Patent Application
20060229386
The present invention is related to treated filler and processes by which it can be produced. Untreated filler slurry can be treated with a treating material and then subjected to conventional drying method(s), to produce the treated filler of the invention. Treated filler has a wide variety of applications including but not limited to battery separators and rubber compositions such as tires.
For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
The present invention includes a process for producing treated filler which comprises treating a slurry comprising untreated filler wherein said untreated filler has not been previously dried, with a treating material chosen from cationic, anionic, nonionic and amphoteric surfactants and mixtures thereof, wherein the treating material is present in an amount of from greater than 1% to 25% by weight of untreated filler, to produce a treated filler slurry; and drying the treated filler slurry using conventional drying techniques.
As used herein and the claims in reference to filler (i.e., treated and/or untreated), the term “not been previously dried” means filler that has not been dried to a moisture content of less than 20 percent by weight. In a non-limiting embodiment, untrreated filler for use in the present invention does not include filler that has been previously dried to a moisture content of less than 20 percent by weight. In another non-limiting embodiment, untreated filler for use in the present invention does not include filler that has been previously dried to a moisture content of less than 20 percent by weight and rehydrated.
As used herein and the claims, the term “filler” means an inorganic oxide that can be used in a polymer to essentially improve at least one property of said polymer, such as but not limited to modulus and tensile strength. As used herein and the claims, the term “untreated filler” means a filler that has not been treated with a treating material comprising cationic, anionic, nonionic and amphoteric surfactants and mixtures thereof in an amount of greater than 1% by weight of the filler. As used herein and the claims, the term “slurry” means a mixture including at least filler and water.
In the present invention, alkali metal silicate can be combined with acid to form untreated filler slurry; the untreated filler slurry can be treated with a treating material to produce treated filler slurry; and the treated filler slurry then can be dried using conventional drying techniques known in the art to produce the treated filler of the present invention. In a non-limiting embodiment, untreated filler slurry can include untreated filler that has not been previously dried. In still another non-limiting embodiment, untreated filler slurry can include untreated filler that has not been previously dried and then rehydrated.
Suitable untreated fillers for use in preparing the treated filler of the present invention can include a wide variety of materials known to one having ordinary skill in the art. Non-limiting examples can include inorganic oxides such as inorganic particulate and amorphous solid materials which possess either oxygen (chemisorbed or covalently bonded) or hydroxyl (bound or free) at an exposed surface, such as but not limited to oxides of the metals in Periods 2, 3, 4, 5 and 6 of Groups lb, IIb, IIIa, IIIb, IVa, IVb (except carbon), Va, VIa, VIla and VIII of the Periodic Table of the Elements in Advanced Inorganic Chemistry: A Comprehensive Text by F. Albert Cotton et al, Fourth Edition, John Wiley and Sons, 1980. Non-limiting examples of suitable inorganic oxides can include but are not limited to aluminum silicates, silica such as silica gel, colloidal silica, precipitated silica, and mixtures thereof.
In a non-limiting embodiment, the inorganic oxide can be silica. In alternate non-limiting embodiments, the silica can be precipitated silica, colloidal silica and mixtures thereof. In further alternate non-limiting embodiments, the silica can have an average ultimate particle size of less than 0.1 micron, or greater than 0.001 micron, or from 0.01 to 0.05 micron, or from 0.015 to 0.02 micron, as measured by electron microscope. In alternate non-limiting embodiments, the silica can have a surface area of from 25 to 1000 square meters per gram, or from 75 to 250 square meters per gram, or from 100 to 200 square meters per gram. The surface area can be measured using conventional techniques known in the art. As used herein and the claims, the surface area is determined by the Brunauer, Emmett, and Teller (BET) method in accordance with ASTM D1993-91. The BET surface area can be determined by fitting five relative-pressure points from a nitrogen sorption isotherm measurement made with a Micromeritics TriStar 3000™ instrument. A FlowPrep-060™ station provides heat and a continuous gas flow to prepare samples for analysis. Prior to nitrogen sorption, the silica samples are dried by heating to a temperature of 160° C. in flowing nitrogen (P5 grade) for at least one (1) hour.
The untreated filler for use in the present invention can be prepared using a variety of methods known to those having ordinary skill in the art. In a non-limiting embodiment, silica for use as untreated filler can be prepared by combining an aqueous solution of soluble metal silicate with acid to form a silica slurry; the silica slurry can be optionally aged; acid or base can be added to the optional aged silica slurry; the silica slurry can be filtered, optionally washed, and then dried using conventional techniques known to a skilled artisan.
Suitable metal silicates can include a wide variety of materials known in the art. Non-limiting examples can include but are not limited to alumina, lithium, sodium, potassium silicate, and mixtures thereof. In alternate non-limiting embodiments, the metal silicate can be represented by the following structural formula: M2O(SiO2)x wherein M can be alumina, lithium, sodium or, potassium, and x can be an integer from 2 to 4.
Suitable acids can be selected from a wide variety of acids known in the art. Non-limiting examples can include but are not limited to mineral acids, organic acids, carbon dioxide and mixtures thereof.
Silica slurry formed by combining metal silicate and acid can be treated with a treating material. Suitable treating materials for use in the present invention can include cationic, anionic, nonionic and amphoteric surfactants, and mixtures thereof.
Non-limiting examples of cationic surfactants can include but are not limited to quarternary ammonium surfactants of the general formula,
RN+(R′)(R″)(R′″)X−
wherein R can represent a straight chain or branched C6 to C22 alkyl; R′, R″ and R′″ can each independently represent H or C1 to C4 alkyl, and X can represent OH, Cl, Br, I, or HSO4.
In alternate non-limiting embodiments, the cationic surfactant can be selected from octadecyltrimethylammonium bromide, dodecylethyldimethylammonium bromide, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, nonylphenyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecylethyldimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, nonylphenyltrimethylammonium chloride, and mixtures thereof.
Non-limiting examples of anionic surfactants can include but are not limited to fatty acids and salts of fatty acids that can be substantially soluble or substantially emulsifiable in water having the general formula,
Z+-O−—CO—R,
wherein Z can represent H, Na, K, Li or NH4, and R can represent straight chain or branched C5 to C22 alkyl; alkyl sarcosinic acids and salts of alkyl sarcosinic acids having the general formula,
Z+-O−—CO—CH2—NC—CO—R,
wherein Z can represent H, Na, K, Li or NH4; and R can represent straight chain or branched C5 to C22 alkyl.
Further non-limiting examples of suitable anionic surfactants for use in the present invention can include sodium stearate, ammonium stearate, ammonium cocoate, sodium laurate, sodium cocyl sarcosinate, sodium lauroyl sarcosinate, sodium soap of tallow, sodium soap of coconut, sodium myristoyl sarcosinate, stearoyl sarcosine acid, and mixtures thereof.
Non-limiting examples of amphoteric surfactants can include but are not limited to amphoacetate glycines having the following general formula,
wherein R can represent straight chain or branched C5 to C22 alkyl; alkyl betaines having the following general formula,
wherein R can represent straight chain or branched C5 to C22 alkyl; alkylamido betaines having the following general formula,
wherein R can represent straight chain or branched C5 to C22 alkyl; sulfo-betaines having the following general formula,
wherein R can represent straight chain or branched C5 to C22 alkyl; phospho-betaines having the following general formula,
wherein R can represent straight chain or branched C5 to C22 alkyl; amphopropionates having the following general formula,
RN+H2CH2CH2COO−
wherein R can represent straight chain or branched C5 to C22 alkyl; and mixtures thereof.
In alternate non-limiting embodiments, the amphoteric surfactant can be chosen from 3-(decyldimethylammonio)propanesulfonate inner salt, 3-(dodecyldimethylammonio)propanesulfonate inner salt, 3-(N,N-dimethylmyristylammonio)propanesulfonate, 3-(N,N-dimethyloctadecylammonio)propanesulfonate, 3-(N,N-dimethyloctadecylammonio)propanesulfonate inner salt, 3-(N,N-dimethylpalmitcylammonio)propanesulfonate, and mixtures thereof.
Non-limiting examples of nonionic surfactants for use in the present invention can include but are not limited to polyethylene oxide alkyl ethers wherein the alkyl group can be straight chain or branched having a chain length of from C6 to C22; polyethylene oxide alkyl esters wherein the alkyl group can be straight chain or branched having a chain length of from C6 to C22; organic amines with straight or branched carbon chains from C6 to C22 having the general formula RN R′R″ wherein R can be from C8 to C22 alkyl and, R′ and R″ can each independently be H or C1 to C4 alkyl such that the molecule can be substantially soluble or substantially emulsifiable in water, such as but not limited to octadecylamine; tertiary amines with carbon chains from C6 to C22; polyethyleneimines; polyacrylamides; glycols and alcohols with straight chain or branched alkyl from C6 to C22 that can form ester linkage (—SiOC—), polyvinyl alcohol; and mixtures thereof.
In alternate non-limiting embodiments the nonionic surfactant can be chosen from polyethylene oxide ethers such as but not limited to hexaethylene glycol monododecylether, hexaethylene glycol monohexadecylether, hexaethylene glycol monotetradecylether, hexaethylene glycol monooctadecylether, heptaethylene glycol monododecylether, heptaethylene glycol monohexadecylether, heptaethylene glycol monotetradecylether, heptaethylene glycol monooctadecylether, nonaethylene glycol monododecylether, octaethylene glycol monododecylether; polyethylene oxide esters such as but not limited to hexaethylene glycol monododecylester, hexaethylene glycol monohexadecylester, hexaethylene glycol monotetradecylester, hexaethylene glycol monooctadecylester, heptaethylene glycol monododecylester, heptaethylene glycol monohexadecylester, heptaethylene glycol monotetradecylester, heptaethylene glycol monooctadecylester, nonaethylene glycol monododecylester, octaethylene glycol monododecylester; polysorbate esters such as polyoxyethylene sorbitan mono fatty acid esters including but not limited to polyoxyethylene sorbitan mono palmitate, polyoxyethylene sorbitan mono oleate, polyoxyethylene sorbitan mono stearate, polyoxyethylene sorbitan difatty acid esters such as polyoxyethylene sorbitan dipalmitate, polyoxyethylene sorbitan dioleate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan monopalmitate monooleate, polyoxyethylene sorbitan tri fatty acid esters such as but not limited to polyoxyethylene sorbitan tristearate; and mixtures thereof.
In alternate non-limiting embodiments, the treating material can have a molecular weight of less than 10000 grams/mole, or less than 5000, or less than 2000, or less than 1000, or greater than 100.
The amount of treating material used in the present invention can vary widely and can depend upon the particular treating material selected. In alternate non-limiting embodiments, the amount of treating material can be greater than 1% based on the weight of untreated filler, or from 1.1% to 25%, or from 1.2% to 20%, or from 2% to 15%.
In the present invention, untreated filler can be treated at various stages throughout the preparation process. In a non-limiting embodiment of the present invention, treatment of untreated filler slurry with a treating material cannot occur prior to initial formation of the untreated filler. In another non-limiting embodiment, treatment of untreated filler slurry with treating material can occur essentially immediately following initial formation of the untreated filler. In still another non-limiting embodiment, treatment of the untreated filler slurry with treating material can occur at any time following initial formation of untreated filler and prior to drying. In general, the initial formation of filler can be observed and/or determined by various conventional methods known in the art. In a non-limiting embodiment, initial formation of filler can occur essentially immediately upon addition of acid to alkali metal silicate solution. In another non-limiting embodiment, initial formation of filler can occur when particle(s) of 5 nm or greater are present. In still another non-limiting embodiment, initial formation of filler can be determined by measuring particle size using known light scattering techniques. In a further non-limiting embodiment, laser light scattering can be used to determine the initial formation of filler by the presence of particle(s) having diameter(s) greater than 40 nm.
In a non-limiting embodiment of the present invention, treatment of the untreated filler slurry with a treating material can occur prior to drying the filler slurry.
In alternate non-limiting embodiments, treating material can be added essentially simultaneously with acid or immediately following acid addition to the alkali metal silicate solution. In further alternate non-limiting embodiments, treating material may not be present in the alkali metal silicate solution prior to initial. formation of untreated filler or the initial addition of acid. In still another non-limiting embodiment, treatment of untreated filler slurry with a treating material can occur at a time such that templated mesoporous structures are not present. Templated mesoporous structures can result from a process whereby a network is formed around a template molecule in such a way that the removal of the template molecule creates a mesoporous structure with morphological and/or stereochemical features related to those of the template molecule. Such process is described in “Template Based Approaches to the Preparation of Amorphous, Nanoporous Silicas”, Chemistry of Materials, (August 1996) Vol. 8, No. 8, pg. 1682, which is incorporated herein by reference.
In a non-limiting embodiment, the treated filler of the present invention can be prepared in accordance with the following process.
Silica slurry can be prepared by combining alkali metal silicate with acid. A solid form of alkali metal silicate can be dissolved in water to produce an “additive” solution. In another non-limiting embodiment, the “additive” solution can be prepared by diluting a concentrated solution of an aqueous alkali metal silicate to a desired concentration of alkali metal. Herein, the weight amount of alkali metal is reported as “M2O”. In alternate non-limiting embodiments, the “additive” solution can contain from 1 to 50 weight percent Sio2, or from 10 to 25 weight percent, or from 15 to 20 weight percent. In further alternate non-limiting embodiments, the “additive” solution can have a SiO2:M2O molar ratio of from 0.1 to 3.9, or from 2.9 to 3.5, or from 3.1 to 3.4.
A portion of the “additive” aqueous alkali metal silicate solution can be diluted with water to prepare an “initial” aqueous alkali metal silicate solution. In alternate non-limiting embodiments, this “initial” solution can contain from 0.1 to 20 weight percent SiO2, or from 0.2 to 15 weight percent, or from 0.3 to 10 weight percent. In further alternate non-limiting embodiments, this “initial” solution can have a SiO2:M2O molar ratio of from 0.1 to 3.9, or from 1.6 to 3.9, or from 2.9 to 3.5, or from 3.1 to 3.4.
In a non-limiting embodiment, this “initial” silicate solution can contain an alkali metal salt of a strong acid. Non-limiting examples of suitable salts can include but are not limited to sodium chloride, sodium sulphate, potassium sulphate or potassium chloride, and other like essentially neutral salts. In a non-limiting embodiment, the amount of salt added can be from 5 to 80 grams per liter. In another non-limiting embodiment, wherein the rate of addition of acid can be greater than 30 minutes, the amount of alkali metal salt can be in the range of 5 to 50 grams per liter.
Acid can be added with agitation to the “initial” aqueous alkali metal silicate solution to neutralize the M2O present to form a first silica slurry. In alternate non-limiting embodiments, at least 10 percent of the M2O present in the “initial” aqueous alkali metal silicate solution can be neutralized, or from 20 to 50 percent, or as much as 100 percent. The percent neutralization can be calculated using conventional techniques known in the art. In a non-limiting embodiment, the percent neutralization can be calculated by assuming that one (1) equivalent of strong acid neutralizes one (1) equivalent of M2O. For example, 1 mole (2 equivalents) of sulfuric acid can neutralize 1 mole (2 equivalents) of M2O. Further, the pH of the reaction mixture can vary. In alternate non-limiting embodiments, the pH can be adjusted to less than 9.5, or greater than 2.6, or less than 9.0, or 8.5 or less. The pH can be measured using various conventional techniques known to a skilled artisan. The pH values recorded herein and the claims are measured in accordance with the procedure described in the Examples section herein.
In general, both the time period during which the acid is added to the solution and the temperature of the reaction mixture during acid addition can vary widely. In alternate non-limiting embodiments, the acid can be added over a time period of at least ten (10) minutes, or less than six hours, or from 0.5 hours to 5 hours, or from 2 hours to 4 hours. In alternate non-limiting embodiments, the temperature of the reaction mixture during the acid addition can be at least 20° C., or less than 100° C., or from 30° C. to 100° C., or from 40° C. to 88° C.
Suitable acids for neutralization can vary widely. The selection of acid can depend on both the rate at which the acid is added to the solution and the temperature of the solution during acid addition. In general, suitable acids can include any acid or acidic material that can be substantially water-soluble and can react with alkali metal silicate to neutralize the alkali thereof. Non-limiting examples can include but are not limited to mineral acids and their acidic salts, such as hydrochloric acid, sulfuric acid, phosphoric acid, sulfurous acid, nitric acid, formic acid, acetic acid, and mixtures thereof. In a non-limiting embodiment, sulfuric acid can be used.
In a non-limiting embodiment, weak gaseous acid can be used to neutralize the alkali metal silicate solution. Non-limiting examples of such gaseous acids can include but are not limited to carbon dioxide, sulfur dioxide, hydrogen sulfide, chlorine and mixtures thereof. In a non-limiting embodiment, carbon dioxide can be used.
In a non-limiting embodiment, the first silica slurry can be allowed to decant for a period of time. The amount of time can vary widely. In alternate non-limiting embodiments, the time period can be from 0.5 to 50 hours, or from 5 to 36 hours, or from 12 to 24 hours. In a non-limiting embodiment, the first silica slurry can be washed during decantation to remove salts in the first silica slurry.
In a non-limiting embodiment, treating material can be added to the first silica slurry. In alternate non-limiting embodiments, treating material can be added prior to decantation, during decantation or following decantation to produce treated silica slurry.
In a further non-limiting embodiment, the washing can be accomplished by diluting the first silica slurry with water to form a second silica slurry. In general, the amount of water used can vary widely. In alternate non-limiting embodiments, the amount of water added can be sufficient to reduce the concentration of silica in the solution such that the second silica slurry can contain less than 15 weight percent SiO2, or less than 10 weight percent, or from 0.5 to 8 weight percent, or from I to 7 weight percent. In further alternate non-limiting embodiments, the amount of water added can be sufficient to reduce the concentration of salt in the solution such that the second silica slurry can contain less than 10 weight percent of salt, or less than 5 weight percent, or from 0.1 to 3 weight percent, or from 0.3 to 1 weight percent.
In a non-limiting embodiment, flocculant can be added to the second silica slurry. Suitable flocculants for use in the present invention can be selected from a wide variety of materials known in the art. In a non-limiting example, the flocculant can be cationic flocculant such as but not limited to polydimethyldiallylammonium chloride. The amount of flocculants added can vary widely. In alternate non-limiting embodiments, the flocculant can be present in amount of from 0.005 to 0.5% by weight of the silica in the second silica slurry, or from 0.05 to 0.25% by weight, or from 0.1 to 0.2% by weight.
In further non-limiting embodiments, the dilution step can be repeated at least one subsequent time.
The temperature of the second silica slurry can vary. In alternate non-limiting embodiments, it can be at least 25° C., or from 45° C. to 97° C.
In a non-limiting embodiment, treating material can be added to the second silica slurry to produce treated silica slurry. In further alternate non-limiting embodiments, treating material can be added prior to adding flocculant, essentially simultaneously with the addition of flocculant, or following addition of flocculant.
In a non-limiting embodiment, another portion of the “additive” aqueous alkali metal silicate solution and acid can be added to the second silica slurry over a period of time to form a third silica slurry. In a non-limiting embodiment, the “additive” solution and acid are added simultaneously to the second silica slurry. In alternate non-limiting embodiments, the addition can be completed in a period of from 5 to 400 minutes, or from 30 to 360 minutes, or from 45 to 240 minutes. The amount of “additive” solution used can vary. In alternate non-limiting embodiments, the amount of “additive” solution can be such that the amount of SiO2 added can be from 0.1 to 50 times the amount of SiO2 present in the “initial” aqueous alkali metal silicate solution, or from 0.5 to 30 times. Suitable acids for use in this neutralization step can vary widely. As aforementioned, the acid can be strong enough to neutralize the alkali metal silicate. Non-limiting examples of such acids can include those previously disclosed herein. Further, the amount of acid or acidic material used can vary.
In alternate non-limiting embodiments, the amount of acid added can be such that at least 20 percent of the M2O contained in the “additive” solution added during the addition can be neutralized, or at least 50 percent, or 100 percent of the M2O.
In alternate non-limiting embodiments, the pH can be maintained at less than 10, or less than 9.5, or 9.0 or less than 8.5.
In a non-limiting embodiment, the third silica slurry can be allowed to decant for a period of time. In a further non-limiting embodiment, water can be added to dilute the third slurry. The decanting and diluting steps as previously described herein for the second silica slurry are applicable to the third silica slurry.
In a non-limiting embodiment, treating material can be added to the third silica slurry to produce treated silica slurry. In further non-limiting embodiments, treating material can be added prior to, during or following decantation.
In alternate non-limiting embodiments of the present invention, the first, second, third or subsequent silica slurry can be treated with treating material chosen from those previously recited herein, in an amount chosen from the ranges previously disclosed herein. In further alternate non-limiting embodiments, the treating material can be added during or after subsequent filtering, or washing steps of the first, second, third or subsequent silica slurry produced in the foregoing process description.
Following treatment, acid then can be added to the treated silica slurry with agitation to adjust the pH of the treated silica slurry. In alternate non-limiting embodiments, the amount of acid added can be such that the pH can be less than 7.0 or greater than 2.6, or from 3.0 to 6.0, or from 4 to 5. Acids suitable for use in this step can vary widely. As stated previously, the acid generally can be strong enough to reduce the pH of the mixture to within the above-disclosed ranges Non-limiting examples of such acids can include those previously disclosed herein.
In another non-limiting embodiment, the treated filler of the present invention can be prepared in accordance with the following process. An “additive” solution and an “initial” solution can be prepared as described in the process above. Further, acid can be added to the “initial” aqueous alkali metal silicate solution as described above to at least partially neutralize the M2O present to form a first silica slurry. The “initial” solution, with or without the addition of acid, is referred to as the “precipitation heel”. In a non-limiting embodiment, the precipitation heel contains no alkali metal silicate. The temperature of the precipitation heel can vary. In alternate non-limiting embodiments, the temperature can be from 20° to boiling point of the slurry, or from 25° to 100° C., or from 30° to 98° C.
Following formation of the “precipitation heel”, a simultaneous addition step can begin wherein aqueous metal silicate and acid can be added essentially simultaneously to the “precipitation heel”. The resultant slurry is referred to as the “simultaneous addition slurry”. The time to complete the simultaneous addition step can vary with the amount of reactants added. In alternate non-limiting embodiments, the time period can be from 10-360 minutes, or from 20-240 minutes, or from 30-180 minutes. The aqueous metal silicate can be chosen from a wide variety of silicates. In a non-limiting embodiment, the silicate used in the simultaneous addition step can be the same as the initial silicate. In alternate non-limiting embodiments, the amount of metal silicate added during the simultaneous addition step can be from 1 to 100 times the amount added during the precipitation heel formation step, or from 2 to 50 times, or from 3 to 30 times.
In another non-limiting embodiment, wherein no aqueous alkali metal silicate solution is present in the precipitation heel, the amount of metal silicate added during the simultaneous addition step can be such that a target silica concentration is reached at the end of the simultaneous addition step. In alternate non-limiting embodiments, the target silica concentration can be from 1 to 150 g/l, or from 10 to 120 g/l, or from 50 to 100 g/l.
In alternate non-limiting embodiments, during the simultaneous addition step, acid can be added in an amount such that a desired concentration of unreacted metal oxide is maintained, or a desired pH level is maintained, or a desired change in metal oxide concentration or pH level vs. time is maintained throughout the simultaneous addition step. In a further non-limiting embodiment, acid can be added during the simultaneous addition step at a rate such that the amount of unreacted metal oxide concentration calculated in the “simultaneous addition slurry” is essentially the same as the amount of unreacted metal oxide concentration measured in the “precipitation heel”. In further alternate non-limiting embodiments, the pH target for the “simultaneous addition slurry” can be at least 6, or not greater than 12, or from 7 to 10. In a non-limiting embodiment, during the simultaneous addition step, the metal silicate flow and acid flow can be initiated at substantially the same time. In alternate non-limiting embodiments, one of the acid flow or the metal silicate flow can begin first to achieve a target pH prior to adding both acid and metal silicate substantially simultaneously. The pH can be measured using various conventional techniques known to a skilled artisan. The pH values recorded herein and the claims are measured in accordance with the procedure described in the Examples section herein.
The temperature of the simultaneous addition step can vary within ranges previously identified herein for the precipitation heel formation step. In a non-limiting embodiment, the temperature can be essentially the same as for the precipitation heel formation step. In another non-limiting embodiment, the target temperature can be different from the precipitation heel formation step.
In a non-limiting embodiment, treating material can be added to the silica slurry during the simultaneous addition step to produce treated silica slurry.
In a non-limiting embodiment, the reactant flows can be stopped and the simultaneous addition slurry allowed to age. The age step can be implemented at any time during the simultaneous addition step. The temperature and time of the age step can vary widely. In alternate non-limiting embodiments, the time period can be from 1 minute to 24 hours, or from 3 hours to 8 hours, or from 10 minutes to 1 hour. In alternate non-limiting embodiments, the temperature of the simultaneous addition slurry can be from 20° to the boiling point of the slurry, or from 40° to 100° C.
In a non-limiting embodiment, essentially all of the aqueous metal silicate can be added during the precipitation heel formation step and acid only can be added during the simultaneous addition step. In this embodiment, an essentially constant unreacted metal oxide concentration or pH may not be maintained during the simultaneous addition step.
The simultaneous addition step can be repeated subsequent times as desired. The resulting slurries can be called “second simultaneous addition slurry”, “third simultaneous addition slurry”, etc. In alternate non-limiting embodiments, the amounts of aqueous metal silicate and acid can be different from the initial simultaneous addition and can range from 0.1 to 100% of the material used in the first simultaneous addition.
In alternate non-limiting embodiments, treating material can be added during the second simultaneous addition slurry, or the third simultaneous addition slurry, or subsequent simultaneous addition slurry to produce treated silica slurry.
In an alternate non-limiting embodiment, following completion of the simultaneous addition step(s), a “post simultaneous addition age step” can be conducted.
In a non-limiting embodiment with post simultaneous addition aging, all reactant flows can be essentially stopped and the silica slurry, called “age slurry”, can be allowed to set and age. In alternate non-limiting embodiments, with post simultaneous addition aging, the acid and/or metal silicate can be allowed to continue to flow into the age slurry until a target age pH is achieved; all reactant flows then can be essentially stopped and the age slurry can be allowed to age, optionally under agitation for a period of time. The pH of the post simultaneous addition age step can vary widely. In alternate non-limiting embodiments, the pH of the post simultaneous age step can be essentially the same as the pH at the end of the simultaneous addition step, or the pH can be at least 6, or not greater than 10, or from 8 to 9. In alternate non-limiting embodiments, the age time can be from 5 minutes to several days, or from 15 minutes to 10 hours, or from 30 to 180 minutes. The age temperature can vary widely. In alternate non-limiting embodiments, the age temperature can be essentially the same as the temperature at the end of the simultaneous addition step, or the temperature can be higher than the temperature of the simultaneous addition step, or the temperature can be as high as the boiling point of the age slurry.
In a non-limiting embodiment, the age slurry can be treated with treating material to produce treated silica slurry.
At the end of the post simultaneous age step, or at the end of the simultaneous addition step where no post simultaneous addition age step was conducted, a final slurry pH adjustment step can take place. The slurry is referred to as the “pH adjustment slurry”. In a non-limiting embodiment, the temperature for the final pH adjustment can be essentially the same as the temperature at the end of the previous step; i.e., the simultaneous addition step or the post simultaneous addition age step. In another non-limiting embodiment, the temperature can be adjusted to a target temperature which can vary. In alternate non-limiting embodiments, the temperature can be from 40° C. to boiling point, or from 60° C. to 100° C. In alternate non-limiting embodiments, the final pH adjustment can include adding acid, metal silicate or base to the pH adjustment slurry in an amount such that a target pH is reached. When the target pH value is reached, the slurry is referred to as the “final pH adjusted slurry”. The pH target for the final pH adjusted slurry can vary widely. In alternate non-limiting embodiments, the pH target can be essentially the same as the post simultaneous aging pH, or at least 2, or not greater than 9, or from 3 to 7, or from 4 to 6.
Suitable acids for neutralization in the above-described steps can vary widely. The selection of acid can depend on the rate at which the acid is added to the solution and the temperature of the solution during acid addition. Suitable acids can include any acid or acidic material that can be essentially water soluble and can react with alkali metal silicate to neutralize the alkali thereof. Non-limiting examples can include but are not limited to mineral acids and their acidic salts, such as hydrochloric acid, sulfuric acid, phosphoric acid, sulfurous acid, nitric acid, formic acid, acetic acid. In a non-limiting embodiment, sulfuric acid can be used.
In a non-limiting embodiment, the pH adjustment slurry can be treated with treating material to produce treated silica slurry.
In another non-limiting embodiment, flocculant can be added to the post simultaneous addition age slurry. Suitable flocculants and the amount added can be selected from those previously described herein.
In alternate non-limiting embodiments of the present invention, silica slurry from the simultaneous addition step, the post simultaneous age step, the pH adjustment step or the final pH adjusted slurry step can be treated with treating material chosen from those previously recited herein, in an amount chosen from the ranges previously disclosed herein. In further alternate non-limiting embodiments, the treating material can be added during or after subsequent filtering, or washing steps of the silica slurry from the simultaneous addition step, the post simultaneous age step, the pH adjustment step and the final pH adjusted slurry step.
In general, for the silica preparation methods described above, the degree of agitation used in the various steps can vary considerably. The agitation employed during the addition of one or more reactants should be at least sufficient to provide a thorough dispersion of the reactants and reaction mixture so as to minimize or essentially preclude more than trivial locally high concentrations of reactants and to ensure that silica deposition occurs substantially uniformly.
For the silica preparation methods described above, the silica slurry can be separated using conventional techniques to substantially separate solids from at least a portion of the liquid. Non-limiting examples of separation techniques can include but are not limited to filtration, centrifugation, decantation, and the like.
In a non-limiting embodiment, following separation, the silica slurry can be washed using a variety of known procedures for washing solids. In a further non-limiting embodiment, water can be passed through a filtercake of treated or untreated silica slurry. In alternate non-limiting embodiments, one or more washing cycles can be employed as desired. A purpose of washing the silica slurry can be to remove salt formed by the neutralization step(s) to desirably low levels. The separation and wash steps can be conducted a number of successive times until the salt is substantially removed. In alternate non-limiting embodiments, the treated or untreated silica slurry can be washed such that the concentration of salt in the dried treated filler is less than or equal to 2 weight percent, or less than or equal to 1 weight percent.
In general, filler slurry can be dried using one or more techniques known to a skilled artisan. Non-limiting examples can include but are not limited to drying the silica slurry in an air oven, vacuum oven, rotary dryer, or spray drying in a column of hot air, or spin flash dryer. Examples of spray dryers can include rotary atomizers and nozzle spray dryers. The temperature at which drying is accomplished can vary widely. In a non-limiting embodiment, the drying temperature can be below the fusion temperature of the treated filler. In further alternate non-limiting embodiments, the drying temperature can be less than 700° C. or greater than 100° C., or from 200° C. to 500° C., or from 100° C. to 350° C. In alternate non-limiting embodiments, the drying process can continue until the treated filler has properties characteristic of a powder or a pellet.
In a non-limiting embodiment of the present invention, untreated filler slurry can be treated with treating material prior to initiating the foregoing drying process.
Following drying, the treated filler can contain water of hydration. The amount of water present in the treated filler can vary. In alternate non-limiting embodiments, the water can be present in an amount of from 0.5% to 20% by weight of the treated filler. At least a portion of this water can be free water. As used herein and the claims, “free water” means that water which can be at least partially driven-off by drying at a temperature from 100° C. to 200° C. In a non-limiting embodiment, free water can constitute from 1% to 10% by weight of the water present in the treated filler. In another non-limiting embodiment, free water can be at least partially driven-off by heating the treated filler for at least 24 hours at a temperature of at least 105° C. As used herein and the claims, any water remaining in the treated filler after such drying process(es), can be referred to as “bound water”. In a non-limiting embodiment, bound water can be at least partially removed by additional heating of the treated filler at calcination temperatures, such as for example, from 1000 to 1200° C. In alternate non-limiting embodiments, bound water can constitute from 2 to 10% by weight, or from 6 to 8% by weight of treated filler.
In a non-limiting embodiment, the treated filler of the present invention can be subjected to conventional size reduction techniques. Such techniques are known in the art and may be exemplified by grinding and pulverizing. In a further non-limiting embodiment, fluid energy milling using air or superheated steam as the working fluid can be employed. Fluid energy mills are known in the art. In a non-limiting embodiment, in fluid energy mills the solid particles can be suspended in a gas stream and conveyed at high velocity in a circular or elliptical path. Some reduction occurs when the particles strike or rub against the walls of the confining chamber, but a significant portion of the reduction is believed to be caused by interparticle attrition.
In another non-limiting embodiment, the treated filler of the present invention can be modified with one or more materials that coat, partially coat, impregnate, and/or partially impregnate the filler. A wide variety of known materials can be used for this purpose. In general, the type of material used depends upon the effect desired. Non-limiting examples of such materials suitable for use can include but are not limited to organic polymers, such as but not limited to hydrocarbon oils, polyesters, polyamides, polyolefins, phenolic resins, aminoplast resins, polysiloxanes, polysilanes, and mixtures thereof. The modification step can be accomplished at essentially any time during or after formation of the treated filler.
The treated filler of the present invention can have a BET surface area that can vary widely. In alternate non-limiting embodiments, the BET surface area can be from 25 to 1000 m2/g, or from 75 to 250 m2/g. Further, the treated filler of the present invention can have a CTAB specific surface area that varies widely. In alternate non-limiting embodiments, the CTAB specific surface area can be from 5 to 750 m2/g, or from 25 to 500 m2/g, or from 75 to 250 m2/g. CTAB is a measure of the external surface area of the treated filler and can be determined using a variety of conventional methods known in the art. The CTAB values recited herein and the claims are measured in accordance with the French Standard Method (French Standard NFT 45-007, Primary Materials for the Rubber Industry: Precipitated Hydrated Silica, Section 5.12, Method A, pp. 64-71, November 1987) which measures the external specific surface area by determining the quantity of CTAB (CetylTrimethylAmmonium Bromide) before and after adsorption at a pH of from 9.0 to 9.5, using a solution of the anionic surfactant Aerosol OT® as the titrant. Unlike other known CTAB methods which use filtration to separate filler, the French Standard Method uses centrifugation. The quantity of CTAB adsorbed for a given weight of treated filler and the space occupied by the CTAB molecule are used to calculate the external specific surface area of the treated filler. The external specific surface area value is expressed in square meters per gram. The detailed procedure used to determine CTAB values recited herein and the claims is set forth in the Examples.
In a non-limiting embodiment of the present invention, the treated filler can have a lower BET surface area than a comparable filler without treatment. In another non-limiting embodiment, the treated filler of the present invention can have a BET surface area value lower than its CTAB surface area.
The present invention is more particularly described in the following examples, which are intended to be illustrative only, since numerous modifications and variations therein will be apparent to those skilled in the art. Unless otherwise specified, all parts and all percentages are by weight.
The following surface area method uses CTAB solution for analyzing the external specific surface area of treated filler according to this invention. The analysis was performed using a Metrohm 751 Titrino automatic titrator, equipped with a Metrohm Interchangeable “Snap-In” 50 milliliter buret and a Brinkmann Probe Colorimeter Model PC 910 equipped with a 550 nm filter. In addition, a Mettler Toledo HB43 or equivalent was used to determine the moisture loss of the filler and a Fisher Scientific Centrific™ Centrifuge Model 225 for separation of the filler and the residual CTAB solution. The excess CTAB was determined by auto titration with a solution of Aerosol OT® until maximum turbidity was attained which is detected with the probe calorimeter. The maximum turbidity point was taken as corresponding to a millivolt reading of 150. Knowing the quantity of CTAB adsorbed for a given weight of filler and the space occupied by the CTAB molecule, the external specific surface area of the treated filler is calculated and reported as square meters per gram on a dry-weight basis.
Solutions required for testing and preparation included a buffer of pH 9.6, hexadecyl-trimethylammonium bromide (CTAB), dioctyl sodium sulfosuccinate (Aerosol OT) and IN sodium hydroxide. The buffer solution of pH 9.6 was prepared by dissolving 3.101 g of orthoboric acid (99%; Fisher Scientific, Inc., technical grade, crystalline) in a one-liter volumetric flask, containing 500 milliliter of deionized water and 3.708g of potassium chloride solids (Fisher Scientific, Inc., technical grade, crystalline). Using a buret, 36.85 milliliter of the 1N sodium hydroxide solution was added. The solution was mixed and diluted to volume. The CTAB solution was prepared using 11.0 g±0.005 g of the powdered CTAB (cetyltrimethylammonium bromide, also known as hexadecyl-trimethylammonium bromide, Fisher Scientific Inc., technical grade) onto a weighing dish. The CTAB powder was transferred to a 2-liter beaker, rinsing the weighing dish with deionized water. Approximately 700 milliliter of the pH 9.6 buffer solution and 1000 milliliter of distilled or deionized water was added into the 2-liter beaker and stirred with a magnetic stir bar. A large watch glass was placed on the beaker and the beaker was stirred at room temperature until the CTAB was totally dissolved. The solution was transferred to a 2-liter volumetric flask rinsing the beaker and stir bar with deionized water. The bubbles were allowed to dissipate, and diluted to volume with deionized water. A large stir bar was added and mixed on a magnetic stirrer for approximately 10 hours. The CTAB solution can be used after 24 hours and for only 15 days. The Aerosol OT® (dioctyl sodium sulfosuccinate, Fisher Scientific Inc., 100% solid) solution was prepared using 3.46 g±0.005 g onto a weighing dish. The Aerosol OT was rinsed into a 2- liter beaker which contained about 1500 milliliter deionized water and a large stir bar. The Aerosol OT solution was dissolved and rinsed into a 2-liter volumetric flask. The solution was diluted to 2-liter volume mark in the volumetric flask. The Aerosol OT® solution was allowed to age for a minimum of 12 days prior to use. The Aerosol OT expires 2 months from preparation date.
Prior to surface area sample preparation, the pH of the CTAB solution was verified and adjusted to a pH of 9.6±0.1 using 1N sodium hydroxide solution. For test calculations a blank sample was prepared and analyzed. 5 milliliters CTAB solution was pipetted and 55 milliliters deionized water was added into a 150-milliliter beaker and analyzed on a Metrohm 751 Titrino automatic titrator. The automatic titrator was programmed for determination of the blank and the samples with following parameters: Measuring point density=2, Signal drift=20, Equilibrium time=20 seconds, Start volume=0 ml, Stop volume=35 ml, and Fixed endpoint=150 mV. The buret tip and the colorimeter probe were placed just below the surface of the solution, positioned such that the tip and the photo probe path length were completely submerged. Both the tip and photo probe were essentially equidistant from the bottom of the beaker and not touching one another. With minimum stirring (setting of 1 on the Metrohm 728 stirrer) the colorimeter was set to 100% T prior to every blank and sample determination and titration was initiated with the Aerosol OT® solution. The end point was recorded as the volume (ml) of titrant at 150 mV.
For test sample preparation, approximately 0.30 grams of powdered filler was weighed into a 50-milliliter container with a stir bar. Granulated filler samples, were riffled (prior to grinding and weighing) to obtain a representative sub-sample. A coffee mill style grinder was used to grind granulated materials. Then 30 milliliters of the pH adjusted CTAB solution was pipetted into the sample container with the 0.30 grams of powdered filler. The filler and CTAB solution was then mixed on a stirrer for 35 minutes. When mixing was completed, the filler and CTAB solution was centrifuged for 20 minutes to separate the filler and excess CTAB solution. When centrifuging was completed, the CTAB solution was pipetted into a clean container minus the separated solids, referred to as the “centrifugate”. For sample analysis, 50 milliliters of deionized water was placed into a 150-milliliter beaker with a stir bar. Then 10 milliliters of the sample centrifugate was pipetted for analysis into the same beaker. The sample was analyzed using the same technique and programmed procedure as used for the blank solution.
For determination of the moisture content, approximately 0.2 grams of silica was weighed onto the Mettler Toledo HB43 while determining the CTAB value. The moisture analyzer was programmed to 105° C. with the shut-off 5 drying criteria. The moisture loss was recorded to the nearest ±0.1%.
The external surface area was calculated using the following equation,
wherein,
In the following Examples, the Apparent Tamped Density (ATD) was measured in accordance with the Apparent Tamped Density Test Method in ISO 787/11, “General Method of Tests for Pigments and Extenders—Part 11: Determination of Tamped Volume and Apparent Density After Tamping”, First Edition, 1981-10-1, with the following exceptions: (1) the sample was not dried prior to measuring ATD, and (2) the sample was not sieved prior to measuring ATD.
In the Examples, BET surface area was measured in accordance with ASTM D 1993-91.
The pH of the filler slurry was measured using an Oakton pH 100 Series meter or an Orion Ross Combination pH Electrode with BNC connector manufactured by Thermo Electron Corporation and purchased from Fisher Scientific. The electrode in preparation for analysis has the electrode-fill hole open, and to maintain an adequate flow rate, Ross pH Electrode Fill solution (Orion product number 8100073) molar potassium chloride (KCl) solution was added to cover the end of the coil. The pH meter was prepared for analysis by recalibrating the meter with pH Buffers 4, 7 and 10 that are traceable to NIST or an equivalent agency. Prior to the reaction pH measurement, the temperature of the reaction was manually entered the into the Oakton pH meter. The electrode was rinsed with deionized water and immersed into the reaction mixture allowing 2 to 3 minutes for the electrode to come to equilibrium. The displayed pH value was recorded. The electrode was removed and rinsed thoroughly with deionized water and gently blotted with an absorbent tissue prior to the next pH measurement.
The pH of the untreated and treated filler was measured utilizing a Fisher Scientific Accumet AR50 pH meter having a measuring resolution of 0.01 pH units equipped with an Orion Ross Combination pH Electrode with BNC connector manufactured by Thermo Electron Corporation and purchased from Fisher Scientific. The Accumet AR50 pH meter used an automatic temperature compensator (ATC) probe for solution temperature measurement. The electrode in preparation for analysis had the electrode-fill hole open and to maintain an adequate flow rate, Ross pH Electrode Fill solution (Orion product number 810007 3), molar potassium chloride (KCl) solution, was added to cover the end of the coil and was at least one inch above the sample level when immersed. After opening the fill hole and upon addition of KCl fill solution the electrode was allowed to equilibrate for at least 15 minutes in pH Buffer 7 prior to recalibration and pH analysis. To prevent the stirrer from heating the beaker during measurements, a piece of insulating material was inserted between the magnetic stirrer and the beaker. The pH meter was prepared for analysis by recalibrating the meter with pH Buffers 4, 7 and 10 that are traceable to NIST or an equivalent agency.
A filler sample weighing approximately 5.0 g÷0.1 g was placed into a 150-mL beaker containing a magnetic Teflon round stir bar, having dimensions 1.25 inches in length and 0.313 inches in diameter. The filler sample for pH determination was ground to a powder with a mortar and pestle prior to measurement. About 100 ml of deionized water was added to the beaker containing the 5.0 g±0.1 g filler sample. The sample was mixed using a Fisher Thermix Stirrer Model 120MR using dial range settings of between 2 to 3. The electrode was rinsed with deionized water and gently blotted with an absorbent tissue prior to immersing into the stirring sample solution. The pH value was recorded to the nearest 0.01 pH unit when the pH Meter obtained a stable pH value reading. The electrode was removed and rinsed thoroughly with deionized water and gently blotted with an absorbent tissue prior to the next analysis.
CM10 Dispersion Test:
The following procedure, known as the CM10 dispersion test, was used to measure undispersed particles in a rubber compound as described below. The measure of non-dispersion was expressed as a CM10 count that was the sum of all the undispersed agglomerates equal to and greater than a 0.3 mm grid. For example, if there are two agglomerates in the 0.3 mm grid and one agglomerate in the 0.6 mm grid, then the CM10 count was equal to 3.
The following rubber compound was used in the CM10 dispersion test to measure the CM10 count. The rubber compound is shown in Table 1.
The above ingredients were introduced and mixed in a Kobelco Stewart Bolling Model “00M” internal mixer in the order and weights given in Table 1. The mixer was preheated using the automatic temperature control unit to a temperature of 37.7 degrees C. before the ingredients were introduced. SBR 1778 and Red Iron oxide were added and mixed at 35 rpm for 1.5 minutes commenced the mixing sequence. To this mix was added filler made according to this invention and mixed for another 0.5 minute at 35 rpm. Then Calsol 510, mixed with 50 grams of silica made in accordance with this invention, was introduced to the previous mixture and mixed for an additional 2 minutes at 35 rpm. The stock was discharged from the mixer at the end of the mixing sequence. The internal mixer temperature at the end of the mixing sequence was between 70 and 85° C.
Upon completion of the mixing sequence in the mixer, the stock was transferred to the two-roll mill (Ferrel 10″ mill) and the milling operation was commenced. The feedstock from the mixing sequence was placed on a cooled 2-roll mill at a temperature of from 15 and 20° C. The thickness of the mill nips was set between 0.20″ to 0.25″. Once the feedstock from the internal mixer bands was on the mill, two side cuts from each side and four end rolls of the rubber was performed, respectively, while milling. After milling, the rubber sheet was removed from the mill.
Two 2″×10″ sections using a 2″×10″ metal template were cut from each end of the sheet. Using scissors, one ten-inch strip approximately one-fourth inch wide was cut from each side of the two 2″×10″ rubber slabs. Four strips or 10 square inches of the entire sheet resulted. The freshly cut side of each strip was examined under a Unitron MSL microscope. The field of vision was 10× magnification (W10×).
The red iron oxide masterbatch additive in this compound served as a colorant to aid in dispersion analysis. The red rubber color background highlighted non-dispersed filler. Since only one dry additive was used in this compound (filler) there weare no interferences in the dispersion results from other similar dry additives. One lens of the microscope had a grid of 0.3 mm in the eyepiece. The area of each square in this grid was 0.30 mm and corresponded to 300 microns, thus two grids corresponded to 0.60 mm or 600 microns.
The criteria for observing non-dispersed filler agglomerates in the range of 300 to 600 microns was as follows: If a filler agglomerate touched two opposite lines of a square in the grid or fills in the square (0.3mm area), this was counted as a non-dispersed agglomerate that was 300 microns in size. Any agglomerate touching two opposite lines from two adjacent squares in the grid or fills in two squares of the grid (0.6 mm area) was counted as a non-dispersed agglomerate that was 600 microns in size. If a non-dispersed filler agglomerate was observed to be larger than one square in the grid but not as large as two squares in the grid then its size was counted as being in the range of 300 to 600 microns and the count/observation was placed in the 300 microns non-dispersed filler count. A similar procedure was used to count non-dispersed filler agglomerates that were larger than two squares in the grid. This data was recorded in the 600 microns and larger non-dispersed agglomerate range.
Mooney viscosity was measured using an automated Mooney Viscometer (MV 2000) with a large rotor, manufactured by Alpha Technologies, Inc. Two pieces of uncured rubber, each with approximate dimensions of 4 cm×4 cm×¼ inch thick were cut from the rubber masterbatch. A hole was cut in one of the pieces to hasten the loading of the rotor. The piece with the hole was placed on a sheet of Mylar film (2 mil thickness, cut into 4 cm by 4 cm squares) to prevent the compound from sticking to the die cavity. The large rotor was then placed in between the dies of the Mooney Viscometer. The platen press was heated to a temperature of 100° C. and the temperature was allowed to stabilize. When the Mooney Viscometer was ready for the test, a green light was illuminated. At that point, the platens were opened and the rotor stem was inserted through the piece of rubber with the hole in it. The second rubber piece was placed on top of the rotor and the rotor was placed back in the heated die cavity and platens were closed. The shield and platens opened when the test was complete.
The following probe sonication procedure was used for analyzing the friability of a filler pellet. A Fisher Scientific Sonic Dismembrator, Model 550 with a tapered horn and a flat tip (probe) was used to breakdown the agglomerates as function of time. The resulting particle size was measured by a laser diffraction particle size instrument, LS 230 manufactured by Beckman Coulter, capable of measuring particle diameters as small as 0.04 micron. Approximately 2 g equivalent of filler, adjusted for moisture, was weighed into a 2 oz wide-mouth bottle containing a 1″ stir bar, and 50 ml of water was then added to the bottle using a graduated cylinder. After stirring for one minute, the bottle was placed in an ice bath and the sonicator probe was inserted into the bottle such that there was a 4 cm probe immersion in the slurry. The sonication amplitude was adjusted for the desired intensity of 6. The sonication amplitude was related to the sonication power in watts and calculated in accordance with the procedure described in “Method 3051: Microwave Assisted Acid Digestion of Sediments, Sludges, Soils and Oils,” under Section 7: Calibration of Microwave Equipment, U.S. Environmental Protection Agency, SW-846, Version 2, December 1997.
The sonicator was run in the continuous mode in 60 second increments until 420 seconds was reached. An aliquot of sample was withdrawn and the particle size was measured by light scattering using a LS 230 (manufactured by Beckman Coulter, Inc.). A filler pellet was deemed to be more friable if it had a smaller mean agglomerate diameter after sonication at a given amplitude setting and time duration than prior to sonication. Friability is defined as the mean particle diameter (micron) after 420 second sonication.
In a 49,000 gallons stainless steel reactor with a central agitator, 14,000 gallons of sodium silicate with an Na2O concentration of 89 g/l was mixed with 27,000 gallons of water to give 41,000 gallons of sodium silicate solution containing 30.4 g/l Na2O. The central agitator was rotated at 45 rpm throughout the reaction. Live steam was used to raise the temperature of the foreshot to 142° F. (61° C.). The solution was carbonated over 4 hours using a fast-slow-fast carbonation cycle or until the pH of the reactor slurry reached 9.3. 100% CO2 gas was introduced below the turbine blade through a 6″ pipe and the CO2 flow was controlled using a mass flow meter. The CO2 flow rates and the total amount of CO2 used in the reaction are shown below in Table 2.
The temperature in the reactor increased gradually to 153° F. (67° C.) after 3.5 hours from the start of the precipitation. At that time, the steam coils were opened fully to increase the temperature of the reactor slurry to 210° F. (99° C.). The slurry temperature reached 210F after 4.5 hours from the start of the precipitation. The slurry was aged for 5 minutes at 21 0° F. The slurry was then pumped to a raw slurry storage tank (RST) with a capacity of 150,000 gallons. This precipitation was repeated continuously. The temperature of the slurry in the raw slurry storage tank was typically around 180° F. (82.2° C.).
300 gallons/min of slurry was pumped from the raw slurry storage tank, also known as RST slurry, was pumped to a series of decantation tanks, at 125-150° F. (51.6-65.5° C.), to remove the carbonate and bicarbonate by products formed in the precipitators. The first decantation tank had 1.5 million gallon capacity and was equipped with a tank scraper that made one revolution in every 45 minutes. The slurry was introduced near the top of the first decantation tank and it took about 8 hours for the silica in the slurry to settle at the bottom of the tank. The overflow from the second decantation tank was mixed with a cationic flocculant solution (WT-40P with 40 weight % active flocculant, purchased from Ciba Specialty Chemicals), 0.25% by weight of silica, and introduced at the top of the first decantation tank. The solids content of the settled slurry from the bottom of the tank, also called first underflow (1UF) slurry, was 3.5% by weight and its pH was around 9.6. The wash water from the top of the first decantation, 1470 gallons/min, also called first overflow (1OF) water was pumped to the sewer.
820 gallons/min of the underflow slurry from the first decantation tank was pumped to the second decantation tank with 1.5 million gallons capacity. The slurry was introduced near the top of the tank and it took about 8 hours for the silica in the slurry to the settle at the bottom of the tank. The solids content of settled slurry from the bottom of the tank, also called second underflow slurry, was 2.5% by weight and its pH was around 9.1. The wash water from the top of the second decantation, 2000 gallons/min, also called second overflow (2OF) water was pumped to the top of the first decantation tank.
1300 gallons/min of the second underflow (2UF) slurry from the second decantation tank was pumped to an acidification tank and was neutralized with 6 Normal HCl. Typically 8-10 gallons/min of HCl are used to neutralize the second underflow slurry. The pH in the acidification tank was 3.5. The slurry from the acidification tank was introduced into the third decantation tank, also with 1.5 million gallons capacity. The slurry was introduced near the top of the tank, and it took about 8 hours for the silica in the slurry to the settle at the bottom of the tank. The solids content of the settled slurry from the bottom of the tank, also called third underflow (3UF) slurry, was 6.5% by weight and its pH was around 5.1. The wash water from the top of the third decantation tank, 2470 gallons/min, also called third overflow (3OF) water was pumped to the top of the second decantation tank. Fresh water, at a flow rate of 1550 gallons/min, was introduced at the top of the tank to complete the decantation cycle.
380 gallons/min of the third underflow (3UF) slurry was passed through a Kason screen with 120-mesh opening (125 microns in diameter) to remove silica agglomerates larger than 125 microns in diameter. The portion of the slurry with silica agglomerates larger than 125 microns, also called Kason oversize slurry, was recycled back to the second decantation tank. The portion of slurry that went through the Kason screen, also called Kason undersize slurry, had 5.5 % by weight of silica. The pH of the slurry was around 5.3. This precipitation was repeated continuously.
180 gal of Kason undersize slurry was used to make the control sample (untreated filler) used in Example 1. This 180 gal of slurry was split into three batches of 60 gal. Each 60 gal of slurry was filtered using a Perrin Pilot filter press with 5 plates (Model No: Perrin #200 Chambers: 30inches X 19 plates). Filter press fill pressure was 20 psi. The amount of wash water used was around 250 gallons. The % by weight of silica in the resulting filter cake was 16.5%. The filter cake was introduced directly into a custom built tumbling rotary dryer (Dimensions—48 inches, Length—7.5 inches, Air flow—20 LPM) rotating at a speed of 35 rpm. A temperature of 300° F. (149° C.) was used to dry the filter cake and a flow of air was used to remove the evaporated water from the dryer. After about 3 hours, dry silica pellets with less than 1% moisture by weight were discharged from the rotary dryer. The dry pellets were then screened through −7 mesh and +28 mesh screens to obtain a pellet fraction between 2800 and 600 microns. The dry silica pellets were conditioned in a humidity controlled room maintained at a temperature of 22° C. and a relative humidity of 50% to raise the moisture content to about 5-6% by weight.
The Kason undersize slurry was reacted with ammonium stearate (AMS) emulsion to obtain desired target values of AMS in the final product. The AMS emulsion containing 27 percent by weight of active ammonium stearate (Geo Specialty Chemicals, Inc.) or 33 percent by weight of active ammonium stearate (Bradford Soaps, Inc.) was used.
The 1 wt % AMS treated filler was prepared by reacting 151 liters of Kason undersize slurry with 170 grams of 27% AMS emulsion at 150° F. (65.5° C.). Upon completion of the AMS addition, the reacted slurry was aged for 15 minutes. After aging, the slurry was neutralized to a pH of 5.5 with concentrated sulfuric acid. The treated slurry was filtered in the filter press with 4 plates as described above. The % by weight of silica in the resulting filter cake was 16.3%. The filter cake was rotary dried as described above. The dry pellets were then screened through −7 mesh and +28 mesh screen to obtain a pellet fraction between 2800 and 600 microns. The dry silica pellets were conditioned in a humidity controlled room maintained at a relative humidity of 50% to raise the moisture content to about 5-6% by weight.
The 3 wt % AMS treated filler was prepared by reacting 151 liters of Kason undersize slurry with 1023 grams of 27% AMS emulsion as described in the previous paragraph. After treatment, the slurry was filtered in the press with 4 plates as described above. The % by weight of silica in the resulting filter cake was 16.3%. The filter cake was rotary dried as described above. The dry pellets were then screened through −7 mesh and +28 mesh screen to obtain a pellet fraction between 2800 and 600 microns. The dry silica pellets were conditioned in a humidity controlled room maintained at a relative humidity of 50% to raise the moisture content to about 5-6% by weight.
Comparative Pellet Preparation:
The rotary dryer discharge of the untreated filler was milled in a hammer mill (Type: SH, Mikro Pulverizer Company) to obtain a powder with a median particle diameter of 30 microns. The hammer-milled powder was fed to a pelletizer type pin mixer (Model 8D32L, Woodward Inc.). The hammer-milled silica powder was fed into the pin mixer using a screw feeder (Tecweigh screw). A feed rate of 7.5 pounds per minute was used. The percent wet cake moisture desired in the product fixeds the amount of water used to pelletize the powder in the pin mixer. The wet cake from the pin mixer had 64 percent by weight of water. The water spray pressure and motor speed were adjusted between 8-30 pounds per square inch and 1400-1700 revolutions per minute, respectively, to obtain pelletized wet cake with good consistency, i.e. essentially the same % moisture by weight. The amount of ammonium stearate added by weight of silica in the pin mixer was varied by adding differing amounts of ammonium stearate emulsion to the pin mixer water. A re-circulating pump was used to keep the ammonium stearate substantially uniformly dispersed in the pin mixer water.
For this untreated comparative sample, 10 lbs of water was used to pelletize the powder in the pin mixer at the powder feed rate of 7.5 pounds per minute.
For 1 wt % AMS treatment, 0.3 lbs of 27 wt % AMS emulsion was added to 9.7 lbs of water used to palletize the powder in the pin mixer at the powder feed rate of 7.5 pounds per minute.
For 3 wt % AMS treatment, 0.6 lbs of 27 wt % AMS emulsion was added to 9.4 lbs of water used to palletize the powder in the pin mixer at the powder feed rate of 7.5 pounds per minute.
For Examples 1d, 1e and 1f, the wet cake from the pin mixer was dried in a Despatch convection oven (Model: LAC1-38B, Despatch Industries, Inc., Box 1320, Minneapolis, MN 55440) at a temperature of 125° C. for 8 hours to obtain dry pellets. The dry pellets were then screened through −7 mesh and +28 mesh pellet screen to obtain a pellet fraction between 2800 and 600 microns.
Examples 1a through 1f were tested for 5 Pt BET surface area, CTAB surface area, ATD, CM10 count, and Mooney viscosity according to the methods described previously. The data are listed in Table 3.
Each CM10 count and Mooney data point represents an average of two rubber batches.
Comparison of the ATD data of the treated fillers (1b, 1c) according to this invention with the ATD of comparative pellets (1e, 1f) made by reacting the rotary dried and hammer-milled untreated filler with AMS in a pin mixer and then oven drying and screening the pin mixer discharge (shown in Table 3) indicates that the treated fillers according to this invention have lower ATD than the treated comparative pellets. In addition, ATD of the treated fillers according to this invention decreased with increasing level of treatment compared to the comparative pellets where the ATD increased with increasing level of treatment.
The results in Table 3 demonstrate that the treated fillers according to this invention had lower CM10 counts compared to pellets made by reacting the rotary dried and hammer-milled untreated filler with AMS in a pin mixer and then oven drying and screening the pin mixer discharge. In addition, the CM10 count of the treated filler according to this invention decreased with increasing level of treatment compared to the pellets where the CM10 count increased with increasing level of treatment.
The Mooney viscosity of the treated fillers according to this invention was lower than the comparative pellets made by reacting the rotary dried and hammer-milled untreated filler with AMS in a pin mixer and then oven drying and screening the pin mixer discharge.
30 liters of Kason undersize slurry from Example 1 with 5.8% by weight of silica and a pH of 6.6 was filtered in a 10-liter Buchner funnel with a filter paper (Whatman Filter Paper No. 54, purchased from Fisher Scientific), under 25 inches of vacuum without washing. The 30 liters were split equally between 3 funnels. The filter cake was combined and the resulting filter cake had 16% by weight of silica. The filter cake was introduced directly into a tumbling pilot rotary dryer and dried as described in Example 1. After 3.5 hours, dry silica pellets with less than 1% moisture by weight were discharged from the rotary dryer. The dry pellets were screened through −7 mesh and +28 mesh screen to obtain a pellet fraction corresponding to a fraction between 2800 and 600 microns. The dry silica pellets were conditioned in a humidity controlled room maintained at a relative humidity of 50% to raise the moisture content to a range of from 5-6% by weight.
Another 30-liter portion of the Kason undersize slurry from Example 1 was reacted with 194 grams of 27% AMS solution to obtain a 3% AMS treated filler. The reacted slurry was filtered in a 10-liter Buchner funnel with a filter paper, under 25 inches of vacuum without washing. The 30 liters were split equally between 3 funnels. The % by weight of silica in the resulting filter cake was 16%. The filter cake was rotary dried and screened as described above. The dry silica pellets were conditioned in a humidity controlled room maintained at a relative humidity of 50% to raise the moisture content to 5-6% by weight.
Examples 2a to 2b were tested for 5 Pt BET surface area, ATD, CM10 count, and Mooney viscosity according to the methods described above.
The results in Table 4 demonstrate that the treated filler (2b), according to this invention exhibited lower ATD than the untreated filler (2a). In addition, the treated filler according to this invention had significantly lower CM10 count and lower Mooney viscosity compared to the untreated filler. The results in Table 4 (Example 2b) when compared to the results in Table 3 (Examples 1b and 1c) demonstrate that the treated filler according to this invention is more dispersible compared to the untreated filler (Examples 1a and 2a), regardless of the type of filtration procedure used to make the treated filler.
The silica was precipitated in a batch process by neutralizing sodium silicate solution using CO2 gas. In a 150-liter stainless steel reactor with a Ekato central agitator, 30.32 liters of sodium silicate with a Na2O concentration of 89 g/l was mixed with 63.68 liters of water to give 94 liters of sodium silicate solution containing 30.1 g/l Na2O. The central agitator was rotated at 250 rpm and the slurry was heated to 151° F. (66.1° C.) via a steam coil. The speed of agitation was kept essentially constant and the temperature was allowed to increase gradually to 153.4° F. (67.4° C. ) during the precipitation. The solution was carbonated over 3 hours using the flow rates shown in Table 5 until the % carbonation in the reactor slurry reached 100% or greater. Time was recorded using a stopwatch. 100% CO2 gas was introduced below the turbine blade through a Bunsen valve and the CO2 flow was controlled using a rotometer. The CO2 cylinder pressure was maintained at 40 psi throughout the reaction. The pH, temperature, and the rotometer readings were recorded and adjusted every thirty minutes, as shown in Table 5.
The percent carbonation in the reaction was determined by titrating the reactor slurry with 1 Normal HCl. The volume of HCl required to reach the first pH endpoint was pre-determined using the foreshot slurry for various pH values (6.8, 6.9, 7.0, 7.1, and 7.2). 25 ml of the foreshot slurry was pipetted to a 250 ml beaker and diluted with 175 ml of deionized water. The diluted slurry was placed on a magnetic stirrer plate and allowed to mix for 1 minute. A 50 ml burette was filled to the zero mark with 1 Normal HCl and the HCl was added drop wise until the first pH end point was reached. The volume of HCl in ml needed to reach first endpoint (A) was recorded.
At half hour intervals during the reaction, 25 ml of the reactor slurry was pipetted to a 250 ml beaker and diluted with 175 ml of DI water. The diluted slurry was placed on a magnetic stirrer plate and allowed to mix for 1 minute. The slurry was then titrated against 1 Normal HCl until the second pH end point (pH of 4.0) was reached. The volume of HCl in ml needed to reach second endpoint (B) was recorded. The % concentration of CO2 in the reactor slurry was calculated as follows, =(B−A)×2×100/B.
After attaining the extent of carbonation, the temperature was increased to 210° F. (99° C.) and the slurry was aged for 1 hour. 30 liters of the aged slurry was mixed with 115 liters of city water in a 150-liter reactor. The diluted slurry was stirred and heated to 158° F. (70° C.). After the temperature reached 158° F., 15 grams of cationic flocculant (WT-40P) was added and the slurry stirred for 15 minutes. Heeat and agitation was turned off and the slurry was allowed to settle overnight. After overnight settling, the first supernatant was removed using a siphon pump, and the volume of the settled slurry after first decantation (60 liters) and pH (9.75) were recorded. The settled slurry was diluted with 90 liters of city water and heated to 158° F. under agitation. After the temperature reached 158° F., the heat and agitation was turned off and the slurry was allowed to settle for another 7 hours. The second supernatant was removed using a siphon pump, and the volume of the settled slurry after second decantation (57 liters) and its pH (9.92) were recorded. The settled slurry was diluted with 93 liters of city water, and heated to 158° F. under agitation. After the temperature reached 158° F., the heat and agitation was turned off and the slurry was allowed to settle overnight. The third supernatant was removed using a siphon pump, and the volume of the settled slurry after third decantation (57 liters) and its pH (9.92) were recorded.
The pH of the settled slurry was adjusted, with agitation, form 9.92 to 3.5 using 6 Normal HCl. The slurry was then heated to 208° F. (97.7° C.) and aged for 1 hour under agitation. The final pH reading was then recorded at 5.5.
20 liters of the neutralized slurry from the previous step, with 6% by weight of silica, was filtered in a Buchner funnel without washing as described in Example 2a. The resulting filter cake had 17.9% by weight of solids. The filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
The remaining slurry that weighed around 22.8 lbs was reacted with 69 grams of 27wt % AMS solution. After the reaction, the pH was adjusted to 6.0 using 6N HCl and filtered in a Buchner funnel. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
The silica precipitation process was carried out as in Example 3a with the exception that the pH of the settled slurry (after third decantation) was adjusted, with agitation, form 9.92 to 3.5 using concentrated sulfuric acid. The slurry was then heated to 208° F. and aged for 1 hour under agitation. The final pH reading was then recorded at 5.5. 20 liters of the neutralized slurry, with 6% by weight of silica, was filtered in a Buchner funnel without washing as described in Example 2a. The resulting filter cake had 18.2% by weight of solids. The filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
The remaining slurry that weighed around 16.6 lbs was reacted with 50 grams of 27wt % AMS solution. After the reaction, the pH was adjusted back to 6.0 using concentrated sulfuric acid and filtered in a Buchner funnel. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
The Examples 3a through 3d were tested for 5 Pt BET surface area, ATD, CM10 count, and Mooney viscosity according to the methods described above.
The results in Table 6 demonstrate that the treated fillers (3b and 3d), according to this invention exhibited lower ATD than the untreated fillers (3a and 3c). In addition, the treated fillers, according to this invention, had significantly lower CM10 count and lower Mooney viscosity compared to the untreated fillers. These results demonstrate that the treated filler (3b and 3d), according to this invention, are more dispersible compared to the untreated filler (3a and 3c), regardless of the type of acid used to neutralize the silica slurry.
For Examples 4a and 4b, a silica precipitation process was carried out as in Example 3a with the following exceptions that 940 grams of NaCl added in the foreshot and the reaction temperature was 105° F. (40.5° C.).
The pH of the settled slurry (after third decantation) was adjusted, with agitation, form 9.92 to 3.5 using 6 Normal HCl. The slurry was then heated to 208° F. (97.7° C.) and aged for 1 hour under agitation. 20 liters of the neutralized slurry, with 5.7% by weight of silica, from the previous step was filtered in a Buchner funnel without washing as described earlier in Example 2. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
The remaining slurry that weighed around 22.7 lbs was reacted with 66 grams of 27 wt % AMS solution. After the reaction, the pH was adjusted to 6.0 using 6N HCI and filtered in a Buchner funnel. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
For Examples 4c and 4d, an additional silica precipitation process was carried out as in Example 3a with the following exceptions that 940 grams of NaCl added in the foreshot and the reaction temperature was 105° F. (40.5° C.).
The pH of the settled slurry (after third decantation) was adjusted, with agitation, form 9.92 to 3.5 using concentrated sulfuric acid. The slurry was then heated to 208° F. and aged for 1 hour under agitation. 20 liters of the neutralized slurry, with 5.7% by weight of silica, was filtered in a Buchner funnel without washing as described earlier. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
The remaining slurry that weighed around 19.2 lbs was reacted with 56 grams of 27wt % AMS solution. After the reaction, the pH was adjusted to 6.0 using concentrated sulfuric acid and filtered in a Buchner funnel. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
Examples 4a through 4d were tested for 5 Pt BET surface area, ATD, CM10 count, and Mooney viscosity according to the methods described above.
The results in Table 7 demonstrate that treated fillers (4b and 4d) according to the invention exhibited lower ATD than untreated fillers (4a and 4c). In addition, treated fillers according to the invention had significantly lower CM10 counts and lower Mooney viscosity compared to untreated fillers. Comparison of the results in Table 7 (4b and 4d) with the results in Table 6 (3b and 3d) demonstrates that treated fillers (3b, 3d, 4b, 4d) according to this invention are more dispersible compared to untreated fillers (3a, 3c, 4a, 4c) regardless of whether or not foreshot electrolyte was added to the reaction.
Examples 5a and 5b were rotary dried; Examples 5c and 5d were spray dried and granulated; and Examples 5e and 5f were oven dried.
20 liters of RST slurry from a precipitation process carried out as in Example 1 was reacted with 5 grams of cationic flocculant (WT-40P) and neutralized with concentrated sulfuric acid to a pH of 5.1. The neutralized slurry was filtered in two Buchner funnels. The filter cake in each funnel was then washed with 10 liters of water. The resulting filter cake, that had 17% by weight of silica, was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
Another 20 liters of RST slurry from a precipitation process carried out as in Example 1 was reacted with 5 grams of cationic flocculant (WT-40P) and 68 grams of 33% AMS solution and then neutralized with concentrated sulfuric acid to a pH of 5.3. The neutralized slurry was filtered in two Buchner fiunnels. The filter cake in each funnel was then washed with 10 liters of water. The resulting filter cake, that had 16.4% by weight of silica, was rotary dried, screened, and equilibrated in a humidity control room as described earlier in Example 1.
50 liters of RST slurry from a precipitation process carried out as in Example 1 was neutralized with concentrated sulfuric acid to a pH of 6.0 and diluted with 100 liters of water in a stainless steel 150-liter reactor and heated to 150° F. (65.5° C.) under agitation. The agitation and heat was turned off and the slurry allowed to settle overnight. The clear supernatant was siphoned off and 80 liters of settled slurry was collected.
20 liters of the 80 liters of the settled slurry from the previous step was filtered using two Buchner funnels. The filter cake in each of the funnels was washed with 10 liters of water. The resulting filter cake, that had 16.7% by weight of silica, was reslurried with just enough water and with agitation to produce a pumpable slurry which was then spray dried in a Niro spray dryer (Utility Model 5 with Type FU-11 rotary atomizer, Niro Inc.).
Granules were prepared from the spray dried powder samples by compaction using the Alexanderwerck, Roller Compactor WP 120/40, granulator (roll diameter 120 mm, roller height 40 mm, rotary speed of rolls 4-15 rpm). The granulation pressure applied by the rolls of the granulator was 25 Bar.
Another 20 liters of the 80 liters of the settled slurry from Example Sc were treated with 143 grams of 33% AMS solution at 150F, aged for 15 minutes, and neutralized with sulfuric acid to a pH of 5.0. The treated slurry was filtered using two Buchner funnels. The filter cake in each of the funnels was washed with 10 liters of water. The resulting filter cake, that had 16. 10% by weight of silica, was reslurried with just enough water and with agitation to produce a pumpable slurry which was then spray dried in a Niro spray dryer with a rotary atomizer. The spray dried powder was granulated under conditions described in Example 5c.
20 liters of the 80 liters of the settled slurry from Example 5c was filtered using two Buchner funnels. The filter cake in each of the funnels was washed with 10 liters of water. The resulting filter cake, that had 16.7% by weight of silica, was dried in a Despatch convection oven (Model: LAC1-38B, Despatch Industries, Inc., Box 1320, Minneapolis, Minn. 55440)) at a temperature of 257° F. (125° C.) for 12 hours to obtain dried pellets. The dried pellets were then screened and conditioned in a humidity control room as described earlier in Example 1.
20 liters of the 80 liters of the settled slurry from Example 5c were treated with 143 grams of 33% AMS solution at 150° F., aged for 15 minutes, and neutralized with sulfuric acid to a pH of 5.0. The treated slurry was filtered using two Buchner funnels. The filter cake in each of the funnels was washed with 10 liters of water. The resulting filter cake, that had 16.10% by weight of silica, was dried in a convection oven as described in the previous paragraph. The dried pellets were then screened and equilibrated in a humidity control room as described earlier in Example 1.
Examples 5a through 5f were tested for 5 Pt BET surface area, CTAB surface area, ATD, CM10 count, and Mooney viscosity according to the methods described above.
The results in Table 8 demonstrate that treated fillers (5b, 5d, 5f) according to the invention exhibited lower ATD than untreated fillers (5a, 5c, 5e) regardless of the drying method employed. In addition, treated fillers (5b, 5d, 5f) according to the invention had significantly lower CM10 count and lower Mooney viscosity compared to untreated fillers (5a, 5c, 5e). These results indicate that treated fillers according to the invention were more dispersible compared to untreated fillers regardless of the drying method employed to prepare treated filler.
50 liters of 2UF slurry from a precipitation process carried out as in Example 1 were neutralized with concentrated sulfuric acid to a pH of 6.0 and screened through 100 mesh sieve (Fisher Scientific Company, ASTM E-11 specification), and diluted with 100 liters with of water and decanted. The clear supernatant was siphoned off and the settled slurry with 6.5 wt % of silica was filtered in five Buchner finnels. The filter cake in each funnel was washed with 5 liters of water. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
Another 50 liters of 2UF slurry from a precipitation process carried out as in Example 1 were neutralized with concentrated sulfuric acid to a pH of 6.0, screened through a 1 00 mesh sieve (Fisher Scientific Company, ASTM E-11 specification), and diluted with 100 liters of water and decanted. The clear supernatant was siphoned off and the settled slurry that weighed 109 lbs and had 6.5 wt % of silica, was reacted with 109 grams of 33% AMS solution and neutralized with concentrated sulfuric acid to a pH of 5.5. The neutralized slurry was filtered in five Buchner funnels. Filter cake in each funnel was washed with 7.5 liters of water. The resulting filter cake was rotary dried, screened, and conditioned in a humidity control room as described in Example 1.
Examples 6a and 6b were tested for 5 Pt BET surface areas, CTAB surface area, ATD, CM10 count, Mooney viscosity, and Friability according to the methods described above.
The results in Table 9 demonstrate that treated filler (6b) according to the invention exhibited lower ATD, had significantly lower CM10 count, and lower Mooney viscosity than untreated filler (6a). In addition, treated filler (6b) according to the invention was more friable compared to untreated filler (6a) as demonstrated by the lower friability value of treated filler (6b).
20 liters of 1UF slurry from a precipitation process carried out as in Example 1 was neutralized with concentrated sulfuric acid to a pH of 6.0 and screened through a 100 mesh sieve and diluted with water 50 liters of water in a stainless steel reactor. Under agitation, the slurry was heated to 158° F. After 15 minutes, the agitation and heat were shut off and the slurry was allowed to decant overnight. Next morning, the clear supernatant was siphoned off and the settled slurry, that had 5.3 wt % of silica, was filtered in two buchner funnels. The filter cake in each funnel was washed with 10 liters of water. The resulting filter cake had 17.8 wt % of silica. The resulting filter cake was rotary dried, screened, and equilibrated in a humidity control room as described earlier in Example 1.
For Example 7b, 80 liters of 1UF from a precipitation process carried out as in Example 1 was neutralized with concentrated sulfuric acid to a pH of 6.0 and screened through a 100 mesh sieve and diluted with water 200 liters of water in a stainless steel reactor. Under agitation, the slurry was heated to 158° F. After 15 minutes, the agitation and heat were shut off and the slurry was allowed to decant overnight. Next morning, the clear supernatant was siphoned off and the settled slurry, that had 5.3 wt % of silica was collected for treatment.
The process used for Example 7b was followed for Examples 7c through 7k with the following exceptions: 90 liters of 1UF slurry was used and 225 liters of water were used for dilution.
Examples 7b through 7k were treated using the treating materials shown in Table 10.
For Examples 7b to 7d and 7h to 7k, the treatments were done at 200° F. (93.3° C.) and the treating material was dissolved in 2 liters of water at 200° F.
For Examples 7e, 7f and 7 g, the treatments were done at 158° F. and the treating material was used as-is.
90 liters of 2UF from a precipitation process carried out as in Example 1 was neutralized with concentrated sulfuric acid to a pH of 6.0, screened through a 100 mesh sieve, and diluted with 225 liters of water in a stainless steel reactor. Under agitation, the slurry was heated to 158° F. After 15 minutes, the agitation and heat were shut off and the slurry was allowed to decant overnight. Next morning, the clear supernatant was siphoned off and the settled slurry, that had 5.3 wt % of silica was collected.
Examples 7m through 7t were treated using the treating materials shown in Table 10.
For Examples 7m and 7q through 7t, the treatments were done at 200° F. and the treating material was dissolved in 2 liters of water at 200° F.
For Examples 7n, 7o and 7p, the treatments were done at 158° F. and the treating material was used as-is.
Examples 7b through 7t were neutralized with concentrated sulfuric acid to a pH of 6.0. The neutralized slurry was filtered in Buchner funnels. The Buchner funnel had a capacity of 10 liters. The filter cake in each funnel was washed with 5 liters of water. The resulting filter cakes had between 16-17% by weight of filler and were rotary dried, screened, and conditioned in a humidity control room as described earlier in Example 1.
Procedure for Preparing Rubber Compounds
A 1.6-liter Kobelco Stewart Bolling Model “00” internal mixer or equivalent was used for mixing the various ingredients. The mixer was equipped with a four-wing rotor and variable speed motor capable of rotor speeds between 1 and 167 revolutions per minute (rpm).
To a 500 milliliter (mL) plastic cup that was lined with a polyethylene bag, Sundex®D 8125 oil (Sun Company, Inc., Refining and Marketing Division, Philadelphia, Pa.) was added in the amount of 34.0 parts per hundred parts of rubber by weight (phr). 2.0 phr Wingstay 100 mixed diaryl p-phenylenediamine (The Goodyear Tire & Rubber Co., Akron, Ohio; supplier: R. T. Vanderbilt Company, Inc., Norwalk, Conn.), and 1.0 phr rubber grade stearic acid (C. P. Hall, Chicago, Ill.) was added on top of the oil.
Before beginning the first pass, 800 grams (g) CV-60 grade natural rubber was put through the mixer to clean it and bring the temperature up to about 149° F. (65° C.). The cooling water was turned on and the bottom door was opened to remove the rubber and to cool the mixer to about 100.4° F. (38° C.).
The first pass was commenced by adding the rubber, viz., 316.7 g (70.0 phr) Solflex 1216 solution styrene-butadiene rubber (The Goodyear Tire & Rubber Co., Akron, Ohio) and 135.8 g (30.0 phr) Budene 1207 butadiene rubber (The Goodyear Tire & Rubber Co., Akron, Ohio) to the mixer and mixing for 0.5 minute at 90 rpm. Add 40 phr of the amorphous precipitated silica to be tested. After a further 2.0 minutes 12.8 phr X50S® 1:1 Si-69 silane coupling agent and N330-HAF carbon black (Degussa Corp., Ridgefield, Park, N.J.; supplier: Struktol Corp. of America, Stow, Ohio) was added. After a further 1.0 minute mixing the ram was raised and swept. 40 phr of the amorphous precipitated silica to be tested was added. After a further 0.5 minute mixing, the polyethylene bag was added and the ingredients contained therein. The stock was mixed for an additional 2 minutes to achieve a maximum temperature in the range of from 140° C. (284° F.) to 160° C. (320° F.) and to complete the first pass in the mixer. Depending upon the type of silica, the rotor speed may need to be increased or decreased to achieve a maximum temperature in the foregoing range within the 6 minute mixing period.
The stock was dumped, weighed, and its temperature was measured with a thermocouple. The stock was sheeted off on a two-roll rubber mill and cut it into strips in preparation for the second pass in the mixer. Approximately 60 grams of stock to a thickness of about 0.1 inch (2.54 millimeters (mm)) was milled, and used to make a pouch for 2.0 phr Santoflex® 13 N- (1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (Monsanto, St. Louis, Missouri), 2.5 phr Kadox® 920C surface treated zinc oxide (Zinc Corporation of America, Monaca, Pennsylvania), and 1.5 phr Okerin® 7240 microcrystalline wax/paraffin wax blend (Astor Corporation, Norcross, Ga.).
Sufficient time was allowed to pass between the completion of the first pass in the mixer and the beginning of the second pass for the mixer to cool to a temperature of 38° C.
With the cooling water running, the second pass was commenced by adding the strips of first pass stock to the mixer that was running at 77 rpm. After a further 2 minutes the pouch containing the Santoflex® 13 N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, Kadox® 920C and the Okering 7240 microcrystalline wax/paraffin wax blend was added. After a further 1 minute mixing the ram was raised and swept. The stock was mixed for an additional 1 minute to achieve a temperature of 150° C. (302° F.) and to complete the second pass in the mixer.
The stock was dumped, weighed, and its temperature was measured with a thermocouple. The stock was sheeted off on a two-roll rubber mill and cut it into strips in preparation for the third pass in the mixer. Approximately 60 grams of stock was milled to a thickness of about 2.54 mm (0.1 inch) and use d to make a pouch for 1.4 phr rubber makers sulfur (Taber, Inc., Barrington, R.I.}, 1.7 phr N-tert-butyl-2-benzothiazole sulfenamide (Monsanto, St. Louis, Mo.), and 2.0 phr diphenylguanidine (Monsanto, St. Louis, Mo.).
Sufficient time was allowed to pass between the completion of the second pass in the mixer and the beginning of the third pass for the mixer to cool to a temperature of 38° C.
With the cooling water running, the third pass was commenced by adding the strips of second pass stock to the mixer that was running at 60 rpm. Immediately thereafter the pouch containing the sulfur, the N-tert-butyl-2-benzothiazole sulfenamide, and the diphenylguanidine was added. After a further 15 seconds the rotor speed was dropped to 60 rpm. After a further 1.5 minutes the ram was raised and swept. The third pass was completed by mixing the stock for no more than an additional 3.5 minutes, and dropping it just before the temperature exceeded 125° C. (257° F.).
Milling Protocol
A 2-roll rubber mill was preheated to 60° C. (140° F.). With the nip setting at 6.35 mm (0.25 inch) and while the mill was running, the stock from the third pass was fed into the mill. The rolling bank was adjusted as necessary to maintain uniform thickness. Eight side cuts and then eight end passes were performed.
The nip setting was adjusted to produce a sheet thickness of 2.032 mm±0.127 mm (0.080 inch+0.005 inch). The stock was sheeted off the mill and laid flat on a clean surface.
Using a stencil, a rectangular sample 101.6 mm×76.2 mm (4 inches×3 inches) was cut from the stock and then stored between clean polyethylene sheets. The stock was conditioned overnight at a temperature of 23° C. (73.4° F.) and a relative humidity of 50%±5%.
Examples 7a to 7t were tested for 5 Pt BET surface area, CTAB surface area, ATD, and Mooney viscosity according to the methods described above.
The results in Table 11 demonstrate that treated fillers (7b to 7k and 7m to 7t) according to the invention exhibited lower ATD and exhibited lower Mooney viscosity than untreated filler (7a and 7l). These results indicate that treated fillers according to the invention are more dispersible compared to untreated filler.
Titration Methods Used for Examples 8 through 11
In the preparation of Examples 8 through 11, the following methods were used to determine Na2O strength of the precipitation heel and the acid number of the precipitation heel and of the slurry during the simultaneous addition step.
Na2O Titration:
The reactor was a round bottom 150 liter stainless steel tank. The tank had two 5 cm baffles placed vertically on opposite sides of the inside of the tank for added mixing. Heating was via steam coils located 46.4 cm down from the top of the tank. The tank had two agitators. Main agitation was accomplished via an Ekato MIG style blade and a secondary high speed agitator was used for acid addition with a cowles style blade turning at 1750 RPM. The secondary high speed agitator was only run when acid was being added to the tank.
Common Raw Materials Used in Examples 8-11:
67.8 liters of water were added to the 150 liter reactor tank and heated to 82° C. via indirect steam coil heat. 2.2 liters of sodium silicate were added at a rate of 440.4 ml/min. to achieve a target Na2O concentration of 2.2 g/l Na2O and an acid value of 6.7. The Na2O concentration and acid value were confirmed by titrating the sodium silicate/water mixture using the Na2O titration method and acid value titration method described above. The temperature was adjusted as necessary to 82° C. via indirect steam coil heating and the precipitation step was initiated. The 150 liter reactor was agitated via the main tank agitator.
The main agitator was left on and a simultaneous addition precipitation step was started. 30.8 liters of sodium silicate and 1.8 liters of sulfuric acid were added simultaneously over a period of 70 minutes. The sodium silicate was added via an open tube near the bottom of the tank at a rate of 440 ml/min. and the sulfuric acid was added directly above the secondary high-speed mixer blades. The acid addition rate averaged 25.7 ml/min. over the course of the 90 min. simultaneous addition step.
At the end of the simultaneous addition step, a 90-minute age step was begun. A batch pH of 9.0 was measured. 0.18 g of Agefloc, a cationic flocculant solution (WT-40P with 40 weight % active flocculent, purchased from Ciba Specialty Chemicals), were added per liter of slurry in the reactor. The secondary high speed agitator was turned off after completion of the addition of flocculant, and the remainder of the 90 minute aging step was completed. During this age step the main agitator was left on and the temperature was maintained at 82° C.
After the age step was completed, 240 ml of sulfuric acid were added at a rate of 25.7 ml/min. to reach a final batch pH of 4.2. After reaching the final batch pH, 225 g of ammonium stearate, a 33% active AMS-water emulsion from Bradford Soap Works (AMS), was poured in the top of the reactor.
50 liters of slurry were removed from the reactor (Example 8) and placed on five 50 cm wide Buchner funnels, 10 liters of slurry per funnel and each funnel was washed with four 2.5 liter water washes. After filtering and washing the slurry on the Buchner funnels, the slurry was in cake form and was referred to as filter cake. The resulting filter cake had a solids content of 16.9 wt. %.
Sample 8b was prepared using the procedure described above for Example 8a, with the following exceptions. During the simultaneous addition step, the sodium silicate was added at a rate of 449 ml/min instead of 440 ml/min; the batch pH measured at the end of the simultaneous addition step was 9.1 instead of 9.0; and 20 ml of sulfuric acid were added to bring the batch pH to 9.0; after the final batch pH was adjusted to 4.2, the amount of ammonium stearate emulsion added was 686 g rather than 225 g to give a treatment level of 3% for the batch instead of 1%.
Filter cake from Examples 8a and 8b were batch dried in a custom-made rotary dryer with inside dimensions of 122 cm in length and 19 cm in diameter. 8 Kg of filter cake was placed in the dryer for each batch. The dryer was heated electrically, the inner shell temperature target was 150° C. during drying and the speed of rotation was 5 RPM. There was an air sweep of 20 liter per minute to remove the moisture. The material was dried until the filler moisture content reached <6.0 wt.
After drying, both samples were hammer milled to a median particle size within the range of 19-20 micrometers. The dried, hammer milled treated filler samples (8a and 8b) were tested for 5-point BET surface area, CTAB surface area, ATD. The results are shown in Table 12
67.5 liters of water were added to the 150 liter reactor tank and heated to 84° C. via indirect steam coil heat. 2.5 liters of sodium silicate were added at a rate of 391 ml/min. to achieve a target Na2O concentration of 2.5 g/l Na2O and an acid value of 7.5. The Na2O concentration and acid value were confirmed by titrating the sodium silicate/water mixture using the Na2O titration method and acid value titration method described above. The temperature was adjusted as necessary to 84° C. via indirect steam coil heating and the precipitation step was initiated. The 150 liter reactor was agitated via the main tank agitator.
The main agitator was left on and a simultaneous addition precipitation step was started. 35.2 liters of sodium silicate and 2.04 liters of sulfuric acid were added simultaneously over a period of 90 minutes. The sodium silicate was added via an open tube near the bottom of the tank at a rate of 391 ml/min. and the sulfuric acid was added directly above the secondary high speed mixer blades. The acid addition rate averaged 22.7 ml/min. over the course of the 90 min. simultaneous addition step.
At the end of the simultaneous addition step, a 90 minute age step was begun. A batch pH of 9.1 was measured and an additional 19 ml of sulfuric acid were added at a rate of 22.7 ml/min. to reach a pH of 9.0. The secondary high speed agitator was turned off. 21 g of Agefloc, a cationic flocculant solution (WT-40P with 40 weight % active flocculant, purchased from Ciba Specialty Chemicals), was diluted with 100 ml of water and poured into the aging slurry. The 90 minute aging step was then completed. During this age step the main agitator was left on and the temperature was maintained at 84° C.
After the age step was completed, 251 ml of sulfuric acid were added at a rate of 22.7 ml/min. to reach a final batch pH of 4.2.
50 liters of slurry were removed from the reactor (Example 9) and placed on five 50 cm wide Buchner funnels, 10 liters of slurry per funnel and each funnel was washed with four 2.5 liter water washes. After filtering and washing the slurry on the Buchner funnels, the slurry was in cake form and was referred to as filter cake.
The remaining slurry from Example 9 was treated with 3 wt. % of 3-(N,N dimethylmyristylammonio)propane sulfonate obtained from Sigma Aldrich (purum ≧98%) based on weight of silica solids. 126 g of 3-(N,N dimethylmyristylammonio)propane sulfonate were dissolved into 1.2 liters of water and poured into the top of the reactor with the main agitator on. The batch was allowed to mix for 10 minutes and the batch pH was measured at 4.2. 50 liters of treated slurry were transferred to five 50 cm Buchner fimnels, 10 liters per fimnel, and each fumnel was washed three times with 2.5 liters of water. After filtering and washing the slurry on the Buchner funnels, the slurry was in cake form and was referred to as filter cake.
Filter cake from Examples 9a and 9b were dried in a custom-made rotary dryer. 19 Kg of filter cake was placed in the dryer for each batch. The dryer was heated electrically, the inner shell temperature set point was 177° C. during drying and the speed of rotation was 8 RPM. There was an air sweep of 40 standard cubic feet per hour (SCFH) to remove the moisture. The material was dried until the filler moisture content reached <6.0 wt. %.
After drying, both samples were hammer milled to a median particle size within the range of 15-18 micrometers.
The dried, hammer milled treated filler sample (9b) and untreated control sample (9a) were tested for 5-point BET surface area, CTAB surface area, ATD. The results are shown in Table 12.
67.5 liters of water was added to the 150 liter reactor tank and heated to 84° C. via indirect steam coil heat. 2.5 liters of sodium silicate were added at a rate of 391 ml/min. to achieve a target Na2O concentration of 2.5 g/l Na2O and an acid value of 7.6. The Na2O concentration and acid value were confirmed by titrating the sodium silicate/water mixture using the Na2O titration method and acid value titration method described above. The temperature was adjusted as necessary to 84° C. via indirect steam coil heating and the precipitation step was initiated. The 150 liter reactor was agitated via the main tank agitator.
The main agitator was left on and a simultaneous addition precipitation step was started. 35.3 liters of sodium silicate and 2.01 liters of sulfuric acid were added simultaneously over a period of 90 minutes. The sodium silicate was added via an open tube near the bottom of the tank at a rate of 392 ml/min. and the sulfuric acid was added directly above the secondary high speed mixer blades. The acid addition rate averaged 22.3 ml/min. over the course of the 90 min. simultaneous addition step.
At the end of the simultaneous addition step, a 90 minute age step was initiated. A batch pH of 9.3 was measured and an additional 60 ml of sulfuric acid were added at a rate of 22.3 ml/min. to reach a pH of 9.0. The secondary high speed agitator was turned off. 21 g of Agefloc, a cationic flocculant solution (WT-40P with 40 weight % active flocculant, purchased from Ciba Specialty Chemicals) were diluted with 100 ml of water was then poured into the aging slurry. The 90 minute aging step was completed. During this age step the main agitator was left on and the temperature was maintained at 84° C.
After the age step was completed, 290 ml of sulfuric acid were added at a rate of 22.3 ml/min. to reach a final batch pH of 4.2.
50 liters of slurry were removed from the reactor (Example 10) and placed on five 50 cm wide Buchner funnels, 10 liters of slurry per funnel and each funnel was washed with four 2.5 liter water washes. After filtering and washing the slurry on the Buchner funnels, the slurry was in cake form and was referred to as filter cake.
The remaining slurry from Example 10 was treated with 3 wt. % of CTAB (Fisher Scientific Inc., technical grade) based on weight of silica solids. 15 liters of 0.55 wt. % CTAB solution were poured into the top of the reactor with the main agitator on. The batch was allowed to mix for five minutes and the batch pH was measured at 4.6.
60 liters of treated slurry were transferred to six 50 cm Buchner funnels, 10 liters per funnel, and each funnel was washed three times with 2.5 liters of water. After filtering and washing the slurry on the Buchner funnels, the slurry was in cake form and was referred to as filter cake.
Filter cake from Examples 10a and 10b were dried in a custom-made rotary dryer. 19 Kg of filter cake was placed in the dryer for each batch. The dryer was heated electrically, the inner shell temperature set point was 177° C. during drying and the speed of rotation was 8 RPM. There was an air sweep of 40 standard cubic feet per hour (SCFH) to remove the moisture. The material was dried until the filler moisture content reached <6.0 wt. %.
After drying, both samples were hammer milled to a median particle size within a range of 16-19 micrometers.
The dried, hammer milled treated filler sample (10b) and untreated control sample (10a) were tested for 5-point BET surface area, CTAB surface area, ATD. The results are shown in Table 12.
67.5 liters of water were added to a 150 liter reactor tank and heated to 84° C. via indirect steam coil heat. 2.5 liters of sodium silicate were added at a rate of 393 ml/min. to achieve a target Na2O concentration of 2.5 g/l Na2O and an acid value of 7.5. The Na2O concentration and acid value were confirmed by titrating the sodium silicate/water mixture using the Na2O titration method and acid value titration method described at the start of the examples section. The temperature was adjusted as necessary to 84° C. via indirect steam coil heating and the precipitation step was initiated. The 150 liter reactor was agitated via the main tank agitator.
The main agitator was left on and a simultaneous addition precipitation step was started. 35.4 liters of sodium silicate and 2.04 liters of sulfuric acid were added simultaneously over a period of 90 minutes. The sodium silicate was added via an open tube near the bottom of the tank at a rate of 393 ml/min. and the sulfuric acid was added directly above the secondary high speed mixer blades. The acid addition rate averaged 22.7 ml/min. over the course of the 90 min. simultaneous addition step.
At the end of the simultaneous addition step, a 90 minute age step was begun. A batch pH of 9.3 was measured and an additional 40 ml of sulfuric acid were added at a rate of 22.7 ml/min. to reach a pH of 9.0. The secondary high speed agitator was turned off. 21 g of Agefloc, a cationic flocculant solution (WT-40P with 40 weight % active flocculant, purchased from Ciba Specialty Chemicals) were diluted with 100 ml of water and poured into the aging slurry. The 90 minute aging step was then completed. During this age step the main agitator was left on and the temperature was maintained at 84° C.
After the age step was completed, 280 ml of sulfuric acid were added at a rate of 22.7 ml/min to reach a final batch pH of 4.2.
50 liters of slurry were removed from the reactor (Example 11) and placed on five 50 cm wide Buchner funnels, 10 liters of slurry per funnel and each funnel was washed with four 2.5 liter water washes. After filtering and washing the slurry on the Buchner funnels, the slurry was in cake form and was referred to as filter cake. The resulting filter cake solids were 16.6 wt. %.
The remaining 53.5 liters of slurry from Example 11 was treated with 3 wt % of Polyoxyethylene (40) monostearate based on weight of silica solids. The Polyoxyethylene (40) monostearate was obtained from Sigma Aldrich, CAS # 9004-99-3. 126 g of Polyoxyethylene (40) monostearate were mixed with 1.2 liters of water at 60° C. and poured into the top of the reactor with the main agitator on. The batch was allowed to mix for five minutes and the batch pH was measured at 4.1.
50 liters of treated slurry was transferred to five 50 cm Buchner funnels, 10 liters per funnel, and each funnel washed three times with four 2.5 liters of water. After filtering and washing the slurry on the Buchner funnels, the slurry was in cake form and was referred to as filter cake.
Filter cake from Examples 11a and 11b was dried in a custom-made rotary dryer. 19 Kg of filter cake were placed in the dryer for each batch. The dryer was heated electrically, the inner shell set point temperature was 177° C. during drying and the speed of rotation was 8 RPM. There was an air sweep of 40 standard cubic feet per hour (SCFH) to remove the moisture. The material was dried until the filler moisture content reached <6.0 wt. %.
After drying, both samples were hammer milled to a median particle size with the range of 15-16 micrometers.
The dried, hammer milled treated filler sample (11b) and untreated control sample (11a) were for 5-point BET surface area, CTAB surface area, ATD. The results are shown in Table 12.
