Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1994-03-21
2001-05-08
Hendrickson, Stuart (Department: 1754)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C423S449100, C524S496000, C152S905000
Reexamination Certificate
active
06228928
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a class of new and novel furnace carbon blacks which are suitable for various applications and particularly well suited for use in rubber compositions. The carbon blacks of the present invention impart improved hysteresis loss and abrasion resistance to rubber compositions, particularly passenger car tires, in which they are incorporated.
BACKGROUND
Carbon blacks are generally produced in a furnace-type reactor by pyrolyzing a hydrocarbon feedstock with hot combustion gases to produce combustion products containing particulate carbon black.
Carbon blacks may be utilized as pigments, fillers, reinforcing agents and for a variety of other applications. For example, carbon blacks are widely utilized as fillers and reinforcing pigments in the compounding and preparation of rubber compositions.
Carbon blacks for rubber use have a variety of grades depending upon their properties and are generally classified on the basis of analytical properties including: surface area, structure (DBP absorption) and the like. Methods of measuring the surface area of carbon black include an electron microscope, nitrogen surface area (N
2
SA) according to the BET method, CTAB surface area according to the adsorption of cetyltrimethylammonium bromide as a surfactant, and iodine adsorption number (I
2
No.). The structure of a carbon black refers to the linkage of carbon black particles due to agglomeration. As the degree of agglomeration becomes greater, the value of this structure becomes higher.
The properties of the grade of carbon black become an important factor in determining various performances of the rubber composition wherein the carbon blacks are incorporated. Carbon blacks are effective in the preparation of rubber vulcanizates intended for usage in preparing tires. It is generally desirable in the production of tires to utilize carbon blacks which impart high levels of abrasion resistance and low levels of rolling resistance to the tires. The reinforcing properties of a carbon black are generally related to the level of abrasion resistance imparted to the rubber compositions. Generally, carbon blacks with increased reinforcing properties result in tires with increased abrasion resistance.
The grade of the carbon black used mainly for tire treads is classified into HAF (high abrasion furnace), ISAF (intermediate super abrasion furnace) and SAF (super abrasion furnace) with SAF carbon black having a higher surface area than ISAF carbon black which has a higher surface area than HAF carbon black. Abrasion resistance generally improves as surface area increases.
The properties of the grade of carbon black become an important factor in determining various performances of the rubber composition wherein the carbon blacks are incorporated. Generally, carbon blacks having a specific surface area higher than ISAF are used for tire treads of trucks and buses wherein natural rubber is used as a main component. HAF type carbon blacks are generally used for passenger car tire treads wherein synthetic rubbers such as styrene butadiene rubber (SBR) are used as a main component.
Higher surface area carbon blacks impart improved abrasion resistance to tires. However, as specific surface area becomes larger, heat build-up of the rubber compound becomes higher and hysteresis becomes greater. The hysteresis of the compounds means the difference between the energy applied to deform a rubber compound, and the energy released as the rubber compound recovers to its initial undeformed state. Tires with lower hysteresis values have reduced rolling resistance and therefore reduce the fuel consumption of the vehicle utilizing the tire.
Thus it would be desirable to develop a carbon black which would impart both improved abrasion resistance and reduced hysteresis to rubber compounds. Tires prepared with such a carbon black would have lower rolling resistance, to improve the fuel economy of the vehicle utilizing the tire, and improved abrasion resistance, to reduce the tread wear of the tire.
One advantage of the present invention is the production of new carbon blacks which impart increased abrasion resistance and reduced hysteresis properties to natural rubbers, synthetic rubbers and blends of natural and synthetic rubbers incorporating the carbon blacks.
Another object of the present invention is new rubber compositions, advantageous for use as tires, particularly passenger car tires, incorporating the new carbon blacks.
Other objects of the present invention will become apparent from the following description and the claims.
SUMMARY OF THE INVENTION
We have discovered a new class of carbon blacks having a nitrogen surface area (N
2
SA) of at least 100 m
2
/g (square meters per gram); a CDBP (dibutyl phthlate absorption number of the crushed carbon black) of at least 105 cc/100 g (cubic centimeters per 100 g); a TINT (Tint value) of from about 90 to about 140, a Dmode (mode diameter of the carbon black aggregate according to the centrifugal sedimentation method) of the following relationship with the TINT: Dmode (nm)≧218−1.12(TINT), (nm=nanometers=meters×10
−9
), preferably Dmode (nm)≧221−1.12 (TINT) ; and a &Dgr;D50/Dmode ratio (ratio of the half width value to the mode diameter, of the carbon black aggregate, according to the centrifugal sedimentation method) of from about 0.6 to about 0.8. We have also discovered a new class of rubber compositions containing these carbon blacks.
Referring to the blacks of the present invention, when the N
2
SA is more than 100 m
2
/g the carbon black is restricted to the ISAF and SAF classes.
When CDBP is less than 105 cc/100 g the balance between the reinforcing properties and hyteresis imparted by the carbon black to rubber compositions, particularly advantageous for use as passenger car tires, is generally unsatisfactory.
When TINT is less than 90, the reinforcing properties imparted by the carbon black to rubber compositions, particularly advantageous for use as passenger car tires, is generally unsatisfactory. When TINT exceeds 140 the carbon blacks disperse poorly during mixing in the formation of rubber compositions particularly advantageous for use as passenger car tires.
When Dmode is less than the calculated value from TINT, the improvement in hysteresis effect, imparted by the carbon blacks to rubber compositions, particularly advantageous for use as passenger car tires, becomes disadvantageously reduced.
When the &Dgr;D50/Dmode ratio is greater than 0.8 the reinforcing properties imparted by the carbon black to rubber compositions, particularly advantageous for use as passenger car tires, is disadvantageously reduced. While Applicants do not wish to be bound by any particular theory, it is believed that this reduction occurs because of wider aggregate size distribution. When the &Dgr;D50/Dmode ratio is less than 0.6 the hyteresis loss value of rubber compositions incorporating the carbon black, particularly advantageous for use as passenger car tires, disadvantageously becomes large.
However, we have discovered that the carbon blacks of the present invention, having analytical properties within the ranges specified, impart improved reinforcing properties and low hysteresis loss to rubber compositions, prepared utilizing natural rubbers, synthetic rubbers or mixtures thereof. As explained above, the improved reinforcing properties of the carbon blacks impart improved abrasion resistance to rubber compositions.
The carbon black of the present invention may be produced in a furnace carbon black reactor having a first (combustion) zone, a transition zone, and a stepped reaction zone wherein the diameter of the portion of the reaction zone nearest the transition zone is smaller than the diameter of a portion of the reaction zone further downstream of the transition zone. A carbon black yielding feedstock is injected in any manner known to the art, into a hot combustion gas stream. The resultant mixture of hot combustion gases and feedstock passes into the reaction zone. Pyr
Branan, Jr. John M.
Bush Ted W.
Green Martin
Ito Takeo
Soeda Mizuo
Cabot Corporation
Hendrickson Stuart
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