concentration of solids in the grinding slurry and, thus, the higher the concentration of solids in the grinding slurry, the higher will be the grinding slurry l5viscosity and density. There is no absolute upper limit to grinding slurry viscosity; however, at some viscosity, a point is reached where no grinding medium is needed, as is the case for plastics compounded in extruders, roll mills, etc. without a grinding medium.
20 The invention also provides a method for milling a powder including steps of providing a starting powder characterized by a starting powder particle size; providing a grinding medium including naturally occurring zirconium silicate sand characterized by a grinding medium density in the range of 25from about 4.Og/cc absolute to about 6.0 g/cc absolute;
providing a liquid medium; mixing the starting powder with the liquid medium to form a milling slurry; milling the milling slurry for a sufficient time to produce a product slurry including a product powder characterized by a desired product 30powder particle size and having substantially the same composition as the starting powder; and separating the product slurry including the product powder from the milling slurry.
f ~ ~ CA 02158969 1999-OS-25 The starting powder used in the method of the invention can be an agglomerated and/or aggregated powder. The agglomerated powder can be characterized by an agglomerated powder particle size less than about 500microns and more Spreferably can be in the range of from about O.Oimicron to about 200microns. For titanium dioxide pigment powders, the agglomerated powder has a particle size of in the range of from about 0.05micron to about 100microns which can be milled to approach the particle size of an individual titanium lOdioxide crystallite.
The starting powder can also be characterized by a starting powder density in the range of from about 0.8g/cc absolute to about 5.Og/cc absolute. The method of the invention is suitable for organic powders which typically have l5densities on the lower end of the above range as well as for inorganic powders such as titanium dioxide, calcium carbonate, bentonite or kaolin or mixtures thereof. The titanium dioxide starting powder can be an agglomerated titanium dioxide pigment which has a density in the range of from about 3.7g/cc 20to about 4.2g/cc.
The naturally occurring zirconium silicate sand used in the method of the invention can also be characterized by a zirconium silicate sand particle size greater than about 100microns and can be in the range of from about 100microns to 25about 1500microns, more preferably in the range of from about 100microns to about 500microns and most preferably in the range of from about 150microns to about 250microns.
The liquid medium used in the method of the invention can be oil or water selected according to the criteria already 30 described.
Milling the milling slurry can be carried out in any suitable milling device which employs a grinding medium, such as, but ' CA 02158969 1999-OS-25 not limited to, a bead mill, cage mill, disc mill or pin mill designed to support a vertical flow or horizontal flow. The milling process can be a batch or continuous process.
The process of separating the product slurry from the milling slurry can be accomplished by distinguishing the product slurry, which contains the product powder along with liquid medium from the milling slurry on the basis of a difference between starting powder and grinding medium physical properties and product powder particle physical lOproperties such as particle size, particle density and particle settling rate. As already described, the product powder may or may not be separated from the liquid medium after the milling process is complete;.however, the grinding medium is usually separated from the liquid medium after the l5milling process is complete. The product powder can be separated from the product slurry and subjected to further processing such as dispersing the powder in a dispersing medium to form a dispersion. Depending upon whether the dispersion is an oil based paint or ink or a water based paint 20or ink or a ceramic or magnetic powder dispersion, the dispersing medium can be selected according to the same criteria as already described for the selection of the liquid medium. If the product powder is to be used in the product slurry, no further dispersing steps are needed.
25 In order to further illustrate the present invention, the following examples are provided. The particular compounds, processes and conditions utilized in the examples are meant to be illustrative of the present invention and are not limited thereto.
PATENT
Example 1 The following example is provided to compare the performance as a grinding medium of conventional, commercially available synthetic zirconium silicate ceramic beads with the Sperformance of standard 10-40 mesh (U.S.)silica sand.
Sand mills having nominal grinding chamber capacities of 275 gallons and overall capacities of 500 gallons were loaded separately with 3000 pounds of synthetic zirconium silicate ceramic beads of nominal 300micron and 210micron size and with 101200 pounds of standard 10-40 mesh (U.S.) silica sand, the highest mill loading feasible with silica sand. The mills loaded with 3000 pounds of synthetic zirconium silicate ceramic beads as well as the mill loaded with 1200 pounds of 10-40 mesh (U.S.) silica sand were operated at 16, 23 and 30 l5gallon per minute flow rates. The feed slurries fed through all mills had a density of 1.35g/cc and contained titanium dioxide, approximately 40% of which was less than 0.5micron in size in water. The size of the titanium dioxide particles in the product slurry was measured using a Leeds and Northrupp 209200 series Microtracl''' particle size analyzer in water with 0.2% sodium hexametaphosphate surfactant at ambient temperature. The results are summarized in Table 1 and indicate that the grinding efficiency of the synthetic zirconium silicate ceramic beads as indicated by the 25percentage of product powder less than or equal to 0.5micron in size compares favorably with the grinding efficiency of 10-40 mesh (U. S.) silica sand.
Table 1 Nhll Flow Rate(gal/min)Grinding Medium %Product<_0.5micron A 30 300micron synthetic66.57 zirconium silicate ceramic beads 30 300micron synthetic64.42 zirconium silicate ceramic beads A 23 300micron synthetic zirconium silicate ceramic beads 23 300micron synthetic70.41 zirconium silicate ceramic beads A 16 300micron synthetic79.96 zirconium silicate ceramic beads g 16 300micron synthetic71.26 zirconium silicate ceramic beads A 30 210micron synthetic85.29 zirconium silicate ceramic beads 30 210micron synthetic74.72 zirconium silicate ceramic beads A 23 210micron synthetic91.51 zirconium silicate ceramic beads g 23 210micron synthetic83.11 zirconium silicate ceramic beads A 16 210micron synthetic95.22 zirconium silicate ceramic beads 16 210micron synthetic95.22 zirconium silicate ceramic beads A 30 10-40 mesh (U.S.)65.17 silica sand g 30 10-40 mesh (U.S.)~ 54.28 silica sand Mill Flow Rate(gal/min)Grinding Medium %Product_<O.Smicron 23 10-40 mesh (U. 61.96 S. ) silica sand g 23 10-40 mesh (U. 57.76 S. ) silica sand 16 10-40 mesh (U. 67.09 S. ) silica sand g 16 10-40 mesh (U. 59.48 S. ) silica sand Furthermore, when the properties of finished pigments processed with the 210micron synthetic zirconium silicate ceramic beads were compared with those of pigments processed Swith silica sand, several improvements with respect to the properties of finished pigments processed with silica sand were observed. The improvements included an approximately 57%
reduction in break time, which is defined as time to incorporate the pigment into an alkyd resin, an approximately 10420 lowering in consistency, which is defined as the torque required to mix an alkyd resin paint system once the pigment is incorporated therein, an approximate 6 unit increase in B235 semi-gloss which is defined as a 60 degree gloss measurement in a latex paint system, a lowering by l5approximately 12 units of B202H haze, which is defined as the relative depth an image can be perceived on a paint surface and an increase of approximately 2 units in B202 gloss, which is defined as a measurement at 20 degrees of reflected light from a paint system made in an acrylic resin.
20 It is noted that the naturally occurring zirconium silicate sand grinding medium, because of its higher density and single phase microstructure, can produce a pigment powder having superior properties to those obtained using the synthetic zirconium silicate ceramic beads as described above.
~~~8969 PATENT
Example 2 Example 2 is provided to compare the performance of synthetic zirconium silicate ceramic beads with the performance of the naturally occurring zirconium silicate sand 5grinding medium of the invention. It is noted that the naturally occurring zirconium silicate sand has a higher density than the 3.8g/cc density of synthetic zirconium silicate products which allows use of smaller naturally occurring zirconium silicate sand particles by comparison with the synthetic zirconium silicate product particle sizes, thereby providing greater grinding efficiency.
Plant trials using the naturally occurring zirconium silicate sand grinding medium having a particle size in the range of from about 180-210microns in a cage mill showed that l5naturally occurring zirconium silicate sand can be used successfully at production flowrates to effect removal of coarse particles, having a particle size greater than 0.5micron in a titanium dioxide pigment. No appreciable loss of media from the mill was observed.
Example 2 was conducted by changing flowrates in mill B, operating with conventional silica sand, and of mill C, operating with naturally occurring zirconium silicate sand.
Sand loadings in mill B and mill C were similar to those used in Example 1, i.e., 1200 pounds of silica sand in mill B and 253000 pounds of naturally occurring zirconium silicate sand in mill C. Samples were obtained concurrently from both sand mills. Mill feed was also sampled to measure any particle size variability in feed particle size.
Particle size data, as provided in Table 2, shows that at 30either a low flowrate (approximately 13 gallons/minute) or at a high flowrate (approximately 35 gallons/minute) the naturally occurring zirconium silicate sand is much more _ 215 8 9 6 9 PATENT
efficient in reducing particle size, compared with the performance of the conventional silica sand.
After a period of continuous operation, both mill overflows were sampled for pigment optical quality and Scontamination.
Contamination of the pigment product from the naturally occurring zirconium silicate sand grinding medium was minimal as measured by x-ray fluorescence examination of the pigment solids found in the mill overflow. Metal contaminant levels l0also measured by x-ray fluorescence were similar to those observed in pigments milled using a conventional silica sand grinding medium. The optical quality of the pigment milled with the naturally occurring zirconium silicate sand as measured by the B381 dry color and brightness test which is l5defined as the total light reflected from a powder compact surface and the spectrum of reflected light i.e. color, was comparable to that obtained for samples milled using conventional silica sand. Results of these tests are summarized in Table 3.
PATENT
Table 2 Pigment Particle Size Data Parameter M~1 B Mill C
Flowrate 13.2 13.2 ~g~~) Median Particle Diameter0.37 0.24 Fraction ofParticles<86.94 99.55 O. Smicron Flowrate 35.2 35.2 ~g~~) Median Particle Diameter0.38 0.37 Fraction of Particles75.64 87.55 <
O. Smicron Table 3 Pigment Chemical Composition and Optical Properties Property Mill B
0.71 0.72 %ZrOZ O.O 1 O.O 1 Calgon 0.06 0.06 Fe ppm 35 34 Ni ppm 10 8 B381 Brightness 97.87 97.94 B381 Color 1.14 1.09 After nineteen days of operation with the naturally occurring zirconium silicate sand, mill C was inspected for signs of wear on the rubber lining using a fiber optic probe inserted through a flange in the underside of the mill.
lOEssentially no signs of wear on the rubber lining were observed as indicated by the condition of the weavelike pattern on the rubber mill lining which is normally present on the surface of freshly lined mills. By contrast, in a mill which had been operated for only one week using a conventional silica sand grinding medium, the mill lining showed considerable wear, especially to the leading edges of the mill rotor bars where the weavelike,pattern had been almost 5completely worn away.
Example 3 The following example is provided to show the differences in particle size, impurity content and grinding performance among naturally occurring zirconium silicate sands obtained lOfrom different natural sources.
Three naturally occurring zirconium silicate sand samples, hereinafter referred to as Sample 1, Sample 2 and Sample 3 were evaluated for particle size using a screen analysis conducted for thirty minutes on a Rotapz'''. Based on l5the data presented in Table 4, Sample 2 and Sample 3 are similar with respect to particle size, while Sample 1 is smaller, which can make it difficult to retain Sample 1 sand in a cage mill during a continuous process.
Table 4 20 Particle Sizes of Zirconium Silicate Sand Samples Sample Origin Sample 1 Sample 2 Sample 3 180 microns 0.61 75.1 67.2 150microns 5.73 16 32.1 less than 93.66 8.9 ~ 0.7 150microns The three naturally occurring zirconium silicate sand samples were also subjected to elemental analysis using x-ray fluorescence techniques. The results of the elemental 25analysis are given in Table 5.
2 I 5 8 9 6 ~ PATENT
Table 5 Elemental Chemical Analysis of Zirconium Silicate Sands Sample Origin Sample 1 Sample 2 Sample 3 Element %Na 0.38 0.41 0.2 0.16 0.16 0.73 %Si 15.15 15.43 14.5 %C1 0.2 0.24 0.1 %Ti 0.13 0.13 0.21 %Y 0.2 0.19 0.19 48.16 47.69 48.88 %~ 0.92 0.99 0.93 %O 34.49 35 34.07 Trace Analysis p (ppm) 659 ___ ___ IC (ppm) ___ ___ 134 Ca (ppm) 327 614 689 Cr (ppm) ___ 177 ___ ~ ~ppm) ___ 201 ___ Fe (ppm) 729 714 711 Sr (ppm) 81 ___ ___ Pb (ppm) 50 ___ ___ Th (ppm) 90 200 180 U (ppm) 180 200 220 A laboratory scale grinding study was also performed with Sthe three naturally occurring zirconium silicate sands. The study was conducted in a cage mill under a standard laboratory sand load of 1.8:1 zirconium sand to pigment load. Table 6 shows the percent of particles passing 0.5micron, i.e., particles having sizes smaller than 0.5micron, after 2, 4 and 108 minutes of grinding, as well as the median particle diameter at these times. The pigment was an untreated interior enamel grade titanium dioxide pigment. Particle sizes were .. _ ' ~ CA 02158969 1999-OS-25 determined using a Microtrac"' particle size analyzer as has been described before.
Table 6 Pigment Grinding Performance Sample Sample Sample Sample Origin 1 2 3 Particle Particle Particle Size Size Size Time Median %Passing Median %Passing M~ %Passing Diameter O.SmicronDiameterO.Smicron Diameter O.Smicron Feed (0 1 21.09 1 21.09 1 21.09 minutes) 2 minutes0.45 61.93 0.48 53.45 0.48 53.66 4 minutes0.38 80.96 0.42 69.84 0.42 71.53 8 minutes0.33 94.02 0.35 87.97 0.36 88.66
Claims (39)
1. A grinding medium comprising:
1) naturally occurring zirconium silicate sand having a density of from about 4g/cc absolute to about 6g/cc absolute and a particle size greater than about 100 microns; and 2) a liquid medium selected from the group consisting of water, oil, organic compounds, and mixtures thereof.
1) naturally occurring zirconium silicate sand having a density of from about 4g/cc absolute to about 6g/cc absolute and a particle size greater than about 100 microns; and 2) a liquid medium selected from the group consisting of water, oil, organic compounds, and mixtures thereof.
2. The grinding medium of claim 1 wherein said zirconium silicate sand particle size is from about 100 microns to about 1500 microns.
3. The grinding medium of claim 1 wherein said naturally occurring zirconium silicate sand and said liquid medium are combined so that they form a grinding slurry.
4. The grinding medium of claim 3 wherein said grinding slurry has a grinding slurry viscosity of from about 1.0 cps to about 10,000 cps.
5. A method for milling a powder comprising the steps of:
1) providing a starting powder characterized by a starting powder particle size;
2) providing a grinding medium comprising naturally occurring zirconium silicate sand characterized by a grinding medium density in the range of from about 4.0g/cc absolute to about 6.0g/cc absolute and a particle size in the range of from about 100 microns to about 500 microns;
3) providing a liquid medium;
4) mixing said starting powder, said grinding medium and said liquid medium to form a milling slurry;
5) milling said milling slurry in a high energy mill for a time sufficient to produce a product slurry including a product powder characterized by a desired product powder particle size and having substantially the same composition as said starting powder; and 6) separating said product slurry including said product powder from said milling slurry so that said grinding medium remains in said milling slurry.
1) providing a starting powder characterized by a starting powder particle size;
2) providing a grinding medium comprising naturally occurring zirconium silicate sand characterized by a grinding medium density in the range of from about 4.0g/cc absolute to about 6.0g/cc absolute and a particle size in the range of from about 100 microns to about 500 microns;
3) providing a liquid medium;
4) mixing said starting powder, said grinding medium and said liquid medium to form a milling slurry;
5) milling said milling slurry in a high energy mill for a time sufficient to produce a product slurry including a product powder characterized by a desired product powder particle size and having substantially the same composition as said starting powder; and 6) separating said product slurry including said product powder from said milling slurry so that said grinding medium remains in said milling slurry.
6. The method of claim 5 wherein the high energy mill has a nominal shear rate of from about 6000 to about 14000 reciprocal minutes and an agitator peripheral speed of from about 1000 to about 2500 feet per minute.
7. The method of claim 6 wherein the high energy mill is selected from the group consisting of disc mills and cage mills.
8. The method of claim 5 wherein said starting powder is an agglomerated powder.
9. The method of claim 8 wherein said agglomerated powder is further characterized by an agglomerated powder particle size and said agglomerated powder particle size is in the range of from about 0.01 micron to about 500 microns.
10. The method of claim 9 wherein the agglomerated powder has a particle size in the range of from about 0.01 micron to about 200 microns.
11. The method of claim 5 wherein said starting powder is an aggregated powder.
12. The method of claim 5 wherein said starting powder and said product powder are further characterized by a powder density in the range of from about 0.8g/cc absolute to about 5g/cc absolute.
13. The method of claim 5 wherein said starting powder is an organic powder.
14. The method of claim 5 wherein said starting powder is an inorganic powder.
15. The method of claim 5 wherein said starting powder is an agglomerated titanium dioxide pigment.
16. The method of claim 5 wherein the zirconium silicate sand particle size is in the range of from about 150 microns to about 250 microns.
17. The method of claim 5 wherein said liquid medium is a liquid medium compatible with said grinding medium and with said starting powder.
18. The method of claim 6 wherein said milling device has a vertical flow design.
19. The method of claim 6 wherein said milling device has a horizontal flow design.
20. The method of claim 5 wherein said step (6) of separating said product slurry from said milling slurry is accomplished by distinguishing said product slurry from said milling slurry on the basis of a difference between starting powder, grinding medium and product powder physical properties wherein the physical properties are selected from the group consisting of particle size, particle density and particle settling rate.
21. The method of claim 5 wherein said steps are performed continuously.
22. The method of claim 5 wherein said steps are performed according to a batch process.
23. The method of claim 5 further comprising steps of separating said product powder from said product slurry and dispersing said product powder in a dispersing medium to form a dispersion.
24. The method of claim 23 wherein said dispersing medium is a liquid medium compatible with said product powder.
25. The method of claim 5 wherein said zirconium silicate sand particle size is the smallest multiple of a milled product powder particle size which can be separated from a milled product powder.
26. The method of claim 5 wherein said liquid medium is a liquid medium selected from the group consisting of water, oil, organic compounds and mixtures thereof.
27. The method of claim 5 wherein said naturally occurring zirconium silicate sand and said liquid medium are combined so that they form a grinding slurry.
28. The method of claim 27 wherein said grinding slurry is further characterized by a grinding slurry viscosity and said grinding slurry viscosity is in the range of from about 1.0 cps to about 10,000 cps.
29. The method of claim 5 wherein the grinding medium has a density in the range of from about 4.6g/cc absolute to about 4.9g/cc absolute.
30. The method of claim 29 wherein the grinding medium has a density in the range of from about 4.75g/cc absolute to about 4.85g/cc absolute.
31. The method of claim 5 wherein said zirconium silicate sand particle size is in the range of from about 150 microns to about 250 microns.
32. The method of claim 28 wherein said grinding slurry is further characterized by a grinding slurry viscosity in the range of from about 1.0 cps to about 500 cps.
33. The method of claim 32 wherein said grinding slurry is further characterized by a grinding slurry viscosity in the range of from about 1.0 cps to about 100 cps.
34. The grinding medium of claim 1 wherein said sand has a density of from about 4.6g/cc absolute to about 4.9g/cc absolute.
35. The grinding medium of claim 1 wherein said sand has a density of from about 4.75g/cc absolute to about 4.85g/cc absolute.
36. The grinding medium of claim 2 wherein said zirconium silicate sand particle size is from about 100 microns to about 500 microns.
37. The grinding medium of claim 2 wherein said zirconium silicate sand particle size is from about 150 microns to about 250 microns.
38. The grinding medium of claim 4 wherein said grinding slurry has a grinding slurry viscosity of from about 1.0 cps to about 500 cps.
39. The grinding medium of claim 4 wherein said grinding slurry has a grinding slurry viscosity of from about 1.0 cps to about 100 cps.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US18608594A | 1994-01-25 | 1994-01-25 | |
| US08/186,085 | 1994-01-25 | ||
| PCT/US1995/000963 WO1995019846A1 (en) | 1994-01-25 | 1995-01-24 | Zirconium silicate grinding medium and method of milling |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2158969A1 CA2158969A1 (en) | 1995-07-27 |
| CA2158969C true CA2158969C (en) | 2000-06-27 |
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| Application Number | Title | Priority Date | Filing Date |
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| CA002158969A Expired - Fee Related CA2158969C (en) | 1994-01-25 | 1995-01-24 | Zirconium silicate grinding medium and method of milling |
Country Status (18)
| Country | Link |
|---|---|
| EP (2) | EP0930098B1 (en) |
| JP (1) | JP2693039B2 (en) |
| KR (1) | KR0164652B1 (en) |
| CN (1) | CN1042104C (en) |
| AT (2) | ATE191160T1 (en) |
| AU (1) | AU671248B2 (en) |
| BR (1) | BR9506238A (en) |
| CA (1) | CA2158969C (en) |
| CZ (1) | CZ284563B6 (en) |
| DE (2) | DE69530132T2 (en) |
| ES (2) | ES2143616T3 (en) |
| FI (1) | FI954466A (en) |
| MX (1) | MX9504066A (en) |
| PL (1) | PL176837B1 (en) |
| SK (1) | SK117895A3 (en) |
| TW (1) | TW276208B (en) |
| WO (1) | WO1995019846A1 (en) |
| ZA (1) | ZA95590B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| GB2315505B (en) * | 1996-07-24 | 1998-07-22 | Sofitech Nv | An additive for increasing the density of a fluid and fluid comprising such additve |
| DE102004040368B3 (en) * | 2004-08-20 | 2006-02-23 | Juhnke, Michael, Dipl.-Ing. | Grinding body for producing very finely ground product has surface consisting of material which is rigid at grinding temperature but not at room temperature |
| US20080022900A1 (en) * | 2006-07-25 | 2008-01-31 | Venkata Rama Rao Goparaju | Process for manufacturing titanium dioxide pigment |
| CN101722085B (en) * | 2008-10-15 | 2012-06-13 | 许兴康 | Grinding technology of high purity sub-nano level superfine zirconium silicate powder |
| CN102795848B (en) * | 2012-08-02 | 2013-10-23 | 江苏锡阳研磨科技有限公司 | Low-temperature sintered zirconium silicate grinding ball and preparation method thereof |
| CN111180719A (en) * | 2020-01-07 | 2020-05-19 | 马鞍山科达普锐能源科技有限公司 | Method for preparing nano silicon by three-stage grinding |
| CN115043620B (en) * | 2022-03-09 | 2023-03-10 | 湖北工业大学 | Method for preparing early-strength precast concrete by taking sand as grinding medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| GB679552A (en) * | 1949-08-29 | 1952-09-17 | British Titan Products | Improvements relating to methods and apparatus for grinding, crushing and disintegrating |
| US3337140A (en) * | 1964-06-03 | 1967-08-22 | Pittsburgh Plate Glass Co | Dispersion process |
| DE2832761B1 (en) * | 1978-07-26 | 1979-10-31 | Basf Ag | Process for converting crude and / or coarsely crystallized perylene tetracarboxylic diimides into a pigment form |
| JPS5815079A (en) * | 1981-07-14 | 1983-01-28 | 日本化学陶業株式会社 | Crusher member comprising zirconia sintered body |
| US4547534A (en) * | 1983-03-18 | 1985-10-15 | Memorex Corporation | Method to disperse fine solids without size reduction |
| JPS60211637A (en) * | 1984-04-05 | 1985-10-24 | Hitachi Maxell Ltd | Production of magnetic recording medium |
| JPH04166246A (en) * | 1990-10-31 | 1992-06-12 | Matsushita Electric Ind Co Ltd | Medium agitating mill and grinding method |
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1995
- 1995-01-24 AT AT95908662T patent/ATE191160T1/en not_active IP Right Cessation
- 1995-01-24 ES ES95908662T patent/ES2143616T3/en not_active Expired - Lifetime
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- 1995-01-24 CZ CZ952357A patent/CZ284563B6/en not_active IP Right Cessation
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- 1995-01-24 SK SK1178-95A patent/SK117895A3/en unknown
- 1995-01-24 EP EP95908662A patent/EP0690749B1/en not_active Expired - Lifetime
- 1995-01-25 ZA ZA95590A patent/ZA95590B/en unknown
- 1995-03-01 TW TW084101912A patent/TW276208B/zh active
- 1995-09-21 FI FI954466A patent/FI954466A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0690749A4 (en) | 1996-10-30 |
| DE69515935D1 (en) | 2000-05-04 |
| CN1042104C (en) | 1999-02-17 |
| AU1690095A (en) | 1995-08-08 |
| CN1122112A (en) | 1996-05-08 |
| EP0930098B1 (en) | 2003-03-26 |
| ES2190624T3 (en) | 2003-08-01 |
| DE69515935T2 (en) | 2000-08-17 |
| SK117895A3 (en) | 1996-01-10 |
| PL310446A1 (en) | 1995-12-11 |
| ES2143616T3 (en) | 2000-05-16 |
| JP2693039B2 (en) | 1997-12-17 |
| PL176837B1 (en) | 1999-08-31 |
| EP0690749A1 (en) | 1996-01-10 |
| EP0690749B1 (en) | 2000-03-29 |
| TW276208B (en) | 1996-05-21 |
| WO1995019846A1 (en) | 1995-07-27 |
| ATE191160T1 (en) | 2000-04-15 |
| EP0930098A1 (en) | 1999-07-21 |
| AU671248B2 (en) | 1996-08-15 |
| CZ284563B6 (en) | 1999-01-13 |
| MX9504066A (en) | 1997-05-31 |
| KR0164652B1 (en) | 1998-12-15 |
| ZA95590B (en) | 1996-07-25 |
| BR9506238A (en) | 1997-09-30 |
| FI954466A0 (en) | 1995-09-21 |
| DE69530132T2 (en) | 2004-01-08 |
| JPH08506527A (en) | 1996-07-16 |
| CZ235795A3 (en) | 1996-02-14 |
| CA2158969A1 (en) | 1995-07-27 |
| KR960700819A (en) | 1996-02-24 |
| DE69530132D1 (en) | 2003-04-30 |
| FI954466A (en) | 1995-09-21 |
| ATE235318T1 (en) | 2003-04-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |