WO1999029623A1 - Silices amorphes precipitees a proprietes physiques ameliorees - Google Patents

Silices amorphes precipitees a proprietes physiques ameliorees Download PDF

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Publication number
WO1999029623A1
WO1999029623A1 PCT/US1998/025012 US9825012W WO9929623A1 WO 1999029623 A1 WO1999029623 A1 WO 1999029623A1 US 9825012 W US9825012 W US 9825012W WO 9929623 A1 WO9929623 A1 WO 9929623A1
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Prior art keywords
silica
precipitated amorphous
acid
product
slurry
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PCT/US1998/025012
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English (en)
Inventor
Barry W. Preston
William C. Fultz
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J.M. Huber Corporation
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Application filed by J.M. Huber Corporation filed Critical J.M. Huber Corporation
Priority to AU16008/99A priority Critical patent/AU1600899A/en
Publication of WO1999029623A1 publication Critical patent/WO1999029623A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
    • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates

Definitions

  • the present invention relates to precipitated amorphous silica products and, more particularly, precipitated amorphous silicas having high liquid absorption and high liquid carrying capacities, as well as a method of production thereof.
  • silicas can be broadly divided into two basic categories of manufacture. These categories are those provided from a liquid phase and those from a vapor phase process.
  • Vapor process silicas called fumed or pyrogenic silicas, are prepared by reacting silicon tetrachloride vapor with an oxygen-hydrogen gas at high temperatures to produce silica hydrogen and chloride.
  • Pyrogenic silicas have high external surface areas and differ from other silicas (e.g. gels, precipitated silicas, and so forth) prepared by the liquid phase process.
  • Liquid phase silicas include precipitated amorphous silicas produced by acidulating an alkali metal silicate with an acid such as sulfuric acid.
  • Liquid phase silicas include silica gels and colloidal silicas.
  • prior art workers have developed new techniques for producing precipitated amorphous silicas having desirable properties.
  • Silica carriers for oils and other liquids are used to deliver precise dosages of absorbed liquid for inclusion in materials such as livestock feed, rubber and plastics. Silica carriers provide a predictable dosage of liquid under conditions where viscosity variations in an unearned liquid would render dosage control extremely difficult. Further, the particulate form of the silica carrier facilitates transport and storage of the carried liquid.
  • carrier silicas for liquids would possess a combination of desirable characteristics which facilitate handling, loading (liquid onto the carrier) and mixing, including high bulk density low friability, high oil absorption and carrying capacities, and good flow properties.
  • U.S. Pat. No. 5,635,214 discloses a sorbent precipitated silica particulates well-suited for conditioning, sobbing liquid active agents, e.g., vitamins, having a BET surface area of at least 170 m 2 /g, a DOP oil absorption value ranging from 220 to 300 ml/IOOg; a fill density in the packed state of at least 0.29; and a mean particle diameter ranging from 80 to 150 ⁇ m, preferably 90 to 130 ⁇ m; and a maximum grain size distribution index of 0.70.
  • sobbing liquid active agents e.g., vitamins
  • sobbing liquid active agents e.g., vitamins
  • 5,635,214 are stated therein as being made by any known technique, such as by reacting a silicate with an acidifying agent by addition of the acid to a silicate base or by simultaneous total or part addition of the acid and the silicate to a water base.
  • a post-treatment is disclosed that also can be conducted, viz., an introduction of a solution of silicate and/or acid into the reaction medium after initial precipitation.
  • the sieve residue value for the embodiment in the precipitated silica having a BET surface area of 400-600 n ⁇ 7g and DBP number of 310 to 360 is taught to be less than 0.01 wt.% particles sized greater than 63 m ⁇ .
  • U.S. Pat. No 4,590,052 discloses a precipitated silica and a process for making same in which the precipitated silica has a ratio of DBP oil index/CTAB specific surface area meeting one other following criteria: a DBP/CTAB ratio value of between 7 to 4 for a CTAB value between 50-100 m 2 /g; a DBP/CTAB ratio value of between 4 to 2.5 for a CTAB value between 100-200 m 2 /g; a DBP/CTAB ratio value of between 2.5 to 2 for a CTAB value between 200-250 m 2 /g; a DBP/CTAB ratio value of between 2 to 1.5 for a CTAB value between 250-300 m 2 /g; or a DBP/CTAB value of between 1.5 to 1.2 for a CTAB value between 300-350 m 2 /g.
  • the 4,590,052 patent states that it maintains a high value of oil absorption (DBP) in silicas with large CTAB surface areas by using a process in which vessel bottoms containing from 60-100 wt.% silicate at 70-95°C have an acid added until a gel appears at which time the addition of acid is interrupted and the gel is aged for a given period of time, then acid addition is resumed until the gel reaches a pH at most equal to about 9, and then a post treatment is performed which generally involves simultaneously adding more acid and silicate at a pH between about 7-9 and then acid addition alone can be continued to adjust the pH of the slurry to a desired value.
  • DBP oil absorption
  • U.S. Pat. 4,708,859 discloses a process for making precipitated silica with high oil absorption capability and controlled primary structure. The steps include providing a colloid of silica from a reaction medium formed from simultaneous addition of acidifying agent and alkaline silicate solution to a reaction vessel, and, after reacting the acid and alkaline silicate, maintaining a constant volume of the reaction medium by drawing off the reaction medium while adding additional acidifying agent and alkaline silicate solution in a constant volume to provide a silica concentration that avoids agglomeration of colloidal particles.
  • U.S. Pat. 5,403,570 discloses dispersible precipitated silica particulates in which the porosities of the final silica particulates are described as being partly dependent on the conditions governing the concentration of electrolyte and silica in the initial sediment of the precipitation reaction. Low concentration of silica electrolyte in the initial sediment and an appropriate proportion of dry solids in the suspension to be dried are described as significant factors in respect of the actual production of the dispersible precipitated silica particulates well adopted for reinforcing elastomer/rubber matrices.
  • U.S. Pat. 5,123,964 discloses a finely divided precipitated silica useful as a delustering agent having a BET value of 150 to 350 m 2 /g.
  • the finely divided precipitated silica of U.S. Pat. 5,123,964 is produced by shearing the precipitated silica produced in a conventional manner using sodium silicate solution and an acidifying agent, in which the silica suspension produced is optionally diluted and optionally has the coarse portion removed, then the silica is filtered off and the recovered solids are redispersed and surface-coated with an emulsion to exhibit a carbon content of 1-8 wt.%.
  • acid addition to an aqueous alkali metal silicate solution is interrupted and discontinued at the first appearance of the opalescence point (a pH of approximately 10.4), and the reaction mass is then aged for a period of time, and thereafter acid introduction is resumed, and preferably simultaneously together with addition of alkali metal silicate solution at essentially constant pH until the precipitation of silica is completed.
  • the present invention relates to precipitated amorphous silicas endowed with high liquid absorption and high liquid carrying capacity in which the % carrying capacity DBP value thereof is greater than 75.0, the linseed oil absorption ranges from 200 to 325 cc/100g, the CTAB specific surface area ranges from 100 to 300 m 2 /g, and the BET specific surface area ranges from 100 to 350 m 2 /g.
  • the inventive precipitated amorphous silica has a % carrying capacity DBP value of greater than 75.5, a linseed oil absorption of about 225 to about 300 cc/100g, a CTAB specific surface area ranging from about 120 to about 225 m 2 /g, and BET specific surface area ranging from about 130 to about 250 m 2 /g
  • the present invention also provides a method for producing such a high liquid carrying capacity precipitated amorphous silica comprising the steps of: (a) providing an aqueous reaction medium containing an alkali metal silicate;
  • An optional additional process step involves aging and/or diluting the reaction slurry between above steps (c) and (d).
  • the separated and recovered precipitated amorphous silica produced by this invention can be spray dried, and then variously milled, pelletized, compacted (e.g., granulated), and otherwise formed, and screened, to adjust the size and shape dimensions and the amount of dust of the final silica product.
  • this invention is versatile enough to accommodate silica production as between two significantly different desired sizing categories of precipitated amorphous silica product with these being an essentially dust-free class having an average particle size (APS) greater than 150 ⁇ m, and another class being finer particles having an APS less than 70 ⁇ m.
  • APS average particle size
  • the precipitated amorphous silicas of the present invention are characterized by a % carrying capacity DBP value that is greater than 75.0, or even greater than 75.5, while maintaining a robust particulate morphology and favorable performance attributes such as a Jinseed oil absorption ranging from 200 to 325 cc/100g, preferably about 220 to * about 300 cc/100g, a CTAB specific surface area ranging from 100 to 300 m 2 /g, preferably about 120 to about 225 m /g, and a BET specific surface area ranging from 100 to 350 m 2 /g, preferably about 130 to about 250 m 2 /g.
  • a Jinseed oil absorption ranging from 200 to 325 cc/100g, preferably about 220 to * about 300 cc/100g
  • CTAB specific surface area ranging from 100 to 300 m 2 /g, preferably about 120 to about 225 m /g
  • BET specific surface area ranging from 100 to 350 m 2
  • the precipitated amorphous silicas of the present invention especially well-suited for carrying oils such as vitamins, and processing oils such as linseed oil and the like.
  • a process is used involving, among other things, an initial acidulation reaction performed at high temperature in conjunction with a diluted silicate feed reactant in which acid addition is continued beyond the opalescence point (i.e., the gel point) until the precipitation reaction is well underway such that precipitated silica aggregates are formed before the initial acidulation step is discontinued and then post-treatment of the reaction slurry is performed.
  • alkali metal silicate includes all the conventional forms of alkali silicates, as for example, metal silicates, disilicates and the like. Water soluble potassium silicates and sodium silicates are particularly advantageous with the latter being preferred.
  • Na 2 O/SiO 2 molar ratios of between about 2.0 to about 3.5 are generally useful, with about 2.5 to 3.3 being preferred.
  • the alkali silicate solution At the time the alkali silicate solution is acidulated in the reactor, it generally can contain between about 4 to 15%, and more preferably between about 4% and 14%, by weight alkali metal silicate based on the total weight of the alkali metal silicate solution.
  • sodium silicate solution at 10.01 wt.% sodium silicate has a specific gravity of 1.088
  • a 1 1.01 wt.% sodium silicate solution has a specific gravity of 1.098
  • a 12.0 wt.% silicate solution has a specific gravity of 1.108
  • a 13.3 wt.% sodium silicate solution has a specific gravity of 1.123.
  • the alkali silicate solution is heated to a temperature generally between about 70°C and 90°C, more preferably between about 80°C and 90°C, and maintained constant at such a temperature throughout the precipitation reaction.
  • an electrolyte such as sodium sulfate
  • an acidulating agent preferably a mineral acid
  • the pH of the aqueous reaction medium reaches a value in the range of from about 8.0 to 10.0, more specifically in the range of about 8.5 to 10.0, and, most specifically in the range of about 9.0 to 10.0.
  • the acidulating agent i.e., the acid, can be a Lewis acid or
  • Br ⁇ nsted acid and preferably a strong mineral acid such as sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, and so forth, and more preferably sulfuric acid added as a dilute solution thereof.
  • Preferred results being obtained of the acidic solution comprises from about 1.5 to 15% by weight acid based on the total weight of the acid solution, and more preferably is about 1 1 % by weight acid.
  • the above-stated objective of providing lower silicate concentrations in the reaction mixture processed in the initial acidulation step is not particularly influenced by the strength of the acid solution being added to the silicate solution.
  • silica products having generally similar properties have been obtained in which the process scheme includes intervening processing between the initial acidulation step and the acid/silicate co-addition step, involving aging the reaction mass under mild agitation for a short period of time (e.g., about 10 to about 30 minutes) to ensure the solids in the slurry are uniformly dispersed.
  • the aging procedure can be used alone or in conjunction with adding dilution water to the reaction mass developed during the initial acidulation step. In any event, after initial acidulation, and any intervening optional aging and/or dilution operation performed immediately following the initial acidulation, simultaneous addition of acid and silicate is initiated into the reactor.
  • the pH of the reaction mass is maintained at a constant value in the range of about 8.0 to about 10.0 during the simultaneous acid and alkali metal silicate solution addition phase by making slight adjustments to the acid flow rate as needed.
  • the silicate flow is stopped after about 30 minutes, or other time period as needed to give the desired final properties, and then acid flow alone is continued until the reaction mass pH drops to about 4.0 to about 6.5, to substantially complete the reaction.
  • an optional variant of this invention is to employ vigorous agitation during the precipitation reaction to cause shearing of the reaction mass into smaller particulate sizes, if desired.
  • the reaction mass is digested at about 70 to 95°C for about 10 minutes up to several hours, preferably about 10 minutes. If desired, longer digestion times can be used to modify surface properties such as BET surface area, pH, and the like.
  • the precipitated amorphous silica aggregates are observed to form the tertiary structure (i.e., agglomerate) in the reaction mixture prior to washing.
  • the pH of the slurry mass may be manually adjusted to the extent necessary to return to the about 4.0 to about 6.5 pH, then the batch is dropped for filtration, washing and recovery.
  • the reaction mass is filtered, and washed with water to reduce the Na 2 SO 4 level to less than 5%, and preferably less than 2%, by weight. Washing of the reaction product is generally conducted after filtering. However, for large batches, diluting the reaction slurry with water before filtration can aid in reducing the Na 2 SO 4 levels in subsequent washing procedures.
  • the pH of the washed filter cake can be adjusted, if necessary, prior to proceeding to dry the washed filter cake, so as to achieve the desired final silica physical properties.
  • the silica obtained can be dried and used as is, or, alternatively, in order to modify the shape and size of the silica product as desired, the recovered silica product can be additionally ground to a desired degree of fineness or converted into larger particles by various techniques including careful control of the solid content of the slurry sent to the dryer. Drying can be effected by any conventional equipment used for drying silica, e.g., spray drying, nozzle drying (e.g., tower or fountain), or • rotary wheel drying, rotating drum drying, flash drying, fluid bed drying, and so forth.
  • the dried silica product generally should have a 4 to 10 wt.% moisture level.
  • Spray dried product of this invention generally has an average particle size of 30 to 500+ ⁇ m.
  • ground silica product of this invention generally will have a size less than 1-20 ⁇ m.
  • Another interesting discovery made in the course of this invention is that if the product is milled to a very small particle size of 20 microns or smaller, e.g., 1 to 20 ⁇ m, and preferably less than 6 ⁇ m, there is a large increase in the total porosity (about twofold) to provide a total pore volume that is greater than 6.0 cc/g for such a product, and the carrying capacity of DBP increases up to 1-2% in value under extensive milling as compared to the premilled silica product material.
  • the air milled product of this invention has been observed to generally have %DBP carrying capacities greater than 76.0, and even greater than 79.0 in some specific instances.
  • Milling can be practiced using any conventional intense milling equipment, e.g., air-jet milling equipment.
  • An air mill employs particle to particle interaction to reduce particle size.
  • the pressure difference between the wall pressure and feed rate forms a vacuum, causing sample * to be pulled from the feed chute into the main body of the mill.
  • Particle reduction occurs when particles collide with each other, and less preferably with the rubber lining on the body of the mill.
  • Increasing the pressure differential increases the amount of particle reduction.
  • Additional controllable variables include feed pressure and back pressure.
  • the mill typically is equipped with a cyclone exit and baghouse, and the cyclone portion can be collected separately, if desired.
  • Granulated products can be made by compressing dried silica into granules.
  • Such techniques typically include dry compacting, direct compression, wet granulation (i.e., using a binder such as water, silica slurry, or the like) and extrusion.
  • the apparatus used to carry out such techniques includes that which is well known to this technology and can be, for example, compacting presses, pelleting machines, rotating drum compacting machines, rotating granulators, and extruders.
  • the magnitude of the compressive force exerted on the dried silica during processing are known to affect the density and liquid carrying capacity of the silica so care must be taken in these procedures not to cause undesired changes in the carrying capacity of the silica.
  • these process parameters, especially compressive force must be carefully controlled to produce an end product suitable as a liquid carrier.
  • the capacity of the carrier will be insufficient; if too little force is applied, the carrier will lack sufficient density and will be friable.
  • the amount of force used to make any granulated or formed product desired must be carefully controlled to keep the loss of carrying capacity to a minimum. In general, as the force is increased or the dwell time increases, larger amounts of carrying capacity are lost.
  • compression of dried silica base stock can be used to form compacted bodies (also referred to as granules) which are about 20-100% denser than the base stock.
  • the compacted bodies are broken up to produce particles of varying size, including a fraction of compressed fines having a particle size of less than about 100 mesh, and preferably less than about 80 mesh.
  • the fines are isolated, then mixed with additional dried silica base stock to form a feedstock mixture.
  • This feedstock mixture is compressed into granules, broken up into smaller particles of varying sizes, then separated to isolate a silica end product from a coarse particle fraction and a fraction of compressed fines.
  • the feedstock mixture is deaerated prior to compression.
  • the coarse particle fraction is preferably broken up and recycled to the separation step, while the compressed fine fractions isolated from the silica carrier end product are preferably recycled for mixing with virgin dried (i.e., uncompacted) silica base stock.
  • Compression of the dried silica base stock can be performed in accordance with conventional silica processing methods, including compression via tandem rolls.
  • the compressive forces applied to the silica can vary depending on the properties of the base stock and the properties of the product desired, but enough force should be applied to produce a granule which will substantially maintain its physical integrity after the compressive forces are removed.
  • the granules are then broken into smaller particles, and the fraction of smallest particles (referred to herein as compressed fines or fines) is isolated.
  • Conventional means for breaking up the granules may be used, with an attrition mill or a flake breaker being preferable.
  • the fines are less than about 100 mesh, and preferably less than about 80 mesh in size.
  • the fines may be isolated by screening, with the use of a 20 mesh top screen (to remove the coarse fraction) and an 80 mesh bottom (to isolate the fine fraction) screen being preferable.
  • Coarser particle fractions which are removed may be milled and recycled or used for other purposes.
  • the bulk density, liquid carrying capacity and flow properties of a silica carrier can further be controlled by combining dried silica base stock with compressed silica fines produced from the breaking up of compressed silica bodies to produce a unique feedstock silica.
  • Important physical and performance properties of the silica carrier end product can be controlled by adjusting the dried silica base stock/compressed fines mixture, independent of the physical properties of the dried silica base stock and of the compressive force applied to the silica feed.
  • the compaction operation can also be performed as a balanced production system wherein compressed fines (from the breaking up of compressed silica bodies) are recycled to a feed stream of dried silica base stock until the rate of fines production becomes substantially constant, whereby the production system is balanced and can be run continuously with great efficiency.
  • the product may be nozzle spray dried and milled (1 to 20 ⁇ m APS);
  • the product may be wheel spray dried, then compacted and screened (>80 micron APS);
  • the product may be wheel spray dried and milled (1 to 20 ⁇ m APS);
  • the product may be wheel spray dried (>30 ⁇ m APS);
  • the product may be wheel spray dried, milled, then compacted and screened (30 to 500+ ⁇ m APS);
  • the product may be nozzle spray dried, then compacted and screened (30 to 500+ ⁇ m);
  • the product may be nozzle spray dried, pelletized and/or screened to a dense pellet (30 to 500+ ⁇ m);
  • the product may be wheel spray dried, pelletized and/or screened to a dense pellet (30 to 500+ ⁇ m);
  • the product may be nozzle spray dried, milled, pelletized and/or screened to a dense pellet (30 to 500+ ⁇ m); or
  • the product may be wheel spray dried, milled, pelletized and/or screened to a dense pellet (30 to 500+ ⁇ m).
  • this invention is versatile enough to accommodate silica production as between two significantly different desired sizing categories of precipitated amorphous silica product with these being an essentially dust-free class having an average particle size (APS) greater than 150 ⁇ m, and another class requiring smaller particles having an APS less than 70 ⁇ m.
  • APS average particle size
  • % carrying capacity of DBP is performed as follows.
  • the procedure for measuring % carrying capacity uses a Spex Mill (Spex Industries, Inc., #8000 Mixer/Mill) which imparts a wrist action non-shear motion to the silica sample being tested.
  • Suitable test jars have a 125 mL capacity are used that can be purchased from VWR Scientific (#IR 120-0125).
  • the test is conducted by simply weighing a sample of silica carrier into the test jar, adding the test liquid, and shaking in the Spex Mill. Carrier weights are measured to 0.01 g accuracy and vary with the carrier being tested.
  • the test jar should be about half full and typical weights are from 5 to 10 grams.
  • Addition of the liquid to the silica powder to be tested is facilitated by making a small hole in the powder, pouring the liquid into it, and covering it with dry powder from the sides. This prevents liquid from sticking to the sides of the jar and the lid while shaking.
  • An equal weight of liquid and carrier are added to the jar and the sample is shaken on the Spex Mill for 30 seconds. This represents 50% carrying capacity as a starting point. If a noticeable amount of liquid adheres to the sides of the jar, it should be scraped off with a spatula prior to adding additional liquid. The sample is observed to confirm that all of the liquid has in fact been taken into the carrier. More liquid is then added to the same jar and the mixture shaken for an additional 30 seconds.
  • average particle size is determined using a Microtrac II (Model 7998) Particle Size Analyzer.
  • CTAB external surface area is determined by absorption of CTAB (cetyltrimethylammonium bromide) on the silica surface, the excess CTAB is separated by centrifugation and determined by titration with sodium lauryl sulfate using a surfactant electrode.
  • the CTAB external surface of the silica product is determined from the quantity of CTAB adsorbed (analysis of CTAB before and after adsorption). More specifically, about 0.5 g of silica product is placed in a 250-ml beaker with 100.00 ml CTAB solution (5.5 g/l). The solution is mixed on an electric stir plate for 1 * hour then centrifuged for 30 minutes at 10,000 rpm.
  • Triton X-100 1 ml of 10% Triton X-100 is added to 5 ml of the clear supernatant in a 100 ml beaker. The pH is then adjusted to 3.0-3.5 with 0.1 N HCI and titration is done with 0.0100 M sodium lauryl sulfate using a surfactant electrode (viz., a Brinkman SUR1501-DL) to determine the endpoint.
  • a surfactant electrode viz., a Brinkman SUR1501-DL
  • Single-point BET is measured in m 2 /g by predrying a sample for two hours at 105°C and then subjecting it to analysis of the surface by a determination using the BET nitrogen adsorption methods based on the techniques developed by Brunaur et al., J. Am. Chem. Soc, 60, (1938).
  • the pore volumes are measured by mercury porosimetry using a Micromeritics Autopore II 9220 apparatus.
  • the pore diameters are calculated by the Washbum equation employing a contact angle Theta equal to 130° and a surface tension gamma equal to 484 dynes/cm.
  • Pour density is determined by weighing 100.0 grams silica product into a 250-mL graduated cylinder and recording the volume occupied.
  • %LOI Loss on ignition
  • %H 2 O moisture loss at 105°C
  • the 5% pH values of the silica products of the present invention can be measured by any conventional pH sensitive electrode.
  • the precipitated amorphous silica of this invention has numerous and diverse utilities.
  • the silica is useful for such applications as the coating of paper, especially in as a coating material for coated papers where high ink absorption is desired, and in catalysis, and, as noted earlier, as a support for conditioning liquids.
  • a number of liquids may be deposited onto the subject silica support to prepare a conditioned composition, e.g., organic acids, linseed oil, surface active agents of the anionic type used in detergents such as sulfonates, or of the nonionic type such as alcohols or phenols, cationic agents such as quaternary ammonium compounds, and also as vulcanization accelerators and antioxidants for use in the rubber industry.
  • liquids • used as supplements in foodstuffs can be conditioned using precipitated amorphous silica products of this invention in which the silica is used as a support for liquid active agents such as vitamins.
  • Vitamins that can be conditioned in this manner include, for example, vitamins A, B, C, D, E and K.
  • the absorption of the liquid onto the silica support can be carried out in any known manner, for example, by dispersing the liquid onto the silica particulates in a mixer.
  • the amount of liquid absorbed is predicated by the end-application in mind.
  • the silica particulates of the invention make it possible to produce conditioned compositions having a liquid contents much in excess of 50% by weight.
  • This invention also permits production of a wide variety of precipitated amorphous silica particulates having high oil carrying capacity.
  • the term "particulate”, as used to characterize the structure of precipitated amorphous silica products of this invention, can mean the same thing as any one of primary (ultimate) particle, aggregate, agglomerate, or granulate, as those terms are understood in the pertinent field of endeavor.
  • the following non-limiting examples will further illustrate the present invention. All parts, ratios, concentrations, and percentages are based upon weight unless otherwise specified.
  • the raw starting materials used to prepare a precipitated amorphous silica were a 13.3% by weight sodium silicate solution having a Na 2 O/SiO 2 molar ratio of 2.5 and a specific gravity of 1.123 (at 15.5°C), and dilute (1 1.4 wt.%) sulfuric acid having a specific gravity of 1.079.
  • the batch procedure involved adding 319 liters of the silicate solution, preheated to 68°C, to a 1500 liter capacity reactor. 81 liters of water was introduced to the reactor, and the silicate solution was heated to 82°C and maintained at that temperature throughout the precipitation reaction.
  • the aqueous reaction medium was mildly agitated during the water addition and heating steps with a Lightnin agitator.
  • the • aqueous reaction medium was agitated for an additional 2 minutes once the aqueous reaction medium temperature reached 82°C, then the specific gravity of the reaction bath was measured to confirm that it was the desired value of approximately 1.098.
  • Addition of dilute acid (at 33°C +/- 1.5°C) commenced into the aqueous reaction medium in the reactor at a flow rate of 3.4 liters/minute, and acid addition was continued until the pH of the aqueous reaction medium dropped to 9.1.
  • acid addition was immediately interrupted and discontinued.
  • aqueous reaction medium i.e., the reaction mass
  • the raw starting materials used to prepare a * precipitated amorphous silica were a 13.3% by weight sodium silicate solution having a Na 2 O/SiO 2 molar ratio of 2.5 and a specific gravity of 1.123 (at 15.5°C), and dilute (11.4 wt.%) sulfuric acid having a specific gravity of 1.079.
  • the batch procedure involved adding 319 liters of the silicate solution, preheated to 68°C, to a 1500 liter capacity reactor. 81 liters of water was introduced to the reactor, and the silicate solution was heated to 82°C and maintained at that temperature throughout the precipitation reaction.
  • the aqueous reaction medium was mildly agitated during the water addition and heating steps with a Lightnin agitator.
  • the aqueous reaction medium was agitated for an additional 2 minutes once the aqueous reaction medium temperature reached 82°C, then the specific gravity of the reaction bath was measured to confirm that it was the desired value of approximately 1.098.
  • Addition of dilute acid (at 33°C +/- 1.5°C) commenced into the aqueous reaction medium in the reactor at a flow rate of 3.4 liters/minute, and acid addition was continued until the pH of the aqueous reaction medium dropped to 9.1.
  • acid addition was immediately interrupted and discontinued.
  • reaction mass was then aged with mild agitation for 15 minutes.
  • the filtered cake • slurry was liquefied briefly ( ⁇ 5 minutes).
  • the pH of the filtered slurry was approximately 6.5 (pH adjustment can be done here if necessary by acid addition). Washing was performed with water.
  • the precipitated amorphous silica aggregates were observed to form the tertiary structure (i.e., agglomerated) prior to the washing step.
  • the filtered and washed cake was wheel spray dried to 3 to 7 wt.% H 2 0 content.
  • the dried silica product displayed the characteristics summarized in Table 1 below.
  • the raw starting materials used to prepare a precipitated amorphous silica were a 13.3% by weight sodium silicate solution having a Na 2 O/SiO 2 molar ratio of 2.5 and a specific gravity of 1.123 (at 15.5°C), and dilute (11.4 wt.%) sulfuric acid having a specific gravity of 1.079.
  • the batch procedure involved adding 319 liters of the silicate solution, preheated to 68°C, to a 1500 liter capacity reactor. 81 liters of water was introduced to the reactor, and the silicate solution was heated to 82°C and maintained at that temperature throughout the precipitation reaction.
  • the aqueous reaction medium was mildly agitated during the water addition and heating steps with a Lightnin agitator.
  • the aqueous reaction medium was agitated for an additional 2 minutes once the aqueous reaction medium temperature reached 82°C, then the specific gravity of the reaction bath was measured to confirm that it was the desired value of approximately 1.098.
  • Addition of dilute acid (at 33°C +/- 1.5°C) commenced into the aqueous reaction medium in the reactor at a flow rate of 3.4 liters/minute, and acid addition was continued until the pH of the aqueous reaction medium dropped to 9.1.
  • acid addition was immediately interrupted and discontinued.
  • 105 liters of water was added to the aqueous reaction medium (i.e., the reaction mass) over a 5-10 minute time period.
  • reaction mass After interruption of the acid addition and addition of the dilution water, the reaction mass was then aged with mild agitation for 15 minutes. Agitation was constant throughout the total 20-25 minute period devoted to the addition of the dilution water and aging period.
  • the filtered cake slurry was liquefied briefly ( ⁇ 5 minutes).
  • the pH of the filtered slurry was approximately 6.5 (pH adjustment can be done here if necessary by acid addition). Washing was performed with water. The precipitated amorphous silica aggregates were observed to form the tertiary structure (i.e., agglomerated) prior to the washing step.
  • the filtered and washed cake was wheel spray dried to 3 to 7 wt.% H 2 O content.
  • the dried silica product displayed the characteristics summarized in Table 1 below.
  • EXAMPLE 4 A separate batch was prepared using the same protocol as described in Example 3 except that, after stopping the silicate flow of the acid-silicate co-addition operation, acid flow was continued instead at a higher rate of 2.0 liters/minute until the reaction mass pH dropped to 5.5. There was no effect evident from changing that acid flow rate.
  • the dried silica product displayed the characteristics summarized in Table 1 below.
  • the raw starting materials used to prepare a precipitated amorphous silica were a 13.3% by weight sodium silicate solution having a Na 2 O/SiO 2 molar ratio of 2.5 and a specific gravity of 1.123 (at 15.5°C), and dilute (1 1.4 wt.%) sulfuric acid having a specific gravity of 1.079.
  • the batch procedure involved adding 319 liters of the silicate solution, preheated to 68°C, to a 1500 liter capacity reactor. 127 liters of water was introduced to the reactor, and the silicate solution was heated to 88°C and maintained at that temperature throughout the precipitation reaction.
  • reaction mass aqueous reaction medium
  • the reaction mass was then aged with mild agitation for 15 minutes. Agitation was constant throughout the total 20-25 minute period devoted to the addition of the dilution water and aging period.
  • the filtered cake slurry was liquefied briefly ( ⁇ 5 minutes).
  • the pH of the filtered slurry was approximately 6.5 (pH adjustment can be done here if necessary by acid addition).
  • Washing was performed with water (60°C).
  • the precipitated amorphous silica aggregates were observed to form the tertiary structure (i.e., agglomerated) prior to the washing step.
  • the filtered and washed cake was wheel spray dried to 3 to 7 wt.% H 2 O content.
  • the dried silica product displayed the characteristics summarized in Table 1 below.
  • the raw starting materials used to prepare a precipitated amorphous silica were a 13.3% by weight sodium silicate solution having a Na 2 O/SiO 2 molar ratio of 2.5 and a specific gravity of 1.123 (at 15.5°C), and dilute (11.4 wt.%) sulfuric acid having a specific gravity of 1.079.
  • the batch procedure involved adding 319 liters of the silicate solution, preheated to 68°C, to a 1500 liter capacity reactor. 81 liters of water was introduced to the reactor, and the silicate solution was heated to 88°C and maintained at that temperature throughout the precipitation reaction.
  • the aqueous reaction medium was mildly agitated during the water addition and heating steps with a Lightnin agitator.
  • the aqueous reaction medium was agitated for an additional 2 minutes once ⁇ the aqueous reaction medium temperature reached 88°C, then the specific gravity of the reaction bath was measured to confirm that it was the desired value of approximately 1.098.
  • Addition of dilute acid (at 33°C +/- 1.5°C) commenced into the aqueous reaction medium in the reactor at a flow rate of 3.4 liters/minute, and acid addition was continued until the pH of the aqueous reaction medium dropped to 9.1.
  • acid addition was immediately interrupted and discontinued, and then 105 liters of water was added to the aqueous reaction medium (i.e., the reaction mass) over a 5-10 minute time period.
  • reaction mass was then aged with mild agitation for 15 minutes. Agitation was constant throughout the total 20-25 minute period devoted to the addition of the dilution water and aging period.
  • simultaneous addition of acid and silicate was initiated into the reactor with the dilute acid flow rate set at 0.9 liters/minute and the sodium silicate solution flow rate set at 2.27 liters/minute.
  • the pH of the reaction mass was maintained at 9.1 +/- 0.1 during the simultaneous addition phase by making slight adjustments to the acid flow rate as needed.
  • Silicate flow was stopped after 30 minutes while acid flow was continued at 2.0 liters/minute until the reaction mass pH dropped to 5.5.
  • the reaction mass was digested at 88°C for 10 minutes. After digestion, the pH was manually adjusted to 5.5 +/-0.1 pH, then the batch was dropped. The reaction mass was filtered and washed on a rotary filter drum. After filtration, the filtered cake slurry was liquefied briefly ( ⁇ 5 minutes). The pH of the filtered slurry was approximately 6.5 (pH adjustment can be done here if necessary by acid addition). Washing was performed with water (60°C). The precipitated amorphous silica aggregates were observed to form the tertiary structure (i.e., agglomerated) prior to the washing step. The filtered and washed cake was wheel spray dried to 3 to X wt.% H 2 O content.
  • a dried silica product made in manner as described in Example 3 was air milled using a single pass on a Jet Pulverizer mill and two passes on a hammer mill. The mill configuration was set to give maximum milling of the feed stock silica.
  • the dried, milled silica product displayed the characteristics summarized in Table 1 below.
  • EXAMPLE 9 A dried silica product made in manner as described in Example 7 was air milled using air milled using a single pass on a Jet Pulverizer mill and two passes on a hammer mill. The mill configuration was set to give maximum milling of the feed stock silica.
  • the dried, milled silica product displayed the characteristics summarized in Table 1 below.
  • EXAMPLE 10 A silica product was prepared in the same manner as described in Example 1 except that the filtered and washed cake was instead nozzle spray dried to 3 to 7 wt.% H 2 0 content.
  • the %DBP carrying capacity of this silica product was measured to be 75.4 together with an APS measured to be 147 ⁇ m, linseed oil absorption of 224 cc/100g, CTAB of 151 n ⁇ 7g, BET of 198 nrrVg, %Na 2 SO 4 of 0.82, pour density of 0.187 g/ml, 5% pH of 6.94, %LOI of 4.2 and %H 2 0 of 4.3.
  • the manner of drying the silica as between wheel or nozzle drying did not appear to significantly effect the %DBP carrying capacity of the product.
  • the HUBERSIL® 1714 silica only had a %DBP carrying capacity of 4.3 together with an APS measured to be 13.8 ⁇ m, linseed oil absorption of 268 cc/100g, CTAB of 145 m 2 /g, and BET of 158 m 2 /g.
  • the SIPERNAT® 50 silica had a %DBP carrying capacity of only 74.1 together with an APS measured to be 37.3 ⁇ m, linseed oil absorption of 276 cc/IOOg, CTAB of 325 n ⁇ 7g, and BET of 524 m 2 /g.
  • the %DBP carrying capacity of the unmilled inventive silica product examples i.e., Examples 1-7), all had %DBP carrying capacities well above 75.0.
  • the air milled SIPERNAT® 50 only had a %DBP carrying capacity of 73.4 together with an APS measured to be 5.31 ⁇ m, linseed oil absorption of 284 cc/100g, CTAB of 338 m 2 /g, and BET of 528 m /g.
  • the %DBP carrying capacity of the air milled inventive silica product examples each had %DBP carrying capacities above 77.0. It was observed that the air milling procedure effected an increase in the %DBP carrying capacities of the inventive dried silica product while the opposite effect was seen for the compared commercial products of HUBERSIL® 1714 and SIPERNAT® 50.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)

Abstract

L'invention concerne des silices amorphes précipitées à forte capacité d'absorption et de transport de liquide, dans lesquelles la silice a un indice d'absorption d'huile caractérisant la capacité de transport dépassant 75 %. L'invention concerne également des procédés d'élaboration correspondants.
PCT/US1998/025012 1997-12-08 1998-11-23 Silices amorphes precipitees a proprietes physiques ameliorees WO1999029623A1 (fr)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1196351A1 (fr) * 1999-04-22 2002-04-17 J.M. Huber Corporation Silice hybride de tres haute structure et fortement absorbante et son procede de fabrication
WO2003014020A1 (fr) * 2001-08-07 2003-02-20 Ppg Industries Ohio, Inc. Substance particulaire a base de silice
WO2008136019A3 (fr) * 2007-05-03 2009-04-30 Council Scient Ind Res Procédé pour la préparation d'une silice précipitée finement divisée
EP1590297B2 (fr) † 2003-01-22 2016-09-21 Evonik Degussa GmbH Silices precipitees de fa on specifique pour des applications dans le domaine du caoutchouc
EP1860066B1 (fr) 2006-05-26 2017-02-22 Evonik Degussa GmbH Silice hydrophile pour masses d'étanchéité

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4590052A (en) * 1984-04-06 1986-05-20 Rhone-Poulenc Chimie De Base Precipitated silica having improved morphological characteristics and process for the production thereof
US5342598A (en) * 1989-07-03 1994-08-30 Rhone-Poulenc Chimie Precipitated silica particulates having controlled porosity
US5403570A (en) * 1991-06-26 1995-04-04 Rhone-Poulenc Chimie Dispersible silica particulates

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4590052A (en) * 1984-04-06 1986-05-20 Rhone-Poulenc Chimie De Base Precipitated silica having improved morphological characteristics and process for the production thereof
US5342598A (en) * 1989-07-03 1994-08-30 Rhone-Poulenc Chimie Precipitated silica particulates having controlled porosity
US5403570A (en) * 1991-06-26 1995-04-04 Rhone-Poulenc Chimie Dispersible silica particulates

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1196351A1 (fr) * 1999-04-22 2002-04-17 J.M. Huber Corporation Silice hybride de tres haute structure et fortement absorbante et son procede de fabrication
EP1196351A4 (fr) * 1999-04-22 2003-04-23 Huber Corp J M Silice hybride de tres haute structure et fortement absorbante et son procede de fabrication
WO2003014020A1 (fr) * 2001-08-07 2003-02-20 Ppg Industries Ohio, Inc. Substance particulaire a base de silice
US7253224B2 (en) 2001-08-07 2007-08-07 Ppg Industries Ohio, Inc. Silica-based particulates
EP1590297B2 (fr) † 2003-01-22 2016-09-21 Evonik Degussa GmbH Silices precipitees de fa on specifique pour des applications dans le domaine du caoutchouc
EP1860066B1 (fr) 2006-05-26 2017-02-22 Evonik Degussa GmbH Silice hydrophile pour masses d'étanchéité
WO2008136019A3 (fr) * 2007-05-03 2009-04-30 Council Scient Ind Res Procédé pour la préparation d'une silice précipitée finement divisée
AU2008246949B2 (en) * 2007-05-03 2012-11-01 Council Of Scientific & Industrial Research A process for the preparation of finely divided precipitated silica
CN101679050B (zh) * 2007-05-03 2012-11-28 科学与工业研究委员会 制备微细的沉淀二氧化硅的方法
KR101559897B1 (ko) 2007-05-03 2015-10-13 카운실 오브 사이언티픽 엔드 인더스트리얼 리서치 미세하게 분할된 침강 실리카의 제조방법

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