WO2001046073A1 - Processus de production d'une suspension epaisse de silice precipite avec repartition controlee du calibre des particules d'agregat - Google Patents

Processus de production d'une suspension epaisse de silice precipite avec repartition controlee du calibre des particules d'agregat Download PDF

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WO2001046073A1
WO2001046073A1 PCT/CA2000/001473 CA0001473W WO0146073A1 WO 2001046073 A1 WO2001046073 A1 WO 2001046073A1 CA 0001473 W CA0001473 W CA 0001473W WO 0146073 A1 WO0146073 A1 WO 0146073A1
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process defined
reaction mixture
silica
silicate
acid
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PCT/CA2000/001473
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Ahti Koski
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Bayer Inc.
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Priority to AU18482/01A priority Critical patent/AU1848201A/en
Publication of WO2001046073A1 publication Critical patent/WO2001046073A1/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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0086—Processes carried out with a view to control or to change the pH-value; Applications of buffer salts; Neutralisation reactions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/18—Stationary reactors having moving elements inside
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00051—Controlling the temperature
    • B01J2219/00054—Controlling or regulating the heat exchange system
    • B01J2219/00056—Controlling or regulating the heat exchange system involving measured parameters
    • B01J2219/00069—Flow rate measurement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00164—Controlling or regulating processes controlling the flow
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00164—Controlling or regulating processes controlling the flow
    • B01J2219/00166—Controlling or regulating processes controlling the flow controlling the residence time inside the reactor vessel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00177—Controlling or regulating processes controlling the pH
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/32—Spheres
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/50—Agglomerated particles
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer

Definitions

  • the present invention relates to a process for the production of a precipitated silica slurry.
  • the present invention also provides a means of controlling the average sizes of the silica particle clusters or aggregates within this slurry.
  • the present invention relates to a monodisperse distribution of silica aggregates and moreover yields clusters or aggregates which have both a fractal morphology and low mechanical strength.
  • “monodisperse” is intended to mean aggregate particles that have a narrow size distribution characterised by the standard deviation about the mean value of their radius.
  • the term "fractal morphology" is intended to mean that each of the particle clusters is a rough or fragmented geometric shape as opposed to “spheroidal morphology” wherein it is meant that the particles have a substantially constant internal radius.
  • the present invention relates to precipitated silica slurries which can advantageously be used in the production of rubber/silica masterbatches.
  • Precipitated silica is well known as a filler material useful in a variety of products.
  • One of the applications in which precipitated silica has achieved particular interest recently is as a filler for polymers. It is particularly useful for the reinforcement of articles made from vulcanized elastomers (e.g., butadiene rubber, styrene-butadiene rubber, natural rubber, EPDM and the like), including tire treads.
  • vulcanized elastomers e.g., butadiene rubber, styrene-butadiene rubber, natural rubber, EPDM and the like
  • the silica or other filler be homogeneously dispersed throughout the elastomer compound in the form of discreet small particles.
  • Dispersed particles with diameters in excess of one micron (10 3 nanometers) are, as a rule, non-reinforcing, and rubber articles containing such large particles may even have less utility than those without any added filler.
  • the average particle size (ASTM C721 and D1366; ISO 787 Part XVII), the specific surface area (ASTM D1933 and D5604; ISO 5794 Part I), the mean projected area of the aggregates (ASTM D3849), and the oil absorption (ASTM D2414; ISO 787 Part V).
  • the average particle size may be determined from the original surface area measurement method of Sears, (G.W. Sears Jr., Analytical Chemistry, Vol. 28, No.
  • CTAB surface area is also an important parameter and may be used to further characterize non-dried silicas.
  • CTAB area is defined as the external surface area, as evaluated by absorption of cetyl trimethyl ammonium bromide with a pH of 9, following the method set forth by Jay, Jansen and Kraus in Rubber Chemistry and Technology, 44, pages 1287-1296 (1971). A full procedure for this test is set forth in United States patent 5,739,197, col. 5-7.
  • dry silica powders are composed of aggregates of primary particles. Larger structures termed “agglomerates” may also be present, usually as a result of the drying process used during the manufacture.
  • agglomerates may also be present, usually as a result of the drying process used during the manufacture.
  • superior reinforcing properties in rubber compounds are obtained from the use of silicas which have both a high specific surface area (i.e. > 200 ⁇ r/gm) coupled with a small average aggregate particle size.
  • dry mixing dry mixing
  • compounds with high viscosities that are difficult to process further by operations such as calendaring, extrusion or molding which are needed to form the desired end-products.
  • the ease of dispersion of a dry silica powder during rubber mixing is recognized as being dependent on the porosity of the aggregate structure.
  • the latter is in turn governed to a large extent by the size and packing of the primary silica particles (see for example, Her, Chapter 5).
  • the degree of aggregate porosity is usually measured by a form of absorption test. Oil is commonly employed for this purpose (ASTM D2414).
  • Silica particle aggregates with high degree of oil absorption have a high internal void volume; i.e., they contain numerous suitably-sized pores into which the oil molecules can migrate.
  • Pores of sizes approaching molecular dimensions (2-200 nanometers) have been classified as “mesopores” by Unger (Klaus Unger, "Structure of Porous Adsorbents", Angew. Chem. Int. Ed., 11 (4) 267 (1972)); during the dry mixing process, the polymer component may also enter these pores.
  • Unger Klaus Unger, "Structure of Porous Adsorbents", Angew. Chem. Int. Ed., 11 (4) 267 (1972)
  • the polymer component may also enter these pores.
  • the shearing and elongational forces of dry mixing cause the rubber-entrained silica particles to fracture and disperse in the bulk polymer.
  • a porous particle also exhibits a diminished fracture strength compared to a similar sized solid particle, and is thus more easily fractured by the forces inherent in the mixing process.
  • filler particles not only need to be well dispersed but their surface also needs to be substantially chemically compatible with the polymers in which they are used as fillers.
  • Special chemical agents are normally employed to reduce the surface polarity of the silica particles when these are used with non-polar hydrocarbon rubbers.
  • these surface-reactive agents usually bifunctional sulfur-containing silanes
  • these surface-reactive agents are added during the mixing cycle, i.e. during Banbury mixing. Chemical reactions take place between these added agents and the silanol groups (Si-OH) on the silica surface during the mixing step and later between the agent and the polymer at the compound curing step. This allows the silica particle to be linked to the polymer backbone.
  • the Bayer patent applications As it is well known that primary particle size and surface area are directly related, silica materials composed of aggregates of very small primary particles have a relatively high surface area. To ensure maximum compatibility of such silica materials with non-polar polymers, as well as to prevent absorption of curative chemicals on the surface, high ratios of expensive surface treating agents per unit silica weight are therefore necessary. Practical limits thus exist on the maximum surface area that can be economically used.
  • the first, more recent approach relies on the controlled hydrolysis (“hydrolytic polycondensation") of a hydrolysable silane (i.e., tetraethoxysilane, TEOS or ethyl silicate) hereafter called “the Stober processes" (W. St ⁇ ber et al., J. Colloid Int. Sci., 26, 62-69, (1968)).
  • the second, more classical approach entails the reaction of an acid (e.g., H 2 SO 4 ) with a water solution of alkali silicate (e.g., Na ⁇ SiO,) ⁇ 5 . 3 34 ).
  • the processes are usually conducted by adding an acid at a predetermined rate to the heated alkali silicate solution contained in a first vessel.
  • the first vessel is agitated throughout the reaction phase and relatively high reaction temperatures (i.e., 60°C to 85°C) are usually employed. Large vessel volumes are typically used.
  • Addition of acid may be interrupted at a certain pH (ie. -8-8.5) and additional silicate may also be added then, or the precipitation may be taken to completion and additional silicate and acid may be added later in a post-treatment (United States patent 4,336,245). These interruptions or post-treatments serve to improve particle aggregate strengths, and are usually referred to as "building" steps.
  • the amount of reinforcement thus conferred to the aggregate is termed the "build-up ratio" (Her, p.557).
  • Build-up ratio is further defined as the ratio of the final weight of silica in the system to the weight of the aggregated silica.
  • Build-up ratios of 4:1 or less are usually required to attain a silica that can be dispersed during dry mixing (Her, p. 557).
  • a certain amount of "build-up” is required to prevent collapse of the particle structure during the ensuing drying step as a result of capillary forces and those of surface tension as water is removed (Her, p. 534-536).
  • FIG. 2b One embodiment of a silica particle during "build-up" is illustrated in Figure 2b.
  • acid is again added to complete the desired degree of neutralization.
  • the contents of the first vessel are then transferred to a ripening tank (e.g., a second vessel equipped with an agitator) wherein particle growth is completed over the course of several hours or days (known within the art as "Ostwalt ripening'").
  • a ripening tank e.g., a second vessel equipped with an agitator
  • the particle size distribution thus narrows and the average particle size increases.
  • This ripening has the further effect of increasing particle strength thereby improving filterability by reducing the number of very small particles. It is these smaller particles which generally pass through the filter and are lost, or if their volume fraction becomes excessive, may clog the filter substrate. Filtering is still the most common process used to separate the silica from the mother liquor.
  • the wet filter cake resulting from the filtering step may be further processed by pressing to remove entrained mother liquor, washing to remove soluble salts, drying (i.e., in a tunnel drier) and finally grinding (i.e., using a hammer mill, jet mixer, ball mill or similar apparatus).
  • These steps yield the finished product as a powder having a broad particle size distribution and an average agglomerate particle size of from about 1 ⁇ m to about 100 ⁇ m, or in some cases even larger.
  • the particles are shattered by the final grinding process, their shapes tend to be angulated rather than fractal or spheroidal, and the flow characteristics of the powders are thus poor.
  • the washed filter cake may be reslurried and then finished by a spray drying process.
  • This process modification yields a more free flowing powder composed of spheroidal particle agglomerates; however because the so- produced dried particles are generally of larger size (i.e. > 50 microns) than those produced by grinding, longer mixing times are generally required to attain the same degree of filler dispersion when such spray-dried powders are used in the rubber compound.
  • the spray drying process does produce a silica with much reduced tendency to dust, which is a desirable feature.
  • an acidic gas may be employed as the precipitating agent.
  • the acidic gas may be added directly to the heated silicate solution or it may be generated in-situ, for instance by the combustion of hydrocarbon (i.e., natural gas, in a submersible burner as described in United States patent 3,372,046) to provide CO 2 and heat.
  • hydrocarbon i.e., natural gas, in a submersible burner as described in United States patent 3,372,046
  • the filter cake may be further washed free of soluble salts, dried and ground to provide an end product having an average agglomerate particle size of from about 0.5 ⁇ m to about 100 ⁇ M.
  • Silicas produced by the above modified processes share the same disadvantages as those produced from direct addition of mineral acid to soluble silicate.
  • Derleth et al (United States patent 5,232,883) describe a process whereby an electrostatically charged alkali silicate solution is sprayed into a chamber containing an acidic gas (i.e. HC1).
  • This process is said to produce a silica comprised of microspheroidal particles of narrow particle size distribution of between 50 to 200 micrometers and with a specific surface in excess of 200 m 2 /g, a pore volume of between 1 and 3.5 cmVg, a roundness factor lower than 1.40, and a variation coefficient of the particle size distribution lower than 60%.
  • these silica particles are designed specifically for use as catalyst supports for alpha-olefin polymerization.
  • Spheroidal silica particles in the 0.5 to 20 micrometer diameter range can also be obtained by agglomeration of colloidal silica in a polymeric matrix of urea and formaldehyde (United States patent 4,010,242).
  • the colloidal silica in this case "Ludox HS”, is made by a precipitation of an alkali silicate utilizing an acid-form ion exchange resin.
  • This patent further directs that the organic matrix must be removed by burning; this process thus suffers from unnecessary complexity and is wasteful of organic materials. Regardless which modification of the acid precipitation prior art approaches is used, (with the exception of United States patent 5,232,883), the silica at the wet filter cake stage typically has a wide particle size distribution (PSD) of aggregates.
  • PSD particle size distribution
  • each silica aggregate is made up of a number of smaller primary (ultimate) particles of varying sizes
  • a wide PSD means that, for a given aggregate: there are a relatively large number of contact points (i.e., between adjacent agglomerated particles) resulting in a particle aggregate with relatively high mechanical strength - see Figure lb, for example. While this strength is detrimental to ease of processing, it is nevertheless necessary to prevent collapse of the particle and the formation of a solid sintered mass during the drying process. Thus, the requirements of the silica for a useful manufacturing process and those which provide for ease of processing during rubber mixing are somewhat at odds. Further, for dried silica materials, a relatively high shear energy is needed to de-agglomerate the particle, and the particle porosity is low. Thus, it is somewhat difficult to conduct surface chemistry on all of the agglomerated particles in the sample.
  • the Bayer patent applications refer to treatment of conventional silica preparations to facilitate dispersion thereof in the elastomer via a masterbatch technique. While the treatment technique is adequate on a small scale, it would be beneficial to have an improved silica preparation, inter alia, which would facilitate treatment of the surface of the silica particles and ultimately facilitate dispersion of the treated silica particles in the elastomer. It is an object of the present invention to obviate or mitigate at least one of the above- mentioned disadvantages of the prior art.
  • the present invention provides a process for production of a precipitated silica slurry comprising the steps of:
  • the silica particles produced in the process have a volume average particle size of at least 5 ⁇ m, more preferably in the range of from about 10 ⁇ m to about 40 ⁇ m.
  • Figures 1 and 2 illustrate schematic views of various forms of silica particulate material
  • Figure 3 illustrates a schematic of a reactor used in the example described herein below and which is the subject of a co-pending patent application;
  • Figures 4 and 6 illustrate particle size distribution curves for a pair of silica slurries based on volume fraction
  • Figures 5 and 7 illustrate particle size distribution curves for a pair of silica slurries based on number fraction
  • Figure 8 illustrates the result of an ultrasonic dispersion test on the number average particle size for a pair of silica slurries
  • Figure 9 illustrates an electron microscope image of a commercially available silica material
  • Figure 10 illustrates an electron microscope image of a silica material made in accordance with the present process.
  • the precipitated silica slurry produced in accordance with the present process has a relatively narrow PSD and moreover the particle aggregates have a fractal morphology.
  • a narrow PSD means that, for a given silica particle: (i) there are a relatively small number of contact points (i.e., between adjacent particles within the aggregate), (ii) only a relatively low shear energy is needed to de-agglomerate the particle since only a few contact points need to be broken, and (iii) it is possible to conduct surface chemistry on substantially all of the surfaces of the aggregate since these are readily accessible (i.e., compared to a slurry having a relatively wide PSD of silica particles).
  • the precipitated silica slurry produced in accordance with the present process may be used advantageously in the hydrophobicizing treatment set out in the Bayer patent applications.
  • the precipitated silica slurry produced in accordance with the present process is not filtered and dried; rather it is subject to further treatment whilst in the nascent slurry form. This allows for production of improved treated silica particles which leads to improved dispersion thereof in an elastomer via the masterbatch technique described in the Bayer patent applications.
  • Step (i) of the present process comprises continuously feeding to a mixing zone an aqueous metal silicate compound, an acid and an electrolyte to produce the reaction mixture.
  • the aqueous metal silicate comprises an alkali metal silicate. More preferably, the alkali metal silicate has the formula
  • M is an alkali metal and x is at least 2.
  • x is in the range of from about 2 to about 4 (including fractional numbers).
  • useful alkali metal silicates may be selected from the group comprising sodium silicate, potassium silicate, ammonium silicate and mixtures thereof.
  • Alkaline earth silicates such as calcium silicate or magnesium silicate may also be used.
  • the most preferred alkali metal silicate is sodium silicate, particular a sodium silicate comprising a SiO- ⁇ Na ⁇ ratio in the range of from about 0.5 to about 4.0, also referred to as 'water glass.'
  • the acid used in Step (i) is conventional.
  • Non-limiting examples of such acids may be selected from the group comprising hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid and mixtures thereof. Acidic gases such as CO 2 , HC1, SO 2 and the like may also be used.
  • the electrolyte used in Step (i) is conventional.
  • the electrolyte comprises an alkali metal salt. More preferably it is a sodium salt.
  • Non-limiting examples of useful sodium salts may be selected from the group comprising sodium chloride, sodium nitrate, sodium carbonate, sodium bicarbonate, sodium chlorate, sodium bromide and mixtures thereof.
  • the reaction mixture produced in Step (i) of the present process is retained in the mixing zone for a period of time sufficient to achieve a uniform distribution of reactants.
  • the residence time of the reaction mixture in the mixing zone is less than about 15 minutes, more preferably less than about 10 minutes, even more preferably less than about 8 minutes, even more preferably less than about 4 minutes, most preferably less than about 1 minute.
  • the ratio of acid to alkali silicate is such that the pH of the reaction mixture in the mixing zone is maintained in the range of from about 6.0 to about 10.0. More preferably, the pH of the reaction mixture in the mixing zone is maintained in the range of from about 7.0 to about 9.0. Most preferably, the pH of the reaction mixture in the mixing zone is maintained in the range of from about 8.0 to about 9.0. Appropriate pH control can be achieved by regulating the amount of acid used in Step (i) of the process whilst keeping the flow of alkali silicate constant.
  • Step (ii) of the present process comprises maintaining the reaction mixture in a quiescent zone at a temperature of less than about 100°C.
  • Step (ii) comprises maintaining the reaction mixture in the quiescent zone at a temperature in the range of less than about 90°C, and most preferably from about 30°C to about 50°C.
  • Step (iii) of the present process comprises continuously removing the reaction mixture from the quiescent zone. This allows continued introduction of silicate, acid and electrolyte in Step (i) thereby rendering the present process continuous.
  • the apparatus for use in the present process comprises a substantially vertical reactor assembly equipped with at least one reactant inlet disposed below a reaction mixture outlet.
  • the preferred reactor assembly is equipped with two reactant inlets disposed substantially near the bottom of the reactor assembly and a single reaction mixture outlet disposed near the top of the reactor.
  • the reactor is equipped with an intensive mixing zone and an intermediate substantially quiescent zone between the mixing zone and the outlet.
  • the preferred reactor assembly further comprises a means to achieve turbulent mixing (e.g., an impeller or the like) disposed in the mixing zone at or near the reactant inlet(s) to achieve essentially complete axial mixing thereof, and a means to reduce any backmixing from the quiescent zone into the mixing zone.
  • Step (i) preferably comprises feeding to the mixing zone: a first feed comprising an aqueous solution of the metal silicate and the electrolyte; and a second feed comprising an aqueous solution of the acid and the electrolyte.
  • the aqueous solution in at least one, preferably both of, the first feed and the second feed comprises a brine solution.
  • the first feed and the second feed are continuously pumped into the reactor via their respective reactant inlets to provide a reaction mixture in the mixing zone.
  • the reaction mixture is subject to intense axial mixing.
  • the occurrence of vertical mixing in the reaction zone is preferably minimized or most preferably avoided by means as described in co-pending Canadian patent application CA 2,292,862.
  • the reaction mixture exits the mixing zone and rises toward the top of the reactor, into a substantially quiescent zone in a plug-flow manner.
  • the reaction mixture now in the form of a precipitated silica slurry, may then be transferred to a settling tank wherein the pH of the slurry is further adjusted, as necessary.
  • the silica particles may be allowed to settle to the bottom of the settling tank after which the mother liquor may be decanted.
  • the silica particles may be further filtered, washed and dried in a conventional manner.
  • the decanted aqueous silica slurry may be used directly in the above-mentioned hydrophobicizing reactions described in the Bayer patent applications - i.e., without the need to filter and dry the silica particles.
  • the decantate which consists of the electrolyte and by-product salts may be recycled.
  • a silicate solution was prepared by dissolving sodium silicate [Na ⁇ SiO ⁇ j 25 ] (28.93 kg) in water (163.5 kg). The ingredients were stirred and heated to 40°C, as required, to produce an aqueous solution of sodium silicate. Thereafter, rock salt (5.13 kg) was added with stirring to the aqueous solution of sodium silicate until all solids had dissolved to produce a brine solution of sodium silicate.
  • An acid solution was prepared by slowly adding with stirring concentrated hydrochloric acid (17.2 kg; 36-38wt% HC1) to tap water (152.8 kg). Thereafter, rock salt (5.13 kg) was added with continued stirring until all solids had dissolved.
  • the silicate solution and the acid solution were independently fed by means of pumps to a reactor shown schematically in Figure 3.
  • the feed rate for each solution was adjusted by means of flow controllers and metered so as to provide a feed rate of 1 to 2 litres per minute for each solution.
  • the solutions were independently fed to the bottom of the reactor assembly where they were intensively axially mixed in a mixing zone. With continued pumping of each solution to the mixing zone, the reaction mixture flowed into a quiescent zone and thence though an outlet into an overflow tank. The pH at the outlet was maintained at 7.3 by adjusting the flow of acid to the acid inlet at the bottom of the reactor assembly. The product exiting the reactor assembly via the overflow was stored in a collection tank. Total residence time in the reactor assembly was between 10 and 25 minutes.
  • a sample of the silica slurry produced in this Example was filtered, washed and then adjusted with water to give a 2.5 wt. % slurry.
  • a 2.5 wt. % slurry of HiSilTM 233 (a commercially available particulate reinforcing silica material) was prepared by adding the dry material to water and shaking manually to disperse.
  • the particle size distribution (PSD) for each slurry was determined by means of laser light scattering using a Malvern MastersizerTM instrument and the manufacturer's directions. The results are illustrated in Figure 5 in terms of the volume average PSD and in Figure 4 as the number average PSD.
  • Figure 5 shows that the particle size distribution of the Example slurry is substantially narrower than that of the HiSilTM 233 slurry.
  • Figure 4 shows that the number average particle size of the Example slurry (1.45 ⁇ m) is much smaller than that of the HiSilTM 233 slurry (4.17 ⁇ m).
  • Example silica and HiSilTM 233 slurries were determined by the following protocol: Exactly 80 milliters of the slurry was placed into a 100 ml. beaker and a small stirring bar was introduced. The beaker was then placed on a magnetic stir plate and the sounding horn of a Branson Sonifier Model W-350 was immersed into the slurry to a depth of 4 cm. The magnetic stirrer was activated at a medium setting and the slurry was stirred for exactly 2 minutes. The sonifier was then activated at a setting of 140 Watts/cm on the dial over a period of 28 minutes.
  • the ratio of the peak height of the original agglomerate peak to the peak height of the decomposed agglomerates may be taken as an indication of dispersibility in rubber.
  • This ratio termed the WF coefficient, is 1.1 for the Example silica and 3.4 for the comparative silica, indicating that the agglomerates in the Example silica are much easier to break down mechanically than those in the comparative silica and the Example silica should thus disperse more readily during rubber mixing.
  • Figure 9 illustrates an electron microscope image of the HiSilTM 233 silica material
  • Figure 10 illustrates an electron microscope image of the Example silica material.
  • a comparison of these two Figures clearly illustrates that the Example silica material is made up of a number of similarly sized aggregate particles (i.e., a narrow PSD) while the comparative silica is made up of particles having a larger variety of particle sizes (i.e., a broad PSD).
  • the smaller average particle size for the Example silica is easily seen when compared to the HiSilTM 233.
  • the fractal nature of the aggregates in the Example silica are distinct from the angulated particles of HiSilTM 233.

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

Abstract

La présente invention concerne un processus continu permettant de produire une suspension épaisse de silice précipité. Dans ce processus, un composé de silice métallique aqueux, un acide et un électrolyte alimentent en continu une zone de mélange de façon à produire un mélange réactionnel. Ce mélange réactionnel est maintenu à une température inférieure à environ 100 °C dans une zone quiescente. Ce mélange réactionnel est continuellement retiré de cette zone quiescente. La suspension épaisse de silice précipité produite selon ce processus présente une répartition de calibre des particules relativement resserrée et elle peut être dispersée plus facilement que les matériaux de silice actuellement disponibles.
PCT/CA2000/001473 1999-12-22 2000-12-15 Processus de production d'une suspension epaisse de silice precipite avec repartition controlee du calibre des particules d'agregat WO2001046073A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU18482/01A AU1848201A (en) 1999-12-22 2000-12-15 Process for the production of a precipitated silica slurry with a controlled aggregate particle size distribution

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA2,292,819 1999-12-22
CA 2292819 CA2292819A1 (fr) 1999-12-22 1999-12-22 Procede de production d'une boue de silice precipitee ayant une distribution de tailles d'agregat controlee

Publications (1)

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WO2001046073A1 true WO2001046073A1 (fr) 2001-06-28

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AU (1) AU1848201A (fr)
CA (1) CA2292819A1 (fr)
WO (1) WO2001046073A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2038054B1 (fr) * 2006-06-23 2012-03-21 YARA International ASA Procédé de préparation de matériaux nanométriques solides par précipitation continue
US8609068B2 (en) 2010-02-24 2013-12-17 J.M. Huber Corporation Continuous silica production process and silica product prepared from same
US9028605B2 (en) 2011-02-25 2015-05-12 J.M. Huber Corporation Coating compositions comprising spheroid silica or silicate
US11873218B2 (en) 2018-03-02 2024-01-16 Pörner Ingenieurgesellschaft M.B.H. Sustainable silicates and methods for their extraction

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1054175A (fr) * 1950-12-02 1954-02-09 Degussa Procédé pour la préparation d'acide silicique très divise
FR1450709A (fr) * 1965-07-09 1966-06-24 Pechiney Saint Gobain Procédé continu de fabrication de silice précipitée
GB1150135A (en) * 1967-07-17 1969-04-30 Oliver Wallis Burke Jr Silica pigments and process for producing same.
US3482937A (en) * 1965-10-20 1969-12-09 Degussa Method of preparing siliceous pigments
US4001379A (en) * 1968-04-27 1977-01-04 Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler Process of making superfine amorphous high structural silicic acid
EP0170579A1 (fr) * 1984-07-11 1986-02-05 Rhone-Poulenc Chimie Silice à prise d'huile élevée et à structure primaire controlée et procédé pour son obtention
EP0704407A1 (fr) * 1994-09-26 1996-04-03 Nippon Paper Industries Co., Ltd. Procédé de préparation d'hydrate d'acide silicique

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1054175A (fr) * 1950-12-02 1954-02-09 Degussa Procédé pour la préparation d'acide silicique très divise
FR1450709A (fr) * 1965-07-09 1966-06-24 Pechiney Saint Gobain Procédé continu de fabrication de silice précipitée
US3482937A (en) * 1965-10-20 1969-12-09 Degussa Method of preparing siliceous pigments
GB1150135A (en) * 1967-07-17 1969-04-30 Oliver Wallis Burke Jr Silica pigments and process for producing same.
US4001379A (en) * 1968-04-27 1977-01-04 Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler Process of making superfine amorphous high structural silicic acid
EP0170579A1 (fr) * 1984-07-11 1986-02-05 Rhone-Poulenc Chimie Silice à prise d'huile élevée et à structure primaire controlée et procédé pour son obtention
EP0704407A1 (fr) * 1994-09-26 1996-04-03 Nippon Paper Industries Co., Ltd. Procédé de préparation d'hydrate d'acide silicique

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2038054B1 (fr) * 2006-06-23 2012-03-21 YARA International ASA Procédé de préparation de matériaux nanométriques solides par précipitation continue
US8609068B2 (en) 2010-02-24 2013-12-17 J.M. Huber Corporation Continuous silica production process and silica product prepared from same
US8945517B2 (en) 2010-02-24 2015-02-03 J. M. Huber Corporation Continuous silica production process and silica product prepared from same
US9327988B2 (en) 2010-02-24 2016-05-03 J.M. Huber Corporation Continuous silica production process and silica product prepared from same
US9617162B2 (en) 2010-02-24 2017-04-11 J.M. Huber Corporation Continuous silica production process and silica product prepared from same
US9028605B2 (en) 2011-02-25 2015-05-12 J.M. Huber Corporation Coating compositions comprising spheroid silica or silicate
US11873218B2 (en) 2018-03-02 2024-01-16 Pörner Ingenieurgesellschaft M.B.H. Sustainable silicates and methods for their extraction

Also Published As

Publication number Publication date
CA2292819A1 (fr) 2001-06-22
AU1848201A (en) 2001-07-03

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