Patent Application
20250101189
When producing certain masterbatches (e.g., carbon black/natural rubber masterbatches), it is a challenge to break up particulate filler agglomerates and maintain filler dispersion prior to mixing with the elastomeric latex. For example, due to its hydrophobic nature, carbon black tends to agglomerate in aqueous media.
It would be desirable to develop new systems and methods for maintaining desired particulate filler morphology and size distribution prior to injecting the particulate filler into a coagulation chamber.
Disclosed, in some embodiments, is a system for producing a masterbatch. The system includes a coagulation chamber having a first inlet and a second inlet; an elastomeric latex source in fluid communication with the first inlet; a sonication chamber in direct fluid communication with the second inlet; and a particulate slurry source configured to provide a particulate slurry to the sonication chamber.
The particulate slurry source may be a carbon black slurry tank.
In some embodiments, the system further includes a high shear mixer between the carbon black slurry tank and the sonication chamber.
The system may further include a pump (e.g., a positive displacement pump) between the carbon black slurry tank and the sonication chamber.
Disclosed, in other embodiments, is a method for producing a masterbatch. The method includes: feeding (e.g., continuously feeding) a first composition containing an elastomeric latex to a coagulation chamber; and feeding (e.g., continuously feeding) a second composition containing a particulate filler from a sonication chamber to the coagulation chamber. The first composition and the second composition are mixed in the coagulation chamber to form the masterbatch.
In some embodiments, the particulate filler includes carbon black.
The elastomeric latex may include natural rubber.
In some embodiments, the second composition is fed to the coagulation chamber at a pressure of at least 300 psig (e.g., from about 500 psig to about 5,000psig).
The second composition may be fed to the coagulation chamber at a velocity of at least about 100 feet per second (e.g., about 100 feet per second to about 800 feet per second).
Disclosed, in further embodiments, is a method for producing an elastomeric composite blend. The method includes: feeding a first composition containing an elastomeric latex to a coagulation chamber; and feeding a second composition containing a particulate filler from a sonication chamber to the coagulation chamber. The first composition and the second composition are mixed in the coagulation chamber to form the masterbatch. The method further includes dry mixing the masterbatch with an additional elastomer to form the elastomer composite blend.
In some embodiments, the additional elastomer includes natural rubber, chlorinated natural rubber, or a homopolymer, copolymer or terpolymer of one or more of 1,3-butadiene, styrene, isoprene, isobutylene, 2,3-dimethyl-1,3-butadiene, acrylonitrile, ethylene, and/or propylene.
The elastomeric blend may contain from about 30 to about 85 phr of the particulate filler.
Disclosed, in further embodiments, are masterbatches and elastomeric composite blends prepared by the methods.
These and other non-limiting aspects and/or objects of the disclosure are more particularly described below.
The following is a brief description of the drawings, which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same.
The present disclosure may be understood more readily by reference to the following detailed description of desired embodiments included therein and the drawings. In the following specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Methods and materials are described below, although methods and materials similar or equivalent can be used in practice or testing of the present disclosure. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and articles disclosed herein are illustrative only and not intended to be limiting.
The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
As used in the specification and in the claims, the term “comprising” may include the embodiments “consisting of” and “consisting essentially of.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases that require the presence of the named ingredients/steps and permit the presence of other ingredients/steps. However, such description should be construed as also describing compositions, mixtures, or processes as “consisting of” and “consisting essentially of” the enumerated ingredients/steps, which allows the presence of only the named ingredients/steps, along with any impurities that might result therefrom, and excludes other ingredients/steps.
Unless indicated to the contrary, the numerical values in the specification should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of the conventional measurement technique of the type used to determine the particular value.
All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (for example, the range of “from 2 to 10” is inclusive of the endpoints, 2 and 10, and all the intermediate values). The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and/or values.
As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified, in some cases. The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” may refer to plus or minus 10% of the indicated number. For example, “about 10%” may indicate a range of 9% to 11%, and “about 1” may mean from 0.9-1.1.
For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.
The present disclosure relates to a masterbatch produced by mixing an elastomeric latex (e.g., a natural rubber-containing latex) with a slurry containing filler particles (e.g., carbon black particles). The slurry and latex are provided to a coagulation chamber and the slurry may be provided at a much higher velocity than the latex to facilitate high velocity collisions between filler particles and rubber particles. Immediately prior to the coagulation chamber, a sonication chamber is utilized to break up particulate filler agglomerates and/or maintain their dispersion prior to mixing with the latex in the coagulation chamber. By including the sonication chamber, particulate filler primary particles will not have time to form aggregates/agglomerates prior to being locked into the coagulated rubber matrix and desired particulate filler morphology and size distribution can be achieved in the slurry fed to the coagulation chamber.
In some embodiments, the sonication device is a continuous tube sono-reactor. The sonication device may include a dedicated ultrasonic generator.
Sonication conditions can be controlled by a dedicated ultrasonic generator. Depending on the design of the ultrasonic generator, it can be operated at a singular power and a singular frequency. In some embodiments, the ultrasonic generator is capable of generating wideband ultrasonic energy and can be operated under multifrequency mode, e.g., from infrasonic up to the MHz domain.
In the embodiment depicted in
Although the depicted embodiment illustrates a sonication chamber upstream of a coagulation chamber, it should be understood that the inclusion of a sonication device to facilitate ultrasonic mixing within the coagulation chamber is also contemplated either as an alternative to the sonication chamber or in addition to the sonication chamber.
In some embodiments, the coagulation chamber is built in or as part of the sonication chamber. In other embodiments, the coagulation chamber itself is a sonication chamber.
It should be understood that the phrase “a sonication chamber in direct fluid communication with the second inlet and/or a sonication device for facilitating ultrasonic mixing within the coagulation chamber” encompasses embodiments with only the sonication chamber in direct fluid communication with the second inlet, only the sonication device for facilitating ultrasonic mixing within the coagulation chamber, and both the sonication chamber in direct fluid communication with the second inlet and the sonication device for facilitating ultrasonic mixing within the coagulation chamber.
The slurry may be used in masterbatch production immediately upon being prepared. Fluid conduits carrying the slurry and any optional holding tanks and the like, should establish or maintain conditions which substantially preserve the dispersion of the carbon black in the slurry. That is, substantial reagglomeration or settling out of the particulate filler in the slurry should be prevented or reduced to the extent reasonably practical. In some embodiments, all flow lines are smooth, with smooth line-to-line interconnections.
Means may also be provided for incorporating various additives into the elastomer masterbatch. An additive fluid comprising one or more additives may be fed to the mixing zone as a separate feed stream. One or more additives may also be pre-mixed, if suitable, with the carbon black slurry or, more typically, with the elastomer latex fluid. Additives may be mixed into the masterbatch subsequently, i.e., during a subsequent dry mixing step. Numerous additives are well known to those skilled in the art and include, for example, antioxidants, antiozonants, plasticizers, processing aids (e.g., liquid polymers, oils, and the like), resins, flame-retardants, extender oils, lubricants, and a mixture of any of two or more thereof. The general use and selection of such additives is well known to those skilled in the art. Their use in the system disclosed here will be readily understood with the benefit of the present disclosure. In accordance with certain alternative embodiments, curative may be incorporated in a similar manner, to produce a curable elastomer composite which may be referred to as a curable base compound.
The carbon black slurry or other particulate filler fluid may be supplied to the coagulant chamber at a pressure above about 100 psig, such as about 300 to 3000 psig, e.g., about 700 psig. In some embodiments, the liquid slurry is fed into the mixing zone at a velocity above 100 ft. per second, e.g., about 100 to about 800 ft. per second, or about 200 to 500 ft. per second.
The masterbatch produced using the system and method of the present disclosure may be used to produce elastomer composite blends. The process for producing such blends may include mixing (i) elastomer masterbatch produced in a continuous flow process involving mixture of elastomer latex and particulate filler fluids at turbulence levels and flow control conditions sufficient to achieve coagulation even without use of traditional coagulating agents, and (ii) additional elastomer added to such elastomer masterbatch in a dry mixing step. Some optional aspects are disclosed in U.S. Pat. No. 6,075,084 to Mabry et al. which is incorporated by reference herein in its entirety.
The processes for producing elastomer composite blends advantageously afford flexibility to allow for better control distribution of filler between two different elastomer phases in an elastomer composite blend as seen in the example of an elastomer composite blend containing natural rubber, butadiene rubber (“BR”) and carbon black filler. For certain applications, it is beneficial to have the carbon black filler primarily in the natural rubber phase of the elastomer composite blend. In accordance with prior known dry/dry mixing techniques, the carbon black can be mixed with the natural rubber using a dry mixing technique, followed by the addition and further dry mixing of BR. A disadvantageously large portion of the carbon black will migrate into the BR phase, due to its affinity for the BR phase and the less than desirable macro-dispersion of the carbon black in the natural rubber phase. In comparison, improved performance properties of comparable elastomer composite blends prepared by the wet/dry mixing method disclosed herein indicate that more of the carbon black is retained in the natural rubber phase when the carbon black is mixed with the natural rubber in the initial wet mixing step, followed by the addition of BR in a subsequent dry mixing step.
In accordance with the wet mixing step of the method disclosed here, feed rates of latex fluid and particulate filler fluid to the mixing zone of a coagulum reactor can be precisely metered to achieve high yield rates, with little free latex and little undispersed filler in the product crumb at the discharge end of the coagulum reactor. Without wishing to be bound by theory, it presently is understood that a quasi-mono-phase system is established in the mixing zone except that coagulum solids are being formed there and/or downstream thereof in the coagulum zone. Extremely high feed velocity of the particulate filler fluid into the mixing zone of the coagulum reactor and velocity differential relative the latex fluid feed are believed to be significant in achieving sufficient turbulence, i.e., sufficiently energetic shear of the latex by the impact of the particulate filler fluid jet for thorough mixing and dispersion of the particulate into the latex fluid and coagulation. High mixing energies yield product masterbatch crumb with excellent dispersion, together with controlled product delivery. The coagulum is created and then formed into a desirable extrudate. The particulate filler fluid and elastomer latex may be fed continuously, meaning that an ongoing flow of coagulated masterbatch is established from the mixing zone to the discharged end of the coagulum reactor while an uninterrupted flow of the feed fluids is maintained. Typically, the uninterrupted flow of the feed fluids and simultaneous discharge of coagulated masterbatch are maintained for one or more hours, e.g., more than 24 hours, and ever perhaps for a week or more.
While various embodiments can employ a variety of different fillers and elastomers, certain portions of the description of method and apparatus aspects of the disclosure will, for convenience, describe a masterbatch comprising natural rubber and carbon black. It will be within the ability of those skilled in the art, given the benefit of this disclosure, to employ the method and apparatus disclosed here in accordance with the principles of operation discussed here to produce masterbatch and elastomer composite blends comprising a number of alternative or additional elastomers, fillers, and other materials. In brief, methods for preparing elastomer masterbatch involve feeding simultaneously (a) a slurry of carbon black or other filler; and (b) a natural rubber latex fluid or other suitable elastomer fluid to a mixing zone of a coagulum reactor. A coagulum zone extends from the mixing zone, and may be of progressively increasing in cross-sectional area in the downstream direction from an entry end to a discharge end. The slurry may be fed to the mixing zone as a continuous, high velocity jet of injected fluid, while the natural rubber latex fluid is fed at relatively low velocity. The high velocity, flow rate and particulate concentration of the filler slurry are sufficient to cause mixture and high shear of the latex fluid, flow turbulence of the mixture within at least an upstream portion of the coagulum zone, and substantially completely coagulate the elastomer latex prior to the discharge end. Substantially complete coagulation can thus be achieved. The continuous flow method of producing the elastomer composites comprises the continuous and simultaneous feeding of the latex fluid and filler slurry to the mixing zone of the coagulum reactor, establishing a continuous, semi-confined flow of a mixture of the latex and filler slurry in the coagulum zone. Elastomer composite crumb in the form of “worms” or globules are discharged from the discharge end of the coagulum reactor as a substantially constant flow concurrently with the on-going feeding of the latex and carbon black slurry streams into the mixing zone of the coagulum reactor. Notably, the plug-type flow and atmospheric or near atmospheric pressure conditions at the discharge end of the coagulum reactor are highly advantageous in facilitating control and collection of the elastomer composite product, such as for immediate or subsequent further processing steps. Feed rates of the natural rubber latex fluid and carbon black slurry to the mixing zone of the coagulum reactor can be precisely metered to achieve high yield rates, with little free latex and little undispersed carbon black in the product crumb at the discharge end of the coagulum reactor. Without wishing to be bound by theory, it is believed that a quasi-mono-phase system is established in the mixing zone except that coagulum solids are being formed there and/or downstream thereof in the coagulum zone. Extremely high feed velocity of the carbon black slurry into the mixing zone of the coagulum reactor and velocity differential relative the natural rubber latex fluid feed are believed to be significant in achieving sufficient turbulence, i.e., sufficiently energetic shear of the latex by the impact of the particulate filler fluid jet for thorough mixing and dispersion of the particulate into the latex fluid and coagulation. High mixing energies yield the novel product with excellent macro-dispersion, together with controlled product delivery. The coagulum is created and then formed into a desirable extrudate.
The masterbatch prepared by the above-described wet mixing technique and apparatus may be formed into an elastomer composite blend by subsequent dry mixing with additional elastomer. Thus, in some embodiments, the present disclosure involves a wet/dry method. The dry mixing step of the wet/dry mixing method can be carried out with commercially available apparatus and techniques including, for example, Banbury mixers and the like. The additional elastomer added during the dry mixing step of the wet/dry mixing method disclosed here can be one or more elastomers which are the same as or different from the elastomer(s) employed to form the masterbatch. Other ingredients also may be added along with the additional elastomer during the dry mix step including, for example, extender oil, additional particulate filler, curatives, etc., in those embodiments wherein additional particulate filler is added during the dry mixing step such additional filler can be the same as or different from the filler(s) used in the masterbatch formed by the wet mixing step.
Suitable elastomer latex fluids include both natural and synthetic elastomer latices and latex blends. The latex is suitable for coagulation by the selected particulate filler and is suitable for the intended purpose or application of the final rubber product. It will be within the ability of those skilled in the art to select suitable elastomer latex or a suitable blend of elastomer latices for use in the methods and apparatus disclosed here, given the benefit of this disclosure. Exemplary elastomers include, but are not limited to, rubbers, polymers (e.g., homopolymers, copolymers and/or terpolymers) of 1,3-butadiene, styrene, isoprene, isobutylene, 2,3-dimethyl-1,3-butadiene, acrylonitrile, ethylene, and/or propylene and the like. The elastomer may have a glass transition temperature (Tg) as measured by differential scanning calorimetry (DSC) ranging from about −120° C. to about 0° C. Examples include, but are not limited to, styrene-butadiene rubber (SBR), natural rubber and its derivatives such as chlorinated rubber, polybutadiene, polyisoprene, poly (styrene-co-butadiene), and the oil extended derivatives of any of them. Blends of any of the foregoing may also be used. The latex may be in an aqueous carrier liquid. Alternatively, the liquid carrier may be a hydrocarbon solvent. In any event, the elastomer latex fluid must be suitable for controlled continuous feed at appropriate velocity, pressure, and concentration into the mixing zone. Non-limiting examples of suitable synthetic rubbers include: copolymers of from about 10 to about 70 percent by weight of styrene and from about 90 to about 30 percent by weight of butadiene such as copolymer of 19 parts styrene and 81 parts butadiene, a copolymer of 30 parts styrene and 70 parts butadiene, a copolymer of 43 parts styrene and 57 parts butadiene and a copolymer of 50 parts styrene and 50 parts butadiene; polymers and copolymers of conjugated dienes such as polybutadiene, polyisoprene, polychloroprene, and the like, and copolymers of such conjugated dienes with an ethylenic group-containing monomer copolymerizable therewith such as styrene, methyl chlorostyrene, acrylonitrile, 2-vinyl-pyridine, 5-methyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine, 2-methyl-5-vinylpyridine, alkyl-substituted acrylates, vinyl ketone, methyl isopropenyl ketone, methyl vinyl either, alphamethylene carboxylic acids and the esters and amides thereof such as acrylic acid and dialkylacrylic acid amide. Also suitable for use herein are copolymers of ethylene and other high alpha olefins such as propylene, butene-1, and pentene-1.
The additional elastomer added during the dry mixing step of the wet/dry mixing method can employ any elastomer or mixture of elastomers suitable to the intended use or application, including those listed above for use in the wet mixing step. In accordance with some embodiments, the elastomer latex employed in the wet mixing step is natural rubber latex and the additional elastomer employed in the dry mixing step is butadiene rubber (BR). In such embodiments, the butadiene rubber may form the minor phase or constituent of the elastomer composite blend, e.g., from 10% to 50% by weight of total elastomer in the elastomer composite blend. In accordance with certain other embodiments, the elastomer latex employed in the wet mixing step is natural rubber latex and the additional elastomer employed in the dry mixing step is styrene-butadiene rubber (SBR). In some embodiments, the SBR may form the major phase or constituent of the elastomer composite blend, e.g., from 50% to 90% by weight of total elastomer in the elastomer composite blend. In accordance with certain other embodiments, the additional elastomer is natural rubber. In accordance with certain other embodiments, the elastomer latex employed in the wet mixing step is butadiene rubber latex and the additional elastomer employed in the dry mixing step is SBR. In such embodiments, the SBR may be from 10% to 90% by weight of total elastomer in the elastomer composite blend. In accordance with certain other embodiments, the elastomer latex employed in the wet mixing step is butadiene rubber latex and the additional elastomer employed in the dry mixing step is natural rubber. In such embodiments, the natural rubber may be the minor constituent or phase of the elastomer composite blend, e.g., from 10% to 50% by weight of total elastomer in the elastomer composite blend. In accordance with certain other embodiments employing butadiene rubber latex in the wet mixing step, the additional elastomer is additional butadiene rubber. In accordance with certain other embodiments, the elastomer latex employed in the wet mixing step is SBR and the additional elastomer is butadiene rubber. In such embodiments, the butadiene rubber may be from 10% to 90% by weight of total elastomer in the elastomer composite blend. In accordance with certain other embodiments, the elastomer latex employed in the wet mixing step is SBR and the additional elastomer is natural rubber. In such embodiments, the natural rubber may be the major constituent or phase, e.g., from 50% to 90% by weight of total elastomer in the elastomer composite blend. In some embodiments, SBR is employed in both the wet mixing and dry mixing steps, thus being essentially 100% of the elastomer in the elastomer composite blend.
As noted further below, the rubber compositions can contain, in addition to the elastomer and filler, curing agents, a coupling agent, and optionally, various processing aids, oil extenders, and antidegradants. In that regard, it should be understood that the elastomer composite blends disclosed here include vulcanized compositions (VR), thermoplastic vulcanizates (TPV), thermoplastic elastomers (TPE), and thermoplastic polyolefins (TPO). TPV, TPE, and TPO materials are further classified by their ability to be extruded and molded several times without substantial loss of performance characteristics. Thus, in making the elastomer composite blends, one or more curing agents such as, for example, sulfur, sulfur donors, activators, accelerators, peroxides, and other systems used to effect vulcanization of the elastomer composition may be used.
Where the elastomer latex employed in the wet mixing step comprises natural rubber latex, the natural rubber latex can comprise field latex or latex concentrate (produced, for example, by evaporation, centrifugation, or creaming). The natural rubber latex must, of course, be suitable for coagulation by the carbon black. The latex is provided typically in an aqueous carrier liquid. Alternatively, the liquid carrier may be a hydrocarbon solvent. In any event, the natural rubber latex fluid must be suitable for controlled continuous feed at appropriate velocity, pressure, and concentration into the mixing zone. The well-known instability of natural rubber latex is advantageously accommodated, in that it is subjected to relatively low pressure and low shear throughout the system until it is entrained into the previously mentioned semi-confined turbulent flow upon encountering the extraordinarily high velocity and kinetic energy of the carbon black slurry in the mixing zone. In some embodiments, for example, the natural rubber is fed to the mixing zone at a pressure of about 5 psig, at a feed velocity in the range of about 3-12 ft. per second, e.g., about 4-6 ft. per second. In some embodiments, the natural rubber latex is fed to the mixing zone at negative pressure, e.g., −5 psig, where the vacuum is created by the educator effect from the high-speed carbon black jet stream. Selection of a suitable latex or blend of latices will be well within the ability of those skilled in the art given the benefit of the present disclosure and the knowledge of selection criteria generally well recognized in the industry.
The slurry may comprise any suitable filler in a suitable carrier fluid. Selection of the carrier fluid will depend largely upon the choice of particulate filler and upon system parameters. Both aqueous and non-aqueous liquids may be used, with water being useful in many embodiments in view of its cost, availability, and suitability of use in the production of carbon black and certain other filler slurries.
When a carbon black filler is used, selection of the carbon black will depend largely upon the intended use of the elastomer composite blend. Optionally, the slurry further includes any material which can be slurried and fed to the mixing zone in accordance with the principles disclosed here. Suitable additional particulate fillers include, for example, conductive fillers, reinforcing fillers, fillers comprising short fibers (typically having an L/D aspect ratio less than 40), flakes, etc. Thus, exemplary particulate fillers which can be employed in producing elastomer masterbatch in accordance with the methods and apparatus disclosed here, are carbon black, fumed silica, precipitated silica, coated carbon black, chemically functionalized carbon blacks, such as those having attached organic groups, and silicon-treated carbon black, either alone or in combination with each other. Silicon-treated carbon black, a silicon containing species such as an oxide or carbide of silicon, is distributed through at least a portion of the carbon black aggregate as an intrinsic part of the carbon black. Conventional carbon blacks exist in the form of aggregates, with each aggregate consisting of a single phase, which is carbon. This phase may exist in the form of a graphitic crystallite and/or amorphous carbon and is usually a mixture of the two forms. As discussed elsewhere herein, carbon black aggregates may be modified by depositing silicon-containing species, such as silica, on at least a portion of the surface of the carbon black aggregates. The result may be described as silicon-coated carbon blacks. The materials described herein as silicon-treated carbon blacks are not carbon black aggregates which have been coated or otherwise modified, but actually represent a different kind of aggregate. In the silicon-treated carbon blacks, the aggregates contain two phases. One phase is carbon, which will still be present as graphitic crystallite and/or amorphous carbon, while the second phase is silica (and possibly other silicon-containing species). Thus, the silicon-containing species phase of the silicon-treated carbon black is an intrinsic part of the aggregate; it is distributed throughout at least a portion of the aggregate. It will be appreciated that the multiphase aggregates are quite different from the silica-coated carbon blacks mentioned above, which consist of pre-formed, single phase carbon black aggregates having silicon-containing species deposited on their surface. Such carbon blacks may be surface-treated in order to place a silica functionality on the surface of the carbon black aggregate. In this process, an existing aggregate is treated so as to deposit or coat silica (as well as possibly other silicon-containing species) on at least a portion of the surface of the aggregate. For example, an aqueous sodium silicate solution may be used to deposit amorphous silica on the surface of carbon black aggregates in an aqueous slurry at high pH, such as 6 or higher. More specifically, carbon black may be dispersed in water to obtain an aqueous slurry consisting, for example, of about 5% by weight carbon black and 95% by weight water. The slurry may be heated to above about 70° C., such as to 85-95° C., and the pH adjusted to above 6, such as to a range of 10-11, with an alkali solution. A separate preparation is made of sodium silicate solution, containing the amount of silica which is desired to be deposited on the carbon black, and an acid solution to bring the sodium silicate solution to a neutral ph. The sodium silicate and acid solutions are added dropwise to the slurry, which is maintained at its starting pH value with acid or alkali solution as appropriate. The temperature of the solution is also maintained. A suggested rate for addition of the sodium silicate solution is to calibrate the dropwise addition to add about 3 weight percent silicic acid, with respect to the total amount of carbon black, per hour. The slurry could be stirred during the addition, and after its completion for from several minutes (such as 30) to a few hours (i.e., 2-3). In contrast, silicon-treated carbon blacks may be obtained by manufacturing carbon black in the presence of volatizable silicon-containing compounds. Such carbon blacks may be produced in a modular or “staged” furnace carbon black reactor having a combustion zone followed by a zone of converging diameter, a feed stock injection zone with restricted diameter, and a reaction zone. A quench zone is located downstream of the reaction zone. Typically, a quenching fluid, generally water, is sprayed into the stream of newly formed carbon black particles flowing from the reaction zone. In producing silicon-treated carbon black, the previously mentioned volatizable silicon-containing compound is introduced into the carbon black reactor at a point upstream of the quench zone. Useful compounds are volatizable compounds at carbon black reactor temperatures. Examples include, but are not limited to, silicates such as tetraethoxy orthosilicate (TEDS) and tetramethoxy orthosilicate, silanes such as tetrachloro silane, and trichloro methylsilane; and silicone polymers such as octamethylcyclotetrasiloxane (OMTS). The flow rate of the volatilizable compound will determine the weight percent of silicon in the treated carbon black. The weight percent of silicon in the treated carbon black typically ranges from about 0.1 percent to 25 percent, e.g., about 0.5 percent to about 10 percent, and about 2 percent to about 6 percent. The volatizable compound may be pre-mixed with the carbon black-forming feed stock and introduced with the feed stock into the reaction zone. Alternatively, the volatizable compound may be introduced to the reaction zone separately, either upstream or downstream from the feed stock injection point.
As noted above, additives may be used, and in this regard coupling agents useful for coupling silica or carbon black should be expected to be useful with the silicon-treated carbon blacks. Carbon blacks and numerous additional suitable particulate fillers are commercially available and are known to those skilled in the art.
Selection of the particulate filler or mixture of particulate fillers will depend largely upon the intended use of the elastomer composite blends. As used herein, particulate filler can include any material which can be slurried and fed to the mixing zone in accordance with the principles disclosed here. Suitable particulate fillers include, for example, conductive fillers, reinforcing fillers, fillers comprising short fibers (typically having an L/D aspect ratio less than 40), flakes, etc. In addition to the carbon black and silica-type fillers mentioned above, fillers can be formed of clay, glass, polymer, such as aramid fiber, etc. It will be within the ability of those skilled in the art to select suitable particulate fillers for use in the method and apparatus disclosed here given the benefit of the present disclosure, and it is expected that any filler suitable for use in elastomer compositions may be incorporated into the elastomer composites using the teachings of the present disclosure. Of course, blends of the various particulate fillers discussed herein may also be used.
It will be understood that carbon blacks having lower surface area per unit weight may be used in higher concentration in the particulate slurry to achieve the same coagulation efficacy as lower concentrations of carbon black having higher surface area per unit weight.
The masterbatch (or other elastomer composite) produced by the wet mixing step optionally undergoes any suitable further processing prior to addition of additional elastomer in the dry mixing step of the wet/dry method disclosed here. Suitable apparatus for the dry mixing step is commercially available and will be apparent to those skilled in the art given the benefit of this disclosure. Suitable dry mixing apparatus include, for example, Banbury mixers, mills, roller mixers, etc. The coagulum from the wet mixing step, with or without any further intermediate processing, is introduced into the Banbury mixer or other mixing device along with the additional elastomer in any suitable order and relative proportion suitable to the intended use or application. It will be within the ability of those skilled in the art, given the benefit of this disclosure to determine suitable order of addition and relative proportion for the wet mixing product and the additional elastomer. Likewise, it will be within the ability of those skilled in the art given the benefit of this disclosure to select suitable additional ingredients for addition during the dry mixing step suitable to the intended use or application, for example, extender oil, curatives, and other additives known for use in elastomer composites and elastomer composite blends of the general type disclosed here.
This written description uses examples to describe the disclosure, including the best mode, and also to enable any person skilled in the art to make and use the disclosure. Other examples that occur to those skilled in the art are intended to be within the scope of the present disclosure if they have structural elements that do not differ from the same concept, or if they include equivalent structural elements with insubstantial differences. It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims
| Number | Date | Country | |
|---|---|---|---|
| 63585072 | Sep 2023 | US |
