Patent Application
20060047055
This invention relates to preparation and use of a pelletized composite comprised of a dispersion of fluffy (low apparent density) carbon black aggregates in a conjugated diene-based elastomer binder therefor instead of a non-elastomeric polymeric binder. Such composite is prepared by blending non-pelletized, fluffy rubber reinforcing carbon black aggregates with an aqueous dispersion or organic solvent solution of at least one conjugated diene-based elastomer, drying the mixture to form a composite thereof and pelletizing the composite. The resultant pelletized composite desirably contains a relatively high carbon black concentration, desirably is free-flowing, and thereby in a form of a deliverable particulate carbon black for blending with at least one other elastomer, and suitable rubber compounding ingredients, to form a rubber composition which may be used to form various carbon black reinforced rubber products as components of articles of manufacture. Such article of manufacture may be, for example, a tire. Such article may also be an industrial product such as, for example, a hose or belt such as a conveyor belt or power transmission belt.
Rubber reinforcing carbon black is often used to reinforce various rubber compositions.
Rubber reinforcing carbon black is typically manufactured by fuming carbon black under controlled conditions at a significantly elevated temperature to form carbon black aggregates in an uncompacted form of very small particle size which, while having a specific gravity in a range of from about 1.6 to about 1.9, depending upon the carbon black grade, but because the carbon black aggregates are separated by a significant amount of empty space (voids), they have a very low apparent density in a range, for example, from about 100 to about 250 kg/m3, and have an appearance of being relatively fluffy in nature and are therefore referred to herein as being “fluffy”.
Such fluffy carbon black aggregates, probably because of their very low apparent density and small particle size, are very dusty in nature and present associated handling problems in an industrial environment for manufacturing carbon black reinforced rubber products.
Accordingly, in order to make such fluffy carbon black aggregates transportable and useable in a form of a non-dusting material, binder materials are conventionally used to glue the carbon blacks together and to therefore significantly reduce the amount of empty space between the carbon black aggregates the composite of carbon black aggregates and binder material is converted to a free flowing pelletized form is pelletized to promote the transportability of the composite. The apparent density of the carbon back aggregates is thereby increased to perhaps an apparent density in a range, for example, of about 270 to about 600 kg/m3, depending somewhat upon the choice of carbon black type, because the voids between the carbon black aggregates are filled with the binder material.
The binder material interacts with the surface of the carbon black aggregates, binds the carbon black aggregates together and provides a degree of hardness to the pellets.
Typical binder materials are non-elastomeric, polymeric materials such as, for example, molasses, soluble cellulose, methyl cellulose and soluble starch materials.
Intuitively, it is necessary that the pellets are broken down during high shear mixing of rubber compositions which contain the pellets in order to provide carbon black reinforcement for the rubber composition itself. However, this process is relatively inefficient and conventionally the pellets break down to fragments of various sizes with only a fraction being broken entirely down to into the original fluffy carbon black aggregate state, or form.
In addition, the surface of the carbon black aggregates are contaminated with the binder material which is typically polar in nature and therefore typically not very compatible with general purpose (GP) elastomers such as, for example, cis 1,4-polyisoprene, cis 1,4-polybutadiene and styrene/butadiene copolymer rubbers which does detracts from and does particularly aid in promoting the fragmentation and dispersion of the carbon black aggregates in such elastomers.
However, it is desired herein to more effectively provide, transport and deliver carbon black aggregates for reinforcement of conjugated diene-based elastomers and particularly elastomers such as, for example, cis 1,4-polyisoprene, cis 1,4-polybutadiene and styrene/butadiene rubbers.
For this invention, it is proposed to provide carbon black aggregates in a form of pellets of a composite comprised of a high concentration of carbon black aggregates in a conjugated diene-based elastomer such as for example, cis 1,4-polyisoprene, cis 1,4-polybutadiene and/or styrene/butadiene copolymer rubbers which is believed to be a significant departure from the aforesaid past practice by both providing the formative pelletized carbon black aggregates in the elastomer binder and by providing a carbon black reinforced conjugated diene-based elastomer composition which is created by blending the pelletized carbon black aggregates under high shear conditions with the conjugated diene-based elastomer(s).
In such manner, the classical, typically polar, binder material is replaced with a conjugated diene-based elastomer which is significantly more compatible with the diene-based elastomer with which it is being mixed.
Moreover, the formative composite preparation and pelletization thereof creates a composite of the fluffy carbon black aggregates by filling in the voids between the carbon black aggregates, thereby increasing their apparent density, with a conjugated diene-based elastomer which typically has a relatively high level of compatibility with conjugated diene-based elastomers, particularly under high shear mixing conditions.
Therefore, even if the pelletized composite should happen to only relatively inefficiently break down during such higher shear mixing into smaller particles of various sizes, the carbon aggregate reinforcement in contact with the conjugated diene-based elastomer binder and therefore remains available to provide effective carbon black reinforcement for the conjugated diene-based elastomer composition in a form of primary carbon black aggregates similar to the original fluffy carbon black aggregates.
Further, such fragments of the composite is provided within the conjugated diene-based elastomer host with which the composite is mixed under high shear conditions in the absence, or exclusive, of the aforesaid foreign material as the aforesaid polar non-elastomer, polymeric binder material which itself, would otherwise tend to inhibit the compatibility with the conjugated diene-based elastomer host.
In this manner then, is envisioned a more efficient manufacturing of rubber products which contain at least one component of a rubber composition which contains a conjugated diene-based elastomer.
It might be mentioned, that heretofore, preparation of various rubber compositions has been suggested such as, for example, by:
For example, see U.S. Pat. Nos. 3,294,733; 3,298,984; 3,317,458; 3,345,324; 3,491,052; 3,767,605, 3,923,707 and 6,232,389.
U.S. Pat. No. 3,317,458, for example, relates to masterbatching a combination of carbon black and silica with a rubber latex.
Various rubber compositions have also heretofore been prepared by mixing an aqueous slurry of carbon black with an organic solvent solution of elastomer(s). For example see U.S. Pat. No. 3,350,342.
U.S. Pat. No. 3,304,281, for example, relates to mixing together a solution of one polymer with a latex of another polymer and then coagulating the rubber crumb from the resulting mixture. The process can be used to incorporate an oil and/or carbon black into the polymer. For example, the oil can be introduced as an aqueous emulsion and the oil emulsion mixed with the latex prior to contact with the solution. Alternatively, all three components can be mixed simultaneously. Alternatively, a carbon black aqueous slurry can be added to the solution-latex mixture or it can be mixed with the latex prior to mixing with the solution.
U.S. Pat. No. 3,491,052 for example, relates to mixing an elastomer in an aqueous latex form with a solution of an elastomer which has been dissolved in a water immiscible organic solvent to form a pseudo-emulsion and recovering the mixed elastomers by adding a latex coagulating agent at a temperature sufficient to vaporize the solvent. Alternatively a rubber pigment (e.g.: carbon black) may be dispersed in the pseudo-emulsion prior to coagulation.
U.S. Pat. No. 3,533,988, for example, relates to blending a hydrocarbon solution of rubber with an aqueous suspension of a rubber reinforcing agent, such as carbon black. In its background discussion, it relates that, theretofore, in order to avoid a disagreeableness of handling dry, dusty carbon black with raw rubber on mixing rolls, a method was developed for producing masterbatch by dispersing carbon black directly into a rubber solution produced by monomer polymerization in the presence of a solvent.
U.S. Pat. No. 6,232,389 relates to preparation of rubber compositions by mixing various rubber compounding ingredients, including carbon black, with elastomers in an aqueous or solvent solution, recovering the mixture and preparing articles of manufacture therewith.
However, it is not seen that any of such revelations teach or suggest the preparation of deliverable pelletized composites of a high concentration of carbon black aggregates in a form of a pelletized composite with a conjugated diene-based elastomeric binder, to the exclusion of a non-elastomer polymeric binder (a non-elastomer polymeric binder being considered herein as a contaminate, particularly in a rubber composition which contains carbon black reinforcing filler derived from a carbon black/non-elastomeric polymeric binder), and the preparation of rubber compositions with such deliverable pellets.
In the description of this invention, the term “phr” relates to parts by weight of an ingredient per 100 parts by weight of rubber.
The terms “rubber” and “elastomer” may be used interchangeably unless otherwise indicated.
The term “fluffy” rubber reinforcing carbon black aggregates, as used herein, means such fluffy carbon black aggregates in an uncompacted form, typically with an apparent density in range, for example, of from about 100 to about 250 kg/m3.
The term “apparent density” as used herein means the ratio of the carbon black weight that fills a volume of one cubic meter (m3) according to ASTM D1513 Test Method for Carbon Black Pellet Pour Density.
The term “specific gravity” if used herein means the true carbon black material specific gravity according to ASTM D792-55 Test Method.
In accordance with this invention, a process of preparing a (deliverable) pelletized particulate carbon black/elastomer composite comprised of a dispersion of fluffy carbon black aggregates in a conjugated diene-based elastomer binder therefor, exclusive of non-elastomer polymeric binder therefore (e.g. for example, molasses, cellulose and/or starch) wherein said process comprises:
Preferably the said dispersed carbon black aggregates of the resulting composite have an apparent density in a range of from about 100 to about 250 kg/m3.
In further accordance with this invention, a pelletized fluffy carbon black/elastomer composite is provided wherein said fluffy carbon black/elastomer composite is comprised of a dispersion of fluffy rubber reinforcing carbon black aggregates in a conjugated diene-based elastomer binder therefor, to the exclusion of a non-elastomer polymeric binder (and particularly to the exclusion of at least one of molasses, cellulose and starch);
Preferably, said fluffy rubber carbon black aggregates used in said composite have an original apparent density in a range of from about 100 to about 250 kg/m3.
In practice, said fluffy carbon black/elastomer composite pellets are preferably primarily of a generally cylindrical shape with an average length in a range of from about 0.1 to about 10 millimeters (mm) and an average aspect ratio (length/diameter ratio) in a range of from about 1/1 to about 3/1.
In additional accordance with this invention, a pelletized composite is provided comprised of a dispersion of said fluffy rubber reinforcing carbon black aggregates in a conjugated diene-based elastomer binder therefor prepared by the process of this invention.
In further accordance with this invention, the process of this invention additionally comprises blending said pellets of said fluffy carbon black/elastomer composite and at least one additional conjugated diene-based elastomer under high shear mixing conditions sufficient to fragmentize said pelletized composite which comprises blending:
In additional accordance with this invention an article of manufacture is provided having a component comprised of said rubber composition and particularly a rubber composition prepared by the process of this invention.
In further accordance with this invention, said article of manufacture is, for example, a tire or an industrial product such as, for example a hose or belt such as, for example a conveyor belt or power transmission belt.
In additional accordance with this invention a tire is provided having a component comprised of the rubber composition of this invention and particularly of a rubber composition prepared by the process of this invention.
In further accordance with this invention a tire is provided having a tread comprised of the rubber composition of this invention and particularly prepared by the process of this invention.
A significant aspect preparation of the pelletized composite of conjugated diene-based elastomer bound fluffy carbon black aggregates is to provide a desired conjugated diene-based elastomer in direct initial contact with the fluffy rubber reinforcing carbon black in the form of a composite thereof, and particularly in a form of a free-flowing (thereby deliverable to the rubber-blending manufacturing process) pellets of said composite instead of an inert non-elastomer material such as, for example, the aforesaid molasses.
This is considered herein to be significant:
Therefore, a significant aspect of the invention is to isolate the original fluffy primary carbon black aggregates by the conjugated diene-based elastomer instead of by somewhat compacting them by more simply filling its voids with a non-elastomer polymeric filler to present relatively incompatible material with the pellets to the conjugated diene-based elastomer rubber composition for which it is desired to provide more effective carbon black reinforcement.
Accordingly, it is considered herein that the fluffy carbon black aggregates contained in the pelletized form remain in their originally fluffy state even though the voids (open spaces) contained in the fluffy carbon black aggregates are filled with the conjugated diene-based elastomer.
This is because the conjugated diene-based elastomer of the fluffy carbon black/elastomer composite is similar in nature and therefore tends to be compatible with the conjugated diene-based elastomer of the rubber composition with which the pellets are mixed so that the resulting carbon black reinforcement of the rubber composition is substantially provided in a manner similar to the fluffy carbon black aggregates being mixed directly with the conjugated diene-based elastomer containing rubber composition.
In one aspect of a practice of the invention, said organic solvent solution of elastomer(s) may be composed of at a plurality of least two individual organic solvent solutions of elastomers
In one aspect of the invention, the said organic solvent solution of at least one elastomer may be a polymerizate (an elastomer together with its solvent in which it has been prepared by polymerization reaction of an appropriate monomer in the presence of a catalyst which might sometimes referred to as a cement).
Representative examples of various rubber reinforcing carbon blacks are reported in The Vanderbilt Rubber Handbook, 13th Edition, 1990, Page 417. It is to be appreciated that reported carbon blacks are in a pelletized form using the aforesaid classical binders (e.g. molasses, etc).
In practice, a significant aspect of this invention is that the fluffy carbon black aggregates can be blended in their low apparent density state (without being physically compacted to a higher density state) with an aqueous emulsion or organic solvent solution of a conjugated diene-based elastomer and the recovered fluffy carbon black-based composite pelletized directly at the carbon black manufacturing plant without incurring a compacting of the carbon black into a pelletized form. For example, the blending of the fluffy carbon black and elastomer emulsion or solution can be performed at the pelletizer stage in which the medium hot fluffy carbon black aggregates (from their own manufacturing process) are sprayed with the elastomer emulsion or solution, in place of a classical starch or molasses solution, to both form and pelletize the fluffy carbon black composite. In this manner then, the fluffy carbon black is compacted in a deliverable form, with its elastomer binder, which can be advantageously shipped, or otherwise transported, to end user (deliverable to rubber compounding process for mixing with other elastomers and suitable rubber compounding ingredients in various rubber article manufacturing plants such as, for example, tire manufacturing plants).
An aspect of the fluffy carbon black/elastomer binder composite preparation process of this invention has a particular advantage in that:
Additional advantages of the process are:
Consequently, it is considered herein that a composite is provided composed of an enhanced uniformity of dispersion of a high concentration (at least 60 weight percent) of the fluffy carbon black aggregates in an elastomeric binder in a free-flowing deliverable (e.g. deliverable to a rubber compounding process for mixing other elastomers and suitable rubber compounding ingredients) pelletized form.
In the practice of the invention, the elastomer binder for the pelletized composite of carbon black aggregates may be various conjugated diene-based elastomers selected from, for example, at least one of elastomeric polymers of at least one of isoprene and 1,3-butadiene and copolymers of styrene and at least one of isoprene and 1,3-butadiene monomers.
Representative of such elastomers are, for example cis 1,4-polyisoprene, 1,3-butadiene, styrene/butadiene copolymers, isoprene/butadiene copolymers, styrene/isoprene/butadiene copolymers and any functionalized versions of such elastomers.
Various organic solvents may be used for process step of this invention. Representative of such solvents are, for example, hexane, benzene, toluene, cyclohexane, heptane, and tetrahydrofuran. Preferred solvents are, for example, hexane, cyclohexane and heptane.
Various rubber compositions may be prepared by blending the said pelletized composite of particulate fluffy carbon black aggregates with the elastomeric binder with various sulfur vulcanizable elastomers and/or additional rubber compounding ingredients by compounding by methods generally known in the rubber compounding art, such as mixing in an internal rubber mixer with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents and reinforcing materials such as, for example, carbon black. As known to those skilled in the art, depending on the intended use of the sulfur vulcanizable and sulfur vulcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.
Typical amounts of tackifier resins, if used, may comprise about 0.5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts of processing aids may comprise 1 to 10 phr, if used. Such processing aids can include, for example, aromatic, naphthenic, and/or paraffinic processing oils. Representative silicas may be, for example, hydrated amorphous silicas. Typical amounts of antioxidants comprise about 1 to about 3 phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others, such as, for example, those disclosed in The Vanderbilt Rubber Handbook (1978), Pages 344 through 346. Typical amounts of antiozonants for the sidewall composition may comprise about 3 to about 6 phr. Typical amounts of fatty acids, if used, which can include stearic acid comprise about 0.5 to about 3 phr. Typical amounts of zinc oxide comprise about 2 to about 6 phr. Typical amounts of waxes comprise about 1 to about 5 phr. Often microcrystalline waxes are used. Typical amounts of peptizers comprise about 0.1 to about 1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.
The vulcanization is conducted in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents include elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur. As known to those skilled in the art, sulfur vulcanizing agents are used in an amount ranging from about 0.5 to about 4 phr, with a range of from about 0.5 to about 2.25 being preferred.
Accelerators, including primary and optionally secondary accelerators, are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. Often accelerators are used in an amount ranging from about 0.5 to about 2.0 phr. Such accelerators may be, for example, various amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. Preferably, the primary accelerator is a sulfenamide. If a second accelerator is used, the secondary accelerator is preferably a guanidine, dithiocarbamate or thiuram compound.
Sometimes a combination of antioxidants, antiozonants and waxes may be collectively referred to as “antidegradants”.
The presence and relative amounts of the various rubber compounding ingredients are not necessarily considered to be an aspect of this invention, except where indicated.
In practice, the recovered polymer composite may be used as a component of an article of manufacture such as, for example, a component of a tire and/or industrial product. Such tire component may be, for example and without limitation, a tire tread, sidewall, apex or other sidewall insert, or wire coat compound. Such industrial product may be, for example and without limitation, a hose, conveyor belt or power transmission belt.
While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.
The Applicants hereby incorporate by reference prior U.S. Provisional Application Ser. No. 60/606,763, filed on Sep. 2, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60606763 | Sep 2004 | US |
